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Sample records for absolute detection limit

  1. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  2. Detection limit

    SciTech Connect

    Porter, P.S.; Ward, R.C.; Bell, H.F.

    1988-08-01

    Water quality monitoring data are plagued with levels of chemicals that are too low to be measured precisely. This discussion will focus on the information needs of water quality management and how these needs are best met for monitoring systems that require many trace-level measurements. We propose that the limit of detection (LOD) or the limit of quantitation (LOQ) not be used to censor data. Although LOD and LOQ aid in the interpretation of individual measurements, they hinder statistical analysis of water quality data. More information is gained when a numerical result and an estimate of measurement precision are reported for every measurement, as opposed to reporting not detected or less than. This article is not intended to be a review of the issues pertaining to the LOD and related concepts.

  3. Absolute limit on rotation of gravitationally bound stars

    NASA Astrophysics Data System (ADS)

    Glendenning, N. K.

    1994-03-01

    The authors seek an absolute limit on the rotational period for a neutron star as a function of its mass, based on the minimal constraints imposed by Einstein's theory of relativity, Le Chatelier's principle, causality, and a low-density equation of state, uncertainties which can be evaluated as to their effect on the result. This establishes a limiting curve in the mass-period plane below which no pulsar that is a neutron star can lie. For example, the minimum possible Kepler period, which is an absolute limit on rotation below which mass-shedding would occur, is 0.33 ms for a M = 1.442 solar mass neutron star (the mass of PSR1913+16). If the limit were found to be broken by any pulsar, it would signal that the confined hadronic phase of ordinary nucleons and nuclei is only metastable.

  4. Absolute limit on rotation of gravitationally bound stars

    SciTech Connect

    Glendenning, N.K.

    1994-03-01

    The authors seek an absolute limit on the rotational period for a neutron star as a function of its mass, based on the minimal constraints imposed by Einstein`s theory of relativity, Le Chatelier`s principle, causality and a low-density equation of state, uncertainties which can be evaluated as to their effect on the result. This establishes a limiting curve in the mass-period plane below which no pulsar that is a neutron star can lie. For example, the minimum possible Kepler period, which is an absolute limit on rotation below which mass-shedding would occur, is 0.33 ms for a M = 1.442 M{circle_dot} neutron star (the mass of PSR1913+16). If the limit were found to be broken by any pulsar, it would signal that the confined hadronic phase of ordinary nucleons and nuclei is only metastable, an extraordinary conclusion.

  5. Absolute rotation detection by Coriolis force measurement using optomechanics

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar; Li, Yong

    2016-10-01

    In this article, we present an application of the optomechanical cavities for absolute rotation detection. Two optomechanical cavities, one in each arm, are placed in a Michelson interferometer. The interferometer is placed on a rotating table and is moved with a uniform velocity of \\dot{\\bar{y}} with respect to the rotating table. The Coriolis force acting on the interferometer changes the length of the optomechanical cavity in one arm, while the length of the optomechanical cavity in the other arm is not changed. The phase shift corresponding to the change in the optomechanical cavity length is measured at the interferometer output to estimate the angular velocity of the absolute rotation. An analytic expression for the minimum detectable rotation rate corresponding to the standard quantum limit of measurable Coriolis force in the interferometer is derived. Squeezing technique is discussed to improve the rotation detection sensitivity by a factor of \\sqrt{{γ }m/{ω }m} at 0 K temperature, where {γ }m and {ω }m are the damping rate and angular frequency of the mechanical oscillator. The temperature dependence of the rotation detection sensitivity is studied.

  6. Absolute density measurement of SD radicals in a supersonic jet at the quantum-noise-limit.

    PubMed

    Mizouri, Arin; Deng, L Z; Eardley, Jack S; Nahler, N Hendrik; Wrede, Eckart; Carty, David

    2013-12-07

    The absolute density of SD radicals in a supersonic jet has been measured down to (1.1 ± 0.1) × 10(5) cm(-3) in a modestly specified apparatus that uses a cross-correlated combination of cavity ring-down and laser-induced fluorescence detection. Such a density corresponds to 215 ± 21 molecules in the probe volume at any given time. The minimum detectable absorption coefficient was quantum-noise-limited and measured to be (7.9 ± 0.6) × 10(-11) cm(-1), in 200 s of acquisition time, corresponding to a noise-equivalent absorption sensitivity for the apparatus of (1.6 ± 0.1) × 10(-9) cm(-1) Hz(-1/2).

  7. System providing limit switch function with simultaneous absolute position output

    NASA Technical Reports Server (NTRS)

    Alhorn, Dean C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

    2006-01-01

    A limit and position sensing system includes a sensor assembly and an emitter. The sensor assembly includes first and second electrical conductors arranged in opposing parallel planes. The first electrical conductor is coiled outwardly from either end thereof in a clockwise fashion to form a first coil region and a second coil region. The second electrical conductor forms a single coil with portions of the single coil's rings lying between the first end and second end of the first electrical conductor being parallel to an axis of the first electrical conductor's plane. Ferromagnetic material is aligned with the first and second electrical conductors and spans beyond (a) the first and second ends of the first electrical conductor, and (b) the portions of the rings of the second electrical conductor's single coil that lie between the first end and second end of the first electrical conductor. The emitter is spaced apart from the sensor assembly and transmits a periodic electromagnetic wave towards the sensor assembly.

  8. Adaptive limit margin detection and limit avoidance

    NASA Astrophysics Data System (ADS)

    Yavrucuk, Ilkay

    ) unmanned helicopter test bed for automatic limit detection and avoidance. Angular rate limits and rotor stall limits are considered. Software-in-the-loop simulation and flight test results of the GTMax are included.

  9. Upward excursion limits from air saturation at 5 ATA (Atmospheres Absolute)

    NASA Astrophysics Data System (ADS)

    Parker, James W.

    1989-01-01

    Present USN submarine rescue capability makes a prolonged exposure of the submarine crew to hyperbaric air a distinct possibility. The exposure may be to pressures as great as 5 atmospheres absolute (ATA), and for periods of time of up to 72 hours. A series of experimental dives were conducted to establish the safe, upward excursion from 5 ATA (132 FSWG); that is, the maximum, immediate reduction in pressure which these individuals can safely tolerate. This specifies the required pressure in the compartment of a mother submarine to which the rescued personnel would be transferred. In order to minimize the effects of pulmonary oxygen toxicity, the limits first were established using a nitrox equivalent of air at 5 ATA. The upward limit from 4.36 ATA (111 FSWG) was found to be 2.97 ATA (65 FSWG). Once this limit had been set, a series of dives were conducted to test this up limit from standard air at 5 ATA.

  10. Nitromethane K-9 Detection Limit

    SciTech Connect

    Strobel, R; Kury, J

    2003-08-29

    The Bureau of Alcohol, Tobacco and Firearms (ATF) trains canine/handler teams to detect explosives for government and other agencies worldwide. After completing the training program the teams are tested on an array containing explosives and numerous other samples designed to distract a canine. Passing this test results in a team's certification. These teams can be considered as ''detection instruments'' freshly calibrated just before leaving the ''factory''. Using these teams to examine special experimental arrays immediately following certification can lead to a better understanding of a canine's detection capabilities. Forty-one of these ''detection instruments'' were used in four test series with arrays containing dilute nitromethane-in-water solutions. (The canines had been trained on the amount of nitromethane vapor in equilibrium with the undiluted liquid explosive.) By diluting liquid nitromethane with water, the amount of explosive vapor can be reduced many orders of magnitude to test the lower limit of the canine's nitromethane vapor detection response. The results are presented in this paper.

  11. Absolute lower limits on the masses of selectrons and sneutrinos in the MSSM

    NASA Astrophysics Data System (ADS)

    ALEPH Collaboration; Heister, A.; Schael, S.; Barate, R.; Brunelière, R.; de Bonis, I.; Decamp, D.; Goy, C.; Jezequel, S.; Lees, J.-P.; Martin, F.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Trocmé, B.; Boix, G.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Graugés, E.; Lopez, J.; Martinez, M.; Merino, G.; Pacheco, A.; Paneque, D.; Ruiz, H.; Colaleo, A.; Creanza, D.; de Filippis, N.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Azzurri, P.; Barklow, T.; Buchmüller, O.; Cattaneo, M.; Cerutti, F.; Clerbaux, B.; Drevermann, H.; Forty, R. W.; Frank, M.; Gianotti, F.; Greening, T. C.; Hansen, J. B.; Harvey, J.; Hutchcroft, D. E.; Janot, P.; Jost, B.; Kado, M.; Mato, P.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Sguazzoni, G.; Tejessy, W.; Teubert, F.; Valassi, A.; Videau, I.; Ward, J. J.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Jousset, J.; Michel, B.; Monteil, S.; Pallin, D.; Pascolo, J. M.; Perret, P.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Brient, J.-C.; Machefert, F.; Rougé, A.; Swynghedauw, M.; Tanaka, R.; Videau, H.; Ciulli, V.; Focardi, E.; Parrini, G.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bossi, F.; Capon, G.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, G. P.; Passalacqua, L.; Kennedy, J.; Lynch, J. G.; Negus, P.; O'Shea, V.; Thompson, A. S.; Wasserbaech, S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Leibenguth, G.; Putzer, A.; Stenzel, H.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Cameron, W.; Davies, G.; Dornan, P. J.; Girone, M.; Hill, R. D.; Marinelli, N.; Nowell, J.; Rutherford, S. A.; Sedgbeer, J. K.; Thompson, J. C.; White, R.; Ghete, V. M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C. K.; Clarke, D. P.; Ellis, G.; Finch, A. J.; Foster, F.; Hughes, G.; Jones, R. W. L.; Pearson, M. R.; Robertson, N. A.; Smizanska, M.; van der Aa, O.; Delaere, C.; Lemaitre, V.; Blumenschein, U.; Hölldorfer, F.; Jakobs, K.; Kayser, F.; Kleinknecht, K.; Müller, A.-S.; Quast, G.; Renk, B.; Sander, H.-G.; Schmeling, S.; Wachsmuth, H.; Zeitnitz, C.; Ziegler, T.; Bonissent, A.; Coyle, P.; Curtil, C.; Ealet, A.; Fouchez, D.; Payre, P.; Tilquin, A.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Hüttmann, K.; Lütjens, G.; Männer, W.; Moser, H.-G.; Settles, R.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacholkowska, A.; Serin, L.; Veillet, J.-J.; de Vivie de Régie, J.-B.; Yuan, C.; Bagliesi, G.; Boccali, T.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Awunor, O.; Blair, G. A.; Cowan, G.; Garcia-Bellido, A.; Green, M. G.; Jones, L. T.; Medcalf, T.; Misiejuk, A.; Strong, J. A.; Teixeira-Dias, P.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Bloch-Devaux, B.; Boumediene, D.; Colas, P.; Fabbro, B.; Lançon, E.; Lemaire, M.-C.; Locci, E.; Perez, P.; Rander, J.; Tuchming, B.; Vallage, B.; Konstantinidis, N.; Litke, A. M.; Taylor, G.; Booth, C. N.; Cartwright, S.; Combley, F.; Hodgson, P. N.; Lehto, M.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Grupen, C.; Hess, J.; Ngac, A.; Prange, G.; Sieler, U.; Borean, C.; Giannini, G.; He, H.; Putz, J.; Rothberg, J.; Armstrong, S. R.; Berkelman, K.; Cranmer, K.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A.; Nielsen, J.; Pan, Y. B.; von Wimmersperg-Toeller, J. H.; Wiedenmann, W.; Wu, J.; Wu, Sau Lan; Wu, X.; Zobernig, G.; Dissertori, G.

    2002-09-01

    The results of searches for selectrons, charginos and neutralinos performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies up to 209 GeV are interpreted in the framework of the Minimal Supersymmetric extension of the Standard Model with R-parity conservation. Under the assumptions of gaugino and sfermion mass unification and no sfermion mixing, an absolute lower limit of 73 GeV/c2 is set on the mass of the lighter selectron e~R at the 95% confidence level. Similarly, limits on the masses of the heavier selectron e~L and of the sneutrino ν~e are set at 107 and 84 GeV/c2, respectively. Additional constraints are derived from the results of the searches for Higgs bosons. The results are also interpreted in the framework of minimal supergravity.

  12. Limits of detection and decision. Part 3

    NASA Astrophysics Data System (ADS)

    Voigtman, E.

    2008-02-01

    It has been shown that the MARLAP (Multi-Agency Radiological Laboratory Analytical Protocols) for estimating the Currie detection limit, which is based on 'critical values of the non-centrality parameter of the non-central t distribution', is intrinsically biased, even if no calibration curve or regression is used. This completed the refutation of the method, begun in Part 2. With the field cleared of obstructions, the true theory underlying Currie's limits of decision, detection and quantification, as they apply in a simple linear chemical measurement system (CMS) having heteroscedastic, Gaussian measurement noise and using weighted least squares (WLS) processing, was then derived. Extensive Monte Carlo simulations were performed, on 900 million independent calibration curves, for linear, "hockey stick" and quadratic noise precision models (NPMs). With errorless NPM parameters, all the simulation results were found to be in excellent agreement with the derived theoretical expressions. Even with as much as 30% noise on all of the relevant NPM parameters, the worst absolute errors in rates of false positives and false negatives, was only 0.3%.

  13. Fuzzy logic based anaesthesia monitoring systems for the detection of absolute hypovolaemia.

    PubMed

    Mansoor Baig, Mirza; Gholamhosseini, Hamid; Harrison, Michael J

    2013-07-01

    Anaesthesia monitoring involves critical diagnostic tasks carried out amongst lots of distractions. Computers are capable of handling large amounts of data at high speed and therefore decision support systems and expert systems are now capable of processing many signals simultaneously in real time. We have developed two fuzzy logic based anaesthesia monitoring systems; a real time smart anaesthesia alarm system (RT-SAAM) and fuzzy logic monitoring system-2 (FLMS-2), an updated version of FLMS for the detection of absolute hypovolaemia. This paper presents the design aspects of these two systems which employ fuzzy logic techniques to detect absolute hypovolaemia, and compares their performances in terms of usability and acceptability. The interpretation of these two systems of absolute hypovolaemia was compared with clinicians' assessments using Kappa analysis, RT-SAAM K=0.62, FLMS-2 K=0.75; an improvement in performance by FLMS-2. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Development and application of absolute quantitative detection by duplex chamber-based digital PCR of genetically modified maize events without pretreatment steps.

    PubMed

    Zhu, Pengyu; Fu, Wei; Wang, Chenguang; Du, Zhixin; Huang, Kunlun; Zhu, Shuifang; Xu, Wentao

    2016-04-15

    The possibility of the absolute quantitation of GMO events by digital PCR was recently reported. However, most absolute quantitation methods based on the digital PCR required pretreatment steps. Meanwhile, singleplex detection could not meet the demand of the absolute quantitation of GMO events that is based on the ratio of foreign fragments and reference genes. Thus, to promote the absolute quantitative detection of different GMO events by digital PCR, we developed a quantitative detection method based on duplex digital PCR without pretreatment. Moreover, we tested 7 GMO events in our study to evaluate the fitness of our method. The optimized combination of foreign and reference primers, limit of quantitation (LOQ), limit of detection (LOD) and specificity were validated. The results showed that the LOQ of our method for different GMO events was 0.5%, while the LOD is 0.1%. Additionally, we found that duplex digital PCR could achieve the detection results with lower RSD compared with singleplex digital PCR. In summary, the duplex digital PCR detection system is a simple and stable way to achieve the absolute quantitation of different GMO events. Moreover, the LOQ and LOD indicated that this method is suitable for the daily detection and quantitation of GMO events. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. 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.

  16. 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

  17. Supramolecular spectrally encoded microgels with double strand probes for absolute and direct miRNA fluorescence detection at high sensitivity.

    PubMed

    Causa, Filippo; Aliberti, Anna; Cusano, Angela M; Battista, Edmondo; Netti, Paolo A

    2015-02-11

    We present novel microgels as a particle-based suspension array for direct and absolute microRNA (miRNA) detection. The microgels feature a flexible molecular architecture, antifouling properties, and enhanced sensitivity with a large dynamic range of detection. Specifically, they possess a core-shell molecular architecture with two different fluorescent dyes for multiplex spectral analyses and are endowed with a fluorescent probe for miRNA detection. Encoding and detection fluorescence signals are distinguishable by nonoverlapping emission spectra. Tunable fluorescence probe conjugation and emission confinement on single microgels allow for ultrasensitive miRNA detection. Indeed, the suspension array has high selectivity and sensitivity with absolute quantification, a detection limit of 10(-15) M, a dynamic range from 10(-9) to 10(-15) M, and higher accuracy than qRT-PCR. The antifouling properties of the microgels also permit the direct measurement of miRNAs in serum, without sample pretreatment or target amplification. A multiplexed assay has been tested for a set of miRNAs chosen as cancer biomarkers.

  18. Simulation model for a silicon Hall sensor in an absolute digital position detection system

    NASA Astrophysics Data System (ADS)

    Pronk, F. A.; Groenland, J. P. J.; Lammerink, T. S. J.

    1986-05-01

    The performance of a digital position detection system with silicon Hall sensors for the detection of coded absolute position data has been investigated. The position information is fixed in one single track as a maximum length sequence of bits by means of longitudinal saturation recording in a hard-magnetic layer. The Hall elements are positioned with their surface parallel to the hard-magnetic layer. An efficient computer simulation model has been realized which calculates the response of a Hall element in the fringing field. The computed results are compared with experimental data on Hall elements which were realised using MOS-IC technology. The simulation model appeared to be sufficiently accurate for a first-order estimation of the performance of an absolute position detection system on the basis of silicon Hall elements. The resolution which can be realized depends strongly on the noise level in the elements and will be of the order of a few hundred μm.

  19. Symbol Detection for Faster-Than-Nyquist Signaling by Sum-of-Absolute-Values Optimization

    NASA Astrophysics Data System (ADS)

    Sasahara, Hampei; Hayashi, Kazunori; Nagahara, Masaaki

    2016-12-01

    In this letter, we propose a new symbol detection method for faster-than-Nyquist signaling (FTNS) systems. Based on frame theory, we formulate a symbol detection problem as a under-determined linear equation on a finite set. The problem is reformulated as a sum-of-absolute-values (SOAV) optimization that can be efficiently solved by the fast iterative shrinkage thresholding algorithm (FISTA). The proximity operator for the convex optimization is derived analytically. Simulation results are given to show that the proposed method can successfully detect symbols in faster-than-Nyquist signaling systems and has lower complexity in terms of computation time.

  20. Multiplex qPCR for Detection and Absolute Quantification of Malaria

    PubMed Central

    Kamau, Edwin; Alemayehu, Saba; Feghali, Karla C.; Saunders, David; Ockenhouse, Christian F.

    2013-01-01

    We describe development of an absolute multiplex quantitative real-time PCR for detection of Plasmodium spp., P. falciparum and P. vivax targets in order to produce an assay amenable to high throughput but with reduced costs. Important qPCR experimental details and information that is critical to performance and reliability of assay results were investigated. Inhibition studies were performed to test and compare co-purification of PCR inhibitors in samples extracted from whole blood using either the manual or automated methods. To establish the most optimal qPCR reaction volume, volume titration of the reaction master mix was performed starting at 10 µl to 1 µl reaction master mix with 1 µl of template DNA in each reaction. As the reaction volume decreased, qPCR assays became more efficient with 1 µl reaction master mix being the most efficient. For more accurate quantification of parasites in a sample, we developed plasmid DNAs for all the three assay targets for absolute quantification. All of absolute qPCR assays performed with efficiency of more than 94%, R2 values greater than 0.99 and the STDEV of each replicate was <0.167. Linear regression plots generated from absolute qPCR assays were used to estimate the corresponding parasite density from relative qPCR in terms of parasite/µl. One copy of plasmid DNA was established to be equivalent to 0.1 parasite/µl for Plasmodium spp. assay, 0.281 parasites for P. falciparum assay and 0.127 parasite/µl for P. vivax assay. This study demonstrates for the first time use of plasmid DNA in absolute quantification of malaria parasite. The use of plasmid DNA standard in quantification of malaria parasite will be critical as efforts are underway to harmonize molecular assays used in diagnosis of malaria. PMID:24009663

  1. Urinary C-peptide creatinine ratio detects absolute insulin deficiency in Type 2 diabetes.

    PubMed

    Hope, S V; Jones, A G; Goodchild, E; Shepherd, M; Besser, R E J; Shields, B; McDonald, T; Knight, B A; Hattersley, A

    2013-11-01

    autoantibodies. Absolute insulin deficiency in Type 2 diabetes may increase the risk of hypoglycaemia and ketoacidosis, as in Type 1 diabetes. Its recognition should help guide treatment, education and management. The urinary C-peptide creatinine ratio is a practical non-invasive method to aid detection of absolute insulin deficiency, with a urinary C-peptide creatinine ratio > 0.2 nmol/mmol being a reliable indicator of retained endogenous insulin secretion. © 2013 The Authors. Diabetic Medicine published by John Wiley & Sons Ltd on behalf of Diabetes UK.

  2. A Novel Pretreatment-Free Duplex Chamber Digital PCR Detection System for the Absolute Quantitation of GMO Samples.

    PubMed

    Zhu, Pengyu; Wang, Chenguang; Huang, Kunlun; Luo, Yunbo; Xu, Wentao

    2016-03-18

    Digital polymerase chain reaction (PCR) has developed rapidly since it was first reported in the 1990s. However, pretreatments are often required during preparation for digital PCR, which can increase operation error. The single-plex amplification of both the target and reference genes may cause uncertainties due to the different reaction volumes and the matrix effect. In the current study, a quantitative detection system based on the pretreatment-free duplex chamber digital PCR was developed. The dynamic range, limit of quantitation (LOQ), sensitivity and specificity were evaluated taking the GA21 event as the experimental object. Moreover, to determine the factors that may influence the stability of the duplex system, we evaluated whether the pretreatments, the primary and secondary structures of the probes and the SNP effect influence the detection. The results showed that the LOQ was 0.5% and the sensitivity was 0.1%. We also found that genome digestion and single nucleotide polymorphism (SNP) sites affect the detection results, whereas the unspecific hybridization within different probes had little side effect. This indicated that the detection system was suited for both chamber-based and droplet-based digital PCR. In conclusion, we have provided a simple and flexible way of achieving absolute quantitation for genetically modified organism (GMO) genome samples using commercial digital PCR detection systems.

  3. A Novel Pretreatment-Free Duplex Chamber Digital PCR Detection System for the Absolute Quantitation of GMO Samples

    PubMed Central

    Zhu, Pengyu; Wang, Chenguang; Huang, Kunlun; Luo, Yunbo; Xu, Wentao

    2016-01-01

    Digital polymerase chain reaction (PCR) has developed rapidly since it was first reported in the 1990s. However, pretreatments are often required during preparation for digital PCR, which can increase operation error. The single-plex amplification of both the target and reference genes may cause uncertainties due to the different reaction volumes and the matrix effect. In the current study, a quantitative detection system based on the pretreatment-free duplex chamber digital PCR was developed. The dynamic range, limit of quantitation (LOQ), sensitivity and specificity were evaluated taking the GA21 event as the experimental object. Moreover, to determine the factors that may influence the stability of the duplex system, we evaluated whether the pretreatments, the primary and secondary structures of the probes and the SNP effect influence the detection. The results showed that the LOQ was 0.5% and the sensitivity was 0.1%. We also found that genome digestion and single nucleotide polymorphism (SNP) sites affect the detection results, whereas the unspecific hybridization within different probes had little side effect. This indicated that the detection system was suited for both chamber-based and droplet-based digital PCR. In conclusion, we have provided a simple and flexible way of achieving absolute quantitation for genetically modified organism (GMO) genome samples using commercial digital PCR detection systems. PMID:26999129

  4. Design, validation, and absolute sensitivity of a novel test for the molecular detection of avian pneumovirus.

    PubMed

    Cecchinato, Mattia; Catelli, Elena; Savage, Carol E; Jones, Richard C; Naylor, Clive J

    2004-11-01

    This study describes attempts to increase and measure sensitivity of molecular tests to detect avian pneumovirus (APV). Polymerase chain reaction (PCR) diagnostic tests were designed for the detection of nucleic acid from an A-type APV genome. The objective was selection of PCR oligonucleotide combinations, which would provide the greatest test sensitivity and thereby enable optimal detection when used for later testing of field materials. Relative and absolute test sensitivities could be determined because of laboratory access to known quantities of purified full-length DNA copies of APV genome derived from the same A-type virus. Four new nested PCR tests were designed in the fusion (F) protein (2 tests), small hydrophobic (SH) protein (1 test), and nucleocapsid (N) protein (1 test) genes and compared with an established test in the attachment (G) protein gene. Known amounts of full-length APV genome were serially diluted 10-fold, and these dilutions were used as templates for the different tests. Sensitivities were found to differ between the tests, the most sensitive being the established G test, which proved able to detect 6,000 copies of the G gene. The G test contained predominantly pyrimidine residues at its 3' termini, and because of this, oligonucleotides for the most sensitive F test were modified to incorporate the same residue types at their 3' termini. This was found to increase sensitivity, so that after full 3' pyrimidine substitutions, the F test became able to detect 600 copies of the F gene.

  5. Constraining absolute neutrino masses via detection of galactic supernova neutrinos at JUNO

    SciTech Connect

    Lu, Jia-Shu; Cao, Jun; Li, Yu-Feng; Zhou, Shun E-mail: caoj@ihep.ac.cn E-mail: zhoush@ihep.ac.cn

    2015-05-01

    A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses m{sub ν} via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be m{sub ν} < (0.83 ± 0.24) eV at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is m{sub ν} < (0.94 ± 0.28) eV at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted.

  6. Study of absolute detection technique with the rotational Raman lidar for atmospheric temperature

    NASA Astrophysics Data System (ADS)

    Li, Shichun; Wei, Pengpeng; Gong, Xin; Hua, Dengxin

    2015-10-01

    The rotational Raman lidar is a valid tool to profile atmospheric temperature. But the fact that its proper operation generally needs a certain collocated device for calibration seriously restricts application in the meteorology and environment fields. We propose an absolute detection technique of atmospheric temperature with the rotational Raman lidar, which is based on the dependence of rotational Raman spectral envelope on temperature. To retrieve atmospheric temperature without calibration, six rotational Raman spectra of nitrogen molecule are chosen from the anti-Strokes branch. A temperature retrieval algorithm is presented and analyzed based on the least square principle. A two-cascade Raman spectroscopic filter is constructed by one first-order diffraction grating, one convex lens, one linear fiber array and 6 groups of fiber Bragg gratings. This lidar is configured with a 300-mJ pulse energy laser and a 250-mm clear aperture telescope. Simulation results show that it can extract the nitrogen molecules rotational Raman spectral lines, and that atmospheric temperature profile obtained through absolute retrieval algorithm can be up to 3.5 km with less than 0.5-K deviation within 17 minutes interval.

  7. Constraining absolute neutrino masses via detection of galactic supernova neutrinos at JUNO

    SciTech Connect

    Lu, Jia-Shu; Cao, Jun; Li, Yu-Feng; Zhou, Shun

    2015-05-26

    A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses m{sub ν} via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be m{sub ν}<(0.83±0.24) eV at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is m{sub ν}<(0.94±0.28) eV at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted.

  8. Absolute distance measurement by intensity detection using a mode-locked femtosecond pulse laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Cao, Shiying; Xing, Shujian; Qu, Xinghua

    2014-05-05

    We propose an interferometric method that enables to measure a distance by the intensity measurement using the scanning of the interferometer reference arm and the recording of the interference fringes including the brightest fringe. With the consideration of the dispersion and absorption of the pulse laser in a dispersive and absorptive medium, we investigate the cross-correlation function between two femtosecond laser pulses in the time domain. We also introduce the measurement principle. We study the relationship between the position of the brightest fringe and the distance measured, which can contribute to the distance measurement. In the experiments, we measure distances using the method of the intensity detection while the reference arm of Michelson interferometer is scanned and the fringes including the brightest fringe is recorded. Firstly we measure a distance in a range of 10 µm. The experimental results show that the maximum deviation is 45 nm with the method of light intensity detection. Secondly, an interference system using three Michelson interferometers is developed, which combines the methods of light intensity detection and time-of-flight. This system can extend the non-ambiguity range of the method of light intensity detection. We can determine a distance uniquely with a larger non-ambiguity range. It is shown that this method and system can realize absolute distance measurement, and the measurement range is a few micrometers in the vicinity of Nl(pp), where N is an integer, and lpp is the pulse-to-pulse length.

  9. Assessment of absolute added correlative coding in optical intensity modulation and direct detection channels

    NASA Astrophysics Data System (ADS)

    Dong-Nhat, Nguyen; Elsherif, Mohamed A.; Malekmohammadi, Amin

    2016-06-01

    The performance of absolute added correlative coding (AACC) modulation format with direct detection has been numerically and analytically reported, targeting metro data center interconnects. Hereby, the focus lies on the performance of the bit error rate, noise contributions, spectral efficiency, and chromatic dispersion tolerance. The signal space model of AACC, where the average electrical and optical power expressions are derived for the first time, is also delineated. The proposed modulation format was also compared to other well-known signaling, such as on-off-keying (OOK) and four-level pulse-amplitude modulation, at the same bit rate in a directly modulated vertical-cavity surface-emitting laser-based transmission system. The comparison results show a clear advantage of AACC in achieving longer fiber delivery distance due to the higher dispersion tolerance.

  10. An imaging technique for detection and absolute calibration of scintillation light

    SciTech Connect

    Pappalardo, Alfio; Cosentino, Luigi; Finocchiaro, Paolo

    2010-03-15

    Triggered by the need of a detection system to be used in experiments of nuclear fusion in laser-generated plasmas, we developed an imaging technique for the measurement and calibration of the scintillation light yield of scintillating materials. As in such experiments, all the reaction products are generated in an ultrashort time frame, the event-by-event data acquisition scheme is not feasible. As an alternative to the emulsion technique (or the equivalent CR39 sheets) we propose a scintillating screen readout by means of a high performance charge coupled device camera. Even though it is not strictly required in the particular application, this technique allows the absolute calibration of the scintillation light yield.

  11. Electrostatic Limit of Detection of Nanowire-Based Sensors.

    PubMed

    Henning, Alex; Molotskii, Michel; Swaminathan, Nandhini; Vaknin, Yonathan; Godkin, Andrey; Shalev, Gil; Rosenwaks, Yossi

    2015-10-07

    Scanning gate microscopy is used to determine the electrostatic limit of detection (LOD) of a nanowire (NW) based chemical sensor with a precision of sub-elementary charge. The presented method is validated with an electrostatically formed NW whose active area and shape are tunable by biasing a multiple gate field-effect transistor (FET). By using the tip of an atomic force microscope (AFM) as a local top gate, the field effect of adsorbed molecules is emulated. The tip induced charge is quantified with an analytical electrostatic model and it is shown that the NW sensor is sensitive to about an elementary charge and that the measurements with the AFM tip are in agreement with sensing of ethanol vapor. This method is applicable to any FET-based chemical and biological sensor, provides a means to predict the absolute sensor performance limit, and suggests a standardized way to compare LODs and sensitivities of various sensors.

  12. ELENA MCP detector: absolute detection efficiency for low-energy neutral atoms

    NASA Astrophysics Data System (ADS)

    Rispoli, R.; De Angelis, E.; Colasanti, L.; Vertolli, N.; Orsini, S.; Scheer, J. A.; Mura, A.; Milillo, A.; Wurz, P.; Selci, S.; Di Lellis, A. M.; Leoni, R.; D'Alessandro, M.; Mattioli, F.; Cibella, S.

    2012-09-01

    Microchannel Plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) on board the BepiColombo mission of ESA to Mercury to be launched in 2015. ELENA is a Time of Flight (TOF) sensor, based on a novel concept using an ultra-sonic oscillating shutter (Start section), which is operated at frequencies up to 50 kHz; a MCP detector is used as a Stop detector. The scientific objective of ELENA is to detect energetic neutral atoms in the range 10 eV - 5 keV, within 76° FOV, perpendicular to the S/C orbital plane. ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion. The major scientific objectives are the interaction between the plasma environment and the planet’s surface, the global particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated by identifying particles released from the surface, via solar wind-induced ion sputtering (< 1eV - < 100 eV) as well as Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E < 30 eV) is a crucial point for this investigation. At the MEFISTO facility of the Physical Institute of the University of Bern (CH), measurements on three different types of MCP (with and without coating) have been performed providing the detection efficiencies in the energy range 10eV - 1keV. Outcomes from such measurements are discussed here.

  13. Ultraviolet photolysis of HCHO: absolute HCO quantum yields by direct detection of the HCO radical photoproduct.

    PubMed

    Carbajo, Paula Gorrotxategi; Smith, Shona C; Holloway, Anne-Louise; Smith, Carina A; Pope, Francis D; Shallcross, Dudley E; Orr-Ewing, Andrew J

    2008-12-04

    Absolute quantum yields for the radical (H + HCO) channel of HCHO photolysis, Phi(HCO), have been measured for the tropospherically relevant range of wavelengths (lambda) between 300 and 330 nm. The HCO photoproduct was directly detected by using a custom-built, combined ultra-violet (UV) absorption and cavity ring down (CRD) detection spectrometer. This instrument was previously employed for high-resolution (spectral resolution approximately 0.0035 nm) measurements of absorption cross-sections of HCHO, sigma(HCHO)(lambda), and relative HCO quantum yields. Absolute Phi(HCO) values were measured at seven wavelengths, lambda = 303.70, 305.13, 308.87, 314.31, 320.67, 325.59, and 329.51 nm, using an independent calibration technique based on the simultaneous UV photolysis of HCHO and Cl(2). These Phi(HCO) measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for Phi(HCO). The absolute Phi(HCO)(lambda) determinations and previously measured sigma(HCHO)(lambda) were used to scale an extensive set of relative HCO yield measurements. The outcome of this procedure is a full suite of data for the product of the absolute radical quantum yield and HCHO absorption cross-section, Phi(HCO)(lambda)sigma(HCHO)(lambda), at wavelengths from 302.6 to 331.0 nm with a wavelength resolution of 0.005 nm. This product of photochemical parameters is combined with high-resolution solar photon flux data to calculate the integrated photolysis rate of HCHO to the radical (H + HCO) channel, J(HCO). Comparison with the latest NASA-JPL recommendations, reported at 1 nm wavelength resolution, suggests an increased J(HCO) of 25% at 0 degrees solar zenith angle (SZA) increasing to 33% at high SZA (80 degrees). The differences in the calculated photolysis rate compared with the current HCHO data arise, in part, from the higher wavelength resolution of the current data set and highlight the importance of using high-resolution spectroscopic

  14. Detection Limits and Selectivity in Electrochemical Detectors.

    ERIC Educational Resources Information Center

    Weber, Stephen G.; Long, John T.

    1988-01-01

    Discusses three aspects of electrochemical detectors: (1) signal and noise generation and signal-to-noise ratio, (2) improvement of qualitative information content, and (3) control of selectivity of the detector. Explains electronic principles of detectors and detection limits. Lists current applications and research. (ML)

  15. Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination.

    PubMed

    Clivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, Massimo

    2016-05-30

    Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S0-3P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.

  16. Quantum limited heterodyne detection of spin noise

    NASA Astrophysics Data System (ADS)

    Cronenberger, S.; Scalbert, D.

    2016-09-01

    Spin noise spectroscopy is a powerful technique for studying spin relaxation in semiconductors. In this article, we propose an extension of this technique based on optical heterodyne detection of spin noise, which provides several key advantages compared to conventional spin noise spectroscopy: detection of high frequency spin noise not limited by detector bandwidth or sampling rates of digitizers, quantum limited sensitivity even in case of very weak probe power, and possible amplification of the spin noise signal. Heterodyne detection of spin noise is demonstrated on insulating n-doped GaAs. From measurements of spin noise spectra up to 0.4 Tesla, we determined the distribution of g-factors, Δg/g = 0.49%.

  17. Revised Age Constraints on Absolute Age Limits for Mercury's Kuiperian and Mansurian Systems

    NASA Astrophysics Data System (ADS)

    Banks, Maria E.; Zhiyong, Xiao; Braden, Sarah E.; Marchi, Simone S.; Barlow, Nadine G.; Chapman, Clark R.; Fassett, Caleb I.

    2015-11-01

    On the basis of morphologically distinct basin and crater deposits, Mercury’s surface units have been subdivided into five time-stratigraphic systems (youngest to oldest): Kuiperian, Mansurian, Calorian, Tolstojan, and pre-Tolstojan. Approximate age limits were initially suggested for these systems on the basis of the lunar-derived impact-flux history. High-resolution and multi-band image data obtained by the MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) spacecraft were used to catalogue fresh impact craters interpreted to have formed during the Mansurian and Kuiperian systems. Mansurian and Kuiperian craters are characterized as morphologically fresh with crisp morphologies, well-preserved rims, few or no superposed craters, continuous ejecta with radial lineaments, and well-defined secondary craters; Kuiperian craters have bright ray systems while Mansurian craters maintain fresh morphologies but no longer have discernable ray systems.The density of fresh craters in these datasets, along with the recent production and chronology function of Marchi et al. [2009], are used to estimate new limits for the boundaries of the two most recent of Mercury’s systems. Given the effects of strength and other parameters (such as density), we estimate a model age for the population of craters that have formed since the onset of the Mansurian of ~1.9 ±0.3 Gyr. Likewise we estimate a model age for the population of craters that have formed since the onset of the Kuiperian of ~300 ±40 Myr. A particularly good fit for the Mansurian crater size frequency distribution (SFD) was found for the NEO-derived crater distribution. The same is true for the Kuiperian SFD, although the fit is not as robust as for the Mansurian SFD.

  18. Effective connectivity associated with auditory error detection in musicians with absolute pitch.

    PubMed

    Parkinson, Amy L; Behroozmand, Roozbeh; Ibrahim, Nadine; Korzyukov, Oleg; Larson, Charles R; Robin, Donald A

    2014-01-01

    It is advantageous to study a wide range of vocal abilities in order to fully understand how vocal control measures vary across the full spectrum. Individuals with absolute pitch (AP) are able to assign a verbal label to musical notes and have enhanced abilities in pitch identification without reliance on an external referent. In this study we used dynamic causal modeling (DCM) to model effective connectivity of ERP responses to pitch perturbation in voice auditory feedback in musicians with relative pitch (RP), AP, and non-musician controls. We identified a network compromising left and right hemisphere superior temporal gyrus (STG), primary motor cortex (M1), and premotor cortex (PM). We specified nine models and compared two main factors examining various combinations of STG involvement in feedback pitch error detection/correction process. Our results suggest that modulation of left to right STG connections are important in the identification of self-voice error and sensory motor integration in AP musicians. We also identify reduced connectivity of left hemisphere PM to STG connections in AP and RP groups during the error detection and corrections process relative to non-musicians. We suggest that this suppression may allow for enhanced connectivity relating to pitch identification in the right hemisphere in those with more precise pitch matching abilities. Musicians with enhanced pitch identification abilities likely have an improved auditory error detection and correction system involving connectivity of STG regions. Our findings here also suggest that individuals with AP are more adept at using feedback related to pitch from the right hemisphere.

  19. Effective connectivity associated with auditory error detection in musicians with absolute pitch

    PubMed Central

    Parkinson, Amy L.; Behroozmand, Roozbeh; Ibrahim, Nadine; Korzyukov, Oleg; Larson, Charles R.; Robin, Donald A.

    2014-01-01

    It is advantageous to study a wide range of vocal abilities in order to fully understand how vocal control measures vary across the full spectrum. Individuals with absolute pitch (AP) are able to assign a verbal label to musical notes and have enhanced abilities in pitch identification without reliance on an external referent. In this study we used dynamic causal modeling (DCM) to model effective connectivity of ERP responses to pitch perturbation in voice auditory feedback in musicians with relative pitch (RP), AP, and non-musician controls. We identified a network compromising left and right hemisphere superior temporal gyrus (STG), primary motor cortex (M1), and premotor cortex (PM). We specified nine models and compared two main factors examining various combinations of STG involvement in feedback pitch error detection/correction process. Our results suggest that modulation of left to right STG connections are important in the identification of self-voice error and sensory motor integration in AP musicians. We also identify reduced connectivity of left hemisphere PM to STG connections in AP and RP groups during the error detection and corrections process relative to non-musicians. We suggest that this suppression may allow for enhanced connectivity relating to pitch identification in the right hemisphere in those with more precise pitch matching abilities. Musicians with enhanced pitch identification abilities likely have an improved auditory error detection and correction system involving connectivity of STG regions. Our findings here also suggest that individuals with AP are more adept at using feedback related to pitch from the right hemisphere. PMID:24634644

  20. Determination of Rate-Limiting Factor for Formation of Beta-Catenin Destruction Complexes Using Absolute Protein Quantification.

    PubMed

    Kitazawa, Masashi; Hatta, Tomohisa; Ogawa, Koji; Fukuda, Eriko; Goshima, Naoki; Natsume, Tohru

    2017-10-06

    Wnt/β-catenin signaling plays important roles in both ontogenesis and development. In the absence of a Wnt stimulus, β-catenin is degraded by a multiprotein "destruction complex" that includes Axin, APC, GSK3B, and FBXW11. Although the key molecules required for transducing Wnt signals have been identified, a quantitative understanding of this pathway has been lacking. Here, we calculated the absolute number of β-catenin destruction complexes by absolute protein quantification using LC-MS/MS. Similar amounts of destruction complex-constituting proteins and β-catenin interacted, and the number of destruction complexes was calculated to be about 1468 molecules/cell. We demonstrated that the calculated number of destruction complexes was valid for control of the β-catenin destruction rate under steady-state conditions. Interestingly, APC had the minimum expression level among the destruction complex components at about 2233 molecules/cell, and this number approximately corresponded to the calculated number of destruction complexes. Decreased APC expression by siRNA transfection decreased the number of destruction complexes, resulting in β-catenin accumulation and stimulation of the transcriptional activity of T-cell factor. Taken together, our results suggest that the amount of APC expression is the rate-limiting factor for the constitution of β-catenin destruction complexes.

  1. Weighted Polynomial Approximation for Automated Detection of Inspiratory Flow Limitation.

    PubMed

    Huang, Sheng-Cheng; Jan, Hao-Yu; Fu, Tieh-Cheng; Lin, Wen-Chen; Lin, Geng-Hong; Lin, Wen-Chi; Tsai, Cheng-Lun; Lin, Kang-Ping

    2017-01-01

    Inspiratory flow limitation (IFL) is a critical symptom of sleep breathing disorders. A characteristic flattened flow-time curve indicates the presence of highest resistance flow limitation. This study involved investigating a real-time algorithm for detecting IFL during sleep. Three categories of inspiratory flow shape were collected from previous studies for use as a development set. Of these, 16 cases were labeled as non-IFL and 78 as IFL which were further categorized into minor level (20 cases) and severe level (58 cases) of obstruction. In this study, algorithms using polynomial functions were proposed for extracting the features of IFL. Methods using first- to third-order polynomial approximations were applied to calculate the fitting curve to obtain the mean absolute error. The proposed algorithm is described by the weighted third-order (w.3rd-order) polynomial function. For validation, a total of 1,093 inspiratory breaths were acquired as a test set. The accuracy levels of the classifications produced by the presented feature detection methods were analyzed, and the performance levels were compared using a misclassification cobweb. According to the results, the algorithm using the w.3rd-order polynomial approximation achieved an accuracy of 94.14% for IFL classification. We concluded that this algorithm achieved effective automatic IFL detection during sleep.

  2. Weighted Polynomial Approximation for Automated Detection of Inspiratory Flow Limitation

    PubMed Central

    Huang, Sheng-Cheng; Jan, Hao-Yu; Fu, Tieh-Cheng; Lin, Geng-Hong; Lin, Wen-Chi; Lin, Kang-Ping

    2017-01-01

    Inspiratory flow limitation (IFL) is a critical symptom of sleep breathing disorders. A characteristic flattened flow-time curve indicates the presence of highest resistance flow limitation. This study involved investigating a real-time algorithm for detecting IFL during sleep. Three categories of inspiratory flow shape were collected from previous studies for use as a development set. Of these, 16 cases were labeled as non-IFL and 78 as IFL which were further categorized into minor level (20 cases) and severe level (58 cases) of obstruction. In this study, algorithms using polynomial functions were proposed for extracting the features of IFL. Methods using first- to third-order polynomial approximations were applied to calculate the fitting curve to obtain the mean absolute error. The proposed algorithm is described by the weighted third-order (w.3rd-order) polynomial function. For validation, a total of 1,093 inspiratory breaths were acquired as a test set. The accuracy levels of the classifications produced by the presented feature detection methods were analyzed, and the performance levels were compared using a misclassification cobweb. According to the results, the algorithm using the w.3rd-order polynomial approximation achieved an accuracy of 94.14% for IFL classification. We concluded that this algorithm achieved effective automatic IFL detection during sleep. PMID:28634497

  3. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  4. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  5. Detection limits with spectral differential imaging data

    NASA Astrophysics Data System (ADS)

    Rameau, J.; Chauvin, G.; Lagrange, A.-M.; Maire, A.-L.; Boccaletti, A.; Bonnefoy, M.

    2015-09-01

    Context. Direct imaging of exoplanets is polluted by speckle noise that severely limits the achievable contrast. Angular and spectral differential imaging have been proposed to make use of the temporal and chromatic properties of the speckles. Both modes, associated with extreme adaptive-optics and coronagraphy, are at the core of the new generation of planet imagers SPHERE and GPI. Aims: We aim to illustrate and characterize the impact of the SDI and SDI+ADI (ASDI) data reduction on the detection of giant planets. We also propose an unbiased method to derive the detection limits from SDI/ASDI data. Methods: Observations of AB Dor B and β Pictoris made with VLT/NaCo were used to simulate and quantify the effects of SDI and ASDI. The novel method is compared to the traditional injection of artificial point sources. Results: The SDI reduction process creates a typical radial positive-negative pattern of any point-source. Its characteristics and its self-subtraction depend on the separation, but also on the spectral properties of the object. This work demonstrates that the self-subtraction cannot be reduced to a simple geometric effect. As a consequence, the detection performances of SDI observations cannot be expressed as a contrast in magnitude with the central star without the knowledge of the spectral properties of detectable companions. In addition, the residual noise cannot be converted into contrast and physical characteristics (mass, temperature) by standard calibration of flux losses. The proposed method takes the SDI bias into account to derive detection limits without the cost of massively injecting artificial sources into the data. Finally, the sensitivity of ASDI observations can be measured only with a control parameter on the algorithms that controls the minimum rotation that is necessary to build the reference image. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, ESO : 60.A

  6. Ultra-sensitive and absolute quantitative detection of Cu(2+) based on DNAzyme and digital PCR in water and drink samples.

    PubMed

    Zhu, Pengyu; Shang, Ying; Tian, Wenying; Huang, Kunlun; Luo, Yunbo; Xu, Wentao

    2017-04-15

    Here, we developed an ultra-sensitive and absolute quantitative detection method of Cu(2+) based on DNAzyme and digital PCR. The binding model between DNAzyme and Cu(2+) and the influence caused by the additional primer sequence were revealed to ensure quantitation independent of standard curves. The binding model of DNAzyme and Cu(2+) showed that one molecular DNAzyme could bind one Cu(2+) in the biosensor step. Thus, the final quantitative results, evaluated by three parallels, showed that the limit of quantitation (LOQ) was as low as 0.5pmol, while the sensitivity was evaluated as 50fmol. The specificity evaluation of our methodologies shows that extremely low crossing signal is existed within the non-specific ions. Moreover, the results of practical detection have shown that the quantitative results were stable and accurate among different food substrates. In conclusion, a flexible quantitative detection method with ultra-sensitivity was developed to detect trace amounts Cu(2+) within different substrates.

  7. PCR detection of aflatoxin producing fungi and its limitations.

    PubMed

    Levin, Robert E

    2012-05-01

    Unlike bacterial toxins that are primarily peptides and are therefore encoded by a single gene, fungal toxins such as the aflatoxins are multi-ring structures and therefore require a sequence of structural genes for their biological synthesis. There is therefore no specific PCR for any one of the four biologically produced aflatoxins. Unfortunately, the structural genes presently in use for PCR detection of aflatoxin producing fungi are also involved in the synthesis of other fungal toxins such as sterigmatocystin by Aspergillus versicolor and Aspergillus nidulans and therefore lack absolute specificity for aflatoxin producing fungi (Table 1). In addition, the genomic presence of several structural genes involved in aflatoxin biosynthesis does not guarantee the production of aflatoxin by all isolates of Aspergillus flavus and Aspergillus parasiticus. The most widely used DNA target regions for discriminating Aspergillus species are those of the rDNA complex, mainly the internal transcribed spacer regions 1 and 2 (ITS1 and ITS2) and the variable regions in the 5'-end of the 28S rRNA gene. Since these sequence regions are unrelated to the structural genes involved in aflatoxin biosynthesis there successful amplification can be used for species identification but do not confirm aflatoxin production. This review therefore presents the various approaches and limitations in the use of the PCR in attempting to detect aflatoxin producing fungi.

  8. Double domain wavelength multiplexed Fizeau interferometer with high resolution dynamic sensing and absolute length detection

    NASA Astrophysics Data System (ADS)

    Antonacci, Julián; Arenas, Gustavo F.; Duchowicz, Ricardo

    2017-04-01

    In this work, we present a simple photonic instrument that has the ability of measuring positions, distances and vibrations with very high resolution by means of two Fizeau interferometers (FI), both using the same optical fiber end as a probe tip itself. On the one hand we have a time domain FI powered with a 1310 nm laser and monitored by an InGaAs detector providing displacement information with resolution around a tenth of nm but regardless of the absolute position of object and of the displacement sense. On the other, a spectral domain FI version based on a super luminescent source (SLED) centred at 800 nm with bandwidth of nearly 40 nm is analysed in real time by means of a digital spectrometer. Each spectrum is acquired in a very small time interval and provides information of both length of the cavity as well as its correct sense of evolution. Resolution of this system is lower than its complementary temporal case, but distance and sense measurements are absolute and can be determined successfully by adequate processing of spectral signal.Both interferometers are optically coupled to a single fiber optic probe and are wavelength modulated.Therefore, combination of both sensors results in a new one which allows the correct knowledge of an object or surfaces under test, i.e. a high resolution of displacement data plus its absolute position and true sense of movement.

  9. Detection of sputtered and evaporated carbon aggregates: relative and absolute electron ionization fragmentation yields

    NASA Astrophysics Data System (ADS)

    Mair, C.; Deutsch, H.; Becker, K.; Märk, T. D.; Vietzke, E.

    2001-03-01

    The present study is a first attempt to determine electron impact ionization efficiencies for C 2 and C 3. A novel method has been applied to obtain the partial cross-section values for the reactions C 2+e→C +,C 2+e→C 2+ and C 3+e→C +,C 3+e→C 2+ and C 3+e→C 3+. The neutral target consisting of C, C 2 and C 3 is produced by thermal evaporation from a heated graphite sample and the neutral precursors in the subsequent ionization process can be distinguished by their different flight-time distributions acquired in the evaporation process. The partial ionization cross-section ratios obtained in this experiment have been calibrated with calculated absolute total ionization cross section curves of C 2 and C 3 using the Deutsch-Märk (DM) formalism.

  10. Detection limits of confocal surface plasmon microscopy

    PubMed Central

    Pechprasarn, Suejit; Somekh, Michael G.

    2014-01-01

    This paper applies rigorous diffraction theory to evaluate the minimum mass sensitivity of a confocal optical microscope designed to excite and detect surface plasmons operating on a planar metallic substrate. The diffraction model is compared with an intuitive ray picture which gives remarkably similar predictions. The combination of focusing the surface plasmons and accurate phase measurement mean that under favorable but achievable conditions detection of small numbers of molecules is possible, however, we argue that reliable detection of single molecules will benefit from the use of structured surfaces. System configurations needed to optimize performance are discussed. PMID:24940537

  11. Comprehensive panel of real-time TaqMan polymerase chain reaction assays for detection and absolute quantification of filoviruses, arenaviruses, and New World hantaviruses.

    PubMed

    Trombley, Adrienne R; Wachter, Leslie; Garrison, Jeffrey; Buckley-Beason, Valerie A; Jahrling, Jordan; Hensley, Lisa E; Schoepp, Randal J; Norwood, David A; Goba, Augustine; Fair, Joseph N; Kulesh, David A

    2010-05-01

    Viral hemorrhagic fever is caused by a diverse group of single-stranded, negative-sense or positive-sense RNA viruses belonging to the families Filoviridae (Ebola and Marburg), Arenaviridae (Lassa, Junin, Machupo, Sabia, and Guanarito), and Bunyaviridae (hantavirus). Disease characteristics in these families mark each with the potential to be used as a biological threat agent. Because other diseases have similar clinical symptoms, specific laboratory diagnostic tests are necessary to provide the differential diagnosis during outbreaks and for instituting acceptable quarantine procedures. We designed 48 TaqMan-based polymerase chain reaction (PCR) assays for specific and absolute quantitative detection of multiple hemorrhagic fever viruses. Forty-six assays were determined to be virus-specific, and two were designated as pan assays for Marburg virus. The limit of detection for the assays ranged from 10 to 0.001 plaque-forming units (PFU)/PCR. Although these real-time hemorrhagic fever virus assays are qualitative (presence of target), they are also quantitative (measure a single DNA/RNA target sequence in an unknown sample and express the final results as an absolute value (e.g., viral load, PFUs, or copies/mL) on the basis of concentration of standard samples and can be used in viral load, vaccine, and antiviral drug studies.

  12. Comprehensive Panel of Real-Time TaqMan™ Polymerase Chain Reaction Assays for Detection and Absolute Quantification of Filoviruses, Arenaviruses, and New World Hantaviruses

    PubMed Central

    Trombley, Adrienne R.; Wachter, Leslie; Garrison, Jeffrey; Buckley-Beason, Valerie A.; Jahrling, Jordan; Hensley, Lisa E.; Schoepp, Randal J.; Norwood, David A.; Goba, Augustine; Fair, Joseph N.; Kulesh, David A.

    2010-01-01

    Viral hemorrhagic fever is caused by a diverse group of single-stranded, negative-sense or positive-sense RNA viruses belonging to the families Filoviridae (Ebola and Marburg), Arenaviridae (Lassa, Junin, Machupo, Sabia, and Guanarito), and Bunyaviridae (hantavirus). Disease characteristics in these families mark each with the potential to be used as a biological threat agent. Because other diseases have similar clinical symptoms, specific laboratory diagnostic tests are necessary to provide the differential diagnosis during outbreaks and for instituting acceptable quarantine procedures. We designed 48 TaqMan™-based polymerase chain reaction (PCR) assays for specific and absolute quantitative detection of multiple hemorrhagic fever viruses. Forty-six assays were determined to be virus-specific, and two were designated as pan assays for Marburg virus. The limit of detection for the assays ranged from 10 to 0.001 plaque-forming units (PFU)/PCR. Although these real-time hemorrhagic fever virus assays are qualitative (presence of target), they are also quantitative (measure a single DNA/RNA target sequence in an unknown sample and express the final results as an absolute value (e.g., viral load, PFUs, or copies/mL) on the basis of concentration of standard samples and can be used in viral load, vaccine, and antiviral drug studies. PMID:20439981

  13. Analysis of Intrinsic Peptide Detectability via Integrated Label-Free and SRM-Based Absolute Quantitative Proteomics.

    PubMed

    Jarnuczak, Andrew F; Lee, Dave C H; Lawless, Craig; Holman, Stephen W; Eyers, Claire E; Hubbard, Simon J

    2016-09-02

    Quantitative mass spectrometry-based proteomics of complex biological samples remains challenging in part due to the variability and charge competition arising during electrospray ionization (ESI) of peptides and the subsequent transfer and detection of ions. These issues preclude direct quantification from signal intensity alone in the absence of a standard. A deeper understanding of the governing principles of peptide ionization and exploitation of the inherent ionization and detection parameters of individual peptides is thus of great value. Here, using the yeast proteome as a model system, we establish the concept of peptide F-factor as a measure of detectability, closely related to ionization efficiency. F-factor is calculated by normalizing peptide precursor ion intensity by absolute abundance of the parent protein. We investigated F-factor characteristics in different shotgun proteomics experiments, including across multiple ESI-based LC-MS platforms. We show that F-factors mirror previously observed physicochemical predictors as peptide detectability but demonstrate a nonlinear relationship between hydrophobicity and peptide detectability. Similarly, we use F-factors to show how peptide ion coelution adversely affects detectability and ionization. We suggest that F-factors have great utility for understanding peptide detectability and gas-phase ion chemistry in complex peptide mixtures, selection of surrogate peptides in targeted MS studies, and for calibration of peptide ion signal in label-free workflows. Data are available via ProteomeXchange with identifier PXD003472.

  14. Exhaustive thin-layer cyclic voltammetry for absolute multianalyte halide detection.

    PubMed

    Cuartero, Maria; Crespo, Gastón A; Ghahraman Afshar, Majid; Bakker, Eric

    2014-11-18

    Water analysis is one of the greatest challenges in the field of environmental analysis. In particular, seawater analysis is often difficult because a large amount of NaCl may mask the determination of other ions, i.e., nutrients, halides, and carbonate species. We demonstrate here the use of thin-layer samples controlled by cyclic voltammetry to analyze water samples for chloride, bromide, and iodide. The fabrication of a microfluidic electrochemical cell based on a Ag/AgX wire (working electrode) inserted into a tubular Nafion membrane is described, which confines the sample solution layer to less than 15 μm. By increasing the applied potential, halide ions present in the thin-layer sample (X(-)) are electrodeposited on the working electrode as AgX, while their respective counterions are transported across the perm-selective membrane to an outer solution. Thin-layer cyclic voltammetry allows us to obtain separated peaks in mixed samples of these three halides, finding a linear relationship between the halide concentration and the corresponding peak area from about 10(-5) to 0.1 M for bromide and iodide and from 10(-4) to 0.6 M for chloride. This technique was successfully applied for the halide analysis in tap, mineral, and river water as well as seawater. The proposed methodology is absolute and potentially calibration-free, as evidenced by an observed 2.5% RSD cell to cell reproducibility and independence from the operating temperature.

  15. Interference peak detection based on FPGA for real-time absolute distance ranging with dual-comb lasers

    NASA Astrophysics Data System (ADS)

    Ni, Kai; Dong, Hao; Zhou, Qian; Xu, Mingfei; Li, Xinghui; Wu, Guanhao

    2015-08-01

    Absolute distance measurement using dual femtosecond comb lasers can achieve higher accuracy and faster measurement speed, which makes it more and more attractive. The data processing flow consists of four steps: interference peak detection, fast Fourier transform (FFT), phase fitting and compensation of index of refraction. A realtime data processing system based on Field-Programmable Gate Array (FPGA) for dual-comb ranging has been newly developed. The design and implementation of the interference peak detection algorithm by FPGA and Verilog language is introduced in this paper, which is viewed as the most complicated part and an important guarantee for system precision and reliability. An adaptive sliding window for scanning is used to detect peaks. In the process of detection, the algorithm stores 16 sample data as a detection unit and calculates the average of each unit. The average result is used to determine the vertical center height of the sliding window. The algorithm estimates the noise intensity of each detection unit, and then calculates the average of the noise strength of successive 128 units. The noise average is used to calculate the signal to noise ratio of the current working environment, which is used to adjust the height of the sliding window. This adaptive sliding window helps to eliminate fake peaks caused by noise. The whole design is based on the way of pipeline, which can improves the real-time throughput of the overall peak detection module. Its execution speed is up to 140MHz in the FPGA, and the peak can be detected in 16 clock cycle when it appears.

  16. Limits on the thermoacoustic detectability of electric and magnetic charges

    SciTech Connect

    Akerlof, C.W.

    1982-09-01

    The energy loss is estimated for a slow magnetic monopole traveling through a conductor. The thermoacoustic signal derived from this process is compared to the acoustic phonon fluctuation pressure. The results show that single-monopole detectability is strongly limited by thermal noise. These calculations also imply severe limits for the detectability of charged-particle cascades.

  17. Absolute mass lower limit for the lightest neutralino of the MSSM from e+e- data at s up to 209 GeV

    NASA Astrophysics Data System (ADS)

    Heister, A.; Schael, S.; Barate, R.; Brunelière, R.; de Bonis, I.; Decamp, D.; Goy, C.; Jézéquel, S.; Lees, J.-P.; Martin, F.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Trocmé, B.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll; Martinez, M.; Pacheco, A.; Ruiz, H.; Colaleo, A.; Creanza, D.; de Filippis, N.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Barklow, T.; Buchmüller, O.; Cattaneo, M.; Clerbaux, B.; Drevermann, H.; Forty, R. W.; Frank, M.; Gianotti, F.; Hansen, J. B.; Harvey, J.; Hutchcroft, D. E.; Janot, P.; Jost, B.; Kado, M.; Mato, P.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Sguazzoni, G.; Teubert, F.; Valassi, A.; Videau, I.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Jousset, J.; Michel, B.; Monteil, S.; Pallin, D.; Pascolo, J. M.; Perret, P.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Kraan, A. C.; Nilsson, B. S.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Brient, J.-C.; Machefert, F.; Rougé, A.; Videau, H.; Ciulli, V.; Focardi, E.; Parrini, G.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bossi, F.; Capon, G.; Cerutti, F.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, G. P.; Passalacqua, L.; Kennedy, J.; Lynch, J. G.; Negus, P.; O'Shea, V.; Thompson, A. S.; Wasserbaech, S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Stenzel, H.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Cameron, W.; Davies, G.; Dornan, P. J.; Girone, M.; Hill, R. D.; Marinelli, N.; Nowell, J.; Rutherford, S. A.; Sedgbeer, J. K.; Thompson, J. C.; White, R.; Ghete, V. M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C. K.; Clarke, D. P.; Ellis, G.; Finch, A. J.; Foster, F.; Hughes, G.; Jones, R. W. L.; Pearson, M. R.; Robertson, N. A.; Smizanska, M.; van der Aa, O.; Delaere, C.; Leibenguth, G.; Lemaitre, V.; Blumenschein, U.; Hölldorfer, F.; Jakobs, K.; Kayser, F.; Kleinknecht, K.; Müller, A.-S.; Renk, B.; Sander, H.-G.; Schmeling, S.; Wachsmuth, H.; Zeitnitz, C.; Ziegler, T.; Bonissent, A.; Coyle, P.; Curtil, C.; Ealet, A.; Fouchez, D.; Payre, P.; Tilquin, A.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Hüttmann, K.; Lütjens, G.; Männer, W.; Moser, H.-G.; Settles, R.; Villegas, M.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph; Jacholkowska, A.; Serin, L.; Veillet, J.-J.; de Vivie de Régie, J.-B.; Azzurri, P.; Bagliesi, G.; Boccali, T.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Awunor, O.; Blair, G. A.; Cowan, G.; Garcia-Bellido, A.; Green, M. G.; Medcalf, T.; Misiejuk, A.; Strong, J. A.; Teixeira-Dias, P.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Ward, J. J.; Bloch-Devaux, B.; Boumediene, D.; Colas, P.; Fabbro, B.; Lançon, E.; Lemaire, M.-C.; Locci, E.; Perez, P.; Rander, J.; Tuchming, B.; Vallage, B.; Litke, A. M.; Taylor, G.; Booth, C. N.; Cartwright, S.; Combley, F.; Hodgson, P. N.; Lehto, M.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Grupen, C.; Hess, J.; Ngac, A.; Prange, G.; Borean, C.; Giannini, G.; He, H.; Putz, J.; Rothberg, J.; Armstrong, S. R.; Berkelman, K.; Cranmer, K.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A.; Nielsen, J.; Pan, Y. B.; von Wimmersperg-Toeller, J. H.; Wiedenmann, W.; Wu, J.; Lan Wu, Sau; Wu, X.; Zobernig, G.; Dissertori, G.; Aleph Collaboration

    2004-03-01

    Charginos and neutralinos are searched for in the data collected by the ALEPH experiment at LEP for centre-of-mass energies up to 209 GeV. The negative result of these searches is combined with those from searches for sleptons and Higgs bosons to derive an absolute lower limit of 43.1 GeV/c2 on the mass of the lightest supersymmetric particle (LSP), assumed to be the lightest neutralino. This limit is obtained in the framework of the MSSM with R-parity conservation and with gaugino and sfermion mass unification at the GUT scale and assuming no mixing in the stau sector. The LSP limit degrades only slightly to 42.4 GeV/c2 if stau mixing is considered. Within the more constrained framework of minimal supergravity, the limit is 50 GeV/c2.

  18. HEPES is not suitable for fluorescence detection of HClO: a novel probe for HClO in absolute PBS.

    PubMed

    Xing, Panfei; Gao, Kuo; Wang, Beng; Gao, Jian; Yan, Hui; Wen, Jia; Li, Weisi; Xu, Yongqian; Li, Hongjuan; Chen, Jianxin; Wang, Wei; Sun, Shiguo

    2016-04-11

    HEPES is not suitable for fluorescence detection of HClO because it can be oxidized by HClO. A novel probe for HClO, which can selectively and sensitively detect HClO in absolute PBS, was developed on the basis of an oxidation reaction with an azo moiety. Furthermore, it works well in live mouse imaging.

  19. Gardening in the zone of death: an experimental assessment of the absolute elevation limit of vascular plants

    PubMed Central

    Dvorský, Miroslav; Chlumská, Zuzana; Altman, Jan; Čapková, Kateřina; Řeháková, Klára; Macek, Martin; Kopecký, Martin; Liancourt, Pierre; Doležal, Jiří

    2016-01-01

    Vascular plants in the western Tibetan Plateau reach 6000 m-the highest elevation on Earth. Due to the significant warming of the region, plant ranges are expected to shift upwards. However, factors governing maximum elevational limits of plant are unclear. To experimentally assess these factors, we transplanted 12 species from 5750 m to 5900 m (upper edge of vegetation) and 6100 m (beyond range) and monitored their survival for six years. In the first three years (2009–2012), there were plants surviving beyond the regional upper limit of vegetation. This supports the hypothesis of dispersal and/or recruitment limitation. Substantial warming, recorded in-situ during this period, very likely facilitated the survival. The survival was ecologically a non-random process, species better adapted to repeated soil freezing and thawing survived significantly better. No species have survived at 6100 m since 2013, probably due to the extreme snowfall in 2013. In conclusion, apart from the minimum heat requirements, our results show that episodic climatic events are decisive determinants of upper elevational limits of vascular plants. PMID:27071305

  20. Gardening in the zone of death: an experimental assessment of the absolute elevation limit of vascular plants.

    PubMed

    Dvorský, Miroslav; Chlumská, Zuzana; Altman, Jan; Čapková, Kateřina; Řeháková, Klára; Macek, Martin; Kopecký, Martin; Liancourt, Pierre; Doležal, Jiří

    2016-04-13

    Vascular plants in the western Tibetan Plateau reach 6000 m--the highest elevation on Earth. Due to the significant warming of the region, plant ranges are expected to shift upwards. However, factors governing maximum elevational limits of plant are unclear. To experimentally assess these factors, we transplanted 12 species from 5750 m to 5900 m (upper edge of vegetation) and 6100 m (beyond range) and monitored their survival for six years. In the first three years (2009-2012), there were plants surviving beyond the regional upper limit of vegetation. This supports the hypothesis of dispersal and/or recruitment limitation. Substantial warming, recorded in-situ during this period, very likely facilitated the survival. The survival was ecologically a non-random process, species better adapted to repeated soil freezing and thawing survived significantly better. No species have survived at 6100 m since 2013, probably due to the extreme snowfall in 2013. In conclusion, apart from the minimum heat requirements, our results show that episodic climatic events are decisive determinants of upper elevational limits of vascular plants.

  1. Gardening in the zone of death: an experimental assessment of the absolute elevation limit of vascular plants

    NASA Astrophysics Data System (ADS)

    Dvorský, Miroslav; Chlumská, Zuzana; Altman, Jan; Čapková, Kateřina; Řeháková, Klára; Macek, Martin; Kopecký, Martin; Liancourt, Pierre; Doležal, Jiří

    2016-04-01

    Vascular plants in the western Tibetan Plateau reach 6000 m-the highest elevation on Earth. Due to the significant warming of the region, plant ranges are expected to shift upwards. However, factors governing maximum elevational limits of plant are unclear. To experimentally assess these factors, we transplanted 12 species from 5750 m to 5900 m (upper edge of vegetation) and 6100 m (beyond range) and monitored their survival for six years. In the first three years (2009–2012), there were plants surviving beyond the regional upper limit of vegetation. This supports the hypothesis of dispersal and/or recruitment limitation. Substantial warming, recorded in-situ during this period, very likely facilitated the survival. The survival was ecologically a non-random process, species better adapted to repeated soil freezing and thawing survived significantly better. No species have survived at 6100 m since 2013, probably due to the extreme snowfall in 2013. In conclusion, apart from the minimum heat requirements, our results show that episodic climatic events are decisive determinants of upper elevational limits of vascular plants.

  2. Receiver operating characteristic-curve limits of detection

    NASA Astrophysics Data System (ADS)

    Wysoczanski, Artur; Voigtman, Edward

    2014-10-01

    Using a simple UV LED-excited ruby fluorescence measurement system, we demonstrate that it is easily possible to obtain unbiased detection limits, despite the system deliberately having non-linear response function and non-Gaussian noise. Even when the noise precision model is heteroscedastic, but otherwise only roughly linear, the receiver operating characteristic (ROC) method readily yields results that are in accordance with a priori canonical specifications of false positives and false negatives at the detection limit. The present work demonstrates that obtaining unbiased detection limits is not abstruse and need not be mathematically complicated. Rather, detection limits continue to serve a useful purpose as part of the characterization of chemical measurement systems.

  3. Narrow scope for resolution-limit-free community detection

    NASA Astrophysics Data System (ADS)

    Traag, V. A.; van Dooren, P.; Nesterov, Y.

    2011-07-01

    Detecting communities in large networks has drawn much attention over the years. While modularity remains one of the more popular methods of community detection, the so-called resolution limit remains a significant drawback. To overcome this issue, it was recently suggested that instead of comparing the network to a random null model, as is done in modularity, it should be compared to a constant factor. However, it is unclear what is meant exactly by “resolution-limit-free,” that is, not suffering from the resolution limit. Furthermore, the question remains what other methods could be classified as resolution-limit-free. In this paper we suggest a rigorous definition and derive some basic properties of resolution-limit-free methods. More importantly, we are able to prove exactly which class of community detection methods are resolution-limit-free. Furthermore, we analyze which methods are not resolution-limit-free, suggesting there is only a limited scope for resolution-limit-free community detection methods. Finally, we provide such a natural formulation, and show it performs superbly.

  4. Size dependence of microscopic Hall sensor detection limits.

    PubMed

    Vervaeke, K; Simoen, E; Borghs, G; Moshchalkov, V V

    2009-07-01

    In this paper the magnetic field detection limits of microscopic Hall sensors are investigated as a function of their lateral size. Hall sensors fabricated from GaAs/AlGaAs heterostructures and silicon are experimentally investigated at different temperatures using Hall effect and noise spectrum measurements. At room temperature a clear size dependence of the detection limit is observed, whereas at low temperatures this dependence is found to disappear. The results are explained using the theory of noise in semiconductors.

  5. Detection limits for real-time source water monitoring using indigenous freshwater microalgae.

    PubMed

    Rodriguez, Miguel; Greenbaum, Elias

    2009-11-01

    This research identified toxin detection limits using the variable fluorescence of naturally occurring microalgae in source drinking water for five chemical toxins with different molecular structures and modes of toxicity. The five chemicals investigated were atrazine, Diuron, paraquat, methyl parathion, and potassium cyanide. Absolute threshold sensitivities of the algae for detection of the toxins in unmodified source drinking water were measured. Differential kinetics between the rate of action of the toxins and natural changes in algal physiology, such as diurnal photoinhibition, are significant enough that effects of the toxin can be detected and distinguished from the natural variance. This is true even for physiologically impaired algae where diminished photosynthetic capacity may arise from uncontrollable external factors such as nutrient starvation. Photoinhibition induced by high levels of solar radiation is a predictable and reversible phenomenon that can be dealt with using a period of dark adaption of 30 minutes or more.

  6. Detection limits for real-time source water monitoring using indigenous freshwater microalgae

    SciTech Connect

    Rodriguez Jr, Miguel; Greenbaum, Elias

    2009-01-01

    This research identified toxin detection limits using the variable fluorescence of naturally occurring microalgae in source drinking water for five chemical toxins with different molecular structures and modes of toxicity. The five chemicals investigated were atrazine, Diuron, paraquat, methyl parathion, and potassium cyanide. Absolute threshold sensitivities of the algae for detection of the toxins in unmodified source drinking water were measured. Differential kinetics between the rate of action of the toxins and natural changes in algal physiology, such as diurnal photoinhibition, are significant enough that effects of the toxin can be detected and distinguished from the natural variance. This is true even for physiologically impaired algae where diminished photosynthetic capacity may arise from uncontrollable external factors such as nutrient starvation. Photoinhibition induced by high levels of solar radiation is a predictable and reversible phenomenon that can be dealt with using a period of dark adaption of 30 minutes or more.

  7. Calculation of the absolute detection efficiency of a moderated /sup 235/U neutron detector on the Tokamak Fusion Test Reactor

    SciTech Connect

    Ku, L.P.; Hendel, H.W.; Liew, S.L.

    1989-02-01

    Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated /sup 235/U neutron detector which is used on the TFTR as a part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semi-empirical model based on matching the calculational results with a small set of experiments produces good agreement (+-15%) for a wide range of source energies and geometries. 20 refs., 6 figs., 4 tabs.

  8. Left-hemisphere activation is associated with enhanced vocal pitch error detection in musicians with absolute pitch.

    PubMed

    Behroozmand, Roozbeh; Ibrahim, Nadine; Korzyukov, Oleg; Robin, Donald A; Larson, Charles R

    2014-02-01

    The ability to process auditory feedback for vocal pitch control is crucial during speaking and singing. Previous studies have suggested that musicians with absolute pitch (AP) develop specialized left-hemisphere mechanisms for pitch processing. The present study adopted an auditory feedback pitch perturbation paradigm combined with ERP recordings to test the hypothesis whether the neural mechanisms of the left-hemisphere enhance vocal pitch error detection and control in AP musicians compared with relative pitch (RP) musicians and non-musicians (NM). Results showed a stronger N1 response to pitch-shifted voice feedback in the right-hemisphere for both AP and RP musicians compared with the NM group. However, the left-hemisphere P2 component activation was greater in AP and RP musicians compared with NMs and also for the AP compared with RP musicians. The NM group was slower in generating compensatory vocal reactions to feedback pitch perturbation compared with musicians, and they failed to re-adjust their vocal pitch after the feedback perturbation was removed. These findings suggest that in the earlier stages of cortical neural processing, the right hemisphere is more active in musicians for detecting pitch changes in voice feedback. In the later stages, the left-hemisphere is more active during the processing of auditory feedback for vocal motor control and seems to involve specialized mechanisms that facilitate pitch processing in the AP compared with RP musicians. These findings indicate that the left hemisphere mechanisms of AP ability are associated with improved auditory feedback pitch processing during vocal pitch control in tasks such as speaking or singing. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Left-hemisphere activation is associated with enhanced vocal pitch error detection in musicians with absolute pitch

    PubMed Central

    Behroozmand, Roozbeh; Ibrahim, Nadine; Korzyukov, Oleg; Robin, Donald A.; Larson, Charles R.

    2014-01-01

    The ability to process auditory feedback for vocal pitch control is crucial during speaking and singing. Previous studies have suggested that musicians with absolute pitch (AP) develop specialized left-hemisphere mechanisms for pitch processing. The present study adopted an auditory feedback pitch perturbation paradigm combined with ERP recordings to test the hypothesis whether the neural mechanisms of the left-hemisphere enhance vocal pitch error detection and control in AP musicians compared with relative pitch (RP) musicians and non-musicians (NM). Results showed a stronger N1 response to pitch-shifted voice feedback in the right-hemisphere for both AP and RP musicians compared with the NM group. However, the left-hemisphere P2 component activation was greater in AP and RP musicians compared with NMs and also for the AP compared with RP musicians. The NM group was slower in generating compensatory vocal reactions to feedback pitch perturbation compared with musicians, and they failed to re-adjust their vocal pitch after the feedback perturbation was removed. These findings suggest that in the earlier stages of cortical neural processing, the right hemisphere is more active in musicians for detecting pitch changes in voice feedback. In the later stages, the left-hemisphere is more active during the processing of auditory feedback for vocal motor control and seems to involve specialized mechanisms that facilitate pitch processing in the AP compared with RP musicians. These findings indicate that the left hemisphere mechanisms of AP ability are associated with improved auditory feedback pitch processing during vocal pitch control in tasks such as speaking or singing. PMID:24355545

  10. The limit of detection for explosives in spectroscopic differential reflectometry

    NASA Astrophysics Data System (ADS)

    Dubroca, Thierry; Vishwanathan, Karthik; Hummel, Rolf E.

    2011-05-01

    In the wake of recent terrorist attacks, such as the 2008 Mumbai hotel explosion or the December 25th 2009 "underwear bomber", our group has developed a technique (US patent #7368292) to apply differential reflection spectroscopy to detect traces of explosives. Briefly, light (200-500 nm) is shone on a surface such as a piece of luggage at an airport. Upon reflection, the light is collected with a spectrometer combined with a CCD camera. A computer processes the data and produces in turn a differential reflection spectrum involving two adjacent areas of the surface. This differential technique is highly sensitive and provides spectroscopic data of explosives. As an example, 2,4,6, trinitrotoluene (TNT) displays strong and distinct features in differential reflectograms near 420 nm. Similar, but distinctly different features are observed for other explosives. One of the most important criteria for explosive detection techniques is the limit of detection. This limit is defined as the amount of explosive material necessary to produce a signal to noise ratio of three. We present here, a method to evaluate the limit of detection of our technique. Finally, we present our sample preparation method and experimental set-up specifically developed to measure the limit of detection for our technology. This results in a limit ranging from 100 nano-grams to 50 micro-grams depending on the method and the set-up parameters used, such as the detector-sample distance.

  11. A Generic HPLC Method for Absolute Quantification of Oxidation in Monoclonal Antibodies and Fc-Fusion Proteins Using UV and MS Detection.

    PubMed

    Regl, Christof; Wohlschlager, Therese; Holzmann, Johann; Huber, Christian G

    2017-08-15

    Oxidation of biopharmaceuticals may affect their bioactivity, serum half-life, and (bio)chemical stability. The Fc domain of IgG monoclonal antibodies (mAbs) contains two methionine residues which are susceptible to oxidation. Here, we present a middle-down approach employing the cysteine protease IdeS under reducing conditions to obtain three mAb subunits of approximately 25 kDa: Fc/2, Fd', and LC. These subunits were separated by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) and detected by UV spectroscopy as well as Orbitrap mass spectrometry (MS), as well as MS upon all-ion fragmentation (AIF-MS). We evaluated the feasibility of three strategies for absolute quantification of oxidation in the Fc region of hydrogen peroxide-stressed Rituximab, using a single, commercially available software platform both for data acquisition and evaluation: UV spectroscopy, full-scan MS, and monitoring of product ions obtained by AIF-MS. UV spectroscopy showed the lowest limits of quantification (LOQ) (0.96 ng μL(-1)) and featured the lowest relative process standard deviation (Vx0%) of 7.2% compared to MS and AIF-MS with LOQs of 1.24-4.32 ng μL(-1) and relative process standard deviations of 9.0-14%, respectively. Our approach is generic in that it allows monitoring and quantification of oxidation in the Fc regions of fully human and humanized IgG1 mAbs as well as of Fc-fusion proteins. This is exemplified by limits of detection of 1.2%, 1.0%, and 1.2% of oxidation in drug products containing the biopharmaceuticals Rituximab, Adalimumab, and Etanercept, respectively. The presented method is an attractive alternative to conventional time-intensive peptide mapping which is prone to artificial oxidation due to extensive sample preparation.

  12. Sniper detection using infrared camera: technical possibilities and limitations

    NASA Astrophysics Data System (ADS)

    Kastek, M.; Dulski, R.; Trzaskawka, P.; Bieszczad, G.

    2010-04-01

    The paper discusses technical possibilities to build an effective system for sniper detection using infrared cameras. Descriptions of phenomena which make it possible to detect sniper activities in infrared spectra as well as analysis of physical limitations were performed. Cooled and uncooled detectors were considered. Three phases of sniper activities were taken into consideration: before, during and after the shot. On the basis of experimental data the parameters defining the target 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. The simulation of detection ranges was done for the assumed scenario of sniper detection task. The infrared sniper detection system was discussed, capable of fulfilling the requirements. The discussion of the results of analysis and simulations was finally presented.

  13. Detection limits of organic compounds achievable with intense, short-pulse lasers.

    PubMed

    Miles, Jordan; De Camillis, Simone; Alexander, Grace; Hamilton, Kathryn; Kelly, Thomas J; Costello, John T; Zepf, Matthew; Williams, Ian D; Greenwood, Jason B

    2015-06-21

    Many organic molecules have strong absorption bands which can be accessed by ultraviolet short pulse lasers to produce efficient ionization. This resonant multiphoton ionization scheme has already been exploited as an ionization source in time-of-flight mass spectrometers used for environmental trace analysis. In the present work we quantify the ultimate potential of this technique by measuring absolute ion yields produced from the interaction of 267 nm femtosecond laser pulses with the organic molecules indole and toluene, and gases Xe, N2 and O2. Using multiphoton ionization cross sections extracted from these results, we show that the laser pulse parameters required for real-time detection of aromatic molecules at concentrations of one part per trillion in air and a limit of detection of a few attomoles are achievable with presently available commercial laser systems. The potential applications for the analysis of human breath, blood and tissue samples are discussed.

  14. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  15. In-flow real-time detection of spectrally encoded microgels for miRNA absolute quantification

    PubMed Central

    Dannhauser, David; Causa, Filippo; Cusano, Angela M.; Rossi, Domenico; Netti, Paolo A.

    2016-01-01

    We present an in-flow ultrasensitive fluorescence detection of microRNAs (miRNAs) using spectrally encoded microgels. We researched and employed a viscoelastic fluid to achieve an optimal alignment of microgels in a straight measurement channel and applied a simple and inexpensive microfluidic layout, allowing continuous fluorescence signal acquisitions with several emission wavelengths. In particular, we chose microgels endowed with fluorescent emitting molecules designed for multiplex spectral analysis of specific miRNA types. We analysed in a quasi-real-time manner circa 80 microgel particles a minute at sample volumes down to a few microliters, achieving a miRNA detection limit of 202 fM in microfluidic flow conditions. Such performance opens up new routes for biosensing applications of particles within microfluidic devices. PMID:27990216

  16. In-flow real-time detection of spectrally encoded microgels for miRNA absolute quantification.

    PubMed

    Dannhauser, David; Causa, Filippo; Battista, Edmondo; Cusano, Angela M; Rossi, Domenico; Netti, Paolo A

    2016-11-01

    We present an in-flow ultrasensitive fluorescence detection of microRNAs (miRNAs) using spectrally encoded microgels. We researched and employed a viscoelastic fluid to achieve an optimal alignment of microgels in a straight measurement channel and applied a simple and inexpensive microfluidic layout, allowing continuous fluorescence signal acquisitions with several emission wavelengths. In particular, we chose microgels endowed with fluorescent emitting molecules designed for multiplex spectral analysis of specific miRNA types. We analysed in a quasi-real-time manner circa 80 microgel particles a minute at sample volumes down to a few microliters, achieving a miRNA detection limit of 202 fM in microfluidic flow conditions. Such performance opens up new routes for biosensing applications of particles within microfluidic devices.

  17. Detecting terrestrial nutrient limitation: a global meta-analysis of foliar nutrient concentrations after fertilization

    NASA Astrophysics Data System (ADS)

    Ostertag, Rebecca; DiManno, Nicole

    2016-03-01

    Examining foliar nutrient concentrations after fertilization provides an alternative method for detecting nutrient limitation of ecosystems, which is logistically simpler to measure than biomass change. We present a meta-analysis of response ratios of foliar nitrogen and phosphorus (RRN, RRP) after addition of fertilizer of nitrogen (N), phosphorus (P), or the two elements in combination, in relation to climate, ecosystem type, life form, family, and methodological factors. Results support other meta-analyses using biomass, and demonstrate there is strong evidence for nutrient limitation in natural communities. However, because N fertilization experiments greatly outnumber P fertilization trials, it is difficult to discern the absolute importance of N vs. P vs. co-limitation across ecosystems. Despite these caveats, it is striking that results did not follow "conventional wisdom" that temperate ecosystems are N-limited and tropical ones are P-limited. In addition, the use of ratios of N-to-P rather than response ratios also are a useful index of nutrient limitation, but due to large overlap in values, there are unlikely to be universal cutoff values for delimiting N vs. P limitation. Differences in RRN and RRP were most significant across ecosystem types, plant families, life forms, and between competitive environments, but not across climatic variables.

  18. Breaking the concentration limit of optical single-molecule detection.

    PubMed

    Holzmeister, Phil; Acuna, Guillermo P; Grohmann, Dina; Tinnefeld, Philip

    2014-02-21

    Over the last decade, single-molecule detection has been successfully utilized in the life sciences and materials science. Yet, single-molecule measurements only yield meaningful results when working in a suitable, narrow concentration range. On the one hand, diffraction limits the minimal size of the observation volume in optical single-molecule measurements and consequently a sample must be adequately diluted so that only one molecule resides within the observation volume. On the other hand, at ultra-low concentrations relevant for sensing, the detection volume has to be increased in order to detect molecules in a reasonable timespan. This in turn results in the loss of an optimal signal-to-noise ratio necessary for single-molecule detection. This review discusses the requirements for effective single-molecule fluorescence applications, reflects on the motivation for the extension of the dynamic concentration range of single-molecule measurements and reviews various approaches that have been introduced recently to solve these issues. For the high-concentration limit, we identify four promising strategies including molecular confinement, optical observation volume reduction, temporal separation of signals and well-conceived experimental designs that specifically circumvent the high concentration limit. The low concentration limit is addressed by increasing the measurement speed, parallelization, signal amplification and preconcentration. The further development of these ideas will expand our possibilities to interrogate research questions with the clarity and precision provided only by the single-molecule approach.

  19. Global limits and interference patterns in dark matter direct detection

    SciTech Connect

    Catena, Riccardo; Gondolo, Paolo

    2015-08-13

    We compare the general effective theory of one-body dark matter nucleon interactions to current direct detection experiments in a global multidimensional statistical analysis. We derive exclusion limits on the 28 isoscalar and isovector coupling constants of the theory, and show that current data place interesting constraints on dark matter-nucleon interaction operators usually neglected in this context. We characterize the interference patterns that can arise in dark matter direct detection from pairs of dark matter-nucleon interaction operators, or from isoscalar and isovector components of the same operator. We find that commonly neglected destructive interference effects weaken standard direct detection exclusion limits by up to one order of magnitude in the coupling constants.

  20. Global limits and interference patterns in dark matter direct detection

    SciTech Connect

    Catena, Riccardo; Gondolo, Paolo E-mail: paolo.gondolo@utah.edu

    2015-08-01

    We compare the general effective theory of one-body dark matter nucleon interactions to current direct detection experiments in a global multidimensional statistical analysis. We derive exclusion limits on the 28 isoscalar and isovector coupling constants of the theory, and show that current data place interesting constraints on dark matter-nucleon interaction operators usually neglected in this context. We characterize the interference patterns that can arise in dark matter direct detection from pairs of dark matter-nucleon interaction operators, or from isoscalar and isovector components of the same operator. We find that commonly neglected destructive interference effects weaken standard direct detection exclusion limits by up to one order of magnitude in the coupling constants.

  1. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  2. Stochastic fluctuations and the detectability limit of network communities

    NASA Astrophysics Data System (ADS)

    Floretta, Lucio; Liechti, Jonas; Flammini, Alessandro; Rios, Paolo De Los

    2013-12-01

    We have analyzed the detectability limits of network communities in the framework of the popular Girvan and Newman benchmark. By carefully taking into account the inevitable stochastic fluctuations that affect the construction of each and every instance of the benchmark, we come to the conclusion that the native, putative partition of the network is completely lost even before the in-degree/out-degree ratio becomes equal to that of a structureless Erdös-Rényi network. We develop a simple iterative scheme, analytically well described by an infinite branching process, to provide an estimate of the true detectability limit. Using various algorithms based on modularity optimization, we show that all of them behave (semiquantitatively) in the same way, with the same functional form of the detectability threshold as a function of the network parameters. Because the same behavior has also been found by further modularity-optimization methods and for methods based on different heuristics implementations, we conclude that indeed a correct definition of the detectability limit must take into account the stochastic fluctuations of the network construction.

  3. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  4. A statistical analysis of the detection limits of fast photometry

    NASA Astrophysics Data System (ADS)

    Mary, D. L.

    2006-06-01

    This work investigates the statistical limits for the detection of stellar variability using ground based fast photometry. We show that when sky transparency variations are very low or have been efficiently removed from the raw light curve, the overall noise is of a Mixed Poisson (MP) nature (photon noise mixed by scintillation). As a consequence, three regimes appear for the detection of photometric variations depending on the star's brightness (scintillation, scintillation and photon noise, photon noise and sky background). The proposed analysis is mainly applied to the Indian sites of Manora Peak (existing 104 cm telescope) and Devasthal (future 1 m automated telescope, and 3 m telescope project). As shown by some examples, it can be applied to any site with the corresponding parameters. For 1 m class telescopes at an altitude of about 2000 m, the frontier magnitudes between the different detection regimes are about 10 mag and 15 mag. By analysing the corresponding statistics of the MP noise periodogram, the minimum amplitude variation that one can detect with a given confidence level is evaluated for each observational setting. For example, with a 3 m telescope at about 2500 m, ≈120 μmag variations would be detected in 2 h with a 99% confidence level for stars brighter than magnitude 12. For a star of 15th magnitude, ≈400 μmag oscillations would still be detected at that level. These detection limits are discussed in the light of observations obtained in Manora peak, and compared to results obtained at different astronomical sites.

  5. Investigation of NMR limits of detection for implantable microcoils.

    PubMed

    Baxan, N; Rengle, A; Pasquet, G; Châteaux, J-F; Briguet, A; Morin, P; Fakri-Bouchet, L

    2007-01-01

    Although NMR has the ability to investigate biological systems non-destructively, its low sensitivity primarily has hampered their investigation compared to other analytical techniques. Therefore, optimi zing radio frequency (RF) coils to improve sensitivity do offer benefits in MR spectroscopy (MRS). Sensitivity may be improved for mass- and volume-limited samples if the size of the detection RF coils matches the sample size. In this paper, the mass- and concentration-limit of detection (LOD(m), LOD(c)) for an implantable microcoil will be estimated by MRS measurements and then compared with their analytical values. For a sample containing a solution of several cerebral metabolites, for the Choline case, the LODm is 5.7 . 10(-9)mol and LODc of 3.8 mM. These preliminary results enable to open largely the biomedical applications based on cerebral metabolism investigation on small animal experiments.

  6. Detection of multimode spatial correlation in PDC and application to the absolute calibration of a CCD camera.

    PubMed

    Brida, Giorgio; Degiovanni, Ivo Pietro; Genovese, Marco; Rastello, Maria Luisa; Ruo-Berchera, Ivano

    2010-09-27

    We propose and demonstrate experimentally a new method based on the spatial entanglement for the absolute calibration of analog detectors. The idea consists on measuring the sub-shot-noise intensity correlation between two branches of parametric down conversion, containing many pairwise correlated spatial modes. We calibrate a scientific CCD camera and a preliminary evaluation of the uncertainty indicates the metrological interest of the method.

  7. Electrostrictive limit and focusing effects in pulsed photoacoustic detection

    NASA Technical Reports Server (NTRS)

    Heritier, J.-M.

    1983-01-01

    We give an analytical solution in the time and frequency domain for the cylindrical pressure wave generated by a laser pulse traveling in a liquid, which is valid over a wide range of laser beam dimensions and pulse durations. This leads to a simple prediction of the ultimate limitation set by the electrostrictive coupling and an easy analysis of the focusing effects on the photoacoustic signal. Two separate detection schemes were considered and show different behavior.

  8. Ultrafast scene detection and recognition with limited visual information.

    PubMed

    Hagmann, Carl Erick; Potter, Mary C

    2016-01-01

    Humans can detect target color pictures of scenes depicting concepts like picnic or harbor in sequences of six or twelve pictures presented as briefly as 13 ms, even when the target is named after the sequence (Potter, Wyble, Hagmann, & McCourt, 2014). Such rapid detection suggests that feedforward processing alone enabled detection without recurrent cortical feedback. There is debate about whether coarse, global, low spatial frequencies (LSFs) provide predictive information to high cortical levels through the rapid magnocellular (M) projection of the visual path, enabling top-down prediction of possible object identities. To test the "Fast M" hypothesis, we compared detection of a named target across five stimulus conditions: unaltered color, blurred color, grayscale, thresholded monochrome, and LSF pictures. The pictures were presented for 13-80 ms in six-picture rapid serial visual presentation (RSVP) sequences. Blurred, monochrome, and LSF pictures were detected less accurately than normal color or grayscale pictures. When the target was named before the sequence, all picture types except LSF resulted in above-chance detection at all durations. Crucially, when the name was given only after the sequence, performance dropped and the monochrome and LSF pictures (but not the blurred pictures) were at or near chance. Thus, without advance information, monochrome and LSF pictures were rarely understood. The results offer only limited support for the Fast M hypothesis, suggesting instead that feedforward processing is able to activate conceptual representations without complementary reentrant processing.

  9. Thermal Infrared Spectral Band Detection Limits for Unidentified Surface Materials

    NASA Technical Reports Server (NTRS)

    Kirkland, Laurel E.; Herr, Kenneth C.; Salisbury, John W.

    2001-01-01

    Infrared emission spectra recorded by airborne or satellite spectrometers can be searched for spectral features to determine the composition of rocks on planetary surfaces. Surface materials are identified by detections of characteristic spectral bands. We show how to define whether to accept an observed spectral feature as a detection when the target material is unknown. We also use remotely sensed spectra measured by the Thermal Emission Spectrometer (TES) and the Spatially Enhanced Broadband Array Spectrograph System to illustrate the importance of instrument parameters and surface properties on band detection limits and how the variation in signal-to-noise ratio with wavelength affects the bands that are most detectable for a given instrument. The spectrometer's sampling interval, spectral resolution, signal-to-noise ratio as a function of wavelength, and the sample's surface properties influence whether the instrument can detect a spectral feature exhibited by a material. As an example, in the 6-13 micrometer wavelength region, massive carbonates exhibit two bands: a very strong, broad feature at approximately 6.5 micrometers and a less intense, sharper band at approximately 11.25 micrometers. Although the 6.5-micrometer band is stronger and broader in laboratory-measured spectra, the 11.25-micrometer band will cause a more detectable feature in TES spectra.

  10. Ultrafast scene detection and recognition with limited visual information

    PubMed Central

    Hagmann, Carl Erick; Potter, Mary C.

    2016-01-01

    Humans can detect target color pictures of scenes depicting concepts like picnic or harbor in sequences of six or twelve pictures presented as briefly as 13 ms, even when the target is named after the sequence (Potter, Wyble, Hagmann, & McCourt, 2014). Such rapid detection suggests that feedforward processing alone enabled detection without recurrent cortical feedback. There is debate about whether coarse, global, low spatial frequencies (LSFs) provide predictive information to high cortical levels through the rapid magnocellular (M) projection of the visual path, enabling top-down prediction of possible object identities. To test the “Fast M” hypothesis, we compared detection of a named target across five stimulus conditions: unaltered color, blurred color, grayscale, thresholded monochrome, and LSF pictures. The pictures were presented for 13–80 ms in six-picture rapid serial visual presentation (RSVP) sequences. Blurred, monochrome, and LSF pictures were detected less accurately than normal color or grayscale pictures. When the target was named before the sequence, all picture types except LSF resulted in above-chance detection at all durations. Crucially, when the name was given only after the sequence, performance dropped and the monochrome and LSF pictures (but not the blurred pictures) were at or near chance. Thus, without advance information, monochrome and LSF pictures were rarely understood. The results offer only limited support for the Fast M hypothesis, suggesting instead that feedforward processing is able to activate conceptual representations without complementary reentrant processing. PMID:28255263

  11. Accuracy, precision, and lower detection limits (a deficit reduction approach)

    SciTech Connect

    Bishop, C.T.

    1993-10-12

    The evaluation of the accuracy, precision and lower detection limits of the determination of trace radionuclides in environmental samples can become quite sophisticated and time consuming. This in turn could add significant cost to the analyses being performed. In the present method, a {open_quotes}deficit reduction approach{close_quotes} has been taken to keep costs low, but at the same time provide defensible data. In order to measure the accuracy of a particular method, reference samples are measured over the time period that the actual samples are being analyzed. Using a Lotus spreadsheet, data are compiled and an average accuracy is computed. If pairs of reference samples are analyzed, then precision can also be evaluated from the duplicate data sets. The standard deviation can be calculated if the reference concentrations of the duplicates are all in the same general range. Laboratory blanks are used to estimate the lower detection limits. The lower detection limit is calculated as 4.65 times the standard deviation of a set of blank determinations made over a given period of time. A Lotus spreadsheet is again used to compile data and LDLs over different periods of time can be compared.

  12. Immuno-analysis of microparticles: probing at the limits of detection

    PubMed Central

    Latham, Sharissa L.; Tiberti, Natalia; Gokoolparsadh, Naveena; Holdaway, Karen; Olivier Couraud, Pierre; Grau, Georges E. R.; Combes, Valery

    2015-01-01

    Microparticle (MP) research is clouded by debate regarding the accuracy and validity of flow cytometry (FCM) as an analytical methodology, as it is influenced by many variables including the pre-analytical conditions, instruments physical capabilities and detection parameters. This study utilises a simplistic in vitro system for generating MP, and through comparative analysis with immuno-electron microscopy (Immuno-EM) assesses the strengths and limitations of probe selection and high-sensitivity FCM. Of the markers examined, MP were most specifically labelled with phosphatidylserine ligands, annexin V and lactadherin, although only ~60% MP are PS positive. Whilst these two ligands detect comparable absolute MP numbers, they interact with the same population in distinct manners; annexin V binding is enhanced on TNF induced MP. CD105 and CD54 expression were, as expected, consistent and enhanced following TNF activation respectively. Their labelling however accounted for as few as 30–40% of MP. The greatest discrepancies between FCM and I-EM were observed in the population solely labelled for the surface antigen. These findings demonstrate that despite significant improvements in resolution, high-sensitivity FCM remains limited in detecting small-size MP expressing low antigen levels. This study highlights factors to consider when selecting endothelial MP probes, as well as interpreting and representing data. PMID:26553743

  13. Detection of radioactive particles offshore by γ-ray spectrometry Part I: Monte Carlo assessment of detection depth limits

    NASA Astrophysics Data System (ADS)

    Maučec, M.; de Meijer, R. J.; Rigollet, C.; Hendriks, P. H. G. M.; Jones, D. G.

    2004-06-01

    A joint research project between the British Geological Survey and Nuclear Geophysics Division of the Kernfysisch Versneller Instituut, Groningen, the Netherlands, was commissioned by the United Kingdom Atomic Energy Authority to establish the efficiency of a towed seabed γ-ray spectrometer for the detection of 137Cs-containing radioactive particles offshore Dounreay, Scotland. Using the MCNP code, a comprehensive Monte Carlo feasibility study was carried out to model various combinations of geological matrices, particle burial depth and lateral displacement, source activity and detector material. To validate the sampling and absolute normalisation procedures of MCNP for geometries including multiple (natural and induced) heterogeneous sources in environmental monitoring, a benchmark experiment was conducted. The study demonstrates the ability of seabed γ-ray spectrometry to locate radioactive particles offshore and to distinguish between γ count rate increases due to particles from those due to enhanced natural radioactivity. The information presented in this study will be beneficial for estimation of the inventory of 137Cs particles and their activity distribution and for the recovery of particles from the sea floor. In this paper, the Monte Carlo assessment of the detection limits is presented. The estimation of the required towing speed and acquisition times and their application to radioactive particle detection and discrimination offshore formed a supplementary part of this study.

  14. Performance on a test of rapid stepping in community-dwelling older adults: validity, relative and absolute reliability and minimum detectable change.

    PubMed

    Goldberg, Allon; Talley, Susan Ann

    2015-01-01

    Reduced stepping speed is associated with balance deficits and falls in older adults. We evaluated psychometric properties of a test of rapid stepping, the Thirty-Rapid-Step test (30-RST) in 37 community-dwelling older adults. Participants performed the 30-RST, dynamic (step execution time, five-times-sit-to-stand test, gait speed, maximum step length and four-square-step test) and static (single-leg-stance-time and postural sway) performance-based tests. Relationships between 30-RST and performance-based tests were evaluated with Spearman's rho. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), 95% limits of agreement and minimum detectable change at the 95% confidence level (MDC95) were computed for the 30-RST. Relationships between 30-RST and dynamic measures were moderate to very good (r = -0.35-0.73, p < 0.05); however, relationships between 30-RST and static balance were weak (r = 0.04-0.19, p > 0.05). The ICC2,1 was 0.85 for 30-RST indicating excellent test-retest reliability. SEM expressed as a percent of mean 30-RST was 8.2%, indicating low measurement error. The MDC95 was 9.4 s, and MDC95 expressed as a percent of mean 30-RST was moderately low at 22.6%. The 30-RST is a valid measure of dynamic balance and mobility with excellent relative and absolute reliability, and may be a useful measure in geriatric clinical settings and studies investigating balance in healthy community-dwelling older adults.

  15. Overcoming interference with the detection of a stable isotopically labeled microtracer in the evaluation of beclabuvir absolute bioavailability using a concomitant microtracer approach.

    PubMed

    Jiang, Hao; Titsch, Craig; Zeng, Jianing; Jones, Barry; Joyce, Philip; Gandhi, Yash; Turley, Wesley; Burrell, Richard; Aubry, Anne F; Arnold, Mark E

    2017-09-05

    The oral absolute bioavailability of beclabuvir in healthy subjects was determined using a microdose (100μg) of the stable isotopically labeled tracer via intravenous (IV) infusion started after oral dosing of beclabuvir (150mg). To simultaneously analyze the concentrations of the IV microtracer ([(13)C6]beclabuvir) and beclabuvir in plasma samples, a liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) method was initially developed. Surprisingly beclabuvir significantly interfered with the IV microtracer detection when using the selected reaction monitoring (SRM) in the assay. An interfering component from the drug substance was observed using a high resolution mass spectrometer (HRMS). The mass-to-charge (m/z) of the interfering component was -32ppm different from the nominal value for the IV microtracer and thus could not be differentiated in the SRM assay by the unit mass resolution. To overcome this interference, we evaluated two approaches by either monitoring an alternative product ion using the SRM assay or isolating the interfering component using the parallel reaction monitoring (PRM) assay on the HRMS. This case study has demonstrated two practical approaches for overcoming interferences with the detection of stable isotopically labeled IV microtracers in the evaluation of absolute bioavailability, which provides users the flexibility in using either LC-MS/MS or HRMS to mitigate unpredicted interferences in the assay to support microtracer absolute bioavailability studies. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

  17. Attentional Capacity Limits Gap Detection during Concurrent Sound Segregation.

    PubMed

    Leung, Ada W S; Jolicoeur, Pierre; Alain, Claude

    2015-11-01

    Detecting a brief silent interval (i.e., a gap) is more difficult when listeners perceive two concurrent sounds rather than one in a sound containing a mistuned harmonic in otherwise in-tune harmonics. This impairment in gap detection may reflect the interaction of low-level encoding or the division of attention between two sound objects, both of which could interfere with signal detection. To distinguish between these two alternatives, we compared ERPs during active and passive listening with complex harmonic tones that could include a gap, a mistuned harmonic, both features, or neither. During active listening, participants indicated whether they heard a gap irrespective of mistuning. During passive listening, participants watched a subtitled muted movie of their choice while the same sounds were presented. Gap detection was impaired when the complex sounds included a mistuned harmonic that popped out as a separate object. The ERP analysis revealed an early gap-related activity that was little affected by mistuning during the active or passive listening condition. However, during active listening, there was a marked decrease in the late positive wave that was thought to index attention and response-related processes. These results suggest that the limitation in detecting the gap is related to attentional processing, possibly divided attention induced by the concurrent sound objects, rather than deficits in preattentional sensory encoding.

  18. Radiometric STFT Analysis of PDV recordings and detectivity limit

    NASA Astrophysics Data System (ADS)

    Bozier, Olivier; Prudhomme, Gabriel; Mercier, Patrick; Berthe, Laurent

    2015-06-01

    Photonic Doppler Velocimetry is a plug-and-play and versatile diagnostic used in dynamic physic experiments to measure velocities. When signals are analyzed using a Short-Time Fourier Transform, multiple velocities can be distinguished: by example, the velocities of moving particle-cloud appear on spectrograms. In order to estimate the back-scattering fluxes of target, we propose an original approach ``PDV Radiometric analysis'' resulting in an expression of time-velocity spectrograms coded in power units. Experiments involving micron-sized particles raise the issue of detection limit; particle-size limit is very difficult to evaluate. From the quantification of noise sources, we derivate an estimation of the spectrogram noise leading to a detectivity limit. It may be compared to back-scattering and collected power from a particle, which is increasing with its size. At least, some results from laser-shock accelerated particles using two different PDV systems are compared: it may show the improvement of sensitivity.

  19. Local resolution-limit-free Potts model for community detection.

    PubMed

    Ronhovde, Peter; Nussinov, Zohar

    2010-04-01

    We report on an exceptionally accurate spin-glass-type Potts model for community detection. With a simple algorithm, we find that our approach is at least as accurate as the best currently available algorithms and robust to the effects of noise. It is also competitive with the best currently available algorithms in terms of speed and size of solvable systems. We find that the computational demand often exhibits superlinear scaling O(L1.3) where L is the number of edges in the system, and we have applied the algorithm to synthetic systems as large as 40 x 10(6) nodes and over 1 x 10(9) edges. A previous stumbling block encountered by popular community detection methods is the so-called "resolution limit." Being a "local" measure of community structure, our Potts model is free from this resolution-limit effect, and it further remains a local measure on weighted and directed graphs. We also address the mitigation of resolution-limit effects for two other popular Potts models.

  20. Assessment of detection limits of fiber-optic distributed temperature sensing for detection of illicit connections.

    PubMed

    Nienhuis, Jaap; de Haan, Cornelis; Langeveld, Jeroen; Klootwijk, Martijn; Clemens, François

    2013-01-01

    Distributed temperature sensing (DTS) with fiber-optic cables is a powerful tool to detect illicit connections in storm sewer systems. High-frequency temperature measurements along the in-sewer cable create a detailed representation of temperature anomalies due to illicit discharges. The detection limits of the monitoring equipment itself are well-known, but there is little information available on detection limits for the discovery of illicit connections, as in mixing of sewers, and attenuation also plays an important role. This paper describes the results of full-scale experiments aiming to quantify the detection limits for illicit connections under various sewer conditions. Based on the results, a new monitoring set-up for (partially) filled sewer conduits has been proposed.

  1. Limitations of Aneuploidy and Anomaly Detection in the Obese Patient.

    PubMed

    Zozzaro-Smith, Paula; Gray, Lisa M; Bacak, Stephen J; Thornburg, Loralei L

    2014-07-17

    Obesity is a worldwide epidemic and can have a profound effect on pregnancy risks. Obese patients tend to be older and are at increased risk for structural fetal anomalies and aneuploidy, making screening options critically important for these women. Failure rates for first-trimester nuchal translucency (NT) screening increase with obesity, while the ability to detect soft-markers declines, limiting ultrasound-based screening options. Obesity also decreases the chances of completing the anatomy survey and increases the residual risk of undetected anomalies. Additionally, non-invasive prenatal testing (NIPT) is less likely to provide an informative result in obese patients. Understanding the limitations and diagnostic accuracy of aneuploidy and anomaly screening in obese patients can help guide clinicians in counseling patients on the screening options.

  2. Detection limits of organic contaminants in drinking water

    SciTech Connect

    Draper, W.M.; Dhoot, J.S.; Dhaliwal, J.S.; Remoy, J.W.; Perera, S.K.; Baumann, F.J.

    1998-06-01

    This article examines some of the experimental variables that can contribute to the observed variability in laboratory performance. The examples provided suggest that method detection limits (MDLs) would be more uniform among laboratories if (1) uniform spike concentrations were used in MDL determination; (2) analytical methods were more uniform as to procedures, reagents, and materials; and (3) tighter guidelines were established for conducting MDL experiments and handling MDL data. The pooling of data from multiple spike levels (or any other means to increase sample size) minimizes random error in MDL determination. Improved control in MDL determination would lead to better information on laboratory capabilities, and this in turn would improve the technical basis for reporting limits, trigger levels, and water quality standards.

  3. A mathematical model to detect inspiratory flow limitation during sleep.

    PubMed

    Mansour, Khaled F; Rowley, James A; Meshenish, A A; Shkoukani, Mahdi A; Badr, M Safwan

    2002-09-01

    The physiological significance of inspiratory flow limitation (IFL) has recently been recognized, but methods of detecting IFL can be subjective. We sought to develop a mathematical model of the upper airway pressure-flow relationship that would objectively detect flow limitation. We present a theoretical discussion that predicts that a polynomial function [F(P) = AP(3) + BP(2) + CP + D, where F(P) is flow and P is supraglottic pressure] best characterizes the pressure-flow relationship and allows for the objective detection of IFL. In protocol 1, step 1, we performed curve-fitting of the pressure-flow relationship of 20 breaths to 5 mathematical functions and found that highest correlation coefficients (R(2)) for quadratic (0.88 +/- 0.10) and polynomial (0.91 +/- 0.05; P < 0.05 for both compared with the other functions) functions. In step 2, we performed error-fit calculations on 50 breaths by comparing the quadratic and polynomial functions and found that the error fit was lowest for the polynomial function (3.3 +/- 0.06 vs. 21.1 +/- 19.0%; P < 0.001). In protocol 2, we performed sensitivity/specificity analysis on two sets of breaths (50 and 544 breaths) by comparing the mathematical determination of IFL to manual determination. Mathematical determination of IFL had high sensitivity and specificity and a positive predictive value (>99% for each). We conclude that a polynomial function can be used to predict the relationship between pressure and flow in the upper airway and objectively determine the presence of IFL.

  4. Role of detection limits in drinking water regulation.

    PubMed

    Calder, Ryan S D; Schmitt, Ketra A

    2010-11-01

    Some commentators on environmental science and policy have claimed that advances in analytical chemistry, reflected by an ability to detect contaminants at ever-decreasing concentrations, lead to regulations stricter than justified by available toxicological data. We evaluate this claim in the context of drinking water regulation, with respect to contaminants regulated under the Safe Drinking Water Act (SDWA). We examine the relationships between historical and present maximum contaminant levels and goals in the greater context of detection capability and evaluate the extent to which different aspects of the regulatory apparatus (i.e., analytical capability, cost-benefit analysis, analysis of competing risks, and available toxicological data) influence the regulatory process. Our findings do not support the claim that decreases in detection limit lead to more stringent regulation in the context of drinking water regulation in the United States. Further, based on our analysis of the National Primary Drinking Water Regulation and existing United States Environmental Protection Agency approaches to establishing the practical quantifiable level, we conclude that in the absence of changes to the underlying toxicological model, regulatory revision is unlikely.

  5. Limits on detectability of mass loss from cool dwarfs

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.; Doyle, J. G.; Redman, R. O.; Mathioudakis, M.

    1992-01-01

    Recent spectroscopic evidence supports the theoretical expectation that certain cool dwarfs may have stellar winds with M-dot values several orders of magnitude larger than the solar rate. For large enough values of M-dot, the emission from the wind is expected to have a spectrum which, at low enough frequencies, becomes a power law, S(v) about v exp alpha with alpha about 0.7. Data from IRAS and VLA suggest that such a spectrum may in fact occur in certain M dwarfs: a key test of the wind spectrum would be provided if the stars could be detected at lambda about 1 mm. We show that the M-dot required to ensure power-law emission is a few times 10 exp -10 solar mass/yr. With M-dot of this order, fluxes at lambda about 1 mm would be tens of mJy. Using the James Clerk Maxwell Telescope, we have tested this prediction on several stars: the data are suggestive but are near the limits of detection. Confirmation of our estimates will be important for evolution and for interstellar medium (ISM) physics: if even a few percent of all M dwarfs are losing mass at the above rates, the mass balance of the ISM will be dominated by M dwarfs.

  6. Fundamental limits of target detection performance in passive polarization imaging.

    PubMed

    Goudail, François; Boffety, Matthieu

    2017-04-01

    We quantitatively determine the target detection performance of different passive polarization imaging architectures perturbed by signal-independent detection noise or signal-dependent Poisson shot noise. We compare the fully adaptive polarimetric imager and the best channel of a static polarimetric imager, and in each case, we compare the use of a polarizer and a polarizing beam splitter as the polarization analyzing device. For all these configurations, we derive a closed-form expression of the target/background separability and quantify the performance gain brought by polarization imaging compared to standard intensity imaging. We show in particular that all the considered polarimetric imaging configurations but one require a minimum value of the polarimetric contrast in order to outperform intensity imaging. The only configuration that always performs better than intensity imaging uses a polarizing beam splitter in the presence of background shot noise. These results are useful in evaluating the fundamental limits of the gain brought by polarization imaging and determining, in practice, which type of imaging architecture is preferable for a given application.

  7. Theoretical limits on detection and analysis of small earthquakes

    NASA Astrophysics Data System (ADS)

    Kwiatek, Grzegorz; Ben-Zion, Yehuda

    2016-08-01

    We investigate theoretical limits on detection and reliable estimates of source characteristics of small earthquakes using synthetic seismograms for shear/tensile dislocations on kinematic circular ruptures and observed seismic noise and properties of several acquisition systems (instrument response, sampling rate). Simulated source time functions for shear/tensile dislocation events with different magnitudes, static stress drops, and rupture velocities provide estimates for the amplitude and frequency content of P and S phases at various observation angles. The source time functions are convolved with a Green's function for a homogenous solid assuming given P, S wave velocities and attenuation coefficients and a given instrument response. The synthetic waveforms are superposed with average levels of the observed ambient seismic noise up to 1 kHz. The combined seismograms are used to calculate signal-to-noise ratios and expected frequency content of P and S phases at various locations. The synthetic simulations of signal-to-noise ratio reproduce observed ratios extracted from several well-recorded data sets. The results provide guidelines on detection of small events in various geological environments, along with information relevant to reliable analyses of earthquake source properties.

  8. Detection limit for activation measurements in ultralow background sites

    NASA Astrophysics Data System (ADS)

    Trache, Livius; Chesneanu, D.; Margineanu, R.; Pantelica, A.; Ghita, D. G.; Burducea, I.; Straticiuc, M.; Tang, X. D.

    2014-09-01

    We used 12C +13C fusion at the beam energies E = 6, 7 and 8 MeV to determine the sensitivity and the limits of activation method measurements in ultralow background sites. A 13C beam of 0.5 μA from the 3 MV Tandem accelerator of the Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH impinged on thick graphite targets. After about 24 hrs of irradiation targets were measured in two different laboratories: one with a heavy shielded Ge detector in the institute (at the surface) and one located underground in the microBequerel laboratory, in the salt mine of Slanic-Prahova, Romania. The 1369- and 2754 keV peaks from 24Na deactivation were clearly observed in the γ-ray spectra obtained for acquisitions lasting a few hours, or a few days. Determination of the detection limit in evaluating the cross sections for the target irradiated at Ec . m = 3 MeV indicates the fact that it is possible to measure gamma spectrum in underground laboratory down to Ec . m = 2 . 6 MeV. Cleaning the spectra with beta-gamma coincidences and increasing beam intensity 20 times will take as further down. The measurements are motivated by the study of the 12 C +12 C reaction at astrophysical energies.

  9. 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.

  10. Wave Detection Beyond the Standard Quantum Limit via EPR Entanglement

    NASA Astrophysics Data System (ADS)

    Ma, Yiqiu; Miao, Haixing; Pang, Belinda; Evans, Matthew; Zhao, Chunnong; Harms, Jan; Schnabel, Roman; Chen, Yanbei

    2017-01-01

    The Standard Quantum Limit in continuous monitoring of a system is given by the trade-off of shot noise and back-action noise. In gravitational-wave detectors, such as Advanced LIGO, both contributions can simultaneously be squeezed in a broad frequency band by injecting a spectrum of squeezed vacuum states with a frequency-dependent squeeze angle. This approach requires setting up an additional long base-line, low-loss filter cavity in a vacuum system at the detector's site. Here, we show that the need for such a filter cavity can be eliminated, by exploiting EPR-entangled signal and idler beams. By harnessing their mutual quantum correlations and the difference in the way each beam propagates in the interferometer, we can engineer the input signal beam to have the appropriate frequency dependent conditional squeezing once the out-going idler beam is detected. Our proposal is appropriate for all future gravitational-wave detectors for achieving sensitivities beyond the Standard Quantum Limit.

  11. Physiological techniques for detecting expiratory flow limitation during tidal breathing.

    PubMed

    Koulouris, N G; Hardavella, G

    2011-09-01

    Patients with severe chronic obstructive pulmonary disease (COPD) often exhale along the same flow-volume curve during quiet breathing as they do during the forced expiratory vital capacity manoeuvre, and this has been taken as an indicator of expiratory flow limitation at rest (EFL(T)). Therefore, EFL(T), namely attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFL(T) leads to small airway injury and promotes dynamic pulmonary hyperinflation, with concurrent dyspnoea and exercise limitation. In fact, EFL(T) occurs commonly in COPD patients (mainly in Global Initiative for Chronic Obstructive Lung Disease III and IV stage), in whom the latter symptoms are common, but is not exclusive to COPD, since it can also be detected in other pulmonary and nonpulmonary diseases like asthma, acute respiratory distress syndrome, heart failure and obesity, etc. The existing up to date physiological techniques of assessing EFL(T) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, noninvasive, practical and accurate new technique.

  12. Assessment of target detection limits in hyperspectral data

    NASA Astrophysics Data System (ADS)

    Gross, W.; Boehler, J.; Schilling, H.; Middelmann, W.; Weyermann, J.; Wellig, P.; Oechslin, R.; Kneubuehler, M.

    2015-10-01

    Hyperspectral remote sensing data can be used for civil and military applications to detect and classify target objects that cannot be reliably separated using broadband sensors. The comparably low spatial resolution is compensated by the fact that small targets, even below image resolution, can still be classified. The goal of this paper is to determine the target size to spatial resolution ratio for successful classification of different target and background materials. Airborne hyperspectral data is used to simulate data with known mixture ratios and to estimate the detection threshold for given false alarm rates. The data was collected in July 2014 over Greding, Germany, using airborne aisaEAGLE and aisaHAWK hyperspectral sensors. On the ground, various target materials were placed on natural background. The targets were four quadratic molton patches with an edge length of 7 meters in the colors black, white, grey and green. Also, two different types of polyethylene (camouflage nets) with an edge length of approximately 5.5 meters were deployed. Synthetic data is generated from the original data using spectral mixtures. Target signatures are linearly combined with different background materials in specific ratios. The simulated mixtures are appended to the original data and the target areas are removed for evaluation. Commonly used classification algorithms, e.g. Matched Filtering, Adaptive Cosine Estimator are used to determine the detection limit. Fixed false alarm rates are employed to find and analyze certain regions where false alarms usually occur first. A combination of 18 targets and 12 backgrounds is analyzed for three VNIR and two SWIR data sets of the same area.

  13. Two-dimensional fluorescence-detected coherent spectroscopy with absolute phasing by confocal imaging of a dynamic grating and 27-step phase-cycling

    SciTech Connect

    De, Arijit K. Fleming, Graham R.; Monahan, Daniele; Dawlaty, Jahan M.

    2014-05-21

    We present a novel experimental scheme for two-dimensional fluorescence-detected coherent spectroscopy (2D-FDCS) using a non-collinear beam geometry with the aid of “confocal imaging” of dynamic (population) grating and 27-step phase-cycling to extract the signal. This arrangement obviates the need for distinct experimental designs for previously developed transmission detected non-collinear two-dimensional coherent spectroscopy (2D-CS) and collinear 2D-FDCS. We also describe a novel method for absolute phasing of the 2D spectrum. We apply this method to record 2D spectra of a fluorescent dye in solution at room temperature and observe “spectral diffusion.”.

  14. Assessment of coulometric array electrochemical detection coupled with HPLC-UV for the absolute quantitation of pharmaceuticals.

    PubMed

    Hicks, Michael B; Salituro, Leah; Mangion, Ian; Schafer, Wes; Xiang, Rong; Gong, Xiaoyi; Welch, Christopher J

    2017-01-26

    The use of a coulometric array detector in tandem with HPLC-UV was evaluated for the absolute quantitation of pharmaceutical compounds without standards, an important capability gap in contemporary pharmaceutical research and development. The high-efficiency LC flow-through electrochemical detector system allows for the rapid evaluation of up to 16 different potentials, aiding in the identification and quantitation of electrochemically reactive species. By quantifying the number of electrons added or removed from an analyte during its passage through the detector, the number of moles of the analyte can be established. Herein we demonstrate that molecules containing common electroactive functional groups (e.g. anilines, phenols, parabens and tertiary alkyl amines) can in some cases be reliably quantified in HPLC-EC-UV without the need for authentic standards. Furthermore, the multichannel nature of the CoulArray detector makes it well suited for optimizing the conditions for electrochemical reaction, allowing the impact of changes in potential, flow rate, temperature and pH to be conveniently studied. The electrochemical oxidation of albacivir, zomepirac, diclofenac, rosiglitazone and several other marketed drugs resulted in large linear ranges, predictable recoveries and excellent quantitation using the total moles of electrons and back-calculating using Faraday's law. Importantly, we observed several instances where subtle structural changes within a given class of molecules (e.g. aromatic ring isomers) led to unanticipated changes in electrochemical behavior. Consequently, some care should be taken when applying the technique to the routine quantitation of compound libraries where standards are not available.

  15. An Absolute Self-Calibrating Pressure Recorder for Campaign-Style Detection of Vertical Seafloor Deformation in the Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

    Cook, M. J.; Roland, E. C.; Sasagawa, G. S.; Schmidt, D. A.; Wilcock, W. S. D.; Zumberge, M. A.

    2016-12-01

    Seawater pressure can be used to detect vertical seafloor deformation because small changes in seafloor height produce measurable pressure changes. Vertical deformation rates in subduction zones due to secular strain are expected to be less than 1 cm/year, signals that are difficult to measure with pressure gauges because of gauge drift. The Self-Calibrating Pressure Recorder (SCPR) was designed to circumvent the problem of gauge drift by employing a deadweight calibrator, which periodically provides a reference pressure that is used to correct for drift in a continuously recorded pressure record. Alternatively, the SCPR can be used to make campaign-style determinations of true seafloor pressure to support long-term deformation measurements and provide an exact reference for nearby pressure gauges. This Absolute Self-Calibrating Pressure Recorder (ASCPR) requires a metrological assessment of measurement parameters to ensure that its absolute accuracy is sufficient to resolve secular deformation. While on a concrete seafloor benchmark, alternating calibration and seawater observations are made every 10-20 minutes for several hours. The difference between the known reference pressure and the seafloor pressure is observed, which allows the calculation of the true, absolute seafloor pressure. In 2014 and 2015, seven concrete benchmarks were placed on the seafloor in the Cascadia subduction zone off central Oregon along a profile that extends from 20 km to 105 km offshore. We surveyed two benchmarks in 2014, 2015, and 2016, a third one in 2015 and 2016, and four more in 2016. Current measurement repeatability varies from 2 to 5 cm, but several corrections still need to be incorporated. The expected resolution is 1 cm.

  16. Neutron activation analysis detection limits using {sup 252}Cf sources

    SciTech Connect

    DiPrete, D.P.; Sigg, R.A.

    2000-07-01

    The Savannah River Technology Center (SRTC) developed a neutron activation analysis (NAA) facility several decades ago using low-flux {sup 252}Cf neutron sources. Through this time, the facility has addressed areas of applied interest in managing the Savannah River Site (SRS). Some applications are unique because of the site's operating history and its chemical-processing facilities. Because sensitivity needs for many applications are not severe, they can be accomplished using an {approximately}6-mg {sup 252}Cf NAA facility. The SRTC {sup 252}Cf facility continues to support applied research programs at SRTC as well as other SRS programs for environmental and waste management customers. Samples analyzed by NAA include organic compounds, metal alloys, sediments, site process solutions, and many other materials. Numerous radiochemical analyses also rely on the facility for production of short-lived tracers, yielding by activation of carriers and small-scale isotope production for separation methods testing. These applications are more fully reviewed in Ref. 1. Although the flux [{approximately}2 x 10{sup 7} n/cm{sup 2}{center_dot}s] is low relative to reactor facilities, more than 40 elements can be detected at low and sub-part-per-million levels. Detection limits provided by the facility are adequate for many analytical projects. Other multielement analysis methods, particularly inductively coupled plasma atomic emission and inductively coupled plasma mass spectrometry, can now provide sensitivities on dissolved samples that are often better than those available by NAA using low-flux isotopic sources. Because NAA allows analysis of bulk samples, (a) it is a more cost-effective choice when its sensitivity is adequate than methods that require digestion and (b) it eliminates uncertainties that can be introduced by digestion processes.

  17. Observer detection limits for a dedicated SPECT breast imaging system

    PubMed Central

    Cutler, S J; Perez, K L; Barnhart, H X; Tornai, M P

    2012-01-01

    An observer-based contrast-detail study is performed in an effort to evaluate the limits of object detectability using a dedicated CZT-based breast SPECT imaging system under various imaging conditions. A custom geometric contrast-resolution phantom was developed that can be used for both positive (‘hot’) and negative contrasts (‘cold’). The 3 cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1 mm to 6 mm with plastic wall thicknesses of <0.25 mm, on a pitch of twice their inner diameters. Scans of the activity filled tubes using simple circular trajectories are obtained in a 215 mL uniform water filled cylinder, varying the rod:background concentration ratios from 10:1 to 1:10 simulating a large range of biological uptake ratios. The rod phantom is then placed inside a non-uniformly shaped 500 mL breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Summed slice and contiguous multi-slice images are evaluated by five independent readers, identifying the smallest distinguishable rod for each concentration and experimental setup. Linear and quadratic regression is used to compare the resulting contrast-detail curves. Results indicate that in a moderately low-noise 500 mL background, using the SPECT camera having 2.5 mm intrinsic pixels, the mean detectable rod was ~3.4 mm at a 10:1 ratio, degrading to ~5.2 mm with the 2.5:1 concentration ratio. The smallest object detail was observed using a 45° tilted trajectory acquisition. The complex 3D projected sine wave acquisition, however, had the most consistent combined intra- and inter-observer results, making it potentially the best imaging approach for consistent results. PMID:20224159

  18. Current limitations and challenges in nanowaste detection, characterisation and monitoring

    SciTech Connect

    Part, Florian; Zecha, Gudrun; Causon, Tim; Sinner, Eva-Kathrin

    2015-09-15

    Highlights: • First review on detection of nanomaterials in complex waste samples. • Focus on nanoparticles in solid, liquid and gaseous waste samples. • Summary of current applicable methods for nanowaste detection and characterisation. • Limitations and challenges of characterisation of nanoparticles in waste. - Abstract: Engineered nanomaterials (ENMs) are already extensively used in diverse consumer products. Along the life cycle of a nano-enabled product, ENMs can be released and subsequently accumulate in the environment. Material flow models also indicate that a variety of ENMs may accumulate in waste streams. Therefore, a new type of waste, so-called nanowaste, is generated when end-of-life ENMs and nano-enabled products are disposed of. In terms of the precautionary principle, environmental monitoring of end-of-life ENMs is crucial to allow assessment of the potential impact of nanowaste on our ecosystem. Trace analysis and quantification of nanoparticulate species is very challenging because of the variety of ENM types that are used in products and low concentrations of nanowaste expected in complex environmental media. In the framework of this paper, challenges in nanowaste characterisation and appropriate analytical techniques which can be applied to nanowaste analysis are summarised. Recent case studies focussing on the characterisation of ENMs in waste streams are discussed. Most studies aim to investigate the fate of nanowaste during incineration, particularly considering aerosol measurements; whereas, detailed studies focusing on the potential release of nanowaste during waste recycling processes are currently not available. In terms of suitable analytical methods, separation techniques coupled to spectrometry-based methods are promising tools to detect nanowaste and determine particle size distribution in liquid waste samples. Standardised leaching protocols can be applied to generate soluble fractions stemming from solid wastes, while

  19. A new standardized absolute quantitative RT-PCR method for detection of tyrosinase mRNAs in melanoma patients: technical and operative instructions.

    PubMed

    Vendittelli, Francesca; Santonocito, Concetta; Paradisi, Andrea; Romitelli, Federica; Concolino, Paola; Silveri, Sara Lanza; Sisto, Teresa; Capizzi, Rodolfo; Catricalà, Caterina; Mulè, Antonio; Di Carlo, Aldo; Zuppi, Cecilia; Capoluongo, Ettore

    2009-11-01

    To develop a new absolute quantitative real-time PCR method for blood mRNA tyrosinase assay and to compare this new method with standard RT-PCR nested. Ten blood of melanoma patients (stages I-III), 5 tissue samples, 2 surgical fresh metastatic skin and 3 lymph nodes paraffin-embedded slices were analysed, and 10 negative controls were used. Ten millilitres of blood was analysed for each individual. Three different protocols for RNA extraction and two reverse transcription methods were used. Specific human tyrosinase cDNA fragment was cloned into pcDNA3+ vector and then titrated for the standard curve construction (from 10(6) to 10(1)copies/microl). Recovery assays for RNA and cells were also performed. Our method was able to detect less than 5 cells/10(8) WBC and about 100 fg of tyrosinase RNA. Very low CVs (<1.5%) were obtained on all samples run in triplicate. Sensitivity and specificity were of 100%. The amount of starting volume of blood was crucial for the determination of copy number since large volumes are necessary for patient's monitoring. Our absolute qRT-PCR assay could be proposed as a new standardized molecular method for the management of melanoma patients, particularly for the follow up of the highest AJCC stages.

  20. Femtomolar concentration detection limit and zeptomole mass detection limit for protein separation by capillary isoelectric focusing and laser-induced fluorescence detection.

    PubMed

    Ramsay, Lauren M; Dickerson, Jane A; Dada, Oluwatosin; Dovichi, Norman J

    2009-03-01

    Fluorescence tends to produce the lowest detection limits for most forms of capillary electrophoresis. Two issues have discouraged its use in capillary isoelectric focusing. The first issue is fluorescent labeling of proteins. Most labeling reagents react with lysine residues and convert the cationic residue to a neutral or anionic product. At best, these reagents perturb the isoelectric point of the protein. At worse, they convert each protein into hundreds of different fluorescent products that confound analysis. The second issue is the large background signal generated by impurities within commercial ampholytes. This background signal is particularly strong when excited in the blue portion of the spectrum, which is required by many common fluorescent labeling reagents. This paper addresses these issues. For labeling, we employ Chromeo P540, which is a fluorogenic reagent that converts cationic lysine residues to cationic fluorescent products. The reaction products are excited in the green, which reduces the background signal generated by impurities present within the ampholytes. To further reduce the background signal, we photobleach ampholytes with high-power photodiodes. Photobleaching reduced the noise in the ampholyte blank by an order of magnitude. Isoelectric focusing performed with photobleached pH 3-10 ampholytes produced concentration detection limits of 270 +/- 25 fM and mass detection limits of 150 +/- 15 zmol for Chromeo P540 labeled beta-lactoglobulin. Concentration detection limits were 520 +/- 40 fM and mass detection limits were 310 +/- 30 zmol with pH 4-8 ampholytes. A homogenate was prepared from a Barrett's esophagus cell line and separated by capillary isoelectric focusing, reproducibly generating dozens of peaks. The sample taken for the separation was equal to the labeled protein homogenate from three cells.

  1. Estimation of the limit of detection using information theory measures.

    PubMed

    Fonollosa, Jordi; Vergara, Alexander; Huerta, Ramón; Marco, Santiago

    2014-01-31

    Definitions of the limit of detection (LOD) based on the probability of false positive and/or false negative errors have been proposed over the past years. Although such definitions are straightforward and valid for any kind of analytical system, proposed methodologies to estimate the LOD are usually simplified to signals with Gaussian noise. Additionally, there is a general misconception that two systems with the same LOD provide the same amount of information on the source regardless of the prior probability of presenting a blank/analyte sample. Based upon an analogy between an analytical system and a binary communication channel, in this paper we show that the amount of information that can be extracted from an analytical system depends on the probability of presenting the two different possible states. We propose a new definition of LOD utilizing information theory tools that deals with noise of any kind and allows the introduction of prior knowledge easily. Unlike most traditional LOD estimation approaches, the proposed definition is based on the amount of information that the chemical instrumentation system provides on the chemical information source. Our findings indicate that the benchmark of analytical systems based on the ability to provide information about the presence/absence of the analyte (our proposed approach) is a more general and proper framework, while converging to the usual values when dealing with Gaussian noise. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Absolute 108Agm characterization based on gamma-gamma coincident detection by two NaI(Tl) detectors.

    PubMed

    Volkovitsky, Peter

    2010-01-01

    A two-dimensional analysis of three coincident gamma-rays in (108)Ag(m) decay, detected by two NaI(Tl) scintillation detectors, allows a direct measurement of the source activity. A modification of the Eldridge-Crowther formulas derived originally for (125)I was done recently for the case of two coincident gamma-rays in (60)Co decay (Volkovitsky and Naudus, 2009). A similar approach is applied to a more complicated case of three coincident gamma-rays in the (108)Ag(m) decay. The large number of experimental quantities, measured both in coincidence and anticoincidence modes, allows the determination of both detector efficiencies for all three gamma-ray photopeaks and to find the source activity. Results are compared with measurements of the activity of the same source with HPGe detectors. Published by Elsevier Ltd.

  3. Satellite based Global Flood Detection System - strengths and limitations

    NASA Astrophysics Data System (ADS)

    Revilla-Romero, Beatriz; Salamon, Peter; Thielen, Jutta; De Groeve, Tom; Zajac, Zuzanna

    2014-05-01

    One of the main problems for global hydrological models is that for many regions only very limited or no observational data for a model assessment is available. This problem could be overcome with filling the gaps using information derived from satellite observations. Thus, an evaluation of the remote sensing signal of the Global Flood Detection System (GFDS) against observed discharge data was performed in order to test the use of this data in sparsely gauged river basins. The study was carried out at 398 locations near the main rivers and in Africa, Asia, Europe, North America and South America. After evaluating different methodologies for extracting the satellite signal, a temporal (4 days) and spatial (4 GFDS pixels) average was chosen to proceed with the analysis. For the 340 stations with a concurrent time series longer than seven years for both, the signal and the in situ observed discharge (obtained mainly from the Global Runoff Data Centre), a calibration based on monthly linear models was carried out. The validation was executed and several skill scores were calculated such as the R2, Nash-Sutcliffe (NSE), and Root Mean Square Error (RMSE). It is important to highlight that, for this study, 230 stations globally had Nash-Sutcliffe efficient score higher than zero, indicating that for specific conditions the satellite signal as used in GFDS can fill the gaps where observations are not available. For example, several locations in African catchments have good performance as in the Niger, Volta and Zambezi for which Nash-Sutcliffe is greater than 0.75. It is known that a number of factors affect total upwelling microwave brightness from a mixed water and land surface measured by a single image pixel. Aiming to better understand how some features of the sites could affect the satellite signal and the correlation with in situ observations, apart from the dependency on the river geometry, a multivariate analysis was carried out between the skill scores (NSE and

  4. Supercontinuum spatial modulation spectroscopy: Detection and noise limitations

    SciTech Connect

    McDonald, M. P.; Vietmeyer, F.; Kuno, M.; Aleksiuk, D.

    2013-11-15

    Supercontinuum spatial modulation spectroscopy is a facile tool for conducting single molecule/particle extinction spectroscopy throughout the visible and near infrared (420–1100 nm). The technique's capabilities are benchmarked using individual Au nanoparticles (NPs) as a standard since they are well studied and display a prominent plasmon resonance in the visible. Extinction spectra of individual Au NPs with diameters (d) ranging from d ∼ 8 to 40 nm are resolved with extinction cross sections (σ{sub ext}) of σ{sub ext} ∼1 × 10{sup −13}–1 ×10{sup −11} cm{sup 2}. Corresponding signal-to-noise ratios range from ∼30 to ∼1400. The technique's limit of detection is determined to be 4.3 × 10{sup −14} cm{sup 2} (4.3 nm{sup 2}). To showcase supercontinuum spatial modulation spectroscopy's broader applicability, extinction spectra are acquired for other model systems, such as individual single-walled carbon nanotubes (SWCNTs) and CdSe nanowires. We show for the first time extinction spectra of individual (8,3) and (6,5) SWCNTs. For both chiralities, their E{sub 11} [(8,3) 1.30 eV (952 nm); (6,5) 1.26 eV (986 nm)] and E{sub 22} [(8,3) 1.86 eV (667 nm); (6,5) 2.19 eV (567 nm)] excitonic resonances are seen with corresponding cross sections of σ{sub ext} ∼ 10{sup −13} cm{sup 2} μm{sup −1}.

  5. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Procedure and method detection limit... method detection limit for measurement of settleable solids. For the purposes of this part, the following... CFR part 136, the method detection limit for measuring settleable solids under this part shall be 0.4...

  6. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Procedure and method detection limit... Procedure and method detection limit for measurement of settleable solids. For the purposes of this part.... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under...

  7. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Procedure and method detection limit... Procedure and method detection limit for measurement of settleable solids. For the purposes of this part.... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under...

  8. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Procedure and method detection limit... method detection limit for measurement of settleable solids. For the purposes of this part, the following... CFR part 136, the method detection limit for measuring settleable solids under this part shall be 0.4...

  9. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Procedure and method detection limit... Procedure and method detection limit for measurement of settleable solids. For the purposes of this part.... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under...

  10. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  11. Detection Limit for the Globally Distributed Falcon Telescope Network and Viability for Exoplanet Detection

    NASA Astrophysics Data System (ADS)

    Novotny, Steven; Polsgrove, Daniel; Chun, Francis; Tippets, Roger; Della-Rose, Devin J.; carlson, randall

    2016-01-01

    The Falcon Telescope Network (FTN) is a globally distributed system of twelve 20-inch robotic telescopes that will be centrally controlled from the Cadet Space Operations Center (CSOC) at the U.S. Air Force Academy in Colorado Springs, CO. In an effort to explore the viability of using the FTN for an exoplanet survey, each site will be characterized to demonstrate the ability to detect and collect accurate photometry on a variety of targets, specifically on nearby (< 25 pc) late-type M Dwarf stars. Values for the limiting magnitude of the optical system using the Sloan Digital Sky Survey i' and z' filters were estimated through a radiative transport approach and validated through a parallel observing campaign. The results of this campaign are presented and will be used as constraints on future projects in exoplanet research, studies in Space Situational Awareness (SSA), and detection and tracking of near-earth objects.

  12. SPA enhanced FPIA-based detection of pesticide residue with ppb/ppt level detection limit.

    PubMed

    Korrapati, Swathi; Pullela, Phani Kumar; Vijayalakshmi, Uthirapathy

    2017-02-01

    Pesticide residue in fruits & vegetables is one of the key issues affecting the export of rural products in India. Pesticide exposure or intake causes major nervous system problems in children. The solutions to quantitate them in field are rare and the pesticide residue detection in the parts per billion (ppb) ranges is challenging. Except ELISA, none of the existing methods can detect pesticide residues in ppb range in the field. We employed a new approach of concentrating field samples and used sodium polyacrylate (SPA) as water absorbing material. The SPA beads concentrate the field samples and obtained a sub ppb range detection using an existing FPIA system and could improve overall sensitivity by 10-100 fold. The developed assay can be done in few seconds. We have used three pesticides 2,4-D, atrazine and methyl parathion with 0.1, 0.5 and 3 ppb detection limit respectively. We developed a simple field ready FPIA device and used sodium poly acrylate (SPA) in this biochemical FPIA to enhance sensitivity. Our tests with spiked field samples offers a possibility of using SPA concentration assisted FPIA in field. This study will have far reaching applications of both qualitative & quantitative analysis chemical analytes in field samples.

  13. Limited irrigation research and infrared thermometry for detecting water stress

    USDA-ARS?s Scientific Manuscript database

    The USDA-ARS Limited Irrigation Research Farm, located outside of Greeley Colorado, is an experiment evaluating management perspectives of limited irrigation water. An overview of the farm systems is shown, including drip irrigation systems, water budgeting, and experimental design, as well as preli...

  14. Remote sensing for detection of soil limitations in agricultural areas.

    NASA Technical Reports Server (NTRS)

    Frazee, C. J.; Myers, V. I.; Westin, F. C.

    1971-01-01

    Research was initiated to establish remote sensing techniques for recognizing and mapping soil limitations to land use. Analysis of soils with limitations to land use because of dense subsoil (claypan) and unfavorable topography (convex sloping or depressional areas) was accomplished by experienced soil scientists utilizing a density slicing system. Maps of soil limitations were produced by photographing the color encoded density slicing analysis of an area. The percentage of each soil limitation was measured by the planimeter feature of the density slicing system. The initial results indicate that a density slicing system has great potential not only for delineating areas of similar soil limitations but also for indicating the percentage composition of an area.

  15. LIMITATIONS ON THE USES OF MULTIMEDIA EXPOSURE MEASUREMENTS FOR MULTIPATHWAY EXPOSURE ASSESSMENT - PART I: HANDLING OBSERVATIONS BELOW DETECTION LIMITS

    EPA Science Inventory

    Multimedia data from two probability-based exposure studies were investigated in terms of how censoring of non-detects affected estimation of population parameters and associations. Appropriate methods for handling censored below-detection-limit (BDL) values in this context were...

  16. LIMITATIONS ON THE USES OF MULTIMEDIA EXPOSURE MEASUREMENTS FOR MULTIPATHWAY EXPOSURE ASSESSMENT - PART I: HANDLING OBSERVATIONS BELOW DETECTION LIMITS

    EPA Science Inventory

    Multimedia data from two probability-based exposure studies were investigated in terms of how censoring of non-detects affected estimation of population parameters and associations. Appropriate methods for handling censored below-detection-limit (BDL) values in this context were...

  17. Absolute brightness of fluorescent microspheres.

    PubMed

    Finger, Isaac; Phillips, Scott; Mobley, Elizabeth; Tucker, Robert; Hess, Henry

    2009-02-07

    The absolute brightness of fluorescent particles, such as dye-containing nano- and microspheres or quantum dots, is a critical design parameter for many applications relying on fluorescence detection. The absolute brightness, defined as the ratio of radiant intensity of emission to illumination intensity of excitation, of nile-red fluorescent microspheres with a 1 micrometre diameter is measured to be 4.2 +/- 1 x 10(-16) m(2)/sr, and the implications for the design of kinesin motor protein-powered "smart dust" devices and the remote detection of fluorescence are discussed.

  18. Limitations for heterodyne detection of Brillouin scattered light

    SciTech Connect

    Allemeier, R.T.; Wagner, J.W.; Telschow, K.L.

    1995-01-01

    One means by which elastic properties of a material may be determined is measuring sound wave velocities in the material, from which elastic moduli of interest can be computed. Velocity can be measured by conventional piezoelectric transduction techniques, by applying laser ultrasonics, or by using Brillouin-scattering methods. Brillouin-scattering techniques for determining the sound wave velocity are particularly attractive since they are completely noninvasive. Only a probe beam of light is required since the thermal energy in the material provides the elastic motion. Heterodyne methods for detection of Brillouin-scattered light are considered one possible means to increase the speed of the scattered light frequency detection. Results of experiments with simulated Brillouin scattering suggest that heterodyne detection of the Brillouin-scattered light is feasible. Experiments to detect Brillouin-scattered light, with water as the scattering medium, were designed and interpreted using the results of the simulated scattering experiments. Overall, results showed that it is difficult to narrow the linewidth for Brillouin scattering to an acceptable level. The results given indicate that heterodyne detection of the Brillouin components requires detection bandwidths that are quite small, perhaps 10 Hz or lower. These small bandwidths can be routinely achieved using lock-in amplifier techniques.

  19. Remote sensing for detection of soil limitations in agricultural areas

    NASA Technical Reports Server (NTRS)

    Frazee, C. J.; Heil, R. D.; Westin, F. C.

    1970-01-01

    Automatic analysis of soil limitations studied by an automatic color TV density slicing system was accomplished. This system color codes the density range of the value component of color of an image. Maps of soil limitations or other similar soil groups are produced by photographing the color coded representation of an area. The planimeter feature of the density slicing system measures the area of each soil limitation providing information on the importance of a soil limitation in an area. The results of this study suggest that an automatic color TV density slicing system has great potential not only for identifying and mapping similar soil areas, but also for indicating the percentage composition of an area.

  20. Exploring the limits of community detection strategies in complex networks

    PubMed Central

    Aldecoa, Rodrigo; Marín, Ignacio

    2013-01-01

    The characterization of network community structure has profound implications in several scientific areas. Therefore, testing the algorithms developed to establish the optimal division of a network into communities is a fundamental problem in the field. We performed here a highly detailed evaluation of community detection algorithms, which has two main novelties: 1) using complex closed benchmarks, which provide precise ways to assess whether the solutions generated by the algorithms are optimal; and, 2) A novel type of analysis, based on hierarchically clustering the solutions suggested by multiple community detection algorithms, which allows to easily visualize how different are those solutions. Surprise, a global parameter that evaluates the quality of a partition, confirms the power of these analyses. We show that none of the community detection algorithms tested provide consistently optimal results in all networks and that Surprise maximization, obtained by combining multiple algorithms, obtains quasi-optimal performances in these difficult benchmarks. PMID:23860510

  1. Determination of a Limited Scope Network's Lightning Detection Efficiency

    NASA Technical Reports Server (NTRS)

    Rompala, John T.; Blakeslee, R.

    2008-01-01

    This paper outlines a modeling technique to map lightning detection efficiency variations over a region surveyed by a sparse array of ground based detectors. A reliable flash peak current distribution (PCD) for the region serves as the technique's base. This distribution is recast as an event probability distribution function. The technique then uses the PCD together with information regarding: site signal detection thresholds, type of solution algorithm used, and range attenuation; to formulate the probability that a flash at a specified location will yield a solution. Applying this technique to the full region produces detection efficiency contour maps specific to the parameters employed. These contours facilitate a comparative analysis of each parameter's effect on the network's detection efficiency. In an alternate application, this modeling technique gives an estimate of the number, strength, and distribution of events going undetected. This approach leads to a variety of event density contour maps. This application is also illustrated. The technique's base PCD can be empirical or analytical. A process for formulating an empirical PCD specific to the region and network being studied is presented. A new method for producing an analytical representation of the empirical PCD is also introduced.

  2. The absolute threshold of cone vision

    PubMed Central

    Koeing, Darran; Hofer, Heidi

    2013-01-01

    We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

  3. Multi-wavelength UV-detection in capillary hydrodynamic fractionation. Data treatment for an absolute estimate of the particle size distribution

    NASA Astrophysics Data System (ADS)

    Clementi, Luis A.; Aguirre, Miren; Leiza, José R.; Gugliotta, Luis M.; Vega, Jorge R.

    2017-03-01

    A new approach is proposed for estimating the particle size distribution (PSD) of hydrophobic colloids by capillary hydrodynamic fractionation (CHDF) based on UV-detection at several wavelengths. At each elution time, the multi-wavelength UV signal is used to estimate the instantaneous PSD at the detector cell by solving the involved inverse problem through an artificial neural network. Then, the global PSD is obtained as a weighted sum of the estimated instantaneous PSDs along the entire elution time interval. With the current approach, the estimation procedure is absolute in the sense that no calibration of diameters is required and the instrumental broadening introduced by the fractionation capillary is automatically compensated for. The proposed method was evaluated on the basis of narrow polystyrene standards, as follows: i) a single standard, to emulate a narrow unimodal PSD; ii) a mixture of three standards of relatively close average diameters, to emulate a broad unimodal PSD; and iii) a mixture of two standards of quite different average diameters, to emulate a bimodal PSD. Experimental results indicate that the new approach is able to produce adequate PSD estimates provided that the particle refractive index is known with a relatively high accuracy.

  4. Reflectance measurements for the detection and mapping of soil limitations

    NASA Technical Reports Server (NTRS)

    Benson, L. A.; Frazee, C. J.

    1973-01-01

    During 1971 and 1972 research was conducted on two fallow fields in the proposed Oahe Irrigation Project to investigate the relationship between the tonal variations observed on aerial photographs and the principal soil limitations of the area. A grid sampling procedure was used to collected detailed field data during the 1972 growing season. The field data was compared to imagery collected on May 14, 1971 at 3050 meters altitude. The imagery and field data were initially evaluated by a visual analysis. Correlation and regression analysis revealed a highly significant correlation and regression analysis revealed a highly significant correlation between the digitized color infrared film data and soil properties such as organic matter content, color, depth to carbonates, bulk density and reflectivity. Computer classification of the multiemulsion film data resulted in maps delineating the areas containing claypan and erosion limitations. Reflectance data from the red spectral band provided the best results.

  5. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m-1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  6. Limit on Remote FTIR Detection of Trace Gases,

    DTIC Science & Technology

    1981-09-01

    sr.cm-l) CCMIN v (pV) HCI 2900-3000 1.3 x 10- 2.5 x 109 20 NO2 2650-2935 1.4 x 10-9 1.3 x 1010 92 DF 2700-2900 2.6 x 10-9 3.5 x 109 i7 HBr 2450-2650 3.9...dwell time =" 10 secs. MIN v - minimum detectable volume concentration for td 1 0 secs., cloud thickness = 10 m, &T Y5C., Tsfc 300K. L -7.. 2H9-58

  7. Limits of Precipitation Detection from Microwave Radiometers and Sounders

    NASA Astrophysics Data System (ADS)

    Munchak, S. J.; Skofronick-Jackson, G.; Johnson, B. T.

    2012-04-01

    The Global Precipitation Measurement (GPM) mission will unify and draw from numerous microwave conical scanning imaging radiometers and cross-track sounders, many of which already in operation, to provide near real-time precipitation estimates worldwide at 3-hour intervals. Some of these instruments were designed for primary purposes unrelated to precipitation remote sensing. Therefore it is worthwhile to evaluate the strengths and weaknesses of each set of channels with respect to precipitation detection to fully understand their role in the GPM constellation. The GPM radiometer algorithm will use an observationally-based Bayesian retrieval with common databases of precipitation profiles for all sensors. Since these databases are still under development and will not be truly complete until the GPM core satellite has completed at least one year of dual-frequency radar observations, a screening method based upon retrieval of non-precipitation parameters related to the surface and atmospheric state is used in this study. A cost function representing the departure of modeled radiances from their observed values plus the departure of surface and atmospheric parameters from the TELSEM emissivity atlas and MERRA reanalysis is used as an indicator of precipitation. Using this method, two datasets are used to evaluate precipitation detection: One year of matched AMSR-E and AMSU-B/MHS overpasses with CloudSat used as validation globally; and SSMIS overpasses over the United States using the National Mosaic and QPE (NMQ) as validation. The Heidke Skill Score (HSS) is used as a metric to evaluate detection skill over different surfaces, seasons, and across different sensors. Non-frozen oceans give the highest HSS for all sensors, followed by bare land and coasts, then snow-covered land and sea ice. Negligible skill is present over ice sheets. Sounders tend to have higher skill than imagers over complex surfaces (coast, snow, and sea ice), whereas imagers have higher skill

  8. Transduction of nanovolt signals: Limits of electric-field detection

    NASA Astrophysics Data System (ADS)

    Kalmijn, J.

    1989-11-01

    Life scientists discussed the extreme electrical sensitivity of marine sharks, skates, and rays. After reviewing the results of earlier studies on the electric sense at the animal and system levels, the participants discussed the basic process of signal transduction in terms of voltage-sensitive ionic channels. Struck by the small charge displacements needed for excitation, they strongly recommended that sensory biologists, physiologists, and biophysicists join in a concerted effort to initiate new research on the ionic mechanisms of electric field detection. To obtain detailed information on the electroreceptive membrane and its ionic channels, high resolution recording techniques will be mandatory.

  9. Absolutely classical spin states

    NASA Astrophysics Data System (ADS)

    Bohnet-Waldraff, F.; Giraud, O.; Braun, D.

    2017-01-01

    We introduce the concept of "absolutely classical" spin states, in analogy to absolutely separable states of bipartite quantum systems. Absolutely classical states are states that remain classical (i.e., a convex sum of projectors on coherent states of a spin j ) under any unitary transformation applied to them. We investigate the maximal size of the ball of absolutely classical states centered on the maximally mixed state and derive a lower bound for its radius as a function of the total spin quantum number. We also obtain a numerical estimate of this maximal radius and compare it to the case of absolutely separable states.

  10. METHODS OF DEALING WITH VALUES BELOW THE LIMIT OF DETECTION USING SAS

    EPA Science Inventory

    Due to limitations of chemical analysis procedures, small concentrations cannot be precisely measured. These concentrations are said to be below the limit of detection (LOD). In statistical analyses, these values are often censored and substituted with a constant value, such ...

  11. METHODS OF DEALING WITH VALUES BELOW THE LIMIT OF DETECTION USING SAS

    EPA Science Inventory

    Due to limitations of chemical analysis procedures, small concentrations cannot be precisely measured. These concentrations are said to be below the limit of detection (LOD). In statistical analyses, these values are often censored and substituted with a constant value, such ...

  12. Hidden evolution: progress and limitations in detecting multifarious natural selection.

    PubMed

    Johnson, Norman A; Kliman, Richard M

    2002-04-01

    From illustrative examples of research on the best-studied group of species to date, Drosophila melanogaster and its closest relatives, we argue that selection is multifarious, but often hidden. Selective fixation of new, highly advantageous alleles is the most parsimonious explanation for a typical pattern of molecular variation observed in genomic regions characterized by very low recombination: drastically reduced DNA sequence variation within species and typical levels of sequence divergence among species. At the same time, the identity of the gene (or genes) influenced by selection is not just difficult to discern; it may be impossible. Studies of the genetic basis of reproductive isolation demonstrate that, although the D. melanogaster complex species appear virtually identical, dozens of currently unidentified genes contribute to hybrid sterility. We argue that these findings are best explained by selectively-driven functional divergence and demonstrate the multifarious nature of selection. Although multifarious selection certainly occurs, the exact characters responsible for differences in survival and reproductive success are unknown. We do not see these inherent limits as a cause for despair or a problem for evolutionary biology. Instead, we hope to raise awareness of these complexities of evolution by highlighting both the progress and the limitations of characterizing multifarious natural selection.

  13. Quantum-limited Terahertz detection without liquid cryogens

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Under this contract, we have successfully designed, fabricated and tested a revolutionary new type of detector for Terahertz (THz) radiation, the tunable antenna-coupled intersubband Terahertz (TACIT) detector. The lowest-noise THz detectors used in the astrophysics community require cooling to temperatures below 4K. This deep cryogenic requirement forces satellites launched for THz- observing missions to include either large volumes of liquid Helium, complex cryocoolers, or both. Cryogenic requirements thus add significantly to the cost, complexity and mass of satellites and limit the duration of their missions. It hence desirable to develop new detector technologies with less stringent cryogenic requirements. Such detectors will not only be important in space-based astrophysics, but also respond to a growing demand for THz technology for earth-based scientific and commercial applications.

  14. Quantum-limited Terahertz detection without liquid cryogens

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Under this contract, we have successfully designed, fabricated and tested a revolutionary new type of detector for Terahertz (THz) radiation, the tunable antenna-coupled intersubband Terahertz (TACIT) detector. The lowest-noise THz detectors used in the astrophysics community require cooling to temperatures below 4K. This deep cryogenic requirement forces satellites launched for THz- observing missions to include either large volumes of liquid Helium, complex cryocoolers, or both. Cryogenic requirements thus add significantly to the cost, complexity and mass of satellites and limit the duration of their missions. It hence desirable to develop new detector technologies with less stringent cryogenic requirements. Such detectors will not only be important in space-based astrophysics, but also respond to a growing demand for THz technology for earth-based scientific and commercial applications.

  15. Analysis of remotely sensed data for detecting soil limitations

    NASA Technical Reports Server (NTRS)

    Benson, L. A.; Frazee, C. J.; Waltz, F. A.

    1973-01-01

    During 1971 and 1972 a detailed study was conducted on a fallow field in the proposed Oahe Irrigation Project to determine the relationship between the tonal variation observed on aerial photographs and the properties of eroded soil. Correlation and regression analysis of digitized, multiemulsion, color infrared film (2443) data and detailed field data revealed a highly significant correlation between film transmittance and several soil properties indicative of the erosion limitation. Computer classification of the multiemulsion film data resulted in maps portraying the eroded soil and the normal soil. Both correlation and computer classification results were best using the reflectance data from the red spectral band. The results showed film transmittance was actually measuring the reflectivity of the soil surface which was increased by the incorporation of the light colored, calcareous parent material exposed by erosion or tillage on soils with thin surface horizons.

  16. Naked-eye detection as a universal approach to lower the limit of detection of enzyme-linked immunoassays.

    PubMed

    O'Connor, Erin F; Paterson, Sureyya; de la Rica, Roberto

    2016-05-01

    Colorimetric biosensors for the detection of analytes with the naked eye are required in environmental monitoring, point-of-care diagnostics, and analyses in resources constrained settings, where detection instruments may not be available. However, instrument-based detection methods are usually more adequate for detecting small variations in the signal compared to naked-eye detection schemes, and consequently the limit of detection of the latter is usually higher than the former. Here, we demonstrate that the limit of detection of colorimetric enzyme-linked immunoassays can be decreased several orders of magnitude when using naked-eye detection instead of a spectrophotometer for detecting the signal. The key step to lower the limit of detection is adding a small volume of chromogenic substrate during the signal generation step. This generates highly colored solutions that can be easily visualized with the naked eye and recorded with the camera of a mobile phone. The proposed method does not require expensive equipment or complex protocols to enhance the signal, and therefore it is a universal approach to lower the limit of detection of colorimetric enzyme-linked immunoassays.

  17. Quantifying limits to detection of early warning for critical transitions

    PubMed Central

    Boettiger, Carl; Hastings, Alan

    2012-01-01

    Catastrophic regime shifts in complex natural systems may be averted through advanced detection. Recent work has provided a proof-of-principle that many systems approaching a catastrophic transition may be identified through the lens of early warning indicators such as rising variance or increased return times. Despite widespread appreciation of the difficulties and uncertainty involved in such forecasts, proposed methods hardly ever characterize their expected error rates. Without the benefits of replicates, controls or hindsight, applications of these approaches must quantify how reliable different indicators are in avoiding false alarms, and how sensitive they are to missing subtle warning signs. We propose a model-based approach to quantify this trade-off between reliability and sensitivity and allow comparisons between different indicators. We show these error rates can be quite severe for common indicators even under favourable assumptions, and also illustrate how a model-based indicator can improve this performance. We demonstrate how the performance of an early warning indicator varies in different datasets, and suggest that uncertainty quantification become a more central part of early warning predictions. PMID:22593100

  18. Current limitations and challenges in nanowaste detection, characterisation and monitoring.

    PubMed

    Part, Florian; Zecha, Gudrun; Causon, Tim; Sinner, Eva-Kathrin; Huber-Humer, Marion

    2015-09-01

    Engineered nanomaterials (ENMs) are already extensively used in diverse consumer products. Along the life cycle of a nano-enabled product, ENMs can be released and subsequently accumulate in the environment. Material flow models also indicate that a variety of ENMs may accumulate in waste streams. Therefore, a new type of waste, so-called nanowaste, is generated when end-of-life ENMs and nano-enabled products are disposed of. In terms of the precautionary principle, environmental monitoring of end-of-life ENMs is crucial to allow assessment of the potential impact of nanowaste on our ecosystem. Trace analysis and quantification of nanoparticulate species is very challenging because of the variety of ENM types that are used in products and low concentrations of nanowaste expected in complex environmental media. In the framework of this paper, challenges in nanowaste characterisation and appropriate analytical techniques which can be applied to nanowaste analysis are summarised. Recent case studies focussing on the characterisation of ENMs in waste streams are discussed. Most studies aim to investigate the fate of nanowaste during incineration, particularly considering aerosol measurements; whereas, detailed studies focusing on the potential release of nanowaste during waste recycling processes are currently not available. In terms of suitable analytical methods, separation techniques coupled to spectrometry-based methods are promising tools to detect nanowaste and determine particle size distribution in liquid waste samples. Standardised leaching protocols can be applied to generate soluble fractions stemming from solid wastes, while micro- and ultrafiltration can be used to enrich nanoparticulate species. Imaging techniques combined with X-ray-based methods are powerful tools for determining particle size, morphology and screening elemental composition. However, quantification of nanowaste is currently hampered due to the problem to differentiate engineered from

  19. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  20. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  1. Traffic management: Assessing various countermeasures to improve detection failure of changes in speed limit signals.

    PubMed

    Harms, Ilse M; Brookhuis, Karel A

    2017-05-01

    Under certain circumstances, drivers fail to notice changes in electronic speed limits. A video-based study was performed to reveal which countermeasures would improve drivers' ability to detect changes in electronic speed limits. Countermeasures included leaving electronic signs blank prior to a speed limit change and adding motion signals by means of flashing amber lights or a wave. A video representing a motorway was shown repeatedly to 255 participants. They were instructed to press the space bar when detecting a change. The video was viewed 13 times before the speed limit changed. Results showed that leaving signs blank prior to the change instead of displaying speed limits continuously did not alter change detection, whereas flashers and waves eroded detection of the changed speed limit. This suggests that using flashers and waves to attract attention to electronic signs in fact decreases people's ability to process the information contained in the signs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Limiter

    DOEpatents

    Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

    1984-10-19

    A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

  3. Methods to determine limit of detection and limit of quantification in quantitative real-time PCR (qPCR).

    PubMed

    Forootan, Amin; Sjöback, Robert; Björkman, Jens; Sjögreen, Björn; Linz, Lucas; Kubista, Mikael

    2017-06-01

    Quantitative Real-Time Polymerase Chain Reaction, better known as qPCR, is the most sensitive and specific technique we have for the detection of nucleic acids. Even though it has been around for more than 30 years and is preferred in research applications, it has yet to win broad acceptance in routine practice. This requires a means to unambiguously assess the performance of specific qPCR analyses. Here we present methods to determine the limit of detection (LoD) and the limit of quantification (LoQ) as applicable to qPCR. These are based on standard statistical methods as recommended by regulatory bodies adapted to qPCR and complemented with a novel approach to estimate the precision of LoD.

  4. Crack Detection for Aircraft Holes with Limited Accessibility Containing Fasteners and Sealant

    NASA Astrophysics Data System (ADS)

    Aldrin, J. C.; Mandeville, J. R.; Judd, D. R.; Mullis, R. T.; Kropas-Hughes, C. V.

    2003-03-01

    This paper presents a study of crack detection methods for holes in structures with limited accessibility containing fasteners with variable interface conditions. For far crack detection, a method was first designed using models, and refined using a signal processing parameter optimization scheme and an iterative neural network training process. For near crack detection, a method incorporating the spatial variation of the principal components was developed. Using these methods, improvements in crack detection performance were achieved.

  5. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  6. Predicting detection limits of enzyme-linked immunosorbent assay (ELISA) and bioanalytical techniques in general.

    PubMed

    Zhang, Shiyun; Garcia-D'Angeli, Alexa; Brennan, Joseph P; Huo, Qun

    2014-01-21

    The detection limit is one of the most important performance parameters for bioanalytical techniques. Here we present a generic method to estimate the detection limit of biomolecular assays based on a step-by-step analysis of the assay procedure. Enzyme-linked immunosorbent assay (ELISA) is used here as an example; however, much of the information presented in this article may be applied to other types of biomolecular assays and analytical techniques. A clear understanding of what affects the detection limit can help researchers to evaluate different bio-analytical techniques properly, and to design better strategies to optimize and achieve the best analytical performance.

  7. 137Cs measurement uncertainties and detection limits for airborne gamma spectrometry (AGS) data analysed using a spectral windows method.

    PubMed

    Cresswell, A J; Sanderson, D C W; White, D C

    2006-02-01

    The uncertainties associated with airborne gamma spectrometry (AGS) measurements analysed using a spectral windows method, and associated detection limits, have been investigated. For individual short measurements over buried 137Cs activity detection limits of 10 kBq m(-2) are achieved. These detection limits are reduced for superficial activity and longer integration times. For superficial activity, detection limits below 1 kBq m(-2) are achievable. A comparison is made with the detection limits for other data processing methods.

  8. Limiter

    DOEpatents

    Cohen, Samuel A.; Hosea, Joel C.; Timberlake, John R.

    1986-01-01

    A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

  9. ROC-Curve Approach for Determining the Detection Limit of a Field Chemical Sensor

    SciTech Connect

    Fraga, Carlos G.; Melville, Angela M.; Wright, Bob W.

    2007-01-31

    The detection limit of a field chemical sensor under realistic operating conditions is determined by receiver operator characteristic (ROC) curves. The chemical sensor is an ion mobility spectrometry (IMS) device used to detect a chemical marker in diesel fuel. The detection limit is the lowest concentration of the marker in diesel fuel that obtains the desired true-positive probability (TPP) and false-positive probability (FPP). A TPP of 0.90 and a FPP of 0.10 were selected as acceptable levels for the field sensor in this study. The detection limit under realistic operating conditions is found to be between to 2 to 4 ppm (w/w). The upper value is the detection limit under challenging conditions. The ROC-based detection limit is very reliable because it is determined from multiple and repetitive sensor analyses under realistic circumstances. ROC curves also clearly illustrate and gauge the effects data preprocessing and sampling environments have on the sensor’s detection limit.

  10. Nanodroplet quantification: pushing the detection limits of micro x-ray fluorescence

    SciTech Connect

    Miller, T. C.; Havrilla, G. J.

    2002-01-01

    In this study, detection limits for a variety of elements were determined on an EDAX Eagle I1 MXRF system equipped with a polycapillary and a Rh X-ray source. Both mass, volume, and spot diameter detection limits were established using dried spot technology, where various volumes and/or masses of different elements were deposited on different substrates, dried, and quantitatively analyzed by MXRF. Preliminary results have shown that sub-nanogram levels of material can be detected in less than 200 pm diameter spot sizes deposited on thin polymer films. Specifically, detection limits were found for a given element as a function of mass deposited for a given spot volume, and volume deposited for a given mass. The effect of the presence of multiple elements in a droplet on the detection limit was also investigated. For example, the detection limit for copper was determined when it was deposited as a single Cu solution and in various multielement mixtures containing from 2 up to 10 different elements. To determine how the substrate affects the detection limit of different species, elemental dried spots were analyzed on different polymer films, including polypropylene and AP 1 . Comparisons were also made to elements deposited on different spherical, resin substrates such as polystyrene beads.

  11. Epidemiologic Evaluation of Measurement Data in the Presence of Detection Limits

    PubMed Central

    Lubin, Jay H.; Colt, Joanne S.; Camann, David; Davis, Scott; Cerhan, James R.; Severson, Richard K.; Bernstein, Leslie; Hartge, Patricia

    2004-01-01

    Quantitative measurements of environmental factors greatly improve the quality of epidemiologic studies but can pose challenges because of the presence of upper or lower detection limits or interfering compounds, which do not allow for precise measured values. We consider the regression of an environmental measurement (dependent variable) on several covariates (independent variables). Various strategies are commonly employed to impute values for interval-measured data, including assignment of one-half the detection limit to nondetected values or of “fill-in” values randomly selected from an appropriate distribution. On the basis of a limited simulation study, we found that the former approach can be biased unless the percentage of measurements below detection limits is small (5–10%). The fill-in approach generally produces unbiased parameter estimates but may produce biased variance estimates and thereby distort inference when 30% or more of the data are below detection limits. Truncated data methods (e.g., Tobit regression) and multiple imputation offer two unbiased approaches for analyzing measurement data with detection limits. If interest resides solely on regression parameters, then Tobit regression can be used. If individualized values for measurements below detection limits are needed for additional analysis, such as relative risk regression or graphical display, then multiple imputation produces unbiased estimates and nominal confidence intervals unless the proportion of missing data is extreme. We illustrate various approaches using measurements of pesticide residues in carpet dust in control subjects from a case–control study of non-Hodgkin lymphoma. PMID:15579415

  12. Shot noise limited detection of OH using the technique of laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Bakalyar, D. M.; Davis, L. I., Jr.; Guo, C.; James, J. V.; Kakos, S.; Morris, P. T.; Wang, C. C.

    1984-01-01

    Nearly shot-noise limited detection of OH using the technique of laser-induced fluorescence is reported. A LIDAR configuration is used to excite fluorescence in a large volume and a narrow-bandwidth interference filter provides spectral discrimination. This arrangement alleviates the effect of ozone interference and facilitates image processing at relatively close distances. The detection limit is determined mainly by the shot-noise of the solar background. Ground-based measurements in Dearborn indicate a detection limit of better than 1 x 10 to the 6th power OH/cubic cm over a forty-minute acquisition period. Under favorable conditions, a comparable detection limit was also observed for airborne measurements.

  13. Quantum limits on the detection sensitivity of a linear detector with feedback

    NASA Astrophysics Data System (ADS)

    Gao, Yang

    2017-03-01

    We show that the detection sensitivity of a linear detector is lower bounded by some quantum limits. For the force sensitivity, which is relevant for atomic force microscopes, the lower bound is given by the so-called ultimate quantum limit (UQL). For the displacement sensitivity, which is relevant for detecting gravitational waves, a generalized lower bound that can overcome the usual UQL is obtained.

  14. Real-time RT-PCR for detection, identification and absolute quantification of viral haemorrhagic septicaemia virus using different types of standards.

    PubMed

    Lopez-Vazquez, C; Bandín, I; Dopazo, C P

    2015-05-21

    In the present study, 2 systems of real-time RT-PCR-one based on SYBR Green and the other on TaqMan-were designed to detect strains from any genotype of viral haemorrhagic septicaemia virus (VHSV), with high sensitivity and repeatability/reproducibility. In addition, the method was optimized for quantitative purposes (qRT-PCR), and standard curves with different types of reference templates were constructed and compared. Specificity was tested against 26 isolates from 4 genotypes. The sensitivity of the procedures was first tested against cell culture isolation, obtaining a limit of detection (LD) of 100 TCID50 ml-1 (100-fold below the LD using cell culture), at a threshold cycle value (Ct) of 36. Sensitivity was also evaluated using RNA from crude (LD = 1 fg; 160 genome copies) and purified virus (100 ag; 16 copies), plasmid DNA (2 copies) and RNA transcript (15 copies). No differences between both chemistries were observed in sensitivity and dynamic range. To evaluate repeatability and reproducibility, all experiments were performed in triplicate and on 3 different days, by workers with different levels of experience, obtaining Ct values with coefficients of variation always <5. This fact, together with the high efficiency and R2 values of the standard curves, encouraged us to analyse the reliability of the method for viral quantification. The results not only demonstrated that the procedure can be used for detection, identification and quantification of this virus, but also demonstrated a clear correlation between the regression lines obtained with different standards, which will help scientists to compare sensitivity results between different studies.

  15. METHODS OF DEALING WITH VALUES BELOW THE LIMIT OF DETECTION USING SAS

    EPA Science Inventory

    Due to limitations of chemical analysis procedures, small values cannot be precisely measured. These values are said to be below the limit of detection (LOD). In statistical analyses, these values are often censored and substituted with a constant value, such as half the LOD,...

  16. METHODS OF DEALING WITH VALUES BELOW THE LIMIT OF DETECTION USING SAS

    EPA Science Inventory

    Due to limitations of chemical analysis procedures, small values cannot be precisely measured. These values are said to be below the limit of detection (LOD). In statistical analyses, these values are often censored and substituted with a constant value, such as half the LOD,...

  17. Analytical Method and Detection Limit Studies for Detection of GB in GB Hydrolysate

    DTIC Science & Technology

    2006-06-01

    performed at pH 8 and room temperature with a J 50:2 hydrolysate:solvent ratio. Extraction recoveries are listed in Table 13. Hexane and isooctane were...22 Solvent Extraction Efficiency Chloroform 50% Methylene Chloride 49 % Hexane 5 % Isooctane None detected Previous studies have indicated that GB

  18. Strategies and limitations for fluorescence detection of XAFS at high flux beamlines

    SciTech Connect

    Heald, Steve M.

    2015-02-17

    The issue of detecting the XAFS signal from dilute samples is discussed in detail with the aim of making best use of high flux beamlines that provide up to 1013photons-1. Various detection methods are compared, including filters with slits, solid state detectors, crystal analyzers and combinations of these. These comparisons rely on simulations that use experimentally determined parameters. It is found that inelastic scattering places a fundamental limit on detection, and that it is important to take proper account of the polarization dependence of the signals. The combination of a filter–slit system with a solid state detector is a promising approach. With an optimized system good performance can be obtained even if the total count rate is limited to 107Hz. Detection schemes with better energy resolution can help at the largest dilutions if their collection efficiency and count rate limits can be improved.

  19. Strategies and Limitations for Fluorescence Detection of XAFS at High Flux Beamlines

    DOE PAGES

    Heald, Steve M.

    2015-03-01

    The issue of detecting the XAFS signal from dilute samples is discussed in detail with the aim of making best use of high flux beamlines that provide up to 10(13)photonss(-1). Various detection methods are compared, including filters with slits, solid state detectors, crystal analyzers and combinations of these. These comparisons rely on simulations that use experimentally determined parameters. It is found that inelastic scattering places a fundamental limit on detection, and that it is important to take proper account of the polarization dependence of the signals. The combination of a filter-slit system with a solid state detector is a promisingmore » approach. With an optimized system good performance can be obtained even if the total count rate is limited to 10(7)Hz. Detection schemes with better energy resolution can help at the largest dilutions if their collection efficiency and count rate limits can be improved.« less

  20. Strategies and limitations for fluorescence detection of XAFS at high flux beamlines

    DOE PAGES

    Heald, Steve M.

    2015-02-17

    The issue of detecting the XAFS signal from dilute samples is discussed in detail with the aim of making best use of high flux beamlines that provide up to 1013photons-1. Various detection methods are compared, including filters with slits, solid state detectors, crystal analyzers and combinations of these. These comparisons rely on simulations that use experimentally determined parameters. It is found that inelastic scattering places a fundamental limit on detection, and that it is important to take proper account of the polarization dependence of the signals. The combination of a filter–slit system with a solid state detector is a promisingmore » approach. With an optimized system good performance can be obtained even if the total count rate is limited to 107Hz. Detection schemes with better energy resolution can help at the largest dilutions if their collection efficiency and count rate limits can be improved.« less

  1. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  2. Estimating the resolution limit of the map equation in community detection

    NASA Astrophysics Data System (ADS)

    Kawamoto, Tatsuro; Rosvall, Martin

    2015-01-01

    A community detection algorithm is considered to have a resolution limit if the scale of the smallest modules that can be resolved depends on the size of the analyzed subnetwork. The resolution limit is known to prevent some community detection algorithms from accurately identifying the modular structure of a network. In fact, any global objective function for measuring the quality of a two-level assignment of nodes into modules must have some sort of resolution limit or an external resolution parameter. However, it is yet unknown how the resolution limit affects the so-called map equation, which is known to be an efficient objective function for community detection. We derive an analytical estimate and conclude that the resolution limit of the map equation is set by the total number of links between modules instead of the total number of links in the full network as for modularity. This mechanism makes the resolution limit much less restrictive for the map equation than for modularity; in practice, it is orders of magnitudes smaller. Furthermore, we argue that the effect of the resolution limit often results from shoehorning multilevel modular structures into two-level descriptions. As we show, the hierarchical map equation effectively eliminates the resolution limit for networks with nested multilevel modular structures.

  3. Fundamental limits of detection with nanowire FET chem/bio sensors in subthreshold and linear regimes

    NASA Astrophysics Data System (ADS)

    Gao, Xuan; Zheng, Gengfeng; Lieber, Charles

    2007-03-01

    Nanowire field effect transistors (NW-FETs) have been demonstrated to be powerful sensors for the detection of biological and chemical species, and thus understanding and pushing their intrinsic sensitivity limits could have a significant impact on a broad-range of applications of these devices. We report studies of the response of silicon-NW-FET sensors as the devices are tuned from linear to subthreshold regimes by electrochemical gating. Conductance versus solution pH data show that operation in the subthreshold regime can increase both the percentage change in conductance and the signal to noise ratio of the device by over ten times compared to the linear regime. We also demonstrate that operating in the subthreshold regime yields improvement in the detection limit for the cancer marker protein PSA with detection down to ˜1.5 fM for a device with ˜0.75 pM detection limit in the linear regime. Analysis of these results shows that the sensitivity improvement is due to the more effective surface charge gating resulting from the reduced screening by carriers. In addition, the effect of NW diameters and the intrinsic charge detection limit for using NW-FET devices will be described. Our work shows that optimization of NW-FET structure and operating conditions can provide a significant enhancement as well as a fundamental understanding of the sensitivity limits for nano-FET sensors.

  4. [On-site detection of bioterrorism-relevant agents : Rapid detection methods for viruses, bacteria and toxins - capabilities and limitations].

    PubMed

    Stern, Daniel; Richter, Martin; Schrick, Livia; Lasch, Peter; Keeren, Kathrin; Polleichtner, Angela; Lemmer, Karin; Nitsche, Andreas; Grunow, Roland; Herzog, Christian; Dorner, Brigitte G; Schaade, Lars

    2016-12-01

    In Europe, besides the threat of terrorist attacks involving conventional methods such as explosive devices and automatic weapons, there is also a potential threat of terrorist groups using non-conventional material like biological agents in the scope of future attacks. Consequently, rapid and reliable detection systems for biological agents are being developed and tested continuously to inform crisis management. For environmental detection, a broad spectrum of different laboratory-based techniques has been developed for relevant biological agents. However for environmental samples, fast and reliable on-site detection methods are desired by first responders for rapid assessment.Based on different functional principles, generic, immunological and nucleic-acid-based on-site detection methods can be distinguished. Those should be facile, fast, sensitive, and specific. However, commercially available kits usually have limited sensitivity and often have not been validated independently. Furthermore in this context, the multitude of relevant biological agents that potentially have to be considered present in complex environmental matrices poses a serious challenge for reliable detection. Therefore, detailed knowledge of the specific scope of applications and the limitations of different analytical systems is necessary to evaluate the results obtained purposefully.The aim of this article is to provide an overview of the analytical principles, benefits and limitations of prevailing on-site environmental detection systems for bioterrorism-relevant viruses, bacteria and toxins. Despite promising developments the informative value of currently available on-site tests is still limited. Thus, expert laboratories have to conduct confirmatory testing.

  5. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  6. Limit of detection of 15{sub N} by gas-chromatography atomic emission detection: Optimization using an experimental design

    SciTech Connect

    Deruaz, D.; Bannier, A.; Pionchon, C.

    1995-08-01

    This paper deals with the optimal conditions for the detection of {sup 15}N determined using a four-factor experimental design from [2{sup 13}C,-1,3 {sup 15}N] caffeine measured with an atomic emission detector (AED) coupled to gas chromatography (GC). Owing to the capability of a photodiodes array, AED can simultaneously detect several elements using their specific emission lines within a wavelength range of 50 nm. So, the emissions of {sup 15}N and {sup 14}N are simultaneously detected at 420.17 nm and 421.46 nm respectively. Four independent experimental factors were tested (1) helium flow rate (plasma gas); (2) methane pressure (reactant gas); (3) oxygen pressure; (4) hydrogen pressure. It has been shown that these four gases had a significant influence on the analytical response of {sup 15}N. The linearity of the detection was determined using {sup 15}N amounts ranging from 1.52 pg to 19 ng under the optimal conditions obtained from the experimental design. The limit of detection was studied using different methods. The limits of detection of {sup 15}N was 1.9 pg/s according to the IUPAC method (International-Union of Pure and Applied Chemistry). The method proposed by Quimby and Sullivan gave a value of 2.3 pg/s and that of Oppenheimer gave a limit of 29 pg/s. For each determination, and internal standard: 1-isobutyl-3.7 dimethylxanthine was used. The results clearly demonstrate that GC AED is sensitive and selective enough to detect and measure {sup 15}N-labelled molecules after gas chromatographic separation.

  7. Absolute radiation detector

    NASA Astrophysics Data System (ADS)

    Martin, John E.

    1996-11-01

    An absolute radiation detector (a cryogenic radiometer) is being developed to replace the existing UK primary national standard cryogenic radiometer with an improved uncertainty. The cryogenic radiometer will be capable of measuring black body radiation and laser radiation with an uncertainty approaching 10 ppm. From these measurements it will be possible to determine the fundamental constant, the Stefan Boltzmann constant, confirming the radiometer as an absolute detector, and link this determination to the SI unit of luminous intensity, the candela. Thus detector and source based scales/standards will be tied to an invariant physical quantity ensuring their long-term stability.

  8. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  9. Limit of detection and limit of quantification development procedures for organochlorine pesticides analysis in water and sediment matrices

    PubMed Central

    2013-01-01

    Background Reliable values for method validity of organochlorine pesticides determination were investigated, in water by solid phase extraction and in sediment by Soxhlet extraction, followed by gas chromatography equipped with an electron capture detector. Organochlorine pesticides are categorized as Persistent Organic Pollutants. Hence, critical decisions to control exposure to these chemicals in the environment are based on their levels in different media; it is important to find valid qualitative and quantitative results for these components. In analytical chemistry, internal quality procedures are applied to produce valid logical results. Result In this study, 18 organochlorine pesticides were targeted for analysis and determination in water and river sediment. Experiments based on signal-to-noise ratio, calibration curve slope and laboratory fortified blank methods were conducted to determine the limits of qualification and quantification. The data were compared with each other. The limitation values, following Laboratory Fortified Blank, showed significant differences in the signal-to-noise ratio and calibration curve slope methods, which are assumed in the results for the sample concentration factor to be 1,000 times in water and 10 times in sediment matrices. The method detection limit values were found to be between 0.001 and 0.005 μg/L (mean of 0.002 ± 0.001) and 0.001 and 0.005 μg/g (mean of 0.001 ± 0.001). The quantification limits were found to be between 0.002 and 0.016 μg/L (mean of 0.006 ± 0.004) and 0.003 and 0.017 μg/g (mean of 0.005 ± 0.003 μg/L) for water and sediment, respectively, based on the laboratory fortified blank method. Because of different slopes in the calibration methods, it was also found that the limitation values for some components from the internal standard were higher than from external standard calibration, because in the latter a factor for injection efficiency is applied for calibration

  10. Modeling the performance limits of novel microcantilever heaters for volatile organic compound detection

    NASA Astrophysics Data System (ADS)

    Jahangir, Ifat; Koley, Goutam

    2017-01-01

    We present a theoretical model estimating the performance limits of novel AlGaN/GaN heterostructure based microcantilever heater sensors to perform advanced volatile organic compound (VOC) detection and mixture analysis. Operating without any specific surface functionalization or treatment; these devices utilize the strong surface polarization of AlGaN as well as the unique device geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range. The presented model incorporates heat transfer, Joule heating, thermal expansion and evaporative heat loss mechanisms, to predict device behaviors such as temperature profiles and sensing performance limits under various steady-state and transient test conditions. In addition, the versatility of the proposed model enables us to successfully predict the capability of the device to perform mixture analysis, and provides guidelines to further optimize the device properties to achieve a limit of detection in sub-ppm concentration.

  11. Hydrazine detection limits in the cigarette smoke matrix using infrared tunable diode laser absorption spectroscopy.

    PubMed

    Plunkett, Susan; Parrish, Milton E; Shafer, Kenneth H; Shorter, Joanne H; Nelson, David D; Zahniser, Mark S

    2002-09-01

    Infrared absorption lines of hydrazine are broad and typically not baseline resolved, with line strengths approximately 100 times weaker than the more widely studied compound ammonia. Hardware and software improvements have been made to a two-color infrared tunable diode laser (IR-TDL) spectrometer in order to improve the limit of detection (LOD) of hydrazine (N2H4) in the cigarette smoke matrix. The detection limit in the smoke matrix was improved from 25 parts-per-million-by-volume (ppmv) to 4.2 ppmv using a 100 m pathlength cell with acquisition of background spectra immediately prior to each sample and 100 ms temporal resolution. This study did not detect hydrazine in cigarette smoke in the 964.4-964.9 cm(-1) spectral region, after mathematically subtracting the spectral contributions of ethylene, ammonia, carbon dioxide, methanol, acrolein, and acetaldehyde. These compounds are found in cigarette smoke and absorb in this spectral region. The LOD is limited by remaining spectral structure from unidentified smoke species. The pseudo random noise (root mean square) in the improved instrument was 2 x 10(-4) absorbance units (base e) which is equivalent to a 0.09 ppmv hydrazine gas sample in the multipass cell. This would correspond to a detection limit of 0.44 ppmv of hydrazine, given the dilution of the smoke by a factor of 5 by the sampling system. This is a factor of 10 less than the 4.2 ppmv detection limit for hydrazine in the smoke matrix, and indicates that the detection limit is primarily a result of the complexity of the matrix rather than the random noise of the TDL instrument.

  12. Limits of passive remote detection of hazardous vapors by computer simulation

    NASA Astrophysics Data System (ADS)

    Flanigan, Dennis F.

    1996-06-01

    Passive infrared is an emerging method for the remote detection of hazardous vapors particularly where warning is the primary consideration. Detection of gases, vapors and aerosols is based on the difference, (Delta) T), between the temperature of the target cloud and the effective radiometric temperature of the background. Computer simulation of spectra has been used to predict the detection limits for several target gases with a low angle sky background. The simulation is based on a 3 layer model that uses MODTRAN, which includes 6 standard atmospheric models, to compute background radiance and atmospheric transmittance. The detection limits, at 2 cm-1 resolution, for sulfur hexafluoride (simulant), Sarin, trichlorethylene, methyl isocyanate (the Bhopal gas), mustard gas, methyl chloride, and sulfur dioxide are discussed for selected cases with the U.S. Standard, and the sub-arctic winter and the tropical models. In this paper the method is illustrated with methyl isocyanate.

  13. Combined use of relative and absolute dating techniques for detecting signals of Alpine landscape evolution during the late Pleistocene and early Holocene

    NASA Astrophysics Data System (ADS)

    Favilli, Filippo; Egli, Markus; Brandova, Dagmar; Ivy-Ochs, Susan; Kubik, Peter; Cherubini, Paolo; Mirabella, Aldo; Sartori, Giacomo; Giaccai, Daniele; Haeberli, Wilfried

    2009-11-01

    A combination of three relative and two absolute (numerical) dating techniques, applied on nine soil profiles in an Alpine environment located in Val di Rabbi (Trentino, Northern Italy), was used to improve the investigation methodology of Alpine sites in response to climate change and to reconstruct the chronology of late Pleistocene and early Holocene landscape evolution. The degree of podzolisation, clay mineral evolution and the element mass balances of each site were investigated. Furthermore, the stable fraction of the soil organic matter (SOM) was extracted with 10% H 2O 2 and 14C-dated. The age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating (SED) with cosmogenic 10Be. Numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements. The combination of 14C-dating of SOM and SED indicated that deglaciation processes in Val di Rabbi were already far advanced by around 14 000 cal BP and that glacier oscillations affected the highest part of the region until about 9000 cal BP. The development of clay minerals is time-dependent and reflects weathering intensity. We found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the H 2O 2 treatment. Calculated element mass balances strongly correlated with the ages derived from 14C measurements. Old soils have lost a major part of base cations (up to 75% compared to the parent material), Fe and Al, which indicates a continuous high weathering intensity. Results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques, showing the dynamics of an Alpine landscape within a relatively small area. The combination of relative and absolute dating techniques is a

  14. Model Based Determination of Detection Limits for Proton Transfer Reaction Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Amann, Anton; Schwarz, Konrad; Wimmer, Gejza; Witkovský, Viktor

    2010-01-01

    Proton Transfer Reaction Mass Spectrometry (PTR-MS) is a chemical ionization mass spectrometric technique which allows to measure trace gases as, for example, in exhaled human breath. The quantification of compounds at low concentrations is desirable for medical diagnostics. Typically, an increase of measuring accuracy can be achieved if the duration of the measuring process is extended. For real time measurements the time windows for measurement are relatively short, in order to get a good time resolution (e.g. with breath-to-breath resolution during exercise on a stationary bicycle). Determination of statistical detection limits is typically based on calibration measurements, but this approach is limited, especially for very low concentrations. To overcome this problem, a calculation of limit of quantification (LOQ) and limit of detection (LOD), respectively, based on a theoretical model of the measurement process is outlined.

  15. Limit of detection of field effect transistor biosensors: Effects of surface modification and size dependence

    NASA Astrophysics Data System (ADS)

    Rajan, Nitin K.; Brower, Kara; Duan, Xuexin; Reed, Mark A.

    2014-02-01

    Field-effect transistor biosensors have shown great promise in the detection of biomolecules. However, a quantitative understanding of what limits the smallest measurable concentration of analyte (limit of detection or LOD) is still missing. By considering the signal-to-noise ratio (SNR), extracted from a combination of noise and I-V characterization, we are able to accurately predict and experimentally confirm a LOD of 0.01 pH. Our results also show that devices with larger area and with amine functionalized surfaces have larger SNR. We are able to extract the associated oxide trap densities and, thus, quantify the improvements in LOD.

  16. Method for improving the limit of detection in a data signal

    DOEpatents

    Synovec, Robert E.; Yueng, Edward S.

    1989-10-17

    A method for improving the limit of detection for a data set in which experimental noise is uncorrelated along a given abscissa and an analytical signal is correlated to the abscissa, the steps comprising collecting the data set, converting the data set into a data signal including an analytical portion and the experimental noise portion, designating and adjusting a baseline of the data signal to center the experimental noise numerically about a zero reference, and integrating the data signal preserving the corresponding information for each point of the data signal. The steps of the method produce an enhanced integrated data signal which improves the limit of detection of the data signal.

  17. Reliability, detection limit and depth resolution of the elastic recoil measurement of hydrogen

    NASA Astrophysics Data System (ADS)

    Hisao, Nagai; Shigeki, Hayashi; Michi, Aratani; Tadashi, Nozaki; Minoru, Yanokura; Isao, Kohno; Osamu, Kuboi; Yoshifumi, Yatsurugi

    1987-08-01

    Reliability, detection limit and depth resolution were studied in the elastic recoil measurement of hydrogen mainly in silicon compounds by bombardment with argon ions accelerated up to 50 MeV. For the quantitative determination of hydrogen, recoil silicon atoms proved to serve satisfactorily as an internal monitor. The detection limit was shown to be about 1 to 2×10 12 (atoms/cm 2 for hydrogen on surface and about 1 wt. ppm for hydrogen in bulk. The depth resolution was found to be about 50 nm in most silicon compounds.

  18. Double-well atom trap for fluorescence detection at the Heisenberg limit

    NASA Astrophysics Data System (ADS)

    Stroescu, Ion; Hume, David B.; Oberthaler, Markus K.

    2015-01-01

    We experimentally demonstrate an atom number detector capable of simultaneous detection of two mesoscopic ensembles with single-atom resolution. Such a sensitivity is a prerequisite for quantum metrology at a precision approaching the Heisenberg limit. Our system is based on fluorescence detection of atoms in a hybrid trap in which a dipole barrier divides a magneto-optical trap into two separated wells. We introduce a noise model describing the various sources contributing to the measurement error and report a limit of up to 500 atoms for single-atom resolution in the atom number difference.

  19. Gravitational radiation detection with spacecraft Doppler tracking - Limiting sensitivities and prospective missions

    NASA Technical Reports Server (NTRS)

    Estabrook, F. B.; Hellings, R. W.; Wahlquist, H. D.; Wolff, R. S.

    1979-01-01

    The prospects of using spacecraft Doppler tracking, in NASA missions, for the detection of gravitational waves are examined. The sensitivity limits of such detection are characterized in terms of plasma scintillation, troposphere scintillation, receiver noise, MDA and ODA quantization error, and clock jitter. Current and possible future NASA missions that will involve gravitational wave experiments are briefly reviewed, including the Galileo, solar polar, Halley/Tempel-2, and solar probe missions.

  20. Determination of Detection Limits and Quantitation Limits for Compounds in a Database of GC/MS by FUMI Theory

    PubMed Central

    Nakashima, Shinya; Hayashi, Yuzuru

    2016-01-01

    The aim of this paper is to propose a stochastic method for estimating the detection limits (DLs) and quantitation limits (QLs) of compounds registered in a database of a GC/MS system and prove its validity with experiments. The approach described in ISO 11843 Part 7 is adopted here as an estimation means of DL and QL, and the decafluorotriphenylphosphine (DFTPP) tuning and retention time locking are carried out for adjusting the system. Coupled with the data obtained from the system adjustment experiments, the information (noise and signal of chromatograms and calibration curves) stored in the database is used for the stochastic estimation, dispensing with the repetition measurements. Of sixty-six pesticides, the DL values obtained by the ISO method were compared with those from the statistical approach and the correlation between them was observed to be excellent with the correlation coefficient of 0.865. The accuracy of the method proposed was also examined and concluded to be satisfactory as well. The samples used are commercial products of pesticides mixtures and the uncertainty from sample preparation processes is not taken into account. PMID:27162706

  1. Bioinformatics in the Thermodynamic Limit: Applications to pre-mRNA Splice Site Detection

    NASA Astrophysics Data System (ADS)

    Daub, Eric G.; Aalberts, Daniel P.

    2004-03-01

    In the thermodynamic limit, physical systems exhibit predictable behavior. Traditional bioinformatics methods of matching patterns from a few cases can be superseded by alternate techniques when the number of instances approaches the thermodynamic limit. By enhancing an already large dataset, we find that we can differentiate real signals from decoys with superior accuracy. We apply our framework to the problem of precursor mRNA splice site detection in human sequences.

  2. Improvements of low-detection-limit filter-free fluorescence sensor developed by charge accumulation operation

    NASA Astrophysics Data System (ADS)

    Tanaka, Kiyotsugu; Choi, Yong Joon; Moriwaki, Yu; Hizawa, Takeshi; Iwata, Tatsuya; Dasai, Fumihiro; Kimura, Yasuyuki; Takahashi, Kazuhiro; Sawada, Kazuaki

    2017-04-01

    We developed a low-detection-limit filter-free fluorescence sensor by a charge accumulation technique. For charge accumulation, a floating diffusion amplifier (FDA), which included a floating diffusion capacitor, a transfer gate, and a source follower circuit, was used. To integrate CMOS circuits with the filter-free fluorescence sensor, we adopted a triple-well process to isolate transistors from the sensor on a single chip. We detected 0.1 nW fluorescence under the illumination of excitation light by 1.5 ms accumulation, which was one order of magnitude greater than that of a previous current detection sensor.

  3. Displacement response, detection limit, and dynamic range of fiber-optic lever sensors

    NASA Technical Reports Server (NTRS)

    He, Gang; Cuomo, Frank W.

    1991-01-01

    The authors present the evaluation of the displacement response, detection limit, and dynamic range of fiber-optic lever sensors in a general format to establish their dependence on fiber sizes, optoelectronic detector specifications, input power, and other relevant parameters. The formations for the normalized reflected optical power change are derived for the evaluation of the optimal sensor response, the linearity range, and the minimum detectable displacement. The theoretical models are verified by an experiment which determines sensor response, modulation index, reflected optical power change, and linear response range through dynamic measurement. The application of this theoretical model to the study of a fiber-optic microphone for acoustic pressure detection is considered.

  4. Displacement response, detection limit, and dynamic range of fiber-optic lever sensors

    NASA Technical Reports Server (NTRS)

    He, Gang; Cuomo, Frank W.

    1991-01-01

    The authors present the evaluation of the displacement response, detection limit, and dynamic range of fiber-optic lever sensors in a general format to establish their dependence on fiber sizes, optoelectronic detector specifications, input power, and other relevant parameters. The formations for the normalized reflected optical power change are derived for the evaluation of the optimal sensor response, the linearity range, and the minimum detectable displacement. The theoretical models are verified by an experiment which determines sensor response, modulation index, reflected optical power change, and linear response range through dynamic measurement. The application of this theoretical model to the study of a fiber-optic microphone for acoustic pressure detection is considered.

  5. Detection of amplitude modulation with squeezed light for sensitivity beyond the shot-noise limit

    NASA Astrophysics Data System (ADS)

    Xiao, Min; Wu, Ling-An; Kimble, H. J.

    1988-06-01

    An improvement in precision beyond the limit set by the vacuum-state or zero-point fluctuations of the electromagnetic field is reported for the detection of amplitude modulation encoded on a weak signal beam. The improvement is achieved by employing the squeezed light from an optical parametric oscillator to reduce the level of fluctuations below the shot-noise limit. An increase in signal-to-noise ratio of 2.5 dB relative to the shot-noise limit is demonstrated.

  6. Depth limitations for in vivo magnetic nanoparticle detection with a compact handheld device

    NASA Astrophysics Data System (ADS)

    Visscher, Martijn; Waanders, Sebastiaan; Pouw, Joost; ten Haken, Bennie

    2015-04-01

    The increasing interest for local detection of magnetic nanoparticles (MNPs) during clinical interventions requires the development of suitable probes that unambiguously detect the MNPs at a depth of several centimeters in the body. The present study quantitatively evaluates the limitations of a conventional magnetometry method using a sinusoidal alternating field. This method is limited by the variability of the magnetic susceptibility of the surrounding diamagnetic tissue. Two different sensors are evaluated in a theoretical model of MNP detection in a tissue volume. For a coil that completely encloses the sample volume, the MNPs can be detected if the total mass contributing to the signal is larger than 4.1 ×10-7 times the tissue mass. For a handheld surface coil, intended to search for the MNPs in a larger tissue volume, an amount of 1 μg of iron oxide cannot be detected by sensors with a diameter larger than 15 mm. To detect a spot with MNPs at 5 cm depth in tissue, it should contain at least 325 μg iron oxide. Therefore, for high-sensitive clinical MNP detection in surgical interventions, techniques with increased specificity for the nonlinear magnetic properties of MNPs are indispensable.

  7. The detection limits of antimicrobial agents in cow's milk by a simple Yoghurt Culture Test.

    PubMed

    Mohsenzadeh, M; Bahrainipour, A

    2008-09-15

    The aim of this study was to study performance of Yoghurt Culture Test (YCT) in the detection of antimicrobial residues in milk. For this purpose, the sensitivity of YCT for 15 antibiotics were determined. For each drug, 8 concentrations were tested. The detection limits of YCT at 2.5 h and 4 h incubation were determined (microg kg(-1)): 15 and 37.5, penicillin G; 4 and 5, ampicillin; 5 and 7.5, amoxycillin; 100 and 200, cephalexin; 80 and 100, cefazoline; 100 and 200, oxytetracycline; 500 and 100, chlortetracycline; 100 and 200, tetracycline; 150 and 200, doxycycline; 200 and 400, sulphadimidine; 500 and 1000, gentamycin; 1000 and 1500, spectinomycin; 400 and 500, erythromycin; 50 and 100, tylosin; 5000 and 10000, chloramphenicol. The YCT detection limits at 2.5 h incubation for ampicillin, cephalexin, tetracycline, oxytetracycline and tylosin are similar to those obtained as Maximum Residue Limit (MRL) according to Regulation 2377/90 EEC as set out by the European Union. In addition the detection limits of YCT for some antibiotics were lower than some of microbial inhibitor test.

  8. Sub-ppt detection limits for copper ions with Gly-Gly-His modified electrodes.

    PubMed

    Yang, W; Jaramillo, D; Gooding, J J; Hibbert, D B; Zhang, R; Willett, G D; Fisher, K J

    2001-10-07

    An electrochemical metal ion sensor has been developed with a detection limit of less than 0.2 ppt by the covalent attachment of the tripeptide Gly-Gly-His as a recognition element to a 3-mercaptopropionic acid modified gold electrode.

  9. ROBUST ESTIMATION OF MEAN AND VARIANCE USING ENVIRONMENTAL DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS

    EPA Science Inventory

    Scientists, especially environmental scientists often encounter trace level concentrations that are typically reported as less than a certain limit of detection, L. Type 1, left-censored data arise when certain low values lying below L are ignored or unknown as they cannot be mea...

  10. ROBUST ESTIMATION OF MEAN AND VARIANCE USING ENVIRONMENTAL DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS

    EPA Science Inventory

    Scientists, especially environmental scientists often encounter trace level concentrations that are typically reported as less than a certain limit of detection, L. Type 1, left-censored data arise when certain low values lying below L are ignored or unknown as they cannot be mea...

  11. Approaches to Improving the Lower Detection Limit of Polymeric Membrane Ion-Selective Electrodes

    PubMed Central

    Szigeti, Zsófia; Vigassy, Tamás; Bakker, Eric; Pretsch, Ernö

    2010-01-01

    More than ten different approaches for improving the lower detection limit of polymeric membrane ion-selective electrodes have been suggested during the recent years. In this contribution, their principles are briefly summarized with a focus to their general practical applicability. The methods that are the most rugged and the easiest to implement in a routine laboratory will be highlighted. PMID:20336172

  12. Detection limits of organochlorine pesticides and related compounds in blood serum

    SciTech Connect

    Wolff, M.S.; Rivera, M.; Baker, D.B. )

    1991-10-01

    Determinations of organochlorine pesticides and similar chemical residues in blood serum have often reported detection limits of 1 ng/mL. When a study group has incurred body burdens lower than this, underestimates and misclassifications of exposure may occur because persons with pesticide residue concentration below the limit of detection are usually treated as zeros.' Thus in order to more accurately assess exposures in such populations, analysis of adipose tissue has been done. Recently, with TCDD, use of a sufficient volume of serum, as much as 0.5 L, in conjunction with appropriate analytical techniques has been shown to achieve detection limits necessary for epidemiological assessments, i.e., comparable to analysis of adipose tissue. In a population-based study involving children in which the authors were involved, it was not feasible to obtain specimens of either adipose or a large volume of serum. There was no compelling health motivation for such measures, nor did they wish to impair participation rates. Therefore, they chose to optimize the existing serum analysis, in order to achieve a detection limit low enough to assess reasonably the anticipated exposures.

  13. Detection limits of antimicrobials in ewe milk by delvotest photometric measurements.

    PubMed

    Althaus, R L; Torres, A; Montero, A; Balasch, S; Molina, M P

    2003-02-01

    The Delvotest method detection limits per manufacturer's instructions at a fixed reading time of 3 h for 24 antimicrobial agents were determined in ewe milk by photometric measurement. For each drug, eight concentrations were tested on 20 ewe milk samples from individual ewes. Detection limits, determined by means of logistic regression models, were (microg/kg): 3, amoxycillin; 2, ampicillin; 18, cloxacillin; 1, penicillin "G"; 34, cefadroxil; 430, cephalosporin "C"; 40, cephalexin; 20, cefoperazone; 33, Ceftiofur; 18, cefuroxime; 6100, streptomycin; 1200, gentamycin; 2600, neomycin; 830, erythromycin; 100, tylosin; 180, doxycycline; 320, oxytetracycline; 590, tetracycline; 88, sulfadiazine; 44, sulfamethoxazole; 140, sulfametoxypyridazine; 48, sulfaquinoxaline; 12,000, chloramphenicol; and 290, trimethoprim. Whereas the beta-lactam antibiotics, sulphonamides, and tylosin were detected by Delvotest method at levels equal to those of maximum residue limits, its sensitivity needs to be enhanced to detect aminoglycosides, tetracyclines, streptomycin, chloramphenicol, and trimethoprim residues in ewe milk or to develop an integrated residue detection system for ewe milk with different sensitive microorganisms for each group of antiinfectious agents.

  14. LED-based UV absorption detector with low detection limits for capillary liquid chromatography.

    PubMed

    Sharma, Sonika; Tolley, H Dennis; Farnsworth, Paul B; Lee, Milton L

    2015-01-20

    A 260 nm deep UV LED-based absorption detector with low detection limits was developed and integrated with a small nanoflow pumping system. The detector is small in size (5.2 × 3.0 cm) and weighs only 85 g (without electronics). This detector was specifically designed and optimized for on-column detection to minimize extra-column band broadening. No optical reference was included due to the low drift in the signal. Two ball lenses, one of which was integrated with the LED, were used to increase light throughput through the capillary column. Stray light was minimized by the use of a band-pass filter and an adjustable slit. Signals down to the parts per billion level (nanomolar) were easily detected with a short-term noise level of 4.4 μAU, confirming a low limit of detection and low noise. The detection limit for adenosine-5'-monophosphate was 230 times lower than any previously reported values. Good linearities (3 orders of magnitude) were obtained using sodium anthraquinone-2-sulfonate, adenosine-5'-monophosphate, dl-tryptophan, and phenol. The LC system was demonstrated by performing isocratic separation of phenolic compounds using a monolithic capillary column (16.5 cm × 150 μm i.d.) synthesized from poly(ethylene glycol) diacrylate.

  15. Theoretical detection limits of magnetic biobarcode sensors and the phase space of nanobiosensing.

    PubMed

    Nair, Pradeep R; Alam, Muhammad A

    2010-11-01

    A scaling theory of the sub atto-molar (aM) detection limits of magnetic particle (MP) based biosensors (e.g., bio-barcode assays) is developed and discussed. Despite the dramatic differences of sensing protocols and detection limits, the MP-based sensors can be interpreted within the same theoretical framework as any other classical biosensor (e.g., nanowire sensors), except that these sensors are differentiated by the geometry of diffusion and the probe (ρ(MP))/target (ρ(T)) density ratio. Our model predicts two regimes for biomolecule detection: For classical biosensors with ρ(MP) ≤ ρ(T), the response time t(s) proportional to 1/ρ(T); while for MP-based biosensors with ρ(MP) > ρ(T), t(s) proportional to 1/ρ(MP). The theory (i) explains the performance improvement of MP-sensors by ρ(MP)/ρ(T) (order of 10(3)-10(6)), broadly validating the sub-aM detection limits reported in literature, (ii) offers intuitive interpretation for the counter-intuitive ρ(T)-independence of detection time in MP-sensors, (iii) shows that statistical fluctuations should reduce with ρ(T) for MP sensors, and (iv) offers obvious routes to sensitivity improvement of classical sensors.

  16. Detection limit of Clostridium botulinum spores in dried mushroom samples sourced from China.

    PubMed

    Malakar, Pradeep K; Plowman, June; Aldus, Clare F; Xing, Zengtao; Zhao, Yong; Peck, Michael W

    2013-08-16

    A survey of dried mushrooms (Lentinula edodes (Shiitake) and Auricularia auricula (Wood Ear)) sourced from China was carried out to determine the natural contamination of these mushrooms with spores of proteolytic Clostridium botulinum and non-proteolytic C. botulinum. The mushrooms were collected from supermarkets and retailers in 21 cities in China during October 2008. Spore loads of C. botulinum in mushrooms have a degree of uncertainty and variability and this study contributes valuable data for determining prevalence of spores of C. botulinum in mushrooms. An optimized detection protocol that combined selective enrichment culture with multiplex PCR was used to test for spores of proteolytic and non-proteolytic C. botulinum. Detection limits were calculated, using a maximum likelihood protocol, from mushroom samples inoculated with defined numbers of spores of proteolytic C. botulinum or non-proteolytic C. botulinum. Based on the maximum likelihood detection limit, it is estimated that dried mushroom A. auricula contained <550spores/kg of proteolytic C. botulinum, and <350spores/kg of non-proteolytic C. botulinum. Dried L. edodes contained <1500spores/kg of proteolytic C. botulinum and it was not possible to determine reliable detection limits for spores of non-proteolytic C. botulinum using the current detection protocol.

  17. The limitations of case-control studies in the detection of environmental carcinogens.

    PubMed Central

    Crombie, I K

    1981-01-01

    The ability of the case-control study to detect human carcinogens has been investigated theoretically for varying fractions of the population exposed to hazards carrying different relative risks. The method is shown to be useful for the investigation of factors to which exposure is widespread (for example, common foods or beverages) but it is of limited use for the study of uncommon types of exposure, such as those associated with occupation. The case-control study is unable to detect very small relative risks (less than 1.5) even where exposure is widespread and large numbers of cases of cancer are occurring in the population. The principal limitation of the method is the maximum number of cases which can be recruited and analysed. It will only be through large-scale collaborative multicentre or international studies that important risk factors will be detected. PMID:7338704

  18. Enhancement of the detection limit for lateral flow immunoassays: evaluation and comparison of bioconjugates.

    PubMed

    Linares, Elisângela M; Kubota, Lauro T; Michaelis, Jens; Thalhammer, Stefan

    2012-01-31

    There is an increasing demand for convenient and accurate point-of-care tools that can detect and diagnose different stages of a disease in remote or impoverished settings. In recent years, lateral flow immunoassays (LFIA) have been indicated as a suitable medical diagnostic tool for these environments because they require little or no sample preparation, provide rapid and reliable results with no electronic components and thus can be manufactured at low costs and operated by unskilled personnel. However, even though they have been successfully applied to acute and chronic disease detection, LFIA based on gold nanoparticles, the standard marker, show serious limitations when high sensitivity is needed, such as early stage disease detection. Moreover, based on the lack of comparative information for label performance, significant optimization of the systems that are currently in use might be possible. To this end, in the presented work, we compare the detection limit between the four most used labels: colloidal-gold, silver enhanced gold, blue latex bead and carbon black nanoparticles. Preliminary results were obtained by using the biotin-streptavidin coupling as a model system and showed that carbon black had a remarkably low detection limit of 0.01 μg/mL in comparison to 0.1 μg/mL, 1 μg/mL and 1mg/mL for silver-coated gold nanoparticles, gold nanoparticles and polystyrene beads, respectively. Therefore, as a proof of concept, carbon black was used in a detection system for Dengue fever. This was achieved by immobilizing monoclonal antibodies for the nonstructural glycoprotein (NS1) of the Dengue virus to carbon black. We found that the colorimetric detection limit of 57 ng/mL for carbon black was ten times lower than the 575 ng/mL observed for standard gold nanoparticles; which makes it sensitive enough to diagnose a patient on the first days of infection. We therefore conclude that, careful screening of detection labels should be performed as a necessary step

  19. Accounting for Limited Detection Efficiency and Localization Precision in Cluster Analysis in Single Molecule Localization Microscopy

    PubMed Central

    Shivanandan, Arun; Unnikrishnan, Jayakrishnan; Radenovic, Aleksandra

    2015-01-01

    Single Molecule Localization Microscopy techniques like PhotoActivated Localization Microscopy, with their sub-diffraction limit spatial resolution, have been popularly used to characterize the spatial organization of membrane proteins, by means of quantitative cluster analysis. However, such quantitative studies remain challenged by the techniques’ inherent sources of errors such as a limited detection efficiency of less than 60%, due to incomplete photo-conversion, and a limited localization precision in the range of 10 – 30nm, varying across the detected molecules, mainly depending on the number of photons collected from each. We provide analytical methods to estimate the effect of these errors in cluster analysis and to correct for them. These methods, based on the Ripley’s L(r) – r or Pair Correlation Function popularly used by the community, can facilitate potentially breakthrough results in quantitative biology by providing a more accurate and precise quantification of protein spatial organization. PMID:25794150

  20. Determination of target detection limits in hyperspectral data using band selection and dimensionality reduction

    NASA Astrophysics Data System (ADS)

    Gross, W.; Boehler, J.; Twizer, K.; Kedem, B.; Lenz, A.; Kneubuehler, M.; Wellig, P.; Oechslin, R.; Schilling, H.; Rotman, S.; Middelmann, W.

    2016-10-01

    Hyperspectral remote sensing data can be used for civil and military applications to robustly detect and classify target objects. High spectral resolution of hyperspectral data can compensate for the comparatively low spatial resolution, which allows for detection and classification of small targets, even below image resolution. Hyperspectral data sets are prone to considerable spectral redundancy, affecting and limiting data processing and algorithm performance. As a consequence, data reduction strategies become increasingly important, especially in view of near-real-time data analysis. The goal of this paper is to analyze different strategies for hyperspectral band selection algorithms and their effect on subpixel classification for different target and background materials. Airborne hyperspectral data is used in combination with linear target simulation procedures to create a representative amount of target-to-background ratios for evaluation of detection limits. Data from two different airborne hyperspectral sensors, AISA Eagle and Hawk, are used to evaluate transferability of band selection when using different sensors. The same target objects were recorded to compare the calculated detection limits. To determine subpixel classification results, pure pixels from the target materials are extracted and used to simulate mixed pixels with selected background materials. Target signatures are linearly combined with different background materials in varying ratios. The commonly used classification algorithms Adaptive Coherence Estimator (ACE) is used to compare the detection limit for the original data with several band selection and data reduction strategies. The evaluation of the classification results is done by assuming a fixed false alarm ratio and calculating the mean target-to-background ratio of correctly detected pixels. The results allow drawing conclusions about specific band combinations for certain target and background combinations. Additionally

  1. Detection limits of the strip test and PCR for genetically modified corn in Brazil.

    PubMed

    Nascimento, V E; Von Pinho, É V R; Von Pinho, R G; do Nascimento, A D

    2012-08-16

    Brazilian legislation establishes a labeling limit for products that contain more than 1% material from genetically modified organisms (GMOs). We assessed the sensitivity of the lateral flow strip test in detection of the GMO corn varieties Bt11 and MON810 and the specificity and sensitivity of PCR techniques for their detection. For the strip test, the GMO seeds were mixed with conventional seeds at levels of 0.2, 0.4 and 0.8% for Bt11, and 0.4, 0.8 and 1.6% for MON810. Three different methodologies were assessed and whole seeds, their endosperm and embryonic axis were used. For the PCR technique, the GMO seeds of each of the two varieties were mixed with conventional seeds at levels of 20, 10, 5, 2, 1, and 0.5%. The seeds were ground and the DNA extracted. For detection of the GMO material, specific primers were used for MON810 and Bt11 and maize zein as an endogenous control. The sensitivity of the strip test varied for both maize varieties and methodologies. The test was positive for Bt11 only at 0.8%, in contrast with the detection limit of 0.4% indicated by the manufacturer. In the multiplex PCR, the primers proved to be specific for the different varieties. These varieties were detected in samples with one GMO seed in 100. Thus, this technique proved to be efficient in detecting contaminations equal to or greater than 1%.

  2. Inclusivity, exclusivity and limit of detection of commercially available real-time PCR assays for the detection of Salmonella.

    PubMed

    Margot, H; Stephan, R; Guarino, S; Jagadeesan, B; Chilton, D; O'Mahony, E; Iversen, C

    2013-08-01

    The traditional cultural detection of Salmonella spp. is both time- and labour-intensive. Salmonella is often a release criterion for the food industry and time to result is therefore an important factor. Storage of finished products and raw materials can be costly and may adversely impact available shelf-life. The application of real-time PCR for the detection of Salmonella spp. in food samples enables a potential time-saving of up to four days. The advancement of real-time PCR coupled with the development of commercially available systems in different formats has made this technology accessible for laboratories in an industrial environment. Ideally these systems are reliable and rapid as well as easy to use. The current study represents a comparative evaluation of seven commercial real-time PCR systems for the detection of Salmonella. Forty-nine target and twenty-nine non-target strains were included in the study to assess inclusivity and exclusivity. The limit of detection for each of the method was determined in four different food products. All systems evaluated were able to correctly identify the 49 Salmonella strains. Nevertheless, false positive results (Citrobacter spp.) were obtained with four of the seven systems. In milk powder and bouillon powder, the limit of detection was similar for all systems, suggesting a minimal matrix effect with these samples. Conversely, for black tea and cocoa powder some systems were prone to inhibition from matrix components. Up to 100% of the samples were inhibited using the proprietary extracts but inhibition could be reduced considerably by application of a DNA clean-up kit.

  3. Signal averaging limitations in heterodyne- and direct-detection laser remote sensing measurements

    NASA Technical Reports Server (NTRS)

    Menyuk, N.; Killinger, D. K.; Menyuk, C. R.

    1983-01-01

    The improvement in measurement uncertainty brought about by the averaging of increasing numbers of pulse return signals in both heterodyne- and direct-detection lidar systems is investigated. A theoretical analysis is presented which shows the standard deviation of the mean measurement to decrease as the inverse square root of the number of measurements, except in the presence of temporal correlation. Experimental measurements based on a dual-hybrid-TEA CO2 laser differential absorption lidar system are reported which demonstrate that the actual reduction in the standard deviation of the mean in both heterodyne- and direct-detection systems is much slower than the inverse square-root dependence predicted for uncorrelated signals, but is in agreement with predictions in the event of temporal correlation. Results thus favor the use of direct detection at relatively short range where the lower limit of the standard deviation of the mean is about 2 percent, but advantages of heterodyne detection at longer ranges are noted.

  4. In-depth Evaluation of Content-Based Phishing Detection to Clarify Its Strengths and Limitations

    NASA Astrophysics Data System (ADS)

    Komiyama, Koichiro; Seko, Toshinori; Ichinose, Yusuke; Kato, Kei; Kawano, Kohei; Yoshiura, Hiroshi

    Zhang et al. proposed a method for content-based phishing detection (CBD) and reported its high performance in detecting phishing sites written in English. However, the evaluations of the CBD method performed by Zhang et al. and others were small-scale and simply measured the detection and error rates, i.e, they did not analyze the causes of the detection errors. Moreover, the effectiveness of the CBD method with non-English sites, such as Japanese and Chinese language sites, has never been tested. This paper reports our in-depth evaluation and analysis of the CBD method using 843 actual phishing sites (including 475 English and 368 Japanese sites), and explains both the strengths of the CBD method and its limitations. Our work provides a base for using the CBD method in the real world.

  5. Gold nanoparticle-based low limit of detection Love wave biosensor for carcinoembryonic antigens.

    PubMed

    Li, Shuangming; Wan, Ying; Su, Yan; Fan, Chunhai; Bhethanabotla, Venkat R

    2017-09-15

    In this work, a Love wave biosensing platform is described for detecting cancer-related biomarker carcinoembryonic antigen (CEA). An ST 90°-X quartz Love wave device with a layer of SiO2 waveguide was combined with gold nanoparticles (Au NPs) to amplify the mass loading effect of the acoustic wave sensor to achieve a limit of detection of 37pg/mL. The strategy involves modifying the Au NPs with anti-CEA antibody conjugates to form nanoprobes in a sandwich immunoassay. The unamplified detection limit of the Love wave biosensor is 9.4ng/mL. This 2-3 order of magnitude reduction in the limit of detection brings the SAW platform into the range useful for clinical diagnosis. Measurement electronics and microfluidics are easily constructed for acoustic wave biosensors, such as the Love wave device described here, allowing for robust platforms for point of care applications for cancer biomarkers in general. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Detection limits can influence the interpretation of pesticide monitoring data in Canadian surface waters.

    PubMed

    de Solla, Shane R; Struger, John; McDaniel, Tana V

    2012-02-01

    Water quality monitoring programs rely on residue data that are frequently left censored, due to some observations occurring below the Method Detection Limit (MDL). Our objective was to determine the influence the MDL has on the interpretation of pesticide residues in surface waters. Water samples from tributaries in southern and central Ontario were collected by Environment Canada from 2003 to 2008 and were analyzed for 27 pesticides, with MDLs that averaged 7.02 ng(-1) L (range 0.39-25.1 ng(-1) L). We then simulated MDLs ranging from 25 to 1700 ng(-1) L, to determine the impact this would have on the reporting of pesticide concentrations and detections. The mean number of pesticides detected simultaneously declined with increasing, i.e. less sensitive MDLs, from 5.02 pesticides (native MDL) to 0.08 pesticides detected (MDL<1700 ng(-1) L). We compared the proportion of sites where pesticides were detected in surface waters under five MDL scenarios for 13 selected pesticides. The proportions decreased sharply with increasing MDLs. We calculated detection probabilities in an effort to compensate for higher MDLs using maximum likelihood; while adjusting for detection probabilities generally improved estimates of the presence of pesticides, as the MDLs increased the ability to compensate for detection probabilities deteriorated and became unviable at high MDLs. Depending on the method of substitution for observations below MDL (replacement with ½ × or 0 × MDL), the mean and median pesticide residues became increasingly over- and underestimated, respectively, at higher MDLs. Although monitoring programs that are focused on exceedences of water quality guidelines may not require low MDLs, the achievable goals of monitoring programs oriented towards other ecological and toxicological objectives may be limited by higher MDLs.

  7. Demonstration of Shot-noise-limited Swept Source OCT Without Balanced Detection.

    PubMed

    Fathipour, Vala; Schmoll, Tilman; Bonakdar, Alireza; Wheaton, Skylar; Mohseni, Hooman

    2017-04-26

    Optical coherence tomography (OCT) has been utilized in a rapidly growing number of clinical and scientific applications. In particular, swept source OCT (SS-OCT) has attracted many attentions due to its excellent performance. So far however, the limitations of existing photon detectors have prevented achieving shot-noise-limited sensitivity without using balanced-detection scheme in SS-OCT, even when superconducting single-photon detectors were used. Unfortunately, balanced-detection increases OCT system size and cost, as it requires many additional components to boost the laser power and maintain near ideal balanced performance across the whole optical bandwidth. Here we show for the first time that a photon detector is capable of achieving shot noise limited performance without using the balanced-detection technique in SS-OCT. We built a system using a so-called electron-injection photodetector, with a cutoff-wavelength of 1700 nm. Our system achieves a shot-noise-limited sensitivity of about -105 dB at a reference laser power of ~350 nW, which is more than 30 times lower laser power compared with the best-reported results. The high sensitivity of the electron-injection detector allows utilization of micron-scale tunable laser sources (e.g. VCSEL) and eliminates the need for fiber amplifiers and highly precise couplers, which are an essential part of the conventional SS-OCT systems.

  8. Advantages, limitations, and diagnostic accuracy of photoscreeners in early detection of amblyopia: a review

    PubMed Central

    Sanchez, Irene; Ortiz-Toquero, Sara; Martin, Raul; de Juan, Victoria

    2016-01-01

    Amblyopia detection is important to ensure proper visual development and avoid permanent decrease of visual acuity. This condition does not produce symptoms, so it is difficult to diagnose if a vision problem actually exists. However, because amblyopia treatment is limited by age, early diagnosis is of paramount relevance. Traditional vision screening (conducted in <3 years) is related with difficulty in getting cooperation from a subject to conduct the eye exam, so accurate objective methods to improve amblyopia detection are necessary. Handheld devices used for photoscreening or autorefraction could offer advantages to improve amblyopia screening because they reduce exploration time to just few seconds, no subject collaboration is needed, and they provide objective information. The purpose of this review is to summarize the main functions and clinical applicability of commercially available devices for early detection of amblyopia and to describe their differences, advantages, and limitations. Although the studies reviewed are heterogeneous (due to wide differences in referral criteria, use of different risk factors, different types of samples studied, etc), these devices provide objective measures in a quick and objective way with a simple outcome report: retest, pass, or refer. However, due to major limitations, these devices are not recommended, and their use in clinical practice is limited. PMID:27555744

  9. Finite-size analysis of the detectability limit of the stochastic block model

    NASA Astrophysics Data System (ADS)

    Young, Jean-Gabriel; Desrosiers, Patrick; Hébert-Dufresne, Laurent; Laurence, Edward; Dubé, Louis J.

    2017-06-01

    It has been shown in recent years that the stochastic block model is sometimes undetectable in the sparse limit, i.e., that no algorithm can identify a partition correlated with the partition used to generate an instance, if the instance is sparse enough and infinitely large. In this contribution, we treat the finite case explicitly, using arguments drawn from information theory and statistics. We give a necessary condition for finite-size detectability in the general SBM. We then distinguish the concept of average detectability from the concept of instance-by-instance detectability and give explicit formulas for both definitions. Using these formulas, we prove that there exist large equivalence classes of parameters, where widely different network ensembles are equally detectable with respect to our definitions of detectability. In an extensive case study, we investigate the finite-size detectability of a simplified variant of the SBM, which encompasses a number of important models as special cases. These models include the symmetric SBM, the planted coloring model, and more exotic SBMs not previously studied. We conclude with three appendices, where we study the interplay of noise and detectability, establish a connection between our information-theoretic approach and random matrix theory, and provide proofs of some of the more technical results.

  10. Minimum detection limit and spatial resolution of thin-sample field-emission electron probe microanalysis.

    PubMed

    Kubo, Yugo; Hamada, Kotaro; Urano, Akira

    2013-12-01

    The minimum detection limit and spatial resolution for a thinned semiconductor sample were determined by electron probe microanalysis (EPMA) using a Schottky field emission (FE) electron gun and wavelength dispersive X-ray spectrometry. Comparison of the FE-EPMA results with those obtained using energy dispersive X-ray spectrometry in conjunction with scanning transmission electron microscopy, confirmed that FE-EPMA is largely superior in terms of detection sensitivity. Thin-sample FE-EPMA is demonstrated as a very effective method for high resolution, high sensitivity analysis in a laboratory environment because a high probe current and high signal-to-noise ratio can be achieved.

  11. Improving the sensitivity limit of surface plasmon resonance biosensors by detecting mixed interference signals

    NASA Astrophysics Data System (ADS)

    Yuan, W.; Ho, H. P.; Suen, Y. K.; Kong, S. K.; Lin, Chinlon

    2007-11-01

    We demonstrate that the sensitivity limit of intensity-based surface plasmon resonance (SPR) biosensors can be enhanced when we combine the effects of the phase and amplitude contributions instead of detecting the amplitude variation only. Experimental results indicate that an enhancement factor of as much as 20 times is achievable, yet with no compromise in measurement dynamic range. While existing SPR biosensor systems are predominantly based on the angular scheme, which relies on detecting intensity variations associated with amplitude changes only, the proposed scheme may serve as a direct system upgrade approach for these systems. The new measurement scheme may therefore lead to a strong impact in the design of SPR biosensors.

  12. Detecting single nanomagnet dynamics beyond the diffraction limit in varying magnetostatic environments

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Brandt, R.; Yahagi, Y.; Hansen, B.; Harteneck, B.; Bokor, J.; Hawkins, A. R.; Schmidt, H.

    2011-01-01

    As areal bit density increases, characterizing individual magnetic bits within dense arrays becomes difficult with diffraction-limited optics. We demonstrate that dynamic magneto-optical detection breaks this diffraction limit if the characteristic behavior of a nanomagnet is sufficiently different from its neighbors'. We use far-field time-resolved Kerr microscopy to resolve the high-frequency magnetization dynamics of a single, small (Ø150 nm) nanomagnet within a low-frequency background from an array of large (Ø500 nm) magnets. We use this technique to observe and quantify the effects of magnetostatic interactions on the single magnet dynamics as the intermagnet spacing is varied.

  13. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  14. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  15. A real-time RT-PCR assay for detection and absolute quantitation of Citrus tristeza virus in different plant tissues.

    PubMed

    Ruiz-Ruiz, Susana; Moreno, Pedro; Guerri, José; Ambrós, Silvia

    2007-11-01

    A real-time RT-PCR assay using SYBR Green was developed for specific and reliable quantitative detection of Citrus tristeza virus (CTV) in infected plants. A general primer set designed from conserved sequences in ORFs 1b and 2 enabled amplification of the genomic RNA (gRNA) while excluding most subgenomic and defective RNAs. Single RT-PCR products of 204 bp (isolate T36) or 186 bp (other isolates) were obtained with no primer-dimer or non-specific amplifications detected. Melting curve analysis revealed distinct melting temperature peaks (T(m)) for severe and mild isolates. External standard curves using RNA transcripts of the selected target allowed a reproducible quantitative assay, with a wide dynamic range of detection starting with 10(2) gRNA copies and with very low variation coefficient values. This protocol enabled reliable assessments of CTV accumulation in different tissues and from different citrus species, grown in the greenhouse or under field conditions, and infected with CTV isolates differing in their pathogenicity. CTV accumulation was higher in bark and fruits than in roots or leaves and showed minimal differences among several susceptible citrus species, but it was significantly lower in sour orange. This quantitative detection assay will be a valuable tool for diagnosis and molecular studies on CTV biology.

  16. Method for improving the limit of detection in a data signal

    DOEpatents

    Synovec, R.E.; Yueng, E.S.

    1989-10-17

    Disclosed is a method for improving the limit of detection for a data set in which experimental noise is uncorrelated along a given abscissa and an analytical signal is correlated to the abscissa, the steps comprising collecting the data set, converting the data set into a data signal including an analytical portion and the experimental noise portion, designating and adjusting a baseline of the data signal to center the experimental noise numerically about a zero reference, and integrating the data signal preserving the corresponding information for each point of the data signal. The steps of the method produce an enhanced integrated data signal which improves the limit of detection of the data signal. 8 figs.

  17. VizieR Online Data Catalog: SAM detection limits of 8 debris disks (Gauchet+, 2016)

    NASA Astrophysics Data System (ADS)

    Gauchet, L.; Lacour, S.; Lagrange, A.-M.; Ehrenreich, D.; Bonnefoy, M.; Girard, J. H.; Boccaletti, A.

    2016-06-01

    VLT/NaCo Sparse Aperture Masking data for 8 debris disks in Lprime spectral band (λ=3.80um, Δλ=0.62um). The stars hosting debris disks observed are: β Pictoris, AU Microscopii, 49 Ceti, {eta} Telescopii, Fomalhaut, g Lupi, HD181327 and HR8799 (with respective calibrator: HR2049, HD197339, HD10100, HD181517, del PsA, HD139960, HD180987, HD218234). No companion were found in the observational data. For each star, we have processed a 5σ detection limit map of the neighbourhood of the star. The primary array of each fits file contains a 237x237 pixel image representing a 900x900 mas portion of the sky plane (i.e. 3mas/pixel). The center of the array correspond to the location of the main star. Detection limit values are stated in relative magnitude compared to that of the main star. (2 data files).

  18. Indirect dark matter detection limits from the ultrafaint Milky Way satellite Segue 1

    NASA Astrophysics Data System (ADS)

    Essig, Rouven; Sehgal, Neelima; Strigari, Louis E.; Geha, Marla; Simon, Joshua D.

    2010-12-01

    We use new kinematic data from the ultrafaint Milky Way satellite Segue 1 to model its dark matter distribution and derive upper limits on the dark matter annihilation cross section. Using gamma-ray flux upper limits from the Fermi satellite and MAGIC, we determine cross section exclusion regions for dark matter annihilation into a variety of different particles including charged leptons. We show that these exclusion regions are beginning to probe the regions of interest for a dark matter interpretation of the electron and positron fluxes from PAMELA, Fermi, and HESS, and that future observations of Segue 1 have strong prospects for testing such an interpretation. We additionally discuss prospects for detecting annihilation with neutrinos using the IceCube detector, finding that in an optimistic scenario a few neutrino events may be detected. Finally, we use the kinematic data to model the Segue 1 dark matter velocity dispersion and constrain Sommerfeld enhanced models.

  19. Flexible Modeling of Survival Data with Covariates Subject to Detection Limits via Multiple Imputation.

    PubMed

    Bernhardt, Paul W; Wang, Huixia Judy; Zhang, Daowen

    2014-01-01

    Models for survival data generally assume that covariates are fully observed. However, in medical studies it is not uncommon for biomarkers to be censored at known detection limits. A computationally-efficient multiple imputation procedure for modeling survival data with covariates subject to detection limits is proposed. This procedure is developed in the context of an accelerated failure time model with a flexible seminonparametric error distribution. The consistency and asymptotic normality of the multiple imputation estimator are established and a consistent variance estimator is provided. An iterative version of the proposed multiple imputation algorithm that approximates the EM algorithm for maximum likelihood is also suggested. Simulation studies demonstrate that the proposed multiple imputation methods work well while alternative methods lead to estimates that are either biased or more variable. The proposed methods are applied to analyze the dataset from a recently-conducted GenIMS study.

  20. Indirect Dark Matter Detection Limits from the Ultra-Faint Milky Way Satellite Segue 1

    SciTech Connect

    Essig, Rouven; Sehgal, Neelima; Strigari, Louis E.; Geha, Marla; Simon, Joshua D.; /Carnegie Inst. Observ.

    2011-08-11

    We use new kinematic data from the ultra-faint Milky Way satellite Segue 1 to model its dark matter distribution and derive upper limits on the dark matter annihilation cross-section. Using gamma-ray ux upper limits from the Fermi satellite and MAGIC, we determine cross-section exclusion regions for dark matter annihilation into a variety of different particles including charged leptons. We show that these exclusion regions are beginning to probe the regions of interest for a dark matter interpretation of the electron and positron uxes from PAMELA, Fermi, and HESS, and that future observations of Segue 1 have strong prospects for testing such an interpretation. We additionally discuss prospects for detecting annihilation with neutrinos using the IceCube detector, finding that in an optimistic scenario a few neutrino events may be detected. Finally we use the kinematic data to model the Segue 1 dark matter velocity dispersion and constrain Sommerfeld enhanced models.

  1. A distribution of tumor size at detection and its limiting form.

    PubMed Central

    Yakovlev, A Y; Hanin, L G; Rachev, S T; Tsodikov, A D

    1996-01-01

    A distribution of tumor size at detection is derived within the framework of a mechanistic model of carcinogenesis with the object of estimating biologically meaningful parameters of tumor latency. Its limiting form appears to be a generalization of the distribution that arises in the length-biased sampling from stationary point processes. The model renders the associated estimation problems tractable. The usefulness of the proposed approach is illustrated with an application to clinical data on premenopausal breast cancer. PMID:8692876

  2. Multi-species detection with dual-pump-CARS: Possibilities and limitations

    NASA Astrophysics Data System (ADS)

    Eichmann, S. C.; Gao, Y.; Weikl, M. C.; Beyrau, F.; Seeger, T.; Leipertz, A.

    Dual-pump coherent anti-Stokes Raman scattering is a promising measurement technique which can be used for combined temperature and multi-species detection in combustion diagnostics. Its application is demonstrated in various flames using different fuels often used as a reference in research laboratories. By means of these examples, the potential and limitations of dual-pump-CARS in combustion processes will be discussed.

  3. Investigation of detection limits for solutes in water measured by laser raman spectrometry

    USGS Publications Warehouse

    Goldberg, M.C.

    1977-01-01

    The influence of experimental parameters on detection sensitivity was determined for laser Raman analysis of dissolved solutes in water. Individual solutions of nitrate, sulfate, carbonate, bicarbonate, monohydrogen phosphate, dihydrogen phosphate, acetate ion, and acetic acid were measured. An equation is derived which expresses the signal-to-noise ratio in terms of solute concentration, measurement time, spectral slit width, laser power fluctuations, and solvent background intensity. Laser beam intensity fluctuations at the sample and solvent background intensity are the most important limiting factors.

  4. Detection limits of pollutants in water for PGNAA using Am Be source

    NASA Astrophysics Data System (ADS)

    Khelifi, R.; Amokrane, A.; Bode, P.

    2007-09-01

    A basic PGNAA facility with an Am-Be neutron source is described to analyze the pollutants in water. The properties of neutron flux were determined by MCNP calculations. In order to determine the efficiency curve of a HPGe detector, the prompt-gamma rays from chlorine were used and an exponential curve was fitted. The detection limits for typical water sample are also estimated using the statistical fluctuations of the background level in the areas of recorded the prompt-gamma spectrum.

  5. Photonic crystal enhanced fluorescence using a quartz substrate to reduce limits of detection

    PubMed Central

    Pokhriyal, Anusha; Lu, Meng; Chaudhery, Vikram; Huang, Cheng-Sheng; Schulz, Stephen; Cunningham, Brian T.

    2010-01-01

    A Photonic Crystal (PC) surface fabricated upon a quartz substrate using nanoimprint lithography has been demonstrated to enhance light emission from fluorescent molecules in close proximity to the PC surface. Quartz was selected for its low autofluorescence characteristics compared to polymer-based PCs, improving the detection sensitivity and signal-to-noise ratio (SNR) of PC Enhanced Fluorescence (PCEF). Nanoimprint lithography enables economical fabrication of the subwavelength PCEF surface structure over entire 1x3 in2 quartz slides. The demonstrated PCEF surface supports a transverse magnetic (TM) resonant mode at a wavelength of λ = 632.8 nm and an incident angle of θ = 11°, which amplifies the electric field magnitude experienced by surface-bound fluorophores. Meanwhile, another TM mode at a wavelength of λ = 690 nm and incident angle of θ = 0° efficiently directs the fluorescent emission toward the detection optics. An enhancement factor as high as 7500 × was achieved for the detection of LD-700 dye spin-coated upon the PC, compared to detecting the same material on an unpatterned glass surface. The detection of spotted Alexa-647 labeled polypeptide on the PC exhibits a 330 × SNR improvement. Using dose-response characterization of deposited fluorophore-tagged protein spots, the PCEF surface demonstrated a 140 × lower limit of detection compared to a conventional glass substrate. PMID:21164826

  6. Photonic crystal enhanced fluorescence using a quartz substrate to reduce limits of detection.

    PubMed

    Pokhriyal, Anusha; Lu, Meng; Chaudhery, Vikram; Huang, Cheng-Sheng; Schulz, Stephen; Cunningham, Brian T

    2010-11-22

    A Photonic Crystal (PC) surface fabricated upon a quartz substrate using nanoimprint lithography has been demonstrated to enhance light emission from fluorescent molecules in close proximity to the PC surface. Quartz was selected for its low autofluorescence characteristics compared to polymer-based PCs, improving the detection sensitivity and signal-to-noise ratio (SNR) of PC Enhanced Fluorescence (PCEF). Nanoimprint lithography enables economical fabrication of the subwavelength PCEF surface structure over entire 1x3 in2 quartz slides. The demonstrated PCEF surface supports a transverse magnetic (TM) resonant mode at a wavelength of λ = 632.8 nm and an incident angle of θ = 11°, which amplifies the electric field magnitude experienced by surface-bound fluorophores. Meanwhile, another TM mode at a wavelength of λ = 690 nm and incident angle of θ = 0° efficiently directs the fluorescent emission toward the detection optics. An enhancement factor as high as 7500 × was achieved for the detection of LD-700 dye spin-coated upon the PC, compared to detecting the same material on an unpatterned glass surface. The detection of spotted Alexa-647 labeled polypeptide on the PC exhibits a 330 × SNR improvement. Using dose-response characterization of deposited fluorophore-tagged protein spots, the PCEF surface demonstrated a 140 × lower limit of detection compared to a conventional glass substrate.

  7. Errors in the determination of the limits of detection using JEOL's electron microprobe interface.

    NASA Astrophysics Data System (ADS)

    Tonkacheev, Dmitry

    2017-04-01

    The first commercially available electron microprobe was made in the middle of XIX century. At the moment, this technique of determination of chemical composition of matter has a lot of applications in Geoscience, even in trace element analysis. During our work in the field of spectroscopy of minerals, it was necessary to determine the EPMA limits of detection for trace elements in sulphides. We measured several samples of synthetic sulfides (sphalerite, covellite) with the concentration of gold in the range from 15 to 5000 ppm using JEOL-JXA8200 in IGEM RAS and JEOL-JXA8230 in MSU equipped with energy-dispersive and 5 wavelength spectrometers, employing different crystals (PETH or LIFH), modes (integral or differential), acceleration voltage, counting time, and the beam size. We calculated the real limit of detection, using the equation from the EPMA JXA-8200 Manual and [Reed, 2000]. Our data did not correspond with the values appears on the screen after the analysis. The difference in estimation of the limits of detection between our and computer's data varies from 8 up to 13 times. We suggested that observed dissimilarity of the typed and the real values may be related to desire JEOL Ltd to promote devices for better selling. We are firmly recommend checking this values while performing the trace element analysis. References JEOL JXA8200 Manual Reed S.J.B. (2000) Quantitative trace analysis by wavelength-dispersive EPMA. Mikrochim. Acta 132 145-151.

  8. Rotating electrode potentiometry: lowering the detection limits of nonequilibrium polyion-sensitive membrane electrodes.

    PubMed

    Ye, Q; Meyerhoff, M E

    2001-01-15

    A rotating electrode configuration is evaluated as a means to lower the detection limits of newly devised polyion-sensitive membrane electrodes (PSEs). Planar potentiometric polycation and polyanion PSEs are prepared by incorporating tridodecylmethylammonium chloride and calcium dinonylnaphthalenesulfonate, respectively, into plasticized PVC or polyurethane membranes and mounting disks of such films on an electrode body housed in a conventional rotating disk electrode apparatus. Rotation of the PSEs at 5000 rpm results in an enhancement in the detection limits toward heparin (polyanion) and protamine (polycation) of at least 1 order of magnitude (to 0.01 unit/mL for heparin; 0.02 microg/mL for protamine) over that observed when the EMF responses of the same electrodes are assessed using a stir-bar to achieve convective mass transport. A linear relationship between omega(-1/2), where omega is the rotating angular frequency, and C1/2, the polyion concentration corresponding to half the total maximum deltaEMF response toward the polyion species, is observed. It is further shown that the rotating polycation sensor can be used as an end-point detector to greatly enhance (relative to nonrotated indicator electrode) the analytical resolution and precision for measurement of low concentrations of heparin when such samples are titrated with protamine. The theoretical basis for lowering the detection limits by rotating PSEs is discussed based on the unique nonequilibrium response mechanism of such sensors.

  9. Predictive inference for best linear combination of biomarkers subject to limits of detection.

    PubMed

    Coolen-Maturi, Tahani

    2017-08-15

    Measuring the accuracy of diagnostic tests is crucial in many application areas including medicine, machine learning and credit scoring. The receiver operating characteristic (ROC) curve is a useful tool to assess the ability of a diagnostic test to discriminate between two classes or groups. In practice, multiple diagnostic tests or biomarkers are combined to improve diagnostic accuracy. Often, biomarker measurements are undetectable either below or above the so-called limits of detection (LoD). In this paper, nonparametric predictive inference (NPI) for best linear combination of two or more biomarkers subject to limits of detection is presented. NPI is a frequentist statistical method that is explicitly aimed at using few modelling assumptions, enabled through the use of lower and upper probabilities to quantify uncertainty. The NPI lower and upper bounds for the ROC curve subject to limits of detection are derived, where the objective function to maximize is the area under the ROC curve. In addition, the paper discusses the effect of restriction on the linear combination's coefficients on the analysis. Examples are provided to illustrate the proposed method. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Passive cylindrical scan by unphased diffraction-limited antennas for low-cost concealed weapon detection

    NASA Astrophysics Data System (ADS)

    Serenelli, Roberto

    2005-05-01

    This paper analyzes a simple low-cost scan system for concealed weapon detection (CWD) on a cooperative subject. The passive imaging system is based on a cylindrical sensing geometry, realized by mechanical vertical scan of a horizontal circle, filled with many diffraction-limited antennas surrounding the subject, over the whole body height. This system is dimensioned to scan an ideally coaxial cylindrical subject of known radius with a fixed spatial resolution. Several system parameters influence the capability of anomaly detection: horizontal spatial resolution (constrained by diffraction limitations on the sensing circle), vertical spatial resolution and radiometric sensitivity (both related to vertical scan settings). Spatial resolution calculations are carried out in function of the working frequency, and achievable resolutions according to diffraction limitations are discussed. A qualitative and quantitative study is done to determine how high radiometric sensitivity (achievable with well-established commercial components) could overcome the poor spatial resolution related to low working frequencies, in view of dielectric anomaly detection; the optimal dwell time (giving a good radiometric/spatial resolution trade-off) is evaluated. Sub-pixel resolution capabilities are briefly considered, together with a least square matching criterium. Performance of an alternative configuration, consisting of a rotating vertical array, is derived from the circular system. Finally, the data fusion from both configurations is suggested.

  11. Radiometric Short-Term Fourier Transform analysis of photonic Doppler velocimetry recordings and detectivity limit

    NASA Astrophysics Data System (ADS)

    Prudhomme, G.; Berthe, L.; Bénier, J.; Bozier, O.; Mercier, P.

    2017-01-01

    Photonic Doppler Velocimetry is a plug-and-play and versatile diagnostic used in dynamic physic experiments to measure velocities. When signals are analyzed using a Short-Time Fourier Transform, multiple velocities can be distinguished: for example, the velocities of moving particle-cloud appear on spectrograms. In order to estimate the back-scattering fluxes of target, we propose an original approach "PDV Radiometric analysis" resulting in an expression of time-velocity spectrograms coded in power units. Experiments involving micron-sized particles raise the issue of detection limit; particle-size limit is very difficult to evaluate. From the quantification of noise sources, we derive an estimation of the spectrogram noise leading to a detectivity limit, which may be compared to the fraction of the incoming power which has been back-scattered by the particle and then collected by the probe. This fraction increases with their size. At last, some results from laser-shock accelerated particles using two different PDV systems are compared: it shows the improvement of detectivity with respect to the Effective Number of Bits (ENOB) of the digitizer.

  12. Evaluation on the detection limit of blood hemoglobin using photolepthysmography based on path-length optimization

    NASA Astrophysics Data System (ADS)

    Sun, Di; Guo, Chao; Zhang, Ziyang; Han, Tongshuai; Liu, Jin

    2016-10-01

    The blood hemoglobin concentration's (BHC) measurement using Photoplethysmography (PPG), which gets blood absorption to near infrared light from the instantaneous pulse of transmitted light intensity, has not been applied to the clinical use due to the non-enough precision. The main challenge might be caused of the non-enough stable pulse signal when it's very weak and it often varies in different human bodies or in the same body with different physiological states. We evaluated the detection limit of BHC using PPG as the measurement precision level, which can be considered as a best precision result because we got the relative stable subject's pulse signals recorded by using a spectrometer with high signal-to-noise ratio (SNR) level, which is about 30000:1 in short term. Moreover, we optimized the used pathlength using the theory based on optimum pathlength to get a better sensitivity to the absorption variation in blood. The best detection limit was evaluated as about 1 g/L for BHC, and the best SNR of pulse for in vivo measurement was about 2000:1 at 1130 and 1250 nm. Meanwhile, we conclude that the SNR of pulse signal should be better than 400:1 when the required detection limit is set to 5 g/L. Our result would be a good reference to the BHC measurement to get a desired BHC measurement precision of real application.

  13. Absolute-structure reports.

    PubMed

    Flack, Howard D

    2013-08-01

    All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.

  14. Microfluidic-SERS Devices for One Shot Limit-of-Detection

    PubMed Central

    Datt, Ashish; Gao, Zhe; Rycenga, Matthew; Burrows, Nathan D.; Greeneltch, Nathan G.; Mirkin, Chad A.; Murphy, Catherine J.; Van Duyne, Richard P.; Haynes, Christy L.

    2014-01-01

    Microfluidic sensing platforms facilitate parallel, low sample volume detection using various optical signal transduction mechanisms. Herein, we introduce a simple mixing microfluidic device, enabling serial dilution of introduced analyte solution that terminates in five discrete sensing elements. We demonstrate the utility of this device with on-chip fluorescence and surface-enhanced Raman scattering (SERS) detection of analytes, and we demonstrate device use both when combined with a traditional inflexible SERS substrate and with SERS-active nanoparticles that are directly incorporated into microfluidic channels to create a flexible SERS platform. The results indicate, with varying sensitivities, that either flexible or inflexible devices can be easily used to create a calibration curve and perform a limit of detection study with a single experiment. PMID:24756225

  15. Limitations in the spectral method for graph partitioning: Detectability threshold and localization of eigenvectors.

    PubMed

    Kawamoto, Tatsuro; Kabashima, Yoshiyuki

    2015-06-01

    Investigating the performance of different methods is a fundamental problem in graph partitioning. In this paper, we estimate the so-called detectability threshold for the spectral method with both un-normalized and normalized Laplacians in sparse graphs. The detectability threshold is the critical point at which the result of the spectral method is completely uncorrelated to the planted partition. We also analyze whether the localization of eigenvectors affects the partitioning performance in the detectable region. We use the replica method, which is often used in the field of spin-glass theory, and focus on the case of bisection. We show that the gap between the estimated threshold for the spectral method and the threshold obtained from Bayesian inference is considerable in sparse graphs, even without eigenvector localization. This gap closes in a dense limit.

  16. Limitations in the spectral method for graph partitioning: Detectability threshold and localization of eigenvectors

    NASA Astrophysics Data System (ADS)

    Kawamoto, Tatsuro; Kabashima, Yoshiyuki

    2015-06-01

    Investigating the performance of different methods is a fundamental problem in graph partitioning. In this paper, we estimate the so-called detectability threshold for the spectral method with both un-normalized and normalized Laplacians in sparse graphs. The detectability threshold is the critical point at which the result of the spectral method is completely uncorrelated to the planted partition. We also analyze whether the localization of eigenvectors affects the partitioning performance in the detectable region. We use the replica method, which is often used in the field of spin-glass theory, and focus on the case of bisection. We show that the gap between the estimated threshold for the spectral method and the threshold obtained from Bayesian inference is considerable in sparse graphs, even without eigenvector localization. This gap closes in a dense limit.

  17. A point-of-care PCR test for HIV-1 detection in resource-limited settings.

    PubMed

    Jangam, Sujit R; Agarwal, Abhishek K; Sur, Kunal; Kelso, David M

    2013-04-15

    A low-cost, fully integrated sample-to-answer, quantitative PCR (qPCR) system that can be used for detection of HIV-1 proviral DNA in infants at the point-of-care in resource-limited settings has been developed and tested. The system is based on a novel DNA extraction method, which uses a glass fiber membrane, a disposable assay card that includes on-board reagent storage, provisions for thermal cycling and fluorescence detection, and a battery-operated portable analyzer. The system is capable of automated PCR mix assembly using a novel reagent delivery system and performing qPCR. HIV-1 and internal control targets are detected using two spectrally separated fluorophores, FAM and Quasar 670. In this report, a proof-of-concept of the platform is demonstrated. Initial results with whole blood demonstrate that the test is capable of detecting HIV-1 in blood samples containing greater than 5000 copies of HIV-1. In resource-limited settings, a point-of-care HIV-1 qPCR test would greatly increase the number of test results that reach the infants caregivers, allowing them to pursue anti-retroviral therapy.

  18. Absolute determination of charge-coupled device quantum detection efficiency using Si K-edge x-ray absorption fine structure

    SciTech Connect

    Dunn, J; Steel, A B

    2012-05-06

    We report a method to determine the quantum detection efficiency and the absorbing layers on a front-illuminated charge-coupled device (CCD). The CCD under study, as part of a crystal spectrometer, measures intense continuum x-ray emission from a picosecond laser-produced plasma and spectrally resolves the Si K-edge x-ray absorption fine structure features due to the electrode gate structure of the device. The CCD response across the Si K-edge shows a large discontinuity as well as a number of oscillations that are identified individually and uniquely from Si, SiO{sub 2}, and Si{sub 3}N{sub 4} layers. From the spectral analysis of the structure and K-edge discontinuity, the active layer thickness and the different absorbing layers thickness can be determined precisely. A precise CCD detection model from 0.2-10 keV can be deduced from this highly sensitive technique.

  19. Detection limit of intragenic deletions with targeted array comparative genomic hybridization

    PubMed Central

    2013-01-01

    Background Pathogenic mutations range from single nucleotide changes to deletions or duplications that encompass a single exon to several genes. The use of gene-centric high-density array comparative genomic hybridization (aCGH) has revolutionized the detection of intragenic copy number variations. We implemented an exon-centric design of high-resolution aCGH to detect single- and multi-exon deletions and duplications in a large set of genes using the OGT 60 K and 180 K arrays. Here we describe the molecular characterization and breakpoint mapping of deletions at the smaller end of the detectable range in several genes using aCGH. Results The method initially implemented to detect single to multiple exon deletions, was able to detect deletions much smaller than anticipated. The selected deletions we describe vary in size, ranging from over 2 kb to as small as 12 base pairs. The smallest of these deletions are only detectable after careful manual review during data analysis. Suspected deletions smaller than the detection size for which the method was optimized, were rigorously followed up and confirmed with PCR-based investigations to uncover the true detection size limit of intragenic deletions with this technology. False-positive deletion calls often demonstrated single nucleotide changes or an insertion causing lower hybridization of probes demonstrating the sensitivity of aCGH. Conclusions With optimizing aCGH design and careful review process, aCGH can uncover intragenic deletions as small as dozen bases. These data provide insight that will help optimize probe coverage in array design and illustrate the true assay sensitivity. Mapping of the breakpoints confirms smaller deletions and contributes to the understanding of the mechanism behind these events. Our knowledge of the mutation spectra of several genes can be expected to change as previously unrecognized intragenic deletions are uncovered. PMID:24304607

  20. Understanding Detection Limits in Fluid Inclusion Analysis Using an Incremental Crush Fast Scan Method for Planetary Science

    NASA Astrophysics Data System (ADS)

    Blamey, N. J. F.; Parnell, J.; Longerich, H. P.

    2012-03-01

    We propose formulae for the determination of the detection and reporting limits applied to fluid inclusion volatile analysis, adapted from LA-ICP-MS formulae, and applicable to samples of limited size that are available in planetary science studies.

  1. Absolute quantum cutting efficiency of Tb3+-Yb3+ co-doped glass

    NASA Astrophysics Data System (ADS)

    Duan, Qianqian; Qin, Feng; Zhao, Hua; Zhang, Zhiguo; Cao, Wenwu

    2013-12-01

    The absolute quantum cutting efficiency of Tb3+-Yb3+ co-doped glass was quantitatively measured by an integrating sphere detection system, which is independent of the excitation power. As the Yb3+ concentration increases, the near infrared quantum efficiency exhibited an exponential growth with an upper limit of 13.5%, but the visible light efficiency was reduced rapidly. As a result, the total quantum efficiency monotonically decreases rather than increases as theory predicted. In fact, the absolute quantum efficiency was far less than the theoretical value due to the low radiative efficiency of Tb3+ (<61%) and significant cross-relaxation nonradiative loss between Yb3+ ions.

  2. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  3. Absolute Bioavailability of Tasimelteon.

    PubMed

    Torres, Rosarelis; Dressman, Marlene A; Kramer, William G; Baroldi, Paolo

    2015-01-01

    Tasimelteon is a novel dual melatonin receptor agonist and is the first treatment approved by the US Food and Drug Administration for Non-24-Hour Sleep-Wake Disorder. This study was conducted to assess the absolute bioavailability of tasimelteon and to further assess the single-dose pharmacokinetics, safety, and tolerability of oral and intravenous (IV) routes of administration of the drug. This study was an open-label, single-dose, randomized, 2-period, 2-treatment, 2-sequence, crossover study in which 14 healthy volunteers were randomly administered tasimelteon as either a 20-mg capsule or IV administration of 2 mg infused over 30 minutes. Each subject received both treatments in a random order, separated by a washout period of 5 ± 2 days. The total clearance and volume of distribution of tasimelteon, from the IV treatment, were 505 mL per minute and 42.7 L, respectively. Based on the statistical comparison of dose-corrected area under the curve to infinity, the absolute bioavailability was 38%, with a 90% confidence interval of 27%-54%. The mean elimination half-life was the same for the oral and IV routes. The exposure ratios, oral-to-IV, for metabolites M9, M11, M12, and M13, were 133.27%, 118.28%, 138.76%, and 112.36%, respectively, suggesting presystemic or first-pass metabolism. Three (21.4%) subjects experienced a treatment-emergent adverse event (TEAE) during the study. All TEAEs were mild, considered related to study medication, and consistent with what has been seen in other studies. There were no deaths, serious adverse events, or discontinuations due to TEAEs. Both tasimelteon treatments were well tolerated during the study.

  4. Detection limits of 405 nm and 633 nm excited PpIX fluorescence for brain tumor detection during stereotactic biopsy

    NASA Astrophysics Data System (ADS)

    Markwardt, Niklas; Götz, Marcus; Haj-Hosseini, Neda; Hollnburger, Bastian; Sroka, Ronald; Stepp, Herbert; Zelenkov, Petr; Rühm, Adrian

    2016-04-01

    5-aminolevulinic-acid-(5-ALA)-induced protoporphyrin IX (PpIX) fluorescence may be used to improve stereotactic brain tumor biopsies. In this study, the sensitivity of PpIX-based tumor detection has been investigated for two potential excitation wavelengths (405 nm, 633 nm). Using a 200 μm fiber in contact with semi-infinite optical phantoms containing ink and Lipovenös, PpIX detection limits of 4.0 nM and 200 nM (relating to 1 mW excitation power) were determined for 405 nm and 633 nm excitation, respectively. Hence, typical PpIX concentrations in glioblastomas of a few μM should be well detectable with both wavelengths. Additionally, blood layers of selected thicknesses were placed between fiber and phantom. Red excitation was shown to be considerably less affected by blood interference: A 50 μm blood layer, for instance, blocked the 405- nm-excited fluorescence completely, but reduced the 633-nm-excited signal by less than 50%. Ray tracing simulations demonstrated that - without blood layer - the sensitivity advantage of 405 nm rises for decreasing fluorescent volume from 50-fold to a maximum of 100-fold. However, at a tumor volume of 1 mm3, which is a typical biopsy sample size, the 633-nm-excited fluorescence signal is only reduced by about 10%. Further simulations revealed that with increasing fiber-tumor distance, the signal drops faster for 405 nm. This reduces the risk of detecting tumor tissue outside the needle's coverage, but diminishes the overlap between optically and mechanically sampled volumes. While 405 nm generally offers a higher sensitivity, 633 nm is more sensitive to distant tumors and considerably superior in case of blood-covered tumor tissue.

  5. Capability of EnKF to assimilate tracer test data at the lower detection limit

    NASA Astrophysics Data System (ADS)

    Bruckmann, Johanna; Vogt, Christian; Clauser, Christoph

    2014-05-01

    We model water flow and estimate permeability distribution to improve regional groundwater management for a tectonically limited hard-rock aquifer. Management of groundwater resources for drinking water supply requires understanding and quantifying of the regional groundwater flow and groundwater budget which depends largely on the petrophysical transport properties (e. g., porosity and permeability) of the underground. We study a structurally complex and thus highly heterogeneous area on a regional scale: the Hastenrather Graben 15 km northeast of Aachen, Germany. Here, groundwater is produced from a carbonate aquifer for drinking water supply. However, direct data on the geometry and petrophysical properties of the underground are sparse and most data are only one-dimensional. For overcoming this limitation and coping with the heterogeneity of the underground we use the Ensemble Kalman Filter (EnKF) for stochastic parameter estimation and statistical ensemble analysis. Assimilating time-dependent tracer test data will help estimating permeability. The fact that the aquifer is used for drinking water supply prevents using of any artificial tracer such as radioactive or fluorescent tracer. Instead, drinking water with a lower salinity compared to the groundwater (e.g., dam water) will be used. The detection limit will be relatively low due to the low salinity contrast between reservoir water and tracer. It might even be in the range of measuring error. For studying the sensitivity of EnKF at the limit of detection we set up a synthetic scenario based on the conditions in our study area. Performing EnKF assimilation runs based on perturbed observations characterized by different measurement error levels yields information on the acceptable signal-to-noise-ratio required by EnKF for successful estimates of the given synthetic permeability distribution. This, in turn, provides information on the limits of the real-world's tracer test at low salinity contrast.

  6. Detection of 15 dB Squeezed States of Light and their Application for the Absolute Calibration of Photoelectric Quantum Efficiency

    NASA Astrophysics Data System (ADS)

    Vahlbruch, Henning; Mehmet, Moritz; Danzmann, Karsten; Schnabel, Roman

    2016-09-01

    Squeezed states of light belong to the most prominent nonclassical resources. They have compelling applications in metrology, which has been demonstrated by their routine exploitation for improving the sensitivity of a gravitational-wave detector since 2010. Here, we report on the direct measurement of 15 dB squeezed vacuum states of light and their application to calibrate the quantum efficiency of photoelectric detection. The object of calibration is a customized InGaAs positive intrinsic negative (p-i-n) photodiode optimized for high external quantum efficiency. The calibration yields a value of 99.5% with a 0.5% (k =2 ) uncertainty for a photon flux of the order 1 017 s-1 at a wavelength of 1064 nm. The calibration neither requires any standard nor knowledge of the incident light power and thus represents a valuable application of squeezed states of light in quantum metrology.

  7. Detection of 15 dB Squeezed States of Light and their Application for the Absolute Calibration of Photoelectric Quantum Efficiency.

    PubMed

    Vahlbruch, Henning; Mehmet, Moritz; Danzmann, Karsten; Schnabel, Roman

    2016-09-09

    Squeezed states of light belong to the most prominent nonclassical resources. They have compelling applications in metrology, which has been demonstrated by their routine exploitation for improving the sensitivity of a gravitational-wave detector since 2010. Here, we report on the direct measurement of 15 dB squeezed vacuum states of light and their application to calibrate the quantum efficiency of photoelectric detection. The object of calibration is a customized InGaAs positive intrinsic negative (p-i-n) photodiode optimized for high external quantum efficiency. The calibration yields a value of 99.5% with a 0.5% (k=2) uncertainty for a photon flux of the order 10^{17}  s^{-1} at a wavelength of 1064 nm. The calibration neither requires any standard nor knowledge of the incident light power and thus represents a valuable application of squeezed states of light in quantum metrology.

  8. Visualizing the limits of low vision in detecting natural image features.

    PubMed

    Hogervorst, Maarten A; van Damme, Wim J M

    2008-10-01

    The purpose of our study was to develop a tool to visualize the limitations posed by visual impairments in detecting small and low-contrast elements in natural images. This visualization tool incorporates existing models of several aspects of visual perception, such as the band-limited contrast model of Peli (J Opt Soc Am A 1996;13:1131-8). The models underlying the visualization tool were elaborated and tested in experiments with human subjects with various visual impairments such as macular degeneration, diabetic retinopathy, glaucoma and subjects with normal vision but under various degraded viewing conditions (including reduced contrast, eccentric viewing). The experiments were designed to determine in three successive steps the contrast sensitivity function that produces a degraded image that can just be discriminated from its original. In the first step, the just detectable blur was determined, while in the next two steps contrast threshold levels were determined for removing high and medium spatial frequencies from the image. Threshold parameters were determined for three image-types (face, stairs, forest) and the relationship with acuity and contrast thresholds (of Landolt-C symbols) was examined. The blur threshold is inversely related to acuity, and this relationship is largely independent of the cause of reduced acuity (visual impairment, contrast reduction or eccentric viewing). We developed a validated visualization tool based on these results that provides a reliable impression of detectability of image features by visual impaired people.

  9. Iron pentacarbonyl detection limits in the cigarette smoke matrix using FT-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Parrish, Milton E.; Plunkett, Susan E.; Harward, Charles N.

    2005-11-01

    Endogenous metals present in tobacco from agricultural practices have been purported to generate metal carbonyls in cigarette smoke. Transition metal catalysts, such as iron oxide, have been investigated for the reduction of carbon monoxide (CO) in cigarette smoke. These studies motivated the development of an analytical method to determine if iron pentacarbonyl [Fe(CO) 5] is present in mainstream smoke from cigarette models having cigarette paper made with iron oxide. An FT-IR puff-by-puff method was developed and the detection limit was determined using two primary reference spectra from different sources to estimate the amount of Fe(CO) 5 present in a high-pressure steel cylinder of CO. We do not detect Fe(CO) 5 in a single 35 mL puff from reference cigarettes or from those cigarette models having cigarette paper made with iron oxide, with a 30-ppbV limit of detection (LOD). Also, it was shown that a filter containing activated carbon would remove Fe(CO) 5.

  10. Evaluation of regression methods when immunological measurements are constrained by detection limits.

    PubMed

    Uh, Hae-Won; Hartgers, Franca C; Yazdanbakhsh, Maria; Houwing-Duistermaat, Jeanine J

    2008-10-17

    The statistical analysis of immunological data may be complicated because precise quantitative levels cannot always be determined. Values below a given detection limit may not be observed (nondetects), and data with nondetects are called left-censored. Since nondetects cannot be considered as missing at random, a statistician faced with data containing these nondetects must decide how to combine nondetects with detects. Till now, the common practice is to impute each nondetect with a single value such as a half of the detection limit, and to conduct ordinary regression analysis. The first aim of this paper is to give an overview of methods to analyze, and to provide new methods handling censored data other than an (ordinary) linear regression. The second aim is to compare these methods by simulation studies based on real data. We compared six new and existing methods: deletion of nondetects, single substitution, extrapolation by regression on order statistics, multiple imputation using maximum likelihood estimation, tobit regression, and logistic regression. The deletion and extrapolation by regression on order statistics methods gave biased parameter estimates. The single substitution method underestimated variances, and logistic regression suffered loss of power. Based on simulation studies, we found that tobit regression performed well when the proportion of nondetects was less than 30%, and that taken together the multiple imputation method performed best. Based on simulation studies, the newly developed multiple imputation method performed consistently well under different scenarios of various proportion of nondetects, sample sizes and even in the presence of heteroscedastic errors.

  11. Detection limits of Legionella pneumophila in environmental samples after co-culture with Acanthamoeba polyphaga

    PubMed Central

    2013-01-01

    Background The efficiency of recovery and the detection limit of Legionella after co-culture with Acanthamoeba polyphaga are not known and so far no investigations have been carried out to determine the efficiency of the recovery of Legionella spp. by co-culture and compare it with that of conventional culturing methods. This study aimed to assess the detection limits of co-culture compared to culture for Legionella pneumophila in compost and air samples. Compost and air samples were spiked with known concentrations of L. pneumophila. Direct culturing and co-culture with amoebae were used in parallel to isolate L. pneumophila and recovery standard curves for both methods were produced for each sample. Results The co-culture proved to be more sensitive than the reference method, detecting 102-103 L. pneumophila cells in 1 g of spiked compost or 1 m3 of spiked air, as compared to 105-106 cells in 1 g of spiked compost and 1 m3 of spiked air. Conclusions Co-culture with amoebae is a useful, sensitive and reliable technique to enrich L. pneumophila in environmental samples that contain only low amounts of bacterial cells. PMID:23442526

  12. Classification using longitudinal trajectory of biomarker in the presence of detection limits.

    PubMed

    Kim, Yeonhee; Kong, Lan

    2016-02-01

    Discriminant analysis is commonly used to evaluate the ability of candidate biomarkers to separate patients into pre-defined groups. Recent extension of discriminant analysis to longitudinal data enables us to improve the classification accuracy based on biomarker profiles rather than on a single biomarker measurement. However, the biomarker measurement is often limited by the sensitivity of the given assay, resulting in data that are censored at either the lower or the upper limit of detection. Inappropriate handling of censored data may affect the classification accuracy of biomarker and hinder the evaluation of its potential discrimination power. We develop a discriminant analysis method for censored longitudinal biomarker data based on mixed models and evaluate its performance by area under the receiver operation characteristic curve. Through the simulation study, we show that our method is better than the simple substitution methods in terms of parameter estimation and evaluating biomarker performance. Application to a biomarker study of patients with acute kidney injury demonstrates that our method may shed light on the potential clinical utility of biomarkers by taking into account both longitudinal trajectory and limit of detection issues.

  13. Improving the detection limit of conformational analysis by utilizing a dual polarization Vernier cascade.

    PubMed

    Hoste, J-W; Soetaert, P; Bienstman, P

    2016-01-11

    The dual polarization microring technique enables the simultaneous and accurate detection of thickness and refractive index of a bound molecular layer. By using three microring resonators in a double Vernier cascade configuration, the dual polarization technique is improved on three distinct levels: an increase of the sensitivity, a suppression of common noise due to self-referencing and the ability to migrate from a standard tunable laser to a cheap broadband LED and an on-chip arrayed waveguide grating as read-out system, allowing for a system which is orders of magnitude faster and cheaper. A dual polarization Vernier cascade proof-of-concept is fabricated and characterized, a read-out computational framework is constructed and it is shown on a theoretical basis that the limit of detection is improved.

  14. Diamond-based electrochemical aptasensor realizing a femtomolar detection limit of bisphenol A.

    PubMed

    Ma, Yibo; Liu, Junsong; Li, Hongdong

    2017-06-15

    In this study, we designed and fabricated an electrochemical impedance aptasensor based on Au nanoparticles (Au-NPs) coated boron-doped diamond (BDD) modified with aptamers, and 6-mercapto-1-hexanol (MCH) for the detection of bisphenol A (BPA). The constructed BPA aptasensor exhibits good linearity from 1.0×10(-14) to 1.0×10(-9)molL(-1). The detection limitation of 7.2×10(-15)molL(-1) was achieved, which can be attributed to the synergistic effect of combining BDD with Au-NPs, aptamers, and MCH. The examine results of BPA traces in Tris-HCl buffer and in milk, UV spectra of aptamer/BPA and interference test revealed that the novel aptasensors are of high sensitivity, specificity, stability and repeatability, which could be promising in practical applications.

  15. Diffuse reflectance optical topography: location of inclusions in 3D and detectability limits

    PubMed Central

    Carbone, N. A.; Baez, G. R.; García, H. A.; Waks Serra, M. V.; Di Rocco, H. O.; Iriarte, D. I.; Pomarico, J. A.; Grosenick, D.; Macdonald, R.

    2014-01-01

    In the present contribution we investigate the images of CW diffusely reflected light for a point-like source, registered by a CCD camera imaging a turbid medium containing an absorbing lesion. We show that detection of μa variations (absorption anomalies) is achieved if images are normalized to background intensity. A theoretical analysis based on the diffusion approximation is presented to investigate the sensitivity and the limitations of our proposal and a novel procedure to find the location of the inclusions in 3D is given and tested. An analysis of the noise and its influence on the detection capabilities of our proposal is provided. Experimental results on phantoms are also given, supporting the proposed approach. PMID:24876999

  16. Displacement detection with a vibrating rf superconducting interference device: beating the standard linear limit.

    PubMed

    Buks, Eyal; Zaitsev, Stav; Segev, Eran; Abdo, Baleegh; Blencowe, M P

    2007-08-01

    We study a configuration for displacement detection consisting of a nanomechanical resonator coupled to both a radio frequency superconducting interference device and to a superconducting stripline resonator. We employ an adiabatic approximation and rotating wave approximation and calculate the displacement sensitivity. We study the performance of such a displacement detector when the stripline resonator is driven into a region of nonlinear oscillations. In this region the system exhibits noise squeezing in the output signal when homodyne detection is employed for readout. We show that displacement sensitivity of the device in this region may exceed the upper bound imposed upon the sensitivity when operating in the linear region. On the other hand, we find that the high displacement sensitivity is accompanied by a slowing down of the response of the system, resulting in a limited bandwidth.

  17. Detecting shifts in diversity limits from molecular phylogenies: what can we know?

    PubMed Central

    McInnes, Lynsey; Orme, C. David L.; Purvis, A.

    2011-01-01

    Large complete species-level molecular phylogenies can provide the most direct information about the macroevolutionary history of clades having poor fossil records. However, extinction will ultimately erode evidence of pulses of rapid speciation in the deep past. Assessment of how well, and for how long, phylogenies retain the signature of such pulses has hitherto been based on a—probably untenable—model of ongoing diversity-independent diversification. Here, we develop two new tests for changes in diversification ‘rules’ and evaluate their power to detect sudden increases in equilibrium diversity in clades simulated with diversity-dependent speciation and extinction rates. Pulses of diversification are only detected easily if they occurred recently and if the rate of species turnover at equilibrium is low; rates reported for fossil mammals suggest that the power to detect a doubling of species diversity falls to 50 per cent after less than 50 Myr even with a perfect phylogeny of extant species. Extinction does eventually draw a veil over past dynamics, suggesting that some questions are beyond the limits of inference, but sudden clade-wide pulses of speciation can be detected after many millions of years, even when overall diversity is constrained. Applying our methods to existing phylogenies of mammals and angiosperms identifies intervals of elevated diversification in each. PMID:21429924

  18. STATISTICAL METHODS FOR ENVIRONMENTAL APPLICATIONS USING DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS AS INCORPORTED IN PROUCL 4.0

    EPA Science Inventory

    Nondetect (ND) or below detection limit (BDL) results cannot be measured accurately, and, therefore, are reported as less than certain detection limit (DL) values. However, since the presence of some contaminants (e.g., dioxin) in environmental media may pose a threat to human he...

  19. STATISTICAL METHODS FOR ENVIRONMENTAL APPLICATIONS USING DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS AS INCORPORTED IN PROUCL 4.0

    EPA Science Inventory

    Nondetect (ND) or below detection limit (BDL) results cannot be measured accurately, and, therefore, are reported as less than certain detection limit (DL) values. However, since the presence of some contaminants (e.g., dioxin) in environmental media may pose a threat to human he...

  20. Yeast Biosensors for Detection of Environmental Pollutants: Current State and Limitations.

    PubMed

    Jarque, Sergio; Bittner, Michal; Blaha, Ludek; Hilscherova, Klara

    2016-05-01

    Yeast biosensors have become suitable tools for the screening and detection of environmental pollutants because of their various advantages compared to other sensing technologies. On the other hand, many limitations remain with regard to their optimal performance and applicability in several contexts, such as low-concentration samples and on-site testing. This review summarizes the current state of yeast biosensors, with special focus on screening and assessment of environmental contaminants, discusses both pros and cons, and suggests steps towards their further development and effective use in the environmental assessment.

  1. New low detection limits for EDXRF analyses on the basis of polycapillary optics and chemical sensors

    NASA Astrophysics Data System (ADS)

    Khamizov, R. K.; Kumakhov, M. A.; Nikitina, S. V.; Mikhin, V. A.

    2005-07-01

    The possibilities of increasing the sensitivity of energy dispersive X-ray fluorescence analysis (EDXRF) of solutions with the use of special preconcentrating sensors are described in the article. The sensors are made from polycapillary tubes or plates consisting of hundred thousands micro-channels, each containing a micro-grain of collecting sorbent. The kinetic regularities for preconcentration of micro-components from solutions are considered. Experimental results are given for EDXRF analyses of different solutions containing metals and other elements in trace amounts, and the detection limits of tens and hundreds ppb are demonstrated. The pilot sample of a new analytical instrument <> is shortly described.

  2. Limit of blank and limit of detection of Plasmodium falciparum thick blood smear microscopy in a routine setting in Central Africa.

    PubMed

    Joanny, Fanny; Löhr, Sascha J Z; Engleitner, Thomas; Lell, Bertrand; Mordmüller, Benjamin

    2014-06-14

    Proper malaria diagnosis depends on the detection of asexual forms of Plasmodium spp. in the blood. Thick blood smear microscopy is the accepted gold standard of malaria diagnosis and is widely implemented. Surprisingly, diagnostic performance of this method is not well investigated and many clinicians in African routine settings base treatment decisions independent of microscopy results. This leads to overtreatment and poor management of other febrile diseases. Implementation of quality control programmes is recommended, but requires sustained funding, external logistic support and constant training and supervision of the staff. This study describes an easily applicable method to assess the performance of thick blood smear microscopy by determining the limit of blank and limit of detection. These two values are representative of the diagnostic quality and allow the correct discrimination between positive and negative samples. Standard-conform methodology was applied and adapted to determine the limit of blank and the limit of detection of two thick blood smear microscopy methods (WHO and Lambaréné method) in a research centre in Lambaréné, Gabon. Duplicates of negative and low parasitaemia thick blood smears were read by several microscopists. The mean and standard deviation of the results were used to calculate the limit of blank and subsequently the limit of detection. The limit of blank was 0 parasites/μL for both methods. The limit of detection was 62 and 88 parasites/μL for the Lambaréné and WHO method, respectively. With a simple, back-of-the-envelope calculation, the performance of two malaria microscopy methods can be measured. These results are specific for each diagnostic unit and cannot be generalized but implementation of a system to control microscopy performance can improve confidence in parasitological results and thereby strengthen malaria control.

  3. Limit of blank and limit of detection of Plasmodium falciparum thick blood smear microscopy in a routine setting in Central Africa

    PubMed Central

    2014-01-01

    Background Proper malaria diagnosis depends on the detection of asexual forms of Plasmodium spp. in the blood. Thick blood smear microscopy is the accepted gold standard of malaria diagnosis and is widely implemented. Surprisingly, diagnostic performance of this method is not well investigated and many clinicians in African routine settings base treatment decisions independent of microscopy results. This leads to overtreatment and poor management of other febrile diseases. Implementation of quality control programmes is recommended, but requires sustained funding, external logistic support and constant training and supervision of the staff. This study describes an easily applicable method to assess the performance of thick blood smear microscopy by determining the limit of blank and limit of detection. These two values are representative of the diagnostic quality and allow the correct discrimination between positive and negative samples. Methods Standard-conform methodology was applied and adapted to determine the limit of blank and the limit of detection of two thick blood smear microscopy methods (WHO and Lambaréné method) in a research centre in Lambaréné, Gabon. Duplicates of negative and low parasitaemia thick blood smears were read by several microscopists. The mean and standard deviation of the results were used to calculate the limit of blank and subsequently the limit of detection. Results The limit of blank was 0 parasites/μL for both methods. The limit of detection was 62 and 88 parasites/μL for the Lambaréné and WHO method, respectively. Conclusion With a simple, back-of-the-envelope calculation, the performance of two malaria microscopy methods can be measured. These results are specific for each diagnostic unit and cannot be generalized but implementation of a system to control microscopy performance can improve confidence in parasitological results and thereby strengthen malaria control. PMID:24929248

  4. Positioning, alignment and absolute pointing of the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Fehr, F.; Distefano, C.; Antares Collaboration

    2010-01-01

    A precise detector alignment and absolute pointing is crucial for point-source searches. The ANTARES neutrino telescope utilises an array of hydrophones, tiltmeters and compasses for the relative positioning of the optical sensors. The absolute calibration is accomplished by long-baseline low-frequency triangulation of the acoustic reference devices in the deep-sea with a differential GPS system at the sea surface. The absolute pointing can be independently verified by detecting the shadow of the Moon in cosmic rays.

  5. First direct detection limits on sub-GeV dark matter from XENON10.

    PubMed

    Essig, Rouven; Manalaysay, Aaron; Mardon, Jeremy; Sorensen, Peter; Volansky, Tomer

    2012-07-13

    The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15  kg day of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where σ(e)<3×10(-38)  cm2 at 90% C.L., while dark-matter masses between 20 MeV and 1 GeV are bounded by σ(e)<10(-37)  cm2 at 90% C.L. This analysis provides a first proof of principle that direct detection experiments can be sensitive to dark-matter candidates with masses well below the GeV scale.

  6. RCRA materials analysis by laser-induced breakdown spectroscopy: Detection limits in soils

    SciTech Connect

    Koskelo, A.; Cremers, D.A.

    1994-09-01

    The goal of the Technical Task Plan (TTP) that this report supports is research, development, testing and evaluation of a portable analyzer for RCRA and other metals. The instrumentation to be built will be used for field-screening of soils. Data quality is expected to be suitable for this purpose. The data presented in this report were acquired to demonstrate the detection limits for laser-induced breakdown spectroscopy (LIBS) of soils using instrument parameters suitable for fieldable instrumentation. The data are not expected to be the best achievable with the high pulse energies available in laboratory lasers. The report presents work to date on the detection limits for several elements in soils using LIBS. The elements targeted in the Technical Task Plan are antimony, arsenic, beryllium, cadmium, chromium, lead, selenium, and zirconium. Data for these elements are presented in this report. Also included are other data of interest to potential customers for the portable LIBS apparatus. These data are for barium, mercury, cesium and strontium. Data for uranium and thorium will be acquired during the tasks geared toward mixed waste characterization.

  7. Approaching the ppb detection limits for copper in water using laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Tawfik, Walid; Sawaf, Sausan

    2014-05-01

    Copper concentrations in drinking-water is very important to be monitored which can cause cancer if it exceed about 10 mg/liter. In the present work, we have developed a simple, low laser power method to improve the detection limits of laser induced plasma spectroscopy LIBS for copper in aqueous solutions with different concentrations. In this method a medium density fiberboard (MDF) wood have been used as a substrate that absorbs the liquid sample to transform laser liquid interaction to laser solid interaction. Using the fundamental wavelength of Nd:YAG laser, the constructed plasma emissions were monitored for elemental analysis. The signal-to-noise ratio SNR was optimized using low laser fluence of 32 J cm-2, and detector (CDD camera) gate delay of 0.5 μs. Both the electron temperature and density of the induced plasma were determined using Boltzmann plot and the FWHM of the Cu at 324.7 nm, respectively. The plasma temperature was found to be 1.197 eV, while the plasma density was about 1.66 x 1019 cm-3. The detection limits for Cu at 324.7 nm is found to be 131 ppb comparable to the results by others using complicated system.

  8. Detecting and quantifying parasite-induced host mortality from intensity data: method comparisons and limitations

    PubMed Central

    Wilber, Mark Q.; Weinstein, Sara B.; Briggs, Cheryl J.

    2016-01-01

    Parasites can significantly impact animal populations by changing host behavior, reproduction and survival. Detecting and quantifying these impacts is critical for understanding disease dynamics and managing wild animal populations. However, for wild hosts infected with macroparasites, it is notoriously difficult to quantify the fatal parasite load and number of animals that have died due to disease. When ethical or logistical constraints prohibit experimental determination of these values, examination of parasite intensity and distribution data may offer an alternative solution. In this study we introduce a novel method for using intensity data to detect and quantify parasite-induced mortality in wildlife populations. Using simulations, we show that this method is more reliable than previously proposed methods while providing quantitative estimates of parasite-induced mortality from empirical data that are consistent with previously published qualitative estimates. However, we stress that this method, and all techniques that estimate parasite-induced mortality from intensity data alone, have several critical assumptions that limit their applicability in the real world. Due to these limitations, these methods should only be used as an exploratory tool to inform more rigorous studies of parasite-induced host mortality. PMID:26475963

  9. Nonparametric statistical methods for comparing two sites based on data with multiple non-detect limits

    NASA Astrophysics Data System (ADS)

    Millard, Steven P.; Deverel, Steven J.

    1988-12-01

    As concern over the effects of trace amounts of pollutants has increased, so has the need for statistical methods that deal appropriately with data that include values reported as "less than" the detection limit. It has become increasingly common for water quality data to include censored values that reflect more than one detection limit for a single analyte. For such multiply censored data sets, standard statistical methods (for example, to compare analyte concentration in two areas) are not valid. In such cases, methods from the biostatistical field of survival analysis are applicable. Several common two-sample censored data rank tests are explained, and their behaviors are studied via a Monte Carlo simulation in which sample sizes and censoring mechanisms are varied under an assumed lognormal distribution. These tests are applied to shallow groundwater chemistry data from two sites in the San Joaquin Valley, California. The best overall test, in terms of maintained α level, is the normal scores test based on a permutation variance. In cases where the α level is maintained, however, the Peto-Prentice statistic based on an asymptotic variance performs as well or better.

  10. Determining Muon Detection Efficiency Rates of Limited Streamer Tube Modules using Cosmic Ray Detector

    SciTech Connect

    Pan, M.

    2004-09-03

    In the Babar detector at the Stanford Linear Accelerator Center, the existing muon detector system in the Instrumented Flux Return gaps is currently being upgraded. Limited Streamer Tubes (LST) have been successful in other projects in the past, and are thus reliable and sensible detectors to use. The tubes have been assembled into modules to strengthen the mechanical structure [2]. Before installation, numerous tests must be performed on the LST modules to ensure that they are in good condition. One important check is to determine the muon detection efficiency rates of the modules. In this study, a cosmic ray detector was built to measure the efficiency rates of the LST modules. Five modules themselves were used as muon triggers. Two z strip planes were also constructed as part of the setup. Singles rate measurements were done on the five modules to ensure that high voltage could be safely applied to the LST. Particle count vs. voltage graphs were generated, and most of the graphs plateau normally. Wire signals from the LST modules as well as induced signals from the strip planes were used to determine the x-y-z coordinates of the muon hits in a stack of modules. Knowing the geometry of the stack, a plot of the potential muon path was generated. Preliminary results on muon detection efficiency rates of the modules in one stack are presented here. Efficiencies of the modules were determined to be between 80% and 90%, but there were large statistical errors (7%) due to the limited time available for cosmic data runs. More data samples will be taken soon; they will hopefully provide more precise measurements, with 1-2% errors for most modules before installation. Future work includes systematic studies of muon detection efficiency as a function of the operating voltage and threshold voltage settings.

  11. Gel-based nonradioactive single-strand conformational polymorphism and mutation detection: limitations and solutions.

    PubMed

    Gupta, Vibhuti; Arora, Reetakshi; Gochhait, Sailesh; Bairwa, Narendra K; Bamezai, Rameshwar N K

    2014-01-01

    Single-strand conformation polymorphism (SSCP) for screening mutations/single-nucleotide polymorphisms (SNPs) is a simple, cost-effective technique, saving an expensive exercise of sequencing each and every polymerase chain reaction product and assisting in choosing only the amplicons of interest with expected mutations. The principle of detection of small changes in DNA sequences is based on changes in single-strand DNA conformations. The changes in electrophoretic mobility that SSCP detects are sequence dependent. The limitations faced in SSCP range from routine polyacrylamide gel electrophoresis (PAGE) problems to the problems of resolving mutant DNA bands. Both these problems can be solved by controlling PAGE conditions and by varying physical and environmental conditions such as pH, temperature, voltage, gel type and percentage, addition of additives or denaturants, and others. Despite much upgrading of the technology for mutation detection, SSCP remains the method of choice to analyze mutations and SNPs in order to understand genomic variations, both spontaneous and induced, and the genetic basis of diseases.

  12. System for detecting and limiting electrical ground faults within electrical devices

    DOEpatents

    Gaubatz, Donald C.

    1990-01-01

    An electrical ground fault detection and limitation system for employment with a nuclear reactor utilizing a liquid metal coolant. Elongate electromagnetic pumps submerged within the liquid metal coolant and electrical support equipment experiencing an insulation breakdown occasion the development of electrical ground fault current. Without some form of detection and control, these currents may build to damaging power levels to expose the pump drive components to liquid metal coolant such as sodium with resultant undesirable secondary effects. Such electrical ground fault currents are detected and controlled through the employment of an isolated power input to the pumps and with the use of a ground fault control conductor providing a direct return path from the affected components to the power source. By incorporating a resistance arrangement with the ground fault control conductor, the amount of fault current permitted to flow may be regulated to the extent that the reactor may remain in operation until maintenance may be performed, notwithstanding the existence of the fault. Monitors such as synchronous demodulators may be employed to identify and evaluate fault currents for each phase of a polyphase power, and control input to the submerged pump and associated support equipment.

  13. AN ALTERNATIVE CALIBRATION OF CR-39 DETECTORS FOR RADON DETECTION BEYOND THE SATURATION LIMIT.

    PubMed

    Franci, Daniele; Aureli, Tommaso; Cardellini, Francesco

    2016-12-01

    Time-integrated measurements of indoor radon levels are commonly carried out using solid-state nuclear track detectors (SSNTDs), due to the numerous advantages offered by this radiation detection technique. However, the use of SSNTD also presents some problems that may affect the accuracy of the results. The effect of overlapping tracks often results in the underestimation of the detected track density, which leads to the reduction of the counting efficiency for increasing radon exposure. This article aims to address the effect of overlapping tracks by proposing an alternative calibration technique based on the measurement of the fraction of the detector surface covered by alpha tracks. The method has been tested against a set of Monte Carlo data and then applied to a set of experimental data collected at the radon chamber of the Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, at the ENEA centre in Casaccia, using CR-39 detectors. It has been proved that the method allows to extend the detectable range of radon exposure far beyond the intrinsic limit imposed by the standard calibration based on the track density. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  14. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  15. Evaluation of MidIR fibre optic reflectance: detection limit, reproducibility and binary mixture discrimination.

    PubMed

    Sessa, Clarimma; Bagán, Héctor; García, José Francisco

    2013-11-01

    MidIR fibre optic reflectance (MidIR-FORS) is a promising analytical technique in the field of science conservation, especially because it is non-destructive. Another advantage of MidIR-FORS is that the obtained information is representative, as a large amount of spectral data can be collected. Although the technique has a high potential and is almost routinely applied, its quality parameters have not been thoroughly studied in the specific application of analysis of artistic materials. The objective of this study is to evaluate the instrumental capabilities of MidIR-FORS for the analysis of artwork materials in terms of detection limit, reproducibility, and mixture characterisation. The study has been focused on oil easel painting and several paints of known composition have been analysed. Paint layers include blue pigments not only because of their important role along art history, but also because their physical and spectroscopic characteristics allow a better evaluation of the MidIR-FORS capabilities. The results of the analysis indicate that MidIR-FORS supplies a signal affected by different factors, such as the optical, morphological and physical properties of the surface, in addition to the composition of materials analysed. Consequently, the detection limits established are relatively high for artistic objects (Prussian blue - PB 2.1-6.5%; Phthalocyanine blue - Pht 6.3-10.2%; synthetic Ultramarine blue - UM 12.1%) and may therefore lead to an incomplete description of the artwork. Reproducibility of the technique over time and across surface has been determined. The results show that the major sources of dispersion are the heterogeneity of the pigments distribution, physical features, and band shape distortions. The total dispersion is around 4% for the most intense bands (oil) and increases up to 26% when weak or overlapped bands are considered (PB, Pht, UM). The application of different pre-treatments (cutoff of fibres absorption, Savizky-Golay smoothing

  16. Evaluation of MidIR fibre optic reflectance: Detection limit, reproducibility and binary mixture discrimination

    NASA Astrophysics Data System (ADS)

    Sessa, Clarimma; Bagán, Héctor; García, José Francisco

    2013-11-01

    MidIR fibre optic reflectance (MidIR-FORS) is a promising analytical technique in the field of science conservation, especially because it is non-destructive. Another advantage of MidIR-FORS is that the obtained information is representative, as a large amount of spectral data can be collected. Although the technique has a high potential and is almost routinely applied, its quality parameters have not been thoroughly studied in the specific application of analysis of artistic materials. The objective of this study is to evaluate the instrumental capabilities of MidIR-FORS for the analysis of artwork materials in terms of detection limit, reproducibility, and mixture characterisation. The study has been focused on oil easel painting and several paints of known composition have been analysed. Paint layers include blue pigments not only because of their important role along art history, but also because their physical and spectroscopic characteristics allow a better evaluation of the MidIR-FORS capabilities. The results of the analysis indicate that MidIR-FORS supplies a signal affected by different factors, such as the optical, morphological and physical properties of the surface, in addition to the composition of materials analysed. Consequently, the detection limits established are relatively high for artistic objects (Prussian blue - PB 2.1-6.5%; Phthalocyanine blue - Pht 6.3-10.2%; synthetic Ultramarine blue - UM 12.1%) and may therefore lead to an incomplete description of the artwork. Reproducibility of the technique over time and across surface has been determined. The results show that the major sources of dispersion are the heterogeneity of the pigments distribution, physical features, and band shape distortions. The total dispersion is around 4% for the most intense bands (oil) and increases up to 26% when weak or overlapped bands are considered (PB, Pht, UM). The application of different pre-treatments (cutoff of fibres absorption, Savizky-Golay smoothing

  17. 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

  18. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  19. The role of refractive index gradient on sensitivity and limit of detection of microdisk sensors

    NASA Astrophysics Data System (ADS)

    Najafi, Zohreh; Vahedi, Mohammad; Behjat, Abbas

    2016-09-01

    This paper presents a new type of microdisk resonator sensor with a gradient refractive index (GRIN) that can achieve higher sensitivity with respect to constant refractive index disks. The behavior of the microdisk resonator is simulated by 2D-FDTD method. The shift in the resonance frequency for different thicknesses of the absorbed layer and different refractive index gradients of the microdisks are studied. The best refractive index gradient function is found that leads to the largest sensitivity and smallest limit of detection. The sensitivity of a GRIN microresonator sensor (GMS) with a convex quadratic refractive index function is approximately 11 times as much as that of homogeneous microdisk sensor, which is the best record among GMSs.

  20. Limited geographic genetic structure detected in a widespread Palearctic corvid, Nucifraga caryocatactes

    PubMed Central

    Burg, Theresa M.

    2014-01-01

    The Eurasian or spotted nutcracker (Nucifraga caryocatactes) is a widespread resident corvid found throughout the Palearctic from Central Europe to Japan. Characterized by periodic bouts of irruptive dispersal in search of Pinus seed crops, this species has potential for high levels of gene flow across its range. Previous analysis of 11 individuals did not find significant range-wide population genetic structure. We investigated population structure using 924 base pairs of mitochondrial DNA control region sequence data from 62 individuals from 12 populations distributed throughout the nutcracker’s range. We complemented this analysis by incorporating additional genetic data from previously published sequences. High levels of genetic diversity and limited population genetic structure were detected suggesting that potential barriers to dispersal do not restrict gene flow in nutcrackers. PMID:25024901

  1. The ability of animal studies to detect serious post marketing adverse events is limited.

    PubMed

    van Meer, Peter J K; Kooijman, Marlous; Gispen-de Wied, Christine C; Moors, Ellen H M; Schellekens, Huub

    2012-12-01

    The value of animal studies to assess drug safety is unclear because many such studies are biased and have methodological shortcomings. We studied whether post-marketing serious adverse reactions to small molecule drugs could have been detected on the basis of animal study data included in drug registration files. Of 93 serious adverse reactions related to 43 small molecule drugs, only 19% were identified in animal studies as a true positive outcome, which suggests that data from animal studies are of limited value to pharmacovigilance activities. Our study shows that drug registration files can be used to study the predictive value of animal studies and that the value of animal studies in all stages of the drug development should be investigated in a collaborative endeavour between regulatory authorities, industry, and academia. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. Model averaging quantiles from data censored by a limit of detection.

    PubMed

    Nysen, Ruth; Faes, Christel; Ferrari, Pietro; Verger, Philippe; Aerts, Marc

    2016-03-01

    In chemical risk assessment, it is important to determine the quantiles of the distribution of concentration data. The selection of an appropriate distribution and the estimation of particular quantiles of interest are largely hindered by the omnipresence of observations below the limit of detection, leading to left-censored data. The log-normal distribution is a common choice, but this distribution is not the only possibility and alternatives should be considered as well. Here, we focus on several distributions that are related to the log-normal distribution or that are seminonparametric extensions of the log-normal distribution. Whereas previous work focused on the estimation of the cumulative distribution function, our interest here goes to the estimation of quantiles, particularly in the left tail of the distribution where most of the left-censored data are located. Two different model averaged quantile estimators are defined and compared for different families of candidate models. The models and methods of selection and averaging are further investigated through simulations and illustrated on data of cadmium concentration in food products. The approach is extended to include covariates and to deal with uncertainty about the values of the limit of detection. These extensions are illustrated with (134) cesium measurements from Fukushima Prefecture, Japan. We can conclude that averaged models do achieve good performance characteristics in case no useful prior knowledge about the true distribution is available; that there is no structural difference in the performance of the direct and indirect method; and that, not surprisingly, only the true or closely approximating model can deal with extremely high percentages of censoring.

  3. Effect of sample aliquot size on the limit of detection and reproducibility of clinical assays.

    PubMed

    Chen, Guorong; Kobayashi, Lori; Nazarenko, Irina

    2007-11-01

    Nucleic acid amplification technologies significantly improved the limit of detection (LOD) for diagnostic assays. The ability of these assays to amplify fewer than 10 target copies of DNA or RNA imposes new requirements on the preparation of clinical samples. We report a statistical method to determine how large of an aliquot is necessary to reproducibly provide a detectable number of cells. We determined the success probability (p) based on aliquot size and sample volume. The binomial distribution, based on p and the concentration of cells in sample, was used to calculate the probability of getting no target objects in an aliquot and to determine the minimum number of objects per aliquot necessary to generate a reproducible clinical assay. The described method was applied to find a minimum aliquot volume required for a set LOD, false-negative rate (FNR), and %CV. For example, to keep FNR <0.01% for 0.5%, 1% and 2% aliquots (minimum 2000, 1000, and 500 cells per sample) are required. Comparison between experimental and predicted FNR demonstrated good correlation for the small volume aliquots and/or low concentration of target. When 4 muL of 200 copies/mL of plasmid is amplified, predicted and experimental FNRs are 47.2% and 44.9%. This probability model is a useful tool to predict the impact of aliquot volume on the LOD and reproducibility of clinical assays. Even for samples for which pathogens are homogeneously distributed, it is theoretically impossible to collect a single pathogen consistently if the concentration of pathogen is below a certain limit.

  4. Sensitivity and noise in GC-MS: Achieving low limits of detection for difficult analytes

    NASA Astrophysics Data System (ADS)

    Fialkov, Alexander B.; Steiner, Urs; Lehotay, Steven J.; Amirav, Aviv

    2007-01-01

    Gas chromatography-mass spectrometry (GC-MS) instrument limit of detection (LOD) is typically listed by major vendors as that of octafluoronaphthalene (OFN). Most current GC-MS instruments can achieve LODs in the low femtogram range. However, GC-MS LODs for realistic analytes in actual samples are often a few orders of magnitude higher than OFN's. Users seldom encounter 1 pg LOD in the single ion monitoring mode in their applications. We define this detectability difference as the "OFN gap." In this paper, we demonstrate and discuss how the OFN gap can be significantly reduced by the use of GC-MS with supersonic molecular beams (SMB). Experimental results were obtained with a recently developed GC-MS with SMB named 1200-SMB, that is based on the conversion of the Varian 1200 system into a GC-MS-MS with SMB. With this 1200-SMB system, the LOD of all types of analytes, including OFN, in real samples is significantly improved through the combination of: (a) enhanced molecular ion; (b) elimination of vacuum background noise; (c) elimination of mass independent noise; (d) elimination of ion source peak tailing and degradation; (e) significantly increased range of thermally labile and low volatility compounds that are amenable for analysis through lower sample elution temperatures; (f) reduced column bleed and ghost peaks through sample elution at lower temperatures; (g) improved compatibility with large volume injections; and (h) reduced matrix interferences through the combination of enhanced molecular ion and MS-MS. As a result, the 1200-SMB LODs of common and/or difficult compounds are much closer to its OFN LOD, even in complex matrices. We crossed the <1 fg OFN LOD milestone to achieve the lowest LOD to date using GC-MS, but more importantly, we attained LOD of 2 fg for diazinon, a common pesticide analyte. In another example, we achieved an LOD of 10 fg for underivatized testosterone, which is not amenable in traditional GC-MS analysis, and conducted many analyses

  5. Limit of Detection in X-ray Diffraction Measurements of Tissue Equivalent Samples

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Vassiljev, N.; Konstantinidis, A.; Griffiths, J.; Speller, R.

    2015-09-01

    There is a suggestion of a new approach to mammography whereby following a conventional mammogram, the radiologist could interrogate suspicious regions using X-ray diffraction whilst the patient is still present and to establish the true extent of disease. A starting point for this work is to quantify the minimum detectable amount of breast cancer within a realistic thickness phantom. Perspex has a similar diffraction pattern to healthy breast tissue whilst water is similar to breast tumour, hence these two materials are used as tissue equivalent test objects for X-ray diffraction measurements. The preliminary results show linear agreement between the ratio of Perspex to water and the ratio of the diffraction peak intensities at 0.7 nm-1 and 1.5 nm-1. The minimum detectable limit for a component of the two ‘tissue’ mix was found to be 4.1%. This suggests that X-ray diffraction can be used to quantify tissue like mixtures down to the 4.1% / 95.9% mix level and hence has a strong potential for delineating the extent of infiltration disease.

  6. Effectiveness of hairpin probe in increasing the limit of detection for gold nanowire based-biosensor

    NASA Astrophysics Data System (ADS)

    Tien Cao, Huu; Pham, Xuan Thanh Tung; Linh Ha, Van; Hieu Le, Van

    2014-12-01

    Electrochemical DNA (E-DNA) sensors, which are rapid, reagentless and readily integrated into microelectronics and microfluidics, appear a promising alternative to optical methods for the detection of specific nucleic acid sequences. In keeping with this, a large number of distinct E-DNA architectures have been reported to date. Most, however, suffer from one or more drawbacks, including low signal gain, signal-off behavior or instability. To remedy these problems, we report here the development of a signal-on E-DNA architecture that achieves both high signal gain and good stability. This new sensor employs a commercially synthesized, asymmetric hairpin DNA as its recognition and signaling probe, the shorter arm of which is labeled with a redox reporting methylene blue at its free end. Unlike all prior E-DNA architectures, in which the recognition probe is attached via a terminal functional group to its underlying electrode, the probe employed here is affixed using a thiol group located internally, in the turn region of the hairpin. Hybridization of a target DNA to the longer arm of the hairpin displaces the shorter arm, allowing the reporter to approach the electrode surface and transfer electrons. The observed signal gain is sufficient to achieve a demonstrated detection limit of 25 pM.

  7. Artifactual mutations resulting from DNA lesions limit detection levels in ultrasensitive sequencing applications

    PubMed Central

    Arbeithuber, Barbara; Makova, Kateryna D.; Tiemann-Boege, Irene

    2016-01-01

    The need in cancer research or evolutionary biology to detect rare mutations or variants present at very low frequencies (<10−5) poses an increasing demand on lowering the detection limits of available methods. Here we demonstrated that amplifiable DNA lesions introduce important error sources in ultrasensitive technologies such as single molecule PCR (smPCR) applications (e.g. droplet-digital PCR), or next-generation sequencing (NGS) based methods. Using templates with known amplifiable lesions (8-oxoguanine, deaminated 5-methylcytosine, uracil, and DNA heteroduplexes), we assessed with smPCR and duplex sequencing that templates with these lesions were amplified very efficiently by proofreading polymerases (except uracil), leading to G->T, and to a lesser extent, to unreported G->C substitutions at 8-oxoguanine lesions, and C->T transitions in amplified uracil containing templates. Long heat incubations common in many DNA extraction protocols significantly increased the number of G->T substitutions. Moreover, in ∼50-80% smPCR reactions we observed the random amplification preference of only one of both DNA strands explaining the known ‘PCR jackpot effect’, with the result that a lesion became indistinguishable from a true mutation or variant. Finally, we showed that artifactual mutations derived from uracil and 8-oxoguanine could be significantly reduced by DNA repair enzymes. PMID:27477585

  8. Three factors limiting the reliable detection of light by retinal ganglion cells of the cat

    PubMed Central

    Barlow, H. B.; Levick, W. R.

    1969-01-01

    1. Responses of cat retinal ganglion cells have been examined with a view to specifying the characteristics that limit the detection of light stimuli. 2. Threshold is defined as the weakest stimulus that can be reliably detected by examination of the output from a retinal ganglion cell; it depends upon (a) the quantum/spike ratio, which is the mean number of additional quantal absorptions required to produce an additional impulse, (b) the temporal course of the response, which determines the time interval within which the maintained discharge is modified, and (c) the statistical distribution of the number of impulses that occur in this time interval in the absence of the stimulus. 3. The quantum/spike ratio changes greatly when adapting luminance is changed, and this is the predominant factor accounting for changes in increment threshold. 4. The time course of the response changes with adaptation level and area of the stimulus. This may account for the changes in temporal integration that occur in analogous psychophysical experiments. 5. Changes in the irregularity of the maintained discharge also affect the threshold of single ganglion cells. This is only a minor factor in the conditions of most of our experiments, but it may be important when unstabilized images and non-equilibrium adaptation conditions are encountered. PMID:5761942

  9. 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.

  10. Artifactual mutations resulting from DNA lesions limit detection levels in ultrasensitive sequencing applications.

    PubMed

    Arbeithuber, Barbara; Makova, Kateryna D; Tiemann-Boege, Irene

    2016-12-01

    The need in cancer research or evolutionary biology to detect rare mutations or variants present at very low frequencies (<10(-5)) poses an increasing demand on lowering the detection limits of available methods. Here we demonstrated that amplifiable DNA lesions introduce important error sources in ultrasensitive technologies such as single molecule PCR (smPCR) applications (e.g. droplet-digital PCR), or next-generation sequencing (NGS) based methods. Using templates with known amplifiable lesions (8-oxoguanine, deaminated 5-methylcytosine, uracil, and DNA heteroduplexes), we assessed with smPCR and duplex sequencing that templates with these lesions were amplified very efficiently by proofreading polymerases (except uracil), leading to G->T, and to a lesser extent, to unreported G->C substitutions at 8-oxoguanine lesions, and C->T transitions in amplified uracil containing templates. Long heat incubations common in many DNA extraction protocols significantly increased the number of G->T substitutions. Moreover, in ∼50-80% smPCR reactions we observed the random amplification preference of only one of both DNA strands explaining the known 'PCR jackpot effect', with the result that a lesion became indistinguishable from a true mutation or variant. Finally, we showed that artifactual mutations derived from uracil and 8-oxoguanine could be significantly reduced by DNA repair enzymes. © The Author 2016. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

  11. Lower Limits on Aperture Size for an ExoEarth Detecting Coronagraphic Mission

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 multi-wavelength 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.

  12. Improved tuberculosis smear detection in resource-limited settings: Combined bleach concentration and LED fluorescence microscopy.

    PubMed

    Reed, Sharon L; Mamo, Girmachew; Gossa, Elias; Jasura, Michele; Getahun, Muluwork; Lemma, Eshetu; Mathews, Christopher; McCutchan, J Allen

    2011-09-01

    Improved diagnostics for tuberculosis is a high priority in resource-limited settings (RLS). Sputum concentration and fluorescence microscopy (FM) are standard techniques in developed countries where appropriate biosafety precautions are possible. Recently, inexpensive fluorescent lenses using LED light sources have made auramine-based FM more feasible in RLS. Sterilization of sputum with bleach protects lab personnel and, combined with concentration, increases the sensitivity of microscopic detection. We compared the effect of both bleach concentration and FM with LED based lenses to culture for the detection of tuberculosis in military medical hospitals in Addis Ababa, Ethiopia. Three sputum specimens were obtained from 409 patients (1227 total). Standard Ziehl-Neelsen (ZN) or auramine staining were compared with direct or bleach-concentrated specimens. The prevalence by culture was 26%. Sensitivity of microscopic diagnosis was increased both by bleach concentration (14%) and auramine staining (5%). The overall yield of smear positivity varied from 21% for direct ZN to 27% for auramine after concentration (P<0.00001, Cochran test for matched proportions). Twenty-nine HIV+ patients were diagnosed with TB, but ten (34%), would have been missed with direct ZN staining. Bleach concentration and auramine staining with new LED fluorescent systems are cost-effective and safe methods to increase the diagnostic yield of smears, including in HIV-infected patients.

  13. Potential and limits of Raman spectroscopy for carotenoid detection in microorganisms: implications for astrobiology

    PubMed Central

    Jehlička, Jan; Edwards, Howell G. M.; Osterrothová, Kateřina; Novotná, Julie; Nedbalová, Linda; Kopecký, Jiří; Němec, Ivan; Oren, Aharon

    2014-01-01

    In this paper, it is demonstrated how Raman spectroscopy can be used to detect different carotenoids as possible biomarkers in various groups of microorganisms. The question which arose from previous studies concerns the level of unambiguity of discriminating carotenoids using common Raman microspectrometers. A series of laboratory-grown microorganisms of different taxonomic affiliation was investigated, such as halophilic heterotrophic bacteria, cyanobacteria, the anoxygenic phototrophs, the non-halophilic heterotrophs as well as eukaryotes (Ochrophyta, Rhodophyta and Chlorophyta). The data presented show that Raman spectroscopy is a suitable tool to assess the presence of carotenoids of these organisms in cultures. Comparison is made with the high-performance liquid chromatography approach of analysing pigments in extracts. Direct measurements on cultures provide fast and reliable identification of the pigments. Some of the carotenoids studied are proposed as tracers for halophiles, in contrast with others which can be considered as biomarkers of other genera. The limits of application of Raman spectroscopy are discussed for a few cases where the current Raman spectroscopic approach does not allow discriminating structurally very similar carotenoids. The database reported can be used for applications in geobiology and exobiology for the detection of pigment signals in natural settings. PMID:25368348

  14. Estimation of intervention effect using paired interval-censored data with clumping below lower detection limit.

    PubMed

    Xu, Ying; Lam, K F; Cowling, Benjamin J; Cheung, Yin Bun

    2015-01-30

    Outcome variables that are semicontinuous with clumping at zero are commonly seen in biomedical research. In addition, the outcome measurement is sometimes subject to interval censoring and a lower detection limit (LDL). This gives rise to interval-censored observations with clumping below the LDL. Level of antibody against influenza virus measured by the hemagglutination inhibition assay is an example. The interval censoring is due to the assay's technical procedure. The clumping below LDL is likely a result of the lack of prior exposure in some individuals such that they either have zero level of antibodies or do not have detectable level of antibodies. Given a pair of such measurements from the same subject at two time points, a binary 'fold-increase' endpoint can be defined according to the ratio of these two measurements, as it often is in vaccine clinical trials. The intervention effect or vaccine immunogenicity can be assessed by comparing the binary endpoint between groups of subjects given different vaccines or placebos. We introduce a two-part random effects model for modeling the paired interval-censored data with clumping below the LDL. Based on the estimated model parameters, we propose to use Monte Carlo approximation for estimation of the 'fold-increase' endpoint and the intervention effect. Bootstrapping is used for variance estimation. The performance of the proposed method is demonstrated by simulation. We analyze antibody data from an influenza vaccine trial for illustration.

  15. Detection limit of fishing boats by the day night band (DNB) on VIIRS

    NASA Astrophysics Data System (ADS)

    Asanuma, Ichio; Yamaguchi, Takashi; Park, John-geol; Mackin, Kenneth J.; Mittleman, John

    2016-09-01

    The detection limit of DNB was proposed as a function of the brightness temperature (BT) at 3.7 μm, where the transmittance of cloud could be observed as a change of surface temperature. The shortwave infrared band exhibited a wide distribution in BT more than the thermal infrared band for the same level of DNB radiance. The lights from surface were identified even under the full Moon condition with the proposed method, where clouds were reflecting the lunar lights. A different distribution of clouds for day to day and a change of the Moon phase with its elevation make this problem more complicated. But the approach of contrast based evaluation of surface lights and lunar reflected lights could be one solution to distinguish the lights from the surface. Currently, a validation is necessary in the future to confirm this algorithm and to validate the detected pixels to be fishing boats with the stable light sources. The time series data of fishing boats could be studied to analyze the region of fishing area relative to the distribution of sea surface temperature and/or chlorophyll-a.

  16. Proposal for gravitational-wave detection beyond the standard quantum limit through EPR entanglement

    NASA Astrophysics Data System (ADS)

    Ma, Yiqiu; Miao, Haixing; Pang, Belinda Heyun; Evans, Matthew; Zhao, Chunnong; Harms, Jan; Schnabel, Roman; Chen, Yanbei

    2017-08-01

    In continuously monitored systems the standard quantum limit is given by the trade-off between shot noise and back-action noise. In gravitational-wave detectors, such as Advanced LIGO, both contributions can be simultaneously squeezed in a broad frequency band by injecting a spectrum of squeezed vacuum states with a frequency-dependent squeeze angle. This approach requires setting up an additional long baseline, low-loss filter cavity in a vacuum system at the detector's site. Here, we show that the need for such a filter cavity can be eliminated, by exploiting Einstein-Podolsky-Rosen (EPR)-entangled signals and idler beams. By harnessing their mutual quantum correlations and the difference in the way each beam propagates in the interferometer, we can engineer the input signal beam to have the appropriate frequency-dependent conditional squeezing once the out-going idler beam is detected. Our proposal is appropriate for all future gravitational-wave detectors for achieving sensitivities beyond the standard quantum limit.

  17. Multivariate normally distributed biomarkers subject to limits of detection and receiver operating characteristic curve inference.

    PubMed

    Perkins, Neil J; Schisterman, Enrique F; Vexler, Albert

    2013-07-01

    Biomarkers are of ever-increasing importance to clinical practice and epidemiologic research. Multiple biomarkers are often measured per patient. Measurement of true biomarker levels is limited by laboratory precision, specifically measuring relatively low, or high, biomarker levels resulting in undetectable levels below, or above, a limit of detection (LOD). Ignoring these missing observations or replacing them with a constant are methods commonly used although they have been shown to lead to biased estimates of several parameters of interest, including the area under the receiver operating characteristic (ROC) curve and regression coefficients. We developed asymptotically consistent, efficient estimators, via maximum likelihood techniques, for the mean vector and covariance matrix of multivariate normally distributed biomarkers affected by LOD. We also developed an approximation for the Fisher information and covariance matrix for our maximum likelihood estimations (MLEs). We apply these results to an ROC curve setting, generating an MLE for the area under the curve for the best linear combination of multiple biomarkers and accompanying confidence interval. Point and confidence interval estimates are scrutinized by simulation study, with bias and root mean square error and coverage probability, respectively, displaying behavior consistent with MLEs. An example using three polychlorinated biphenyls to classify women with and without endometriosis illustrates how the underlying distribution of multiple biomarkers with LOD can be assessed and display increased discriminatory ability over naïve methods. Properly addressing LODs can lead to optimal biomarker combinations with increased discriminatory ability that may have been ignored because of measurement obstacles. Published by Elsevier Inc.

  18. Extending the Dynamic Range in Metabolomics Experiments by Automatic Correction of Peaks Exceeding the Detection Limit.

    PubMed

    Lisec, Jan; Hoffmann, Friederike; Schmitt, Clemens; Jaeger, Carsten

    2016-08-02

    Metabolomics, the analysis of potentially all small molecules within a biological system, has become a valuable tool for biomarker identification and the elucidation of biological processes. While metabolites are often present in complex mixtures at extremely different concentrations, the dynamic range of available analytical methods to capture this variance is generally limited. Here, we show that gas chromatography coupled to atmospheric pressure chemical ionization mass spectrometry (GC-APCI-MS), a state of the art analytical technology applied in metabolomics analyses, shows an average linear range (LR) of 2.39 orders of magnitude for a set of 62 metabolites from a representative compound mixture. We further developed a computational tool to extend this dynamic range on average by more than 1 order of magnitude, demonstrated with a dilution series of the compound mixture, using robust and automatic reconstruction of intensity values exceeding the detection limit. The tool is freely available as an R package (CorrectOverloadedPeaks) from CRAN ( https://cran.r-project.org/ ) and can be incorporated in a metabolomics data processing pipeline facilitating large screening assays.

  19. Implications of limits of detection of various methods for Bacillus anthracis in computing risks to human health.

    PubMed

    Herzog, Amanda B; McLennan, S Devin; Pandey, Alok K; Gerba, Charles P; Haas, Charles N; Rose, Joan B; Hashsham, Syed A

    2009-10-01

    Used for decades for biological warfare, Bacillus anthracis (category A agent) has proven to be highly stable and lethal. Quantitative risk assessment modeling requires descriptive statistics of the limit of detection to assist in defining the exposure. Furthermore, the sensitivities of various detection methods in environmental matrices are vital information for first responders. A literature review of peer-reviewed journal articles related to methods for detection of B. anthracis was undertaken. Articles focused on the development or evaluation of various detection approaches, such as PCR, real-time PCR, immunoassay, etc. Real-time PCR and PCR were the most sensitive methods for the detection of B. anthracis, with median instrument limits of detection of 430 and 440 cells/ml, respectively. There were very few peer-reviewed articles on the detection methods for B. anthracis in the environment. The most sensitive limits of detection for the environmental samples were 0.1 CFU/g for soil using PCR-enzyme-linked immunosorbent assay (ELISA), 17 CFU/liter for air using an ELISA-biochip system, 1 CFU/liter for water using cultivation, and 1 CFU/cm(2) for stainless steel fomites using cultivation. An exponential dose-response model for the inhalation of B. anthracis estimates of risk at concentrations equal to the environmental limit of detection determined the probability of death if untreated to be as high as 0.520. Though more data on the environmental limit of detection would improve the assumptions made for the risk assessment, this study's quantification of the risk posed by current limitations in the knowledge of detection methods should be considered when employing those methods in environmental monitoring and cleanup strategies.

  20. Breath Analysis Using Laser Spectroscopic Techniques: Breath Biomarkers, Spectral Fingerprints, and Detection Limits

    PubMed Central

    Wang, Chuji; Sahay, Peeyush

    2009-01-01

    Breath analysis, a promising new field of medicine and medical instrumentation, potentially offers noninvasive, real-time, and point-of-care (POC) disease diagnostics and metabolic status monitoring. Numerous breath biomarkers have been detected and quantified so far by using the GC-MS technique. Recent advances in laser spectroscopic techniques and laser sources have driven breath analysis to new heights, moving from laboratory research to commercial reality. Laser spectroscopic detection techniques not only have high-sensitivity and high-selectivity, as equivalently offered by the MS-based techniques, but also have the advantageous features of near real-time response, low instrument costs, and POC function. Of the approximately 35 established breath biomarkers, such as acetone, ammonia, carbon dioxide, ethane, methane, and nitric oxide, 14 species in exhaled human breath have been analyzed by high-sensitivity laser spectroscopic techniques, namely, tunable diode laser absorption spectroscopy (TDLAS), cavity ringdown spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), cavity enhanced absorption spectroscopy (CEAS), cavity leak-out spectroscopy (CALOS), photoacoustic spectroscopy (PAS), quartz-enhanced photoacoustic spectroscopy (QEPAS), and optical frequency comb cavity-enhanced absorption spectroscopy (OFC-CEAS). Spectral fingerprints of the measured biomarkers span from the UV to the mid-IR spectral regions and the detection limits achieved by the laser techniques range from parts per million to parts per billion levels. Sensors using the laser spectroscopic techniques for a few breath biomarkers, e.g., carbon dioxide, nitric oxide, etc. are commercially available. This review presents an update on the latest developments in laser-based breath analysis. PMID:22408503

  1. Breath analysis using laser spectroscopic techniques: breath biomarkers, spectral fingerprints, and detection limits.

    PubMed

    Wang, Chuji; Sahay, Peeyush

    2009-01-01

    Breath analysis, a promising new field of medicine and medical instrumentation, potentially offers noninvasive, real-time, and point-of-care (POC) disease diagnostics and metabolic status monitoring. Numerous breath biomarkers have been detected and quantified so far by using the GC-MS technique. Recent advances in laser spectroscopic techniques and laser sources have driven breath analysis to new heights, moving from laboratory research to commercial reality. Laser spectroscopic detection techniques not only have high-sensitivity and high-selectivity, as equivalently offered by the MS-based techniques, but also have the advantageous features of near real-time response, low instrument costs, and POC function. Of the approximately 35 established breath biomarkers, such as acetone, ammonia, carbon dioxide, ethane, methane, and nitric oxide, 14 species in exhaled human breath have been analyzed by high-sensitivity laser spectroscopic techniques, namely, tunable diode laser absorption spectroscopy (TDLAS), cavity ringdown spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), cavity enhanced absorption spectroscopy (CEAS), cavity leak-out spectroscopy (CALOS), photoacoustic spectroscopy (PAS), quartz-enhanced photoacoustic spectroscopy (QEPAS), and optical frequency comb cavity-enhanced absorption spectroscopy (OFC-CEAS). Spectral fingerprints of the measured biomarkers span from the UV to the mid-IR spectral regions and the detection limits achieved by the laser techniques range from parts per million to parts per billion levels. Sensors using the laser spectroscopic techniques for a few breath biomarkers, e.g., carbon dioxide, nitric oxide, etc. are commercially available. This review presents an update on the latest developments in laser-based breath analysis.

  2. Solid Phase Extraction of Large Volume of Water and Beverage Samples to Improve Detection Limits for GC-MS Analysis of Bisphenol A and Four Other Bisphenols.

    PubMed

    Cao, Xu-Liang; Popovic, Svetlana

    2017-09-21

    Solid phase extraction (SPE) of large volumes of water and beverage products was investigated for the GC-MS analysis of bisphenol A (BPA), bisphenol AF (BPAF), bisphenol F (BPF), bisphenol E (BPE), and bisphenol B (BPB). While absolute recoveries of the method were improved for water and some beverage products (e.g., diet cola, iced tea), breakthrough may also have occurred during SPE of 200 mL of other beverages (e.g., BPF in cola). Improvements in method detection limits were observed with the analysis of large sample volumes for all bisphenols at ppt (pg/g) to sub-ppt levels. This improvement was found to be proportional to sample volumes for water and beverage products with less interferences and noise levels around the analytes. Matrix effects and interferences were observed during SPE of larger volumes (100 and 200 mL) of the beverage products, and affected the accurate analysis of BPF. This improved method was used to analyse bisphenols in various beverage samples, and only BPA was detected, with levels ranging from 0.022 to 0.030 ng/g for products in PET bottles, and 0.085 to 0.32 ng/g for products in cans.

  3. Subnanomolar Detection Limit Application of Ion-Selective Electrodes with Three-Dimensionally Ordered Macroporous (3DOM) Carbon Solid Contacts

    PubMed Central

    Lai, Chun-Ze; Joyer, Marti M.; Fierke, Melissa A.; Petkovich, Nicholas D.; Stein, Andreas; Bühlmann, Philippe

    2009-01-01

    Solid-contact ion-selective electrodes (SC-ISEs) can exhibit very low detection limits and, in contrast to conventional ISEs, do not require an optimization of the inner filling solution. This work shows that subnanomolar detection limits can also be achieved with SC-ISEs with three-dimensionally ordered macroporous (3DOM) carbon contacts, which have been shown recently to exhibit excellent long-term stabilities and good resistance to the interferences from oxygen and light. The detection limit of 3DOM carbon-contacted electrodes with plasticized poly(vinyl chloride) as membrane matrix can be improved with a high polymer content of the sensing membrane, a large ratio of ionophore and ionic sites, and conditioning with a low concentration of analyte ions. This permits detection limits as low as 1.6×10−7 M for K+ and 4.0×10−11 M for Ag+. PMID:20046876

  4. The minimum detection limits of RDX and TNT deposited on various surfaces as determined by ion mobility spectroscopy

    SciTech Connect

    Rodacy, P.

    1993-08-01

    An Ion Mobility Spectrometer (IMS) was used to determine the detection limits of RDX and TNT on six different substrates. The preparation of the explosive deposits on the surfaces is examined as well as effects due to the size, uniformity, method of application, and time that a deposit has been on a surface. Sampling methods are discussed along with effects of the surface topology. The transfer of explosives from a hand to a surface, and methods to reduce the detection limits are presented.

  5. Detection limits for actinides in a monochromatic, wavelength-dispersive x-ray fluorescence instrument

    SciTech Connect

    Collins, Michael L; Havrilla, George J

    2009-01-01

    Recent developments in x-ray optics have made it possible to examine the L x-rays of actinides using doubly-curved crystals in a bench-top device. A doubly-curved crystal (DCC) acts as a focusing monochromatic filter for polychromatic x-rays. A Monochromatic, Wavelength-Dispersive X-Ray Fluorescence (MWDXRF) instrument that uses DCCs to measure Cm and Pu in reprocessing plant liquors was proposed in 2007 by the authors at Los Alamos National Laboratory. A prototype design of this MWDXRF instrument was developed in collaboration with X-ray Optical Systems Inc. (XOS), of East Greenbush, New York. In the MWDXRF instrument, x-rays from a Rhodium-anode x-ray tube are passed through a primary DCC to produce a monochromatic beam of 20.2-keV photons. This beam is focused on a specimen that may contain actinides. The 20.2-keV interrogating beam is just above the L3 edge of Californium; each actinide (with Z = 90 to 98) present in the specimen emits characteristic L x-rays as the result of L3-shell vacancies. In the LANL-XOS prototype MWDXRf, these x-rays enter a secondary DCC optic that preferentially passes 14.961-keV photons, corresponding to the L-alpha-1 x-ray peak of Curium. In the present stage of experimentation, Curium-bearing specimens have not been analyzed with the prototype MWDXRF instrument. Surrogate materials for Curium include Rubidium, which has a K-beta-l x-ray at 14.961 keV, and Yttrium, which has a K-alpha-1 x-ray at 14.958 keV. In this paper, the lower limit of detection for Curium in the LANL-XOS prototype MWDXRF instrument is estimated. The basis for this estimate is described, including a description of computational models and benchmarking techniques used. Detection limits for other actinides are considered, as well as future safeguards applications for MWDXRF instrumentation.

  6. Detection limits of tidal-wetland sequences to identify variable rupture modes of megathrust earthquakes

    NASA Astrophysics Data System (ADS)

    Shennan, Ian; Garrett, Ed; Barlow, Natasha

    2016-10-01

    Recent paleoseismological studies question whether segment boundaries identified for 20th and 21st century great, >M8, earthquakes persist through multiple earthquake cycles or whether smaller segments with different boundaries rupture and cause significant hazards. The smaller segments may include some currently slipping rather than locked. In this review, we outline general principles regarding indicators of relative sea-level change in tidal wetlands and the conditions in which paleoseismic indicators must be distinct from those resulting from non-seismic processes. We present new evidence from sites across southcentral Alaska to illustrate different detection limits of paleoseismic indicators and consider alternative interpretations for marsh submergence and emergence. We compare predictions of coseismic uplift and subsidence derived from geophysical models of earthquakes with different rupture modes. The spatial patterns of agreement and misfits between model predictions and quantitative reconstructions of coseismic submergence and emergence suggest that no earthquake within the last 4000 years had a pattern of rupture the same as the Mw 9.2 Alaska earthquake in 1964. From the Alaska examples and research from other subduction zones we suggest that If we want to understand whether a megathrust ruptures in segments of variable length in different earthquakes, we need to be site-specific as to what sort of geological-based criteria eliminate the possibility of a particular rupture mode in different earthquakes. We conclude that coastal paleoseismological studies benefit from a methodological framework that employs rigorous evaluation of five essential criteria and a sixth which may be very robust but only occur at some sites: 1 - lateral extent of peat-mud or mud-peat couplets with sharp contacts; 2 - suddenness of submergence or emergence, and replicated within each site; 3 - amount of vertical motion, quantified with 95% error terms and replicated within each

  7. Detecting regime shifts in marine systems with limited biological data: An example from southeast Australia

    NASA Astrophysics Data System (ADS)

    Litzow, Michael A.; Hobday, Alistair J.; Frusher, Stewart D.; Dann, Peter; Tuck, Geoffrey N.

    2016-02-01

    The ability to detect ecological regime shifts in a data-limited setting was investigated, using southeast Australian ecosystems as a model. Community variability was summarized for 1968-2008 with the first two principal components (PCs) of recruitment estimates for six fish stocks and reproductive parameters for four seabird species; regional climate was summarized for 1953-2008 with the first two PCs for three parameters (sea surface temperature [SST], sea surface salinity, surface nitrate) measured at two stations; and basin-scale climate variability was summarized for 1950-2012 with mean South Pacific SST and the first two PCs of detrended South Pacific SST. The first two biology PCs explained 45% of total community variability. The first two PCs of basin-scale SST showed abrupt shifts similar to "regime" behavior observed in other ocean basins, and the first PC of basin-scale SST showed significant covariation with the first PC of regional climate. Together, these results are consistent with the strong community variability and decadal-scale red noise climatic variability associated with Northern Hemisphere regime shifts. However, statistical model selection showed that the first two PCs of regional climate and the first PC of biology time series all exhibited linear change, rather than abrupt shifts. This result is consistent with previous studies documenting rapid linear change in the climate and biology of southeast Australian shelf ecosystems, and we conclude that there is no evidence for regime shift behavior in the region's ecology. However, analysis of a large set of previously-published biological time series from the North Pacific (n = 64) suggests that studies using fewer than ∼30 biological time series, such as this one, may be unable to detect regime shifts. Thus we conclude that the nature of ecological variability in the region cannot be determined with available data. The development of additional long-term biological observations is needed

  8. Detecting differential transmissibilities that affect the size of self-limited outbreaks.

    PubMed

    Blumberg, Seth; Funk, Sebastian; Pulliam, Juliet R C

    2014-10-01

    Our ability to respond appropriately to infectious diseases is enhanced by identifying differences in the potential for transmitting infection between individuals. Here, we identify epidemiological traits of self-limited infections (i.e. infections with an effective reproduction number satisfying [0 < R eff < 1) that correlate with transmissibility. Our analysis is based on a branching process model that permits statistical comparison of both the strength and heterogeneity of transmission for two distinct types of cases. Our approach provides insight into a variety of scenarios, including the transmission of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in the Arabian peninsula, measles in North America, pre-eradication smallpox in Europe, and human monkeypox in the Democratic Republic of the Congo. When applied to chain size data for MERS-CoV transmission before 2014, our method indicates that despite an apparent trend towards improved control, there is not enough statistical evidence to indicate that R eff has declined with time. Meanwhile, chain size data for measles in the United States and Canada reveal statistically significant geographic variation in R eff, suggesting that the timing and coverage of national vaccination programs, as well as contact tracing procedures, may shape the size distribution of observed infection clusters. Infection source data for smallpox suggests that primary cases transmitted more than secondary cases, and provides a quantitative assessment of the effectiveness of control interventions. Human monkeypox, on the other hand, does not show evidence of differential transmission between animals in contact with humans, primary cases, or secondary cases, which assuages the concern that social mixing can amplify transmission by secondary cases. Lastly, we evaluate surveillance requirements for detecting a change in the human-to-human transmission of monkeypox since the cessation of cross-protective smallpox vaccination. Our

  9. Comparison of different DIAGNOdent cut-off limits for in vivo detection of occlusal caries.

    PubMed

    Heinrich-Weltzien, Roswitha; Kühnisch, J; Oehme, T; Ziehe, A; Stösser, L; García-Godoy, F

    2003-01-01

    This study tested recently recommended cut-off limits for the laser fluorescence based device DIAGNOdent (KaVo) for detection of occlusal caries. Two hundred and forty-eight permanent molars from 94 patients (mean age 19.2 years) of a general dental practice were included. After professional tooth cleaning, the teeth were examined visually and by the laser fluorescence method. The extent of occlusal lesions (gold standard) was determined after minimal operative intervention. Upon fissure opening, 24 teeth had enamel caries and 224 teeth revealed dentin caries, of which 58 and 166, respectively, were up to or beyond half the dentin. The optimal cut-off limits based on the highest kappa-values (0.51 and 0.54) were > 18 for superficial dentinal caries (D3) and > 37 for deep dentinal caries (D4). The comparison with DIAGNOdent cut-offs given by the manufacturer (n = 4) and those based on clinical trials with in vivo validation (n = 4) and in vitro studies with histological validation (n = 3) revealed a considerable variation in performance. Recommended cut-offs between 17 and 21 for superficial dentin lesions were in the same order of magnitude (0.48-0.51). On the D4 level, only the manufacturer's cut-off of > 34 achieved the best performance (0.51). According to the highest kappa-values and the area under the ROC curves (D3: A(z) = 0.903; D4: A(z) = 0.830), the agreement between the extent of validated caries and laser fluorescence value is still unsatisfactory.

  10. Cryogenic, Absolute, High Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

    2001-01-01

    A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

  11. Absolute measurement of optical attenuation

    NASA Astrophysics Data System (ADS)

    Wetsel, Grover C., Jr.; Stotts, Steven A.

    1983-06-01

    We have discovered that laser beam deflection spectroscopy can be used for the absolute measurement of wave or particle beam attenuation in condensed matter. The concept has been experimentally evaluated by successfully measuring the absolute optical attenuation in a crystal of U3+:CaF2 at 514 nm. A theoretical model that explains the experiment and characterizes the range of applicability of the method has been developed.

  12. Probe-Specific Procedure to Estimate Sensitivity and Detection Limits for 19F Magnetic Resonance Imaging

    PubMed Central

    Taylor, Alexander J.; Granwehr, Josef; Lesbats, Clémentine; Krupa, James L.; Six, Joseph S.; Pavlovskaya, Galina E.; Thomas, Neil R.; Auer, Dorothee P.; Meersmann, Thomas; Faas, Henryk M.

    2016-01-01

    Due to low fluorine background signal in vivo, 19F is a good marker to study the fate of exogenous molecules by magnetic resonance imaging (MRI) using equilibrium nuclear spin polarization schemes. Since 19F MRI applications require high sensitivity, it can be important to assess experimental feasibility during the design stage already by estimating the minimum detectable fluorine concentration. Here we propose a simple method for the calibration of MRI hardware, providing sensitivity estimates for a given scanner and coil configuration. An experimental “calibration factor” to account for variations in coil configuration and hardware set-up is specified. Once it has been determined in a calibration experiment, the sensitivity of an experiment or, alternatively, the minimum number of required spins or the minimum marker concentration can be estimated without the need for a pilot experiment. The definition of this calibration factor is derived based on standard equations for the sensitivity in magnetic resonance, yet the method is not restricted by the limited validity of these equations, since additional instrument-dependent factors are implicitly included during calibration. The method is demonstrated using MR spectroscopy and imaging experiments with different 19F samples, both paramagnetically and susceptibility broadened, to approximate a range of realistic environments. PMID:27727294

  13. Pushing the detection limit of infrared spectroscopy for structural analysis of dilute protein samples.

    PubMed

    Baldassarre, Maurizio; Barth, Andreas

    2014-11-07

    Fourier-transform infrared spectroscopy is a powerful and versatile tool to investigate the structure and dynamics of proteins in solution. The intrinsically low extinction coefficient of the amide I mode, the main structure-related oscillator, together with the high infrared absorptivity of aqueous media, requires that proteins are studied at high concentrations (>10 mg L(-1)). This may represent a challenge in the study of aggregation-prone proteins and peptides, and questions the significance of structural data obtained for proteins physiologically existing at much lower concentrations. Here we describe the development of a simple experimental approach that increases the detection limit of protein structure analysis by infrared spectroscopy. Our approach relies on custom-made filters to isolate the amide I region (1700-1600 cm(-1)) from irrelevant spectral regions. The sensitivity of the instrument is then increased by background attenuation, an approach consisting in the use of a neutral density filter, such as a non-scattering metal grid, to attentuate the intensity of the background spectrum. When the filters and grid are combined, a 2.4-fold improvement in the noise level can be obtained. We have successfully tested this approach using a highly diluted solution of pyruvate kinase in deuterated medium (0.2% w/v), and found that it provides spectra of a quality comparable to those recorded with a 10-fold higher protein concentration.

  14. 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.

  15. Protein immunoassay methods for detection of biotech crops: applications, limitations, and practical considerations.

    PubMed

    Stave, James W

    2002-01-01

    Immunoassay methods are available for detection and quantitation of proteins expressed by most biotechnology-derived crops in commercial production. The 2 most common test formats are enzyme-linked immunosorbent assay (ELISA) and immunochromatographic (lateral flow) strip tests. Two ELISA methods, one for Roundup Ready soybeans and one for MON810 CrylAb corn, were the subject of large international collaborative studies and were demonstrated to quantitatively determine the concentrations of biotech crops in samples of ground grain. Quantitative ELISA methods are also useful for analysis of processed fractions of agricultural commodities such as soybean toasted meal or corn flour. Both strip tests and ELISAs for biotech crops are currently being used on a large scale in the United States to manage the sale and distribution of grain. In these applications, tests are used to determine if the concentration of biotech grain is above or below specified threshold limits. Using existing U.S. Department of Agriculture sampling techniques, the reliability of the threshold determination is expressed in terms of statistical confidence rather than analytical precision. Combining the use of protein immunoassays with Identity Preservation systems provides an effective means of characterizing the raw and processed agricultural inputs to the food production system in a way that allows food producers to comply with labeling laws.

  16. Estimation of exposure distribution adjusting for association between exposure level and detection limit.

    PubMed

    Yang, Yuchen; Shelton, Brent J; Tucker, Thomas T; Li, Li; Kryscio, Richard; Chen, Li

    2017-08-15

    In environmental exposure studies, it is common to observe a portion of exposure measurements to fall below experimentally determined detection limits (DLs). The reverse Kaplan-Meier estimator, which mimics the well-known Kaplan-Meier estimator for right-censored survival data with the scale reversed, has been recommended for estimating the exposure distribution for the data subject to DLs because it does not require any distributional assumption. However, the reverse Kaplan-Meier estimator requires the independence assumption between the exposure level and DL and can lead to biased results when this assumption is violated. We propose a kernel-smoothed nonparametric estimator for the exposure distribution without imposing any independence assumption between the exposure level and DL. We show that the proposed estimator is consistent and asymptotically normal. Simulation studies demonstrate that the proposed estimator performs well in practical situations. A colon cancer study is provided for illustration. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  17. Visual acuity of the honey bee retina and the limits for feature detection

    PubMed Central

    Rigosi, Elisa; Wiederman, Steven D.; O’Carroll, David C.

    2017-01-01

    Visual abilities of the honey bee have been studied for more than 100 years, recently revealing unexpectedly sophisticated cognitive skills rivalling those of vertebrates. However, the physiological limits of the honey bee eye have been largely unaddressed and only studied in an unnatural, dark state. Using a bright display and intracellular recordings, we here systematically investigated the angular sensitivity across the light adapted eye of honey bee foragers. Angular sensitivity is a measure of photoreceptor receptive field size and thus small values indicate higher visual acuity. Our recordings reveal a fronto-ventral acute zone in which angular sensitivity falls below 1.9°, some 30% smaller than previously reported. By measuring receptor noise and responses to moving dark objects, we also obtained direct measures of the smallest features detectable by the retina. In the frontal eye, single photoreceptors respond to objects as small as 0.6° × 0.6°, with >99% reliability. This indicates that honey bee foragers possess significantly better resolution than previously reported or estimated behaviourally, and commonly assumed in modelling of bee acuity. PMID:28383025

  18. A comparative investigation of methods for longitudinal data with limits of detection through a case study.

    PubMed

    Fu, P; Hughes, J; Zeng, G; Hanook, S; Orem, J; Mwanda, O W; Remick, S C

    2016-02-01

    The statistical analysis of continuous longitudinal data may be complicated since quantitative levels of bioassay cannot always be determined. Values beyond the limits of detection (LOD) in the assays may not be observed and thus censored, rendering complexity to the analysis of such data. This article examines how both left-censoring and right censoring of HIV-1 plasma RNA measurements, collected for the study on AIDS-related Non-Hodgkin's lymphoma (AR-NHL) in East Africa, affects the quantification of viral load and explores the natural history of viral load measurements over time in AR-NHL patients receiving anticancer chemotherapy. Data analyses using Monte Carlo EM algorithm (MCEM) are compared to analyses where the LOD or LOD/2 (left censoring) value is substituted for the censored observations, and also to other methods such as multiple imputation, and maximum likelihood estimation for censored data (generalized Tobit regression). Simulations are used to explore the sensitivity of the results to changes in the model parameters. In conclusion, the antiretroviral treatment was associated with a significant decrease in viral load after controlling the effects of other covariates. A simulation study with finite sample size shows MCEM is the least biased method and the estimates are least sensitive to the censoring mechanism. © The Author(s) 2012.

  19. Review of plasmonic fiber optic biochemical sensors: improving the limit of detection.

    PubMed

    Caucheteur, Christophe; Guo, Tuan; Albert, Jacques

    2015-05-01

    This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiber-optic analogues of the Kretschmann-Raether prism SPR platforms, made from geometry-modified multimode and single-mode optical fibers (unclad, side-polished, tapered, and U-shaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively.

  20. Magnetic Lenz lenses improve the limit-of-detection in nuclear magnetic resonance.

    PubMed

    Spengler, Nils; While, Peter T; Meissner, Markus V; Wallrabe, Ulrike; Korvink, Jan G

    2017-01-01

    A high NMR detection sensitivity is indispensable when dealing with mass and volume-limited samples, or whenever a high spatial resolution is required. The use of miniaturised RF coils is a proven way to increase sensitivity, but situations may arise where space restrictions could prevent the use of a small resonant coil, e.g., in the interior of the smallest practicable micro-coils. We present the use of magnetic lenses, denoted as Lenz lenses due to their working principle, to focus the magnetic flux of an RF coil into a smaller volume and thereby locally enhance the sensitivity of the NMR experiment-at the expense of the total sensitive volume. Besides focusing, such lenses facilitate re-guiding or re-shaping of magnetic fields much like optical lenses do with light beams. For the first time we experimentally demonstrate the use of Lenz lenses in magnetic resonance and provide a compact mathematical description of the working principle. Through simulations we show that optimal arrangements can be found.

  1. 237Np absolute delayed neutron yield measurements

    NASA Astrophysics Data System (ADS)

    Doré, D.; Ledoux, X.; Nolte, R.; Gagnon-Moisan, F.; Thulliez, L.; Litaize, O.; Roettger, S.; Serot, O.

    2017-09-01

    237Np absolute delayed neutron yields have been measured at different incident neutron energies from 1.5 to 16 MeV. The experiment was performed at the Physikalisch-Technische Bundesanstalt (PTB) facility where the Van de Graaff accelerator and the cyclotron CV28 delivered 9 different neutron energy beams using p+T, d+D and d+T reactions. The detection system is made up of twelve 3He tubes inserted into a polyethylene cylinder. In this paper, the experimental setup and the data analysis method are described. The evolution of the absolute DN yields as a function of the neutron incident beam energies are presented and compared to experimental data found in the literature and data from the libraries.

  2. Absolute-magnitude distributions of supernovae

    SciTech Connect

    Richardson, Dean; Wright, John; Jenkins III, Robert L.; Maddox, Larry

    2014-05-01

    The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.

  3. F and Cl detection limits in secondary ion mass spectrometry measurements of Si and SiO{sub 2} samples

    SciTech Connect

    Pivovarov, A. L.; Guryanov, G. M.

    2010-09-15

    Usually, F and Cl negative secondary ion currents forming background signals determine detection limits for these elements in secondary ion mass spectrometry (SIMS) measurements. Technique involving changing the primary-ion current was used to determine that the ''memory effect'' is the main source of the background signal for these elements. It is shown that energy distributions of F and Cl ions forming background signals are distinctly narrower than energy distributions of these ions reflecting element bulk concentration in a Si wafer. Using this fact, the F and Cl detection limits in Si were improved by energy filtering of secondary ions. For experimental conditions used, the filtering of the secondary ion energy in a region around 60-70 eV improves the F and Cl detection limits by a factor of more than 6. The effect of an electron beam used for charge neutralization of insulator samples in a negative SIMS mode on the F and Cl detection limits was also investigated. It is shown that the simultaneous use of the primary ion and electron beams causes a synergistic increase of the background signals. It was determined that both F and Cl detection limits for the SiO{sub 2} sample are almost the same as for the Si sample when the electron and ion beams are applied simultaneously. The possible mechanism of this effect is discussed.

  4. Factors influencing the detection limit of the lateral-flow sandwich immunoassay: a case study with potato virus X.

    PubMed

    Safenkova, Irina; Zherdev, Anatoly; Dzantiev, Boris

    2012-06-01

    Key factors influencing the analyte detection limit of the sandwich immunochromatographic assay (ICA), namely, the size of gold nanoparticles, the antibody concentration, the conjugation pH, and characteristics of membranes, are discussed. The impacts of these factors were quantitatively characterized and compared for the first time using the same antigen (potato virus X). The antibody-colloidal gold conjugates synthesized at pH 9.0-9.5 (the pH was examined in the range from 7.5 to 10.0) and at an antibody concentration of 15 μg/mL (the concentration was tested from 10 to 100 μg/mL) demonstrated maximum binding with the analyte. The relationship between the size of gold nanoparticles and the ICA detection limit was determined. The detection limit decreases from 80 to 3 ng/mL (for antibodies with K (D) = 1.0 × 10(-9) M, data were obtained using a BIAcore X instrument) for a series of particles with a diameter from 6.4 to 33.4 nm (electron microscopy and dynamic light scattering data). In the case of larger particles (52 nm in diameter), the detection limit increases and reaches 9 ng/mL. A 10 mM phosphate buffer, pH 8, and a 50 mM phosphate buffer, pH 7, were the conditions of choice for the deposition of reactants. Taking into account these facts, we developed a lateral-flow test system for the rapid (10 min) detection of potato virus X in plant leaves. The ICA provided a visual detection limit of 3 ng/mL. In the case of the instrumental processing, potato virus X can be determined in the concentration range from 3 to 300 ng/mL with a detection limit 2 ng/mL.

  5. Extending the lower limits of force detection using micromachined silicon cantilevers

    NASA Astrophysics Data System (ADS)

    Stowe, Timothy David

    2000-09-01

    The force resolution of a micromachined cantilever is ultimately limited by thermal contact with the surrounding environment and the intrinsic energy dissipation within the cantilever. By optimizing the cantilever geometry to reduce energy dissipation, this thesis demonstrates that a force resolution of 1.7 × 10-18N/ Hz can be achieved in a low temperature vacuum environment. This force resolution represents a world record for microcantilever-based force detection. In order to optimize the cantilever design, a custom micromachining process was developed for fabricating free-standing single-crystal-silicon cantilevers as thin as 400 angstroms. For such thin cantilevers, surface- related energy dissipation was shown to limit the low temperature mechanical Q. Methods for reducing the surface disorder by removing the native surface oxide typically resulted in a four-fold increase in Q and therefore improved force resolution. The fabricated cantilevers typically had spring constants less than 10 -4 N/m, or a hundred times lower than the spring constants of cantilevers commonly used in scanning probe microscopy. When used in scanning probe microscopy experiments, the cantilevers were aligned perpendicular to the sample surface in order to eliminate the problem of tip-to-sample snap-in. This novel geometry allowed the study of lateral forces between the cantilever tip and the sample. Changes in the cantilever resonant frequency were shown to predominately reflect the electrostatic nature of the surface being investigated. One surface interaction that was investigated in detail was the reduction of cantilever Q near various surfaces in vacuum. This non-contact dissipative phenomenon was related to electrical losses caused by induced charge motion in the sample and/or in the cantilever tip. In silicon samples, a quantitative theory relating the additional surface-induced cantilever damping to the electrical power dissipated was developed. Furthermore

  6. Absolute radiometric calibration of advanced remote sensing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1982-01-01

    The distinction between the uses of relative and absolute spectroradiometric calibration of remote sensing systems is discussed. The advantages of detector-based absolute calibration are described, and the categories of relative and absolute system calibrations are listed. The limitations and problems associated with three common methods used for the absolute calibration of remote sensing systems are addressed. Two methods are proposed for the in-flight absolute calibration of advanced multispectral linear array systems. One makes use of a sun-illuminated panel in front of the sensor, the radiance of which is monitored by a spectrally flat pyroelectric radiometer. The other uses a large, uniform, high-radiance reference ground surface. The ground and atmospheric measurements required as input to a radiative transfer program to predict the radiance level at the entrance pupil of the orbital sensor are discussed, and the ground instrumentation is described.

  7. Osteosarcoma Microenvironment: Whole-Slide Imaging and Optimized Antigen Detection Overcome Major Limitations in Immunohistochemical Quantification

    PubMed Central

    Kunz, Pierre; Fellenberg, Jörg; Moskovszky, Linda; Sápi, Zoltan; Krenacs, Tibor; Poeschl, Johannes; Lehner, Burkhard; Szendrõi, Miklos; Ewerbeck, Volker; Kinscherf, Ralf; Fritzsching, Benedikt

    2014-01-01

    Background In osteosarcoma survival rates could not be improved over the last 30 years. Novel biomarkers are warranted to allow risk stratification of patients for more individual treatment following initial diagnosis. Although previous studies of the tumor microenvironment have identified promising candidates, novel biomarkers have not been translated into routine histopathology. Substantial difficulties regarding immunohistochemical detection and quantification of antigens in decalcified and heterogeneous osteosarcoma might largely explain this translational short-coming. Furthermore, we hypothesized that conventional hot spot analysis is often not representative for the whole section when applied to heterogeneous tissues like osteosarcoma. We aimed to overcome these difficulties for major biomarkers of the immunovascular microenvironment. Methods Immunohistochemistry was systematically optimized for cell surface (CD31, CD8) and intracellular antigens (FOXP3) including evaluation of 200 different antigen retrieval conditions. Distribution patterns of these antigens were analyzed in formalin-fixed and paraffin-embedded samples from 120 high-grade central osteosarcoma biopsies and computer-assisted whole-slide analysis was compared with conventional quantification methods including hot spot analysis. Results More than 96% of osteosarcoma samples were positive for all antigens after optimization of immunohistochemistry. In contrast, standard immunohistochemistry retrieved false negative results in 35–65% of decalcified osteosarcoma specimens. Standard hot spot analysis was applicable for homogeneous distributed FOXP3+ and CD8+ cells. However, heterogeneous distribution of vascular CD31 did not allow reliable quantification with hot spot analysis in 85% of all samples. Computer-assisted whole-slide analysis of total CD31- immunoreactive area proved as the most appropriate quantification method. Conclusion Standard staining and quantification procedures are not

  8. Compact quantum dot-antibody conjugates for FRET immunoassays with subnanomolar detection limits.

    PubMed

    Mattera, Lucia; Bhuckory, Shashi; Wegner, K David; Qiu, Xue; Agnese, Fabio; Lincheneau, Christophe; Senden, Tim; Djurado, David; Charbonnière, Loïc J; Hildebrandt, Niko; Reiss, Peter

    2016-06-07

    A novel two-step approach for quantum dot (QD) functionalization and bioconjugation is presented, which yields ultra-compact, stable, and highly luminescent antibody-QD conjugates suitable for use in FRET immunoassays. Hydrophobic InPZnS/ZnSe/ZnS (emission wavelength: 530 nm), CdSe/ZnS (605 nm), and CdSeTe/ZnS (705 nm) QDs were surface functionalized with zwitterionic penicillamine, enabling aqueous phase transfer under conservation of the photoluminescence properties. Post-functionalization with a heterobifunctional crosslinker, containing a lipoic acid group and a maleimide function, enabled the subsequent coupling to sulfhydryl groups of proteins. This was demonstrated by QD conjugation with fragmented antibodies (F(ab)). The obtained F(ab)-QD conjugates range among the smallest antibody-functionalized nanoprobes ever reported, with a hydrodynamic diameter <13 nm, PL quantum yield up to 66% at 705 nm, and colloidal stability of several months in various buffers. They were applied as FRET acceptors in homogeneous, time-gated immunoassays using Tb-antibodies as FRET donors, both coupled by an immunological sandwich complex between the two antibodies and a PSA (prostate specific antigen) biomarker. The advantages of the compact surface coating for FRET could be demonstrated by an 6.2 and 2.5 fold improvement of the limit of detection (LOD) for PSA compared to commercially available hydrophilic QDs emitting at 605 and 705 nm, respectively. While the commercial QDs contain identical inorganic cores responsible for their fluorescence, they are coated with a comparably thick amphiphilic polymer layer leading to much larger hydrodynamic diameters (>26 nm without biomolecules). The LODs of 0.8 and 3.7 ng mL(-1) obtained in 50 μL serum samples are below the clinical cut-off level of PSA (4 ng mL(-1)) and demonstrate their direct applicability in clinical diagnostics.

  9. Detection limits of multi-spectral optical imaging under the skin surface

    NASA Astrophysics Data System (ADS)

    Binzoni, T.; Vogel, A.; Gandjbakhche, A. H.; Marchesini, R.

    2008-02-01

    The present work shows that the optical/biological information contained in a typical spectral image mainly reflects the properties of a small (conic like) volume of tissue situated vertically under each individual pixel. The objects appearing on a spectral image reasonably reproduce the correct geometrical shape and size (like a non-deformed shadow) of underlying inclusions of pathological tissue. The information contained in a spectral image comes from a depth that does not exceed ~2-3 mm. The number of photons that visit a given tissue voxel situated at a depth larger than ~2 mm represents less than the 1% of the total number of photons reaching the corresponding detection pixel (forming the image). A pathological inclusion (e.g. a pool of blood or vascular tumor) situated at a depth of ~0.5 mm with a thickness of 0.5 mm produces an image intensity contrast of ~5% (for images taken at wavelengths in the 600-1000 nm range) when compared to the normal skin background. The same inclusion at a depth of 20 µm provides a contrast decreasing from 55 to 20% with respect to an increase in wavelength. The dermis/hypodermis interface behaves as a partial barrier for the photons, limiting their access to deeper skin regions. The image contrast depends on the depth and the type of chromophore contained in the inclusion. An increase in the concentration of a given molecule may produce different contrast, independently of the depth, depending on the characteristics of the skin layer where this change occurs.

  10. Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner

    PubMed Central

    El-Sharkawy, AbdEl-Monem M.; Sotiriadis, Paul P.; Bottomley, Paul A.; Atalar, Ergin

    2007-01-01

    Temperature detection using microwave radiometry has proven value for noninvasively measuring the absolute temperature of tissues inside the body. However, current clinical radiometers operate in the gigahertz range, which limits their depth of penetration. We have designed and built a noninvasive radiometer which operates at radio frequencies (64 MHz) with ∼100-kHz bandwidth, using an external RF loop coil as a thermal detector. The core of the radiometer is an accurate impedance measurement and automatic matching circuit of 0.05 Ω accuracy to compensate for any load variations. The radiometer permits temperature measurements with accuracy of ±0.1°K, over a tested physiological range of 28° C–40° C in saline phantoms whose electric properties match those of tissue. Because 1.5 T magnetic resonance imaging (MRI) scanners also operate at 64 MHz, we demonstrate the feasibility of integrating our radiometer with an MRI scanner to monitor RF power deposition and temperature dosimetry, obtaining coarse, spatially resolved, absolute thermal maps in the physiological range. We conclude that RF radiometry offers promise as a direct, noninvasive method of monitoring tissue heating during MRI studies and thereby providing an independent means of verifying patient-safe operation. Other potential applications include titration of hyper- and hypo-therapies. PMID:18026562

  11. Exploring the Limits of Waveform Correlation Event Detection as Applied to Three Earthquake Aftershock Sequences

    NASA Astrophysics Data System (ADS)

    Young, C. J.; Carr, D.; Resor, M.; Duffey, S.

    2009-12-01

    Swarms of earthquakes and/or aftershock sequences can dramatically increase the level of seismicity in a region for a period of time lasting from days to months, depending on the swarm or sequence. Such occurrences can provide a large amount of useful information to seismologists. For those who monitor seismic events for possible nuclear explosions, however, these swarms/sequences are a nuisance. In an explosion monitoring system, each event must be treated as a possible nuclear test until it can be proven, to a high degree of confidence, not to be. Seismic events recorded by the same station with highly correlated waveforms almost certainly have a similar location and source type, so clusters of events within a swarm can quickly be identified as earthquakes. We have developed a number of tools that can be used to exploit the high degree of waveform similarity expected to be associated with swarms/sequences. Dendro Tool measures correlations between known events. The Waveform Correlation Detector is intended to act as a detector, finding events in raw data which correlate with known events. The Self Scanner is used to find all correlated segments within a raw data steam and does not require an event library. All three techniques together provide an opportunity to study the similarities of events in an aftershock sequence in different ways. To comprehensively characterize the benefits and limits of waveform correlation techniques, we studied 3 aftershock sequences, using our 3 tools, at multiple stations. We explored the effects of station distance and event magnitudes on correlation results. Lastly, we show the reduction in detection threshold and analyst workload offered by waveform correlation techniques compared to STA/LTA based detection. We analyzed 4 days of data from each aftershock sequence using all three methods. Most known events clustered in a similar manner across the toolsets. Up to 25% of catalogued events were found to be a member of a cluster. In

  12. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  13. Boosting the Quantitative Inorganic Surface-Enhanced Raman Scattering Sensing to the Limit: The Case of Nitrite/Nitrate Detection.

    PubMed

    Correa-Duarte, Miguel A; Pazos Perez, Nicolas; Guerrini, Luca; Giannini, Vincenzo; Alvarez-Puebla, Ramon A

    2015-03-05

    A high-performance ionic-sensing platform has been developed by an interdisciplinary approach, combining the classical colorimetric Griess reaction and new concepts of nanotechnology, such as plasmonic coupling of nanoparticles and surface-enhanced Raman scattering (SERS) spectroscopy. This approach exploits the advantages of combined SERS/surface-enhanced resonant Raman Scattering (SERRS) by inducing the formation of homogeneous hot spots and a colored complex in resonance with the laser line, to yield detection limits for nitrite down to the subpicomolar level. The performance of this new method was compared with the classical Griess reaction and ionic chromatography showing detection limits about 6 and 3 orders of magnitude lower, respectively.

  14. Analysis of the limiting noise and identification of some factors that dictate the detection limits in a low-power inductively coupled argon plasma system

    NASA Astrophysics Data System (ADS)

    Boumans, P. W. J. M.; McKenna, R. J.; Bosveld, M.

    The background signal defined as the output signal ( xB) of the photomultiplier and the relative standard deviation (RSD) of xB at the wavelengths of 36 prominent analysis lines in the 190-320 nm region were measured under ICP compromise conditions for simultaneous multi-element analysis using a monochromator with an experimental spectral bandwidth of 0.015 nm. The RSD was found to vary systematically with xB according to the theoretically expected relationship RSD = (α B2 + gβ/ xB) 1/2 where α B(≈0.5%) is the constant source flicker noise contribution, gβ/ xB the shot-noise contribution and gβ a coefficient containing the photomultiplier (PMT) gain g. Dark current detector noise was negligible, at least in part, owing to the use of lock-in amplification. The validity of relationship (0) was tested for various types of PMT and for both pure aqueous solutions and solutions with 1 to 3% w/v amounts of either calcium chloride, sodium chloride, or a mixture of nickel and cobalt nitrates. Only in the case of the nickel-cobalt matrix were some departures found and these were attributable to line coincidences. Relationship (0) was found to apply also to net line signals, the flicker noise term, α s, then being about 1% instead of 0.5% for the present ICP system. Detection limits for 36 prominent lines of the elements As, Au, B, Be, Bi, Ge, In, Mg, Mn, Ni, P, Pb, Sb, Se, Sn and Zn were computed on the basis of relationship (0) and measured signal-to-background ratios (SBR). The results permitted an assessment of the separate effects that SBR, source flicker noise and shot noise have on the detection limits and this facilitated a detailed comparison of the detection limits obtained in this work with those reported by Winge, Peterson and Fassel [ Appl. Spectrosc.33, 106 (1979)]. The measurements of detection limits were extended to solutions with matrices (calcium chloride, sodium chloride, and a mixture of nickel and cobalt nitrates) to test the validity of the

  15. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum using Phased Array Ultrasound

    NASA Technical Reports Server (NTRS)

    Johnston, P. H.

    2008-01-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  16. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum Using Phased Array Ultrasound

    NASA Astrophysics Data System (ADS)

    Johnston, P. H.

    2009-03-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  17. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  18. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  19. System for absolute measurements by interferometric sensors

    NASA Astrophysics Data System (ADS)

    Norton, Douglas A.

    1993-03-01

    The most common problem of interferometric sensors is their inability to measure absolute path imbalance. Presented in this paper is a signal processing system that gives absolute, unambiguous reading of optical path difference for almost any style of interferometric sensor. Key components are a wide band (incoherent) optical source, a polychromator, and FFT electronics. Advantages include no moving parts in the signal processor, no active components at the sensor location, and the use of standard single mode fiber for sensor illumination and signal transmission. Actual absolute path imbalance of the interferometer is determined without using fringe counting or other inferential techniques. The polychromator extracts the interference information that occurs at each discrete wavelength within the spectral band of the optical source. The signal processing consists of analog and digital filtering, Fast Fourier analysis, and a peak detection and interpolation algorithm. This system was originally designed for use in a remote pressure sensing application that employed a totally passive fiber optic interferometer. A performance qualification was made using a Fabry-Perot interferometer and a commercially available laser interferometer to measure the reference displacement.

  20. The absolute dynamic ocean topography (ADOT)

    NASA Astrophysics Data System (ADS)

    Bosch, Wolfgang; Savcenko, Roman

    The sea surface slopes relative to the geoid (an equipotential surface) basically carry the in-formation on the absolute velocity field of the surface circulation. Pure oceanographic models may remain unspecific with respect to the absolute level of the ocean topography. In contrast, the geodetic approach to estimate the ocean topography as difference between sea level and the geoid gives by definition an absolute dynamic ocean topography (ADOT). This approach requires, however, a consistent treatment of geoid and sea surface heights, the first being usually derived from a band limited spherical harmonic series of the Earth gravity field and the second observed with much higher spectral resolution by satellite altimetry. The present contribution shows a procedure for estimating the ADOT along the altimeter profiles, preserving as much sea surface height details as the consistency w.r.t. the geoid heights will allow. The consistent treatment at data gaps and the coast is particular demanding and solved by a filter correction. The ADOT profiles are inspected for their innocent properties towards the coast and compared to external estimates of the ocean topography or the velocity field of the surface circulation as derived, for example, by ARGO floats.

  1. Unveiling the Gamma-Ray Source Count Distribution Below the Fermi Detection Limit with Photon Statistics

    DOE PAGES

    Zechlin, Hannes-S.; Cuoco, Alessandro; Donato, Fiorenza; ...

    2016-07-26

    The source-count distribution as a function of their flux, dN/dS, is one of the main quantities characterizing gamma-ray source populations. In this paper, we employ statistical properties of the Fermi Large Area Telescope (LAT) photon counts map to measure the composition of the extragalactic gamma-ray sky at high latitudes (|b| greater-than or slanted equal to 30°) between 1 and 10 GeV. We present a new method, generalizing the use of standard pixel-count statistics, to decompose the total observed gamma-ray emission into (a) point-source contributions, (b) the Galactic foreground contribution, and (c) a truly diffuse isotropic background contribution. Using the 6more » yr Fermi-LAT data set (P7REP), we show that the dN/dS distribution in the regime of so far undetected point sources can be consistently described with a power law with an index between 1.9 and 2.0. We measure dN/dS down to an integral flux of ~2 x 10-11cm-2s-1, improving beyond the 3FGL catalog detection limit by about one order of magnitude. The overall dN/dS distribution is consistent with a broken power law, with a break at 2.1+1.0-1.3 x 10-8cm-2s-1. The power-law index n1 = 3.1+0.7-0.5 for bright sources above the break hardens to n2 = 1.97 ± 0.03 for fainter sources below the break. A possible second break of the dN/dS distribution is constrained to be at fluxes below 6.4 x 10-11cm-2s-1 at 95% confidence level. Finally, the high-latitude gamma-ray sky between 1 and 10 GeV is shown to be composed of ~25% point sources, ~69.3% diffuse Galactic foreground emission, and ~6% isotropic diffuse background.« less

  2. Rapid methods for the detection of foodborne bacterial pathogens: principles, applications, advantages and limitations

    PubMed Central

    Law, Jodi Woan-Fei; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Lee, Learn-Han

    2015-01-01

    The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases. PMID:25628612

  3. Rapid methods for the detection of foodborne bacterial pathogens: principles, applications, advantages and limitations.

    PubMed

    Law, Jodi Woan-Fei; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Lee, Learn-Han

    2014-01-01

    The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases.

  4. Compact quantum dot-antibody conjugates for FRET immunoassays with subnanomolar detection limits

    NASA Astrophysics Data System (ADS)

    Mattera, Lucia; Bhuckory, Shashi; Wegner, K. David; Qiu, Xue; Agnese, Fabio; Lincheneau, Christophe; Senden, Tim; Djurado, David; Charbonnière, Loïc J.; Hildebrandt, Niko; Reiss, Peter

    2016-05-01

    A novel two-step approach for quantum dot (QD) functionalization and bioconjugation is presented, which yields ultra-compact, stable, and highly luminescent antibody-QD conjugates suitable for use in FRET immunoassays. Hydrophobic InPZnS/ZnSe/ZnS (emission wavelength: 530 nm), CdSe/ZnS (605 nm), and CdSeTe/ZnS (705 nm) QDs were surface functionalized with zwitterionic penicillamine, enabling aqueous phase transfer under conservation of the photoluminescence properties. Post-functionalization with a heterobifunctional crosslinker, containing a lipoic acid group and a maleimide function, enabled the subsequent coupling to sulfhydryl groups of proteins. This was demonstrated by QD conjugation with fragmented antibodies (F(ab)). The obtained F(ab)-QD conjugates range among the smallest antibody-functionalized nanoprobes ever reported, with a hydrodynamic diameter <13 nm, PL quantum yield up to 66% at 705 nm, and colloidal stability of several months in various buffers. They were applied as FRET acceptors in homogeneous, time-gated immunoassays using Tb-antibodies as FRET donors, both coupled by an immunological sandwich complex between the two antibodies and a PSA (prostate specific antigen) biomarker. The advantages of the compact surface coating for FRET could be demonstrated by an 6.2 and 2.5 fold improvement of the limit of detection (LOD) for PSA compared to commercially available hydrophilic QDs emitting at 605 and 705 nm, respectively. While the commercial QDs contain identical inorganic cores responsible for their fluorescence, they are coated with a comparably thick amphiphilic polymer layer leading to much larger hydrodynamic diameters (>26 nm without biomolecules). The LODs of 0.8 and 3.7 ng mL-1 obtained in 50 μL serum samples are below the clinical cut-off level of PSA (4 ng mL-1) and demonstrate their direct applicability in clinical diagnostics.A novel two-step approach for quantum dot (QD) functionalization and bioconjugation is presented, which yields

  5. On the theoretical limits of detecting cyclic changes in cardiac high-energy phosphates and creatine kinase reaction kinetics using in vivo ³¹P MRS.

    PubMed

    Weiss, Kilian; Bottomley, Paul A; Weiss, Robert G

    2015-06-01

    Adenosine triphosphate (ATP) is absolutely required to fuel normal cyclic contractions of the heart. The creatine kinase (CK) reaction is a major energy reserve reaction that rapidly converts creatine phosphate (PCr) to ATP during the cardiac cycle and at times of stress and ischemia, but is significantly impaired in conditions such as hypertrophy and heart failure. Because the magnitudes of possible in vivo cyclic changes in cardiac high-energy phosphates (HEPs) during the cardiac cycle are not well known from previous work, this study uses mathematical modeling to assess whether, and to what extent, cyclic variations in HEPs and in the rate of ATP synthesis through CK (CK flux) could exist in the human heart, and whether they could be measured with current in vivo (31)P MRS methods. Multi-site exchange models incorporating enzymatic rate equations were used to study the cyclic dynamics of the CK reaction, and Bloch equations were used to simulate (31)P MRS saturation transfer measurements of the CK reaction. The simulations show that short-term buffering of ATP by CK requires temporal variations over the cardiac cycle in the CK reaction velocities modeled by enzymatic rate equations. The maximum variation in HEPs in the normal human heart beating at 60 min(-1) was approximately 0.4 mM and proportional to the velocity of ATP hydrolysis. Such HEP variations are at or below the current limits of detection by in vivo (31)P MRS methods. Bloch equation simulations show that (31)P MRS saturation transfer estimates the time-averaged, pseudo-first-order forward rate constant, k(f,ap)', of the CK reaction, and that periodic short-term fluctuations in kf ' and CK flux are not likely to be detectable in human studies employing current in vivo (31)P MRS methods.

  6. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  7. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  8. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  9. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  10. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  11. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  12. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    PubMed

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-06

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

  13. Rational design of potentiometric trace level ion sensors. A Ag+-selective electrode with a 100 ppt detection limit.

    PubMed

    Ceresa, Alan; Radu, Aleksandar; Peper, Shane; Bakker, Eric; Pretsch, Ernö

    2002-08-15

    Submicromolar to picomolar lower detection limits have recently been obtained with various polymer membrane ion-selective electrodes by minimizing biases due to ion fluxes through the membrane. For the best performance, the compositions of the membrane and inner solution should be optimized for each application. Given the number of parameters to be adjusted, it has been difficult to find the best parameters for a target sample. In this paper, a much simplified and more practical steady-state model of zero-current ion fluxes is derived, which is based on measurable parameters. The model allows one to predict achievable lower detection limits for a membrane with given selectivities. It can also be used to predict the optimal composition of the inner filling solution for the measurement of samples with a known, typical ionic background. Selectivity coefficients of monovalent and divalent analyte ions required for desired detection limits in drinking water are calculated. As an application of the proposed general recipe, a silver-selective electrode is developed on the basis of the ionophore O,O''-bis[2-(methylthio)ethyl]-tert-butylcalix[4]arene. With the predicted optimal composition of the inner electrolyte, its lower detection limit is found to be 10(-9) M or 100 ppt Ag+ with an ionic background of 10(-5) M LiNO3, which is very close to the expected value.

  14. Minimum detection limits and applications of proton and helium induced X-ray emission using transition-edge sensor array

    NASA Astrophysics Data System (ADS)

    Käyhkö, M.; Palosaari, M. R. J.; Laitinen, M.; Arstila, K.; Maasilta, I. J.; Fowler, J. W.; Doriese, W. B.; Ullom, J. N.; Sajavaara, T.

    2017-09-01

    We have determined minimum detection limits, MDLs, for elements 14 ⩽ Z ⩽ 86 using a transition-edge sensor array, TES array, and as a comparison using an Amptek X-123SDD silicon drift detector, SDD. This was done using a 3 MeV proton beam and a 5.1 MeV helium beam. MDLs were determined for a thin film sample on top of C substrate, and for a bulk sample containing mostly Al. Due to the higher peak-to-background ratio, lower detection limits were obtainable using the TES array for most of the elements. However, for elements 30 ⩽ Z ⩽ 45 the performance of the TES array was not as good as the SDD performance. This is due to the limitations of the TES used at energies >10 keV. The greatest advantage of TES comes, however, when detecting low intensity peaks close to high intensity peaks. Such a case was demonstrated by measuring a fly ash with overlapping Ti, V, Ba, and Ce peaks, where minimum detection limits of V, Ba, and Ce were decreased by factor of 620, 400, and 680, respectively, compared to the SDD.

  15. SUPPLEMENT TO EPA COMPENDIUM METHOD TO-15 - REDUCTION OF METHOD DETECTION LIMITS TO MEET VAPOR INTRUSION MONITORING NEEDS

    EPA Science Inventory

    The Supplement to EPA Compendium Method TO-15 provides guidance for reducing the method detection limit (MDL) for the compound 1,1- dichloroethene (1,1-DCE) and for other volatile organic compounds (VOCs) from 0.5 ppbv, as cited in Method TO-15, to much lower concentrations. R...

  16. SUPPLEMENT TO EPA COMPENDIUM METHOD TO-15 - REDUCTION OF METHOD DETECTION LIMITS TO MEET VAPOR INTRUSION MONITORING NEEDS

    EPA Science Inventory

    The Supplement to EPA Compendium Method TO-15 provides guidance for reducing the method detection limit (MDL) for the compound 1,1-dichloroethene (1,1-DCE) and for other volatile organic compounds (VOCs) from 0.5 parts per billion by volume (ppbv), as cited in Method TO-15, to ...

  17. 40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... processing steps of the analytical method be included in the determination of the method detection limit. The... corresponds to an instrument signal/noise ratio in the range of 2.5 to 5. If the criteria for qualitative identification of the analyte is based upon pattern recognition techniques, the least abundant signal...

  18. SUPPLEMENT TO EPA COMPENDIUM METHOD TO-15 - REDUCTION OF METHOD DETECTION LIMITS TO MEET VAPOR INTRUSION MONITORING NEEDS

    EPA Science Inventory

    The Supplement to EPA Compendium Method TO-15 provides guidance for reducing the method detection limit (MDL) for the compound 1,1-dichloroethene (1,1-DCE) and for other volatile organic compounds (VOCs) from 0.5 parts per billion by volume (ppbv), as cited in Method TO-15, to ...

  19. SUPPLEMENT TO EPA COMPENDIUM METHOD TO-15 - REDUCTION OF METHOD DETECTION LIMITS TO MEET VAPOR INTRUSION MONITORING NEEDS

    EPA Science Inventory

    The Supplement to EPA Compendium Method TO-15 provides guidance for reducing the method detection limit (MDL) for the compound 1,1- dichloroethene (1,1-DCE) and for other volatile organic compounds (VOCs) from 0.5 ppbv, as cited in Method TO-15, to much lower concentrations. R...

  20. Qualitative Contrast between Knowledge-Limited Mixed-State and Variable-Resources Models of Visual Change Detection

    ERIC Educational Resources Information Center

    Nosofsky, Robert M.; Donkin, Chris

    2016-01-01

    We report an experiment designed to provide a qualitative contrast between knowledge-limited versions of mixed-state and variable-resources (VR) models of visual change detection. The key data pattern is that observers often respond "same" on big-change trials, while simultaneously being able to discriminate between same and small-change…

  1. Qualitative Contrast between Knowledge-Limited Mixed-State and Variable-Resources Models of Visual Change Detection

    ERIC Educational Resources Information Center

    Nosofsky, Robert M.; Donkin, Chris

    2016-01-01

    We report an experiment designed to provide a qualitative contrast between knowledge-limited versions of mixed-state and variable-resources (VR) models of visual change detection. The key data pattern is that observers often respond "same" on big-change trials, while simultaneously being able to discriminate between same and small-change…

  2. Maximum detection range limitation of pulse laser radar with Geiger-mode avalanche photodiode array

    NASA Astrophysics Data System (ADS)

    Luo, Hanjun; Xu, Benlian; Xu, Huigang; Chen, Jingbo; Fu, Yadan

    2015-05-01

    When designing and evaluating the performance of laser radar system, maximum detection range achievable is an essential parameter. The purpose of this paper is to propose a theoretical model of maximum detection range for simulating the Geiger-mode laser radar's ranging performance. Based on the laser radar equation and the requirement of the minimum acceptable detection probability, and assuming the primary electrons triggered by the echo photons obey Poisson statistics, the maximum range theoretical model is established. By using the system design parameters, the influence of five main factors, namely emitted pulse energy, noise, echo position, atmospheric attenuation coefficient, and target reflectivity on the maximum detection range are investigated. The results show that stronger emitted pulse energy, lower noise level, more front echo position in the range gate, higher atmospheric attenuation coefficient, and higher target reflectivity can result in greater maximum detection range. It is also shown that it's important to select the minimum acceptable detection probability, which is equivalent to the system signal-to-noise ratio for producing greater maximum detection range and lower false-alarm probability.

  3. Detecting Anatomical Landmarks From Limited Medical Imaging Data Using Two-Stage Task-Oriented Deep Neural Networks.

    PubMed

    Zhang, Jun; Liu, Mingxia; Shen, Dinggang

    2017-10-01

    One of the major challenges in anatomical landmark detection, based on deep neural networks, is the limited availability of medical imaging data for network learning. To address this problem, we present a two-stage task-oriented deep learning method to detect large-scale anatomical landmarks simultaneously in real time, using limited training data. Specifically, our method consists of two deep convolutional neural networks (CNN), with each focusing on one specific task. Specifically, to alleviate the problem of limited training data, in the first stage, we propose a CNN based regression model using millions of image patches as input, aiming to learn inherent associations between local image patches and target anatomical landmarks. To further model the correlations among image patches, in the second stage, we develop another CNN model, which includes a) a fully convolutional network that shares the same architecture and network weights as the CNN used in the first stage and also b) several extra layers to jointly predict coordinates of multiple anatomical landmarks. Importantly, our method can jointly detect large-scale (e.g., thousands of) landmarks in real time. We have conducted various experiments for detecting 1200 brain landmarks from the 3D T1-weighted magnetic resonance images of 700 subjects, and also 7 prostate landmarks from the 3D computed tomography images of 73 subjects. The experimental results show the effectiveness of our method regarding both accuracy and efficiency in the anatomical landmark detection.

  4. Optimizing the Thermal Read-Out Technique for MIP-Based Biomimetic Sensors: Towards Nanomolar Detection Limits

    PubMed Central

    Geerets, Bram; Peeters, Marloes; van Grinsven, Bart; Bers, Karolien; de Ceuninck, Ward; Wagner, Patrick

    2013-01-01

    In previous work, the novel heat-transfer method (HTM) for the detection of small molecules with Molecularly Imprinted Polymers (MIP)-type receptors was presented. In this study we focus on optimization of this sensor performance, with as final aim to lower the detection limit by reducing the noise level. It was determined that the noise originates foremost from the power supply, which can be controlled by varying the PID parameters. Therefore, the effect of the individual parameters was evaluated by tuning P, I and D separately at a temperature of 37 °C, giving a first indication of the optimal configuration. Next, a temperature profile was programmed and the standard deviation of the heat-transfer resistance over the entire regime was studied for a set of parameters. The optimal configuration, P1-I6-D0, reduced the noise level with nearly a factor of three compared to the original parameters of P10-I5-D0. With the optimized settings, the detection of L-nicotine in buffer solutions was studied and the detection limit improved significantly from 100 nM to 35 nM. Summarizing, optimization of the PID parameters and thereby improving the detection limit is a key parameter for first applications of the HTM-method for MIP receptors in analytical research. PMID:23863857

  5. Detection and quantification limits: basic concepts, international harmonization, and outstanding ("low-level") issues.

    PubMed

    Currie, L A

    2004-01-01

    A brief review is given of concepts, basic definitions, and terminology for metrological detection and quantification capabilities, representing harmonized recommendations and norms of the International Union of Pure and Applied Chemistry (IUPAC) and the International Organization for Standardization (ISO), respectively. Treatment of the (low-level) blank and variance function are discussed in some detail, together with special problems arising with detection decisions and the reporting of low-level data. Key references to the international documents follow, as well as specialized references addressing very low-level counting data, skewed environmental blank distributions, and multiple and multivariate detection decisions.

  6. H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area

    NASA Technical Reports Server (NTRS)

    Hoffman, G. Lyle; Glosson, John; Helou, George; Salpeter, E. E.; Sandage, A.

    1987-01-01

    New single-beam Arecibo H I observations of 298 late-type galaxies in the Virgo Cluster drawn mostly from the new catalog of Binggeli, Sandage, and Tammann (1985) are presented. Two hundred seventeen of these constitute a magnitude-limited 'complete sample' of such galaxies, types Sdm through Im and BCD. Sixty-one percent of this 'complete sample' was detected, greatly enhancing the store of redshifts and H I masses for such galaxies in the Virgo Cluster. For detected galaxies, heliocentric velocities, 50 percent profile widths, and single-beam fluxes are presented. For those that escaped detection, upper limits are computed to the flux appropriate to the redshift range (-600 to +3000 km/s).

  7. Absolute peptide quantification by lutetium labeling and nanoHPLC-ICPMS with isotope dilution analysis.

    PubMed

    Rappel, Christina; Schaumlöffel, Dirk

    2009-01-01

    The need of analytical methods for absolute quantitative protein analysis spurred research on new developments in recent years. In this work, a novel approach was developed for accurate absolute peptide quantification based on metal labeling with lutetium diethylenetriamine pentaacetic acid (Lu-DTPA) and nanoflow high-performance liquid chromatography-inductively coupled plasma isotope dilution mass spectrometry (nanoHPLC-ICP-IDMS). In a two-step procedure peptides were derivatized at amino groups with diethylenetriamine pentaacetic anhydride (DTPAA) followed by chelation of lutetium. Electrospray ionization mass spectrometry (ESI MS) of the reaction product demonstrated highly specific peptide labeling. Under optimized nanoHPLC conditions the labeled peptides were baseline-separated, and the excess labeling reagent did not interfere. A 176Lu-labeled spike was continuously added to the column effluent for quantification by ICP-IDMS. The recovery of a Lu-DTPA-labeled standard peptide was close to 100% indicating high labeling efficiency and accurate absolute quantification. The precision of the entire method was 4.9%. The detection limit for Lu-DTPA-tagged peptides was 179 amol demonstrating that lutetium-specific peptide quantification was by 4 orders of magnitude more sensitive than detection by natural sulfur atoms present in cysteine or methionine residues. Furthermore, the application to peptides in insulin tryptic digest allowed the identification of interfering reagents decreasing the labeling efficiency. An additional advantage of this novel approach is the analysis of peptides, which do not naturally feature ICPMS-detectable elements.

  8. Limits on surface gravities of Kepler planet-candidate host stars from non-detection of solar-like oscillations

    SciTech Connect

    Campante, T. L.; Chaplin, W. J.; Handberg, R.; Miglio, A.; Davies, G. R.; Elsworth, Y. P.; Lund, M. N.; Arentoft, T.; Christensen-Dalsgaard, J.; Karoff, C.; Kjeldsen, H.; Lundkvist, M.; Huber, D.; Hekker, S.; García, R. A.; Basu, S.; Bedding, T. R.; Gilliland, R. L.; Kawaler, S. D.; and others

    2014-03-10

    We present a novel method for estimating lower-limit surface gravities (log g) of Kepler targets whose data do not allow the detection of solar-like oscillations. The method is tested using an ensemble of solar-type stars observed in the context of the Kepler Asteroseismic Science Consortium. We then proceed to estimate lower-limit log g for a cohort of Kepler solar-type planet-candidate host stars with no detected oscillations. Limits on fundamental stellar properties, as provided by this work, are likely to be useful in the characterization of the corresponding candidate planetary systems. Furthermore, an important byproduct of the current work is the confirmation that amplitudes of solar-like oscillations are suppressed in stars with increased levels of surface magnetic activity.

  9. ARE WE THERE YET? TIME TO DETECTION OF NANOHERTZ GRAVITATIONAL WAVES BASED ON PULSAR-TIMING ARRAY LIMITS

    SciTech Connect

    Taylor, S. R.; Vallisneri, M.; Ellis, J. A.; Mingarelli, C. M. F.; Lazio, T. J. W.; Haasteren, R. van

    2016-03-01

    Decade-long timing observations of arrays of millisecond pulsars have placed highly constraining upper limits on the amplitude of the nanohertz gravitational-wave stochastic signal from the mergers of supermassive black hole binaries (∼10{sup −15} strain at f = 1 yr{sup −1}). These limits suggest that binary merger rates have been overestimated, or that environmental influences from nuclear gas or stars accelerate orbital decay, reducing the gravitational-wave signal at the lowest, most sensitive frequencies. This prompts the question whether nanohertz gravitational waves (GWs) are likely to be detected in the near future. In this Letter, we answer this question quantitatively using simple statistical estimates, deriving the range of true signal amplitudes that are compatible with current upper limits, and computing expected detection probabilities as a function of observation time. We conclude that small arrays consisting of the pulsars with the least timing noise, which yield the tightest upper limits, have discouraging prospects of making a detection in the next two decades. By contrast, we find large arrays are crucial to detection because the quadrupolar spatial correlations induced by GWs can be well sampled by many pulsar pairs. Indeed, timing programs that monitor a large and expanding set of pulsars have an ∼80% probability of detecting GWs within the next 10 years, under assumptions on merger rates and environmental influences ranging from optimistic to conservative. Even in the extreme case where 90% of binaries stall before merger and environmental coupling effects diminish low-frequency gravitational-wave power, detection is delayed by at most a few years.

  10. Are We There Yet? Time to Detection of Nanohertz Gravitational Waves Based on Pulsar-timing Array Limits

    NASA Astrophysics Data System (ADS)

    Taylor, S. R.; Vallisneri, M.; Ellis, J. A.; Mingarelli, C. M. F.; Lazio, T. J. W.; van Haasteren, R.

    2016-03-01

    Decade-long timing observations of arrays of millisecond pulsars have placed highly constraining upper limits on the amplitude of the nanohertz gravitational-wave stochastic signal from the mergers of supermassive black hole binaries (˜10-15 strain at f = 1 yr-1). These limits suggest that binary merger rates have been overestimated, or that environmental influences from nuclear gas or stars accelerate orbital decay, reducing the gravitational-wave signal at the lowest, most sensitive frequencies. This prompts the question whether nanohertz gravitational waves (GWs) are likely to be detected in the near future. In this Letter, we answer this question quantitatively using simple statistical estimates, deriving the range of true signal amplitudes that are compatible with current upper limits, and computing expected detection probabilities as a function of observation time. We conclude that small arrays consisting of the pulsars with the least timing noise, which yield the tightest upper limits, have discouraging prospects of making a detection in the next two decades. By contrast, we find large arrays are crucial to detection because the quadrupolar spatial correlations induced by GWs can be well sampled by many pulsar pairs. Indeed, timing programs that monitor a large and expanding set of pulsars have an ˜80% probability of detecting GWs within the next 10 years, under assumptions on merger rates and environmental influences ranging from optimistic to conservative. Even in the extreme case where 90% of binaries stall before merger and environmental coupling effects diminish low-frequency gravitational-wave power, detection is delayed by at most a few years.

  11. Rapid Detection Strategies for the Global Threat of Zika Virus: Current State, New Hypotheses, and Limitations.

    PubMed

    Shukla, Shruti; Hong, Sung-Yong; Chung, Soo Hyun; Kim, Myunghee

    2016-01-01

    The current scenario regarding the widespread Zika virus (ZIKV) has resulted in numerous diagnostic studies, specifically in South America and in locations where there is frequent entry of travelers returning from ZIKV-affected areas, including pregnant women with or without clinical symptoms of ZIKV infection. The World Health Organization, WHO, announced that millions of cases of ZIKV are likely to occur in the USA in the near future. This situation has created an alarming public health emergency of international concern requiring the detection of this life-threatening viral candidate due to increased cases of newborn microcephaly associated with ZIKV infection. Hence, this review reports possible methods and strategies for the fast and reliable detection of ZIKV with particular emphasis on current updates, knowledge, and new hypotheses that might be helpful for medical professionals in poor and developing countries that urgently need to address this problem. In particular, we emphasize liposome-based biosensors. Although these biosensors are currently among the less popular tools for human disease detection, they have become useful tools for the screening and detection of pathogenic bacteria, fungi, and viruses because of their versatile advantageous features compared to other sensing devices. This review summarizes the currently available methods employed for the rapid detection of ZIKV and suggests an innovative approach involving the application of a liposome-based hypothesis for the development of new strategies for ZIKV detection and their use as effective biomedicinal tools.

  12. Rapid Detection Strategies for the Global Threat of Zika Virus: Current State, New Hypotheses, and Limitations

    PubMed Central

    Shukla, Shruti; Hong, Sung-Yong; Chung, Soo Hyun; Kim, Myunghee

    2016-01-01

    The current scenario regarding the widespread Zika virus (ZIKV) has resulted in numerous diagnostic studies, specifically in South America and in locations where there is frequent entry of travelers returning from ZIKV-affected areas, including pregnant women with or without clinical symptoms of ZIKV infection. The World Health Organization, WHO, announced that millions of cases of ZIKV are likely to occur in the USA in the near future. This situation has created an alarming public health emergency of international concern requiring the detection of this life-threatening viral candidate due to increased cases of newborn microcephaly associated with ZIKV infection. Hence, this review reports possible methods and strategies for the fast and reliable detection of ZIKV with particular emphasis on current updates, knowledge, and new hypotheses that might be helpful for medical professionals in poor and developing countries that urgently need to address this problem. In particular, we emphasize liposome-based biosensors. Although these biosensors are currently among the less popular tools for human disease detection, they have become useful tools for the screening and detection of pathogenic bacteria, fungi, and viruses because of their versatile advantageous features compared to other sensing devices. This review summarizes the currently available methods employed for the rapid detection of ZIKV and suggests an innovative approach involving the application of a liposome-based hypothesis for the development of new strategies for ZIKV detection and their use as effective biomedicinal tools. PMID:27822207

  13. Pushing the limits of nickel detection to nanomolar range using a set of engineered bioluminescent Escherichia coli.

    PubMed

    Cayron, Julien; Prudent, Elsa; Escoffier, Camille; Gueguen, Erwan; Mandrand-Berthelot, Marie-Andrée; Pignol, David; Garcia, Daniel; Rodrigue, Agnès

    2017-01-01

    The detection of nickel in water is of great importance due to its harmfulness for living organism. A way to detect Ni is the use of whole-cell biosensors. The aim of the present work was to build a light-emitting bacterial biosensor for the detection of Ni with high specificity and low detection limit properties. For that purpose, the regulatory circuit implemented relied on the RcnR Ni/Co metallo-regulator and its rcnA natural target promoter fused to the lux reporter genes. To convert RcnR to specifically detect Ni, several mutations were tested and the C35A retained. Deleting the Ni efflux pump rcnA and introducing genes encoding several Ni-uptake systems lowered the detection thresholds. When these constructs were assayed in several Escherichia coli strains, it appeared that the detection thresholds were highly variable. The TD2158 wild-type E. coli gave rise to a biosensor ten times more active and sensitive than its W3110 E. coli K12 equivalent. This biosensor was able to confidently detect Ni concentrations as little as 80 nM (4.7 μg l(-1)), which makes its use compatible with the norms governing the drinking water quality.

  14. Portable TXRF Spectrometer with 10-11g Detection Limit and Portable XRF Spectromicroscope with Sub-mm Spatial Resolution

    NASA Astrophysics Data System (ADS)

    Kunimura, Shinsuke; Hatakeyama, So; Sasaki, Nobuharu; Yamamoto, Takashi; Kawai, Jun

    2010-04-01

    A portable total reflection X-ray fluorescence (TXRF) spectrometer that we have developed is applied to trace elemental analysis of water solutions. Although a 5 W X-ray tube is used in the portable TXRF spectrometer, detection limits of several ppb are achieved for 3d transition metal elements and trace elements in a leaching solution of soils, a leaching solution of solder, and alcoholic beverages are detected. Portable X-ray fluorescence (XRF) spectromicroscopes with a 1 W X-ray tube and an 8 W X-ray tube are also presented. Using the portable XRF spectromicroscope with the 1 W X-ray tube, 93 ppm of Cr is detected with an about 700 μm spatial resolution. Spatially resolved elemental analysis of a mug painted with blue, red, green, and white is performed using the two portable spectromicroscopes, and the difference in elemental composition at each paint is detected.

  15. Portable TXRF Spectrometer with 10{sup -11}g Detection Limit and Portable XRF Spectromicroscope with Sub-mm Spatial Resolution

    SciTech Connect

    Kunimura, Shinsuke; Hatakeyama, So; Sasaki, Nobuharu; Yamamoto, Takashi; Kawai, Jun

    2010-04-06

    A portable total reflection X-ray fluorescence (TXRF) spectrometer that we have developed is applied to trace elemental analysis of water solutions. Although a 5 W X-ray tube is used in the portable TXRF spectrometer, detection limits of several ppb are achieved for 3d transition metal elements and trace elements in a leaching solution of soils, a leaching solution of solder, and alcoholic beverages are detected. Portable X-ray fluorescence (XRF) spectromicroscopes with a 1 W X-ray tube and an 8 W X-ray tube are also presented. Using the portable XRF spectromicroscope with the 1 W X-ray tube, 93 ppm of Cr is detected with an about 700 {mu}m spatial resolution. Spatially resolved elemental analysis of a mug painted with blue, red, green, and white is performed using the two portable spectromicroscopes, and the difference in elemental composition at each paint is detected.

  16. Prediction of the limits of detection of hazardous vapors by passive infrared with the use of modtran

    NASA Astrophysics Data System (ADS)

    Flanigan, Dennis F.

    1996-10-01

    Passive infrared remote detection of hazardous gases, vapors, and aerosols is based on the difference, T , between the air temperature of the threat vapor cloud and the effective radiative temperature of the background. In this paper I address the problem of detection with a low-angle-sky background. I used Modtran to predict T and atmospheric transmittance for standard atmospheric models. The detection limits, at 2-cm 1 resolution, are discussed for sulfur hexafluoride, Sarin, trichloroethylene, methyl isocyanate, mustard gas, methyl chloride, and sulfur dioxide for selected cases with the U.S. Standard, the Subarctic Winter, and the Tropical models. I used a particularly interesting case of Sarin detection with the Subarctic Winter atmospheric model to illustrate the power of Modtran to predict subtle changes in T with angle of elevation (AOE).

  17. Limits in detecting an individual dopant atom embedded in a crystal.

    PubMed

    Mittal, Anudha; Mkhoyan, K Andre

    2011-07-01

    Annular dark field scanning transmission electron microscope (ADF-STEM) images allow detection of individual dopant atoms located on the surface of or inside a crystal. Contrast between intensities of an atomic column containing a dopant atom and a pure atomic column in ADF-STEM image depends strongly on specimen parameters and microscope conditions. Analysis of multislice-based simulations of ADF-STEM images of crystals doped with one substitutional dopant atom for a wide range of crystal thicknesses, types and locations of dopant atom inside the crystal, and crystals with different atoms reveal some interesting trends and non-intuitive behaviours in visibility of the dopant atom. The results provide practical guidelines to determine the optimal microscope and specimen conditions to detect a dopant atom in experiment, obtain information about the 3-d location of a dopant atom, and recognize cases where detecting a single dopant atom is not possible. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Improved detection limits of toxic biochemical species based on impedance measurements in electrochemical biosensors.

    PubMed

    Narakathu, B B; Atashbar, M Z; Bejcek, B E

    2010-10-15

    An impedance based electrochemical biosensor was designed and fabricated for the detection of various chemical and biological species, with glass as substrate material and gold interdigitated electrodes. A flow cell with inlet and outlet ports for the microfluidic chamber was designed and fabricated using acrylic material with a reservoir volume of 78 μl. The feasibility of the fabricated sensor for detecting very low concentration of chemical and biological species was demonstrated. Electrochemical impedance spectroscopy (EIS) was employed as the detection technique. The impedance based response of the two-terminal device revealed a very high sensitivity with low concentrations of mouse monoclonal IgG, sarcosine, cadmium sulphide (CdS) and potassium chloride (KCl) at pico mole levels. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Modeling of a Single-Notch Microfiber Coupler for High-Sensitivity and Low Detection-Limit Refractive Index Sensing

    PubMed Central

    Zhang, Jiali; Shi, Lei; Zhu, Song; Xu, Xinbiao; Zhang, Xinliang

    2016-01-01

    A highly sensitive refractive index sensor with low detection limit based on an asymmetric optical microfiber coupler is proposed. It is composed of a silica optical microfiber and an As2Se3 optical microfiber. Due to the asymmetry of the microfiber materials, a single-notch transmission spectrum is demonstrated by the large refractive index difference between the two optical microfibers. Compared with the symmetric coupler, the bandwidth of the asymmetric structure is over one order of magnitude narrower than that of the former. Therefore, the asymmetric optical microfiber coupler based sensor can reach over one order of magnitude smaller detection limit, which is defined as the minimal detectable refractive index change caused by the surrounding analyte. With the advantage of large evanescent field, the results also show that a sensitivity of up to 3212 nm per refractive index unit with a bandwidth of 12 nm is achieved with the asymmetric optical microfiber coupler. Furthermore, a maximum sensitivity of 4549 nm per refractive index unit can be reached while the radii of the silica optical microfiber and As2Se3 optical microfiber are 0.5 μm and a 0.128 μm, respectively. This sensor component may have important potential for low detection-limit physical and biochemical sensing applications. PMID:27187386

  20. Absolute calibration of optical flats

    SciTech Connect

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  1. Physics of negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Abraham, Eitan; Penrose, Oliver

    2017-01-01

    Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying "volume" entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  2. Detection of bacteria based on the thermomechanical noise of a nanomechanical resonator: origin of the response and detection limits.

    PubMed

    Ramos, D; Tamayo, J; Mertens, J; Calleja, M; Villanueva, L G; Zaballos, A

    2008-01-23

    We have measured the effect of bacteria adsorption on the resonant frequency of microcantilevers as a function of the adsorption position and vibration mode. The resonant frequencies were measured from the Brownian fluctuations of the cantilever tip. We found that the sign and amount of the resonant frequency change is determined by the position and extent of the adsorption on the cantilever with regard to the shape of the vibration mode. To explain these results, a theoretical one-dimensional model is proposed. We obtain analytical expressions for the resonant frequency that accurately fit the data obtained by the finite element method. More importantly, the theory data shows a good agreement with the experiments. Our results indicate that there exist two opposite mechanisms that can produce a significant resonant frequency shift: the stiffness and the mass of the bacterial cells. Based on the thermomechanical noise, we analyse the regions of the cantilever of lowest and highest sensitivity to the attachment of bacteria. The combination of high vibration modes and the confinement of the adsorption to defined regions of the cantilever allows the detection of single bacterial cells by only measuring the Brownian fluctuations. This study can be extended to smaller cantilevers and other biological systems such as proteins and nucleic acids.

  3. Improved detection limits using a hand-held optical imager with coregistration capabilities.

    PubMed

    Erickson, Sarah J; Martinez, Sergio L; Gonzalez, Jean; Caldera, Lizeth; Godavarty, Anuradha

    2010-07-15

    Optical imaging is emerging as a non-invasive and non-ionizing method for breast cancer diagnosis. A hand-held optical imager has been developed with coregistration facilities towards flexible imaging of different tissue volumes and curvatures in near real-time. Herein, fluorescence-enhanced optical imaging experiments are performed to demonstrate deeper target detection under perfect and imperfect (100:1) uptake conditions in (liquid) tissue phantoms and in vitro. Upon summation of multiple scans (fluorescence intensity images), fluorescent targets are detected at greater depths than from single scan alone.

  4. Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

    NASA Technical Reports Server (NTRS)

    Hoge, F. E.; Swift, R. N.

    1983-01-01

    Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

  5. Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

    NASA Technical Reports Server (NTRS)

    Hoge, F. E.; Swift, R. N.

    1983-01-01

    Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

  6. Improving the detection limit of airborne NO2 remote sensing by using DOAS in a wide spectral window

    NASA Astrophysics Data System (ADS)

    Kuhlmann, Gerrit; Brunner, Dominik

    2017-04-01

    Airborne imaging spectrometers such as the Airborne Prism Experiment (APEX) instrument can be used for mapping the spatial distribution of air pollutants such as nitrogen dioxide (NO2) with a high spatial resolution of a few tens of meters. The detection limit of the NO2 retrieval is limited by the signal-to-noise ratio (SNR) and other characteristics of the sensor. For airborne imaging spectrometers the SNR can be small, because the radiance signal obtained for a combination of small ground pixel and short observation time is small. As a result, NO2 fitting errors can be large and the detection limit correspondingly low. Here we demonstrate that the detection limit for NO2 can be improved if the DOAS fit is applied to a wide spectral window from 410 to 510 nm. However, retrieving over such a wide window required several modifications of the standard DOAS approach. In particular, we replaced the standard low-order polynomial with a cubic spline and computed wavelength-dependent air mass factors instead of a single air mass factor with the SCIATRAN radiative transfer model. The algorithm was implemented with a new custom-made library flexDOAS which allows for flexible development of DOAS retrievals in Python and supports non-linear parameter fitting and integration of a priori information. The retrieval was tested both with synthetic spectra and applied to real observations from an APEX campaign conducted over Zurich. For the retrieval with wide spectral window (410-510 nm), the fitting error was significantly reduced by about 20% compared to a retrieval with a narrow window (470-510 nm). In conclusion, fitting over a wider spectral window has the potential to significantly reduce the fitting error and thereby improve the detection limit but requires a more advanced treatment of the smooth background radiance and the application of wavelength-dependent air mass factors.

  7. The detection of landmines by neutron backscattering: exploring the limits of the technique.

    PubMed

    Viesti, G; Lunardon, M; Nebbia, G; Barbui, M; Cinausero, M; D'Erasmo, G; Palomba, M; Pantaleo, A; Obhodas, J; Valković, V

    2006-06-01

    Neutron backscattering (NB) sensors have been proposed for Humanitarian De-mining applications. Recently, a prototype hand-held system integrating a NB sensor in a metal detector has been developed within the EU-funded DIAMINE Project. The results obtained in terms of performance of the NB systems and limitations in its use are presented in this work. It is found that the performance of NB sensors is strongly limited by the presence of the soil moisture and by its small-scale variations. The use of the neutron hit distribution to reduce false alarms is explored.

  8. Least Absolute Relative Error Estimation.

    PubMed

    Chen, Kani; Guo, Shaojun; Lin, Yuanyuan; Ying, Zhiliang

    2010-01-01

    Multiplicative regression model or accelerated failure time model, which becomes linear regression model after logarithmic transformation, is useful in analyzing data with positive responses, such as stock prices or life times, that are particularly common in economic/financial or biomedical studies. Least squares or least absolute deviation are among the most widely used criterions in statistical estimation for linear regression model. However, in many practical applications, especially in treating, for example, stock price data, the size of relative error, rather than that of error itself, is the central concern of the practitioners. This paper offers an alternative to the traditional estimation methods by considering minimizing the least absolute relative errors for multiplicative regression models. We prove consistency and asymptotic normality and provide an inference approach via random weighting. We also specify the error distribution, with which the proposed least absolute relative errors estimation is efficient. Supportive evidence is shown in simulation studies. Application is illustrated in an analysis of stock returns in Hong Kong Stock Exchange.

  9. Fringe order correction for the absolute phase recovered by two selected spatial frequency fringe projections in fringe projection profilometry

    NASA Astrophysics Data System (ADS)

    Ding, Yi; Peng, Kai; Yu, Miao; Lu, Lei; Zhao, Kun

    2017-08-01

    The performance of the two selected spatial frequency phase unwrapping methods is limited by a phase error bound beyond which errors will occur in the fringe order leading to a significant error in the recovered absolute phase map. In this paper, we propose a method to detect and correct the wrong fringe orders. Two constraints are introduced during the fringe order determination of two selected spatial frequency phase unwrapping methods. A strategy to detect and correct the wrong fringe orders is also described. Compared with the existing methods, we do not need to estimate the threshold associated with absolute phase values to determine the fringe order error, thus making it more reliable and avoiding the procedure of search in detecting and correcting successive fringe order errors. The effectiveness of the proposed method is validated by the experimental results.

  10. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

  11. Limitations of a localized surface plasmon resonance sensor on Salmonella detection

    USDA-ARS?s Scientific Manuscript database

    We have designed a localized surface plasmon resonance (LSPR) biosensor to perform the whole cell detection of Salmonella using gold nanoparticls fabricated by oblique angle deposition technique. The LSPR sensor showed a plasmon peak shift due to the Salmonella antigen and anti-Salmonella antibody r...

  12. Limitations of the Score-Difference Method in Detecting Cheating in Recognition Test Situations.

    ERIC Educational Resources Information Center

    Roberts, Dennis M.

    1987-01-01

    This study examines a score-difference model for the detection of cheating based on the difference between two scores for an examinee: one based on the appropriate scoring key and another based on an alternative, inappropriate key. It argues that the score-difference method could falsely accuse students as cheaters. (Author/JAZ)

  13. Comparison of laser excited fluorescence and photoacoustic limits of detection for static and flow cells

    SciTech Connect

    Voigtman, E.; Jurgensen, A.; Winefordner, J.D.

    1981-10-01

    The fluorescence and photoacoustic characteristics of a windowless flow cell intended for liquid chromatographic applications are compared with respective characteristics of a static cuvette cell. In addition, a photoionization mode of operation for the flow cell is exhibited which utilizes the ionization products of two-photon excitation of polynuclear aromatic hydrocarbons in n-alkanes to effect a sensitive detection of those PAHs.

  14. Detecting the limits of northern and southern lineages of tanoak in northern California

    Treesearch

    Eduardo Sandoval-Castro; Richard S. Dodd

    2015-01-01

    Two chloroplast lineages of tanoak (Notholithocarpus densiflorus) meet between Korbel and Hoopa in the North Coast of California. Our earlier work suggests these lineages arose from southern and northern glacial refugia and this region represents their colonizing fronts. Earlier, we detected only one population of mixed lineages, suggesting that...

  15. Detection limits of quantitative and digital PCR assays and their influence in presence-absence surveys of environmental DNA

    USGS Publications Warehouse

    Hunter, Margaret; Dorazio, Robert M.; Butterfield, John S.; Meigs-Friend, Gaia; Nico, Leo; Ferrante, Jason

    2017-01-01

    A set of universal guidelines is needed to determine the limit of detection (LOD) in PCR-based analyses of low concentration DNA. In particular, environmental DNA (eDNA) studies require sensitive and reliable methods to detect rare and cryptic species through shed genetic material in environmental samples. Current strategies for assessing detection limits of eDNA are either too stringent or subjective, possibly resulting in biased estimates of species’ presence. Here, a conservative LOD analysis grounded in analytical chemistry is proposed to correct for overestimated DNA concentrations predominantly caused by the concentration plateau, a nonlinear relationship between expected and measured DNA concentrations. We have used statistical criteria to establish formal mathematical models for both quantitative and droplet digital PCR. To assess the method, a new Grass Carp (Ctenopharyngodon idella) TaqMan assay was developed and tested on both PCR platforms using eDNA in water samples. The LOD adjustment reduced Grass Carp occupancy and detection estimates while increasing uncertainty – indicating that caution needs to be applied to eDNA data without LOD correction. Compared to quantitative PCR, digital PCR had higher occurrence estimates due to increased sensitivity and dilution of inhibitors at low concentrations. Without accurate LOD correction, species occurrence and detection probabilities based on eDNA estimates are prone to a source of bias that cannot be reduced by an increase in sample size or PCR replicates. Other applications also could benefit from a standardized LOD such as GMO food analysis, and forensic and clinical diagnostics.

  16. Driving down the Detection Limit in Microstructured Fiber-Based Chemical Dip Sensors

    PubMed Central

    Schartner, Erik P.; Ebendorff-Heidepriem, Heike; Warren-Smith, Stephen C.; White, Richard T.; Monro, Tanya M.

    2011-01-01

    We present improvements to fluorescence sensing in soft-glass microstructured optical fibers that result in significantly improved sensitivity relative to previously published results. Concentrations of CdSe quantum dots down to 10 pM levels have been demonstrated. We show that the primary limitation to the sensitivity of these systems is the intrinsic fluorescence of the glass itself. PMID:22163778

  17. The 1000-th MASTER detection and SALT limit: Fast Doublet OT

    NASA Astrophysics Data System (ADS)

    Balanutsa, P.; Lipunov, V.; Gorbovskoy, E.; Buckley, D.; Kniazev, A.; Tiurina, N.; Kornilov, V.; Samus, N.; Kuznetsov, A.; Vlasenko, D.; Gorbunov, I.; Popova, E.; Vladimirov, V.; Shumkov, V.; Potter, S.; Kotze, M.; Gress, O.; Budnev, N.; Yazev, S.; Ivanov, K.; Tlatov, A.; Senik, V.; Dormidontov, D.; Parhomenko, A. V.; Yurkov, V.; Sergienko, Yu.; Gabovich, A.; Sinyakov, E.; Rebolo, R.; Serra-Ricart, M.; Lodieu, N.; Israelian, G.; Suarez-Andres, L.; Levato, Hugo; Astronomicas, Carlos Saffe Instituto de Ciencias; Espacio, de la Tierra y. del; Podesta, Ricardo; Mallamaci, Claudio; Lopez, Carlos; Podesta, Federico

    2015-12-01

    MASTER-SAAO (Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 349171) discovered the 1000th OT source at (RA, Dec) = 05h 10m 14.58s -29d 09m 00.6s on 2015-12-16.97115 UT. The OT unfiltered magnitude is 18.8m (the limit is 20.4m).

  18. Detection and identification of serum monoclonal immunoglobulin by immunoisoelectric focusing. Limits of sensitivity and use during relapse of multiple myeloma.

    PubMed Central

    Sinclair, D; Kumararatne, D S; Stott, D

    1984-01-01

    The limits of detection of four classes of monoclonal immunoglobulin and free light chain in serum by isoelectric focusing and immunoisoelectric focusing have been determined and the sensitivity of these techniques compared with that obtained using immunoelectrophoresis and zonal electrophoresis with immunofixation. Immunoisoelectric focusing was 10-40 times more sensitive than immunoelectrophoresis and could be used to detect concentrations of monoclonal immunoglobulin that were undetectable by zonal electrophoresis with immunofixation. The relevance of this work in monitoring multiple myeloma during treatment and relapse is discussed. Images PMID:6421894

  19. Absolute flatness testing of large synchrotron optics

    NASA Astrophysics Data System (ADS)

    Lin, Weihao; He, Yumei; Song, Li; Luo, Hongxin; Wang, Jie

    2014-09-01

    Interferometry is one of the most efficient techniques in surface figure testing while the transmission surface usually limits the accuracy. Besides, standard figure interferometers often have a typical aperture of about 150 mm diameter which can not satisfy the need of large optics calibration. A novel method for characterizing the absolute surface figure of long grazing-incidence optics used in synchrotron radiation beamlines is presented. We demonstrate oblique incidence interferometry to overcome the aperture limitation. Furthermore, multiple rotating measurements are used to remove the transmission surface errors. The new solution is simple and easy without dismantling the transmission flat throughout the calibration procedure. The theoretical derivation, experiment results and uncertainty analysis are presented.

  20. Absolute instability of a viscous hollow jet.

    PubMed

    Gañán-Calvo, Alfonso M

    2007-02-01

    An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail. Asymptotic analyses for low and high Reynolds numbers are provided, showing that old and well-established limiting dispersion relations [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Dover, New York, 1961)] should be used with caution. In the creeping flow limit, the analysis shows that, if the hollow jet is filled with any finite density and viscosity fluid, a steady jet could be made arbitrarily small (compatible with the continuum hypothesis) if the coflowing liquid moves faster than a critical velocity.

  1. Joint data detection and parameter estimation: Fundamental limits and applications to optical fiber communications

    NASA Astrophysics Data System (ADS)

    Coskun, Orhan

    For ≥10-Gbit/s bit rates that are transmitted over ≥100 km, it is essential that chromatic The traditional method of sending a training signal to identify a channel, followed by data, may be viewed as a simple code for the unknown channel. Results in blind sequence detection suggest that performance similar to this traditional approach can be obtained without training. However, for short packets and/or time-recursive algorithms, significant error floors exist due to the existence of sequences that are indistinguishable without knowledge of the channel. In this work, we first reconsider training signal design in light of recent results in blind sequence detection. We design training codes which combine modulation and training. In order to design these codes, we find an expression for the pairwise error probability of the joint maximum likelihood (JML) channel and sequence estimator. This expression motivates a pairwise distance for the JML receiver based on principal angles between the range spaces of data matrices. The general code design problem (generalized sphere packing) is formulated as the clique problem associated with an unweighted, undirected graph. We provide optimal and heuristic algorithms for this clique problem. For short packets, we demonstrate that significant improvements are possible by jointly considering the design of the training, modulation, and receiver processing. As a practical blind data detection example, data reception in a fiber optical channel is investigated. To get the most out of the data detection methods, auxiliary algorithms such as sampling phase adjustment, decision threshold estimation algorithms are suggested. For the parallel implementation of detectors, semiring structure is introduced both for decision feedback equalizer (DFE) and maximum likelihood sequence detection (MLSD). Timing jitter is another parameter that affects the BER performance of the system. A data-aided clock recovery algorithm reduces the jitter of

  2. Increased levels of HIV RNA detected in samples with viral loads close to the detection limit collected in Plasma Preparation Tubes (PPT).

    PubMed

    Griffith, Brigitte P; Mayo, Donald R

    2006-02-01

    The accurate and reliable quantification of HIV RNA is an essential part of the management of HIV infected individuals, and elucidation of factors that may affect HIV RNA measurements, such as the use of Vacutainer Plasma Preparation Tubes (PPT), is crucial. The objective of this study was to determine if plasma samples with viral loads close to the lower limit of the dynamic range of the assay collected in PPT tubes had increased levels of HIV RNA as compared to samples collected in standard EDTA tubes. HIV RNA levels were compared in 112 paired plasma samples collected in PPT and standard EDTA tubes. All samples had been frozen prior to testing. Discrepancies between PPT and EDTA tubes did not occur for samples with high viral loads. However, in samples with viral loads close to the lower limit of the dynamic range, levels of HIV RNA detected were higher in a large proportion of PPT as compared to the corresponding EDTA plasma samples. Forty percent of plasma pairs had no detectable HIV RNA in the EDTA aliquot, but had low levels of HIV RNA in the corresponding PPT aliquot. This prospective study underlines the need for cautious interpretation of small transient viral load changes in samples with values close to the detection limit.

  3. Decreasing the Limits of Detection and Analysis Time of Ion Current Rectification Biosensing Measurements via a Mechanically Applied Pressure Differential.

    PubMed

    Schibel, Anna E P; Ervin, Eric N

    2015-07-07

    Improving on the analytical capabilities of a measurement is a fundamental challenge with all assays, particularly decreasing the limit of detection while maintaining a practical associated analysis time. Of late, ion current rectification (ICR) biosensing measurements have received a great deal of attention as an analyte-specific, label-free assay. In ICR biosensing, a nanopore coated with an analyte specific binding molecule (e.g., an antibody, an aptamer, etc.) is used to detect a target analyte based on the ability of the target analyte to alter the ICR response of the nanopore upon it binding to the aperture interior. This binding changes the local surface charge and/or size of the nanopore aperture, thus altering its ICR response in a time dependent manner. Here, we report the ability to enhance the transport of a target analyte molecule to and through the aperture of an antibody modified glass nanopore membrane (AMGNM) with the application of a mechanically applied pressure differential. We demonstrate that there is an optimal pressure that balances the flux of the target analyte through the AMGNM aperture with its ability to be bound and detected. Applying the optimal pressure differential allows for picomolar concentrations of the cleaved form of synaptosomal-associated protein 25 (cSNAP-25) to be detected within the same analysis time as micromolar concentrations detected without the use of the pressure differential. The methodology presented here significantly expands the utility of ICR biosensing measurements for detecting low-abundance biomolecules by lowering the limit of detection and reducing the associated analysis time.

  4. Reducing the Detection Limit for Tetraphenylborate in Tank 50H Waste

    SciTech Connect

    WHITE, THOMASL.

    2004-07-14

    SRTC personnel are developing a technique that can determine the concentration of tetraphenylborate (TPB) at 300 grams in 100,000 gallons of salt solution (0.8 mg/L) in the presence of0.378 Ci/gal of Cs-137. The current High Performance Liquid Chromatography (HPLC) method of analysis can determine the TPB concentration at 5 mg/L and higher. The limit of quantitation was lowered by modification of the sample preparation steps. The HPLC sample preparation method currently used requires neutralization of the tank waste sample followed by extraction with acetonitrile. This method dilutes the tank waste sample 6.5 to 1 increasing the limit of quantitation. The method described in this report concentrates the sample two-fold lowering the limit of quantitation from 5 mg/L to 0.25mg/L. Researchers used solvent extraction of undiluted tank waste to isolate, and concentrate (two-fold) samples of tank supernate and Plant Inhibited Water (PIW) that simulated tank supernate at the cesium level of approximately 0.3 Ci/gal. The 137Cs content in the tank supernate measured 0.65 Ci/gal prior to a two-fold dilution with PIW. The concentration of the TPB was determined by HPLC on a reversed-phase HPLC column using methanol, acetonitrile, and buffered water as the mobile phase. Important Findings: The 0.8 mg/L quantitation limit was met in the presence of radioactive cesium. A 93 per cent reduction in activity in the acetonitrile layer was achieved. A five-mL acetonitrile aliquot from the extraction of a tank waste sample containing 0.378 Ci/gal of Cs-137 could be handled in a radiological hood and comply with the less than 5 mR/hr hood limit. This method is applicable to tank waste solutions of high ionic strength (greater than 2.0 M Na). The ionic strength of tank waste solutions of low ionic strength will need to be adjusted by the addition of NaOH or 5.6 M average salt solution to facilitate the formation of two layers (organic and aqueous). Increasing the ionic strength of tank

  5. Detection of airflow limitation using a handheld spirometer in a primary care setting

    PubMed Central

    Ching, Siew-Mooi; Pang, Yong-Kek; Price, David; Cheong, Ai-Theng; Lee, Ping-Yein; Irmi, Ismail; Faezah, Hassan; Ruhaini, Ismail; Chia, Yook-Chin

    2014-01-01

    Background and objective Early diagnosis of chronic obstructive pulmonary disease (COPD) in primary care settings is difficult to achieve chiefly due to lack of availability of spirometry. This study estimated the prevalence of airflow limitation among chronic smokers using a handheld spirometer in this setting. Methods This is a cross-sectional study performed on consecutive patients who were ≥40 years old with ≥10 pack-years smoking history. Face-to-face interviews were carried out to obtain demographic data and relevant information. Handheld spirometry was performed according to a standard protocol using the COPd-6 device (Model 4000, Vitalograph, Ennis, Ireland) in addition to standard spirometry. Airflow limitation was defined as ratio of forced expiratory volume in 1 s (FEV1)/forced expiratory volume in 6 s <0.75 (COPd-6) or FEV1/forced vital capacity <0.7. Multiple logistic regression analyses were used to determine predictors of airflow limitation. Results A total of 416 patients were recruited with mean age of 53 years old. The prevalence of airflow limitation was 10.6% (n = 44) with COPd-6 versus 6% as gauged using standard spirometry. Risk factors for airflow limitation were age >65 years (odds ratio (OR) 3.732 95% confidence interval (CI): 1.100–1.280), a history of ‘bad health’ (OR 2.524, 95% CI: 1.037–6.142) and low to normal body mass index (OR 2.914, 95% CI: 1.191–7.190). Conclusions In a primary care setting, handheld spirometry (COPd-6) found a prevalence of airflow limitation of ∼10% in smokers. Patients were older, not overweight and had an ill-defined history of health problems. SUMMARY AT A GLANCE Prevalence of COPD is unknown in Malaysia. The prevalence of COPD using a handheld spirometer (COPd-6TM) was 10.6% versus 6% as gauged using standard spirometry. Predictors of COPD were older age, lower BMI and a history of ‘bad health’. Case-finding for COPD should be targeted in this special population. PMID:24708063

  6. Study of Laser Produced Plasma of Limiter of the Aditya Tokomak for Detection of Molecular Bands

    NASA Astrophysics Data System (ADS)

    Rai, Awadhesh Kumar

    2016-06-01

    The tokamak wall protection is one of the prime concerns, and for this purpose, limiters are used. Graphite is commonly used as a limiter material and first wall material for complete coverage of the internal vacuum vessel surfaces of the tokamak. From the past few years, we are working to identify and quantify the impurities deposited on the different part of Aditya Tokamak in collaboration with the Scientists at Institute of Plasma Research, Ahmedabad, India using Laser Induced Breakdown Spectroscopy (LIBS) [1-3]. Laser induced breakdown spectroscopy (LIBS) spectra of limiter of Aditya Tokamak have been recorded in the spectral range of 200-900 nm in open atmosphere. Along with atomic and ionic spectral lines of the constituent elements of the limiter (1-3), LIBS spectra also give the molecular bands. When a high power laser beam is focused on the sample, laser induced plasma is produced on its surface. In early stage of the plasma Back ground continuum is dominated due to free-free or free-bound emission. Just after few nanoseconds the light from the plasma is dominated by ionic emission. Atomic emission spectra is dominated from the laser induced plasma during the first few microsecond after an ablation pulse where as molecular spectra is generated later when the plasma further cools down. For this purpose the LIBS spectra has been recorded with varying gate delay and gate width. The spectra of the limiter show the presence of molecular bands of CN and C2. To get better signal to background ratios of the molecular bands, different experimental parameters like gate delay, gate width, collection angle and collection point (spatial analysis off the plasama) of the plasma have been optimized. Thus the present paper deals with the variation of spectral intensity of the molecular bands with different experimental parameters. Keywords: Limiter, Molecular bands, C2, CN. References: 1. Proof-of-concept experiment for On-line LIBS Analysis of Impurity Layer Deposited on

  7. Characterization and comparison of defects detection limits of three ultrasonic non destructive methods

    NASA Astrophysics Data System (ADS)

    Péronnet, E.; Eyma, F.; Welemane, H.; Pescay, C.

    2010-06-01

    This work deals with the Liquid Resin Infusion (LRI) process developed within the research program “FUSelage COMPosite” of DAHER SOCATA. This manufacturing process enables the realization of complex composite structures or fuselage elements in a single phase (mono-material), which considerably reduce connections and relative difficulties. The concern here is the investigation of non destructive testing (NDT) methods that can be applied to LRI-structures in order to define their capacities for defect detection, and especially their associated critical defect size. In aviation industry, the AITM standards require the ultrasonic testing as NDT for composite materials. Therefore the aim of this work is to characterize and compare three different and complementary ultrasonic techniques on composite specimens. Such analysis allows to define the NDT application field of each method in term of defect detection.

  8. One spatial filter limits speed of detecting low and middle frequency gratings.

    PubMed

    Thomas, J P; Fagerholm, P; Bonnet, C

    1999-05-01

    Reaction times for detecting sinusoidal gratings depend jointly on grating contrast and spatial frequency. We examine whether the effect of spatial frequency results from low-pass filtering in a single channel or reflects processing of different frequencies by two or more different processing streams. Observers performed a speeded two-alternative spatial forced-choice detection. Errors and reaction times were measured. Contrasts varied from 0.05 to 0.67, and spatial frequencies from 0.72 to 6.51 cpd. No effect of uncertainty about spatial frequency was found, arguing against multiple channels. The data are well fit by a single channel model driven by a low pass filter.

  9. Taking whispering gallery-mode single virus detection and sizing to the limit

    NASA Astrophysics Data System (ADS)

    Dantham, V. R.; Holler, S.; Kolchenko, V.; Wan, Z.; Arnold, S.

    2012-07-01

    We report the label-free detection and sizing by a microcavity of the smallest individual RNA virus, MS2, with a mass only ˜1% of InfluenzaA (6 vs. 512 ag). Although detection of such a small bio-nano-particle has been beyond the reach of a bare spherical microcavity, it was accomplished with ease (S/N = 8, Q = 4 × 105) using a single dipole stimulated plasmonic-nanoshell as a microcavity wavelength shift enhancer, providing an enhancement of ˜70×, in agreement with theory. Unique wavelength shift statistics are recorded consistent with an ultra-uniform genetically programmed substance that is drawn to the plasmonic hot spots by light-forces.

  10. Detection and Imaging of Moving Targets with LiMIT SAR Data

    DTIC Science & Technology

    2017-03-03

    movers by applying a set of possible motion corrections to the image, and use a novel matched filter to detect the movers in this space . We can then image...include space time adaptive processing (STAP) or displaced phase center antenna (DPCA) [4]–[7]. Page et al. combined constant acceleration target...motion focusing with space -time adaptive processing (STAP), and included the refocusing parameters in the STAP steering vector. Due to inhomogenous

  11. Lower limit of detection: definition and elaboration of a proposed position for radiological effluent and environmental measurements

    SciTech Connect

    Currie, L.A.

    1984-09-01

    A manual is provided to define and illustrate a proposed use of the Lower Limit of Detection (LLD) for Radiological Effluent and Environmental Measurements. The manual contains a review of information regarding LLD practices gained from site visits; a review of the literature and a summary of basic principles underlying the concept of detection in Nuclear and Analytical Chemistry; a detailed presentation of the application of LLD principles to a range of problem categories (simple counting to multinuclide spectroscopy), including derivations, equations, and numerical examples; and a brief examination of related issues such as reference samples, numerical quality control, and instrumental limitations. An appendix contains a summary of notation and terminology, a bibliography, and worked-out examples. 100 references, 10 figures, 7 tables.

  12. Super-resolving quantum radar: Coherent-state sources with homodyne detection suffice to beat the diffraction limit

    SciTech Connect

    Jiang, Kebei; Lee, Hwang; Gerry, Christopher C.; Dowling, Jonathan P.

    2013-11-21

    There has been much recent interest in quantum metrology for applications to sub-Raleigh ranging and remote sensing such as in quantum radar. For quantum radar, atmospheric absorption and diffraction rapidly degrades any actively transmitted quantum states of light, such as N00N states, so that for this high-loss regime the optimal strategy is to transmit coherent states of light, which suffer no worse loss than the linear Beer's law for classical radar attenuation, and which provide sensitivity at the shot-noise limit in the returned power. We show that coherent radar radiation sources, coupled with a quantum homodyne detection scheme, provide both longitudinal and angular super-resolution much below the Rayleigh diffraction limit, with sensitivity at shot-noise in terms of the detected photon power. Our approach provides a template for the development of a complete super-resolving quantum radar system with currently available technology.

  13. Current Challenges and Limitations in Antibody-Based Detection of Citrullinated Histones

    PubMed Central

    Neeli, Indira; Radic, Marko

    2016-01-01

    Studies on NETosis demand reliable and convenient markers to monitor the progress of this form of cell death. Because a determining step in the release of nuclear chromatin NETs requires the conversion of arginine residues to citrulline residues in histones by peptidylarginine deiminase, citrullinated histones can provide such a marker. Here, we evaluate antibody reagents for the detection of citrulline residues in histones and observe alarming differences between commercial antisera and mouse and rabbit monoclonal antibodies in their ability to detect their nominal target residues. Differences between antibodies that are currently used to detect citrulline residues in histones could jeopardize efforts to reach a scientific consensus and instead lead to inconsistent and even conflicting conclusions regarding the regulation of histone deimination. Our results will assist others in planning their initial or ongoing studies on peptidylarginine deiminase activity with the use of currently available antibodies. Furthermore, we argue that, along with the careful attention to experimental conditions and calcium concentrations, validated antibody reagents are urgently needed to avoid possible setbacks in the research on NETosis. PMID:27933065

  14. Concentration of prion protein from biological samples to increase the limits of detection by immunoassay.

    PubMed

    Davidowitz, Eliot; Eljuga, Lucy; Dover, Katarzyna; Tian, Jean; Grossman, Abraham

    2005-06-01

    An RNA-ligand-based adsorbent has been shown to concentrate prion protein (PrP) from solutions in a model system. The work presented here extends the utility of the RNA-based adsorbent to brain homogenates of cow, sheep, mule deer (Odocoileus hemionus) and elk (Cervus elaphus). Brain homogenates were diluted either in buffer, representing specimens used in post-mortem tests, or in serum, modelling specimens used in biological-fluid-based tests. The RNA adsorbent was effective in binding PrPC (cellular PrP,) and PrPres (proteinase K-resistant PrP) from the brain homogenates of all the species tested in both model systems. The three antibodies against PrP used in the experiments identified PrP in immunoblot analysis after concentrating PrP from brain homogenates with the adsorbent, indicating the general applicability of this technology for improving the detection of PrP in immunoassays. Utilization of RNA adsorbent increased the level of detection of PrPres by immunoblot over several-hundredfold. The results obtained suggest that this RNA adsorbent can be used to increase detection in current post-mortem immunoassays and for the development of a blood-based ante-mortem test.

  15. Clinical utility and limitations of FDG PET in detecting recurrent hepatocellular carcinoma in postoperative patients.

    PubMed

    Hayakawa, Nobuyuki; Nakamoto, Yuji; Nakatani, Koya; Hatano, Etsuro; Seo, Satoru; Higashi, Tatsuya; Saga, Tsuneo; Uemoto, Shinji; Togashi, Kaori

    2014-12-01

    The clinical usefulness of positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) for the detection of recurrent hepatocellular carcinoma (HCC) is controversial because HCC displays varying FDG avidity. The purposes of this study were to re-evaluate the utility of FDG PET for the detection of recurrent HCC, and to assess its prognostic value in a large series of postoperative patients. We retrospectively reviewed 113 scans in 86 patients undergoing FDG PET after curative surgery for HCC. These scans were performed for suspected recurrence on radiologic imaging (group A: n = 44) because of an elevated tumor marker level with negative prior imaging results (group B: n = 32) or with no suspicion of recurrence (group C: n = 37). FDG PET's accuracy for recurrence detection and its value as a predictor of survival were assessed. The sensitivity, specificity, and diagnostic accuracy were 53, 100, and 55 % for group A; 34, 100, and 41 % for group B; and 11, 100, and 78 % for group C, respectively. A change in therapy resulted from the scan results in 7, 9, and 8 % in groups A, B, and C, respectively. The combined sensitivities for intra- and extrahepatic recurrence were 30 and 42 %, respectively. Histopathological features at initial surgery did not affect the sensitivity. The overall survival of patients with positive scans was significantly poorer than that of patients with negative scans (P = 0.008). The sensitivity of FDG PET for recurrent HCC was low, with little change in treatment resulting. However, it can predict prognosis in postoperative patients.

  16. The Capabilities and Limitations of Clinical Magnetic Resonance Imaging for Detecting Kidney Stones: A Retrospective Study

    PubMed Central

    Bridges, Mellena D.

    2016-01-01

    The purpose of this work was to investigate the performance of currently available magnetic resonance imaging (MRI) for detecting kidney stones, compared to computed tomography (CT) results, and to determine the characteristics of successfully detected stones. Patients who had undergone both abdominal/pelvic CT and MRI exams within 30 days were studied. The images were reviewed by two expert radiologists blinded to the patients' respective radiological diagnoses. The study consisted of four steps: (1) reviewing the MRI images and determining whether any kidney stone(s) are identified; (2) reviewing the corresponding CT images and confirming whether kidney stones are identified; (3) reviewing the MRI images a second time, armed with the information from the corresponding CT, noting whether any kidney stones are positively identified that were previously missed; (4) for all stones MRI-confirmed on previous steps, the radiologist experts being asked to answer whether in retrospect, with knowledge of size and location on corresponding CT, these stones would be affirmed as confidently identified on MRI or not. In this best-case scenario involving knowledge of stones and their locations on concurrent CT, radiologist experts detected 19% of kidney stones on MRI, with stone size being a major factor for stone identification. PMID:27980535

  17. Detection of acidification limit in anaerobic membrane bioreactors at ambient temperature.

    PubMed

    Kjerstadius, Hamse; de Vrieze, Jo; la Cour Jansen, Jes; Davidsson, Åsa

    2016-12-01

    High-volume, low-strength industrial wastewaters constitute a large potential for biogas production, which could be realized by membrane bioreactors operating at the ambient temperature of the wastewater. However, the start-up of low-temperature anaerobic processes using unadapted inoculum can be sensitive to overloading, which results in acidification. This study assessed if a novel acidification limit test can be used to identify stable organic loading rates as well as process over-loading. The test is based on easy-to-apply batch experiments for determination of the hydrolysis rate constant and the specific methanogenic activity of the acetotrophic and hydrogenotrophic pathways. For evaluation, two anaerobic membrane bioreactors, treating synthetic dairy wastewater at an ambient temperature of 24 °C, were used with a slow or a rapid start-up regime, respectively. Tests for hydrolysis rate and methanogenic activity were performed throughout the experiment and were used to calculate acidification limits for each system throughout the start-up. The acidification limit test was able to successfully identify both stable operation of one reactor and process failure of the other reactor as the organic loading rate increased. The reactor failure was caused by over-loading the acetotrophic pathway and coincided with microbial changes observed in real-time PCR and moving window analysis. Overall, the acidification limit tests seem promising as an easy applicable method for estimating what organic loading rate can be utilized, without risking acidification of anaerobic systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Vertical Root Fracture Detection Using Limited-FOV Cone-Beam Computed Tomography

    DTIC Science & Technology

    2012-06-01

    could not be predictably identified with current limited-FOV CBCT technology unless there was a visible separation of tooth segments. Key Words...canals (8), diagnosing apical pathosis (9,10), assessing external root resorption (11) and locating calcified canals. Images provide a 3-dimensional...data analysis. The “uncertain” group was considered “not fractured” because clinically, an endodontist would not extract a tooth if he was

  19. Early breast cancer screening using iron/iron oxide-based nanoplatforms with sub-femtomolar limits of detection

    PubMed Central

    Samarakoon, Thilani N; Yapa, Asanka S; Abayaweera, Gayani; Basel, Matthew T; Maynez, Pamela; Ortega, Raquel; Toledo, Yubisela; Bossmann, Leonie; Robinson, Colette; Janik, Katharine E; Koper, Olga B; Li, Ping; Motamedi, Massoud; Higgins, Daniel A; Gadbury, Gary

    2016-01-01

    Summary Proteases, including matrix metalloproteinases (MMPs), tissue serine proteases, and cathepsins (CTS) exhibit numerous functions in tumor biology. Solid tumors are characterized by changes in protease expression levels by tumor and surrounding tissue. Therefore, monitoring protease levels in tissue samples and liquid biopsies is a vital strategy for early cancer detection. Water-dispersable Fe/Fe3O4-core/shell based nanoplatforms for protease detection are capable of detecting protease activity down to sub-femtomolar limits of detection. They feature one dye (tetrakis(carboxyphenyl)porphyrin (TCPP)) that is tethered to the central nanoparticle by means of a protease-cleavable consensus sequence and a second dye (Cy 5.5) that is directly linked. Based on the protease activities of urokinase plasminogen activator (uPA), MMPs 1, 2, 3, 7, 9, and 13, as well as CTS B and L, human breast cancer can be detected at stage I by means of a simple serum test. By monitoring CTS B and L stage 0 detection may be achieved. This initial study, comprised of 46 breast cancer patients and 20 apparently healthy human subjects, demonstrates the feasibility of protease-activity-based liquid biopsies for early cancer diagnosis. PMID:27335730

  20. Early breast cancer screening using iron/iron oxide-based nanoplatforms with sub-femtomolar limits of detection.

    PubMed

    Udukala, Dinusha N; Wang, Hongwang; Wendel, Sebastian O; Malalasekera, Aruni P; Samarakoon, Thilani N; Yapa, Asanka S; Abayaweera, Gayani; Basel, Matthew T; Maynez, Pamela; Ortega, Raquel; Toledo, Yubisela; Bossmann, Leonie; Robinson, Colette; Janik, Katharine E; Koper, Olga B; Li, Ping; Motamedi, Massoud; Higgins, Daniel A; Gadbury, Gary; Zhu, Gaohong; Troyer, Deryl L; Bossmann, Stefan H

    2016-01-01

    Proteases, including matrix metalloproteinases (MMPs), tissue serine proteases, and cathepsins (CTS) exhibit numerous functions in tumor biology. Solid tumors are characterized by changes in protease expression levels by tumor and surrounding tissue. Therefore, monitoring protease levels in tissue samples and liquid biopsies is a vital strategy for early cancer detection. Water-dispersable Fe/Fe3O4-core/shell based nanoplatforms for protease detection are capable of detecting protease activity down to sub-femtomolar limits of detection. They feature one dye (tetrakis(carboxyphenyl)porphyrin (TCPP)) that is tethered to the central nanoparticle by means of a protease-cleavable consensus sequence and a second dye (Cy 5.5) that is directly linked. Based on the protease activities of urokinase plasminogen activator (uPA), MMPs 1, 2, 3, 7, 9, and 13, as well as CTS B and L, human breast cancer can be detected at stage I by means of a simple serum test. By monitoring CTS B and L stage 0 detection may be achieved. This initial study, comprised of 46 breast cancer patients and 20 apparently healthy human subjects, demonstrates the feasibility of protease-activity-based liquid biopsies for early cancer diagnosis.

  1. Limits of visual detection for finasteride polymorphs in prepared binary mixtures: analysis by X-ray powder diffraction.

    PubMed

    Bezzon, Vinícius D N; Antonio, Selma G; Paiva-Santos, Carlos O

    2014-11-01

    Finasteride (FNT) is a drug that inhibits human enzyme type II 5α-reductase that metabolizes testosterone into dihydrotestosterone. There are two enantiotropic polymorphs with known crystal structure: designated as forms I and II. Identification and control of these polymorphic forms in mixtures can be performed using X-ray powder diffraction (XRPD) data and Rietveld method (RM). As experimental conditions may limit the detection of minority phases in mixtures, it is interesting to show what are these limits for some usual and one high-resolution equipment. So, in this work, we discuss the parameters to find the limit of the detection in binary mixtures of forms I and II of FNT according to each experimental condition. The samples analyzed were binary mixtures prepared with anhydrous polymorphs of the drug FNT. These samples were measured in four diffractometers with different experimental condition. These equipments represent the main resolutions generally used for drug analysis by XRPD. For the development of this work, a batch of form I was obtained pure, and another batch with forms I and II was used to obtain pure form II by heat treatment. Depending on the experimental condition, the polymorphs could be detected in a proportion as low as 0.5 wt%. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3567-3575, 2014.

  2. Detection Limits for Close Eclipsing and transiting Sub-Stellar and Planetary Companions to White Dwarfs in the WASP Survey

    NASA Astrophysics Data System (ADS)

    Faedi, Francesca; West, Richard G.; Burleigh, Matt R.; Goad, Mike R.; Hebb, Leslie

    2011-03-01

    We used photometric data from the WASP (Wide-Angle Search for Planets) survey to explore the possibility of detecting eclipses and transit signals of brown dwarfs, gas giants and terrestrial companions in close orbit around white dwarfs. We performed extensive Monte Carlo simulations and we found that for Gaussian random noise WASP is sensitive to companions as small as the Moon orbiting a V~12 white dwarf. For fainter stars WASP is sensitive to increasingly larger bodies. Our sensitivity drops in the presence of co-variant noise structure in the data, nevertheless Earth-size bodies remain readily detectable in relatively low S/N data. We searched for eclipses and transit signals in a sample of 194 white dwarfs in the WASP archive however, no evidence for companions was found. We used our results to place tentative upper limits to the frequency of such systems. While we can only place weak limits on the likely frequency of Earth-sized or smaller companions; brown dwarfs and gas giants (radius~=RJup) with periods <=0.2 days must certainly be rare (<10%). More stringent constraints requires significantly larger white dwarf samples, higher observing cadence and continuous coverage. The short duration of eclipses and transits of white dwarfs compared to the cadence of WASP observations appears to be one of the main factors limiting the detection rate in a survey optimised for planetary transits of main sequence stars.

  3. Statistical analysis of water-quality data containing multiple detection limits: S-language software for regression on order statistics

    USGS Publications Warehouse

    Lee, L.; Helsel, D.

    2005-01-01

    Trace contaminants in water, including metals and organics, often are measured at sufficiently low concentrations to be reported only as values below the instrument detection limit. Interpretation of these "less thans" is complicated when multiple detection limits occur. Statistical methods for multiply censored, or multiple-detection limit, datasets have been developed for medical and industrial statistics, and can be employed to estimate summary statistics or model the distributions of trace-level environmental data. We describe S-language-based software tools that perform robust linear regression on order statistics (ROS). The ROS method has been evaluated as one of the most reliable procedures for developing summary statistics of multiply censored data. It is applicable to any dataset that has 0 to 80% of its values censored. These tools are a part of a software library, or add-on package, for the R environment for statistical computing. This library can be used to generate ROS models and associated summary statistics, plot modeled distributions, and predict exceedance probabilities of water-quality standards. ?? 2005 Elsevier Ltd. All rights reserved.

  4. Limits of detection in debris disks around young stars with NaCo/Sparse Aperture Masking observations

    NASA Astrophysics Data System (ADS)

    Gauchet, L.; Lacour, S.

    2014-09-01

    To understand the formation and evolution of solar systems and planets formations in the stars neighbourhood, we need to obtain information of their state at different time of their evolution. Here, we focus on debris disks around young stars aged of ten to few tens of Myr, we analyze NaCo/Sparse Aperture Masking (SAM) observations in the L' band (3.8 μm) of eight objects (beta Pictoris, AU Mic, 49 Ceti, eta Tel, Fomalhaut, G Lupi, HD182327 and HR8799). The aim is to get limits of detection about the mass of the debris orbiting around their stars. The SAM technique consists in transforming a single telescope into a Fizeau interferometer using a non redundant mask inserted in a pupil plane of the instrument. The analysis of the observations was completed with the sparse aperture mode pipeline. Interference fringes are fitted to obtain complex visibilities of the object, then the closure phases are calibrated and evaluated. Finally, a map of the detection limits is obtained as it is related to the closure phases previously estimated. In order to obtain an estimation of the mass corresponding to the luminosity measured with the reduction pipeline we are using theoretical isochrones interpolated into synthetic color tables. The results are maps of detection limits in unit of Jupiter Mass in a range of up to 450 mas around the stars.

  5. Planet Detection Statistics From the HARPS Low-Precision, Volume Limited Sample, After 8 Years of Data Taking.

    NASA Astrophysics Data System (ADS)

    Lo Curto, Gaspare

    2011-09-01

    The HARPS volume limited sample targets main sequence stars within a shell around Earth from 50pc to 57.5pc. From the still ongoing low precision (2-3m/s) survey started 8 years ago, we detected up to now 46 planets, of which 11 in multiple systems. The giant planet yield from our data is of more than 10% when considering only the stars observed with enough data points to reconstruct an orbit. Among those, 15% show long term drifts which are compatible with a signal from an orbiting companion, and 70% have a large, but yet unexplained radial velocity signal. I will describe the original sample and compare it with the subsample of our target stars with detected planets. Finally I will discuss our detections in the context of all the planet candidates to date.

  6. Detection, Size, Measurement, and Structural Analysis Limits for the 2MASS, UKIDSS-LAS, and VISTA VIKING Surveys

    NASA Astrophysics Data System (ADS)

    Andrews, Stephen K.; Kelvin, Lee S.; Driver, Simon P.; Robotham, Aaron S. G.

    2014-01-01

    The 2MASS, UKIDSS-LAS, and VISTA VIKING surveys have all now observed the GAMA 9hr region in the Ks band. Here we compare the detection rates, photometry, basic size measurements, and single-component GALFIT structural measurements for a sample of 37 591 galaxies. We explore the sensitivity limits where the data agree for a variety of issues including: detection, star-galaxy separation, photometric measurements, size and ellipticity measurements, and Sérsic measurements. We find that 2MASS fails to detect at least 20% of the galaxy population within all magnitude bins, however for those that are detected we find photometry is robust (± 0.2 mag) to 14.7 AB mag and star-galaxy separation to 14.8 AB mag. For UKIDSS-LAS we find incompleteness starts to enter at a flux limit of 18.9 AB mag, star-galaxy separation is robust to 16.3 AB mag, and structural measurements are robust to 17.7 AB mag. VISTA VIKING data are complete to approximately 20.0 AB mag and structural measurements appear robust to 18.8 AB mag.

  7. Quantum cascade laser-based substance detection: approaching the quantum noise limit

    NASA Astrophysics Data System (ADS)

    Kuffner, Peter C.; Conroy, Kathryn J.; Boyson, Toby K.; Milford, Greg; Mabrok, Mohamed A.; Kallapur, Abhijit G.; Petersen, Ian R.; Calzada, Maria E.; Spence, Thomas G.; Kirkbride, Kennith P.; Harb, Charles C.

    2011-06-01

    A consortium of researchers at University of New South Wales (UNSW@ADFA), and Loyola University New Orleans (LU NO), together with Australian government security agencies (e.g., Australian Federal Police), are working to develop highly sensitive laser-based forensic sensing strategies applicable to characteristic substances that pose chemical, biological and explosives (CBE) threats. We aim to optimise the potential of these strategies as high-throughput screening tools to detect prohibited and potentially hazardous substances such as those associated with explosives, narcotics and bio-agents.

  8. Sulfur Limits of Detection and Spectral Interference Corrections for DWPF Sludge Matrices by Inductively Coupled Plasma Emission Spectrometry

    SciTech Connect

    JURGENSEN, AR

    2004-04-20

    The Savannah River Technology Center (SRTC) has been requested to perform sulfur (S) analysis on digested radioactive sludge and supernatant samples by Inductively Coupled Plasma Emission Spectrometry (ICP-ES). The amount of sulfur is a concern because there are sulfur limits for the incoming feed, due to glass melter, process vessel, and off-gas line corrosion concerns and limited sulfur solubility in the glass wasteform. Recent changes in the washing strategy and stream additions change the amount of sulfur in the sludge. Increasing the sulfur concentration in the sludge challenges the current limits, so accurately determining the amount of sulfur present in a sludge batch is paramount. There are two important figures of merit that need to be evaluated for this analysis. The first is the detection limit (LOD), the smallest concentration of an element that can be detected with a defined certainty. This issue is important since the sulfur concentration in these process streams is l ow. Another critical analytical parameter is the effect on the S quantitation from potential spectral interferences. Spectral interferences are caused by background emission from plasma recombination events, scattered and stray light from the line emission of high concentration elements, or molecular band emission and from direct or tailing spectral line overlap from a matrix element. Any existing spectral overlaps could give false positives or increase the measured S concentrations in these matrices.

  9. Detection of strength limiting defects in cellular glasses by dielectric measurements

    NASA Technical Reports Server (NTRS)

    Gammell, P. M.; Adams, M. A.

    1981-01-01

    The foamed glasses that are being considered for structural support in solar thermal energy system silvered glass concentrator mirrors are assessed for strength-limiting defects by a nondestructive technique which measures the capacitance of well defined regions. The feasibility of locating large defects is demonstrated for the case of one type of cellular mass. Observed capacitance variations are believed to be due to small voids or other irregularities in the material. If the defects are equal to or greater than approximately 20 times the glass matrix pore size, they can be resolved with sufficient accuracy to delineate their spatial extent.

  10. Photon noise limited radiation detection with lens-antenna coupled microwave kinetic inductance detectors

    NASA Astrophysics Data System (ADS)

    Yates, S. J. C.; Baselmans, J. J. A.; Endo, A.; Janssen, R. M. J.; Ferrari, L.; Diener, P.; Baryshev, A. M.

    2011-08-01

    Microwave kinetic inductance detectors (MKIDs) have shown great potential for sub-mm instrumentation because of the high scalability of the technology. Here, we demonstrate for the first time in the sub-mm band (0.1-2 mm) a photon noise limited performance of a small antenna coupled MKID detector array and we describe the relation between photon noise and MKID intrinsic generation-recombination noise. Additionally, we use the observed photon noise to measure the optical efficiency of detectors to be 0.8 ± 0.2.

  11. Photon noise limited radiation detection with lens-antenna coupled microwave kinetic inductance detectors

    SciTech Connect

    Yates, S. J. C.; Baselmans, J. J. A.; Diener, P.; Endo, A.; Janssen, R. M. J.; Ferrari, L.; Baryshev, A. M.

    2011-08-15

    Microwave kinetic inductance detectors (MKIDs) have shown great potential for sub-mm instrumentation because of the high scalability of the technology. Here, we demonstrate for the first time in the sub-mm band (0.1-2 mm) a photon noise limited performance of a small antenna coupled MKID detector array and we describe the relation between photon noise and MKID intrinsic generation-recombination noise. Additionally, we use the observed photon noise to measure the optical efficiency of detectors to be 0.8 {+-} 0.2.

  12. An analysis of small target feature detection limits using optic flow

    NASA Astrophysics Data System (ADS)

    Conroy, Joseph; Gremillion, Gregory; Mathis, Allison; Nothwang, William

    2015-05-01

    The neurophysiology of insects suggests that they are able to track conspecifics, which manifest as small targets, against a variety of backgrounds with ease. This perception occurs at the same stage as motion perception suggesting a role for optic flow in target discrimination. Optic flow also is an attractive method of perception for visual system design due to the possibility of parallel processing that lends itself to implementation in hardware acceleration. This paper investigates some of the limits for reliable target discrimination solely from an optic flow field which are dependent on algorithm parameters, the nature of the target, and imager noise properties.

  13. Enhanced detection limit by dark mode perturbation in 2D photonic crystal slab refractive index sensors.

    PubMed

    Nicolaou, Costa; Lau, Wah Tung; Gad, Raanan; Akhavan, Hooman; Schilling, Ryan; Levi, Ofer

    2013-12-16

    We demonstrate for the first time a 300nm thick, 300μm × 300μm 2D dielectric photonic crystal slab membrane with a quality factor of 10,600 by coupling light to slightly perturbed dark modes through alternating nano-hole sizes. The newly created fundamental guided resonances greatly reduce nano-fabrication accuracy requirements. Moreover, we created a new layer architecture resulting in electric field enhancement at the interface between the slab and sensing regions, and spectral sensitivity of >800 nm/RIU, that is, >0.8 of the single-mode theoretical upper limit of spectral sensitivity.

  14. Limitations of malaria reactive case detection in an area of low and unstable transmission on the Myanmar-Thailand border.

    PubMed

    Parker, Daniel M; Landier, Jordi; von Seidlein, Lorenz; Dondorp, Arjen; White, Lisa; Hanboonkunupakarn, Borimas; Maude, Richard J; Nosten, François H

    2016-11-25

    the same sample size. The results of these simulations indicate that reactive case detection for clinical cases using RDTs has limited ability in halting transmission in regions of low and unstable transmission. This is linked to high spatial heterogeneity of cases, acquisition of malaria infections outside the village, as well missing asymptomatic infections. When cases are few and sporadic, reactive case detection would result in major time and budgetary losses.

  15. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  16. Phase-noise limitations in continuous-variable quantum key distribution with homodyne detection

    NASA Astrophysics Data System (ADS)

    Corvaja, Roberto

    2017-02-01

    In continuous-variables quantum key distribution with coherent states, the advantage of performing the detection by using standard telecoms components is counterbalanced by the lack of a stable phase reference in homodyne detection due to the complexity of optical phase-locking circuits and to the unavoidable phase noise of lasers, which introduces a degradation on the achievable secure key rate. Pilot-assisted phase-noise estimation and postdetection compensation techniques are used to implement a protocol with coherent states where a local laser is employed and it is not locked to the received signal, but a postdetection phase correction is applied. Here the reduction of the secure key rate determined by the laser phase noise, for both individual and collective attacks, is analytically evaluated and a scheme of pilot-assisted phase estimation proposed, outlining the tradeoff in the system design between phase noise and spectral efficiency. The optimal modulation variance as a function of the phase-noise amount is derived.

  17. Detecting and quantifying parasite-induced host mortality from intensity data: method comparisons and limitations.

    PubMed

    Wilber, Mark Q; Weinstein, Sara B; Briggs, Cheryl J

    2016-01-01

    Parasites can significantly impact animal populations by changing host behaviour, reproduction and survival. Detecting and quantifying these impacts is critical for understanding disease dynamics and managing wild animal populations. However, for wild hosts infected with macroparasites, it is notoriously difficult to quantify the fatal parasite load and number of animals that have died due to disease. When ethical or logistical constraints prohibit experimental determination of these values, examination of parasite intensity and distribution data may offer an alternative solution. In this study we introduce a novel method for using intensity data to detect and quantify parasite-induced mortality in wildlife populations. We use simulations to show that this method is more reliable than previously proposed methods while providing quantitative estimates of parasite-induced mortality from empirical data that are consistent with previously published qualitative estimates. However this method, and all techniques that estimate parasite-induced mortality from intensity data alone, have several important assumptions that must be scrutinised before applying those to real-world data. Given that these assumptions are met, our method is a new exploratory tool that can help inform more rigorous studies of parasite-induced host mortality.

  18. Automatic microseismic event detection by band-limited phase-only correlation

    NASA Astrophysics Data System (ADS)

    Wu, Shaojiang; Wang, Yibo; Zhan, Yi; Chang, Xu

    2016-12-01

    Identification and detection of microseismic events is a significant issue in source locations and source mechanism analysis. The number of the records is notably large, especially in the case of some real-time monitoring, and while the majority of microseismic events are highly weak and sparse, automatic algorithms are indispensable. In this study, we introduce an effective method for the identification and detection of microseismic events by judging whether the P-wave phase exists in a local segment from a single three-component microseismic records. The new judging algorithm consists primarily of the following key steps: 1) transform the waveform time series into time-varying spectral representations using the S-transform; 2) calculate the similarity of the frequency content in the time-frequency domain using the phase-only correlation function; and 3) identify the P-phase by the combination analysis between any two components. The proposed algorithm is compared to a similar approach using the cross-correlation in the time domain between any two components and later tested with synthetic microseismic datasets and real field-recorded datasets. The results indicate that the proposed algorithm is able to distinguish similar and dissimilar waveforms, even for low signal noise ratio and emergent events, which is important for accurate and rapid selection of microseismic events from a large number of records. This method can be applied to other geophysical analyses based on the waveform data.

  19. Tone-deaf ears in moths may limit the acoustic detection of two-tone bats.

    PubMed

    Mora, Emanuel C; Fernández, Yohami; Hechavarría, Julio; Pérez, Martha

    2014-01-01

    Frequency alternation in the echolocation of insectivorous bats has been interpreted in relation to ranging and duty cycle, i.e. advantages for echolocation. The shifts in frequency of the calls of these so-called two-tone bats, however, may also play its role in the success of their hunting behavior for a preferred prey, the tympanate moth. How the auditory receptors (e.g. the A1 and A2 cells) in the moth's ear detect such frequency shifts is currently unknown. Here, we measured the auditory responses of the A1 cell in the noctuid Spodoptera frugiperda to the echolocation hunting sequence of Molossus molossus, a two-tone bat. We also manipulated the bat calls to control for the frequency shifts by lowering the frequency band of the search and approach calls. The firing response of the A1 receptor cell significantly decreases with the shift to higher frequencies during the search and approach phases of the hunting sequence of M. molossus; this could be explained by the receptor's threshold curve. The frequency dependence of the decrease in the receptor's response is supported by the results attained with the manipulated sequence: search and approach calls with the same minimum frequency are detected by the moth at the same threshold intensity. The two-tone bat M. molossus shows a call frequency alternation behavior that may enable it to overcome moth audition even in the mid-frequency range (i.e. 20-50 kHz) where moths hear best.

  20. Fast detection of biomolecules in diffusion-limited regime using micromechanical pillars.

    PubMed

    Melli, Mauro; Scoles, Giacinto; Lazzarino, Marco

    2011-10-25

    We have developed a micromechanical sensor based on vertically oriented oscillating beams, in which contrary to what is normally done (for example with oscillating cantilevers) the sensitive area is located at the free end of the oscillator. In the micropillar geometry used here, analyte adsorption is confined only to the tip of the micropillar, thus reducing the volume from which the analyte molecules must diffuse to saturate the surface to a sphere of radius more than 2 orders of magnitude smaller than the corresponding linear distance valid for adsorption on a macroscopic surface. Hence the absorption rate is 3 orders of magnitude faster than on a typical 200 × 20 square micrometer cantilever. Pillar oscillations are detected by means of an optical lever method, but the geometry is suitable for multiplexing with compact integrated detection. We demonstrate our technology by investigating the formation of a single-strand DNA self-assembled monolayer (SAM) consisting of less than 10(6) DNA molecules and by measuring their hybridization efficiency. We show that the binding rate is 1000 times faster than on a "macroscopic" surface. We also show that the hybridization of a SAM of maximum density DNA is 40% or 4 times the value reported in the literature. These results suggest that the lower values previously reported in the literature can be attributed to incomplete saturation of the surface due to the slower adsorption rate on the "macroscopic" surfaces used.

  1. Detectability limitations with 3-D point reconstruction algorithms using digital radiography

    SciTech Connect

    Lindgren, Erik

    2015-03-31

    The estimated impact of pores in clusters on component fatigue will be highly conservative when based on 2-D rather than 3-D pore positions. To 3-D position and size defects using digital radiography and 3-D point reconstruction algorithms in general require a lower inspection time and in some cases work better with planar geometries than X-ray computed tomography. However, the increase in prior assumptions about the object and the defects will increase the intrinsic uncertainty in the resulting nondestructive evaluation output. In this paper this uncertainty arising when detecting pore defect clusters with point reconstruction algorithms is quantified using simulations. The simulation model is compared to and mapped to experimental data. The main issue with the uncertainty is the possible masking (detectability zero) of smaller defects around some other slightly larger defect. In addition, the uncertainty is explored in connection to the expected effects on the component fatigue life and for different amount of prior object-defect assumptions made.

  2. Absolute limit for the capillary rise of a fluid

    NASA Astrophysics Data System (ADS)

    Caupin, Frédéric; Cole, Milton W.; Balibar, Sébastien; Treiner, Jacques

    2008-06-01

    Small capillaries can provide strong binding to fluids confined within them. We analyze this behavior with a simple microscopic theory, considering two geometries, a slit pore and a cylindrical pore. A goal is to achieve the maximum possible capillary rise (H) within each type of pore. The attraction for very small capillaries can result in a large value of H, exceeding 100 km in a number of cases (e.g., hydrogen, methane and water in cylindrical graphitic pores). The specific value of H depends on the details of the pore and the fluid-surface interaction. It is maximized in the case of small cylindrical pores, strong interactions and small adsorbate mass. Explicit calculations are presented for graphite and MgO substrates. Experimental tests are possible with an ultracentrifuge, where the high effective gravitational field reduces H.

  3. Time-dependent phenomena in the potential response of ion-selective electrodes treated by the Nernst-Planck-Poisson model. Part 2: Transmembrane processes and detection limit.

    PubMed

    Sokalski, Tomasz; Kucza, Witold; Danielewski, Marek; Lewenstam, Andrzej

    2009-06-15

    The detection limit of ion-selective electrodes (ISEs) is of great interest because of the many possible practical applications of ISEs in trace analysis. Existing theoretical interpretations of the detection limit of ISEs are restricted by severe assumptions such as steady-state and electroneutrality, which hamper theorizing on this problem. For this reason, the Nernst-Planck-Poisson (NPP) equations are used to predict and visualize the detection limit variability under nonequilibrium conditions. For the first time, the NPP model is applied to the so-called inverse problem: finding the optimal measurement time and inner solution concentration for lowering the detection limit.

  4. Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides.

    PubMed

    Maier, Stefan A; Kik, Pieter G; Atwater, Harry A; Meltzer, Sheffer; Harel, Elad; Koel, Bruce E; Requicha, Ari A G

    2003-04-01

    Achieving control of light-material interactions for photonic device applications at nanoscale dimensions will require structures that guide electromagnetic energy with a lateral mode confinement below the diffraction limit of light. This cannot be achieved by using conventional waveguides or photonic crystals. It has been suggested that electromagnetic energy can be guided below the diffraction limit along chains of closely spaced metal nanoparticles that convert the optical mode into non-radiating surface plasmons. A variety of methods such as electron beam lithography and self-assembly have been used to construct metal nanoparticle plasmon waveguides. However, all investigations of the optical properties of these waveguides have so far been confined to collective excitations, and direct experimental evidence for energy transport along plasmon waveguides has proved elusive. Here we present observations of electromagnetic energy transport from a localized subwavelength source to a localized detector over distances of about 0.5 microm in plasmon waveguides consisting of closely spaced silver rods. The waveguides are excited by the tip of a near-field scanning optical microscope, and energy transport is probed by using fluorescent nanospheres.

  5. Absolute calibration of fusion gamma ray detector on TFTR

    NASA Astrophysics Data System (ADS)

    Medley, S. S.; Roquemore, A. L.; Cecil, F. E.

    1992-10-01

    An in situ measurement of the absolute detection efficiency of the fusion gamma ray detector on TFTR has been completed. The efficiency was determined by measuring the yield of the 4.44 MeV gamma ray from a plutonium-berrylium source situated within the vacuum vessel. The absolute detection efficiency at 4.44 MeV is extended to higher energies using the known energy dependence of the gamma ray attenuation coefficients in the vessel port cover, the detector neutron moderator, and the scintillator. The absolute detection efficiency (full energy peak detected gamma rays per source gamma ray) varies from 8.6E-9 at 4.44 MeV to 1.1E-8 at 17 MeV and is insensitive at the few percent level to relatively large variations in the radial profile of the gamma ray source distribution in the plasma. The absolute detection efficiency is used to determine the total d-3He reaction rate during recent deuterium neutral beam heated 3He plasmas on TFTR.

  6. Linear ultrasonic motor for absolute gravimeter.

    PubMed

    Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

    2017-02-01

    Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters.

  7. Considerations on the determination of the limit of detection and the limit of quantification in one-dimensional and comprehensive two-dimensional gas chromatography.

    PubMed

    Krupčík, Ján; Májek, Pavel; Gorovenko, Roman; Blaško, Jaroslav; Kubinec, Robert; Sandra, Pat

    2015-05-29

    Methods based on the blank signal as proposed by IUPAC procedure and on the signal to noise ratio (S/N) as listed in the ISO-11843-1 norm for determination of the limit of detection (LOD) and quantitation (LOQ) in one-dimensional capillary gas chromatography (1D-GC) and comprehensive two-dimensional capillary gas chromatography (CG×GC) are described in detail and compared for both techniques. Flame ionization detection was applied and variables were the data acquisition frequency and, for CG×GC, also the modulation time. It has been stated that LOD and LOQ estimated according to IUPAC might be successfully used for 1D-GC-FID method. Moreover, LOD and LOQ decrease with decrease of data acquisition frequency (DAF). For GC×GC-FID, estimation of LOD by IUPAC gave poor reproducibility of results while for LOQ reproducibility was acceptable (within ±10% rel.). The LOD and LOQ determined by the S/N concept both for 1D-GC-FID and GC×GC-FID methods are ca. three times higher than those values estimated by the standard deviation of the blank. Since the distribution pattern of modulated peaks for any analyte separated by GC×GC is random and cannot be predicted, LOQ and LOD may vary within 30% for 3s modulation time. Concerning sensitivity, 1D-GC-FID at 2Hz and of GC×GC-FID at 50Hz shows a ca. 5 times enhancement of sensitivity in the modulated signal output.

  8. The Approach to Reducing the Detection Limit for LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Poteshin, S. S.; Sysoev, Alexey A.; Torbotryas, R.

    This work is a part of the RED-100 big project. The aim of the RED-100 experiment is to detect the presently undiscovered coherent neutrino scattering off xenon atomic nuclei. The manufacture of such detectors requires ultrapure materials with very low content of natural radioactive elements. So the pure titanium was selected to assay the uranium and thorium contaminations on 1 ng/g level. In this paper we investigate the possibility of reducing the LOD for LA-ICP-MS analysis by increasing the pulse repetition rate of solid-state laser irradiation up to 4,000 Hz and appropriate adjusting the irradiation power. LODs for U and Th in titanium matrix estimation fell in the sub 10-10 g g- 1 level.

  9. 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.

  10. Silver- and Coomassie-staining protocols: detection limits and compatibility with ESI MS.

    PubMed

    Winkler, Christiane; Denker, Katrin; Wortelkamp, Stefanie; Sickmann, Albert

    2007-06-01

    Staining protocols for PAGE have to be sensitive and should not impair further MS analysis of selected samples. In this study, the MS compatibility of different silver- and Coomassie-staining protocols with a nano-LC-MS/MS system was systematically elucidated. Altogether, 13 different silver-staining, 1 imidazole-staining and 2 Coomassie-staining protocols were used and compared to each other for their achieved sequence coverage and their detection sensitivity. Three proteins were used as model proteins (bovine serum albumin, rabbit L-lactate dehydrogenase, bovine milk beta-lactoglobulin) in decreasing concentration (12 pmol down to 30 fmol) and different staining protocols were applied. The conclusion of this study is that two silver-staining protocols (Blum, H. et al.,. Electrophoresis 1987, 8, 93-99 and Shevchenko, A. et al.,. Anal. Chem. 1996, 68, 850-858) combine good sequence coverage and good sensitivity and are recommended for nano-LC-MS/MS analysis.

  11. The Impact of an ECV Service is Limited by Antenatal Breech Detection: A Retrospective Cohort Study.

    PubMed

    Hemelaar, Joris; Lim, Lee N; Impey, Lawrence W

    2015-06-01

    External cephalic version (ECV) reduces the chance of breech presentation at term birth and lowers the chance of a cesarean delivery. ECV services are now in place in many units in the United Kingdom but their effectiveness is unknown. The aim of this study was to investigate the reasons for breech presentation at term birth. We performed a retrospective cohort study of 394 consecutive babies who were in breech presentation at term birth in a large United Kingdom maternity unit that offers ECV. The cohort was analyzed over two time periods 10 years apart: 1998-1999 and 2008-2009. Only 33.8 percent of women had undergone a (failed) ECV attempt. This low proportion was mainly because breech presentation was not diagnosed antenatally (27.9%). Other contributing factors were: ECV not offered by clinicians (12.2%), ECV declined by women (14%), and contraindications to ECV (10.7%). Over the 10-year period, the proportion of breech presentations that were not diagnosed antenatally increased from 23.2 to 32.5 percent (p = 0.04), which constituted 52.8 percent of women who had not undergone an ECV attempt in 2008-2009. Failure of clinicians to offer ECV reduced from 21.6 to 3.0 percent (p = 0.0001) and the proportion of women declining ECV decreased from 19.1 to 9.0 percent (p = 0.005). Overall, ECV attempts increased from 28.9 to 38.5 percent (p = 0.05). Although ECV counseling, referral, and attempt rates have increased, failure to detect breech presentation antenatally is the principal barrier to successful ECV. Improved breech detection would have a greater impact than methods to increase ECV success rates. © 2015 Wiley Periodicals, Inc.

  12. Coronary artery disease detection - limitations of stress testing in left ventricular dysfunction

    PubMed Central

    Bomb, Ritin; Kumar, Senthil; Chockalingam, Anand

    2017-01-01

    Incidental diagnosis of left ventricular systolic dysfunction (LVD) is common in clinical practice. The prevalence of asymptomatic LVD (Ejection Fraction, EF < 50%) is 6.0% in men and 0.8% in women and is twice as common as symptomatic LVD. The timely and definitive exclusion of an ischemic etiology is central to optimizing care and reducing mortality in LVD. Advances in cardiovascular imaging provide many options for imaging of patients with left ventricular dysfunction. Clinician experience, patient endurance, imaging modality characteristics, cost and safety determine the choice of testing. In this review, we have compared the diagnostic utility of established tests - nuclear and echocardiographic stress testing with newer techniques like coronary computerized tomography and cardiac magnetic resonance imaging and highlight their inherent limitations in patients with underlying left ventricular dysfunction. PMID:28515848

  13. Detection of HBr and upper limit for HOBr: Bromine partitioning in the stratosphere

    SciTech Connect

    Johnson, D.G.; Traub, W.A.; Chance, K.V.

    1995-06-01

    The authors determine mixing ratio profiles for HBr and upper limits for HOBr in the stratosphere with precisions up to 1.7 and 4.8 parts per trillion, respectively, using the combined data from 7 flights of their far-infrared spectrometer. The measurements suggest that in the range 22-34 km the average mixing ratio of HBr is 2.0{+-}0.8, and that the average mixing ratio of HOBr is less than 2.8 ppt. Their measurements of HBr are in reasonable agreement with a photochemical model which includes 0 or 2% production of HBr through the reaction of BrO with HO{sub 2}, but in strong disagreement with a model including 5 or 10% HBr production. 15 refs., 2 figs., 2 tabs.

  14. Coronary artery disease detection - limitations of stress testing in left ventricular dysfunction.

    PubMed

    Bomb, Ritin; Kumar, Senthil; Chockalingam, Anand

    2017-04-26

    Incidental diagnosis of left ventricular systolic dysfunction (LVD) is common in clinical practice. The prevalence of asymptomatic LVD (Ejection Fraction, EF < 50%) is 6.0% in men and 0.8% in women and is twice as common as symptomatic LVD. The timely and definitive exclusion of an ischemic etiology is central to optimizing care and reducing mortality in LVD. Advances in cardiovascular imaging provide many options for imaging of patients with left ventricular dysfunction. Clinician experience, patient endurance, imaging modality characteristics, cost and safety determine the choice of testing. In this review, we have compared the diagnostic utility of established tests - nuclear and echocardiographic stress testing with newer techniques like coronary computerized tomography and cardiac magnetic resonance imaging and highlight their inherent limitations in patients with underlying left ventricular dysfunction.

  15. Quantification of circulating steroids in individual zebrafish using stacking to achieve nanomolar detection limits with capillary electrophoresis and UV-visible absorbance detection.

    PubMed

    Nyakubaya, Vincent T; Durney, Brandon C; Ellington, Marriah C G; Kantes, Amber D; Reed, Paige A; Walter, Shaylyn E; Stueckle, Jennifer Ripley; Holland, Lisa A

    2015-09-01

    Capillary electrophoresis and UV-visible absorbance detection are used with sample stacking to achieve detection limits ranging from 0.2 to 2 ng/mL (0.8 to 6 nM) for steroids. Stacking is accomplished using negatively charged cyclodextrin steroid-carrier molecules at a discrete pH interface between the reconstituted sample and the separation electrolyte. Steroids are then separated in under 5 min using capillary electrophoresis that incorporates secondary equilibria via sodium dodecyl sulfate and cyclodextrin. The effectiveness of the method for measurements of multiple steroids in limited sample volumes is demonstrated in individual female fish with total circulating blood volumes of 5 μL or less. Steroid recoveries from plasma following a sample processing method developed with commercial extraction cartridges range from 81 to 109 % for 17α,20β-dihydroxy-pregn-4-en-3-one, testosterone, 11-ketotestosterone, estrone, 17β-estradiol, and 17α-ethinyl estradiol. When applied to reproductively active female zebrafish, changes were detected in the levels of circulating steroids as a result of exposure to different solvents and 17β-estradiol.

  16. Absolute distance sensing by two laser optical interferometry.

    PubMed

    Thurner, Klaus; Braun, Pierre-François; Karrai, Khaled

    2013-11-01

    We have developed a method for absolute distance sensing by two laser optical interferometry. A particularity of this technique is that a target distance is determined in absolute and is no longer limited to within an ambiguity range affecting usually multiple wavelength interferometers. We implemented the technique in a low-finesse Fabry-Pérot miniature fiber based interferometer. We used two diode lasers, both operating in the 1550 nm wavelength range. The wavelength difference is chosen to create a 25 μm long periodic beating interferometric pattern allowing a nanometer precise position measurement but limited to within an ambiguity range of 25 μm. The ambiguity is then eliminated by scanning one of the wavelengths over a small range (3.4 nm). We measured absolute distances in the sub-meter range and this with just few nanometer repeatability.

  17. Detection limits of quantitative and digital PCR assays and their influence in presence-absence surveys of environmental DNA.

    PubMed

    Hunter, Margaret E; Dorazio, Robert M; Butterfield, John S S; Meigs-Friend, Gaia; Nico, Leo G; Ferrante, Jason A

    2017-03-01

    A set of universal guidelines is needed to determine the limit of detection (LOD) in PCR-based analyses of low-concentration DNA. In particular, environmental DNA (eDNA) studies require sensitive and reliable methods to detect rare and cryptic species through shed genetic material in environmental samples. Current strategies for assessing detection limits of eDNA are either too stringent or subjective, possibly resulting in biased estimates of species' presence. Here, a conservative LOD analysis grounded in analytical chemistry is proposed to correct for overestimated DNA concentrations predominantly caused by the concentration plateau, a nonlinear relationship between expected and measured DNA concentrations. We have used statistical criteria to establish formal mathematical models for both quantitative and droplet digital PCR. To assess the method, a new Grass Carp (Ctenopharyngodon idella) TaqMan assay was developed and tested on both PCR platforms using eDNA in water samples. The LOD adjustment reduced Grass Carp occupancy and detection estimates while increasing uncertainty-indicating that caution needs to be applied to eDNA data without LOD correction. Compared to quantitative PCR, digital PCR had higher occurrence estimates due to increased sensitivity and dilution of inhibitors at low concentrations. Without accurate LOD correction, species occurrence and detection probabilities based on eDNA estimates are prone to a source of bias that cannot be reduced by an increase in sample size or PCR replicates. Other applications also could benefit from a standardized LOD such as GMO food analysis and forensic and clinical diagnostics. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

  18. Performance limitations of a free-space optical communication satellite network owing to vibrations: heterodyne detection.

    PubMed

    Arnon, S; Rotman, S R; Kopeika, N S

    1998-09-20

    Free-space optical communication between satellites in a distributed network can permit high data rates of communication between different places on Earth. To establish optical communication between any two satellites requires that the line of sight of their optics be aligned during the entire communication time. Because of the large distance between the satellites and the alignment accuracy required, the pointing from one satellite to another is complicated because of vibrations of the pointing system caused by two fundamental stochastic mechanisms: tracking noise created by the electro-optic tracker and vibrations derived from mechanical components. Vibration of the transmitter beam in the receiver plane causes a decrease in the received optical power. Vibrations of the receiver telescope relative to the received beam decrease the heterodyne mixing efficiency. These two factors increase the bit-error rate of a coherent detection network. We derive simple mathematical models of the network bit-error rate versus the system parameters and the transmitter and receiver vibration statistics. An example of a practical optical heterodyne free-space satellite optical communication network is presented. From this research it is clear that even low-amplitude vibration of the satellite-pointing systems dramatically decreases network performance.

  19. Detecting changes in water limitation in the West using integrated ecosystem modeling approaches

    NASA Astrophysics Data System (ADS)

    Poulter, B.; Hoy, J.; Emmett, K.; Cross, M.; Maneta, M. P.; Al-Chokhachy, R.

    2016-12-01

    Water in the western United States is the critical currency for determining a range of ecosystem services, such as wildlife habitat, carbon sequestration, and timber and water resources for an expanding human population. The current generation of catchment models trades a detailed representation of hydrologic processes for a generalization of vegetation processes and thus ignores many land-surface feedbacks that are driven by physiological responses to atmospheric CO2 and changes in vegetation structure following disturbance and climate change. Here we demonstrate how catchment scale modeling can better couple vegetation dynamics and disturbance processes to reconstruct historic streamflow, stream temperature and vegetation greening for the Greater Yellowstone Ecosystem. Using a new catchment routing model coupled to the LPJ-GUESS dynamic global vegetation model, simulations are made at 1 km spatial resolution using two different climate products. Decreased winter snowpack has led to increasing spring runoff and declines in summertime slow, and increasing the likelihood that stream temperature exceeds thresholds for cold-water fish growth. Since the mid-1980s, vegetation greening is projected by both the model and detected from space-borne normalized difference vegetation index observations. These greening trends are superimposed on a landscape matrix defined by frequent disturbance and intensive land management, making the climate and CO2 fingerprint difficult to discern. Integrating dynamical vegetation models with in-situ and spaceborne measurements to understand and interpret catchment-scale trends in water availability has potential to better disentangle historical climate, CO2, and human drivers and their ecosystem consequences.

  20. Using proximity biotinylation to detect herpesvirus entry glycoprotein interactions: Limitations for integral membrane glycoproteins.

    PubMed

    Lajko, Michelle; Haddad, Alexander F; Robinson, Carolyn A; Connolly, Sarah A

    2015-09-01

    Herpesvirus entry into cells requires coordinated interactions among several viral transmembrane glycoproteins. Viral glycoproteins bind to receptors and interact with other glycoproteins to trigger virus-cell membrane fusion. Details of these glycoprotein interactions are not well understood because they are likely transient and/or low affinity. Proximity biotinylation is a promising protein-protein interaction assay that can capture transient interactions in live cells. One protein is linked to a biotin ligase and a second protein is linked to a short specific acceptor peptide (AP). If the two proteins interact, the ligase will biotinylate the AP, without requiring a sustained interaction. To examine herpesvirus glycoprotein interactions, the ligase and AP were linked to herpes simplex virus 1 (HSV1) gD and Epstein Barr virus (EBV) gB. Interactions between monomers of these oligomeric proteins (homotypic interactions) served as positive controls to demonstrate assay sensitivity. Heterotypic combinations served as negative controls to determine assay specificity, since HSV1 gD and EBV gB do not interact functionally. Positive controls showed strong biotinylation, indicating that viral glycoprotein proximity can be detected. Unexpectedly, the negative controls also showed biotinylation. These results demonstrate the special circumstances that must be considered when examining interactions among glycosylated proteins that are constrained within a membrane.

  1. Specificity and detection limit of a dermal temperature histamine sensitization test for absence of residual pertussis toxin in vaccines.

    PubMed

    Jensen, Sten E; Illigen, Kristin E Engelhart; Badsberg, Jens Henrik; Hasløv, Kaare R

    2012-01-01

    Currently, an assay based on fatal sensitization of mice to histamine challenge is widely used for testing absence of residual pertussis toxin in acellular pertussis containing vaccines. For replacement of this lethal end-point assay, an alternative method based on body temperature measurement in mice has been presented, and in this study the specificity and detection limit of a dermal temperature-based assay were assessed. Test preparations containing pertussis toxin were prepared in aluminum-adjuvanted pertussis toxoid vaccine and injected intraperitoneally in histamine sensitive mice. Later the mice were challenged with histamine and the pertussis toxin-induced decrease in dermal temperature recorded. By comparison of mice treated with pertussis toxoid vaccine spiked with pertussis toxin with mice treated with pertussis toxoid vaccine alone, the assay gave a response that specifically could detect presence of pertussis toxin. The acellular pertussis containing vaccine did not interfere with the pertussis toxin-induced temperature response recorded. In tests for presence of pertussis toxin in the pertussis vaccine preparation, the detection limit of the assay was estimated to approximately 5 ng pertussis toxin per human dose of pertussis toxoid. The dermal temperature-based assay was found to be a valid method to be applied in routine quality control of vaccines.

  2. Planetary detection limits taking into account stellar noise. I. Observational strategies to reduce stellar oscillation and granulation effects

    NASA Astrophysics Data System (ADS)

    Dumusque, X.; Udry, S.; Lovis, C.; Santos, N. C.; Monteiro, M. J. P. F. G.

    2011-01-01

    Context. Stellar noise produced by oscillations, granulation phenomena (granulation, mesogranulation, and supergranulation), and activity affects radial velocity measurements. The signature of the corresponding effect in radial velocity is small, around the meter-per-second, but already too large for the detection of Earth-mass planets in habitable zones. Aims: We address the important role played by observational strategies in averaging out the radial velocity signature of stellar noise. We also derive the planetary mass detection limits expected in the presence of stellar noise. Methods: We start with HARPS asteroseismology measurements for four stars (β Hyi, α Cen A, μ Ara, and τ Ceti) available in the ESO archive and very precise measurements of α Cen B. This sample covers different spectral types from G2 to K1 and different evolutionary stages, from subgiant to dwarf stars. Since data span between 5 and 8 days, only stellar noise sources with timescales shorter than this time span will be extracted from these observations. Therefore, we are able to study oscillation modes and granulation phenomena without being significantly affected by activity noise present on longer timescales. For those five stars, we generate synthetic radial velocity measurements after fitting the corresponding models of stellar noise in Fourier space. These measurements allow us to study the radial velocity variation due to stellar noise for different observational strategies as well as the corresponding planetary mass detection limits. Results: Applying three measurements per night of 10 min exposure each, 2 h apart, seems to most efficiently average out the stellar noise considered. For quiet K1V stars such as α Cen B, this strategy allows us to detect planets of about three times the mass of Earth with an orbital period of 200 days, corresponding to the habitable zone of the star. Moreover, our simulations suggest that planets smaller than typically 5 M⊕ can be detected with

  3. Early detection of diabetic kidney disease: Present limitations and future perspectives

    PubMed Central

    Lin, Chih-Hung; Chang, Yi-Cheng; Chuang, Lee-Ming

    2016-01-01

    Diabetic kidney disease (DKD) is one of the most common diabetic complications, as well as the leading cause of chronic kidney disease and end-stage renal disease around the world. To prevent the dreadful consequence, development of new assays for diagnostic of DKD has always been the priority in the research field of diabetic complications. At present, urinary albumin-to-creatinine ratio and estimated glomerular filtration rate (eGFR) are the standard methods for assessing glomerular damage and renal function changes in clinical practice. However, due to diverse tissue involvement in different individuals, the so-called “non-albuminuric renal impairment” is not uncommon, especially in patients with type 2 diabetes. On the other hand, the precision of creatinine-based GFR estimates is limited in hyperfiltration status. These facts make albuminuria and eGFR less reliable indicators for early-stage DKD. In recent years, considerable progress has been made in the understanding of the pathogenesis of DKD, along with the elucidation of its genetic profiles and phenotypic expression of different molecules. With the help of ever-evolving technologies, it has gradually become plausible to apply the thriving information in clinical practice. The strength and weakness of several novel biomarkers, genomic, proteomic and metabolomic signatures in assisting the early diagnosis of DKD will be discussed in this article. PMID:27525056

  4. Limited genetic variability and phenotypic plasticity detected for cavitation resistance in a Mediterranean pine.

    PubMed

    Lamy, Jean-Baptiste; Delzon, Sylvain; Bouche, Pauline S; Alia, Ricardo; Vendramin, Giovanni Giuseppe; Cochard, Hervé; Plomion, Christophe

    2014-02-01

    Resistance to cavitation is a major determinant of plant survival under severe drought and can be used to quantify species adaptive potential. Interspecific variation in this key trait is well defined in woody species, but intraspecific variation (level and structure) resulting from standing genetic variation and phenotypic plasticity has never been determined. Combining for the first time in situ characterization of natural populations and two reciprocal common gardens in dry and wet sites, we estimated variance components (phenotypic, genetic, environmental, and genetic × environmental) of cavitation resistance based on 513 genotypes of a Mediterranean pine, Pinus pinaster. Despite the selected populations being climatically contrasted, phenotypic plasticity in resistance to cavitation remained low and was essentially attributed to family level. Between-population variation in cavitation resistance for both phenotypic and genetic variation was limited. These results strongly suggest that cavitation resistance is buffered against genetic and to a lesser extent environmental variation (canalization) in maritime pine. Consequently, in a drier world, the increasing drought tolerance of Pinus species might be severely constrained by the low level of cavitation resistance variation, resulting in a large-scale loss of productivity.

  5. Detection and prediction limits for identifying highly confusable drug names from experimental data.

    PubMed

    Lambert, Bruce L; Bhaumik, Runa; Zhao, Weihan; Bhaumik, Dulal K

    2016-01-01

    Confusions between drug names that look and sound alike are common, costly, harmful, and difficult to prevent. One prevention strategy is to screen proposed new drug names for confusability before approving them. Widespread acceptance of preapproval tests of confusability is compromised by the lack of experimental designs and statistical methods to support valid inferences about whether a proposed new name is unacceptably confusing. One way of identifying confusing names is to conduct memory and perception experiments on a set of drug names which would include both the new name and a set of control names (e.g., names already on the market). The experiment would yield an observed error rate for every name. Inferences about the acceptability of the new name can be made by comparing the error rate of the new name to the distribution of error rates of the control names. We describe four memory and perception experiments on drug names, carried out using clinicians as participants. Each experiment included drug names designated as test and control names. We demonstrate how to use a combination of logistic regression, Poisson prediction limits, and highly assured credible intervals to identify and apply a threshold for identifying unacceptably confusing names. Our models show an excellent fit to the data. These experimental designs and analytic methods should be useful in the preapproval testing of proposed new drug names and in similar regulatory scenarios where it is necessary to draw inferences about the comparative safety or effectiveness of new vs. old products.

  6. Estimating the computational limits of detection of microbial non-model organisms.

    PubMed

    Kuhring, Mathias; Renard, Bernhard Y

    2015-10-01

    Mass spectrometry has become a key instrument for proteomic studies of single bacteria as well as microbial communities. However, the identification of spectra from MS/MS experiments is still challenging, in particular for non-model organisms. Due to the limited amount of related protein reference sequences, underexplored organisms often remain completely unidentified or their spectra match to peptides of uncertain degree of relation. Alternative strategies such as error-tolerant spectra searches or proteogenomic approaches may reduce the amount of unidentified spectra and lead to peptide matches on more related taxonomic levels. However, to what extent these strategies may be successful is difficult to judge prior to an MS/MS experiment. In this contribution, we introduce a method to estimate the suitability of databases of interest. Further, it allows estimating the possible influence of error-tolerant searches and proteogenomic approaches on databases of interest with respect to the number of unidentified spectra and the taxonomic distances of identified spectra. Furthermore, we provide an implementation of our approach that supports experimental design by evaluating the benefit and need of different search strategies with respect to present databases and organisms under study. We provide several examples which highlight the different effects of additional search strategies on databases and organisms with varying amount of known relative species available.

  7. Quantum-limited detection of millimeter waves using superconducting tunnel junctions

    SciTech Connect

    Mears, C.A.

    1991-09-01

    The quasiparticle tunneling current in a superconductor-insulator- superconductor (SIS) tunnel junction is highly nonlinear. Such a nonlinearity can be used to mix two millimeter wave signals to produce a signal at a much lower intermediate frequency. We have constructed several millimeter and sub-millimeter wave SIS mixers in order to study high frequency response of the quasiparticle tunneling current and the physics of high frequency mixing. We have made the first measurement of the out-of-phase tunneling currents in an SIS tunnel junction. We have developed a method that allows us to determine the parameters of the high frequency embedding circuit by studying the details of the pumped I-V curve. We have constructed a 80--110 GHz waveguide-based mixer test apparatus that allows us to accurately measure the gain and added noise of the SIS mixer under test. Using extremely high quality tunnel junctions, we have measured an added mixer noise of 0.61 {plus minus} 0.36 quanta, which is within 25 percent of the quantum limit imposed by the Heisenberg uncertainty principle. This measured performance is in excellent agreement with that predicted by Tucker's theory of quantum mixing. We have also studied quasioptically coupled millimeter- and submillimeter-wave mixers using several types of integrated tuning elements. 83 refs.

  8. Quantum-limited detection of millimeter waves using superconducting tunnel junctions

    SciTech Connect

    Mears, C.A.

    1991-09-01

    The quasiparticle tunneling current in a superconductor-insulator- superconductor (SIS) tunnel junction is highly nonlinear. Such a nonlinearity can be used to mix two millimeter wave signals to produce a signal at a much lower intermediate frequency. We have constructed several millimeter and sub-millimeter wave SIS mixers in order to study high frequency response of the quasiparticle tunneling current and the physics of high frequency mixing. We have made the first measurement of the out-of-phase tunneling currents in an SIS tunnel junction. We have developed a method that allows us to determine the parameters of the high frequency embedding circuit by studying the details of the pumped I-V curve. We have constructed a 80--110 GHz waveguide-based mixer test apparatus that allows us to accurately measure the gain and added noise of the SIS mixer under test. Using extremely high quality tunnel junctions, we have measured an added mixer noise of 0.61 {plus_minus} 0.36 quanta, which is within 25 percent of the quantum limit imposed by the Heisenberg uncertainty principle. This measured performance is in excellent agreement with that predicted by Tucker`s theory of quantum mixing. We have also studied quasioptically coupled millimeter- and submillimeter-wave mixers using several types of integrated tuning elements. 83 refs.

  9. Absolute nonlocality via distributed computing without communication

    NASA Astrophysics Data System (ADS)

    Czekaj, Ł.; Pawłowski, M.; Vértesi, T.; Grudka, A.; Horodecki, M.; Horodecki, R.

    2015-09-01

    Understanding the role that quantum entanglement plays as a resource in various information processing tasks is one of the crucial goals of quantum information theory. Here we propose an alternative perspective for studying quantum entanglement: distributed computation of functions without communication between nodes. To formalize this approach, we propose identity games. Surprisingly, despite no signaling, we obtain that nonlocal quantum strategies beat classical ones in terms of winning probability for identity games originating from certain bipartite and multipartite functions. Moreover we show that, for a majority of functions, access to general nonsignaling resources boosts success probability two times in comparison to classical ones for a number of large enough outputs. Because there are no constraints on the inputs and no processing of the outputs in the identity games, they detect very strong types of correlations: absolute nonlocality.

  10. Enabling electrical biomolecular detection in high ionic concentrations and enhancement of the detection limit thereof by coupling a nanofluidic crystal with reconfigurable ion concentration polarization.

    PubMed

    Ouyang, Wei; Han, Jongyoon; Wang, Wei

    2017-10-06

    The regulation effect of surface charges on the transport of electrons in nanomaterials and ions in nanofluidic devices has been widely used to develop highly sensitive and label-free electrical biosensors. The intrinsic limitation to the clinical application of surface charge-effect nano-electrical biosensors is that they usually do not function in physiological conditions normally with high ionic concentrations (∼160 mM), in which the surface charges are screened within a short distance (<1 nm at 160 mM). In this work, we developed a general strategy that enables surface charge-effect electrical biomolecular detection in physiological conditions with an integrated mechanism for enhancement of the limit of detection (LOD) by in situ preconcentration of target molecules during incubation and creation of a transient low ionic concentration environment during the signal read-out step using reconfigurable ion concentration polarization (ICP). We demonstrated the effectiveness of this strategy in a simple nanofluidic biosensor named a nanofluidic crystal (NFC), which can be prepared within hours and without expensive equipment. Our results indicate that the ion depletion effect of ICP could lower the ionic concentration by at least 200 fold and provide a stable ionic environment for over 15 s, enabling electrical detection of proteins and DNAs in serum and urine with LODs of 1-10 nM. We further reconfigured the device to preconcentrate target biomolecules before detection using the enrichment effect of ICP, obtaining LODs of 10-100 pM for proteins and DNAs in physiological conditions. By overcoming the inherent constraint on buffer conditions and the issues regarding fabrication, we believe that this work represents significant progress towards the practical application of surface charge-effect nano-electrical biosensors in point-of-care diagnostics and clinical medicine.

  11. Absolute Measurement of Electron Cloud Density

    SciTech Connect

    Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L

    2007-06-21

    Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.

  12. Nouvelles Limites sur la Detection Directe de la Matiere Sombre avec l'Experience PICASSO

    NASA Astrophysics Data System (ADS)

    Piro, Marie-Cecile

    Astronomical and cosmological observations strongly suggest the presence of an exotic form of non-relativistic, non-baryonic matter that would represent 26% of the actual energy-matter content of the Universe. This so-called cold dark matter would be composed of Weakly Interactive Massive Particles (WIMP). PICASSO (Project In CAnada to Search for Supersymmetric Objects) aims to detect directly one of the dark matter candidates proposed in the framework of supersymmetric extensions of the standard model : the neutralino. The experiment is installed in the SNOLAB underground laboratory at Sudbury (Ontario) and uses superheated C4F10 droplets detectors, a variant of bubble chamber technique. Phase transitions in the superheated liquids are triggered by 19F recoils caused by the elastic collision with neutralinos and create an acoustic signal which is recorded by piezoelectric sensors. This thesis presents recent progress in PICASSO leading to a substantially increased sensitivity in the search of neutralinos. New fabrication and purification procedures allowed a background reduction of about a factor 10 of the major detectors contamination caused by alpha emitters. Detailed studies allowed to localize these emitters in the detectors. In addition, data analysis efforts were able to improve substantially the discrimination between alpha particle induced events and those created by nuclear recoils. New analysis tools were also developed in order to discriminate between particle induced and non-particle induced events, such as electronic backgrounds and acoustic noise signals. An important new background suppression mechanism at higher temperatures led to the present improved sensitivity of PICASSO at low WIMP masses.

  13. Molecular Detection of Culture-Confirmed Bacterial Bloodstream Infections with Limited Enrichment Time

    PubMed Central

    Moore, Miranda S.; McCann, Chase D.

    2013-01-01

    Conventional blood culturing using automated instrumentation with phenotypic identification requires a significant amount of time to generate results. This study investigated the speed and accuracy of results generated using PCR and pyrosequencing compared to the time required to obtain Gram stain results and final culture identification for cases of culture-confirmed bloodstream infections. Research and physician-ordered blood cultures were drawn concurrently. Aliquots of the incubating research blood culture fluid were removed hourly between 5 and 8 h, at 24 h, and again at 5 days. DNA was extracted from these 6 time point aliquots and analyzed by PCR and pyrosequencing for bacterial rRNA gene targets. These results were then compared to those of the physician-ordered blood culture. PCR and pyrosequencing accurately identified 92% of all culture-confirmed cases after a mean enrichment time of 5.8 ± 2.9 h. When the time needed to complete sample processing was included for PCR and pyrosequencing protocols, the molecular approach yielded results in 11.8 ± 2.9 h compared to means of 27.9 ± 13.6 h to obtain the Gram stain results and 81.6 ± 24.0 h to generate the final culture-based identification. The molecular approach enabled accurate detection of most bacteria present in incubating blood culture bottles on average about 16 h sooner than Gram stain results became available and approximately 3 days sooner than the phenotypic identification was entered in the Laboratory Information System. If implemented, this more rapid molecular approach could minimize the number of doses of unnecessary or ineffective antibiotics administered to patients. PMID:23985915

  14. Pushing the limits: detecting H2 emission from faint bipolar planetary nebulae in the IPHAS sample

    NASA Astrophysics Data System (ADS)

    Ramos-Larios, G.; Guerrero, M. A.; Sabin, L.; Santamaría, E.

    2017-09-01

    We have obtained deep narrowband images in the near-infrared H2 λ2.122 μm emission line for a sample of 15 faint Isaac Newton Telescope Photometric H α Survey (IPHAS) bipolar planetary nebulae (PNe) to search for molecular material. H2 emission is found in most of them (14 out of 15), mostly associated with rings at their equatorial regions and with their bipolar lobes. These detections add to the high occurrence of H2 emission among bipolar PNe reported in previous works, resulting from the large reservoir of molecular material in these sources and the suitable excitation conditions for H2 emission. The correlation between detailed bipolar morphology and H2 luminosity is also confirmed: bipolar PNe with broad equatorial rings (R-BPNe) have almost no continuum emission, are H2 brighter and have larger H2/Br γ line ratio than bipolar PNe with pinched equatorial waists (W-BPNe). The origin of this dichotomy is unclear. The larger size and age of R-BPNe are consistent with shock excitation of H2, whereas ultraviolet pumping is most likely the excitation mechanism in the smaller and younger W-BPNe, which would explain their lower H2 luminosity. Although both types of bipolar PNe seem to proceed from the same progenitor population, this does not imply that R-BPNe descend from W-BPNe. Otherwise, we note that some of the H2-weak bipolar PNe harbor post-common envelope binary systems and symbiotic stars. Finally, we suggest that the long-living H2 emission from R-BPNe arises from a discrete distribution of compact knots embedded within the ionized gas at the equatorial region.

  15. Detection of coxarthrosis in femoral head radiographic images seems limited mainly to vertically oriented pattern features.

    PubMed

    Rapan, Sasa; Jovanović, Savo; Gulan, Gordan; Kurbel, Sven

    2013-03-01

    Out of 120 conventional hip joint X-rays, two indepenendent examiners have chosen 27 healthy and 62 coxarthrotic joints. Central parts of femoral head images were digitalized (300 points/inch) and pixel density values analysed. Two methods were applied separately to horizontal rows and to vertical columns: variance coefficient calculation and power coefficients of Fourier harmonics. The arithmetic mean and median of variance coefficient for 256 pixel columns were both significantly higher in data of osteoarthrotic femurs (Mann-Whitney U-test, p = 0.0046 and p = 0.0011, respectively), while no difference was found for horizontal rows. The arithmetic mean and median of variance coefficient for 128 pixels long columns were significantly lower in data of osteoarthrotic femurs (p < 0.001) with wider standard deviation (p = 0.0274), while standard deviation was significantly lower in rows of coxarthrotic heads (p < 0.001). Fourier analysis of 128 pixel vertical columns showed significantly higher values in coxarthrotic femoral heads (from 1st harmonic, wave length of 10.8 mm to 33rd harmonic, wave length of 0.328 mm, p < 0.05). Fourier analysis of 128 pixel horizontal rows did not differ much between coxarthrotic and normal femoral heads. Only valuds for the 60th and 61st harmonic (wavelength near 0.2 mm) showed significantly lower power in coxarthrotic images than in controls (p < 0.01). Results suggest that in the analyzed set of digitalized x-ray femoral head images, information regarding osteoarthrotic changes in the central part of femoral head is detectable mainly through mathematic postprocessing of vertically oriented patterns.

  16. Recovery efficiency and limit of detection of aerosolized Bacillus anthracis Sterne from environmental surface samples.

    PubMed

    Estill, Cheryl Fairfield; Baron, Paul A; Beard, Jeremy K; Hein, Misty J; Larsen, Lloyd D; Rose, Laura; Schaefer, Frank W; Noble-Wang, Judith; Hodges, Lisa; Lindquist, H D Alan; Deye, Gregory J; Arduino, Matthew J

    2009-07-01

    After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolized Bacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm(2)). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm(2)) or wipe or vacuum (929 cm(2)) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm(2)) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm(2) for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm(2) for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detected B. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans.

  17. Tracheal aspirate Gram stain has limited sensitivity and specificity for detecting Staphylococcus aureus.

    PubMed

    Tetenta, Sodienye; Metersky, Mark L

    2011-01-01

    The increasing incidence of respiratory infections due to methicillin resistant Staphylococcus aureus has resulted in increased empirical use of antibiotics active against this pathogen. There are limited data available as to whether the Gram stain of respiratory tract secretions accurately predicts growth of S. aureus. We theorized that the distinctive morphology of S. aureus would allow rapid, accurate identification of the organism in respiratory secretions. The authors reviewed all available Gram stains of tracheal aspirates sent to our hospital's microbiology laboratory between 1 April 2008 and 31 October 2008, while blinded to the culture result, and recorded the presence or absence of organisms with a morphology consistent with S. aureus. These results were correlated with the semiquantitative culture result. Among 136 tracheal aspirates studied, 50 (37%) grew S. aureus. The Gram stain was read as positive for organisms consistent with S. aureus in 34 of these. Among 86 samples that did not grow S. aureus, the Gram stain was read as negative in 62. Therefore, the Gram stain had a sensitivity of 68%, a specificity of 72%, a negative predictive value of 80% and a positive predictive value of 59% for culture of S. aureus. False negative Gram stains were more likely when the culture revealed only rare or small growth of S. aureus (P = 0.01). In this study, the tracheal aspirate Gram stain read by an experienced clinician who was not a microbiologist, was not accurate enough to reliably predict the growth of S. aureus. © 2010 The Authors. Respirology © 2010 Asian Pacific Society of Respirology.

  18. Absolute measurement of detector quantum efficiency using parametric downconversion.

    PubMed

    Rarity, J G; Ridley, K D; Tapster, P R

    1987-11-01

    We show that a parametric downconversion crystal emitting angle resolved coincident photon pairs can be used to measure the absolute quantum efficiency of a photon counting detection system. We have measured the quantum efficiency of a silicon avalanche photodiode, operated in Geiger mode, as a function of operating voltage and compare this to results obtained using a conventional method.

  19. Modeling absolute plate and plume motions

    NASA Astrophysics Data System (ADS)

    Bodinier, G. P.; Wessel, P.; Conrad, C. P.

    2016-12-01

    Paleomagnetic evidence for plume drift has made modeling of absolute plate motions challenging, especially since direct observations of plume drift are lacking. Predictions of plume drift arising from mantle convection models and broadly satisfying observed paleolatitudes have so far provided the only framework for deriving absolute plate motions over moving hotspots. However, uncertainties in mantle rheology, temperature, and initial conditions make such models nonunique. Using simulated and real data, we will show that age progressions along Pacific hotspot trails provide strong constraints on plume motions for all major trails, and furthermore that it is possible to derive models for relative plume drift from these data alone. Relative plume drift depends on the inter-hotspot distances derived from age progressions but lacks a fixed reference point and orientation. By incorporating paleolatitude histories for the Hawaii and Louisville chains we add further constraints on allowable plume motions, yet one unknown parameter remains: a longitude shift that applies equally to all plumes. To obtain a solution we could restrict either the Hawaii or Louisville plume to have latitudinal motion only, thus satisfying paleolatitude constraints. Yet, restricting one plume to latitudinal motion while all others move freely is not realistic. Consequently, it is only possible to resolve the motion of hotspots relative to an overall and unknown longitudinal shift as a function of time. Our plate motions are therefore dependent on the same shift via an unknown rotation about the north pole. Yet, as plume drifts are consequences of mantle convection, our results place strong constraints on the pattern of convection. Other considerations, such as imposed limits on plate speed, plume speed, proximity to LLSVP edges, model smoothness, or relative plate motions via ridge-spotting may add further constraints that allow a unique model of Pacific absolute plate and plume motions to be

  20. Vertical deformation and absolute gravity

    NASA Astrophysics Data System (ADS)

    Fang, Ming; Hager, Bradford H.

    2001-08-01

    Crustal deformation in the Greenland and Antarctic areas is strongly influenced by both postglacial rebound and contemporary mass redistribution. We explore the relationship between the displacement field and the gravitational disturbance for a viscoelastic Maxwell Earth with an arbitrary radial viscosity profile. We seek to determine whether the effects of viscous relaxation in the memory of surface mass change can be separated from the effects of present day mass variation by combined measurements of vertical displacement and absolute gravity when the viscosity profile in the Earth's interior is unknown. Our conclusion is positive. Specifically, the non-elastic effects can be reduced substantially by combined measurements of displacement and gravity change for a Maxwell viscoelastic Earth regardless of its radial viscosity profile. The underlying physics has nothing to do with the mathematical structure of viscous relaxation modes. Rather, it is due to the fact that the non-elastic response of a Maxwell Earth is nearly incompressible.