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Sensitivity Improvement (sensitivity + improvement)
Selected AbstractsSensitivity improvement of the receiver module in the passive tag-based RFID readerINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 11 2009Jonghun Chun Abstract In this paper, we have designed an RFID reader receiver system for improving the performance of the passive Tag-based 908.5,914,MHz RFID reader, and analyzed the system performance vis-à-vis frequency, reader, and tag properties. The commercial receiver system causes a loss in sensitivity because of its 24 capacitors and six inductors. To improve the overall sensitivity of the receiver, we have designed a system using a circulator, low noise amplifier (LNA) and a SAW filter. The experimental results show that the use of a circulator to separate the Tx/Rx paths eliminates interference, the LNA improves the sensitivity of the Rx module and SAW filter eliminates the noise and spurious components in the received signal. Copyright © 2009 John Wiley & Sons, Ltd. [source] XTC MRI: Sensitivity improvement through parameter optimizationMAGNETIC RESONANCE IN MEDICINE, Issue 6 2007Kai Ruppert Abstract Xenon polarization Transfer Contrast (XTC) MRI pulse sequences permit the gas exchange of hyperpolarized xenon-129 in the lung to be measured quantitatively. However, the pulse sequence parameter values employed in previously published work were determined empirically without considering the now-known gas exchange rates and the underlying lung physiology. By using a theoretical model for the consumption of magnetization during data acquisition, the noise intensity in the computed gas-phase depolarization maps was minimized as a function of the gas-phase depolarization rate. With such optimization the theoretical model predicted an up to threefold improvement in precision. Experiments in rabbits demonstrated that for typical imaging parameter values the optimized XTC pulse sequence yielded a median noise intensity of only about 3% in the depolarization maps. Consequently, the reliable detection of variations in the average alveolar wall thickness of as little as 300 nm can be expected. This improvement in the precision of the XTC MRI technique should lead to a substantial increase in its sensitivity for detecting pathological changes in lung function. Magn Reson Med 57:1099,1109, 2007. © 2007 Wiley-Liss, Inc. [source] Sensitivity improvement of circular dichroism detection in HPLC by using a low-pass electronic noise filter: Application to the enantiomeric determination purity of a basic drugCHIRALITY, Issue 2 2007Marie Lorin Abstract The quality control of chiral drugs requires the determination of their enantiomeric purity. Nowadays, circular dichroism (CD) spectroscopy is gaining increasing importance in pharmaceutical analysis because of the commercially available CD detector in liquid chromatography. The separation of the two enantiomers of a basic drug (efaroxan) was achieved by high performance liquid chromatography using an amylose-derivated column with both UV and CD detections. A baseline-resolved separation (resolution: 5) was obtained after optimization of the mobile phase composition with hexane-ethanol-diethylamine (90:10:0.05; v/v/v). The use of a commercial low-pass electronic noise filter of the CD signal has improved the signal-to-noise ratio by a factor twelve and allowed the quantitation of each enantiomer in the 1.25,300 ,g ml,1 concentration range. The CD linear calibration curve, expressed in terms of stereoisomer height ratio versus concentration ratio, was plotted over the 0.4,6% range. A correlation coefficient greater than 0.999 was obtained by least-squares regression and the limit of detection for the distomer/eutomer ratio was estimated at 0.14%. Although the method validation showed good repeatability on the retention times (RSD < 0.9%), on the peak height ratios (RSD < 8.7%) of each enantiomer only up to 99.2% enantiomeric purity was achieved. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] Pressure and gas composition effects on the operation of the pulsed flame photometric detectorISRAEL JOURNAL OF CHEMISTRY, Issue 2 2001Gad Frishman The effect of pressure and hydrogen/oxygen ratio of a burning gas mixture on pulsed flame emission time-dependence was investigated in the range of 0.1,5 atm using a specially designed pulsed flame photometric detector (PFPD). We studied the pressure and gas composition effect on the pulsed flame delayed light emission of sulfur, phosphorus, and nitrogen-containing organic compounds. The optimal pressure conditions for nitrogen detection, intensity, and emission time delay was found to be 0.4 bar, at which the detection sensitivity could be improved by a factor of 2. For phosphorus, the optimal pressure obtained was 1.3 bar with 40% sensitivity improvement (compared with 1 bar). In the case of sulfur detection, two emission maxima were obtained, at 1.1 and 0.6 bar, at H/O ratio of 5. Increasing the H/O ratio resulted in the appearance of only one peak at 1 bar, and enhancement of the sensitivity by a factor of 2.4 at H/O ratio of 10.3. From the analytical point of view, we found that emission intensity is practically unchanged by the pressure and the H/O ratio for all three elements investigated in the range of 0.8,1.1 bar and H/O of 5,6. Thus, in addition to excellent sensitivity and improved selectivity, the PFPD can be applied under a variety of atmospheric pressure conditions in field environmental applications. [source] Measurement of caffeine and five of the major metabolites in urine by high-performance liquid chromatography/tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2005Allan Weimann Abstract Analysis of caffeine and its metabolites is of interest with respect to caffeine exposure, for kinetic and metabolism studies and for opportunistic in vivo estimation of drug metabolizing enzyme activity in humans and animals. For the latter, analysis is usually done by high-performance liquid chromatography (HPLC) with UV detection. However, this method is close to the detection limit for certain of the metabolites and requires very long chromatography, 30,60 min. We have developed a fast method for the quantification of caffeine and its metabolites 1-methylxanthine, 1-methyluric acid, 1,7-dimethyluric acid, 5-acetylamino-6-amino-3-methyluracil (AAMU) and 5-acetylamino-6-formylamino-3-methyluracil (AFMU) by HPLC tandem mass spectrometry (MS/MS) in urine that requires only its dilution with buffer and centrifugation before injection into the HPLC/MS/MS system. The chromatography lasts 7 min and is followed by 4.5 min for re-equilibration of the HPLC column, giving a total analysis time of 11.5 min. The method provides a great sensitivity improvement with detection limits for all analytes ,25 nM in real samples. Also, the analysis provides much improvement in capacity to ,125 samples per 24 h. Intra- and inter-day coefficients of variation of a single analysis are <6.5% for all the analytes. The inter-day coefficient of variation of duplicate analyses is <4.8% for all analytes. The method is automated, including automated integration, and it is fast, robust and suitable for large-scale investigations in humans and animals. Copyright © 2005 John Wiley & Sons, Ltd. [source] Five-port receiver with improved sensitivityMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008Fernando Rangel de Sousa Abstract This article reports the architecture of a five-port receiver without vector base circuit generators in which three antennas provide three phase-shifted copies of the received signal. A 2.4-GHz prototype was implemented for concept proofing, and the measurements point to a sensitivity improvement of 6 dB with respect to comparable classic five-port receivers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2945,2947, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23858 [source] High Sensibility of Quantum Dots to Metal Ions Inspired by Hydroxyapatite MicrobeadsCHINESE JOURNAL OF CHEMISTRY, Issue 6 2010Xiang Wang Abstract An approach for the sensitive and selective determination of Ag+, Cu2+ and Hg2+ ions was developed based on the fluorescence quenching of mercaptopropionic acid (MPA) capped CdTe quantum dots in the existence of hydroxyapatite (HAP) nanoribbon spherulites. Among various metal ions investigated, it was found that the fluorescence of CdTe QDs was only sensitive to Ag+, Cu2+ and Hg2+ ions. The addition of HAP into the CdTe system could bring forward a sensitivity improvement of about 1 to 2 orders of magnitude in the detection of Ag+ and Cu2+ compared with the plain CdTe system without the existence of HAP; while there was no sensitization effect for Hg2+. Under optimal conditions, the detection limits for Ag+, Cu2+ and Hg2+ were 20, 56 and 3.0 nmol·L,1, respectively, and the linear ranges were 0.02,50, 0.056,54 and 0.003,2.4 µmol·L,1, respectively. Mechanisms of both QDs fluorescence quenching by metal ions and the sensitization effect by HAP were also discussed. [source] Parallel transmit and receive technology in high-field magnetic resonance neuroimagingINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2010Andrew G. Webb Abstract The major radiofrequency engineering challenges of high-field MR neuroimaging are as follows: (1) to produce a strong, homogeneous transmit B1 field, while remaining within regulatory guidelines for tissue power deposition and (2) to receive the signal with the maximum signal-to-noise and the greatest flexibility in terms of utilizing the benefits of parallel imaging. Borrowing from developments in electromagnetic hyperthermia, the first challenge has been met by the use of transmit arrays, in which the input power to each element of the array can be varied in terms of magnitude and phase. Optimization of these parameters, as well as the form of the applied RF pulse, leads to very homogeneous B1 fields throughout the brain. The design of large receive arrays, using impedance-mismatched preamplifiers and geometrical overlap for interelement isolation, has resulted in significant sensitivity improvements as well as large acceleration factors in parallel imaging. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 2,13, 2010 [source] Evaluation of axial DC offsets during scanning of a quadrupole ion trap for sensitivity improvementsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2001Timothy Vaden In the normal operation of quadrupole ion trap mass spectrometers, approximately half of the trapped ions are ejected through the source endcap during a mass-selective instability scan. This reduces the sensitivity of the instrument by ,50%. In this preliminary study, a circuit was constructed that produced a dipolar DC offset on the axial modulation waveform to recover this lost ion current. A variable (0 to 10,V DC), positive and negative offset was applied to the source and detector endcap, respectively. This DC offset axially displaced the ion cloud toward the detector endcap increasing the probability of detection. Several compounds, including 11 pesticides, were evaluated. Sensitivity enhancements ranged from 13 to 97% (theoretical 100%). No spectral resolution problems were observed; however, a compound-dependent mass discrimination was observed in several cases. This mass discrimination problem is currently under investigation. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||