Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Sensors, Volume 9, Issue 6 (June 2009), Pages 4022-5039

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-56
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Magneto-Optical Relaxation Measurements of Functionalized Nanoparticles as a Novel Biosensor
Sensors 2009, 9(6), 4022-4033; doi:10.3390/s90604022
Received: 27 March 2009 / Revised: 21 May 2009 / Accepted: 25 May 2009 / Published: 26 May 2009
Cited by 4 | PDF Full-text (135 KB) | HTML Full-text | XML Full-text
Abstract
Measurements of magneto-optical relaxation signals of magnetic nanoparticles functionalized with biomolecules are a novel biosensing tool. Upon transmission of a laser beam through a nanoparticle suspension in a pulsed magnetic field, the properties of the laser beam change. This can be detected [...] Read more.
Measurements of magneto-optical relaxation signals of magnetic nanoparticles functionalized with biomolecules are a novel biosensing tool. Upon transmission of a laser beam through a nanoparticle suspension in a pulsed magnetic field, the properties of the laser beam change. This can be detected by optical methods. Biomolecular binding events leading to aggregation of nanoparticles are ascertainable by calculating the relaxation time and from this, the hydrodynamic diameters of the involved particles from the optical signal. Interaction between insulin-like growth factor 1 (IGF-1) and its antibody was utilized for demonstration of the measurement setup applicability as an immunoassay. Furthermore, a formerly developed kinetic model was utilized in order to determine kinetic parameters of the interaction. Beside utilization of the method as an immunoassay it can be applied for the characterization of diverse magnetic nanoparticles regarding their size and size distribution. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Figures

Open AccessArticle The “Wireless Sensor Networks for City-Wide Ambient Intelligence (WISE-WAI)” Project
Sensors 2009, 9(6), 4056-4082; doi:10.3390/s90604056
Received: 19 March 2009 / Revised: 1 May 2009 / Accepted: 19 May 2009 / Published: 27 May 2009
Cited by 17 | PDF Full-text (1115 KB) | HTML Full-text | XML Full-text
Abstract
This paper gives a detailed technical overview of some of the activities carried out in the context of the “Wireless Sensor networks for city-Wide Ambient Intelligence (WISEWAI)” project, funded by the Cassa di Risparmio di Padova e Rovigo Foundation, Italy. The main [...] Read more.
This paper gives a detailed technical overview of some of the activities carried out in the context of the “Wireless Sensor networks for city-Wide Ambient Intelligence (WISEWAI)” project, funded by the Cassa di Risparmio di Padova e Rovigo Foundation, Italy. The main aim of the project is to demonstrate the feasibility of large-scale wireless sensor network deployments, whereby tiny objects integrating one or more environmental sensors (humidity, temperature, light intensity), a microcontroller and a wireless transceiver are deployed over a large area, which in this case involves the buildings of the Department of Information Engineering at the University of Padova. We will describe how the network is organized to provide full-scale automated functions, and which services and applications it is configured to provide. These applications include long-term environmental monitoring, alarm event detection and propagation, single-sensor interrogation, localization and tracking of objects, assisted navigation, as well as fast data dissemination services to be used, e.g., to rapidly re-program all sensors over-the-air. The organization of such a large testbed requires notable efforts in terms of communication protocols and strategies, whose design must pursue scalability, energy efficiency (while sensors are connected through USB cables for logging and debugging purposes, most of them will be battery-operated), as well as the capability to support applications with diverse requirements. These efforts, the description of a subset of the results obtained so far, and of the final objectives to be met are the scope of the present paper. Full article
Open AccessArticle A Distributed Geo-Routing Algorithm for Wireless Sensor Networks
Sensors 2009, 9(6), 4083-4103; doi:10.3390/s90604083
Received: 24 April 2009 / Revised: 21 May 2009 / Accepted: 25 May 2009 / Published: 27 May 2009
Cited by 8 | PDF Full-text (372 KB) | HTML Full-text | XML Full-text
Abstract
Geographic wireless sensor networks use position information for greedy routing. Greedy routing works well in dense networks, whereas in sparse networks it may fail and require a recovery algorithm. Recovery algorithms help the packet to get out of the communication void. However, [...] Read more.
Geographic wireless sensor networks use position information for greedy routing. Greedy routing works well in dense networks, whereas in sparse networks it may fail and require a recovery algorithm. Recovery algorithms help the packet to get out of the communication void. However, these algorithms are generally costly for resource constrained position-based wireless sensor networks (WSNs). In this paper, we propose a void avoidance algorithm (VAA), a novel idea based on upgrading virtual distance. VAA allows wireless sensor nodes to remove all stuck nodes by transforming the routing graph and forwarding packets using only greedy routing. In VAA, the stuck node upgrades distance unless it finds a next hop node that is closer to the destination than it is. VAA guarantees packet delivery if there is a topologically valid path. Further, it is completely distributed, immediately responds to node failure or topology changes and does not require planarization of the network. NS-2 is used to evaluate the performance and correctness of VAA and we compare its performance to other protocols. Simulations show our proposed algorithm consumes less energy, has an efficient path and substantially less control overheads. Full article
Open AccessArticle Synthesis of the System Modeling and Signal Detecting Circuit of a Novel Vacuum Microelectronic Accelerometer
Sensors 2009, 9(6), 4104-4118; doi:10.3390/s90604104
Received: 5 May 2009 / Revised: 15 May 2009 / Accepted: 22 May 2009 / Published: 27 May 2009
PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g [...] Read more.
A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %. Full article
Open AccessArticle A Portable and Autonomous Magnetic Detection Platform for Biosensing
Sensors 2009, 9(6), 4119-4137; doi:10.3390/s90604119
Received: 24 April 2009 / Revised: 19 May 2009 / Accepted: 22 May 2009 / Published: 27 May 2009
Cited by 35 | PDF Full-text (733 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a prototype of a platform for biomolecular recognition detection. The system is based on a magnetoresistive biochip that performs biorecognition assays by detecting magnetically tagged targets. All the electronic circuitry for addressing, driving and reading out signals from spin-valve [...] Read more.
This paper presents a prototype of a platform for biomolecular recognition detection. The system is based on a magnetoresistive biochip that performs biorecognition assays by detecting magnetically tagged targets. All the electronic circuitry for addressing, driving and reading out signals from spin-valve or magnetic tunnel junctions sensors is implemented using off-the-shelf components. Taking advantage of digital signal processing techniques, the acquired signals are processed in real time and transmitted to a digital analyzer that enables the user to control and follow the experiment through a graphical user interface. The developed platform is portable and capable of operating autonomously for nearly eight hours. Experimental results show that the noise level of the described platform is one order of magnitude lower than the one presented by the previously used measurement set-up. Experimental results also show that this device is able to detect magnetic nanoparticles with a diameter of 250 nm at a concentration of about 40 fM. Finally, the biomolecular recognition detection capabilities of the platform are demonstrated by performing a hybridization assay using complementary and non-complementary probes and a magnetically tagged 20mer single stranded DNA target. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessArticle Design and Fabrication of a MEMS Flow Sensor and Its Application in Precise Liquid Dispensing
Sensors 2009, 9(6), 4138-4150; doi:10.3390/s90604138
Received: 17 April 2009 / Revised: 4 May 2009 / Accepted: 13 May 2009 / Published: 2 June 2009
Cited by 6 | PDF Full-text (344 KB) | HTML Full-text | XML Full-text
Abstract
A high speed MEMS flow sensor to enhance the reliability and accuracy of a liquid dispensing system is proposed. Benefitting from the sensor information feedback, the system can self-adjust the open time of the solenoid valve to accurately dispense desired volumes of [...] Read more.
A high speed MEMS flow sensor to enhance the reliability and accuracy of a liquid dispensing system is proposed. Benefitting from the sensor information feedback, the system can self-adjust the open time of the solenoid valve to accurately dispense desired volumes of reagent without any pre-calibration. First, an integrated high-speed liquid flow sensor based on the measurement of the pressure difference across a flow channel is presented. Dimensions of the micro-flow channel and two pressure sensors have been appropriately designed to meet the static and dynamic requirements of the liquid dispensing system. Experiments results show that the full scale (FS) flow measurement ranges up to 80 μL/s, with a nonlinearity better than 0.51% FS. Secondly, a novel closed-loop control strategy is proposed to calculate the valve open time in each dispensing cycle, which makes the system immune to liquid viscosity, pressure fluctuation, and other sources of error. Finally, dispensing results show that the system can achieve better dispensing performance, and the coefficient of variance (CV) for liquid dispensing is below 3% at 1 μL and below 4% at 100 nL. Full article
Open AccessArticle Global Oxygen Detection in Water Using Luminescent Probe on Anodized Aluminum
Sensors 2009, 9(6), 4151-4163; doi:10.3390/s90604151
Received: 29 April 2009 / Revised: 19 May 2009 / Accepted: 31 May 2009 / Published: 2 June 2009
Cited by 7 | PDF Full-text (457 KB) | HTML Full-text | XML Full-text
Abstract
We have developed anodized-aluminum pressure-sensitive paint (AA-PSP) as a global oxygen sensor in water. Platinum (II) meso-tetra(pentafluorophenyl)porphine is selected as a luminophore based on a dipping deposition study. The developed AA-PSP is characterized using water calibration setup by controlling dissolved oxygen [...] Read more.
We have developed anodized-aluminum pressure-sensitive paint (AA-PSP) as a global oxygen sensor in water. Platinum (II) meso-tetra(pentafluorophenyl)porphine is selected as a luminophore based on a dipping deposition study. The developed AA-PSP is characterized using water calibration setup by controlling dissolved oxygen concentration. It is shown that AA-PSP yields 4.0% change in luminescence per 1 mg/L of oxygen concentration at 23°C. Other characteristics, such as temperature dependency, photo-degradation, and physical stability, are discussed in this paper. This AA-PSP is used to demonstrate its capability of global oxygen detection in water using the impingement of oxygen rich water (20 mg/L). Even though the difference in water is only the concentration of oxygen, we can obtain global oxygen information of the jet impingement using a fast frame rate camera. Oxygen maps as well as cross-sectional distributions are shown every 0.1 s. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Fluorescence Detection and Discrimination of ss- and ds-DNA with a Water Soluble Oligopyrene Derivative
Sensors 2009, 9(6), 4164-4177; doi:10.3390/s90604164
Received: 9 April 2009 / Revised: 1 May 2009 / Accepted: 21 May 2009 / Published: 2 June 2009
Cited by 10 | PDF Full-text (416 KB) | HTML Full-text | XML Full-text
Abstract
A novel water-soluble cationic conjugated oligopyrene derivative, oligo(N1,N1,N1,N4,N4,N4-hexamethyl-2-(4-(pyren-1-yl) butane-1,4-diaminium bromide) (OHPBDB), was synthesized by a combination of chemical and electrochemical synthesis techniques. Each oligomer chain has five pyrene derivative repeating [...] Read more.
A novel water-soluble cationic conjugated oligopyrene derivative, oligo(N1,N1,N1,N4,N4,N4-hexamethyl-2-(4-(pyren-1-yl) butane-1,4-diaminium bromide) (OHPBDB), was synthesized by a combination of chemical and electrochemical synthesis techniques. Each oligomer chain has five pyrene derivative repeating units and brings 10 positive charges. OHPBDB showed high and rapid fluorescence quenching in aqueous media upon addition of trace amounts of single-stranded (ss) and double-stranded (ds) DNA. The Stern-Volmer constants for ss- and ds-DNA were measured to be as high as 1.3 × 108 mol-1·L and 1.2 × 108 mol-1·L, respectively. On the other hand, distinct fluorescence enhancement of OHPBDB upon addition of large amount of ss-DNA or ds-DNA was observed. Furthermore, ss-DNA showed much stronger fluorescence enhancement than that of ds-DNA, thus yielding a clear and simple signal useful for the discrimination between ss- and ds-DNA in aqueous media. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Metric Potential of a 3D Measurement System Based on Digital Compact Cameras
Sensors 2009, 9(6), 4178-4194; doi:10.3390/s90604178
Received: 28 April 2009 / Revised: 17 May 2009 / Accepted: 25 May 2009 / Published: 3 June 2009
Cited by 11 | PDF Full-text (1028 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an optical measuring system based on low cost, high resolution digital cameras. Once the cameras are synchronised, the portable and adjustable system can be used to observe living beings, bodies in motion, or deformations of very different sizes. Each [...] Read more.
This paper presents an optical measuring system based on low cost, high resolution digital cameras. Once the cameras are synchronised, the portable and adjustable system can be used to observe living beings, bodies in motion, or deformations of very different sizes. Each of the cameras has been modelled individually and studied with regard to the photogrammetric potential of the system. We have investigated the photogrammetric precision obtained from the crossing of rays, the repeatability of results, and the accuracy of the coordinates obtained. Systematic and random errors are identified in validity assessment of the definition of the precision of the system from crossing of rays or from marking residuals in images. The results have clearly demonstrated the capability of a low-cost multiple-camera system to measure with sub-millimetre precision. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Design and Evaluation of a Wireless Sensor Network Based Aircraft Strength Testing System
Sensors 2009, 9(6), 4195-4210; doi:10.3390/s90604195
Received: 31 March 2009 / Revised: 9 April 2009 / Accepted: 13 April 2009 / Published: 3 June 2009
Cited by 13 | PDF Full-text (938 KB) | HTML Full-text | XML Full-text
Abstract
The verification of aerospace structures, including full-scale fatigue and static test programs, is essential for structure strength design and evaluation. However, the current overall ground strength testing systems employ a large number of wires for communication among sensors and data acquisition facilities. [...] Read more.
The verification of aerospace structures, including full-scale fatigue and static test programs, is essential for structure strength design and evaluation. However, the current overall ground strength testing systems employ a large number of wires for communication among sensors and data acquisition facilities. The centralized data processing makes test programs lack efficiency and intelligence. Wireless sensor network (WSN) technology might be expected to address the limitations of cable-based aeronautical ground testing systems. This paper presents a wireless sensor network based aircraft strength testing (AST) system design and its evaluation on a real aircraft specimen. In this paper, a miniature, high-precision, and shock-proof wireless sensor node is designed for multi-channel strain gauge signal conditioning and monitoring. A cluster-star network topology protocol and application layer interface are designed in detail. To verify the functionality of the designed wireless sensor network for strength testing capability, a multi-point WSN based AST system is developed for static testing of a real aircraft undercarriage. Based on the designed wireless sensor nodes, the wireless sensor network is deployed to gather, process, and transmit strain gauge signals and monitor results under different static test loads. This paper shows the efficiency of the wireless sensor network based AST system, compared to a conventional AST system. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle RoPEUS: A New Robust Algorithm for Static Positioning in Ultrasonic Systems
Sensors 2009, 9(6), 4211-4229; doi:10.3390/s90604211
Received: 8 April 2009 / Revised: 6 May 2009 / Accepted: 14 May 2009 / Published: 3 June 2009
Cited by 4 | PDF Full-text (368 KB) | HTML Full-text | XML Full-text
Abstract
A well known problem for precise positioning in real environments is the presence of outliers in the measurement sample. Its importance is even bigger in ultrasound based systems since this technology needs a direct line of sight between emitters and receivers. Standard [...] Read more.
A well known problem for precise positioning in real environments is the presence of outliers in the measurement sample. Its importance is even bigger in ultrasound based systems since this technology needs a direct line of sight between emitters and receivers. Standard techniques for outlier detection in range based systems do not usually employ robust algorithms, failing when multiple outliers are present. The direct application of standard robust regression algorithms fails in static positioning (where only the current measurement sample is considered) in real ultrasound based systems mainly due to the limited number of measurements and the geometry effects. This paper presents a new robust algorithm, called RoPEUS, based on MM estimation, that follows a typical two-step strategy: 1) a high breakdown point algorithm to obtain a clean sample, and 2) a refinement algorithm to increase the accuracy of the solution. The main modifications proposed to the standard MM robust algorithm are a built in check of partial solutions in the first step (rejecting bad geometries) and the off-line calculation of the scale of the measurements. The algorithm is tested with real samples obtained with the 3D-LOCUS ultrasound localization system in an ideal environment without obstacles. These measurements are corrupted with typical outlying patterns to numerically evaluate the algorithm performance with respect to the standard parity space algorithm. The algorithm proves to be robust under single or multiple outliers, providing similar accuracy figures in all cases. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Figures

Open AccessArticle Analysis of the Emitted Wavelet of High-Resolution Bowtie GPR Antennas
Sensors 2009, 9(6), 4230-4246; doi:10.3390/s90604230
Received: 8 April 2009 / Revised: 26 May 2009 / Accepted: 1 June 2009 / Published: 3 June 2009
Cited by 10 | PDF Full-text (1761 KB) | HTML Full-text | XML Full-text
Abstract
Most Ground Penetrating Radars (GPR) cover a wide frequency range by emitting very short time wavelets. In this work, we study in detail the wavelet emitted by two bowtie GPR antennas with nominal frequencies of 800 MHz and 1 GHz. Knowledge of [...] Read more.
Most Ground Penetrating Radars (GPR) cover a wide frequency range by emitting very short time wavelets. In this work, we study in detail the wavelet emitted by two bowtie GPR antennas with nominal frequencies of 800 MHz and 1 GHz. Knowledge of this emitted wavelet allows us to extract as much information as possible from recorded signals, using advanced processing techniques and computer simulations. Following previously published methodology used by Rial et al. [1], which ensures system stability and reliability in data acquisition, a thorough analysis of the wavelet in both time and frequency domain is performed. Most of tests were carried out with air as propagation medium, allowing a proper analysis of the geometrical attenuation factor. Furthermore, we attempt to determine, for each antenna, a time zero in the records to allow us to correctly assign a position to the reflectors detected by the radar. Obtained results indicate that the time zero is not a constant value for the evaluated antennas, but instead depends on the characteristics of the material in contact with the antenna. Full article
(This article belongs to the Section Remote Sensors)
Figures

Open AccessArticle Extended Averaged Learning Subspace Method for Hyperspectral Data Classification
Sensors 2009, 9(6), 4247-4270; doi:10.3390/s90604247
Received: 14 May 2009 / Revised: 27 May 2009 / Accepted: 1 June 2009 / Published: 3 June 2009
Cited by 7 | PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
Averaged learning subspace methods (ALSM) have the advantage of being easily implemented and appear to outperform in classification problems of hyperspectral images. However, there remain some open and challenging problems, which if addressed, could further improve their performance in terms of classification [...] Read more.
Averaged learning subspace methods (ALSM) have the advantage of being easily implemented and appear to outperform in classification problems of hyperspectral images. However, there remain some open and challenging problems, which if addressed, could further improve their performance in terms of classification accuracy. We carried out experiments mainly by using two kinds of improved subspace methods (namely, dynamic and fixed subspace methods), in conjunction with the [0,1] and [-1,+1] normalization methods. We used different performance indicators to support our experimental studies: classification accuracy, computation time, and the stability of the parameter settings. Results are presented for the AVIRIS Indian Pines data set. Experimental analysis showed that the fixed subspace method combined with the [0,1] normalization method yielded higher classification accuracy than other subspace methods. Moreover, ALSMs are easily applied: only two parameters need to be set, and they can be applied directly to hyperspectral data. In addition, they can completely identify training samples in a finite number of iterations. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle Coronatine Gene Expression In Vitro and In Planta, and Protein Accumulation During Temperature Downshift in Pseudomonas syringae
Sensors 2009, 9(6), 4272-4285; doi:10.3390/s90604272
Received: 1 April 2009 / Revised: 22 May 2009 / Accepted: 26 May 2009 / Published: 3 June 2009
Cited by 7 | PDF Full-text (650 KB) | HTML Full-text | XML Full-text
Abstract
The plant pathogenic bacterium Pseudomonas syringae PG4180 synthesizes high levels of the phytotoxin coronatine (COR) at the virulence-promoting temperature of 18 °C, but negligible amounts at 28 °C. Temperature-dependent COR gene expression is regulated by a modified two-component system, consisting of a [...] Read more.
The plant pathogenic bacterium Pseudomonas syringae PG4180 synthesizes high levels of the phytotoxin coronatine (COR) at the virulence-promoting temperature of 18 °C, but negligible amounts at 28 °C. Temperature-dependent COR gene expression is regulated by a modified two-component system, consisting of a response regulator, CorR, the histidine protein kinase CorS, and a third component, termed CorP. We analyzed at transcriptional and translational levels the expression of corS and the cma operon involved in COR biosynthesis after a temperature downshift from 28 to 18 °C. Expression of cma was induced within 20 min and increased steadily whereas corS expression was only slightly temperature-dependent. Accumulation of CmaB correlated with accumulation of cma mRNA. However, cma transcription was suppressed by inhibition of de novo protein biosynthesis. A transcriptional fusion of the cma promoter to a promoterless egfp gene was used to monitor the cma expression in vitro and in planta. A steady induction of cma::egfp by temperature downshift was observed in both environments. The results indicate that PG4180 responds to a temperature decrease with COR gene expression. However, COR gene expression and protein biosynthesis increased steadily, possibly reflecting adaptation to long-term rather than rapid temperature changes. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Development of Membrane Selective Electrode for Determination of the Antipsychotic Sulpiride in Pharmaceuticals and Urine
Sensors 2009, 9(6), 4309-4322; doi:10.3390/s90604309
Received: 20 April 2009 / Revised: 27 May 2009 / Accepted: 1 June 2009 / Published: 3 June 2009
Cited by 3 | PDF Full-text (268 KB) | HTML Full-text | XML Full-text
Abstract
The construction and electrochemical response characteristics of a poly(vinyl chloride) (PVC) membrane selective electrode for the determination of sulpiride (SPD) are described. The sensing membrane comprised an ion-exchanger formed between the protonated drug and tetraphenylborate (TPB-) in a plasticized PVC matrix. The influence of membrane composition on the electrode response was studied. The electrode showed a fast, stable and Nernstian response over a sulpiride concentration range (1 × 10-4– 1 × 10-2 M) with a mean slope of 58.4 ± 0.9 mV dec-1 of concentration, a mean detection limit of 4.2 × 10-5 ± 1.2 × 10-5 M, a wide working pH range (2 – 8) and a fast response time (< 15 s). The electrode showed good selectivity towards sulpiride with respect to some inorganic and organic compounds. When the electrode was applied to the determination of sulpiride in pharmaceuticals and human urine, a high percentage of recovery was attained with no need for sample pretreatment procedures because of the lack of interfering matrix effects. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Standard CMOS Fabrication of a Sensitive Fully Depleted Electrolyte-Insulator-Semiconductor Field Effect Transistor for Biosensor Applications
Sensors 2009, 9(6), 4366-4379; doi:10.3390/s90604366
Received: 25 March 2009 / Revised: 20 May 2009 / Accepted: 25 May 2009 / Published: 4 June 2009
Cited by 8 | PDF Full-text (904 KB) | HTML Full-text | XML Full-text
Abstract
Microfabricated semiconductor devices are becoming increasingly relevant for detection of biological and chemical components. The integration of active biological materials together with sensitive transducers offers the possibility of generating highly sensitive, specific, selective and reliable biosensors. This paper presents the fabrication of [...] Read more.
Microfabricated semiconductor devices are becoming increasingly relevant for detection of biological and chemical components. The integration of active biological materials together with sensitive transducers offers the possibility of generating highly sensitive, specific, selective and reliable biosensors. This paper presents the fabrication of a sensitive, fully depleted (FD), electrolyte-insulator-semiconductor field-effect transistor (EISFET) made with a silicon-on-insulator (SOI) wafer of a thin 10-30 nm active SOI layer. Initial results are presented for device operation in solutions and for bio-sensing. Here we report the first step towards a high volume manufacturing of a CMOS-based biosensor that will enable various types of applications including medical and enviro nmental sensing. Full article
Figures

Open AccessArticle Modeling of Aerosol Vertical Profiles Using GIS and Remote Sensing
Sensors 2009, 9(6), 4380-4389; doi:10.3390/s90604380
Received: 15 April 2009 / Revised: 28 May 2009 / Accepted: 2 June 2009 / Published: 4 June 2009
Cited by 9 | PDF Full-text (311 KB) | HTML Full-text | XML Full-text
Abstract
The use of Geographic Information Systems (GIS) and Remote Sensing (RS) by climatologists, environmentalists and urban planners for three dimensional modeling and visualization of the landscape is well established. However no previous study has implemented these techniques for 3D modeling of atmospheric [...] Read more.
The use of Geographic Information Systems (GIS) and Remote Sensing (RS) by climatologists, environmentalists and urban planners for three dimensional modeling and visualization of the landscape is well established. However no previous study has implemented these techniques for 3D modeling of atmospheric aerosols because air quality data is traditionally measured at ground points, or from satellite images, with no vertical dimension. This study presents a prototype for modeling and visualizing aerosol vertical profiles over a 3D urban landscape in Hong Kong. The method uses a newly developed technique for the derivation of aerosol vertical profiles from AERONET sunphotometer measurements and surface visibility data, and links these to a 3D urban model. This permits automated modeling and visualization of aerosol concentrations at different atmospheric levels over the urban landscape in near-real time. Since the GIS platform permits presentation of the aerosol vertical distribution in 3D, it can be related to the built environment of the city. Examples are given of the applications of the model, including diagnosis of the relative contribution of vehicle emissions to pollution levels in the city, based on increased near-surface concentrations around weekday rush-hour times. The ability to model changes in air quality and visibility from ground level to the top of tall buildings is also demonstrated, and this has implications for energy use and environmental policies for the tall mega-cities of the future. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle The Use of Flow-Injection Analysis with Chemiluminescence Detection of Aqueous Ferrous Iron in Waters Containing High Concentrations of Organic Compounds
Sensors 2009, 9(6), 4390-4406; doi:10.3390/s90604390
Received: 7 April 2009 / Revised: 1 June 2009 / Accepted: 3 June 2009 / Published: 4 June 2009
Cited by 4 | PDF Full-text (212 KB) | HTML Full-text | XML Full-text
Abstract
An evaluation of flow-injection analysis with chemiluminescence detection (FIA-CL) to quantify Fe2+(aq) in freshwaters was performed. Iron-coordinating and/or iron-reducing compounds, dissolved organic matter (DOM), and samples from two natural water systems were used to amend standard solutions of Fe2+ [...] Read more.
An evaluation of flow-injection analysis with chemiluminescence detection (FIA-CL) to quantify Fe2+(aq) in freshwaters was performed. Iron-coordinating and/or iron-reducing compounds, dissolved organic matter (DOM), and samples from two natural water systems were used to amend standard solutions of Fe2+(aq). Slopes of the response curves from ferrous iron standards (1 – 100 nM) were compared to the response curves of iron standards containing the amendments. Results suggest that FIA-CL is not suitable for systems containing ascorbate, hydroxylamine, cysteine or DOM. Little or no change in sensitivity occurred in solutions of oxalate and glycine or in natural waters with little organic matter. Full article
(This article belongs to the Section Chemical Sensors)
Figures

Open AccessArticle Underwater Acoustic Sensors Based on Fiber Bragg Gratings
Sensors 2009, 9(6), 4446-4454; doi:10.3390/s90604446
Received: 19 May 2009 / Revised: 3 June 2009 / Accepted: 3 June 2009 / Published: 5 June 2009
Cited by 13 | PDF Full-text (156 KB) | HTML Full-text | XML Full-text
Abstract
We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone [...] Read more.
We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessArticle A High Isolation Series-Shunt RF MEMS Switch
Sensors 2009, 9(6), 4455-4464; doi:10.3390/s90604455
Received: 13 May 2009 / Revised: 20 May 2009 / Accepted: 22 May 2009 / Published: 5 June 2009
Cited by 8 | PDF Full-text (430 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a wide band compact high isolation microelectromechanical systems (MEMS) switch implemented on a coplanar waveguide (CPW) with three ohmic switch cells, which is based on the series-shunt switch design. The ohmic switch shows a low intrinsic loss of 0.1 [...] Read more.
This paper presents a wide band compact high isolation microelectromechanical systems (MEMS) switch implemented on a coplanar waveguide (CPW) with three ohmic switch cells, which is based on the series-shunt switch design. The ohmic switch shows a low intrinsic loss of 0.1 dB and an isolation of 24.8 dB at 6 GHz. The measured average pull-in voltage is 28 V and switching time is 47 µs. In order to shorten design period of the high isolation switch, a structure-based small-signal model for the 3-port ohmic MEMS switch is developed and parameters are extracted from the measured results. Then a high isolation switch has been developed where each 3-port ohmic MEMS switch is closely located. The agreement of the measured and modeled radio frequency (RF) performance demonstrates the validity of the electrical equivalent model. Measurements of the series-shunt switch indicate an outstanding isolation of more than 40 dB and a low insertion loss of 0.35 dB from DC to 12 GHz with total chip size of 1 mm × 1.2 mm. Full article
Open AccessArticle SITHON: A Wireless Network of in Situ Optical Cameras Applied to the Early Detection-Notification-Monitoring of Forest Fires
Sensors 2009, 9(6), 4465-4482; doi:10.3390/s90604465
Received: 14 April 2009 / Revised: 25 May 2009 / Accepted: 4 June 2009 / Published: 8 June 2009
Cited by 6 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
Abstract
The SITHON system, a fully wireless optical imaging system, integrating a network of in-situ optical cameras linking to a multi-layer GIS database operated by Control Operating Centres, has been developed in response to the need for early detection, notification and monitoring of [...] Read more.
The SITHON system, a fully wireless optical imaging system, integrating a network of in-situ optical cameras linking to a multi-layer GIS database operated by Control Operating Centres, has been developed in response to the need for early detection, notification and monitoring of forest fires. This article presents in detail the architecture and the components of SITHON, and demonstrates the first encouraging results of an experimental test with small controlled fires over Sithonia Peninsula in Northern Greece. The system has already been scheduled to be installed in some fire prone areas of Greece. Full article
(This article belongs to the Section Chemical Sensors)
Figures

Open AccessArticle Multi-Aperture CMOS Sun Sensor for Microsatellite Attitude Determination
Sensors 2009, 9(6), 4503-4524; doi:10.3390/s90604503
Received: 31 March 2009 / Revised: 19 May 2009 / Accepted: 26 May 2009 / Published: 9 June 2009
Cited by 23 | PDF Full-text (753 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the high precision digital sun sensor under development at the University of Naples. The sensor determines the sun line orientation in the sensor frame from the measurement of the sun position on the focal plane. It exploits CMOS technology [...] Read more.
This paper describes the high precision digital sun sensor under development at the University of Naples. The sensor determines the sun line orientation in the sensor frame from the measurement of the sun position on the focal plane. It exploits CMOS technology and an original optical head design with multiple apertures. This allows simultaneous multiple acquisitions of the sun as spots on the focal plane. The sensor can be operated either with a fixed or a variable number of sun spots, depending on the required field of view and sun-line measurement precision. Multiple acquisitions are averaged by using techniques which minimize the computational load to extract the sun line orientation with high precision. Accuracy and computational efficiency are also improved thanks to an original design of the calibration function relying on neural networks. Extensive test campaigns are carried out using a laboratory test facility reproducing sun spectrum, apparent size and distance, and variable illumination directions. Test results validate the sensor concept, confirming the precision improvement achievable with multiple apertures, and sensor operation with a variable number of sun spots. Specifically, the sensor provides accuracy and precision in the order of 1 arcmin and 1 arcsec, respectively. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessArticle Building Facade Reconstruction by Fusing Terrestrial Laser Points and Images
Sensors 2009, 9(6), 4525-4542; doi:10.3390/s90604525
Received: 23 April 2009 / Revised: 21 May 2009 / Accepted: 5 June 2009 / Published: 9 June 2009
Cited by 26 | PDF Full-text (3996 KB) | HTML Full-text | XML Full-text
Abstract
Laser data and optical data have a complementary nature for three dimensional feature extraction. Efficient integration of the two data sources will lead to a more reliable and automated extraction of three dimensional features. This paper presents a semiautomatic building facade reconstruction [...] Read more.
Laser data and optical data have a complementary nature for three dimensional feature extraction. Efficient integration of the two data sources will lead to a more reliable and automated extraction of three dimensional features. This paper presents a semiautomatic building facade reconstruction approach, which efficiently combines information from terrestrial laser point clouds and close range images. A building facade’s general structure is discovered and established using the planar features from laser data. Then strong lines in images are extracted using Canny extractor and Hough transformation, and compared with current model edges for necessary improvement. Finally, textures with optimal visibility are selected and applied according to accurate image orientations. Solutions to several challenge problems throughout the collaborated reconstruction, such as referencing between laser points and multiple images and automated texturing, are described. The limitations and remaining works of this approach are also discussed. Full article
(This article belongs to the Special Issue LiDAR for 3D City Modeling)
Open AccessArticle Optimal Detection Range of RFID Tag for RFID-based Positioning System Using the k-NN Algorithm
Sensors 2009, 9(6), 4543-4558; doi:10.3390/s90604543
Received: 6 May 2009 / Revised: 3 June 2009 / Accepted: 9 June 2009 / Published: 10 June 2009
Cited by 8 | PDF Full-text (1326 KB) | HTML Full-text | XML Full-text
Abstract
Positioning technology to track a moving object is an important and essential component of ubiquitous computing environments and applications. An RFID-based positioning system using the k-nearest neighbor (k-NN) algorithm can determine the position of a moving reader from observed [...] Read more.
Positioning technology to track a moving object is an important and essential component of ubiquitous computing environments and applications. An RFID-based positioning system using the k-nearest neighbor (k-NN) algorithm can determine the position of a moving reader from observed reference data. In this study, the optimal detection range of an RFID-based positioning system was determined on the principle that tag spacing can be derived from the detection range. It was assumed that reference tags without signal strength information are regularly distributed in 1-, 2- and 3-dimensional spaces. The optimal detection range was determined, through analytical and numerical approaches, to be 125% of the tag-spacing distance in 1-dimensional space. Through numerical approaches, the range was 134% in 2-dimensional space, 143% in 3-dimensional space. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Characterization of Long-period Grating Refractive Index Sensors and Their Applications
Sensors 2009, 9(6), 4559-4571; doi:10.3390/s90604559
Received: 25 May 2009 / Revised: 6 June 2009 / Accepted: 9 June 2009 / Published: 10 June 2009
Cited by 27 | PDF Full-text (985 KB) | HTML Full-text | XML Full-text
Abstract
The influence of grating length and bend radius of long-period gratings (LPGs) on refractive index sensing was examined. Sensitivity to refractive indexes smaller than that of silica could be enhanced by bending LPGs. Bent LPGs lost sensitivity to refractive indexes higher than [...] Read more.
The influence of grating length and bend radius of long-period gratings (LPGs) on refractive index sensing was examined. Sensitivity to refractive indexes smaller than that of silica could be enhanced by bending LPGs. Bent LPGs lost sensitivity to refractive indexes higher than that of silica, whereas a 20-mm-long LPG arranged in a straight line had considerable sensitivity. These experimental results demonstrated that the sensitivity characteristics of LPGs to refractive index could be controlled by grating length and bend radius. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle 3D Vision by Using Calibration Pattern with Inertial Sensor and RBF Neural Networks
Sensors 2009, 9(6), 4572-4585; doi:10.3390/s90604572
Received: 17 April 2009 / Revised: 13 May 2009 / Accepted: 5 June 2009 / Published: 11 June 2009
Cited by 5 | PDF Full-text (1524 KB) | HTML Full-text | XML Full-text
Abstract
Camera calibration is a crucial prerequisite for the retrieval of metric information from images. The problem of camera calibration is the computation of camera intrinsic parameters (i.e., coefficients of geometric distortions, principle distance and principle point) and extrinsic parameters (i.e., 3D spatial [...] Read more.
Camera calibration is a crucial prerequisite for the retrieval of metric information from images. The problem of camera calibration is the computation of camera intrinsic parameters (i.e., coefficients of geometric distortions, principle distance and principle point) and extrinsic parameters (i.e., 3D spatial orientations: ω, φ, κ, and 3D spatial translations: tx, ty, tz). The intrinsic camera calibration (i.e., interior orientation) models the imaging system of camera optics, while the extrinsic camera calibration (i.e., exterior orientation) indicates the translation and the orientation of the camera with respect to the global coordinate system. Traditional camera calibration techniques require a predefined mathematical-camera model and they use prior knowledge of many parameters. Definition of a realistic camera model is quite difficult and computation of camera calibration parameters are error-prone. In this paper, a novel implicit camera calibration method based on Radial Basis Functions Neural Networks is proposed. The proposed method requires neither an exactly defined camera model nor any prior knowledge about the imaging-setup or classical camera calibration parameters. The proposed method uses a calibration grid-pattern rotated around a static-fixed axis. The rotations of the calibration grid-pattern have been acquired by using an Xsens MTi-9 inertial sensor and in order to evaluate the success of the proposed method, 3D reconstruction performance of the proposed method has been compared with the performance of a traditional camera calibration method, Modified Direct Linear Transformation (MDLT). Extensive simulation results show that the proposed method achieves a better performance than MDLT aspect of 3D reconstruction. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Development of a Prototype Miniature Silicon Microgyroscope
Sensors 2009, 9(6), 4586-4605; doi:10.3390/s90604586
Received: 22 April 2009 / Revised: 25 May 2009 / Accepted: 4 June 2009 / Published: 11 June 2009
Cited by 10 | PDF Full-text (1334 KB) | HTML Full-text | XML Full-text
Abstract
A miniature vacuum-packaged silicon microgyroscope (SMG) with symmetrical and decoupled structure was designed to prevent unintended coupling between drive and sense modes. To ensure high resonant stability and strong disturbance resisting capacity, a self-oscillating closed-loop circuit including an automatic gain control (AGC) [...] Read more.
A miniature vacuum-packaged silicon microgyroscope (SMG) with symmetrical and decoupled structure was designed to prevent unintended coupling between drive and sense modes. To ensure high resonant stability and strong disturbance resisting capacity, a self-oscillating closed-loop circuit including an automatic gain control (AGC) loop based on electrostatic force feedback is adopted in drive mode, while, dual-channel decomposition and reconstruction closed loops are applied in sense mode. Moreover, the temperature effect on its zero bias was characterized experimentally and a practical compensation method is given. The testing results demonstrate that the useful signal and quadrature signal will not interact with each other because their phases are decoupled. Under a scale factor condition of 9.6 mV/o/s, in full measurement range of ± 300 deg/s, the zero bias stability reaches 15o/h with worse-case nonlinearity of 400 ppm, and the temperature variation trend of the SMG bias is thus largely eliminated, so that the maximum bias value is reduced to one tenth of the original after compensation from -40 oC to 80 oC. Full article
Open AccessArticle Exact Weighted-FBP Algorithm for Three-Orthogonal-Circular Scanning Reconstruction
Sensors 2009, 9(6), 4606-4614; doi:10.3390/s90604606
Received: 28 April 2009 / Revised: 21 May 2009 / Accepted: 12 June 2009 / Published: 12 June 2009
PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
Recently, 3D image fusion reconstruction using a FDK algorithm along threeorthogonal circular isocentric orbits has been proposed. On the other hand, we know that 3D image reconstruction based on three-orthogonal circular isocentric orbits is sufficient in the sense of Tuy data sufficiency [...] Read more.
Recently, 3D image fusion reconstruction using a FDK algorithm along threeorthogonal circular isocentric orbits has been proposed. On the other hand, we know that 3D image reconstruction based on three-orthogonal circular isocentric orbits is sufficient in the sense of Tuy data sufficiency condition. Therefore the datum obtained from three-orthogonal circular isocentric orbits can derive an exact reconstruction algorithm. In this paper, an exact weighted-FBP algorithm with three-orthogonal circular isocentric orbits is derived by means of Katsevich’s equations of filtering lines based on a circle trajectory and a modified weighted form of Tuy’s reconstruction scheme. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A New and Inexpensive Pyranometer for the Visible Spectral Range
Sensors 2009, 9(6), 4615-4634; doi:10.3390/s90604615
Received: 20 May 2009 / Revised: 10 June 2009 / Accepted: 10 June 2009 / Published: 12 June 2009
Cited by 13 | PDF Full-text (793 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine [...] Read more.
This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162. Full article
(This article belongs to the Section Chemical Sensors)
Figures

Open AccessArticle Immobilization of HRP in Mesoporous Silica and Its Application for the Construction of Polyaniline Modified Hydrogen Peroxide Biosensor
Sensors 2009, 9(6), 4635-4648; doi:10.3390/s90604635
Received: 21 April 2009 / Revised: 3 June 2009 / Accepted: 5 June 2009 / Published: 12 June 2009
Cited by 22 | PDF Full-text (2871 KB) | HTML Full-text | XML Full-text
Abstract
Polyaniline (PANI), an attractive conductive polymer, has been successfully applied in fabricating various types of enzyme-based biosensors. In this study, we have employed mesoporous silica SBA-15 to stably entrap horseradish peroxidase (HRP), and then deposited the loaded SBA-15 on the PANI modified [...] Read more.
Polyaniline (PANI), an attractive conductive polymer, has been successfully applied in fabricating various types of enzyme-based biosensors. In this study, we have employed mesoporous silica SBA-15 to stably entrap horseradish peroxidase (HRP), and then deposited the loaded SBA-15 on the PANI modified platinum electrode to construct a GA/SBA-15(HRP)/PANI/Pt biosensor. The mesoporous structures and morphologies of SBA-15 with or without HRP were characterized. Enzymatic protein assays were employed to evaluate HRP immobilization efficiency. Our results demonstrated that the constructed biosensor displayed a fine linear correlation between cathodic response and H2O2 concentration in the range of 0.02 to 18.5 mM, with enhanced sensitivity. In particular, the current approach provided the PANI modified biosensor with improved stability for multiple measurements. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A High Resolution Color Image Restoration Algorithm for Thin TOMBO Imaging Systems
Sensors 2009, 9(6), 4649-4668; doi:10.3390/s90604649
Received: 20 May 2009 / Revised: 5 June 2009 / Accepted: 5 June 2009 / Published: 15 June 2009
Cited by 3 | PDF Full-text (3801 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a blind image restoration algorithm to reconstruct a high resolution (HR) color image from multiple, low resolution (LR), degraded and noisy images captured by thin (< 1mm) TOMBO imaging systems. The proposed algorithm is an extension of our grayscale algorithm reported in [1] to the case of color images. In this color extension, each Point Spread Function (PSF) of each captured image is assumed to be different from one color component to another and from one imaging unit to the other. For the task of image restoration, we use all spectral information in each captured image to restore each output pixel in the reconstructed HR image, i.e., we use the most efficient global category of point operations. First, the composite RGB color components of each captured image are extracted. A blind estimation technique is then applied to estimate the spectra of each color component and its associated blurring PSF. The estimation process is formed in a way that minimizes significantly the interchannel cross-correlations and additive noise. The estimated PSFs together with advanced interpolation techniques are then combined to compensate for blur and reconstruct a HR color image of the original scene. Finally, a histogram normalization process adjusts the balance between image color components, brightness and contrast. Simulated and experimental results reveal that the proposed algorithm is capable of restoring HR color images from degraded, LR and noisy observations even at low Signal-to-Noise Energy ratios (SNERs). The proposed algorithm uses FFT and only two fundamental image restoration constraints, making it suitable for silicon integration with the TOMBO imager. Full article
(This article belongs to the Special Issue Image Sensors)
Figures

Open AccessArticle High Resolution Remote Sensing of Densely Urbanised Regions: a Case Study of Hong Kong
Sensors 2009, 9(6), 4695-4708; doi:10.3390/s90604695
Received: 29 April 2009 / Revised: 11 June 2009 / Accepted: 15 June 2009 / Published: 15 June 2009
Cited by 3 | PDF Full-text (2640 KB) | HTML Full-text | XML Full-text
Abstract
Data on the urban environment such as climate or air quality is usually collected at a few point monitoring stations distributed over a city. However, the synoptic viewpoint of satellites where a whole city is visible on a single image permits the [...] Read more.
Data on the urban environment such as climate or air quality is usually collected at a few point monitoring stations distributed over a city. However, the synoptic viewpoint of satellites where a whole city is visible on a single image permits the collection of spatially comprehensive data at city-wide scale. In spite of rapid developments in remote sensing systems, deficiencies in image resolution and algorithm development still exist for applications such as air quality monitoring and urban heat island analysis. This paper describes state-of-the-art techniques for enhancing and maximising the spatial detail available from satellite images, and demonstrates their applications to the densely urbanised environment of Hong Kong. An Emissivity Modulation technique for spatial enhancement of thermal satellite images permits modelling of urban microclimate in combination with other urban structural parameters at local scale. For air quality monitoring, a Minimum Reflectance Technique (MRT) has been developed for MODIS 500 m images. The techniques described can promote the routine utilization of remotely sensed images for environmental monitoring in cities of the 21st century. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Secure Cluster Head Sensor Elections Using Signal Strength Estimation and Ordered Transmissions
Sensors 2009, 9(6), 4709-4727; doi:10.3390/s90604709
Received: 1 April 2009 / Revised: 20 May 2009 / Accepted: 3 June 2009 / Published: 16 June 2009
Cited by 5 | PDF Full-text (282 KB) | HTML Full-text | XML Full-text
Abstract
In clustered sensor networks, electing CHs (Cluster Heads) in a secure manner is very important because they collect data from sensors and send the aggregated data to the sink. If a compromised node is elected as a CH, it can illegally acquire [...] Read more.
In clustered sensor networks, electing CHs (Cluster Heads) in a secure manner is very important because they collect data from sensors and send the aggregated data to the sink. If a compromised node is elected as a CH, it can illegally acquire data from all the members and even send forged data to the sink. Nevertheless, most of the existing CH election schemes have not treated the problem of the secure CH election. Recently, random value based protocols have been proposed to resolve the secure CH election problem. However, these schemes cannot prevent an attacker from suppressing its contribution for the change of CH election result and from selectively forwarding its contribution for the disagreement of CH election result. In this paper, we propose a modified random value scheme to prevent these disturbances. Our scheme dynamically adjusts the forwarding order of contributions and discards a received contribution when its signal strength is lower than the specified level to prevent these malicious actions. The simulation results have shown that our scheme effectively prevents attackers from changing and splitting an agreement of CH election result. Also, they have shown that our scheme is relatively energy-efficient than other schemes. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Figures

Open AccessArticle Optimization-Based Channel Constrained Data Aggregation Routing Algorithms in Multi-Radio Wireless Sensor Networks
Sensors 2009, 9(6), 4766-4788; doi:10.3390/s90604766
Received: 6 May 2009 / Revised: 5 June 2009 / Accepted: 12 June 2009 / Published: 17 June 2009
Cited by 6 | PDF Full-text (718 KB) | HTML Full-text | XML Full-text
Abstract
In wireless sensor networks, data aggregation routing could reduce the number of data transmissions so as to achieve energy efficient transmission. However, data aggregation introduces data retransmission that is caused by co-channel interference from neighboring sensor nodes. This kind of co-channel interference [...] Read more.
In wireless sensor networks, data aggregation routing could reduce the number of data transmissions so as to achieve energy efficient transmission. However, data aggregation introduces data retransmission that is caused by co-channel interference from neighboring sensor nodes. This kind of co-channel interference could result in extra energy consumption and significant latency from retransmission. This will jeopardize the benefits of data aggregation. One possible solution to circumvent data retransmission caused by co-channel interference is to assign different channels to every sensor node that is within each other’s interference range on the data aggregation tree. By associating each radio with a different channel, a sensor node could receive data from all the children nodes on the data aggregation tree simultaneously. This could reduce the latency from the data source nodes back to the sink so as to meet the user’s delay QoS. Since the number of radios on each sensor node and the number of non-overlapping channels are all limited resources in wireless sensor networks, a challenging question here is to minimize the total transmission cost under limited number of non-overlapping channels in multi-radio wireless sensor networks. This channel constrained data aggregation routing problem in multi-radio wireless sensor networks is an NP-hard problem. I first model this problem as a mixed integer and linear programming problem where the objective is to minimize the total transmission subject to the data aggregation routing, channel and radio resources constraints. The solution approach is based on the Lagrangean relaxation technique to relax some constraints into the objective function and then to derive a set of independent subproblems. By optimally solving these subproblems, it can not only calculate the lower bound of the original primal problem but also provide useful information to get the primal feasible solutions. By incorporating these Lagrangean multipliers as the link arc weight, the optimization-based heuristics are proposed to get energy-efficient data aggregation tree with better resource (channel and radio) utilization. From the computational experiments, the proposed optimization-based approach is superior to existing heuristics under all tested cases. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Effect of Cadmium Chloride on Metallothionein Levels in Carp
Sensors 2009, 9(6), 4789-4803; doi:10.3390/s90604789
Received: 10 June 2009 / Revised: 16 June 2009 / Accepted: 17 June 2009 / Published: 17 June 2009
Cited by 15 | PDF Full-text (195 KB) | HTML Full-text | XML Full-text
Abstract
Due to anthropogenic activities, heavy metals still represent a threat for various trophic levels. If aquatic animals are exposed to heavy metals, we can obviously observe considerable toxicity. It is well known that organisms treated with heavy metals synthesize low molecular mass [...] Read more.
Due to anthropogenic activities, heavy metals still represent a threat for various trophic levels. If aquatic animals are exposed to heavy metals, we can obviously observe considerable toxicity. It is well known that organisms treated with heavy metals synthesize low molecular mass compounds rich in cysteine. In this work the effects of cadmium chloride (2.5, 5, 7.5, 10 and 12.5 mg/L) on common carp (Cyprinus carpio) was investigated. We determined cadmium content in tissue of muscle, liver and kidney by atomic absorption spectrometry with electrothermal atomization and content of metallothionein (MT) in the same tissues by the Brdicka reaction. Electrochemical methods can be considered as suitable and sensitive tools for MT determination in carp tissues. Results of our study showed a gradually enhancing of cadmium content in muscle with time and dose of cadmium chloride in water. MT levels in liver reached both high levels (above 130 ng/g) in fish exposed to 2.5, 5 and 7.5 mg/L and low level (to 50 ng/g) in fish exposed to 10 and 12.5 mg/L of cadmium chloride. This finding confirms that the synthesis of metallothioneins and binding capacity of these proteins is restricted. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Medium Access Control for Opportunistic Concurrent Transmissions under Shadowing Channels
Sensors 2009, 9(6), 4824-4844; doi:10.3390/s90604824
Received: 12 June 2009 / Revised: 16 June 2009 / Accepted: 17 June 2009 / Published: 18 June 2009
Cited by 5 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
We study the problem of how to alleviate the exposed terminal effect in multihop wireless networks in the presence of log-normal shadowing channels. Assuming node location information, we propose an extension of the IEEE 802.11 MAC protocol that schedules concurrent transmissions in [...] Read more.
We study the problem of how to alleviate the exposed terminal effect in multihop wireless networks in the presence of log-normal shadowing channels. Assuming node location information, we propose an extension of the IEEE 802.11 MAC protocol that schedules concurrent transmissions in the presence of log-normal shadowing, thus mitigating the exposed terminal problem and improving network throughput and delay performance. We observe considerable improvements in throughput and delay achieved over the IEEE 802.11 MAC under various network topologies and channel conditions in ns-2 simulations, which justify the importance of considering channel randomness in MAC protocol design for multihop wireless networks. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle On the Relevance of Using OpenWireless Sensor Networks in Environment Monitoring
Sensors 2009, 9(6), 4845-4868; doi:10.3390/s90604845
Received: 3 April 2009 / Revised: 4 June 2009 / Accepted: 10 June 2009 / Published: 19 June 2009
Cited by 3 | PDF Full-text (1087 KB) | HTML Full-text | XML Full-text
Abstract
This paper revisits the problem of the readiness for field deployments of wireless- sensor networks by assessing the relevance of using Open Hardware and Software motes for environment monitoring. We propose a new prototype wireless sensor network that finetunes SquidBee motes to [...] Read more.
This paper revisits the problem of the readiness for field deployments of wireless- sensor networks by assessing the relevance of using Open Hardware and Software motes for environment monitoring. We propose a new prototype wireless sensor network that finetunes SquidBee motes to improve the life-time and sensing performance of an environment monitoring system that measures temperature, humidity and luminosity. Building upon two outdoor sensing scenarios, we evaluate the performance of the newly proposed energy-aware prototype solution in terms of link quality when expressed by the Received Signal Strength, Packet Loss and the battery lifetime. The experimental results reveal the relevance of using the Open Hardware and Software motes when setting up outdoor wireless sensor networks. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Figures

Open AccessArticle Applications of Remote Sensing to Alien Invasive Plant Studies
Sensors 2009, 9(6), 4869-4889; doi:10.3390/s90604869
Received: 8 May 2009 / Revised: 3 June 2009 / Accepted: 18 June 2009 / Published: 19 June 2009
Cited by 49 | PDF Full-text (334 KB) | HTML Full-text | XML Full-text
Abstract
Biological invasions can affect ecosystems across a wide spectrum of bioclimatic conditions. Therefore, it is often important to systematically monitor the spread of species over a broad region. Remote sensing has been an important tool for large-scale ecological studies in the past [...] Read more.
Biological invasions can affect ecosystems across a wide spectrum of bioclimatic conditions. Therefore, it is often important to systematically monitor the spread of species over a broad region. Remote sensing has been an important tool for large-scale ecological studies in the past three decades, but it was not commonly used to study alien invasive plants until the mid 1990s. We synthesize previous research efforts on remote sensing of invasive plants from spatial, temporal and spectral perspectives. We also highlight a recently developed state-of-the-art image fusion technique that integrates passive and active energies concurrently collected by an imaging spectrometer and a scanning-waveform light detection and ranging (LiDAR) system, respectively. This approach provides a means to detect the structure and functional properties of invasive plants of different canopy levels. Finally, we summarize regional studies of biological invasions using remote sensing, discuss the limitations of remote sensing approaches, and highlight current research needs and future directions. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle A Novel Label-Free Optical Biosensor Using Synthetic Oligonucleotides from E. coli O157:H7: Elementary Sensitivity Tests
Sensors 2009, 9(6), 4890-4900; doi:10.3390/s90604890
Received: 24 April 2009 / Revised: 10 June 2009 / Accepted: 15 June 2009 / Published: 19 June 2009
Cited by 20 | PDF Full-text (520 KB) | HTML Full-text | XML Full-text
Abstract
SiO2-TiO2 thin films for use as fiber optic guiding layers of optical DNA biosensors were fabricated by the sol-gel dip coating technique. The chemical structure and the surface morphology of the films were characterized before immobilization. Single probe DNA [...] Read more.
SiO2-TiO2 thin films for use as fiber optic guiding layers of optical DNA biosensors were fabricated by the sol-gel dip coating technique. The chemical structure and the surface morphology of the films were characterized before immobilization. Single probe DNA strands were immobilized on the surface and the porosity of the films before the hybridization process was measured. Refractive index values of the films were measured using a Metricon 2010 prism coupler. On the surface of each film, 12 different spots were taken for measurement and calculation of the mean refractive index values with their standard deviations. The increased refractive index values after the immobilization of single DNA strands indicated that immobilization was successfully achieved. A further refractive index increase after the hybridization with target single DNA strands showed the possibility of detection of the E. coli O157:H7 EDL933 species using strands of 20-mers (5’-TAATATCGGTTGCGGAGGTG -3’) sequence. Full article
(This article belongs to the Section Biosensors)
Figures

Open AccessArticle CoCMA: Energy-Efficient Coverage Control in Cluster-Based Wireless Sensor Networks Using a Memetic Algorithm
Sensors 2009, 9(6), 4918-4940; doi:10.3390/s90604918
Received: 20 May 2009 / Revised: 14 June 2009 / Accepted: 19 June 2009 / Published: 22 June 2009
Cited by 9 | PDF Full-text (2398 KB) | HTML Full-text | XML Full-text
Abstract
Deployment of wireless sensor networks (WSNs) has drawn much attention in recent years. Given the limited energy for sensor nodes, it is critical to implement WSNs with energy efficiency designs. Sensing coverage in networks, on the other hand, may degrade gradually over [...] Read more.
Deployment of wireless sensor networks (WSNs) has drawn much attention in recent years. Given the limited energy for sensor nodes, it is critical to implement WSNs with energy efficiency designs. Sensing coverage in networks, on the other hand, may degrade gradually over time after WSNs are activated. For mission-critical applications, therefore, energy-efficient coverage control should be taken into consideration to support the quality of service (QoS) of WSNs. Usually, coverage-controlling strategies present some challenging problems: (1) resolving the conflicts while determining which nodes should be turned off to conserve energy; (2) designing an optimal wake-up scheme that avoids awakening more nodes than necessary. In this paper, we implement an energy-efficient coverage control in cluster-based WSNs using a Memetic Algorithm (MA)-based approach, entitled CoCMA, to resolve the challenging problems. The CoCMA contains two optimization strategies: a MA-based schedule for sensor nodes and a wake-up scheme, which are responsible to prolong the network lifetime while maintaining coverage preservation. The MA-based schedule is applied to a given WSN to avoid unnecessary energy consumption caused by the redundant nodes. During the network operation, the wake-up scheme awakens sleeping sensor nodes to recover coverage hole caused by dead nodes. The performance evaluation of the proposed CoCMA was conducted on a cluster-based WSN (CWSN) under either a random or a uniform deployment of sensor nodes. Simulation results show that the performance yielded by the combination of MA and wake-up scheme is better than that in some existing approaches. Furthermore, CoCMA is able to activate fewer sensor nodes to monitor the required sensing area.
Source Code Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Improving Temporal Coverage of an Energy-Efficient Data Extraction Algorithm for Environmental Monitoring Using Wireless Sensor Networks
Sensors 2009, 9(6), 4941-4954; doi:10.3390/s90604941
Received: 6 March 2009 / Revised: 19 May 2009 / Accepted: 5 June 2009 / Published: 23 June 2009
Cited by 4 | PDF Full-text (703 KB) | HTML Full-text | XML Full-text
Abstract
Collecting raw data from a wireless sensor network for environmental monitoring applications can be a difficult task due to the high energy consumption involved. This is especially difficult when the application requires specialized sensors that have very high energy consumption, e.g. hydrological [...] Read more.
Collecting raw data from a wireless sensor network for environmental monitoring applications can be a difficult task due to the high energy consumption involved. This is especially difficult when the application requires specialized sensors that have very high energy consumption, e.g. hydrological sensors for monitoring marine environments. This paper introduces a technique for reducing energy consumption by minimizing sensor sampling operations. In addition, we illustrate how a randomized algorithm can be used to improve temporal coverage such that the time between the occurrence of an event and its detection can be minimized. We evaluate our approach using real data collected from a sensor network deployment on the Great Barrier Reef. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
Open AccessArticle Design of a Smart Ultrasonic Transducer for Interconnecting Machine Applications
Sensors 2009, 9(6), 4986-5000; doi:10.3390/s90604986
Received: 10 May 2009 / Revised: 9 June 2009 / Accepted: 10 June 2009 / Published: 24 June 2009
Cited by 2 | PDF Full-text (377 KB) | HTML Full-text | XML Full-text
Abstract
A high-frequency ultrasonic transducer for copper or gold wire bonding has been designed, analyzed, prototyped and tested. Modeling techniques were used in the design phase and a practical design procedure was established and used. The transducer was decomposed into its elementary components. [...] Read more.
A high-frequency ultrasonic transducer for copper or gold wire bonding has been designed, analyzed, prototyped and tested. Modeling techniques were used in the design phase and a practical design procedure was established and used. The transducer was decomposed into its elementary components. For each component, an initial design was obtained with simulations using a finite elements model (FEM). Simulated ultrasonic modules were built and characterized experimentally through the Laser Doppler Vibrometer (LDV) and electrical resonance spectra. Compared with experimental data, the FEM could be iteratively adjusted and updated. Having achieved a remarkably highly-predictive FEM of the whole transducer, the design parameters could be tuned for the desired applications, then the transducer is fixed on the wire bonder with a complete holder clamping was calculated by the FEM. The approach to mount ultrasonic transducers on wire bonding machines also is of major importance for wire bonding in modern electronic packaging. The presented method can lead to obtaining a nearly complete decoupling clamper design of the transducer to the wire bonder. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Study of Alternative GPS Network Meteorological Sensors in Taiwan: Case Studies of the Plum Rains and Typhoon Sinlaku
Sensors 2009, 9(6), 5001-5021; doi:10.3390/s90605001
Received: 11 June 2009 / Revised: 18 June 2009 / Accepted: 19 June 2009 / Published: 24 June 2009
Cited by 8 | PDF Full-text (2035 KB) | HTML Full-text | XML Full-text
Abstract
Plum rains and typhoons are important weather systems in the Taiwan region. They can cause huge economic losses, but they are also considered as important water resources as they strike Taiwan annually and fill the reservoirs around the island. There are many [...] Read more.
Plum rains and typhoons are important weather systems in the Taiwan region. They can cause huge economic losses, but they are also considered as important water resources as they strike Taiwan annually and fill the reservoirs around the island. There are many meteorological sensors available for investigating the characteristics of weather and climate systems. Recently, the use of GPS as an alternative meteorological sensor has become popular due to the catastrophic impact of global climate change. GPS provides meteorological parameters mainly from the atmosphere. Precise Point Positioning (PPP) is a proven algorithm that has attracted attention in GPS related studies. This study uses GPS measurements collected at more than fifty reference stations of the e-GPS network in Taiwan. The first data set was collected from June 1st 2008 to June 7th 2008, which corresponds to the middle of the plum rain season in Taiwan. The second data set was collected from September 11th to September 17th 2008 during the landfall of typhoon Sinlaku. The data processing strategy is to process the measurements collected at the reference stations of the e-GPS network using the PPP technique to estimate the zenith tropospheric delay (ZTD) values of the sites; thus, the correlations between the ZTD values and the variation of rainfall during the plum rains and typhoon are analyzed. In addition, several characteristics of the meteorological events are identified using spatial and temporal analyses of the ZTD values estimated with the GPS network PPP technique. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle A Hop-Count Analysis Scheme for Avoiding Wormhole Attacks in MANET
Sensors 2009, 9(6), 5022-5039; doi:10.3390/s90605022
Received: 22 April 2009 / Revised: 20 May 2009 / Accepted: 22 June 2009 / Published: 24 June 2009
Cited by 15 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
MANET, due to the nature of wireless transmission, has more security issues compared to wired environments. A specific type of attack, the Wormhole attack does not require exploiting any nodes in the network and can interfere with the route establishment process. Instead [...] Read more.
MANET, due to the nature of wireless transmission, has more security issues compared to wired environments. A specific type of attack, the Wormhole attack does not require exploiting any nodes in the network and can interfere with the route establishment process. Instead of detecting wormholes from the role of administrators as in previous methods, we implement a new protocol, MHA, using a hop-count analysis from the viewpoint of users without any special environment assumptions. We also discuss previous works which require the role of administrator and their reliance on impractical assumptions, thus showing the advantages of MHA. Full article
(This article belongs to the Section Chemical Sensors)

Review

Jump to: Research, Other

Open AccessReview Nanomaterials - Acetylcholinesterase Enzyme Matrices for Organophosphorus Pesticides Electrochemical Sensors: A Review
Sensors 2009, 9(6), 4034-4055; doi:10.3390/s90604034
Received: 15 April 2009 / Revised: 14 May 2009 / Accepted: 25 May 2009 / Published: 26 May 2009
Cited by 71 | PDF Full-text (781 KB) | HTML Full-text | XML Full-text
Abstract
Acetylcholinesterase (AChE) is an important cholinesterase enzyme present in the synaptic clefts of living organisms. It maintains the levels of the neurotransmitter acetylcholine by catalyzing the hydrolysis reaction of acetylcholine to thiocholine. This catalytic activity of AChE is drastically inhibited by trace [...] Read more.
Acetylcholinesterase (AChE) is an important cholinesterase enzyme present in the synaptic clefts of living organisms. It maintains the levels of the neurotransmitter acetylcholine by catalyzing the hydrolysis reaction of acetylcholine to thiocholine. This catalytic activity of AChE is drastically inhibited by trace amounts of organophosphorus (OP) pesticides present in the environment. As a result, effective monitoring of OP pesticides in the environment is very desirable and has been done successfully in recent years with the use of nanomaterial-based AChE sensors. In such sensors, the enzyme AChE has been immobilized onto nanomaterials like multiwalled carbon nanotubes, gold nanoparticles, zirconia nanoparticles, cadmium sulphide nano particles or quantum dots. These nanomaterial matrices promote significant enhancements of OP pesticide determinations, with the thiocholine oxidation occurring at much lower oxidation potentials. Moreover, nanomaterial-based AChE sensors with rapid response, increased operational and long storage stability are extremely well suited for OP pesticide determination over a wide concentration range. In this review, the unique advantages of using nanomaterials as AChE immobilization matrices are discussed. Further, detection limits, sensitivities and correlation coefficients obtained using various electroanalytical techniques have also been compared with chromatographic techniques. Full article
Figures

Open AccessReview An Overview of the Use of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) Model for the Study of Land-Atmosphere Interactions
Sensors 2009, 9(6), 4286-4308; doi:10.3390/s90604286
Received: 21 April 2009 / Revised: 26 May 2009 / Accepted: 1 June 2009 / Published: 3 June 2009
Cited by 11 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a [...] Read more.
Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a comprehensive and systematic review of one such SVAT model suitable for use in mesoscale or boundary layer studies, originally developed by [1]. This model, which has evolved significantly both architecturally and functionally since its foundation, has been widely applied in over thirty interdisciplinary science investigations, and it is currently used as a learning resource for students in a number of educational institutes globally. The present review is also regarded as very timely, since a variation of a method using this specific SVAT model along with satellite observations is currently being considered in a scheme being developed for the operational retrieval of soil surface moisture by the US National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellites that are due to be launched from 2016 onwards. Full article
(This article belongs to the Section Remote Sensors)
Figures

Open AccessReview Solid State Gas Sensor Research in Germany – a Status Report
Sensors 2009, 9(6), 4323-4365; doi:10.3390/s90604323
Received: 25 March 2009 / Revised: 4 May 2009 / Accepted: 26 May 2009 / Published: 3 June 2009
Cited by 58 | PDF Full-text (1911 KB) | HTML Full-text | XML Full-text
Abstract
This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the [...] Read more.
This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Open AccessReview Antibody-Based Sensors: Principles, Problems and Potential for Detection of Pathogens and Associated Toxins
Sensors 2009, 9(6), 4407-4445; doi:10.3390/s90604407
Received: 7 April 2009 / Revised: 26 May 2009 / Accepted: 26 May 2009 / Published: 5 June 2009
Cited by 82 | PDF Full-text (617 KB) | HTML Full-text | XML Full-text
Abstract
Antibody-based sensors permit the rapid and sensitive analysis of a range of pathogens and associated toxins. A critical assessment of the implementation of such formats is provided, with reference to their principles, problems and potential for ‘on-site’ analysis. Particular emphasis is placed [...] Read more.
Antibody-based sensors permit the rapid and sensitive analysis of a range of pathogens and associated toxins. A critical assessment of the implementation of such formats is provided, with reference to their principles, problems and potential for ‘on-site’ analysis. Particular emphasis is placed on the detection of foodborne bacterial pathogens, such as Escherichia coli and Listeria monocytogenes, and additional examples relating to the monitoring of fungal pathogens, viruses, mycotoxins, marine toxins and parasites are also provided. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessReview An Overview of Recent Strategies in Pathogen Sensing
Sensors 2009, 9(6), 4483-4502; doi:10.3390/s90604483
Received: 27 April 2009 / Revised: 31 May 2009 / Accepted: 8 June 2009 / Published: 8 June 2009
Cited by 51 | PDF Full-text (387 KB) | HTML Full-text | XML Full-text
Abstract
Pathogenic bacteria are one of the major concerns in food industries and water treatment facilities because of their rapid growth and deleterious effects on human health. The development of fast and accurate detection and identification systems for bacterial strains has long been [...] Read more.
Pathogenic bacteria are one of the major concerns in food industries and water treatment facilities because of their rapid growth and deleterious effects on human health. The development of fast and accurate detection and identification systems for bacterial strains has long been an important issue to researchers. Although confirmative for the identification of bacteria, conventional methods require time-consuming process involving either the test of characteristic metabolites or cellular reproductive cycles. In this paper, we review recent sensing strategies based on micro- and nano-fabrication technology. These technologies allow for a great improvement of detection limit, therefore, reduce the time required for sample preparation. The paper will be focused on newly developed nano- and micro-scaled biosensors, novel sensing modalities utilizing microfluidic lab-on-a-chip, and array technology for the detection of pathogenic bacteria. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessReview Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices
Sensors 2009, 9(6), 4669-4694; doi:10.3390/s90604669
Received: 22 April 2009 / Revised: 21 May 2009 / Accepted: 12 June 2009 / Published: 15 June 2009
Cited by 43 | PDF Full-text (756 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume [...] Read more.
In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO2 and C2H4 using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Figures

Open AccessReview A Review of Wireless Sensor Technologies and Applications in Agriculture and Food Industry: State of the Art and Current Trends
Sensors 2009, 9(6), 4728-4750; doi:10.3390/s90604728
Received: 27 April 2009 / Revised: 5 June 2009 / Accepted: 11 June 2009 / Published: 16 June 2009
Cited by 171 | PDF Full-text (310 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the present paper is to review the technical and scientific state of the art of wireless sensor technologies and standards for wireless communications in the Agri-Food sector. These technologies are very promising in several fields such as environmental monitoring, [...] Read more.
The aim of the present paper is to review the technical and scientific state of the art of wireless sensor technologies and standards for wireless communications in the Agri-Food sector. These technologies are very promising in several fields such as environmental monitoring, precision agriculture, cold chain control or traceability. The paper focuses on WSN (Wireless Sensor Networks) and RFID (Radio Frequency Identification), presenting the different systems available, recent developments and examples of applications, including ZigBee based WSN and passive, semi-passive and active RFID. Future trends of wireless communications in agriculture and food industry are also discussed. Full article
(This article belongs to the Section Chemical Sensors)
Figures

Open AccessReview Optical Slot-Waveguide Based Biochemical Sensors
Sensors 2009, 9(6), 4751-4765; doi:10.3390/s90604751
Received: 27 May 2009 / Revised: 9 June 2009 / Accepted: 15 June 2009 / Published: 16 June 2009
Cited by 55 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text
Abstract
Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the [...] Read more.
Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the high-refractive-index core of the waveguide. In addition, slot-waveguides can be fabricated by employing CMOS compatible materials and technology, enabling miniaturization, integration with electronic, photonic and fluidic components in a chip, and mass production. These advantages have made the use of slot-waveguides for highly sensitive biochemical optical integrated sensors an emerging field. In this paper, recent achievements in slot-waveguide based biochemical sensing will be reviewed. These include slot-waveguide ring resonator based refractometric label-free biosensors, label-based optical sensing, and nano-opto-mechanical sensors. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Figures

Open AccessReview Microfluidic Systems for Pathogen Sensing: A Review
Sensors 2009, 9(6), 4804-4823; doi:10.3390/s90604804
Received: 28 April 2009 / Revised: 4 June 2009 / Accepted: 8 June 2009 / Published: 17 June 2009
Cited by 101 | PDF Full-text (144 KB) | HTML Full-text | XML Full-text
Abstract
Rapid pathogen sensing remains a pressing issue today since conventional identification methodsare tedious, cost intensive and time consuming, typically requiring from 48 to 72 h. In turn, chip based technologies, such as microarrays and microfluidic biochips, offer real alternatives capable of filling [...] Read more.
Rapid pathogen sensing remains a pressing issue today since conventional identification methodsare tedious, cost intensive and time consuming, typically requiring from 48 to 72 h. In turn, chip based technologies, such as microarrays and microfluidic biochips, offer real alternatives capable of filling this technological gap. In particular microfluidic biochips make the development of fast, sensitive and portable diagnostic tools possible, thus promising rapid and accurate detection of a variety of pathogens. This paper will provide a broad overview of the novel achievements in the field of pathogen sensing by focusing on methods and devices that compliment microfluidics. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Figures

Open AccessReview Distributed Joint Source-Channel Coding in Wireless Sensor Networks
Sensors 2009, 9(6), 4901-4917; doi:10.3390/s90604901
Received: 3 April 2009 / Revised: 15 May 2009 / Accepted: 3 June 2009 / Published: 22 June 2009
Cited by 7 | PDF Full-text (192 KB) | HTML Full-text | XML Full-text
Abstract
Considering the fact that sensors are energy-limited and the wireless channel conditions in wireless sensor networks, there is an urgent need for a low-complexity coding method with high compression ratio and noise-resisted features. This paper reviews the progress made in distributed joint [...] Read more.
Considering the fact that sensors are energy-limited and the wireless channel conditions in wireless sensor networks, there is an urgent need for a low-complexity coding method with high compression ratio and noise-resisted features. This paper reviews the progress made in distributed joint source-channel coding which can address this issue. The main existing deployments, from the theory to practice, of distributed joint source-channel coding over the independent channels, the multiple access channels and the broadcast channels are introduced, respectively. To this end, we also present a practical scheme for compressing multiple correlated sources over the independent channels. The simulation results demonstrate the desired efficiency. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessReview Metal Oxides and Ion-Exchanging Surfaces as pH Sensors in Liquids: State-of-the-Art and Outlook
Sensors 2009, 9(6), 4955-4985; doi:10.3390/s90604955
Received: 19 May 2009 / Revised: 14 June 2009 / Accepted: 16 June 2009 / Published: 23 June 2009
Cited by 47 | PDF Full-text (1272 KB) | HTML Full-text | XML Full-text
Abstract
Novel applications of online pH determinations at temperatures from -35 °C to 130 °C in technical and biological media, which are all but ideal aqueous solutions, require new approaches to pH monitoring. The glass electrode, introduced nearly hundred years ago, [...] Read more.
Novel applications of online pH determinations at temperatures from -35 °C to 130 °C in technical and biological media, which are all but ideal aqueous solutions, require new approaches to pH monitoring. The glass electrode, introduced nearly hundred years ago, and chemical sensors based on field effect transistors (ISFET) show specific drawbacks with respect to handling and long-time stability. Proton sensitive metal oxides seem to be a promising and alternative to the state-of-the-art measuring methods, and might overcome some problems of classical hydrogen electrodes and reference electrodes. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Figures

Other

Jump to: Research, Review

Open AccessCorrection Publisher's Note - Pagination Error
Sensors 2009, 9(6), 4271; doi:10.3390/s90604271
Published: 4 June 2009
PDF Full-text (100 KB) | HTML Full-text | XML Full-text
Abstract Publisher's Note added on 4 June 2009: There is a pagination error in Sensors 2009, 9(6) with page 4271 missing. Thus, page 4271 is taken as a blank page. Full article

Journal Contact

MDPI AG
Sensors Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
sensors@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Sensors
Back to Top