Application of a Real-Time, Calculable Limiting Form of the Renyi Entropy for Molecular Imaging of Tumors

PubMed Central

Marsh, J. N.; Wallace, K. D.; McCarthy, J. E.; Wickerhauser, M. V.; Maurizi, B. N.; Lanza, G. M.; Wickline, S. A.; Hughes, M. S.

2011-01-01

Previously, we reported new methods for ultrasound signal characterization using entropy, Hf; a generalized entropy, the Renyi entropy, If(r); and a limiting form of Renyi entropy suitable for real-time calculation, If,∞. All of these quantities demonstrated significantly more sensitivity to subtle changes in scattering architecture than energy-based methods in certain settings. In this study, the real-time calculable limit of the Renyi entropy, If,∞, is applied for the imaging of angiogenic murine neovasculature in a breast cancer xenograft using a targeted contrast agent. It is shown that this approach may be used to detect reliably the accumulation of targeted nanoparticles at five minutes post-injection in this in vivo model. PMID:20679020

Implementation of a channelized Hotelling observer model to assess image quality of x-ray angiography systems.

PubMed

Favazza, Christopher P; Fetterly, Kenneth A; Hangiandreou, Nicholas J; Leng, Shuai; Schueler, Beth A

2015-01-01

Evaluation of flat-panel angiography equipment through conventional image quality metrics is limited by the scope of standard spatial-domain image quality metric(s), such as contrast-to-noise ratio and spatial resolution, or by restricted access to appropriate data to calculate Fourier domain measurements, such as modulation transfer function, noise power spectrum, and detective quantum efficiency. Observer models have been shown capable of overcoming these limitations and are able to comprehensively evaluate medical-imaging systems. We present a spatial domain-based channelized Hotelling observer model to calculate the detectability index (DI) of our different sized disks and compare the performance of different imaging conditions and angiography systems. When appropriate, changes in DIs were compared to expectations based on the classical Rose model of signal detection to assess linearity of the model with quantum signal-to-noise ratio (SNR) theory. For these experiments, the estimated uncertainty of the DIs was less than 3%, allowing for precise comparison of imaging systems or conditions. For most experimental variables, DI changes were linear with expectations based on quantum SNR theory. DIs calculated for the smallest objects demonstrated nonlinearity with quantum SNR theory due to system blur. Two angiography systems with different detector element sizes were shown to perform similarly across the majority of the detection tasks.

Identification of Patient Zero in Static and Temporal Networks: Robustness and Limitations

NASA Astrophysics Data System (ADS)

Antulov-Fantulin, Nino; Lančić, Alen; Šmuc, Tomislav; Štefančić, Hrvoje; Šikić, Mile

2015-06-01

Detection of patient zero can give new insights to epidemiologists about the nature of first transmissions into a population. In this Letter, we study the statistical inference problem of detecting the source of epidemics from a snapshot of spreading on an arbitrary network structure. By using exact analytic calculations and Monte Carlo estimators, we demonstrate the detectability limits for the susceptible-infected-recovered model, which primarily depend on the spreading process characteristics. Finally, we demonstrate the applicability of the approach in a case of a simulated sexually transmitted infection spreading over an empirical temporal network of sexual interactions.

[Detection of antibodies against Legionella pneumophila from pleural effusion--a case report of Legionnaire's pneumonia with pleural effusion].

PubMed

Xu, L; Wang, P; Chen, S

1994-06-01

Using TAT and ELISA, 50 samples of pleural effusion and sera from patients infected with non-Legionella pneumophila were detected for antibodies against Legionella pneumophila serogroups 1 and 6, respectively. The average titre and upper limit value (99%, mean + 2.326S) calculated. In addition, a pleural effusion and a serum from a patient with Legionnaire's pneumonia were also detected by TAT and ELISA. The result showed that the titre of this antibody in his pleural effusion was not only over the upper limit, but also higher than that in his serum.

Application of a real-time, calculable limiting form of the Renyi entropy for molecular imaging of tumors.

PubMed

Marsh, Jon N; Wallace, Kirk D; McCarthy, John E; Wickerhauser, Mladen V; Maurizi, Brian N; Lanza, Gregory M; Wickline, Samuel A; Hughes, Michael S

2010-08-01

Previously, we reported new methods for ultrasound signal characterization using entropy, H(f); a generalized entropy, the Renyi entropy, I(f)(r); and a limiting form of Renyi entropy suitable for real-time calculation, I(f),(infinity). All of these quantities demonstrated significantly more sensitivity to subtle changes in scattering architecture than energy-based methods in certain settings. In this study, the real-time calculable limit of the Renyi entropy, I(f),(infinity), is applied for the imaging of angiogenic murine neovasculature in a breast cancer xenograft using a targeted contrast agent. It is shown that this approach may be used to reliably detect the accumulation of targeted nanoparticles at five minutes post-injection in this in vivo model.

HPLC separation post-column reaction, UV-visible and fluorescence detection of trace UO/sub 2//sup 2 +//U/sup 4 +/ species in aqueous solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karimi, A.R.

In this study a method for the measurement of uranium in natural waters at sub-ppB concentration levels by the separation and determination of U/sup 4 +/ and UO/sub 2//sup 2 +/ species is proposed. Reversed phase high performance liquid chromatography, followed by a post-column reaction and a sensitive UV-visible detection system was the method of choice to determine qualitatively and quantitatively the two uranium species. Also a cation-exchange and fluorescence detection system was studied for separation and determination of UO/sub 2//sup 2 +/ ions. Uranyl ion was selectively complexed with L-phenylalanine moetie in the sample solution containing U/sup 4 +/more » ions. Uranium (IV)/U(VI)-ligand was separated on a C/sub 18/ column with acetate buffer. Hexanesulfonate was found to be the choice for ion-pair reagent. The separation was best done with the acetate buffer at .01 M concentration and pH of 3.5. Absorption of the two species were measured after a post-column reaction with Arsenazo-III. Chromatographic parameters were calculated and a calibration curves were constructed. The detection limit for the procedure was 0.7 ..mu..g/mo and 1.2..mu..g/ml for U(IV) and U(VI) respectively. When U(VI) was separated on the cation-exchange column the limit of detection was calculated to be 1 ..mu..g/ml. The direct fluorometric method for U(VI) measurement results in a detection limit of 2 ppB and upper concentration limit of 2 ppM. The effect of interfering ions in the direct method of determination could be eliminated by dilution of sample solution.« less

Real-time calculation of a limiting form of the Renyi entropy applied to detection of subtle changes in scattering architecture

PubMed Central

Hughes, M. S.; McCarthy, J. E.; Wickerhauser, M. V.; Marsh, J. N.; Arbeit, J. M.; Fuhrhop, R. W.; Wallace, K. D.; Thomas, T.; Smith, J.; Agyem, K.; Lanza, G. M.; Wickline, S. A.

2009-01-01

Previously a new method for ultrasound signal characterization using entropy Hf was reported, and it was demonstrated that in certain settings, further improvements in signal characterization could be obtained by generalizing to Renyi entropy-based signal characterization If(r) with values of r near 2 (specifically r=1.99) [M. S. Hughes et al., J. Acoust. Soc. Am. 125, 3141–3145 (2009)]. It was speculated that further improvements in sensitivity might be realized at the limit r→2. At that time, such investigation was not feasible due to excessive computational time required to calculate If(r) near this limit. In this paper, an asymptotic expression for the limiting behavior of If(r) as r→2 is derived and used to present results analogous to those obtained with If(1.99). Moreover, the limiting form If,∞ is computable directly from the experimentally measured waveform f(t) by an algorithm that is suitable for real-time calculation and implementation. PMID:19894818

Lower Limits on Aperture Size for an ExoEarth Detecting Coronagraphic Mission

NASA Technical Reports Server (NTRS)

Stark, Christopher C.; Roberge, Aki; Mandell, Avi; Clampin, Mark; Domagal-Goldman, Shawn D.; McElwain, Michael W.; Stapelfeldt, Karl R.

2015-01-01

The yield of Earth-like planets will likely be a primary science metric for future space-based missions that will drive telescope aperture size. Maximizing the exoEarth candidate yield is therefore critical to minimizing the required aperture. Here we describe a method for exoEarth candidate yield maximization that simultaneously optimizes, for the first time, the targets chosen for observation, the number of visits to each target, the delay time between visits, and the exposure time of every observation. This code calculates both the detection time and multiwavelength spectral characterization time required for planets. We also refine the astrophysical assumptions used as inputs to these calculations, relying on published estimates of planetary occurrence rates as well as theoretical and observational constraints on terrestrial planet sizes and classical habitable zones. Given these astrophysical assumptions, optimistic telescope and instrument assumptions, and our new completeness code that produces the highest yields to date, we suggest lower limits on the aperture size required to detect and characterize a statistically motivated sample of exoEarths.

Implementation of a channelized Hotelling observer model to assess image quality of x-ray angiography systems

PubMed Central

Favazza, Christopher P.; Fetterly, Kenneth A.; Hangiandreou, Nicholas J.; Leng, Shuai; Schueler, Beth A.

2015-01-01

Abstract. Evaluation of flat-panel angiography equipment through conventional image quality metrics is limited by the scope of standard spatial-domain image quality metric(s), such as contrast-to-noise ratio and spatial resolution, or by restricted access to appropriate data to calculate Fourier domain measurements, such as modulation transfer function, noise power spectrum, and detective quantum efficiency. Observer models have been shown capable of overcoming these limitations and are able to comprehensively evaluate medical-imaging systems. We present a spatial domain-based channelized Hotelling observer model to calculate the detectability index (DI) of our different sized disks and compare the performance of different imaging conditions and angiography systems. When appropriate, changes in DIs were compared to expectations based on the classical Rose model of signal detection to assess linearity of the model with quantum signal-to-noise ratio (SNR) theory. For these experiments, the estimated uncertainty of the DIs was less than 3%, allowing for precise comparison of imaging systems or conditions. For most experimental variables, DI changes were linear with expectations based on quantum SNR theory. DIs calculated for the smallest objects demonstrated nonlinearity with quantum SNR theory due to system blur. Two angiography systems with different detector element sizes were shown to perform similarly across the majority of the detection tasks. PMID:26158086

A novel ECG detector performance metric and its relationship with missing and false heart rate limit alarms.

PubMed

Daluwatte, Chathuri; Vicente, Jose; Galeotti, Loriano; Johannesen, Lars; Strauss, David G; Scully, Christopher G

Performance of ECG beat detectors is traditionally assessed on long intervals (e.g.: 30min), but only incorrect detections within a short interval (e.g.: 10s) may cause incorrect (i.e., missed+false) heart rate limit alarms (tachycardia and bradycardia). We propose a novel performance metric based on distribution of incorrect beat detection over a short interval and assess its relationship with incorrect heart rate limit alarm rates. Six ECG beat detectors were assessed using performance metrics over long interval (sensitivity and positive predictive value over 30min) and short interval (Area Under empirical cumulative distribution function (AUecdf) for short interval (i.e., 10s) sensitivity and positive predictive value) on two ECG databases. False heart rate limit and asystole alarm rates calculated using a third ECG database were then correlated (Spearman's rank correlation) with each calculated performance metric. False alarm rates correlated with sensitivity calculated on long interval (i.e., 30min) (ρ=-0.8 and p<0.05) and AUecdf for sensitivity (ρ=0.9 and p<0.05) in all assessed ECG databases. Sensitivity over 30min grouped the two detectors with lowest false alarm rates while AUecdf for sensitivity provided further information to identify the two beat detectors with highest false alarm rates as well, which was inseparable with sensitivity over 30min. Short interval performance metrics can provide insights on the potential of a beat detector to generate incorrect heart rate limit alarms. Published by Elsevier Inc.

Quantification of susceptibility change at high-concentrated SPIO-labeled target by characteristic phase gradient recognition.

PubMed

Zhu, Haitao; Nie, Binbin; Liu, Hua; Guo, Hua; Demachi, Kazuyuki; Sekino, Masaki; Shan, Baoci

2016-05-01

Phase map cross-correlation detection and quantification may produce highlighted signal at superparamagnetic iron oxide nanoparticles, and distinguish them from other hypointensities. The method may quantify susceptibility change by performing least squares analysis between a theoretically generated magnetic field template and an experimentally scanned phase image. Because characteristic phase recognition requires the removal of phase wrap and phase background, additional steps of phase unwrapping and filtering may increase the chance of computing error and enlarge the inconsistence among algorithms. To solve problem, phase gradient cross-correlation and quantification method is developed by recognizing characteristic phase gradient pattern instead of phase image because phase gradient operation inherently includes unwrapping and filtering functions. However, few studies have mentioned the detectable limit of currently used phase gradient calculation algorithms. The limit may lead to an underestimation of large magnetic susceptibility change caused by high-concentrated iron accumulation. In this study, mathematical derivation points out the value of maximum detectable phase gradient calculated by differential chain algorithm in both spatial and Fourier domain. To break through the limit, a modified quantification method is proposed by using unwrapped forward differentiation for phase gradient generation. The method enlarges the detectable range of phase gradient measurement and avoids the underestimation of magnetic susceptibility. Simulation and phantom experiments were used to quantitatively compare different methods. In vivo application performs MRI scanning on nude mice implanted by iron-labeled human cancer cells. Results validate the limit of detectable phase gradient and the consequent susceptibility underestimation. Results also demonstrate the advantage of unwrapped forward differentiation compared with differential chain algorithms for susceptibility quantification at high-concentrated iron accumulation. Copyright © 2015 Elsevier Inc. All rights reserved.

Theoretical detection threshold of the proton-acoustic range verification technique.

PubMed

Ahmad, Moiz; Xiang, Liangzhong; Yousefi, Siavash; Xing, Lei

2015-10-01

Range verification in proton therapy using the proton-acoustic signal induced in the Bragg peak was investigated for typical clinical scenarios. The signal generation and detection processes were simulated in order to determine the signal-to-noise limits. An analytical model was used to calculate the dose distribution and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. In this method, the acoustic waves propagating from the Bragg peak were generated by the general 3D pressure wave equation implemented using a finite element method. Various beam pulse widths (0.1-10 μs) were simulated by convolving the acoustic waves with Gaussian kernels. A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth bandpass filter with consideration of random noise based on a model of thermal noise in the transducer. The signal-to-noise ratio on a per-proton basis was calculated, determining the minimum number of protons required to generate a detectable pulse. The maximum spatial resolution of the proton-acoustic imaging modality was also estimated from the signal spectrum. The calculated noise in the transducer was 12-28 mPa, depending on the transducer central frequency (70-380 kHz). The minimum number of protons detectable by the technique was on the order of 3-30 × 10(6) per pulse, with 30-800 mGy dose per pulse at the Bragg peak. Wider pulses produced signal with lower acoustic frequencies, with 10 μs pulses producing signals with frequency less than 100 kHz. The proton-acoustic process was simulated using a realistic model and the minimal detection limit was established for proton-acoustic range validation. These limits correspond to a best case scenario with a single large detector with no losses and detector thermal noise as the sensitivity limiting factor. Our study indicated practical proton-acoustic range verification may be feasible with approximately 5 × 10(6) protons/pulse and beam current.

Theoretical detection threshold of the proton-acoustic range verification technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Moiz; Yousefi, Siavash; Xing, Lei, E-mail: lei@stanford.edu

2015-10-15

Purpose: Range verification in proton therapy using the proton-acoustic signal induced in the Bragg peak was investigated for typical clinical scenarios. The signal generation and detection processes were simulated in order to determine the signal-to-noise limits. Methods: An analytical model was used to calculate the dose distribution and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. In this method, the acoustic waves propagating from the Bragg peak were generated by the general 3D pressure wave equation implemented using a finite element method.more » Various beam pulse widths (0.1–10 μs) were simulated by convolving the acoustic waves with Gaussian kernels. A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth bandpass filter with consideration of random noise based on a model of thermal noise in the transducer. The signal-to-noise ratio on a per-proton basis was calculated, determining the minimum number of protons required to generate a detectable pulse. The maximum spatial resolution of the proton-acoustic imaging modality was also estimated from the signal spectrum. Results: The calculated noise in the transducer was 12–28 mPa, depending on the transducer central frequency (70–380 kHz). The minimum number of protons detectable by the technique was on the order of 3–30 × 10{sup 6} per pulse, with 30–800 mGy dose per pulse at the Bragg peak. Wider pulses produced signal with lower acoustic frequencies, with 10 μs pulses producing signals with frequency less than 100 kHz. Conclusions: The proton-acoustic process was simulated using a realistic model and the minimal detection limit was established for proton-acoustic range validation. These limits correspond to a best case scenario with a single large detector with no losses and detector thermal noise as the sensitivity limiting factor. Our study indicated practical proton-acoustic range verification may be feasible with approximately 5 × 10{sup 6} protons/pulse and beam current.« less

Theoretical detection threshold of the proton-acoustic range verification technique

PubMed Central

Ahmad, Moiz; Xiang, Liangzhong; Yousefi, Siavash; Xing, Lei

2015-01-01

Purpose: Range verification in proton therapy using the proton-acoustic signal induced in the Bragg peak was investigated for typical clinical scenarios. The signal generation and detection processes were simulated in order to determine the signal-to-noise limits. Methods: An analytical model was used to calculate the dose distribution and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. In this method, the acoustic waves propagating from the Bragg peak were generated by the general 3D pressure wave equation implemented using a finite element method. Various beam pulse widths (0.1–10 μs) were simulated by convolving the acoustic waves with Gaussian kernels. A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth bandpass filter with consideration of random noise based on a model of thermal noise in the transducer. The signal-to-noise ratio on a per-proton basis was calculated, determining the minimum number of protons required to generate a detectable pulse. The maximum spatial resolution of the proton-acoustic imaging modality was also estimated from the signal spectrum. Results: The calculated noise in the transducer was 12–28 mPa, depending on the transducer central frequency (70–380 kHz). The minimum number of protons detectable by the technique was on the order of 3–30 × 106 per pulse, with 30–800 mGy dose per pulse at the Bragg peak. Wider pulses produced signal with lower acoustic frequencies, with 10 μs pulses producing signals with frequency less than 100 kHz. Conclusions: The proton-acoustic process was simulated using a realistic model and the minimal detection limit was established for proton-acoustic range validation. These limits correspond to a best case scenario with a single large detector with no losses and detector thermal noise as the sensitivity limiting factor. Our study indicated practical proton-acoustic range verification may be feasible with approximately 5 × 106 protons/pulse and beam current. PMID:26429247

Research on capability of detecting ballistic missile by near space infrared system

NASA Astrophysics Data System (ADS)

Lu, Li; Sheng, Wen; Jiang, Wei; Jiang, Feng

2018-01-01

The infrared detection technology of ballistic missile based on near space platform can effectively make up the shortcomings of high-cost of traditional early warning satellites and the limited earth curvature of ground-based early warning radar. In terms of target detection capability, aiming at the problem that the formula of the action distance based on contrast performance ignores the background emissivity in the calculation process and the formula is only valid for the monochromatic light, an improved formula of the detecting range based on contrast performance is proposed. The near space infrared imaging system parameters are introduced, the expression of the contrastive action distance formula based on the target detection of the near space platform is deduced. The detection range of the near space infrared system for the booster stage ballistic missile skin, the tail nozzle and the tail flame is calculated. The simulation results show that the near-space infrared system has the best effect on the detection of tail-flame radiation.

Hybrid Monte Carlo/Deterministic Methods for Accelerating Active Interrogation Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peplow, Douglas E.; Miller, Thomas Martin; Patton, Bruce W

2013-01-01

The potential for smuggling special nuclear material (SNM) into the United States is a major concern to homeland security, so federal agencies are investigating a variety of preventive measures, including detection and interdiction of SNM during transport. One approach for SNM detection, called active interrogation, uses a radiation source, such as a beam of neutrons or photons, to scan cargo containers and detect the products of induced fissions. In realistic cargo transport scenarios, the process of inducing and detecting fissions in SNM is difficult due to the presence of various and potentially thick materials between the radiation source and themore » SNM, and the practical limitations on radiation source strength and detection capabilities. Therefore, computer simulations are being used, along with experimental measurements, in efforts to design effective active interrogation detection systems. The computer simulations mostly consist of simulating radiation transport from the source to the detector region(s). Although the Monte Carlo method is predominantly used for these simulations, difficulties persist related to calculating statistically meaningful detector responses in practical computing times, thereby limiting their usefulness for design and evaluation of practical active interrogation systems. In previous work, the benefits of hybrid methods that use the results of approximate deterministic transport calculations to accelerate high-fidelity Monte Carlo simulations have been demonstrated for source-detector type problems. In this work, the hybrid methods are applied and evaluated for three example active interrogation problems. Additionally, a new approach is presented that uses multiple goal-based importance functions depending on a particle s relevance to the ultimate goal of the simulation. Results from the examples demonstrate that the application of hybrid methods to active interrogation problems dramatically increases their calculational efficiency.« less

Real-time calculation of a limiting form of the Renyi entropy applied to detection of subtle changes in scattering architecture.

PubMed

Hughes, M S; McCarthy, J E; Wickerhauser, M V; Marsh, J N; Arbeit, J M; Fuhrhop, R W; Wallace, K D; Thomas, T; Smith, J; Agyem, K; Lanza, G M; Wickline, S A

2009-11-01

Previously a new method for ultrasound signal characterization using entropy H(f) was reported, and it was demonstrated that in certain settings, further improvements in signal characterization could be obtained by generalizing to Renyi entropy-based signal characterization I(f)(r) with values of r near 2 (specifically r=1.99) [M. S. Hughes et al., J. Acoust. Soc. Am. 125, 3141-3145 (2009)]. It was speculated that further improvements in sensitivity might be realized at the limit r-->2. At that time, such investigation was not feasible due to excessive computational time required to calculate I(f)(r) near this limit. In this paper, an asymptotic expression for the limiting behavior of I(f)(r) as r-->2 is derived and used to present results analogous to those obtained with I(f)(1.99). Moreover, the limiting form I(f,infinity) is computable directly from the experimentally measured waveform f(t) by an algorithm that is suitable for real-time calculation and implementation.

Determination of volatile compounds in wine by gas chromatography-flame ionization detection: comparison between the U.S. Environmental Protection Agency 3sigma approach and Hubaux-Vos calculation of detection limits using ordinary and bivariate least squares.

PubMed

Caruso, Rosario; Scordino, Monica; Traulo, Pasqualino; Gagliano, Giacomo

2012-01-01

A capillary GC-flame ionization detection (FID) method to determine volatile compounds (ethyl acetate, 1,1-diethoxyethane, methyl alcohol, 1-propanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-butanol, and 2-butanol) in wine was investigated in terms of calculation of detection limits and calibration method. The main objectives were: (1) calculation of regression coefficient parameters by ordinary least-squares (OLS) and bivariate least-squares (BLS) regression models, taking into account errors in both axes; (2) estimation of linear dynamic range (LDR) according to International Conference on Harmonization recommendations; (3) performance evaluation of a method by using three different internal standards (ISs) such as acetonitrile, acetone, and 1-pentanol; (4) evaluation of LODs according to the U.S. Environmental Protection Agency (EPA) 3sigma approach and the Hubaux-Vos (H-V) method; (5) application of H-V theory to a gas chromatographic analytical method and to a food matrix; and (6) accuracy assessment of the method relative to methyl alcohol content through a Unione Italiana Vini (UIV) interlaboratory proficiency test. Calibration curves calculated via BLS and OLS show similar slopes, while intercepts are closer to zero in the first case, independent of the chosen IS. The studied ISs show a substantially equivalent behavior, even though the IS closer to the analyte retention time seems to be more appropriate in terms of LDR and LOD. Results indicate an underestimation of LODs using the EPA 3sigma approach instead of the more realistic H-V method, both with OLS and BLS regression models. Methanol contents compared with UIV average values indicate recovery between 90 and 110%.

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

PubMed

Altiokka, G; Atkosar, Z; Can, N O

2002-10-15

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively. Copyright 2002 Elsevier Science B.V.

Analytical and sampling constraints in ²¹⁰Pb dating.

PubMed

MacKenzie, A B; Hardie, S M L; Farmer, J G; Eades, L J; Pulford, I D

2011-03-01

²¹⁰Pb dating provides a valuable, widely used means of establishing recent chronologies for sediments and other accumulating natural deposits. The Constant Rate of Supply (CRS) model is the most versatile and widely used method for establishing ²¹⁰Pb chronologies but, when using this model, care must be taken to account for limitations imposed by sampling and analytical factors. In particular, incompatibility of finite values for empirical data, which are constrained by detection limit and core length, with terms in the age calculation, which represent integrations to infinity, can generate erroneously old ages for deeper sections of cores. The bias in calculated ages increases with poorer limit of detection and the magnitude of the disparity increases with age. The origin and magnitude of this effect are considered below, firstly for an idealized, theoretical ²¹⁰Pb profile and secondly for a freshwater lake sediment core. A brief consideration is presented of the implications of this potential artefact for sampling and analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Automated Meteor Fluxes with a Wide-Field Meteor Camera Network

NASA Technical Reports Server (NTRS)

Blaauw, R. C.; Campbell-Brown, M. D.; Cooke, W.; Weryk, R. J.; Gill, J.; Musci, R.

2013-01-01

Within NASA, the Meteoroid Environment Office (MEO) is charged to monitor the meteoroid environment in near ]earth space for the protection of satellites and spacecraft. The MEO has recently established a two ]station system to calculate automated meteor fluxes in the millimeter ]size ]range. The cameras each consist of a 17 mm focal length Schneider lens on a Watec 902H2 Ultimate CCD video camera, producing a 21.7 x 16.3 degree field of view. This configuration has a red ]sensitive limiting meteor magnitude of about +5. The stations are located in the South Eastern USA, 31.8 kilometers apart, and are aimed at a location 90 km above a point 50 km equidistant from each station, which optimizes the common volume. Both single station and double station fluxes are found, each having benefits; more meteors will be detected in a single camera than will be seen in both cameras, producing a better determined flux, but double station detections allow for non ]ambiguous shower associations and permit speed/orbit determinations. Video from the cameras are fed into Linux computers running the ASGARD (All Sky and Guided Automatic Real ]time Detection) software, created by Rob Weryk of the University of Western Ontario Meteor Physics Group. ASGARD performs the meteor detection/photometry, and invokes the MILIG and MORB codes to determine the trajectory, speed, and orbit of the meteor. A subroutine in ASGARD allows for the approximate shower identification in single station meteors. The ASGARD output is used in routines to calculate the flux in units of #/sq km/hour. The flux algorithm employed here differs from others currently in use in that it does not assume a single height for all meteors observed in the common camera volume. In the MEO system, the volume is broken up into a set of height intervals, with the collecting areas determined by the radiant of active shower or sporadic source. The flux per height interval is summed to obtain the total meteor flux. As ASGARD also computes the meteor mass from the photometry, a mass flux can be also calculated. Weather conditions in the southeastern United States are seldom ideal, which introduces the difficulty of a variable sky background. First a weather algorithm indicates if sky conditions are clear enough to calculate fluxes, at which point a limiting magnitude algorithm is employed. The limiting magnitude algorithm performs a fit of stellar magnitudes vs camera intensities. The stellar limiting magnitude is derived from this and easily converted to a limiting meteor magnitude for the active shower or sporadic source.

Size-exclusion chromatography of perfluorosulfonated ionomers.

PubMed

Mourey, T H; Slater, L A; Galipo, R C; Koestner, R J

2011-08-26

A size-exclusion chromatography (SEC) method in N,N-dimethylformamide containing 0.1 M LiNO(3) is shown to be suitable for the determination of molar mass distributions of three classes of perfluorosulfonated ionomers, including Nafion(®). Autoclaving sample preparation is optimized to prepare molecular solutions free of aggregates, and a solvent exchange method concentrates the autoclaved samples to enable the use of molar-mass-sensitive detection. Calibration curves obtained from light scattering and viscometry detection suggest minor variation in the specific refractive index increment across the molecular size distributions, which introduces inaccuracies in the calculation of local absolute molar masses and intrinsic viscosities. Conformation plots that combine apparent molar masses from light scattering detection with apparent intrinsic viscosities from viscometry detection partially compensate for the variations in refractive index increment. The conformation plots are consistent with compact polymer conformations, and they provide Mark-Houwink-Sakurada constants that can be used to calculate molar mass distributions without molar-mass-sensitive detection. Unperturbed dimensions and characteristic ratios calculated from viscosity-molar mass relationships indicate unusually free rotation of the perfluoroalkane backbones and may suggest limitations to applying two-parameter excluded volume theories for these ionomers. Copyright © 2011 Elsevier B.V. All rights reserved.

Detection of cat-eye effect echo based on unit APD

NASA Astrophysics Data System (ADS)

Wu, Dong-Sheng; Zhang, Peng; Hu, Wen-Gang; Ying, Jia-Ju; Liu, Jie

2016-10-01

The cat-eye effect echo of optical system can be detected based on CCD, but the detection range is limited within several kilometers. In order to achieve long-range even ultra-long-range detection, it ought to select APD as detector because of the high sensitivity of APD. The detection system of cat-eye effect echo based on unit APD is designed in paper. The implementation scheme and key technology of the detection system is presented. The detection performances of the detection system including detection range, detection probability and false alarm probability are modeled. Based on the model, the performances of the detection system are analyzed using typical parameters. The results of numerical calculation show that the echo signal-to-noise ratio is greater than six, the detection probability is greater than 99.9% and the false alarm probability is less tan 0.1% within 20 km detection range. In order to verify the detection effect, we built the experimental platform of detection system according to the design scheme and carry out the field experiments. The experimental results agree well with the results of numerical calculation, which prove that the detection system based on the unit APD is feasible to realize remote detection for cat-eye effect echo.

Prognosis for a mid-infrared magnetic rotation spectrometer for the in situ detection of atmospheric free radicals

NASA Astrophysics Data System (ADS)

Blake, Thomas A.; Chackerian, Charles, Jr.; Podolske, James R.

1996-02-01

Mid-infrared magnetic rotation spectroscopy (MRS) experiments on nitric oxide (NO) are quantitatively modeled by theoretical calculations. The verified theory is used to specify an instrument that can make in situ measurements on NO and NO2 in the Earth's atmosphere at a sensitivity level of a few parts in 1012 by volume per second. The prototype instrument used in the experiments has an extrapolated detection limit for NO of 30 parts in 109 for a 1-s integration time over a 12-cm path length. The detection limit is an extrapolation of experimental results to a signal-to-noise ratio of one, where the noise is considered to be one-half the peak-to-peak baseline noise. Also discussed are the various factors that can limit the sensitivity of a MRS spectrometer that uses liquid-nitrogen-cooled lead-salt diode lasers and photovoltaic detectors.

A prototype detection system for atmospheric monitoring of xenon radioisotopes

NASA Astrophysics Data System (ADS)

Czyz, Steven A.; Farsoni, Abi T.; Ranjbar, Lily

2018-03-01

The design of a radioxenon detection system utilizing a CdZeTe crystal and a plastic scintillator coupled to an array of SiPMs to conduct beta-gamma coincidence detection for atmospheric radioxenon monitoring, as well as the measurement of 135Xe and 133/133mXe, have been detailed previously. This paper presents recent measurements of 133/133mXe and 131mXe and the observation of conversion electrons in their coincidence spectra, as well as a 48-hour background measurement to calculate the Minimum Detectable Concentration (MDC) of radioxenon isotopes in the system. The identification of Regions of Interest (ROIs) in the coincidence spectra yielded from the radioxenon measurements, and the subsequent calculation of the MDCs of the system for 135Xe, 133/133mXe, and 131mXe, are also discussed. Calculated MDCs show that the detection system preforms respectably when compared to other state of the art radioxenon detection systems and achieved an MDC of less than 1 mBq/m3 for 131mXe, 133Xe, and 133mXe, in accordance with limits set by the Comprehensive Nuclear-Test-Ban Treaty (CTBTO). The system also provides the advantage of room temperature operation, compactness, low noise operation and having simple readout electronics.

Theoretical detection limit of PIXE analysis using 20 MeV proton beams

NASA Astrophysics Data System (ADS)

Ishii, Keizo; Hitomi, Keitaro

2018-02-01

Particle-induced X-ray emission (PIXE) analysis is usually performed using proton beams with energies in the range 2∼3 MeV because at these energies, the detection limit is low. The detection limit of PIXE analysis depends on the X-ray production cross-section, the continuous background of the PIXE spectrum and the experimental parameters such as the beam currents and the solid angle and detector efficiency of X-ray detector. Though the continuous background increases as the projectile energy increases, the cross-section of the X-ray increases as well. Therefore, the detection limit of high energy proton PIXE is not expected to increase significantly. We calculated the cross sections of continuous X-rays produced in several bremsstrahlung processes and estimated the detection limit of a 20 MeV proton PIXE analysis by modelling the Compton tail of the γ-rays produced in the nuclear reactions, and the escape effect on the secondary electron bremsstrahlung. We found that the Compton tail does not affect the detection limit when a thin X-ray detector is used, but the secondary electron bremsstrahlung escape effect does have an impact. We also confirmed that the detection limit of the PIXE analysis, when used with 4 μm polyethylene backing film and an integrated beam current of 1 μC, is 0.4∼2.0 ppm for proton energies in the range 10∼30 MeV and elements with Z = 16-90. This result demonstrates the usefulness of several 10 MeV cyclotrons for performing PIXE analysis. Cyclotrons with these properties are currently installed in positron emission tomography (PET) centers.

Laboratory and Astronomical Detection of the Negative Molecular Ion C3N-

NASA Astrophysics Data System (ADS)

Thaddeus, P.; Gottlieb, C. A.; Gupta, H.; Brünken, S.; McCarthy, M. C.; Agúndez, M.; Guélin, M.; Cernicharo, J.

2008-04-01

The negative molecular ion C3N- has been detected at millimeter wavelengths in a low-pressure laboratory discharge, and then with frequencies derived from the laboratory data in the molecular envelope of IRC+10216. Spectroscopic constants derived from laboratory measurements of 12 transitions between 97 and 378 GHz allow the rotational spectrum to be calculated well into the submillimeter-wave band to 0.03 km s-1 or better in equivalent radial velocity. Four transitions of C3N- were detected in IRC+10216 with the IRAM 30 m telescope at precisely the frequencies calculated from the laboratory measurements. The column density of C3N- is 0.5% that of C3N, or approximately 20 times greater than that of C4H- relative to C4H. The C3N- abundance in IRC+10216 is compared with a chemical model calculation by Petrie & Herbst. An upper limit in TMC-1 for C3N- relative to C3N (<0.8%) and a limit for C4H- relative to C4H (<0.004%) that is 5 times lower than that found in IRC+10216, were obtained from observations with the NRAO 100 m Green Bank Telescope (GBT). The fairly high concentration of C3N- achieved in the laboratory implies that other molecular anions containing the CN group may be within reach.

A dynamical approach in exploring the unknown mass in the Solar system using pulsar timing arrays

NASA Astrophysics Data System (ADS)

Guo, Y. J.; Lee, K. J.; Caballero, R. N.

2018-04-01

The error in the Solar system ephemeris will lead to dipolar correlations in the residuals of pulsar timing array for widely separated pulsars. In this paper, we utilize such correlated signals, and construct a Bayesian data-analysis framework to detect the unknown mass in the Solar system and to measure the orbital parameters. The algorithm is designed to calculate the waveform of the induced pulsar-timing residuals due to the unmodelled objects following the Keplerian orbits in the Solar system. The algorithm incorporates a Bayesian-analysis suit used to simultaneously analyse the pulsar-timing data of multiple pulsars to search for coherent waveforms, evaluate the detection significance of unknown objects, and to measure their parameters. When the object is not detectable, our algorithm can be used to place upper limits on the mass. The algorithm is verified using simulated data sets, and cross-checked with analytical calculations. We also investigate the capability of future pulsar-timing-array experiments in detecting the unknown objects. We expect that the future pulsar-timing data can limit the unknown massive objects in the Solar system to be lighter than 10-11-10-12 M⊙, or measure the mass of Jovian system to a fractional precision of 10-8-10-9.

Estimating bergamot juice adulteration of lemon juice by high-performance liquid chromatography (HPLC) analysis of flavanone glycosides.

PubMed

Cautela, Domenico; Laratta, Bruna; Santelli, Francesca; Trifirò, Antonio; Servillo, Luigi; Castaldo, Domenico

2008-07-09

The chemical composition of 30 samples of juices obtained from bergamot (Citrus bergamia Risso and Poit.) fruits is reported and compared to the genuineness parameters adopted by Association of the Industry of Juice and Nectars (AIJN) for lemon juice. It was found that the compositional differences between the two juices are distinguishable, although with difficulty. However, these differences are not strong enough to detect the fraudulent addition of bergamot juice to lemon juice. Instead, we found the high-performance liquid chromatography (HPLC) analysis of the flavanones naringin, neohesperidin, and neoeriocitrin, which are present in bergamot juice and practically absent in the lemon juice, is a convenient way to detect and quantify the fraudulent addition of bergamot juice. The method has been validated by calculating the detection and quantification limits according to Eurachem procedures. Employing neoeriocitrin (detection limit = 0.7 mg/L) and naringin (detection limit = 1 mg/L) as markers, it is possible to detect the addition of bergamot juice to lemon juice at the 1% level. When using neohesperidin as a marker (detection limit = 1 mg/L), the minimal percentage of detectable addition of bergamot juice was about 2%. Finally, it is reported that the pattern of flavonoid content of the bergamot juice is similar to those of chinotto (Citrus myrtifolia Raf) and bitter orange (Citrus aurantium L.) juices and that it is possible to distinguish the three kinds of juices by HPLC analysis.

Analysis of the accuracy and precision of the McMaster method in detection of the eggs of Toxocara and Trichuris species (Nematoda) in dog faeces.

PubMed

Kochanowski, Maciej; Dabrowska, Joanna; Karamon, Jacek; Cencek, Tomasz; Osiński, Zbigniew

2013-07-01

The aim of this study was to determine the accuracy and precision of McMaster method with Raynaud's modification in the detection of the eggs of the nematodes Toxocara canis (Werner, 1782) and Trichuris ovis (Abildgaard, 1795) in faeces of dogs. Four variants of McMaster method were used for counting: in one grid, two grids, the whole McMaster chamber and flotation in the tube. One hundred sixty samples were prepared from dog faeces (20 repetitions for each egg quantity) containing 15, 25, 50, 100, 150, 200, 250 and 300 eggs of T. canis and T. ovis in 1 g of faeces. To compare the influence of kind of faeces on the results, samples of dog faeces were enriched at the same levels with the eggs of another nematode, Ascaris suum Goeze, 1782. In addition, 160 samples of pig faeces were prepared and enriched only with A. suum eggs in the same way. The highest limit of detection (the lowest level of eggs that were detected in at least 50% of repetitions) in all McMaster chamber variants were obtained for T. canis eggs (25-250 eggs/g faeces). In the variant with flotation in the tube, the highest limit of detection was obtained for T. ovis eggs (100 eggs/g). The best results of the limit of detection, sensitivity and the lowest coefficients of variation were obtained with the use of the whole McMaster chamber variant. There was no significant impact of properties of faeces on the obtained results. Multiplication factors for the whole chamber were calculated on the basis of the transformed equation of the regression line, illustrating the relationship between the number of detected eggs and that of the eggs added to the'sample. Multiplication factors calculated for T. canis and T. ovis eggs were higher than those expected using McMaster method with Raynaud modification.

Detection of Landmines by Neutron Backscattering: Effects of Soil Moisture on the Detection System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baysoy, D. Y.; Subasi, M.

2010-01-21

Detection of buried land mines by using neutron backscattering technique (NBS) is a well established method. It depends on detecting a hydrogen anomaly in dry soil. Since a landmine and its plastic casing contain much more hydrogen atoms than the dry soil, this anomaly can be detected by observing a rise in the number of neutrons moderated to thermal or epithermal energy. But, the presence of moisture in the soil limits the effectiveness of the measurements. In this work, a landmine detection system using the NBS technique was designed. A series of Monte Carlo calculations was carried out to determinemore » the limits of the system due to the moisture content of the soil. In the simulations, an isotropic fast neutron source ({sup 252}Cf, 100 mug) and a neutron detection system which consists of five {sup 3}He detectors were used in a practicable geometry. In order to see the effects of soil moisture on the efficiency of the detection system, soils with different water contents were tested.« less

Application of infrared uncooled cameras in surveillance systems

NASA Astrophysics Data System (ADS)

Dulski, R.; Bareła, J.; Trzaskawka, P.; PiÄ tkowski, T.

2013-10-01

The recent necessity to protect military bases, convoys and patrols gave serious impact to the development of multisensor security systems for perimeter protection. One of the most important devices used in such systems are IR cameras. The paper discusses technical possibilities and limitations to use uncooled IR camera in a multi-sensor surveillance system for perimeter protection. Effective ranges of detection depend on the class of the sensor used and the observed scene itself. Application of IR camera increases the probability of intruder detection regardless of the time of day or weather conditions. It also simultaneously decreased the false alarm rate produced by the surveillance system. The role of IR cameras in the system was discussed as well as technical possibilities to detect human being. Comparison of commercially available IR cameras, capable to achieve desired ranges was done. The required spatial resolution for detection, recognition and identification was calculated. The simulation of detection ranges was done using a new model for predicting target acquisition performance which uses the Targeting Task Performance (TTP) metric. Like its predecessor, the Johnson criteria, the new model bounds the range performance with image quality. The scope of presented analysis is limited to the estimation of detection, recognition and identification ranges for typical thermal cameras with uncooled microbolometer focal plane arrays. This type of cameras is most widely used in security systems because of competitive price to performance ratio. Detection, recognition and identification range calculations were made, and the appropriate results for the devices with selected technical specifications were compared and discussed.

Dosimetry audit of radiotherapy treatment planning systems.

PubMed

Bulski, Wojciech; Chełmiński, Krzysztof; Rostkowska, Joanna

2015-07-01

In radiotherapy Treatment Planning Systems (TPS) various calculation algorithms are used. The accuracy of dose calculations has to be verified. Numerous phantom types, detectors and measurement methodologies are proposed to verify the TPS calculations with dosimetric measurements. A heterogeneous slab phantom has been designed within a Coordinated Research Project (CRP) of the IAEA. The heterogeneous phantom was developed in the frame of the IAEA CRP. The phantom consists of frame slabs made with polystyrene and exchangeable inhomogeneity slabs equivalent to bone or lung tissue. Special inserts allow to position thermoluminescent dosimeters (TLD) capsules within the polystyrene slabs below the bone or lung equivalent slabs and also within the lung equivalent material. Additionally, there are inserts that allow to position films or ionisation chamber in the phantom. Ten Polish radiotherapy centres (of 30 in total) were audited during on-site visits. Six different TPSs and five calculation algorithms were examined in the presence of inhomogeneities. Generally, most of the results from TLD were within 5 % tolerance. Differences between doses calculated by TPSs and measured with TLD did not exceed 4 % for bone and polystyrene equivalent materials. Under the lung equivalent material, on the beam axis the differences were lower than 5 %, whereas inside the lung equivalent material, off the beam axis, in some cases they were of around 7 %. The TLD results were confirmed with the ionisation chamber measurements. The comparison results of the calculations and the measurements allow to detect limitations of TPS calculation algorithms. The audits performed with the use of heterogeneous phantom and TLD seem to be an effective tool for detecting the limitations in the TPS performance or beam configuration errors at audited radiotherapy departments. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Fault Detection of Aircraft System with Random Forest Algorithm and Similarity Measure

PubMed Central

Park, Wookje; Jung, Sikhang

2014-01-01

Research on fault detection algorithm was developed with the similarity measure and random forest algorithm. The organized algorithm was applied to unmanned aircraft vehicle (UAV) that was readied by us. Similarity measure was designed by the help of distance information, and its usefulness was also verified by proof. Fault decision was carried out by calculation of weighted similarity measure. Twelve available coefficients among healthy and faulty status data group were used to determine the decision. Similarity measure weighting was done and obtained through random forest algorithm (RFA); RF provides data priority. In order to get a fast response of decision, a limited number of coefficients was also considered. Relation of detection rate and amount of feature data were analyzed and illustrated. By repeated trial of similarity calculation, useful data amount was obtained. PMID:25057508

Dark matter effective field theory scattering in direct detection experiments

DOE PAGES

Schneck, K.

2015-05-01

We examine the consequences of the effective field theory (EFT) of dark matter–nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implicationsmore » of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

Dark matter effective field theory scattering in direct detection experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneck, K.; Cabrera, B.; Cerdeño, D. G.

2015-05-18

We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. Here. we demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. In conclusion, we discussmore » the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

Dark matter effective field theory scattering in direct detection experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneck, K.; Cabrera, B.; Cerdeño, D. G.

2015-05-18

We examine the consequences of the effective field theory (EFT) of dark matter–nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implicationsmore » of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

Dark Matter Indirect Detection with Gamma Rays

DOE PAGES

Patrick Harding, J.

2017-07-27

Searches for weakly interacting massive particle (WIMP) dark matter with gamma-ray instruments are a way to get a unique observational handle on the particle nature of dark matter. I will discuss the details of how to perform these searches, both for annihilating and decaying WIMPs. I will discuss the calculation of the gamma-ray flux from possible sources of dark matter annihilation or decay and show examples of limits which have been calculated using these techniques.

Apparatus and method for radioactive waste screening

DOEpatents

Akers, Douglas W.; Roybal, Lyle G.; Salomon, Hopi; Williams, Charles Leroy

2012-09-04

An apparatus and method relating to screening radioactive waste are disclosed for ensuring that at least one calculated parameter for the measurement data of a sample falls within a range between an upper limit and a lower limit prior to the sample being packaged for disposal. The apparatus includes a radiation detector configured for detecting radioactivity and radionuclide content of the of the sample of radioactive waste and generating measurement data in response thereto, and a collimator including at least one aperture to direct a field of view of the radiation detector. The method includes measuring a radioactive content of a sample, and calculating one or more parameters from the radioactive content of the sample.

Detecting isotopic ratio outliers

NASA Astrophysics Data System (ADS)

Bayne, C. K.; Smith, D. H.

An alternative method is proposed for improving isotopic ratio estimates. This method mathematically models pulse-count data and uses iterative reweighted Poisson regression to estimate model parameters to calculate the isotopic ratios. This computer-oriented approach provides theoretically better methods than conventional techniques to establish error limits and to identify outliers.

The detection and stabilisation of limit cycle for deterministic finite automata

NASA Astrophysics Data System (ADS)

Han, Xiaoguang; Chen, Zengqiang; Liu, Zhongxin; Zhang, Qing

2018-04-01

In this paper, the topological structure properties of deterministic finite automata (DFA), under the framework of the semi-tensor product of matrices, are investigated. First, the dynamics of DFA are converted into a new algebraic form as a discrete-time linear system by means of Boolean algebra. Using this algebraic description, the approach of calculating the limit cycles of different lengths is given. Second, we present two fundamental concepts, namely, domain of attraction of limit cycle and prereachability set. Based on the prereachability set, an explicit solution of calculating domain of attraction of a limit cycle is completely characterised. Third, we define the globally attractive limit cycle, and then the necessary and sufficient condition for verifying whether all state trajectories of a DFA enter a given limit cycle in a finite number of transitions is given. Fourth, the problem of whether a DFA can be stabilised to a limit cycle by the state feedback controller is discussed. Criteria for limit cycle-stabilisation are established. All state feedback controllers which implement the minimal length trajectories from each state to the limit cycle are obtained by using the proposed algorithm. Finally, an illustrative example is presented to show the theoretical results.

DEVELOPMENT OF A METHOD FOR THE OBSERVATION OF LIGHTNING IN PROTOPLANETARY DISKS USING ION LINES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muranushi, Takayuki; Akiyama, Eiji; Inutsuka, Shu-ichiro

2015-12-20

In this paper, we propose observational methods for detecting lightning in protoplanetary disks. We do so by calculating the critical electric field strength in the lightning matrix gas (LMG), the parts of the disk where the electric field is strong enough to cause lightning. That electric field accelerates multiple positive ion species to characteristic terminal velocities. In this paper, we present three distinct discharge models with corresponding critical electric fields. We simulate the position–velocity diagrams and the integrated emission maps for the models. We calculate the measure-of-sensitivity values for detection of the models and for distinguishing between the models. Atmore » the distance of TW Hya (54 pc), LMG that occupies 2π in azimuth and has 25 AU < r < 50 AU is detectable at 1200σ to 4000σ. The lower limits of the radii of 5σ-detectable LMG clumps are between 1.6 AU and 5.3 AU, depending on the models.« less

Ultrahigh-Sensitivity Piezoresistive Pressure Sensors for Detection of Tiny Pressure.

PubMed

Li, Hongwei; Wu, Kunjie; Xu, Zeyang; Wang, Zhongwu; Meng, Yancheng; Li, Liqiang

2018-06-20

High-sensitivity pressure sensors are crucial for the ultrasensitive touch technology and E-skin, especially at the tiny-pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to 200 kPa -1 and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa -1 using short-channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 μs), excellent reproducibility and stability, and low power consumption. Remarkably, the sensor shows excellent detection capacity in the tiny-pressure range, including light-emitting diode switching with a pressure of 7 Pa, ringtone (2-20 Pa) recognition, and ultrasensitive (0.1 Pa) electronic glove. This work represents a performance and strategic progress in the field of pressure sensing.

Power and sample size for multivariate logistic modeling of unmatched case-control studies.

PubMed

Gail, Mitchell H; Haneuse, Sebastien

2017-01-01

Sample size calculations are needed to design and assess the feasibility of case-control studies. Although such calculations are readily available for simple case-control designs and univariate analyses, there is limited theory and software for multivariate unconditional logistic analysis of case-control data. Here we outline the theory needed to detect scalar exposure effects or scalar interactions while controlling for other covariates in logistic regression. Both analytical and simulation methods are presented, together with links to the corresponding software.

Perfluorotributylamine: A novel long-lived greenhouse gas

NASA Astrophysics Data System (ADS)

Hong, Angela C.; Young, Cora J.; Hurley, Michael D.; Wallington, Timothy J.; Mabury, Scott A.

2013-11-01

Perfluorinated compounds impact the Earth's radiative balance. Perfluorotributylamine (PFTBA) belongs to the perfluoroalkyl amine class of compounds; these have not yet been investigated as long-lived greenhouse gases (LLGHGs). Atmospheric measurements of PFTBA made in Toronto, ON, detected a mixing ratio of 0.18 parts per trillion by volume. An instantaneous radiative efficiency of 0.86 W m-2 ppb-1 was calculated from its IR absorption spectra, and a lower limit of 500 years was estimated for its atmospheric lifetime. PFTBA has the highest radiative efficiency of any compound detected in the atmosphere. If the concentration in Toronto is representative of the change in global background concentration since the preindustrial period, then the radiative forcing of PFTBA is 1.5 × 10-4 W m-2. We calculate the global warming potential of PFTBA over a 100 year time horizon to be 7100. Detection of PFTBA demonstrates that perfluoroalkyl amines are a class of LLGHGs worthy of future study.

A novel fluorescein-based "turn-on" probe for the detection of hydrazine and its application in living cells

NASA Astrophysics Data System (ADS)

Xu, Wen-Zhi; Liu, Wei-Yan; Zhou, Ting-Ting; Yang, Yu-Tao; Li, Wei

2018-03-01

We constructed a novel probe for hydrazine detection based on ICT and PET mechanism. Phthalimide and acetyl ester groups were used as the recognition units. Addition of hydrazine produced a turn-on fluorescence at 525 nm along with the fluorescent color change from dark to yellow. The probe could selectively detect hydrazine over other related interfering species. The detection limit of the probe for hydrazine was calculated to be 0.057 μM which was lower than the EPA standard (0.320 μM). Furthermore, the probe could also be applied for the imaging of hydrazine in living cells.

Transfer of estradiol to human milk. [Radioimmunoassay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nilsson, S.; Nygren, K.G.; Johansson, E.D.B.

1978-11-15

A radioimmunoassay for the measurement of estradiol in human milk is evaluated. The detection limit was found to be 25 pg of estradiol per milliliter of milk. In milk samples collected from four lactating women during three to four months and from one pregnant and lactating woman, the concentration of estradiol was found to be below the detection limit of the assay. When six lactating women were given vaginal suppositories containing 50 or 100 mg of estradiol, it was possible to estimate the estradiol concentration in milk. A ratio of transfer of estradiol from plasma to milk during physiologic conditionsmore » is calculated to be less than 100 : 10.« less

A new ratiometric and colorimetric chemosensor for cyanide anion based on coumarin-hemicyanine hybrid.

PubMed

Yang, Zhenghao; Liu, Zhipeng; Chen, Yuncong; Wang, Xiaoqing; He, Weijiang; Lu, Yi

2012-07-14

A hybrid coumarin-hemicyanine dye, Cou-BT, was developed as a new ratiometric and colorimetric sensor for cyanide with a sensing mechanism via nucleophilic addition of cyanide anion to the benzothiolium group. Cou-BT shows high sensitivity and selectivity for cyanide detection over other common anion species in aqueous acetonitrile solution. The calculated pseudo-first-order rate constant for cyanide anion addition was (2.13 ± 0.08) × 10(-2) s(-1) at 298 K, and the detection limit was estimated to be 0.64 μM. The DFT and TDDFT calculation results suggest that the ratiometric and colorimetric sensing behavior of Cou-BT upon its reaction with cyanide was due to the interrupted π-conjugation and blocked ICT progress.

[Detection of intraorbital foreign material using MDCT].

PubMed

Hoffstetter, P; Friedrich, C; Framme, C; Hoffstetter, M; Zorger, N; Stierstorfer, K; Ross, C; Uller, W; Müller-Wille, R; Rennert, J; Jung, E M; Schreyer, A G

2011-06-01

To judge the possibilities of detection of orbital foreign bodies in multidetector CT (MDCT) with a focus on glass slivers. Experimental systematic measuring of Hounsfield Units (HU) of 20 different materials, containing 16 different types of glass with 4 different types of ophthalmic lenses among them. The measurements were performed using a standardized protocol with an orbita phantom being scanned with 16-slice MDCT. Using the resulting density values, the smallest detectable volume was calculated. Using this data we produced slivers of 5 different glass types in the sub-millimeter range and calculated their volume. Those micro-slivers underwent another CT scan using the same protocol as mentioned above to experimentally discern and confirm the detection limit for micro-slivers made of different materials. Glass has comparatively high density values of at least 2000 HU. The density of glasses with strong refraction is significantly higher and reaches up to 12 400 HU. We calculated a minimum detectable volume of 0.07 mm (3) for glass with a density of 2000 HU. Only glass slivers with a density higher than 8300 HU were experimentally detectable in the sub-millimeter range up to a volume as small as 0.01 mm (3). Less dense glass slivers could not be seen, even though their volume was above the theoretically calculated threshold for detection. Due to its high density of at least 2000 HU, glass is usually easily recognizable as an orbital foreign body. The detection threshold depends on the object's density and size and can be as low as 0.01 mm (3) in the case of glass with strong refraction and thus high density. The detection of glass as an orbital foreign body seems to be secure for slivers with a volume of at least 0.2 mm (3) for all types of glass. © Georg Thieme Verlag KG Stuttgart · New York.

Automated Optical Meteor Fluxes and Preliminary Results of Major Showers

NASA Technical Reports Server (NTRS)

Blaauw, R.; Campbell-Brown, M.; Cooke, W.; Kingery, A.; Weryk, R.; Gill, J.

2014-01-01

NASA's Meteoroid Environment Office (MEO) recently established a two-station system to calculate daily automated meteor fluxes in the millimeter-size-range for both single-station and double-station meteors. The cameras each consist of a 17 mm focal length Schneider lens (f/0.95) on a Watec 902H2 Ultimate CCD video camera, producing a 21.7x15.5 degree field of view. This configuration sees meteors down to a magnitude of +6. This paper outlines the concepts of the system, the hardware and software, and results of 3,000+ orbits from the first 18 months of operations. Video from the cameras are run through ASGARD (All Sky and Guided Automatic Real-time Detection), which performs the meteor detection/photometry, and invokes MILIG and MORB (Borovicka 1990) codes to determine the trajectory, speed, and orbit of the meteor. A subroutine in ASGARD allows for approximate shower identification in single-station detections. The ASGARD output is used in routines to calculate the flux. Before a flux can be calculated, a weather algorithm indicates if sky conditions are clear enough to calculate fluxes, at which point a limiting magnitude algorithm is employed. The limiting stellar magnitude is found using astrometry.net (Lang et al. 2012) to identify stars and translated to the corresponding shower and sporadic limiting meteor magnitude. It is found every 10 minutes and is able to react to quickly changing sky conditions. The extensive testing of these results on the Geminids and Eta Aquariids is shown. The flux involves dividing the number of meteors by the collecting area of the system, over the time interval for which that collecting area is valid. The flux algorithm employed here differs from others currently in use in that it does not make the gross oversimplication of choosing a single height to calculate the collection area of the system. In the MEO system, the volume is broken up into a set of height intervals, with the collecting areas determined by the position of the active shower or sporadic source radiant. The flux per height interval is calculated and summed to obtain the total meteor flux. Both single station and double station fluxes are currently found daily. Geminid fluxes on the peak night in 2012 (12-14-2012) were 0.058 meteors/km2/hr as found with double-station meteors and 0.057 meteors/ km2/hr as found with single-station meteors, to a limiting magnitude of +6.5. Both of those numbers are in agreement with the well-calibrated fluxes from the Canadian Meteor Orbit Radar. Along with flux algorithms and initial flux results, presented will be results from the first 18 months of operation, covering 3,000+ meteoroid orbits.

Search for Neutrinos in Super-Kamiokande Associated with the GW170817 Neutron-star Merger

NASA Astrophysics Data System (ADS)

Abe, K.; Bronner, C.; Hayato, Y.; Ikeda, M.; Iyogi, K.; Kameda, J.; Kato, Y.; Kishimoto, Y.; Marti, Ll.; Miura, M.; Moriyama, S.; Nakahata, M.; Nakajima, Y.; Nakano, Y.; Nakayama, S.; Orii, A.; Pronost, G.; Sekiya, H.; Shiozawa, M.; Sonoda, Y.; Takeda, A.; Takenaka, A.; Tanaka, H.; Tasaka, S.; Yano, T.; Akutsu, R.; Kajita, T.; Nishimura, Y.; Okumura, K.; Tsui, K. M.; Labarga, L.; Fernandez, P.; Blaszczyk, F. d. M.; Kachulis, C.; Kearns, E.; Raaf, J. L.; Stone, J. L.; Sulak, L. R.; Berkman, S.; Tobayama, S.; Bian, J.; Elnimr, M.; Kropp, W. R.; Locke, S.; Mine, S.; Weatherly, P.; Smy, M. B.; Sobel, H. W.; Takhistov, V.; Ganezer, K. S.; Hill, J.; Kim, J. Y.; Lim, I. T.; Park, R. G.; Li, Z.; O’Sullivan, E.; Scholberg, K.; Walter, C. W.; Gonin, M.; Imber, J.; Mueller, Th. A.; Ishizuka, T.; Nakamura, T.; Jang, J. S.; Choi, K.; Learned, J. G.; Matsuno, S.; Amey, J.; Litchfield, R. P.; Ma, W. Y.; Uchida, Y.; Wascko, M. O.; Catanesi, M. G.; Intonti, R. A.; Radicioni, E.; De Rosa, G.; Ali, A.; Collazuol, G.; Ludovici, L.; Cao, S.; Friend, M.; Hasegawa, T.; Ishida, T.; Ishii, T.; Kobayashi, T.; Nakadaira, T.; Nakamura, K.; Oyama, Y.; Sakashita, K.; Sekiguchi, T.; Tsukamoto, T.; Abe, KE.; Hasegawa, M.; Suzuki, A. T.; Takeuchi, Y.; Hayashino, T.; Hirota, S.; Jiang, M.; Mori, M.; Nakamura, KE.; Nakaya, T.; Wendell, R. A.; Anthony, L. H. V.; McCauley, N.; Pritchard, A.; Fukuda, Y.; Itow, Y.; Murase, M.; Muto, F.; Mijakowski, P.; Frankiewicz, K.; Jung, C. K.; Li, X.; Palomino, J. L.; Santucci, G.; Viela, C.; Wilking, M. J.; Yanagisawa, C.; Fukuda, D.; Ishino, H.; Ito, S.; Kibayashi, A.; Koshio, Y.; Nagata, H.; Sakuda, M.; Xu, C.; Kuno, Y.; Wark, D.; Di Lodovico, F.; Richards, B.; Molina Sedgwick, S.; Tacik, R.; Kim, S. B.; Cole, A.; Thompson, L.; Okazawa, H.; Choi, Y.; Ito, K.; Nishijima, K.; Koshiba, M.; Suda, Y.; Yokoyama, M.; Calland, R. G.; Hartz, M.; Martens, K.; Murdoch, M.; Quilain, B.; Simpson, C.; Suzuki, Y.; Vagins, M. R.; Hamabe, D.; Kuze, M.; Okajima, Y.; Yoshida, T.; Ishitsuka, M.; Martin, J. F.; Nantais, C. M.; Tanaka, H. A.; Towstego, T.; Konaka, A.; Chen, S.; Wan, L.; Minamino, A.; The Super-Kamiokande Collaboration

2018-04-01

We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the first detected gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to ∼100 PeV, in a time window ±500 s around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is {16.0}-0.6+0.7 ({21.3}-0.8+1.1) cm‑2 for muon neutrinos (muon antineutrinos), with an error range of ±5° around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of ‑2. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is 6.6 × 107 cm‑2 for anti-electron neutrinos under the assumption of a Fermi–Dirac spectrum with average energy of 20 MeV.

Polarization-resolved sensing with tilted fiber Bragg gratings: theory and limits of detection

NASA Astrophysics Data System (ADS)

Bialiayeu, Aliaksandr; Ianoul, Anatoli; Albert, Jacques

2015-08-01

Polarization based sensing with tilted fiber Bragg grating (TFBG) sensors is analysed theoretically by two alternative approaches. The first method is based on tracking the grating transmission for two orthogonal states of linear polarized light that are extracted from the measured Jones matrix or Stokes vectors of the TFBG transmission spectra. The second method is based on the measurements along the system principle axes and polarization dependent loss (PDL) parameter, also calculated from measured data. It is shown that the frequent crossing of the Jones matrix eigenvalues as a function of wavelength leads to a non-physical interchange of the calculated principal axes; a method to remove this unwanted mathematical artefact and to restore the order of the system eigenvalues and the corresponding principal axes is provided. A comparison of the two approaches reveals that the PDL method provides a smaller standard deviation and therefore lower limit of detection in refractometric sensing. Furthermore, the polarization analysis of the measured spectra allows for the identification of the principal states of polarization of the sensor system and consequentially for the calculation of the transmission spectrum for any incident polarization state. The stability of the orientation of the system principal axes is also investigated as a function of wavelength.

Direct detection of sub-GeV dark matter with semiconductor targets

DOE PAGES

Essig, Rouven; Fernández-Serra, Marivi; Mardon, Jeremy; ...

2016-05-09

Dark matter in the sub-GeV mass range is a theoretically motivated but largely unexplored paradigm. Such light masses are out of reach for conventional nuclear recoil direct detection experiments, but may be detected through the small ionization signals caused by dark matter-electron scattering. Semiconductors are well-studied and are particularly promising target materials because their O(1 eV) band gaps allow for ionization signals from dark matter particles as light as a few hundred keV. Current direct detection technologies are being adapted for dark matter-electron scattering. In this paper, we provide the theoretical calculations for dark matter-electron scattering rate in semiconductors, overcomingmore » several complications that stem from the many-body nature of the problem. We use density functional theory to numerically calculate the rates for dark matter-electron scattering in silicon and germanium, and estimate the sensitivity for upcoming experiments such as DAMIC and SuperCDMS. We find that the reach for these upcoming experiments has the potential to be orders of magnitude beyond current direct detection constraints and that sub-GeV dark matter has a sizable modulation signal. We also give the first direct detection limits on sub-GeV dark matter from its scattering off electrons in a semiconductor target (silicon) based on published results from DAMIC. We make available publicly our code, QEdark, with which we calculate our results. Our results can be used by experimental collaborations to calculate their own sensitivities based on their specific setup. In conclusion, the searches we propose will probe vast new regions of unexplored dark matter model and parameter space.« less

Detection of Interstellar HC5O in TMC-1 with the Green Bank Telescope

NASA Astrophysics Data System (ADS)

McGuire, Brett A.; Burkhardt, Andrew M.; Shingledecker, Christopher N.; Kalenskii, Sergei V.; Herbst, Eric; Remijan, Anthony J.; McCarthy, Michael C.

2017-07-01

We report the detection of the carbon-chain radical HC5O for the first time in the interstellar medium toward the cold core TMC-1 using the 100 m Green Bank Telescope. We observe four hyperfine components of this radical in the J=17/2\\to 15/2 rotational transition that originates from the {}2{{{\\Pi }}}1/2 fine structure level of its ground state and calculate an abundance of n/{n}{H2}=1.7× {10}-10, assuming an excitation temperature of {T}{ex}=7 K. No indication of HC3O, HC4O, or HC6O, is found in these or archival observations of the source, while we report tentative evidence for HC7O. We compare calculated upper limits and the abundance of HC5O to predictions based on (1) the abundance trend of the analogous HC n N family in TMC-1 and (2) a gas-grain chemical model. We find that the gas-grain chemical model well reproduces the observed abundance of HC5O, as well as the upper limits of HC3O, HC6O, and HC7O, but HC4O is overproduced. The prospects for astronomical detection of both shorter and longer HC n O chains are discussed.

Dissipation rate study and pre-harvest intervals calculation of imidacloprid and oxamyl in exported Egyptian green beans and chili peppers after pestigation treatment.

PubMed

Hanafi, Ahmad; Dasenaki, Marilena; Bletsou, Anna; Thomaidis, Nikolaos S

2018-02-01

Two QuEChERS-based methods were developed and validated, using liquid chromatography-tandem mass spectrometric detection, in order to accurately determine residues of imidacloprid and oxamyl in green beans and chili peppers after treatment via irrigation system under field conditions in Egyptian farms. The validation included experiments for specificity, linearity, trueness, precision, matrix effect and limits of detection and quantification according to European Commission standards. The dissipation rates of both pesticides in green beans and chili peppers were studied and the pre-harvest intervals (PHIs) were calculated. The LOQ values of imidacloprid were 0.47 and 2.6μg/kg in green beans and chili peppers, respectively, while for oxamyl the LOQs were 2.9 and 0.67μg/kg, respectively. No PHI of imidacloprid is required, while for oxamyl it was found that still after 21days, its residues' concentration on both crops was significantly higher than the maximum residue limit. Copyright © 2017 Elsevier Ltd. All rights reserved.

The serum anion gap in the evaluation of acid-base disorders: what are its limitations and can its effectiveness be improved?

PubMed

Kraut, Jeffrey A; Nagami, Glenn T

2013-11-01

The serum anion gap has been utilized to identify errors in the measurement of electrolytes, to detect paraproteins, and, most relevant to the nephrologist, to evaluate patients with suspected acid-base disorders. In regard to the latter purpose, traditionally an increased anion gap is identified when it exceeds the upper limit of normal for a particular clinical laboratory measurement. However, because there is a wide range of normal values (often 8-10 mEq/L), an increase in anion concentration can be present in the absence of an increased anion gap. In addition, the type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum [HCO3(-)] being greater with lactic acidosis compared with ketoacidosis. This review examines the methods of calculation of the serum anion gap in textbooks and published literature, the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance. Limitations of the present methods of determining the normal anion gap and change in the anion gap are highlighted. The possibility of identifying the baseline value for individuals to optimize the use of the calculation in the detection of metabolic acidosis is suggested.

Determination of BPA, BPB, BPF, BADGE and BFDGE in canned energy drinks by molecularly imprinted polymer cleaning up and UPLC with fluorescence detection.

PubMed

Gallo, Pasquale; Di Marco Pisciottano, Ilaria; Esposito, Francesco; Fasano, Evelina; Scognamiglio, Gelsomina; Mita, Gustavo Damiano; Cirillo, Teresa

2017-04-01

A new method for simultaneous determination of five bisphenols in canned energy drinks by UPLC with fluorescence detection, after clean up on molecularly imprinted polymers, is herein described. The method was validated at two concentration levels, calculating trueness, repeatability and within-laboratory reproducibility, specificity, linearity of detector response, the limits of quantifications and the limits of detection for each bisphenol. The method is specific, reliable and very sensitive, allowing for determination of bisphenol F diglycidyl ether (BFDGE), bisphenol A (BPA), bisphenol B (BPB), bisphenol F (BPF) and bisphenol A diglycidyl ether (BADGE) down to 0.50ng/mL; it was employed to determine contamination levels from these bisphenols in forty energy drinks of different brands, collected from the market in Naples. BPA was detected in 17 out of 40 samples (42.5%); in some energy drinks also BPF, BADGE and BFDGE were determined. Copyright © 2016 Elsevier Ltd. All rights reserved.

Increased efficacy for in-house validation of real-time PCR GMO detection methods.

PubMed

Scholtens, I M J; Kok, E J; Hougs, L; Molenaar, B; Thissen, J T N M; van der Voet, H

2010-03-01

To improve the efficacy of the in-house validation of GMO detection methods (DNA isolation and real-time PCR, polymerase chain reaction), a study was performed to gain insight in the contribution of the different steps of the GMO detection method to the repeatability and in-house reproducibility. In the present study, 19 methods for (GM) soy, maize canola and potato were validated in-house of which 14 on the basis of an 8-day validation scheme using eight different samples and five on the basis of a more concise validation protocol. In this way, data was obtained with respect to the detection limit, accuracy and precision. Also, decision limits were calculated for declaring non-conformance (>0.9%) with 95% reliability. In order to estimate the contribution of the different steps in the GMO analysis to the total variation variance components were estimated using REML (residual maximum likelihood method). From these components, relative standard deviations for repeatability and reproducibility (RSD(r) and RSD(R)) were calculated. The results showed that not only the PCR reaction but also the factors 'DNA isolation' and 'PCR day' are important factors for the total variance and should therefore be included in the in-house validation. It is proposed to use a statistical model to estimate these factors from a large dataset of initial validations so that for similar GMO methods in the future, only the PCR step needs to be validated. The resulting data are discussed in the light of agreed European criteria for qualified GMO detection methods.

Highly Sensitive and Selective Uranium Detection in Natural Water Systems Using a Luminescent Mesoporous Metal-Organic Framework Equipped with Abundant Lewis Basic Sites: A Combined Batch, X-ray Absorption Spectroscopy, and First Principles Simulation Investigation.

PubMed

Liu, Wei; Dai, Xing; Bai, Zhuanling; Wang, Yanlong; Yang, Zaixing; Zhang, Linjuan; Xu, Lin; Chen, Lanhua; Li, Yuxiang; Gui, Daxiang; Diwu, Juan; Wang, Jianqiang; Zhou, Ruhong; Chai, Zhifang; Wang, Shuao

2017-04-04

Uranium is not only a strategic resource for the nuclear industry but also a global contaminant with high toxicity. Although several strategies have been established for detecting uranyl ions in water, searching for new uranium sensor material with great sensitivity, selectivity, and stability remains a challenge. We introduce here a hydrolytically stable mesoporous terbium(III)-based MOF material compound 1, whose channels are as large as 27 Å × 23 Å and are equipped with abundant exposed Lewis basic sites, the luminescence intensity of which can be efficiently and selectively quenched by uranyl ions. The detection limit in deionized water reaches 0.9 μg/L, far below the maximum contamination standard of 30 μg/L in drinking water defined by the United States Environmental Protection Agency, making compound 1 currently the only MOF material that can achieve this goal. More importantly, this material exhibits great capability in detecting uranyl ions in natural water systems such as lake water and seawater with pH being adjusted to 4, where huge excesses of competing ions are present. The uranyl detection limits in Dushu Lake water and in seawater were calculated to be 14.0 and 3.5 μg/L, respectively. This great detection capability originates from the selective binding of uranyl ions onto the Lewis basic sites of the MOF material, as demonstrated by synchrotron radiation extended X-ray adsorption fine structure, X-ray adsorption near edge structure, and first principles calculations, further leading to an effective energy transfer between the uranyl ions and the MOF skeleton.

The limit of detection in scintigraphic imaging with I-131 in patients with differentiated thyroid carcinoma

NASA Astrophysics Data System (ADS)

Hänscheid, H.; Lassmann, M.; Buck, A. K.; Reiners, C.; Verburg, F. A.

2014-05-01

Radioiodine scintigraphy influences staging and treatment in patients with differentiated thyroid carcinoma. The limit of detection for fractional uptake in an iodine avid focus in a scintigraphic image was determined from the number of lesion net counts and the count density of the tissue background. The count statistics were used to calculate the diagnostic activity required to elevate the signal from a lesion with a given uptake significantly above a homogeneous background with randomly distributed counts per area. The dependences of the minimal uptake and the minimal size of lesions visible in a scan on several parameters of influence were determined by linking the typical biokinetics observed in iodine avid tissue to the lesion mass and to the absorbed dose received in a radioiodine therapy. The detection limits for fractional uptake in a neck lesion of a typical patient are about 0.001% after therapy with 7000 MBq, 0.01% for activities typically administered in diagnostic assessments (74-185 MBq), and 0.1% after the administration of 10 MBq I-131. Lesions at the limit of detection in a diagnostic scan with biokinetics eligible for radioiodine therapy are small with diameters of a few millimeters. Increasing the diagnostic activity by a factor of 4 reduces the diameter of visible lesions by 25% or about 1 mm. Several other determinants have a comparable or higher influence on the limit of detection than the administered activity; most important are the biokinetics in both blood pool and target tissue and the time of measurement. A generally valid recommendation for the timing of the scan is impossible as the time of the highest probability to detect iodine avid tissue depends on the administered activity as well as on the biokinetics in the lesion and background in the individual patient.

Fast obstacle detection based on multi-sensor information fusion

NASA Astrophysics Data System (ADS)

Lu, Linli; Ying, Jie

2014-11-01

Obstacle detection is one of the key problems in areas such as driving assistance and mobile robot navigation, which cannot meet the actual demand by using a single sensor. A method is proposed to realize the real-time access to the information of the obstacle in front of the robot and calculating the real size of the obstacle area according to the mechanism of the triangle similarity in process of imaging by fusing datum from a camera and an ultrasonic sensor, which supports the local path planning decision. In the part of image analyzing, the obstacle detection region is limited according to complementary principle. We chose ultrasonic detection range as the region for obstacle detection when the obstacle is relatively near the robot, and the travelling road area in front of the robot is the region for a relatively-long-distance detection. The obstacle detection algorithm is adapted from a powerful background subtraction algorithm ViBe: Visual Background Extractor. We extracted an obstacle free region in front of the robot in the initial frame, this region provided a reference sample set of gray scale value for obstacle detection. Experiments of detecting different obstacles at different distances respectively, give the accuracy of the obstacle detection and the error percentage between the calculated size and the actual size of the detected obstacle. Experimental results show that the detection scheme can effectively detect obstacles in front of the robot and provide size of the obstacle with relatively high dimensional accuracy.

Atom-Based Sensing of Weak Radio Frequency Electric Fields Using Homodyne Readout

PubMed Central

Kumar, Santosh; Fan, Haoquan; Kübler, Harald; Sheng, Jiteng; Shaffer, James P.

2017-01-01

We utilize a homodyne detection technique to achieve a new sensitivity limit for atom-based, absolute radio-frequency electric field sensing of 5 μV cm−1 Hz−1/2. A Mach-Zehnder interferometer is used for the homodyne detection. With the increased sensitivity, we investigate the dominant dephasing mechanisms that affect the performance of the sensor. In particular, we present data on power broadening, collisional broadening and transit time broadening. Our results are compared to density matrix calculations. We show that photon shot noise in the signal readout is currently a limiting factor. We suggest that new approaches with superior readout with respect to photon shot noise are needed to increase the sensitivity further. PMID:28218308

Strong decays of DJ(3000 ) and Ds J(3040 )

NASA Astrophysics Data System (ADS)

Li, Si-Chen; Wang, Tianhong; Jiang, Yue; Tan, Xiao-Ze; Li, Qiang; Wang, Guo-Li; Chang, Chao-Hsi

2018-03-01

In this paper, we systematically calculate two-body strong decays of newly observed DJ(3000 ) and Ds J(3040 ) with 2 P (1+) and 2 P (1+') assignments in an instantaneous approximation of the Bethe-Salpeter equation method. Our results show that both resonances can be explained as the 2 P (1+') with broad width via 3P1 and 1P1 mixing in D and Ds families. For DJ(3000 ), the total width is 229.6 MeV in our calculation, close to the upper limit of experimental data, and the dominant decay channels are D2*π , D*π , and D*(2600 )π . For Ds J(3040 ), the total width is 157.4 MeV in our calculation, close to the lower limit of experimental data, and the dominant channels are D*K and D*K*. These results are consistent with observed channels in experiments. Given the very little information that has been obtained from experiments and the large error bars of the total decay widths, we recommend the detection of dominant channels in our calculation.

Quality control of test iodine in urine by spectrophotometry UV-Vis

NASA Astrophysics Data System (ADS)

Huda, Thorikul; Nafisah, Durotun; Kumorowulan, Suryati; Lestari, Sri

2017-12-01

A quality control of iodine test in with UV-Vis spectrophotometry has been done. The purpose of this research is to find out whether the test results of samples conducted by Clinical Office of Research and Development Of GAKI (BP2GAKI) laboratory are still controlled, feasible and reliable, and still consistent over time, as indicated by the control chart. Quality control parameters are linearity, precision, accuracy, limit of detection, and limit of quantification. Based on the quality control that has been done, obtained linearity (r)= -0.9974, the detection limit and the limit of quantitation are respectively 2.26 µg/L and 7.54 µg/L, while the accuracy is calculated by %recovery and precision with value % RSD are 97.4161% and 1.7136% respectively. The quality control of iodine test in urine using the control chart shows excellent or stable results for 30 days and no variation of the results is very different for each day.

Very high energy observations of the BL Lac objects 3C 66A and OJ 287

NASA Astrophysics Data System (ADS)

Lindner, T.; Hanna, D. S.; Kildea, J.; Ball, J.; Bramel, D. A.; Carson, J.; Covault, C. E.; Driscoll, D.; Fortin, P.; Gingrich, D. M.; Jarvis, A.; Mueller, C.; Mukherjee, R.; Ong, R. A.; Ragan, K.; Scalzo, R. A.; Williams, D. A.; Zweerink, J.

2007-11-01

Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we have observed the BL Lac objects 3C 66A and OJ 287. These are members of the class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three LBLs predicted by Costamante and Ghisellini [L. Costamante, G. Ghisellini, Astron. Astrophys. 384 (2002) 56] to be potential sources of very high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae, has recently been detected by the MAGIC collaboration [J. Albert et al., arXiv:astro-ph/0703084v1 (2007)]. Our observations have not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab. These limits assume a Crab-like energy spectrum with an effective energy threshold of 185 GeV.

Simultaneous Determination of Six Benzodiazepines in Spiked Soft Drinks by High Performance Liquid Chromatography with Ultra Violet Detection (HPLC-UV)

PubMed Central

Soltaninejad, Kambiz; Karimi, Mohammad; Nateghi, Alireza; Daraei, Bahram

2016-01-01

A high performance liquid chromatographic method with ultra violet detection for simultaneous analysis of six benzodiazepines (BZDs) (chlordiazepoxide, diazepam, clonazepam, midazolam , flurazpam, and lorazepam) has been developed for forensic screening of adulterated non-alcoholic drinks. Samples were analyzed after a simple procedure for preparation using pH adjustment and filtering. Isocratic elution on a C18 column (250mm × 4.6 mm, 5μm) in the temperature 45ºC with a mobile phase consisting of 15mM phosphate buffer: methanol (50:50 v/v) at a flow rate 1.4 mL/min has been done. The column eluent was monitored with a UV detector at 245 nm. This allowed a rapid detection and identification as well as quantization of the eluting peaks. Calibration curves for all drugs in the range of 0.5- 10 µg/ mL that all the linear regression and has more than 0.996. Recovery rates for the BZDs were in the range 93.7- 108.7%. The limits of detection were calculated between 0.01- 0.02 µg/ mL. Also, the limits of quantification were 0.03- 0.05 µg/mL. Within-day and between -day coefficient of variation for all BZDs at all concentrations in the range of 0.45 - 7.69 % was calculated. The procedure can provide a simple, sensitive and fast method for the screening of six BZDs in adulterated soft drinks in forensic analysis. PMID:27642316

Optimization and validation of moving average quality control procedures using bias detection curves and moving average validation charts.

PubMed

van Rossum, Huub H; Kemperman, Hans

2017-02-01

To date, no practical tools are available to obtain optimal settings for moving average (MA) as a continuous analytical quality control instrument. Also, there is no knowledge of the true bias detection properties of applied MA. We describe the use of bias detection curves for MA optimization and MA validation charts for validation of MA. MA optimization was performed on a data set of previously obtained consecutive assay results. Bias introduction and MA bias detection were simulated for multiple MA procedures (combination of truncation limits, calculation algorithms and control limits) and performed for various biases. Bias detection curves were generated by plotting the median number of test results needed for bias detection against the simulated introduced bias. In MA validation charts the minimum, median, and maximum numbers of assay results required for MA bias detection are shown for various bias. Their use was demonstrated for sodium, potassium, and albumin. Bias detection curves allowed optimization of MA settings by graphical comparison of bias detection properties of multiple MA. The optimal MA was selected based on the bias detection characteristics obtained. MA validation charts were generated for selected optimal MA and provided insight into the range of results required for MA bias detection. Bias detection curves and MA validation charts are useful tools for optimization and validation of MA procedures.

Comparative studies by IR, Raman, and surface-enhanced Raman spectroscopy of azodicarbonamide, biurea and semicarbazide hydrochloride

NASA Astrophysics Data System (ADS)

Xie, Yunfei; Li, Pei; Zhang, Jin; Wang, Heya; Qian, He; Yao, Weirong

2013-10-01

Azodicarbonamide is widely applied in the food industry as a new flour gluten fortifier in China, Canada, the United States, and some other countries, whose metabolites of biurea and semicarbazide hydrochloride are reaction products during baking. In this study, IR, Raman and surface-enhanced Raman scattering (SERS) spectra of azodicarbonamide, biurea, and semicarbazide hydrochloride have been studied, and vibrational bands have been assigned on the basis of density functional theory (DFT) calculations. The calculated Raman spectra were in good agreement with experimental Raman spectra. The SERS method coupled with active gold substrates has also been applied for detection of the three chemicals with pure water as solvent, with the limit of detection of this method being as low as 10 μg/mL (less than 45 μg/mL). These results showed that azodicarbonamide and its metabolites could be detected by the vibrational spectra technique, which might be applied as a powerful tool for the rapid detection on these species derived from agents added to flour.

Sensitivity Limits of Rydberg Atom-Based Radio Frequency Electric Field Sensing

NASA Astrophysics Data System (ADS)

Jahangiri, Akbar J.; Kumar, Santosh; Kuebler, Harald; Fan, Haoquan; Shaffer, James P.

2017-04-01

We present progress on Rydberg atom-based RF electric field sensing using Rydberg state electromagnetically induced transparency (EIT) in room temperature atomic vapor cells. In recent experiments on homodyne detection with a Mach-Zehnder interferometer and frequency modulation spectroscopy with active control of residual amplitude modulation we determined that photon shot noise on the probe laser detector limits the sensitivity. Another factor that limits the accuracy is residual Doppler broadening due to the wave-vector mismatch between the coupling and the probe lasers. The sensor as limited by project noise can be orders of magnitude better. A multi-photon scheme is presented that can eliminate the residual Doppler effect by matching the wave-vectors of three lasers and reduce the photon shot noise limit by correctly choosing the Rabi frequencies of the first two steps of the EIT scheme. Using density matrix calculations, we predict that the three-photon approach can improve the detection sensitivity to below 200 nV cm-1 Hz- 1 / 2 and expand the Autler-Townes regime which improves the accuracy. This work is supported by DARPA and the NRO.

Association of incidental emphysema with annual lung function decline and future development of airflow limitation

PubMed Central

Koo, Hyeon-Kyoung; Jin, Kwang Nam; Kim, Deog Kyeom; Chung, Hee Soon; Lee, Chang-Hoon

2016-01-01

Objectives Emphysema is one of the prognostic factors for rapid lung function decline in patients with COPD, but the impact of incidentally detected emphysema on population without spirometric abnormalities has not been evaluated. This study aimed to determine whether emphysema detected upon computed tomography (CT) screening would accelerate the rate of lung function decline and influence the possibility of future development of airflow limitation in a population without spirometric abnormalities. Materials and methods Subjects who participated in a routine screening for health checkup and follow-up pulmonary function tests for at least 3 years between 2004 and 2010 were retrospectively enrolled. The percentage of low-attenuation area below −950 Hounsfield units (%LAA−950) was calculated automatically. A calculated value of %LAA−950 that exceeded 10% was defined as emphysema. Adjusted annual lung function decline was analyzed using random-slope, random-intercept mixed linear regression models. Results A total of 628 healthy subjects within the normal range of spriometric values were included. Multivariable analysis showed that the emphysema group exhibited a faster decline in forced vital capacity (−33.9 versus −18.8 mL/year; P=0.02). Emphysema was not associated with the development of airflow limitation during follow-up. Conclusion Incidental emphysema quantified using CT scan was significantly associated with a more rapid decline in forced vital capacity in the population with normative spirometric values. However, an association between emphysema and future development of airflow limitation was not observed. PMID:26893550

A gold nanoparticle-based semi-quantitative and quantitative ultrasensitive paper sensor for the detection of twenty mycotoxins

NASA Astrophysics Data System (ADS)

Kong, Dezhao; Liu, Liqiang; Song, Shanshan; Suryoprabowo, Steven; Li, Aike; Kuang, Hua; Wang, Libing; Xu, Chuanlai

2016-02-01

A semi-quantitative and quantitative multi-immunochromatographic (ICA) strip detection assay was developed for the simultaneous detection of twenty types of mycotoxins from five classes, including zearalenones (ZEAs), deoxynivalenols (DONs), T-2 toxins (T-2s), aflatoxins (AFs), and fumonisins (FBs), in cereal food samples. Sensitive and specific monoclonal antibodies were selected for this assay. The semi-quantitative results were obtained within 20 min by the naked eye, with visual limits of detection for ZEAs, DONs, T-2s, AFs and FBs of 0.1-0.5, 2.5-250, 0.5-1, 0.25-1 and 2.5-10 μg kg-1, and cut-off values of 0.25-1, 5-500, 1-10, 0.5-2.5 and 5-25 μg kg-1, respectively. The quantitative results were obtained using a hand-held strip scan reader, with the calculated limits of detection for ZEAs, DONs, T-2s, AFs and FBs of 0.04-0.17, 0.06-49, 0.15-0.22, 0.056-0.49 and 0.53-1.05 μg kg-1, respectively. The analytical results of spiked samples were in accordance with the accurate content in the simultaneous detection analysis. This newly developed ICA strip assay is suitable for the on-site detection and rapid initial screening of mycotoxins in cereal samples, facilitating both semi-quantitative and quantitative determination.A semi-quantitative and quantitative multi-immunochromatographic (ICA) strip detection assay was developed for the simultaneous detection of twenty types of mycotoxins from five classes, including zearalenones (ZEAs), deoxynivalenols (DONs), T-2 toxins (T-2s), aflatoxins (AFs), and fumonisins (FBs), in cereal food samples. Sensitive and specific monoclonal antibodies were selected for this assay. The semi-quantitative results were obtained within 20 min by the naked eye, with visual limits of detection for ZEAs, DONs, T-2s, AFs and FBs of 0.1-0.5, 2.5-250, 0.5-1, 0.25-1 and 2.5-10 μg kg-1, and cut-off values of 0.25-1, 5-500, 1-10, 0.5-2.5 and 5-25 μg kg-1, respectively. The quantitative results were obtained using a hand-held strip scan reader, with the calculated limits of detection for ZEAs, DONs, T-2s, AFs and FBs of 0.04-0.17, 0.06-49, 0.15-0.22, 0.056-0.49 and 0.53-1.05 μg kg-1, respectively. The analytical results of spiked samples were in accordance with the accurate content in the simultaneous detection analysis. This newly developed ICA strip assay is suitable for the on-site detection and rapid initial screening of mycotoxins in cereal samples, facilitating both semi-quantitative and quantitative determination. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09171c

Determination of Vitamin E in Cereal Products and Biscuits by GC-FID.

PubMed

Pasias, Ioannis N; Kiriakou, Ioannis K; Papakonstantinou, Lila; Proestos, Charalampos

2018-01-01

A rapid, precise and accurate method for the determination of vitamin E (α-tocopherol) in cereal products and biscuits has been developed. The uncertainty was calculated for the first time, and the methods were performed for different cereal products and biscuits, characterized as "superfoods". The limits of detection and quantification were calculated. The accuracy and precision were estimated using the certified reference material FAPAS T10112QC, and the determined values were in good accordance with the certified values. The health claims according to the daily reference values for vitamin E were calculated, and the results proved that the majority of the samples examined showed a percentage daily value higher than 15%.

Determination of Vitamin E in Cereal Products and Biscuits by GC-FID

PubMed Central

Kiriakou, Ioannis K.; Papakonstantinou, Lila

2018-01-01

A rapid, precise and accurate method for the determination of vitamin E (α-tocopherol) in cereal products and biscuits has been developed. The uncertainty was calculated for the first time, and the methods were performed for different cereal products and biscuits, characterized as “superfoods”. The limits of detection and quantification were calculated. The accuracy and precision were estimated using the certified reference material FAPAS T10112QC, and the determined values were in good accordance with the certified values. The health claims according to the daily reference values for vitamin E were calculated, and the results proved that the majority of the samples examined showed a percentage daily value higher than 15%. PMID:29301245

Actinides in deer tissues at the rocky flats environmental technology site.

PubMed

Todd, Andrew S; Sattelberg, R Mark

2005-11-01

Limited hunting of deer at the future Rocky Flats National Wildlife Refuge has been proposed in U.S. Fish and Wildlife planning documents as a compatible wildlife-dependent public use. Historically, Rocky Flats site activities resulted in the contamination of surface environmental media with actinides, including isotopes of americium, plutonium, and uranium. In this study, measurements of actinides [Americium-241 (241Am); Plutonium-238 (238Pu); Plutonium-239,240 (239,240Pu); uranium-233,244 (233,234U); uranium-235,236 (235,236U); and uranium-238 (238U)] were completed on select liver, muscle, lung, bone, and kidney tissue samples harvested from resident Rocky Flats deer (N = 26) and control deer (N = 1). In total, only 17 of the more than 450 individual isotopic analyses conducted on Rocky Flats deer tissue samples measured actinide concentrations above method detection limits. Of these 17 detects, only 2 analyses, with analytical uncertainty values added, exceeded threshold values calculated around a 1 x 10(-6) risk level (isotopic americium, 0.01 pCi/g; isotopic plutonium, 0.02 pCi/g; isotopic uranium, 0.2 pCi/g). Subsequent, conservative risk calculations suggest minimal human risk associated with ingestion of these edible deer tissues. The maximum calculated risk level in this study (4.73 x 10(-6)) is at the low end of the U.S. Environmental Protection Agency's acceptable risk range.

Investigating the probability of detection of typical cavity shapes through modelling and comparison of geophysical techniques

NASA Astrophysics Data System (ADS)

James, P.

2011-12-01

With a growing need for housing in the U.K., the government has proposed increased development of brownfield sites. However, old mine workings and natural cavities represent a potential hazard before, during and after construction on such sites, and add further complication to subsurface parameters. Cavities are hence a limitation to certain redevelopment and their detection is an ever important consideration. The current standard technique for cavity detection is a borehole grid, which is intrusive, non-continuous, slow and expensive. A new robust investigation standard in the detection of cavities is sought and geophysical techniques offer an attractive alternative. Geophysical techniques have previously been utilised successfully in the detection of cavities in various geologies, but still has an uncertain reputation in the engineering industry. Engineers are unsure of the techniques and are inclined to rely on well known techniques than utilise new technologies. Bad experiences with geophysics are commonly due to the indiscriminate choice of particular techniques. It is imperative that a geophysical survey is designed with the specific site and target in mind at all times, and the ability and judgement to rule out some, or all, techniques. To this author's knowledge no comparative software exists to aid technique choice. Also, previous modelling software limit the shapes of bodies and hence typical cavity shapes are not represented. Here, we introduce 3D modelling software (Matlab) which computes and compares the response to various cavity targets from a range of techniques (gravity, gravity gradient, magnetic, magnetic gradient and GPR). Typical near surface cavity shapes are modelled including shafts, bellpits, various lining and capping materials, and migrating voids. The probability of cavity detection is assessed in typical subsurface and noise conditions across a range of survey parameters. Techniques can be compared and the limits of detection distance assessed. The density of survey points required to achieve a required probability of detection can be calculated. The software aids discriminate choice of technique, improves survey design, and increases the likelihood of survey success; all factors sought in the engineering industry. As a simple example, the response from magnetometry, gravimetry, and gravity gradient techniques above an example 3m deep, 1m cube air cavity in limestone across a 15m grid was calculated. The maximum responses above the cavity are small (amplitudes of 0.018nT, 0.0013mGal, 8.3eotvos respectively), but at typical site noise levels the detection reliability is over 50% for the gradient gravity method on a single survey line. Increasing the number of survey points across the site increases the reliability of detection of the anomaly by the addition of probabilities. We can calculate the probability of detection at different profile spacings to assess the best possible survey design. At 1m spacing the overall probability of by the gradient gravity method is over 90%, and over 60% for magnetometry (at 3m spacing the probability drops to 32%). The use of modelling in near surface surveys is a useful tool to assess the feasibility of a range of techniques to detect subtle signals. Future work will integrate this work with borehole measured parameters.

New duel fluorescent "on-off" and colorimetric sensor for Copper(II): Copper(II) binds through N coordination and pi cation interaction to sensor.

PubMed

Kumar, Jutika; Bhattacharyya, Pradip K; Das, Diganta Kumar

2015-03-05

Schiff base derived from naphthylamine and benzil (L) binds to two Cu(2+) ions, one by coordination through N of the Schiff base and another by pi cation interaction through benzil rings. This bonding pattern determined by DFT calculation has been proved by matching electronic spectrum obtained from TDDFT calculation to the experimental one. L acts as "on-off" fluorescent and bare eye detectable colorimetric (purple color) sensor for Cu(2+) ion over the metal ions - Na(+), K(+), Ca(2+) Mn(2+), Co(2+) Ni(2+), Zn(2+), Pb(2+), Cd(2+), Hg(2+), Ag(+), Hg(2+) and Al(3+) in 1:1 v/v CH3CN:H2O. These metal ions do not interfere the fluorescent/colorimetric sensing. As fluorescent sensor the linear range of detection is 5×10(-5) to 3×10(-4)M and detection limit 10(-5)M. Copyright © 2014 Elsevier B.V. All rights reserved.

New duel fluorescent 'on-off' and colorimetric sensor for Copper(II): Copper(II) binds through N coordination and pi cation interaction to sensor

NASA Astrophysics Data System (ADS)

Kumar, Jutika; Bhattacharyya, Pradip K.; Das, Diganta Kumar

2015-03-01

Schiff base derived from naphthylamine and benzil (L) binds to two Cu2+ ions, one by coordination through N of the Schiff base and another by pi cation interaction through benzil rings. This bonding pattern determined by DFT calculation has been proved by matching electronic spectrum obtained from TDDFT calculation to the experimental one. L acts as "on-off" fluorescent and bare eye detectable colorimetric (purple color) sensor for Cu2+ ion over the metal ions - Na+, K+, Ca2+ Mn2+, Co2+ Ni2+, Zn2+, Pb2+, Cd2+, Hg2+, Ag+, Hg2+ and Al3+ in 1:1 v/v CH3CN:H2O. These metal ions do not interfere the fluorescent/colorimetric sensing. As fluorescent sensor the linear range of detection is 5 × 10-5 to 3 × 10-4 M and detection limit 10-5 M.

Optimized velocity distributions for direct dark matter detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibarra, Alejandro; Rappelt, Andreas, E-mail: ibarra@tum.de, E-mail: andreas.rappelt@tum.de

We present a method to calculate, without making assumptions about the local dark matter velocity distribution, the maximal and minimal number of signal events in a direct detection experiment given a set of constraints from other direct detection experiments and/or neutrino telescopes. The method also allows to determine the velocity distribution that optimizes the signal rates. We illustrate our method with three concrete applications: i) to derive a halo-independent upper limit on the cross section from a set of null results, ii) to confront in a halo-independent way a detection claim to a set of null results and iii) tomore » assess, in a halo-independent manner, the prospects for detection in a future experiment given a set of current null results.« less

Disappearance of six pesticides in fresh and processed zucchini, bioavailability and health risk assessment.

PubMed

Oliva, J; Cermeño, S; Cámara, M A; Martínez, G; Barba, A

2017-08-15

A field study was carried out on the dissipation of three insecticides and three fungicides during the freezing of zucchini. A simultaneous residue analysis method is validated using QuEChERS extraction with acetonitrile and CG-MS and LC-MS analysis. The residues detected after field application never exceeded the established maximum residue limits. The processing factors calculated (fresh product/frozen product) are lower than 1, indicating a clear influence of the stages of the freezing process, especially the washing and blanching. The in vitro study of bioavailability establishes a low percentage of stomach absorption capacity. The level of residues detected in fresh zucchini and the Estimated Daily Intake calculated for Spain suggest that there is no risk of acute toxicity due to dietary exposure. Copyright © 2017 Elsevier Ltd. All rights reserved.

ADRPM-VII applied to the long-range acoustic detection problem

NASA Technical Reports Server (NTRS)

Shalis, Edward; Koenig, Gerald

1990-01-01

An acoustic detection range prediction model (ADRPM-VII) has been written for IBM PC/AT machines running on the MS-DOS operating system. The software allows the user to predict detection distances of ground combat vehicles and their associated targets when they are involved in quasi-military settings. The program can also calculate individual attenuation losses due to spherical spreading, atmospheric absorption, ground reflection and atmospheric refraction due to temperature and wind gradients while varying parameters effecting the source-receiver problem. The purpose here is to examine the strengths and limitations of ADRPM-VII by modeling the losses due to atmospheric refraction and ground absorption, commonly known as excess attenuation, when applied to the long range detection problem for distances greater than 3 kilometers.

a Method of Time-Series Change Detection Using Full Polsar Images from Different Sensors

NASA Astrophysics Data System (ADS)

Liu, W.; Yang, J.; Zhao, J.; Shi, H.; Yang, L.

2018-04-01

Most of the existing change detection methods using full polarimetric synthetic aperture radar (PolSAR) are limited to detecting change between two points in time. In this paper, a novel method was proposed to detect the change based on time-series data from different sensors. Firstly, the overall difference image of a time-series PolSAR was calculated by ominous statistic test. Secondly, difference images between any two images in different times ware acquired by Rj statistic test. Generalized Gaussian mixture model (GGMM) was used to obtain time-series change detection maps in the last step for the proposed method. To verify the effectiveness of the proposed method, we carried out the experiment of change detection by using the time-series PolSAR images acquired by Radarsat-2 and Gaofen-3 over the city of Wuhan, in China. Results show that the proposed method can detect the time-series change from different sensors.

Rapid detection of in vitro antituberculous drug resistance among smear-positive respiratory samples using microcolony detection-based direct drug susceptibility testing method.

PubMed

Iftikhar, Irim; Irfan, Seema; Farooqi, Joveria; Azizullah, Zahida; Hasan, Rumina

2017-01-01

With the rise in multidrug-resistant tuberculosis, there is a search for newer techniques that will rapidly detect drug-resistant Mycobacterium tuberculosis. Although molecular techniques can detect resistance, culture is still considered gold standard, especially in resource-limited settings where quick, cheap, and easy techniques are needed. The aim of the study was to evaluate microcolony method thin layer agar (TLA) for quick detection of resistance against the first- and second-line antituberculous drugs in clinical isolates. This was a cross-sectional study performed at Aga Khan University Hospital. A total of 87 Z-N stain smear-positive pulmonary samples were received and indirect drug susceptibility test (ID-DST) was performed using Lowenstein-Jensen and mycobacteria growth indicator tube. Direct DST was performed using TLA on 7H10 agar. TLA was observed twice weekly under microscope for 4 weeks. Sensitivity, specificity, and accuracy were calculated for TLA using indirect susceptibility method as the gold standard. Level of agreement was calculated using Kappa score. TLA showed sensitivity of 89% and 95.2% for isoniazid and rifampicin, while for ethionamide, ofloxacin, and injectable aminoglycosides, it was 96.6%, 92.1%, and 100%, respectively. Specificity for the first-line drugs was >95% while second-line drugs ranged from 70% to 100%. Mean time to positivity was 10.2 days by TLA as compared to 43.1 days by ID-DST. TLA is a quick and reliable method in identifying resistance, especially in resource-limited settings. However, additional liquid culture can be set up as backup, especially in patients on therapy to avoid false negative results.

Remote-sensing vibrometry at 1550 nm wavelength

NASA Astrophysics Data System (ADS)

Dräbenstedt, A.; Sauer, J.; Rembe, C.

2012-06-01

Laser-Doppler vibrometry (LDV) is a proven technique for vibration analysis of mechanical structures. A wavelength of 633 nm is usually employed because of the availability of the relatively inexpensive Helium-Neon laser source which has a good coherence behavior. However, coherence break-down through the beat of multiple longitudinal modes and the limited detector carrier-to-noise-ratio (CNR) at a measurement laser power of 1 mW have prevented a wide use of LDV in remote sensing applications. Such applications in civil engineering are bridges, towers or wind turbines. The lower photon energy of IR light at 1550 nm wavelength increases the CNR by a factor 2.4. This helps especially in the condition where the carrier power decreases below the FM threshold. We have designed a heterodyne interferometer which allows the shot noise limited detection at 1550 nm wavelength close to the theoretical possible CNR. We present calculations of the fundamental noise contributions in interferometric light detection for a comparison of the achievable CNR between common HeNe vibrometers and IR vibrometers. The calculations are backed by measurements that show the devices working close to the theoretical limits. The achievable noise level of the demodulated velocity signal is shown in dependence from the standoff distance. Our novel heterodyne interferometer has been transferred to the Polytec product RSV-150. An application example of this new sensor will be demonstrated.

Exploring the limits of identifying sub-pixel thermal features using ASTER TIR data

USGS Publications Warehouse

Vaughan, R.G.; Keszthelyi, L.P.; Davies, A.G.; Schneider, D.J.; Jaworowski, C.; Heasler, H.

2010-01-01

Understanding the characteristics of volcanic thermal emissions and how they change with time is important for forecasting and monitoring volcanic activity and potential hazards. Satellite instruments view volcanic thermal features across the globe at various temporal and spatial resolutions. Thermal features that may be a precursor to a major eruption, or indicative of important changes in an on-going eruption can be subtle, making them challenging to reliably identify with satellite instruments. The goal of this study was to explore the limits of the types and magnitudes of thermal anomalies that could be detected using satellite thermal infrared (TIR) data. Specifically, the characterization of sub-pixel thermal features with a wide range of temperatures is considered using ASTER multispectral TIR data. First, theoretical calculations were made to define a "thermal mixing detection threshold" for ASTER, which quantifies the limits of ASTER's ability to resolve sub-pixel thermal mixing over a range of hot target temperatures and % pixel areas. Then, ASTER TIR data were used to model sub-pixel thermal features at the Yellowstone National Park geothermal area (hot spring pools with temperatures from 40 to 90 ??C) and at Mount Erebus Volcano, Antarctica (an active lava lake with temperatures from 200 to 800 ??C). Finally, various sources of uncertainty in sub-pixel thermal calculations were quantified for these empirical measurements, including pixel resampling, atmospheric correction, and background temperature and emissivity assumptions.

The Serum Anion Gap in the Evaluation of Acid-Base Disorders: What Are Its Limitations and Can Its Effectiveness Be Improved?

PubMed Central

Nagami, Glenn T.

2013-01-01

Summary The serum anion gap has been utilized to identify errors in the measurement of electrolytes, to detect paraproteins, and, most relevant to the nephrologist, to evaluate patients with suspected acid-base disorders. In regard to the latter purpose, traditionally an increased anion gap is identified when it exceeds the upper limit of normal for a particular clinical laboratory measurement. However, because there is a wide range of normal values (often 8–10 mEq/L), an increase in anion concentration can be present in the absence of an increased anion gap. In addition, the type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum [HCO3−] being greater with lactic acidosis compared with ketoacidosis. This review examines the methods of calculation of the serum anion gap in textbooks and published literature, the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance. Limitations of the present methods of determining the normal anion gap and change in the anion gap are highlighted. The possibility of identifying the baseline value for individuals to optimize the use of the calculation in the detection of metabolic acidosis is suggested. PMID:23833313

Limit on neutrinoless ββ decay of 136Xe from the first phase of KamLAND-Zen and comparison with the positive claim in 76Ge.

PubMed

Gando, A; Gando, Y; Hanakago, H; Ikeda, H; Inoue, K; Ishidoshiro, K; Kato, R; Koga, M; Matsuda, S; Mitsui, T; Motoki, D; Nakada, T; Nakamura, K; Obata, A; Oki, A; Ono, Y; Otani, M; Shimizu, I; Shirai, J; Suzuki, A; Takemoto, Y; Tamae, K; Ueshima, K; Watanabe, H; Xu, B D; Yamada, S; Yoshida, H; Kozlov, A; Yoshida, S; Banks, T I; Freedman, S J; Fujikawa, B K; Han, K; O'Donnell, T; Berger, B E; Efremenko, Y; Karwowski, H J; Markoff, D M; Tornow, W; Detwiler, J A; Enomoto, S; Decowski, M P

2013-02-08

We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of (136)Xe. We obtain a lower limit for the neutrinoless double-beta decay half-life of T(1/2)(0ν)>1.9×10(25) yr at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give T(1/2)(0ν)>3.4×10(25) yr at 90% C.L., which corresponds to a Majorana neutrino mass limit of <(120-250) meV based on a representative range of available matrix element calculations. Using those calculations, this result excludes the Majorana neutrino mass range expected from the neutrinoless double-beta decay detection claim in (76)Ge, reported by a part of the Heidelberg-Moscow Collaboration, at more than 97.5% C.L.

Sensitive Procedures for Determining the Permeation Resistance of Chlorinated Polyethylene Against Liquid Propellants

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Williams, James H.; Fries, Joseph (Technical Monitor)

1999-01-01

The permeation resistance of chlorinated polyethylene (CPE) used in totally encapsulating chemical protective suits against the aerospace fuels hydrazine, monomethylhydrazine, and uns-dimethylhydrazine was determined by measuring the breakthrough time (BT) and time-averaged vapor transmission rate (VTR) using procedures consistent with ASTM F 739 and ASTM F 1383. Two exposure scenarios were simulated: a 2 hour (h) fuel vapor exposure, and a liquid fuel "splash" followed by a 2 h vapor exposure. To simulate internal suit pressure during operation, a positive differential pressure of 0.3 in. water (75 Pa) on the collection side of the permeation apparatus was used. Using the available data, a model was developed to estimate propellant concentrations inside an air-line fed, totally encapsulating chemical protective suit. Concentrations were calculated under simulated conditions of fixed vapor transmission rate, variable breathing air flow rate, and variable splash exposure area. Calculations showed that the maximum allowable permeation rates of hydrazine fuels through CPE were of the order of 0.05 to 0.08 ng/sq cm min for encapsulating suits with low breathing air flow rates (of the order of 5 scfm or 140 L min-1). Above these permeation rates, the 10 parts-per-billion (ppb) threshold limit value time-weighted average could be exceeded. To evaluate suit performance at 10 ppb threshold-limiting value/time-weighted average level concentrations, use of a sensitive analytical method such as cation exchange high performance liquid chromatography with amperometric detection was found to be essential. The analytical detection limit determines the lowest measurable VTR, which in turn governed the lowest per meant concentration that could be calculated inside the totally encapsulating chemical protective suit.

High-throughput method for macrolides and lincosamides antibiotics residues analysis in milk and muscle using a simple liquid-liquid extraction technique and liquid chromatography-electrospray-tandem mass spectrometry analysis (LC-MS/MS).

PubMed

Jank, Louise; Martins, Magda Targa; Arsand, Juliana Bazzan; Campos Motta, Tanara Magalhães; Hoff, Rodrigo Barcellos; Barreto, Fabiano; Pizzolato, Tânia Mara

2015-11-01

A fast and simple method for residue analysis of the antibiotics classes of macrolides (erythromycin, azithromycin, tylosin, tilmicosin and spiramycin) and lincosamides (lincomycin and clindamycin) was developed and validated for cattle, swine and chicken muscle and for bovine milk. Sample preparation consists in a liquid-liquid extraction (LLE) with acetonitrile, followed by liquid chromatography-electrospray-tandem mass spectrometry analysis (LC-ESI-MS/MS), without the need of any additional clean-up steps. Chromatographic separation was achieved using a C18 column and a mobile phase composed by acidified acetonitrile and water. The method was fully validated according the criteria of the Commission Decision 2002/657/EC. Validation parameters such as limit of detection, limit of quantification, linearity, accuracy, repeatability, specificity, reproducibility, decision limit (CCα) and detection capability (CCβ) were evaluated. All calculated values met the established criteria. Reproducibility values, expressed as coefficient of variation, were all lower than 19.1%. Recoveries range from 60% to 107%. Limits of detection were from 5 to 25 µg kg(-1).The present method is able to be applied in routine analysis, with adequate time of analysis, low cost and a simple sample preparation protocol. Copyright © 2015. Published by Elsevier B.V.

Radioastronomie d'amateur, détection de pulsars a 21 cm

NASA Astrophysics Data System (ADS)

Maintoux, Jean-Jacques

2017-01-01

Since the discovery of PSR B1919+21 in 1967, the study of radio pulsars has been so far the work of professional teams using large aperture arrays or single dish antennas. While the discovery of new pulsars is so far out of reach of amateurs astronomers with limited resources, we report the successful detection of 3 pulsars at 1420MHz with a 3.3m prime focus dish antenna, namely: B0329+54, B0950+08 and B1133+16. According to the Neutron Star list [6], this sets a new detection record given the very limited aperture of the antenna. In this paper, we expose how the sensibility and stability to achieve such detection was obtained with our constrained setup, then we discuss the data processing aspects, including the period calculation and folding for each PSR, as well as pulse profiles. With the upcoming upgrades to the telescope, more detections are likely to come. An ongoing observation of B2020+28 already yields promising results. Follow the last results here : http://www.f1ehn.org "radioastro"

Design of mitochondria-targeted colorimetric and ratiometric fluorescent probes for rapid detection of SO2 derivatives in living cells

NASA Astrophysics Data System (ADS)

Yang, Yutao; Zhou, Tingting; Bai, Bozan; Yin, Caixia; Xu, Wenzhi; Li, Wei

2018-05-01

Two mitochondria-targeted colorimetric and ratiometric fluorescent probes for SO2 derivatives were constructed based on the SO2 derivatives-triggered Michael addition reaction. The probes exhibit high specificity toward HSO3-/SO32- by interrupting their conjugation system resulting in a large ratiometric blue shift of 46-121 nm in their emission spectrum. The two well-resolved emission bands can ensure accurate detection of HSO3-. The detection limits were calculated to be 1.09 and 1.35 μM. Importantly, probe 1 and probe 2 were successfully used to fluorescence ratiometric imaging of endogenous HSO3- in BT-474 cells.

Development and validation of a method for determination of corticosteroids in pig fat using liquid chromatography-tandem mass spectrometry.

PubMed

Tölgyesi, Adám; Sharma, Virender K; Fekete, Jeno

2011-02-15

A new method was developed to determine five corticosteroids (prednisolone, methylprednisone, flumethasone, dexamethasone, and methylprednisolone) in pig fat samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) utilizing an optimized liquid-liquid extraction (LLE) and subsequent solid-phase extraction (SPE) for sample clean-up. In the sample preparation, a pig fat sample was dissolved in n-hexane and then extracted into the methanol-water (50/50, v/v) mixture that enabled extraction of only medium polar corticosteroids and not the non-polar components of matrices. This extract was cleaned-up and concentrated on polymeric Oasis HLB SPE cartridge. Separation involved isocratic solvent (methanol-acetate buffer, pH 5.4) and Ascentis Express Fused-Core type HLPC column; reduced the analysis time to 7.5 min, which is at least two times lower than time required for separation using conventional techniques. Other advantage of the developed method is the minimized ion suppression of LC-MS/MS analysis, which allowed detection of corticosteroids in sub μg/kg. Method was validated according to European Union (EU) Commission Decision 2002/657/EC. Measured parameters such as selectivity, linearity, recovery, within-laboratory reproducibility, decision limit, and detection capability satisfied the EU Directive. Ranges of mean recoveries and within-laboratory reproducibility were 81-100% and 8.0-20.5%, respectively. Decision limits were calculated in the range from 4.5 to 11.9 μg/kg for MRL compounds and varied from 0.1 to 0.2 μg/kg for banned substances. Limit of detections (LODs), calculated as three time signal-to-noise ratio, were in the range of 0.1-0.3 μg/kg. Copyright © 2010 Elsevier B.V. All rights reserved.

Dark-ages reionization and galaxy formation simulation - IV. UV luminosity functions of high-redshift galaxies

NASA Astrophysics Data System (ADS)

Liu, Chuanwu; Mutch, Simon J.; Angel, P. W.; Duffy, Alan R.; Geil, Paul M.; Poole, Gregory B.; Mesinger, Andrei; Wyithe, J. Stuart B.

2016-10-01

In this paper, we present calculations of the UV luminosity function (LF) from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations project, which combines N-body, semi-analytic and seminumerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from z ˜ 5 through to z ˜ 10. We investigate the luminosity-star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of 0.1-0.3 dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our calculated luminosities to investigate the LF below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below current detection limits and becomes flat at MUV ≳ -14. We find that 48 (17) per cent of the total UV flux at z ˜ 6 (10) has been detected above an observational limit of MUV ˜ -17, and that galaxies fainter than MUV ˜ -17 are the main source of ionizing photons for reionization. We investigate the luminosity-stellar mass relation, and find a correlation for galaxies with MUV < -14 that has the form M_{ast } ∝ 10^{-0.47M_UV}, in good agreement with observations, but which flattens for fainter galaxies. We determine the luminosity-halo mass relation to be M_vir ∝ 10^{-0.35M_UV}, finding that galaxies with MUV = -20 reside in host dark matter haloes of 1011.0±0.1 M⊙ at z ˜ 6, and that this mass decreases towards high redshift.

Low-Complexity Noncoherent Signal Detection for Nanoscale Molecular Communications.

PubMed

Li, Bin; Sun, Mengwei; Wang, Siyi; Guo, Weisi; Zhao, Chenglin

2016-01-01

Nanoscale molecular communication is a viable way of exchanging information between nanomachines. In this investigation, a low-complexity and noncoherent signal detection technique is proposed to mitigate the inter-symbol-interference (ISI) and additive noise. In contrast to existing coherent detection methods of high complexity, the proposed noncoherent signal detector is more practical when the channel conditions are hard to acquire accurately or hidden from the receiver. The proposed scheme employs the molecular concentration difference to detect the ISI corrupted signals and we demonstrate that it can suppress the ISI effectively. The difference in molecular concentration is a stable characteristic, irrespective of the diffusion channel conditions. In terms of complexity, by excluding matrix operations or likelihood calculations, the new detection scheme is particularly suitable for nanoscale molecular communication systems with a small energy budget or limited computation resource.

Detection of argan oil adulteration with vegetable oils by high-performance liquid chromatography-evaporative light scattering detection.

PubMed

Salghi, Rachid; Armbruster, Wolfgang; Schwack, Wolfgang

2014-06-15

Triacylglycerol profiles were selected as indicator of adulteration of argan oils to carry out a rapid screening of samples for the evaluation of authenticity. Triacylglycerols were separated by high-performance liquid chromatography-evaporative light scattering detection. Different peak area ratios were defined to sensitively detect adulteration of argan oil with vegetable oils such as sunflower, soy bean, and olive oil up to the level of 5%. Based on four reference argan oils, mean limits of detection and quantitation were calculated to approximately 0.4% and 1.3%, respectively. Additionally, 19 more argan oil reference samples were analysed by high-performance liquid chromatography-refractive index detection, resulting in highly comparative results. The overall strategy demonstrated a good applicability in practise, and hence a high potential to be transferred to routine laboratories. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Use of Spontaneous Raman Scattering for Hydrogen Leak Detection

NASA Technical Reports Server (NTRS)

Degroot, Wim A.

1994-01-01

A fiber optic probe has been built and demonstrated that utilizes back scattered spontaneous Raman spectroscopy to detect and identify gaseous species. The small probe, coupled to the laser and data acquisition equipment with optical fibers, has applications in gaseous leak detection and process monitoring. The probe design and data acquisition system are described. Raman scattering theory has been reviewed and the results of intensity calculations of hydrogen and nitrogen Raman scattering are given. Because the device is in its developmental stage, only preliminary experimental results are presented here. Intensity scans across the rotational-vibrational Raman lines of nitrogen and hydrogen are presented. Nitrogen at a partial pressure of 0.077 MPa was detected. Hydrogen at a partial pressure of 2 kPa approached the lower limit of detectability with the present apparatus. Potential instrument improvements that would allow more sensitive and rapid hydrogen detection are identified.

Defining overweight and obesity among Greek children living in Thessaloniki: International versus local reference standards.

PubMed

Christoforidis, A; Dimitriadou, M; Papadopolou, E; Stilpnopoulou, D; Katzos, G; Athanassiou-Metaxa, M

2011-04-01

Body Mass Index (BMI) offers a simple and reasonable measure of obesity that, with the use of the appropriate reference, can help in the early detection of children with weight problems. Our aim was to compare the two most commonly used international BMI references and the national Greek BMI reference in identifying Greek children being overweight and obese. A group of 1557 children (820 girls and 737 boys, mean age: 11.42 ± 3.51 years) were studied. Weight and height was measured using standard methods, and BMI was calculated. Overweight and obesity were determined using the International Obesity Task Force (IOTF) standards, the Centers for Disease Control and Prevention (CDC) BMI-forage curves and the most recent Greek BMI-for-age curves. RESULTS showed that the IOTF's cut-off limits identifies a significantly higher prevalence of overweight (22.4%) compared with both the CDC's (11.8%, p=0.03) and the Greek's (7.4%, p=0.002) cut-off limits. However, the prevalence of obesity was generally increased when it was determined using the CDC's cut-off limits (13.9%) compared to the prevalence calculated with both the IOTF's (6.5%, p=0.05) and the Greek's (6.9%, n.s.) cut off limits. The use of the national Greek reference standards for BMI underestimates the true prevalence of overweight and obesity. On the contrary, both the IOTF and the CDC standards, although independently, detect an increased number of overweight and obese children and thus they should be adopted in the clinical practice for an earlier identification and a timelier intervention.

Optimizing detector geometry for trace element mapping by X-ray fluorescence.

PubMed

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2015-05-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. Copyright © 2015. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Optimizing detector geometry for trace element mapping by X-ray fluorescence

PubMed Central

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2016-01-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. PMID:25600825

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

rFRET: A comprehensive, Matlab-based program for analyzing intensity-based ratiometric microscopic FRET experiments.

PubMed

Nagy, Peter; Szabó, Ágnes; Váradi, Tímea; Kovács, Tamás; Batta, Gyula; Szöllősi, János

2016-04-01

Fluorescence or Förster resonance energy transfer (FRET) remains one of the most widely used methods for assessing protein clustering and conformation. Although it is a method with solid physical foundations, many applications of FRET fall short of providing quantitative results due to inappropriate calibration and controls. This shortcoming is especially valid for microscopy where currently available tools have limited or no capability at all to display parameter distributions or to perform gating. Since users of multiparameter flow cytometry usually apply these tools, the absence of these features in applications developed for microscopic FRET analysis is a significant limitation. Therefore, we developed a graphical user interface-controlled Matlab application for the evaluation of ratiometric, intensity-based microscopic FRET measurements. The program can calculate all the necessary overspill and spectroscopic correction factors and the FRET efficiency and it displays the results on histograms and dot plots. Gating on plots and mask images can be used to limit the calculation to certain parts of the image. It is an important feature of the program that the calculated parameters can be determined by regression methods, maximum likelihood estimation (MLE) and from summed intensities in addition to pixel-by-pixel evaluation. The confidence interval of calculated parameters can be estimated using parameter simulations if the approximate average number of detected photons is known. The program is not only user-friendly, but it provides rich output, it gives the user freedom to choose from different calculation modes and it gives insight into the reliability and distribution of the calculated parameters. © 2016 International Society for Advancement of Cytometry. © 2016 International Society for Advancement of Cytometry.

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

PubMed Central

Lübbe, Jannis; Temmen, Matthias; Rode, Sebastian; Rahe, Philipp; Kühnle, Angelika

2013-01-01

Summary The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d z at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d Δ f at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured d z, we predict d Δ f for specific filter settings, a given level of detection-system noise spectral density d z ds and the cantilever-thermal-noise spectral density d z th. We find an excellent agreement between the calculated and measured values for d Δ f. Furthermore, we demonstrate that thermal noise in d Δ f, defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth. PMID:23400758

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy.

PubMed

Lübbe, Jannis; Temmen, Matthias; Rode, Sebastian; Rahe, Philipp; Kühnle, Angelika; Reichling, Michael

2013-01-01

The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip-surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d(z) at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d(Δ) (f) at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip-surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured d(z), we predict d(Δ) (f) for specific filter settings, a given level of detection-system noise spectral density d(z) (ds) and the cantilever-thermal-noise spectral density d(z) (th). We find an excellent agreement between the calculated and measured values for d(Δ) (f). Furthermore, we demonstrate that thermal noise in d(Δ) (f), defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth.

Network capability estimation. Vela network evaluation and automatic processing research. Technical report. [NETWORTH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snell, N.S.

1976-09-24

NETWORTH is a computer program which calculates the detection and location capability of seismic networks. A modified version of NETWORTH has been developed. This program has been used to evaluate the effect of station 'downtime', the signal amplitude variance, and the station detection threshold upon network detection capability. In this version all parameters may be changed separately for individual stations. The capability of using signal amplitude corrections has been added. The function of amplitude corrections is to remove possible bias in the magnitude estimate due to inhomogeneous signal attenuation. These corrections may be applied to individual stations, individual epicenters, ormore » individual station/epicenter combinations. An option has been added to calculate the effect of station 'downtime' upon network capability. This study indicates that, if capability loss due to detection errors can be minimized, then station detection threshold and station reliability will be the fundamental limits to network performance. A baseline network of thirteen stations has been performed. These stations are as follows: Alaskan Long Period Array, (ALPA); Ankara, (ANK); Chiang Mai, (CHG); Korean Seismic Research Station, (KSRS); Large Aperture Seismic Array, (LASA); Mashhad, (MSH); Mundaring, (MUN); Norwegian Seismic Array, (NORSAR); New Delhi, (NWDEL); Red Knife, Ontario, (RK-ON); Shillong, (SHL); Taipei, (TAP); and White Horse, Yukon, (WH-YK).« less

β-decay half-life of V50 calculated by the shell model

NASA Astrophysics Data System (ADS)

Haaranen, M.; Srivastava, P. C.; Suhonen, J.; Zuber, K.

2014-10-01

In this work we survey the detectability of the β- channel of 2350V leading to the first excited 2+ state in 2450Cr. The electron-capture (EC) half-life corresponding to the transition of 2350V to the first excited 2+ state in 2250Ti had been measured earlier. Both of the mentioned transitions are 4th-forbidden non-unique. We have performed calculations of all the involved wave functions by using the nuclear shell model with the GXPF1A interaction in the full f-p shell. The computed half-life of the EC branch is in good agreement with the measured one. The predicted half-life for the β- branch is in the range ≈2×1019 yr whereas the present experimental lower limit is 1.5×1018 yr. We discuss also the experimental lay-out needed to detect the β--branch decay.

Improved Limits for Higgs-Portal Dark Matter from LHC Searches.

PubMed

Hoferichter, Martin; Klos, Philipp; Menéndez, Javier; Schwenk, Achim

2017-11-03

Searches for invisible Higgs decays at the Large Hadron Collider constrain dark matter Higgs-portal models, where dark matter interacts with the standard model fields via the Higgs boson. While these searches complement dark matter direct-detection experiments, a comparison of the two limits depends on the coupling of the Higgs boson to the nucleons forming the direct-detection nuclear target, typically parametrized in a single quantity f_{N}. We evaluate f_{N} using recent phenomenological and lattice-QCD calculations, and include for the first time the coupling of the Higgs boson to two nucleons via pion-exchange currents. We observe a partial cancellation for Higgs-portal models that makes the two-nucleon contribution anomalously small. Our results, summarized as f_{N}=0.308(18), show that the uncertainty of the Higgs-nucleon coupling has been vastly overestimated in the past. The improved limits highlight that state-of-the-art nuclear physics input is key to fully exploiting experimental searches.

Monopole search below the Parker limit with the MACRO detector at Gran Sasso

NASA Technical Reports Server (NTRS)

Tarle, G.

1985-01-01

The MACRO detector approved for the Gran Sasso Underground Laboratory in Italy will be the first capable of performing a definitive search for super-massive grand unified theory (GUT) monopoles at a level significantly below the Parker flux limit of 10 to the minus 15th power square centimeters Sr(-1) 5(-1). GUT monopoles will move at very low velocities (V approx. 0.001 c) relative to the Earth and a multifaceted detection technique is required to assume their unambiguous identification. Calculations of scintillator response to slow monopoles and measurements of scintillation efficiency for low energy protons have shown that bare monopoles and electrically charged monopoles moving at velocities as low as 5 x .0001 c will produce detectable scintillation signals. The time-of-flight between two thick (25 cm) liquid scintillation layers separated by 4.3m will be used in conjunction with waveform digitization of signals of extended duration in each thick scintillator to provide a redundant signature for slow penetrating particles. Limited streamer tubes filled with He and n-pentane will detect bare monopoles with velocities as low as 1 x 0.0001 c by exploiting monopole induced level mixing and the Penning effect.

Modeling the SHG activities of diverse protein crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haupert, Levi M.; DeWalt, Emma L.; Simpson, Garth J.

2012-10-18

A symmetry-additiveab initiomodel for second-harmonic generation (SHG) activity of protein crystals was applied to assess the likely protein-crystal coverage of SHG microscopy. Calculations were performed for 250 proteins in nine point-group symmetries: a total of 2250 crystals. The model suggests that the crystal symmetry and the limit of detection of the instrument are expected to be the strongest predictors of coverage of the factors considered, which also included secondary-structural content and protein size. Much of the diversity in SHG activity is expected to arise primarily from the variability in the intrinsic protein response as well as the orientation within themore » crystal lattice. Two or more orders-of-magnitude variation in intensity are expected even within protein crystals of the same symmetry. SHG measurements of tetragonal lysozyme crystals confirmed detection, from which a protein coverage of ~84% was estimated based on the proportion of proteins calculated to produce SHG responses greater than that of tetragonal lysozyme. Good agreement was observed between the measured and calculated ratios of the SHG intensity from lysozyme in tetragonal and monoclinic lattices.« less

Utilization of Photochemically Induced Fluorescence Detection for HPLC Determination of Genotoxic Impurities in the Vortioxetine Manufacturing Process.

PubMed

Douša, Michal; Doubský, Jan; Srbek, Jan

2016-07-01

An analytical reversed-phase high-performance liquid chromatography (HPLC) method for the detection and quantitative determination of two genotoxic impurities at ppm level present in the vortioxetine manufacturing process is described. Applying the concept of threshold of toxicological concern, a limit of 75 ppm each for both genotoxic impurities was calculated based on the maximum daily dose of active pharmaceutical ingredients. The novel reversed-phase HPLC method with photochemically induced fluorescence detection was developed on XSELECT Charged Surface Hybrid Phenyl-Hexyl column using the mobile phase consisted a mixture of 10 mM ammonium formate pH 3.0 and acetonitrile. The elution was performed using an isocratic composition of 48:52 (v/v) at a flow rate of 1.0 mL/min. The photochemically induced fluorescence detection is based on the use of UV irradiation at 254 nm through measuring the fluorescence intensity at 300 nm and an excitation wavelength of 272 nm to produce fluorescent derivatives of both genotoxic impurities. The online photochemical conversion and detection is easily accomplished for two expected genotoxic impurities and provides a sufficiently low limit detection and quantification for the target analysis. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Measurements of electron detection efficiencies in solid state detectors.

NASA Technical Reports Server (NTRS)

Lupton, J. E.; Stone, E. C.

1972-01-01

Detailed laboratory measurement of the electron response of solid state detectors as a function of incident electron energy, detector depletion depth, and energy-loss discriminator threshold. These response functions were determined by exposing totally depleted silicon surface barrier detectors with depletion depths between 50 and 1000 microns to the beam from a magnetic beta-ray spectrometer. The data were extended to 5000 microns depletion depth using the results of previously published Monte Carlo electron calculations. When the electron counting efficiency of a given detector is plotted as a function of energy-loss threshold for various incident energies, the efficiency curves are bounded by a smooth envelope which represents the upper limit to the detection efficiency. These upper limit curves, which scale in a simple way, make it possible to easily estimate the electron sensitivity of solid-state detector systems.

Measurement of tritium with high efficiency by using liquid scintillation counter with plastic scintillator.

PubMed

Furuta, Etsuko; Ohyama, Ryu-ichiro; Yokota, Shigeaki; Nakajo, Toshiya; Yamada, Yuka; Kawano, Takao; Uda, Tatsuhiko; Watanabe, Yasuo

2014-11-01

The detection efficiencies of tritium samples by using liquid scintillation counter with hydrophilic plastic scintillator (PS) was approximately 48% when the sample of 20 μL was held between 2 PS sheets treated by plasma. The activity and count rates showed a good relationship between 400 Bq to 410 KBq mL(-1). The calculated detection limit of 2 min measurement by the PS was 13 Bq mL(-1) when a confidence was 95%. The plasma method for PS produces no radioactive waste. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rare Earth Optical Temperature Sensor

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Wolford, David S.

2000-01-01

A new optical temperature sensor suitable for high temperatures (greater than 1700 K) and harsh environments is introduced. The key component of the sensor is the rare earth material contained at the end of a sensor that is in contact with the sample being measured. The measured narrow wavelength band emission from the rare earth is used to deduce the sample temperature. A simplified relation between the temperature and measured radiation was verified experimentally. The upper temperature limit of the sensor is determined by material limits to be approximately 2000 C. The lower limit, determined by the minimum detectable radiation, is found to be approximately 700 K. At high temperatures 1 K resolution is predicted. Also, millisecond response times are calculated.

Identifying QT prolongation from ECG impressions using a general-purpose Natural Language Processor

PubMed Central

Denny, Joshua C.; Miller, Randolph A.; Waitman, Lemuel Russell; Arrieta, Mark; Peterson, Joshua F.

2009-01-01

Objective Typically detected via electrocardiograms (ECGs), QT interval prolongation is a known risk factor for sudden cardiac death. Since medications can promote or exacerbate the condition, detection of QT interval prolongation is important for clinical decision support. We investigated the accuracy of natural language processing (NLP) for identifying QT prolongation from cardiologist-generated, free-text ECG impressions compared to corrected QT (QTc) thresholds reported by ECG machines. Methods After integrating negation detection to a locally-developed natural language processor, the KnowledgeMap concept identifier, we evaluated NLP-based detection of QT prolongation compared to the calculated QTc on a set of 44,318 ECGs obtained from hospitalized patients. We also created a string query using regular expressions to identify QT prolongation. We calculated sensitivity and specificity of the methods using manual physician review of the cardiologist-generated reports as the gold standard. To investigate causes of “false positive” calculated QTc, we manually reviewed randomly selected ECGs with a long calculated QTc but no mention of QT prolongation. Separately, we validated the performance of the negation detection algorithm on 5,000 manually-categorized ECG phrases for any medical concept (not limited to QT prolongation) prior to developing the NLP query for QT prolongation. Results The NLP query for QT prolongation correctly identified 2,364 of 2,373 ECGs with QT prolongation with a sensitivity of 0.996 and a positive predictive value of 1.000. There were no false positives. The regular expression query had a sensitivity of 0.999 and positive predictive value of 0.982. In contrast, the positive predictive value of common QTc thresholds derived from ECG machines was 0.07–0.25 with corresponding sensitivities of 0.994–0.046. The negation detection algorithm had a recall of 0.973 and precision of 0.982 for 10,490 concepts found within ECG impressions. Conclusions NLP and regular expression queries of cardiologists’ ECG interpretations can more effectively identify QT prolongation than the automated QTc intervals reported by ECG machines. Future clinical decision support could employ NLP queries to detect QTc prolongation and other reported ECG abnormalities. PMID:18938105

Determination of methyl mercury by aqueous phase Eehylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection

USGS Publications Warehouse

De Wild, John F.; Olsen, Mark L.; Olund, Shane D.

2002-01-01

A recent national sampling of streams in the United States revealed low methyl mercury concentrations in surface waters. The resulting median and mean concentrations, calculated from 104 samples, were 0.06 nanograms per liter (ng/L) and 0.15 ng/L, respectively. This level of methyl mercury in surface water in the United States has created a need for analytical techniques capable of detecting sub-nanogram per liter concentrations. In an attempt to create a U.S. Geological Survey approved method, the Wisconsin District Mercury Laboratory has adapted a distillation/ethylation/ gas-phase separation method with cold vapor atomic fluorescence spectroscopy detection for the determination of methyl mercury in filtered and unfiltered waters. This method is described in this report. Based on multiple analyses of surface water and ground-water samples, a method detection limit of 0.04 ng/L was established. Precision and accuracy were evaluated for the method using both spiked and unspiked ground-water and surface-water samples. The percent relative standard deviations ranged from 10.2 to 15.6 for all analyses at all concentrations. Average recoveries obtained for the spiked matrices ranged from 88.8 to 117 percent. The precision and accuracy ranges are within the acceptable method-performance limits. Considering the demonstrated detection limit, precision, and accuracy, the method is an effective means to quantify methyl mercury in waters at or below environmentally relevant concentrations

Solid-state electron spin lifetime limited by phononic vacuum modes.

PubMed

Astner, T; Gugler, J; Angerer, A; Wald, S; Putz, S; Mauser, N J; Trupke, M; Sumiya, H; Onoda, S; Isoya, J; Schmiedmayer, J; Mohn, P; Majer, J

2018-04-01

Longitudinal relaxation is the process by which an excited spin ensemble decays into its thermal equilibrium with the environment. In solid-state spin systems, relaxation into the phonon bath usually dominates over the coupling to the electromagnetic vacuum 1-9 . In the quantum limit, the spin lifetime is determined by phononic vacuum fluctuations 10 . However, this limit was not observed in previous studies due to thermal phonon contributions 11-13 or phonon-bottleneck processes 10, 14,15 . Here we use a dispersive detection scheme 16,17 based on cavity quantum electrodynamics 18-21 to observe this quantum limit of spin relaxation of the negatively charged nitrogen vacancy (NV - ) centre 22 in diamond. Diamond possesses high thermal conductivity even at low temperatures 23 , which eliminates phonon-bottleneck processes. We observe exceptionally long longitudinal relaxation times T 1 of up to 8 h. To understand the fundamental mechanism of spin-phonon coupling in this system we develop a theoretical model and calculate the relaxation time ab initio. The calculations confirm that the low phononic density of states at the NV - transition frequency enables the spin polarization to survive over macroscopic timescales.

Effect of Metal Artifacts on Detection of Vertical Root Fractures Using Two Cone Beam Computed Tomography Systems.

PubMed

Safi, Yaser; Aghdasi, Mohammad Mehdi; Ezoddini-Ardakani, Fatemeh; Beiraghi, Samira; Vasegh, Zahra

2015-01-01

Vertical root fracture (VRF) is common in endodontically treated teeth. Conventional and digital radiographies have limitations for detection of VRFs. Cone-beam computed tomography (CBCT) offers greater detection accuracy of VRFs in comparison with conventional radiography. This study compared the effects of metal artifacts on detection of VRFs by using two CBCT systems. Eighty extracted premolars were selected and sectioned at the level of the cemento enamel junction (CEJ). After preparation, root canals were filled with gutta-percha. Subsequently, two thirds of the root fillings were removed for post space preparation and a custom-made post was cemented into each canal. The teeth were randomly divided into two groups (n=40). In the test group, root fracture was created with Instron universal testing machine. The control teeth remained intact. CBCT scans of all teeth were obtained with either New Tom VGI or Soredex Scanora 3D. Three observers analyzed the images for detection of VRF. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for VRF detection and percentage of probable cases were calculated for each imaging system and compared using non-parametric tests considering the non-normal distribution of data. The inter-observer reproducibility was calculated using the weighted kappa coefficient. There were no statistically significant differences in sensitivity, specificity, PPV and NPV between the two CBCT systems. The effect of metal artifacts on VRF detection was not significantly different between the two CBCT systems.

Capacitively coupled EMG detection via ultra-low-power microcontroller STFT.

PubMed

Roland, Theresa; Baumgartner, Werner; Amsuess, Sebastian; Russold, Michael F

2017-07-01

As motion artefacts are a major problem with electromyography sensors, a new algorithm is developed to differentiate artefacts to contraction EMG. The performance of myoelectric prosthesis is increased with this algorithm. The implementation is done for an ultra-low-power microcontroller with limited calculation resources and memory. Short Time Fourier Transformation is used to enable real-time application. The sum of the differences (SOD) of the currently measured EMG to a reference contraction EMG is calculated. The SOD is a new parameter introduced for EMG classification. The satisfactory error rates are determined by measurements done with the capacitively coupling EMG prototype, recently developed by the research group.

A rhodol-based fluorescent chemosensor for hydrazine and its application in live cell bioimaging

NASA Astrophysics Data System (ADS)

Tiensomjitr, Khomsan; Noorat, Rattha; Wechakorn, Kanokorn; Prabpai, Samran; Suksen, Kanoknetr; Kanjanasirirat, Phongthon; Pewkliang, Yongyut; Borwornpinyo, Suparerk; Kongsaeree, Palangpon

2017-10-01

A rhodol cinnamate fluorescent chemosensor (RC) has been developed for selective detection of hydrazine (N2H4). In aqueous medium, the rhodol-based probe exhibited high selectivity for hydrazine among other molecules. The addition of hydrazine triggered a fluorescence emission with 48-fold enhancement based on hydrazinolysis and a subsequent ring-opening process. The chemical probe also displayed a selective colorimetric response toward N2H4 from colorless solution to pink, readily observed by the naked eye. The detection limit of RC for hydrazine was calculated to be 300 nM (9.6 ppb). RC is membrane permeable and was successfully demonstrated to detect hydrazine in live HepG2 cells by confocal fluorescence microscopy.

A retention index calculator simplifies identification of plant volatile organic compounds.

PubMed

Lucero, Mary; Estell, Rick; Tellez, María; Fredrickson, Ed

2009-01-01

Plant volatiles (PVOCs) are important targets for studies in natural products, chemotaxonomy and biochemical ecology. The complexity of PVOC profiles often limits research to studies targeting only easily identified compounds. With the availability of mass spectral libraries and recent growth of retention index (RI) libraries, PVOC identification can be achieved using only gas chromatography coupled to mass spectrometry (GCMS). However, RI library searching is not typically automated, and until recently, RI libraries were both limited in scope and costly to obtain. To automate RI calculation and lookup functions commonly utilised in PVOC analysis. Formulae required for calculating retention indices from retention time data were placed in a spreadsheet along with lookup functions and a retention index library. Retention times obtained from GCMS analysis of alkane standards and Koeberlinia spinosa essential oil were entered into the spreadsheet to determine retention indices. Indices were used in combination with mass spectral analysis to identify compounds contained in Koeberlinia spinosa essential oil. Eighteen compounds were positively identified. Total oil yield was low, with only 5 ppm in purple berries. The most abundant compounds were octen-3-ol and methyl salicylate. The spreadsheet accurately calculated RIs of the detected compounds. The downloadable spreadsheet tool developed for this study provides a calculator and RI library that works in conjuction with GCMS or other analytical techniques to identify PVOCs in plant extracts.

Guidelines for calculating and enhancing detection efficiency of PIT tag interrogation systems

USGS Publications Warehouse

Connolly, Patrick J.

2010-01-01

With increasing use of passive integrated transponder (PIT) tags and reliance on stationary PIT tag interrogation systems to monitor fish populations, guidelines are offered to inform users how best to use limited funding and human resources to create functional systems that maximize a desired level of detection and precision. The estimators of detection efficiency and their variability as described by Connolly et al. (2008) are explored over a span of likely performance metrics. These estimators were developed to estimate detection efficiency without relying on a known number of fish passing the system. I present graphical displays of the results derived from these estimators to show the potential efficiency and precision to be gained by adding an array or by increasing the number of PIT-tagged fish expected to move past an interrogation system.

Optical demodulation system for digitally encoded suspension array in fluoroimmunoassay

NASA Astrophysics Data System (ADS)

He, Qinghua; Li, Dongmei; He, Yonghong; Guan, Tian; Zhang, Yilong; Shen, Zhiyuan; Chen, Xuejing; Liu, Siyu; Lu, Bangrong; Ji, Yanhong

2017-09-01

A laser-induced breakdown spectroscopy and fluorescence spectroscopy-coupled optical system is reported to demodulate digitally encoded suspension array in fluoroimmunoassay. It takes advantage of the plasma emissions of assembled elemental materials to digitally decode the suspension array, providing a more stable and accurate recognition to target biomolecules. By separating the decoding procedure of suspension array and adsorption quantity calculation of biomolecules into two independent channels, the cross talk between decoding and label signals in traditional methods had been successfully avoided, which promoted the accuracy of both processes and realized more sensitive quantitative detection of target biomolecules. We carried a multiplexed detection of several types of anti-IgG to verify the quantitative analysis performance of the system. A limit of detection of 1.48×10-10 M was achieved, demonstrating the detection sensitivity of the optical demodulation system.

Highly selective and sensitive determination of Cu2+ in drink and water samples based on a 1,8-diaminonaphthalene derived fluorescent sensor

NASA Astrophysics Data System (ADS)

Sun, Tao; Li, Yang; Niu, Qingfen; Li, Tianduo; Liu, Yan

2018-04-01

A new simple and efficient fluorescent sensor L based on 1,8-diaminonaphthalene Schiff-base for highly sensitive and selective determination of Cu2+ in drink and water has been developed. This Cu2+-selective detection over other tested metal ions displayed an obvious color change from blue to colorless easily detected by naked eye. The detection limit is determined to be as low as 13.2 nM and the response time is very fast within 30 s. The 1:1 binding mechanism was well confirmed by fluorescence measurements, IR analysis and DFT calculations. Importantly, this sensor L was employed for quick detection of Cu2+ in drink and environmental water samples with satisfactory results, providing a simple, rapid, reliable and feasible Cu2+-sensing method.

Basin-scale observations of isoprene and monoterpenes in the Arctic and Atlantic Oceans

NASA Astrophysics Data System (ADS)

Carpenter, L.; Hackenberg, S.; Andrews, S.; Minaeian, J.; Chance, R.; Arnold, S.; Spracklen, D. V.; Walker, H.; Brewin, R. J.; Tarran, G.; Tilstone, G.; Small, A.; Bouman, H. A.

2016-12-01

We report surface ocean concentrations, atmospheric mixing ratios and calculated sea-to-air fluxes of isoprene and six monoterpenes (α- and β-pinene, myrcene, Δ 3-carene, ocimene, and limonene) spanning approximately 130 degrees of latitude (80 °N- 50 °S) in the Arctic and Atlantic Oceans. Oceanic isoprene concentrations showed covariance with a number of concurrently monitored biological parameters, and these relationships were dependent on sea surface temperatures. Parameterisations of isoprene seawater concentrations based on linear regression analyses of these relationships perform well for Arctic and Atlantic data. Levels of all monoterpenes were generally low, with oceanic concentrations ranging from below the detection limit of <1 pmol L-1 to 5 pmol L-1 . In air, monoterpene mixing ratios varied from below the detection limit ( 1 pptv) to 5 pptv, after careful filtering for ship-related contamination. Unlike in previous studies, no clear trends or relationships of the monoterpenes with biological data were found. Limonene showed generally the highest levels in water (up to 84 pmol L-1 in the Atlantic Ocean) and air; however this was attributed mostly to shipborne contamination. We calculate global sea-air fluxes of isoprene and monoterpenes based on this data and compare to previous estimates.

Design and analysis of a spectro-angular surface plasmon resonance biosensor operating in the visible spectrum

NASA Astrophysics Data System (ADS)

Filion-Côté, Sandrine; Roche, Philip J. R.; Foudeh, Amir M.; Tabrizian, Maryam; Kirk, Andrew G.

2014-09-01

Surface plasmon resonance (SPR) sensing is one of the most widely used methods to implement biosensing due to its sensitivity and capacity for label-free detection. Whilst most commercial SPR sensors operate in the angular regime, it has recently been shown that an increase in sensitivity and a greater robustness against noise can be achieved by measuring the reflectivity when varying both the angle and wavelength simultaneously, in a so-called spectro-angular SPR biosensor. A single value decomposition method is used to project the two-dimensional spectro-angular reflection signal onto a basis set and allow the image obtained from an unknown refractive index sample to be compared very accurately with a pre-calculated reference set. Herein we demonstrate that a previously reported system operated in the near infra-red has a lower detection limit when operating in the visible spectrum due to the improved spatial resolution and numerical precision of the image sensor. The SPR biosensor presented here has an experimental detection limit of 9.8 × 10-7 refractive index unit. To validate the system as a biosensor, we also performed the detection of synthetic RNA from pathogenic Legionella pneumophila with the developed biosensing platform.

Polythiophene nanofilms for sensitive fluorescence detection of viruses in drinking water.

PubMed

Wankar, Shashwati; Turner, Nicholas W; Krupadam, Reddithota J

2016-08-15

Molecular imprints of the tobacco necrosis virus (TNV) have been formed within polythiophene nanofilms with an approximate thickness of 200nm. These films have been electrochemically deposited onto conducting Au surfaces. Upon rebinding, the TNV-polythiophene complex changes the fluorescence intensity of the nanofilm. The fluorescence intensity at 410nm was observed to be proportional to the concentration of viruses in the range of 0.1-10ngL(-1) (0.15-15pg) with the lower calculated detection limit of 2.29ngL(-1) (3.4pg). The intensity of the fluorescence emission is not affected by the thickness of the polythiophene film and the nature of TNV specific binding sites. Kinetic data analyses showed that the nanofilm responds to TNV within 2min; and cross-selectivity studies with tobacco mosaic virus (TMV) showed an excellent specificity for the targeted TNV. These binding experiments demonstrate the potential of fluorescence emission for the specific, label free and rapid detection of viruses using nanofilm sensors. Taking into account the lower limit of detection, the fluorescence sensing reported here is reliable, simple to perform, rapid, cost-effective and offers a sensitive analytical method for virus detection in water resources. Copyright © 2016 Elsevier B.V. All rights reserved.

Validation of a high-performance liquid chromatographic method with UV detection for the determination of ethopabate residues in poultry liver.

PubMed

Granja, Rodrigo H M M; Niño, Alfredo M Montes; Zucchetti, Roberto A M; Niño, Rosario E Montes; Salerno, Alessandro G

2008-01-01

Ethopabate is frequently used in the prophylaxis and treatment of coccidiosis in poultry. Residues of this drug in food present a potential risk to consumers. A simple, rapid, and sensitive column high-performance liquid chromatographic (HPLC) method with UV detection for determination of ethopabate in poultry liver is presented. The drug is extracted with acetonitrile. After evaporation, the residue is dissolved with an acetone-hexane mixture and cleaned up by solid-phase extraction using Florisil columns. The analyte is then eluted with methanol. LC analysis is carried out on a C18 5 microm Gemini column, 15 cm x 4.6 mm. Ethopabate is quantified by means of UV detection at 270 nm. Parameters such as decision limit, detection capability, precision, recovery, ruggedness, and measurement uncertainty were calculated according to method validation guidelines provided in 2002/657/EC and ISO/IEC 17025:2005. Decision limit and detection capability were determined to be 2 and 3 microg/kg, respectively. Average recoveries from poultry samples fortified with 10, 15, and 20 microg/kg levels of ethopabate were 100-105%. A complete statistical analysis was performed on the results obtained, including an estimation of the method uncertainty. The method is to be implemented into Brazil's residue monitoring and control program for ethopabate.

Defining overweight and obesity among Greek children living in Thessaloniki: International versus local reference standards

PubMed Central

Christoforidis, A; Dimitriadou, M; Papadopolou, E; Stilpnopoulou, D; Katzos, G; Athanassiou-Metaxa, M

2011-01-01

Background: Body Mass Index (BMI) offers a simple and reasonable measure of obesity that, with the use of the appropriate reference, can help in the early detection of children with weight problems. Our aim was to compare the two most commonly used international BMI references and the national Greek BMI reference in identifying Greek children being overweight and obese. Methods: A group of 1557 children (820 girls and 737 boys, mean age: 11.42 ± 3.51 years) were studied. Weight and height was measured using standard methods, and BMI was calculated. Overweight and obesity were determined using the International Obesity Task Force (IOTF) standards, the Centers for Disease Control and Prevention (CDC) BMI-forage curves and the most recent Greek BMI-for-age curves. Results: Results showed that the IOTF's cut-off limits identifies a significantly higher prevalence of overweight (22.4%) compared with both the CDC's (11.8%, p=0.03) and the Greek's (7.4%, p=0.002) cut-off limits. However, the prevalence of obesity was generally increased when it was determined using the CDC's cut-off limits (13.9%) compared to the prevalence calculated with both the IOTF's (6.5%, p=0.05) and the Greek's (6.9%, n.s.) cut off limits. Conclusions: The use of the national Greek reference standards for BMI underestimates the true prevalence of overweight and obesity. On the contrary, both the IOTF and the CDC standards, although independently, detect an increased number of overweight and obese children and thus they should be adopted in the clinical practice for an earlier identification and a timelier intervention. PMID:22110296

Direct determination of arsenic in steel by glow discharge optical emission spectrometry with argon-helium mixed gas.

PubMed

Wagatsuma, Kazuaki

2003-02-01

In glow discharge optical emission spectrometry, an argon-helium mixed gas plasma was investigated to improve the detection sensitivity of arsenic in steel samples. The emission line of arsenic was enhanced and the background intensity was simultaneously reduced when an Ar-He plasma was employed instead of an Ar plasma, which is effective for the sensitive determination of arsenic. The detection limits were calculated to be 0.009 mass% for a 700-V Ar plasma, 0.004 mass% for a 700-V Ar-He plasma, and 0.001 mass% for a 900-V Ar-He plasma.

Research on the trace detection of carbon dioxide gas and modulation parameter optimization based on the TDLAS technology

NASA Astrophysics Data System (ADS)

Zhao, Peng; Tao, Jun; Yu, Chang-rui; Li, Ye

2014-02-01

Based on the technology of tunable diode laser absorption spectroscopy, modulation of the center wavelength of 2004 nm distributed feedback laser diode at a room-temperature, the second harmonic amplitude of CO2 at 2004nm can be obtained. The CO2 concentration can be calculated via the Beer-Lambert law. Sinusoidal modulation parameter is an important factor that affects the sensitivity and accuracy of the system, through the research on the relationship between sinusoidal modulation signal frequency, amplitude and Second harmonic linetype, we finally achieve the detection limit of 10ppm under 12 m optical path.

SU-E-J-193: Application of Surface Mapping in Detecting Swallowing for Head-&-Neck Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, D; Xie, X; Mehta, V

2015-06-15

Purpose: Recent evidence is emerging that long term swallowing function may be improved after radiotherapy for head-&-neck cancer if doses are limited to certain swallowing structures. Immobilization of patients with head-&-neck cancer is typically done with a mask. This mask, however, doesn’t limit patient swallowing. Patient voluntary or involuntary swallowing may introduce significant tumor motion, which can lead to suboptimal delivery. In this study, we have examined the feasibility of using surface mapping technology to detect patient swallowing during treatment and evaluated its magnitude. Methods: The C-RAD Catalyst system was used to detect the patient surface map. A volunteer lyingmore » on the couch was used to simulate the patient under treatment. A virtual marker was placed near the throat and was used to monitor the swallowing action. The target motion calculated by the Catalyst system through deformable registration was also collected. Two treatment isocenters, one placed close to the throat and the other placed posterior to the base-of-tongue, were used to check the sensitivity of surface mapping technique. Results: When the patient’s throat is not in the shadow of the patient’s chest, the Catalyst system can clearly identify the swallowing motion. In our tests, the vertical motion of the skin can reach to about 5mm. The calculated target motion can reach up to 1 cm. The magnitude of this calculated target motion is more dramatic when the plan isocenter is closer to the skin surface, which suggests that the Catalyst motion tracking technique is more sensitive to the swallowing motion with a shallower isocenter. Conclusion: Surface mapping can clearly identify patient swallowing during radiation treatment. This information can be used to evaluate the dosimetric impact of the involuntary swallowing. It may also be used to potentially gate head-&-neck radiation treatments. A prospective IRB approved study is currently enrolling patients in our institution. Research was funded through an Elekta grant.« less

Development of Subspace-based Hybrid Monte Carlo-Deterministric Algorithms for Reactor Physics Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdel-Khalik, Hany S.; Zhang, Qiong

2014-05-20

The development of hybrid Monte-Carlo-Deterministic (MC-DT) approaches, taking place over the past few decades, have primarily focused on shielding and detection applications where the analysis requires a small number of responses, i.e. at the detector locations(s). This work further develops a recently introduced global variance reduction approach, denoted by the SUBSPACE approach is designed to allow the use of MC simulation, currently limited to benchmarking calculations, for routine engineering calculations. By way of demonstration, the SUBSPACE approach is applied to assembly level calculations used to generate the few-group homogenized cross-sections. These models are typically expensive and need to be executedmore » in the order of 10 3 - 10 5 times to properly characterize the few-group cross-sections for downstream core-wide calculations. Applicability to k-eigenvalue core-wide models is also demonstrated in this work. Given the favorable results obtained in this work, we believe the applicability of the MC method for reactor analysis calculations could be realized in the near future.« less

Evaluation of a microbiological indicator test for antibiotic detection in ewe and goat milk.

PubMed

Comunian, R; Paba, A; Dupré, I; Daga, E S; Scintu, M F

2010-12-01

Antibiotics are widely used for therapeutic and prophylactic purposes in dairy animals. The presence of residual antibiotics in milk could cause potentially serious problems in human health and have technological implication in the manufacturing of dairy products. The aim of this study was to evaluate Delvotest Accelerator (DSM Food Specialties, Delft, the Netherlands), a new system for a fully automated microbial test to detect antibiotic residues in ewe and goat milk. Forty-three samples of raw, whole, refrigerated bulk-tank milk samples (22 of ewe milk and 21 of goat milk) were analyzed during the whole lactation period. Four concentrations of 4 antibiotics were diluted in milk: penicillin G at 1, 2, 3, and 4 μg/L; sulfadiazine at 25, 50, 100, and 200 μg/L; tetracycline at 50, 100, 200, and 400 μg/L; and gentamicin at 25, 50, 100, and 200 μg/L. The detection limit of the Delvotest Accelerator was calculated as the range of antibiotic concentrations within which 95% of positive result lie. The range of detection limit of penicillin G and sulfadiazine was easily detected by Delvotest Accelerator at or below the European Union maximum residue limits, both for ewe and goat milk samples. In contrast, the system showed a lower ability to detect tetracycline and gentamicin both for ewe and goat milk samples. Very low percentages of false-positive outcomes were obtained. Lactation phase did not seem to be a crucial factor affecting the ability of the Delvotest Accelerator to detect spiked milk samples. A higher detection ability was observed for goat milk samples compared with ewe milk samples. A negative correlation between the percentage of positive milk samples detected and milk fat, protein, and lactose contents was observed for gentamicin only. Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Simultaneous fluorescent detection of multiple metal ions based on the DNAzymes and graphene oxide.

PubMed

Yun, Wen; Wu, Hong; Liu, Xingyan; Fu, Min; Jiang, Jiaolai; Du, Yunfeng; Yang, Lizhu; Huang, Yu

2017-09-15

A novel fluorescent detection strategy for simultaneous detection of Cu 2+ , Pb 2+ and Mg 2+ based on DNAzyme branched junction structure with three kinds of DNAzymes and graphene oxide (GO) was presented. Three fluorophores labeled DNA sequences consisted with enzyme-strand (E-DNA) and substrate strand (S-DNA) were annealed to form DNAzyme branched junction structure. In the presence of target metal ion, the DNAzyme was activated to cleave the fluorophore labeled S-DNA. The S-DNA fragments were released and adsorbed onto GO surface to quench the fluorescent signal. The detection limit was calculated to be 1 nM for Cu 2+ , 200 nM for Mg 2+ , and 0.3 nM for Pb 2+ , respectively. This strategy was successfully used for simultaneous detection of Cu 2+ , Mg 2+ and Pb 2+ in human serum. Moreover, it had potential application for simultaneous detection of multiple metal ions in environmental and biological samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Binding mode dependent signaling for the detection of Cu2 +: An experimental and theoretical approach with practical applications

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Khan, Mehebub Ali; Ganguly, Aniruddha; Masum, Abdulla Al; Alam, Md. Akhtarul; Guchhait, Nikhil

2018-02-01

Two amido-schiff bases (3-Hydroxy-naphthalene-2-carboxylic acid pyren-1-ylmethylene-hydrazide and Naphthalene-2-carboxylic acid pyren-1-ylmethylene-hydrazide) have been synthesized having a common structural unit and only differs by a -OH group in the naphthalene ring. Both of them can detect Cu2 + ion selectively in semi-aqueous medium in distinctly different output modes (one detects Cu2 + by naked-eye color change where as the other detects Cu2 + by fluorescence enhancement). The difference in the binding of Cu 2 + with the compounds is the reason for this observation. The detection limit is found to be micromolar region for compound which contains -OH group whereas the compound without -OH group detects copper in nano-molar region. DFT calculations have been performed in order to demonstrate the structure of the compounds and their copper complexes. Practical utility has been explored by successful paper strip response of both the compounds. The biological applications have been evaluated in RAW 264.7.

Investigation of the source of residual phthalate in sundried salt.

PubMed

Kim, Jin Hyo; Lee, Jin Hwan; Kim, So-Young

2014-03-01

Phthalate contamination in sundried salt has recently garnered interest in Korea. Phthalate concentrations were investigated in Korean sundried salts, source waters, and aqueous extracts from polyvinyl chloride materials used in salt ponds. Preliminary screening results for phthalates in Korean sundried salts revealed that only di(2-ethylhexyl)phthalate (DEHP) was over the limit of detection, with an 8.6% detection rate, and the concentration ranged from below the limit of detection to 0.189 mg/kg. The tolerable daily intake contribution ratio of the salt was calculated to be only 0.001%. Residual phthalates were below 0.026 mg/liter in source water, and the aqueous extracted di-n-butylphthalate, benzylbutylphthalate, and DEHP, which are considered endocrine disruptors, were below 0.029 mg/kg as derived from the polyvinyl chloride materials in salt ponds. The transfer ratios of the six phthalates from seawater to sundried salts were investigated; transfer ratio was correlated with vapor pressure (r(2) = 0.9875). Thus, di-n-butylphthalate, benzylbutylphthalate, DEHP, and di-n-octylphthalate can be considered highly likely residual pollutants in some consumer salts.

Assessing the detectability of antioxidants in two-dimensional high-performance liquid chromatography.

PubMed

Bassanese, Danielle N; Conlan, Xavier A; Barnett, Neil W; Stevenson, Paul G

2015-05-01

This paper explores the analytical figures of merit of two-dimensional high-performance liquid chromatography for the separation of antioxidant standards. The cumulative two-dimensional high-performance liquid chromatography peak area was calculated for 11 antioxidants by two different methods--the areas reported by the control software and by fitting the data with a Gaussian model; these methods were evaluated for precision and sensitivity. Both methods demonstrated excellent precision in regards to retention time in the second dimension (%RSD below 1.16%) and cumulative second dimension peak area (%RSD below 3.73% from the instrument software and 5.87% for the Gaussian method). Combining areas reported by the high-performance liquid chromatographic control software displayed superior limits of detection, in the order of 1 × 10(-6) M, almost an order of magnitude lower than the Gaussian method for some analytes. The introduction of the countergradient eliminated the strong solvent mismatch between dimensions, leading to a much improved peak shape and better detection limits for quantification. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A search for methane in the atmosphere of Mars using ground-based mid infrared heterodyne spectroscopy

NASA Astrophysics Data System (ADS)

Sonnabend, G.; Stupar, D.; Sornig, M.; Stangier, T.; Kostiuk, T.; Livengood, T. A.

2013-09-01

We report our search for methane in the atmosphere of Mars using high-spectral resolution heterodyne spectroscopy in the 7.8 μm wavelength region. Resolving power and frequency precision of >106 of the technique enable identification and full resolution of a targeted spectral line in the terrestrial-Mars spectrum observed from the ground. Observations were carried out on two occasions, in April 2010 and May 2012 at the McMath-Pierce Solar Telescope and the NASA Infrared Telescope Facility, respectively. A single line in the ν4 band of methane at 1282.62448 cm-1 was targeted in both cases. No absorption due to methane was detected and only upper limits of ∼100 ppb for the martian atmospheric methane concentration were retrieved. Lack of observing time (due to weather) and telluric opacity greater than anticipated led to reduced signal-to-noise ratios (SNR). Based on current measurements and calculations, under proper viewing conditions, we estimate an achievable detection limit of ∼10 ppb using the infrared heterodyne technique - adequate for confirming reported detections of methane based on other techniques.

Diazonium Salt-Based Surface-Enhanced Raman Spectroscopy Nanosensor: Detection and Quantitation of Aromatic Hydrocarbons in Water Samples

PubMed Central

Tijunelyte, Inga; Betelu, Stéphanie; Moreau, Jonathan; Ignatiadis, Ioannis; Berho, Catherine; Lidgi-Guigui, Nathalie; Guénin, Erwann; David, Catalina; Vergnole, Sébastien; Rinnert, Emmanuel; Lamy de la Chapelle, Marc

2017-01-01

Here, we present a surface-enhanced Raman spectroscopy (SERS) nanosensor for environmental pollutants detection. This study was conducted on three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BaP), fluoranthene (FL), and naphthalene (NAP). SERS substrates were chemically functionalized using 4-dodecyl benzenediazonium-tetrafluoroborate and SERS analyses were conducted to detect the pollutants alone and in mixtures. Compounds were first measured in water-methanol (9:1 volume ratio) samples. Investigation on solutions containing concentrations ranging from 10−6 g L−1 to 10−3 g L−1 provided data to plot calibration curves and to determine the performance of the sensor. The calculated limit of detection (LOD) was 0.026 mg L−1 (10−7 mol L−1) for BaP, 0.064 mg L−1 (3.2 × 10−7 mol L−1) for FL, and 3.94 mg L−1 (3.1 × 10−5 mol L−1) for NAP, respectively. The correlation between the calculated LOD values and the octanol-water partition coefficient (Kow) of the investigated PAHs suggests that the developed nanosensor is particularly suitable for detecting highly non-polar PAH compounds. Measurements conducted on a mixture of the three analytes (i) demonstrated the ability of the developed technology to detect and identify the three analytes in the mixture; (ii) provided the exact quantitation of pollutants in a mixture. Moreover, we optimized the surface regeneration step for the nanosensor. PMID:28538680

Diazonium Salt-Based Surface-Enhanced Raman Spectroscopy Nanosensor: Detection and Quantitation of Aromatic Hydrocarbons in Water Samples.

PubMed

Tijunelyte, Inga; Betelu, Stéphanie; Moreau, Jonathan; Ignatiadis, Ioannis; Berho, Catherine; Lidgi-Guigui, Nathalie; Guénin, Erwann; David, Catalina; Vergnole, Sébastien; Rinnert, Emmanuel; Lamy de la Chapelle, Marc

2017-05-24

Here, we present a surface-enhanced Raman spectroscopy (SERS) nanosensor for environmental pollutants detection. This study was conducted on three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BaP), fluoranthene (FL), and naphthalene (NAP). SERS substrates were chemically functionalized using 4-dodecyl benzenediazonium-tetrafluoroborate and SERS analyses were conducted to detect the pollutants alone and in mixtures. Compounds were first measured in water-methanol (9:1 volume ratio) samples. Investigation on solutions containing concentrations ranging from 10 -6 g L -1 to 10 -3 g L -1 provided data to plot calibration curves and to determine the performance of the sensor. The calculated limit of detection (LOD) was 0.026 mg L -1 (10 -7 mol L -1 ) for BaP, 0.064 mg L -1 (3.2 × 10 -7 mol L -1 ) for FL, and 3.94 mg L -1 (3.1 × 10 -5 mol L -1 ) for NAP, respectively. The correlation between the calculated LOD values and the octanol-water partition coefficient (K ow ) of the investigated PAHs suggests that the developed nanosensor is particularly suitable for detecting highly non-polar PAH compounds. Measurements conducted on a mixture of the three analytes (i) demonstrated the ability of the developed technology to detect and identify the three analytes in the mixture; (ii) provided the exact quantitation of pollutants in a mixture. Moreover, we optimized the surface regeneration step for the nanosensor.

Surface Cleaning Techniques: Ultra-Trace ICP-MS Sample Preparation and Assay of HDPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Overman, Nicole R.; Hoppe, Eric W.; Addleman, Raymond S.

2013-06-01

The world’s most sensitive radiation detection and assay systems depend upon ultra-low background (ULB) materials to reduce unwanted radiological backgrounds. Herein, we evaluate methods to clean HDPE, a material of interest to ULB systems and the means to provide rapid assay of surface and bulk contamination. ULB level material and ultra-trace level detection of actinide elements is difficult to attain, due to the introduction of contamination from sample preparation equipment such as pipette tips, sample vials, forceps, etc. and airborne particulate. To date, literature available on the cleaning of such polymeric materials and equipment for ULB applications and ultra-trace analysesmore » is limited. For these reasons, a study has been performed to identify an effective way to remove surface contamination from polymers in an effort to provide improved instrumental detection limits. Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was utilized to assess the effectiveness of a variety of leachate solutions for removal of inorganic uranium and thorium surface contamination from polymers, specifically high density polyethylene (HDPE). HDPE leaching procedures were tested to optimize contaminant removal of thorium and uranium. Calibration curves for thorium and uranium ranged from 15 ppq (fg/mL) to 1 ppt (pg/mL). Detection limits were calculated at 6 ppq for uranium and 7 ppq for thorium. Results showed the most effective leaching reagent to be clean 6 M nitric acid for 72 hour exposures. Contamination levels for uranium and thorium found in the leachate solutions were significant for ultralow level radiation detection applications.« less

Regional monitoring activities, June 1958

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersen, B.V.

1958-07-17

The Klamath Falls measurements indicated old fallout materials were present on the vegetation. Cs{sup 137} on Zone B vegetation (200 East Area) averaged 4.1 {times} 10{sup -6} {mu}c/gm this month, compared to an average of 4.4 {times} 10{sup -6} {mu}c/gm last month. Other special measurements this month included calculation of reactor effluent water originated radioisotopes present in samples of Zone Z (Franklin County Irrigation District) vegetation analyzed by gamma spectroscopy. Monthly average values were below the detection limit of about 2 {times} 10{sup -6} {mu}c/gm for Zn{sup 65} and Cr{sup 57}. Maximum Zn{sup 65} concentration was 1.7 {times} 10{sup -6}more » {mu}c/gm on samples collected May 28, 1958. Crop samples of strawberries, green beans, apricots, and potatoes from the Franklin County Irrigation District were taken during June. Analytical results are not yet available. Analytical detection limits for isotopes expected in crop samples were requested at 1/500 of the public limit for human intake of the isotopes.« less

Detection of biological particles by the use of circular dichroism measurements improved by scattering theory

NASA Astrophysics Data System (ADS)

Rosen, David L.; Pendleton, J. David

1995-09-01

Light scattered from optically active spheres was theoretically analyzed for biodetection. The circularly polarized signal of near-forward scattering from circularly dichroic spheres was calculated. Both remote and point biodetection were considered. The analysis included the effect of a circular aperture and beam block at the detector. If the incident light is linearly polarized, a false signal would limit the sensitivity of the biodetector. If the incident light is randomly polarized, shot noise would limit the sensitivity. Suggested improvements to current techniques include a beam block, precise angular measurements, randomly polarized light, index-matching fluid, and larger apertures for large particles.

Satellite passive remote sensing of off-shore pollutants, volume 2

NASA Technical Reports Server (NTRS)

1979-01-01

Satellite detection and monitoring of off-shore dumped pollutants, other than oil, are discussed. Summaries of satellite sensor performance in three spectral bands (visible, infrared, and microwave) are presented. The bulk of the report gives all the calculations, trade-offs and limitations of the three sensor systems. It is asserted that the problem of pollution monitoring is not a sensor problem but a problem of mathematical modeling and data processing.

Review of Methods and Algorithms for Dynamic Management of CBRNE Collection Assets

DTIC Science & Technology

2013-07-01

where they should be looking. An example sensor is a satellite with a limited energy budget, which may have power to operate, say, only 10 percent of...calculations by incorporating sensor data with initial dispersion estimates.1 DTRA and the Joint Science and Technology Office for Chem- Bio Defense (JSTO-CBD...detection performance through remote processing and fusion of sensor data and modeling of the operational environment. DTRA is actively developing

Automatic Reacquisition of Satellite Positions by Detecting Their Expected Streaks in Astronomical Images

NASA Astrophysics Data System (ADS)

Levesque, M.

Artificial satellites, and particularly space junk, drift continuously from their known orbits. In the surveillance-of-space context, they must be observed frequently to ensure that the corresponding orbital parameter database entries are up-to-date. Autonomous ground-based optical systems are periodically tasked to observe these objects, calculate the difference between their predicted and real positions and update object orbital parameters. The real satellite positions are provided by the detection of the satellite streaks in the astronomical images specifically acquired for this purpose. This paper presents the image processing techniques used to detect and extract the satellite positions. The methodology includes several processing steps including: image background estimation and removal, star detection and removal, an iterative matched filter for streak detection, and finally false alarm rejection algorithms. This detection methodology is able to detect very faint objects. Simulated data were used to evaluate the methodology's performance and determine the sensitivity limits where the algorithm can perform detection without false alarm, which is essential to avoid corruption of the orbital parameter database.

First laboratory detection of an absorption line of the first overtone electric quadrupolar band of N2 by CRDS near 2.2 μm

NASA Astrophysics Data System (ADS)

Čermák, P.; Vasilchenko, S.; Mondelain, D.; Kassi, S.; Campargue, A.

2017-01-01

The extremely weak 2-0 O(14) electric quadrupole transition of N2 has been detected by very high sensitivity Cavity Ring Down spectroscopy near 4518 cm-1. It is the first N2 absorption line in the first overtone band reported so far from laboratory experiments. By combining a feedback narrowed Distributed Feedback laser diode with a passive cell tracking technique, a limit of detection of αmin ∼ 1.2 × 10-11 cm-1 was achieved after one day of spectra averaging. The N2 2-0 O(14) line position and line intensity (about 1.5 × 10-30 cm/molecule) agree with calculated values provided in the HITRAN2012 database.

Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter. [International Cometary Explorer (ICE)

NASA Technical Reports Server (NTRS)

Ahearn, Michael F.; Mcfadden, Lucy A.; Feldman, Paul D.; Boehnhardt, Hermann; Rahe, Juergen; Festou, Michael; Brandt, John C.; Maran, Stephen P.; Niedner, Malcom B.; Smith, Andrew M.

1986-01-01

The IUE spectrophotometry of Comet P/Giacobini-Zinner was acquired in support of the International Cometary Explorer (ICE) mission. The abundances (or upper limits) of UV-active species were calculated. During the ICE encounter the H2O production rate was 3 times 10 to the 28th power/sec, + or - 50%, consistent with values derived from the ICE experiments. Comparison of the abundance of CO2(+) ions with the total electron density measured by the plasma electron experiment on ICE indicates a deficiency of ions relative to electrons indicating a population of ions not detected by remote sensing. The absence of detectable Mg(+) rules out this species as a possible ion of M/Q = 24 detected by the Ion Composition Instrument, part of the ICE complement of instruments.

Naphthaldimine-based simple glucose derivative as a highly selective sensor for colorimetric detection of Cu2+ ion in aqueous media

NASA Astrophysics Data System (ADS)

Dolai, Bholanath; Bhaumik, Atanu; Pramanik, Nabakumar; Ghosh, Kalyan Sundar; Atta, Ananta Kumar

2018-07-01

Naphthaldimine-based glucose derivatives 1 and 3 have been designed, synthesized and characterized. In aqueous media, glucose derivative 1, exhibited high selectivity and sensitivity towards Cu2+ ion in comparison with various cations and anions. In presence of Cu2+, sensor 1 has provided significant naked-eye detectable color change. The formation of 1-Cu2+ complex has been analyzed by UV-vis spectroscopy, 1H NMR titration experiments, mass spectrometry and DFT (density functional theory) calculations. Limit of detection of 1 as a colorimetric sensor for Cu2+ ion is found to be 0.23 μM, much lower than recommended value of World Health Organization (WHO), which makes to Cu2+ sensor 1 more effective and useful.

High-temperature unimolecular decomposition of ethyl propionate

NASA Astrophysics Data System (ADS)

Giri, Binod Raj; AlAbbad, Mohammed; Farooq, Aamir

2016-11-01

This work reports rate coefficients of the thermal unimolecular decomposition reaction of ethyl propionate (EP) behind reflected shock waves over the temperature range of 976-1300 K and pressures of 825-1875 Torr. The reaction progress was monitored by detecting C2H4 near 10.532 μm using CO2 gas laser absorption. In addition, G3//MP2/aug-cc-pVDZ and master equation calculations were performed to assess the pressure- and temperature-dependence of the reaction. Our calculations revealed that C2H4 elimination occurs via a six-centered retro-ene transition state. Our measured rate data are close to the high-pressure limit and showed no discernable temperature fall off.

Comparison of algorithms for automatic border detection of melanoma in dermoscopy images

NASA Astrophysics Data System (ADS)

Srinivasa Raghavan, Sowmya; Kaur, Ravneet; LeAnder, Robert

2016-09-01

Melanoma is one of the most rapidly accelerating cancers in the world [1]. Early diagnosis is critical to an effective cure. We propose a new algorithm for more accurately detecting melanoma borders in dermoscopy images. Proper border detection requires eliminating occlusions like hair and bubbles by processing the original image. The preprocessing step involves transforming the RGB image to the CIE L*u*v* color space, in order to decouple brightness from color information, then increasing contrast, using contrast-limited adaptive histogram equalization (CLAHE), followed by artifacts removal using a Gaussian filter. After preprocessing, the Chen-Vese technique segments the preprocessed images to create a lesion mask which undergoes a morphological closing operation. Next, the largest central blob in the lesion is detected, after which, the blob is dilated to generate an image output mask. Finally, the automatically-generated mask is compared to the manual mask by calculating the XOR error [3]. Our border detection algorithm was developed using training and test sets of 30 and 20 images, respectively. This detection method was compared to the SRM method [4] by calculating the average XOR error for each of the two algorithms. Average error for test images was 0.10, using the new algorithm, and 0.99, using SRM method. In comparing the average error values produced by the two algorithms, it is evident that the average XOR error for our technique is lower than the SRM method, thereby implying that the new algorithm detects borders of melanomas more accurately than the SRM algorithm.

A real-time fluorescent sensor specific to Mg2+: crystallographic evidence, DFT calculation and its use for quantitative determination of magnesium in drinking water.

PubMed

Men, Guangwen; Chen, Chunrong; Zhang, Shitong; Liang, Chunshuang; Wang, Ying; Deng, Mengyu; Shang, Hongxing; Yang, Bing; Jiang, Shimei

2015-02-14

An "off-the-shelf" fluorescence "turn-on" Mg(2+) chemosensor 3,5-dichlorosalicylaldehyde (BCSA) was rationally designed and developed. This proposed sensor works based on Mg(2+)-induced formation of the 2 : 1 BCSA-Mg(2+) complex. The coordination of BSCA to Mg(2+) increases its structural rigidity generating a chelation-enhanced fluorescence (CHEF) effect which was confirmed by single crystal XRD studies of the BSCA-Mg(2+) complex and TD/DFT calculations. This sensor exhibits high sensitivity and selectivity for the quantitative monitoring of Mg(2+) with a wide detection range (0-40 μM), a low detection limit (2.89 × 10(-7) mol L(-1)) and a short response time (<0.5 s). It can also resist the interference from the other co-existing metal ions, especially Ca(2+). Consequently, this fluorescent sensor can be utilized to monitor Mg(2+) in real time within actual samples from drinking water.

WDR-PK-AK-018

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollister, R

2009-08-26

Method - CES SOP-HW-P556 'Field and Bulk Gamma Analysis'. Detector - High-purity germanium, 40% relative efficiency. Calibration - The detector was calibrated on February 8, 2006 using a NIST-traceable sealed source, and the calibration was verified using an independent sealed source. Count Time and Geometry - The sample was counted for 20 minutes at 72 inches from the detector. A lead collimator was used to limit the field-of-view to the region of the sample. The drum was rotated 180 degrees halfway through the count time. Date and Location of Scans - June 1,2006 in Building 235 Room 1136. Spectral Analysismore » Spectra were analyzed with ORTEC GammaVision software. Matrix and geometry corrections were calculated using OR TEC Isotopic software. A background spectrum was measured at the counting location. No man-made radioactivity was observed in the background. Results were determined from the sample spectra without background subtraction. Minimum detectable activities were calculated by the Nureg 4.16 method. Results - Detected Pu-238, Pu-239, Am-241 and Am-243.« less

Mover Position Detection for PMTLM Based on Linear Hall Sensors through EKF Processing

PubMed Central

Yan, Leyang; Zhang, Hui; Ye, Peiqing

2017-01-01

Accurate mover position is vital for a permanent magnet tubular linear motor (PMTLM) control system. In this paper, two linear Hall sensors are utilized to detect the mover position. However, Hall sensor signals contain third-order harmonics, creating errors in mover position detection. To filter out the third-order harmonics, a signal processing method based on the extended Kalman filter (EKF) is presented. The limitation of conventional processing method is first analyzed, and then EKF is adopted to detect the mover position. In the EKF model, the amplitude of the fundamental component and the percentage of the harmonic component are taken as state variables, and they can be estimated based solely on the measured sensor signals. Then, the harmonic component can be calculated and eliminated. The proposed method has the advantages of faster convergence, better stability and higher accuracy. Finally, experimental results validate the effectiveness and superiority of the proposed method. PMID:28383505

Portable and low-cost colorimetric office paper-based device for phenacetin detection in seized cocaine samples.

PubMed

da Silva, Gabriela O; de Araujo, William R; Paixão, Thiago R L C

2018-01-01

An office paper-based colorimetric device is proposed as a portable, rapid, and low-cost sensor for forensic applications aiming to detect phenacetin used as adulterant in illicit seized materials such as cocaine. The proposed method uses white office paper as the substrate and wax printing technology to fabricate the detection zones. Based on the optimum conditions, a linear analytical curve was obtained for phenacetin concentrations ranging from 0 to 64.52µgmL ‒1 , and the straight line was in accordance with the following equation: (Magenta percentage color) = 1.19 + 0.458 (C Phe /µgmL ‒1 ), R 2 = 0.990. The limit of detection was calculated as 3.5µgmL ‒1 (3σ/slope). The accuracy of the proposed method was evaluated using real seized cocaine samples and the spike-recovery procedure. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantum-statistical theory of microwave detection using superconducting tunnel junctions

NASA Astrophysics Data System (ADS)

Deviatov, I. A.; Kuzmin, L. S.; Likharev, K. K.; Migulin, V. V.; Zorin, A. B.

1986-09-01

A quantum-statistical theory of microwave and millimeter-wave detection using superconducting tunnel junctions is developed, with a rigorous account of quantum, thermal, and shot noise arising from fluctuation sources associated with the junctions, signal source, and matching circuits. The problem of the noise characterization in the quantum sensitivity range is considered and a general noise parameter Theta(N) is introduced. This parameter is shown to be an adequate figure of merit for most receivers of interest while some devices can require a more complex characterization. Analytical expressions and/or numerically calculated plots for Theta(N) are presented for the most promising detection modes including the parametric amplification, heterodyne mixing, and quadratic videodetection, using both the quasiparticle-current and the Cooper-pair-current nonlinearities. Ultimate minimum values of Theta(N) for each detection mode are compared and found to be in agreement with limitations imposed by the quantum-mechanical uncertainty principle.

Study of the interaction of 6-mercaptopurine with protein by microdialysis coupled with LC and electrochemical detection based on functionalized multi-wall carbon nanotubes modified electrode.

PubMed

Cao, Xu-Ni; Lin, Li; Zhou, Yu-Yan; Zhang, Wen; Shi, Guo-Yue; Yamamoto, Katsunobu; Jin, Li-Tong

2003-07-14

Microdialysis sampling coupled with liquid chromatography and electrochemical detection (LC-ECD) was developed and applied to study the interaction of 6-Mercaptopurine (6-MP) with bovine serum albumin (BSA). In the LC-ECD, the multi-wall carbon nanotubes fuctionalized with carboxylic groups modified electrode (MWNT-COOH CME) was used as the working electrode for the determination of 6-MP. The results indicated that this chemically modified electrode (CME) exhibited efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP were linear to its concentrations ranging from 4.0 x 10(-7) to 1.0 x 10(-4) mol l(-1) with the calculated detection limit (S/N = 3) of 2.0 x 10(-7) mol l(-1). The method had been successfully applied to assess the association constant (K) and the number of the binding sites (n) on a BSA molecular, which calculated by Scatchard equation, were 3.97 x 10(3) mol(-1) l and 1.51, respectively. This method provided a fast, sensible and simple technique for the study of drug-protein interactions.

Magnetoencephalographic accuracy profiles for the detection of auditory pathway sources.

PubMed

Bauer, Martin; Trahms, Lutz; Sander, Tilmann

2015-04-01

The detection limits for cortical and brain stem sources associated with the auditory pathway are examined in order to analyse brain responses at the limits of the audible frequency range. The results obtained from this study are also relevant to other issues of auditory brain research. A complementary approach consisting of recordings of magnetoencephalographic (MEG) data and simulations of magnetic field distributions is presented in this work. A biomagnetic phantom consisting of a spherical volume filled with a saline solution and four current dipoles is built. The magnetic fields outside of the phantom generated by the current dipoles are then measured for a range of applied electric dipole moments with a planar multichannel SQUID magnetometer device and a helmet MEG gradiometer device. The inclusion of a magnetometer system is expected to be more sensitive to brain stem sources compared with a gradiometer system. The same electrical and geometrical configuration is simulated in a forward calculation. From both the measured and the simulated data, the dipole positions are estimated using an inverse calculation. Results are obtained for the reconstruction accuracy as a function of applied electric dipole moment and depth of the current dipole. We found that both systems can localize cortical and subcortical sources at physiological dipole strength even for brain stem sources. Further, we found that a planar magnetometer system is more suitable if the position of the brain source can be restricted in a limited region of the brain. If this is not the case, a helmet-shaped sensor system offers more accurate source estimation.

Screening of European coffee final products for occurrence of ochratoxin A (OTA).

PubMed

vd Stegen, G; Jörissen, U; Pittet, A; Saccon, M; Steiner, W; Vincenzi, M; Winkler, M; Zapp, J; Schlatter, C

1997-04-01

Samples (633) of final coffee products were drawn from the markets of different European countries relative to the market share of each product type and brand. These samples were analysed in a cooperative action with nine different laboratories. With low limits of detection (mean detection limit approximately 0.5 ng/g) no OTA was found in over half of the samples (334 negatives). In the remaining samples occurrence of OTA at a rather low level was seen. Only four samples (all instants) exceeded a level of 10 ng/g, whereas for both instants, and roast and grounds (R & G), over three-quarters of the samples were in the range from nondetectable to 1 ng/g. The overall mean for all R & Gs was 0.8 ng/g and for all instant 1.3 ng/g (for samples in which no OTA was detected, half of the detection limit was included in this calculation). In the brewing methods frequently used in Europe the OTA is essentially fully extracted. Consumption of four cups of coffee per day (approximately 24 g R & G or approximately 8 g instant coffee) contributes on average 19 or 10 ng/day respectively. Four cups/day is above the per caput consumption level in most European contries. Compared with the Provisional Tolerable Weekly Intake (PTWI) recently set by the Joint FAO/WHO Expert Committee on Food Additives at 100 ng/kg bodyweight/week, consumption of 28 cups/week contributes up to 2% to the PTWI.

Radio and gamma-ray properties of extragalactic jets from the TANAMI sample

DOE PAGES

Böck, M.; Kadler, M.; Müller, C.; ...

2016-05-04

The TANAMI program has been observing parsec-scale radio jets of southern (declination south of - 30°) γ-ray bright AGN, simultaneously with Fermi/LAT monitoring of their γ-ray emission, via high-resolution radio imaging with Very Long Baseline Interferometry techniques. In this paper, we present the radio and γ-rayproperties of the TANAMI sources based on one year of contemporaneous TANAMI and Fermi/LAT data. A large fraction (72%) of the TANAMI sample can be associated with bright γ-ray sources for this time range. Association rates differ for different optical classes with all BL Lacs, 76% of quasars, and just 17% of galaxies detected bymore » the LAT. Upper limits were established on the γ-ray flux from TANAMI sources not detected by LAT. This analysis led to the identification of three new Fermi sources whose detection was later confirmed. The γ-ray and radio luminosities are related by L γ ∝ L r 0.89±0.04. The brightness temperatures of the radio cores increase with the average γ-ray luminosity and the presence of brightness temperatures above the inverse Compton limit implies strong Doppler boosting in those sources. The undetected sources have lower γ/radio luminosity ratios and lower contemporaneous brightness temperatures. Finally, unless the Fermi/LAT-undetected blazars are much γ-ray-fainter than the Fermi/LAT-detected sources, their γ-ray luminosity should not be significantly lower than the upper limits calculated here.« less

Validation of the AUDIT-C in adults seeking help with their drinking online.

PubMed

Khadjesari, Zarnie; White, Ian R; McCambridge, Jim; Marston, Louise; Wallace, Paul; Godfrey, Christine; Murray, Elizabeth

2017-01-04

The abbreviated Alcohol Use Disorder Identification Test for Consumption (AUDIT-C) is rapidly becoming the alcohol screening tool of choice for busy practitioners in clinical settings and by researchers keen to limit assessment burden and reactivity. Cut-off scores for detecting drinking above recommended limits vary by population, setting, country and potentially format. This validation study aimed to determine AUDIT-C thresholds that indicated risky drinking among a population of people seeking help over the Internet. The data in this study were collected in the pilot phase of the Down Your Drink trial, which recruited people seeking help over the Internet and randomised them to a web-based intervention or an information-only website. Sensitivity, specificity, and positive and negative likelihood ratios were calculated for AUDIT-C scores, relative to weekly consumption that indicated drinking above limits and higher risk drinking. Receiver-operating characteristic (ROC) curves were created to assess the performance of different cut-off scores on the AUDIT-C for men and women. Past week alcohol consumption was used as the reference-standard and was collected via the TOT-AL, a validated online measure of past week drinking. AUDIT-C scores were obtained from 3720 adults (2053 female and 1667 male) searching the internet for help with drinking, mostly from the UK. The area under the ROC curve for risky drinking was 0.84 (95% CI 0.80, 0.87) (female) and 0.80 (95% CI 0.76, 0.84) (male). AUDIT-C cut-off scores for detecting risky drinking that maximise the sum of sensitivity and specificity were ≥8 for women and ≥8 for men; whereas those identifying the highest proportion of correctly classified individuals were ≥4 for women and ≥5 for men. AUDIT-C cut-off scores for detecting higher risk drinking were also calculated. AUDIT-C cut-off scores for identifying alcohol consumption above weekly limits in this largely UK based study population were substantially higher than those reported in other validation studies. Researchers and practitioners should select AUDIT-C cut-off scores according to the purpose of identifying risky drinkers and hence the relative importance of sensitivity and/or specificity.

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE PAGES

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris; ...

2015-01-01

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Nanoparticle size detection limits by single particle ICP-MS for 40 elements.

PubMed

Lee, Sungyun; Bi, Xiangyu; Reed, Robert B; Ranville, James F; Herckes, Pierre; Westerhoff, Paul

2014-09-02

The quantification and characterization of natural, engineered, and incidental nano- to micro-size particles are beneficial to assessing a nanomaterial's performance in manufacturing, their fate and transport in the environment, and their potential risk to human health. Single particle inductively coupled plasma mass spectrometry (spICP-MS) can sensitively quantify the amount and size distribution of metallic nanoparticles suspended in aqueous matrices. To accurately obtain the nanoparticle size distribution, it is critical to have knowledge of the size detection limit (denoted as Dmin) using spICP-MS for a wide range of elements (other than a few available assessed ones) that have been or will be synthesized into engineered nanoparticles. Herein is described a method to estimate the size detection limit using spICP-MS and then apply it to nanoparticles composed of 40 different elements. The calculated Dmin values correspond well for a few of the elements with their detectable sizes that are available in the literature. Assuming each nanoparticle sample is composed of one element, Dmin values vary substantially among the 40 elements: Ta, U, Ir, Rh, Th, Ce, and Hf showed the lowest Dmin values, ≤10 nm; Bi, W, In, Pb, Pt, Ag, Au, Tl, Pd, Y, Ru, Cd, and Sb had Dmin in the range of 11-20 nm; Dmin values of Co, Sr, Sn, Zr, Ba, Te, Mo, Ni, V, Cu, Cr, Mg, Zn, Fe, Al, Li, and Ti were located at 21-80 nm; and Se, Ca, and Si showed high Dmin values, greater than 200 nm. A range of parameters that influence the Dmin, such as instrument sensitivity, nanoparticle density, and background noise, is demonstrated. It is observed that, when the background noise is low, the instrument sensitivity and nanoparticle density dominate the Dmin significantly. Approaches for reducing the Dmin, e.g., collision cell technology (CCT) and analyte isotope selection, are also discussed. To validate the Dmin estimation approach, size distributions for three engineered nanoparticle samples were obtained using spICP-MS. The use of this methodology confirms that the observed minimum detectable sizes are consistent with the calculated Dmin values. Overall, this work identifies the elements and nanoparticles to which current spICP-MS approaches can be applied, in order to enable quantification of very small nanoparticles at low concentrations in aqueous media.

Using large volume samplers for the monitoring of particle bound micro pollutants in rivers

NASA Astrophysics Data System (ADS)

Kittlaus, Steffen; Fuchs, Stephan

2015-04-01

The requirements of the WFD as well as substance emission modelling at the river basin scale require stable monitoring data for micro pollutants. The monitoring concepts applied by the local authorities as well as by many scientists use single sampling techniques. Samples from water bodies are usually taken in volumes of about one litre and depending on predetermined time steps or through discharge thresholds. For predominantly particle bound micro pollutants the small sample size of about one litre results in a very small amount of suspended particles. To measure micro pollutant concentrations in these samples is demanding and results in a high uncertainty of the measured concentrations, if the concentration is above the detection limit in the first place. In many monitoring programs most of the measured values were below the detection limit. This results in a high uncertainty if river loads were calculated from these data sets. The authors propose a different approach to gain stable concentration values for particle bound micro pollutants from river monitoring: A mixed sample of about 1000 L was pumped in a tank with a dirty-water pump. The sampling usually is done discharge dependant by using a gauge signal as input for the control unit. After the discharge event is over or the tank is fully filled, the suspended solids settle in the tank for 2 days. After this time a clear separation of water and solids can be shown. A sample (1 L) from the water phase and the total mass of the settled solids (about 10 L) are taken to the laboratory for analysis. While the micro pollutants can't hardly be detected in the water phase, the signal from the sediment is high above the detection limit, thus certain and very stable. From the pollutant concentration in the solid phase and the total tank volume the initial pollutant concentration in the sample can be calculated. If the concentration in the water phase is detectable, it can be used to correct the total load. This relatively low cost approach (less costs for analysis because of small sample number) allows to quantify the pollutant load, to derive dissolved-solid partition coefficients and to quantify the pollutant load in different particle size classes.

Using a Calculated Pulse Rate with an Artificial Neural Network to Detect Irregular Interbeats.

PubMed

Yeh, Bih-Chyun; Lin, Wen-Piao

2016-03-01

Heart rate is an important clinical measure that is often used in pathological diagnosis and prognosis. Valid detection of irregular heartbeats is crucial in the clinical practice. We propose an artificial neural network using the calculated pulse rate to detect irregular interbeats. The proposed system measures the calculated pulse rate to determine an "irregular interbeat on" or "irregular interbeat off" event. If an irregular interbeat is detected, the proposed system produces a danger warning, which is helpful for clinicians. If a non-irregular interbeat is detected, the proposed system displays the calculated pulse rate. We include a flow chart of the proposed software. In an experiment, we measure the calculated pulse rates and achieve an error percentage of < 3% in 20 participants with a wide age range. When we use the calculated pulse rates to detect irregular interbeats, we find such irregular interbeats in eight participants.

SU-E-T-484: In Vivo Dosimetry Tolerances in External Beam Fast Neutron Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, L; Gopan, O

Purpose: Optical stimulated luminescence (OSL) dosimetry with Landauer Al2O3:C nanodots was developed at our institution as a passive in vivo dosimetry (IVD) system for patients treated with fast neutron therapy. The purpose of this study was to establish clinically relevant tolerance limits for detecting treatment errors requiring further investigation. Methods: Tolerance levels were estimated by conducting a series of IVD expected dose calculations for square field sizes ranging between 2.8 and 28.8 cm. For each field size evaluated, doses were calculated for open and internal wedged fields with angles of 30°, 45°, or 60°. Theoretical errors were computed for variationsmore » of incorrect beam configurations. Dose errors, defined as the percent difference from the expected dose calculation, were measured with groups of three nanodots placed in a 30 x 30 cm solid water phantom, at beam isocenter (150 cm SAD, 1.7 cm Dmax). The tolerances were applied to IVD patient measurements. Results: The overall accuracy of the nanodot measurements is 2–3% for open fields. Measurement errors agreed with calculated errors to within 3%. Theoretical estimates of dosimetric errors showed that IVD measurements with OSL nanodots will detect the absence of an internal wedge or a wrong wedge angle. Incorrect nanodot placement on a wedged field is more likely to be caught if the offset is in the direction of the “toe” of the wedge where the dose difference in percentage is about 12%. Errors caused by an incorrect flattening filter size produced a 2% measurement error that is not detectable by IVD measurement alone. Conclusion: IVD with nanodots will detect treatment errors associated with the incorrect implementation of the internal wedge. The results of this study will streamline the physicists’ investigations in determining the root cause of an IVD reading that is out of normally accepted tolerances.« less

Upper limits on the 21 cm power spectrum at z = 5.9 from quasar absorption line spectroscopy

NASA Astrophysics Data System (ADS)

Pober, Jonathan C.; Greig, Bradley; Mesinger, Andrei

2016-11-01

We present upper limits on the 21 cm power spectrum at z = 5.9 calculated from the model-independent limit on the neutral fraction of the intergalactic medium of x_{H I} < 0.06 + 0.05 (1σ ) derived from dark pixel statistics of quasar absorption spectra. Using 21CMMC, a Markov chain Monte Carlo Epoch of Reionization analysis code, we explore the probability distribution of 21 cm power spectra consistent with this constraint on the neutral fraction. We present 99 per cent confidence upper limits of Δ2(k) < 10-20 mK2 over a range of k from 0.5 to 2.0 h Mpc-1, with the exact limit dependent on the sampled k mode. This limit can be used as a null test for 21 cm experiments: a detection of power at z = 5.9 in excess of this value is highly suggestive of residual foreground contamination or other systematic errors affecting the analysis.

Electro-optical system for gunshot detection: analysis, concept, and performance

NASA Astrophysics Data System (ADS)

Kastek, M.; Dulski, R.; Madura, H.; Trzaskawka, P.; Bieszczad, G.; Sosnowski, T.

2011-08-01

The paper discusses technical possibilities to build an effective electro-optical sensor unit for sniper detection using infrared cameras. This unit, comprising of thermal and daylight cameras, can operate as a standalone device but its primary application is a multi-sensor sniper and shot detection system. At first, the analysis was presented of three distinguished phases of sniper activity: before, during and after the shot. On the basis of experimental data the parameters defining the relevant sniper signatures were determined which are essential in assessing the capability of infrared camera to detect sniper activity. A sniper body and muzzle flash were analyzed as targets and the descriptions of phenomena which make it possible to detect sniper activities in infrared spectra as well as analysis of physical limitations were performed. The analyzed infrared systems were simulated using NVTherm software. The calculations for several cameras, equipped with different lenses and detector types were performed. The simulation of detection ranges was performed for the selected scenarios of sniper detection tasks. After the analysis of simulation results, the technical specifications of infrared sniper detection system were discussed, required to provide assumed detection range. Finally the infrared camera setup was proposed which can detected sniper from 1000 meters range.

[Evaluation of four methods for detecting methicillin-resistant Staphylococcus aureus isolates from clinical specimens at a regional hospital in Mexico].

PubMed

Acosta-Pérez, Gabriel; Rodríguez-Ábrego, Gabriela; Longoria-Revilla, Ernesto; Castro-Mussot, María Eugenia

2012-01-01

To estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in clinical isolates and to compare different methods for detection of MRSA in a lab with limited available personnel and resources. 140 Staphylococcus aureus strains isolated from patients in several departments were assayed for β-lactamase production, MIC-Vitek 2 oxacillin, ChromID MRSA, disk diffusion in agar for cefoxitin 30 μg and PBP2a detection. The results of conventional tests were compared with the "gold standard" PCR test for mecA gene. Cohen´s kappa index was also calculated in order to evaluate the intra assay agreement between the used methods. The found prevalence was 90.7%. Sensitivity and specificity were: disk diffusion for cefoxitin 97 and 92% respectively, MIC Vitek 2-XL 97 and 69%, ChromoID MRSA 97 and 85%, and PBP2a detection 98 and 100%. All methods are very good for detecting MRSA, choosing a method to use will depend on each laboratory infrastructure.

Curcumin-Based "Enhanced SNAr" Promoted Ultrafast Fluorescent Probe for Thiophenols Detection in Aqueous Solution and in Living Cells.

PubMed

Yue, Yongkang; Huo, Fangjun; Zhang, Yongbin; Chao, Jianbin; Martínez-Máñez, Ramón; Yin, Caixia

2016-11-01

We report herein a highly selective and sensitive turn-on fluorescent probe (compound 1) with a fast response time (less than 2 min) for thiophenol detection based on an "enhanced S N Ar" reaction between thiophenols and a sulfonyl-ester moiety covalently attach to curcumin. Reaction of 1 in Hepes-MeOH (1:1, v/v, pH 7.4) in the presence of 4-methylthiophenol (MTP) resulted in a remarkable enhancement of the fluorescence. A linear response in the presence of MTP of the relative fluorescent intensity (F - F 0 ) of 1 at 536 nm in the 0-40 μM MTP concentration range was found. A limit of detection (LOD) for the detection of MTP of 26 nM, based on the definition by IUPAC (C DL = 3 Sb/m), was calculated. Probe 1 was applied to monitor and imaging exogenous MTP in live cells and to the detection of MTP in real water samples.

The impact of registration accuracy on imaging validation study design: A novel statistical power calculation.

PubMed

Gibson, Eli; Fenster, Aaron; Ward, Aaron D

2013-10-01

Novel imaging modalities are pushing the boundaries of what is possible in medical imaging, but their signal properties are not always well understood. The evaluation of these novel imaging modalities is critical to achieving their research and clinical potential. Image registration of novel modalities to accepted reference standard modalities is an important part of characterizing the modalities and elucidating the effect of underlying focal disease on the imaging signal. The strengths of the conclusions drawn from these analyses are limited by statistical power. Based on the observation that in this context, statistical power depends in part on uncertainty arising from registration error, we derive a power calculation formula relating registration error, number of subjects, and the minimum detectable difference between normal and pathologic regions on imaging, for an imaging validation study design that accommodates signal correlations within image regions. Monte Carlo simulations were used to evaluate the derived models and test the strength of their assumptions, showing that the model yielded predictions of the power, the number of subjects, and the minimum detectable difference of simulated experiments accurate to within a maximum error of 1% when the assumptions of the derivation were met, and characterizing sensitivities of the model to violations of the assumptions. The use of these formulae is illustrated through a calculation of the number of subjects required for a case study, modeled closely after a prostate cancer imaging validation study currently taking place at our institution. The power calculation formulae address three central questions in the design of imaging validation studies: (1) What is the maximum acceptable registration error? (2) How many subjects are needed? (3) What is the minimum detectable difference between normal and pathologic image regions? Copyright © 2013 Elsevier B.V. All rights reserved.

Performance of statistical process control methods for regional surgical site infection surveillance: a 10-year multicentre pilot study.

PubMed

Baker, Arthur W; Haridy, Salah; Salem, Joseph; Ilieş, Iulian; Ergai, Awatef O; Samareh, Aven; Andrianas, Nicholas; Benneyan, James C; Sexton, Daniel J; Anderson, Deverick J

2017-11-24

Traditional strategies for surveillance of surgical site infections (SSI) have multiple limitations, including delayed and incomplete outbreak detection. Statistical process control (SPC) methods address these deficiencies by combining longitudinal analysis with graphical presentation of data. We performed a pilot study within a large network of community hospitals to evaluate performance of SPC methods for detecting SSI outbreaks. We applied conventional Shewhart and exponentially weighted moving average (EWMA) SPC charts to 10 previously investigated SSI outbreaks that occurred from 2003 to 2013. We compared the results of SPC surveillance to the results of traditional SSI surveillance methods. Then, we analysed the performance of modified SPC charts constructed with different outbreak detection rules, EWMA smoothing factors and baseline SSI rate calculations. Conventional Shewhart and EWMA SPC charts both detected 8 of the 10 SSI outbreaks analysed, in each case prior to the date of traditional detection. Among detected outbreaks, conventional Shewhart chart detection occurred a median of 12 months prior to outbreak onset and 22 months prior to traditional detection. Conventional EWMA chart detection occurred a median of 7 months prior to outbreak onset and 14 months prior to traditional detection. Modified Shewhart and EWMA charts additionally detected several outbreaks earlier than conventional SPC charts. Shewhart and SPC charts had low false-positive rates when used to analyse separate control hospital SSI data. Our findings illustrate the potential usefulness and feasibility of real-time SPC surveillance of SSI to rapidly identify outbreaks and improve patient safety. Further study is needed to optimise SPC chart selection and calculation, statistical outbreak detection rules and the process for reacting to signals of potential outbreaks. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Soil carbon inventories under a bioenergy crop (switchgrass): Measurement limitations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garten, C.T. Jr.; Wullschleger, S.D.

Approximately 5 yr after planting, coarse root carbon (C) and soil organic C (SOC) inventories were compared under different types of plant cover at four switchgrass (Panicum virgatum L.) production field trials in the southeastern USA. There was significantly more coarse root C under switchgrass (Alamo variety) and forest cover than tall fescue (Festuca arundinacea Schreb.), corn (Zea mays L.), or native pastures of mixed grasses. Inventories of SOC under switchgrass were not significantly greater than SOC inventories under other plant covers. At some locations the statistical power associated with ANOVA of SOC inventories was low, which raised questions aboutmore » whether differences in SOC could be detected statistically. A minimum detectable difference (MDD) for SOC inventories was calculated. The MDD is the smallest detectable difference between treatment means once the variation, significance level, statistical power, and sample size are specified. The analysis indicated that a difference of {approx}50 mg SOC/cm{sup 2} or 5 Mg SOC/ha, which is {approx}10 to 15% of existing SOC, could be detected with reasonable sample sizes and good statistical power. The smallest difference in SOC inventories that can be detected, and only with exceedingly large sample sizes, is {approx}2 to 3%. These measurement limitations have implications for monitoring and verification of proposals to ameliorate increasing global atmospheric CO{sub 2} concentrations by sequestering C in soils.« less

Median nitrate concentrations in groundwater in the New Jersey Highlands Region estimated using regression models and land-surface characteristics

USGS Publications Warehouse

Baker, Ronald J.; Chepiga, Mary M.; Cauller, Stephen J.

2015-01-01

The Kaplan-Meier method of estimating summary statistics from left-censored data was applied in order to include nondetects (left-censored data) in median nitrate-concentration calculations. Median concentrations also were determined using three alternative methods of handling nondetects. Treatment of the 23 percent of samples that were nondetects had little effect on estimated median nitrate concentrations because method detection limits were mostly less than median values.

Highly Sensitive Detection of UV Radiation Using a Uranium Coordination Polymer.

PubMed

Liu, Wei; Dai, Xing; Xie, Jian; Silver, Mark A; Zhang, Duo; Wang, Yanlong; Cai, Yawen; Diwu, Juan; Wang, Jian; Zhou, Ruhong; Chai, Zhifang; Wang, Shuao

2018-02-07

The accurate detection of UV radiation is required in a wide range of chemical industries and environmental or biological related applications. Conventional methods taking advantage of semiconductor photodetectors suffer from several drawbacks such as sophisticated synthesis and manufacturing procedure, not being able to measure the accumulated UV dosage as well as high defect density in the material. Searching for new strategies or materials serving as precise UV dosage sensor with extremely low detection limit is still highly desirable. In this work, a radiation resistant uranium coordination polymer [UO 2 (L)(DMF)] (L = 5-nitroisophthalic acid, DMF = N,N-dimethylformamide, denoted as compound 1) was successfully synthesized through mild solvothermal method and investigated as a unique UV probe with the detection limit of 2.4 × 10 -7 J. On the basis of the UV dosage dependent luminescence spectra, EPR analysis, single crystal structure investigation, and the DFT calculation, the UV-induced radical quenching mechanism was confirmed. Importantly, the generated radicals are of significant stability which offers the opportunity for measuring the accumulated UV radiation dosage. Furthermore, the powder material of compound 1 was further upgraded into membrane material without loss in luminescence intensity to investigate the real application potentials. To the best of our knowledge, compound 1 represents the most sensitive coordination polymer based UV dosage probe reported to date.

Development of a cw-laser-based cavity-ringdown sensor aboard a spacecraft for trace air constituents

NASA Technical Reports Server (NTRS)

Awtry, A. R.; Miller, J. H.

2002-01-01

The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous-wave (cw), external-cavity tunable diode laser centered at 1.55 micrometers is used to pump an optical cavity absorption cell in cw-cavity ringdown spectroscopy (cw-CRDS). Preliminary results are presented that demonstrate the sensitivity, selectivity and reproducibility of this method. Detection limits of 2.0 ppm for CO, 2.5 ppm for CO2, 1.8 ppm for H2O, 19.4 ppb for NH3, 7.9 ppb for HCN and 4.0 ppb for C2H2 are calculated.

Fraunhofer filters to reduce solar background for optical communications

NASA Technical Reports Server (NTRS)

Kerr, E. L.

1986-01-01

A wavelength that lies within a spectral interval of reduced solar emission (a Fraunhofer line) can carry optical communications with reduced interference from direct or reflected background sunlight. Suitable Fraunhofer lines are located within the tuning range of good candidate lasers. The laser should be tunable dynamically to track Doppler shifts in the sunlight incident on any solar system body that may appear in the background as viewed by the receiver. A Fraunhofer filter used with a direct-detection receiver should be tuned to match the Doppler shifts of the source and background. The required tuning calculated here for various situations is also required if, instead, one uses a heterodyne receiver with limited post-detection bandwidth.

Towards real-time medical diagnostics using hyperspectral imaging technology

NASA Astrophysics Data System (ADS)

Bjorgan, Asgeir; Randeberg, Lise L.

2015-07-01

Hyperspectral imaging provides non-contact, high resolution spectral images which has a substantial diagnostic potential. This can be used for e.g. diagnosis and early detection of arthritis in finger joints. Processing speed is currently a limitation for clinical use of the technique. A real-time system for analysis and visualization using GPU processing and threaded CPU processing is presented. Images showing blood oxygenation, blood volume fraction and vessel enhanced images are among the data calculated in real-time. This study shows the potential of real-time processing in this context. A combination of the processing modules will be used in detection of arthritic finger joints from hyperspectral reflectance and transmittance data.

New limits for the 2 νββ decay of 96Zr to excited nuclear states of 96Mo

NASA Astrophysics Data System (ADS)

Finch, Sean; Tornow, Werner

2015-10-01

The final results from our search for the 2 νββ decay of 96Zr to excited 0+ and 2+ states of 96Mo are presented. Such measurements provide valuable test cases for 2 νββ -decay nuclear matrix element calculations, which in turn are used to tune 0 νββ -decay nuclear matrix element calculations. After undergoing double- β decay to an excited state, the excited daughter nucleus decays to the ground state, emitting two coincident γ rays. These two γ rays are detected in coincidence by two HPGe detectors sandwiching the 96Zr sample, with a NaI veto in anti-coincidence. This experimental apparatus, located at the Kimballton Underground Research Facility (KURF), has previously measured the 2 νββ decay of 100Mo and 150Nd to excited nuclear states. Experimental limits on the T1 / 2 and corresponding nuclear matrix element are presented for each of these decays. As a byproduct of this experiment, limits were also set on the single- β decay of 96Zr. Supported by DOE Grant: DE-FG02-97ER41033.

Pulsed multiwavelength laser ranging system. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Abshire, J. B.

1982-01-01

A pulsed multiwavelength laser ranging system for measuring atmospheric delay was built and tested, and its theoretical performance limits were calculated. The system uses a dye modelocked ND:YAG laser, which transmits 70 psec wide pulses simultaneously at 1064, 532, and 355 nm. The differential delay of the 1064 and 355 nm pulses is measured by a specially calibrated waveform digitizer to estimate the dry atmospheric delay. The delay time of the 532 nm pulse is used to measure the target distance. Static crossed field photomultipliers are used as detectors for all wavelengths. Theoretical analysis shows that path curvature and atmospheric turbulence are fundamental limits to the ranging accuracy of both single and multicolor systems operating over horizontal paths. For two color systems, an additional error is caused by the uncertainty in the path averaged water vapor. The standard deviation of the multicolor instrument's timing measurements is directly proportional to the laser pulse width plus photomultiplier jitter divided by the square root of the received photoelectron number. The prototype system's maximum range is km, which is limited by atmospheric and system transmission losses at 355 nm. System signal detection and false alarm calculations are also presented.

Determination of β-blockers in pharmaceutical and human urine by capillary electrophoresis with electrochemiluminescence detection and studies on the pharmacokinetics.

PubMed

Wang, Yuanchao; Wu, Qiong; Cheng, Meirong; Cai, Cheng

2011-04-15

A novel method for simultaneous determination of atenolol, metoprolol and esmolol was proposed by capillary electrophoresis (CE) separation and electrochemiluminescence (ECL) detection. Poly-β-cyclodextrin (Poly-β-CD) was used as an additive in the running buffer to improve the separation of three analytes. The conditions for CE separation, ECL detection and effect of Poly-β-CD were investigated in detail. The three β-blockers with very similar structures were well separated and detected under the optimum conditions. The linear ranges of the standard solution for atenolol and esmolol were 2.5-125 μmol/L with a detection limit (S/N=3) of 0.5 μmol/L, and for metoprolol was 0.5-25 μmol/L with a detection limit of 0.1 μmol/L. For three β-blockers from spiked aqueous and urine samples, the accuracy and precision including intraday and interday experiments were performed by calculating the recovery, the relative standard deviations of the ECL intensity and the migration time, respectively. The developed method was applied to the determination of metoprolol content in commercial pharmaceutical, and the analytical results are in good agreement with the nominal value with recoveries in the range of 98.7-105%. The proposed method was also applied to the monitoring of pharmacokinetics for metoprolol in human body. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

The search for radio emission from exoplanets using LOFAR low-frequency beam-formed observations

NASA Astrophysics Data System (ADS)

Turner, Jake D.; Griessmeier, Jean-Mathias; Zarka, Philippe

2018-01-01

Detection of radio emission from exoplanets can provide information on the star-planet system that is very difficult or impossible to study otherwise, such as the planet’s magnetic field, magnetosphere, rotation period, orbit inclination, and star-planet interactions. Such a detection in the radio domain would open up a whole new field in the study of exoplanets, however, currently there are no confirmed detections of an exoplanet at radio frequencies. In this study, we discuss our ongoing observational campaign searching for exoplanetary radio emissions using beam-formed observations within the Low Band of the Low-Frequency Array (LOFAR). To date we have observed three exoplanets: 55 Cnc, Upsilon Andromedae, and Tau Boötis. These planets were selected according to theoretical predictions, which indicated them as among the best candidates for an observation. During the observations we usually recorded three beams simultaneously, one on the exoplanet and two on patches of nearby “empty” sky. An automatic pipeline was created to automatically find RFI, calibrate the data due to instrumental effects, and to search for emission in the exoplanet beam. Additionally, we observed Jupiter with LOFAR with the same exact observational setup as the exoplanet observations. The main goals of the Jupiter observations are to train the detection algorithm and to calculate upper limits in the case of a non-detection. Data analysis is currently ongoing. Conclusions reached at the time of the meeting, about detection of or upper limit to the planetary signal, will be presented.

LOFAR Searches for Radio Exoplanets

NASA Astrophysics Data System (ADS)

Turner, Jake; Griessmeier, Jean-Mathias; Zarka, Philippe; Vasylieva, Iaroslavna

2018-06-01

Detection of radio emission from exoplanets can provide information on the star-planet system that is very difficult or impossible to study otherwise, such as the planet’s magnetic field, magnetosphere, rotation period, orbit inclination, and star-planet interactions. Such a detection in the radio domain would open up a whole new field in the study of exoplanets, however, currently there are no confirmed detections of an exoplanet at radio frequencies. In this study, we discuss our ongoing observational campaign searching for exoplanetary radio emissions using beam-formed observations within the Low Band of the Low-Frequency Array (LOFAR). To date we have observed three exoplanets: 55 Cnc, Upsilon Andromedae, and Tau Boötis. These planets were selected according to theoretical predictions, which indicated them as among the best candidates for an observation. During the observations we usually recorded three beams simultaneously, one on the exoplanet and two on patches of nearby “empty” sky. An automatic pipeline was created to automatically find RFI, calibrate the data due to instrumental effects, and to search for emission in the exoplanet beam. Additionally, we observed Jupiter with LOFAR with the same exact observational setup as the exoplanet observations. The main goals of the Jupiter observations are to train the detection algorithm and to calculate upper limits in the case of a non-detection. Data analysis is currently ongoing. Conclusions reached at the time of the meeting, about detection of or upper limit to the planetary signal, will be presented.

Is there a stable B2Π state for the CNO molecule?

NASA Astrophysics Data System (ADS)

Marian, Christel; Hess, Bernd A.; Schöttke, Sigrid; Buenker, Robert J.

1987-07-01

We report MRD-CI calculations on the ground state X2Π and the excited states A2Σ + and B2Π of the CNO molecule in linear geometry. The surfaces for oxygen and carbon extraction are calculated using a limited CI expansion of 47 configuration state functions; in the vicinity of the minima obtained with this procedure large-scale CI calculations are carried out including deter-mination of the spin-orbit splitting of the 2Π states of the minima. We find that the B2Π state will be difficult to detect spectroscopically due to an avoided crossing just at the equilibrium geometry of the ground state at RCN = 2.25 a.u., RNO = 2.30 a.u. Accordingly we find two shallow minima for B2Π at RCN = 2.33 a.u., RNO = 2.91 a.u. and RCN = 2.78 a.u., RNO = 2.28 a.u., respectively.

In Vivo Measurement of Glenohumeral Joint Contact Patterns

NASA Astrophysics Data System (ADS)

Bey, Michael J.; Kline, Stephanie K.; Zauel, Roger; Kolowich, Patricia A.; Lock, Terrence R.

2009-12-01

The objectives of this study were to describe a technique for measuring in-vivo glenohumeral joint contact patterns during dynamic activities and to demonstrate application of this technique. The experimental technique calculated joint contact patterns by combining CT-based 3D bone models with joint motion data that were accurately measured from biplane x-ray images. Joint contact patterns were calculated for the repaired and contralateral shoulders of 20 patients who had undergone rotator cuff repair. Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition (i.e., repaired versus contralateral). Abduction angle had a significant effect on the superior/inferior contact center position, with the average joint contact center of the repaired shoulder 12.1% higher on the glenoid than the contralateral shoulder. This technique provides clinically relevant information by calculating in-vivo joint contact patterns during dynamic conditions and overcomes many limitations associated with conventional techniques for quantifying joint mechanics.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor

NASA Astrophysics Data System (ADS)

Lan, Linxin; Li, Tianduo; Wei, Tao; Pang, He; Sun, Tao; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-03-01

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN- with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN- on the vinyl Cdbnd C bond has been successfully confirmed by the optical measurements, 1H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19 μM, which is much lower than the maximum permission concentration in drinking water (1.9 μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN- in field measurements.

Egg yolk antibodies for detection and neutralization of Clostridium botulinum type A neurotoxin.

PubMed

Trott, D L; Yang, M; Gonzalez, J; Larson, A E; Tepp, W H; Johnson, E A; Cook, M E

2009-05-01

The objective of this research project was to determine the usefulness of an egg antibody platform for producing materials for the detection and neutralization of botulinum type A neurotoxin. Yield estimates for detection and neutralizing antibodies produced using methods described were calculated. Antibody specific to botulinum toxoid A (aToxoid) and toxin A (aBoNT/A) was produced by immunizing hens with botulinum toxoid A (toxoid) followed by increasing amounts of botulinum neurotoxin A (BoNT/A) in Freund incomplete adjuvant. Egg yolks were extracted with polyethylene glycol (PEG) for antibody detection and neutralization experiments. A model aToxoid/toxoid immunoassay using only egg yolk antibody was developed and had a detection limit of 1 pg/ml of toxoid. In an indirect enzyme-linked immunosorbent assay of BoNT/A-specific antibody, the aBoNT/A contained more BoNT/A-specific antibody than did the aToxoid, and aBoNT/A was as effective as commercial rabbit antibody. The aToxoid provided no protection against BoNT/A in a standard mouse neutralization assay; however, 1 mg of PEG-extracted aBoNT/A neutralized 4,000 lethal doses of BoNT/A injected intraperitoneally. Based on these results, we calculated that in 1 month one hen could produce more than 100 liters of antibody detection reagents or enough antibody to neutralize approximately 11.6 million mouse lethal doses of botulinum toxin. Utilization of an egg antibody platform is potentially rapid (28 to 70 days) and scalable to kilogram quantities using current egg production facilities with as few as 1,000 hens.

Non-invasive prenatal screening versus prenatal diagnosis by array comparative genomic hybridization: a comparative retrospective study.

PubMed

Sotiriadis, Alexandros; Papoulidis, Ioannis; Siomou, Elisavet; Papageorgiou, Elena; Eleftheriades, Makarios; Papadopoulos, Vasilios; Alexiou, Maria; Manolakos, Emmanouil; Athanasiadis, Apostolos

2017-06-01

To calculate the proportion of array comparative genomic hybridization (aCGH) pathogenic results, that would not be detectable by non-invasive prenatal screening (NIPS). This is a comparative study using data from 2779 fetuses, which underwent invasive prenatal diagnosis, and the samples were analyzed using aCGH. The simulated NIPS assay would test for trisomies 21, 18, 13, monosomy X, 47, XXX, 47, XYY, and 47, XXY. Indications for invasive testing were grouped into categories and the absolute, relative rates of pathogenic/likely pathogenic results of aCGH analysis that would not be detectable by NIPS were calculated. The expected rate of aCGH-detected abnormalities that would not be detectable by NIPS was 28.0% (95% CI 14.3-47.6) for nuchal translucency (NT) 95 to 99th centile; 14.3% (95% 5.0-34.6) for NT > 99th centile; 34.2% (95% CI 21.1-50.1) for high-risk first-trimester results (regardless of NT); 52.4% (95% CI 32.4-71.7) for second-trimester markers; and 50.0% (95% CI 26.8-73.2) for advanced maternal age. The overall rate of aCGH pathogenic/likely pathogenic results was 5.0% and 44.0% (95% CI 36.0-52.2) of them would not be detected by NIPS. Approximately half of the abnormal aCGH results would not be detectable by standard NIPS assays, highlighting the necessity of pre-test counseling, and illustrating the limitations of NIPS. © 2017 John Wiley & Sons, Ltd. © 2017 John Wiley & Sons, Ltd.

12 CFR 32.4 - Calculation of lending limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Calculation of lending limits. 32.4 Section 32.4 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY LENDING LIMITS § 32.4 Calculation of lending limits. (a) Calculation date. For purposes of determining compliance with 12 U.S.C. 84...

Captan and fenitrothion dissipation in field-treated cauliflowers and effect of household processing.

PubMed

Fernández-Cruz, María L; Barreda, Mercedes; Villarroya, Mercedes; Peruga, Arantzazu; Llanos, Susana; García-Baudín, José M

2006-07-01

Field trial studies have been performed with captan and fenitrothion on cauliflower to propose maximum residue limits and to study the dissipation of the pesticides. Residue levels have been determined at different times following good laboratory practice using gas chromatography with mass spectrometric detection. The behaviour of residue levels of these compounds after household processing has been analysed using gas chromatography with electron capture detection. Seven days after treatment, residue levels of captan could be detected, but not of fenitrothion. The half-lives of dissipation for captan and fenitrothion were calculated as 0.9 and 1.8 days respectively. Washing did not significantly affect the residual amounts of captan and fenitrothion observed in raw vegetables; however, after cooking, captan had degraded completely, whereas residue levels of fenitrothion were not modified significantly.

Improving the detection of wind fields from LIDAR aerosol backscatter using feature extraction

NASA Astrophysics Data System (ADS)

Bickel, Brady R.; Rotthoff, Eric R.; Walters, Gage S.; Kane, Timothy J.; Mayor, Shane D.

2016-04-01

The tracking of winds and atmospheric features has many applications, from predicting and analyzing weather patterns in the upper and lower atmosphere to monitoring air movement from pig and chicken farms. Doppler LIDAR systems exist to quantify the underlying wind speeds, but cost of these systems can sometimes be relatively high, and processing limitations exist. The alternative is using an incoherent LIDAR system to analyze aerosol backscatter. Improving the detection and analysis of wind information from aerosol backscatter LIDAR systems will allow for the adoption of these relatively low cost instruments in environments where the size, complexity, and cost of other options are prohibitive. Using data from a simple aerosol backscatter LIDAR system, we attempt to extend the processing capabilities by calculating wind vectors through image correlation techniques to improve the detection of wind features.

Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

NASA Technical Reports Server (NTRS)

Wannier, P. G.; Sahai, R.

1987-01-01

Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

Modeling and research of a space-based spacecraft infrared detection system.

PubMed

Li, Wenhao; Liu, Zhaohui; Mu, You; Yang, Rui; Zhang, Xing

2017-03-20

When a spacecraft is in orbit, it is almost impossible to check its working condition. Almost all payload would generate waste heat when working, which is usually ejected by a radiator. By observing the radiator, we can catch a glimpse of a spacecraft's inner information. A thorough model of a space-based infrared detection system is analyzed, taking the radiator into account, which, to the best of our knowledge, has seldom been considered. The calculation result shows that infrared radiation reflected by spacecraft is weak compared with the spacecraft's self-radiation in 8-12 μm, and the contrast ratio between the radiator and surrounding area could be the criterion for judging the working condition of a spacecraft. The limit of detection distance is also increased due the higher temperature of the radiator.

Optical and Electrochemical Aptasensors for Sensitive Detection of Streptomycin in Blood Serum and Milk.

PubMed

Ramezani, Mohammad; Abnous, Khalil; Taghdisi, Seyed Mohammad

2017-01-01

Detection and quantitation of antibiotic residues in blood serum and foodstuffs are in great demand. We have developed aptasensors for detection of streptomycin using electrochemical and optical methods. In the first method, an electrochemical aptasensor was developed for sensitive and selective detection of streptomycin, based on combination of exonuclease I (Exo I), complementary strand of aptamer (CS), arch shaped structure of aptamer (Apt)-CS conjugate, and gold electrode. The designed electrochemical aptasensor exhibited high selectivity toward streptomycin with a limit of detection (LOD) as low as 11.4 nM. Moreover, the developed electrochemical aptasensor was successfully used to detect streptomycin in milk and serum with LODs of 14.1 and 15.3 nM, respectively. In the second method, fluorescence quenching and colorimetric aptasensors were designed for detection of streptomycin based on aqueous gold nanoparticles (AuNPs) and double-stranded DNA (dsDNA). In the absence of streptomycin, aptamer/FAM-labeled complementary strand dsDNA is stable, resulting in the aggregation of AuNPs by salt bridge and an obvious color change from red to blue and strong emission of fluorescence. The colorimetric and fluorescence quenching aptasensors showed excellent selectivity toward streptomycin with limit of detections as low as 73.1 and 47.6 nM, respectively. The presented aptasensors were successfully used to detect streptomycin in milk and serum. For serum, LODs were determined to be 58.2 and 102.4 nM for fluorescence quenching and colorimetric aptasensors, respectively. For milk, LODs were calculated to be 56.2 and 108.7 nM for fluorescence quenching and colorimetric aptasensors, respectively.

Hunting Faint Dwarf Galaxies in the Field Using Integrated Light Surveys

NASA Astrophysics Data System (ADS)

Danieli, Shany; van Dokkum, Pieter; Conroy, Charlie

2018-03-01

We discuss the approach of searching the lowest mass dwarf galaxies, ≲ {10}6 {M}ȯ , in the general field, using integrated light surveys. By exploring the limiting surface brightness-spatial resolution (μ eff,lim‑θ) parameter space, we suggest that faint field dwarfs in the Local Volume, between 3 and 10 Mpc, are expected to be detected very effectively and in large numbers using integrated light photometric surveys, complementary to the classical star counts method. We use a sample of dwarf galaxies in the Local Group to construct relations between their photometric and structural parameters, M *–μ eff,V and M *–R eff. We use these relations, along with assumed functional forms for the halo mass function and the stellar mass–halo mass (SMHM) relation, to calculate the lowest detectable stellar masses in the Local Volume and the expected number of galaxies as a function of the limiting surface brightness and spatial resolution. The number of detected galaxies depends mostly on the limiting surface brightness for distances >3 Mpc, while spatial resolution starts to play a role for galaxies at distances >8 Mpc. Surveys with μ eff,lim ∼ 30 mag arcsec‑2 should be able to detect galaxies with stellar masses down to ∼104 M ⊙ in the Local Volume. Depending on the form of the SMHM relation, the expected number of dwarf galaxies with distances between 3 and 10 Mpc is 0.04–0.35 per square degree, assuming a limiting surface brightness of ∼29–30 mag arcsec‑2 and a spatial resolution <4″. We plan to search for a population of low-mass dwarf galaxies in the field by performing a blank wide field photometric survey with the Dragonfly Telephoto Array, an imaging system optimized for the detection of extended ultra low surface brightness structures.

Modeling the non-recycled Fermi Gamma-ray pulsar population

DOE PAGES

Perera, B. B. P.; McLaughlin, M. A.; Cordes, J. M.; ...

2013-09-25

Here, we use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L γ depends on the period P and the period derivativemore » $$\\dot{P}$$. We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L γ on P and $$\\dot{P}$$, including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is $$L_\\gamma \\propto P^{-a} \\dot{P}^{b}$$ where a = 1.36 ± 0.03 and b = 0.44 ± 0.02, similar to but not identical to the commonly assumed $$L_\\gamma \\propto \\sqrt{\\dot{E}} \\propto P^{-1.5} \\dot{P}^{0.5}$$. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7π for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2σ upper limit on the average braking index and a 2σ lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 × 1010 G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the 2 yr sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected 5 yr sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. As a result, we note that these predictions significantly depend on our model assumptions.« less

Enumerating Pathogenic Microorganism Surrogates for Groundwater Experiments Using Solid-Phase Cytometry

NASA Astrophysics Data System (ADS)

Stevenson, M. E.; Blaschke, A. P.; Kirschner, A.

2010-12-01

Regulators need a dependable method that would enable them to calculate with confidence the setback distance of a drinking water well from a potential point of contamination. Since it is not permissible to perform field tests using pathogenic microorganisms, it is necessary to predict the transport of dangerous microbes in a different way, using surrogates. One such surrogate method involves using bacteriophages, which are viruses that are pathogenic to bacteria, but are not dangerous to humans. Another possible surrogate to model the potential travel time of microbial contamination is the use of synthetic microspheres; we will test microspheres ranging in size from 0.025 to 1 µm. The constraining factor for comparing the transport of microspheres and bacteriophages is the detection limit of the measuring apparatus. Appropriate measuring techniques are mandatory for a comparison. Traditionally, bacteriophages are measured using plaque forming analysis, the detection limit being one plaque forming unit per petri dish. In our study, the use of solid-phase cytometry for enumerating microspheres for wellhead protection projects is being investigated, as the detection limit using this technology is one cell per filter. To the best of our knowledge, there is no other technique available that enables a comparable detection limit. The solid-phase cytometer used for this study is a ChemScan RDI (Chemunex, France). For comparison, epifluorescence microscopy will also be used. The ChemScan RDI device automatically drives an epifluorescent microscope to the site of each cell detected, in order to confirm the validity of the reading. In this way, it is possible to observe whether clumping together of microspheres is a problem or if non-target cells were labelled. Keywords: Microspheres, Solid-phase cytometry, ChemScan, Drinking water protection Acknowledgements: We would like to thank the Austrian Science Fund (FWF) for financial support as part of the Doctoral Program on Water Resource Systems (DK Plus W1219-N22) and the Vienna Waterworks (MA 31) as part of the GWRS-Vienna project.

Systematic review on the role of serum tumor markers in the detection of recurrent pancreatic cancer.

PubMed

Daamen, Lois A; Groot, Vincent P; Heerkens, Hanne D; Intven, Martijn P W; van Santvoort, Hjalmar C; Molenaar, I Quintus

2018-04-01

Biomarker testing can be helpful to monitor disease progression after resection of pancreatic cancer. This systematic review aims to give an overview of the literature on the diagnostic value of serum tumor markers for the detection of recurrent pancreatic cancer during follow-up. A systematic search was performed to 2 October 2017. All studies reporting on the diagnostic value of postoperatively measured serum biomarkers for the detection of pancreatic cancer recurrence were included. Data on diagnostic accuracy of tumor markers were extracted. Forest plots and pooled values of sensitivity and specificity were calculated. Four articles described test results of CA 19-9. A pooled sensitivity and specificity of respectively 0.73 (95% CI 0.66-0.80) and 0.83 (95% CI 0.73-0.91) were calculated. One article reported on CEA, showing a sensitivity of 50% and specificity of 65%. No other serum tumor markers were discussed for surveillance purposes in the current literature. Although testing of serum CA 19-9 has considerable limitations, CA 19-9 remains the most used serum tumor marker for surveillance after surgical resection of pancreatic cancer. Further studies are needed to assess the role of serum tumor marker testing in the detection of recurrent pancreatic cancer and to optimize surveillance strategies. Copyright © 2017 International Hepato-Pancreato-Biliary Association Inc. Published by Elsevier Ltd. All rights reserved.

Novel electrochemical sensor based on functionalized graphene for simultaneous determination of adenine and guanine in DNA.

PubMed

Huang, Ke-Jing; Niu, De-Jun; Sun, Jun-Yong; Han, Cong-Hui; Wu, Zhi-Wei; Li, Yan-Li; Xiong, Xiao-Qin

2011-02-01

A nano-material carboxylic acid functionalized graphene (graphene-COOH) was prepared and used to construct a novel biosensor for the simultaneous detection of adenine and guanine. The direct electrooxidation behaviors of adenine and guanine on the graphene-COOH modified glassy carbon electrode (graphene-COOH/GCE) were carefully investigated by cyclic voltammetry and differential pulse voltammetry. The results indicated that both adenine and guanine showed the increase of the oxidation peak currents with the negative shift of the oxidation peak potentials in contrast to that on the bare glassy carbon electrode. The electrochemical parameters of adenine and guanine on the graphene-COOH/GCE were calculated and a simple and reliable electroanalytical method was developed for the detection of adenine and guanine, respectively. The modified electrode exhibited good behaviors in the simultaneous detection of adenine and guanine with the peak separation as 0.334V. The detection limit for individual determination of guanine and adenine was 5.0×10(-8)M and 2.5×10(-8)M (S/N=3), respectively. Furthermore, the measurements of thermally denatured single-stranded DNA were carried out and the value of (G+C)/(A+T) of single-stranded DNA was calculated as 0.80. The biosensor exhibited some advantages, such as simplicity, rapidity, high sensitivity, good reproducibility and long-term stability. Copyright © 2010 Elsevier B.V. All rights reserved.

Measurement of hydroxyl radical production in ultrasonic aqueous solutions by a novel chemiluminescence method.

PubMed

Hu, Yufei; Zhang, Zhujun; Yang, Chunyan

2008-07-01

Measurement methods for ultrasonic fields are important for reasons of safety. The investigation of an ultrasonic field can be performed by detecting the yield of hydroxyl radicals resulting from ultrasonic cavitations. In this paper, a novel method is introduced for detecting hydroxyl radicals by a chemiluminescence (CL) reaction of luminol-hydrogen peroxide (H2O2)-K5[Cu(HIO6)2](DPC). The yield of hydroxyl radicals is calculated directly by the relative CL intensity according to the corresponding concentration of H2O2. This proposed CL method makes it possible to perform an in-line and real-time assay of hydroxyl radicals in an ultrasonic aqueous solution. With flow injection (FI) technology, this novel CL reaction is sensitive enough to detect ultra trace amounts of H2O2 with a limit of detection (3sigma) of 4.1 x 10(-11) mol L(-1). The influences of ultrasonic output power and ultrasonic treatment time on the yield of hydroxyl radicals by an ultrasound generator were also studied. The results indicate that the amount of hydroxyl radicals increases with the increase of ultrasonic output power (< or = 15 W mL(-1)). There is a linear relationship between the time of ultrasonic treatment and the yield of H2O2. The ultrasonic field of an ultrasonic cleaning baths has been measured by calculating the yield of hydroxyl radicals.

Constraining the High-Energy Emission from Gamma-Ray Bursts with Fermi

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Harding, A. K.; Hays, E.; Racusin, J. L.; Sonbas, E.; Stamatikos, M.; Guirec, S.

2012-01-01

We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the nuF(sub v) spectra (E(sub pk)). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E(sub pk) than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cut-off in their high-energy spectra, which if assumed to be due to gamma gamma attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

Constraining the high-energy emission from gamma-ray bursts with Fermi

DOE PAGES

Ackermann, M.; Ajello, M.; Baldini, L.; ...

2012-07-17

Here, we examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We also compare these limits with the fluxes that would be expected from extrapolations of spectral fitsmore » presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νF ν spectra (E pk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E pk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. Furthermore, all of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.« less

Photon theory hypothesis about photon tunneling microscope's subwavelength resolution

NASA Astrophysics Data System (ADS)

Zhu, Yanbin; Ma, Junfu

1995-09-01

The foundation for the invention of the photon scanning tunneling microscope (PSTM) are the near field scanning optical microscope, the optical fiber technique, the total internal reflection, high sensitive opto-electronic detecting technique and computer technique etc. Recent research results show the subwavelength resolution of 1 - 3 nm is obtained. How to explain the PSTM has got such high subwavelength resolution? What value is the PSTM's limiting of subwavelength resolution? For resolving these problems this paper presented a photon theory hypothesis about PSTM that is based on the following two basic laws: (1) Photon is not only a carrier bringing energy and optical information, but also is a particle occupied fixed space size. (2) When a photon happened reflection, refraction, scattering, etc., only changed its energy and optical information carried, its particle size doesn't change. g (DOT) pphoton equals constant. Using these two basic laws to PSTM, the `evanescent field' is practically a weak photon distribution field and the detecting fiber tip diameter is practically a `gate' which size controlled the photon numbers into fiber tip. Passing through some calculation and inference, the following three conclusions can be given: (1) Under the PSTM's detection system sensitivity is high enough, the diameter D of detecting fiber tip and the near field detecting distance Z are the two most important factors to decide the subwavelength resolution of PSTM. (2) The limiting of PSTM's resolution will be given upon the conditions of D equals pphoton and Z equals pphoton, where pphoton is one photon size. (2) The final resolution limit R of PSTM will be lim R equals pphoton, D yields pphoton, Z yields pphoton.

Determining the 95% limit of detection for waterborne pathogen analyses from primary concentration to qPCR.

PubMed

Stokdyk, Joel P; Firnstahl, Aaron D; Spencer, Susan K; Burch, Tucker R; Borchardt, Mark A

2016-06-01

The limit of detection (LOD) for qPCR-based analyses is not consistently defined or determined in studies on waterborne pathogens. Moreover, the LODs reported often reflect the qPCR assay alone rather than the entire sample process. Our objective was to develop an approach to determine the 95% LOD (lowest concentration at which 95% of positive samples are detected) for the entire process of waterborne pathogen detection. We began by spiking the lowest concentration that was consistently positive at the qPCR step (based on its standard curve) into each procedural step working backwards (i.e., extraction, secondary concentration, primary concentration), which established a concentration that was detectable following losses of the pathogen from processing. Using the fraction of positive replicates (n = 10) at this concentration, we selected and analyzed a second, and then third, concentration. If the fraction of positive replicates equaled 1 or 0 for two concentrations, we selected another. We calculated the LOD using probit analysis. To demonstrate our approach we determined the 95% LOD for Salmonella enterica serovar Typhimurium, adenovirus 41, and vaccine-derived poliovirus Sabin 3, which were 11, 12, and 6 genomic copies (gc) per reaction (rxn), respectively (equivalent to 1.3, 1.5, and 4.0 gc L(-1) assuming the 1500 L tap-water sample volume prescribed in EPA Method 1615). This approach limited the number of analyses required and was amenable to testing multiple genetic targets simultaneously (i.e., spiking a single sample with multiple microorganisms). An LOD determined this way can facilitate study design, guide the number of required technical replicates, aid method evaluation, and inform data interpretation. Published by Elsevier Ltd.

Constraining the High-energy Emission from Gamma-Ray Bursts with Fermi

NASA Astrophysics Data System (ADS)

Fermi Large Area Telescope Team; Ackermann, M.; Ajello, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Brigida, M.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Granot, J.; Grenier, I. A.; Grove, J. E.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Jóhannesson, G.; Kataoka, J.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J.; McGlynn, S.; Michelson, P. F.; Mitthumsiri, W.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Ryde, F.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stawarz, Łukasz; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Uehara, T.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Fermi Gamma-ray Burst Monitor Team; Connaughton, V.; Briggs, M. S.; Guirec, S.; Goldstein, A.; Burgess, J. M.; Bhat, P. N.; Bissaldi, E.; Camero-Arranz, A.; Fishman, J.; Fitzpatrick, G.; Foley, S.; Gruber, D.; Jenke, P.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; van der Horst, A. J.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.

2012-08-01

We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νF ν spectra (E pk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E pk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

Determining the 95% limit of detection for waterborne pathogen analyses from primary concentration to qPCR

USGS Publications Warehouse

Stokdyk, Joel P.; Firnstahl, Aaron; Spencer, Susan K.; Burch, Tucker R; Borchardt, Mark A.

2016-01-01

The limit of detection (LOD) for qPCR-based analyses is not consistently defined or determined in studies on waterborne pathogens. Moreover, the LODs reported often reflect the qPCR assay alone rather than the entire sample process. Our objective was to develop an approach to determine the 95% LOD (lowest concentration at which 95% of positive samples are detected) for the entire process of waterborne pathogen detection. We began by spiking the lowest concentration that was consistently positive at the qPCR step (based on its standard curve) into each procedural step working backwards (i.e., extraction, secondary concentration, primary concentration), which established a concentration that was detectable following losses of the pathogen from processing. Using the fraction of positive replicates (n = 10) at this concentration, we selected and analyzed a second, and then third, concentration. If the fraction of positive replicates equaled 1 or 0 for two concentrations, we selected another. We calculated the LOD using probit analysis. To demonstrate our approach we determined the 95% LOD for Salmonella enterica serovar Typhimurium, adenovirus 41, and vaccine-derived poliovirus Sabin 3, which were 11, 12, and 6 genomic copies (gc) per reaction (rxn), respectively (equivalent to 1.3, 1.5, and 4.0 gc L−1 assuming the 1500 L tap-water sample volume prescribed in EPA Method 1615). This approach limited the number of analyses required and was amenable to testing multiple genetic targets simultaneously (i.e., spiking a single sample with multiple microorganisms). An LOD determined this way can facilitate study design, guide the number of required technical replicates, aid method evaluation, and inform data interpretation.

Currie detection limits in gamma-ray spectroscopy.

PubMed

De Geer, Lars-Erik

2004-01-01

Currie Hypothesis testing is applied to gamma-ray spectral data, where an optimum part of the peak is used and the background is considered well known from nearby channels. With this, the risk of making Type I errors is about 100 times lower than commonly assumed. A programme, PeakMaker, produces random peaks with given characteristics on the screen and calculations are done to facilitate a full use of Poisson statistics in spectrum analyses. SHORT TECHNICAL NOTE SUMMARY: The Currie decision limit concept applied to spectral data is reinterpreted, which gives better consistency between the selected error risk and the observed error rates. A PeakMaker program is described and the few count problem is analyzed.

Quantifying the Complete Mineral Assemblages in Rocks of GUSEV Crater, Mars

NASA Technical Reports Server (NTRS)

McSween, H. Y.; Ruff, S. W.; Morris, R. V.; Gellert, R.

2007-01-01

Determining the complete mineralogy of Mars rocks by remote sensing has remained a challenge, because of inherent limitations in the minerals that can be detected and uncertainties in spectral modeling. A subset of the igneous rocks of Gusev crater provide a unique opportunity to determine modal mineralogy, because of limited alteration and the analytical capabilities of the Athena instrument package. Here we estimate the absolute (wt. %) abundances of Fe-bearing minerals from Moessbauer spectra (previously reported only as "areas for component subspectra"), and compare these results to the normative mineralogy calculated from APXS elemental analyses. We also test our preferred mineralogy by comparison of Mini-TES spectra with synthetic thermal emission spectra.

Challenges in miniaturized automotive long-range lidar system design

NASA Astrophysics Data System (ADS)

Fersch, Thomas; Weigel, Robert; Koelpin, Alexander

2017-05-01

This paper discusses the current technical limitations posed on endeavors to miniaturize lidar systems for use in automotive applications and how to possibly extend those limits. The focus is set on long-range scanning direct time of flight LiDAR systems using APD photodetectors. Miniaturization evokes severe problems in ensuring absolute laser safety while maintaining the systems' performance in terms of maximum range, signal-to-noise ratio, detection probability, pixel density, or frame rate. Based on hypothetical but realistic specifications for an exemplary system the complete lidar signal path is calculated. The maximum range of the system is used as a general performance indicator. It is determined with the minimum signal-to-noise ratio required to detect an object. Various system parameters are varied to find their impact on the system's range. The reduction of the laser's pulse width and the right choice for the transimpedance amplifier's amplification have shown to be practicable measures to double the system's range.

Remote sensing of OH in the atmosphere using the technique of laser-induced fluorescence

NASA Technical Reports Server (NTRS)

Wang, C. C.

1983-01-01

The use of a laser-induced fluorescence technique for the sensitive measurement of the atmospheric hydroxyl radical is discussed. Results of laboratory studies of the fluorescence and other spectroscopic properties of OH which allow the calculation of OH concentrations from the returned signals for various altitudes, water vapor contents and temperatures are presented. The experimental setup used for airborne OH measurements is then described, with particular attention given to the use of a telescope for excitation and light collection in a coaxial configuration and the periodic tuning of the exciting radiation necessary to obtain an OH signal in the presence of strong solar and nonresonant fluorescence backgrounds. The best detection limit obtained to date with the system is noted to be about 700,000 OH/cu cm, and it is expected that, with planned improvements in detection and tuning schemes, limits in the neighborhood of 1,000,000 OH/cu cm will be achieved routinely.

Micro-Droplet Detection Method for Measuring the Concentration of Alkaline Phosphatase-Labeled Nanoparticles in Fluorescence Microscopy

PubMed Central

Li, Rufeng; Wang, Yibei; Xu, Hong; Fei, Baowei; Qin, Binjie

2017-01-01

This paper developed and evaluated a quantitative image analysis method to measure the concentration of the nanoparticles on which alkaline phosphatase (AP) was immobilized. These AP-labeled nanoparticles are widely used as signal markers for tagging biomolecules at nanometer and sub-nanometer scales. The AP-labeled nanoparticle concentration measurement can then be directly used to quantitatively analyze the biomolecular concentration. Micro-droplets are mono-dispersed micro-reactors that can be used to encapsulate and detect AP-labeled nanoparticles. Micro-droplets include both empty micro-droplets and fluorescent micro-droplets, while fluorescent micro-droplets are generated from the fluorescence reaction between the APs adhering to a single nanoparticle and corresponding fluorogenic substrates within droplets. By detecting micro-droplets and calculating the proportion of fluorescent micro-droplets to the overall micro-droplets, we can calculate the AP-labeled nanoparticle concentration. The proposed micro-droplet detection method includes the following steps: (1) Gaussian filtering to remove the noise of overall fluorescent targets, (2) a contrast-limited, adaptive histogram equalization processing to enhance the contrast of weakly luminescent micro-droplets, (3) an red maximizing inter-class variance thresholding method (OTSU) to segment the enhanced image for getting the binary map of the overall micro-droplets, (4) a circular Hough transform (CHT) method to detect overall micro-droplets and (5) an intensity-mean-based thresholding segmentation method to extract the fluorescent micro-droplets. The experimental results of fluorescent micro-droplet images show that the average accuracy of our micro-droplet detection method is 0.9586; the average true positive rate is 0.9502; and the average false positive rate is 0.0073. The detection method can be successfully applied to measure AP-labeled nanoparticle concentration in fluorescence microscopy. PMID:29160812

Micro-Droplet Detection Method for Measuring the Concentration of Alkaline Phosphatase-Labeled Nanoparticles in Fluorescence Microscopy.

PubMed

Li, Rufeng; Wang, Yibei; Xu, Hong; Fei, Baowei; Qin, Binjie

2017-11-21

This paper developed and evaluated a quantitative image analysis method to measure the concentration of the nanoparticles on which alkaline phosphatase (AP) was immobilized. These AP-labeled nanoparticles are widely used as signal markers for tagging biomolecules at nanometer and sub-nanometer scales. The AP-labeled nanoparticle concentration measurement can then be directly used to quantitatively analyze the biomolecular concentration. Micro-droplets are mono-dispersed micro-reactors that can be used to encapsulate and detect AP-labeled nanoparticles. Micro-droplets include both empty micro-droplets and fluorescent micro-droplets, while fluorescent micro-droplets are generated from the fluorescence reaction between the APs adhering to a single nanoparticle and corresponding fluorogenic substrates within droplets. By detecting micro-droplets and calculating the proportion of fluorescent micro-droplets to the overall micro-droplets, we can calculate the AP-labeled nanoparticle concentration. The proposed micro-droplet detection method includes the following steps: (1) Gaussian filtering to remove the noise of overall fluorescent targets, (2) a contrast-limited, adaptive histogram equalization processing to enhance the contrast of weakly luminescent micro-droplets, (3) an red maximizing inter-class variance thresholding method (OTSU) to segment the enhanced image for getting the binary map of the overall micro-droplets, (4) a circular Hough transform (CHT) method to detect overall micro-droplets and (5) an intensity-mean-based thresholding segmentation method to extract the fluorescent micro-droplets. The experimental results of fluorescent micro-droplet images show that the average accuracy of our micro-droplet detection method is 0.9586; the average true positive rate is 0.9502; and the average false positive rate is 0.0073. The detection method can be successfully applied to measure AP-labeled nanoparticle concentration in fluorescence microscopy.

Two novel cyanobacterial bioluminescent whole-cell bioreporters based on superoxide dismutases MnSod and FeSod to detect superoxide anion.

PubMed

Hurtado-Gallego, J; Martín-Betancor, K; Rodea-Palomares, I; Leganés, F; Rosal, R; Fernández-Piñas, F

2018-06-01

This work describes the construction of two novel self-luminescent bioreporter strains of the cyanobacterium Nostoc sp. PCC 7120 by fusing the promoter region of the sodA and sodB genes (encoding the superoxide dismutases MnSod and FeSod, respectively) to luxCDABE from Photorhabdus luminescens aimed at detecting pollutants that generate reactive oxygen species (ROS), particularly O 2 - . Bioreporters were tested against methyl viologen (MV) as the inducer of superoxide anion (O 2 - ). Both bioreporters were specific for O 2 - and Limits of detection (LODs) and Maximum Permissive Concentrations (MPCs) were calculated: Nostoc sp. PCC 7120 pBG2154 (sodA) had a range of detection from 400 to 1000 pM of MV and for Nostoc sp. PCC 7120 pBG2165 (sodB) the range of detection was from 500 to 1800 pM of MV after 5 h-exposure. To further validate the bioreporters, they were tested with the emerging pollutant Triclosan which induced bioluminescence in both strains. Furthermore, the bioreporters performance was tested in two real environmental samples with different water matrix complexity, spiked with MV. Both bioreporters were induced by O 2 - in these environmental samples. In the case of the river water sample, the amount of bioavailable MV as calculated from the bioreporters output was similar to that nominally added. For the waste water sample, the bioavailable MV concentration detected by the bioreporters was one order of magnitude lower than nominal. These differences could be due to MV complexation with organic matter and/or co-occurring organic contaminants. These results confirm their high sensitivity to O 2 - and their suitability to detect oxidative stress-generating pollutants in fresh-waters. Copyright © 2018 Elsevier Ltd. All rights reserved.

A Disposable Tear Glucose Biosensor—Part 2: System Integration and Model Validation

PubMed Central

La Belle, Jeffrey T.; Bishop, Daniel K.; Vossler, Stephen R.; Patel, Dharmendra R.; Cook, Curtiss B.

2010-01-01

Background We presented a concept for a tear glucose sensor system in an article by Bishop and colleagues in this issue of Journal of Diabetes Science and Technology. A unique solution to collect tear fluid and measure glucose was developed. Individual components were selected, tested, and optimized, and system error modeling was performed. Further data on prototype testing are now provided. Methods An integrated fluidics portion of the prototype was designed, cast, and tested. A sensor was created using screen-printed sensors integrated with a silicone rubber fluidics system and absorbent polyurethane foam. A simulated eye surface was prepared using fluid-saturated poly(2-hydroxyethyl methacrylate) sheets, and the disposable prototype was tested for both reproducibility at 0, 200, and 400 μM glucose (n = 7) and dynamic range of glucose detection from 0 to 1000 μM glucose. Results From the replicated runs, an established relative standard deviation of 15.8% was calculated at 200 μM and a lower limit of detection was calculated at 43.4 μM. A linear dynamic range was demonstrated from 0 to 1000 μM with an R2 of 99.56%. The previously developed model predicted a 14.9% variation. This compares to the observed variance of 15.8% measured at 200 μM glucose. Conclusion With the newly designed fluidics component, an integrated tear glucose prototype was assembled and tested. Testing of this integrated prototype demonstrated a satisfactory lower limit of detection for measuring glucose concentration in tears and was reproducible across a physiological sampling range. The next step in the device design process will be initial animal studies to evaluate the current prototype for factors such as eye irritation, ease of use, and correlation with blood glucose. PMID:20307390

A disposable tear glucose biosensor-part 2: system integration and model validation.

PubMed

La Belle, Jeffrey T; Bishop, Daniel K; Vossler, Stephen R; Patel, Dharmendra R; Cook, Curtiss B

2010-03-01

We presented a concept for a tear glucose sensor system in an article by Bishop and colleagues in this issue of Journal of Diabetes Science and Technology. A unique solution to collect tear fluid and measure glucose was developed. Individual components were selected, tested, and optimized, and system error modeling was performed. Further data on prototype testing are now provided. An integrated fluidics portion of the prototype was designed, cast, and tested. A sensor was created using screen-printed sensors integrated with a silicone rubber fluidics system and absorbent polyurethane foam. A simulated eye surface was prepared using fluid-saturated poly(2-hydroxyethyl methacrylate) sheets, and the disposable prototype was tested for both reproducibility at 0, 200, and 400 microM glucose (n = 7) and dynamic range of glucose detection from 0 to 1000 microM glucose. From the replicated runs, an established relative standard deviation of 15.8% was calculated at 200 microM and a lower limit of detection was calculated at 43.4 microM. A linear dynamic range was demonstrated from 0 to 1000 microM with an R(2) of 99.56%. The previously developed model predicted a 14.9% variation. This compares to the observed variance of 15.8% measured at 200 microM glucose. With the newly designed fluidics component, an integrated tear glucose prototype was assembled and tested. Testing of this integrated prototype demonstrated a satisfactory lower limit of detection for measuring glucose concentration in tears and was reproducible across a physiological sampling range. The next step in the device design process will be initial animal studies to evaluate the current prototype for factors such as eye irritation, ease of use, and correlation with blood glucose. (c) 2010 Diabetes Technology Society.

Application of partial inversion pulse to ultrasonic time-domain correlation method to measure the flow rate in a pipe

NASA Astrophysics Data System (ADS)

Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

2017-11-01

This paper proposes the application of a novel ultrasonic pulse, called a partial inversion pulse (PIP), to the measurement of the velocity profile and flow rate in a pipe using the ultrasound time-domain correlation (UTDC) method. In general, the measured flow rate depends on the velocity profile in the pipe; thus, on-site calibration is the only method of checking the accuracy of on-site flow rate measurements. Flow rate calculation using UTDC is based on the integration of the measured velocity profile. The advantages of this method compared with the ultrasonic pulse Doppler method include the possibility of the velocity range having no limitation and its applicability to flow fields without a sufficient amount of reflectors. However, it has been previously reported that the measurable velocity range for UTDC is limited by false detections. Considering the application of this method to on-site flow fields, the issue of velocity range is important. To reduce the effect of false detections, a PIP signal, which is an ultrasound signal that contains a partially inverted region, was developed in this study. The advantages of the PIP signal are that it requires little additional hardware cost and no additional software cost in comparison with conventional methods. The effects of inversion on the characteristics of the ultrasound transmission were estimated through numerical calculation. Then, experimental measurements were performed at a national standard calibration facility for water flow rate in Japan. The experimental results demonstrate that measurements made using a PIP signal are more accurate and yield a higher detection ratio than measurements using a normal pulse signal.

A practical approach to determination of laboratory GC-MS limits of detection.

PubMed

Underwood, P J; Kananen, G E; Armitage, E K

1997-01-01

Determination of limit of detection (LOD) values in a forensic laboratory serves a fundamental forensic requirement for assay performance. In addition to demonstrating assay capability, LOD values can also be used to fulfill certification requirements of a high-volume forensic drug laboratory. The LOD was defined as the lowest concentration of drug that the laboratory can detect in a specimen with forensic certainty at a minimum of 85% of the time. Overall batch acceptance criteria included acceptable quantitation of control materials (within 20% of target), acceptable chromatography (symmetry, peak integration, peak shape, peak, and baseline resolution), retention time within +/-1% of the extracted standard, and mass ion ratios within +/-20% of the extracted standard mass ion ratios. Individual specimen acceptance criteria were the same as the batch acceptance criteria excluding the quantitation requirement. Data were collected from all instruments on different runs. A minimum of ten data points was required for each certified instrument, and a minimum of 85% of data points was acceptable. Quantitation within +/-20% of the LOD concentration was not required, but acceptable mass ratios were required. Data points with poor chromatography (internal standard failed mass ratios; interference of the baseline, for example, shoulders; asymmetry; and baseline resolution) was omitted from the acceptable rate calculation. Data points with good chromatography with failed mass ion ratios were included in the acceptable rate calculation. With these criteria, we established the following LODs: 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid, 2 ng/mL; benzoylecgonine, 5 ng/mL; phencyclidine, 2.5 ng/mL; amphetamine, 150 ng/mL; methamphetamine, 100 ng/mL; codeine, 500 ng/mL; and morphine, 1000 ng/mL.

Residential exposure to radiofrequency fields from mobile phone base stations, and broadcast transmitters: a population-based survey with personal meter.

PubMed

Viel, J F; Clerc, S; Barrera, C; Rymzhanova, R; Moissonnier, M; Hours, M; Cardis, E

2009-08-01

Both the public perceptions, and most published epidemiologic studies, rely on the assumption that the distance of a particular residence from a base station or a broadcast transmitter is an appropriate surrogate for exposure to radiofrequency fields, although complex propagation characteristics affect the beams from antennas. The main goal of this study was to characterise the distribution of residential exposure from antennas using personal exposure meters. A total of 200 randomly selected people were enrolled. Each participant was supplied with a personal exposure meter for 24 h measurements, and kept a time-location-activity diary. Two exposure metrics for each radiofrequency were then calculated: the proportion of measurements above the detection limit (0.05 V/m), and the maximum electric field strength. Residential address was geocoded, and distance from each antenna was calculated. Much of the time, the recorded field strength was below the detection level (0.05 V/m), the FM band standing apart with a proportion above the detection threshold of 12.3%. The maximum electric field strength was always lower than 1.5 V/m. Exposure to GSM and DCS waves peaked around 280 m and 1000 m from the antennas. A downward trend was found within a 10 km range for FM. Conversely, UMTS, TV 3, and TV 4&5 signals did not vary with distance. Despite numerous limiting factors entailing a high variability in radiofrequency exposure assessment, but owing to a sound statistical technique, we found that exposures from GSM and DCS base stations increase with distance in the near source zone, to a maximum where the main beam intersects the ground. We believe these results will contribute to the ongoing public debate over the location of base stations and their associated emissions.

Observations of the high vibrational levels of the B ' ' B ¯ 1 Σu + state of H2

NASA Astrophysics Data System (ADS)

Chartrand, A. M.; Duan, W.; Ekey, R. C.; McCormack, E. F.

2016-01-01

Double-resonance laser spectroscopy via the E F 1 Σg + , v ' = 6 , J ' = 0 -2 state was used to probe the high vibrational levels of the B ' ' B ¯ 1 Σu + state of molecular hydrogen. Resonantly enhanced multiphoton ionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v = 51-66 levels for the B ' ' B ¯ state of H2 are reported, which, taken with previous results, span the v = 46-69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spectrosc. 238, 118-126 (2006)]. The average difference between the 84 measured energies and calculated energies is -3.8 cm-1 with a standard deviation of 5.3 cm-1. This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the 1 Σu + and 1 Πu + states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit.

Early Breast Cancer Diagnosis Using Microwave Imaging via Space-Frequency Algorithm

NASA Astrophysics Data System (ADS)

Vemulapalli, Spandana

The conventional breast cancer detection methods have limitations ranging from ionizing radiations, low specificity to high cost. These limitations make way for a suitable alternative called Microwave Imaging, as a screening technique in the detection of breast cancer. The discernible differences between the benign, malignant and healthy breast tissues and the ability to overcome the harmful effects of ionizing radiations make microwave imaging, a feasible breast cancer detection technique. Earlier studies have shown the variation of electrical properties of healthy and malignant tissues as a function of frequency and hence stimulates high bandwidth requirement. A Ultrawideband, Wideband and Narrowband arrays have been designed, simulated and optimized for high (44%), medium (33%) and low (7%) bandwidths respectively, using the EM (electromagnetic software) called FEKO. These arrays are then used to illuminate the breast model (phantom) and the received backscattered signals are obtained in the near field for each case. The Microwave Imaging via Space-Time (MIST) beamforming algorithm in the frequency domain, is next applied to these near field backscattered monostatic frequency response signals for the image reconstruction of the breast model. The main purpose of this investigation is to access the impact of bandwidth and implement a novel imaging technique for use in the early detection of breast cancer. Earlier studies show the implementation of the MIST imaging algorithm on the time domain signals via a frequency domain beamformer. The performance evaluation of the imaging algorithm on the frequency response signals has been carried out in the frequency domain. The energy profile of the breast in the spatial domain is created via the frequency domain Parseval's theorem. The beamformer weights calculated using these the MIST algorithm (not including the effect of the skin) has been calculated for Ultrawideband, Wideband and Narrowband arrays, respectively. Quality metrics such as dynamic range, radiometric resolution etc. are also evaluated for all the three types of arrays.

Modeling the SHG activities of diverse protein crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haupert, Levi M.; DeWalt, Emma L.; Simpson, Garth J., E-mail: gsimpson@purdue.edu

2012-11-01

The origins of the diversity in the SHG signal from protein crystals are investigated and potential protein-crystal coverage by SHG microscopy is assessed. A symmetry-additive ab initio model for second-harmonic generation (SHG) activity of protein crystals was applied to assess the likely protein-crystal coverage of SHG microscopy. Calculations were performed for 250 proteins in nine point-group symmetries: a total of 2250 crystals. The model suggests that the crystal symmetry and the limit of detection of the instrument are expected to be the strongest predictors of coverage of the factors considered, which also included secondary-structural content and protein size. Much ofmore » the diversity in SHG activity is expected to arise primarily from the variability in the intrinsic protein response as well as the orientation within the crystal lattice. Two or more orders-of-magnitude variation in intensity are expected even within protein crystals of the same symmetry. SHG measurements of tetragonal lysozyme crystals confirmed detection, from which a protein coverage of ∼84% was estimated based on the proportion of proteins calculated to produce SHG responses greater than that of tetragonal lysozyme. Good agreement was observed between the measured and calculated ratios of the SHG intensity from lysozyme in tetragonal and monoclinic lattices.« less

A source-attractor approach to network detection of radiation sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Qishi; Barry, M. L..; Grieme, M.

Radiation source detection using a network of detectors is an active field of research for homeland security and defense applications. We propose Source-attractor Radiation Detection (SRD) method to aggregate measurements from a network of detectors for radiation source detection. SRD method models a potential radiation source as a magnet -like attractor that pulls in pre-computed virtual points from the detector locations. A detection decision is made if a sufficient level of attraction, quantified by the increase in the clustering of the shifted virtual points, is observed. Compared with traditional methods, SRD has the following advantages: i) it does not requiremore » an accurate estimate of the source location from limited and noise-corrupted sensor readings, unlike the localizationbased methods, and ii) its virtual point shifting and clustering calculation involve simple arithmetic operations based on the number of detectors, avoiding the high computational complexity of grid-based likelihood estimation methods. We evaluate its detection performance using canonical datasets from Domestic Nuclear Detection Office s (DNDO) Intelligence Radiation Sensors Systems (IRSS) tests. SRD achieves both lower false alarm rate and false negative rate compared to three existing algorithms for network source detection.« less

Validation of an In Vitro Bioaccessibility Test Method for Estimation of Bioavailability of Arsenic from Soil and Sediment

DTIC Science & Technology

2012-12-01

calibrated using a certified mineral or pure metal standard and counting times are chosen to provide 3-sigma detection limits of between 100-200 ppm...also submit “blind” duplicates for analyses. The precision of the data generated by the “EMPA point count ” will be evaluated by calculating RPD values...important to consider the variation in results among all samples studied for a particular media, since the overall particle count is very large. Data

Quantitative Determination of Wax Contamination in Polystyrene HIPE Foam Using Solid-State NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cluff, Kyle James; Goodwin, Lynne Alese; Hamilton, Christopher Eric

Differences in molecular mobility between polystyrene foam and Brij-78 wax results in vast differences in the 1H nuclear magnetic resonance (NMR) linewidth. This allows for the convenient determination of wax content in the polystyrene foam components of inertial confinement fusion targets via solid-state NMR. Lastly, contamination levels as low as 0.1% are easily recognized and quantified, and the detection limit is calculated to be 0.02% even when only 32 transients are recorded.

Quantitative Determination of Wax Contamination in Polystyrene HIPE Foam Using Solid-State NMR

DOE PAGES

Cluff, Kyle James; Goodwin, Lynne Alese; Hamilton, Christopher Eric; ...

2017-11-29

Differences in molecular mobility between polystyrene foam and Brij-78 wax results in vast differences in the 1H nuclear magnetic resonance (NMR) linewidth. This allows for the convenient determination of wax content in the polystyrene foam components of inertial confinement fusion targets via solid-state NMR. Lastly, contamination levels as low as 0.1% are easily recognized and quantified, and the detection limit is calculated to be 0.02% even when only 32 transients are recorded.

Beam/seam alignment control for electron beam welding

DOEpatents

Burkhardt, Jr., James H.; Henry, J. James; Davenport, Clyde M.

1980-01-01

This invention relates to a dynamic beam/seam alignment control system for electron beam welds utilizing video apparatus. The system includes automatic control of workpiece illumination, near infrared illumination of the workpiece to limit the range of illumination and camera sensitivity adjustment, curve fitting of seam position data to obtain an accurate measure of beam/seam alignment, and automatic beam detection and calculation of the threshold beam level from the peak beam level of the preceding video line to locate the beam or seam edges.

Reconciling Ground-Based and Space-Based Estimates of the Frequency of Occurrence and Radiative Effect of Clouds around Darwin, Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Protat, Alain; Young, Stuart; McFarlane, Sally A.

2014-02-01

The objective of this paper is to investigate whether estimates of the cloud frequency of occurrence and associated cloud radiative forcing as derived from ground-based and satellite active remote sensing and radiative transfer calculations can be reconciled over a well instrumented active remote sensing site located in Darwin, Australia, despite the very different viewing geometry and instrument characteristics. It is found that the ground-based radar-lidar combination at Darwin does not detect most of the cirrus clouds above 10 km (due to limited lidar detection capability and signal obscuration by low-level clouds) and that the CloudSat radar - Cloud-Aerosol Lidar withmore » Orthogonal Polarization (CALIOP) combination underreports the hydrometeor frequency of occurrence below 2 km height, due to instrument limitations at these heights. The radiative impact associated with these differences in cloud frequency of occurrence is large on the surface downwelling shortwave fluxes (ground and satellite) and the top-of atmosphere upwelling shortwave and longwave fluxes (ground). Good agreement is found for other radiative fluxes. Large differences in radiative heating rate as derived from ground and satellite radar-lidar instruments and RT calculations are also found above 10 km (up to 0.35 Kday-1 for the shortwave and 0.8 Kday-1 for the longwave). Given that the ground-based and satellite estimates of cloud frequency of occurrence and radiative impact cannot be fully reconciled over Darwin, caution should be exercised when evaluating the representation of clouds and cloud-radiation interactions in large-scale models and limitations of each set of instrumentation should be considered when interpreting model-observations differences.« less

The test-retest reliability and minimal detectable change of spatial and temporal gait variability during usual over-ground walking for younger and older adults.

PubMed

Almarwani, Maha; Perera, Subashan; VanSwearingen, Jessie M; Sparto, Patrick J; Brach, Jennifer S

2016-02-01

Gait variability is a marker of gait performance and future mobility status in older adults. Reliability of gait variability has been examined mainly in community dwelling older adults who are likely to fluctuate over time. The purpose of this study was to compare test-retest reliability and determine minimal detectable change (MDC) of spatial and temporal gait variability in younger and older adults. Forty younger (mean age=26.6 ± 6.0 years) and 46 older adults (mean age=78.1 ± 6.2 years) were included in the study. Gait characteristics were measured twice, approximately 1 week apart, using a computerized walkway (GaitMat II). Participants completed 4 passes on the GaitMat II at their self-selected walking speed. Test-retest reliability was calculated using Intra-class correlation coefficients (ICCs(2,1)), 95% limits of agreement (95% LoA) in conjunction with Bland-Altman plots, relative limits of agreement (LoA%) and standard error of measurement (SEM). The MDC at 90% and 95% level were also calculated. ICCs of gait variability ranged 0.26-0.65 in younger and 0.28-0.74 in older adults. The LoA% and SEM were consistently higher (i.e. less reliable) for all gait variables in older compared to younger adults except SEM for step width. The MDC was consistently larger for all gait variables in older compared to younger adults except step width. ICCs were of limited utility due to restricted ranges in younger adults. Based on absolute reliability measures and MDC, younger had greater test-retest reliability and smaller MDC of spatial and temporal gait variability compared to older adults. Copyright © 2015 Elsevier B.V. All rights reserved.

Tacholess order-tracking approach for wind turbine gearbox fault detection

NASA Astrophysics Data System (ADS)

Wang, Yi; Xie, Yong; Xu, Guanghua; Zhang, Sicong; Hou, Chenggang

2017-09-01

Monitoring of wind turbines under variable-speed operating conditions has become an important issue in recent years. The gearbox of a wind turbine is the most important transmission unit; it generally exhibits complex vibration signatures due to random variations in operating conditions. Spectral analysis is one of the main approaches in vibration signal processing. However, spectral analysis is based on a stationary assumption and thus inapplicable to the fault diagnosis of wind turbines under variable-speed operating conditions. This constraint limits the application of spectral analysis to wind turbine diagnosis in industrial applications. Although order-tracking methods have been proposed for wind turbine fault detection in recent years, current methods are only applicable to cases in which the instantaneous shaft phase is available. For wind turbines with limited structural spaces, collecting phase signals with tachometers or encoders is difficult. In this study, a tacholess order-tracking method for wind turbines is proposed to overcome the limitations of traditional techniques. The proposed method extracts the instantaneous phase from the vibration signal, resamples the signal at equiangular increments, and calculates the order spectrum for wind turbine fault identification. The effectiveness of the proposed method is experimentally validated with the vibration signals of wind turbines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abe, K.; Haga, K.; Hayato, Y.

We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational-wave events, GW150914 and GW151226, as well as LVT151012, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of ±500 s around the gravitational-wave detection time. Four neutrino candidates are found for GW150914, and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90% confidence level upper limits on the combined neutrino fluence for both gravitational-wave events, which depends onmore » event energy and topologies. Considering the upward-going muon data set (1.6 GeV–100 PeV), the neutrino fluence limit for each gravitational-wave event is 14–37 (19–50) cm{sup −2} for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational-wave events range from 2.4 × 10{sup 4} to 7.0 × 10{sup 9} cm{sup −2}.« less

Limits of linearity and detection for some drugs of abuse.

PubMed

Needleman, S B; Romberg, R W

1990-01-01

The limits of linearity (LOL) and detection (LOD) are important factors in establishing the reliability of an analytical procedure for accurately assaying drug concentrations in urine specimens. Multiple analyses of analyte over an extended range of concentrations provide a measure of the ability of the analytical procedure to correctly identify known quantities of drug in a biofluid matrix. Each of the seven drugs of abuse gives linear analytical responses from concentrations at or near their LOD to concentrations several-fold higher than those generally encountered in the drug screening laboratory. The upper LOL exceeds the Department of Navy (DON) cutoff values by factors of approximately 2 to 160. The LOD varies from 0.4 to 5.0% of the DON cutoff value for each drug. The limit of quantitation (LOQ) is calculated as the LOD + 7 SD. The range for LOL is greater for drugs analyzed with deuterated internal standards compared with those using conventional internal standards. For THC acid, cocaine, PCP, and morphine, LOLs are 8 to 160-fold greater than the defined cutoff concentrations. For the other drugs, the LOL's are only 2 to 4-fold greater than the defined cutoff concentrations.

Search for Neutrinos in Super-Kamiokande Associated with Gravitational-wave Events GW150914 and GW151226

NASA Astrophysics Data System (ADS)

Abe, K.; Haga, K.; Hayato, Y.; Ikeda, M.; Iyogi, K.; Kameda, J.; Kishimoto, Y.; Miura, M.; Moriyama, S.; Nakahata, M.; Nakajima, T.; Nakano, Y.; Nakayama, S.; Orii, A.; Sekiya, H.; Shiozawa, M.; Takeda, A.; Tanaka, H.; Tasaka, S.; Tomura, T.; Akutsu, R.; Kajita, T.; Kaneyuki, K.; Nishimura, Y.; Richard, E.; Okumura, K.; Labarga, L.; Fernandez, P.; Blaszczyk, F. d. M.; Gustafson, J.; Kachulis, C.; Kearns, E.; Raaf, J. L.; Stone, J. L.; Sulak, L. R.; Berkman, S.; Nantais, C. M.; Tobayama, S.; Goldhaber, M.; Kropp, W. R.; Mine, S.; Weatherly, P.; Smy, M. B.; Sobel, H. W.; Takhistov, V.; Ganezer, K. S.; Hartfiel, B. L.; Hill, J.; Hong, N.; Kim, J. Y.; Lim, I. T.; Park, R. G.; Himmel, A.; Li, Z.; O’Sullivan, E.; Scholberg, K.; Walter, C. W.; Ishizuka, T.; Nakamura, T.; Jang, J. S.; Choi, K.; Learned, J. G.; Matsuno, S.; Smith, S. N.; Friend, M.; Hasegawa, T.; Ishida, T.; Ishii, T.; Kobayashi, T.; Nakadaira, T.; Nakamura, K.; Oyama, Y.; Sakashita, K.; Sekiguchi, T.; Tsukamoto, T.; Suzuki, A. T.; Takeuchi, Y.; Yano, T.; Cao, S. V.; Hiraki, T.; Hirota, S.; Huang, K.; Jiang, M.; Minamino, A.; Nakaya, T.; Patel, N. D.; Wendell, R. A.; Suzuki, K.; Fukuda, Y.; Itow, Y.; Suzuki, T.; Mijakowski, P.; Frankiewicz, K.; Hignight, J.; Imber, J.; Jung, C. K.; Li, X.; Palomino, J. L.; Santucci, G.; Wilking, M. J.; Yanagisawa, C.; Fukuda, D.; Ishino, H.; Kayano, T.; Kibayashi, A.; Koshio, Y.; Mori, T.; Sakuda, M.; Xu, C.; Kuno, Y.; Tacik, R.; Kim, S. B.; Okazawa, H.; Choi, Y.; Nishijima, K.; Koshiba, M.; Totsuka, Y.; Suda, Y.; Yokoyama, M.; Bronner, C.; Calland, R. G.; Hartz, M.; Martens, K.; Marti, Ll.; Suzuki, Y.; Vagins, M. R.; Martin, J. F.; Tanaka, H. A.; Konaka, A.; Chen, S.; Wan, L.; Zhang, Y.; Wilkes, R. J.; The Super-Kamiokande Collaboration

2016-10-01

We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational-wave events, GW150914 and GW151226, as well as LVT151012, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of ±500 s around the gravitational-wave detection time. Four neutrino candidates are found for GW150914, and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90% confidence level upper limits on the combined neutrino fluence for both gravitational-wave events, which depends on event energy and topologies. Considering the upward-going muon data set (1.6 GeV–100 PeV), the neutrino fluence limit for each gravitational-wave event is 14–37 (19–50) cm‑2 for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational-wave events range from 2.4 × 104 to 7.0 × 109 cm‑2.

Coupled-cluster and density functional theory studies of the electronic 0-0 transitions of the DNA bases.

PubMed

Ovchinnikov, Vasily A; Sundholm, Dage

2014-04-21

The 0-0 transitions of the electronic excitation spectra of the lowest tautomers of the four nucleotide (DNA) bases have been studied using linear-response approximate coupled-cluster singles and doubles (CC2) calculations. Excitation energies have also been calculated at the linear-response time-dependent density functional theory (TDDFT) level using the B3LYP functional. Large basis sets have been employed for ensuring that the obtained excitation energies are close to the basis-set limit. Zero-point vibrational energy corrections have been calculated at the B3LYP and CC2 levels for the ground and excited states rendering direct comparisons with high-precision spectroscopy measurements feasible. The obtained excitation energies for the 0-0 transitions of the first excited states of guanine tautomers are in good agreement with experimental values confirming the experimental assignment of the energetic order of the tautomers of the DNA bases. For the experimentally detected guanine tautomers, the first excited state corresponds to a π→π* transition, whereas for the tautomers of adenine, thymine, and the lowest tautomer of cytosine the transition to the first excited state has n →π* character. The calculations suggest that the 0-0 transitions of adenine, thymine, and cytosine are not observed in the absorption spectrum due to the weak oscillator strength of the formally symmetry-forbidden transitions, while 0-0 transitions of thymine have been detected in fluorescence excitation spectra.

Deformed Shape Calculation of a Full-Scale Wing Using Fiber Optic Strain Data from a Ground Loads Test

NASA Technical Reports Server (NTRS)

Jutte, Christine V.; Ko, William L.; Stephens, Craig A.; Bakalyar, John A.; Richards, W. Lance

2011-01-01

A ground loads test of a full-scale wing (175-ft span) was conducted using a fiber optic strain-sensing system to obtain distributed surface strain data. These data were input into previously developed deformed shape equations to calculate the wing s bending and twist deformation. A photogrammetry system measured actual shape deformation. The wing deflections reached 100 percent of the positive design limit load (equivalent to 3 g) and 97 percent of the negative design limit load (equivalent to -1 g). The calculated wing bending results were in excellent agreement with the actual bending; tip deflections were within +/- 2.7 in. (out of 155-in. max deflection) for 91 percent of the load steps. Experimental testing revealed valuable opportunities for improving the deformed shape equations robustness to real world (not perfect) strain data, which previous analytical testing did not detect. These improvements, which include filtering methods developed in this work, minimize errors due to numerical anomalies discovered in the remaining 9 percent of the load steps. As a result, all load steps attained +/- 2.7 in. accuracy. Wing twist results were very sensitive to errors in bending and require further development. A sensitivity analysis and recommendations for fiber implementation practices, along with, effective filtering methods are included

Reappraisal of dark matter co-annihilating with a top or bottom partner

NASA Astrophysics Data System (ADS)

Keung, Wai-Yee; Low, Ian; Zhang, Yue

2017-07-01

We revisit the calculation of the relic density of dark matter particles co-annihilating with a top or bottom partner by properly including the QCD bound-states (onia) effects of the colored partners as well as the relevant electroweak processes, which become important in the low-mass region. We carefully set up the complete framework that incorporates the relevant contributions and investigate their effects on the cosmologically preferred mass spectrum, which turn out to be comparable in size to those coming from the Sommerfeld enhancement. We apply the calculation to three scenarios: bino-stop and bino-sbottom co-annihilations in supersymmetry and a vector dark matter co-annihilating with a fermionic top partner. In addition, we confront our analysis of the relic abundance with recent direct detection experiments and collider searches at the LHC, which have important implications in the bino-stop and bino-sbottom scenarios. In particular, in the bino-stop case, recent LHC limits have excluded regions of parameter space with a direct detection rate that is above the neutrino floor.

Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia-Lechuga, M.; Laser Processing Group, Instituto de Óptica “Daza de Valdés,” CSIC, 28006-Madrid; Fuentes, L. M.

2014-10-07

We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed tomore » resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.« less

A highly sensitive and selective off-on fluorescent chemosensor for hydrazine based on coumarin β-diketone

NASA Astrophysics Data System (ADS)

Wu, Wei-Na; Wu, Hao; Wang, Yuan; Mao, Xian-Jie; Zhao, Xiao-Lei; Xu, Zhou-Qing; Fan, Yun-Chang; Xu, Zhi-Hong

2018-01-01

A coumarin-based sensor C1, namely 3-acetoacetylcoumarin was designed, synthesized and applied for hydrazine detection. Hydrazinolysis of the chemosensor gives a fluorescent coumarin-pyrazole product C1 - N2H4 [3-(3-methyl-1H-pyrazol-5-yl)coumarin], and thus resulting in a prominent fluorescence off-on response toward hydrazine under physiological conditions. The probe is highly selective toward hydrazine over cations, anions and other biologically/environmentally abundant analytes. The detection limit of the probe is 3.2 ppb. The sensing mechanism was supported by 1H NMR, IR, MS and DFT calculation. The application of the fluorescent probe in monitoring intracellular hydrazine in glioma cell line U251 was also demonstrated.

A new high selective and sensitive turn-on fluorescent and ratiometric absorption chemosensor for Cu2+ based on benzimidazole in aqueous solution and its application in live cell.

PubMed

Bing, Qijing; Wang, Lin; Li, Donglin; Wang, Guang

2018-09-05

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu 2+ was designed and synthesized. Fluorescence and UV-vis spectra studies demonstrated that L can detect Cu 2+ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu 2+ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu 2+ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu 2+ displayed L had cell permeability and detection ability for Cu 2+ in live cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Sensitivity enhancement of capacitive tumor necrosis factor-α detection by deposition of nanoparticles on interdigitated electrode

NASA Astrophysics Data System (ADS)

Yagati, Ajay Kumar; Park, Jinsoo; Kim, Jungsuk; Ju, Heongkyu; Chang, Keun-A.; Cho, Sungbo

2016-06-01

An interdigitated electrodes (IDE) modified with gold nanoparticles (AuNPs) was fabricated to enhance the capacitive detection of tumor necrosis factor-α (TNF-α) and compared with a bare IDE. A TNF-α immunosensor was developed by covalently conjugating TNF-α antibodies with 3-mercaptopropionic acid by a carbodiimide/N-hydroxysuccinimide reaction on the AuNP/IDE. After the application of human serum samples containing various concentrations of TNF-α to the sensing electrode, changes in both the impedance spectrum and the electrode interfacial capacitance were measured. The capacitance changes were dependent on the TNF-α concentration in the range of 1 pg ml-1 to 10 ng ml-1, and the device had the calculated detection limit of 0.83 pg ml-1. The developed AuNP/IDE-based immunosensor was successfully used for the capacitive detection of the binding of TNF-α to its antibody, and was found to be feasible for the analysis of TNF-α in human blood serum.

Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balazs, Csaba; Conrad, Jan; Farmer, Ben

Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential γ-ray signals from dark matter (DM) annihilation above ~50 GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate γ-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC)more » and direct detection experiments. Here, for DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.« less

Ultrasensitive Plasmonic Biosensors for Real-Time Parallel Detection of Alpha-L-Fucosidase and Cardiac-Troponin-I in Whole Human Blood.

PubMed

Han, Xu; Shokri Kojori, Hossein; Leblanc, Roger M; Kim, Sung Jin

2018-06-19

Cancers and many other diseases, such as hepatocellular carcinoma (HCC) and cardiovascular diseases (CVD), have threatened human lives for centuries. Therefore, a novel technique for such disease prediction is in an urgent demand for timely treatment. Biomarkers, alpha-L-fucosidase (AFU) for HCC and cardiac troponin I (cTnI) for CVD, have proven to be essential in the role of disease detection. Herein, we report on an ultrasensitive plasmonic biosensor that converts plasmonic absorption to electrical current in order to detect AFU and cTnI using whole human blood in a real-time and parallel fashion. The detection limit was calculated to be 0.016 U/L for AFU and 0.015 ng/mL for cTnI, respectively. Combined with the versatility of the strategies for different biomarkers, these results demonstrate that the developed biosensor exhibits a promising application for the prediction of cancers and many other diseases.

Superhydrophobic Ag nanostructures on polyaniline membranes with strong SERS enhancement.

PubMed

Liu, Weiyu; Miao, Peng; Xiong, Lu; Du, Yunchen; Han, Xijiang; Xu, Ping

2014-11-07

We demonstrate here a facile fabrication of n-dodecyl mercaptan-modified superhydrophobic Ag nanostructures on polyaniline membranes for molecular detection based on SERS technique, which combines the superhydrophobic condensation effect and the high enhancement factor. It is calculated that the as-fabricated superhydrophobic substrate can exhibit a 21-fold stronger molecular condensation, and thus further amplifies the SERS signal to achieve more sensitive detection. The detection limit of the target molecule, methylene blue (MB), on this superhydrophobic substrate can be 1 order of magnitude higher than that on the hydrophilic substrate. With high reproducibility, the feasibility of using this SERS-active superhydrophobic substrate for quantitative molecular detection is explored. A partial least squares (PLS) model was established for the quantification of MB by SERS, with correlation coefficient R(2) = 95.1% and root-mean-squared error of prediction (RMSEP) = 0.226. We believe this superhydrophobic SERS substrate can be widely used in trace analysis due to its facile fabrication, high signal reproducibility and promising SERS performance.

Application of the Hotelling and ideal observers to detection and localization of exoplanets.

PubMed

Caucci, Luca; Barrett, Harrison H; Devaney, Nicholas; Rodríguez, Jeffrey J

2007-12-01

The ideal linear discriminant or Hotelling observer is widely used for detection tasks and image-quality assessment in medical imaging, but it has had little application in other imaging fields. We apply it to detection of planets outside of our solar system with long-exposure images obtained from ground-based or space-based telescopes. The statistical limitations in this problem include Poisson noise arising mainly from the host star, electronic noise in the image detector, randomness or uncertainty in the point-spread function (PSF) of the telescope, and possibly a random background. PSF randomness is reduced but not eliminated by the use of adaptive optics. We concentrate here on the effects of Poisson and electronic noise, but we also show how to extend the calculation to include a random PSF. For the case where the PSF is known exactly, we compare the Hotelling observer to other observers commonly used for planet detection; comparison is based on receiver operating characteristic (ROC) and localization ROC (LROC) curves.

Application of the Hotelling and ideal observers to detection and localization of exoplanets

PubMed Central

Caucci, Luca; Barrett, Harrison H.; Devaney, Nicholas; Rodríguez, Jeffrey J.

2008-01-01

The ideal linear discriminant or Hotelling observer is widely used for detection tasks and image-quality assessment in medical imaging, but it has had little application in other imaging fields. We apply it to detection of planets outside of our solar system with long-exposure images obtained from ground-based or space-based telescopes. The statistical limitations in this problem include Poisson noise arising mainly from the host star, electronic noise in the image detector, randomness or uncertainty in the point-spread function (PSF) of the telescope, and possibly a random background. PSF randomness is reduced but not eliminated by the use of adaptive optics. We concentrate here on the effects of Poisson and electronic noise, but we also show how to extend the calculation to include a random PSF. For the case where the PSF is known exactly, we compare the Hotelling observer to other observers commonly used for planet detection; comparison is based on receiver operating characteristic (ROC) and localization ROC (LROC) curves. PMID:18059905

Application of the Nimbus 5 ESMR to rainfall detection over land surfaces

NASA Technical Reports Server (NTRS)

Meneely, J. M.

1975-01-01

The ability of the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR) to detect rainfall over land surfaces was evaluated. The ESMR brightness temperatures (Tb sub B) were compared with rainfall reports from climatological stations for a limited number of rain events over portions of the U.S. The greatly varying emissivity of land surfaces precludes detection of actively raining areas. Theoretical calculations using a ten-layer atmospheric model showed this to be an expected result. Detection of rain which had fallen was deemed feasible over certain types of land surfaces by comparing the Tb sub B fields before and after the rain fell. This procedure is reliable only over relatively smooth terrain having a substantial fraction of bare soil, such as exists in major agricultural regions during the dormant or early growing seasons. Soil moisture budgets were computed at selected sites to show how the observed emissivity responded to changes in the moisture content of the upper soil zone.

Piezoelectric immunosensors for the detection of individual antibiotics and the total content of penicillin antibiotics in foodstuffs.

PubMed

Karaseva, N A; Ermolaeva, T N

2014-03-01

Piezoelectric immunosensors on the basis of homologous and group-specificantibodies have been developed for detecting penicillin G, ampicillin, and the total content of penicillin antibiotics. The receptor coating of the sensor was obtained by the immobilization of penicillin G or ampicillin hapten-protein conjugates on the polypyrrole film obtained by electropolymerization and activated by glutaraldehyde. The affinity constants and the cross reactivity coefficients have been calculated. This made it possible to estimate the affinity and specificity of the polyclonal and monoclonal antibodies used. The calibration curves are linear in the range of concentrations 2.5-250.0 ng ml(-1) (penicillin G), 2.5-500.0 ng ml(-1) (ampicillin), and 1-500 ng ml(-1) (group of penicillin). The limits of detection are 0.8 ng ml(-1), 3.9 ng ml(-1), which are lower than MRL, established for penicillin antibiotics. The sensors were tested in detecting penicillins in milk, pork, beef, liver. Copyright © 2013 Elsevier B.V. All rights reserved.

Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments

DOE PAGES

Balazs, Csaba; Conrad, Jan; Farmer, Ben; ...

2017-10-04

Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential γ-ray signals from dark matter (DM) annihilation above ~50 GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate γ-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC)more » and direct detection experiments. Here, for DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.« less

Silver nanoparticles-based colorimetric array for the detection of Thiophanate-methyl

NASA Astrophysics Data System (ADS)

Zheng, Mingda; Wang, Yingying; Wang, Chenge; Wei, Wei; Ma, Shuang; Sun, Xiaohan; He, Jiang

2018-06-01

A simple and selective colorimetric sensor based on citrate capped silver nanoparticles (Cit-AgNPs) is proposed for the detection of Thiophanate-methyl (TM) with high sensitivity and selectivity. The method based on the color change of Cit-AgNPs from yellow to cherry red with the addition of TM to Cit-AgNPs that caused a red-shift on the surface plasmon resonance (SPR) band from 394 nm to 525 nm due to the hydrogen-bonding and substitution. The density functional theory (DFT) method was also calculated the interactions between the TM and citrate ions. Under the optimized conditions, a linear relationship between the absorption ratio (A525nm/A394nm) and TM concentration was found in the range of 2-100 μM with correlation coefficient (R2) of 0.988. The detection limit of TM was 0.12 μM by UV-vis spectrometer. Moreover, the applicability of colorimetric sensor is successfully verified by the detection of TM in environmental samples with good recoveries.

39 CFR 3010.21 - Calculation of annual limitation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 39 Postal Service 1 2010-07-01 2010-07-01 false Calculation of annual limitation. 3010.21 Section 3010.21 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL REGULATION OF RATES FOR MARKET DOMINANT PRODUCTS Rules for Applying the Price Cap § 3010.21 Calculation of annual limitation. (a) The calculation...

Inhibition of the electron cyclotron maser instability in the dense magnetosphere of a hot Jupiter

NASA Astrophysics Data System (ADS)

Daley-Yates, S.; Stevens, I. R.

2018-06-01

Hot Jupiter (HJ) type exoplanets are expected to produce strong radio emission in the MHz range via the Electron Cyclotron Maser Instability (ECMI). To date, no repeatable detections have been made. To explain the absence of observational results, we conduct 3D adaptive mess refinement (AMR) magnetohydrodynamic (MHD) simulations of the magnetic interactions between a solar type star and HJ using the publicly available code PLUTO. The results are used to calculate the efficiency of the ECMI at producing detectable radio emission from the planets magnetosphere. We also calculate the frequency of the ECMI emission, providing an upper and lower bounds, placing it at the limits of detectability due to Earth's ionospheric cutoff of ˜10 MHz. The incident kinetic and magnetic power available to the ECMI is also determined and a flux of 0.075 mJy for an observer at 10 pc is calculated. The magnetosphere is also characterized and an analysis of the bow shock which forms upstream of the planet is conducted. This shock corresponds to the thin shell model for a colliding wind system. A result consistent with a colliding wind system. The simulation results show that the ECMI process is completely inhibited by the planets expanding atmosphere, due to absorption of UV radiation form the host star. The density, velocity, temperature and magnetic field of the planetary wind are found to result in a magnetosphere where the plasma frequency is raised above that due to the ECMI process making the planet undetectable at radio MHz frequencies.

Pedestrian injury mitigation by autonomous braking.

PubMed

Rosén, Erik; Källhammer, Jan-Erik; Eriksson, Dick; Nentwich, Matthias; Fredriksson, Rikard; Smith, Kip

2010-11-01

The objective of this study was to calculate the potential effectiveness of a pedestrian injury mitigation system that autonomously brakes the car prior to impact. The effectiveness was measured by the reduction of fatally and severely injured pedestrians. The database from the German In-Depth Accident Study (GIDAS) was queried for pedestrians hit by the front of cars from 1999 to 2007. Case by case information on vehicle and pedestrian velocities and trajectories were analysed to estimate the field of view needed for a vehicle-based sensor to detect the pedestrians one second prior to the crash. The pre-impact braking system was assumed to activate the brakes one second prior to crash and to provide a braking deceleration up to the limit of the road surface conditions, but never to exceed 0.6 g. New impact speeds were then calculated for pedestrians that would have been detected by the sensor. These calculations assumed that all pedestrians who were within a given field of view but not obstructed by surrounding objects would be detected. The changes in fatality and severe injury risks were quantified using risk curves derived by logistic regression of the accident data. Summing the risks for all pedestrians, relationships between mitigation effectiveness, sensor field of view, braking initiation time, and deceleration were established. The study documents that the effectiveness at reducing fatally (severely) injured pedestrians in frontal collisions with cars reached 40% (27%) at a field of view of 40 degrees. Increasing the field of view further led to only marginal improvements in effectiveness. 2010 Elsevier Ltd. All rights reserved.

[Analytical performances of real-time PCR by Abbott RealTime CMV with m2000 for the detection of cytomegalovirus in urine].

PubMed

De Monte, Anne; Cannavo, Isabelle; Caramella, Anne; Ollier, Laurence; Giordanengo, Valérie

2016-01-01

Congenital cytomegalovirus (CMV) infection is the leading cause of sensoneurinal disability due to infectious congenital disease. The diagnosis of congenital CMV infection is based on the search of CMV in the urine within the first two weeks of life. Viral culture of urine is the gold standard. However, the PCR is highly sensitive and faster. It is becoming an alternative choice. The objective of this study is the validation of real-time PCR by Abbott RealTime CMV with m2000 for the detection of cytomegalovirus in urine. Repeatability, reproducibility, detection limit and inter-sample contamination were evaluated. Urine samples from patients (n=141) were collected and analyzed simultaneously in culture and PCR in order to assess the correlation of these two methods. The sensitivity and specificity of PCR were also calculated. The Abbott RealTime CMV PCR in urine is an automated and sensitive method (detection limit 200 UI/mL). Fidelity is very good (standard deviation of repeatability: 0.08 to 0.15 LogUI/mL and reproducibility 0.18 LogUI/mL). We can note a good correlation between culture and Abbott RealTime CMV PCR (kappa 96%). When considering rapid culture as reference, real-time PCR was highly sensitive (100%) and specific (98.2%). The real-time PCR by Abbott RealTime CMV with m2000 is optimal for CMV detection in urine.

Determination of bupropion using liquid chromatography with fluorescence detection in pharmaceutical preparations, human plasma and human urine.

PubMed

Ulu, Sevgi Tatar; Tuncel, Muzaffer

2012-05-01

A novel pre-column derivatization reversed-phase high-performance liquid chromatography with fluorescence detection is described for the determination of bupropion in pharmaceutical preparation, human plasma and human urine using mexiletine as internal standard. The proposed method is based on the reaction of 4-chloro-7-nitrobenzofurazan (NBD-Cl) with bupropion to produce a fluorescent derivative. The derivative formed is monitored on a C18 (150 mm × 4.6 mm i.d., 5 µm) column using a mobile phase consisting of methanol-water 75:25 (v/v), at a flow-rate of 1.2 mL/min and detected fluorimetrically at λ(ex) = 458 and λ(em) = 533 nm. The assay was linear over the concentration ranges of 5-500 and 10-500 ng/mL for plasma and urine, respectively. The limits of detection and quantification were calculated to be 0.24 and 0.72 ng/mL for plasma and urine, respectively (inter-day results). The recoveries obtained for plasma and urine were 97.12% ± 0.45 and 96.00% ± 0.45, respectively. The method presents good performance in terms of precision, accuracy, specificity, linearity, detection and quantification limits and robustness. The proposed method is applied to determine bupropion in commercially available tablets. The results were compared with an ultraviolet spectrophotometry method using t- and F-tests. © The Author [2012]. Published by Oxford University Press. All rights reserved.

Airborne Nanoparticle Detection By Sampling On Filters And Laser-Induced Breakdown Spectroscopy Analysis

NASA Astrophysics Data System (ADS)

Dewalle, Pascale; Sirven, Jean-Baptiste; Roynette, Audrey; Gensdarmes, François; Golanski, Luana; Motellier, Sylvie

2011-07-01

Nowadays, due to their unique physical and chemical properties, engineered nanoparticles are increasingly used in a variety of industrial sectors. However, questions are raised about the safety of workers who produce and handle these particles. Therefore it is necessary to assess the potential exposure by inhalation of these workers. There is thereby a need to develop a suitable instrumentation which can detect selectively the presence of engineered nanoparticles in the ambient atmosphere. In this paper Laser-Induced Breakdown Spectroscopy (LIBS) is used to meet this target. LIBS can be implemented on site since it is a fast and direct technique which requires no sample preparation. The approach consisted in sampling Fe2O3 and TiO2 nanoparticles on a filter, respectively a mixed cellulose ester membrane and a polycarbonate membrane, and to measure the surface concentration of Fe and Ti by LIBS. Then taking into account the sampling parameters (flow, duration, filter surface) we could calculate a detection limit in volume concentration in the atmosphere. With a sampling at 10 L/min on a 10 cm2 filter during 1 min, we obtained detection limits of 56 μg/m3 for Fe and 22 μg/m3 for Ti. These figures, obtained in real time, are significantly below existing workplace exposure recommendations of the EU-OSHA and of the NIOSH. These results are very encouraging and will be completed in a future work on airborne carbon nanotube detection.

Faecal pollution along the southeastern coast of Florida and insight into the use of pepper mild mottle virus as an indicator.

PubMed

Symonds, E M; Sinigalliano, C; Gidley, M; Ahmed, W; McQuaig-Ulrich, S M; Breitbart, M

2016-11-01

To identify faecal pollution along the southeastern Florida coast and determine the performance of a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method for pepper mild mottle virus (PMMoV). In 2014, bimonthly surface water samples were collected from inlets, exposed to runoff and septic seepage, and coastal sites, exposed to ocean outfalls. Analysis of culturable enterococci and a suite of microbial source tracking (MST) markers (BacHum, CowM2, DogBact, HF183, HPyV, PMMoV) revealed faecal pollution, primarily of human origin, at all sites. Since PMMoV was detected more frequently than other MST markers, the process limits of quantification (undiluted to 10 -2 dilution) and detection (10 -2 dilution) for the RT-qPCR method were determined by seeding untreated wastewater into the coastal waters. Simulated quantitative microbial risk assessment, employing human norovirus as a reference pathogen, calculated a 0·286 median risk of gastrointestinal illness associated with the PMMoV limit of detection. All sites met the U.S. EPA recreational water criteria, despite detection of domestic wastewater-associated MST markers. PMMoV correlated only with human-associated MST markers. This study demonstrated that PMMoV is an important domestic wastewater-associated marker that should be included in the MST toolbox; therefore, future studies should thoroughly investigate the health risks associated with its detection and quantification in environmental waters. © 2016 The Society for Applied Microbiology.

A highly selective long-wavelength fluorescent probe for hydrazine and its application in living cell imaging

NASA Astrophysics Data System (ADS)

Hao, Yuanqiang; Zhang, Yintang; Ruan, Kehong; Meng, Fanteng; Li, Ting; Guan, Jinsheng; Du, Lulu; Qu, Peng; Xu, Maotian

2017-09-01

A highly selective long-wavelength turn-on fluorescent probe has been developed for the detection of N2H4. The probe was prepared by conjugation the tricyanofuran-based D-π-A system with a recognizing moiety of acetyl group. In the presence of N2H4, the probe can be effectively hydrazinolysized and produce a turn-on fluorescent emission at 610 nm as well as a large red-shift in the absorption spectrum corresponding to a color change from yellow to blue. The sensing mechanism was confirmed by HPLC, MS, UV-vis, emission spectroscopic and theoretical calculation studies. The probe displayed high selectivity and sensitivity for N2H4 with a LOD (limit of detection) of 0.16 μM. Moreover, the probe was successfully utilized for the detection of hydrazine in living cells.

A novel polydentate ligand chromophore for simultaneously colorimetric detection of trace Ag + and Fe3 +

NASA Astrophysics Data System (ADS)

Yan, Zhengquan; Zhao, Qi; Wen, Meijun; Hu, Lei; Zhang, Xuezhong; You, Jinmao

2017-11-01

A novel polydentate ligand chromophore, 3,6-di-(N-ethyl-N-ethoxyl phenylazo) acridine (EEPA), was identified and synthesized. After its structure was characterized by FTIR, 1H NMR, mass spectra and element analyses, it was noted to find that there was a simultaneously colorimetric response to Ag+ and Fe3 + accompanying with different color changes, i.e., from brown to light purple for Ag+ and further to purple-red for Fe3 +, respectively. Their different action mechanisms, a 1:2 complex mode for EEPA-Ag+ and 1:1 for EEPA-Fe3 +, were investigated and confirmed by means of Job's plot and theoretical calculation. EEPA would be a potential colorimetric chemo-dosimeter for simultaneous detection of Ag+ and Fe3 + with the detection limits of 1.6 nmol·L- 1 and 69 nmol·L- 1, respectively.

Sensitive fluorescence on-off probes for the fast detection of a chemical warfare agent mimic.

PubMed

Khan, Muhammad Shar Jhahan; Wang, Ya-Wen; Senge, Mathias O; Peng, Yu

2018-01-15

Two highly sensitive probes bearing a nucleophilic imine moiety have been utilized for the selective detection of chemical warfare agent (CWA) mimics. Diethyl chlorophosphate (DCP) was used as mimic CWAs. Both iminocoumarin-benzothiazole-based probes not only demonstrated a remarkable fluorescence ON-OFF response and good recognition, but also exhibited fast response times (10s) along with color changes upon addition of DCP. Limits of detection for the two sensors 1 and 2 were calculated as 0.065μM and 0.21μM, respectively, which are much lower than most other reported probes. These two probes not only show high sensitivity and selectivity in solution, but can also be applied for the recognition of DCP in the gas state, with significant color changes easily observed by the naked eye. Copyright © 2017 Elsevier B.V. All rights reserved.

Achieving Real-Time Tracking Mobile Wireless Sensors Using SE-KFA

NASA Astrophysics Data System (ADS)

Kadhim Hoomod, Haider, Dr.; Al-Chalabi, Sadeem Marouf M.

2018-05-01

Nowadays, Real-Time Achievement is very important in different fields, like: Auto transport control, some medical applications, celestial body tracking, controlling agent movements, detections and monitoring, etc. This can be tested by different kinds of detection devices, which named "sensors" as such as: infrared sensors, ultrasonic sensor, radars in general, laser light sensor, and so like. Ultrasonic Sensor is the most fundamental one and it has great impact and challenges comparing with others especially when navigating (as an agent). In this paper, concerning to the ultrasonic sensor, sensor(s) detecting and delimitation by themselves then navigate inside a limited area to estimating Real-Time using Speed Equation with Kalman Filter Algorithm as an intelligent estimation algorithm. Then trying to calculate the error comparing to the factual rate of tracking. This paper used Ultrasonic Sensor HC-SR04 with Arduino-UNO as Microcontroller.

Characterization of sintered SiC by using NDE

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1988-01-01

Capabilities of projection microfocus X-radiography and of ultrasonic velocity and attenuation for characterizing silicon carbide specimens were assessed. Silicon carbide batches covered a range of densities and different microstructural characteristics. Room-temperature, four-point flexural strength tests were conducted. Fractography was used to identify types, sizes, and locations of fracture origins. Fracture toughness values were calculated from fracture strength and flaw characterization data. Detection capabilities of radiography for fracture-causing flaws were evaluated. Applicability of ultrasonics for verifying material strength and toughness was examined. Radiography proved useful in detecting high-density inclusions and isolated voids, but failed in detecting surface and subsurface agglomerates and large grains as fracture origins. Ultrasonic velocity dependency on density was evident. Attenuation dependency on density and mean pore size was clearly demonstrated. Understanding attenuation as a function of toughness was limited by shortcomings in K sub IC determination.

A Series of Fluorescent and Colorimetric Chemodosimeters for Selective Recognition of Cyanide Based on the FRET Mechanism.

PubMed

Hua, Ying-Xi; Shao, Yongliang; Wang, Ya-Wen; Peng, Yu

2017-06-16

A series of fluorescence "turn-on" probes (PY, AN, NA, B1, and B2) have been developed and successfully applied to detect cyanide anions based on the Michael addition reaction and FRET mechanism. These probes demonstrated good selectivity, high sensitivity, and very fast recognition for CN - . In particular, the fluorescence response of probe NA finished within 3 s. Low limits of detection (down to 63 nM) are also obtained in these probes with remarkable fluorescence enhancement factors. In addition, fluorescence colors of these probes turned to blue, yellow, or orange upon sensing CN - . In UV-vis mode, all of them showed ratiometric response for CN - . 1 H NMR titration experiments and TDDFT calculations were taken to verify the mechanism of the specific reaction and fluorescence properties of the corresponding compounds. Moreover, silica gel plates with these probes were also fabricated and utilized to detect cyanide.

Comparison of Non-Culture-Based Methods for Detection of Systemic Fungal Infections, with an Emphasis on Invasive Candida Infections

PubMed Central

White, P. Lewis; Archer, Alice E.; Barnes, Rosemary A.

2005-01-01

The accepted limitations associated with classic culture techniques for the diagnosis of invasive fungal infections have lead to the emergence of many non-culture-based methods. With superior sensitivities and quicker turnaround times, non-culture-based methods may aid the diagnosis of invasive fungal infections. In this review of the diagnostic service, we assessed the performances of two antigen detection techniques (enzyme-linked immunosorbent assay [ELISA] and latex agglutination) with a molecular method for the detection of invasive Candida infection and invasive aspergillosis. The specificities for all three assays were high (≥97%), although the Candida PCR method had enhanced sensitivity over both ELISA and latex agglutination with values of 95%, 75%, and 25%, respectively. However, calculating significant sensitivity values for the Aspergillus detection methods was not feasible due to a low number of proven/probable cases. Despite enhanced sensitivity, the PCR method failed to detect nucleic acid in a probable case of invasive Candida infection that was detected by ELISA. In conclusion, both PCR and ELISA techniques should be used in unison to aid the detection of invasive fungal infections. PMID:15872239

Validation of an enzyme-linked immunosorbent assay screening method and a liquid chromatography-tandem mass spectrometry confirmation method for the identification and quantification of ketamine and norketamine in urine samples from Malaysia.

PubMed

Harun, Norlida; Anderson, Robert A; Miller, Eleanor I

2009-01-01

An ELISA and a liquid chromatography-tandem mass spectrometry (LC-MS-MS) confirmation method were developed and validated for the identification and quantitation of ketamine and its major metabolite norketamine in urine samples. The Neogen ketamine microplate ELISA was optimized with respect to sample and enzyme conjugate volumes and the sample preincubation time before addition of the enzyme conjugate. The ELISA kit was validated to include an assessment of the dose-response curve, intra- and interday precision, limit of detection (LOD), and cross-reactivity. The sensitivity and specificity were calculated by comparison to the results from the validated LC-MS-MS confirmation method. An LC-MS-MS method was developed and validated with respect to LOD, lower limit of quantitation (LLOQ), linearity, recovery, intra- and interday precision, and matrix effects. The ELISA dose-response curve was a typical S-shaped binding curve, with a linear portion of the graph observed between 25 and 500 ng/mL for ketamine. The cross-reactivity of 200 ng/mL norketamine to ketamine was 2.1%, and no cross-reactivity was detected with 13 common drugs tested at 10,000 ng/mL. The ELISA LOD was calculated to be 5 ng/mL. Both intra- (n = 10) and interday (n = 50) precisions were below 5.0% at 25 ng/mL. The LOD for ketamine and norketamine was calculated statistically to be 0.6 ng/mL. The LLOQ values were also calculated statistically and were 1.9 ng/mL and 2.1 ng/mL for ketamine and norketamine, respectively. The test linearity was 0-1200 ng/mL with correlation coefficient (R(2)) > 0.99 for both analytes. Recoveries at 50, 500, and 1000 ng/mL range from 97.9% to 113.3%. Intra- (n = 5) and interday (n = 25) precisions between extracts for ketamine and norketamine were excellent (< 10%). Matrix effects analysis showed an average ion suppression of 5.7% for ketamine and an average ion enhancement of 13.0% for norketamine for urine samples collected from six individuals. A comparison of ELISA and LC-MS-MS results demonstrated a sensitivity, specificity, and efficiency of 100%. These results indicated that a cutoff value of 25 ng/mL ketamine in the ELISA screen is particularly suitable and reliable for urine testing in a forensic toxicology setting. Furthermore, both ketamine and norketamine were detected in all 34 urine samples collected from individuals socializing in pubs by the Royal Malaysian Police. Ketamine concentrations detected by LC-MS-MS ranged from 22 to 31,670 ng/mL, and norketamine concentrations ranged from 25 to 10,990 ng/mL. The concentrations of ketamine and norketamine detected in the samples are most ikely indicative of ketamine abuse.

Handheld echocardiography versus auscultation for detection of rheumatic heart disease.

PubMed

Godown, Justin; Lu, Jimmy C; Beaton, Andrea; Sable, Craig; Mirembe, Grace; Sanya, Richard; Aliku, Twalib; Yu, Sunkyung; Lwabi, Peter; Webb, Catherine L; Ensing, Gregory J

2015-04-01

Rheumatic heart disease (RHD) remains a major public health concern in developing countries, and routine screening has the potential to improve outcomes. Standard portable echocardiography (STAND) is far more sensitive than auscultation for the detection of RHD but remains cost-prohibitive in resource-limited settings. Handheld echocardiography (HAND) is a lower-cost alternative. The purpose of this study was to assess the incremental value of HAND over auscultation to identify RHD. RHD screening was completed for schoolchildren in Gulu, Uganda, by using STAND performed by experienced echocardiographers. Any child with mitral or aortic regurgitation or stenosis plus a randomly selected group of children with normal STAND findings underwent HAND and auscultation. STAND and HAND studies were interpreted by 6 experienced cardiologists using the 2012 World Heart Federation criteria. Sensitivity and specificity of HAND and auscultation for the detection of RHD and pathologic mitral or aortic regurgitation were calculated by using STAND as the gold standard. Of 4773 children who underwent screening with STAND, a subgroup of 1317 children underwent HAND and auscultation. Auscultation had uniformly poor sensitivity for the detection of RHD or valve disease. Sensitivity was significantly improved by using HAND compared with auscultation for the detection of definite RHD (97.8% vs 22.2%), borderline or definite RHD (78.4% vs 16.4%), and pathologic aortic insufficiency (81.8% vs 13.6%). Auscultation alone is a poor screening test for RHD. HAND significantly improves detection of RHD and may be a cost-effective screening strategy for RHD in resource-limited settings. Copyright © 2015 by the American Academy of Pediatrics.

Feasibility study of 235U and 239Pu characterization in radioactive waste drums using neutron-induced fission delayed gamma rays

NASA Astrophysics Data System (ADS)

Nicol, T.; Pérot, B.; Carasco, C.; Brackx, E.; Mariani, A.; Passard, C.; Mauerhofer, E.; Collot, J.

2016-10-01

This paper reports a feasibility study of 235U and 239Pu characterization in 225 L bituminized waste drums or 200 L concrete waste drums, by detecting delayed fission gamma rays between the pulses of a deuterium-tritium neutron generator. The delayed gamma yields were first measured with bare samples of 235U and 239Pu in REGAIN, a facility dedicated to the assay of 118 L waste drums by Prompt Gamma Neutron Activation Analysis (PGNAA) at CEA Cadarache, France. Detectability in the waste drums is then assessed using the MCNPX model of MEDINA (Multi Element Detection based on Instrumental Neutron Activation), another PGNAA cell dedicated to 200 L drums at FZJ, Germany. For the bituminized waste drum, performances are severely hampered by the high gamma background due to 137Cs, which requires the use of collimator and shield to avoid electronics saturation, these elements being very penalizing for the detection of the weak delayed gamma signal. However, for lower activity concrete drums, detection limits range from 10 to 290 g of 235U or 239Pu, depending on the delayed gamma rays of interest. These detection limits have been determined by using MCNPX to calculate the delayed gamma useful signal, and by measuring the experimental gamma background in MEDINA with a 200 L concrete drum mock-up. The performances could be significantly improved by using a higher interrogating neutron emission and an optimized experimental setup, which would allow characterizing nuclear materials in a wide range of low and medium activity waste packages.

Screen-printed electrode modified with carbon black and chitosan: a novel platform for acetylcholinesterase biosensor development.

PubMed

Talarico, Daria; Arduini, Fabiana; Amine, Aziz; Cacciotti, Ilaria; Moscone, Danila; Palleschi, Giuseppe

2016-10-01

We report a screen-printed electrode (SPE) modified with a dispersion of carbon black (CB) and chitosan by drop casting. A cyclic voltammetry technique towards ferricyanide, caffeic acid, hydroquinone, and thiocholine was performed and an improvement of the electrochemical response with respect to bare SPE as well as SPE modified only with chitosan was observed. The possibility to detect thiocholine at a low applied potential with high sensitivity was exploited and an acetylcholinesterase (AChE) biosensor was developed. A dispersion of CB, chitosan, and AChE was used to fabricate this biosensor in one step by drop casting. The enzymatic activity of the immobilized AChE was determined measuring the enzymatic product thiocholine at +300 mV. Owing to the capability of organophosphorus pesticides to inhibit AChE, this biosensor was used to detect these pollutants, and paraoxon was taken as model compound. The enzyme inhibition was linearly related to the concentration of paraoxon up to 0.5 μg L(-1), and a low detection limit equal to 0.05 μg L(-1) (calculated as 10% of inhibition) was achieved. This biosensor was challenged for paraoxon detection in drinking waters with satisfactory recovery values. The use of AChE embedded in a dispersion of CB and chitosan allowed an easy and fast production of a sensitive biosensor suitable for paraoxon detection in drinking waters at legal limit levels. Graphical Abstract Biosensors based on screen-printed electrodes modified with Acetylcholinesterase, Carbon Black, and Chitosan for organophosphorus pesticide detection.

HADES RV Programme with HARPS-N at TNG. II. Data treatment and simulations

NASA Astrophysics Data System (ADS)

Perger, M.; García-Piquer, A.; Ribas, I.; Morales, J. C.; Affer, L.; Micela, G.; Damasso, M.; Suárez-Mascareño, A.; González-Hernández, J. I.; Rebolo, R.; Herrero, E.; Rosich, A.; Lafarga, M.; Bignamini, A.; Sozzetti, A.; Claudi, R.; Cosentino, R.; Molinari, E.; Maldonado, J.; Maggio, A.; Lanza, A. F.; Poretti, E.; Pagano, I.; Desidera, S.; Gratton, R.; Piotto, G.; Bonomo, A. S.; Martinez Fiorenzano, A. F.; Giacobbe, P.; Malavolta, L.; Nascimbeni, V.; Rainer, M.; Scandariato, G.

2017-02-01

Context. The distribution of exoplanets around low-mass stars is still not well understood. Such stars, however, present an excellent opportunity for reaching down to the rocky and habitable planet domains. The number of current detections used for statistical purposes remains relatively modest and different surveys, using both photometry and precise radial velocities, are searching for planets around M dwarfs. Aims: Our HARPS-N red dwarf exoplanet survey is aimed at the detection of new planets around a sample of 78 selected stars, together with the subsequent characterization of their activity properties. Here we investigate the survey performance and strategy. Methods: From 2700 observed spectra, we compare the radial velocity determinations of the HARPS-N DRS pipeline and the HARPS-TERRA code, calculate the mean activity jitter level, evaluate the planet detection expectations, and address the general question of how to define the strategy of spectroscopic surveys in order to be most efficient in the detection of planets. Results: We find that the HARPS-TERRA radial velocities show less scatter and we calculate a mean activity jitter of 2.3 m s-1 for our sample. For a general radial velocity survey with limited observing time, the number of observations per star is key for the detection efficiency. In the case of an early M-type target sample, we conclude that approximately 50 observations per star with exposure times of 900 s and precisions of approximately 1 ms-1 maximizes the number of planet detections. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC).

Rapid, in situ detection of cocaine residues based on paper spray ionization coupled with ion mobility spectrometry.

PubMed

Li, Ming; Zhang, Jingjing; Jiang, Jie; Zhang, Jing; Gao, Jing; Qiao, Xiaolin

2014-04-07

In this paper, a novel approach based on paper spray ionization coupled with ion mobility spectrometry (PSI-IMS) was developed for rapid, in situ detection of cocaine residues in liquid samples and on various surfaces (e.g. glass, marble, skin, wood, fingernails), without tedious sample pretreatment. The obvious advantages of PSI are its low cost, easy operation and simple configuration without using nebulizing gas or discharge gas. Compared with mass spectrometry, ion mobility spectrometry (IMS) takes advantage of its low cost, easy operation, and simple configuration without requiring a vacuum system. Therefore, IMS is a more congruous detection method for PSI in the case of rapid, in situ analysis. For the analysis of cocaine residues in liquid samples, dynamic responses from 5 μg mL(-1) to 200 μg mL(-1) with a linear coefficient (R(2)) of 0.992 were obtained. In this case, the limit of detection (LOD) was calculated to be 2 μg mL(-1) as signal to noise (S/N) was 3 with a relative standard deviation (RSD) of 6.5% for 11 measurements (n = 11). Cocaine residues on various surfaces such as metal, glass, marble, wood, skin, and fingernails were also directly analyzed before wiping the surfaces with a piece of paper. The LOD was calculated to be as low as 5 ng (S/N = 3, RSD = 6.3%, n = 11). This demonstrates the capability of the PSI-IMS method for direct detection of cocaine residues at scenes of cocaine administration. Our results show that PSI-IMS is a simple, sensitive, rapid and economical method for in situ detection of this illicit drug, which could help governments to combat drug abuse.

New approach to the fast screening of plant oil samples for F-, Cl-, Br- and S-organic compounds on the trace level.

PubMed

Chivarzin, M E; Revelsky, I A; Nikoshina, A V; Buldyzkova, A N; Chepeliansky, D A; Revelsky, A I; Buriak, A K

2016-04-01

The fast method of the simultaneous determination of F(-), Cl(-), Br(-) and SO4(2-) anions in the deionized water on the trace level by ion chromatography using thorough cleaning of respective water containers, 10 μM NaHCO3 water solution as eluent, short Metrohm (50 × 4 mm) separation column and a large water volume injection is proposed. Calculated detection limits are 10(-9)-10(-8)% depending on the element. The method for the fast screening of plant oil samples for the total fluorine-, chlorine-, bromine- and sulfur-organic compounds content (calculated for the respective elements) on the trace level is developed. It is based on the high temperature combustion of oil sample in oxygen flow, absorption of the conversion products in deionized water and whole absorbate volume analysis for F(-), Cl(-), Br(-) and SO4(2-) anions, corresponding to the respective elements, using the developed method of these anions analysis by ion chromatography. The samples of soya, olive, sunflower and cotton seed oil were analyzed. The method detection limits (for 1mg sample) were 2 × 10(-6)%, 2 × 10(-6)%, 5 × 10(-6)% and 5 × 10(-6)% for fluorine, chlorine, bromine and sulfur, respectively. The relative standard deviation was ≤ 15%. The method gives the compressed information about the total content of all target and nontarget fluorine-, chlorine-, bromine- and sulfur-organic compounds in plant oils. Copyright © 2015. Published by Elsevier B.V.

Microcomputer aided tracking (MCAT)

NASA Astrophysics Data System (ADS)

Mays, A. B.; Cross, D. C.; Walters, J. L.

1983-07-01

The goal of the MCAT project was to investigate the effectiveness of operator initiated tracks followed by automatic tracking. Adding this capability to a display was intended to relieve operator overload and fatigue which results when the operator is limited to grease pencil tracking. MCAT combines several microprocessors and a microcomputer-driven PPI(Plan Position Indications) with graphics capability. The operator is required to make the initial detection and MCAT then performs automatic detection and tracking in a limited area centered around the detection. This approach was chosen because it is far less costly than a full-up auto detect and track approach. MCAT is intended for use in a non-NTDS (Naval Tactical Data System) environment where operator aids are minimal at best. There are approximately 200 non-NTDS ships in today's Navy. Each of these ships has a combat information center (CIC) which includes numerous PPIs typically SPA-25s, SPA-66s, SPA-50s) and various manual means (e.g., air summary plotboards, NC-2 plotters) of producing summary plots and performing calculations (e.g., maneuvering board paper) pertinent to tracks in progress. The operator's duties are time-consuming and there are many things that could be done via computer control and graphics displays that the non-NTDS operate must now do manually. Because there is much manual information handling, accumulation of data is slow and there is a large probability of error.

Evaluation of Novel Broad-Range Real-Time PCR Assay for Rapid Detection of Human Pathogenic Fungi in Various Clinical Specimens▿

PubMed Central

Vollmer, Tanja; Störmer, Melanie; Kleesiek, Knut; Dreier, Jens

2008-01-01

In the present study, a novel broad-range real-time PCR was developed for the rapid detection of human pathogenic fungi. The assay targets a part of the 28S large-subunit ribosomal RNA (rDNA) gene. We investigated its application for the most important human pathogenic fungal genera, including Aspergillus, Candida, Cryptococcus, Mucor, Penicillium, Pichia, Microsporum, Trichophyton, and Scopulariopsis. Species were identified in PCR-positive reactions by direct DNA sequencing. A noncompetitive internal control was applied to prevent false-negative results due to PCR inhibition. The minimum detection limit for the PCR was determined to be one 28S rDNA copy per PCR, and the 95% detection limit was calculated to 15 copies per PCR. To assess the clinical applicability of the PCR method, intensive-care patients with artificial respiration and patients with infective endocarditis were investigated. For this purpose, 76 tracheal secretion samples and 70 heart valve tissues were analyzed in parallel by real-time PCR and cultivation. No discrepancies in results were observed between PCR analysis and cultivation methods. Furthermore, the application of the PCR method was investigated for other clinical specimens, including cervical swabs, nail and horny skin scrapings, and serum, blood, and urine samples. The combination of a broad-range real-time PCR and direct sequencing facilitates rapid screening for fungal infection in various clinical specimens. PMID:18385440

Evaluation of novel broad-range real-time PCR assay for rapid detection of human pathogenic fungi in various clinical specimens.

PubMed

Vollmer, Tanja; Störmer, Melanie; Kleesiek, Knut; Dreier, Jens

2008-06-01

In the present study, a novel broad-range real-time PCR was developed for the rapid detection of human pathogenic fungi. The assay targets a part of the 28S large-subunit ribosomal RNA (rDNA) gene. We investigated its application for the most important human pathogenic fungal genera, including Aspergillus, Candida, Cryptococcus, Mucor, Penicillium, Pichia, Microsporum, Trichophyton, and Scopulariopsis. Species were identified in PCR-positive reactions by direct DNA sequencing. A noncompetitive internal control was applied to prevent false-negative results due to PCR inhibition. The minimum detection limit for the PCR was determined to be one 28S rDNA copy per PCR, and the 95% detection limit was calculated to 15 copies per PCR. To assess the clinical applicability of the PCR method, intensive-care patients with artificial respiration and patients with infective endocarditis were investigated. For this purpose, 76 tracheal secretion samples and 70 heart valve tissues were analyzed in parallel by real-time PCR and cultivation. No discrepancies in results were observed between PCR analysis and cultivation methods. Furthermore, the application of the PCR method was investigated for other clinical specimens, including cervical swabs, nail and horny skin scrapings, and serum, blood, and urine samples. The combination of a broad-range real-time PCR and direct sequencing facilitates rapid screening for fungal infection in various clinical specimens.

Comparison of Clean-Up Methods for Ochratoxin A on Wine, Beer, Roasted Coffee and Chili Commercialized in Italy

PubMed Central

Prelle, Ambra; Spadaro, Davide; Denca, Aleksandra; Garibaldi, Angelo; Gullino, Maria Lodovica

2013-01-01

The most common technique used to detect ochratoxin A (OTA) in food matrices is based on extraction, clean-up, and chromatography detection. Different clean-up cartridges, such as immunoaffinity columns (IAC), molecular imprinting polymers (MIP), Mycosep™ 229, Mycospin™, and Oasis® HLB (Hydrophilic Lipophilic balance) as solid phase extraction were tested to optimize the purification for red wine, beer, roasted coffee and chili. Recovery, reproducibility, reproducibility, limit of detection (LOD) and limit of quantification (LOQ) were calculated for each clean-up method. IAC demonstrated to be suitable for OTA analysis in wine and beer with recovery rate >90%, as well as Mycosep™ for wine and chili. On the contrary, MIP columns were the most appropriate to clean up coffee. A total of 120 samples (30 wines, 30 beers, 30 roasted coffee, 30 chili) marketed in Italy were analyzed, by applying the developed clean-up methods. Twenty-seven out of 120 samples analyzed (22.7%: two wines, five beers, eight coffees, and 12 chili) resulted positive to OTA. A higher incidence of OTA was found in chili (40.0%) more than wine (6.6%), beers (16.6%) and coffee (26.6%). Moreover, OTA concentration in chili was the highest detected, reaching 47.8 µg/kg. Furthermore, three samples (2.5%), two wines and one chili, exceeded the European threshold. PMID:24152987

OECD Maximum Residue Limit Calculator

EPA Pesticide Factsheets

With the goal of harmonizing the calculation of maximum residue limits (MRLs) across the Organisation for Economic Cooperation and Development, the OECD has developed an MRL Calculator. View the calculator.

Reference Intervals of Alpha-Fetoprotein and Carcinoembryonic Antigen in the Apparently Healthy Population.

PubMed

Zhang, Gao-Ming; Guo, Xu-Xiao; Ma, Xiao-Bo; Zhang, Guo-Ming

2016-12-12

BACKGROUND The aim of this study was to calculate 95% reference intervals and double-sided limits of serum alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) according to the CLSI EP28-A3 guideline. MATERIAL AND METHODS Serum AFP and CEA values were measured in samples from 26 000 healthy subjects in the Shuyang area receiving general health checkups. The 95% reference intervals and upper limits were calculated by using MedCalc. RESULTS We provided continuous reference intervals from 20 years old to 90 years old for AFP and CEA. The reference intervals were: AFP, 1.31-7.89 ng/ml (males) and 1.01-7.10 ng/ml (females); CEA, 0.51-4.86 ng/ml (males) and 0.35-3.45ng/ml (females). AFP and CEA were significantly positively correlated with age in both males (r=0.196 and r=0.198) and females (r=0.121 and r=0.197). CONCLUSIONS Different races or populations and different detection systems may result in different reference intervals for AFP and CEA. Continuous reference intervals of age changes are more accurate than age groups.

Studies on the interactions of 3,6-diaminoacridine derivatives with human serum albumin by fluorescence spectroscopy.

PubMed

Gökoğlu, Elmas; Kıpçak, Fulya; Seferoğlu, Zeynel

2014-11-01

This study reports the preparation and investigation of the modes of binding of the two symmetric 3,6-diaminoacridine derivatives obtained from proflavine, which are 3,6-diphenoxycarbonyl aminoacridine and 3,6-diethoxycarbonyl aminoacridine to human serum albumin (HSA). The interaction of HSA with the derivatives was investigated using fluorescence quenching and ultraviolet-visible absorption spectra at pH 7.2 and different temperatures. The results suggest that the derivatives used can interact strongly with HSA and are the formation of HSA-derivative complexes and hydrophobic interactions as the predominant intermolecular forces in stabilizing for each complex. The Stern-Volmer quenching constants, binding constants, binding sites and corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated at different temperatures. The binding distance (r) ~ 3 nm between the donor (HSA) and acceptors (3,6-diethoxycarbonyl aminoacridine, 3,6-diphenoxycarbonyl aminoacridine and proflavine) was obtained according to Förster's non-radiative energy transfer theory. Moreover, the limit of detection and limit of quantification of derivatives were calculated in the presence of albumin. Copyright © 2014 John Wiley & Sons, Ltd.

A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine-capped CdTe quantum dots synthesized by the reflux method.

PubMed

Ding, Xiaojie; Qu, Lingbo; Yang, Ran; Zhou, Yuchen; Li, Jianjun

2015-06-01

Cysteamine (CA)-capped CdTe quantum dots (QDs) (CA-CdTe QDs) were prepared by the reflux method and utilized as an efficient nano-sized fluorescent sensor to detect mercury (II) ions (Hg(2+) ). Under optimum conditions, the fluorescence quenching effect of CA-CdTe QDs was linear at Hg(2+) concentrations in the range of 6.0-450 nmol/L. The detection limit was calculated to be 4.0 nmol/L according to the 3σ IUPAC criteria. The influence of 10-fold Pb(2+) , Cu(2+) and Ag(+) on the determination of Hg(2+) was < 7% (superior to other reports based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA-CdTe QDs probe, which was prepared using a one-pot synthetic method. This CA-CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method. Copyright © 2014 John Wiley & Sons, Ltd.

Functional graphene-gold nano-composite fabricated electrochemical biosensor for direct and rapid detection of bisphenol A.

PubMed

Pan, Daodong; Gu, Yuanyuan; Lan, Hangzhen; Sun, Yangying; Gao, Huiju

2015-01-01

In this research, the graphene with excellent dispersity is prepared successfully by introducing gold nanoparticle to separate the individual sheets. Various techniques are adopted to characterize the prepared graphene and graphene-gold nanoparticle composite materials. This fabricated new composite material is used as the support material to construct a novel tyrosinase based biosensor for detection of bisphenol A (BPA). The electrochemical performances of the proposed new enzyme biosensor were investigated by differential pulse voltammetry (DPV) method. The proposed biosensor exhibited excellent performance for BPA determination with a wide linear range (2.5×10(-3)-3.0 μM), a highly reproducible response (RSD of 2.7%), low interferences and long-term stability. And more importantly, the calculated detection limit of the proposed biosensor was as low as 1 nM. Compared with other detection methods, this graphene-gold nanoparticle composite based tyrosinase biosensor is proved to be a promising and reliable tool for rapid detection of BPA for on-site analysis of emergency BPA related pollution affairs. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of MTBE concentrations in groundwater of urban and nonurban areas in Germany.

PubMed

Kolb, Axel; Püttmann, Wilhelm

2006-11-01

The occurrence of the gasoline oxygenate methyl tert-butyl ether (MTBE) in groundwater samples from known fuel-contaminated sites (n=29 samples), nonurban (n=74) and urban sites (n=67) in Germany was investigated. The analyses revealed detection frequencies of 58% (contaminated sites), 24% (nonurban sites) and 63% (urban sites) at a detection limit of 0.01 microgL(-1). Median (maximum) MTBE concentrations were calculated for nonurban and urban samples as 0.18 microgL(-1) (2.2 microgL(-1)) and 0.06 microgL(-1) (48 microg L(-1)). The data from nonurban samples revealed MTBE detections mainly at public supply wells with higher pumping rates than monitoring wells. MTBE was more frequently detected in urban samples, most probably due to the higher atmospheric input and direct liquid emissions from motorways or gas stations. Higher concentrations above 1.0 microgL(-1) in urban areas were found in wells located at industrial sites, where also a MTBE plume was accidentally detected during the study. The prevalence of MTBE in shallow aquifers was comparable to those in the USA.

Graphene oxide as sensitive layer in Love-wave surface acoustic wave sensors for the detection of chemical warfare agent simulants.

PubMed

Sayago, Isabel; Matatagui, Daniel; Fernández, María Jesús; Fontecha, José Luis; Jurewicz, Izabela; Garriga, Rosa; Muñoz, Edgar

2016-02-01

A Love-wave device with graphene oxide (GO) as sensitive layer has been developed for the detection of chemical warfare agent (CWA) simulants. Sensitive films were fabricated by airbrushing GO dispersions onto Love-wave devices. The resulting Love-wave sensors detected very low CWA simulant concentrations in synthetic air at room temperature (as low as 0.2 ppm for dimethyl-methylphosphonate, DMMP, a simulant of sarin nerve gas, and 0.75 ppm for dipropylene glycol monomethyl ether, DPGME, a simulant of nitrogen mustard). High responses to DMMP and DPGME were obtained with sensitivities of 3087 and 760 Hz/ppm respectively. Very low limit of detection (LOD) values (9 and 40 ppb for DMMP and DPGME, respectively) were calculated from the achieved experimental data. The sensor exhibited outstanding sensitivity, good linearity and repeatability to all simulants tested. The detection mechanism is here explained in terms of hydrogen bonding formation between the tested CWA simulants and GO. Copyright © 2015 Elsevier B.V. All rights reserved.

Sample size calculations for randomized clinical trials published in anesthesiology journals: a comparison of 2010 versus 2016.

PubMed

Chow, Jeffrey T Y; Turkstra, Timothy P; Yim, Edmund; Jones, Philip M

2018-06-01

Although every randomized clinical trial (RCT) needs participants, determining the ideal number of participants that balances limited resources and the ability to detect a real effect is difficult. Focussing on two-arm, parallel group, superiority RCTs published in six general anesthesiology journals, the objective of this study was to compare the quality of sample size calculations for RCTs published in 2010 vs 2016. Each RCT's full text was searched for the presence of a sample size calculation, and the assumptions made by the investigators were compared with the actual values observed in the results. Analyses were only performed for sample size calculations that were amenable to replication, defined as using a clearly identified outcome that was continuous or binary in a standard sample size calculation procedure. The percentage of RCTs reporting all sample size calculation assumptions increased from 51% in 2010 to 84% in 2016. The difference between the values observed in the study and the expected values used for the sample size calculation for most RCTs was usually > 10% of the expected value, with negligible improvement from 2010 to 2016. While the reporting of sample size calculations improved from 2010 to 2016, the expected values in these sample size calculations often assumed effect sizes larger than those actually observed in the study. Since overly optimistic assumptions may systematically lead to underpowered RCTs, improvements in how to calculate and report sample sizes in anesthesiology research are needed.

A SEARCH FOR MAGNESIUM IN EUROPA'S ATMOSPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoerst, S. M.; Brown, M. E., E-mail: sarah.horst@colorado.edu

Europa's tenuous atmosphere results from sputtering of the surface. The trace element composition of its atmosphere is therefore related to the composition of Europa's surface. Magnesium salts are often invoked to explain Galileo Near Infrared Mapping Spectrometer spectra of Europa's surface, thus magnesium may be present in Europa's atmosphere. We have searched for magnesium emission in the Hubble Space Telescope Faint Object Spectrograph archival spectra of Europa's atmosphere. Magnesium was not detected and we calculate an upper limit on the magnesium column abundance. This upper limit indicates that either Europa's surface is depleted in magnesium relative to sodium and potassium,more » or magnesium is not sputtered as efficiently resulting in a relative depletion in its atmosphere.« less

Fast and robust estimation of ophthalmic wavefront aberrations

NASA Astrophysics Data System (ADS)

Dillon, Keith

2016-12-01

Rapidly rising levels of myopia, particularly in the developing world, have led to an increased need for inexpensive and automated approaches to optometry. A simple and robust technique is provided for estimating major ophthalmic aberrations using a gradient-based wavefront sensor. The approach is based on the use of numerical calculations to produce diverse combinations of phase components, followed by Fourier transforms to calculate the coefficients. The approach does not utilize phase unwrapping nor iterative solution of inverse problems. This makes the method very fast and tolerant to image artifacts, which do not need to be detected and masked or interpolated as is needed in other techniques. These features make it a promising algorithm on which to base low-cost devices for applications that may have limited access to expert maintenance and operation.

Limitation of the Predominant-Period Estimator for Earthquake Early Warning and the Initial Rupture of Earthquakes

NASA Astrophysics Data System (ADS)

Yamada, T.; Ide, S.

2007-12-01

Earthquake early warning is an important and challenging issue for the reduction of the seismic damage, especially for the mitigation of human suffering. One of the most important problems in earthquake early warning systems is how immediately we can estimate the final size of an earthquake after we observe the ground motion. It is relevant to the problem whether the initial rupture of an earthquake has some information associated with its final size. Nakamura (1988) developed the Urgent Earthquake Detection and Alarm System (UrEDAS). It calculates the predominant period of the P wave (τp) and estimates the magnitude of an earthquake immediately after the P wave arrival from the value of τpmax, or the maximum value of τp. The similar approach has been adapted by other earthquake alarm systems (e.g., Allen and Kanamori (2003)). To investigate the characteristic of the parameter τp and the effect of the length of the time window (TW) in the τpmax calculation, we analyze the high-frequency recordings of earthquakes at very close distances in the Mponeng mine in South Africa. We find that values of τpmax have upper and lower limits. For larger earthquakes whose source durations are longer than TW, the values of τpmax have an upper limit which depends on TW. On the other hand, the values for smaller earthquakes have a lower limit which is proportional to the sampling interval. For intermediate earthquakes, the values of τpmax are close to their typical source durations. These two limits and the slope for intermediate earthquakes yield an artificial final size dependence of τpmax in a wide size range. The parameter τpmax is useful for detecting large earthquakes and broadcasting earthquake early warnings. However, its dependence on the final size of earthquakes does not suggest that the earthquake rupture is deterministic. This is because τpmax does not always have a direct relation to the physical quantities of an earthquake.

Shifted termination assay (STA) fragment analysis to detect BRAF V600 mutations in papillary thyroid carcinomas

PubMed Central

2013-01-01

Background BRAF mutation is an important diagnostic and prognostic marker in patients with papillary thyroid carcinoma (PTC). To be applicable in clinical laboratories with limited equipment, diverse testing methods are required to detect BRAF mutation. Methods A shifted termination assay (STA) fragment analysis was used to detect common V600 BRAF mutations in 159 PTCs with DNAs extracted from formalin-fixed paraffin-embedded tumor tissue. The results of STA fragment analysis were compared to those of direct sequencing. Serial dilutions of BRAF mutant cell line (SNU-790) were used to calculate limit of detection (LOD). Results BRAF mutations were detected in 119 (74.8%) PTCs by STA fragment analysis. In direct sequencing, BRAF mutations were observed in 118 (74.2%) cases. The results of STA fragment analysis had high correlation with those of direct sequencing (p < 0.00001, κ = 0.98). The LOD of STA fragment analysis and direct sequencing was 6% and 12.5%, respectively. In PTCs with pT3/T4 stages, BRAF mutation was observed in 83.8% of cases. In pT1/T2 carcinomas, BRAF mutation was detected in 65.9% and this difference was statistically significant (p = 0.007). Moreover, BRAF mutation was more frequent in PTCs with extrathyroidal invasion than tumors without extrathyroidal invasion (84.7% versus 62.2%, p = 0.001). To prepare and run the reactions, direct sequencing required 450 minutes while STA fragment analysis needed 290 minutes. Conclusions STA fragment analysis is a simple and sensitive method to detect BRAF V600 mutations in formalin-fixed paraffin-embedded clinical samples. Virtual Slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5684057089135749 PMID:23883275

Investigation of the Sensitivity of Transmission Raman Spectroscopy for Polymorph Detection in Pharmaceutical Tablets.

PubMed

Feng, Hanzhou; Bondi, Robert W; Anderson, Carl A; Drennen, James K; Igne, Benoît

2017-08-01

Polymorph detection is critical for ensuring pharmaceutical product quality in drug substances exhibiting polymorphism. Conventional analytical techniques such as X-ray powder diffraction and solid-state nuclear magnetic resonance are utilized primarily for characterizing the presence and identity of specific polymorphs in a sample. These techniques have encountered challenges in analyzing the constitution of polymorphs in the presence of other components commonly found in pharmaceutical dosage forms. Laborious sample preparation procedures are usually required to achieve satisfactory data interpretability. There is a need for alternative techniques capable of probing pharmaceutical dosage forms rapidly and nondestructively, which is dictated by the practical requirements of applications such as quality monitoring on production lines or when quantifying product shelf lifetime. The sensitivity of transmission Raman spectroscopy for detecting polymorphs in final tablet cores was investigated in this work. Carbamazepine was chosen as a model drug, polymorph form III is the commercial form, whereas form I is an undesired polymorph that requires effective detection. The concentration of form I in a direct compression tablet formulation containing 20% w/w of carbamazepine, 74.00% w/w of fillers (mannitol and microcrystalline cellulose), and 6% w/w of croscarmellose sodium, silicon dioxide, and magnesium stearate was estimated using transmission Raman spectroscopy. Quantitative models were generated and optimized using multivariate regression and data preprocessing. Prediction uncertainty was estimated for each validation sample by accounting for all the main variables contributing to the prediction. Multivariate detection limits were calculated based on statistical hypothesis testing. The transmission Raman spectroscopic model had an absolute prediction error of 0.241% w/w for the independent validation set. The method detection limit was estimated at 1.31% w/w. The results demonstrated that transmission Raman spectroscopy is a sensitive tool for polymorphs detection in pharmaceutical tablets.

Experimentally, How Dark Are Black Hole Mergers?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annis, James; Soares-Santos, Marcelle

2016-09-29

The first Advanced LIGO observing run detected two black hole merger events with confidence and likely a third. Many groups organized to followup the events in the optical even though the strong theoretical prior that no optical emission should be seen. We carry through the logic of this by asking about the experimental upper limits to the optical light from Advanced LIGO black hole mergere events. We inventory the published optical searches for transient events associated with the black hole mergers. We describe the factors that go into a formal limit on the visibility of an event (sky area coverage,more » the coverage factor of the camera, the fraction of sky not covered by intervening objects), and list what is known from the literature of the followup teams quantitative assessment of each factor. Where possible we calculate the total probability from each group that the source was imaged. The calculation of confidence level is reviewed for the case of no background. We find that an experimental 95% upper limit on the magnitude of a black hole requires the sum of the total probabilities over all events to be more than 3. In the first Advanced LIGO observing run we were far from reaching that threshold.« less

Tolerance limits and methodologies for IMRT measurement-based verification QA: Recommendations of AAPM Task Group No. 218.

PubMed

Miften, Moyed; Olch, Arthur; Mihailidis, Dimitris; Moran, Jean; Pawlicki, Todd; Molineu, Andrea; Li, Harold; Wijesooriya, Krishni; Shi, Jie; Xia, Ping; Papanikolaou, Nikos; Low, Daniel A

2018-04-01

Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review aimed at improving the understanding and consistency of these processes as well as recommendations for methodologies and tolerance limits in patient-specific IMRT QA. The performance of the dose difference/distance-to-agreement (DTA) and γ dose distribution comparison metrics are investigated. Measurement methods are reviewed and followed by a discussion of the pros and cons of each. Methodologies for absolute dose verification are discussed and new IMRT QA verification tools are presented. Literature on the expected or achievable agreement between measurements and calculations for different types of planning and delivery systems are reviewed and analyzed. Tests of vendor implementations of the γ verification algorithm employing benchmark cases are presented. Operational shortcomings that can reduce the γ tool accuracy and subsequent effectiveness for IMRT QA are described. Practical considerations including spatial resolution, normalization, dose threshold, and data interpretation are discussed. Published data on IMRT QA and the clinical experience of the group members are used to develop guidelines and recommendations on tolerance and action limits for IMRT QA. Steps to check failed IMRT QA plans are outlined. Recommendations on delivery methods, data interpretation, dose normalization, the use of γ analysis routines and choice of tolerance limits for IMRT QA are made with focus on detecting differences between calculated and measured doses via the use of robust analysis methods and an in-depth understanding of IMRT verification metrics. The recommendations are intended to improve the IMRT QA process and establish consistent, and comparable IMRT QA criteria among institutions. © 2018 American Association of Physicists in Medicine.

Turn-off fluorescence sensor for the detection of ferric ion in water using green synthesized N-doped carbon dots and its bio-imaging.

PubMed

Edison, Thomas Nesakumar Jebakumar Immanuel; Atchudan, Raji; Shim, Jae-Jin; Kalimuthu, Senthilkumar; Ahn, Byeong-Cheol; Lee, Yong Rok

2016-05-01

This paper reports turn-off fluorescence sensor for Fe(3+) ion in water using fluorescent N-doped carbon dots as a probe. A simple and efficient hydrothermal carbonization of Prunus avium fruit extract for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is described. This green approach proceeds quickly and provides good quality N-CDs. The mean size of synthesized N-CDs was approximately 7nm calculated from the high-resolution transmission electron microscopic images. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed the presence of -OH, -NH2, -COOH, and -CO functional groups over the surface of CDs. The N-CDs showed excellent fluorescent properties, and emitted blue fluorescence at 411nm upon excitation at 310nm. The calculated quantum yield of the synthesized N-CDs is 13% against quinine sulfate as a reference fluorophore. The synthesized N-CDs were used as a fluorescent probe towards the selective and sensitive detection of biologically important Fe(3+) ions in water by fluorescence spectroscopy and for bio-imaging of MDA-MB-231 cells. The limit of detection (LOD) and the Stern-Volmer quenching constant for the synthesized N-CDs were 0.96μM and 2.0958×10(3)M of Fe(3+) ions. The green synthesized N-CDs are efficiently used as a promising candidate for the detection of Fe(3+) ions and bio-imaging. Copyright © 2016 Elsevier B.V. All rights reserved.

On-line solid-phase microextraction of triclosan, bisphenol A, chlorophenols, and selected pharmaceuticals in environmental water samples by high-performance liquid chromatography-ultraviolet detection.

PubMed

Kim, Dalho; Han, Jungho; Choi, Yongwook

2013-01-01

A method using on-line solid-phase microextraction (SPME) on a carbowax-templated fiber followed by liquid chromatography (LC) with ultraviolet (UV) detection was developed for the determination of triclosan in environmental water samples. Along with triclosan, other selected phenolic compounds, bisphenol A, and acidic pharmaceuticals were studied. Previous SPME/LC or stir-bar sorptive extraction/LC-UV for polar analytes showed lack of sensitivity. In this study, the calculated octanol-water distribution coefficient (log D) values of the target analytes at different pH values were used to estimate polarity of the analytes. The lack of sensitivity observed in earlier studies is identified as a lack of desorption by strong polar-polar interactions between analyte and solid-phase. Calculated log D values were useful to understand or predict the interaction between analyte and solid phase. Under the optimized conditions, the method detection limit of selected analytes by using on-line SPME-LC-UV method ranged from 5 to 33 ng L(-1), except for very polar 3-chlorophenol and 2,4-dichlorophenol which was obscured in wastewater samples by an interfering substance. This level of detection represented a remarkable improvement over the conventional existing methods. The on-line SPME-LC-UV method, which did not require derivatization of analytes, was applied to the determination of TCS including phenolic compounds and acidic pharmaceuticals in tap water and river water and municipal wastewater samples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chien-Yi; Hill, Richard J.; Solon, Mikhail P.

WIMP-nucleon scattering is analyzed at ordermore » $1/M$ in Heavy WIMP Effective Theory. The $1/M$ power corrections, where $$M\\gg m_W$$ is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total $1/M$ correction, and a total cross section close to the universal limit for $$M \\gtrsim {\\rm few} \\times 100\\,{\\rm GeV}$$. For the SU(2) composite scalar, the $1/M$ corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total $1/M$ correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.« less

Direct electrochemistry and electrocatalysis of hemoglobin in graphene oxide and ionic liquid composite film.

PubMed

Sun, Wei; Gong, Shixing; Shi, Fan; Cao, Lili; Ling, Luyang; Zheng, Weizhe; Wang, Wencheng

2014-07-01

In this paper a novel sensing platform based on graphene oxide (GO), ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate and Nafion for the immobilization of hemoglobin (Hb) was adopted with a carbon ionic liquid electrode (CILE) as the substrate electrode, which was denoted as Nafion/Hb-GO-IL/CILE. Spectroscopic results suggested that Hb molecules were not denatured in the composite. A pair of well-defined redox peaks appeared on the cyclic voltammogram, which was attributed to the realization of direct electron transfer of Hb on the electrode. Electrochemical behaviors of Hb entrapped in the film were carefully investigated by cyclic voltammetry with the electrochemical parameters calculated. Based on the catalytic ability of the immobilized Hb, Nafion/Hb-GO-IL/CILE exhibited excellent electrocatalytic behavior towards the reduction of different substrates such as trichloroacetic acid in the concentration range from 0.01 to 40.0mM with the detection limit as 3.12 μM (3σ), H2O2 in the concentration range from 0.08 to 635.0 μM with the detection limit as 0.0137 μM (3σ) and NaNO2 in the concentration range from 0.5 to 800.0 μM with the detection limit as 0.0104 μM (3σ). So the proposed bioelectrode could be served as a new third-generation electrochemical sensor without mediator. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of Lipschitz Regularity and Multiscale Techniques for the Automatic Detection of Oil Spills in Synthetic Aperture Radar Imagery

NASA Astrophysics Data System (ADS)

Ajadi, O. A.; Meyer, F. J.; Tello, M.

2015-12-01

This research presents a promising new method for the detection and tracking of oil spills from Synthetic Aperture Radar (SAR) data. The method presented here combines a number of advanced image processing techniques in order to overcome some common performance limitations of SAR-based oil spill detection. Principal among these limitations are: (1) the radar cross section of the ocean surface strongly depends on wind and wave activities and is therefore highly variable; (2) the radar cross section of oil covered waters is often indistinguishable from other dark ocean features such as low wind areas or oil lookalikes, leading to ambiguities in oil spill detection. In this paper, we introduce two novel image analysis techniques to largely mitigate the aforementioned performance limitations, namely Lipschitz regularity (LR) and Wavelet transforms. We used LR, an image texture parameter akin to the slope of the local power spectrum, in our approach to mitigate these limitations. We show that the LR parameter is much less sensitive to variations of wind and waves than the original image amplitude, lending itself well for normalizing image content. Beyond its benefit for image normalization, we also show that the LR transform enhances the contrast between oil-covered and oil-free ocean surfaces and therefore improves overall spill detection performance. To calculate LR, the SAR images are decomposed using two-dimensional continuous wavelet transform (2D-CWT), which are furthermore transformed into Holder space to measure LR. Finally, we demonstrate that the implementation of wavelet transforms provide additional benefits related to the adaptive reduction of speckle noise. We show how LR and CWT are integrated into our image analysis workflow for application to oil spill detection. To describe the performance of this approach under controlled conditions, we applied our method to simulated SAR data of wind driven oceans containing oil spills of various properties. We also show applications to several real life oil spill scenarios using a series of L-band ALOS PALSAR images and X-band TerraSAR-X images acquired during the Deep Water Horizon spill in the Gulf of Mexico in 2010. From our analysis, we concluded that the LR and CWT have distinct advantages in oil spill detection and lead to high performance spill mapping results.

Analysis of the iron Kα line from 4U 1728-34 with NuSTAR and Swift

NASA Astrophysics Data System (ADS)

Sleator, Clio; Tomsick, John; King, Ashley L.; Miller, Jon M.; Boggs, Steven E.

2016-01-01

We report on a simultaneous NuSTAR and Swift observation of the neutron star low-mass X-ray binary 4U 1728-34. We detected and removed four Type 1 X-ray bursts during the observation in order to study the persistent emission. The continuum spectrum is hard and well described by a black body and cutoff power law. Residuals between 6-8 keV indicate strong evidence of a broad Fe Kα line. By modeling the spectrum with a relativistically blurred reflection model, we find an upper limit for the inner disk radius Rin ≤ 1.77 ISCO. From this upper limit, we find that RNS ≤ 20 km, assuming M=1.4M⊙ and a=0.15 (where a=cJ/GM2 is calculated from the previously measured burst oscillation frequency). We discuss how this limit could be improved for neutron star LMXBs in the future.

Exploring the detection limits of infrared near-field microscopy regarding small buried structures and pushing them by exploiting superlens-related effects.

PubMed

Jung, Lena; Hauer, Benedikt; Li, Peining; Bornhöfft, Manuel; Mayer, Joachim; Taubner, Thomas

2016-03-07

We present a study on subsurface imaging with an infrared scattering-type scanning near-field optical microscope (s-SNOM). The depth-limitation for the visibility of gold nanoparticles with a diameter of 50 nm under Si 3 N 4 is determined to about 50 nm. We first investigate spot size and signal strength concerning their particle-size dependence for a dielectric cover layer with positive permittivity. The experimental results are confirmed by model calculations and a comparison to TEM images. In the next step, we investigate spectroscopically also the regime of negative permittivity of the capping layer and its influence on lateral resolution and signal strength in experiment and simulations. The explanation of this observation combines subsurface imaging and superlensing, and shows up limitations of the latter regarding small structure sizes.

Probability of Detection of Genotyping Errors and Mutations as Inheritance Inconsistencies in Nuclear-Family Data

PubMed Central

Douglas, Julie A.; Skol, Andrew D.; Boehnke, Michael

2002-01-01

Gene-mapping studies routinely rely on checking for Mendelian transmission of marker alleles in a pedigree, as a means of screening for genotyping errors and mutations, with the implicit assumption that, if a pedigree is consistent with Mendel’s laws of inheritance, then there are no genotyping errors. However, the occurrence of inheritance inconsistencies alone is an inadequate measure of the number of genotyping errors, since the rate of occurrence depends on the number and relationships of genotyped pedigree members, the type of errors, and the distribution of marker-allele frequencies. In this article, we calculate the expected probability of detection of a genotyping error or mutation as an inheritance inconsistency in nuclear-family data, as a function of both the number of genotyped parents and offspring and the marker-allele frequency distribution. Through computer simulation, we explore the sensitivity of our analytic calculations to the underlying error model. Under a random-allele–error model, we find that detection rates are 51%–77% for multiallelic markers and 13%–75% for biallelic markers; detection rates are generally lower when the error occurs in a parent than in an offspring, unless a large number of offspring are genotyped. Errors are especially difficult to detect for biallelic markers with equally frequent alleles, even when both parents are genotyped; in this case, the maximum detection rate is 34% for four-person nuclear families. Error detection in families in which parents are not genotyped is limited, even with multiallelic markers. Given these results, we recommend that additional error checking (e.g., on the basis of multipoint analysis) be performed, beyond routine checking for Mendelian consistency. Furthermore, our results permit assessment of the plausibility of an observed number of inheritance inconsistencies for a family, allowing the detection of likely pedigree—rather than genotyping—errors in the early stages of a genome scan. Such early assessments are valuable in either the targeting of families for resampling or discontinued genotyping. PMID:11791214

Minimum detectable gas concentration performance evaluation method for gas leak infrared imaging detection systems.

PubMed

Zhang, Xu; Jin, Weiqi; Li, Jiakun; Wang, Xia; Li, Shuo

2017-04-01

Thermal imaging technology is an effective means of detecting hazardous gas leaks. Much attention has been paid to evaluation of the performance of gas leak infrared imaging detection systems due to several potential applications. The minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) are commonly used as the main indicators of thermal imaging system performance. This paper establishes a minimum detectable gas concentration (MDGC) performance evaluation model based on the definition and derivation of MDTD. We proposed the direct calculation and equivalent calculation method of MDGC based on the MDTD measurement system. We build an experimental MDGC measurement system, which indicates the MDGC model can describe the detection performance of a thermal imaging system to typical gases. The direct calculation, equivalent calculation, and direct measurement results are consistent. The MDGC and the minimum resolvable gas concentration (MRGC) model can effectively describe the performance of "detection" and "spatial detail resolution" of thermal imaging systems to gas leak, respectively, and constitute the main performance indicators of gas leak detection systems.

Simultaneous determination of seven phthalic acid esters in beverages using ultrasound and vortex-assisted dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

PubMed

Yılmaz, Pelin Köseoğlu; Ertaş, Abdulselam; Kolak, Ufuk

2014-08-01

A sensitive, rapid, and simple high-performance liquid chromatography with UV detection method was developed for the simultaneous determination of seven phthalic acid esters (dimethyl phthalate, dipropyl phthalate, di-n-butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate, di-(2-ethylhexyl) phthalate, and di-n-octyl phthalate) in several kinds of beverage samples. Ultrasound and vortex-assisted dispersive liquid-liquid microextraction method was used. The separation was performed using an Intersil ODS-3 column (C18 , 250 × 4.6 mm, 5.0 μm) and a gradient elution with a mobile phase consisting of MeOH/ACN (50:50) and 0.2 M KH2 PO4 buffer. Analytes were detected by a UV detector at 230 nm. The developed method was validated in terms of linearity, limit of detection, limit of quantification, repeatability, accuracy, and recovery. Calibration equations and correlation coefficients (> 0.99) were calculated by least squares method with weighting factor. The limit of detection and quantification were in the range of 0.019-0.208 and 0.072-0.483 μg/L. The repeatability and intermediate precision were determined in terms of relative standard deviation to be within 0.03-3.93 and 0.02-4.74%, respectively. The accuracy was found to be in the range of -14.55 to 15.57% in terms of relative error. Seventeen different beverage samples in plastic bottles were successfully analyzed, and ten of them were found to be contaminated by different phthalic acid esters. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SU-E-T-144: Effective Analysis of VMAT QA Generated Trajectory Log Files for Medical Accelerator Predictive Maintenance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Able, CM; Baydush, AH; Nguyen, C

Purpose: To determine the effectiveness of SPC analysis for a model predictive maintenance process that uses accelerator generated parameter and performance data contained in trajectory log files. Methods: Each trajectory file is decoded and a total of 131 axes positions are recorded (collimator jaw position, gantry angle, each MLC, etc.). This raw data is processed and either axis positions are extracted at critical points during the delivery or positional change over time is used to determine axis velocity. The focus of our analysis is the accuracy, reproducibility and fidelity of each axis. A reference positional trace of the gantry andmore » each MLC is used as a motion baseline for cross correlation (CC) analysis. A total of 494 parameters (482 MLC related) were analyzed using Individual and Moving Range (I/MR) charts. The chart limits were calculated using a hybrid technique that included the use of the standard 3σ limits and parameter/system specifications. Synthetic errors/changes were introduced to determine the initial effectiveness of I/MR charts in detecting relevant changes in operating parameters. The magnitude of the synthetic errors/changes was based on: TG-142 and published analysis of VMAT delivery accuracy. Results: All errors introduced were detected. Synthetic positional errors of 2mm for collimator jaw and MLC carriage exceeded the chart limits. Gantry speed and each MLC speed are analyzed at two different points in the delivery. Simulated Gantry speed error (0.2 deg/sec) and MLC speed error (0.1 cm/sec) exceeded the speed chart limits. Gantry position error of 0.2 deg was detected by the CC maximum value charts. The MLC position error of 0.1 cm was detected by the CC maximum value location charts for every MLC. Conclusion: SPC I/MR evaluation of trajectory log file parameters may be effective in providing an early warning of performance degradation or component failure for medical accelerator systems.« less

Calculation of effective penetration depth in X-ray diffraction for pharmaceutical solids.

PubMed

Liu, Jodi; Saw, Robert E; Kiang, Y-H

2010-09-01

The use of the glancing incidence X-ray diffraction configuration to depth profile surface phase transformations is of interest to pharmaceutical scientists. The Parratt equation has been used to depth profile phase changes in pharmaceutical compacts. However, it was derived to calculate 1/e penetration at glancing incident angles slightly below the critical angle of condensed matter and is, therefore, applicable to surface studies of materials such as single crystalline nanorods and metal thin films. When the depth of interest is 50-200 microm into the surface, which is typical for pharmaceutical solids, the 1/e penetration depth, or skin depth, can be directly calculated from an exponential absorption law without utilizing the Parratt equation. In this work, we developed a more relevant method to define X-ray penetration depth based on the signal detection limits of the X-ray diffractometer. Our definition of effective penetration depth was empirically verified using bilayer compacts of varying known thicknesses of mannitol and lactose.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor.

PubMed

Lan, Linxin; Li, Tianduo; Wei, Tao; Pang, He; Sun, Tao; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-03-15

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN - with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN - on the vinyl CC bond has been successfully confirmed by the optical measurements, 1 H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19μM, which is much lower than the maximum permission concentration in drinking water (1.9μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN - in field measurements. Copyright © 2017 Elsevier B.V. All rights reserved.

A ratiometric strategy -based electrochemical sensing interface for the sensitive and reliable detection of imidacloprid.

PubMed

Li, Xueyan; Kan, Xianwen

2018-04-30

In this study, a ratiometric strategy-based electrochemical sensor was developed by electropolymerization of thionine (THI) and β-cyclodextrin (β-CD) composite films on a glassy carbon electrode surface for imidacloprid (IMI) detection. THI played the role of an inner reference element to provide a built-in correction. In addition, the modified β-CD showed good selective enrichment for IMI to improve the sensitivity and anti-interference ability of the sensor. The current ratio between IMI and THI was calculated as the detected signal for IMI sensing. Compared with common single-signal sensing, the proposed ratiometric strategy showed a higher linear range and a lower limit of detection of 4.0 × 10-8-1.0 × 10-5 mol L-1 and 1.7 × 10-8 mol L-1, respectively, for IMI detection. On the other hand, the ratiometric strategy endowed the sensor with good accuracy, reproducibility, and stability. The sensor was also used for IMI determination in real samples with satisfactory results. The simple, effective, and reliable way reported in this study can be further used to prepare ratiometric strategy-based electrochemical sensors for the selective and sensitive detection of other compounds with good accuracy and stability.

A Technique for Real-Time Ionospheric Ranging Error Correction Based On Radar Dual-Frequency Detection

NASA Astrophysics Data System (ADS)

Lyu, Jiang-Tao; Zhou, Chen

2017-12-01

Ionospheric refraction is one of the principal error sources for limiting the accuracy of radar systems for space target detection. High-accuracy measurement of the ionospheric electron density along the propagation path of radar wave is the most important procedure for the ionospheric refraction correction. Traditionally, the ionospheric model and the ionospheric detection instruments, like ionosonde or GPS receivers, are employed for obtaining the electron density. However, both methods are not capable of satisfying the requirements of correction accuracy for the advanced space target radar system. In this study, we propose a novel technique for ionospheric refraction correction based on radar dual-frequency detection. Radar target range measurements at two adjacent frequencies are utilized for calculating the electron density integral exactly along the propagation path of the radar wave, which can generate accurate ionospheric range correction. The implementation of radar dual-frequency detection is validated by a P band radar located in midlatitude China. The experimental results present that the accuracy of this novel technique is more accurate than the traditional ionospheric model correction. The technique proposed in this study is very promising for the high-accuracy radar detection and tracking of objects in geospace.

Highly reproducible and sensitive silver nanorod array for the rapid detection of Allura Red in candy

NASA Astrophysics Data System (ADS)

Yao, Yue; Wang, Wen; Tian, Kangzhen; Ingram, Whitney Marvella; Cheng, Jie; Qu, Lulu; Li, Haitao; Han, Caiqin

2018-04-01

Allura Red (AR) is a highly stable synthetic red azo dye, which is widely used in the food industry to dye food and increase its attraction to consumers. However, the excessive consumption of AR can result in adverse health effects to humans. Therefore, a highly reproducible silver nanorod (AgNR) array was developed for surface enhanced Raman scattering (SERS) detection of AR in candy. The relative standard deviation (RSD) of AgNR substrate obtained from the same batch and different batches were 5.7% and 11.0%, respectively, demonstrating the high reproducibility. Using these highly reproducible AgNR arrays as the SERS substrates, AR was detected successfully, and its characteristic peaks were assigned by the density function theory (DFT) calculation. The limit of detection (LOD) of AR was determined to be 0.05 mg/L with a wide linear range of 0.8-100 mg/L. Furthermore, the AgNR SERS arrays can detect AR directly in different candy samples within 3 min without any complicated pretreatment. These results suggest the AgNR array can be used for rapid and qualitative SERS detection of AR, holding a great promise for expanding SERS application in food safety control field.

Towards quantifying global aerosol radiative effects using lidar

NASA Astrophysics Data System (ADS)

Thorsen, T. J.

2017-12-01

Spaceborne lidar observations alleviate many of the limitations of passivesensors and have great potential to provide accurate global all-sky estimatesof the aerosol direct radiative effect (DRE). However, analysis of CALIPSOlidar observations show that CALIPSO does not detect allradiatively-significant aerosol, i.e. aerosol that directly modifies theEarth's radiation budget. We estimated that using CALIPSO observationsresults in an underestimate of the magnitude of the global mean aerosol DREby up to 54%. The CATS lidar on-board the ISS is shown to have a poorersensitivity than CALIPSO and the expected sensitivity of the upcoming ATLIDlidar on EarthCARE indicates that calculations of the aerosol DRE willcontinue to be significantly biased. Improvements to our knowledge of aerosol forcing, which contributes thelargest uncertainty to climate sensitivity, could be achieved by a futurespace-based HSRL mission. To this end, high-accuracy ground-based andairborne lidar datasets have been used to compute the detection sensitivityrequired to accurately resolve the aerosol DRE. Multiwavelength HSRLmeasurements also can retrieve vertically-resolved aerosol optical propertiesneeded for radiative transfer calculations which are not provided by currentsatellite observations. Current satellite observations also do not provideall the quantities needed to compute the aerosol direct radiative forcing,i.e. the radiative effect of just anthropogenic aerosols. A multiwavelengthHSRL allows for a more refined aerosol classification to be made enablingboth calculations of anthropogenic aerosol radiative effects and betterconstraints on global models.

Ab initio simulation of diffractometer instrumental function for high-resolution X-ray diffraction1

PubMed Central

Mikhalychev, Alexander; Benediktovitch, Andrei; Ulyanenkova, Tatjana; Ulyanenkov, Alex

2015-01-01

Modeling of the X-ray diffractometer instrumental function for a given optics configuration is important both for planning experiments and for the analysis of measured data. A fast and universal method for instrumental function simulation, suitable for fully automated computer realization and describing both coplanar and noncoplanar measurement geometries for any combination of X-ray optical elements, is proposed. The method can be identified as semi-analytical backward ray tracing and is based on the calculation of a detected signal as an integral of X-ray intensities for all the rays reaching the detector. The high speed of calculation is provided by the expressions for analytical integration over the spatial coordinates that describe the detection point. Consideration of the three-dimensional propagation of rays without restriction to the diffraction plane provides the applicability of the method for noncoplanar geometry and the accuracy for characterization of the signal from a two-dimensional detector. The correctness of the simulation algorithm is checked in the following two ways: by verifying the consistency of the calculated data with the patterns expected for certain simple limiting cases and by comparing measured reciprocal-space maps with the corresponding maps simulated by the proposed method for the same diffractometer configurations. Both kinds of tests demonstrate the agreement of the simulated instrumental function shape with the measured data. PMID:26089760

Accurate potential energy curves, spectroscopic parameters, transition dipole moments, and transition probabilities of 21 low-lying states of the CO+ cation

NASA Astrophysics Data System (ADS)

Xing, Wei; Shi, Deheng; Zhang, Jicai; Sun, Jinfeng; Zhu, Zunlue

2018-05-01

This paper calculates the potential energy curves of 21 Λ-S and 42 Ω states, which arise from the first two dissociation asymptotes of the CO+ cation. The calculations are conducted using the complete active space self-consistent field method, which is followed by the valence internally contracted multireference configuration interaction approach with the Davidson correction. To improve the reliability and accuracy of the potential energy curves, core-valence correlation and scalar relativistic corrections, as well as the extrapolation of potential energies to the complete basis set limit are taken into account. The spectroscopic parameters and vibrational levels are determined. The spin-orbit coupling effect on the spectroscopic parameters and vibrational levels is evaluated. To better study the transition probabilities, the transition dipole moments are computed. The Franck-Condon factors and Einstein coefficients of some emissions are calculated. The radiative lifetimes are determined for a number of vibrational levels of several states. The transitions between different Λ-S states are evaluated. Spectroscopic routines for observing these states are proposed. The spectroscopic parameters, vibrational levels, transition dipole moments, and transition probabilities reported in this paper can be considered to be very reliable and can be used as guidelines for detecting these states in an appropriate spectroscopy experiment, especially for the states that were very difficult to observe or were not detected in previous experiments.

The instrumental method of plutonium determination

NASA Astrophysics Data System (ADS)

Knyazev, B. B.; Kazachevskiy, I. V.; Solodukhin, V. P.; Lukashenko, S. N.; Knatova, M. K.; Kashirskiy, V. V.

2003-01-01

A method of direct instrumental determination of plutonium isotopes in soil samples is described. For the method a special program of spectra processing and activity calculation had to be prepared. The detection limit of 239+240Pu in absence of interfering radiation is about 200 Bq/kg (by 3.3σ criteria). Examples are given of the method application for the study of radionuclide soil composition in separate objects of Semipalatinsk Nuclear Test Site (SNTS). It is shown that for different objects under study the correlation degree between plutonium and americium activities may change rather substantially.

The Swift/BAT Hard X-Ray Survey

NASA Technical Reports Server (NTRS)

Tueller, Jack; Markwardt, C. B.; Mushotzky, R. F.; Barthelmy, S. D.; Gehrels, N.; Krimm, H. A.; Skinner, G. K.; Falcone, A.; Kennea, J. A.

2006-01-01

The BAT instrument on Swift is a wide field (70 deg. '100 deg.) coded aperture instrument with a CdZnTe detector array sensitive to energies of 14-200 keV. Each day, the BAT survey typically covers 60% of the sky to a detection limit of 30 millicrab. BAT makes hard X-ray light curves of similar sensitivity and coverage to the X-ray light curves from XTE/ASM, but in an energy range where sources show remarkably different behavior. Integrating the BAT data produces an all sky map with a source detection limit at 15 months of a few 10(exp -11) ergs per square centimeter per second, depending on the exposure. This is the first uniform all-sky survey at energies high enough to be unaffected by absorption since HEAO 1 in 1977-8. BAT has detected greater than 200 AGN and greater than 180 galactic sources. At high galactic latitudes, the BAT sources are usually easy to identify, but many are heavily absorbed and there are a few quite surprising identifications. The BAT selected galaxies can be used to calculate LogN/LogS and the luminosity function for AGN which are complete and free from common systematics. Several crucial parameters for understanding the cosmic hard x-ray background are now determined.

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay.

PubMed

Feng, Liang; Li, Hui; Li, Xiao; Chen, Liang; Shen, Zheng; Guan, Yafeng

2012-09-19

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3×6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (K(sp)). The indicator-metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing. Copyright © 2012 Elsevier B.V. All rights reserved.

Automated system for on-line determination of dimethylarsinic and inorganic arsenic by hydride generation-atomic fluorescence spectrometry.

PubMed

Chaparro, L L; Ferrer, L; Cerdà, V; Leal, L O

2012-09-01

A multisyringe flow-injection approach has been coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS) with UV photo-oxidation for dimethylarsinic (DMA), inorganic As and total As determination, depending on the pre-treatment given to the sample (extraction or digestion). The implementation of a UV lamp allows on-line photo-oxidation of DMA and the following arsenic detection, whereas a bypass leads the flow directly to the HG-AFS system, performing inorganic arsenic determination. DMA concentration is calculated by the difference of total inorganic arsenic and measurement of the photo-oxidation step. The detection limits for DMA and inorganic arsenic were 0.09 and 0.47 μg L(-1), respectively. The repeatability values accomplished were of 2.4 and 1.8%, whereas the injection frequencies were 24 and 28 injections per hour for DMA and inorganic arsenic, respectively. This method was validated by means of a solid reference material BCR-627 (muscle of tuna) with good agreement with the certified values. Satisfactory results for DMA and inorganic arsenic determination were obtained in several water matrices. The proposed method offers several advantages, such as increasing the sampling frequency, low detection limits and decreasing reagents and sample consumption, which leads to lower waste generation.

Analysis of explosives using corona discharge ionization combined with ion mobility spectrometry-mass spectrometry.

PubMed

Lee, Jihyeon; Park, Sehwan; Cho, Soo Gyeong; Goh, Eun Mee; Lee, Sungman; Koh, Sung-Suk; Kim, Jeongkwon

2014-03-01

Corona discharge ionization combined with ion mobility spectrometry-mass spectrometry (IMS-MS) was utilized to investigate five common explosives: cyclonite (RDX), trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotetramethylenetetranitramine (HMX), and 2,4-dinitrotoluene (DNT). The MS scan and the selected ion IMS analyses confirmed the identities of the existing ion species and their drift times. The ions observed were RDX·NO3(-), TNT(-), PETN·NO3(-), HMX·NO3(-), and DNT(-), with average drift times of 6.93 ms, 10.20 ms, 9.15 ms, 12.24 ms, 11.30 ms, and 8.89 ms, respectively. The reduced ion mobility values, determined from a standard curve calculated by linear regression of (normalized drift times)(-1) versus literature K0 values, were 2.09, 1.38, 1.55, 1.15, 1.25, and 1.60 cm(2) V(-1) s(-1), respectively. The detection limits were found to be 0.1 ng for RDX, 10 ng for TNT, 0.5 ng for PETN, 5.0 ng for HMX, and 10 ng for DNT. Simplified chromatograms were observed when nitrogen, as opposed to air, was used as the drift gas, but the detection limits were approximately 10 times worse (i.e., less sensitivity of detection). © 2013 Elsevier B.V. All rights reserved.

Optical readout of displacements of nanowires along two mutually perpendicular directions

NASA Astrophysics Data System (ADS)

Fu, Chenghua

2017-05-01

Nanowires are good force transducers due to their low mass. The singleness of the direction of the motion detection in a certain system is an existing limitation, and to overcome the limitation is the key point in this article. Optical methods, such as polarized light interferometry and light scattering, are generally used for detecting the displacement of nanowires. Typically, either light interference or light scattering is considered when relating the displacement of a nanowire with the photodetector's measurements. In this work, we consider both the light interference along the optical axis and light scattering perpendicular to the optical axis of a micro-lens fiber optic interferometer. Identifying the displacement along the two directions and the corresponding vibration conversion efficiency coefficients for the nanowire is a significant part of our study. Our analysis shows that the optimal working point of the micro-lens fiber optic interferometer can realize the detection of displacement along the optical axis without the disturbance coming from the motion perpendicular to the optical axis, and vice versa. We use Mie scattering theory to calculate the scattering light for the reason that the size of the nanowire is comparable to the wavelength of light. Our results could provide a guide for optical readout experiments of the displacement of nanowires.

Measurement of K-27, an oxime-type cholinesterase reactivator by high-performance liquid chromatography with electrochemical detection from different biological samples.

PubMed

Gyenge, Melinda; Kalász, Huba; Petroianu, George A; Laufer, Rudolf; Kuca, Kamil; Tekes, Kornélia

2007-08-17

K-27 is a bisquaternary asymmetric pyridinium aldoxime-type cholinesterase reactivator of use in the treatment of poisoning with organophosphorous esterase inhibitors. A sensitive, simple and reliable reverse-phase high-performance liquid chromatographic method with electrochemical detection was developed for the measurement of K-27 concentrations in rat brain, cerebrospinal fluid, serum and urine samples. Male Wistar rats were treated intramuscularly with K-27 and the samples were collected 60 min later. Separation was carried out on an octadecyl silica stationary phase and a disodium phosphate solution (pH 3.7) containing citric acid, octane sulphonic acid and acetonitrile served as mobile phase. Measurements were carried out at 30 degrees C at E(ox) 0.65 V. The calibration curve was linear through the range of 10-250 ng/mL. Accuracy, precision and the limit of detection calculated were satisfactory according to internationally accepted criteria. Limit of quantitation was 10 ng/mL. The method developed is reliable and sensitive enough for monitoring K-27 levels from different biological samples including as little as 10 microL of cerebrospinal fluid. The method--with slight modification in the composition of the mobile phase--can be used to measure a wide range of other related pyridinium aldoxime-type cholinesterase reactivators.

Fluorescence calibration method for single-particle aerosol fluorescence instruments

NASA Astrophysics Data System (ADS)

Shipley Robinson, Ellis; Gao, Ru-Shan; Schwarz, Joshua P.; Fahey, David W.; Perring, Anne E.

2017-05-01

Real-time, single-particle fluorescence instruments used to detect atmospheric bioaerosol particles are increasingly common, yet no standard fluorescence calibration method exists for this technique. This gap limits the utility of these instruments as quantitative tools and complicates comparisons between different measurement campaigns. To address this need, we have developed a method to produce size-selected particles with a known mass of fluorophore, which we use to calibrate the fluorescence detection of a Wideband Integrated Bioaerosol Sensor (WIBS-4A). We use mixed tryptophan-ammonium sulfate particles to calibrate one detector (FL1; excitation = 280 nm, emission = 310-400 nm) and pure quinine particles to calibrate the other (FL2; excitation = 280 nm, emission = 420-650 nm). The relationship between fluorescence and mass for the mixed tryptophan-ammonium sulfate particles is linear, while that for the pure quinine particles is nonlinear, likely indicating that not all of the quinine mass contributes to the observed fluorescence. Nonetheless, both materials produce a repeatable response between observed fluorescence and particle mass. This procedure allows users to set the detector gains to achieve a known absolute response, calculate the limits of detection for a given instrument, improve the repeatability of the instrumental setup, and facilitate intercomparisons between different instruments. We recommend calibration of single-particle fluorescence instruments using these methods.

Ultrahigh polarimetric image contrast enhancement for skin cancer diagnosis using InN plasmonic nanoparticles in the terahertz range

NASA Astrophysics Data System (ADS)

Ney, Michael; Abdulhalim, Ibrahim

2015-12-01

Mueller matrix imaging sensitivity, to delicate water content changes in tissue associated with early stages of skin cancer, is demonstrated by numerical modeling to be enhanced by localized surface plasmon resonance (LSPR) effects at the terahertz (THz) range when InN nanoparticles (NPs) coated with Parylene-C are introduced into the skin. A skin tissue model tailored for THz wavelengths is established for a Monte Carlo simulation of polarized light propagation and scattering, and a comparative study based on simulated Mueller matrices is presented considering different NPs' parameters and insertion into the skin methods. The insertion of NPs presenting LSPR in the THz is demonstrated to enable the application of polarization-based sample characterization techniques adopted from the scattering dominated visible wavelengths domain for the, otherwise, relatively low scattering THz domain, where such approach is irrelevant without the NPs. Through these Mueller polarimetry techniques, the detection of water content variations in the tissue is made possible and with high sensitivity. This study yields a limit of detection down to 0.0018% for relative changes in the water content based on linear degree of polarization-an improvement of an order of magnitude relative to the limit of detection without NPs calculated in a previous ellipsometric study.

Ultrahigh polarimetric image contrast enhancement for skin cancer diagnosis using InN plasmonic nanoparticles in the terahertz range.

PubMed

Ney, Michael; Abdulhalim, Ibrahim

2015-01-01

Mueller matrix imaging sensitivity, to delicate water content changes in tissue associated with early stages of skin cancer, is demonstrated by numerical modeling to be enhanced by localized surface plasmon resonance (LSPR) effects at the terahertz (THz) range when InN nanoparticles (NPs) coated with Parylene-C are introduced into the skin. A skin tissue model tailored for THz wavelengths is established for a Monte Carlo simulation of polarized light propagation and scattering, and a comparative study based on simulated Mueller matrices is presented considering different NPs’ parameters and insertion into the skin methods. The insertion of NPs presenting LSPR in the THz is demonstrated to enable the application of polarization-based sample characterization techniques adopted from the scattering dominated visible wavelengths domain for the, otherwise, relatively low scattering THz domain, where such approach is irrelevant without the NPs. Through these Mueller polarimetry techniques, the detection of water content variations in the tissue is made possible and with high sensitivity. This study yields a limit of detection down to 0.0018% for relative changes in the water content based on linear degree of polarization--an improvement of an order of magnitude relative to the limit of detection without NPs calculated in a previous ellipsometric study.

Green synthesis of carbon dots functionalized silver nanoparticles for the colorimetric detection of phoxim.

PubMed

Zheng, Mingda; Wang, Chenge; Wang, Yingying; Wei, Wei; Ma, Shuang; Sun, Xiaohan; He, Jiang

2018-08-01

In this work, Lycii Fructus as raw materials for green synthesis of fluorescent carbon dots (CDs) reduce AgNO 3 . The CDs-AgNPs were synthesized by one-step method. CDs were applied to stabilize AgNPs due to abundant functional groups on the surface of CDs. In presence of phoxim, the dispersed CDs-AgNPs get aggregated and the absorption peak with red shift from 400 nm to 525 nm, resulting in the color changed from yellow to red. Under optimized conditions, the absorbance ratio at A 525 nm /A 400 nm was related linearly to the concentrations of phoxim in the range of 0.1-100 μM. The detection limit was calculated to 0.04 μM, which is lower than maximum residue limits of phoxim in samples in China. The colorimetric sensor was successfully utilized to monitoring phoxim in environmental and fruit samples with good recoveries ranges from 87% to 110.0%. These results showed the sensor had a promising application prospect in real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

The Use and Abuse of Limits of Detection in Environmental Analytical Chemistry

PubMed Central

Brown, Richard J. C.

2008-01-01

The limit of detection (LoD) serves as an important method performance measure that is useful for the comparison of measurement techniques and the assessment of likely signal to noise performance, especially in environmental analytical chemistry. However, the LoD is only truly related to the precision characteristics of the analytical instrument employed for the analysis and the content of analyte in the blank sample. This article discusses how other criteria, such as sampling volume, can serve to distort the quoted LoD artificially and make comparison between various analytical methods inequitable. In order to compare LoDs between methods properly, it is necessary to state clearly all of the input parameters relating to the measurements that have been used in the calculation of the LoD. Additionally, the article discusses that the use of LoDs in contexts other than the comparison of the attributes of analytical methods, in particular when reporting analytical results, may be confusing, less informative than quoting the actual result with an accompanying statement of uncertainty, and may act to bias descriptive statistics. PMID:18690384

Rapid and simple method for the determination of emodin in tartary buckwheat (Fagopyrum tataricum) by high-performance liquid chromatography coupled to a diode array detector.

PubMed

Peng, Lian-Xin; Wang, Jing-Bo; Hu, Li-Xue; Zhao, Jiang-Lin; Xiang, Da-Bing; Zou, Liang; Zhao, Gang

2013-01-30

A simple and rapid method for determining emodin, an active factor presented in tartary buckwheat (Fagopyrum tataricum), by high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD) has been developed. Emodin was separated from an extract of buckwheat on a Kromasil-ODS C(18) (250 mm × 4.6 mm × 5 μm) column. The separation is achieved within 15 min on the ODS column. Emodin can be quantified using an external standard method detecting at 436 nm. Good linearity is obtained with a correlation coefficient exceeding 0.9992. The limit of detection and the limit of quantification are 5.7 and 19 μg/L, respectively. This method shows good reproducibility for the quantification of the emodin with a relative standard deviation value of 4.3%. Under optimized extraction conditions, the recovery of emodin was calculated as >90%. The validated method is successfully applied to quantify the emodin in tartary buckwheat and its products.

Evaluation of Radiation Doses Due to Consumption of Contaminated Food Items and Calculation of Food Class-Specific Derived Intervention Levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinzelman, K M; Mansfield, W G

This document evaluates the expected radiation dose due to the consumption of several specific food classes (dairy, meat, produce, etc.) contaminated with specific radionuclides, and relates concentration levels in food to the detection abilities of typical aboratory analysis/measurement methods. The attached charts present the limiting organ dose as a function of the radionuclide concentration in a particular food class, and allow the user to compare these concentrations and doses to typical analytical detection apabilities. The expected radiation dose depends on several factors: the age of the individual; the radionuclide present in the food; the concentration of the radionuclide in themore » food; and the amount of food consumed. Food consumption rates for individuals of various ges were taken from the 1998 United States Food and Drug Administration (FDA) document, Accidental Radioactive Contamination of HUman Food and Animal Feeds: Recommendations for State and Local Agencies. In that document, the FDA defines the erived Intervention Level (DIL), which is the concentration of a particular radionuclide in food that if consumed could result in an individual receiving a radiation dose exceeding the Protection Action Guide (PAG) thresholds for intervention. This document also resents odified, food class specific DIL, which is calculated using a somewhat modified version of the FDA's procedure. This document begins with an overview of the FDA's DIL calculation, followed by a description of the food class specific DIL calculations, and finally charts of the radiation dose per radioactivity concentration for several food class/radionuclide combinations.« less

Decision support methods for the detection of adverse events in post-marketing data.

PubMed

Hauben, M; Bate, A

2009-04-01

Spontaneous reporting is a crucial component of post-marketing drug safety surveillance despite its significant limitations. The size and complexity of some spontaneous reporting system databases represent a challenge for drug safety professionals who traditionally have relied heavily on the scientific and clinical acumen of the prepared mind. Computer algorithms that calculate statistical measures of reporting frequency for huge numbers of drug-event combinations are increasingly used to support pharamcovigilance analysts screening large spontaneous reporting system databases. After an overview of pharmacovigilance and spontaneous reporting systems, we discuss the theory and application of contemporary computer algorithms in regular use, those under development, and the practical considerations involved in the implementation of computer algorithms within a comprehensive and holistic drug safety signal detection program.

The Limits of Coding with Joint Constraints on Detected and Undetected Error Rates

NASA Technical Reports Server (NTRS)

Dolinar, Sam; Andrews, Kenneth; Pollara, Fabrizio; Divsalar, Dariush

2008-01-01

We develop a remarkably tight upper bound on the performance of a parameterized family of bounded angle maximum-likelihood (BA-ML) incomplete decoders. The new bound for this class of incomplete decoders is calculated from the code's weight enumerator, and is an extension of Poltyrev-type bounds developed for complete ML decoders. This bound can also be applied to bound the average performance of random code ensembles in terms of an ensemble average weight enumerator. We also formulate conditions defining a parameterized family of optimal incomplete decoders, defined to minimize both the total codeword error probability and the undetected error probability for any fixed capability of the decoder to detect errors. We illustrate the gap between optimal and BA-ML incomplete decoding via simulation of a small code.

A highly selective colorimetric and fluorescent chemosensor for Al(III) based-on simple naphthol in aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Zhaodi; Xu, Huajie; Sheng, Liangquan; Chen, Shuisheng; Huang, Deqian; Liu, Jie

2016-03-01

A colorimetric and fluorescent chemosensor (L) for Al(III) was synthesized and fully characterized. L could be both used as a colorimetric and fluorescent chemosensor for the detection of Al3 + ions with low detection limit (8.87 × 10- 7 M) in CH3CN-H2O (1:1, v/v) solution. The binding ratio of L-Al3 + was determined from the Job plot (absorption and fluorescence spectra) and MALDI-TOF MS data to be 1:1. The binding constant (Ka) of Al3 + binding to L was calculated to be 4.8 × 105 M- 1 from a Benesi-Hildebrand plot. Moreover, the binding site of L with Al3 + was determined by 1H NMR titration experiment.

MODELING THE NON-RECYCLED FERMI GAMMA-RAY PULSAR POPULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perera, B. B. P.; McLaughlin, M. A.; Cordes, J. M.

2013-10-10

We use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L{sub γ} depends on the period P and the period derivative P-dot . We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L{sub γ} on P and P-dot , including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is L{sub γ}∝P{sup -a} P-dot {sup b} where a = 1.36 ± 0.03 and b = 0.44 ± 0.02, similar tomore » but not identical to the commonly assumed L{sub γ}∝√( E-dot )∝P{sup -1.5} P-dot {sup 0.5}. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7π for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2σ upper limit on the average braking index and a 2σ lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 × 10{sup 10} G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the 2 yr sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected 5 yr sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. We note that these predictions significantly depend on our model assumptions.« less

Estimative of conversion fractions of AGN magnetic luminosity to produce ultra high energy cosmic rays from the observation of Fermi-LAT gamma rays

NASA Astrophysics Data System (ADS)

Coimbra-Araújo, Carlos H.; Anjos, Rita C.

2017-01-01

A fraction of the magnetic luminosity (LB) produced by Kerr black holes in some active galactic nuclei (AGNs) can produce the necessary energy to accelerate ultra high energy cosmic rays (UHECRs) beyond the GZK limit, observed, e.g., by the Pierre Auger experiment. Nevertheless, the direct detection of those UHECRs has a lack of information about the direction of the source from where those cosmic rays are coming, since charged particles are deflected by the intergalactic magnetic field. This problem arises the needing of alternative methods to evaluate the luminosity of UHECRs (LCR) from a given source. Methods proposed in literature range from the observation of upper limits in gamma rays to the observation of upper limits in neutrinos produced by cascade effects during the propagation of UHECRs. In this aspect, the present work proposes a method to calculate limits of the main possible conversion fractions ηCR = LCR/LB for nine UHECR AGN Seyfert sources based on the respective observation of gamma ray upper limits from Fermi-LAT data.

Automated detection of Martian water ice clouds: the Valles Marineris

NASA Astrophysics Data System (ADS)

Ogohara, Kazunori; Munetomo, Takafumi; Hatanaka, Yuji; Okumura, Susumu

2016-10-01

We need to extract water ice clouds from the large number of Mars images in order to reveal spatial and temporal variations of water ice cloud occurrence and to meteorologically understand climatology of water ice clouds. However, visible images observed by Mars orbiters for several years are too many to visually inspect each of them even though the inspection was limited to one region. Therefore, an automated detection algorithm of Martian water ice clouds is necessary for collecting ice cloud images efficiently. In addition, it may visualize new aspects of spatial and temporal variations of water ice clouds that we have never been aware. We present a method for automatically evaluating the presence of Martian water ice clouds using difference images and cross-correlation distributions calculated from blue band images of the Valles Marineris obtained by the Mars Orbiter Camera onboard the Mars Global Surveyor (MGS/MOC). We derived one subtracted image and one cross-correlation distribution from two reflectance images. The difference between the maximum and the average, variance, kurtosis, and skewness of the subtracted image were calculated. Those of the cross-correlation distribution were also calculated. These eight statistics were used as feature vectors for training Support Vector Machine, and its generalization ability was tested using 10-fold cross-validation. F-measure and accuracy tended to be approximately 0.8 if the maximum in the normalized reflectance and the difference of the maximum and the average in the cross-correlation were chosen as features. In the process of the development of the detection algorithm, we found many cases where the Valles Marineris became clearly brighter than adjacent areas in the blue band. It is at present unclear whether the bright Valles Marineris means the occurrence of water ice clouds inside the Valles Marineris or not. Therefore, subtracted images showing the bright Valles Marineris were excluded from the detection of water ice clouds

LH launcher Arcs Formation and Detection on JET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baranov, Yu. F.; Challis, C. D.; Kirov, K.

2011-12-23

Mechanisms of arc formation have been analyzed and the critical electric fields for the multipactor effect calculated, compared to the experimental values and found to be within the normal operational space of the LH system on JET. It has been shown that the characteristic electron energy (20-1000)eV for the highest multipactor resonances (N = 4-9) are within the limits of secondary electron yield above 1 required for multipactoring. Electrons with these energies provide the highest gas desorption efficiency when hitting the waveguide walls. The effect of higher waveguide modes and magnetic field on the multipactor was also considered. The distributionmore » function for electrons accelerated by LH waves in front of the launcher has been calculated. The field emission currents have been estimated and found to be small. It is proposed that emission of Fel5, 16 lines, which can be obtained with improved diagnostics, could be used to detect arcs that are missed by a protection system based on the reflected power. The reliability and time response of these signals are discussed. A similar technique based on the observation of the emission of low ionized atoms can be used for a fast detection of other undesirable events to avoid sputtering or melting of the plasma facing components such as RF antenna. These techniques are especially powerful if they are based on emission uniquely associated with specific locations and components.« less

Transdiagnostic Risk Calculator for the Automatic Detection of Individuals at Risk and the Prediction of Psychosis: Second Replication in an Independent National Health Service Trust.

PubMed

Fusar-Poli, Paolo; Werbeloff, Nomi; Rutigliano, Grazia; Oliver, Dominic; Davies, Cathy; Stahl, Daniel; McGuire, Philip; Osborn, David

2018-06-12

The benefits of indicated primary prevention among individuals at Clinical High Risk for Psychosis (CHR-P) are limited by the difficulty in detecting these individuals. To overcome this problem, a transdiagnostic, clinically based, individualized risk calculator has recently been developed and subjected to a first external validation in 2 different catchment areas of the South London and Maudsley (SLaM) NHS Trust. Second external validation of real world, real-time electronic clinical register-based cohort study. All individuals who received a first ICD-10 index diagnosis of nonorganic and nonpsychotic mental disorder within the Camden and Islington (C&I) NHS Trust between 2009 and 2016 were included. The model previously validated included age, gender, ethnicity, age by gender, and ICD-10 index diagnosis to predict the development of any ICD-10 nonorganic psychosis. The model's performance was measured using Harrell's C-index. This study included a total of 13702 patients with an average age of 40 (range 16-99), 52% were female, and most were of white ethnicity (64%). There were no CHR-P or child/adolescent services in the C&I Trust. The C&I and SLaM Trust samples also differed significantly in terms of age, gender, ethnicity, and distribution of index diagnosis. Despite these significant differences, the original model retained an acceptable predictive performance (Harrell's C of 0.73), which is comparable to that of CHR-P tools currently recommended for clinical use. This risk calculator may pragmatically support an improved transdiagnostic detection of at-risk individuals and psychosis prediction even in NHS Trusts in the United Kingdom where CHR-P services are not provided.

Characterization of the Oxidation State of 229 Th Recoils Implanted in MgF2 for the Search of the Low-lying 229 Th Isomeric State

NASA Astrophysics Data System (ADS)

Barker, Beau; Meyer, Edmund; Schacht, Mike; Collins, Lee; Wilkerson, Marianne; Zhao, Xinxin

2016-05-01

The low-lying (7.8 eV) isomeric state in 229 Th has the potential to become a nuclear frequency standard. 229 Th recoils from 233 U decays have been collected in MgF2 for use in the direct search of the transition. Of interest is the oxidation state of the implanted 229 Th atoms as this can have an influence on the decay mechanisms and photon emission rate. Too determine the oxidation state of the implanted 229 Th recoils we have employed laser induced florescence (LIF), and plan-wave pseudopotential DFT calculations to search for emission from thorium ions in oxidation states less than + 4. Our search focused on detecting emission from Th3+ ions. The DFT calculations predicted the Th3+ state to be the most likely to be present in the crystal after Th4+. We also calculated the band structure for the Th3+ doped MgF2 crystal. For LIF spectra a number of excitation wavelengths were employed, emission spectra in the visible to near-IR were recorded along with time-resolved emission spectra. We have found no evidence for Th3+ in the MgF2 plates. We also analyzed the detection limit of our apprentice and found that the minimum number of Th3+ atoms that we could detect is quite small compared to the number of implanted 229 Th recoils. The number of implanted 229 Th recoils was derived from a γ-ray spectrum by monitoring emission from the daughters of 228 Th. These were present in the MgF2 plates due to a 232 U impurity, which decays to 228 Th, in the source. LA-UR-16-20442.

Low-Level Detection of a Bacillus Anthracis Simulant using Love-Wave Biosensors on 36 Degree YX LiTaO3

DOE Office of Scientific and Technical Information (OSTI.GOV)

BRANCH,DARREN W.; BROZIK,SUSAN M.

Crucial to low-level detection of biowarfare agents in aqueous environments is the mass sensitivity optimization of Love-wave acoustic sensors. The present work is an experimental study of 36{sup o} YX cut LiTaO{sub 3} based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit (DL) of Love-wave based sensors is a strong function of the overlying waveguide, two waveguide materials have been investigated, which are polyimide and polystyrene. To determine the mass sensitivity of Love-wave sensor, bovine serum albumin (BSA) protein was injected into the Love-wave test cell while recording magnitude and phase shift acrossmore » each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1-2 ng/cm{sup 2}, as compared to polystyrene where DL = 2.0 ng/cm{sup 2}. Suitable chemistries were used to orient antibodies on the Love-wave sensor using adsorbed protein G. The thickness of each biofilm was measured using ellipsometry from which the surface concentrations were calculated. The monoclonal antibody BD8 with a high degree of selectivity for anthrax spores was used to capture the non-pathogenic simulant B. thuringiensis B8 spores. Bacillus Subtilis spores were used as a negative control to determine whether significant non-specific binding would occur. Spore aliquots were prepared using an optical counting method, which permitted removal of background particles for consistent sample preparation. This work demonstrates that Love-wave devices can be used to detect B. anthracis simulant below reported infectious levels.« less

A methodology for spectral wave model evaluation

NASA Astrophysics Data System (ADS)

Siqueira, S. A.; Edwards, K. L.; Rogers, W. E.

2017-12-01

Model evaluation is accomplished by comparing bulk parameters (e.g., significant wave height, energy period, and mean square slope (MSS)) calculated from the model energy spectra with those calculated from buoy energy spectra. Quality control of the observed data and choice of the frequency range from which the bulk parameters are calculated are critical steps in ensuring the validity of the model-data comparison. The compared frequency range of each observation and the analogous model output must be identical, and the optimal frequency range depends in part on the reliability of the observed spectra. National Data Buoy Center 3-m discus buoy spectra are unreliable above 0.3 Hz due to a non-optimal buoy response function correction. As such, the upper end of the spectrum should not be included when comparing a model to these data. Bioufouling of Waverider buoys must be detected, as it can harm the hydrodynamic response of the buoy at high frequencies, thereby rendering the upper part of the spectrum unsuitable for comparison. An important consideration is that the intentional exclusion of high frequency energy from a validation due to data quality concerns (above) can have major implications for validation exercises, especially for parameters such as the third and fourth moments of the spectrum (related to Stokes drift and MSS, respectively); final conclusions can be strongly altered. We demonstrate this by comparing outcomes with and without the exclusion, in a case where a Waverider buoy is believed to be free of biofouling. Determination of the appropriate frequency range is not limited to the observed spectra. Model evaluation involves considering whether all relevant frequencies are included. Guidance to make this decision is based on analysis of observed spectra. Two model frequency lower limits were considered. Energy in the observed spectrum below the model lower limit was calculated for each. For locations where long swell is a component of the wave climate, omitting the energy in the frequency band between the two lower limits tested can lead to an incomplete characterization of model performance. This methodology was developed to aid in selecting a comparison frequency range that does not needlessly increase computational expense and does not exclude energy to the detriment of model performance analysis.

The Detection Rate of Early UV Emission from Supernovae: A Dedicated Galex/PTF Survey and Calibrated Theoretical Estimates

NASA Astrophysics Data System (ADS)

Ganot, Noam; Gal-Yam, Avishay; Ofek, Eran. O.; Sagiv, Ilan; Waxman, Eli; Lapid, Ofer; Kulkarni, Shrinivas R.; Ben-Ami, Sagi; Kasliwal, Mansi M.; The ULTRASAT Science Team; Chelouche, Doron; Rafter, Stephen; Behar, Ehud; Laor, Ari; Poznanski, Dovi; Nakar, Ehud; Maoz, Dan; Trakhtenbrot, Benny; WTTH Consortium, The; Neill, James D.; Barlow, Thomas A.; Martin, Christofer D.; Gezari, Suvi; the GALEX Science Team; Arcavi, Iair; Bloom, Joshua S.; Nugent, Peter E.; Sullivan, Mark; Palomar Transient Factory, The

2016-03-01

The radius and surface composition of an exploding massive star, as well as the explosion energy per unit mass, can be measured using early UV observations of core-collapse supernovae (SNe). We present the first results from a simultaneous GALEX/PTF search for early ultraviolet (UV) emission from SNe. Six SNe II and one Type II superluminous SN (SLSN-II) are clearly detected in the GALEX near-UV (NUV) data. We compare our detection rate with theoretical estimates based on early, shock-cooling UV light curves calculated from models that fit existing Swift and GALEX observations well, combined with volumetric SN rates. We find that our observations are in good agreement with calculated rates assuming that red supergiants (RSGs) explode with fiducial radii of 500 R ⊙, explosion energies of 1051 erg, and ejecta masses of 10 M ⊙. Exploding blue supergiants and Wolf-Rayet stars are poorly constrained. We describe how such observations can be used to derive the progenitor radius, surface composition, and explosion energy per unit mass of such SN events, and we demonstrate why UV observations are critical for such measurements. We use the fiducial RSG parameters to estimate the detection rate of SNe during the shock-cooling phase (<1 day after explosion) for several ground-based surveys (PTF, ZTF, and LSST). We show that the proposed wide-field UV explorer ULTRASAT mission is expected to find >85 SNe per year (˜0.5 SN per deg2), independent of host galaxy extinction, down to an NUV detection limit of 21.5 mag AB. Our pilot GALEX/PTF project thus convincingly demonstrates that a dedicated, systematic SN survey at the NUV band is a compelling method to study how massive stars end their life.

The techniques of quality operations computational and experimental researches of the launch vehicles in the drawing-board stage

NASA Astrophysics Data System (ADS)

Rozhaeva, K.

2018-01-01

The aim of the researchis the quality operations of the design process at the stage of research works on the development of active on-Board system of the launch vehicles spent stages descent with liquid propellant rocket engines by simulating the gasification process of undeveloped residues of fuel in the tanks. The design techniques of the gasification process of liquid rocket propellant components residues in the tank to the expense of finding and fixing errors in the algorithm calculation to increase the accuracy of calculation results is proposed. Experimental modelling of the model liquid evaporation in a limited reservoir of the experimental stand, allowing due to the false measurements rejection based on given criteria and detected faults to enhance the results reliability of the experimental studies; to reduce the experiments cost.

Online Serum PFOA Calculator for Adults

PubMed Central

2017-01-01

Summary: Perfluorooctanoic acid (PFOA) is a persistent environmental contaminant that has been detected in >100 public water systems in the United States alone. A variety of epidemiological investigations of PFOA have been published, mostly using measured or modeled serum PFOA concentrations as the exposure metric. Comparison of drinking water PFOA concentrations to those study findings or to typical serum concentrations requires pharmacokinetic modeling. This brief communication describes an online Javascript calculator that easily plots the expected serum PFOA concentration over time and at steady state for adults after starting or stopping consumption of PFOA-contaminated water. Two examples of usage are provided, including increasing serum PFOA after ongoing consumption of contaminated water at the federal limit, and decreasing serum PFOA after carbon filtration began in a contaminated water system. https://doi.org/10.1289/EHP2820 PMID:29068316

Determination of (210)Pb and (210)Po in water using the extractive scintillation cocktail Polex™.

PubMed

Landstetter, Claudia; Hiegesberger, Bernd; Sinojmeri, Merita; Katzlberger, Christian

2014-11-01

Method validation was performed to achieve the accreditation for our determination method of (210)Pb and (210)Po in water. A Pb(NO3)2 carrier is added to the sample and lead is precipitated with Na2SxH2O. (210)Po is co-precipitated and the extractive scintillation cocktail Polex(™) is used to determine (210)Po and (210)Pb. Uranium is also extracted by Polex(™). It can be removed by washing the precipitate with 1% HNO3. The ingrowth of (210)Pb from (222)Rn during transportation time must be calculated. It has to be subtracted from the original (210)Pb in the sample and taken into account for the calculation of the lower limit of detection. Copyright © 2014 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penner, J.E.

The magnitude of the chlorofluoromethane (CFM) induced depletion of the ozone layer is considered a key problem in atmospheric research. The historical rise in the atmospheric concentrations of CFCl/sub 3/, and CF/sub 2/Cl/sub 2/, the major CFM species, is well documented. Atmospheric CO/sub 2/ has also been increasing. Instead of depleting O/sub 3/, the expected effect of CO/sub 2/ is to increase its concentration. The simultaneous effects of these perturbations were studied. Results indicate that increases in CO/sub 2/ can significantly alter the predicted ozone trend. This will complicate efforts to detect the trend in O/sub 3/ caused by increasesmore » in CFM's. Since the calculated effects of these perturbations are largest at high altitudes, one might expect to detect changes in high altitude O/sub 3/ sooner than those in total O/sub 3/. Therefore a comparison was made between the calculated change in O/sub 3/ at high altitude and statistical detection limits for abnormal change as developed from Umkehr data from Arosa, Switzerland. Its significance for trend detection is discussed. Finally, since CO/sub 2/ effects will be important in the next 50 to 100 years, the effects of temperature changes from CO/sub 2/ increase on O/sub 3/ loss rates from different families were examined. Significant changes in the NO/sub x/-catalyzed ozone loss rates that have not previously been discussed were found. It is concluded that the O/sub 3/ decrease at steady state from the coupled CFM and CO/sub 2/ perturbation is larger than the decrease calculated by summing the separate effects of these perturbations. The expected increase in CO/sub 2/ can significantly affect predicted O/sub 3/ trends in the next 50 to 100 years. O/sub 3/ changes in Umkehr level 7 are more detectible, in a statistical sense, than those at higher levels. The temperature effect of CO/sub 2/ on the NO/sub x-catalyzed O/sub 3/ destruction rate was found to be as large or larger than the effect of temperature on the pure oxygen loss rate.« less

Thin silica shell coated Ag assembled nanostructures for expanding generality of SERS analytes

PubMed Central

Kang, Yoo-Lee; Lee, Minwoo; Kang, Homan; Kim, Jaehi; Pham, Xuan-Hung; Kim, Tae Han; Hahm, Eunil; Lee, Yoon-Sik; Jeong, Dae Hong

2017-01-01

Surface-enhanced Raman scattering (SERS) provides a unique non-destructive spectroscopic fingerprint for chemical detection. However, intrinsic differences in affinity of analyte molecules to metal surface hinder SERS as a universal quantitative detection tool for various analyte molecules simultaneously. This must be overcome while keeping close proximity of analyte molecules to the metal surface. Moreover, assembled metal nanoparticles (NPs) structures might be beneficial for sensitive and reliable detection of chemicals than single NP structures. For this purpose, here we introduce thin silica-coated and assembled Ag NPs (SiO2@Ag@SiO2 NPs) for simultaneous and quantitative detection of chemicals that have different intrinsic affinities to silver metal. These SiO2@Ag@SiO2 NPs could detect each SERS peak of aniline or 4-aminothiophenol (4-ATP) from the mixture with limits of detection (LOD) of 93 ppm and 54 ppb, respectively. E-field distribution based on interparticle distance was simulated using discrete dipole approximation (DDA) calculation to gain insight into enhanced scattering of these thin silica coated Ag NP assemblies. These NPs were successfully applied to detect aniline in river water and tap water. Results suggest that SiO2@Ag@SiO2 NP-based SERS detection systems can be used as a simple and universal detection tool for environment pollutants and food safety. PMID:28570633

Using a refrigerant leak detector to monitor waste gases from halogenated anesthetics.

PubMed

Rasmussen, Henrik; Thorud, Syvert

2007-09-01

Although halogenated gas anesthetics are indispensable in laboratory animal medicine, they are hazardous when present in the working environment. A simple technique of real-time leak detection and environmental spot monitoring can provide valuable adjunct information to current techniques of time-weighted monitoring. We investigated the minimal limit of detection of halothane, isoflurane, sevoflurane, and desflurane of a leak detector for halogenated gas refrigerants which provides a qualitative response only. We connected a container to an infrared gas analyzer to create a 135-l closed-circuit system and injected liquid halothane, isoflurane, sevoflurane, and desflurane to create calculated gas concentrations of 0.7 to 3.4 parts per million (ppm). The infrared absorbance and response of the leak detector were recorded, and a total of 5 measurements were made per concentration. The actual gas concentrations were calculated by comparison with the agent-specific absorbance standard curve. The leak detector clearly and consistently responded to halothane, isoflurane, sevoflurane, and desflurane from minimal concentrations of 2.1 +/- 0.2, 1.4 +/- 0.04, 0.8 +/- 0.04, and 1.2 +/- 0.4 ppm, respectively, as determined by infrared analysis. Although the detector does not provide numerical and time-weighted results, leak testing of equipment and repeated monitoring of the environment (spot monitoring) can provide valuable real-time information. In addition, with appropriate consideration of the methodological limitations, spot monitoring can be used to predict the likelihood of compliance with time-weighted exposure recommendations. A leak detector therefore represents a simple, effective, and inexpensive instrument for monitoring the leakage of halogenated anesthetic gases from equipment and into the working environment.

Evaluation of FUS-2000 urine analyzer: analytical properties and particle recognition.

PubMed

Beňovská, Miroslava; Wiewiorka, Ondřej; Pinkavová, Jana

This study evaluates the performance of microscopic part of a hybrid analyzer FUS-2000 (Dirui Industrial Co., Changchun, China), its analytical properties and particle recognition. The evaluation of trueness, repeatability, detection limit, carry-over, linearity range and analytical stability was performed according to Dirui protocol guidelines designed by Dirui Company to guarantee the quality of the instrument. Trueness for low, medium and high-value concentrations was calculated with bias of 15.5, 4.7 and -6.6%, respectively. Detection limit of 5 Ery/μl was confirmed. Coefficient of variation of 11.0, 5.2 and 3.8% was measured for within-run repeatability of low, medium and high concentration. Between-run repeatability for daily quality control had coefficient of variation of 3.0%. Carry-over did not exceed 0.05%. Linearity was confirmed for range of 0-16,000 particles/μl (R 2  = 0.9997). The analytical stability had coefficient of variation of 4.3%. Out of 1258 analyzed urine samples, 362 positive were subjected to light microscopy urine sediment analysis and compared to the analyzer results. Cohen's kappa coefficients were calculated to express the concordance. Squared kappa coefficient was 0.927 (red blood cells), 0.888 (white blood cells), 0.908 (squamous epithelia), 0.634 (transitional epithelia), 0.628 (hyaline casts), 0.843 (granular casts) and 0.623 (bacteria). Single kappa coefficients were 0.885 (yeasts) and 0.756 (crystals), respectively. Aforementioned results show good analytical performance of the analyzer and tight agreement with light microscopy of urine sediment.

Electrical gain in interband cascade infrared photodetectors

NASA Astrophysics Data System (ADS)

Huang, Wenxiang; Li, Lu; Lei, Lin; Massengale, Jeremy A.; Yang, Rui Q.; Mishima, Tetsuya D.; Santos, Michael B.

2018-03-01

In order to achieve improved understanding and gain insights into the device operation of interband cascade infrared photodetectors (ICIPs) and ultimately to optimize the design, we present a comparative study of five long-wavelength (LW) ICIPs based on a type-II InAs/GaSb superlattice. This study shows how the device responsivity is affected by the individual absorber thicknesses and the number of cascade stages, through the impact of light attenuation. Additionally, this study further validates that the electrical gain universally exists in non-current-matched ICIPs. With multiple cascade stages to suppress noise, these LW ICIPs achieved superior device performance at high temperatures, in terms of Johnson-noise limited detectivities, compared to commercial MCT detectors. Furthermore, a theory is developed to quantitatively describe the electrical gain in ICIPs and our calculations are in good agreement with the experimental results. Based on the theory, the optimal number of stages for maximizing the device detectivity D* is identified with inclusion of the electrical gain. Our calculation shows that this optimal number of stages is relatively large in the presence of the gain and the maximized D* has a relatively weak dependence on the absorber thickness when it is sufficiently thin.

An improved method for direct estimation of free cyanide in drinking water by Ion Chromatography-Pulsed Amperometry Detection (IC-PAD) on gold working electrode.

PubMed

Kumar Meher, Alok; Labhsetwar, Nitin; Bansiwal, Amit

2018-02-01

In the present work a fast, reliable and safe Ion Exchange Chromatography-Pulsed Amperometry Detection (IC-PAD) method for direct determination of free cyanide in drinking water has been reported. To the best of our knowledge for the first time we are reporting the application of Gold working electrode for detection of free cyanide in a chromatography system. The system shows a wide linear range up to 8000µg/L. The electrode was found to have improved sensitivity and selectivity in the presence of interfering ions. The detection limit of the system was calculated to be 2µg/L. Long term evaluation of the electrode was found to be stable. Reproducible results were obtained from analysis of drinking water samples with recoveries of 98.3-101.2% and Relative Standard Deviations (RSD) of <2%. This study proves the potential application of the newly developed method for the analysis of free cyanide in drinking water. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of glycosaminoglycan-derived disaccharides by capillary electrophoresis using laser-induced fluorescence detection

PubMed Central

Chang, Yuqing; Yang, Bo; Zhao, Xue; Linhardt, Robert J.

2012-01-01

A quantitative and highly sensitive method for the analysis of glycosaminoglycan (GAG)-derived disaccharides is presented that relies on capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. This method enables complete separation of seventeen GAG-derived disaccharides in a single run. Unsaturated disaccharides were derivatized with 2-aminoacridone (AMAC) to improve sensitivity. The limit of detection was at the attomole level and about 100-fold more sensitive than traditional CE-ultraviolet detection. A CE separation timetable was developed to achieve complete resolution and shorten analysis time. The RSD of migration time and peak areas at both low and high concentrations of unsaturated disaccharides are all less than 2.7% and 3.2%, respectively, demonstrating that this is a reproducible method. This analysis was successfully applied to cultured Chinese hamster ovary cell samples for determination of GAG disaccharides. The current method simplifies GAG extraction steps, and reduces inaccuracy in calculating ratios of heparin/heparan sulfate to chondroitin sulfate/dermatan sulfate, resulting from the separate analyses of a single sample. PMID:22609076

Ion-exclusion/cation-exchange chromatography with dual detection of the conductivity and spectrophotometry for the simultaneous determination of common inorganic anionic species and cations in river and wastewater.

PubMed

Nakatani, Nobutake; Kozaki, Daisuke; Mori, Masanobu; Hasebe, Kiyoshi; Nakagoshi, Nobukazu; Tanaka, Kazuhiko

2011-01-01

Simultaneous determinations of common inorganic anionic species (SO(4)(2-), Cl(-), NO(3)(-), phosphate and silicate) and cations (Na(+), NH(4)(+), K(+), Mg(2+) and Ca(2+)) were conducted using an ion-chromatography system with dual detection of conductivity and spectrophotometry in tandem. The separation of ionic species on a weakly acidic cation-exchange resin was accomplished using a mixture of 100 mM ascorbic acid and 4 mM 18-crown-6 as an acidic eluent (pH 2.6), after which the ions were detected using a conductivity detector. Subsequently, phosphate and silicate were analyzed based on derivatization with molybdate and spectrophotometry at 700 nm. The detection limits at S/N = 3 ranged from 0.11 to 2.9 µM for analyte ionic species. This method was applied to practical river water and wastewater with acceptable criteria for the anion-cation balance and comparisons of the measured and calculated electrical conductivity, demonstrating the usefulness of the present method for water quality monitoring.

12 CFR 1.4 - Calculation of limits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... separately to the Type III and Type V securities held by a bank. (e) Limit on investment company holdings—(1... investment limits at that interval until further notice. (d) Calculation of Type III and Type V securities holdings—(1) General. In calculating the amount of its investment in Type III or Type V securities issued...

A study on flammability limits of fuel mixtures.

PubMed

Kondo, Shigeo; Takizawa, Kenji; Takahashi, Akifumi; Tokuhashi, Kazuaki; Sekiya, Akira

2008-07-15

Flammability limit measurements were made for various binary and ternary mixtures prepared from nine different compounds. The compounds treated are methane, propane, ethylene, propylene, methyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. The observed values of lower flammability limits of mixtures were found to be in good agreement to the calculated values by Le Chatelier's formula. As for the upper limits, however, some are close to the calculated values but some are not. It has been found that the deviations of the observed values of upper flammability limits from the calculated ones are mostly to lower concentrations. Modification of Le Chatelier's formula was made to better fit to the observed values of upper flammability limits. This procedure reduced the average difference between the observed and calculated values of upper flammability limits to one-third of the initial value.

Analysis of imidacloprid residues in fruits, vegetables, cereals, fruit juices, and baby foods, and daily intake estimation in and around Lucknow, India.

PubMed

Kapoor, Upasana; Srivastava, M K; Srivastava, Ashutosh Kumar; Patel, D K; Garg, Veena; Srivastava, L P

2013-03-01

A total of 250 samples-including fruits, fruit juices, and baby foods (50 samples each), vegetables (70 samples), and cereals (30 samples)-were collected from Lucknow, India, and analyzed for the presence of imidacloprid residues. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) method of extraction coupled with high-performance liquid chromatographic analysis were carried out, and imidacloprid residues were qualitatively confirmed by liquid chromatography-mass spectrometry. Imidacloprid was not detected in samples of fruit juices and baby foods. It was, however, detected in 38 samples of fruits, vegetables, and cereals, which is about 15.20% of the total samples. Of samples of fruits, 22% showed the presence of imidacloprid, and 2% of samples showed residues above the maximal residue limit. Although imidacloprid was detected in 24% of vegetable samples, only 5.71% showed the presence of imidacloprid above the maximal residue limit. However, 33% of cereal samples showed the presence of imidacloprid, and about 3% of samples were above the maximal residue limit. The calculated estimated daily intake ranged between 0.004 and 0.131 µg/kg body weight, and the hazard indices ranged from 0.007 to 0.218 for these food commodities. It is therefore indicated that lifetime consumption of vegetables, fruits, fruit juices, baby foods, wheat, rice, and pulses may not pose a health hazard for the population of Lucknow because the hazard indices for imidacloprid residues were below one. Copyright © 2012 SETAC.

Power corrections to the universal heavy WIMP-nucleon cross section

NASA Astrophysics Data System (ADS)

Chen, Chien-Yi; Hill, Richard J.; Solon, Mikhail P.; Wijangco, Alexander M.

2018-06-01

WIMP-nucleon scattering is analyzed at order 1 / M in Heavy WIMP Effective Theory. The 1 / M power corrections, where M ≫mW is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total 1 / M correction, and a total cross section close to the universal limit for M ≳ few × 100GeV. For the SU(2) composite scalar, the 1 / M corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total 1 / M correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.

Solid-phase microextraction coupled to gas chromatography for the determination of 2,3-dimethyl-2,3-dinitrobutane as a marking agent for explosives.

PubMed

Li, Xiujuan; Zeng, Zhaorui; Zeng, Yi

2007-06-15

This paper investigates the detection of 2,3-dimethyl-2,3-dinitrobutane (DMNB), a marking agent in explosives, by gas chromatography (GC) with electron capture detection using solid-phase microextraction (SPME) as a sample preparation technique. The 25,27-dihydroxy-26,28-oxy (2',7'-dioxo-3',6'-diazaoctyl) oxy-p-tert-butylcalix[4]arene/hydroxy-terminated silicone oil coated fiber was highly sensitive to trap DMNB from ammonium nitrate matrix. The analysis was performed by extracting 2g of explosives for 30s at room temperature and then immediately introducing into the heated GC injector for 1min of thermal desorption. The method showed good linearity in the range from 0.01 to 1.0mug/g. The relative standard deviations for these extractions were <8%. The calculated limit of detection for DMNB (S/N=3) was 4.43x10(-4)mug/g, which illustrates that the proposed systems are suitable for explosive detection at trace level. This is the first report of an SPME-GC system shown to extract marking agent in explosives for subsequent detection in a simple, rapid, sensitive, and inexpensive manner.

Highly selective and sensitive method for Cu2 + detection based on chiroptical activity of L-Cysteine mediated Au nanorod assemblies

NASA Astrophysics Data System (ADS)

Abbasi, Shahryar; Khani, Hamzeh

2017-11-01

Herein, we demonstrated a simple and efficient method to detect Cu2 + based on amplified optical activity in the chiral nanoassemblies of gold nanorods (Au NRs). L-Cysteine can induce side-by-side or end-to-end assembly of Au NRs with an evident plasmonic circular dichroism (PCD) response due to coupling between surface plasmon resonances (SPR) of Au NRs and the chiral signal of L-Cys. Because of the obvious stronger plasmonic circular dichrosim (CD) response of the side-by-side assembly compared with the end-to-end assemblies, SS assembled Au NRs was selected as a sensitive platform and used for Cu2 + detection. In the presence of Cu2 +, Cu2 + can catalyze O2 oxidation of cysteine to cystine. With an increase in Cu2 + concentration, the L-Cysteine-mediated assembly of Au NRs decreased because of decrease in the free cysteine thiol groups, and the PCD signal decreased. Taking advantage of this method, Cu2 + could be detected in the concentration range of 20 pM-5 nM. Under optimal conditions, the calculated detection limit was found to be 7 pM.

Electromagnetic diagnostic techniques for hypervelocity projectile detection, velocity measurement, and size characterization: Theoretical concept and first experimental test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uhlig, W. Casey; Heine, Andreas, E-mail: andreas.heine@emi.fraunhofer.de

2015-11-14

A new measurement technique is suggested to augment the characterization and understanding of hypervelocity projectiles before impact. The electromagnetic technique utilizes magnetic diffusion principles to detect particles, measure velocity, and indicate relative particle dimensions. It is particularly suited for detection of small particles that may be difficult to track utilizing current characterization methods, such as high-speed video or flash radiography but can be readily used for large particle detection, where particle spacing or location is not practical for other measurement systems. In this work, particles down to 2 mm in diameter have been characterized while focusing on confining the detection signalmore » to enable multi-particle characterization with limited particle-to-particle spacing. The focus of the paper is on the theoretical concept and the analysis of its applicability based on analytical and numerical calculation. First proof-of-principle experimental tests serve to further validate the method. Some potential applications are the characterization of particles from a shaped-charge jet after its break-up and investigating debris in impact experiments to test theoretical models for the distribution of particles size, number, and velocity.« less

Effects of Sampling and Spatio/Temporal Granularity in Traffic Monitoring on Anomaly Detectability

NASA Astrophysics Data System (ADS)

Ishibashi, Keisuke; Kawahara, Ryoichi; Mori, Tatsuya; Kondoh, Tsuyoshi; Asano, Shoichiro

We quantitatively evaluate how sampling and spatio/temporal granularity in traffic monitoring affect the detectability of anomalous traffic. Those parameters also affect the monitoring burden, so network operators face a trade-off between the monitoring burden and detectability and need to know which are the optimal paramter values. We derive equations to calculate the false positive ratio and false negative ratio for given values of the sampling rate, granularity, statistics of normal traffic, and volume of anomalies to be detected. Specifically, assuming that the normal traffic has a Gaussian distribution, which is parameterized by its mean and standard deviation, we analyze how sampling and monitoring granularity change these distribution parameters. This analysis is based on observation of the backbone traffic, which exhibits spatially uncorrelated and temporally long-range dependence. Then we derive the equations for detectability. With those equations, we can answer the practical questions that arise in actual network operations: what sampling rate to set to find the given volume of anomaly, or, if the sampling is too high for actual operation, what granularity is optimal to find the anomaly for a given lower limit of sampling rate.

Determination of ammonium on an integrated microchip with LED-induced fluorescence detection.

PubMed

Xue, Shuhua; Uchiyama, Katsumi; Li, Hai-Fang

2012-01-01

A simply fabricated microfluidic device integrated with a fluorescence detection system has been developed for on-line determination of ammonium in aqueous samples. A 365-nm light-emitting diode (LED) as an excitation source and a minor band pass filter were mounted into a polydimethylsiloxane (PDMS)-based microchip for the purpose of miniaturization of the entire analytical system. The ammonium sample reacted with o-phthaldialdehyde (OPA) on-chip with sodium sulfite as reducing reagent to produce a fluorescent isoindole derivative, which can emit fluorescence signal at about 425 nm when excited at 365 nm. Effects of pH, flow rate of solutions, concentrations of OPA-reagent, phosphate and sulfite salt were investigated. The calibration curve of ammonium in the range of 0.018-1.8 microg/mL showed a good linear relationship with R2 = 0.9985, and the detection limit was (S/N = 3) 3.6 x 10(-4) microg/mL. The relative standard deviation was 2.8% (n = 11) by calculating at 0.18 microg/mL ammonium for repeated detection. The system was applied to determine the ammonium concentration in rain and river waters, even extent to other analytes fluorescence detection by the presented device.

Assessing endotoxins in equine-derived snake antivenoms: Comparison of the USP pyrogen test and the Limulus Amoebocyte Lysate assay (LAL).

PubMed

Solano, Gabriela; Gómez, Aarón; León, Guillermo

2015-10-01

Snake antivenoms are parenterally administered; therefore, endotoxin content must be strictly controlled. Following international indications to calculate endotoxin limits, it was determined that antivenom doses between 20 mL and 120 mL should not exceed 17.5 Endotoxin Units per milliliter (EU/mL) and 2.9 EU/mL, respectively. The rabbit pyrogen test (RPT) has been used to evaluate endotoxin contamination in antivenoms, but some laboratories have recently implemented the LAL assay. We compared the capability of both tests to evaluate endotoxin contamination in antivenoms, and we found that both methods can detect all endotoxin concentrations in the range of the antivenom specifications. The acceptance criteria of RPT and LAL must be harmonized by calculating the endotoxin limit as the quotient of the threshold pyrogenic dose and the therapeutic dose and the dose administered to rabbits as the quotient of the threshold pyrogenic dose and the endotoxin limit. Since endotoxins from Gram-negative bacteria exert different pyrogenicity, if contamination occurred, antivenom batches that induce pyrogenic reactions may be found in spite of passing LAL specifications. Although LAL assay can be used to assess endotoxin content throughout the antivenom manufacturing process, we recommend that the release of final products be based on the results of both methods. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterisation of a new, highly effective method for detecting nematode eggs (Ascaris spp., Toxocara spp., Trichuris spp.) in sewage sludge containing flocculants.

PubMed

Zdybel, Jolanta; Karamon, Jacek; Różycki, Mirosław; Bilska-Zając, Ewa; Kłapeć, Teresa; Cencek, Tomasz

2016-11-01

Because traditional methods used for sewage sludge parasitological examinations have low sensitivity, a new, highly effective method (own method - OM) was devised. The principle of this method is to eliminate the flocculent effect on the structure of sewage sludge by mechanically damaging floccules in the presence of surfactants and to increase the effectiveness of egg isolation processes in large volumes of liquids. The objective of this study was to estimate the effectiveness of the OM in detecting nematode eggs in sewage sludge samples containing flocculants. In the first stage, the effectiveness of the OM was compared to 4 other methods routinely used in parasitological examinations of dehydrated sewage sludge. Next, method standardisation was performed using sewage sludge samples supplemented with eggs from 3 parasite species (Ascaris suum, Toxocara canis and Trichuris vulpis). The study demonstrated that OM efficiency was 6-65 times greater than other methods, depending on the method and type of detected eggs. Limit of detection (LOD) calculations for the OM were performed on samples supplemented with a known number of parasite eggs resulting in 10, 5 and 3 eggs/50 g of sample for A. suum, T. vulpis and T. canis eggs, respectively. The limits of quantification (LOQ) of the OM were established as 200 eggs/50 g of sample for A. suum and T. vulpis eggs and 50 eggs/50 g of sample for T. canis eggs. The rectilinear regression functions, which determined the relationship between the number of eggs detected in OM measurements and the number of eggs contained in the samples, were characterised by high and statistically significant coefficients of determination (r 2 ). The slopes of the trend lines were 0.3188, 0.3821 and 0.3276, and the intercepts were -11.223, -9.0261 and -23.15 for A. suum, T. canis and T. vulpis eggs, respectively. Method sensitivity, calculated as the slope coefficient of the regression function and expressed as a percentage, ranged from 32% to 38% depending on egg type. The study confirmed that the OM may be applied to quantify parasite eggs in dehydrated sewage sludge containing polyelectrolytes. Copyright © 2016 Elsevier Inc. All rights reserved.

Structural health monitoring ultrasonic thickness measurement accuracy and reliability of various time-of-flight calculation methods

NASA Astrophysics Data System (ADS)

Eason, Thomas J.; Bond, Leonard J.; Lozev, Mark G.

2016-02-01

The accuracy, precision, and reliability of ultrasonic thickness structural health monitoring systems are discussed in-cluding the influence of systematic and environmental factors. To quantify some of these factors, a compression wave ultrasonic thickness structural health monitoring experiment is conducted on a flat calibration block at ambient temperature with forty four thin-film sol-gel transducers and various time-of-flight thickness calculation methods. As an initial calibration, the voltage response signals from each sensor are used to determine the common material velocity as well as the signal offset unique to each calculation method. Next, the measurement precision of the thickness error of each method is determined with a proposed weighted censored relative maximum likelihood analysis technique incorporating the propagation of asymmetric measurement uncertainty. The results are presented as upper and lower confidence limits analogous to the a90/95 terminology used in industry recognized Probability-of-Detection assessments. Future work is proposed to apply the statistical analysis technique to quantify measurement precision of various thickness calculation methods under different environmental conditions such as high temperature, rough back-wall surface, and system degradation with an intended application to monitor naphthenic acid corrosion in oil refineries.

A highly selective and sensitive fluorescent chemosensor and its application for rapid on-site detection of Al3 +

NASA Astrophysics Data System (ADS)

Yue, Xiao-li; Wang, Zhao-qing; Li, Chao-rui; Yang, Zheng-yin

2018-03-01

In this paper, a simple naphthalene-based derivative (HL) has been designed and synthesized as a Al3 +-selective fluorescent chemosensor based on the PET mechanism. HL exhibited high selectivity and sensitivity towards Al3 + over other commonly coexisting metal ions in ethanol with a detection limit of 2.72 nM. The 1:1 binding stoichiometry of the complex (HL-Al3 +) was determined from the Job's plot based on fluorescence titrations and the ESI-MS spectrum data. Moreover, the binding site of HL with Al3 + was assured by the 1H NMR titration experiment. The binding constant (Ka) of the complex (HL-Al3 +) was calculated to be 5.06 × 104 M- 1 according to the Benesi-Hildebrand equation. In addition, the recognizing process of HL towards Al3 + was chemically reversible by adding Na2EDTA. Importantly, HL could directly and rapidly detect aluminum ion through the filter paper without resorting to additional instrumental analysis.

Charge transfer and adsorption-desorption kinetics in carbon nanotube and graphene gas sensing

NASA Astrophysics Data System (ADS)

Liang, Sang-Zi; Chen, Gugang; Harutyunyan, Avetik; Cole, Milton; Sofo, Jorge

2014-03-01

Detection of molecules in the gas phase by carbon nanotube and graphene has great application potentials due to the high sensitivity and surface-to-volume ratio. In chemiresistor, the conductance of the materials has been proposed to change as a result of charge transfer from the adsorbed molecules. Due to self-interaction errors, calculations using LDA or GGA density functionals have an innate disadvantage in dealing with charge transfer situations. A model which takes into consideration the dielectric interaction between the graphene surface and the molecule is employed to estimate the distance where charge transfer becomes favorable. Adsorption-desorption kinetics is studied with a modified Langmuir model, including sites from which the molecules do not desorb within the experimental time. Assuming a constant mobility, the model reproduces existing experimental conductance data. Its parameters provide information about the microscopic process during the detection and varying them allows optimization of aspects of sensor performance, including sensitivity, detection limit and response time. This work is supported by Honda Research Institute USA, Inc.

A Simple and Sensitive Method for Auramine O Detection Based on the Binding Interaction with Bovin Serum Albumin.

PubMed

Yan, Jingjing; Huang, Xin; Liu, Shaopu; Yang, Jidong; Yuan, Yusheng; Duan, Ruilin; Zhang, Hui; Hu, Xiaoli

2016-01-01

A simple, rapid and effective method for auramine O (AO) detection was proposed by fluorescence and UV-Vis absorption spectroscopy. In the BR buffer system (pH 7.0), AO had a strong quenching ability to the fluorescence of bovin serum albumin (BSA) by dynamic quenching. In terms of the thermodynamic parameters calculated as ΔH > 0 and ΔS > 0, the resulting binding of BSA and AO was mainly attributed to the hydrophobic interaction forces. The linearity of this method was in the concentration range from 0.16 to 50 μmol L(-1) with a detection limit of 0.05 μmol L(-1). Based on fluorescence resonance energy transfer (FRET), the distance r (1.36 nm) between donor (BSA) and acceptor (AO) was obtained. Furthermore, the effects of foreign substances and ionic strength were evaluated under the optimum reaction conditions. BSA as a selective probe could be applied to the analysis of AO in medicines with satisfactory results.

Visual detection and sequential injection determination of aluminium using a cinnamoyl derivative.

PubMed

Elečková, Lenka; Alexovič, Michal; Kuchár, Juraj; Balogh, Ioseph S; Andruch, Vasil

2015-02-01

A cinnamoyl derivative, 3-[4-(dimethylamino)cinnamoyl]-4-hydroxy-6-methyl-3,4-2H-pyran-2-one, was used as a ligand for the determination of aluminium. Upon the addition of an acetonitrile solution of the ligand to an aqueous solution containing Al(III) and a buffer solution at pH 8, a marked change in colour from yellow to orange is observed. The colour intensity is proportional to the concentration of Al(III); thus, the 'naked-eye' detection of aluminium is possible. The reaction is also applied for sequential injection determination of aluminium. Beer׳s law is obeyed in the range from 0.055 to 0.66 mg L(-1) of Al(III). The limit of detection, calculated as three times the standard deviation of the blank test (n=10), was found to be 4 μg L(-1) for Al(III). The method was applied for the determination of aluminium in spiked water samples and pharmaceutical preparations. Copyright © 2014 Elsevier B.V. All rights reserved.

New turn-on fluorescent and colorimetric probe for cyanide detection based on BODIPY-salicylaldehyde and its application in cell imaging.

PubMed

Sukato, Rangsarit; Sangpetch, Nuanphan; Palaga, Tanapat; Jantra, Suthikorn; Vchirawongkwin, Viwat; Jongwohan, Chanantida; Sukwattanasinitt, Mongkol; Wacharasindhu, Sumrit

2016-08-15

Development of cyanide sensor is important as the anion is harmful to human health and the environment. Herein, a new colorimetric and fluorescent probe GSB based on boron dipyrrole-methene (BODIPY) containing salicylaldehyde group for cyanide detection has been reported. GSB undergoes exclusive colorimetric change from orange to colorless and exhibits selective fluorescence turn-on at 504nm upon the addition of cyanide. Other 13 anions give almost no interference under physiological condition. Detection limit of the new cyanide-sensing GSB is 0.88μM, which is below World Health Organization (WHO) recommended level in drinking water. A calculation by density functional theory (DFT) shows suppression of photoinduced electron transfer (PET) mechanism along with the interruption of π-conjugation between salicylaldehyde and BODIPY core by cyanide anion. Cell imaging studies demonstrated that GSB is compatible and capable of sensing cyanide anion in living cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Application of Polypyrrole Multi-Walled Carbon Nanotube Composite Layer for Detection of Mercury, Lead and Iron Ions Using Surface Plasmon Resonance Technique

PubMed Central

Sadrolhosseini, Amir Reza; Noor, A. S. M.; Bahrami, Afarin; Lim, H. N.; Talib, Zainal Abidin; Mahdi, Mohd. Adzir

2014-01-01

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°. PMID:24733263

Improved detection of radioactive material using a series of measurements

NASA Astrophysics Data System (ADS)

Mann, Jenelle

The goal of this project is to develop improved algorithms for detection of radioactive sources that have low signal compared to background. The detection of low signal sources is of interest in national security applications where the source may have weak ionizing radiation emissions, is heavily shielded, or the counting time is short (such as portal monitoring). Traditionally to distinguish signal from background the decision threshold (y*) is calculated by taking a long background count and limiting the false negative error (alpha error) to 5%. Some problems with this method include: background is constantly changing due to natural environmental fluctuations and large amounts of data are being taken as the detector continuously scans that are not utilized. Rather than looking at a single measurement, this work investigates looking at a series of N measurements and develops an appropriate decision threshold for exceeding the decision threshold n times in a series of N. This methodology is investigated for a rectangular, triangular, sinusoidal, Poisson, and Gaussian distribution.

Reference Intervals of Alpha-Fetoprotein and Carcinoembryonic Antigen in the Apparently Healthy Population

PubMed Central

Zhang, Gao-Ming; Guo, Xu-Xiao; Ma, Xiao-Bo; Zhang, Guo-Ming

2016-01-01

Background The aim of this study was to calculate 95% reference intervals and double-sided limits of serum alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) according to the CLSI EP28-A3 guideline. Material/Methods Serum AFP and CEA values were measured in samples from 26 000 healthy subjects in the Shuyang area receiving general health checkups. The 95% reference intervals and upper limits were calculated by using MedCalc. Results We provided continuous reference intervals from 20 years old to 90 years old for AFP and CEA. The reference intervals were: AFP, 1.31–7.89 ng/ml (males) and 1.01–7.10 ng/ml (females); CEA, 0.51–4.86 ng/ml (males) and 0.35–3.45ng/ml (females). AFP and CEA were significantly positively correlated with age in both males (r=0.196 and r=0.198) and females (r=0.121 and r=0.197). Conclusions Different races or populations and different detection systems may result in different reference intervals for AFP and CEA. Continuous reference intervals of age changes are more accurate than age groups. PMID:27941709

Corneal topometry by fringe projection: limits and possibilities

NASA Astrophysics Data System (ADS)

Windecker, Robert; Tiziani, Hans J.; Thiel, H.; Jean, Benedikt J.

1996-01-01

A fast and accurate measurement of corneal topography is an important task especially since laser induced corneal reshaping has been used for the correction of ametropia. The classical measuring system uses Placido rings for the measurement and calculation of the topography or local curvatures. Another approach is the projection of a known fringe map to be imaged onto the surface under a certain angle of incidence. We present a set-up using telecentric illumination and detection units. With a special grating we get a synthetic wavelength with a nearly sinusoidal profile. In combination with a very fast data acquisition the topography can be evaluated using as special selfnormalizing phase evaluation algorithm. It calculates local Fourier coefficients and corrects errors caused by imperfect illumination or inhomogeneous scattering by fringe normalization. The topography can be determined over 700 by 256 pixel. The set-up is suitable to measure optically rough silicon replica of the human cornea as well as the cornea in vivo over a field of 8 mm and more. The resolution is mainly limited by noise and is better than two micrometers. We discuss the principle benefits and the drawbacks compared with standard Placido technique.

Inverse modeling of April 2013 radioxenon detections

NASA Astrophysics Data System (ADS)

Hofman, Radek; Seibert, Petra; Philipp, Anne

2014-05-01

Significant concentrations of radioactive xenon isotopes (radioxenon) were detected by the International Monitoring System (IMS) for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in April 2013 in Japan. Particularly, three detections of Xe-133 made between 2013-04-07 18:00 UTC and 2013-04-09 06:00 UTC at the station JPX38 are quite notable with respect to the measurement history of the station. Our goal is to analyze the data and perform inverse modeling under different assumptions. This work is useful with respect to nuclear test monitoring as well as for the analysis of and response to nuclear emergencies. Two main scenarios will be pursued: (i) Source location is assumed to be known (DPRK test site). (ii) Source location is considered unknown. We attempt to estimate the source strength and the source strength along with its plausible location compatible with the data in scenario (i) and (ii), respectively. We are considering also the possibility of a vertically distributed source. Calculations of source-receptor sensitivity (SRS) fields and the subsequent inversion are aimed at going beyond routine calculations performed by the CTBTO. For SRS calculations, we employ the Lagrangian particle dispersion model FLEXPART with high resolution ECMWF meteorological data (grid cell sizes of 0.5, 0.25 and ca. 0.125 deg). This is important in situations where receptors or sources are located in complex terrain which is the case of the likely source of detections-the DPRK test site. SRS will be calculated with convection enabled in FLEXPART which will also increase model accuracy. In the variational inversion procedure attention will be paid not only to all significant detections and their uncertainties but also to non-detections which can have a large impact on inversion quality. We try to develop and implement an objective algorithm for inclusion of relevant data where samples from temporal and spatial vicinity of significant detections are added in an iterative manner and the inversion is recalculated in each iteration. This procedure should gradually narrow down the set of hypotheses on the source term, where the source term is here understood as an emission in both spatial and temporal domains. Especially in scenario (ii) we expect a strong impact of non-detections for the reduction of possible solutions. For these and also other purposes like statistical quantification of typical background values, measurements from all IMS noble gas stations north of 30 deg S for a period from January to June 2013 were extracted from vDEC platform. We would like to acknowledge the Preparatory Commission for the CTBTO for kindly providing limited access to the IMS data. This work contains only opinions of the authors, which can not in any case establish legal engagement of the Provisional Technical Secretariat of the CTBTO. This work is partially financed through the project "PREPARE: Innovative integrated tools and platforms for radiological emergency preparedness and post-accident response in Europe" (FP7, Grant 323287).

Material limitations on the detection limit in refractometry.

PubMed

Skafte-Pedersen, Peder; Nunes, Pedro S; Xiao, Sanshui; Mortensen, Niels Asger

2009-01-01

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min {Δn} ≳ η, with n + iη being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window (λ ≳ 1100 nm) of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because the silicon absorbs strongly.

A Three-Dimensional Receiver Operator Characteristic Surface Diagnostic Metric

NASA Technical Reports Server (NTRS)

Simon, Donald L.

2011-01-01

Receiver Operator Characteristic (ROC) curves are commonly applied as metrics for quantifying the performance of binary fault detection systems. An ROC curve provides a visual representation of a detection system s True Positive Rate versus False Positive Rate sensitivity as the detection threshold is varied. The area under the curve provides a measure of fault detection performance independent of the applied detection threshold. While the standard ROC curve is well suited for quantifying binary fault detection performance, it is not suitable for quantifying the classification performance of multi-fault classification problems. Furthermore, it does not provide a measure of diagnostic latency. To address these shortcomings, a novel three-dimensional receiver operator characteristic (3D ROC) surface metric has been developed. This is done by generating and applying two separate curves: the standard ROC curve reflecting fault detection performance, and a second curve reflecting fault classification performance. A third dimension, diagnostic latency, is added giving rise to 3D ROC surfaces. Applying numerical integration techniques, the volumes under and between the surfaces are calculated to produce metrics of the diagnostic system s detection and classification performance. This paper will describe the 3D ROC surface metric in detail, and present an example of its application for quantifying the performance of aircraft engine gas path diagnostic methods. Metric limitations and potential enhancements are also discussed

Ultra-sensitive chemiluminescence imaging DNA hybridization method in the detection of mosquito-borne viruses and parasites.

PubMed

Zhang, Yingjie; Liu, Qiqi; Zhou, Biao; Wang, Xiaobo; Chen, Suhong; Wang, Shengqi

2017-01-25

Mosquito-borne viruses (MBVs) and parasites (MBPs) are transmitted through hematophagous arthropods-mosquitoes to homoiothermous vertebrates. This study aims at developing a detection method to monitor the spread of mosquito-borne diseases to new areas and diagnose the infections caused by MBVs and MBPs. In this assay, an ultra-sensitive chemiluminescence (CL) detection method was developed and used to simultaneously detect 19 common MBVs and MBPs. In vitro transcript RNA, virus-like particles (VLPs), and plasmids were established as positive or limit of detection (LOD) reference materials. MBVs and MBPs could be genotyped with high sensitivity and specificity. The cut-off values of probes were calculated. The absolute LODs of this strategy to detect serially diluted in vitro transcribed RNAs of MBVs and serially diluted plasmids of MBPs were 10 2 -10 3 copies/μl and 10 1 -10 2 copies/μl, respectively. Further, the LOD of detecting a strain of pre-quantified JEV was 10 1.8 -10 0.8 PFU/ml, fitted well in a linear regression model (coefficient of determination = 0.9678). Ultra-sensitive CL imaging DNA hybridization was developed and could simultaneously detect various MBVs and MBPs. The method described here has the potential to provide considerable labor savings due to its ability to screen for 19 mosquito-borne pathogens simultaneously.

Anti-D immunoglobulin preparations: the stability of anti-D concentrations and the error of the assay of anti-D.

PubMed

Hughes-Jones, N C; Hunt, V A; Maycock, W D; Wesley, E D; Vallet, L

1978-01-01

An analysis of the assay of 28 preparations of anti-D immunoglobulin using a radioisotope method carried out at 6-montly intervals for 2--4.5 years showed an average fall in anti-D concentration of 10.6% each year, with 99% confidence limits of 6.8--14.7%. The fall in anti-D concentration after storage at 37 degrees C for 1 month was less than 8%, the minimum change that could be detected. No significant change in physical characteristics of the immunoglobulin were detected. The error of a single estimate of anti-D by the radioisotope method (125I-labelled anti-IgG) used here was calculated to be such that the true value probably (p = 0.95) lay between 66 and 150% of the estimated value.

Development of an extraction method for perchlorate in soils.

PubMed

Cañas, Jaclyn E; Patel, Rashila; Tian, Kang; Anderson, Todd A

2006-03-01

Perchlorate originates as a contaminant in the environment from its use in solid rocket fuels and munitions. The current US EPA methods for perchlorate determination via ion chromatography using conductivity detection do not include recommendations for the extraction of perchlorate from soil. This study evaluated and identified appropriate conditions for the extraction of perchlorate from clay loam, loamy sand, and sandy soils. Based on the results of this evaluation, soils should be extracted in a dry, ground (mortar and pestle) state with Milli-Q water in a 1 ratio 1 soil ratio water ratio and diluted no more than 5-fold before analysis. When sandy soils were extracted in this manner, the calculated method detection limit was 3.5 microg kg(-1). The findings of this study have aided in the establishment of a standardized extraction method for perchlorate in soil.

Annular tautomerism: experimental observations and quantum mechanics calculations.

PubMed

Cruz-Cabeza, Aurora J; Schreyer, Adrian; Pitt, William R

2010-06-01

The use of MP2 level quantum mechanical (QM) calculations on isolated heteroaromatic ring systems for the prediction of the tautomeric propensities of whole molecules in a crystalline environment was examined. A Polarisable Continuum Model was used in the calculations to account for environment effects on the tautomeric relative stabilities. The calculated relative energies of tautomers were compared to relative abundances within the Cambridge Structural Database (CSD) and the Protein Data Bank (PDB). The work was focussed on 84 annular tautomeric forms of 34 common ring systems. Good agreement was found between the calculations and the experimental data even if the quantity of these data was limited in many cases. The QM results were compared to those produced by much faster semiempirical calculations. In a search for other sources of the useful experimental data, the relative numbers of known compounds in which prototropic positions were often substituted by heavy atoms were also analysed. A scheme which groups all annular tautomeric transformations into 10 classes was developed. The scheme was designed to encompass a comprehensive set of known and theoretically possible tautomeric ring systems generated as part of a previous study. General trends across analogous ring systems were detected as a result. The calculations and statistics collected on crystallographic data as well as the general trends observed should be useful for the better modelling of annular tautomerism in the applications such as computer-aided drug design, small molecule crystal structure prediction, the naming of compounds and the interpretation of protein-small molecule crystal structures.

Annular tautomerism: experimental observations and quantum mechanics calculations

NASA Astrophysics Data System (ADS)

Cruz-Cabeza, Aurora J.; Schreyer, Adrian; Pitt, William R.

2010-06-01

The use of MP2 level quantum mechanical (QM) calculations on isolated heteroaromatic ring systems for the prediction of the tautomeric propensities of whole molecules in a crystalline environment was examined. A Polarisable Continuum Model was used in the calculations to account for environment effects on the tautomeric relative stabilities. The calculated relative energies of tautomers were compared to relative abundances within the Cambridge Structural Database (CSD) and the Protein Data Bank (PDB). The work was focussed on 84 annular tautomeric forms of 34 common ring systems. Good agreement was found between the calculations and the experimental data even if the quantity of these data was limited in many cases. The QM results were compared to those produced by much faster semiempirical calculations. In a search for other sources of the useful experimental data, the relative numbers of known compounds in which prototropic positions were often substituted by heavy atoms were also analysed. A scheme which groups all annular tautomeric transformations into 10 classes was developed. The scheme was designed to encompass a comprehensive set of known and theoretically possible tautomeric ring systems generated as part of a previous study. General trends across analogous ring systems were detected as a result. The calculations and statistics collected on crystallographic data as well as the general trends observed should be useful for the better modelling of annular tautomerism in the applications such as computer-aided drug design, small molecule crystal structure prediction, the naming of compounds and the interpretation of protein—small molecule crystal structures.

Square wave voltammetry at the dropping mercury electrode: Experimental

USGS Publications Warehouse

Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.

1977-01-01

Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.

Study on the early warning mechanism for the security of blast furnace hearths

NASA Astrophysics Data System (ADS)

Zhao, Hong-bo; Huo, Shou-feng; Cheng, Shu-sen

2013-04-01

The campaign life of blast furnace (BF) hearths has become the limiting factor for safety and high efficiency production of modern BFs. However, the early warning mechanism of hearth security has not been clear. In this article, based on heat transfer calculations, heat flux and erosion monitoring, the features of heat flux and erosion were analyzed and compared among different types of hearths. The primary detecting elements, mathematical models, evaluating standards, and warning methods were discussed. A novel early warning mechanism with the three-level quantificational standards was proposed for BF hearth security.

Non-aggregation based label free colorimetric sensor for the detection of Cu2+ based on catalyzing etching of gold nanorods by dissolve oxygen.

PubMed

Liu, Jia-Ming; Jiao, Li; Lin, Li-Ping; Cui, Ma-Lin; Wang, Xin-Xing; Zhang, Li-Hong; Zheng, Zhi-Yong; Jiang, Shu-Lian

2013-12-15

A label-free non-aggregation colorimetric sensor has been designed for the detection of Cu(2+), based on Cu(2+) catalyzing etching of gold nanorods (AuNRs) along longitudinal axis induced by dissolve oxygen in the presence of S2O3(2-), which caused the aspect ratio (length/width) of AuNRs to decrease and the color of the solution to distinctly change. The linear range and the detection limit (LD, calculated by 10 Sb/k, n=11) of this sensor were 0.080-4.8 µM Cu(2+) and 0.22 µM Cu(2+), respectively. This sensor has been utilized to detect Cu(2+) in tap water and human serum samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy (ICP-MS), showing its remarkable practicality. In order to prove the possibility of catalyzing AuNRs non-aggregation colorimetric sensor for the detection of Cu(2+), the morphological structures of AuNRs were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism of colorimetric sensor for the detection of Cu(2+) was also discussed. © 2013 Elsevier B.V. All rights reserved.

Modeling and analysis of a microresonating biosensor for detection of Salmonella bacteria in human blood.

PubMed

Bahadoran, Mahdi; Noorden, Ahmad Fakhrurrazi Ahmad; Chaudhary, Kashif; Mohajer, Faeze Sadat; Aziz, Muhammad Safwan; Hashim, Shahrin; Ali, Jalil; Yupapin, Preecha

2014-07-18

A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO2-TiO2 material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine the output signal's intensities in the blood with and without presence of Salmonella. The change in refractive index due to the reaction of Salmonella bacteria with its applied antibody on the flagellin layer loaded on the sensing and detecting microresonator causes the increase in through and dropper port's intensities of the output signal which leads to the detection of SB in blood. A shift in the output signal wavelength is observed with resolution of 0.01 nm. The change in intensity and shift in wavelength is analyzed with respect to the change in the refractive index which contributes toward achieving an ultra-high sensitivity of 95,500 nm/RIU which is almost two orders higher than that of reported from single ring sensors and the limit of detection is in the order of 1 × 10(-8) RIU. In applications, such a system can be employed for a high sensitive and fast detection of bacteria.

Modeling and Analysis of a Microresonating Biosensor for Detection of Salmonella Bacteria in Human Blood

PubMed Central

Bahadoran, Mahdi; Noorden, Ahmad Fakhrurrazi Ahmad; Chaudhary, Kashif; Mohajer, Faeze Sadat; Aziz, Muhammad Safwan; Hashim, Shahrin; Ali, Jalil; Yupapin, Preecha

2014-01-01

A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO2-TiO2 material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine the output signal's intensities in the blood with and without presence of Salmonella. The change in refractive index due to the reaction of Salmonella bacteria with its applied antibody on the flagellin layer loaded on the sensing and detecting microresonator causes the increase in through and dropper port's intensities of the output signal which leads to the detection of SB in blood. A shift in the output signal wavelength is observed with resolution of 0.01 nm. The change in intensity and shift in wavelength is analyzed with respect to the change in the refractive index which contributes toward achieving an ultra-high sensitivity of 95,500 nm/RIU which is almost two orders higher than that of reported from single ring sensors and the limit of detection is in the order of 1 × 10−8 RIU. In applications, such a system can be employed for a high sensitive and fast detection of bacteria. PMID:25046015

Multispectral photoacoustic tomography for detection of small tumors inside biological tissues

NASA Astrophysics Data System (ADS)

Hirasawa, Takeshi; Okawa, Shinpei; Tsujita, Kazuhiro; Kushibiki, Toshihiro; Fujita, Masanori; Urano, Yasuteru; Ishihara, Miya

2018-02-01

Visualization of small tumors inside biological tissue is important in cancer treatment because that promotes accurate surgical resection and enables therapeutic effect monitoring. For sensitive detection of tumor, we have been developing photoacoustic (PA) imaging technique to visualize tumor-specific contrast agents, and have already succeeded to image a subcutaneous tumor of a mouse using the contrast agents. To image tumors inside biological tissues, extension of imaging depth and improvement of sensitivity were required. In this study, to extend imaging depth, we developed a PA tomography (PAT) system that can image entire cross section of mice. To improve sensitivity, we discussed the use of the P(VDF-TrFE) linear array acoustic sensor that can detect PA signals with wide ranges of frequencies. Because PA signals produced from low absorbance optical absorbers shifts to low frequency, we hypothesized that the detection of low frequency PA signals improves sensitivity to low absorbance optical absorbers. We developed a PAT system with both a PZT linear array acoustic sensor and the P(VDF-TrFE) sensor, and performed experiment using tissue-mimicking phantoms to evaluate lower detection limits of absorbance. As a result, PAT images calculated from low frequency components of PA signals detected by the P(VDF-TrFE) sensor could visualize optical absorbers with lower absorbance.

Performance of Four Transport and Storage Systems for Molecular Detection of Multidrug-Resistant Tuberculosis

PubMed Central

Rabodoarivelo, Marie Sylvianne; Imperiale, Bélen; andrianiavomikotroka, Rina; Brandao, Angela; Kumar, Parveen; Singh, Sarman; Ferrazoli, Lucilaine; Morcillo, Nora; Rasolofo, Voahangy; Palomino, Juan Carlos; Vandamme, Peter; Martin, Anandi

2015-01-01

Background Detection of drug-resistant tuberculosis is essential for the control of the disease but it is often hampered by the limitation of transport and storage of samples from remote locations to the reference laboratory. We performed a retrospective field study to evaluate the performance of four supports enabling the transport and storage of samples to be used for molecular detection of drug resistance using the GenoType MTBDRplus. Methods Two hundred Mycobacterium tuberculosis strains were selected and spotted on slides, FTA cards, GenoCards, and in ethanol. GenoType MTBDRplus was subsequently performed with the DNA extracted from these supports. Sensitivity and specificity were calculated and compared to the results obtained by drug susceptibility testing. Results For all supports, the overall sensitivity and specificity for detection of resistance to RIF was between 95% and 100%, and for INH between 95% and 98%. Conclusion The four transport and storage supports showed a good sensitivity and specificity for the detection of resistance to RIF and INH in M. tuberculosis strains using the GenoType MTBDRplus. These supports can be maintained at room temperature and could represent an important alternative cost-effective method useful for rapid molecular detection of drug-resistant TB in low-resource settings. PMID:26431352

Cooling Models for Old White Dwarfs

NASA Astrophysics Data System (ADS)

Hansen, Brad M. S.

1999-08-01

We present new white dwarf cooling models that incorporate an accurate outer boundary condition based on new opacity and detailed radiative transfer calculations. We find that helium-atmosphere dwarfs cool considerably faster than has previously been claimed, while old hydrogen-atmosphere dwarfs will deviate significantly from blackbody appearance. We use our new models to derive age limits for the Galactic disk. We find that the Liebert, Dahn, & Monet luminosity function yields an age of only 6 Gyr if it is complete to stated limits. However, age estimates of individual dwarfs and the luminosity function of Oswalt et al. are both consistent with disk ages as large as ~11 Gyr. We have also used our models to place constraints on white dwarf dark matter in the Galactic halo. We find that previous attempts using inadequate cooling models were too severe and that direct detection limits allow a halo that is 11 Gyr old. If the halo is composed solely of helium-atmosphere dwarfs, the lower age limit is only 7.5 Gyr. We also demonstrate the importance of studying the cooling sequences of white dwarfs in globular clusters.

Coronal Emission from dG Halo Stars

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Harnden, F. R.

2005-01-01

The halo dG star HD 114762 was observed with the XMM-Newton satellite on 28-29 June 2004, during orbit 834, and the data were processed using the XMM-Newton Science Analysis System (SAS), version 6.0.0. Somewhat surprisingly, the target was NOT detected during this approx.30 ks exposure, which yielded instead a count rate upper limit of less than 0.0041 cts/s. We computed an X-ray flux upper limit by assuming a Raymond-Smith thermal spectrum of coronal temperature 1 million degrees K, typical of quiet old stars, a hydrogen column density of 2-10$^{19)$ cm$^{-2)$ and sub-solar abundances of 0.2. Our calculated X-ray luminosity upper limit in the 0.25-7.8 keV band is L$_x < 4.95 $\\time$10$^{26)$ erg/s, where we have assumed a stellar distance of 28 pc. This relatively low upper limit has implications for the capability of metal poor stars to host solar-like dynamos, as we will report in a forthcoming paper (now in preparation).

Material Limitations on the Detection Limit in Refractometry

PubMed Central

Skafte-Pedersen, Peder; Nunes, Pedro S.; Xiao, Sanshui; Mortensen, Niels Asger

2009-01-01

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min {Δn} ≳ η, with n + iη being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window (λ ≳ 1100 nm) of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because the silicon absorbs strongly. PMID:22291513

Capillary-HPLC with tandem mass spectrometry in analysis of alkaloid dyestuffs - a new approach.

PubMed

Dąbrowski, Damian; Lech, Katarzyna; Jarosz, Maciej

2018-05-01

Development of the identification method of alkaloid compounds in Amur cork tree as well as not examined so far Oregon grape and European Barberry shrubs are presented. The novel approach to separation of alkaloids was applied and the capillary-high-performance liquid chromatography (capillary-HPLC) system was used, which has never previously been reported for alkaloid-based dyestuffs analysis. Its optimization was conducted with three different stationary phases (unmodified octadecylsilane-bonded silica, octadecylsilane modified with polar groups and silica-bonded pentaflourophenyls) as well as with different solvent buffers. Detection of the isolated compounds was carried out using diode-array detector (DAD) and tandem mass spectrometer with electrospray ionization (ESI MS/MS). The working parameters of ESI were optimized, whereas the multiple reactions monitoring (MRM) parameters of MS/MS detection were chosen based on the product ion spectra of the quasi-molecular ions. Calibration curve of berberine has been estimated (y = 1712091x + 4785.03 with the correlation coefficient 0.9999). Limit of detection and limit of quantification were calculated to be 3.2 and 9.7 ng/mL, respectively. Numerous alkaloids (i.e., berberine, jatrorrhizine and magnoflorine, as well as phellodendrine, menisperine and berbamine) were identified in the extracts from alkaloid plants and silk and wool fibers dyed with these dyestuffs, among them their markers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast and simultaneous determination of 12 polyphenols in apple peel and pulp by using chemometrics-assisted high-performance liquid chromatography with diode array detection.

PubMed

Wang, Tong; Wu, Hai-Long; Xie, Li-Xia; Zhu, Li; Liu, Zhi; Sun, Xiao-Dong; Xiao, Rong; Yu, Ru-Qin

2017-04-01

In this work, a smart chemometrics-enhanced strategy, high-performance liquid chromatography, and diode array detection coupled with second-order calibration method based on alternating trilinear decomposition algorithm was proposed to simultaneously quantify 12 polyphenols in different kinds of apple peel and pulp samples. The proposed strategy proved to be a powerful tool to solve the problems of coelution, unknown interferences, and chromatographic shifts in the process of high-performance liquid chromatography analysis, making it possible for the determination of 12 polyphenols in complex apple matrices within 10 min under simple conditions of elution. The average recoveries with standard deviations, and figures of merit including sensitivity, selectivity, limit of detection, and limit of quantitation were calculated to validate the accuracy of the proposed method. Compared to the quantitative analysis results from the classic high-performance liquid chromatography method, the statistical and graphical analysis showed that our proposed strategy obtained more reliable results. All results indicated that our proposed method used in the quantitative analysis of apple polyphenols was an accurate, fast, universal, simple, and green one, and it was expected to be developed as an attractive alternative method for simultaneous determination of multitargeted analytes in complex matrices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Representation of photon limited data in emission tomography using origin ensembles

NASA Astrophysics Data System (ADS)

Sitek, A.

2008-06-01

Representation and reconstruction of data obtained by emission tomography scanners are challenging due to high noise levels in the data. Typically, images obtained using tomographic measurements are represented using grids. In this work, we define images as sets of origins of events detected during tomographic measurements; we call these origin ensembles (OEs). A state in the ensemble is characterized by a vector of 3N parameters Y, where the parameters are the coordinates of origins of detected events in a three-dimensional space and N is the number of detected events. The 3N-dimensional probability density function (PDF) for that ensemble is derived, and we present an algorithm for OE image estimation from tomographic measurements. A displayable image (e.g. grid based image) is derived from the OE formulation by calculating ensemble expectations based on the PDF using the Markov chain Monte Carlo method. The approach was applied to computer-simulated 3D list-mode positron emission tomography data. The reconstruction errors for a 10 000 000 event acquisition for simulated ranged from 0.1 to 34.8%, depending on object size and sampling density. The method was also applied to experimental data and the results of the OE method were consistent with those obtained by a standard maximum-likelihood approach. The method is a new approach to representation and reconstruction of data obtained by photon-limited emission tomography measurements.

Electrochemical current rectification-a novel signal amplification strategy for highly sensitive and selective aptamer-based biosensor.

PubMed

Feng, Lingyan; Sivanesan, Arumugam; Lyu, Zhaozi; Offenhäusser, Andreas; Mayer, Dirk

2015-04-15

Electrochemical aptamer-based (E-AB) sensors represent an emerging class of recently developed sensors. However, numerous of these sensors are limited by a low surface density of electrode-bound redox-oligonucleotides which are used as probe. Here we propose to use the concept of electrochemical current rectification (ECR) for the enhancement of the redox signal of E-AB sensors. Commonly, the probe-DNA performs a change in conformation during target binding and enables a nonrecurring charge transfer between redox-tag and electrode. In our system, the redox-tag of the probe-DNA is continuously replenished by solution-phase redox molecules. A unidirectional electron transfer from electrode via surface-linked redox-tag to the solution-phase redox molecules arises that efficiently amplifies the current response. Using this robust and straight-forward strategy, the developed sensor showed a substantial signal amplification and consequently improved sensitivity with a calculated detection limit of 114nM for ATP, which was improved by one order of magnitude compared with the amplification-free detection and superior to other previous detection results using enzymes or nanomaterials-based signal amplification. To the best of our knowledge, this is the first demonstration of an aptamer-based electrochemical biosensor involving electrochemical rectification, which can be presumably transferred to other biomedical sensor systems. Copyright © 2014 Elsevier B.V. All rights reserved.

A Simple Bimodular Nonlinear Element

NASA Astrophysics Data System (ADS)

Mikhailov, S. G.; Rudenko, O. V.

2018-05-01

We have studied the dynamics of an artificial nonlinear element representing a flexible membrane with oscillation limiters and a static pressing force. Such an element has the property of "bimodularity" and demonstrates "modular" nonlinearity. We have constructed a mathematical model that describes these oscillations. Their shapes have been calculated. We follow the analogy with a classical object—Galileo's pendulum. We demonstrate that for a low-frequency excitation of the membrane, the level of the harmonics in the spectrum is higher than in the vicinity of the resonance frequency. We have established a strong dependence of the level of the harmonics on the magnitude of the pressing force for a weak perturbation. We propose a design scheme for a device in the quasi-static approximation possessing the property of bimodularity. We perform an experiment that confirms its operability. We show a qualitative coincidence of the experimental results and calculations when detecting an amplitude-modulated signal.

Validation of a Custom-made Software for DQE Assessment in Mammography Digital Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayala-Dominguez, L.; Perez-Ponce, H.; Brandan, M. E.

2010-12-07

This works presents the validation of a custom-made software, designed and developed in Matlab, intended for routine evaluation of detective quantum efficiency DQE, according to algorithms described in the IEC 62220-1-2 standard. DQE, normalized noise power spectrum NNPS and pre-sampling modulation transfer function MTF were calculated from RAW images from a GE Senographe DS (FineView disabled) and a Siemens Novation system. Calculated MTF is in close agreement with results obtained with alternative codes: MTF lowbar tool (Maidment), ImageJ plug-in (Perez-Ponce) and MIQuaELa (Ayala). Overall agreement better than {approx_equal}90% was found in MTF; the largest differences were observed at frequencies closemore » to the Nyquist limit. For the measurement of NNPS and DQE, agreement is similar to that obtained in the MTF. These results suggest that the developed software can be used with confidence for image quality assessment.« less

Tire-road friction estimation and traction control strategy for motorized electric vehicle.

PubMed

Jin, Li-Qiang; Ling, Mingze; Yue, Weiqiang

2017-01-01

In this paper, an optimal longitudinal slip ratio system for real-time identification of electric vehicle (EV) with motored wheels is proposed based on the adhesion between tire and road surface. First and foremost, the optimal longitudinal slip rate torque control can be identified in real time by calculating the derivative and slip rate of the adhesion coefficient. Secondly, the vehicle speed estimation method is also brought. Thirdly, an ideal vehicle simulation model is proposed to verify the algorithm with simulation, and we find that the slip ratio corresponds to the detection of the adhesion limit in real time. Finally, the proposed strategy is applied to traction control system (TCS). The results showed that the method can effectively identify the state of wheel and calculate the optimal slip ratio without wheel speed sensor; in the meantime, it can improve the accelerated stability of electric vehicle with traction control system (TCS).

Cybersecurity, massive data processing, community interaction, and other developments at WWW-based computational X-ray Server

NASA Astrophysics Data System (ADS)

Stepanov, Sergey

2013-03-01

X-Ray Server (x-server.gmca.aps.anl.gov) is a WWW-based computational server for modeling of X-ray diffraction, reflection and scattering data. The modeling software operates directly on the server and can be accessed remotely either from web browsers or from user software. In the later case the server can be deployed as a software library or a data fitting engine. As the server recently surpassed the milestones of 15 years online and 1.5 million calculations, it accumulated a number of technical solutions that are discussed in this paper. The developed approaches to detecting physical model limits and user calculations failures, solutions to spam and firewall problems, ways to involve the community in replenishing databases and methods to teach users automated access to the server programs may be helpful for X-ray researchers interested in using the server or sharing their own software online.

Tire-road friction estimation and traction control strategy for motorized electric vehicle

PubMed Central

Jin, Li-Qiang; Yue, Weiqiang

2017-01-01

In this paper, an optimal longitudinal slip ratio system for real-time identification of electric vehicle (EV) with motored wheels is proposed based on the adhesion between tire and road surface. First and foremost, the optimal longitudinal slip rate torque control can be identified in real time by calculating the derivative and slip rate of the adhesion coefficient. Secondly, the vehicle speed estimation method is also brought. Thirdly, an ideal vehicle simulation model is proposed to verify the algorithm with simulation, and we find that the slip ratio corresponds to the detection of the adhesion limit in real time. Finally, the proposed strategy is applied to traction control system (TCS). The results showed that the method can effectively identify the state of wheel and calculate the optimal slip ratio without wheel speed sensor; in the meantime, it can improve the accelerated stability of electric vehicle with traction control system (TCS). PMID:28662053

Standard Reference Line Combined with One-Point Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) to Quantitatively Analyze Stainless and Heat Resistant Steel.

PubMed

Fu, Hongbo; Wang, Huadong; Jia, Junwei; Ni, Zhibo; Dong, Fengzhong

2018-01-01

Due to the influence of major elements' self-absorption, scarce observable spectral lines of trace elements, and relative efficiency correction of experimental system, accurate quantitative analysis with calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is in fact not easy. In order to overcome these difficulties, standard reference line (SRL) combined with one-point calibration (OPC) is used to analyze six elements in three stainless-steel and five heat-resistant steel samples. The Stark broadening and Saha - Boltzmann plot of Fe are used to calculate the electron density and the plasma temperature, respectively. In the present work, we tested the original SRL method, the SRL with the OPC method, and intercept with the OPC method. The final calculation results show that the latter two methods can effectively improve the overall accuracy of quantitative analysis and the detection limits of trace elements.

Point sources of emerging contaminants along the Colorado River Basin: Source water for the arid Southwestern United States

USGS Publications Warehouse

Jones-Lepp, Tammy L.; Sanchez, Charles; Alvarez, David A.; Wilson, Doyle C.; Taniguchi-Fu, Randi-Laurant

2012-01-01

Emerging contaminants (ECs) (e.g., pharmaceuticals, illicit drugs, personal care products) have been detected in waters across the United States. The objective of this study was to evaluate point sources of ECs along the Colorado River, from the headwaters in Colorado to the Gulf of California. At selected locations in the Colorado River Basin (sites in Colorado, Utah, Nevada, Arizona, and California), waste stream tributaries and receiving surface waters were sampled using either grab sampling or polar organic chemical integrative samplers (POCIS). The grab samples were extracted using solid-phase cartridge extraction (SPE), and the POCIS sorbents were transferred into empty SPEs and eluted with methanol. All extracts were prepared for, and analyzed by, liquid chromatography–electrospray-ion trap mass spectrometry (LC–ESI-ITMS). Log DOW values were calculated for all ECs in the study and compared to the empirical data collected. POCIS extracts were screened for the presence of estrogenic chemicals using the yeast estrogen screen (YES) assay. Extracts from the 2008 POCIS deployment in the Las Vegas Wash showed the second highest estrogenicity response. In the grab samples, azithromycin (an antibiotic) was detected in all but one urban waste stream, with concentrations ranging from 30 ng/L to 2800 ng/L. Concentration levels of azithromycin, methamphetamine and pseudoephedrine showed temporal variation from the Tucson WWTP. Those ECs that were detected in the main surface water channels (those that are diverted for urban use and irrigation along the Colorado River) were in the region of the limit-of-detection (e.g., 10 ng/L), but most were below detection limits.

High-volume extraction of nucleic acids by magnetic bead technology for ultrasensitive detection of bacteria in blood components.

PubMed

Störmer, Melanie; Kleesiek, Knut; Dreier, Jens

2007-01-01

Nucleic acid isolation, the most technically demanding and laborious procedure performed in molecular diagnostics, harbors the potential for improvements in automation. A recent development is the use of magnetic beads covered with nucleic acid-binding matrices. We adapted this technology with a broad-range 23S rRNA real-time reverse transcription (RT)-PCR assay for fast and sensitive detection of bacterial contamination of blood products. We investigated different protocols for an automated high-volume extraction method based on magnetic-separation technology for the extraction of bacterial nucleic acids from platelet concentrates (PCs). We added 2 model bacteria, Staphylococcus epidermidis and Escherichia coli, to a single pool of apheresis-derived, single-donor platelets and assayed the PCs by real-time RT-PCR analysis with an improved primer-probe system and locked nucleic acid technology. Co-amplification of human beta(2)-microglobulin mRNA served as an internal control (IC). We used probit analysis to calculate the minimum concentration of bacteria that would be detected with 95% confidence. For automated magnetic bead-based extraction technology with the real-time RT-PCR, the 95% detection limit was 29 x 10(3) colony-forming units (CFU)/L for S. epidermidis and 22 x 10(3) CFU/L for E. coli. No false-positive results occurred, either due to nucleic acid contamination of reagents or externally during testing of 1030 PCs. High-volume nucleic acid extraction improved the detection limit of the assay. The improvement of the primer-probe system and the integration of an IC make the RT-PCR assay appropriate for bacteria screening of platelets.

Application of principal component regression and partial least squares regression in ultraviolet spectrum water quality detection

NASA Astrophysics Data System (ADS)

Li, Jiangtong; Luo, Yongdao; Dai, Honglin

2018-01-01

Water is the source of life and the essential foundation of all life. With the development of industrialization, the phenomenon of water pollution is becoming more and more frequent, which directly affects the survival and development of human. Water quality detection is one of the necessary measures to protect water resources. Ultraviolet (UV) spectral analysis is an important research method in the field of water quality detection, which partial least squares regression (PLSR) analysis method is becoming predominant technology, however, in some special cases, PLSR's analysis produce considerable errors. In order to solve this problem, the traditional principal component regression (PCR) analysis method was improved by using the principle of PLSR in this paper. The experimental results show that for some special experimental data set, improved PCR analysis method performance is better than PLSR. The PCR and PLSR is the focus of this paper. Firstly, the principal component analysis (PCA) is performed by MATLAB to reduce the dimensionality of the spectral data; on the basis of a large number of experiments, the optimized principal component is extracted by using the principle of PLSR, which carries most of the original data information. Secondly, the linear regression analysis of the principal component is carried out with statistic package for social science (SPSS), which the coefficients and relations of principal components can be obtained. Finally, calculating a same water spectral data set by PLSR and improved PCR, analyzing and comparing two results, improved PCR and PLSR is similar for most data, but improved PCR is better than PLSR for data near the detection limit. Both PLSR and improved PCR can be used in Ultraviolet spectral analysis of water, but for data near the detection limit, improved PCR's result better than PLSR.

Chemical Exchange Saturation Transfer in Chemical Reactions: A Mechanistic Tool for NMR Detection and Characterization of Transient Intermediates.

PubMed

Lokesh, N; Seegerer, Andreas; Hioe, Johnny; Gschwind, Ruth M

2018-02-07

The low sensitivity of NMR and transient key intermediates below detection limit are the central problems studying reaction mechanisms by NMR. Sensitivity can be enhanced by hyperpolarization techniques such as dynamic nuclear polarization or the incorporation/interaction of special hyperpolarized molecules. However, all of these techniques require special equipment, are restricted to selective reactions, or undesirably influence the reaction pathways. Here, we apply the chemical exchange saturation transfer (CEST) technique for the first time to NMR detect and characterize previously unobserved transient reaction intermediates in organocatalysis. The higher sensitivity of CEST and chemical equilibria present in the reaction pathway are exploited to access population and kinetics information on low populated intermediates. The potential of the method is demonstrated on the proline-catalyzed enamine formation for unprecedented in situ detection of a DPU stabilized zwitterionic iminium species, the elusive key intermediate between enamine and oxazolidinones. The quantitative analysis of CEST data at 250 K revealed the population ratio of [Z-iminium]/[exo-oxazolidinone] 0.02, relative free energy +8.1 kJ/mol (calculated +7.3 kJ/mol), and free energy barrier of +45.9 kJ/mol (ΔG ⧧ calc. (268 K) = +42.2 kJ/mol) for Z-iminium → exo-oxazolidinone. The findings underpin the iminium ion participation in enamine formation pathway corroborating our earlier theoretical prediction and help in better understanding. The reliability of CEST is validated using 1D EXSY-build-up techniques at low temperature (213 K). The CEST method thus serves as a new tool for mechanistic investigations in organocatalysis to access key information, such as chemical shifts, populations, and reaction kinetics of intermediates below the standard NMR detection limit.

Astrophysical tests for radiative decay of neutrinos and fundamental physics implications

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Brown, R. W.

1981-01-01

The radiative lifetime tau for the decay of massious neutrinos was calculated using various physical models for neutrino decay. The results were then related to the astrophysical problem of the detectability of the decay photons from cosmic neutrinos. Conversely, the astrophysical data were used to place lower limits on tau. These limits are all well below predicted values. However, an observed feature at approximately 1700 A in the ultraviolet background radiation at high galactic latitudes may be from the decay of neutrinos with mass approximately 14 eV. This would require a decay rate much larger than the predictions of standard models but could be indicative of a decay rate possible in composite models or other new physics. Thus an important test for substructure in leptons and quarks or other physics beyond the standard electroweak model may have been found.

Search for dark matter WIMPs using upward through-going muons in Super-Kamiokande

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, S.; Earl, M.; Kearns, E.

2004-10-15

We present the results of indirect searches for Weakly Interacting Massive Particles (WIMPs), with 1679.6 live days of data from the Super-Kamiokande detector using neutrino-induced upward through-going muons. The search is performed by looking for an excess of high energy muon neutrinos from WIMP annihilations in the Sun, the core of the Earth, and the Galactic Center, as compared to the number expected from the atmospheric neutrino background. No statistically significant excess was seen. We calculate the flux limits in various angular cones around each of the above celestial objects. We obtain conservative model-independent upper limits on the WIMP-nucleon crossmore » section as a function of WIMP mass, and compare these results with the corresponding results from direct dark matter detection experiments.« less

An assessment of public health surveillance of Zika virus infection and potentially associated outcomes in Latin America.

PubMed

Bautista, Leonelo E; Herrera, Víctor M

2018-05-24

We evaluated whether outbreaks of Zika virus (ZIKV) infection, newborn microcephaly, and Guillain-Barré syndrome (GBS) in Latin America may be detected through current surveillance systems, and how cases detected through surveillance may increase health care burden. We estimated the sensitivity and specificity of surveillance case definitions using published data. We assumed a 10% ZIKV infection risk during a non-outbreak period and hypothetical increases in risk during an outbreak period. We used sensitivity and specificity estimates to correct for non-differential misclassification, and calculated a misclassification-corrected relative risk comparing both periods. To identify the smallest hypothetical increase in risk resulting in a detectable outbreak we compared the misclassification-corrected relative risk to the relative risk corresponding to the upper limit of the endemic channel (mean + 2 SD). We also estimated the proportion of false positive cases detected during the outbreak. We followed the same approach for microcephaly and GBS, but assumed the risk of ZIKV infection doubled during the outbreak, and ZIKV infection increased the risk of both diseases. ZIKV infection outbreaks were not detectable through non-serological surveillance. Outbreaks were detectable through serologic surveillance if infection risk increased by at least 10%, but more than 50% of all cases were false positive. Outbreaks of severe microcephaly were detected if ZIKV infection increased prevalence of this condition by at least 24.0 times. When ZIKV infection did not increase the prevalence of severe microcephaly, 34.7 to 82.5% of all cases were false positive, depending on diagnostic accuracy. GBS outbreaks were detected if ZIKV infection increased the GBS risk by at least seven times. For optimal GBS diagnosis accuracy, the proportion of false positive cases ranged from 29 to 54% and from 45 to 56% depending on the incidence of GBS mimics. Current surveillance systems have a low probability of detecting outbreaks of ZIKV infection, severe microcephaly, and GBS, and could result in significant increases in health care burden, due to the detection of large numbers of false positive cases. In view of these limitations, Latin American countries should consider alternative options for surveillance.

Refractometric detection of liquids using tapered optical fiber and suspended core microstructured fiber: a comparison of methods.

PubMed

Martan, T; Nemecek, T; Komanec, M; Ahmad, R; Zvanovec, S

2017-03-20

Detecting explosive, flammable, or toxic industrial liquids reliably and accurately is a matter of civic responsibility that cannot be treated lightly. Tapered optical fibers (TOFs) and suspended core microstructured optical fibers (SC MOFs) were separately used as sensors of liquids without being compared to each other. We present a highly sensitive time-stable TOF sensor incorporated in the pipeline system for the in-line regime of measurement. This paper is furthermore focused on the comparison of this TOF and SC MOF of similar parameters for the detection of selected liquids. A validated method that incorporates TOF and SC MOF of small core (waist) diameter for refractometric detection is presented. The principle of detection is based on the overlap of an enhanced evanescent wave with a liquid analyte that either fills the cladding holes of the SC MOF or surrounds the waist area of the TOF. Optical power within the evanescent wave for both sensing structures and selected liquid analytes is analyzed. Measurement results concerning TOF and SC MOF are compared. Calculations to ascertain the limit of detection (LOD) for each sensor and the sensitivity (S) to refractive indices of liquid analytes in the range of 1.4269 to 1.4361 were performed at a wavelength of 1550 nm with the lowest refractive index step of 0.0007. Results affirming that S=600.96  dB/RIU and LOD=0.0733  RIU for the SC MOF and S=1143.2  dB/RIU and LOD of 0.0026 RIU for the TOF sensor were achieved, clearly illustrating that TOF-based sensors can reach close to two times greater sensitivity and 30 times higher limit of detection. This paper extends the comparison of the fiber sensors by discussing the potential applications.

First-principles calculations of optical transitions at native defects and impurities in ZnO

NASA Astrophysics Data System (ADS)

Lyons, John L.; Varley, Joel B.; Janotti, Anderson; Van de Walle, Chris G.

2018-02-01

Optical spectroscopy is a powerful approach for detecting defects and impurities in ZnO, an important electronic material. However, knowledge of how common optical signals are linked with defects and impurities is still limited. The Cu-related green luminescence is among the best understood luminescence signals, but theoretical descriptions of Cu-related optical processes have not agreed with experiment. Regarding native defects, assigning observed lines to specific defects has proven very difficult. Using first-principles calculations, we calculate the properties of native defects and impurities in ZnO and their associated optical signals. Oxygen vacancies are predicted to give luminescence peaks lower than 1 eV; while related zinc dangling bonds can lead to luminescence near 2.4 eV. Zinc vacancies lead to luminescence peaks below 2 eV, as do the related oxygen dangling bonds. However, when complexed with hydrogen impurities, zinc vacancies can cause higher-energy transitions, up to 2.3 eV. We also find that the Cu-related green luminescence is related to a (+/0) deep donor transition level.

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers.

PubMed

Sanjay, Sharma T; Dou, Maowei; Sun, Jianjun; Li, XiuJun

2016-07-26

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings.

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers

PubMed Central

Sanjay, Sharma T.; Dou, Maowei; Sun, Jianjun; Li, XiuJun

2016-01-01

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings. PMID:27456979

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers

NASA Astrophysics Data System (ADS)

Sanjay, Sharma T.; Dou, Maowei; Sun, Jianjun; Li, Xiujun

2016-07-01

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings.

Respiratory mechanics by least squares fitting in mechanically ventilated patients: application on flow-limited COPD patients.

PubMed

Volta, Carlo A; Marangoni, Elisabetta; Alvisi, Valentina; Capuzzo, Maurizia; Ragazzi, Riccardo; Pavanelli, Lina; Alvisi, Raffaele

2002-01-01

Although computerized methods of analyzing respiratory system mechanics such as the least squares fitting method have been used in various patient populations, no conclusive data are available in patients with chronic obstructive pulmonary disease (COPD), probably because they may develop expiratory flow limitation (EFL). This suggests that respiratory mechanics be determined only during inspiration. Eight-bed multidisciplinary ICU of a teaching hospital. Eight non-flow-limited postvascular surgery patients and eight flow-limited COPD patients. Patients were sedated, paralyzed for diagnostic purposes, and ventilated in volume control ventilation with constant inspiratory flow rate. Data on resistance, compliance, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) obtained by applying the least squares fitting method during inspiration, expiration, and the overall breathing cycle were compared with those obtained by the traditional method (constant flow, end-inspiratory occlusion method). Our results indicate that (a) the presence of EFL markedly decreases the precision of resistance and compliance values measured by the LSF method, (b) the determination of respiratory variables during inspiration allows the calculation of respiratory mechanics in flow limited COPD patients, and (c) the LSF method is able to detect the presence of PEEPi,dyn if only inspiratory data are used.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, H.B.; Hu, Y.J.; Bernstein, E.R.

Small methanol clusters are formed by expanding a mixture of methanol vapor seeded in helium and are detected using vacuum UV (vuv) (118 nm) single-photon ionization/linear time-of-flight mass spectrometer (TOFMS). Protonated cluster ions, (CH{sub 3}OH){sub n-1}H{sup +} (n=2-8), formed through intracluster ion-molecule reactions following ionization, essentially correlate to the neutral clusters, (CH{sub 3}OH){sub n}, in the present study using 118 nm light as the ionization source. Both experimental and Born-Haber calculational results clarify that not enough excess energy is released into protonated cluster ions to initiate further fragmentation in the time scale appropriate for linear TOFMS. Size-specific spectra for (CH{submore » 3}OH){sub n} (n=4 to 8) clusters in the OH stretch fundamental region are recorded by IR+vuv (118 nm) nonresonant ion-dip spectroscopy through the detection chain of IR multiphoton predissociation and subsequent vuv single-photon ionization. The general structures and gross features of these cluster spectra are consistent with previous theoretical calculations. The lowest-energy peak contributed to each cluster spectrum is redshifted with increasing cluster size from n=4 to 8, and limits near {approx}3220 cm{sup -1} in the heptamer and octamer. Moreover, IR+vuv nonresonant ionization detected spectroscopy is employed to study the OH stretch first overtone of the methanol monomer. The rotational temperature of the clusters is estimated to be at least 50 K based on the simulation of the monomer rotational envelope under clustering conditions.« less

Cyanomethanimine Isomers in Cold Interstellar Clouds: Insights from Electronic Structure and Kinetic Calculations

NASA Astrophysics Data System (ADS)

Vazart, Fanny; Latouche, Camille; Skouteris, Dimitrios; Balucani, Nadia; Barone, Vincenzo

2015-09-01

New insights into the formation of interstellar cyanomethanimine, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction CN + CH2 = NH. This reaction is a facile formation route of Z,E-C-cyanomethanimine, even under the extreme conditions of density and temperature typical of cold interstellar clouds. E-C-cyanomethanimine has been recently identified in Sgr B2(N) in the Green Bank Telescope (GBT) PRIMOS survey by P. Zaleski et al. and no efficient formation routes have been envisaged so far. The rate coefficient expression for the reaction channel leading to the observed isomer E-C-cyanomethanimine is 3.15 × 10-10 × (T/300)0.152 × e(-0.0948/T). According to the present study, the more stable Z-C-cyanomethanimine isomer is formed with a slightly larger yield (4.59 × 10-10 × (T/300)0.153 × e(-0.0871/T). As the detection of E-isomer is favored due to its larger dipole moment, the missing detection of the Z-isomer can be due to the sensitivity limit of the GBT PRIMOS survey and the detection of the Z-isomer should be attempted with more sensitive instrumentation. The CN + CH2 = NH reaction can also play a role in the chemistry of the upper atmosphere of Titan where the cyanomethanimine products can contribute to the buildup of the observed nitrogen-rich organic aerosols that cover the moon.

Predicting runoff induced mass loads in urban watersheds: Linking land use and pyrethroid contamination.

PubMed

Chinen, Kazue; Lau, Sim-Lin; Nonezyan, Michael; McElroy, Elizabeth; Wolfe, Becky; Suffet, Irwin H; Stenstrom, Michael K

2016-10-01

Pyrethroid pesticide mass loadings in the Ballona Creek Watershed were calculated using the volume-concentration method with a Geographic Information Systems (GIS) to explore potential relationships between urban land use, impervious surfaces, and pyrethroid runoff flowing into an urban stream. A calibration of the GIS volume-concentration model was performed using 2013 and 2014 wet-weather sampling data. Permethrin and lambda-cyhalothrin were detected as the highest concentrations; deltamethrin, lambda-cyhalothrin, permethrin and cyfluthrin were the most frequently detected synthetic pyrethroids. Eight neighborhoods within the watershed were highlighted as target areas based on a Weighted Overlay Analysis (WOA) in GIS. Water phase concentration of synthetic pyrethroids (SPs) were calculated from the reported usage. The need for stricter BMP and consumer product controls was identified as a possible way of reducing the detections of pyrethroids in Ballona Creek. This model has significant implications for determining mass loadings due to land use influence, and offers a flexible method to extrapolate data for a limited amount of samplings for a larger watershed, particularly for chemicals that are not subject to environmental monitoring. Offered as a simple approach to watershed management, the GIS-volume concentration model has the potential to be applied to other target pesticides and is useful for simulating different watershed scenarios. Further research is needed to compare results against other similar urban watersheds situated in mediterranean climates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Baseline trace metals in water and sediment of the Baleh River-a tropical river in Sarawak, Malaysia.

PubMed

Sim, Siong Fong; Chai, Hui Ping; Nyanti, Lee; Ling, Teck Yee; Grinang, Jongkar

2016-09-01

Quantitative indices are classically employed to evaluate the contamination status of metals with reference to the baseline concentrations. The baselines vary considerably across different geographical zones. It is imperative to determine the local geochemical baseline to evaluate the contamination status. No study has been done to establish the background concentrations in tropical rivers of this region. This paper reports the background concentrations of metals in water and sediment of the Baleh River, Sarawak, derived based on the statistical methods where the areas possibly disturbed are distinguished from the undisturbed area. The baseline levels of six elements in water determined were Al (0.34 mg/L), Fe (0.51 mg/L), Mn (0.12 mg/L), Cu (0.01 mg/L), Pb (0.03 mg/L), and Zn (0.05 mg/L). Arsenic and selenium were below the detection limit. For sediment, the background values were established according to statistical methods including (mean + 2σ), iterative 2σ, cumulative distribution frequency, interquartile, and calculation distribution function. The background values derived using the iterative 2σ algorithm and calculated distribution function were relatively lower. The baseline levels calculated were within the range reported in the literatures mainly from tropical and sub-tropical regions. The upper limits proposed for nine elements in sediment were Al (100,879 mg/kg), Cr (75.45 mg/kg), Cu (34.59 mg/kg), Fe (37,823 mg/kg), Mn (793 mg/kg), Ni (22.88 mg/kg), Pb (27.26 mg/kg), Zn (70.64 mg/kg), and Hg (0.33 mg/kg). Quantitative indices calculated suggest low risk of contamination at the Baleh River.

Determination of thimerosal in pharmaceutical industry effluents and river waters by HPLC coupled to atomic fluorescence spectrometry through post-column UV-assisted vapor generation.

PubMed

Acosta, Gimena; Spisso, Adrián; Fernández, Liliana P; Martinez, Luis D; Pacheco, Pablo H; Gil, Raúl A

2015-03-15

A high performance liquid chromatography coupled with atomic fluorescence spectrometry method for the determination of thimerosal (sodium ethylmercury thiosalicylate, C9H9HgNaO2S), ethylmercury, and inorganic mercury is proposed. Mercury vapor is generated by the post-column reduction of mercury species in formic acid media using UV-radiation. Thimerosal is quantitatively converted to Hg(II) followed by the reduction of Hg(II) to Hg(0). This method is applied to the determination of thimerosal (THM), ethylmercury (EtHg) and inorganic Hg in samples of a pharmaceutical industry effluent, and in waters of the San Luis River situated in the west side of San Luis city (Middle West, Argentine) where the effluents are dumped. The limit of detections, calculated on the basis of the 3σ criterion, where 0.09, 0.09 and 0.07 μg L(-1) for THM, EtHg(II) and for Hg(II), respectively. Linearity was attained from levels close to the detection limit up to at least 100 μg L(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Thermally stable hybrid polyarylidene(azomethine-ether)s polymers (PAAP): an ultrasensitive arsenic(III) sensor approach

PubMed Central

Rahman, Mohammed M.; Hussein, Mahmoud A.; Aly, Kamal I.; Asiri, Abdullah M.

2018-01-01

ABSTRACT A new category of thermally stable hybrid polyarylidene(azomethine-ether)s and copolyarylidene(azomethine-ether)s (PAAP) based on diarylidenecycloalkanones has been synthesized using solution polycondensation method. For potential cationic sensor development, a thin layer of PAAP onto a flat glassy carbon electrode (GCE, surface area: 0.0316 cm2) was prepared with conducting nafion (5%) coating agent to fabricate a sensitive and selective arsenic (III) [As3+] ion in short response time in neutral buffer system. The fabricated cationic sensor was measured the analytical performances such as higher sensitivity, linear dynamic range, detection limit, reproducibility, and long-term stability towards As3+ ions. The sensitivity and detection limit were calculated as 2.714 μAμM−1cm−2 and 6.8 ± 0.1 nM (SNR of 3; 3N/S) respectively from the calibration curve. This novel approach can be initiated a well-organized route of an efficient development of heavy selective arsenic sensor for hazardous pollutants in biological, environmental, and health care fields. Real sample analysis for various environmental sample was performed with PAAP-modified-GCE. PMID:29844770

Analytical possibilities of different X-ray fluorescence systems for determination of trace elements in aqueous samples pre-concentrated with carbon nanotubes

NASA Astrophysics Data System (ADS)

Marguí, E.; Zawisza, B.; Skorek, R.; Theato, T.; Queralt, I.; Hidalgo, M.; Sitko, R.

2013-10-01

This study was aimed to achieve improved instrumental sensitivity and detection limits for multielement determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Se, Pb and Cd in liquid samples by using different X-ray fluorescence (XRF) configurations (a benchtop energy-dispersive X-ray fluorescence spectrometer, a benchtop polarised energy-dispersive X-ray fluorescence spectrometer and a wavelength-dispersive X-ray fluorescence spectrometer). The preconcentration of metals from liquid solutions consisted on a solid-phase extraction using carbon nanotubes (CNTs) as solid sorbents. After the extraction step, the aqueous sample was filtered and CNTs with the absorbed elements were collected onto a filter paper which was directly analyzed by XRF. The calculated detection limits in all cases were in the low ng mL- 1 range. Nevertheless, results obtained indicate the benefits, in terms of sensitivity, of using polarized X-ray sources using different secondary targets in comparison to conventional XRF systems, above all if Cd determination is required. The developed methodologies, using the aforementioned equipments, have been applied for multielement determination in water samples from an industrial area of Poland.

On-line preconcentration/determination of lead in Ilex paraguariensis samples (mate tea) using polyurethane foam as filter and USN-ICP-OES.

PubMed

Marchisio, P F; Sales, A; Cerutti, S; Marchevski, E; Martinez, L D

2005-09-30

The present paper proposes an on-line preconcentration procedure for lead determination in Ilex paraguariensis (St. Hilaire) samples by ultrasonic nebulization associated to inductively coupled plasma optical emission spectrometry (USN-ICP-OES). It is based on the precipitation of lead(II) ion on a minicolumn packed with polyurethane foam using 2-(5-bromo-2-pyridilazo)-5-diethylaminophenol (5-Br-PADAP) as precipitating reagent. The collected analyte precipitate was quantitatively eluted from the minicolumn with 20% (v/v) nitric acid. An enhancement factor of 225-fold was obtained (15 for USN and 15 for preconcentration). The detection limit (DL) value for the preconcentration of 10.0 ml of sample was 40.0 ng/l. The relative standard deviation (R.S.D.) was 3.0% for a Pb concentration of 1 microg/l, calculated from the peak heights obtained. The calibration graph using the preconcentration system for lead was linear with a correlation coefficient of 0.9997, at levels near the detection limits up to at least 100 microg/l. The preconcentration procedure was successfully applied to the determination of lead in mate tea samples.

25 CFR 1000.141 - Is there a predetermined cap or limit on indirect cost rates or a fixed formula for calculating...

Code of Federal Regulations, 2010 CFR

2010-04-01

... 25 Indians 2 2010-04-01 2010-04-01 false Is there a predetermined cap or limit on indirect cost rates or a fixed formula for calculating indirect cost rates? 1000.141 Section 1000.141 Indians OFFICE... cap or limit on indirect cost rates or a fixed formula for calculating indirect cost rates? No...

Real-time PCR detection and quantification of nine potential sources of fecal contamination by analysis of mitochondrial Cytochrome b targets

USGS Publications Warehouse

Schill, W.B.; Mathes, M.V.

2008-01-01

We designed and tested real-time PCR probe/primer sets to detect and quantify Cytochrome b sequences of mitochondrial DNA (mtDNA) from nine vertebrate species of pet (dog), farm (cow, chicken, sheep, horse, pig), wildlife (Canada goose, white-tailed deer), and human. Linear ranges of the assays were from 101 to 108 copies/??l. To formally test the performance of the assays, twenty blinded fecal suspension samples were analyzed by real-time PCR to identify the source of the feces. Sixteen of the twenty samples were correctly and unambiguously identified. Average sensitivity was calculated to be 0.850, while average specificity was found to be 0.994. One beef cow sample was not detected, but mtDNA from 11 other beef cattle of both sexes and varying physiological states was found in concentrations similar (3.45 ?? 107 copies/g) to thatfound in human feces (1.1 ?? 107 copies/g). Thus, environmental conditions and sample handling are probably important factors for successful detection of fecal mtDNA. When sewage samples were analyzed, only human mtDNA (7.2 ?? 104 copies/100 mL) was detected. With a detection threshold of 250 copies/reaction, an efficient concentration and purification method resulted in a final detection limit for human feces of 1.8 mg/100 mL water.

Capillary moving-boundary isotachophoresis with electrospray ionization mass-spectrometric detection and hydrogen ion used as essential terminator: Methodology for sensitive analysis of hydroxyderivatives of s-triazine herbicides in waters.

PubMed

Malá, Zdena; Gebauer, Petr

2017-10-06

Capillary isotachophoresis (ITP) is an electrophoretic technique offering high sensitivity due to permanent stacking of the migrating analytes. Its combination with electrospray-ionization mass-spectrometric (ESI-MS) detection is limited by the narrow spectrum of ESI-compatible components but can be compensated by experienced system architecture. This work describes a methodology for sensitive analysis of hydroxyderivatives of s-triazine herbicides, based on implementation of the concepts of moving-boundary isotachophoresis and of H + as essential terminating component into cationic ITP with ESI-MS detection. Theoretical description of such kind of system is given and equations for zone-related boundary mobilities are derived, resulting in a much more general definition of the effective mobility of the terminating H + zone than used so far. Explicit equations allowing direct calculation for selected simple systems are derived. The presented theory allows prediction of stacking properties of particular systems and easy selection of suitable electrolyte setups. A simple ESI-compatible system composed of acetic acid and ammonium with H + and ammonium as a mixed terminator was selected for the analysis of 2-hydroxyatrazine and 2-hydroxyterbutylazine, degradation products of s-triazine herbicides. The proposed method was tested with direct injection without any sample pretreatment and provided excellent linearity and high sensitivity with limits of detection below 100ng/L (0.5nM). Example analyses of unspiked and spiked drinking and river water are shown. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced Propagating Surface Plasmon Signal Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Y.; Joly, Alan G.; El-Khoury, Patrick Z.

2016-12-21

Overcoming the dissipative nature of propagating surface plasmons (PSPs) is pre-requisite to realizing functional plasmonic circuitry, in which large bandwidth signals can be manipulated over length scales far-below the diffraction limit of light. To this end, we report on a novel PSP enhanced signal detection technique achieved in an all-metallic substrate. We take advantage of two strategically spatio-temporally separated phase-locked femtosecond laser pulses, incident onto lithographically patterned PSP coupling structures. We follow PSP propagation with joint femtosecond temporal and nanometer spatial resolution in a time-resolved non-linear photoemission electron microscopy scheme. Initially, a PSP signal wave packet is launched from amore » hole etched into the silver surface from where it propagates through an open trench structure and is decoded through the use of a timed probe pulse. FDTD calculations demonstrate that PSP signal waves may traverse open trenches in excess of 10 microns in diameter, thereby allowing remote detection even through vacuum regions. This arrangement results in a 10X enhancement in photoemission relative to readout from the bare metal surface. The enhancement is attributed to an all-optical homodyne detection technique that mixes signal and reference PSP waves in a non-linear scheme. Larger readout trenches achieve higher readout levels, however reduced transmission through the trench limits the trench size to 6 microns for maximum readout levels. However, the use of an array of trenches increases the maximum enhancement to near 30X. The attainable enhancement factor may be harnessed to achieve extended coherent PSP propagation in ultrafast plasmonic circuitry.« less

Limits to the Cassiopeia A 44Ti Line Flux and Constraints on the Ejecta Energy and the Compact Source

NASA Astrophysics Data System (ADS)

Rothschild, R. E.; Lingenfelter, R. E.

2003-01-01

Two long observations of the Cas A supernova remnant were made by the Rossi X-Ray Timing Explorer in 1996 and 1997 to search for hard X-ray line emission at 67.9 and 78.4 keV from the decay of 44Ti formed during the supernova event. Continuum flux was detected up to 100 keV, but the 44Ti lines were not detected. The 90% confidence upper limit to the line flux is 3.6×10-5 photons cm-2 s-1. This is consistent with the recent BeppoSAX detection and with the Compton Gamma Ray Observatory/Imaging Compton Telescope (CGRO/COMPTEL) detection of the companion transition line flux for 44Sc decay. The mean BeppoSAX-COMPTEL flux indicates that 1.5+/-0.3×10-4 Msolar of 44Ti was produced in the supernova explosion. On the basis of recent theoretical calculations and optical observations suggesting a WN Wolf-Rayet progenitor with an initial mass of >=25 Msolar, the observed 44Ti yield implies that the Cas A supernova ejecta energy was ~2×1051 ergs, and as a result a neutron star was formed, rather than a black hole. We suggest that Cas A is possibly in the early stages of the anomalous X-ray pulsar/soft gamma-ray repeater (AXP/SGR) scenario in which the pushback disk has yet to form, and when the disk does form, the accretion will increase the luminosity to that of present-day AXP/SGRs, and pulsed emission will commence.

[Quantitative analysis of Cu in water by collinear DP-LIBS].

PubMed

Zheng, Mei-Lan; Yao, Ming-Yin; Chen, Tian-Bing; Lin, Yong-Zeng; Li, Wen-Bing; Liu, Mu-Hua

2014-07-01

The purpose of this research is to study the influence of double pulse laser induced breakdown spectroscopy (DP-LIBS) on the sensitivity of Cu in water. The water solution of Cu was tested by collinear DP-LIBS in this article. The results show that spectral intensity of Cu can be enhanced obviously by DP-LIBS, compared with single pulse laser induced breakdown spectroscopy (SP-LIBS). Besides, the experimental results were significantly impacted by delay time between laser pulse and spectrometer acquisition, delay time of double laser pulse and energy of laser pulse and so on. The paper determined the best conditions for DP-LIBS detecting Cu in water. The optimal acquisition delay time was 1 380 ns. The best laser pulse delay time was 25 ns. The most appropriate energy of double laser pulse was 100 mJ. Characteristic analysis of spectra of Cu at 324.7 and 327.4 nm was done for quantitative analysis. The detection limit was 3.5 microg x mL(-1) at 324.7 nm, and the detection limit was 4.84 microg x mL(-1) at 327.4 nm. The relative standard deviation of the two characteristic spectral lines was within 10%. The calibration curve of characteristic spectral line, established by 327.4 nm, was verified with 500 microg x mL(-1) sample. Concentration of the sample was 446 microg x mL(-1) calculated by the calibration curve. This research shows that the detection sensitivity of Cu in water can be improved by DP-LIBS. At the same time, it had high stability.

A nucleic acid strand displacement system for the multiplexed detection of tuberculosis-specific mRNA using quantum dots

NASA Astrophysics Data System (ADS)

Gliddon, H. D.; Howes, P. D.; Kaforou, M.; Levin, M.; Stevens, M. M.

2016-05-01

The development of rapid, robust and high performance point-of-care diagnostics relies on the advancement and combination of various areas of research. We have developed an assay for the detection of multiple mRNA molecules that combines DNA nanotechnology with fluorescent nanomaterials. The core switching mechanism is toehold-mediated strand displacement. We have used fluorescent quantum dots (QDs) as signal transducers in this assay, as they bring many benefits including bright fluorescence and multiplexing abilities. The resulting assay is capable of multiplexed detection of long RNA targets against a high concentration of background non-target RNA, with high sensitivity and specificity and limits of detection in the nanomolar range using only a standard laboratory plate reader. We demonstrate the utility of our QD-based system for the detection of two genes selected from a microarray-derived tuberculosis-specific gene expression signature. Levels of up- and downregulated gene transcripts comprising this signature can be combined to give a disease risk score, making the signature more amenable for use as a diagnostic marker. Our QD-based approach to detect these transcripts could pave the way for novel diagnostic assays for tuberculosis.The development of rapid, robust and high performance point-of-care diagnostics relies on the advancement and combination of various areas of research. We have developed an assay for the detection of multiple mRNA molecules that combines DNA nanotechnology with fluorescent nanomaterials. The core switching mechanism is toehold-mediated strand displacement. We have used fluorescent quantum dots (QDs) as signal transducers in this assay, as they bring many benefits including bright fluorescence and multiplexing abilities. The resulting assay is capable of multiplexed detection of long RNA targets against a high concentration of background non-target RNA, with high sensitivity and specificity and limits of detection in the nanomolar range using only a standard laboratory plate reader. We demonstrate the utility of our QD-based system for the detection of two genes selected from a microarray-derived tuberculosis-specific gene expression signature. Levels of up- and downregulated gene transcripts comprising this signature can be combined to give a disease risk score, making the signature more amenable for use as a diagnostic marker. Our QD-based approach to detect these transcripts could pave the way for novel diagnostic assays for tuberculosis. Electronic supplementary information (ESI) available: Base pair mismatch tuning of CProbes. Binding capacity of the QDs. Theoretical limit of detection (LOD) for the monoplex systems. Kinetics of strand displacement. Kinetics of QProbe-CProbe binding. LOD and saturation point calculations. See DOI: 10.1039/c6nr00484a

Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Fuchs, Hendrik; Novelli, Anna; Rolletter, Michael; Hofzumahaus, Andreas; Pfannerstill, Eva Y.; Kessel, Stephan; Edtbauer, Achim; Williams, Jonathan; Michoud, Vincent; Dusanter, Sebastien; Locoge, Nadine; Zannoni, Nora; Gros, Valerie; Truong, Francois; Sarda-Esteve, Roland; Cryer, Danny R.; Brumby, Charlotte A.; Whalley, Lisa K.; Stone, Daniel; Seakins, Paul W.; Heard, Dwayne E.; Schoemaecker, Coralie; Blocquet, Marion; Coudert, Sebastien; Batut, Sebastien; Fittschen, Christa; Thames, Alexander B.; Brune, William H.; Ernest, Cheryl; Harder, Hartwig; Muller, Jennifer B. A.; Elste, Thomas; Kubistin, Dagmar; Andres, Stefanie; Bohn, Birger; Hohaus, Thorsten; Holland, Frank; Li, Xin; Rohrer, Franz; Kiendler-Scharr, Astrid; Tillmann, Ralf; Wegener, Robert; Yu, Zhujun; Zou, Qi; Wahner, Andreas

2017-10-01

Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapour, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection < 1 s-1 at a time resolution of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s-1 at a time resolution of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concentrations of carbon monoxide (CO), water vapour or nitric oxide (NO). In further experiments, mixtures of organic reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and aromatic compounds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile organic compounds in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to reference measurements or to calculated reactivity were observed by CRM instruments in the presence of terpenes and oxygenated organic compounds (mixing ratio of OH reactants were up to 10 ppbv). In some of these experiments, only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapour on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flow-tube instrument combined with the direct detection of OH by chemical ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concentrations but were accurate for low reactivity (< 15 s-1) and low NO (< 5 ppbv) conditions.

Interaction of cosmic ray muons with spent nuclear fuel dry casks and determination of lower detection limit

NASA Astrophysics Data System (ADS)

Chatzidakis, S.; Choi, C. K.; Tsoukalas, L. H.

2016-08-01

The potential non-proliferation monitoring of spent nuclear fuel sealed in dry casks interacting continuously with the naturally generated cosmic ray muons is investigated. Treatments on the muon RMS scattering angle by Moliere, Rossi-Greisen, Highland and, Lynch-Dahl were analyzed and compared with simplified Monte Carlo simulations. The Lynch-Dahl expression has the lowest error and appears to be appropriate when performing conceptual calculations for high-Z, thick targets such as dry casks. The GEANT4 Monte Carlo code was used to simulate dry casks with various fuel loadings and scattering variance estimates for each case were obtained. The scattering variance estimation was shown to be unbiased and using Chebyshev's inequality, it was found that 106 muons will provide estimates of the scattering variances that are within 1% of the true value at a 99% confidence level. These estimates were used as reference values to calculate scattering distributions and evaluate the asymptotic behavior for small variations on fuel loading. It is shown that the scattering distributions between a fully loaded dry cask and one with a fuel assembly missing initially overlap significantly but their distance eventually increases with increasing number of muons. One missing fuel assembly can be distinguished from a fully loaded cask with a small overlapping between the distributions which is the case of 100,000 muons. This indicates that the removal of a standard fuel assembly can be identified using muons providing that enough muons are collected. A Bayesian algorithm was developed to classify dry casks and provide a decision rule that minimizes the risk of making an incorrect decision. The algorithm performance was evaluated and the lower detection limit was determined.

Behavioral Characteristics and CO+CO2 Production Rates of Halley-Type Comets Observed by NEOWISE

NASA Astrophysics Data System (ADS)

Rosser, Joshua David; Bauer, James M.; Mainzer, Amy K.; Kramer, Emily A.; Masiero, Joseph R.; Nugent, Carrie; Sonnett, Sarah M.; Fernandez, Yanga R.; Wright, Edward L.; WISE, NEOWISE

2017-10-01

From the NEOWISE dataset of comet images, 11 different Halley-Type Comets (HTCs) were identified and analyzed for dust production rates (Afρ), CO+CO2 production rates (QCO2), and nucleus size. The objects considered ranged in heliocentric distance from 1.21 AU to 2.66 AU and were only considered when showing signs of reasonable activity. When multiple epochs were included and when combined with data from previous WISE and NEOWISE studies, our dataset totaled to 21 observations; 13 of which included active comets, and 7 for which we calculated upper limits of production. Comet P/2010 JC81 was removed from consideration due to clear inactivity. For this study, active comets are defined as those which exhibit excess signal of at least 3σ in the 4.6 μm detection band, while comets for which upper limits were calculated demonstrated excess signal of 1σ in the 4.6 μm detection band. Furthermore, we confirmed the nucleus size of 27P, P/2006 HR30, C/2010 L5, P/2012 NJ, C/2016 S1. We found that given the range in heliocentric distance for this sample of HTCs, Afρ ranged from 0.790 ± 0.036 to 2.64 ± 0.14, and QCO2 ranged from 25.08 ± 0.08 to 26.71 ± 0.12. No significant correlation between dust production and heliocentric distance, nor CO+CO2 production with heliocentric distance was found for this population. This poster will display production rates and other physical properties of these HTCs, as well as place the ensemble of HTC production rate properties into context.

Transit Spectroscopy of Extrasolar Planet HD209458b: The Radiative Transfer Model

NASA Astrophysics Data System (ADS)

Rojo, P.; Harrington, J.; Dermody, J.; Zeehandelaar, D.; Deming, D.; Wiedemann, G.; Seager, S.; Iro, N.; Fortney, J. J.; Burrows, A.

2004-11-01

We have developed a new code that calculates the modulation of a star's spectrum as a planet transits. We are applying this model to data from the VLT, Palomar, Keck, and IRTF to search for water on HD209458b, the transiting planet with the brightest primary. Observations of HD209458b's stellar spectrum modulation have yielded the first detections of exoplanetary sodium (Charbonneau et al. 2001), hydrogen, oxygen and carbon (Vidal-Madjar et al. 2003, 2004). Molecules, however, have still avoided detection. Water is predicted to be abundant at all plausible temperatures, but the modulation for most of the observable features is <0.04%. By simultaneously fitting for many excited water features while avoiding telluric water lines, we can significantly increase our signal. Our model predicts the modulation given line data, system geometry, and thermal and abundance profiles for any transiting planet. We will use this code to compare the observed modulation for HD209458b with that predicted by different planetary theories, do calculations for specific instruments with different resolutions and wavelength ranges, and constrain the abundances of detected species. We find that integrating the extinction over altitude produces significantly better results than assuming that the planet is an opaque disk whose radius is the altitude of optical depth unity. The latter is a widely used simplification. Our work will allow us to establish or place strong limits on the water abundance in HD209458b's atmosphere. Even a non-detection will be important, as it will require significant modifications to existing theory and/or will justify the need for better space-based instruments. This work was supported by NASA grant NAG5-13154.

The Power of Low Back Pain Trials: A Systematic Review of Power, Sample Size, and Reporting of Sample Size Calculations Over Time, in Trials Published Between 1980 and 2012.

PubMed

Froud, Robert; Rajendran, Dévan; Patel, Shilpa; Bright, Philip; Bjørkli, Tom; Eldridge, Sandra; Buchbinder, Rachelle; Underwood, Martin

2017-06-01

A systematic review of nonspecific low back pain trials published between 1980 and 2012. To explore what proportion of trials have been powered to detect different bands of effect size; whether there is evidence that sample size in low back pain trials has been increasing; what proportion of trial reports include a sample size calculation; and whether likelihood of reporting sample size calculations has increased. Clinical trials should have a sample size sufficient to detect a minimally important difference for a given power and type I error rate. An underpowered trial is one within which probability of type II error is too high. Meta-analyses do not mitigate underpowered trials. Reviewers independently abstracted data on sample size at point of analysis, whether a sample size calculation was reported, and year of publication. Descriptive analyses were used to explore ability to detect effect sizes, and regression analyses to explore the relationship between sample size, or reporting sample size calculations, and time. We included 383 trials. One-third were powered to detect a standardized mean difference of less than 0.5, and 5% were powered to detect less than 0.3. The average sample size was 153 people, which increased only slightly (∼4 people/yr) from 1980 to 2000, and declined slightly (∼4.5 people/yr) from 2005 to 2011 (P < 0.00005). Sample size calculations were reported in 41% of trials. The odds of reporting a sample size calculation (compared to not reporting one) increased until 2005 and then declined (Equation is included in full-text article.). Sample sizes in back pain trials and the reporting of sample size calculations may need to be increased. It may be justifiable to power a trial to detect only large effects in the case of novel interventions. 3.

Aerial Measuring System Sensor Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. S. Detwiler

2002-04-01

This project deals with the modeling the Aerial Measuring System (AMS) fixed-wing and rotary-wing sensor systems, which are critical U.S. Department of Energy's National Nuclear Security Administration (NNSA) Consequence Management assets. The fixed-wing system is critical in detecting lost or stolen radiography or medical sources, or mixed fission products as from a commercial power plant release at high flying altitudes. The helicopter is typically used at lower altitudes to determine ground contamination, such as in measuring americium from a plutonium ground dispersal during a cleanup. Since the sensitivity of these instruments as a function of altitude is crucial in estimatingmore » detection limits of various ground contaminations and necessary count times, a characterization of their sensitivity as a function of altitude and energy is needed. Experimental data at altitude as well as laboratory benchmarks is important to insure that the strong effects of air attenuation are modeled correctly. The modeling presented here is the first attempt at such a characterization of the equipment for flying altitudes. The sodium iodide (NaI) sensors utilized with these systems were characterized using the Monte Carlo N-Particle code (MCNP) developed at Los Alamos National Laboratory. For the fixed wing system, calculations modeled the spectral response for the 3-element NaI detector pod and High-Purity Germanium (HPGe) detector, in the relevant energy range of 50 keV to 3 MeV. NaI detector responses were simulated for both point and distributed surface sources as a function of gamma energy and flying altitude. For point sources, photopeak efficiencies were calculated for a zero radial distance and an offset equal to the altitude. For distributed sources approximating an infinite plane, gross count efficiencies were calculated and normalized to a uniform surface deposition of 1 {micro}Ci/m{sup 2}. The helicopter calculations modeled the transport of americium-241 ({sup 241}Am) as this is the ''marker'' isotope utilized by the system for Pu detection. The helicopter sensor array consists of 2 six-element NaI detector pods, and the NaI pod detector response was simulated for a distributed surface source of {sup 241}Am as a function of altitude.« less

On Aethalometer measurement uncertainties and an instrument correction factor for the Arctic

NASA Astrophysics Data System (ADS)

Backman, John; Schmeisser, Lauren; Virkkula, Aki; Ogren, John A.; Asmi, Eija; Starkweather, Sandra; Sharma, Sangeeta; Eleftheriadis, Konstantinos; Uttal, Taneil; Jefferson, Anne; Bergin, Michael; Makshtas, Alexander; Tunved, Peter; Fiebig, Markus

2017-12-01

Several types of filter-based instruments are used to estimate aerosol light absorption coefficients. Two significant results are presented based on Aethalometer measurements at six Arctic stations from 2012 to 2014. First, an alternative method of post-processing the Aethalometer data is presented, which reduces measurement noise and lowers the detection limit of the instrument more effectively than boxcar averaging. The biggest benefit of this approach can be achieved if instrument drift is minimised. Moreover, by using an attenuation threshold criterion for data post-processing, the relative uncertainty from the electronic noise of the instrument is kept constant. This approach results in a time series with a variable collection time (Δt) but with a constant relative uncertainty with regard to electronic noise in the instrument. An additional advantage of this method is that the detection limit of the instrument will be lowered at small aerosol concentrations at the expense of temporal resolution, whereas there is little to no loss in temporal resolution at high aerosol concentrations ( > 2.1-6.7 Mm-1 as measured by the Aethalometers). At high aerosol concentrations, minimising the detection limit of the instrument is less critical. Additionally, utilising co-located filter-based absorption photometers, a correction factor is presented for the Arctic that can be used in Aethalometer corrections available in literature. The correction factor of 3.45 was calculated for low-elevation Arctic stations. This correction factor harmonises Aethalometer attenuation coefficients with light absorption coefficients as measured by the co-located light absorption photometers. Using one correction factor for Arctic Aethalometers has the advantage that measurements between stations become more inter-comparable.

Diagnostic accuracy of two multiplex real-time polymerase chain reaction assays for the diagnosis of meningitis in children in a resource-limited setting.

PubMed

Khumalo, Jermaine; Nicol, Mark; Hardie, Diana; Muloiwa, Rudzani; Mteshana, Phindile; Bamford, Colleen

2017-01-01

Accurate etiological diagnosis of meningitis is important, but difficult in resource-limited settings due to prior administration of antibiotics and lack of viral diagnostics. We aimed to develop and validate 2 real-time multiplex PCR (RT-PCR) assays for the detection of common causes of community-acquired bacterial and viral meningitis in South African children. We developed 2 multiplex RT- PCRs for detection of S. pneumoniae, N. meningitidis, H. influenzae, enteroviruses, mumps virus and herpes simplex virus. We tested residual CSF samples from children presenting to a local paediatric hospital over a one-year period, whose CSF showed an abnormal cell count. Results were compared with routine diagnostic tests and the final discharge diagnosis. We calculated accuracy of the bacterial RT-PCR assay compared to CSF culture and using World Health Organisation definitions of laboratory-confirmed bacterial meningitis. From 292 samples, bacterial DNA was detected in 12 (4.1%) and viral nucleic acids in 94 (32%). Compared to CSF culture, the sensitivity and specificity of the bacterial RT-PCR was 100% and 97.2% with complete agreement in organism identification. None of the cases positive by viral RT-PCR had a bacterial cause confirmed on CSF culture. Only 9/90 (10%) of patients diagnosed clinically as bacterial meningitis or partially treated bacterial meningitis tested positive with the bacterial RT-PCR. In this population the use of 2 multiplex RT-PCRs targeting 6 common pathogens gave promising results. If introduced into routine diagnostic testing, these multiplex RT-PCR assays would supplement other diagnostic tests, and have the potential to limit unnecessary antibiotic therapy and hospitalisation.

Diagnostic accuracy of two multiplex real-time polymerase chain reaction assays for the diagnosis of meningitis in children in a resource-limited setting

PubMed Central

Khumalo, Jermaine; Nicol, Mark; Hardie, Diana; Muloiwa, Rudzani; Mteshana, Phindile

2017-01-01

Introduction Accurate etiological diagnosis of meningitis is important, but difficult in resource-limited settings due to prior administration of antibiotics and lack of viral diagnostics. We aimed to develop and validate 2 real-time multiplex PCR (RT-PCR) assays for the detection of common causes of community-acquired bacterial and viral meningitis in South African children. Methods We developed 2 multiplex RT- PCRs for detection of S. pneumoniae, N. meningitidis, H. influenzae, enteroviruses, mumps virus and herpes simplex virus. We tested residual CSF samples from children presenting to a local paediatric hospital over a one-year period, whose CSF showed an abnormal cell count. Results were compared with routine diagnostic tests and the final discharge diagnosis. We calculated accuracy of the bacterial RT-PCR assay compared to CSF culture and using World Health Organisation definitions of laboratory-confirmed bacterial meningitis. Results From 292 samples, bacterial DNA was detected in 12 (4.1%) and viral nucleic acids in 94 (32%). Compared to CSF culture, the sensitivity and specificity of the bacterial RT-PCR was 100% and 97.2% with complete agreement in organism identification. None of the cases positive by viral RT-PCR had a bacterial cause confirmed on CSF culture. Only 9/90 (10%) of patients diagnosed clinically as bacterial meningitis or partially treated bacterial meningitis tested positive with the bacterial RT-PCR. Discussion In this population the use of 2 multiplex RT-PCRs targeting 6 common pathogens gave promising results. If introduced into routine diagnostic testing, these multiplex RT-PCR assays would supplement other diagnostic tests, and have the potential to limit unnecessary antibiotic therapy and hospitalisation. PMID:28346504

Quantitation of the immunological adjuvants, monophosphoryl lipid A and Quil A in poly (lactic-co-glycolic acid) nanoparticles using high performance liquid chromatography with evaporative light scattering detection.

PubMed

Bobbala, Sharan; McDowell, Arlene; Hook, Sarah

2015-01-15

Monophosphoryl lipid A (MPL) and Quil A are two immunological adjuvants commonly used in vaccines. At present no simple, validated methods for the quantification of Quil A and MPL have been previously reported therefore the aim of the current study was to develop a simple, fast and validated method to quantify MPL and Quil A using high performance liquid chromatography evaporative light scattering detection (HPLC-ELSD). The HPLC-ELSD technique was carried out using a ZORBAX Eclipse XDB-C8 column (2.1×50 mm; particle size, 3.5 μm) in an isocratic elution mode at 25 °C. MPL was eluted at a retention time of 1.8 min with methanol-water as the mobile phase and a detector temperature of 75 °C. Quil A was resolved as three peaks with retention times of 4.1, 5.5 and 6.4 min with a detector temperature of 30 °C and with water-acetonitrile and 0.01% formic acid as the mobile phase. The nebulizer pressure and gain were set at 3.5 bar and 10, respectively. Calibration curves plotted for both the adjuvants had an R(2)>0.997. Accuracy, intra- and inter-day precision were within the accepted limits. The limit of detection for MPL and Quil A were calculated as 1.343 and 2.06 μg/mL, respectively. The limit of quantification was 2.445 for MPL and 8.97 μg/mL for Quil A. This analytical method was used to quantify the entrapment and in vitro release of MPL and Quil A in a poly lactic-co-glycolic acid (PLGA) nanoparticle vaccine. Copyright © 2014 Elsevier B.V. All rights reserved.

Leak detection by mass balance effective for Norman Wells line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liou, J.C.P.

Mass-balance calculations for leak detection have been shown as effective as a leading software system, in a comparison based on a major Canadian crude-oil pipeline. The calculations and NovaCorp`s Leakstop software each detected 4% (approximately) or greater leaks on Interprovincial Pipe Line (IPL) Inc.`s Norman Wells pipeline. Insufficient data exist to assess performances of the two methods for leaks smaller than 4%. Pipeline leak detection using such software-based systems are common. Their effectiveness is measured by how small and how quickly a leak can be detected. Algorithms used and measurement uncertainties determine leak detectability.

Investigation of absolute and relative response for three different liquid chromatography/tandem mass spectrometry systems; the impact of ionization and detection saturation.

PubMed

Nilsson, Lars B; Skansen, Patrik

2012-06-30

The investigations in this article were triggered by two observations in the laboratory; for some liquid chromatography/tandem mass spectrometry (LC/MS/MS) systems it was possible to obtain linear calibration curves for extreme concentration ranges and for some systems seemingly linear calibration curves gave good accuracy at low concentrations only when using a quadratic regression function. The absolute and relative responses were tested for three different LC/MS/MS systems by injecting solutions of a model compound and a stable isotope labeled internal standard. The analyte concentration range for the solutions was 0.00391 to 500 μM (128,000×), giving overload of the chromatographic column at the highest concentrations. The stable isotope labeled internal standard concentration was 0.667 μM in all samples. The absolute response per concentration unit decreased rapidly as higher concentrations were injected. The relative response, the ratio for the analyte peak area to the internal standard peak area, per concentration unit was calculated. For system 1, the ionization process was found to limit the response and the relative response per concentration unit was constant. For systems 2 and 3, the ion detection process was the limiting factor resulting in decreasing relative response at increasing concentrations. For systems behaving like system 1, simple linear regression can be used for any concentration range while, for systems behaving like systems 2 and 3, non-linear regression is recommended for all concentration ranges. Another consequence is that the ionization capacity limited systems will be insensitive to matrix ion suppression when an ideal internal standard is used while the detection capacity limited systems are at risk of giving erroneous results at high concentrations if the matrix ion suppression varies for different samples in a run. Copyright © 2012 John Wiley & Sons, Ltd.

The study of in vivo quantification of aluminum (Al) in human bone with a compact DD generator-based neutron activation analysis (NAA) system.

PubMed

Byrne, Patrick; Mostafaei, Farshad; Liu, Yingzi; Blake, Scott P; Koltick, David; Nie, Linda H

2016-05-01

The feasibility and methodology of using a compact DD generator-based neutron activation analysis system to measure aluminum in hand bone has been investigated. Monte Carlo simulations were used to simulate the moderator, reflector, and shielding assembly and to estimate the radiation dose. A high purity germanium (HPGe) detector was used to detect the Al gamma ray signals. The minimum detectable limit (MDL) was found to be 11.13 μg g(-1) dry bone (ppm). An additional HPGe detector would improve the MDL by a factor of 1.4, to 7.9 ppm. The equivalent dose delivered to the irradiated hand was calculated by Monte Carlo to be 11.9 mSv. In vivo bone aluminum measurement with the DD generator was found to be feasible among general population with an acceptable dose to the subject.

Fiber Optic Thermal Detection of Composite Delaminations

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Winfree, William P.

2011-01-01

A recently developed technique is presented for thermographic detection of delaminations in composites by performing temperature measurements with fiber optic Bragg gratings. A single optical fiber with multiple Bragg gratings employed as surface temperature sensors was bonded to the surface of a composite with subsurface defects. The investigated structure was a 10-ply composite specimen with prefabricated delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared and found to be consistent with the calculations using numerical simulation techniques. Also discussed are methods including various heating sources and patterns, and their limitations for performing in-situ structural health monitoring.

Comparisons between conventional optical imaging and parametric indirect microscopic imaging on human skin detection

NASA Astrophysics Data System (ADS)

Liu, Guoyan; Gao, Kun; Liu, Xuefeng; Ni, Guoqiang

2016-10-01

We report a new method, polarization parameters indirect microscopic imaging with a high transmission infrared light source, to detect the morphology and component of human skin. A conventional reflection microscopic system is used as the basic optical system, into which a polarization-modulation mechanics is inserted and a high transmission infrared light source is utilized. The near-field structural characteristics of human skin can be delivered by infrared waves and material coupling. According to coupling and conduction physics, changes of the optical wave parameters can be calculated and curves of the intensity of the image can be obtained. By analyzing the near-field polarization parameters in nanoscale, we can finally get the inversion images of human skin. Compared with the conventional direct optical microscope, this method can break diffraction limit and achieve a super resolution of sub-100nm. Besides, the method is more sensitive to the edges, wrinkles, boundaries and impurity particles.

Bayesian least squares deconvolution

NASA Astrophysics Data System (ADS)

Asensio Ramos, A.; Petit, P.

2015-11-01

Aims: We develop a fully Bayesian least squares deconvolution (LSD) that can be applied to the reliable detection of magnetic signals in noise-limited stellar spectropolarimetric observations using multiline techniques. Methods: We consider LSD under the Bayesian framework and we introduce a flexible Gaussian process (GP) prior for the LSD profile. This prior allows the result to automatically adapt to the presence of signal. We exploit several linear algebra identities to accelerate the calculations. The final algorithm can deal with thousands of spectral lines in a few seconds. Results: We demonstrate the reliability of the method with synthetic experiments and we apply it to real spectropolarimetric observations of magnetic stars. We are able to recover the magnetic signals using a small number of spectral lines, together with the uncertainty at each velocity bin. This allows the user to consider if the detected signal is reliable. The code to compute the Bayesian LSD profile is freely available.

A luminescent europium complex for the selective detection of trace amounts of aldicarb sulfoxide and prometryne

NASA Astrophysics Data System (ADS)

Anwar, Zeinab M.; Ibrahim, Ibrahim A.; Abdel-Salam, Enas T.; Kamel, Rasha M.; El-Asfoury, Mahmoud H.

2017-05-01

The interaction between luminescent Eu(TAN)2(Phen) ternary complex (where TAN = 4,4,4-Trifluoro-1-(2-naphthyl)-1,3-butanedione and Phen = 1,10 phenanthroline) with prometryne and aldicarb sulfoxide was studied by fluorescence spectroscopic technique. The results showed that the luminescence of europium complex was strongly quenched at λ = 614 nm by prometryne and aldicarb sulfoxide at pH 7.4 using PIPES buffer solution. The quenching mechanism was discussed to be a static quenching procedure, which was proved by the Stern Volmer (KSV) constants at different temperatures where the detection limits are 0.33 and 0.18 μmol L-1 for prometryne and aldicarb sulfoxide, respectively. According to Lineweaver-Burk equation at different temperatures, the thermodynamic parameters, ΔH, ΔS and ΔG associated with the interaction of the complex with the two pesticides were calculated.

A highly selective fluorescent chemosensor for CN- based on a novel bis(salamo)-type tetraoxime ligand

NASA Astrophysics Data System (ADS)

Wang, Fei; Gao, Lei; Zhao, Qing; Zhang, Yang; Dong, Wen-Kui; Ding, Yu-Jie

2018-02-01

The optical properties of a novel chemosensor for cyanide anions based on a symmetric bis(salamo)-type ligand (H3L) were investigated by UV-Vis and fluorescence spectroscopy in MeOH/H2O (1:1 v/v) solution. Sensor H3L can selectively sense CN- based on prominent color changes among other anions. The chemosensor exhibits an apparent fluorescence enhancement at 482 nm to CN- which because cyanide ions interact with Cdbnd N bonds. Combining the corrected Benesi-Hildebrand formula, the binding constant of the formed host-guest complex was calculated as 2.42 × 105 M- 1. Meanwhile, the detection limit of the sensor toward CN- was 8.91 × 10- 7 M. It is worth noting that the designed sensor can be used for rapid detection of cyanide anions in basic pH range, and has great practical value.

Evolution of the Ultrasonic Inspection Requirements of Heavy Rotor Forgings Over the Past Decades

NASA Astrophysics Data System (ADS)

Vrana, J.; Zimmer, A.; Bailey, K.; Angal, R.; Zombo, P.; Büchner, U.; Buschmann, A.; Shannon, R. E.; Lohmann, H.-P.; Heinrich, W.

2010-02-01

Heavy rotor forgings for land-based power generation turbines and generators are inspected ultrasonically. Several decades ago the first inspections were conducted using manual, straight beam, contact transducers with simple, non-descript reporting requirements. The development of ultrasonic inspection capabilities, the change in design engineer requirements, improvements of fracture mechanics calculations, experience with turbine operation, experience with the inspection technology, and probability of detection drove the changes that have resulted in the current day inspection requirements: sizing technologies were implemented, detection limits were lowered, angle and pitch/catch (dual crystal) scans were introduced, and most recently automated equipment for the inspection was required. Due to all these changes, model based sizing techniques, like DGS, and modern ultrasonic techniques, like phased array, are being introduced globally. This paper describes the evolution of the ultrasonic inspection requirements over the last decades and presents an outlook for tomorrow.

(1 + 1) resonant enhanced multiphoton ionization via the A2Sigma(+) state of NO - Ionic rotational branching ratios and their intensity dependence

NASA Technical Reports Server (NTRS)

Rudolph, H.; Mckoy, V.; Dixit, S. N.; Huo, W. M.

1988-01-01

Rotational branching ratios resulting from the (1 + 1) resonant enhanced multiphoton ionization spectroscopy of NO via the 0-0 transition of the A-X band for the four possible branches that can be assigned as R(21.5) are explored using calculation performed in the frozen-core approximation at the Hartree-Fock level. The four different branches, of which three are distinctly different in the perturbative limit, have rather different branching ratios. The mixed R12 + Q22(21.5) branch, which is not intense and has the lowest transition energy, appears to give the best agreement with experimental branching ratio for parallel detection. The agreement is less satisfactory for perpendicular detection. Neither the effect of finite-acceptance angle of the photoelectron detector nor high intensities can explain the discrepancy.

Acridine-based fluorescence chemosensors for selective sensing of Fe3+ and Ni2+ ions

NASA Astrophysics Data System (ADS)

Wang, Chaoyu; Fu, Jiaxin; Yao, Kun; Xue, Kun; Xu, Kuoxi; Pang, Xiaobin

2018-06-01

Two novel acridine-based fluorescence chemosensors (L1 and L2) were prepared and their metal ions sensing properties were investigated. L1 (L2) exhibited an excellent selective fluorescence response toward Fe3+ (Ni2+) and the stoichiometry ratio of L1-Fe3+ and L2-Ni2+ were 1:1. The detection limits of L1 and L2 were calculated by the fluorescence titration to be 4.13 μM and 1.52 μM, respectively, which were below the maximum permissive level of Fe3+ and Ni2+ ions in drinking water set by the EPA. The possible mechanism of the fluorescence detection of Fe3+ and Ni2+ had been proposed according to the analysis of Job's plot, IR spectra and ESI-MS. The determination of Fe3+ and Ni2+ ions in living cells had been applied successfully.

Pyridine-ring containing twisttetraazaacene: Synthesis, physical properties, crystal structure and picric acid sensing.

PubMed

Yu, Xianglin; Wan, Jiaqi; Chen, Shao; Li, Miao; Gao, Junkuo; Yang, Li; Wang, Huisheng; Chen, Dugang; Pan, Zhiquan; Li, Junbo

2017-11-01

Novel pyridine-ring containing twisttetraazaacene 9,14-diphenylpyreno[4,5-g]isoquinoline (1) and its full-carbon derivative 9,14-diphenyldibenzo[de,qr]tetracene (2) have been synthesized and fully characterized. Studies showed that compound 1 could identify picric acid (PA) over other common nitro compounds with high selectivity and sensitivity. Upon the addition of PA, the emission peak of compound 1 in CH 3 CN was red shifted from 447 to 555nm with a fluorescence quenching efficiency as high as 95%, the detection limit was calculated to be 2.42μM, while its full-carbon derivative (2) could not exhibit this kind of performance. The possible mechanism with the enhanced PA detection efficiency in pyridine-ring containing twisttetraazaacene (1) than its full-carbon derivative (2) was also investigated. Copyright © 2017 Elsevier B.V. All rights reserved.

Biosensor based on tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode for detection of epinephrine

PubMed Central

Apetrei, Irina Mirela; Apetrei, Constantin

2013-01-01

A biosensor comprising tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode has been developed. The sensitive element, ie, tyrosinase, was immobilized using a drop-and-dry method followed by cross-linking. Tyrosinase maintained high bioactivity on this nanomaterial, catalyzing the oxidation of epinephrine to epinephrine-quinone, which was electrochemically reduced (−0.07 V versus Ag/AgCl) on the biosensor surface. Under optimum conditions, the biosensor showed a linear response in the range of 10–110 μM. The limit of detection was calculated to be 2.54 μM with a correlation coefficient of 0.977. The repeatability, expressed as the relative standard deviation for five consecutive determinations of 10−5 M epinephrine solution was 3.4%. A good correlation was obtained between results obtained by the biosensor and those obtained by ultraviolet spectrophotometric methods. PMID:24348034

ac Modeling and impedance spectrum tests of the superconducting magnetic field coils for the Wendelstein 7-X fusion experiment.

PubMed

Ehmler, Hartmut; Köppen, Matthias

2007-10-01

The impedance spectrum test was employed for detection of short circuits within Wendelstein 7-X (W7-X) superconducting magnetic field coils. This test is based on measuring the complex impedance over several decades of frequency. The results are compared to predictions of appropriate electrical equivalent circuits of coils in different production states or during cold test. When the equivalent circuit is not too complicated the impedance can be represented by an analytic function. A more detailed analysis is performed with a network simulation code. The overall agreement of measured and calculated or simulated spectra is good. Two types of short circuits which appeared are presented and analyzed. The detection limit of the method is discussed. It is concluded that combined high-voltage ac and low-voltage impedance spectrum tests are ideal means to rule out short circuits in the W7-X coils.

Traffic intensity monitoring using multiple object detection with traffic surveillance cameras

NASA Astrophysics Data System (ADS)

Hamdan, H. G. Muhammad; Khalifah, O. O.

2017-11-01

Object detection and tracking is a field of research that has many applications in the current generation with increasing number of cameras on the streets and lower cost for Internet of Things(IoT). In this paper, a traffic intensity monitoring system is implemented based on the Macroscopic Urban Traffic model is proposed using computer vision as its source. The input of this program is extracted from a traffic surveillance camera which has another program running a neural network classification which can identify and differentiate the vehicle type is implanted. The neural network toolbox is trained with positive and negative input to increase accuracy. The accuracy of the program is compared to other related works done and the trends of the traffic intensity from a road is also calculated. relevant articles in literature searches, great care should be taken in constructing both. Lastly the limitation and the future work is concluded.

Synthesis of positively charged CdTe quantum dots and detection for uric acid

NASA Astrophysics Data System (ADS)

Zhang, Tiliang; Sun, Xiangying; Liu, Bin

2011-09-01

The CdTe dots (QDs) coated with 2-Mercaptoethylamine was prepared in aqueous solution and characterized with fluorescence spectroscopy, UV-Vis absorption spectra, high-resolution transmission electron microscopy and infrared spectroscopy. When the λex = 350 nm, the fluorescence peak of positively charged CdTe quantum dots is at 592 nm. The uric acid is able to quench their fluorescence. Under optimum conditions, the change of fluorescence intensity is linearly proportional to the concentration of uric acid in the range 0.4000-3.600 μmol L -1, and the limit of detection calculated according to IUPAC definitions is 0.1030 μmol L -1. Compared with routine method, the present method determines uric acid in human serum with satisfactory results. The mechanism of this strategy is due to the interaction of the tautomeric keto/hydroxyl group of uric acid and the amino group coated at the CdTe QDs.

An efficient Monte Carlo-based algorithm for scatter correction in keV cone-beam CT

NASA Astrophysics Data System (ADS)

Poludniowski, G.; Evans, P. M.; Hansen, V. N.; Webb, S.

2009-06-01

A new method is proposed for scatter-correction of cone-beam CT images. A coarse reconstruction is used in initial iteration steps. Modelling of the x-ray tube spectra and detector response are included in the algorithm. Photon diffusion inside the imaging subject is calculated using the Monte Carlo method. Photon scoring at the detector is calculated using forced detection to a fixed set of node points. The scatter profiles are then obtained by linear interpolation. The algorithm is referred to as the coarse reconstruction and fixed detection (CRFD) technique. Scatter predictions are quantitatively validated against a widely used general-purpose Monte Carlo code: BEAMnrc/EGSnrc (NRCC, Canada). Agreement is excellent. The CRFD algorithm was applied to projection data acquired with a Synergy XVI CBCT unit (Elekta Limited, Crawley, UK), using RANDO and Catphan phantoms (The Phantom Laboratory, Salem NY, USA). The algorithm was shown to be effective in removing scatter-induced artefacts from CBCT images, and took as little as 2 min on a desktop PC. Image uniformity was greatly improved as was CT-number accuracy in reconstructions. This latter improvement was less marked where the expected CT-number of a material was very different to the background material in which it was embedded.

Beef quality parameters estimation using ultrasound and color images

PubMed Central

2015-01-01

Background Beef quality measurement is a complex task with high economic impact. There is high interest in obtaining an automatic quality parameters estimation in live cattle or post mortem. In this paper we set out to obtain beef quality estimates from the analysis of ultrasound (in vivo) and color images (post mortem), with the measurement of various parameters related to tenderness and amount of meat: rib eye area, percentage of intramuscular fat and backfat thickness or subcutaneous fat. Proposal An algorithm based on curve evolution is implemented to calculate the rib eye area. The backfat thickness is estimated from the profile of distances between two curves that limit the steak and the rib eye, previously detected. A model base in Support Vector Regression (SVR) is trained to estimate the intramuscular fat percentage. A series of features extracted on a region of interest, previously detected in both ultrasound and color images, were proposed. In all cases, a complete evaluation was performed with different databases including: color and ultrasound images acquired by a beef industry expert, intramuscular fat estimation obtained by an expert using a commercial software, and chemical analysis. Conclusions The proposed algorithms show good results to calculate the rib eye area and the backfat thickness measure and profile. They are also promising in predicting the percentage of intramuscular fat. PMID:25734452

Real-time distortion correction for visual inspection systems based on FPGA

NASA Astrophysics Data System (ADS)

Liang, Danhua; Zhang, Zhaoxia; Chen, Xiaodong; Yu, Daoyin

2008-03-01

Visual inspection is a kind of new technology based on the research of computer vision, which focuses on the measurement of the object's geometry and location. It can be widely used in online measurement, and other real-time measurement process. Because of the defects of the traditional visual inspection, a new visual detection mode -all-digital intelligent acquisition and transmission is presented. The image processing, including filtering, image compression, binarization, edge detection and distortion correction, can be completed in the programmable devices -FPGA. As the wide-field angle lens is adopted in the system, the output images have serious distortion. Limited by the calculating speed of computer, software can only correct the distortion of static images but not the distortion of dynamic images. To reach the real-time need, we design a distortion correction system based on FPGA. The method of hardware distortion correction is that the spatial correction data are calculated first under software circumstance, then converted into the address of hardware storage and stored in the hardware look-up table, through which data can be read out to correct gray level. The major benefit using FPGA is that the same circuit can be used for other circularly symmetric wide-angle lenses without being modified.

A novel electron tunneling infrared detector

NASA Technical Reports Server (NTRS)

Kenny, T. W.; Waltman, S. B.; Reynolds, J. K.; Kaiser, W. J.

1990-01-01

The pneumatic infrared detector, originally developed by Golay in the late 1940s, uses the thermal expansion of one cm(exp 3) of xenon at room temperature to detect the heat deposited by infrared radiation. This detector was limited by thermal fluctuations within a 10 Hz bandwidth, but suffered from long thermal time constants and a fragile structure. Nevertheless, it represents the most sensitive room temperature detector currently available in the long wavelength infrared (LWIR). Fabrication of this type of detector on smaller scales has been limited by the lack of a suitably sensitive transducer. Researchers designed a detector based on this principle, but which is constructed entirely from micromachined silicon, and uses a vacuum tunneling transducer to detect the expansion of the trapped gas. Because this detector is fabricated using micromachining techniques, miniaturization and integration into one and two-dimensional arrays is feasible. The extreme sensitivity of vacuum tunneling to changes in electrode separation will allow a prototype of this detector to operate in the limit of thermal fluctuations over a 10 kHz bandwidth. A calculation of the predicted response and noise of the prototype is presented with the general formalism of thermal detectors. At present, most of the components of the prototype have been fabricated and tested independently. In particular, a characterization of the micromachined electron tunneling transducer has been carried out. The measured noise in the tunnel current is within a decade of the limit imposed by shot noise, and well below the requirements for the operation of an infrared detector with the predicted sensitivity. Assembly and characterization of the prototype infrared detector will be carried out promptly.

A simplified approach to the determination of N-nitroso glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection.

PubMed

Kim, Manuela; Stripeikis, Jorge; Iñón, Fernando; Tudino, Mabel

2007-05-15

A simple and sensitive HPLC post-derivatization method with colorimetric detection has been developed for the determination of N-nitroso glyphosate in samples of technical glyphosate. Separation of the analyte was accomplished using an anionic exchange resin (2.50mmx4.00mm i.d., 15mum particle size, functional group: quaternary ammonium salt) with Na(2)SO(4) 0.0075M (pH 11.5) (flow rate: 1.0mLmin(-1)) as mobile phase. After separation, the eluate was derivatized with a colorimetric reagent containing sulfanilamide 0.3% (w/v), [N-(1-naphtil)ethilendiamine] 0.03% (w/v) and HCl 4.5M in a thermostatized bath at 95 degrees C. Detection was performed at 546nm. All stages of the analytical procedure were optimized taking into account the concept of analytical minimalism: less operation times and costs; lower sample, reagents and energy consumption and minimal waste. The limit of detection (k=3) calculated for 10 blank replicates was 0.04mgL(-1) (0.8mgkg(-1)) in the solid sample which is lower than the maximum tolerable accepted by the Food and Agriculture Organization of the United Nations.

Anticancer drug-DNA interactions measured using a photoinduced electron-transfer mechanism based on luminescent quantum dots.

PubMed

Yuan, Jipei; Guo, Weiwei; Yang, Xiurong; Wang, Erkang

2009-01-01

A sensing system based on the photoinduced electron transfer of quantum dots (QDs) was designed to measure the interaction of anticancer drug and DNA, taking mitoxantrone (MTX) as a model drug. MTX adsorbed on the surface of QDs can quench the photoluminescence (PL) of QDs through the photoinduced electron-transfer process; and then the addition of DNA will bring the restoration of QDs PL intensity, as DNA can bind with MTX and remove it from QDs. Sensitive detection of MTX with the detection limit of 10 nmol L(-1) and a linear detection range from 10 nmol L(-1) to 4.5 micromol L(-1) was achieved. The dependence of PL intensity on DNA amount was successfully utilized to investigate the interactions between MTX and DNA. Both the binding constants and the sizes of binding site of MTX-DNA interactions were calculated based on the equations deduced for the PL recovery process. The binding constant obtained in our experiment was generally consistent with previous reports. The sensitive and speedy detection of MTX as well as the avoidance of modification or immobilization process made this system suitable and promising in the drug-DNA interaction studies.

Microplate based optical biosensor for L-Dopa using tyrosinase from Amorphophallus campanulatus.

PubMed

Saini, Amardeep Singh; Kumar, Jitendra; Melo, Jose Savio

2014-11-07

Developing a biosensor which is capable of simultaneously monitoring l-Dopa levels in multiple samples besides requiring small reaction volume is of great value. The present study describes the detection of l-Dopa using tyrosinase enzyme extracted from Amorphophallus campanulatus and immobilized on the surface of the microplate wells. Among the different approaches used for immobilizing tyrosinase onto the microplate wells, glutaraldehyde treatment was found to be most effective. Besides enzyme activity, ESEM-EDS (environmental scanning electron microscope-energy dispersive system) and Atomic Force Microscopy (AFM) were also carried out to confirm the immobilization of tyrosinase enzyme onto the microplate well surface. This immobilized biocomponent was then integrated with an optical transducer for l-Dopa detection and it showed good reproducibility. The sensing property of the system was studied by measuring the initial rate of dopachrome formation at 475 nm. The calibration plot gave a linear range of detection from 10-1000 μM and the detection limit was calculated to be 3 μM. The immobilized biocomponent was stable for 41 days and was reused up to nine times. Spiked samples (blood plasma) were also analyzed using this biocomponent. This microplate based biosensor thus provides a convenient system for detection of multiple samples in a single run. Copyright © 2014 Elsevier B.V. All rights reserved.

Highly selective and sensitive method for Cu2+ detection based on chiroptical activity of L-Cysteine mediated Au nanorod assemblies.

PubMed

Abbasi, Shahryar; Khani, Hamzeh

2017-11-05

Herein, we demonstrated a simple and efficient method to detect Cu 2+ based on amplified optical activity in the chiral nanoassemblies of gold nanorods (Au NRs). L-Cysteine can induce side-by-side or end-to-end assembly of Au NRs with an evident plasmonic circular dichroism (PCD) response due to coupling between surface plasmon resonances (SPR) of Au NRs and the chiral signal of L-Cys. Because of the obvious stronger plasmonic circular dichrosim (CD) response of the side-by-side assembly compared with the end-to-end assemblies, SS assembled Au NRs was selected as a sensitive platform and used for Cu 2+ detection. In the presence of Cu 2+ , Cu 2+ can catalyze O 2 oxidation of cysteine to cystine. With an increase in Cu 2+ concentration, the L-Cysteine-mediated assembly of Au NRs decreased because of decrease in the free cysteine thiol groups, and the PCD signal decreased. Taking advantage of this method, Cu 2+ could be detected in the concentration range of 20pM-5nM. Under optimal conditions, the calculated detection limit was found to be 7pM. Copyright © 2017 Elsevier B.V. All rights reserved.

Tunable Fabry-Perot etalon-based long-wavelength infrared imaging spectroradiometer.

PubMed

Marinelli, W J; Gittins, C M; Gelb, A H; Green, B D

1999-04-20

Imaging spectrometry enables passive, stand-off detection and analysis of the chemical composition of gas plumes and surfaces over wide geographic areas. We describe the use of a long-wavelength infrared imaging spectroradiometer, comprised of a low-order tunable Fabry-Perot etalon coupled to a HgCdTe detector array, to perform multispectral detection of chemical vapor plumes. The tunable Fabry-Perot etalon used in this research provides coverage of the 9.5-14-microm spectral region with a resolution of 7-9 cm(-1). The etalon-based imaging system provides the opportunity to image a scene at only those wavelengths needed for chemical species identification and quantification and thereby minimize the data volume necessary for selective species detection. We present initial results using a brassboard imaging system for stand-off detection and quantification of chemical vapor plumes against near-ambient-temperature backgrounds. These data show detection limits of 22 parts per million by volume times meter (ppmv x m) and 0.6 ppmv x m for dimethyl methyphosphonate and SF6, respectively, for a gas/background DeltaT of 6 K. The system noise-equivalent spectral radiance is approximately 2 microW cm(-2) sr(-1) microm(-1). Model calculations are presented comparing the measured sensitivity of the sensor to the anticipated signal levels for two chemical release scenarios.

Smartphone-Based Dual-Modality Imaging System for Quantitative Detection of Color or Fluorescent Lateral Flow Immunochromatographic Strips

NASA Astrophysics Data System (ADS)

Hou, Yafei; Wang, Kan; Xiao, Kun; Qin, Weijian; Lu, Wenting; Tao, Wei; Cui, Daxiang

2017-04-01

Nowadays, lateral flow immunochromatographic assays are increasingly popular as a diagnostic tool for point-of-care (POC) test based on their simplicity, specificity, and sensitivity. Hence, quantitative detection and pluralistic popular application are urgently needed in medical examination. In this study, a smartphone-based dual-modality imaging system was developed for quantitative detection of color or fluorescent lateral flow test strips, which can be operated anywhere at any time. In this system, the white and ultra-violet (UV) light of optical device was designed, which was tunable with different strips, and the Sobel operator algorithm was used in the software, which could enhance the identification ability to recognize the test area from the background boundary information. Moreover, this technology based on extraction of the components from RGB format (red, green, and blue) of color strips or only red format of the fluorescent strips can obviously improve the high-signal intensity and sensitivity. Fifty samples were used to evaluate the accuracy of this system, and the ideal detection limit was calculated separately from detection of human chorionic gonadotropin (HCG) and carcinoembryonic antigen (CEA). The results indicated that smartphone-controlled dual-modality imaging system could provide various POC diagnoses, which becomes a potential technology for developing the next-generation of portable system in the near future.

FISHing for bacteria in food--a promising tool for the reliable detection of pathogenic bacteria?

PubMed

Rohde, Alexander; Hammerl, Jens Andre; Appel, Bernd; Dieckmann, Ralf; Al Dahouk, Sascha

2015-04-01

Foodborne pathogens cause millions of infections every year and are responsible for considerable economic losses worldwide. The current gold standard for the detection of bacterial pathogens in food is still the conventional cultivation following standardized and generally accepted protocols. However, these methods are time-consuming and do not provide fast information about food contaminations and thus are limited in their ability to protect consumers in time from potential microbial hazards. Fluorescence in situ hybridization (FISH) represents a rapid and highly specific technique for whole-cell detection. This review aims to summarize the current data on FISH-testing for the detection of pathogenic bacteria in different food matrices and to evaluate its suitability for the implementation in routine testing. In this context, the use of FISH in different matrices and their pretreatment will be presented, the sensitivity and specificity of FISH tests will be considered and the need for automation shall be discussed as well as the use of technological improvements to overcome current hurdles for a broad application in monitoring food safety. In addition, the overall economical feasibility will be assessed in a rough calculation of costs, and strengths and weaknesses of FISH are considered in comparison with traditional and well-established detection methods. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

A hierarchical detection method in external communication for self-driving vehicles based on TDMA.

PubMed

Alheeti, Khattab M Ali; Al-Ani, Muzhir Shaban; McDonald-Maier, Klaus

2018-01-01

Security is considered a major challenge for self-driving and semi self-driving vehicles. These vehicles depend heavily on communications to predict and sense their external environment used in their motion. They use a type of ad hoc network termed Vehicular ad hoc networks (VANETs). Unfortunately, VANETs are potentially exposed to many attacks on network and application level. This paper, proposes a new intrusion detection system to protect the communication system of self-driving cars; utilising a combination of hierarchical models based on clusters and log parameters. This security system is designed to detect Sybil and Wormhole attacks in highway usage scenarios. It is based on clusters, utilising Time Division Multiple Access (TDMA) to overcome some of the obstacles of VANETs such as high density, high mobility and bandwidth limitations in exchanging messages. This makes the security system more efficient, accurate and capable of real time detection and quick in identification of malicious behaviour in VANETs. In this scheme, each vehicle log calculates and stores different parameter values after receiving the cooperative awareness messages from nearby vehicles. The vehicles exchange their log data and determine the difference between the parameters, which is utilised to detect Sybil attacks and Wormhole attacks. In order to realize efficient and effective intrusion detection system, we use the well-known network simulator (ns-2) to verify the performance of the security system. Simulation results indicate that the security system can achieve high detection rates and effectively detect anomalies with low rate of false alarms.

Calculating Confidence, Uncertainty, and Numbers of Samples When Using Statistical Sampling Approaches to Characterize and Clear Contaminated Areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piepel, Gregory F.; Matzke, Brett D.; Sego, Landon H.

2013-04-27

This report discusses the methodology, formulas, and inputs needed to make characterization and clearance decisions for Bacillus anthracis-contaminated and uncontaminated (or decontaminated) areas using a statistical sampling approach. Specifically, the report includes the methods and formulas for calculating the • number of samples required to achieve a specified confidence in characterization and clearance decisions • confidence in making characterization and clearance decisions for a specified number of samples for two common statistically based environmental sampling approaches. In particular, the report addresses an issue raised by the Government Accountability Office by providing methods and formulas to calculate the confidence that amore » decision area is uncontaminated (or successfully decontaminated) if all samples collected according to a statistical sampling approach have negative results. Key to addressing this topic is the probability that an individual sample result is a false negative, which is commonly referred to as the false negative rate (FNR). The two statistical sampling approaches currently discussed in this report are 1) hotspot sampling to detect small isolated contaminated locations during the characterization phase, and 2) combined judgment and random (CJR) sampling during the clearance phase. Typically if contamination is widely distributed in a decision area, it will be detectable via judgment sampling during the characterization phrase. Hotspot sampling is appropriate for characterization situations where contamination is not widely distributed and may not be detected by judgment sampling. CJR sampling is appropriate during the clearance phase when it is desired to augment judgment samples with statistical (random) samples. The hotspot and CJR statistical sampling approaches are discussed in the report for four situations: 1. qualitative data (detect and non-detect) when the FNR = 0 or when using statistical sampling methods that account for FNR > 0 2. qualitative data when the FNR > 0 but statistical sampling methods are used that assume the FNR = 0 3. quantitative data (e.g., contaminant concentrations expressed as CFU/cm2) when the FNR = 0 or when using statistical sampling methods that account for FNR > 0 4. quantitative data when the FNR > 0 but statistical sampling methods are used that assume the FNR = 0. For Situation 2, the hotspot sampling approach provides for stating with Z% confidence that a hotspot of specified shape and size with detectable contamination will be found. Also for Situation 2, the CJR approach provides for stating with X% confidence that at least Y% of the decision area does not contain detectable contamination. Forms of these statements for the other three situations are discussed in Section 2.2. Statistical methods that account for FNR > 0 currently only exist for the hotspot sampling approach with qualitative data (or quantitative data converted to qualitative data). This report documents the current status of methods and formulas for the hotspot and CJR sampling approaches. Limitations of these methods are identified. Extensions of the methods that are applicable when FNR = 0 to account for FNR > 0, or to address other limitations, will be documented in future revisions of this report if future funding supports the development of such extensions. For quantitative data, this report also presents statistical methods and formulas for 1. quantifying the uncertainty in measured sample results 2. estimating the true surface concentration corresponding to a surface sample 3. quantifying the uncertainty of the estimate of the true surface concentration. All of the methods and formulas discussed in the report were applied to example situations to illustrate application of the methods and interpretation of the results.« less

Laser Diagnostics for Reacting Flows

DTIC Science & Technology

2010-01-11

noise characteristics of the diagnostic will be in the shot - noise limit , a fundamental limit of the LIF signal intensity... noise related to the discrete nature of photons. In the shot - noise limit , the fluctuation detection limit can be predicted using nVP B S f f  1...detection limit was shot - noise limited . Figure 2.2.3 illustrates the fluctuation detection limits for line LIF imaging. Figure 2.2.3a

Transition probabilities in neutron-rich Se,8684

NASA Astrophysics Data System (ADS)

Litzinger, J.; Blazhev, A.; Dewald, A.; Didierjean, F.; Duchêne, G.; Fransen, C.; Lozeva, R.; Sieja, K.; Verney, D.; de Angelis, G.; Bazzacco, D.; Birkenbach, B.; Bottoni, S.; Bracco, A.; Braunroth, T.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Ellinger, E.; Farnea, E.; Fioretto, E.; Gernhäuser, R.; Goasduff, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hackstein, M.; Hess, H.; Ibrahim, F.; Jolie, J.; Jungclaus, A.; Kolos, K.; Korten, W.; Leoni, S.; Lunardi, S.; Maj, A.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatovic, T.; Million, B.; Möller, O.; Modamio, V.; Montagnoli, G.; Montanari, D.; Morales, A. I.; Napoli, D. R.; Niikura, M.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Sahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Valiente Dobón, J. J.; Vandone, V.; Vogt, A.

2015-12-01

Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se,8684 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the γ -ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 86Se the level lifetime of the yrast 21+ state and an upper limit for the lifetime of the 41+ state are determined for the first time. The results of 86Se are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in 86Se are calculated. In semimagic 84Se level lifetimes of the yrast 41+ and 61+ states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B (E 2 ;21+→01+) and B (E 2 ;61+→41+) fairly well and point out problems in reproducing the experimental B (E 2 ;41+→21+) .

Back to Classics: Teaching Limits through Infinitesimals.

ERIC Educational Resources Information Center

Todorov, Todor D.

2001-01-01

Criticizes the method of using calculators for the purpose of selecting candidates for L, for the limit value of a function. Suggests an alternative: a working formula for calculating the limit value L of a real function in terms of infinitesimals. (Author/ASK)

40 CFR 403.6 - National pretreatment standards: Categorical standards.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Control Authority calculating equivalent mass-per-day limitations under paragraph (c)(2) of this section... production shall be estimated using projected production. (4) A Control Authority calculating equivalent... Control Authority convert the limits to equivalent mass limits. The determination to convert concentration...

40 CFR 403.6 - National pretreatment standards: Categorical standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Control Authority calculating equivalent mass-per-day limitations under paragraph (c)(2) of this section... production shall be estimated using projected production. (4) A Control Authority calculating equivalent... Control Authority convert the limits to equivalent mass limits. The determination to convert concentration...

40 CFR 403.6 - National pretreatment standards: Categorical standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Control Authority calculating equivalent mass-per-day limitations under paragraph (c)(2) of this section... production shall be estimated using projected production. (4) A Control Authority calculating equivalent... Control Authority convert the limits to equivalent mass limits. The determination to convert concentration...

40 CFR 403.6 - National pretreatment standards: Categorical standards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Control Authority calculating equivalent mass-per-day limitations under paragraph (c)(2) of this section... production shall be estimated using projected production. (4) A Control Authority calculating equivalent... Control Authority convert the limits to equivalent mass limits. The determination to convert concentration...

40 CFR 403.6 - National pretreatment standards: Categorical standards.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Control Authority calculating equivalent mass-per-day limitations under paragraph (c)(2) of this section... production shall be estimated using projected production. (4) A Control Authority calculating equivalent... Control Authority convert the limits to equivalent mass limits. The determination to convert concentration...

Tracking surface and subsurface lakes on the Greenland Ice Sheet using Sentinel-1 SAR and Landsat-8 OLI imagery

NASA Astrophysics Data System (ADS)

Miles, Katie; Willis, Ian; Benedek, Corinne; Williamson, Andrew; Tedesco, Marco

2017-04-01

Supraglacial lakes (SGLs) on the Greenland Ice Sheet (GrIS) are an important component of the ice sheet's mass balance and hydrology, with their drainage affecting ice dynamics. This study uses imagery from the recently launched Sentinel-1A Synthetic Aperture Radar (SAR) to investigate SGLs in West Greenland. SAR can image through cloud and in darkness, overcoming some of the limitations of commonly used optical sensors. A semi automated algorithm is developed to detect surface lakes from Sentinel images during the 2015 summer. It generally detects water in all locations where a Landsat-8 NDWI classification (with a relatively high threshold value) detects water. A combined set of images from Landsat-8 and Sentinel-1 is used to track lake behaviour at a comparable temporal resolution to that which is possible with MODIS, but at a higher spatial resolution. A fully automated lake drainage detection algorithm is used to investigate both rapid and slow drainages for both small and large lakes through the summer. Our combined Landsat-Sentinel dataset, with a temporal resolution of three days, could track smaller lakes (mean 0.089 km2) than are resolvable in MODIS (minimum 0.125 km2). Small lake drainage events (lakes smaller than can be detected using MODIS) were found to occur at lower elevations ( 200 m) and slightly earlier in the melt season than larger events, as were slow lake drainage events compared to rapid events. The Sentinel imagery allows the analysis to be extended manually into the early winter to calculate the dates and elevations of lake freeze-through more precisely than is possible with optical imagery (mean 30 August, 1270 m mean elevation). Finally, the Sentinel imagery allows subsurface lakes (which are invisible to optical sensors) to be detected, and, for the first time, their dates of appearance and freeze-through to be calculated (mean 9 August and 7 October, respectively). These subsurface lakes occur at higher elevations than the surface lakes detected in this study (1593 m mean elevation). Sentinel imagery therefore provides great potential for tracking melting, water movement and freezing within the firn zone of the GrIS.

Ensuring the validity of calculated subcritical limits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, H.K.

1977-01-01

The care taken at the Savannah River Laboratory and Plant to ensure the validity of calculated subcritical limits is described. Close attention is given to ANSI N16.1-1975, ''Validation of Calculational Methods for Nuclear Criticality Safety.'' The computer codes used for criticality safety computations, which are listed and are briefly described, have been placed in the SRL JOSHUA system to facilitate calculation and to reduce input errors. A driver module, KOKO, simplifies and standardizes input and links the codes together in various ways. For any criticality safety evaluation, correlations of the calculational methods are made with experiment to establish bias. Occasionallymore » subcritical experiments are performed expressly to provide benchmarks. Calculated subcritical limits contain an adequate but not excessive margin to allow for uncertainty in the bias. The final step in any criticality safety evaluation is the writing of a report describing the calculations and justifying the margin.« less

Colonic polyps: application value of computer-aided detection in computed tomographic colonography.

PubMed

Zhang, Hui-Mao; Guo, Wei; Liu, Gui-Feng; An, Dong-Hong; Gao, Shuo-Hui; Sun, Li-Bo; Yang, Hai-Shan

2011-02-01

Colonic polyps are frequently encountered in clinics. Computed tomographic colonography (CTC), as a painless and quick detection, has high values in clinics. In this study, we evaluated the application value of computer-aided detection (CAD) in CTC detection of colonic polyps in the Chinese population. CTC was performed with a GE 64-row multidetector computed tomography (MDCT) scanner. Data of 50 CTC patients (39 patients positive for at least one polyp of ≥ 0.5 cm in size and the other 11 patients negative by endoscopic detection) were retrospectively reviewed first without computer-aided detection (CAD) and then with CAD by four radiologists (two were experienced and another two inexperienced) blinded to colonoscopy findings. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of detected colonic polyps, as well as the areas under the ROC curves (Az value) with and without CAD were calculated. CAD increased the overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the colonic polyps detected by experienced and inexperienced readers. The sensitivity in detecting small polyps (5 - 9 mm) with CAD in experienced and inexperienced readers increased from 82% and 44% to 93% and 82%, respectively (P > 0.05 and P < 0.001). With the use of CAD, the overall false positive rate and false negative rate for the detection of polyps by experienced and inexperienced readers decreased in different degrees. Among 13 sessile polyps not detected by CAD, two were ≥ 1.0 cm, eleven were 5 - 9 mm in diameter, and nine were flat-shaped lesions. The application of CAD in combination with CTC can increase the ability to detect colonic polyps, particularly for inexperienced readers. However, CAD is of limited value for the detection of flat polyps.

Cost and detection rate of glaucoma screening with imaging devices in a primary care center

PubMed Central

Anton, Alfonso; Fallon, Monica; Cots, Francesc; Sebastian, María A; Morilla-Grasa, Antonio; Mojal, Sergi; Castells, Xavier

2017-01-01

Purpose To analyze the cost and detection rate of a screening program for detecting glaucoma with imaging devices. Materials and methods In this cross-sectional study, a glaucoma screening program was applied in a population-based sample randomly selected from a population of 23,527. Screening targeted the population at risk of glaucoma. Examinations included optic disk tomography (Heidelberg retina tomograph [HRT]), nerve fiber analysis, and tonometry. Subjects who met at least 2 of 3 endpoints (HRT outside normal limits, nerve fiber index ≥30, or tonometry ≥21 mmHg) were referred for glaucoma consultation. The currently established (“conventional”) detection method was evaluated by recording data from primary care and ophthalmic consultations in the same population. The direct costs of screening and conventional detection were calculated by adding the unit costs generated during the diagnostic process. The detection rate of new glaucoma cases was assessed. Results The screening program evaluated 414 subjects; 32 cases were referred for glaucoma consultation, 7 had glaucoma, and 10 had probable glaucoma. The current detection method assessed 677 glaucoma suspects in the population, of whom 29 were diagnosed with glaucoma or probable glaucoma. Glaucoma screening and the conventional detection method had detection rates of 4.1% and 3.1%, respectively, and the cost per case detected was 1,410 and 1,435€, respectively. The cost of screening 1 million inhabitants would be 5.1 million euros and would allow the detection of 4,715 new cases. Conclusion The proposed screening method directed at population at risk allows a detection rate of 4.1% and a cost of 1,410 per case detected. PMID:28243057

Clinical validation of a highly sensitive assay to detect EGFR mutations in plasma cell-free DNA from patients with advanced lung adenocarcinoma.

PubMed

Li, Yuping; Xu, Hanyan; Su, Shanshan; Ye, Junru; Chen, Junjie; Jin, Xuru; Lin, Quan; Zhang, Dongqing; Ye, Caier; Chen, Chengshui

2017-01-01

Circulating tumor DNA (ctDNA) is a promising biomarker for noninvasive epidermal growth factor receptor (EGFR) mutations detection in lung cancer patients, but the existing methods have limitations in sensitivity or in availability. In this study, we evaluated the performance of a novel assay called ADx-SuperARMS in detecting EGFR mutations in plasma cell-free DNA from patients with advanced lung adenocarcinoma. A total of 109 patients with metastatic advanced adenocarcinoma were recruited who provided both blood samples and matched tumor tissue samples. EGFR mutation status in plasma samples were tested with ADx-SuperARMS EGFR assay and tumor tissue samples were tested with ADx-ARMS EGFR assay. The clinical sensitivity, specificity, positive prediction value (PPV), and negative prediction value (NPV) of ADx-SuperARMS EGFR assay were calculated by using EGFR mutation status in tumor tissue as standard reference. A receiver operating characteristic (ROC) analysis was implemented and an area under the curve (AUC) was calculated to evaluate sensitivity and specificity of exon 19 deletion (E19Del) and L858R mutation detection. The objective response rate (ORR) were calculated according to the EGFR mutation status determined by ADx-superARMS as well. 0.2% analytical sensitivity and 100% specificity of the ADx-SuperARMS EGFR assays for EGFR E19Del, L858R, and T790M mutants were confirmed by using a series of diluted cell line DNA. In the clinical study, EGFR mutations were detected in 45.9% (50/109) of the plasma samples and in 56.9% (62/109) of the matched tumor tissue samples. The sensitivity, specificity, PPV and NPV of the ADx-SuperARMS EGFR assay for plasma EGFR mutation detection were 82.0% (50/61), 100% (48/48), 100% (50/50), and 81.4% (48/59), respectively. In ROC analysis, ADx-SuperARMS achieved sensitivity and specificity of 88% and 99% in E19Dels as well as sensitivity and specificity of 89% and 100% in L858R, respectively. Among the 35 patients who were plasma EGFR mutation positive and treated with first generation of EGFR-tyrosine kinase inhibitors (TKIs), 23 (65.7%) achieved partial response, 11 (31.4%) sustained disease, and 1 (2.9%) progressive disease. The ORR and disease control rate (DCR) were 65.7% and 97.1%, respectively. ADx-SuperARMS EGFR assay is likely to be a highly sensitive and specific method to noninvasively detect plasma EGFR mutations of patients with advanced lung adenocarcinoma. The EGFR mutations detected by ADx-SuperARMS EGFR assay could predict the efficacy of the treatment with first generation of EGFR-TKIs. Hence, EGFR blood testing with ADx-SuperARMS could address the unmet clinical needs.

Prospects for Jovian seismological observations following the impact of comet Shoemaker-Levy 9

NASA Technical Reports Server (NTRS)

Deming, Drake

1994-01-01

The impact of each fragment of comet SL-9 will produce a downward-propagating pressure wave which will travel at the sound speed through the jovian interior. Since the sound speed increases with depth, most of the energy in the pressure pulse will be strongly refracted and return to the surface, as recently computed by Marley (1994). This wave may in principle be observable as it propagates into the stratosphere, using sufficiently sensitive thermal infrared imaging. If so, it will provide a unique opportunity to constrain models of the jovian interior. This paper extends Marley's calculations to include the effect of the limited spatial resolution which will be characteristic of real observations. The wave pattern on the disk will consist of closely spaced regions of alternating temperature increases and decreases. Spatial averaging will significantly reduce the observed amplitude for resolutions attainable using earth-based telescopes, but the waves should remain above the detection limit.

Swift X-Ray Upper Limits on Type Ia Supernova Environments

NASA Technical Reports Server (NTRS)

Russell, B. R.; Immler, S.

2012-01-01

We have considered 53 Type Ia supernovae (SNe Ia) observed by the Swift X-Ray Telescope. None of the SNe Ia are individually detected at any time or in stacked images. Using these data and assuming that the SNe Ia are a homogeneous class of objects, we have calculated upper limits to the X-ray luminosity (0.2-10 keV) and mass-loss rate of L(sub 0.2-10) < 1.7 X 10(exp 38) erg/s and M(dot) < l.l X 10(exp -6) solar M/ yr x (V(sub w))/(10 km/s), respectively. The results exclude massive or evolved stars as the companion objects in SN Ia progenitor systems, but allow the possibility of main sequence or small stars, along with double degenerate systems consisting of two white dwarfs, consistent with results obtained at other wavelengths (e.g., UV, radio) in other studies.

THE MURCHISON WIDEFIELD ARRAY 21 cm POWER SPECTRUM ANALYSIS METHODOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Daniel C.; Beardsley, A. P.; Bowman, Judd D.

2016-07-10

We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed,more » accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.« less

Simultaneous analysis of coccidiostats and sulfonamides in non-target feed by HPLC-MS/MS and validation following the Commission Decision 2002/657/EC.

PubMed

Gavilán, Rosa Elvira; Nebot, Carolina; Patyra, Ewelina; Miranda, Jose Manuel; Franco, Carlos Manuel; Cepeda, Alberto

2018-05-02

Taking into consideration the maximum level for coccidiostats included in the European Regulation 574/2011 and the fact that the presence of residues of sulfonamides in non-target feed is forbidden, the aim of this article is to present an analytical method based on HPLC-MS/MS for the identification and quantification of sulfonamides and coccidiostats in non-target feeds. The method was validated following Decision 2002/657/EC and recovery, repeatability, and reproducibility were within the limits stablished in the Decision. For coccidiostats, the decision limit and detection capability were calculated for the different species taking into account the maximum level allowed in Regulation 574/2011. The applicability of the method was investigated in 50 feed samples collected from dairy farms, 50 obtained from feed mills, and 10 interlaboratory feed samples.

Strategy for determination of LOD and LOQ values--some basic aspects.

PubMed

Uhrovčík, Jozef

2014-02-01

The paper is devoted to the evaluation of limit of detection (LOD) and limit of quantification (LOQ) values in concentration domain by using 4 different approaches; namely 3σ and 10σ approaches, ULA2 approach, PBA approach and MDL approach. Brief theoretical analyses of all above mentioned approaches are given together with directions for their practical use. Calculations and correct calibration design are exemplified by using of electrothermal atomic absorption spectrometry for determination of lead in drinking water sample. These validation parameters reached 1.6 μg L(-1) (LOD) and 5.4 μg L(-1) (LOQ) by using 3σ and 10σ approaches. For obtaining relevant values of analyte concentration the influence of calibration design and measurement methodology were examined. The most preferred technique has proven to be a method of preconcentration of the analyte on the surface of the graphite cuvette (boost cycle). © 2013 Elsevier B.V. All rights reserved.

Lindemann histograms as a new method to analyse nano-patterns and phases

NASA Astrophysics Data System (ADS)

Makey, Ghaith; Ilday, Serim; Tokel, Onur; Ibrahim, Muhamet; Yavuz, Ozgun; Pavlov, Ihor; Gulseren, Oguz; Ilday, Omer

The detection, observation, and analysis of material phases and atomistic patterns are of great importance for understanding systems exhibiting both equilibrium and far-from-equilibrium dynamics. As such, there is intense research on phase transitions and pattern dynamics in soft matter, statistical and nonlinear physics, and polymer physics. In order to identify phases and nano-patterns, the pair correlation function is commonly used. However, this approach is limited in terms of recognizing competing patterns in dynamic systems, and lacks visualisation capabilities. In order to solve these limitations, we introduce Lindemann histogram quantification as an alternative method to analyse solid, liquid, and gas phases, along with hexagonal, square, and amorphous nano-pattern symmetries. We show that the proposed approach based on Lindemann parameter calculated per particle maps local number densities to material phase or particles pattern. We apply the Lindemann histogram method on dynamical colloidal self-assembly experimental data and identify competing patterns.

Analysis of spreadable cheese by Raman spectroscopy and chemometric tools.

PubMed

Oliveira, Kamila de Sá; Callegaro, Layce de Souza; Stephani, Rodrigo; Almeida, Mariana Ramos; de Oliveira, Luiz Fernando Cappa

2016-03-01

In this work, FT-Raman spectroscopy was explored to evaluate spreadable cheese samples. A partial least squares discriminant analysis was employed to identify the spreadable cheese samples containing starch. To build the models, two types of samples were used: commercial samples and samples manufactured in local industries. The method of supervised classification PLS-DA was employed to classify the samples as adulterated or without starch. Multivariate regression was performed using the partial least squares method to quantify the starch in the spreadable cheese. The limit of detection obtained for the model was 0.34% (w/w) and the limit of quantification was 1.14% (w/w). The reliability of the models was evaluated by determining the confidence interval, which was calculated using the bootstrap re-sampling technique. The results show that the classification models can be used to complement classical analysis and as screening methods. Copyright © 2015 Elsevier Ltd. All rights reserved.