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Sensors, Volume 9, Issue 9 (September 2009), Pages 6604-7579

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Sensing a Changing World
Sensors 2009, 9(9), 6819-6822; doi:10.3390/s90906819
Received: 23 June 2009 / Revised: 26 August 2009 / Accepted: 26 August 2009 / Published: 28 August 2009
Cited by 2 | PDF Full-text (89 KB) | HTML Full-text | XML Full-text
Abstract
The workshop “Sensing a Changing World” was held in Wageningen, The Netherlands, from November 19–21, 2008. The main goal of the workshop was to explore and discuss recent developments in sensors and (wireless) sensor networks for monitoring environmental processes and human spatial [...] Read more.
The workshop “Sensing a Changing World” was held in Wageningen, The Netherlands, from November 19–21, 2008. The main goal of the workshop was to explore and discuss recent developments in sensors and (wireless) sensor networks for monitoring environmental processes and human spatial behavior in a changing world. The challenge is then to develop concepts and applications that can provide timely and on-demand knowledge to end-users in different domains over a range of different spatial and temporal scales. During this workshop over 50 participants, representing 15 countries, presented and discussed their recent research. The workshop provided a broad overview of state-of-the-art research in a broad range of application fields: oceanography, air quality, biodiversity and vegetation, health, tourism, water management, and agriculture. In addition the workshop identified the future research challenges. One of the outcomes of the workshop was a special issue in the journal Sensors with contributions presented at the workshop. This editorial of the special issue aims to provide an overview of the discussions held during the workshop. It highlights the ideas of the authors and participants of the workshop about directions of future research for further development of sensor-webs for “sensing” spatial phenomena. The “big” question was are we already able to sense a changing world? And if the answer is positive, then what are we going to sense and for what? Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)

Research

Jump to: Editorial, Review, Other

Open AccessArticle An Improved Approach for Terrain Correction: Application to Northeast Asia’s Highest Peak (Mt. Jade, Taiwan)
Sensors 2009, 9(9), 6604-6612; doi:10.3390/s90906604
Received: 24 July 2009 / Revised: 13 August 2009 / Accepted: 20 August 2009 / Published: 24 August 2009
PDF Full-text (370 KB) | HTML Full-text | XML Full-text
Abstract
Mt. Jade (or “Yushan” in Chinese) is the highest peak in northeast Asia. The topography is very rugged and complicated. Such terrain makes it difficult to obtain the correct results for terrain corrections (TCs). This paper developed an improved approach, named cone-section [...] Read more.
Mt. Jade (or “Yushan” in Chinese) is the highest peak in northeast Asia. The topography is very rugged and complicated. Such terrain makes it difficult to obtain the correct results for terrain corrections (TCs). This paper developed an improved approach, named cone-section method, to compute the TCs of the Mt. Jade area using a high-resolution digital elevation model (DEM) on a 9" × 9" grid. The corrections were calculated to the distance of 100 km with an average rock density of 2.57 × 103 kg•m-3. This investigation compared the results of TCs from the cone-section method with those from the cylinder prism and Gaussian quadrature methods using a 9" × 9" elevation grid for the inner zone and a 90" × 90" elevation grid for the outer zone. The inner and outer radii were set to 20 and 200 km, respectively. The comparisons showed that the cone-section algorithm is consistent with the Gaussian quadrature. Furthermore, the cone-section method is an appropriate approach for TCs in high elevation areas, yielding results that outperform the cylinder prism method. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle An Electrochemical Sensor Based on Nanostructured Hollandite-type Manganese Oxide for Detection of Potassium Ions
Sensors 2009, 9(9), 6613-6625; doi:10.3390/s90906613
Received: 8 April 2009 / Revised: 3 June 2009 / Accepted: 3 June 2009 / Published: 24 August 2009
Cited by 12 | PDF Full-text (643 KB) | HTML Full-text | XML Full-text
Abstract
The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based [...] Read more.
The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and the subsequent extraction of the potassium ions into the hollandite structure. In this work, an amperometric procedure at an operating potential of 0.80 V (versus SCE) is exploited for amperometric monitoring. The current signals are linearly proportional to potassium ion concentration in the range 4.97 × 10−5 to 9.05 × 10−4 mol L−1, with a correlation coefficient of 0.9997. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Energy Balanced Strategies for Maximizing the Lifetime of Sparsely Deployed Underwater Acoustic Sensor Networks
Sensors 2009, 9(9), 6626-6651; doi:10.3390/s90906626
Received: 9 June 2009 / Revised: 9 August 2009 / Accepted: 10 August 2009 / Published: 24 August 2009
Cited by 26 | PDF Full-text (352 KB) | HTML Full-text | XML Full-text
Abstract
Underwater acoustic sensor networks (UWA-SNs) are envisioned to perform monitoring tasks over the large portion of the world covered by oceans. Due to economics and the large area of the ocean, UWA-SNs are mainly sparsely deployed networks nowadays. The limited battery resources [...] Read more.
Underwater acoustic sensor networks (UWA-SNs) are envisioned to perform monitoring tasks over the large portion of the world covered by oceans. Due to economics and the large area of the ocean, UWA-SNs are mainly sparsely deployed networks nowadays. The limited battery resources is a big challenge for the deployment of such long-term sensor networks. Unbalanced battery energy consumption will lead to early energy depletion of nodes, which partitions the whole networks and impairs the integrity of the monitoring datasets or even results in the collapse of the entire networks. On the contrary, balanced energy dissipation of nodes can prolong the lifetime of such networks. In this paper, we focus on the energy balance dissipation problem of two types of sparsely deployed UWA-SNs: underwater moored monitoring systems and sparsely deployed two-dimensional UWA-SNs. We first analyze the reasons of unbalanced energy consumption in such networks, then we propose two energy balanced strategies to maximize the lifetime of networks both in shallow and deep water. Finally, we evaluate our methods by simulations and the results show that the two strategies can achieve balanced energy consumption per node while at the same time prolong the networks lifetime. Full article
Open AccessArticle Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H2 Gas Sensor
Sensors 2009, 9(9), 6652-6669; doi:10.3390/s90906652
Received: 2 July 2009 / Revised: 20 August 2009 / Accepted: 20 August 2009 / Published: 26 August 2009
Cited by 32 | PDF Full-text (7133 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique [...] Read more.
Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5–20 nm wide and 20–40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al2O3 substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H2) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H2 sensitivity of ~164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessArticle Detecting the Land-Cover Changes Induced by Large-Physical Disturbances Using Landscape Metrics, Spatial Sampling, Simulation and Spatial Analysis
Sensors 2009, 9(9), 6670-6700; doi:10.3390/s90906670
Received: 25 May 2009 / Revised: 16 July 2009 / Accepted: 24 August 2009 / Published: 26 August 2009
Cited by 6 | PDF Full-text (5932 KB) | HTML Full-text | XML Full-text
Abstract
The objectives of the study are to integrate the conditional Latin Hypercube Sampling (cLHS), sequential Gaussian simulation (SGS) and spatial analysis in remotely sensed images, to monitor the effects of large chronological disturbances on spatial characteristics of landscape changes including spatial heterogeneity [...] Read more.
The objectives of the study are to integrate the conditional Latin Hypercube Sampling (cLHS), sequential Gaussian simulation (SGS) and spatial analysis in remotely sensed images, to monitor the effects of large chronological disturbances on spatial characteristics of landscape changes including spatial heterogeneity and variability. The multiple NDVI images demonstrate that spatial patterns of disturbed landscapes were successfully delineated by spatial analysis such as variogram, Moran’I and landscape metrics in the study area. The hybrid method delineates the spatial patterns and spatial variability of landscapes caused by these large disturbances. The cLHS approach is applied to select samples from Normalized Difference Vegetation Index (NDVI) images from SPOT HRV images in the Chenyulan watershed of Taiwan, and then SGS with sufficient samples is used to generate maps of NDVI images. In final, the NDVI simulated maps are verified using indexes such as the correlation coefficient and mean absolute error (MAE). Therefore, the statistics and spatial structures of multiple NDVI images present a very robust behavior, which advocates the use of the index for the quantification of the landscape spatial patterns and land cover change. In addition, the results transferred by Open Geospatial techniques can be accessed from web-based and end-user applications of the watershed management. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Fabrication of a Multi-Walled Nanotube (MWNT) Ionic Liquid Electrode and Its Application for Sensing Phenolics in Red Wines
Sensors 2009, 9(9), 6701-6714; doi:10.3390/s90906701
Received: 16 June 2009 / Revised: 14 July 2009 / Accepted: 18 August 2009 / Published: 26 August 2009
Cited by 17 | PDF Full-text (889 KB) | HTML Full-text | XML Full-text
Abstract
A multi-walled nanotube (MWNT) ionic liquid was prepared by the immobilization of 1-butylimidazole bromide onto an epoxy group on a poly(glycidyl methacrylate)-grafted MWNT, which was synthesized by radiation-induced graft polymerization of glycidyl methacrylate onto MWNT in an aqueous solution. Subsequently, a MWNT [...] Read more.
A multi-walled nanotube (MWNT) ionic liquid was prepared by the immobilization of 1-butylimidazole bromide onto an epoxy group on a poly(glycidyl methacrylate)-grafted MWNT, which was synthesized by radiation-induced graft polymerization of glycidyl methacrylate onto MWNT in an aqueous solution. Subsequently, a MWNT ionic liquid electrode was fabricated by hand-casting MWNT ionic liquid, tyrosinase, and chitosan solution as a binder on indium tin oxide (ITO) glass. The sensing ranges of the MWNT ionic liquid electrode with immobilized tyrosinase was in the range of 0.01-0.08 mM in a phosphate buffer solution. The optimal conditions such as pH, temperature, and effects of different phenolic compounds were determined. The total phenolic compounds of three commercial red wines were also determined on the tyrosinase-immobilized biosensor. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Detecting Intra-Fraction Motion in Patients Undergoing Radiation Treatment Using a Low-Cost Wireless Accelerometer
Sensors 2009, 9(9), 6715-6729; doi:10.3390/s90906715
Received: 31 May 2009 / Revised: 1 August 2009 / Accepted: 18 August 2009 / Published: 27 August 2009
Cited by 5 | PDF Full-text (384 KB) | HTML Full-text | XML Full-text
Abstract
The utility of a novel, high-precision, non-intrusive, wireless, accelerometerbased patient orientation monitoring system (APOMS) in determining orientation change in patients undergoing radiation treatment is reported here. Using this system a small wireless accelerometer sensor is placed on a patient’s skin, broadcasting its [...] Read more.
The utility of a novel, high-precision, non-intrusive, wireless, accelerometerbased patient orientation monitoring system (APOMS) in determining orientation change in patients undergoing radiation treatment is reported here. Using this system a small wireless accelerometer sensor is placed on a patient’s skin, broadcasting its orientation to the receiving station connected to a PC in the control area. A threshold-based algorithm is developed to identify the exact amount of the patient’s head orientation change. Through real-time measurements, an audible alarm can alert the radiation therapist if the user-defined orientation threshold is violated. Our results indicate that, in spite of its low-cost and simplicity, the APOMS is highly sensitive and offers accurate measurements. Furthermore, the APOMS is patient friendly, vendor neutral, and requires minimal user training. The versatile architecture of the APOMS makes it potentially suitable for variety of applications, including study of correlation between external and internal markers during Image-Guided Radiation Therapy (IGRT), with no major changes in hardware setup or algorithm. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Preparation, Characterization and Sensitive Gas Sensing of Conductive Core-sheath TiO2-PEDOT Nanocables
Sensors 2009, 9(9), 6752-6763; doi:10.3390/s90906752
Received: 10 August 2009 / Revised: 20 August 2009 / Accepted: 21 August 2009 / Published: 27 August 2009
Cited by 27 | PDF Full-text (578 KB) | HTML Full-text | XML Full-text
Abstract
Conductive core-sheath TiO2-PEDOT nanocables were prepared using electrospun TiO2 nanofibers as template, followed by vapor phase polymerization of EDOT. Various techniques were employed to characterize the sample. The results reveal that the TiO2 core has an average diameter of [...] Read more.
Conductive core-sheath TiO2-PEDOT nanocables were prepared using electrospun TiO2 nanofibers as template, followed by vapor phase polymerization of EDOT. Various techniques were employed to characterize the sample. The results reveal that the TiO2 core has an average diameter of ~78 nm while the PEDOT sheath has a uniform thickness of ~6 nm. The as-prepared TiO2-PEDOT nanocables display a fast and reversible response to gaseous NO2 and NH3 with a limit of detection as low as 7 ppb and 675 ppb (S/N=3), respectively. This study provides a route for the synthesis of conductive nanostructures which show excellent performance for sensing applications. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle A Geometric Modelling Approach to Determining the Best Sensing Coverage for 3-Dimensional Acoustic Target Tracking in Wireless Sensor Networks
Sensors 2009, 9(9), 6764-6794; doi:10.3390/s90906764
Received: 25 June 2009 / Revised: 10 August 2009 / Accepted: 19 August 2009 / Published: 27 August 2009
Cited by 8 | PDF Full-text (2027 KB) | HTML Full-text | XML Full-text
Abstract
Existing 3-dimensional acoustic target tracking methods that use wired/wireless networked sensor nodes to track targets based on four sensing coverage do not always compute the feasible spatio-temporal information of target objects. To investigate this discrepancy in a formal setting, we propose a [...] Read more.
Existing 3-dimensional acoustic target tracking methods that use wired/wireless networked sensor nodes to track targets based on four sensing coverage do not always compute the feasible spatio-temporal information of target objects. To investigate this discrepancy in a formal setting, we propose a geometric model of the target tracking problem alongside its equivalent geometric dual model that is easier to solve. We then study and prove some properties of dual model by exploiting its relationship with algebra. Based on these properties, we propose a four coverage axis line method based on four sensing coverage and prove that four sensing coverage always yields two dual correct answers; usually one of them is infeasible. By showing that the feasible answer can be only sometimes identified by using a simple time test method such as the one proposed by ourselves, we prove that four sensing coverage fails to always yield the feasible spatiotemporal information of a target object. We further prove that five sensing coverage always gives the feasible position of a target object under certain conditions that are discussed in this paper. We propose three extensions to four coverage axis line method, namely, five coverage extent point method, five coverage extended axis lines method, and five coverage redundant axis lines method. Computation and time complexities of all four proposed methods are equal in the worst cases as well as on average being equal to Θ(1) each. Proposed methods and proved facts about capabilities of sensing coverage degree in this paper can be used in all other methods of acoustic target tracking like Bayesian filtering methods. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Figures

Open AccessArticle On the Application of Different Event-Based Sampling Strategies to the Control of a Simple Industrial Process
Sensors 2009, 9(9), 6795-6818; doi:10.3390/s90906795
Received: 7 July 2009 / Revised: 20 August 2009 / Accepted: 24 August 2009 / Published: 27 August 2009
Cited by 39 | PDF Full-text (744 KB) | HTML Full-text | XML Full-text
Abstract
This paper is an experimental study of the utilization of different event-based strategies for the automatic control of a simple but very representative industrial process: the level control of a tank. In an event-based control approach it is the triggering of a [...] Read more.
This paper is an experimental study of the utilization of different event-based strategies for the automatic control of a simple but very representative industrial process: the level control of a tank. In an event-based control approach it is the triggering of a specific event, and not the time, that instructs the sensor to send the current state of the process to the controller, and the controller to compute a new control action and send it to the actuator. In the document, five control strategies based on different event-based sampling techniques are described, compared, and contrasted with a classical time-based control approach and a hybrid one. The common denominator in the time, the hybrid, and the event-based control approaches is the controller: a proportional-integral algorithm with adaptations depending on the selected control approach. To compare and contrast each one of the hybrid and the pure event-based control algorithms with the time-based counterpart, the two tasks that a control strategy must achieve (set-point following and disturbance rejection) are independently analyzed. The experimental study provides new proof concerning the ability of event-based control strategies to minimize the data exchange among the control agents (sensors, controllers, actuators) when an error-free control of the process is not a hard requirement. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessArticle Research of DOA Estimation Based on Single MEMS Vector Hydrophone
Sensors 2009, 9(9), 6823-6834; doi:10.3390/s90906823
Received: 5 February 2009 / Revised: 29 June 2009 / Accepted: 24 August 2009 / Published: 31 August 2009
Cited by 18 | PDF Full-text (694 KB) | HTML Full-text | XML Full-text
Abstract
The MEMS vector hydrophone is a novel acoustic sensor with a “four-beamcilia” structure. Based on the MEMS vector hydrophone with this structure, the paper studies the method of estimated direction of arrival (DOA). According to various research papers, many algorithms can be [...] Read more.
The MEMS vector hydrophone is a novel acoustic sensor with a “four-beamcilia” structure. Based on the MEMS vector hydrophone with this structure, the paper studies the method of estimated direction of arrival (DOA). According to various research papers, many algorithms can be applied to vector hydrophones. The beam-forming approach and bar graph approach are described in detail. Laboratory tests by means of the a standing-wave tube are performed to validate the theoretical results. Both the theoretical analysis and the results of tests prove that the proposed MEMS vector hydrophone possesses the desired directional function. Full article
Open AccessArticle Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Size Dependence and Influence of Substrate
Sensors 2009, 9(9), 6836-6852; doi:10.3390/s90906836
Received: 7 August 2009 / Revised: 20 August 2009 / Accepted: 20 August 2009 / Published: 31 August 2009
Cited by 15 | PDF Full-text (483 KB) | HTML Full-text | XML Full-text
Abstract
Whispering gallery modes in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing changes in the refractive index of the beads’ environment by exposing them to water/glycerol mixtures of varying composition. The mode positions are analyzed by simultaneous [...] Read more.
Whispering gallery modes in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing changes in the refractive index of the beads’ environment by exposing them to water/glycerol mixtures of varying composition. The mode positions are analyzed by simultaneous fitting for mode number, bead radius, and environmental index. Down to a diameter of 8 μm, the sensor response follows the index of the bulk solution very well. For smaller bead sizes, some deviations occur, in particular for fluid indices not too different from that of water, which might be attributed to the presence of the substrate. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance
Sensors 2009, 9(9), 6853-6868; doi:10.3390/s90906853
Received: 30 June 2009 / Revised: 26 August 2009 / Accepted: 27 August 2009 / Published: 31 August 2009
Cited by 7 | PDF Full-text (1210 KB) | HTML Full-text | XML Full-text
Abstract
This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes [...] Read more.
This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 ºC for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 ºC, low standard deviation to the sensor response (±0.35) and no signal hysteresis. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle Detecting Specific Health-Related Events Using an Integrated Sensor System for Vital Sign Monitoring
Sensors 2009, 9(9), 6897-6912; doi:10.3390/s90906897
Received: 11 June 2009 / Accepted: 24 August 2009 / Published: 1 September 2009
Cited by 12 | PDF Full-text (965 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a new method for the detection of apnea/hypopnea periods in physiological data is presented. The method is based on the intelligent combination of an integrated sensor system for long-time cardiorespiratory signal monitoring and dedicated signal-processing packages. Integrated sensors are [...] Read more.
In this paper, a new method for the detection of apnea/hypopnea periods in physiological data is presented. The method is based on the intelligent combination of an integrated sensor system for long-time cardiorespiratory signal monitoring and dedicated signal-processing packages. Integrated sensors are a PVDF film and conductive fabric sheets. The signal processing package includes dedicated respiratory cycle (RC) and QRS complex detection algorithms and a new method using the respiratory cycle variability (RCV) for detecting apnea/hypopnea periods in physiological data. Results show that our method is suitable for online analysis of long time series data. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle Changes in Physiological Parameters Induced by Indoor Simulated Driving: Effect of Lower Body Exercise at Mid-Term Break
Sensors 2009, 9(9), 6913-6933; doi:10.3390/s90906913
Received: 26 June 2009 / Revised: 17 August 2009 / Accepted: 25 August 2009 / Published: 1 September 2009
Cited by 13 | PDF Full-text (271 KB) | HTML Full-text | XML Full-text
Abstract
The study monitored physiological parameter changes after 120-min of simulated driving. Blood pressures, heart rate (HR), heart rate variability (HRV) and palm temperatures were measured using an ANSWatch® monitor. Subjects were divided into two groups (A & B). Both groups performed 2-hour driving, but group B additionally took a 15-min exercise break. Heart rate, systolic pressure, LF/HF, and palm temperature decreased for group A after driving; for group B only HR and palm temperatures decreased. HRV and parasympathetic indices HF(AU) and HF(NU) increased for group A, while HRV and sympathetic index LF(AU) increased in group B. Group A had higher fatigue scores than group B. ANS activation may overcome some fatigue symptoms, but the recovery is nonetheless incomplete. Exercise break is proven to be an effective remedy, especially if accompanied by the ANS actions. The normalized parasympathetic index HF(NU), the normalized sympathetic index LF(NU), and the sympatho-vagal balance index LF/HF are three most promising parameters that could be further developed to monitor driver fatigue. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Silver(I) Ions Ultrasensitive Detection at Carbon Electrodes―Analysis of Waters, Tobacco Cells and Fish Tissues
Sensors 2009, 9(9), 6934-6950; doi:10.3390/s90906934
Received: 22 June 2009 / Revised: 12 August 2009 / Accepted: 24 August 2009 / Published: 1 September 2009
Cited by 18 | PDF Full-text (391 KB) | HTML Full-text | XML Full-text
Abstract
We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 μM. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 [...] Read more.
We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 μM. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 mL) or carbon pencil was used. Limits of detection estimated by dilution of a standard were 1 (carbon tip) or 10 nM (carbon pencil). Further we employed flow injection analysis coupled with carbon tip to detect silver(I) ions released in various beverages and mineral waters. During first, second and third week the amount of silver(I) ions releasing into water samples was under the detection limit of the technique used for their quantification. At the end of a thirteen weeks long experiment the content of silver(I) ions was several times higher compared to the beginning of release detected in the third week and was on the order of tens of nanomoles. In subsequent experiments the influence of silver(I) ions (0, 5 and 10 μM) on a plant model system (tobacco BY-2 cells) during a fourday exposition was investigated. Silver(I) ions were highly toxic to the cells, which was revealed by a double staining viability assay. Moreover we investigated the effect of silver(I) ions (0, 0.3, 0.6, 1.2 and 2.5 μM) on guppies (Poecilia reticulata). Content of Ag(I) increased with increasing time of the treatment and applied concentrations in fish tissues. It can be concluded that a carbon tip or carbon pencil coupled with a miniaturized potentiostat can be used for detection of silver(I) ions in environmental samples and thus represents a small, portable, low cost and easy-to-use instrument for such purposes. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Design and Analyses of a MEMS Based Resonant Magnetometer
Sensors 2009, 9(9), 6951-6966; doi:10.3390/s90906951
Received: 2 July 2009 / Revised: 18 July 2009 / Accepted: 27 July 2009 / Published: 2 September 2009
Cited by 17 | PDF Full-text (910 KB) | HTML Full-text | XML Full-text
Abstract
A novel design of a MEMS torsional resonant magnetometer based on Lorentz force is presented and fabricated. The magnetometer consists of a silicon resonator, torsional beam, excitation coil, capacitance plates and glass substrate. Working in a resonant condition, the sensor’s vibration amplitude [...] Read more.
A novel design of a MEMS torsional resonant magnetometer based on Lorentz force is presented and fabricated. The magnetometer consists of a silicon resonator, torsional beam, excitation coil, capacitance plates and glass substrate. Working in a resonant condition, the sensor’s vibration amplitude is converted into the sensing capacitance change, which reflects the outside magnetic flux-density. Based on the simulation, the key structure parameters are optimized and the air damping effect is estimated. The test results of the prototype are in accordance with the simulation results of the designed model. The resolution of the magnetometer can reach 30 nT. The test results indicate its sensitivity of more than 400 mV/μT when operating in a 10 Pa vacuum environment. Full article
Open AccessArticle Application of Close Range Photogrammetry to Deck Measurement in Recreational Ships
Sensors 2009, 9(9), 6991-7002; doi:10.3390/s90906991
Received: 13 July 2009 / Revised: 13 August 2009 / Accepted: 31 August 2009 / Published: 3 September 2009
Cited by 7 | PDF Full-text (277 KB) | HTML Full-text | XML Full-text
Abstract
In this article, we present results that demonstrate the utility of close range photogrammetry in the measurement of decks in recreational craft as an alternate measurement system to the one based on direct acquisition of coordinates. The areas of deck covered with [...] Read more.
In this article, we present results that demonstrate the utility of close range photogrammetry in the measurement of decks in recreational craft as an alternate measurement system to the one based on direct acquisition of coordinates. The areas of deck covered with teakwood for aesthetic or security reasons were measured. Both methods were compared in terms of precision of measurements, time consumption, equipment cost, and ease of manipulation and equipment transportation. Based on the results, we conclude that photogrammetry has advantages in almost every aspect with respect to the direct method. Consequently, photogrammetry is suggested as a suitable method for coordinate measurement of decks in recreational ships. However, in some special circumstances, where ships have wide corridors with few obstacles the direct method can be more appropriate than the photogrammetric method. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessArticle Preparation of a Nanosized As2O3/Mn0.5Zn0.5Fe2O4 Complex and Its Anti-Tumor Effect on Hepatocellular Carcinoma Cells
Sensors 2009, 9(9), 7058-7068; doi:10.3390/s90907058
Received: 25 June 2009 / Revised: 17 August 2009 / Accepted: 3 September 2009 / Published: 4 September 2009
Cited by 8 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
Manganese-zinc-ferrite nanoparticles (Mn0.5Zn0.5Fe2O4, MZF-NPs) prepared by an improved co-precipitation method and were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Then thermodynamic testing of various doses of MZF-NPs [...] Read more.
Manganese-zinc-ferrite nanoparticles (Mn0.5Zn0.5Fe2O4, MZF-NPs) prepared by an improved co-precipitation method and were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Then thermodynamic testing of various doses of MZF-NPs was performed in vitro. The cytotoxicity of the Mn0.5Zn0.5Fe2O4 nanoparticles in vitro was tested by the MTT assay. A nanosized As2O3/Mn0.5Zn0.5Fe2O4 complex was made by an impregnation process. The complex’s shape, component, envelop rate and release rate of As2O3 were measured by SEM, EDS and atom fluorescence spectrometry, respectively. The therapeutic effect of nanosized As2O3/Mn0.5Zn0.5Fe2O4 complex combined with magnetic fluid hyperthermia (MFH) on human hepatocelluar cells were evaluated in vitro by an MTT assay and flow cytometry. The results indicated that Mn0.5Zn0.5Fe2O4 and nanosized As2O3/Mn0.5Zn0.5Fe2O4 complex were both prepared successfully. The Mn0.5Zn0.5Fe2O4 nanoparticles had powerful absorption capabilities in a high-frequency alternating electromagnetic field, and had strong magnetic responsiveness. Moreover, Mn0.5Zn0.5Fe2O4 didn’t show cytotoxicity in vitro. The therapeutic result reveals that the nanosized As2O3/Mn0.5Zn0.5Fe2O4 complex can significantly inhibit the growth of hepatoma carcinoma cells. Full article
Open AccessArticle REMOTE, a Wireless Sensor Network Based System to Monitor Rowing Performance
Sensors 2009, 9(9), 7069-7082; doi:10.3390/s90907069
Received: 15 July 2009 / Revised: 5 August 2009 / Accepted: 3 September 2009 / Published: 4 September 2009
Cited by 9 | PDF Full-text (4066 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we take a hard look at the performance of REMOTE, a sensor network based application that provides a detailed picture of a boat movement, individual rower performance, or his/her performance compared with other crew members. The application analyzes data [...] Read more.
In this paper, we take a hard look at the performance of REMOTE, a sensor network based application that provides a detailed picture of a boat movement, individual rower performance, or his/her performance compared with other crew members. The application analyzes data gathered with a WSN strategically deployed over a boat to obtain information on the boat and oar movements. Functionalities of REMOTE are compared to those of RowX [1] outdoor instrument, a commercial wired sensor instrument designed for similar purposes. This study demonstrates that with smart geometrical configuration of the sensors, rotation and translation of the oars and boat can be obtained. Three different tests are performed: laboratory calibration allows us to become familiar with the accelerometer readings and validate the theory, ergometer tests which help us to set the acquisition parameters, and on boat tests shows the application potential of this technologies in sports. Full article
(This article belongs to the Special Issue Motion Detectors)
Open AccessArticle Using the Optical Mouse Sensor as a Two-Euro Counterfeit Coin Detector
Sensors 2009, 9(9), 7083-7096; doi:10.3390/s90907083
Received: 7 August 2009 / Revised: 20 August 2009 / Accepted: 21 August 2009 / Published: 4 September 2009
Cited by 13 | PDF Full-text (339 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the sensor of an optical mouse is presented as a counterfeit coin detector applied to the two-Euro case. The detection process is based on the short distance image acquisition capabilities of the optical mouse sensor where partial images of [...] Read more.
In this paper, the sensor of an optical mouse is presented as a counterfeit coin detector applied to the two-Euro case. The detection process is based on the short distance image acquisition capabilities of the optical mouse sensor where partial images of the coin under analysis are compared with some partial reference coin images for matching. Results show that, using only the vision sense, the counterfeit acceptance and rejection rates are very similar to those of a trained user and better than those of an untrained user. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessArticle Image-Based Airborne Sensors: A Combined Approach for Spectral Signatures Classification through Deterministic Simulated Annealing
Sensors 2009, 9(9), 7132-7149; doi:10.3390/s90907132
Received: 31 July 2009 / Revised: 19 August 2009 / Accepted: 3 September 2009 / Published: 8 September 2009
Cited by 3 | PDF Full-text (380 KB) | HTML Full-text | XML Full-text
Abstract
The increasing technology of high-resolution image airborne sensors, including those on board Unmanned Aerial Vehicles, demands automatic solutions for processing, either on-line or off-line, the huge amountds of image data sensed during the flights. The classification of natural spectral signatures in images [...] Read more.
The increasing technology of high-resolution image airborne sensors, including those on board Unmanned Aerial Vehicles, demands automatic solutions for processing, either on-line or off-line, the huge amountds of image data sensed during the flights. The classification of natural spectral signatures in images is one potential application. The actual tendency in classification is oriented towards the combination of simple classifiers. In this paper we propose a combined strategy based on the Deterministic Simulated Annealing (DSA) framework. The simple classifiers used are the well tested supervised parametric Bayesian estimator and the Fuzzy Clustering. The DSA is an optimization approach, which minimizes an energy function. The main contribution of DSA is its ability to avoid local minima during the optimization process thanks to the annealing scheme. It outperforms simple classifiers used for the combination and some combined strategies, including a scheme based on the fuzzy cognitive maps and an optimization approach based on the Hopfield neural network paradigm. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle A Non-Intrusive GMA Welding Process Quality Monitoring System Using Acoustic Sensing
Sensors 2009, 9(9), 7150-7166; doi:10.3390/s90907150
Received: 3 June 2009 / Revised: 23 July 2009 / Accepted: 18 August 2009 / Published: 9 September 2009
Cited by 5 | PDF Full-text (996 KB) | HTML Full-text | XML Full-text
Abstract
Most of the inspection methods used for detection and localization of welding disturbances are based on the evaluation of some direct measurements of welding parameters. This direct measurement requires an insertion of sensors during the welding process which could somehow alter the [...] Read more.
Most of the inspection methods used for detection and localization of welding disturbances are based on the evaluation of some direct measurements of welding parameters. This direct measurement requires an insertion of sensors during the welding process which could somehow alter the behavior of the metallic transference. An inspection method that evaluates the GMA welding process evolution using a non-intrusive process sensing would allow not only the identification of disturbances during welding runs and thus reduce inspection time, but would also reduce the interference on the process caused by the direct sensing. In this paper a nonintrusive method for weld disturbance detection and localization for weld quality evaluation is demonstrated. The system is based on the acoustic sensing of the welding electrical arc. During repetitive tests in welds without disturbances, the stability acoustic parameters were calculated and used as comparison references for the detection and location of disturbances during the weld runs. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Prediction of Force Measurements of a Microbend Sensor Based on an Artificial Neural Network
Sensors 2009, 9(9), 7167-7176; doi:10.3390/s90907167
Received: 27 July 2009 / Revised: 31 August 2009 / Accepted: 3 September 2009 / Published: 9 September 2009
Cited by 8 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
Artificial neural network (ANN) based prediction of the response of a microbend fiber optic sensor is presented. To the best of our knowledge no similar work has been previously reported in the literature. Parallel corrugated plates with three deformation cycles, 6 mm [...] Read more.
Artificial neural network (ANN) based prediction of the response of a microbend fiber optic sensor is presented. To the best of our knowledge no similar work has been previously reported in the literature. Parallel corrugated plates with three deformation cycles, 6 mm thickness of the spacer material and 16 mm mechanical periodicity between deformations were used in the microbend sensor. Multilayer Perceptron (MLP) with different training algorithms, Radial Basis Function (RBF) network and General Regression Neural Network (GRNN) are used as ANN models in this work. All of these models can predict the sensor responses with considerable errors. RBF has the best performance with the smallest mean square error (MSE) values of training and test results. Among the MLP algorithms and GRNN the Levenberg-Marquardt algorithm has good results. These models successfully predict the sensor responses, hence ANNs can be used as useful tool in the design of more robust fiber optic sensors. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Game and Balance Multicast Architecture Algorithms for Sensor Grid
Sensors 2009, 9(9), 7177-7202; doi:10.3390/s90907177
Received: 20 June 2009 / Accepted: 18 August 2009 / Published: 9 September 2009
Cited by 4 | PDF Full-text (396 KB) | HTML Full-text | XML Full-text
Abstract
We propose a scheme to attain shorter multicast delay and higher efficiency in the data transfer of sensor grid. Our scheme, in one cluster, seeks the central node, calculates the space and the data weight vectors. Then we try to find a [...] Read more.
We propose a scheme to attain shorter multicast delay and higher efficiency in the data transfer of sensor grid. Our scheme, in one cluster, seeks the central node, calculates the space and the data weight vectors. Then we try to find a new vector composed by linear combination of the two old ones. We use the equal correlation coefficient between the new and old vectors to find the point of game and balance of the space and data factorsbuild a binary simple equation, seek linear parameters, and generate a least weight path tree. We handled the issue from a quantitative way instead of a qualitative way. Based on this idea, we considered the scheme from both the space and data factor, then we built the mathematic model, set up game and balance relationship and finally resolved the linear indexes, according to which we improved the transmission efficiency of sensor grid. Extended simulation results indicate that our scheme attains less average multicast delay and number of links used compared with other well-known existing schemes. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Thick-Film Carbon Dioxide Sensor via Anodic Adsorbate Stripping Technique and Its Structural Dependence
Sensors 2009, 9(9), 7203-7216; doi:10.3390/s90907203
Received: 30 July 2009 / Revised: 27 August 2009 / Accepted: 31 August 2009 / Published: 9 September 2009
Cited by 4 | PDF Full-text (560 KB) | HTML Full-text | XML Full-text
Abstract
A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the [...] Read more.
A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the platinum nanoparticles. The sensing output was linearly related to the CO2 presented. Stability measurements demonstrated that the decline of the active surface area and the sensitivity of the sensor were 8% and 13%, respectively, over a two week period of time. The sensor response appeared to be a structural dependence of the crystallographic orientation of platinum electrode. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Sensing Landscape History with an Interactive Location Based Service
Sensors 2009, 9(9), 7217-7233; doi:10.3390/s90907217
Received: 4 August 2009 / Revised: 4 September 2009 / Accepted: 8 September 2009 / Published: 9 September 2009
Cited by 4 | PDF Full-text (727 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces the STEAD approach for interpreting data acquired by a “human sensor”, who uses an informal interactive location-based service (iLBS) to sense cultural-historic facts and anecdotes of, and in the landscape. This user-generated data is collected outdoors and in situ [...] Read more.
This paper introduces the STEAD approach for interpreting data acquired by a “human sensor”, who uses an informal interactive location-based service (iLBS) to sense cultural-historic facts and anecdotes of, and in the landscape. This user-generated data is collected outdoors and in situ. The approach consists of four related facets (who, what, where, when). Three of the four facets are discussed and illustrated by user generated data collected during a Dutch survey in 2008. These data represent the personal cultural-historic knowledge and anecdotes of 150 people using a customized iLBS for experiencing the cultural history of a landscape. The “who” facet shows three dominant mentality groups (cosmopolitans, modern materialists and post modern hedonists) that generated user content. The “what” facet focuses on three subject types of pictures and four picture framing classes. Pictures of the place type showed to be dominant and foreground framing class was slightly favourite. The “where” facet is explored via density, distribution, and distance of the pictures made. The illustrations of the facets indirectly show the role of the “human sensor” with respect to the domain of interest. The STEAD approach needs further development of the when-facet and of the relations between the four facets. Finally the results of the approach may support data archives of iLBS applications. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
Open AccessArticle Detection and Classification of Human Body Odor Using an Electronic Nose
Sensors 2009, 9(9), 7234-7249; doi:10.3390/s90907234
Received: 24 June 2009 / Revised: 19 August 2009 / Accepted: 3 September 2009 / Published: 9 September 2009
Cited by 42 | PDF Full-text (563 KB) | HTML Full-text | XML Full-text
Abstract
An electronic nose (E-nose) has been designed and equipped with software that can detect and classify human armpit body odor. An array of metal oxide sensors was used for detecting volatile organic compounds. The measurement circuit employs a voltage divider resistor to [...] Read more.
An electronic nose (E-nose) has been designed and equipped with software that can detect and classify human armpit body odor. An array of metal oxide sensors was used for detecting volatile organic compounds. The measurement circuit employs a voltage divider resistor to measure the sensitivity of each sensor. This E-nose was controlled by in-house developed software through a portable USB data acquisition card with a principle component analysis (PCA) algorithm implemented for pattern recognition and classification. Because gas sensor sensitivity in the detection of armpit odor samples is affected by humidity, we propose a new method and algorithms combining hardware/software for the correction of the humidity noise. After the humidity correction, the E-nose showed the capability of detecting human body odor and distinguishing the body odors from two persons in a relative manner. The E-nose is still able to recognize people, even after application of deodorant. In conclusion, this is the first report of the application of an E-nose for armpit odor recognition. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle Bistatic Radar Configuration for Soil Moisture Retrieval: Analysis of the Spatial Coverage
Sensors 2009, 9(9), 7250-7265; doi:10.3390/s90907250
Received: 21 August 2009 / Revised: 8 September 2009 / Accepted: 9 September 2009 / Published: 10 September 2009
Cited by 4 | PDF Full-text (444 KB) | HTML Full-text | XML Full-text
Abstract
Some outcomes of a feasibility analysis of a spaceborne bistatic radar mission for soil moisture retrieval are presented in this paper. The study starts from the orbital design of the configuration suitable for soil moisture estimation identified in a previous study. This [...] Read more.
Some outcomes of a feasibility analysis of a spaceborne bistatic radar mission for soil moisture retrieval are presented in this paper. The study starts from the orbital design of the configuration suitable for soil moisture estimation identified in a previous study. This configuration is refined according to the results of an analysis of the spatial resolution. The paper focuses on the assessment of the spatial coverage i.e., on the verification that an adequate overlap between the footprints of the antennas is ensured and on the duty cycle, that is the fraction of orbital period during which the bistatic data are acquired. A non-cooperating system is considered, in which the transmitter is the C-band Advanced Synthetic Aperture Radar aboard Envisat. The best performances in terms of duty cycle are achieved if the transmitter operates in Wide Swath Mode. The higher resolution Image Swath Modes that comply with the selected configuration have a duty cycle that is never less than 12% and can exceed 21%. When Envisat operates in Wide Swath Mode, the bistatic system covers a wide latitude range across the equator, while in some of the Image Swath Modes, the bistatic measurements, collected from the same orbit, cover mid-latitude areas. In the latter case, it might be possible to achieve full coverage in an Envisat orbit repeat cycle, while, for a very large latitude range such as that covered in Wide Swath Mode, bistatic acquisitions could be obtained over about 65% of the area. Full article
(This article belongs to the Special Issue Sensor Configuration and Smart Sensors)
Open AccessArticle A Hybrid Adaptive Routing Algorithm for Event-Driven Wireless Sensor Networks
Sensors 2009, 9(9), 7287-7307; doi:10.3390/s90907287
Received: 22 July 2009 / Revised: 27 August 2009 / Accepted: 7 September 2009 / Published: 10 September 2009
Cited by 11 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
Routing is a basic function in wireless sensor networks (WSNs). For these networks, routing algorithms depend on the characteristics of the applications and, consequently, there is no self-contained algorithm suitable for every case. In some scenarios, the network behavior (traffic load) may [...] Read more.
Routing is a basic function in wireless sensor networks (WSNs). For these networks, routing algorithms depend on the characteristics of the applications and, consequently, there is no self-contained algorithm suitable for every case. In some scenarios, the network behavior (traffic load) may vary a lot, such as an event-driven application, favoring different algorithms at different instants. This work presents a hybrid and adaptive algorithm for routing in WSNs, called Multi-MAF, that adapts its behavior autonomously in response to the variation of network conditions. In particular, the proposed algorithm applies both reactive and proactive strategies for routing infrastructure creation, and uses an event-detection estimation model to change between the strategies and save energy. To show the advantages of the proposed approach, it is evaluated through simulations. Comparisons with independent reactive and proactive algorithms show improvements on energy consumption. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle Hazardous Odor Recognition by CMAC Based Neural Networks
Sensors 2009, 9(9), 7308-7319; doi:10.3390/s90907308
Received: 1 July 2009 / Revised: 19 August 2009 / Accepted: 3 September 2009 / Published: 11 September 2009
Cited by 7 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
Electronic noses are being developed as systems for the automated detection and classification of odors, vapors, and gases. Artificial neural networks (ANNs) have been used to analyze complex data and to recognize patterns, and have shown promising results in recognition of volatile [...] Read more.
Electronic noses are being developed as systems for the automated detection and classification of odors, vapors, and gases. Artificial neural networks (ANNs) have been used to analyze complex data and to recognize patterns, and have shown promising results in recognition of volatile compounds and odors in electronic nose applications. When an ANN is combined with a sensor array, the number of detectable chemicals is generally greater than the number of unique sensor types. The odor sensing system should be extended to new areas since its standard style where the output pattern from multiple sensors with partially overlapped specificity is recognized by a neural network or multivariate analysis. This paper describes the design, implementation and performance evaluations of the application developed for hazardous odor recognition using Cerebellar Model Articulation Controller (CMAC) based neural networks. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Power Conservation through Energy Efficient Routing in Wireless Sensor Networks
Sensors 2009, 9(9), 7320-7342; doi:10.3390/s90907320
Received: 10 August 2009 / Revised: 9 September 2009 / Accepted: 10 September 2009 / Published: 11 September 2009
Cited by 37 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
The power awareness issue is the primary concern within the domain of Wireless Sensor Networks (WSNs). Most power dissipation ocurrs during communication, thus routing protocols in WSNs mainly aim at power conservation. Moreover, a routing protocol should be scalable, so that its [...] Read more.
The power awareness issue is the primary concern within the domain of Wireless Sensor Networks (WSNs). Most power dissipation ocurrs during communication, thus routing protocols in WSNs mainly aim at power conservation. Moreover, a routing protocol should be scalable, so that its effectiveness does not degrade as the network size increases. In response to these issues, this work describes the development of an efficient routing protocol, named SHPER (Scaling Hierarchical Power Efficient Routing). Full article
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Open AccessArticle Estimation of Parameters Obtained by Electrochemical Impedance Spectroscopy on Systems Containing High Capacities
Sensors 2009, 9(9), 7365-7373; doi:10.3390/s90907365
Received: 29 July 2009 / Revised: 3 September 2009 / Accepted: 7 September 2009 / Published: 11 September 2009
Cited by 7 | PDF Full-text (382 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Electrochemical systems with high capacities demand devices for electrochemical impedance spectroscopy (EIS) with ultra-low frequencies (in order of mHz), that are almost impossible to accomplish with analogue techniques, but this becomes possible by using a computer technique and accompanying digital equipment. Recently, [...] Read more.
Electrochemical systems with high capacities demand devices for electrochemical impedance spectroscopy (EIS) with ultra-low frequencies (in order of mHz), that are almost impossible to accomplish with analogue techniques, but this becomes possible by using a computer technique and accompanying digital equipment. Recently, an original software and hardware for electrochemical measurements, intended for electrochemical systems exhibiting high capacities, such as supercapacitors, has been developed. One of the included methods is EIS. In this paper, the method of calculation of circuit parameters from an EIS curve is described. The results of testing on a physical model of an electrochemical system, constructed of known elements (including a 1.6 F capacitor) in a defined arrangement, proved the validity of the system and the method. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Modelling and Calibration Technique of Laser Triangulation Sensors for Integration in Robot Arms and Articulated Arm Coordinate Measuring Machines
Sensors 2009, 9(9), 7374-7396; doi:10.3390/s90907374
Received: 14 July 2009 / Revised: 9 September 2009 / Accepted: 10 September 2009 / Published: 11 September 2009
Cited by 17 | PDF Full-text (1115 KB) | HTML Full-text | XML Full-text
Abstract
A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of [...] Read more.
A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of a single calibration gauge object, a one-step calibration method to obtain both intrinsic―laser plane, CCD sensor and camera geometry―and extrinsic parameters related to the AACMM main frame has been developed. This allows the integration of LTS and AACMM mathematical models without the need of additional optimization methods after the prior sensor calibration, usually done in a coordinate measuring machine (CMM) before the assembly of the sensor in the arm. The experimental tests results for accuracy and repeatability show the suitable performance of this technique, resulting in a reliable, quick and friendly calibration method for the AACMM final user. The presented method is also valid for sensor integration in robot arms and CMMs. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
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Open AccessArticle Chalcogenide Glass Optical Waveguides for Infrared Biosensing
Sensors 2009, 9(9), 7398-7411; doi:10.3390/s90907398
Received: 8 July 2009 / Revised: 4 September 2009 / Accepted: 8 September 2009 / Published: 15 September 2009
Cited by 52 | PDF Full-text (609 KB) | HTML Full-text | XML Full-text
Abstract
Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the [...] Read more.
Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 μm wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio)sensors. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle A Real-Time Smart Sensor for High-Resolution Frequency Estimation in Power Systems
Sensors 2009, 9(9), 7412-7429; doi:10.3390/s90907412
Received: 2 July 2009 / Revised: 9 September 2009 / Accepted: 14 September 2009 / Published: 15 September 2009
Cited by 21 | PDF Full-text (419 KB) | HTML Full-text | XML Full-text
Abstract
Power quality monitoring is a theme in vogue and accurate frequency measurement of the power line is a major issue. This problem is particularly relevant for power generating systems since the generated signal must comply with restrictive standards. The novelty of this [...] Read more.
Power quality monitoring is a theme in vogue and accurate frequency measurement of the power line is a major issue. This problem is particularly relevant for power generating systems since the generated signal must comply with restrictive standards. The novelty of this work is the development of a smart sensor for real-time high-resolution frequency measurement in accordance with international standards for power quality monitoring. The proposed smart sensor utilizes commercially available current clamp, hall-effect sensor or resistor as primary sensor. The signal processing is carried out through the chirp z-transform. Simulations and experimental results show the efficiency of the proposed smart sensor. Full article
(This article belongs to the Special Issue Sensor Configuration and Smart Sensors)
Open AccessArticle A Capacitive Humidity Sensor Based on Multi-Wall Carbon Nanotubes (MWCNTs)
Sensors 2009, 9(9), 7431-7444; doi:10.3390/s90907431
Received: 29 June 2009 / Revised: 11 August 2009 / Accepted: 24 August 2009 / Published: 16 September 2009
Cited by 26 | PDF Full-text (485 KB) | HTML Full-text | XML Full-text
Abstract
A new type of capacitive humidity sensor is introduced in this paper. The sensor consists of two plate electrodes coated with MWCNT films and four pieces of isolating medium at the four corners of the sensor. According to capillary condensation, the capacitance [...] Read more.
A new type of capacitive humidity sensor is introduced in this paper. The sensor consists of two plate electrodes coated with MWCNT films and four pieces of isolating medium at the four corners of the sensor. According to capillary condensation, the capacitance signal of the sensor is sensitive to relative humidity (RH), which could be transformed to voltage signal by a capacitance to voltage converter circuit. The sensor is tested using different saturated saline solutions at the ambient temperature of 25 °C, which yielded approximately 11% to 97% RH, respectively. The function of the MWCNT films, the effect of electrode distance, the temperature character and the repeatability of the sensor are discussed in this paper. Full article
Open AccessArticle Neuro-Genetic Optimization of the Diffuser Elements for Applications in a Valveless Diaphragm Micropumps System
Sensors 2009, 9(9), 7481-7497; doi:10.3390/s90907481
Received: 11 June 2009 / Revised: 5 August 2009 / Accepted: 31 August 2009 / Published: 18 September 2009
Cited by 8 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a hybridized neuro-genetic optimization methodology realized by embedding numerical simulations trained artificial neural networks (ANN) into a genetic algorithm (GA) is used to optimize the flow rectification efficiency of the diffuser element for a valveless diaphragm micropump application. A [...] Read more.
In this study, a hybridized neuro-genetic optimization methodology realized by embedding numerical simulations trained artificial neural networks (ANN) into a genetic algorithm (GA) is used to optimize the flow rectification efficiency of the diffuser element for a valveless diaphragm micropump application. A higher efficiency ratio of the diffuser element consequently yields a higher flow rate for the micropump. For that purpose, optimization of the diffuser element is essential to determine the maximum pumping rate that the micropump is able to generate. Numerical simulations are initially carried out using CoventorWare® to analyze the effects of varying parameters such as diffuser angle, Reynolds number and aspect ratio on the volumetric flow rate of the micropump. A limited range of simulation results will then be used to train the neural network via back-propagation algorithm and optimization process commence subsequently by embedding the trained ANN results as a fitness function into GA. The objective of the optimization is to maximize the efficiency ratio of the diffuser element for the range of parameters investigated. The optimized efficiency ratio obtained from the neuro-genetic optimization is 1.38, which is higher than any of the maximum efficiency ratio attained from the overall parametric studies, establishing the superiority of the optimization method. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Platform for a Hydrocarbon Exhaust Gas Sensor Utilizing a Pumping Cell and a Conductometric Sensor
Sensors 2009, 9(9), 7498-7508; doi:10.3390/s90907498
Received: 5 August 2009 / Revised: 15 September 2009 / Accepted: 18 September 2009 / Published: 18 September 2009
Cited by 2 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the [...] Read more.
Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle A Wavelet Neural Network for SAR Image Segmentation
Sensors 2009, 9(9), 7509-7515; doi:10.3390/s90907509
Received: 29 July 2009 / Revised: 9 September 2009 / Accepted: 12 September 2009 / Published: 22 September 2009
Cited by 3 | PDF Full-text (404 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a wavelet neural network (WNN) for SAR image segmentation by combining the wavelet transform and an artificial neural network. The WNN combines the multiscale analysis ability of the wavelet transform and the classification capability of the artificial neural network [...] Read more.
This paper proposes a wavelet neural network (WNN) for SAR image segmentation by combining the wavelet transform and an artificial neural network. The WNN combines the multiscale analysis ability of the wavelet transform and the classification capability of the artificial neural network by setting the wavelet function as the transfer function of the neural network. Several SAR images are segmented by the network whose transfer functions are the Morlet and Mexihat functions, respectively. The experimental results show the proposed method is very effective and accurate. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Remote-Sensing Image Classification Based on an Improved Probabilistic Neural Network
Sensors 2009, 9(9), 7516-7539; doi:10.3390/s90907516
Received: 12 June 2009 / Revised: 2 September 2009 / Accepted: 16 September 2009 / Published: 23 September 2009
Cited by 21 | PDF Full-text (2211 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a hybrid classifier for polarimetric SAR images. The feature sets consist of span image, the H/A/α decomposition, and the GLCM-based texture features. Then, a probabilistic neural network (PNN) was adopted for classification, and a novel algorithm proposed to enhance [...] Read more.
This paper proposes a hybrid classifier for polarimetric SAR images. The feature sets consist of span image, the H/A/α decomposition, and the GLCM-based texture features. Then, a probabilistic neural network (PNN) was adopted for classification, and a novel algorithm proposed to enhance its performance. Principle component analysis (PCA) was chosen to reduce feature dimensions, random division to reduce the number of neurons, and Brent’s search (BS) to find the optimal bias values. The results on San Francisco and Flevoland sites are compared to that using a 3-layer BPNN to demonstrate the validity of our algorithm in terms of confusion matrix and overall accuracy. In addition, the importance of each improvement of the algorithm was proven. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
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Open AccessArticle Detecting Proteins in Highly Autofluorescent Cells Using Quantum Dot Antibody Conjugates
Sensors 2009, 9(9), 7540-7549; doi:10.3390/s90907540
Received: 3 August 2009 / Revised: 10 September 2009 / Accepted: 22 September 2009 / Published: 23 September 2009
Cited by 8 | PDF Full-text (1302 KB) | HTML Full-text | XML Full-text
Abstract
We have applied quantum dot (Qdot) antibody conjugates as a biomolecular probe for cellular proteins important in biogeochemical cycling in the sea. Conventional immunological methods have been hampered by the strong autofluorescence found in cyanobacteria cells. Qdot conjugates provide an ideal alternative [...] Read more.
We have applied quantum dot (Qdot) antibody conjugates as a biomolecular probe for cellular proteins important in biogeochemical cycling in the sea. Conventional immunological methods have been hampered by the strong autofluorescence found in cyanobacteria cells. Qdot conjugates provide an ideal alternative for studies that require long-term imaging of cells such as detection of low abundance cellular antigens by fluorescence microscopy. The advantage of Qdot labeled probes over conventional immunological methods is the photostability of the probe. Phycoerythrin bleaches in cyanobacterial cells under prolonged UV or blue light excitation, which means that the semiconducting nanocrystal probe, the Qdot, can yield a strong fluorescent signal without interference from cellular pigments. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
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Open AccessArticle Precise 3D Lug Pose Detection Sensor for Automatic Robot Welding Using a Structured-Light Vision System
Sensors 2009, 9(9), 7550-7565; doi:10.3390/s90907550
Received: 21 July 2009 / Revised: 9 September 2009 / Accepted: 22 September 2009 / Published: 23 September 2009
Cited by 11 | PDF Full-text (1265 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we propose a precise 3D lug pose detection sensor for automatic robot welding of a lug to a huge steel plate used in shipbuilding, where the lug is a handle to carry the huge steel plate. The proposed sensor [...] Read more.
In this study, we propose a precise 3D lug pose detection sensor for automatic robot welding of a lug to a huge steel plate used in shipbuilding, where the lug is a handle to carry the huge steel plate. The proposed sensor consists of a camera and four laser line diodes, and its design parameters are determined by analyzing its detectable range and resolution. For the lug pose acquisition, four laser lines are projected on both lug and plate, and the projected lines are detected by the camera. For robust detection of the projected lines against the illumination change, the vertical threshold, thinning, Hough transform and separated Hough transform algorithms are successively applied to the camera image. The lug pose acquisition is carried out by two stages: the top view alignment and the side view alignment. The top view alignment is to detect the coarse lug pose relatively far from the lug, and the side view alignment is to detect the fine lug pose close to the lug. After the top view alignment, the robot is controlled to move close to the side of the lug for the side view alignment. By this way, the precise 3D lug pose can be obtained. Finally, experiments with the sensor prototype are carried out to verify the feasibility and effectiveness of the proposed sensor. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Multi-Unmanned Aerial Vehicle (UAV) Cooperative Fault Detection Employing Differential Global Positioning (DGPS), Inertial and Vision Sensors
Sensors 2009, 9(9), 7566-7579; doi:10.3390/s90907566
Received: 26 August 2009 / Revised: 14 September 2009 / Accepted: 21 September 2009 / Published: 24 September 2009
Cited by 23 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a method to increase the reliability of Unmanned Aerial Vehicle (UAV) sensor Fault Detection and Identification (FDI) in a multi-UAV context. Differential Global Positioning System (DGPS) and inertial sensors are used for sensor FDI in each UAV. The method [...] Read more.
This paper presents a method to increase the reliability of Unmanned Aerial Vehicle (UAV) sensor Fault Detection and Identification (FDI) in a multi-UAV context. Differential Global Positioning System (DGPS) and inertial sensors are used for sensor FDI in each UAV. The method uses additional position estimations that augment individual UAV FDI system. These additional estimations are obtained using images from the same planar scene taken from two different UAVs. Since accuracy and noise level of the estimation depends on several factors, dynamic replanning of the multi-UAV team can be used to obtain a better estimation in case of faults caused by slow growing errors of absolute position estimation that cannot be detected by using local FDI in the UAVs. Experimental results with data from two real UAVs are also presented. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)

Review

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Open AccessReview Dendritic Cells as Danger-Recognizing Biosensors
Sensors 2009, 9(9), 6730-6751; doi:10.3390/s90906730
Received: 2 July 2009 / Revised: 19 August 2009 / Accepted: 24 August 2009 / Published: 27 August 2009
Cited by 6 | PDF Full-text (1622 KB) | HTML Full-text | XML Full-text
Abstract
Dendritic cells (DCs) are antigen presenting cells that are characterized by a potent capacity to initiate immune responses. DCs comprise several subsets with distinct phenotypes. After sensing any danger(s) to the host via their innate immune receptors such as Toll-like receptors, DCs [...] Read more.
Dendritic cells (DCs) are antigen presenting cells that are characterized by a potent capacity to initiate immune responses. DCs comprise several subsets with distinct phenotypes. After sensing any danger(s) to the host via their innate immune receptors such as Toll-like receptors, DCs become mature and subsequently present antigens to CD4+ T cells. Since DCs possess the intrinsic capacity to polarize CD4+ helper cells, it is critical to understand the immunological roles of DCs for clinical applications. Here, we review the different DC subsets, their danger-sensing receptors and immunological functions. Furthermore, the cytokine reporter mouse model for studying DC activation is introduced. Full article
(This article belongs to the Special Issue Dendritic Sensors: From Dendrimer Molecules to Dendritic Cells)
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Open AccessReview An Overview on Wireless Sensor Networks Technology and Evolution
Sensors 2009, 9(9), 6869-6896; doi:10.3390/s90906869
Received: 25 July 2009 / Revised: 24 August 2009 / Accepted: 25 August 2009 / Published: 31 August 2009
Cited by 139 | PDF Full-text (455 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSNs) enable new applications and require non-conventional paradigms for protocol design due to several constraints. Owing to the requirement for low device complexity together with low energy consumption (i.e., long network lifetime), a proper balance between communication and signal/data [...] Read more.
Wireless sensor networks (WSNs) enable new applications and require non-conventional paradigms for protocol design due to several constraints. Owing to the requirement for low device complexity together with low energy consumption (i.e., long network lifetime), a proper balance between communication and signal/data processing capabilities must be found. This motivates a huge effort in research activities, standardization process, and industrial investments on this field since the last decade. This survey paper aims at reporting an overview of WSNs technologies, main applications and standards, features in WSNs design, and evolutions. In particular, some peculiar applications, such as those based on environmental monitoring, are discussed and design strategies highlighted; a case study based on a real implementation is also reported. Trends and possible evolutions are traced. Emphasis is given to the IEEE 802.15.4 technology, which enables many applications of WSNs. Some example of performance characteristics of 802.15.4-based networks are shown and discussed as a function of the size of the WSN and the data type to be exchanged among nodes. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessReview Gram-Negative Bacterial Sensors for Eukaryotic Signal Molecules
Sensors 2009, 9(9), 6967-6990; doi:10.3390/s90906967
Received: 8 June 2009 / Revised: 24 August 2009 / Accepted: 25 August 2009 / Published: 2 September 2009
Cited by 14 | PDF Full-text (272 KB) | HTML Full-text | XML Full-text
Abstract
Ample evidence exists showing that eukaryotic signal molecules synthesized and released by the host can activate the virulence of opportunistic pathogens. The sensitivity of prokaryotes to host signal molecules requires the presence of bacterial sensors. These prokaryotic sensors, or receptors, have a [...] Read more.
Ample evidence exists showing that eukaryotic signal molecules synthesized and released by the host can activate the virulence of opportunistic pathogens. The sensitivity of prokaryotes to host signal molecules requires the presence of bacterial sensors. These prokaryotic sensors, or receptors, have a double function: stereospecific recognition in a complex environment and transduction of the message in order to initiate bacterial physiological modifications. As messengers are generally unable to freely cross the bacterial membrane, they require either the presence of sensors anchored in the membrane or transporters allowing direct recognition inside the bacterial cytoplasm. Since the discovery of quorum sensing, it was established that the production of virulence factors by bacteria is tightly growth-phase regulated. It is now obvious that expression of bacterial virulence is also controlled by detection of the eukaryotic messengers released in the micro-environment as endocrine or neuro-endocrine modulators. In the presence of host physiological stress many eukaryotic factors are released and detected by Gram-negative bacteria which in return rapidly adapt their physiology. For instance, Pseudomonas aeruginosa can bind elements of the host immune system such as interferon-γ and dynorphin and then through quorum sensing circuitry enhance its virulence. Escherichia coli sensitivity to the neurohormones of the catecholamines family appears relayed by a recently identified bacterial adrenergic receptor. In the present review, we will describe the mechanisms by which various eukaryotic signal molecules produced by host may activate Gram-negative bacteria virulence. Particular attention will be paid to Pseudomonas, a genus whose representative species, P. aeruginosa, is a common opportunistic pathogen. The discussion will be particularly focused on the pivotal role played by these new types of pathogen sensors from the sensing to the transduction mechanism involved in virulence factors regulation. Finally, we will discuss the consequence of the impact of host signal molecules on commensally or opportunistic pathogens associated with different human tissue. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessReview Primary Cilia: Highly Sophisticated Biological Sensors
Sensors 2009, 9(9), 7003-7020; doi:10.3390/s90907003
Received: 2 July 2009 / Revised: 31 July 2009 / Accepted: 1 September 2009 / Published: 3 September 2009
Cited by 23 | PDF Full-text (374 KB) | HTML Full-text | XML Full-text
Abstract
Primary cilia, thin hair-like structures protruding from the apical surface of most mammalian cells, have gained the attention of many researchers over the past decade. Primary cilia are microtubule-filled sensory organelles that are enclosed within the ciliary membrane. They originate at the [...] Read more.
Primary cilia, thin hair-like structures protruding from the apical surface of most mammalian cells, have gained the attention of many researchers over the past decade. Primary cilia are microtubule-filled sensory organelles that are enclosed within the ciliary membrane. They originate at the cell surface from the mother centriole that becomes the mature basal body. In this review, we will discuss recent literatures on the roles of cilia as sophisticated sensory organelles. With particular emphasis on vascular endothelia and renal epithelia, the mechanosensory role of cilia in sensing fluid shear stress will be discussed. Also highlighted is the ciliary involvement in cell cycle regulation, development, cell signaling and cancer. Finally, primary cilia-related disorders will be briefly described. Full article
(This article belongs to the Section Biosensors)
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Open AccessReview On-Line Metrology with Conoscopic Holography: Beyond Triangulation
Sensors 2009, 9(9), 7021-7037; doi:10.3390/s90907021
Received: 23 July 2009 / Revised: 26 August 2009 / Accepted: 28 August 2009 / Published: 4 September 2009
Cited by 14 | PDF Full-text (1757 KB) | HTML Full-text | XML Full-text
Abstract
On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are [...] Read more.
On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are needed, and when there are difficult operating conditions. Other methods are, in general, not applicable in hostile environments or inadequate for on-line measurement. In this paper we review the latest research in Conoscopic Holography, an interferometric technique that has been applied successfully in this kind of applications, ranging from submicrometric roughness measurements, to long standoff sensors for surface defect detection in steel at high temperatures. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain)
Open AccessReview Escherichia coli, an Intestinal Microorganism, as a Biosensor for Quantification of Amino Acid Bioavailability
Sensors 2009, 9(9), 7038-7057; doi:10.3390/s90907038
Received: 2 June 2009 / Revised: 19 August 2009 / Accepted: 26 August 2009 / Published: 4 September 2009
Cited by 11 | PDF Full-text (537 KB) | HTML Full-text | XML Full-text
Abstract
In animal diets optimal amino acid quantities and balance among amino acids is of great nutritional importance. Essential amino acid deficiencies have negative impacts on animal physiology, most often expressed in sub-optimal body weight gains. Over supplementation of diets with amino acids [...] Read more.
In animal diets optimal amino acid quantities and balance among amino acids is of great nutritional importance. Essential amino acid deficiencies have negative impacts on animal physiology, most often expressed in sub-optimal body weight gains. Over supplementation of diets with amino acids is costly and can increase the nitrogen emissions from animals. Although in vivo animal assays for quantification of amino acid bioavailability are well established, Escherichia coli-based bioassays are viable potential alternatives in terms of accuracy, cost, and time input. E. coli inhabits the gastrointestinal tract and although more abundant in colon, a relatively high titer of E. coli can also be isolated from the small intestine, where primary absorption of amino acids and peptides occur. After feed proteins are digested, liberated amino acids and small peptides are assimilated by both the small intestine and E. coli. The similar pattern of uptake is a necessary prerequisite to establish E. coli cells as accurate amino acid biosensors. In fact, amino acid transporters in both intestinal and E. coli cells are stereospecific, delivering only the respective biological L-forms. The presence of free amino- and carboxyl groups is critical for amino acid and dipeptide transport in both biological subjects. Di-, tri- and tetrapeptides can enter enterocytes; likewise only di-, tri- and tetrapeptides support E. coli growth. These similarities in addition to the well known bacterial genetics make E. coli an optimal bioassay microorganism for the assessment of nutritionally available amino acids in feeds. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessReview Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications
Sensors 2009, 9(9), 7097-7110; doi:10.3390/s90907097
Received: 10 June 2009 / Revised: 27 August 2009 / Accepted: 29 August 2009 / Published: 7 September 2009
Cited by 15 | PDF Full-text (803 KB) | HTML Full-text | XML Full-text
Abstract
Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting [...] Read more.
Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because they allow the use of standard photo-lithographic processes, which reduces significantly the time required for sensor encapsulation and membrane deposition and the amount of manual work required for this, all items of importance for sensor mass production. Problems associated with the application of this kind of polymers in sensors are analysed and estimation of future trends in this field of research are presented. Full article
(This article belongs to the Special Issue ISFET Sensors)
Open AccessReview Ion-Sensitive Field-Effect Transistor for Biological Sensing
Sensors 2009, 9(9), 7111-7131; doi:10.3390/s90907111
Received: 4 August 2009 / Revised: 27 August 2009 / Accepted: 31 August 2009 / Published: 7 September 2009
Cited by 107 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text
Abstract
In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main [...] Read more.
In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main advances in this field over the past few years, explore its application prospects, and discuss the main issues, approaches, and challenges, with the aim of stimulating a broader interest in developing ISFET-based biosensors and extending their applications for reliable and sensitive analysis of various biomolecules such as DNA, proteins, enzymes, and cells. Full article
(This article belongs to the Special Issue ISFET Sensors)
Open AccessReview Semiconductor Quantum Dots in Chemical Sensors and Biosensors
Sensors 2009, 9(9), 7266-7286; doi:10.3390/s90907266
Received: 14 July 2009 / Revised: 3 September 2009 / Accepted: 8 September 2009 / Published: 10 September 2009
Cited by 174 | PDF Full-text (868 KB) | HTML Full-text | XML Full-text
Abstract
Quantum dots are nanometre-scale semiconductor crystals with unique optical properties that are advantageous for the development of novel chemical sensors and biosensors. The surface chemistry of luminescent quantum dots has encouraged the development of multiple probes based on linked recognition molecules such [...] Read more.
Quantum dots are nanometre-scale semiconductor crystals with unique optical properties that are advantageous for the development of novel chemical sensors and biosensors. The surface chemistry of luminescent quantum dots has encouraged the development of multiple probes based on linked recognition molecules such as peptides, nucleic acids or small-molecule ligands. This review overviews the design of sensitive and selective nanoprobes, ranging from the type of target molecules to the optical transduction scheme. Representative examples of quantum dot-based optical sensors from this fast-moving field have been selected and are discussed towards the most promising directions for future research. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessReview Nanomaterial-Assisted Signal Enhancement of Hybridization for DNA Biosensors: A Review
Sensors 2009, 9(9), 7343-7364; doi:10.3390/s90907343
Received: 28 July 2009 / Revised: 31 August 2009 / Accepted: 7 September 2009 / Published: 11 September 2009
Cited by 26 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
Detection of DNA sequences has received broad attention due to its potential applications in a variety of fields. As sensitivity of DNA biosensors is determined by signal variation of hybridization events, the signal enhancement is of great significance for improving the sensitivity [...] Read more.
Detection of DNA sequences has received broad attention due to its potential applications in a variety of fields. As sensitivity of DNA biosensors is determined by signal variation of hybridization events, the signal enhancement is of great significance for improving the sensitivity in DNA detection, which still remains a great challenge. Nanomaterials, which possess some unique chemical and physical properties caused by nanoscale effects, provide a new opportunity for developing novel nanomaterial-based signal-enhancers for DNA biosensors. In this review, recent progress concerning this field, including some newly-developed signal enhancement approaches using quantum-dots, carbon nanotubes and their composites reported by our group and other researchers are comprehensively summarized. Reports on signal enhancement of DNA biosensors by non-nanomaterials, such as enzymes and polymer reagents, are also reviewed for comparison. Furthermore, the prospects for developing DNA biosensors using nanomaterials as signal-enhancers in future are also indicated. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessReview The pH Response and Sensing Mechanism of n-Type ZnO/Electrolyte Interfaces
Sensors 2009, 9(9), 7445-7480; doi:10.3390/s90907445
Received: 26 August 2009 / Accepted: 9 September 2009 / Published: 16 September 2009
Cited by 24 | PDF Full-text (2269 KB) | HTML Full-text | XML Full-text
Abstract
Ever since the discovery of the pH-sensing properties of ZnO crystals, researchers have been exploring their potential in electrochemical applications. The recent expansion and availability of chemical modification methods has made it possible to generate a new class of electrochemically active ZnO [...] Read more.
Ever since the discovery of the pH-sensing properties of ZnO crystals, researchers have been exploring their potential in electrochemical applications. The recent expansion and availability of chemical modification methods has made it possible to generate a new class of electrochemically active ZnO nanorods. This reduction in size of ZnO (to a nanocrystalline form) using new growth techniques is essentially an example of the nanotechnology fabrication principle. The availability of these ZnO nanorods opens up an entire new and exciting research direction in the field of electrochemical sensing. This review covers the latest advances and mechanism of pH-sensing using ZnO nanorods, with an emphasis on the nano-interface mechanism. We discuss methods for calculating the effect of surface states on pH-sensing at a ZnO/electrolyte interface. All of these current research topics aim to explain the mechanism of pH-sensing using a ZnO bulk- or nano-scale single crystal. An important goal of these investigations is the translation of these nanotechnology-modified nanorods into potential novel applications. Full article
(This article belongs to the Special Issue Metal-Oxide Based Nanosensors)

Other

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Open AccessCorrection Qiu, R. et al. A Unified Multi-Functional Dynamic Spectrum Access Framework: Tutorial, Theory and Multi-GHzWideband Testbed. Sensors 2009, 9, 6530-6603
Sensors 2009, 9(9), 6835; doi:10.3390/s90906835
Received: 31 August 2009 / Accepted: 31 August 2009 / Published: 31 August 2009
Cited by 2 | PDF Full-text (84 KB) | HTML Full-text | XML Full-text
Abstract We found that the affiliation of author Vasu Chakravarthy was incorrect in our paper published in Sensors recently. [...] Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessCorrection Correction: Stević, Z. et al. Estimation of Parameters Obtained by Electrochemical Impedance Spectroscopy on Systems Containing High Capacities. Sensors 2009, 9, 7365-7373
Sensors 2009, 9(9), 7397; doi:10.3390/s90907397
Received: 14 September 2009 / Accepted: 14 September 2009 / Published: 14 September 2009
PDF Full-text (106 KB) | HTML Full-text | XML Full-text
Abstract In the original published version of this paper, the name and affiliation of the third coauthor was listed by mistake. [...] Full article
(This article belongs to the Section Chemical Sensors)
Open AccessCorrection Correction: Ramos-Pérez, I. et al. Calibration of Correlation Radiometers Using Pseudo-Random Noise Signals. Sensors 2009, 9, 6131-6149
Sensors 2009, 9(9), 7430; doi:10.3390/s90907430
Received: 15 September 2009 / Accepted: 15 September 2009 / Published: 15 September 2009
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Abstract It has come to our attention that in the original version of a paper published in Sensors recently, the names of four co-authors were misspelled with several hyphens missing. [...] Full article

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