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Sensors, Volume 10, Issue 6 (June 2010) , Pages 5294-6274

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Open AccessArticle Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Response to Specific Interactions
Sensors 2010, 10(6), 6257-6274; https://doi.org/10.3390/s100606257
Received: 8 January 2010 / Revised: 12 March 2010 / Accepted: 9 June 2010 / Published: 22 June 2010
Cited by 32 | Viewed by 6980 | PDF Full-text (935 KB) | HTML Full-text | XML Full-text
Abstract
Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis [...] Read more.
Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis of the observed shifts in the WGM wavelength positions are applied and used to quantify the adsorbed mass densities, which are then compared with the results of a comparative surface plasmon resonance (SPR) study. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Nitrite Biosensor Based on Co-immobilization of Nitrite Reductase and Viologen-modified Chitosan on a Glassy Carbon Electrode
Sensors 2010, 10(6), 6241-6256; https://doi.org/10.3390/s100606241
Received: 18 May 2010 / Revised: 8 June 2010 / Accepted: 14 June 2010 / Published: 22 June 2010
Cited by 13 | Viewed by 6434 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
An electrochemical nitrite biosensor based on co-immobilization of copper- containing nitrite reductase (Cu-NiR, from Rhodopseudomonas sphaeroides forma sp. denitrificans) and viologen-modified chitosan (CHIT-V) on a glassy carbon electrode (GCE) is presented. Electron transfer (ET) between a conventional GCE and immobilized Cu-NiR was [...] Read more.
An electrochemical nitrite biosensor based on co-immobilization of copper- containing nitrite reductase (Cu-NiR, from Rhodopseudomonas sphaeroides forma sp. denitrificans) and viologen-modified chitosan (CHIT-V) on a glassy carbon electrode (GCE) is presented. Electron transfer (ET) between a conventional GCE and immobilized Cu-NiR was mediated by the co-immobilized CHIT-V. Redox-active viologen was covalently linked to a chitosan backbone, and the thus produced CHIT-V was co-immobilized with Cu-NiR on the GCE surface by drop-coating of hydrophilic polyurethane (HPU). The electrode responded to nitrite with a limit of detection (LOD) of 40 nM (S/N = 3). The sensitivity, linear response range, and response time (t90%) were 14.9 nA/mM, 0.04−11 mM (r2 = 0.999) and 15 s, respectively. The corresponding Lineweaver-Burk plot showed that the apparent Michaelis-Menten constant (KMapp) was 65 mM. Storage stability of the biosensor (retaining 80% of initial activity) was 65 days under ambient air and room temperature storage conditions. Reproducibility of the sensor showed a relative standard deviation (RSD) of 2.8% (n = 5) for detection of 1 mM of nitrite. An interference study showed that anions commonlyfound in water samples such as chlorate, chloride, sulfate and sulfite did not interfere with the nitrite detection. However, nitrate interfered with a relative sensitivity of 64% and this interference effect was due to the intrinsic character of the NiR employed in this study. Full article
(This article belongs to the Section Biosensors)
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Open AccessReview Glucose Signaling-Mediated Coordination of Cell Growth and Cell Cycle in Saccharomyces Cerevisiae
Sensors 2010, 10(6), 6195-6240; https://doi.org/10.3390/s100606195
Received: 7 May 2010 / Revised: 26 May 2010 / Accepted: 27 May 2010 / Published: 21 June 2010
Cited by 58 | Viewed by 9079 | PDF Full-text (790 KB) | HTML Full-text | XML Full-text
Abstract
Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their [...] Read more.
Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes. Full article
(This article belongs to the Special Issue Glucose Sensors)
Open AccessArticle SirT1—A Sensor for Monitoring Self-Renewal and Aging Process in Retinal Stem Cells
Sensors 2010, 10(6), 6172-6194; https://doi.org/10.3390/s100606172
Received: 8 January 2010 / Revised: 28 February 2010 / Accepted: 3 May 2010 / Published: 21 June 2010
Cited by 19 | Viewed by 8293 | PDF Full-text (763 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Retinal stem cells bear potency of proliferation, self-renewal, and differentiation into many retinal cells. Utilizing appropriate sensors one can effectively detect the self-renewal and aging process abilities. Silencing information regulator (SirT1), a member of the sirtuin family, is a NAD-dependent histone deacetylase and [...] Read more.
Retinal stem cells bear potency of proliferation, self-renewal, and differentiation into many retinal cells. Utilizing appropriate sensors one can effectively detect the self-renewal and aging process abilities. Silencing information regulator (SirT1), a member of the sirtuin family, is a NAD-dependent histone deacetylase and an essential mediator for longevity in normal cells by calorie restriction. We firstly investigate the SirT1 mRNA expression in retinal stem cells from rats and 19 human eyes of different ages. Results revealed that SirT1 expression was significantly decreased in in vivo aged eyes, associated with poor self-renewal abilities. Additionally, SirT1 mRNA levels were dose-dependently increased in resveratrol- treated retinal stem cells. The expression of SirT1 on oxidative stress-induced damage was significantly decreased, negatively correlated with the level of intracellular reactive oxygen species production. Treatment with resveratrol could effectively further reduce oxidative stress induced by H2O2 treatment in retinal stem cells. Importantly, the anti-oxidant effects of resveratrol in H2O2-treated retinal stem cells were significantly abolished by knockdown of SirT1 expression (sh-SirT1). SirT1 expression provides a feasible sensor in assessing self-renewal and aging process in retinal stem cells. Resveratrol can prevent reactive oxygen species-induced damages via increased retinal SirT1 expression. Full article
(This article belongs to the Special Issue Delft Workshop 2008-2009—Sensors and Imagers: a VLSI Perspective)
Open AccessReview Review on the Modeling of Electrostatic MEMS
Sensors 2010, 10(6), 6149-6171; https://doi.org/10.3390/s100606149
Received: 9 March 2010 / Revised: 18 May 2010 / Accepted: 24 May 2010 / Published: 21 June 2010
Cited by 80 | Viewed by 9722 | PDF Full-text (660 KB) | HTML Full-text | XML Full-text
Abstract
Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, [...] Read more.
Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessArticle An Emergency-Adaptive Routing Scheme for Wireless Sensor Networks for Building Fire Hazard Monitoring
Sensors 2010, 10(6), 6128-6148; https://doi.org/10.3390/s100606128
Received: 8 May 2010 / Revised: 4 June 2010 / Accepted: 7 June 2010 / Published: 21 June 2010
Cited by 3 | Viewed by 5651 | PDF Full-text (487 KB) | HTML Full-text | XML Full-textRetraction
Abstract
This paper has been retracted on 4 March 2011. The paper is republished with the authorship and acknowledgements fully disclosed as Sensors 2011, 11, 2899-2919; doi:10.3390/s110302899. Available at https://www.mdpi.com/1424-8220/11/3/2899/. Full article
Open AccessArticle Development of an Ion Sensitive Field Effect Transistor Based Urea Biosensor with Solid State Reference Systems
Sensors 2010, 10(6), 6115-6127; https://doi.org/10.3390/s100606115
Received: 14 April 2010 / Revised: 25 May 2010 / Accepted: 1 June 2010 / Published: 21 June 2010
Cited by 8 | Viewed by 5432 | PDF Full-text (521 KB) | HTML Full-text | XML Full-text
Abstract
Ion sensitive field-effect transistor (ISFET) based urease biosensors with solid state reference systems for single-ended and two-ended differential readout electronics were investigated. The sensing membranes of the biosensors were fabricated with urease immobilized in a conducting polymer-based matrix. The responses of 12.9~198.1 mV [...] Read more.
Ion sensitive field-effect transistor (ISFET) based urease biosensors with solid state reference systems for single-ended and two-ended differential readout electronics were investigated. The sensing membranes of the biosensors were fabricated with urease immobilized in a conducting polymer-based matrix. The responses of 12.9~198.1 mV for the urea concentrations of 8~240 mg/dL reveal that the activity of the enzyme was not significantly decreased. Biosensors combined with solid state reference systems were fabricated, and the evaluation results demonstrated the feasibility of miniaturization. For the differential system, the optimal transconductance match for biosensor and reference field-effect transistors (REFET) pair was determined through the modification of the membranes of the REFETs and enzyme field-effect transistors (EnFETs). The results show that the transconductance curve of polymer based REFET can match with that of the EnFET by adjusting the photoresist/NafionTM ratio. The match of the transconductance curves for the differential pairs provides a wide dynamic operating measurement range. Accordingly, the miniaturized quasi-reference electrode (QRE)/REFET/EnFET combination with differential arrangement achieved similar urea response curves as those measured by a conventional large sized discrete sensor. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Background Subtraction Approach Based on Independent Component Analysis
Sensors 2010, 10(6), 6092-6114; https://doi.org/10.3390/s100606092
Received: 26 April 2010 / Revised: 16 May 2010 / Accepted: 28 May 2010 / Published: 18 June 2010
Cited by 17 | Viewed by 7182 | PDF Full-text (7971 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a new approach to background subtraction based on independent component analysis is presented. This approach assumes that background and foreground information are mixed in a given sequence of images. Then, foreground and background components are identified, if their probability density [...] Read more.
In this work, a new approach to background subtraction based on independent component analysis is presented. This approach assumes that background and foreground information are mixed in a given sequence of images. Then, foreground and background components are identified, if their probability density functions are separable from a mixed space. Afterwards, the components estimation process consists in calculating an unmixed matrix. The estimation of an unmixed matrix is based on a fast ICA algorithm, which is estimated as a Newton-Raphson maximization approach. Next, the motion components are represented by the mid-significant eigenvalues from the unmixed matrix. Finally, the results show the approach capabilities to detect efficiently motion in outdoors and indoors scenarios. The results show that the approach is robust to luminance conditions changes at scene. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Compact Tunable Diode Laser Absorption Spectrometer to Monitor CO2 at 2.7 µm Wavelength in Hypersonic Flows
Sensors 2010, 10(6), 6081-6091; https://doi.org/10.3390/s100606081
Received: 21 May 2010 / Revised: 4 June 2010 / Accepted: 8 June 2010 / Published: 17 June 2010
Cited by 12 | Viewed by 9865 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based [...] Read more.
Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Arrhythmia ECG Noise Reduction by Ensemble Empirical Mode Decomposition
Sensors 2010, 10(6), 6063-6080; https://doi.org/10.3390/s100606063
Received: 29 April 2010 / Revised: 20 May 2010 / Accepted: 10 June 2010 / Published: 17 June 2010
Cited by 77 | Viewed by 8030 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
A novel noise filtering algorithm based on ensemble empirical mode decomposition (EEMD) is proposed to remove artifacts in electrocardiogram (ECG) traces. Three noise patterns with different power—50 Hz, EMG, and base line wander – were embedded into simulated and real ECG signals. Traditional [...] Read more.
A novel noise filtering algorithm based on ensemble empirical mode decomposition (EEMD) is proposed to remove artifacts in electrocardiogram (ECG) traces. Three noise patterns with different power—50 Hz, EMG, and base line wander – were embedded into simulated and real ECG signals. Traditional IIR filter, Wiener filter, empirical mode decomposition (EMD) and EEMD were used to compare filtering performance. Mean square error between clean and filtered ECGs was used as filtering performance indexes. Results showed that high noise reduction is the major advantage of the EEMD based filter, especially on arrhythmia ECGs. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle A New Collaborative Knowledge-Based Approach for Wireless Sensor Networks
Sensors 2010, 10(6), 6044-6062; https://doi.org/10.3390/s100606044
Received: 28 April 2010 / Revised: 15 May 2010 / Accepted: 5 June 2010 / Published: 17 June 2010
Cited by 7 | Viewed by 6375 | PDF Full-text (259 KB) | HTML Full-text | XML Full-text
Abstract
This work presents a new approach for collaboration among sensors in Wireless Sensor Networks. These networks are composed of a large number of sensor nodes with constrained resources: limited computational capability, memory, power sources, etc. Nowadays, there is a growing interest in the [...] Read more.
This work presents a new approach for collaboration among sensors in Wireless Sensor Networks. These networks are composed of a large number of sensor nodes with constrained resources: limited computational capability, memory, power sources, etc. Nowadays, there is a growing interest in the integration of Soft Computing technologies into Wireless Sensor Networks. However, little attention has been paid to integrating Fuzzy Rule-Based Systems into collaborative Wireless Sensor Networks. The objective of this work is to design a collaborative knowledge-based network, in which each sensor executes an adapted Fuzzy Rule-Based System, which presents significant advantages such as: experts can define interpretable knowledge with uncertainty and imprecision, collaborative knowledge can be separated from control or modeling knowledge and the collaborative approach may support neighbor sensor failures and communication errors. As a real-world application of this approach, we demonstrate a collaborative modeling system for pests, in which an alarm about the development of olive tree fly is inferred. The results show that knowledge-based sensors are suitable for a wide range of applications and that the behavior of a knowledge-based sensor may be modified by inferences and knowledge of neighbor sensors in order to obtain a more accurate and reliable output. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Fast Scene Recognition and Camera Relocalisation for Wide Area Augmented Reality Systems
Sensors 2010, 10(6), 6017-6043; https://doi.org/10.3390/s100606017
Received: 29 April 2010 / Revised: 29 May 2010 / Accepted: 2 June 2010 / Published: 14 June 2010
Cited by 4 | Viewed by 4715 | PDF Full-text (3672 KB) | HTML Full-text | XML Full-text
Abstract
This paper focuses on online scene learning and fast camera relocalisation which are two key problems currently limiting the performance of wide area augmented reality systems. Firstly, we propose to use adaptive random trees to deal with the online scene learning problem. The [...] Read more.
This paper focuses on online scene learning and fast camera relocalisation which are two key problems currently limiting the performance of wide area augmented reality systems. Firstly, we propose to use adaptive random trees to deal with the online scene learning problem. The algorithm can provide more accurate recognition rates than traditional methods, especially with large scale workspaces. Secondly, we use the enhanced PROSAC algorithm to obtain a fast camera relocalisation method. Compared with traditional algorithms, our method can significantly reduce the computation complexity, which facilitates to a large degree the process of online camera relocalisation. Finally, we implement our algorithms in a multithreaded manner by using a parallel-computing scheme. Camera tracking, scene mapping, scene learning and relocalisation are separated into four threads by using multi-CPU hardware architecture. While providing real-time tracking performance, the resulting system also possesses the ability to track multiple maps simultaneously. Some experiments have been conducted to demonstrate the validity of our methods. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle Wavelet Analysis for Wind Fields Estimation
Sensors 2010, 10(6), 5994-6016; https://doi.org/10.3390/s100605994
Received: 11 May 2010 / Revised: 30 May 2010 / Accepted: 5 June 2010 / Published: 14 June 2010
Cited by 14 | Viewed by 5184 | PDF Full-text (5580 KB) | HTML Full-text | XML Full-text
Abstract
Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing [...] Read more.
Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing undecimated wavelet transform approaches, by including à trous with B3 spline scaling function, in addition to other wavelet bases as Gabor and Mexican-hat. The purpose is to extract more reliable directional information, when wind speed values range from 5 to 10 ms−1. Using C-band empirical models, associated with the estimated directional information, we calculate local wind speed values and compare our results with QuikSCAT scatterometer data. The proposed approach has potential application in the evaluation of oil spills and wind farms. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle A Fiber Optic Doppler Sensor and Its Application in Debonding Detection for Composite Structures
Sensors 2010, 10(6), 5975-5993; https://doi.org/10.3390/s100605975
Received: 30 April 2010 / Revised: 20 May 2010 / Accepted: 29 May 2010 / Published: 14 June 2010
Cited by 11 | Viewed by 4929 | PDF Full-text (769 KB) | HTML Full-text | XML Full-text
Abstract
Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by [...] Read more.
Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Exploring Infrared Sensoring for Real Time Welding Defects Monitoring in GTAW
Sensors 2010, 10(6), 5962-5974; https://doi.org/10.3390/s100605962
Received: 25 April 2010 / Revised: 15 May 2010 / Accepted: 30 May 2010 / Published: 14 June 2010
Cited by 12 | Viewed by 5934 | PDF Full-text (918 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding [...] Read more.
This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding pool temperature is related to the weld penetration depth; therefore, by monitoring the temperature, the arc pool temperature and penetration depth are also monitored. Various experiments were performed; in some of them the current was varied and the temperature changes were registered, in others, defects were induced throughout the path of the weld bead for a fixed current. These simulated defects resulted in abrupt changes in the average temperature values, thus providing an indication of the presence of a defect. The data has been registered with an acquisition card. To identify defects in the samples under infrared emissions, the timing series were analyzed through graphics and statistic methods. The selection of this technique demonstrates the potential for infrared emission as a welding monitoring parameter sensor. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Application of a Hybrid 3D-2D Laser Scanning System to the Characterization of Slate Slabs
Sensors 2010, 10(6), 5949-5961; https://doi.org/10.3390/s100605949
Received: 19 April 2010 / Revised: 21 April 2010 / Accepted: 11 May 2010 / Published: 14 June 2010
Cited by 5 | Viewed by 8100 | PDF Full-text (872 KB) | HTML Full-text | XML Full-text
Abstract
Dimensional control based on 3D laser scanning techniques is widely used in practice. We describe the application of a hybrid 3D-2D laser scanning system to the characterization of slate slabs with structural defects that are difficult for the human eye to characterize objectively. [...] Read more.
Dimensional control based on 3D laser scanning techniques is widely used in practice. We describe the application of a hybrid 3D-2D laser scanning system to the characterization of slate slabs with structural defects that are difficult for the human eye to characterize objectively. Our study is based on automating the process using a 3D laser scanner and a 2D camera. Our results demonstrate that the application of this hybrid system optimally characterizes slate slabs in terms of the defects described by the Spanish UNE-EN 12326-1 standard. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessReview Recent Applications of Fluorescence Recovery after Photobleaching (FRAP) to Membrane Bio-Macromolecules
Sensors 2010, 10(6), 5927-5948; https://doi.org/10.3390/s100605927
Received: 20 April 2010 / Revised: 10 May 2010 / Accepted: 28 May 2010 / Published: 10 June 2010
Cited by 28 | Viewed by 8374 | PDF Full-text (425 KB) | HTML Full-text | XML Full-text
Abstract
This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies. Initially, we discuss the lateral diffusion of membrane proteins, as measured by FRAP. Then, we talk about the use of FRAP to [...] Read more.
This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies. Initially, we discuss the lateral diffusion of membrane proteins, as measured by FRAP. Then, we talk about the use of FRAP to probe interactions between membrane proteins by obtaining fundamental information such as geometry and stoichiometry of the interacting complex. Afterwards, we discuss some applications of FRAP at the cellular level as well as the level of organisms. We conclude by comparing diffusion coefficients obtained by FRAP and several other alternative methods. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessArticle GPS-Free Localization Algorithm for Wireless Sensor Networks
Sensors 2010, 10(6), 5899-5926; https://doi.org/10.3390/s100605899
Received: 29 January 2010 / Revised: 26 April 2010 / Accepted: 20 May 2010 / Published: 9 June 2010
Cited by 25 | Viewed by 11734 | PDF Full-text (568 KB) | HTML Full-text | XML Full-text
Abstract
Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper. [...] Read more.
Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper. First, we develop a standardized clustering-based approach for the local coordinate system formation wherein a multiplication factor is introduced to regulate the number of master and slave nodes and the degree of connectivity among master nodes. Second, using homogeneous coordinates, we derive a transformation matrix between two Cartesian coordinate systems to efficiently merge them into a global coordinate system and effectively overcome the flip ambiguity problem. The algorithm operates asynchronously without a centralized controller; and does not require that the location of the sensors be known a priori. A set of parameter-setting guidelines for the proposed algorithm is derived based on a probability model and the energy requirements are also investigated. A simulation analysis on a specific numerical example is conducted to validate the mathematical analytical results. We also compare the performance of the proposed algorithm under a variety multiplication factor, node density and node communication radius scenario. Experiments show that our algorithm outperforms existing mechanisms in terms of accuracy and convergence time. Full article
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Open AccessArticle Liquid-Phase Packaging of a Glucose Oxidase Solution with Parylene Direct Encapsulation and an Ultraviolet Curing Adhesive Cover for Glucose Sensors
Sensors 2010, 10(6), 5888-5898; https://doi.org/10.3390/s100605888
Received: 20 April 2010 / Revised: 15 May 2010 / Accepted: 30 May 2010 / Published: 9 June 2010
Cited by 7 | Viewed by 6324 | PDF Full-text (789 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 μL) [...] Read more.
We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 μL) of glucose oxidase solution through chemical vapor deposition. The cover and reaction chamber were constructed on Parylene film using a UV-curable adhesive and photolithography. The package was processed at room temperature to avoid denaturation of the glucose oxidase. The glucose oxidase solution was encapsulated and unsealed. Glucose sensing was demonstrated using standard amperometric detection at glucose concentrations between 0.1 and 100 mM, which covers the glucose concentration range of diabetic patients. Our proposed Parylene encapsulation and UV-adhesive cover form a liquid phase glucose-oxidase package that has the advantages of room temperature processing and direct liquid encapsulation of a small volume solution without use of conventional solidifying chemicals. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessArticle An RFID-Based Intelligent Vehicle Speed Controller Using Active Traffic Signals
Sensors 2010, 10(6), 5872-5887; https://doi.org/10.3390/s100605872
Received: 23 April 2010 / Revised: 25 May 2010 / Accepted: 28 May 2010 / Published: 9 June 2010
Cited by 52 | Viewed by 10340 | PDF Full-text (943 KB) | HTML Full-text | XML Full-text
Abstract
These days, mass-produced vehicles benefit from research on Intelligent Transportation System (ITS). One prime example of ITS is vehicle Cruise Control (CC), which allows it to maintain a pre-defined reference speed, to economize on fuel or energy consumption, to avoid speeding fines, or [...] Read more.
These days, mass-produced vehicles benefit from research on Intelligent Transportation System (ITS). One prime example of ITS is vehicle Cruise Control (CC), which allows it to maintain a pre-defined reference speed, to economize on fuel or energy consumption, to avoid speeding fines, or to focus all of the driver’s attention on the steering of the vehicle. However, achieving efficient Cruise Control is not easy in roads or urban streets where sudden changes of the speed limit can happen, due to the presence of unexpected obstacles or maintenance work, causing, in inattentive drivers, traffic accidents. In this communication we present a new Infrastructure to Vehicles (I2V) communication and control system for intelligent speed control, which is based upon Radio Frequency Identification (RFID) technology for identification of traffic signals on the road, and high accuracy vehicle speed measurement with a Hall effect-based sensor. A fuzzy logic controller, based on sensor fusion of the information provided by the I2V infrastructure, allows the efficient adaptation of the speed of the vehicle to the circumstances of the road. The performance of the system is checked empirically, with promising results. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Development of a Quartz Crystal Microbalance Biosensor with Aptamers as Bio-recognition Element
Sensors 2010, 10(6), 5859-5871; https://doi.org/10.3390/s100605859
Received: 30 March 2010 / Revised: 20 April 2010 / Accepted: 15 May 2010 / Published: 9 June 2010
Cited by 51 | Viewed by 7083 | PDF Full-text (295 KB) | HTML Full-text | XML Full-text
Abstract
The ultimate goal in any biosensor development project is its use for actual sample detection. Recently, there has been an interest in biosensors with aptamers as bio-recognition elements, but reported examples all deal with standards, not human serum. In order to verify the [...] Read more.
The ultimate goal in any biosensor development project is its use for actual sample detection. Recently, there has been an interest in biosensors with aptamers as bio-recognition elements, but reported examples all deal with standards, not human serum. In order to verify the differences of aptamer-based biosensor and antibody-based biosensor in clinical detection, a comparison of the performance of aptamer-based and antibody-based quartz crystal microbalance (QCM) biosensors for the detection of immunoglobulin E (IgE) in human serum was carried out. Aptamers (or antibodies) specific to IgE were immobilized on the gold surface of a quartz crystal. The frequency shifts of the QCM were measured. The linear range with the antibody (10–240 μg/L) compared to that of the aptamer (2.5–200 μg/L), but a lower detection limit could be observed in the aptamer-based biosensor. The reproducibility of the two biosensors was comparable. The aptamers were equivalent or superior to antibodies in terms of specificity and sensitivity. In addition, the aptamer receptors could tolerate repeated affine layer regeneration after ligand binding and recycling of the biosensor with little loss of sensitivity. When stored for three weeks, the frequency shifts of the aptamer-coated crystals were all greater than 90% of those on the response at the first day. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements
Sensors 2010, 10(6), 5845-5858; https://doi.org/10.3390/s100605847
Received: 30 April 2010 / Revised: 26 May 2010 / Accepted: 1 June 2010 / Published: 9 June 2010
Cited by 5 | Viewed by 5570 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
Abstract
Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were [...] Read more.
Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (~3 μm) and sand (~300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Using Automated Point Dendrometers to Analyze Tropical Treeline Stem Growth at Nevado de Colima, Mexico
Sensors 2010, 10(6), 5827-5844; https://doi.org/10.3390/s100605827
Received: 10 May 2010 / Revised: 2 June 2010 / Accepted: 4 June 2010 / Published: 9 June 2010
Cited by 30 | Viewed by 7089 | PDF Full-text (416 KB) | HTML Full-text | XML Full-text
Abstract
The relationship between wood growth and environmental variability at the tropical treeline of North America was investigated using automated, solar-powered sensors (a meteorological station and two dendrometer clusters) installed on Nevado de Colima, Mexico (19° 35’ N, 103° 37’ W, 3,760 m a.s.l.). [...] Read more.
The relationship between wood growth and environmental variability at the tropical treeline of North America was investigated using automated, solar-powered sensors (a meteorological station and two dendrometer clusters) installed on Nevado de Colima, Mexico (19° 35’ N, 103° 37’ W, 3,760 m a.s.l.). Pure stands of Pinus hartwegii Lindl. (Mexican mountain pine) were targeted because of their suitability for tree-ring analysis in low-latitude, high-elevation, North American Monsoon environments. Stem size and hydroclimatic variables recorded at half-hour intervals were summarized on a daily timescale. Power outages, insect outbreaks, and sensor failures limited the analysis to non-consecutive months during 2001–2003 at one dendrometer site, and during 2002–2005 at the other. Combined data from the two sites showed that maximum radial growth rates occur in late spring (May), as soil temperature increases, and incoming short-wave radiation reaches its highest values. Early season (April–May) radial increment correlated directly with temperature, especially of the soil, and with solar radiation. Stem expansion at the start of the summer monsoon (June–July) was mostly influenced by moisture, and revealed a drought signal, while late season relationships were more varied. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle Power Consumption Analysis of Operating Systems for Wireless Sensor Networks
Sensors 2010, 10(6), 5809-5826; https://doi.org/10.3390/s100605809
Received: 19 April 2010 / Revised: 10 May 2010 / Accepted: 25 May 2010 / Published: 8 June 2010
Cited by 31 | Viewed by 8897 | PDF Full-text (722 KB) | HTML Full-text | XML Full-text
Abstract
In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring [...] Read more.
In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring a fair evaluation, a benchmark composed of four applications has been developed, covering the most typical tasks that a Wireless Sensor Network performs. The results show the instant and average current consumption of the devices during the execution of these applications. The experimental measurements provide a good insight into the power mode in which the device components are running at every moment, and they can be used to compare the performance of different operating systems executing the same tasks. Full article
Open AccessArticle Label Free Detection of CD4+ and CD8+ T Cells Using the Optofluidic Ring Resonator
Sensors 2010, 10(6), 5798-5808; https://doi.org/10.3390/s100605798
Received: 3 April 2010 / Revised: 16 May 2010 / Accepted: 1 June 2010 / Published: 8 June 2010
Cited by 34 | Viewed by 5028 | PDF Full-text (252 KB) | HTML Full-text | XML Full-text
Abstract
We have demonstrated label free detection of CD4+ and CD8+ T-Lymphocyte whole cells and CD4+ T-Lymphocyte cell lysis using the optofluidic ring resonator (OFRR) sensor. The OFRR sensing platform incorporates microfluidics and photonics in a setup that utilizes small sample volume and achieves [...] Read more.
We have demonstrated label free detection of CD4+ and CD8+ T-Lymphocyte whole cells and CD4+ T-Lymphocyte cell lysis using the optofluidic ring resonator (OFRR) sensor. The OFRR sensing platform incorporates microfluidics and photonics in a setup that utilizes small sample volume and achieves a fast detection time. In this work, white blood cells were isolated from healthy blood and the concentrations were adjusted to match T-Lymphocyte levels of individuals infected with HIV. Detection was accomplished by immobilizing CD4 and CD8 antibodies on the inner surface of the OFRR. Sensing results show excellent detection of CD4+ and CD8+ T-Lymphocyte cells at medically significant concentrations with a detection time of approximately 30 minutes. This work will lead to a rapid and low-cost sensing device that can provide a CD4 and CD8 count as a measure of HIV progression. Full article
(This article belongs to the Section Biosensors)
Open AccessReview Sensor Systems for Prognostics and Health Management
Sensors 2010, 10(6), 5774-5797; https://doi.org/10.3390/s100605774
Received: 20 April 2010 / Revised: 27 May 2010 / Accepted: 28 May 2010 / Published: 8 June 2010
Cited by 111 | Viewed by 11071 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM [...] Read more.
Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM to monitor environmental, operational, and performance-related characteristics. The gathered data can be analyzed to assess product health and predict remaining life. In this paper, the considerations for sensor system selection for PHM applications, including the parameters to be measured, the performance needs, the electrical and physical attributes, reliability, and cost of the sensor system, are discussed. The state-of-the-art sensor systems for PHM and the emerging trends in technologies of sensor systems for PHM are presented. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Enzymatic Determination of Diglyceride Using an Iridium Nano-Particle Based Single Use, Disposable Biosensor
Sensors 2010, 10(6), 5758-5773; https://doi.org/10.3390/s100605758
Received: 26 April 2010 / Revised: 15 May 2010 / Accepted: 28 May 2010 / Published: 8 June 2010
Cited by 3 | Viewed by 5843 | PDF Full-text (1892 KB) | HTML Full-text | XML Full-text
Abstract
A single use, disposable iridium-nano particle contained biosensor had been developed for the determination of diglyceride (DG). In this study hydrogen peroxide, formed through the enzymatic breakdown of DG via lipase, glycerol kinase and glycerol 3-phosphate oxidase, was electrochemically oxidized at an applied [...] Read more.
A single use, disposable iridium-nano particle contained biosensor had been developed for the determination of diglyceride (DG). In this study hydrogen peroxide, formed through the enzymatic breakdown of DG via lipase, glycerol kinase and glycerol 3-phosphate oxidase, was electrochemically oxidized at an applied potential of +0.5 V versus the Ag/AgCl reference electrode. The oxidation current was then used to quantify the diglyceride concentration. Optimum enzyme concentrations and the surfactant loading used were established for successful sensor response. Good linear performance was observed over a DG concentration range of 0 to 25 µM in phosphate buffer and bovine serum media. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Windows on the Human Body – in Vivo High-Field Magnetic Resonance Research and Applications in Medicine and Psychology
Sensors 2010, 10(6), 5724-5757; https://doi.org/10.3390/s100605724
Received: 3 March 2010 / Revised: 2 April 2010 / Accepted: 17 May 2010 / Published: 8 June 2010
Cited by 9 | Viewed by 6569 | PDF Full-text (3169 KB) | HTML Full-text | XML Full-text
Abstract
Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic [...] Read more.
Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic information from the human body with unsurpassed quality. Recent achievements in high and ultra-high field MR (at 3 and 7 Tesla) are described, and representative research applications in Medicine and Psychology in Austria are discussed. Finally, an overview of current and prospective research in multi-modal imaging, potential clinical applications, as well as current limitations and challenges is given. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Austria)
Open AccessArticle Real-Time Plasma Process Condition Sensing and Abnormal Process Detection
Sensors 2010, 10(6), 5703-5723; https://doi.org/10.3390/s100605703
Received: 25 April 2010 / Revised: 15 May 2010 / Accepted: 25 May 2010 / Published: 8 June 2010
Cited by 7 | Viewed by 6493 | PDF Full-text (423 KB) | HTML Full-text | XML Full-text
Abstract
The plasma process is often used in the fabrication of semiconductor wafers. However, due to the lack of real-time etching control, this may result in some unacceptable process performances and thus leads to significant waste and lower wafer yield. In order to maximize [...] Read more.
The plasma process is often used in the fabrication of semiconductor wafers. However, due to the lack of real-time etching control, this may result in some unacceptable process performances and thus leads to significant waste and lower wafer yield. In order to maximize the product wafer yield, a timely and accurately process fault or abnormal detection in a plasma reactor is needed. Optical emission spectroscopy (OES) is one of the most frequently used metrologies in in-situ process monitoring. Even though OES has the advantage of non-invasiveness, it is required to provide a huge amount of information. As a result, the data analysis of OES becomes a big challenge. To accomplish real-time detection, this work employed the sigma matching method technique, which is the time series of OES full spectrum intensity. First, the response model of a healthy plasma spectrum was developed. Then, we defined a matching rate as an indictor for comparing the difference between the tested wafers response and the health sigma model. The experimental results showed that this proposal method can detect process faults in real-time, even in plasma etching tools. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Gait Event Detection on Level Ground and Incline Walking Using a Rate Gyroscope
Sensors 2010, 10(6), 5683-5702; https://doi.org/10.3390/s100605683
Received: 23 March 2010 / Revised: 24 May 2010 / Accepted: 25 May 2010 / Published: 4 June 2010
Cited by 49 | Viewed by 7104 | PDF Full-text (371 KB) | HTML Full-text | XML Full-text
Abstract
Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper [...] Read more.
Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects walking outdoors on level ground, and up and down an incline. Performance was compared with a reference pressure measurement system. The mean difference between the gyroscope and the reference was less than –25 ms for IC and less than 75 ms for FO for all terrains. Detection success was over 98%. These results provide preliminary evidence supporting the use of the gyroscope for gait event detection on inclines as well as level walking. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
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