Next Issue
Previous Issue

E-Mail Alert

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

Journal Browser

Journal Browser

Table of Contents

Sensors, Volume 7, Issue 12 (December 2007), Pages 3012-3559

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-34
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Influence of Damping on the Dynamical Behavior of the Electrostatic Parallel-plate and Torsional Actuators with Intermolecular Forces
Sensors 2007, 7(12), 3012-3026; doi:10.3390/s7123012
Received: 5 November 2007 / Accepted: 27 November 2007 / Published: 29 November 2007
Cited by 18 | PDF Full-text (324 KB) | HTML Full-text | XML Full-text
Abstract
The influence of damping on the dynamical behavior of the electrostaticparallel-plate and torsional actuators with the van der Waals (vdW) or Casimir force(torque) is presented. The values of the pull-in parameters and the number of theequilibrium points do not change whether there [...] Read more.
The influence of damping on the dynamical behavior of the electrostaticparallel-plate and torsional actuators with the van der Waals (vdW) or Casimir force(torque) is presented. The values of the pull-in parameters and the number of theequilibrium points do not change whether there is damping or not. The ability ofequilibrium points is varied with the appearance of damping. One equilibrium point is anunstable saddle with a different damping coefficient, the other equilibrium point is astable node when the damping coefficient is greater than some critical value, andotherwise it is a stable focus. Then there are two heteroclinic orbits passing from theunstable saddle point to the stable node or focus. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Reducing the Discrepancy Between ASTER and MODIS Land Surface Temperature Products
Sensors 2007, 7(12), 3043-3057; doi:10.3390/s7123043
Received: 25 October 2007 / Accepted: 2 December 2007 / Published: 4 December 2007
Cited by 19 | PDF Full-text (833 KB) | HTML Full-text | XML Full-text
Abstract
Human-induced global warming has significantly increased the importance ofsatellite monitoring of land surface temperature (LST) on a global scale. The MODerate-resolution Imaging Spectroradiometer (MODIS) provides a 1-km resolution LST productwith almost daily coverage of the Earth, invaluable to both local and global [...] Read more.
Human-induced global warming has significantly increased the importance ofsatellite monitoring of land surface temperature (LST) on a global scale. The MODerate-resolution Imaging Spectroradiometer (MODIS) provides a 1-km resolution LST productwith almost daily coverage of the Earth, invaluable to both local and global change studies.The Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) provides aLST product with a high spatial resolution of 90-m and a 16-day recurrent cycle,simultaneously acquired at the same height and nadir view as MODIS. ASTER andMODIS are complementary in resolution, offering a unique opportunity for scale-relatedstudies. ASTER and MODIS LST have been widely used but the errors in LST were mostlydisregarded. Correction of ASTER-to-MODIS LST discrepancies is essential for studiesreliant upon the joint use of these sensors. In this study, we compared three correctionapproaches: the Wan et al.’s approach, the refined Wan et al.’s approach, and thegeneralized split window (GSW) algorithm based approach. The Wan et al.’s approachcorrects the MODIS 1-km LST using MODIS 5-km LST. The refined approach modifiesthe Wan et al.’s approach through incorporating ASTER emissivity and MODIS 5-km data.The GSW algorithm approach does not use MODIS 5-km but only ASTER emissivity data. We examined the case over a semi-arid terrain area for the part of the Loess Plateau of China. All the approaches reduced the ASTER-to-MODIS LST discrepancy effectively. With terrain correction, the original ASTER-to-MODIS LST difference reduced from 2.7±1.28 K to -0.1±1.87 K for the Wan et al.’s approach, 0.2±1.57 K for the refined approach, and 0.1±1.33 K for the GSW algorithm based approach. Among all the approaches, the GSW algorithm based approach performed best in terms of mean, standard deviation, root mean square root, and correlation coefficient. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Development of a Space-charge-sensing System
Sensors 2007, 7(12), 3058-3070; doi:10.3390/s7123058
Received: 21 October 2007 / Accepted: 30 November 2007 / Published: 4 December 2007
Cited by 4 | PDF Full-text (917 KB) | HTML Full-text | XML Full-text
Abstract
A system for remotely measuring the distribution of air space charge in real time is developed. The system consists of a loudspeaker and an electric field antenna. By propagating a burst of directional sound wave from the speaker, a modulation in the [...] Read more.
A system for remotely measuring the distribution of air space charge in real time is developed. The system consists of a loudspeaker and an electric field antenna. By propagating a burst of directional sound wave from the speaker, a modulation in the space charge and, therefore, an electric field change at ground is produced. The distribution of the space charge density is derived from the E-field change which can be measured by the E- field antenna. The developed system has been confirmed by both laboratory and field experiments. Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
Open AccessCommunication Three Cavity Tunable MEMS Fabry Perot Interferometer
Sensors 2007, 7(12), 3071-3083; doi:10.3390/s7123071
Received: 25 October 2007 / Accepted: 29 November 2007 / Published: 4 December 2007
Cited by 2 | PDF Full-text (362 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a four-mirror tunable micro electro-mechanical systems (MEMS)Fabry Perot Interferometer (FPI) concept is proposed with the mathematical model. Thespectral range of the proposed FPI lies in the infrared spectrum ranging from 2400 to 4018(nm). FPI can be finely tuned by [...] Read more.
In this paper a four-mirror tunable micro electro-mechanical systems (MEMS)Fabry Perot Interferometer (FPI) concept is proposed with the mathematical model. Thespectral range of the proposed FPI lies in the infrared spectrum ranging from 2400 to 4018(nm). FPI can be finely tuned by deflecting the two middle mirrors (or by changing the threecavity lengths). Two different cases were separately considered for the tuning. In case one,tuning was achieved by deflecting mirror 2 only and in case two, both mirrors 2 and 3 weredeflected for the tuning of the FPI. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Animals as Mobile Biological Sensors for Forest Fire Detection
Sensors 2007, 7(12), 3084-3099; doi:10.3390/s7123084
Received: 7 November 2007 / Accepted: 3 December 2007 / Published: 4 December 2007
Cited by 17 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a mobile biological sensor system that can assist in earlydetection of forest fires one of the most dreaded natural disasters on the earth. The main ideapresented in this paper is to utilize animals with sensors as Mobile Biological Sensors(MBS). [...] Read more.
This paper proposes a mobile biological sensor system that can assist in earlydetection of forest fires one of the most dreaded natural disasters on the earth. The main ideapresented in this paper is to utilize animals with sensors as Mobile Biological Sensors(MBS). The devices used in this system are animals which are native animals living inforests, sensors (thermo and radiation sensors with GPS features) that measure thetemperature and transmit the location of the MBS, access points for wireless communicationand a central computer system which classifies of animal actions. The system offers twodifferent methods, firstly: access points continuously receive data about animals’ locationusing GPS at certain time intervals and the gathered data is then classified and checked tosee if there is a sudden movement (panic) of the animal groups: this method is called animalbehavior classification (ABC). The second method can be defined as thermal detection(TD): the access points get the temperature values from the MBS devices and send the datato a central computer to check for instant changes in the temperatures. This system may beused for many purposes other than fire detection, namely animal tracking, poachingprevention and detecting instantaneous animal death. Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
Open AccessArticle Fiber Optic Sensors For Detection of Toxic and Biological Threats
Sensors 2007, 7(12), 3100-3118; doi:10.3390/s7123100
Received: 2 October 2007 / Accepted: 29 November 2007 / Published: 4 December 2007
Cited by 44 | PDF Full-text (696 KB) | HTML Full-text | XML Full-text
Abstract
Protection of public and military personnel from chemical and biological warfareagents is an urgent and growing national security need. Along with this idea, we havedeveloped a novel class of fiber optic chemical sensors, for detection of toxic and biologicalmaterials. The design of [...] Read more.
Protection of public and military personnel from chemical and biological warfareagents is an urgent and growing national security need. Along with this idea, we havedeveloped a novel class of fiber optic chemical sensors, for detection of toxic and biologicalmaterials. The design of these fiber optic sensors is based on a cladding modificationapproach. The original passive cladding of the fiber, in a small section, was removed and thefiber core was coated with a chemical sensitive material. Any change in the opticalproperties of the modified cladding material, due to the presence of a specific chemicalvapor, changes the transmission properties of the fiber and result in modal powerredistribution in multimode fibers. Both total intensity and modal power distribution (MPD)measurements were used to detect the output power change through the sensing fibers. TheMPD technique measures the power changes in the far field pattern, i.e. spatial intensitymodulation in two dimensions. Conducting polymers, such as polyaniline and polypyrrole,have been reported to undergo a reversible change in conductivity upon exposure tochemical vapors. It is found that the conductivity change is accompanied by optical propertychange in the material. Therefore, polyaniline and polypyrrole were selected as the modifiedcladding material for the detection of hydrochloride (HCl), ammonia (NH3), hydrazine(H4N2), and dimethyl-methl-phosphonate (DMMP) {a nerve agent, sarin stimulant},respectively. Several sensors were prepared and successfully tested. The results showeddramatic improvement in the sensor sensitivity, when the MPD method was applied. In thispaper, an overview on the developed class of fiber optic sensors is presented and supportedwith successful achieved results. Full article
Open AccessArticle Lanthanide Recognition: an Asymetric Erbium Microsensor Based on a Hydrazone Derivative
Sensors 2007, 7(12), 3119-3135; doi:10.3390/s7123119
Received: 9 August 2007 / Accepted: 25 October 2007 / Published: 5 December 2007
Cited by 77 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text
Abstract
N'-(2-hydroxy-1,2-diphenylethylidene)benzohydrazide (HDB) was found tohave a very selective and sensitive behavior towards erbium(III) ions, in comparison tothirteen lanthanide ions, inner transition and representative metal ions and was hence usedas a neutral ion carrier in construction of an Er(III) microelectrode. Theoretical calculationsand conductance [...] Read more.
N'-(2-hydroxy-1,2-diphenylethylidene)benzohydrazide (HDB) was found tohave a very selective and sensitive behavior towards erbium(III) ions, in comparison tothirteen lanthanide ions, inner transition and representative metal ions and was hence usedas a neutral ion carrier in construction of an Er(III) microelectrode. Theoretical calculationsand conductance studies of HDB to erbium and some other metal ions were carried out andconfirmed selectivity toward Er(III) ions.The best performance was obtained with a membrane contain 3% potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as an anionic additive, 72% dibutyl phthalate (DBP) assolvent mediator, 5% HDB, and 20% poly(vinyl chloride) (PVC). The proposed Er(III)microelectrode exhibits a near Nernstian response of 17.5±0.5 mV per decade of erbiumactivity, and a very wide linear range 1.0×10-3-3.0×10-10 M. It can work well in the pHrange of 3.0-9.0. The lower detection limit (LDL) of the microelectrode was calculated tobe 2.0×10-10 M. Full article
Open AccessArticle Non-Destructive Evaluation of Historical Paper Based on pH Estimation from VOC Emissions
Sensors 2007, 7(12), 3136-3145; doi:10.3390/s7123136
Received: 12 November 2007 / Accepted: 4 December 2007 / Published: 5 December 2007
Cited by 29 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
Volatile organic compounds (VOCs) emitted from materials during degradationcan be a valuable source of information. In this work, the emissions of furfural and aceticacid from cellulose were studied using solid-phase micro-extraction (SPME) incombination with gas chromatography-mass spectrometry. Two sampling techniques wereemployed: static [...] Read more.
Volatile organic compounds (VOCs) emitted from materials during degradationcan be a valuable source of information. In this work, the emissions of furfural and aceticacid from cellulose were studied using solid-phase micro-extraction (SPME) incombination with gas chromatography-mass spectrometry. Two sampling techniques wereemployed: static headspace sampling using SPME for 1 h at 40 oC after 18-h samplepreparation at 80 oC in a closed glass vial, and contact SPME in a stack of paper (or abook). While a number of VOCs are emitted from paper under conditions of natural oraccelerated degradation, two compounds were confirmed to be of particular diagnosticvalue: acetic acid and furfural. The emissions of furfural are shown to correlate with pH ofthe cellulosic environment. Since pH is one of the most important parameters regardingdurability of this material, the developed method could be used for non-destructiveevaluation of historical paper. Full article
Open AccessArticle About Optimal Fractional Hold Circuits for Inter- sample Output Reconstruction in Sampled-data Systems
Sensors 2007, 7(12), 3146-3155; doi:10.3390/s7123146
Received: 14 November 2007 / Accepted: 28 November 2007 / Published: 4 December 2007
Cited by 6 | PDF Full-text (250 KB) | HTML Full-text | XML Full-text
Abstract
The design of fractional order-holds (FROH) of correcting gains β ∈ [ − 1 , 1 ](potentially and possibly including zero-order-holds, ZOH with β=0, and first-order-holds,FROH with β=1) is discussed related to achieving output deviations being close withrespect to its sampled values. [...] Read more.
The design of fractional order-holds (FROH) of correcting gains β ∈ [ − 1 , 1 ](potentially and possibly including zero-order-holds, ZOH with β=0, and first-order-holds,FROH with β=1) is discussed related to achieving output deviations being close withrespect to its sampled values. A squared error time- integral between the current output andits sampled values is minimized to yield the appropriate correcting gain of the FROH in ananalytic way. Full article
Open AccessArticle Near-Field Thermometry Sensor Based on the Thermal Resonance of a Microcantilever in Aqueous Medium
Sensors 2007, 7(12), 3156-3165; doi:10.3390/s7123156
Received: 1 November 2007 / Accepted: 4 December 2007 / Published: 6 December 2007
Cited by 9 | PDF Full-text (382 KB) | HTML Full-text | XML Full-text
Abstract
A new concept using a near-field thermometry sensor is presented, employing atipless microcantilever experimentally validated for an aqueous medium within approximatelyone cantilever width from the solid interface. By correlating the thermal Brownian vibratingmotion of the microcantilever with the surrounding liquid temperature, the [...] Read more.
A new concept using a near-field thermometry sensor is presented, employing atipless microcantilever experimentally validated for an aqueous medium within approximatelyone cantilever width from the solid interface. By correlating the thermal Brownian vibratingmotion of the microcantilever with the surrounding liquid temperature, the near-fieldmicroscale temperature distributions at the probing site are determined at separation distancesof z = 5, 10, 20, and 40 μm while the microheater temperature is maintained at 50°C, 70°C, or90°C. In addition, the near-field correction of the correlation is discussed to account for thequenched cantilever vibration frequencies, which are quenched due to the no-slip solid-wallinterference. Higher thermal sensitivity and spatial resolution is expected when the vibrationfrequencies increase with a relatively short and thick cantilever and the dimensions of themicrocantilever are reduced. Use of the microcantilever thermometry sensor can also reduce thecomplexity and mitigate the high cost associated with existing microfabricated thermocouplesor thermoresistive sensors. Full article
Open AccessArticle Thermally Stable Merocyanine Form of Photochromic Spiropyran with Aluminum Ion as a Reversible Photo-driven Sensor in Aqueous Solution
Sensors 2007, 7(12), 3166-3178; doi:10.3390/s7123166
Received: 30 October 2007 / Accepted: 3 November 2007 / Published: 6 December 2007
Cited by 65 | PDF Full-text (410 KB) | HTML Full-text | XML Full-text
Abstract
A reversible photo-driven sensor for aluminum ions based on photochromicspiropyran was reported with rapid response time. The detection of aluminum wasperformed via the chelation of aluminum ions with the merocyanine form (MC) ofphotochromic spiropyran. 1H NMR studies confirmed the conversation from [...] Read more.
A reversible photo-driven sensor for aluminum ions based on photochromicspiropyran was reported with rapid response time. The detection of aluminum wasperformed via the chelation of aluminum ions with the merocyanine form (MC) ofphotochromic spiropyran. 1H NMR studies confirmed the conversation from the MC forminto the Al3+ -MC form. Addition of aluminum ions to the spiropyran (SP) in a MeCN/H2Omixture results in obvious color changes with a loss in absorbance at 539 nm and anenhancement in absorbance at about 420 nm after irradiation at 365 nm. The metal chelationcomplex (Al3+ -MC) can also be converted into the original SP form by irradiation withvisible light. Aluminum ions can be detected down to 0.5 μM levels in a fast response ofless than 5 seconds with no interference from other ionic species. Full article
(This article belongs to the Special Issue Supramolecular Sensors)
Open AccessArticle Fuzzy Logic Control Based QoS Management in Wireless Sensor/Actuator Networks
Sensors 2007, 7(12), 3179-3191; doi:10.3390/s7123179
Received: 30 November 2007 / Accepted: 5 December 2007 / Published: 6 December 2007
Cited by 29 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor/actuator networks (WSANs) are emerging rapidly as a newgeneration of sensor networks. Despite intensive research in wireless sensor networks(WSNs), limited work has been found in the open literature in the field of WSANs. Inparticular, quality-of-service (QoS) management in WSANs remains an [...] Read more.
Wireless sensor/actuator networks (WSANs) are emerging rapidly as a newgeneration of sensor networks. Despite intensive research in wireless sensor networks(WSNs), limited work has been found in the open literature in the field of WSANs. Inparticular, quality-of-service (QoS) management in WSANs remains an important issue yetto be investigated. As an attempt in this direction, this paper develops a fuzzy logic controlbased QoS management (FLC-QM) scheme for WSANs with constrained resources and indynamic and unpredictable environments. Taking advantage of the feedback controltechnology, this scheme deals with the impact of unpredictable changes in traffic load on theQoS of WSANs. It utilizes a fuzzy logic controller inside each source sensor node to adaptsampling period to the deadline miss ratio associated with data transmission from the sensorto the actuator. The deadline miss ratio is maintained at a pre-determined desired level sothat the required QoS can be achieved. The FLC-QM has the advantages of generality,scalability, and simplicity. Simulation results show that the FLC-QM can provide WSANswith QoS support. Full article
Open AccessArticle Design Considerations for Aural Vital Signs Using PZT Piezoelectric Ceramics Sensor Based on the Computerization Method
Sensors 2007, 7(12), 3192-3208; doi:10.3390/s7123192
Received: 23 July 2007 / Accepted: 3 December 2007 / Published: 11 November 2007
Cited by 2 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
The purpose was to illustrate how system developed for measurement of the aural vital signs such as patient’s heart and lung sounds in the hospital. For heart sounds measurement must operate the frequency response between 20 – 800 Hz, and lung sounds [...] Read more.
The purpose was to illustrate how system developed for measurement of the aural vital signs such as patient’s heart and lung sounds in the hospital. For heart sounds measurement must operate the frequency response between 20 – 800 Hz, and lung sounds measurement must operate the frequency response between 160 – 4,000 Hz. The method was designed PZT piezoelectric ceramics for both frequency response in the same PZT sensor. It converts a signal from aural vital sign form to voltage signal. The signal is suitably amplified and re-filtered in band pass frequency band. It is converted to digital signal by an analog to digital conversion circuitry developed for the purpose. The results were that all signals can fed to personal computer through the sound card port. With the supporting software for drawing of graphic on the screen, the signal for a specific duration is accessed and stored in the computer’s memory in term of each patient’s data. In conclusion, the data of each patient call dot pcg (.pcg) for drawing graph and dot wave (.wave) for sound listening or automatic sending via electronic mail to the physician for later analysis of interpreting the sounds on the basis of their time domain and frequency domain representation to diagnose heart disorders. Full article
Open AccessArticle Integrating Map Algebra and Statistical Modeling for Spatio- Temporal Analysis of Monthly Mean Daily Incident Photosynthetically Active Radiation (PAR) over a Complex Terrain
Sensors 2007, 7(12), 3242-3257; doi:10.3390/s7123242
Received: 21 November 2007 / Accepted: 11 December 2007 / Published: 12 December 2007
Cited by 1 | PDF Full-text (4226 KB) | HTML Full-text | XML Full-text
Abstract
This study aims at quantifying spatio-temporal dynamics of monthly mean dailyincident photosynthetically active radiation (PAR) over a vast and complex terrain such asTurkey. The spatial interpolation method of universal kriging, and the combination ofmultiple linear regression (MLR) models and map algebra techniques [...] Read more.
This study aims at quantifying spatio-temporal dynamics of monthly mean dailyincident photosynthetically active radiation (PAR) over a vast and complex terrain such asTurkey. The spatial interpolation method of universal kriging, and the combination ofmultiple linear regression (MLR) models and map algebra techniques were implemented togenerate surface maps of PAR with a grid resolution of 500 x 500 m as a function of fivegeographical and 14 climatic variables. Performance of the geostatistical and MLR modelswas compared using mean prediction error (MPE), root-mean-square prediction error(RMSPE), average standard prediction error (ASE), mean standardized prediction error(MSPE), root-mean-square standardized prediction error (RMSSPE), and adjustedcoefficient of determination (R2adj.). The best-fit MLR- and universal kriging-generatedmodels of monthly mean daily PAR were validated against an independent 37-year observeddataset of 35 climate stations derived from 160 stations across Turkey by the Jackknifingmethod. The spatial variability patterns of monthly mean daily incident PAR were moreaccurately reflected in the surface maps created by the MLR-based models than in thosecreated by the universal kriging method, in particular, for spring (May) and autumn(November). The MLR-based spatial interpolation algorithms of PAR described in thisstudy indicated the significance of the multifactor approach to understanding and mappingspatio-temporal dynamics of PAR for a complex terrain over meso-scales. Full article
Open AccessArticle Detection of Brominated By-Products Using a Sensor Array Based on Nanostructured Thin Films of Conducting Polymers
Sensors 2007, 7(12), 3258-3271; doi:10.3390/s7123258
Received: 20 September 2007 / Accepted: 19 November 2007 / Published: 12 December 2007
Cited by 8 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
The detection of the carcinogenic trihalomethanes (THM) in public water supplysystems using low-cost equipment has become an essential feature, since these compoundsmay be generated as by-products of water-treatment processes. Here we report on a sensorarray that extends the concept of an “electronic [...] Read more.
The detection of the carcinogenic trihalomethanes (THM) in public water supplysystems using low-cost equipment has become an essential feature, since these compoundsmay be generated as by-products of water-treatment processes. Here we report on a sensorarray that extends the concept of an “electronic tongue” to detect small amounts ofbromoform, bromodichloromethane and dibromochloromethane, with detection limits aslow as 0.02 mg L-1. The sensor array was made up of 10 sensing units, in whichnanostructured films of conducting and natural polymers were deposited onto goldinterdigitated electrodes. The principle of detection was impedance spectroscopy, withmeasurements carried out in the range between 1 Hz to 1 MHz. Using data at 1 kHz, atwhich the electrical response varied considerably by changing the analyte, we demonstratedwith principal component analysis (PCA) that samples with the 3 brominatedtrihalomethanes can be distinguished from each other and for various concentrations. Full article
(This article belongs to the Special Issue Electrochemical Sensors Based on Conductive Polymers)
Open AccessArticle PVC Membrane Sensors for Potentiometric Determination of Acebutolol
Sensors 2007, 7(12), 3272-3286; doi:10.3390/s7123272
Received: 11 July 2007 / Accepted: 8 October 2007 / Published: 13 December 2007
Cited by 9 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
Abstract
The construction and general performance characteristics of two novelpotentiometric membrane sensors responsive to the acebutolol are described. Thesensors are based on the use of ion-association complexes of acebutolol (AC) withtetraphenylborate(TPB) (I) and phosphomolybdate(PM) (II) as exchange sites in a PVCmatrix. The sensors [...] Read more.
The construction and general performance characteristics of two novelpotentiometric membrane sensors responsive to the acebutolol are described. Thesensors are based on the use of ion-association complexes of acebutolol (AC) withtetraphenylborate(TPB) (I) and phosphomolybdate(PM) (II) as exchange sites in a PVCmatrix. The sensors show a fast, stable and near- Nernstian for the mono charge cationof AC over the concentration range 1×10-3 - ~10-6 M at 25 °C over the pH range 2.0 -6.0 with cationic slope of 51.5 ± 0.5 and 53.0 ± 0.5 per concentration decade for AC-Iand AC-II sensors respectively. The lower detection limit is 6×10-6 M and 4×0-6 M withthe response time 20-30 s in the same order of both sensors. Selectivity coefficients ofAC related to a number of interfering cation and some organic compounds wereinvestigated. There are negligible interferences are caused by most of the investigatedspecies. The direct determination of 3 - 370 μg/ml of AC shows an average recovery of 99.4 and 99.5% and a mean relative standard deviation of 1 . 5 % at 100.0 μg/ml forsensor I and II respectively. The results obtained by determination of AC in tablets usingthe proposed sensors which comparable favorably with those obtained by the Britishpharmacopoeia method. In the present investigation the electrodes have been utilized asend point indicator for some precipitation titration reactions. Full article
(This article belongs to the Special Issue Electrochemical Sensors Based on Conductive Polymers)
Open AccessArticle From Hearing to Listening: Design and Properties of an Actively Tunable Electronic Hearing Sensor
Sensors 2007, 7(12), 3287-3298; doi:10.3390/s7123287
Received: 5 December 2007 / Accepted: 13 December 2007 / Published: 14 December 2007
Cited by 10 | PDF Full-text (1581 KB) | HTML Full-text | XML Full-text
Abstract
An important step towards understanding the working principles of the mammalian hearing sensor is the concept of an active cochlear amplifier. Theoretical arguments and physiological measurements suggest that the active cochlear amplifiers originate from systems close to a Hopf bifurcation. Efforts to model the mammalian hearing sensor on these grounds have, however, either had problems in reproducing sufficiently close essential aspects of the biological example (Magnasco, M.O. Phys. Rev. Lett. 90, 058101 (2003); Duke, T. & Jülicher, F. Phys. Rev. Lett. 90, 158101 (2003)), or required complicated spatially coupled differential equation systems that are unfeasible for transient signals (Kern, A. & Stoop, R. Phys. Rev. Lett. 91, 128101 (2003)). Here, we demonstrate a simple system of electronically coupled Hopf amplifiers that not only leads to the desired biological response behavior, but also has real-time capacity. The obtained electronic Hopf cochlea shares all salient signal processing features exhibited by the mammalian cochlea and thus provides a simple and efficient design of an artificial mammalian hearing sensor. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Switzerland)
Open AccessArticle Gold Nanoparticles With Special Shapes: Controlled Synthesis, Surface-enhanced Raman Scattering, and The Application in Biodetection
Sensors 2007, 7(12), 3299-3311; doi:10.3390/s7123299
Received: 12 November 2007 / Accepted: 12 December 2007 / Published: 14 December 2007
Cited by 70 | PDF Full-text (1409 KB) | HTML Full-text | XML Full-text
Abstract
Specially shaped gold nanoparticles have intrigued considerable attention becausethey usually possess high-sensitivity surface-enhanced Raman scattering (SERS) and thusresult in large advantages in trace biodetermination. In this article, starch-capped goldnanoparticles with hexagon and boot shapes were prepared through using a nontoxic andbiologically benign [...] Read more.
Specially shaped gold nanoparticles have intrigued considerable attention becausethey usually possess high-sensitivity surface-enhanced Raman scattering (SERS) and thusresult in large advantages in trace biodetermination. In this article, starch-capped goldnanoparticles with hexagon and boot shapes were prepared through using a nontoxic andbiologically benign aqueous-phase synthetic route. Shape effects of gold nanoparticles onSERS properties were mainly investigated, and found that different-shaped goldnanoparticles possess different SERS properties. Especially, the boot-shaped nanoparticlescould induce more 100-fold SERS enhancements in sensitivity as compared with those fromgold nanospheres. The extremely strong SERS properties of gold nanoboots have beensuccessfully applied to the detection of avidin. The unique nanoboots with high-sensitivitySERS properties are also expected to find use in many other fields such as biolabel,bioassay, biodiagnosis, and even clinical diagnosis and therapy. Full article
Open AccessArticle Evaluation of Grassland Dynamics in the Northern-Tibet Plateau of China Using Remote Sensing and Climate Data
Sensors 2007, 7(12), 3312-3328; doi:10.3390/s7123312
Received: 13 October 2007 / Accepted: 14 December 2007 / Published: 17 December 2007
Cited by 21 | PDF Full-text (591 KB) | HTML Full-text | XML Full-text
Abstract
The grassland ecosystem in the Northern-Tibet Plateau (NTP) of China is verysensitive to weather and climate conditions of the region. In this study, we investigate thespatial and temporal variations of the grassland ecosystem in the NTP using theNOAA/AVHRR ten-day maximum NDVI composite [...] Read more.
The grassland ecosystem in the Northern-Tibet Plateau (NTP) of China is verysensitive to weather and climate conditions of the region. In this study, we investigate thespatial and temporal variations of the grassland ecosystem in the NTP using theNOAA/AVHRR ten-day maximum NDVI composite data of 1981-2001. The relationshipsamong Vegetation Peak-Normalized Difference Vegetation Index (VP-NDVI) and climatevariables were quantified for six counties within the NTP. The notable and unevenalterations of the grassland in response to variation of climate and human impact in theNTP were revealed. Over the last two decades of the 20th century, the maximum greennessof the grassland has exhibited high increase, slight increase, no-change, slight decrease andhigh decrease, each occupies 0.27%, 8.71%, 77.27%, 13.06% and 0.69% of the total area ofthe NTP, respectively. A remarkable increase (decrease) in VP-NDVI occurred in thecentral-eastern (eastern) NTP whereas little change was observed in the western andnorthwestern NTP. A strong negative relationship between VP-NDVI and ET0 was foundin sub-frigid, semi-arid and frigid- arid regions of the NTP (i.e., Nakchu, Shantsa, Palgonand Amdo counties), suggesting that the ET0 is one limiting factor affecting grasslanddegradation. In the temperate-humid, sub-frigid and sub-humid regions of the NTP (Chaliand Sokshan counties), a significant inverse correlation between VP-NDVI and populationindicates that human activities have adversely affected the grassland condition as waspreviously reported in the literature. Results from this research suggest that the alterationand degradation of the grassland in the lower altitude of the NTP over the last two decades of the 20th century are likely caused by variations of climate and anthropogenic activities. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle pH Sensitivity of Novel PANI/PVB/PS3 Composite Films
Sensors 2007, 7(12), 3329-3346; doi:10.3390/s7123329
Received: 29 November 2007 / Accepted: 18 December 2007 / Published: 19 December 2007
Cited by 19 | PDF Full-text (480 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports on the results from the investigation into the pH sensitivity ofnovel PANI/PVB/PS3 composite films. The conductimetric sensing mode was chosen as itis one of the most promising alternatives to the mainstream pH-sensing methods and it is theleast investigated due [...] Read more.
This paper reports on the results from the investigation into the pH sensitivity ofnovel PANI/PVB/PS3 composite films. The conductimetric sensing mode was chosen as itis one of the most promising alternatives to the mainstream pH-sensing methods and it is theleast investigated due to the popularity of other approaches. The films were deposited usingboth screen-printing and a drop-coating method. It was found that the best response to pHwas obtained from the screen-printed thick films, which demonstrated a change inconductance by as much as three orders of magnitude over the pH range pH2-pH11. Thedevices exhibited a stable response over 96 hours of operation. Several films were immersedin buffer solutions of different pH values for 96 hours and these were then investigated usingXPS. The resulting N 1s spectra for the various films confirmed that the change inconductance was due to deprotonation of the PANI polymer backbone. SEM andProfilometry were also undertaken and showed that no considerable changes in themorphology of the films took place and that the films did not swell or contract due toexposure to test solutions. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Based pH Sensors)
Open AccessArticle Lidar-based Studies of Aerosol Optical Properties Over Coastal Areas
Sensors 2007, 7(12), 3347-3365; doi:10.3390/s7123347
Received: 1 November 2007 / Accepted: 17 December 2007 / Published: 19 December 2007
Cited by 3 | PDF Full-text (239 KB) | HTML Full-text | XML Full-text
Abstract
Aerosol size distribution and concentration strongly depend on wind speed,direction, and measuring point location in the marine boundary layer over coastal areas.The marine aerosol particles which are found over the sea waves in high wind conditionsaffect visible and near infrared propagation for [...] Read more.
Aerosol size distribution and concentration strongly depend on wind speed,direction, and measuring point location in the marine boundary layer over coastal areas.The marine aerosol particles which are found over the sea waves in high wind conditionsaffect visible and near infrared propagation for paths that pass very close to the surface aswell as the remote sensing measurements of the sea surface. These particles are producedby various air sea interactions. This paper presents the results of measurements taken atnumerous coastal stations between 1992 and 2006 using an FLS-12 lidar system togetherwith other supporting instrumentation. The investigations demonstrated that near-waterlayers in coastal areas differ significantly from those over open seas both in terms ofstructure and physical properties. Taking into consideration the above mentioned factors,aerosol concentrations and optical properties were determined in the marine boundary layeras a function of offshore distance and altitude at various coastal sites in two seasons. Thelidar results show that the remote sensing algorithms used currently in coastal areas needverification and are not fully reliable. Full article
(This article belongs to the Special Issue Ocean Remote Sensing)
Open AccessArticle A Novel Pulse Measurement System by Using Laser Triangulation and a CMOS Image Sensor
Sensors 2007, 7(12), 3366-3385; doi:10.3390/s7123366
Received: 2 November 2007 / Accepted: 18 December 2007 / Published: 19 December 2007
Cited by 26 | PDF Full-text (2246 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel, non-invasive, non-contact system to measure pulsewaveforms of artery via applying laser triangulation method to detect skin surfacevibration. The proposed arterial pulsation measurement (APM) system chiefly consists of alaser diode and a low cost complementary metal-oxide semiconductor (CMOS) [...] Read more.
This paper presents a novel, non-invasive, non-contact system to measure pulsewaveforms of artery via applying laser triangulation method to detect skin surfacevibration. The proposed arterial pulsation measurement (APM) system chiefly consists of alaser diode and a low cost complementary metal-oxide semiconductor (CMOS) imagesensor. Laser triangulation and centroid method are combined with the Fast FourierTransform (FFT) in this study. The shape and frequency of the arterial pulsation can bedetected rapidly by using our APM system. The relative variation of the pulse at differentmeasurement points near wrist joint is used as a prognostic guide in traditional Chinesemedicine (TCM). An extensive series of experiments was conducted to evaluate theperformance of the designed APM system. From experimental results, the pulse amplitudeand frequency at the Chun point (related to the small intestine) of left hand showed anobvious increase after having food. In these cases, the peak to peak amplitudes and thefrequencies of arterial pulsations range from 38 to 48 μm and from 1.27 to 1.35 Hz,respectively. The height of arterial pulsations on the area near wrist joint can be estimatedwith a resolution of better than 4 μm. This research demonstrates that applying a CMOSimage sensor in designing a non-contact, portable, easy-to-use, low cost pulse measurementsystem is feasible. Also, the designed APM system is well suited for evaluating and pre-diagnosing the health of a human being in TCM clinical practice. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
Open AccessArticle Modeling and Fabrication of Micro FET Pressure Sensor with Circuits
Sensors 2007, 7(12), 3386-3398; doi:10.3390/s7123386
Received: 19 November 2007 / Accepted: 18 December 2007 / Published: 19 November 2007
Cited by 24 | PDF Full-text (2328 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the simulation, fabrication and characterization of a microFET (field effect transistor) pressure sensor with readout circuits. The pressure sensorincludes 16 sensing cells in parallel. Each sensing cell that is circular shape is composed ofan MOS (metal oxide semiconductor) and [...] Read more.
This paper presents the simulation, fabrication and characterization of a microFET (field effect transistor) pressure sensor with readout circuits. The pressure sensorincludes 16 sensing cells in parallel. Each sensing cell that is circular shape is composed ofan MOS (metal oxide semiconductor) and a suspended membrane, which the suspendedmembrane is the movable gate of the MOS. The CoventorWare is used to simulate thebehaviors of the pressure sensor, and the HSPICE is employed to evaluate the characteristicsof the circuits. The pressure sensor integrated with circuits is manufactured using thecommercial 0.35 μm CMOS (complementary metal oxide semiconductor) process and apost-process. In order to obtain the suspended membranes, the pressure sensor requires apost-CMOS process. The post-process adopts etchants to etch the sacrificial layers in thepressure sensors to release the suspended membranes, and then the etch holes in the pressuresensor are sealed by LPCVD (low pressure chemical vapor deposition) parylene. Thepressure sensor produces a change in current when applying a pressure to the sensing cells.The circuits are utilized to convert the current variation of the pressure sensor into thevoltage output. Experimental results show that the pressure sensor has a sensitivity of 0.032mV/kPa in the pressure range of 0-500 kPa. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Six-Degree-of-Freedom Sensor Fish Design and Instrumentation
Sensors 2007, 7(12), 3399-3415; doi:10.3390/s7123399
Received: 27 November 2007 / Accepted: 18 December 2007 / Published: 19 December 2007
Cited by 22 | PDF Full-text (1609 KB) | HTML Full-text | XML Full-text
Abstract
Fish passing through dams may be injured or killed despite advances in turbinedesign, project operations and other fish bypass systems. The six-degree-of-freedom (6DOF)Sensor Fish device is an autonomous sensor package that characterizes the physical conditionsand physical stresses to which fish are exposed [...] Read more.
Fish passing through dams may be injured or killed despite advances in turbinedesign, project operations and other fish bypass systems. The six-degree-of-freedom (6DOF)Sensor Fish device is an autonomous sensor package that characterizes the physical conditionsand physical stresses to which fish are exposed when they pass through complex hydraulicenvironments. It has been used to identify the locations and operations where conditions aresevere enough to injure or kill fish. During the design process, a set of governing equationsof motion for the Sensor Fish was derived and simulated to understand the design implica-tions of instrument selection and placement within the body of the device. The Sensor Fishpackage includes three rotation sensors, three acceleration sensors, a pressure sensor, and atemperature sensor with a sampling frequency of 2,000 Hz. Its housing is constructed of clearpolycarbonate plastic. It is 24.5 mm in diameter and 90 mm in length and weighs about 43 g,similar to the size and density of a yearling salmon smolt. The accuracy of the pressure sensorwas determined to be within 0.2 psi. In laboratory acceptance tests, the relative errors of boththe linear acceleration and angular velocity measurements were determined to be less than5%. An exposure is defined as a significant event when the acceleration reaches predefinedthresholds. Based on the different characteristic of acceleration and rotation velocities, theexposure event is categorized as either a collision between the Sensor Fish and a solid struc-ture or shear caused by turbulence. Since its development in 2005, the 6DOF Sensor Fish hasbeen deployed successfully at many major dams in the United States. Full article
Open AccessArticle Satellite-based Flood Modeling Using TRMM-based Rainfall Products
Sensors 2007, 7(12), 3416-3427; doi:10.3390/s7123416
Received: 30 November 2007 / Accepted: 18 December 2007 / Published: 20 December 2007
Cited by 25 | PDF Full-text (422 KB) | HTML Full-text | XML Full-text
Abstract
Increasingly available and a virtually uninterrupted supply of satellite-estimatedrainfall data is gradually becoming a cost-effective source of input for flood predictionunder a variety of circumstances. However, most real-time and quasi-global satelliterainfall products are currently available at spatial scales ranging from 0.25o [...] Read more.
Increasingly available and a virtually uninterrupted supply of satellite-estimatedrainfall data is gradually becoming a cost-effective source of input for flood predictionunder a variety of circumstances. However, most real-time and quasi-global satelliterainfall products are currently available at spatial scales ranging from 0.25o to 0.50o andhence, are considered somewhat coarse for dynamic hydrologic modeling of basin-scaleflood events. This study assesses the question: what are the hydrologic implications ofuncertainty of satellite rainfall data at the coarse scale? We investigated this question onthe 970 km2 Upper Cumberland river basin of Kentucky. The satellite rainfall productassessed was NASA’s Tropical Rainfall Measuring Mission (TRMM) Multi-satellitePrecipitation Analysis (TMPA) product called 3B41RT that is available in pseudo real timewith a latency of 6-10 hours. We observed that bias adjustment of satellite rainfall data canimprove application in flood prediction to some extent with the trade-off of more falsealarms in peak flow. However, a more rational and regime-based adjustment procedureneeds to be identified before the use of satellite data can be institutionalized among floodmodelers. Full article
(This article belongs to the Special Issue Remote Sensing of Land Surface Properties, Patterns and Processes)
Open AccessArticle Determination of Primary Spectral Bands for Remote Sensing of Aquatic Environments
Sensors 2007, 7(12), 3428-3441; doi:10.3390/s7123428
Received: 5 November 2007 / Accepted: 17 December 2007 / Published: 20 December 2007
Cited by 31 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
Abstract
About 30 years ago, NASA launched the first ocean-color observing satellite:the Coastal Zone Color Scanner. CZCS had 5 bands in the visible-infrared domain with anobjective to detect changes of phytoplankton (measured by concentration of chlorophyll) inthe oceans. Twenty years later, for the [...] Read more.
About 30 years ago, NASA launched the first ocean-color observing satellite:the Coastal Zone Color Scanner. CZCS had 5 bands in the visible-infrared domain with anobjective to detect changes of phytoplankton (measured by concentration of chlorophyll) inthe oceans. Twenty years later, for the same objective but with advanced technology, theSea-viewing Wide Field-of-view Sensor (SeaWiFS, 7 bands), the Moderate-ResolutionImaging Spectrometer (MODIS, 8 bands), and the Medium Resolution ImagingSpectrometer (MERIS, 12 bands) were launched. The selection of the number of bands andtheir positions was based on experimental and theoretical results achieved before thedesign of these satellite sensors. Recently, Lee and Carder (2002) demonstrated that foradequate derivation of major properties (phytoplankton biomass, colored dissolved organicmatter, suspended sediments, and bottom properties) in both oceanic and coastalenvironments from observation of water color, it is better for a sensor to have ~15 bands inthe 400 – 800 nm range. In that study, however, it did not provide detailed analysesregarding the spectral locations of the 15 bands. Here, from nearly 400 hyperspectral (~ 3-nm resolution) measurements of remote-sensing reflectance (a measure of water color)taken in both coastal and oceanic waters covering both optically deep and optically shallowwaters, first- and second-order derivatives were calculated after interpolating themeasurements to 1-nm resolution. From these derivatives, the frequency of zero values foreach wavelength was accounted for, and the distribution spectrum of such frequencies wasobtained. Furthermore, the wavelengths that have the highest appearance of zeros wereidentified. Because these spectral locations indicate extrema (a local maximum orminimum) of the reflectance spectrum or inflections of the spectral curvature, placing the bands of a sensor at these wavelengths maximizes the potential of capturing (and then restoring) the spectral curve, and thus maximizes the potential of accurately deriving properties of the water column and/or bottom of various aquatic environments with a multi-band sensor. Full article
(This article belongs to the Special Issue Ocean Remote Sensing)
Open AccessArticle Use of a Dynamic Enclosure Approach to Test the Accuracy of the NDIR Sensor: Evaluation Based on the CO2 Equilibration Pattern
Sensors 2007, 7(12), 3459-3471; doi:10.3390/s7123459
Received: 7 November 2007 / Accepted: 19 December 2007 / Published: 20 December 2007
Cited by 3 | PDF Full-text (351 KB) | HTML Full-text | XML Full-text
Abstract
As part of a quality assurance (QA) study for sensor systems, an enclosureapproach is applied to assess the accuracy of non-dispersive infrared (NDIR)-based CO2sensors. To examine the performance of the sensor system, an enclosure chambercontaining six sensor units of the [...] Read more.
As part of a quality assurance (QA) study for sensor systems, an enclosureapproach is applied to assess the accuracy of non-dispersive infrared (NDIR)-based CO2sensors. To examine the performance of the sensor system, an enclosure chambercontaining six sensor units of the two model types (B-530 and H-500) was equilibratedwith calibrated CO2 standards at varying concentration levels. Initially, the equilibrationpattern was analyzed by CO2-free gas (0 ppm) at varying flow rates (i.e., 100, 200, 500, and1000 mL min-1). Results of the test yielded a highly predictable and quantifiable empiricalrelationship as a function of such parameters as CO2 concentration, flow rate, andequilibration time for the enclosure system. Hence, when the performance of the NDIR-method was evaluated at other concentrations (i.e., 500 and 1000 ppm), all the sensor unitsshowed an excellent compatibility, at least in terms of the correlation coefficients (r >0.999, p = 0.01). According to our analysis, the NDIR sensor system seems to attain anoverall accuracy near the 5% level. The relative performance of the NDIR sensor for CO2analysis is hence comparable with (or superior to) other methods previously investigated.The overall results of this study indicate that NDIR sensors can be used to provide highlyaccurate and precise analyses of CO2 both in absolute and relative terms. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
Open AccessArticle Combination of On-line pH and Oxygen Transfer Rate Measurement in Shake Flasks by Fiber Optical Technique and Respiration Activity MOnitoring System (RAMOS)
Sensors 2007, 7(12), 3472-3480; doi:10.3390/s7123472
Received: 3 December 2007 / Accepted: 20 December 2007 / Published: 20 December 2007
Cited by 25 | PDF Full-text (312 KB) | HTML Full-text | XML Full-text
Abstract
Shake flasks are commonly used for process development in biotechnologyindustry. For this purpose a lot of information is required from the growth conditions duringthe fermentation experiments. Therefore, Anderlei et al. developed the RAMOS technology[1, 2], which proviedes on-line oxygen and carbondioxide transfer [...] Read more.
Shake flasks are commonly used for process development in biotechnologyindustry. For this purpose a lot of information is required from the growth conditions duringthe fermentation experiments. Therefore, Anderlei et al. developed the RAMOS technology[1, 2], which proviedes on-line oxygen and carbondioxide transfer rates in shake flasks.Besides oxygen consumption, the pH in the medium also plays an important role for thesuccessful cultivation of micro-organisms and for process development. For online pHmeasurement fiber optical methods based on fluorophores are available. Here a combinationof the on-line Oxygen Transfer Rate (OTR) measurements in the RAMOS device with anon-line, fiber optical pH measurement is presented. To demonstrate the application of thecombined measurement techniques, Escherichia coli cultivations were performed and on-line pH measurements were compared with off-line samples. The combination of on-lineOTR and pH measurements gives a lot of information about the cultivation and, therefore, itis a powerful technique for monitoring shake flask experiments as well as for processdevelopment. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Based pH Sensors)
Open AccessArticle Naked-eye and Selective Detection of Mercury (II) Ions in Mixed Aqueous Media Using a Cellulose-based Support
Sensors 2007, 7(12), 3481-3488; doi:10.3390/s7123481
Received: 8 November 2007 / Accepted: 20 December 2007 / Published: 21 December 2007
Cited by 32 | PDF Full-text (858 KB) | HTML Full-text | XML Full-text
Abstract
A test paper for high-selectivity detecting Hg2+ ions in mixed acetonitrile-watersolutions has been achieved using a bis(ferrocenyl) azine, as chromogenic chemosensormolecule, and a solid cellulose fibre, as a substrate. Depending on the amount of mercuryions in contact with the detecting molecule [...] Read more.
A test paper for high-selectivity detecting Hg2+ ions in mixed acetonitrile-watersolutions has been achieved using a bis(ferrocenyl) azine, as chromogenic chemosensormolecule, and a solid cellulose fibre, as a substrate. Depending on the amount of mercuryions in contact with the detecting molecule a spectacular color change in the celluloseindicator is produced, being possible to determine the concentration of Hg2+ ions either bynaked eye or spectroscopically. Full article
(This article belongs to the Special Issue Molecular Recognition and Sensors, Including Molecular Imprinting)
Open AccessArticle Analysis of Mean Access Delay in Variable-Window CSM
Sensors 2007, 7(12), 3535-3559; doi:10.3390/s7123535
Received: 10 October 2007 / Accepted: 21 December 2007 / Published: 21 December 2007
Cited by 8 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
The paper addresses the problem of the mean access delay characteristics in termof the channel load for networked sensor/control systems in LonWorks/EIA-709 technology.The system modelling is focused on the Media Access Control protocol that provides theload prediction and determines the key network [...] Read more.
The paper addresses the problem of the mean access delay characteristics in termof the channel load for networked sensor/control systems in LonWorks/EIA-709 technology.The system modelling is focused on the Media Access Control protocol that provides theload prediction and determines the key network characteristics. The network model assumesthe consistency of load prediction between the nodes, and that the Transaction ControlSublayer does not introduce limitations on the data transmission. The latter means that thenumbers of concurrent outgoing transactions being in progress are unlimited. Furthermore, itis assumed that the destination addresses of transmitted messages are distributed rather thanconcentrated on particular nodes. The analytical approach based on Markov chains isapplied. The calculation of transition probabilities of the Markov chain is exemplified by theload scenario where all the transactions are acknowledged, unicast, and the optionalcollision detection is enabled. On the basis of the stochastic analysis, the probabilities of asuccessful transmission and collision, respectively, are computed. Furthermore, thenumerical results of the mean access delay are reported. The simulative validation ofanalytical results is provided. Full article
(This article belongs to the Special Issue Intelligent Sensors)

Review

Jump to: Research

Open AccessReview State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
Sensors 2007, 7(12), 3027-3042; doi:10.3390/s7123027
Received: 20 August 2007 / Accepted: 26 November 2007 / Published: 30 November 2007
Cited by 51 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory [...] Read more.
This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Based pH Sensors)
Open AccessReview Remote Sensing Sensors and Applications in Environmental Resources Mapping and Modelling
Sensors 2007, 7(12), 3209-3241; doi:10.3390/s7123209
Received: 8 November 2007 / Accepted: 26 November 2007 / Published: 11 November 2007
Cited by 35 | PDF Full-text (1584 KB) | HTML Full-text | XML Full-text
Abstract
The history of remote sensing and development of different sensors for environmental and natural resources mapping and data acquisition is reviewed and reported. Application examples in urban studies, hydrological modeling such as land-cover and floodplain mapping, fractional vegetation cover and impervious surface [...] Read more.
The history of remote sensing and development of different sensors for environmental and natural resources mapping and data acquisition is reviewed and reported. Application examples in urban studies, hydrological modeling such as land-cover and floodplain mapping, fractional vegetation cover and impervious surface area mapping, surface energy flux and micro-topography correlation studies is discussed. The review also discusses the use of remotely sensed-based rainfall and potential evapotranspiration for estimating crop water requirement satisfaction index and hence provides early warning information for growers. The review is not an exhaustive application of the remote sensing techniques rather a summary of some important applications in environmental studies and modeling. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessReview An Overview of Label-free Electrochemical Protein Sensors
Sensors 2007, 7(12), 3442-3458; doi:10.3390/s7123442
Received: 4 December 2007 / Accepted: 18 December 2007 / Published: 20 December 2007
Cited by 68 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
Electrochemical-based protein sensors offer sensitivity, selectivity and reliabilityat a low cost, making them very attractive tools for protein detection. Although the sensorsuse a broad range of different chemistries, they all depend on the solid electrode surface,interactions with the target protein and the [...] Read more.
Electrochemical-based protein sensors offer sensitivity, selectivity and reliabilityat a low cost, making them very attractive tools for protein detection. Although the sensorsuse a broad range of different chemistries, they all depend on the solid electrode surface,interactions with the target protein and the molecular recognition layer. Traditionally, redoxenzymes have provided the molecular recognition elements from which target proteins haveinteracted with. This necessitates that the redox-active enzymes couple with electrodesurfaces and usually requires the participation of added diffusional components, or assemblyof the enzymes in functional chemical matrices. These complications, among many others,have seen a trend towards non-enzymatic-based electrochemical protein sensors. Severalelectrochemical detection approaches have been exploited. Basically, these have fallen intotwo categories: labeled and label-free detection systems. The former rely on a redox-activesignal from a reporter molecule or a label, which changes upon the interaction of the targetprotein. In this review, we discuss the label-free electrochemical detection of proteins,paying particular emphasis to those that exploit intrinsic redox-active amino acids. Full article
Open AccessReview Optical Fiber Sensing Using Quantum Dots
Sensors 2007, 7(12), 3489-3534; doi:10.3390/s7123489
Received: 19 November 2007 / Accepted: 20 December 2007 / Published: 21 December 2007
Cited by 58 | PDF Full-text (1618 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in the application of semiconductor nanocrystals, or quantumdots, as biochemical sensors are reviewed. Quantum dots have unique optical properties thatmake them promising alternatives to traditional dyes in many luminescence basedbioanalytical techniques. An overview of the more relevant progresses in the [...] Read more.
Recent advances in the application of semiconductor nanocrystals, or quantumdots, as biochemical sensors are reviewed. Quantum dots have unique optical properties thatmake them promising alternatives to traditional dyes in many luminescence basedbioanalytical techniques. An overview of the more relevant progresses in the application ofquantum dots as biochemical probes is addressed. Special focus will be given toconfigurations where the sensing dots are incorporated in solid membranes and immobilizedin optical fibers or planar waveguide platforms. Full article
(This article belongs to the Special Issue Optical Biosensors)

Journal Contact

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