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Sensors, Volume 12, Issue 4 (April 2012) , Pages 3789-5194

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Open AccessReview Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors
Sensors 2012, 12(4), 5170-5194; https://doi.org/10.3390/s120405170
Received: 23 February 2012 / Revised: 19 March 2012 / Accepted: 12 April 2012 / Published: 20 April 2012
Cited by 47 | Viewed by 5648 | PDF Full-text (1457 KB) | HTML Full-text | XML Full-text
Abstract
The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In [...] Read more.
The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessReview HPV-Associated Head and Neck Cancer: Molecular and Nano-Scale Markers for Prognosis and Therapeutic Stratification
Sensors 2012, 12(4), 5159-5169; https://doi.org/10.3390/s120405159
Received: 1 March 2012 / Revised: 27 March 2012 / Accepted: 18 April 2012 / Published: 20 April 2012
Cited by 12 | Viewed by 3515 | PDF Full-text (203 KB) | HTML Full-text | XML Full-text
Abstract
Over the last 10 years, it has become clear that patients with head and neck cancer can be stratified into two distinct subgroups on the basis of the etiology of their disease. Patients with human papillomavirus-related cancers have significantly better survival rates and [...] Read more.
Over the last 10 years, it has become clear that patients with head and neck cancer can be stratified into two distinct subgroups on the basis of the etiology of their disease. Patients with human papillomavirus-related cancers have significantly better survival rates and may necessitate different therapeutic approaches than those with tobacco and/or alcohol related cancers. This review discusses the various biomarkers currently in use for identification of patients with HPV-positive cancers with a focus on the advantages and limitations of molecular and nano-scale markers. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
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Open AccessArticle Benefits of Combined GPS/GLONASS with Low-Cost MEMS IMUs for Vehicular Urban Navigation
Sensors 2012, 12(4), 5134-5158; https://doi.org/10.3390/s120405134
Received: 13 February 2012 / Revised: 21 March 2012 / Accepted: 16 April 2012 / Published: 19 April 2012
Cited by 34 | Viewed by 4680 | PDF Full-text (1150 KB) | HTML Full-text | XML Full-text
Abstract
The integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) has been very actively researched for many years due to the complementary nature of the two systems. In particular, during the last few years the integration with micro-electromechanical system (MEMS) [...] Read more.
The integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) has been very actively researched for many years due to the complementary nature of the two systems. In particular, during the last few years the integration with micro-electromechanical system (MEMS) inertial measurement units (IMUs) has been investigated. In fact, recent advances in MEMS technology have made possible the development of a new generation of low cost inertial sensors characterized by small size and light weight, which represents an attractive option for mass-market applications such as vehicular and pedestrian navigation. However, whereas there has been much interest in the integration of GPS with a MEMS-based INS, few research studies have been conducted on expanding this application to the revitalized GLONASS system. This paper looks at the benefits of adding GLONASS to existing GPS/INS(MEMS) systems using loose and tight integration strategies. The relative benefits of various constraints are also assessed. Results show that when satellite visibility is poor (approximately 50% solution availability) the benefits of GLONASS are only seen with tight integration algorithms. For more benign environments, a loosely coupled GPS/GLONASS/INS system offers performance comparable to that of a tightly coupled GPS/INS system, but with reduced complexity and development time. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Method for Optimal Sensor Deployment on 3D Terrains Utilizing a Steady State Genetic Algorithm with a Guided Walk Mutation Operator Based on the Wavelet Transform
Sensors 2012, 12(4), 5116-5133; https://doi.org/10.3390/s120405116
Received: 17 January 2012 / Revised: 19 March 2012 / Accepted: 12 April 2012 / Published: 19 April 2012
Cited by 19 | Viewed by 3763 | PDF Full-text (740 KB) | HTML Full-text | XML Full-text
Abstract
One of the most critical issues of Wireless Sensor Networks (WSNs) is the deployment of a limited number of sensors in order to achieve maximum coverage on a terrain. The optimal sensor deployment which enables one to minimize the consumed energy, communication time [...] Read more.
One of the most critical issues of Wireless Sensor Networks (WSNs) is the deployment of a limited number of sensors in order to achieve maximum coverage on a terrain. The optimal sensor deployment which enables one to minimize the consumed energy, communication time and manpower for the maintenance of the network has attracted interest with the increased number of studies conducted on the subject in the last decade. Most of the studies in the literature today are proposed for two dimensional (2D) surfaces; however, real world sensor deployments often arise on three dimensional (3D) environments. In this paper, a guided wavelet transform (WT) based deployment strategy (WTDS) for 3D terrains, in which the sensor movements are carried out within the mutation phase of the genetic algorithms (GAs) is proposed. The proposed algorithm aims to maximize the Quality of Coverage (QoC) of a WSN via deploying a limited number of sensors on a 3D surface by utilizing a probabilistic sensing model and the Bresenham’s line of sight (LOS) algorithm. In addition, the method followed in this paper is novel to the literature and the performance of the proposed algorithm is compared with the Delaunay Triangulation (DT) method as well as a standard genetic algorithm based method and the results reveal that the proposed method is a more powerful and more successful method for sensor deployment on 3D terrains. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Humidity-Induced Charge Leakage and Field Attenuation in Electric Field Microsensors
Sensors 2012, 12(4), 5105-5115; https://doi.org/10.3390/s120405105
Received: 15 March 2012 / Revised: 6 April 2012 / Accepted: 9 April 2012 / Published: 19 April 2012
Cited by 3 | Viewed by 3249 | PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the Boltzmann [...] Read more.
The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the Boltzmann distribution equation at various relative humidities for borosilicate glass and polytetrafluoroethylene surfaces. At various humidities, water film thickness has been calculated, and the induced charge leakage and field attenuation have been theoretically investigated. Experiments have been performed with microsensors to verify the theoretical predictions and the results are in good agreement. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions
Sensors 2012, 12(4), 5067-5104; https://doi.org/10.3390/s120405067
Received: 8 March 2012 / Revised: 26 March 2012 / Accepted: 16 April 2012 / Published: 19 April 2012
Cited by 3 | Viewed by 3398 | PDF Full-text (1165 KB) | HTML Full-text | XML Full-text
Abstract
Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time [...] Read more.
Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Identification of Cross-Country Skiing Movement Patterns Using Micro-Sensors
Sensors 2012, 12(4), 5047-5066; https://doi.org/10.3390/s120405047
Received: 12 March 2012 / Revised: 5 April 2012 / Accepted: 9 April 2012 / Published: 18 April 2012
Cited by 31 | Viewed by 4637 | PDF Full-text (3208 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated the potential of micro-sensors for use in the identification of the main movement patterns used in cross-country skiing. Data were collected from four elite international and four Australian athletes in Europe and in Australia using a MinimaxXTM unit containing [...] Read more.
This study investigated the potential of micro-sensors for use in the identification of the main movement patterns used in cross-country skiing. Data were collected from four elite international and four Australian athletes in Europe and in Australia using a MinimaxXTM unit containing accelerometer, gyroscope and GPS sensors. Athletes performed four skating techniques and three classical techniques on snow at moderate velocity. Data from a single micro-sensor unit positioned in the centre of the upper back was sufficient to visually identify cyclical movement patterns for each technique. The general patterns for each technique were identified clearly across all athletes while at the same time distinctive characteristics for individual athletes were observed. Differences in speed, snow condition and gradient of terrain were not controlled in this study and these factors could have an effect on the data patterns. Development of algorithms to process the micro-sensor data into kinematic measurements would provide coaches and scientists with a valuable performance analysis tool. Further research is needed to develop such algorithms and to determine whether the patterns are consistent across a range of different speeds, snow conditions and terrain, and for skiers of differing ability. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Penalty Dynamic Programming Algorithm for Dim Targets Detection in Sensor Systems
Sensors 2012, 12(4), 5028-5046; https://doi.org/10.3390/s120405028
Received: 12 March 2012 / Revised: 20 March 2012 / Accepted: 10 April 2012 / Published: 18 April 2012
Cited by 8 | Viewed by 3124 | PDF Full-text (851 KB) | HTML Full-text | XML Full-text
Abstract
In order to detect and track multiple maneuvering dim targets in sensor systems, an improved dynamic programming track-before-detect algorithm (DP-TBD) called penalty DP-TBD (PDP-TBD) is proposed. The performances of tracking techniques are used as a feedback to the detection part. The feedback is [...] Read more.
In order to detect and track multiple maneuvering dim targets in sensor systems, an improved dynamic programming track-before-detect algorithm (DP-TBD) called penalty DP-TBD (PDP-TBD) is proposed. The performances of tracking techniques are used as a feedback to the detection part. The feedback is constructed by a penalty term in the merit function, and the penalty term is a function of the possible target state estimation, which can be obtained by the tracking methods. With this feedback, the algorithm combines traditional tracking techniques with DP-TBD and it can be applied to simultaneously detect and track maneuvering dim targets. Meanwhile, a reasonable constraint that a sensor measurement can originate from one target or clutter is proposed to minimize track separation. Thus, the algorithm can be used in the multi-target situation with unknown target numbers. The efficiency and advantages of PDP-TBD compared with two existing methods are demonstrated by several simulations. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Visualizing Sweetness: Increasingly Diverse Applications for Fluorescent-Tagged Glucose Bioprobes and Their Recent Structural Modifications
Sensors 2012, 12(4), 5005-5027; https://doi.org/10.3390/s120405005
Received: 28 February 2012 / Revised: 3 April 2012 / Accepted: 9 April 2012 / Published: 18 April 2012
Cited by 46 | Viewed by 4167 | PDF Full-text (581 KB) | HTML Full-text | XML Full-text
Abstract
Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the 1980s, [...] Read more.
Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the 1980s, but it is only in the past decade that their use as a glucose sensor has increased significantly. These analogues were developed for monitoring glucose uptake in blood cells, but their recent applications include tracking glucose uptake by tumor cells and imaging brain cell metabolism. This review outlines the development of fluorescent-tagged glucose analogues, describes their recent structural modifications and discusses their increasingly diverse biological applications. Full article
Open AccessArticle Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control
Sensors 2012, 12(4), 4986-5004; https://doi.org/10.3390/s120404986
Received: 21 February 2012 / Revised: 28 March 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 4 | Viewed by 3021 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different [...] Read more.
In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC) is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Endogenous Bioactive Peptides as Potential Biomarkers for Atherosclerotic Coronary Heart Disease
Sensors 2012, 12(4), 4974-4985; https://doi.org/10.3390/s120404974
Received: 8 February 2012 / Revised: 22 March 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 17 | Viewed by 3434 | PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
Cardiovascular disease is the leading cause of death worldwide, with high medical costs and rates of disability. It is therefore important to evaluate the use of cardiovascular biomarkers in the early diagnosis of coronary artery disease (CAD). We have screened a variety of [...] Read more.
Cardiovascular disease is the leading cause of death worldwide, with high medical costs and rates of disability. It is therefore important to evaluate the use of cardiovascular biomarkers in the early diagnosis of coronary artery disease (CAD). We have screened a variety of recently identified bioactive peptides candidates in anticipation that they would allow detection of atherosclerotic CAD. Especially, we have focused on novel anti-atherogenic peptides as indicators and negative risk factors for CAD. In vitro, in vivo and clinical studies indicated that human adiponectin, heregulin-β1, glucagon-like peptide-1 (GLP-1), and salusin-α, peptides of 244, 71, 30, and 28 amino acids, respectively, attenuate the development and progression of atherosclerotic lesions by suppressing macrophage foam cell formation via down-regulation of acyl-coenzyme A: cholesterol acyltransferase-1. Circulating levels of these peptides in the blood are significantly decreased in patients with CAD compared to patients without CAD. Receiver operating characteristic analyses showed that salusin-α is a more useful biomarker, with better sensitivity and specificity, compared with the others for detecting CAD. Therefore, salusin-α, heregulin-β1, adiponectin, and/or GLP-1, alone or in various combinations, may be useful as biomarkers for atherosclerotic CAD. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessCommunication Dynamic Sensing of Localized Corrosion at the Metal/Solution Interface
Sensors 2012, 12(4), 4962-4973; https://doi.org/10.3390/s120404962
Received: 15 February 2012 / Revised: 10 April 2012 / Accepted: 11 April 2012 / Published: 18 April 2012
Cited by 2 | Viewed by 2709 | PDF Full-text (1668 KB) | HTML Full-text | XML Full-text
Abstract
A Mach-Zehnder interferometer is employed to detect localized corrosion at the metal/solution interface in the potentiodynamic sweep of the iron electrode in solutions. During the electrochemical reactions, local variations of the electrolyte’s refractive index, which correlate with the concentration of dissolved species, change [...] Read more.
A Mach-Zehnder interferometer is employed to detect localized corrosion at the metal/solution interface in the potentiodynamic sweep of the iron electrode in solutions. During the electrochemical reactions, local variations of the electrolyte’s refractive index, which correlate with the concentration of dissolved species, change the optical path length (OPL) of the object beam when the beam passes through the electrolyte. The distribution of the OPL difference was obtained to present the concentration change of the metal ions visually, which enable direct evidence of corrosion processes. The OPL difference distribution shows localized and general corrosion during the anodic dissolution of the iron electrode in solutions with and without chloride ions, respectively. This method provides an approach for dynamic detection of localized corrosion at the metal/solution interface. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle Gold Nanoparticles Functionalized with Peptides for Specific Affinity Aggregation Assays of Estrogen Receptors and Their Agonists
Sensors 2012, 12(4), 4952-4961; https://doi.org/10.3390/s120404952
Received: 26 March 2012 / Revised: 9 April 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 10 | Viewed by 3197 | PDF Full-text (361 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nuclear receptors regulate the transcription of genes and various functions such as development, differentiation, homeostasis, and behavior by formation of complexes with ligand and co-activator. Recent findings have shown that agonists of a ligand may have a toxic effect on cellular/tissular function through [...] Read more.
Nuclear receptors regulate the transcription of genes and various functions such as development, differentiation, homeostasis, and behavior by formation of complexes with ligand and co-activator. Recent findings have shown that agonists of a ligand may have a toxic effect on cellular/tissular function through improper activation of nuclear receptors. In this study, a simple assay system of hetero-complexes of three different molecules (estrogen receptor, ligand, and co-activator peptide) has been developed. This assay system employs functionalized gold nanoparticles (GNPs: 15 nm in diameter). The surfaces of the GNPs were modified by a 12- or 20-amino-acid peptide that contains the sequence of co-activator for activating nuclear receptor by an agonist ligand. Owing to the affinity of the peptide, the functionalized GNPs aggregate faster when the nuclear receptor and the agonist ligand are also present. The aggregation of GNPs can be identified by shifts in adsorption spectrum, which give information about the specificity of agonist ligands. Similarly, this spectrum shift can measure concentration of known agonist ligand. This simple agonist screening will be employed as high through-put analysis (HTA) in the discovery of drugs that act through nuclear receptors. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Assessing Ambiguity of Context Data in Intelligent Environments: Towards a More Reliable Context Managing System
Sensors 2012, 12(4), 4934-4951; https://doi.org/10.3390/s120404934
Received: 22 February 2012 / Revised: 3 April 2012 / Accepted: 6 April 2012 / Published: 17 April 2012
Cited by 24 | Viewed by 3362 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text
Abstract
Modeling and managing correctly the user context in Smart Environments is important to achieve robust and reliable systems. When modeling reality we must take into account its ambiguous nature. Considering the uncertainty and vagueness in context data information it is possible to attain [...] Read more.
Modeling and managing correctly the user context in Smart Environments is important to achieve robust and reliable systems. When modeling reality we must take into account its ambiguous nature. Considering the uncertainty and vagueness in context data information it is possible to attain a more precise picture of the environment, thus leading to a more accurate inference process. To achieve these goals we present an ontology that models the ambiguity in intelligent environments and a data fusion and inference process that takes advantage of that extra information to provide better results. Our system can assess the certainty of the captured measurements, discarding the unreliable ones and combining the rest into a unified vision of the current user context. It also models the vagueness of the system, combining it with the uncertainty to obtain a richer inference process. Full article
Open AccessArticle A New Methodology for Vibration Error Compensation of Optical Encoders
Sensors 2012, 12(4), 4918-4933; https://doi.org/10.3390/s120404918
Received: 7 February 2012 / Revised: 30 March 2012 / Accepted: 31 March 2012 / Published: 17 April 2012
Cited by 21 | Viewed by 3095 | PDF Full-text (885 KB) | HTML Full-text | XML Full-text
Abstract
Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating movement [...] Read more.
Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating movement of the scanning head is registered by the encoder system as a displacement, introducing an error into the counter to be added up to graduation, system and installation errors. Behavior improvement can be based on different techniques trying to compensate the error from measurement signals processing. In this work a new “ad hoc” methodology is presented to compensate the error of the encoder when is working under the influence of vibration. The methodology is based on fitting techniques to the Lissajous figure of the deteriorated measurement signals and the use of a look up table, giving as a result a compensation procedure in which a higher accuracy of the sensor is obtained. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Modelling of Amperometric Biosensor Used for Synergistic Substrates Determination
Sensors 2012, 12(4), 4897-4917; https://doi.org/10.3390/s120404897
Received: 6 March 2012 / Revised: 2 April 2012 / Accepted: 4 April 2012 / Published: 16 April 2012
Cited by 5 | Viewed by 2889 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the operation of an amperometric biosensor producing a chemically amplified signal is modelled numerically. The chemical amplification is achieved by using synergistic substrates. The model is based on non-stationary reaction-diffusion equations. The model involves three layers (compartments): a layer of [...] Read more.
In this paper the operation of an amperometric biosensor producing a chemically amplified signal is modelled numerically. The chemical amplification is achieved by using synergistic substrates. The model is based on non-stationary reaction-diffusion equations. The model involves three layers (compartments): a layer of enzyme solution entrapped on the electrode surface, a dialysis membrane covering the enzyme layer and an outer diffusion layer which is modelled by the Nernst approach. The equation system is solved numerically by using the finite difference technique. The biosensor response and sensitivity are investigated by altering the model parameters influencing the enzyme kinetics as well as the mass transport by diffusion. The biosensor action was analyzed with a special emphasis to the effect of the chemical amplification. The simulation results qualitatively explain and confirm the experimentally observed effect of the synergistic substrates conversion on the biosensor response. Full article
(This article belongs to the Section Biosensors)
Open AccessEditorial Sensors in Collaboration Increase Individual Potentialities
Sensors 2012, 12(4), 4892-4896; https://doi.org/10.3390/s120404892
Received: 6 April 2012 / Accepted: 12 April 2012 / Published: 13 April 2012
Cited by 3 | PDF Full-text (138 KB) | HTML Full-text | XML Full-text
Abstract
Different applications require different sensor technologies and methods to achieve specific goals. Particular sensor designs are focused on solving problems. It is well-known that individual sensors can be limited when complex problems or applications are involved or the application requires sensing in different [...] Read more.
Different applications require different sensor technologies and methods to achieve specific goals. Particular sensor designs are focused on solving problems. It is well-known that individual sensors can be limited when complex problems or applications are involved or the application requires sensing in different locations or even different geographical areas. [...] Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Transformation of Ground Vibration Signal for Debris-Flow Monitoring and Detection in Alarm Systems
Sensors 2012, 12(4), 4870-4891; https://doi.org/10.3390/s120404870
Received: 9 February 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Cited by 17 | Viewed by 3416 | PDF Full-text (1572 KB) | HTML Full-text | XML Full-text
Abstract
Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris [...] Read more.
Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris flows. However, the recording of geophone signals usually requires storing a huge amount of data, which leads to problems in storage capacity and power consumption. This paper presents a method to transform and simplify the signals measured by geophones. The key input parameter is the ground velocity threshold, which removes the seismic noise that is not related to debris flows. A signal conditioner was developed to implement the transformation and the ground velocity threshold was set by electrical resistors. The signal conditioner was installed at various European monitoring sites to test the method. Results show that data amount and power consumption can be greatly reduced without losing much information on the main features of the debris flows. However, the outcome stresses the importance of choosing a ground vibration threshold, which must be accurately calibrated. The transformation is also suitable to detect other rapid mass movements and to distinguish among different processes, which points to a possible implementation in alarm systems. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Facile One-Step Microwave-Assisted Route towards Ni Nanospheres/Reduced Graphene Oxide Hybrids for Non-Enzymatic Glucose Sensing
Sensors 2012, 12(4), 4860-4869; https://doi.org/10.3390/s120404860
Received: 24 February 2012 / Revised: 14 March 2012 / Accepted: 23 March 2012 / Published: 13 April 2012
Cited by 61 | Viewed by 5006 | PDF Full-text (734 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a facile one-step microwave-assisted method for deposition of monodisperse Ni nanospheres on reduced graphene oxide (rGO) sheets to form Ni-rGO nanohybrids is discussed. In the presence of hydrazine monohydrate, Ni nanospheres are grown onto rGO sheets using nickel precursor and [...] Read more.
In this work, a facile one-step microwave-assisted method for deposition of monodisperse Ni nanospheres on reduced graphene oxide (rGO) sheets to form Ni-rGO nanohybrids is discussed. In the presence of hydrazine monohydrate, Ni nanospheres are grown onto rGO sheets using nickel precursor and GO as starting materials in ethylene glycol (EG) solution under a low level of microwave irradiation (300 W) for 20 min, during which GO is also reduced to rGO. The as-prepared nanohybrids exhibit well-dispersed Ni nanosphere (about 80 nm in diameter) loadings and effective reduction of graphene oxide. The resulting Ni-rGO nanohybrids-modified glassy carbon electrode (GCE) shows significantly improved electrochemical performance in nonenzymatic amperometric glucose detection. In addition, interference from the oxidation of common interfering species under physiological conditions, such as ascorbic acid (AA) and uric acid (UA), is effectively avoided. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest
Sensors 2012, 12(4), 4846-4859; https://doi.org/10.3390/s120404846
Received: 15 March 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Cited by 46 | Viewed by 4472 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected [...] Read more.
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis. Full article
Open AccessArticle Reconfigurable Routing Protocol for Free Space Optical Sensor Networks
Sensors 2012, 12(4), 4824-4845; https://doi.org/10.3390/s120404824
Received: 21 February 2012 / Revised: 23 March 2012 / Accepted: 31 March 2012 / Published: 13 April 2012
Cited by 2 | Viewed by 3181 | PDF Full-text (879 KB) | HTML Full-text | XML Full-text
Abstract
Recently, free space optical sensor networks (FSOSNs), which are based on free space optics (FSO) instead of radio frequency (RF), have gained increasing visibility over traditional wireless sensor networks (WSNs) due to their advantages such as larger capacity, higher security, and lower cost. [...] Read more.
Recently, free space optical sensor networks (FSOSNs), which are based on free space optics (FSO) instead of radio frequency (RF), have gained increasing visibility over traditional wireless sensor networks (WSNs) due to their advantages such as larger capacity, higher security, and lower cost. However, the performance of FSOSNs is restricted to the requirement of a direct line-of-sight (LOS) path between a sender and a receiver pair. Once a node dies of energy depletion, the network would probably suffer from a dramatic decrease of connectivity, resulting in a huge loss of data packets. Thus, this paper proposes a reconfigurable routing protocol (RRP) to overcome this problem by dynamically reconfiguring the network virtual topology. The RRP works in three phases: (1) virtual topology construction, (2) routing establishment, and (3) reconfigurable routing. When data transmission begins, the data packets are first routed through the shortest hop paths. Then a reconfiguration is initiated by the node whose residual energy falls below a threshold. Nodes affected by this dying node are classified into two types, namely maintenance nodes and adjustment nodes, and they are reconfigured according to the types. An energy model is designed to evaluate the performance of RRP through OPNET simulation. Our simulation results indicate that the RRP achieves better performance compared with the simple-link protocol and a direct reconfiguration scheme in terms of connectivity, network lifetime, packet delivery ratio and the number of living nodes. Full article
(This article belongs to the Section Sensor Networks)
Open AccessEditorial Advances in Sensors-Centric Microprocessors and System-on-Chip
Sensors 2012, 12(4), 4820-4823; https://doi.org/10.3390/s120404820
Received: 11 April 2012 / Accepted: 12 April 2012 / Published: 12 April 2012
PDF Full-text (126 KB) | HTML Full-text | XML Full-text
Abstract
Sensors-based systems are nowadays an extended technology for many markets due to their great potential in the collection of data from the environment and the processing of such data for different purposes. A typical example is the wireless sensor devices, where the outer [...] Read more.
Sensors-based systems are nowadays an extended technology for many markets due to their great potential in the collection of data from the environment and the processing of such data for different purposes. A typical example is the wireless sensor devices, where the outer temperature, humidity, luminosity and many other parameters can be acquired, measured and processed in order to build useful and fascinating applications that contribute to human welfare. In this scenario, the processing architectures of the sensors-based systems play a very important role. The requirements that are necessary for many such applications (real-time processing, low-power consumption, reduced size, reliability, security and many others) means that research on advanced architectures of Microprocessors and System-on-Chips (SoC) is needed to design and implement a successful product. In this sense, there are many challenges and open questions in this area that need to be addressed. [...] Full article
(This article belongs to the Special Issue Microprocessors and System-on-Chip)
Open AccessArticle Nanocharacterization of Soft Biological Samples in Shear Mode with Quartz Tuning Fork Probes
Sensors 2012, 12(4), 4803-4819; https://doi.org/10.3390/s120404803
Received: 16 February 2012 / Revised: 29 March 2012 / Accepted: 30 March 2012 / Published: 12 April 2012
Cited by 17 | Viewed by 3432 | PDF Full-text (1839 KB) | HTML Full-text | XML Full-text
Abstract
Quartz tuning forks are extremely good resonators and their use is growing in scanning probe microscopy. Nevertheless, only a few studies on soft biological samples have been reported using these probes. In this work, we present the methodology to develop and use these [...] Read more.
Quartz tuning forks are extremely good resonators and their use is growing in scanning probe microscopy. Nevertheless, only a few studies on soft biological samples have been reported using these probes. In this work, we present the methodology to develop and use these nanosensors to properly work with biological samples. The working principles, fabrication and experimental setup are presented. The results in the nanocharacterization of different samples in different ambients are presented by using different working modes: amplitude modulation with and without the use of a Phase-Locked Loop (PLL) and frequency modulation. Pseudomonas aeruginosa bacteria are imaged in nitrogen using amplitude modulation. Microcontact printed antibodies are imaged in buffer using amplitude modulation with a PLL. Finally, metastatic cells are imaged in air using frequency modulation. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle Fiber Optic Sensor for Acoustic Detection of Partial Discharges in Oil-Paper Insulated Electrical Systems
Sensors 2012, 12(4), 4793-4802; https://doi.org/10.3390/s120404793
Received: 16 January 2012 / Revised: 31 March 2012 / Accepted: 5 April 2012 / Published: 12 April 2012
Cited by 44 | Viewed by 5454 | PDF Full-text (1497 KB) | HTML Full-text | XML Full-text
Abstract
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic [...] Read more.
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
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Open AccessReview Multiple Classifier System for Remote Sensing Image Classification: A Review
Sensors 2012, 12(4), 4764-4792; https://doi.org/10.3390/s120404764
Received: 22 February 2012 / Revised: 22 March 2012 / Accepted: 6 April 2012 / Published: 12 April 2012
Cited by 138 | Viewed by 6185 | PDF Full-text (22962 KB) | HTML Full-text | XML Full-text
Abstract
Over the last two decades, multiple classifier system (MCS) or classifier ensemble has shown great potential to improve the accuracy and reliability of remote sensing image classification. Although there are lots of literatures covering the MCS approaches, there is a lack of a [...] Read more.
Over the last two decades, multiple classifier system (MCS) or classifier ensemble has shown great potential to improve the accuracy and reliability of remote sensing image classification. Although there are lots of literatures covering the MCS approaches, there is a lack of a comprehensive literature review which presents an overall architecture of the basic principles and trends behind the design of remote sensing classifier ensemble. Therefore, in order to give a reference point for MCS approaches, this paper attempts to explicitly review the remote sensing implementations of MCS and proposes some modified approaches. The effectiveness of existing and improved algorithms are analyzed and evaluated by multi-source remotely sensed images, including high spatial resolution image (QuickBird), hyperspectral image (OMISII) and multi-spectral image (Landsat ETM+).Experimental results demonstrate that MCS can effectively improve the accuracy and stability of remote sensing image classification, and diversity measures play an active role for the combination of multiple classifiers. Furthermore, this survey provides a roadmap to guide future research, algorithm enhancement and facilitate knowledge accumulation of MCS in remote sensing community. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Adapting an Ant Colony Metaphor for Multi-Robot Chemical Plume Tracing
Sensors 2012, 12(4), 4737-4763; https://doi.org/10.3390/s120404737
Received: 17 March 2012 / Revised: 26 March 2012 / Accepted: 31 March 2012 / Published: 12 April 2012
Cited by 22 | Viewed by 3337 | PDF Full-text (774 KB) | HTML Full-text | XML Full-text
Abstract
We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization [...] Read more.
We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Rao and Wald Tests for Nonhomogeneous Scenarios
Sensors 2012, 12(4), 4730-4736; https://doi.org/10.3390/s120404730
Received: 12 March 2012 / Revised: 28 March 2012 / Accepted: 29 March 2012 / Published: 12 April 2012
Cited by 6 | Viewed by 2629 | PDF Full-text (78 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we focus on the design of adaptive receivers for nonhomogeneous scenarios. More precisely, at the design stage we assume a mismatch between the covariance matrix of the noise in the cell under test and that of secondary data. Under the [...] Read more.
In this paper, we focus on the design of adaptive receivers for nonhomogeneous scenarios. More precisely, at the design stage we assume a mismatch between the covariance matrix of the noise in the cell under test and that of secondary data. Under the above assumption, we show that the Wald test is the adaptive matched filter, while the Rao test coincides with the receiver obtained by using the Rao test design criterion in homogeneous environment, hence providing a theoretical explanation of the enhanced selectivity of this receiver. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On the Selection of Transmission Range in Underwater Acoustic Sensor Networks
Sensors 2012, 12(4), 4715-4729; https://doi.org/10.3390/s120404715
Received: 2 March 2012 / Revised: 5 April 2012 / Accepted: 5 April 2012 / Published: 11 April 2012
Cited by 16 | Viewed by 3524 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
Transmission range plays an important role in the deployment of a practical underwater acoustic sensor network (UWSN), where sensor nodes equipping with only basic functions are deployed at random locations with no particular geometrical arrangements. The selection of the transmission range directly influences [...] Read more.
Transmission range plays an important role in the deployment of a practical underwater acoustic sensor network (UWSN), where sensor nodes equipping with only basic functions are deployed at random locations with no particular geometrical arrangements. The selection of the transmission range directly influences the energy efficiency and the network connectivity of such a random network. In this paper, we seek analytical modeling to investigate the tradeoff between the energy efficiency and the network connectivity through the selection of the transmission range. Our formulation offers a design guideline for energy-efficient packet transmission operation given a certain network connectivity requirement. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessCommunication Improvement of Toluene Selectivity via the Application of an Ethanol Oxidizing Catalytic Cell Upstream of a YSZ-Based Sensor for Air Monitoring Applications
Sensors 2012, 12(4), 4706-4714; https://doi.org/10.3390/s120404706
Received: 29 February 2012 / Revised: 16 March 2012 / Accepted: 20 March 2012 / Published: 11 April 2012
Cited by 16 | Viewed by 2847 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor utilizing a NiO sensing-electrode (SE) towards toluene (C7H8) and interfering gases (C3H6, H2, CO, NO2 and C2H5OH) were evaluated [...] Read more.
The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor utilizing a NiO sensing-electrode (SE) towards toluene (C7H8) and interfering gases (C3H6, H2, CO, NO2 and C2H5OH) were evaluated with a view to selective C7H8 monitoring in indoor atmospheres. The fabricated YSZ-based sensor showed preferential responses toward 480 ppb C2H5OH, rather than the target 50 ppb C7H8 at an operational temperature of 450 °C under humid conditions (RH ⋍ 32%). To overcome this limitation, the catalytic activity of Cr2O3, SnO2, Fe2O3 and NiO powders were evaluated for their selective ethanol oxidation ability. Among these oxides, SnO2 was found to selectively oxidize C2H5OH, thus improving C7H8 selectivity. An inline pre-catalytic cell loaded with SnO2 powder was installed upstream of the YSZ-based sensor utilizing NiO-SE, which enabled the following excellent abilities by selectively catalyzing common interfering gases; sensitive ppb level detection of C7H8 lower than the established Japanese Guideline value; low interferences from 50 ppb C3H6, 500 ppb H2, 100 ppb CO, 40 ppb NO2, as well as 480 ppb C2H5OH. These operational characteristics are all indicative that the developed sensor may be suitable for real-time C7H8 concentration monitoring in indoor environments. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper
Sensors 2012, 12(4), 4697-4705; https://doi.org/10.3390/s120404697
Received: 5 January 2012 / Revised: 23 February 2012 / Accepted: 26 March 2012 / Published: 11 April 2012
Cited by 24 | Viewed by 3075 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The [...] Read more.
A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity. Full article
(This article belongs to the Section Physical Sensors)
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