Science.gov

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. Absolute charge calibration of scintillating screens for relativistic electron detection

    SciTech Connect

    Buck, A.; Popp, A.; Schmid, K.; Karsch, S.; Krausz, F.; Zeil, K.; Jochmann, A.; Kraft, S. D.; Sauerbrey, R.; Cowan, T.; Schramm, U.; Hidding, B.; Kudyakov, T.; Sears, C. M. S.; Veisz, L.; Pawelke, J.

    2010-03-15

    We report on new charge calibrations and linearity tests with high-dynamic range for eight different scintillating screens typically used for the detection of relativistic electrons from laser-plasma based acceleration schemes. The absolute charge calibration was done with picosecond electron bunches at the ELBE linear accelerator in Dresden. The lower detection limit in our setup for the most sensitive scintillating screen (KODAK Biomax MS) was 10 fC/mm{sup 2}. The screens showed a linear photon-to-charge dependency over several orders of magnitude. An onset of saturation effects starting around 10-100 pC/mm{sup 2} was found for some of the screens. Additionally, a constant light source was employed as a luminosity reference to simplify the transfer of a one-time absolute calibration to different experimental setups.

  3. Absolute charge calibration of scintillating screens for relativistic electron detection

    NASA Astrophysics Data System (ADS)

    Buck, A.; Zeil, K.; Popp, A.; Schmid, K.; Jochmann, A.; Kraft, S. D.; Hidding, B.; Kudyakov, T.; Sears, C. M. S.; Veisz, L.; Karsch, S.; Pawelke, J.; Sauerbrey, R.; Cowan, T.; Krausz, F.; Schramm, U.

    2010-03-01

    We report on new charge calibrations and linearity tests with high-dynamic range for eight different scintillating screens typically used for the detection of relativistic electrons from laser-plasma based acceleration schemes. The absolute charge calibration was done with picosecond electron bunches at the ELBE linear accelerator in Dresden. The lower detection limit in our setup for the most sensitive scintillating screen (KODAK Biomax MS) was 10 fC/mm2. The screens showed a linear photon-to-charge dependency over several orders of magnitude. An onset of saturation effects starting around 10-100 pC/mm2 was found for some of the screens. Additionally, a constant light source was employed as a luminosity reference to simplify the transfer of a one-time absolute calibration to different experimental setups.

  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 cross section for recoil detection of deuterium

    NASA Astrophysics Data System (ADS)

    Besenbacher, F.; Stensgaard, I.; Vase, P.

    1986-04-01

    The D( 4He, D) 4He cross section used for recoil detection of deuterium (D) has been calibrated on an absolute scale against the cross section of the D( 3He, α)p nuclear reaction which is often used for D profiling. For 4He energies ranging from 0.8 to ~1.8 MeV. the D( 4He, D) 4He cross section varies only slightly with incident energy and recoil angle θ (for 0° ⩽ 8 ⩽ 35°) and has a value of ~ 500 mb/sr which is significantly higher than the ~ 65 mb/sr c.m.s. cross section of the D( 3He, α)p nuclear reaction. For 4He energies ranging from ~ 1.9 to ~ 2.3 MeV, the D( 4He,D) 4He cross section exhibits a fairly narrow resonance peak (fwhm ~ 70 keV), with a maximum value (for θ = 0°) of ~ 8.5 b/sr, corresponding to a 4He energy of ~ 2130 keV. The large values of the cross section in connection with the described energy dependence makes the use of forward-recoil detection of D attractive for many purposes, e.g., D Jepth profiling (with an extreme gain in sensitivity), absolute concentration or coverage measurements, and lattice-location experiments by transmission channeling.

  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

    2013-12-01

    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). PMID:24145480

  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. 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.

  9. 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%.

  10. 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. PMID:27016439

  11. Limits of detection and decision. Part 4

    NASA Astrophysics Data System (ADS)

    Voigtman, E.

    2008-02-01

    Probability density functions (PDFs) have been derived for a number of commonly used limit of detection definitions, including several variants of the Relative Standard Deviation of the Background-Background Equivalent Concentration (RSDB-BEC) method, for a simple linear chemical measurement system (CMS) having homoscedastic, Gaussian measurement noise and using ordinary least squares (OLS) processing. All of these detection limit definitions serve as both decision and detection limits, thereby implicitly resulting in 50% rates of Type 2 errors. It has been demonstrated that these are closely related to Currie decision limits, if the coverage factor, k, is properly defined, and that all of the PDFs are scaled reciprocals of noncentral t variates. All of the detection limits have well-defined upper and lower limits, thereby resulting in finite moments and confidence limits, and the problem of estimating the noncentrality parameter has been addressed. As in Parts 1-3, extensive Monte Carlo simulations were performed and all the simulation results were found to be in excellent agreement with the derived theoretical expressions. Specific recommendations for harmonization of detection limit methodology have also been made.

  12. 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

    2016-01-01

    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

  13. 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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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 mν 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 mν < (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 mν < (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.

  16. 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.

  17. 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.

  18. Absolute diode laser-based in situ detection of HCl in gasification processes

    NASA Astrophysics Data System (ADS)

    Ortwein, P.; Woiwode, W.; Fleck, S.; Eberhard, M.; Kolb, T.; Wagner, S.; Gisi, M.; Ebert, V.

    2010-10-01

    The release of HCl is an important parameter for industrial combustion and gasification processes, which must be determined in the ppm range for active process control and optimization. Based on a low power vertical-cavity surface-emitting laser (VCSEL) at 1.74 μm, we developed a new tuneable diode laser absorption spectrometer for calibration-free, absolute in situ HCl detection using the H35Cl (2 ← 0) R(3) absorption line with minimized cross-sensitivity to CO2 and H2O. The spectrometer was applied to in situ measurements in a gasification process ( T = 1,130°C, P = 1 atm, L = 28 cm) and yielded an optical resolution of 2.3·10-4, i.e. a HCl sensitivity of 45 ppm (13 ppm·m).

  19. 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.

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

    PubMed

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

    2015-10-01

    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. PMID:26173993

  1. Factors limiting the extent of absolute bioavailability of pradefovir in rat.

    PubMed

    Xiao, Qingqing; Yang, Wanqiu; Wang, Dan; Chen, Lin; Yuan, Linwen; Ding, Yitao; Yang, Jin

    2016-10-01

    1. Pradefovir was designed as an oral liver target prodrug of 9-(2-phosphonylmethoxyethyl) adenine (PMEA). Liver targeting arises through first pass hepatic metabolism by cytochrome P-450 3A4 (CYP3A4). For CYP3A4 primarily exists in intestines and liver, intestinal metabolism may impair its liver selectivity and oral bioavailability, and then impair its efficacy and safety. It was important to reveal details of the disposition of pradefovir in intestines and liver in a preclinical study. 2. The absolute bioavailability of pradefovir was 4.75% based on the intravenous and oral AUC0-24 h in rats. Pradefovir was stable in intestinal segments and microsomes. The fractions of the dose absorbed from the GI tract were 20.3% and 15.3% from intravenous and oral administration of pradefovir in rats and portal vein-cannulated rat models, respectively. The liver extraction ratio was predicted to be 49.2% from liver microsomes system, based on the monitoring substrate loss rate. Rat intestines' Ussing chamber experiment indicated that P-glycoprotein (P-gp) transporter and paracellular pathway may involve in intestinal transportation. 3. Activation of pradefovir mainly occurs in the liver. Low intestinal absorption was the main reason of low bioavailability of pradefovir in rats. The result was suggestive for the disposition of pradefovir in human intestine and liver. PMID:26846680

  2. 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

  3. 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. PMID:27410109

  4. 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.

  5. Realistic limits for subpixel movement detection.

    PubMed

    Mas, David; Perez, Jorge; Ferrer, Belen; Espinosa, Julian

    2016-07-01

    Object tracking with subpixel accuracy is of fundamental importance in many fields since it provides optimal performance at relatively low cost. Although there are many theoretical proposals that lead to resolution increments of several orders of magnitude, in practice this resolution is limited by the imaging systems. In this paper we propose and demonstrate through simple numerical models a realistic limit for subpixel accuracy. The final result is that maximum achievable resolution enhancement is connected with the dynamic range of the image, i.e., the detection limit is 1/2(nr.bits). The results here presented may aid in proper design of superresolution experiments in microscopy, surveillance, defense, and other fields. PMID:27409179

  6. 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

  7. 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…

  8. 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

    2016-09-01

    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. PMID:27454336

  9. 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

  10. 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.

  11. APIC: Absolute Position Interfero Coronagraph for direct exoplanet detection: first laboratory results

    NASA Astrophysics Data System (ADS)

    Allouche, Fatmé; Glindemann, Andreas; Aristidi, Eric; Vakili, Farrokh

    2010-07-01

    For the detection and direct imaging of exoplanets, when the intensity ratio between a star and its orbiting planet can largely exceed 106, coronagraphic methods are mandatory. In 1996, a concept of achromatic interferocoronagraph (AIC) was presented by J. Gay and Y. Rabbia for the detection of very faint stellar companions, such as exoplanets. In an earlier paper, we presented a modified version of the AIC permitting to determine the relative position of these faint companions with respect to the parent star, a problem unsolved in the original design of the AIC. Our modification lied in the use of cylindrical lens doublets as field rotator. By placing two of them in one arm of the interferometric set-up of AIC, we destroyed the axis of symmetry induced by the AIC's original design. Our theoretical study, along with the numerical computations, presented then, and the preliminary test bench results aiming at validating the cylindrical lens doublet field rotation capability, presented in this paper, show that the axis of symmetry is destroyed when one of the cylindrical doublets is rotated around the optic axis.

  12. A calibration-independent laser-induced incandescence technique for soot measurement by detecting absolute light intensity.

    PubMed

    Snelling, David R; Smallwood, Gregory J; Liu, Fengshan; Gülder, Omer L; Bachalo, William D

    2005-11-01

    Laser-induced incandescence (LII) has proved to be a useful diagnostic tool for spatially and temporally resolved measurement of particulate (soot) volume fraction and primary particle size in a wide range of applications, such as steady flames, flickering flames, and Diesel engine exhausts. We present a novel LII technique for the determination of soot volume fraction by measuring the absolute incandescence intensity, avoiding the need for ex situ calibration that typically uses a source of particles with known soot volume fraction. The technique developed in this study further extends the capabilities of existing LII for making practical quantitative measurements of soot. The spectral sensitivity of the detection system is determined by calibrating with an extended source of known radiance, and this sensitivity is then used to interpret the measured LII signals. Although it requires knowledge of the soot temperature, either from a numerical model of soot particle heating or experimentally determined by detecting LII signals at two different wavelengths, this technique offers a calibration-independent procedure for measuring soot volume fraction. Application of this technique to soot concentration measurements is demonstrated in a laminar diffusion flame. PMID:16270566

  13. Detection and absolute quantitation of Tomato torrado virus (ToTV) by real time RT-PCR.

    PubMed

    Herrera-Vásquez, José Angel; Rubio, Luis; Alfaro-Fernández, Ana; Debreczeni, Diana Elvira; Font-San-Ambrosio, Isabel; Falk, Bryce W; Ferriol, Inmaculada

    2015-09-01

    Tomato torrado virus (ToTV) causes serious damage to the tomato industry and significant economic losses. A quantitative real-time reverse-transcription polymerase chain reaction (RT-qPCR) method using primers and a specific TaqMan(®) MGB probe for ToTV was developed for sensitive detection and quantitation of different ToTV isolates. A standard curve using RNA transcripts enabled absolute quantitation, with a dynamic range from 10(4) to 10(10) ToTV RNA copies/ng of total RNA. The specificity of the RT-qPCR was tested with twenty-three ToTV isolates from tomato (Solanum lycopersicum L.), and black nightshade (Solanum nigrum L.) collected in Spain, Australia, Hungary and France, which covered the genetic variation range of this virus. This new RT-qPCR assay enables a reproducible, sensitive and specific detection and quantitation of ToTV, which can be a valuable tool in disease management programs and epidemiological studies. PMID:25956672

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

    2016-01-01

    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 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

  1. USE OF METHOD DETECTION LIMITS IN ENVIRONMENTAL MEASUREMENTS

    EPA Science Inventory

    Environmental measurements often produce values below the method detection limit (MDL). Because low or zero values may be used in determining compliance with regulatory limits, in determining emission factors (typical concentrations emitted by a given type of source), or in model...

  2. Statistical behavior of ten million experimental detection limits

    NASA Astrophysics Data System (ADS)

    Voigtman, Edward; Abraham, Kevin T.

    2011-02-01

    Using a lab-constructed laser-excited fluorimeter, together with bootstrapping methodology, the authors have generated many millions of experimental linear calibration curves for the detection of rhodamine 6G tetrafluoroborate in ethanol solutions. The detection limits computed from them are in excellent agreement with both previously published theory and with comprehensive Monte Carlo computer simulations. Currie decision levels and Currie detection limits, each in the theoretical, chemical content domain, were found to be simply scaled reciprocals of the non-centrality parameter of the non-central t distribution that characterizes univariate linear calibration curves that have homoscedastic, additive Gaussian white noise. Accurate and precise estimates of the theoretical, content domain Currie detection limit for the experimental system, with 5% (each) probabilities of false positives and false negatives, are presented.

  3. 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.

  4. 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. PMID:25929227

  5. 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.

  6. 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.

  7. SOURCE DETECTION IN INTERFEROMETRIC VISIBILITY DATA. I. FUNDAMENTAL ESTIMATION LIMITS

    SciTech Connect

    Trott, Cathryn M.; Wayth, Randall B.; Macquart, Jean-Pierre R.; Tingay, Steven J.

    2011-04-20

    Transient radio signals of astrophysical origin present an avenue for studying the dynamic universe. With the next generation of radio interferometers being planned and built, there is great potential for detecting and studying large samples of radio transients. Currently used image-based techniques for detecting radio sources have not been demonstrated to be optimal, and there is a need for development of more sophisticated algorithms and methodology for comparing different detection techniques. A visibility-space detector benefits from our good understanding of visibility-space noise properties and does not suffer from the image artifacts and need for deconvolution in image-space detectors. In this paper, we propose a method for designing optimal source detectors using visibility data, building on statistical decision theory. The approach is substantially different to conventional radio astronomy source detection. Optimal detection requires an accurate model for the data, and we present a realistic model for the likelihood function of radio interferometric data, including the effects of calibration, signal confusion, and atmospheric phase fluctuations. As part of this process, we derive fundamental limits on the calibration of an interferometric array, including the case where many relatively weak 'in-beam' calibrators are used. These limits are then applied, along with a model for atmospheric phase fluctuations, to determine the limits on measuring source position, flux density, and spectral index, in the general case. We then present an optimal visibility-space detector using realistic models for an interferometer.

  8. 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.

  9. Physical Limitations of Neutron-Based Explosives Detection Systems

    NASA Astrophysics Data System (ADS)

    Womble, Phillip; Barzilov, Alexander; Paschal, Jon; Hopper, Lindsay; Moore, Ryan; Board, Jeremy; Houchins, Eric; Rice, Ian; Howard, Joseph

    2006-10-01

    Recent events in Madrid and London have once again focused attention on the problem of threat detection using elemental analysis. Neutron-based systems are utilized to perform bulk chemical analysis due to their high chemical specificity and their fairly rapid response time. While there are many acronyms for these systems, their working principle is typically to interrogate the sample with a beam of neutrons and to identify and quantify secondary particle emissions (e.g. photons) and relate these emissions back to number of atoms present of a given element. These systems perform optimally when their designers and operators are aware of the physical limitations inherent in these devices. For example, minimum detection limits are strongly constrained by the signal-to-noise ratio in a given system. The purpose of this paper is not to denigrate any of these systems but to discuss the strengths and limitations of various approaches.

  10. 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. .

  11. Lower limits of detection for thermal luminescent dosimeters

    SciTech Connect

    Spacher, P.J. ); Mis, F.J.; Klueber, M.R. )

    1990-08-01

    This paper reports that Groups of Panasonic UD-802 thermoluminescent dosimeters (TLDs) were irradiated to successively increasing doses of Cesium-137 gamma radiation (0.662 MeV gamma rays) and then processed using a Panasonic UD-710 automatic TLD reader. The results were subjected to statistical tests to determine the critical level, the level of detection, and the less-than level. The critical level is equivalent to 1.7 mrad, the lower limit of detection is equivalent to 5 mrad and the less-than level has a high range value of 7.5 mrad.

  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. 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.

  14. 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.

  15. Absolute neutrino mass measurements

    NASA Astrophysics Data System (ADS)

    Wolf, Joachim

    2011-10-01

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2β) searches, single β-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy. Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium β-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope (137Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R&D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2β decay and single β-decay.

  16. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  17. Detection limits of albedo changes induced by climate engineering

    NASA Astrophysics Data System (ADS)

    Seidel, Dian J.; Feingold, Graham; Jacobson, Andrew R.; Loeb, Norman

    2014-02-01

    A key question surrounding proposals for climate engineering by increasing Earth's reflection of sunlight is the feasibility of detecting engineered albedo increases from short-duration experiments or prolonged implementation of solar-radiation management. We show that satellite observations permit detection of large increases, but interannual variability overwhelms the maximum conceivable albedo increases for some schemes. Detection of an abrupt global average albedo increase <0.002 (comparable to a ~0.7 W m-2 reduction in radiative forcing) would be unlikely within a year, given a five-year prior record. A three-month experiment in the equatorial zone (5° N-5° S), a potential target for stratospheric aerosol injection, would need to cause an ~0.03 albedo increase, three times larger than that due to the Mount Pinatubo eruption, to be detected. Detection limits for three-month experiments in 1° (latitude and longitude) regions of the subtropical Pacific, possible targets for cloud brightening, are ~0.2 larger than might be expected from some model simulations.

  18. 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. PMID:26226073

  19. 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.

  20. Detection limits for nanoparticles in solution with classical turbidity spectra

    NASA Astrophysics Data System (ADS)

    Le Blevennec, G.

    2013-09-01

    Detection of nanoparticles in solution is required to manage safety and environmental problems. Spectral transmission turbidity method has now been known for a long time. It is derived from the Mie Theory and can be applied to any number of spheres, randomly distributed and separated by large distance compared to wavelength. Here, we describe a method for determination of size, distribution and concentration of nanoparticles in solution using UV-Vis transmission measurements. The method combines Mie and Beer Lambert computation integrated in a best fit approximation. In a first step, a validation of the approach is completed on silver nanoparticles solution. Verification of results is realized with Transmission Electronic Microscopy measurements for size distribution and an Inductively Coupled Plasma Mass Spectrometry for concentration. In view of the good agreement obtained, a second step of work focuses on how to manage the concentration to be the most accurate on the size distribution. Those efficient conditions are determined by simple computation. As we are dealing with nanoparticles, one of the key points is to know what the size limits reachable are with that kind of approach based on classical electromagnetism. In taking into account the transmission spectrometer accuracy limit we determine for several types of materials, metals, dielectrics, semiconductors the particle size limit detectable by such a turbidity method. These surprising results are situated at the quantum physics frontier.

  1. Fluorescent-Core Microcapillaries: Detection Limits for Biosensing Applications

    NASA Astrophysics Data System (ADS)

    McFarlane, Shalon A.

    This work develops a refractive-index sensor based on whispering gallery modes (WGMs) in glass microcapillaries. The capillary channel is coated with a layer of fluorescent silicon quantum dots (QDs), which provides a fluorescence source that also supports the WGMs. When different fluids are pumped into the channel, the fluorescence spectrum responds as the resonances shift to different frequencies. A study of the WGM spectral shift analysis techniques improved the detection limits to ˜10-4 refractive index units, and permitted the development of sensorgram-type analyses in which the channel fluid is probed continuously in time. The feasibility of the device as a microfluidic biosensor was demonstrated by first functionalizing the silica surface and then detecting the binding of biotin and streptavidin to the capillary channel. These structures could be attractive as microfluidic biological sensors, since they are easy to fabricate, mechanically robust, and relatively inexpensive compared to other technologies.

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

    PubMed

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

    2014-01-01

    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. PMID:26237478

  3. 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.

  4. Single Sagnac's Interferometers Instrumentation, based in the Best Detection Limit.

    NASA Astrophysics Data System (ADS)

    Palma-Vargas, Salvador; Ramírez-Ibarra, Angélica; Sandoval-Romero, G. Eduardo

    2008-04-01

    An interferometric system of volume optics and fiber optic were constructed and proved, showing the instrumentation technique made for these devices, supported in the new technologies of optical detection, amplification, analogical and digital filtrate and single data acquisition. Based on the Sagnac's effect of volume optics and fiber optic, the interferometer of Sagnac has many applications, nevertheless the methods of construction, design and instrumentation for the sensors manufacture of based on both designs are not very well-known, is for that reason that in this work approaches some of the methodologies for the design and construction of these devices, obtaining higher sensitivity and better contribution in its respective interferometric paths, for the sensing of different physical parameters in which they are applied. We used the single design for each interferometer, proposing the best detection limit for each one. The data acquisition was made with the proposal to obtain quick results, using the audio card of a PC, obtaining a real time measurements and digital processing of the signal in a single way.

  5. 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.

  6. 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.

  7. A study of the relation between the limit of detection and the limit of quantitation in inductively coupled plasma spectrochemistry

    NASA Astrophysics Data System (ADS)

    Carré, M.; Excoffier, S.; Mermet, J. M.

    1997-12-01

    The limit of quantitation based on a repeatability threshold concept is compared with the limit of detection in induction coupled plasma atomic emission spectrometry (ICP-AES) and induction coupled plasma mass spectrometry (ICP-MS). A 5%-based limit of quantitation would normally correspond to 10 times the 3-σ based limit of detection. However, because of a possible lack of linearity of the calibration graph at low concentrations, some additional noise not taken into consideration and the possible use of time-correlated multichannel detection, this ratio of 10 cannot be used in every case. It is suggested that a suitable way of determining the limit of quantitation is to establish the plot of the percentage relative standard deviation (RSD) of the net signal as a function of the concentration in a range from the limit of detection to 50 times this limit.

  8. High-fidelity target sequencing of individual molecules identified using barcode sequences: de novo detection and absolute quantitation of mutations in plasma cell-free DNA from cancer patients

    PubMed Central

    Kukita, Yoji; Matoba, Ryo; Uchida, Junji; Hamakawa, Takuya; Doki, Yuichiro; Imamura, Fumio; Kato, Kikuya

    2015-01-01

    Circulating tumour DNA (ctDNA) is an emerging field of cancer research. However, current ctDNA analysis is usually restricted to one or a few mutation sites due to technical limitations. In the case of massively parallel DNA sequencers, the number of false positives caused by a high read error rate is a major problem. In addition, the final sequence reads do not represent the original DNA population due to the global amplification step during the template preparation. We established a high-fidelity target sequencing system of individual molecules identified in plasma cell-free DNA using barcode sequences; this system consists of the following two steps. (i) A novel target sequencing method that adds barcode sequences by adaptor ligation. This method uses linear amplification to eliminate the errors introduced during the early cycles of polymerase chain reaction. (ii) The monitoring and removal of erroneous barcode tags. This process involves the identification of individual molecules that have been sequenced and for which the number of mutations have been absolute quantitated. Using plasma cell-free DNA from patients with gastric or lung cancer, we demonstrated that the system achieved near complete elimination of false positives and enabled de novo detection and absolute quantitation of mutations in plasma cell-free DNA. PMID:26126624

  9. High-fidelity target sequencing of individual molecules identified using barcode sequences: de novo detection and absolute quantitation of mutations in plasma cell-free DNA from cancer patients.

    PubMed

    Kukita, Yoji; Matoba, Ryo; Uchida, Junji; Hamakawa, Takuya; Doki, Yuichiro; Imamura, Fumio; Kato, Kikuya

    2015-08-01

    Circulating tumour DNA (ctDNA) is an emerging field of cancer research. However, current ctDNA analysis is usually restricted to one or a few mutation sites due to technical limitations. In the case of massively parallel DNA sequencers, the number of false positives caused by a high read error rate is a major problem. In addition, the final sequence reads do not represent the original DNA population due to the global amplification step during the template preparation. We established a high-fidelity target sequencing system of individual molecules identified in plasma cell-free DNA using barcode sequences; this system consists of the following two steps. (i) A novel target sequencing method that adds barcode sequences by adaptor ligation. This method uses linear amplification to eliminate the errors introduced during the early cycles of polymerase chain reaction. (ii) The monitoring and removal of erroneous barcode tags. This process involves the identification of individual molecules that have been sequenced and for which the number of mutations have been absolute quantitated. Using plasma cell-free DNA from patients with gastric or lung cancer, we demonstrated that the system achieved near complete elimination of false positives and enabled de novo detection and absolute quantitation of mutations in plasma cell-free DNA. PMID:26126624

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    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.

  11. 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

  12. Reducing the detection limits of rare earth elements in steels

    SciTech Connect

    Raskevich, V.K.; Maiboroda, I.K.; Frishberg, A.A.; Panfilova, S.Ya.

    1986-12-01

    Chemical and chemicospectral analysis methods make it possible to determine rare-earth elements (REE) reliably in steels, but they are time-consuming and laborious. X-ray fluorescence methods are also characterized by the complicated procedure of preparing standard and production specimens for analysis. In this paper, the authors attempt to develop a spectrographic method of determining the REEs in the steel using standard equipment. The authors prepare synthetic standard specimens for determining Ce, Nd, La, Pr, and Y in steels of various grades by adding titrated solutions of the salts of the determined elements to the powder of the steel without REE with subsequent evaporation, drying, and mixing. The steels were ground by the mechanical method. On the basis of the resulting detection limits and analysis accuracy, the proposed method can be recommended for inspection of the technological process in melting steels and for preparation of standard specimens in the plant. The method is 5-7 times faster than the chemicospectral method.

  13. Improving the limits of detection in potentiometric sensors

    NASA Astrophysics Data System (ADS)

    van der Bent, J. F.; Puik, E. C. N.; Tong, H. D.; van Rijn, C. J. M.

    2015-12-01

    Potentiometric sensors will generally suffer from unwanted responses as a result to changing temperatures by generating an electromotive force. Typically, this voltage drift has a non-linear character and therefore it is difficult to compensate using linear algorithms implemented in the analogue domain. A solution is proposed to improve the sensor characteristics by combining the digitized output of two CO2 rubidium silver iodide sensors with a specially designed digital algorithm to improve the limits of detection (LOD). Experiments show that this method has the capability to improve the LOD of the sensor with a factor 4.5x during temperature variations of 22 °C over a measurement period of 22 h. It enables potentiometric sensors to be used in low power wireless sensor networks for long term air quality control. Furthermore, the influence of depletion of the rubidium silver iodide electrolyte layer can be effectively compensated by determining the decay of the active layer according to the Nernst equation. Knowing the function of depletion over time helps to correct the sensor output and thereby improves the accuracy of the sensor.

  14. Supercontinuum spatial modulation spectroscopy: Detection and noise limitations

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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 (σext) of σext ˜1 × 10-13-1 ×10-11 cm2. Corresponding signal-to-noise ratios range from ˜30 to ˜1400. The technique's limit of detection is determined to be 4.3 × 10-14 cm2 (4.3 nm2). 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 E11 [(8,3) 1.30 eV (952 nm); (6,5) 1.26 eV (986 nm)] and E22 [(8,3) 1.86 eV (667 nm); (6,5) 2.19 eV (567 nm)] excitonic resonances are seen with corresponding cross sections of σext ˜ 10-13 cm2 μm-1.

  15. 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

  16. 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}.

  17. 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…

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. Analysis of couch position tolerance limits to detect mistakes in patient setup.

    PubMed

    Hadley, Scott W; Balter, James M; Lam, Kwok L

    2009-01-01

    This work investigates the use of the tolerance limits on the treatment couch position to detect mistakes in patient positioning and warn users of possible treatment errors. Computer controlled radiotherapy systems use the position of the treatment couch as a surrogate for patient position and a tolerance limit is applied against a planned position. When the couch is out of tolerance a warning is sent to a user to indicate a possible mistake in setup. A tight tolerance may catch all positioning mistakes while as the same time sending too many warnings; while a loose tolerance will not catch all mistakes. We develop a statistical model of the absolute position for the three translational axes of the couch. The couch position for any fraction is considered a random variable x(i). The ideal planned couch position x(p) is unknown before a patient starts treatment and must be estimated from the daily positions x(i). As such x(p) is also a random variable. The tolerance, tol, is applied to the difference between the daily and planned position, d(i) = x(i) - x(p). The di is a linear combination of random variables and therefore the density of di is the convolution of distributions of xi and xp. Tolerance limits are based on the standard deviation of d(i) such that couch positions that are more than 2 standard deviation away are considered out of tolerance. Using this framework we investigate two methods of setting x(p) and tolerance limits. The first, called first day acquire (FDA), is to take couch position on the first day as the planned position. The second is to use the cumulative average (CumA) over previous fractions as the planned position. The standard deviation of d(i) shrinks as more samples are used to determine x(p) and so the tolerance limit shrinks as a function of fraction number when a CumA technique is used. The metrics of sensitivity and specificity were used to characterize the performance of the two methods to correctly identify a couch position as in

  3. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  4. 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.

  5. Experimental and Calculation Study of Absolute Efficiency of {gamma}-Ray Detection with the Coaxial HPGe-Detector GC 5019 at E{gamma}=0.24-18.565 MeV

    SciTech Connect

    Generalov, L.N.; Lebedev, B.L.; Livke, A.V.; Modenov, A.B.; Chirkin, V.A.

    2005-05-24

    In the range E{gamma}=0.24-18.565 MeV investigations were carried out of the absolute efficiency of {gamma}-ray detection with the HPGe-detector GC 5019 (CANBERRA). The investigations were performed in connection with measurements of proton radiation capture reaction cross sections on the lightest nuclei.

  6. Implants as absolute anchorage.

    PubMed

    Rungcharassaeng, Kitichai; Kan, Joseph Y K; Caruso, Joseph M

    2005-11-01

    Anchorage control is essential for successful orthodontic treatment. Each tooth has its own anchorage potential as well as propensity to move when force is applied. When teeth are used as anchorage, the untoward movements of the anchoring units may result in the prolonged treatment time, and unpredictable or less-than-ideal outcome. To maximize tooth-related anchorage, techniques such as differential torque, placing roots into the cortex of the bone, the use of various intraoral devices and/or extraoral appliances have been implemented. Implants, as they are in direct contact with bone, do not possess a periodontal ligament. As a result, they do not move when orthodontic/orthopedic force is applied, and therefore can be used as "absolute anchorage." This article describes different types of implants that have been used as orthodontic anchorage. Their clinical applications and limitations are also discussed. PMID:16463910

  7. 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 ...

  8. 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.

  9. 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. PMID:26970749

  10. 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.

  11. Subnanomolar detection limit of stripping voltammetric Ca²⁺-selective electrode: effects of analyte charge and sample contamination.

    PubMed

    Kabagambe, Benjamin; Garada, Mohammed B; Ishimatsu, Ryoichi; Amemiya, Shigeru

    2014-08-01

    Ultrasensitive ion-selective electrode measurements based on stripping voltammetry are an emerging sensor technology with low- and subnanomolar detection limits. Here, we report on stripping voltammetry of down to 0.1 nM Ca(2+) by using a thin-polymer-coated electrode and demonstrate the advantageous effects of the divalent charge on sensitivity. A simple theory predicts that the maximum concentration of an analyte ion preconcentrated in the thin membrane depends exponentially on the charge and that the current response based on exhaustive ion stripping from the thin membrane is proportional to the square of the charge. The theoretical predictions are quantitatively confirmed by using a thin ionophore-doped polymer membrane spin-coated on a conducting-polymer-modified electrode. The potentiostatic transfer of hydrophilic Ca(2+) from an aqueous sample into the hydrophobic double-polymer membrane is facilitated by an ionophore with high Ca(2+) affinity and selectivity. The resultant concentration of the Ca(2+)-ionophore complex in the ~1 μm-thick membrane can be at least 5 × 10(6) times higher than the aqueous Ca(2+) concentration. The stripping voltammetric current response to the divalent ion is enhanced to achieve a subnanomolar detection limit under the condition where a low-nanomolar detection limit is expected for a monovalent ion. Significantly, charge-dependent sensitivity is attractive for the ultrasensitive detection of multivalent ions with environmental and biomedical importance such as heavy metal ions and polyionic drugs. Importantly, this stripping voltammetric approach enables the absolute determination of subnanomolar Ca(2+) contamination in ultrapure water containing 10 mM supporting electrolytes, i.e., an 8 orders of magnitude higher background concentration. PMID:24992261

  12. 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.

  13. 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.

  14. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    .... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under... for measurement of settleable solids. 434.64 Section 434.64 Protection of Environment ENVIRONMENTAL... Procedure and method detection limit for measurement of settleable solids. For the purposes of this...

  15. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... CFR part 136, the method detection limit for measuring settleable solids under this part shall be 0.4... for measurement of settleable solids. 434.64 Section 434.64 Protection of Environment ENVIRONMENTAL... method detection limit for measurement of settleable solids. For the purposes of this part, the...

  16. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    .... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under... for measurement of settleable solids. 434.64 Section 434.64 Protection of Environment ENVIRONMENTAL... Procedure and method detection limit for measurement of settleable solids. For the purposes of this...

  17. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    .... Notwithstanding any provision of 40 CFR part 136, the method detection limit for measuring settleable solids under... for measurement of settleable solids. 434.64 Section 434.64 Protection of Environment ENVIRONMENTAL... Procedure and method detection limit for measurement of settleable solids. For the purposes of this...

  18. 40 CFR 434.64 - Procedure and method detection limit for measurement of settleable solids.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... CFR part 136, the method detection limit for measuring settleable solids under this part shall be 0.4... for measurement of settleable solids. 434.64 Section 434.64 Protection of Environment ENVIRONMENTAL... method detection limit for measurement of settleable solids. For the purposes of this part, the...

  19. 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

  20. Absolute nuclear material assay

    DOEpatents

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

    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.

  1. 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.

  2. Search times and probability of detection in time-limited search

    NASA Astrophysics Data System (ADS)

    Wilson, David; Devitt, Nicole; Maurer, Tana

    2005-05-01

    When modeling the search and target acquisition process, probability of detection as a function of time is important to war games and physical entity simulations. Recent US Army RDECOM CERDEC Night Vision and Electronics Sensor Directorate modeling of search and detection has focused on time-limited search. Developing the relationship between detection probability and time of search as a differential equation is explored. One of the parameters in the current formula for probability of detection in time-limited search corresponds to the mean time to detect in time-unlimited search. However, the mean time to detect in time-limited search is shorter than the mean time to detect in time-unlimited search and the relationship between them is a mathematical relationship between these two mean times. This simple relationship is derived.

  3. The multivariate detection limit for Mycoplasma pneumoniae as determined by Nanorod Array-Surface Enhanced Raman Spectroscopy and comparison with limit of detection by qPCR

    PubMed Central

    Henderson, Kelley C.; Sheppard, Edward S.; Rivera-Betancourt, Omar E.; Choi, Joo-Young; Dluhy, Richard A.; Thurman, Kathleen A.; Winchell, Jonas M.; Krause, Duncan C.

    2015-01-01

    Mycoplasma pneumoniae is a cell wall-less bacterial pathogen of the human respiratory tract that accounts for up to 20% of community-acquired pneumonia. At present, the standard for detection and genotyping is quantitative polymerase chain reaction (qPCR), which can exhibit excellent sensitivity but lacks standardization and has limited practicality for widespread, point-of-care use. We previously described a Ag nanorod array-surface enhanced Raman spectroscopy (NA-SERS) biosensing platform capable of detecting M. pneumoniae in simulated and true clinical throat swab samples with statistically significant specificity and sensitivity. We report here that differences in sample preparation influence the integrity of mycoplasma cells for NA-SERS analysis, which in turn impacts the resulting spectra. We have established a multivariate detection limit (MDL) using NA-SERS for M. pneumoniae intact-cell sample preparations. Using an adaptation of International Union of Pure and Applied Chemistry (IUPAC)-recommended methods for analyzing multivariate data sets, we found that qPCR had roughly 10× better detection limits than NA-SERS when expressed in CFU/ml and DNA concentration (fg). However, the NA-SERS MDL for intact M. pneumoniae was 5.3 ± 1.0 genome equivalents (cells/μl). By comparison, qPCR of a parallel set of samples yielded a limit of detection of 2.5 ± 0.25 cells/μl. Therefore, for certain standard metrics NA-SERS provides a multivariate detection limit for M. pneumoniae that is essentially identical to that determined via qPCR. PMID:25335653

  4. The multivariate detection limit for Mycoplasma pneumoniae as determined by nanorod array-surface enhanced Raman spectroscopy and comparison with limit of detection by qPCR.

    PubMed

    Henderson, Kelley C; Sheppard, Edward S; Rivera-Betancourt, Omar E; Choi, Joo-Young; Dluhy, Richard A; Thurman, Kathleen A; Winchell, Jonas M; Krause, Duncan C

    2014-12-21

    Mycoplasma pneumoniae is a cell wall-less bacterial pathogen of the human respiratory tract that accounts for up to 20% of community-acquired pneumonia. At present, the standard for detection and genotyping is quantitative polymerase chain reaction (qPCR), which can exhibit excellent sensitivity but lacks standardization and has limited practicality for widespread, point-of-care use. We previously described a Ag nanorod array-surface enhanced Raman spectroscopy (NA-SERS) biosensing platform capable of detecting M. pneumoniae in simulated and true clinical throat swab samples with statistically significant specificity and sensitivity. We report here that differences in sample preparation influence the integrity of mycoplasma cells for NA-SERS analysis, which in turn impacts the resulting spectra. We have established a multivariate detection limit (MDL) using NA-SERS for M. pneumoniae intact-cell sample preparations. Using an adaptation of International Union of Pure and Applied Chemistry (IUPAC)-recommended methods for analyzing multivariate data sets, we found that qPCR had roughly 10× better detection limits than NA-SERS when expressed in CFU ml(-1) and DNA concentration (fg). However, the NA-SERS MDL for intact M. pneumoniae was 5.3 ± 1.0 genome equivalents (cells per μl). By comparison, qPCR of a parallel set of samples yielded a limit of detection of 2.5 ± 0.25 cells per μl. Therefore, for certain standard metrics NA-SERS provides a multivariate detection limit for M. pneumoniae that is essentially identical to that determined via qPCR. PMID:25335653

  5. Detection limits in inductively coupled plasma atomic emission spectrometry: an approach to the breakdown of the ratios of detection limits reported for different equipments

    NASA Astrophysics Data System (ADS)

    Boumans, P. W. J. M.; Vrakking, J. J. A. M.

    This paper deals with the differences among detection limits in inductively coupled plasma atomic emission spectrometry (ICP-AES) as reported for different experimental facilities. The factor by which such detection limits differ can be split into three factors to account separately for the differences between the sources, the resolving powers of the spectrometers and the noise characteristics of the systems. The approach uses earlier results about the behaviour of the relative standard deviation (RSD) of the background signal and, as a new feature, an experimentally established linear relationship between the ratio of signal-to-background ratios, (SBR) HR/(SBR) MR, and the inverse ratio of the effective line widths, (Δλ eff) MR/(Δλ eff) HR, where "HR" and "MR" refer to high and medium spectral resolution as achieved by applying narrow (60μm) and wide (210μm) slits in a 1.5-m echelle monochromator. The approach is applied to the breakdown of the ratios of detection limits reported by winge et al. ( Appl. Spectrosc.33, 206 (1979)) for a 27-MHz ICP and those found in this work for a 50-MHz ICP. Data for some 100 prominent ICP lines in the wavelength region between about 280 and 325 nm were processed. It is shown that the approach leads to a rational comparison of detection limits.

  6. 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.

  7. 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

  8. 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.

  9. 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. PMID:25993885

  10. Statistical method for determining and comparing limits of detection of bioassays.

    PubMed

    Holstein, Carly A; Griffin, Maryclare; Hong, Jing; Sampson, Paul D

    2015-10-01

    The current bioassay development literature lacks the use of statistically robust methods for calculating the limit of detection of a given assay. Instead, researchers often employ simple methods that provide a rough estimate of the limit of detection, often without a measure of the confidence in the estimate. This scarcity of robust methods is likely due to a realistic preference for simple and accessible methods and to a lack of such methods that have reduced the concepts of limit of detection theory to practice for the specific application of bioassays. Here, we have developed a method for determining limits of detection for bioassays that is statistically robust and reduced to practice in a clear and accessible manner geared at researchers, not statisticians. This method utilizes a four-parameter logistic curve fit to translate signal intensity to analyte concentration, which is a curve that is commonly employed in quantitative bioassays. This method generates a 95% confidence interval of the limit of detection estimate to provide a measure of uncertainty and a means by which to compare the analytical sensitivities of different assays statistically. We have demonstrated this method using real data from the development of a paper-based influenza assay in our laboratory to illustrate the steps and features of the method. Using this method, assay developers can calculate statistically valid limits of detection and compare these values for different assays to determine when a change to the assay design results in a statistically significant improvement in analytical sensitivity. PMID:26376354

  11. 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.

  12. Detection of satellite remnants in the Galactic halo with Gaia- III. Detection limits for ultrafaint dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Antoja, T.; Mateu, C.; Aguilar, L.; Figueras, F.; Antiche, E.; Hernández-Pérez, F.; Brown, A. G. A.; Valenzuela, O.; Aparicio, A.; Hidalgo, S.; Velázquez, H.

    2015-10-01

    We present a method to identify ultrafaint dwarf galaxies (UFDGs) candidates in the halo of the Milky Way using the future Gaia catalogue and we explore its detection limits and completeness. The method is based on the Wavelet Transform and searches for overdensities in the combined space of sky coordinates and proper motions, using kinematics in the search for the first time. We test the method with a Gaia mock catalogue that has the Gaia Universe Model Snapshot as a background, and use a library of around 30 000 UFDGs simulated as Plummer spheres with a single stellar population. For the UFDGs, we use a wide range of structural and orbital parameters that go beyond the range spanned by real systems, where some UFDGs may remain undetected. We characterize the detection limits as function of the number of observable stars by Gaia in the UFDGs with respect to that of the background and their apparent sizes in the sky and proper motion planes. We find that the addition of proper motions in the search improves considerably the detections compared to a photometric survey at the same magnitude limit. Our experiments suggest that Gaia will be able to detect UFDGs that are similar to some of the known UFDGs even if the limit of Gaia is around 2 mag brighter than that of SDSS, with the advantage of having a full-sky catalogue. We also see that Gaia could even find some UFDGs that have lower surface brightness than the SDSS limit.

  13. 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,...

  14. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  15. Attogram detection limit for aqueous dye samples by laser-induced fluorescence

    SciTech Connect

    Dovichi, N.J.; Martin, J.C.; Keller, R.A.

    1983-02-18

    A modified flow cytometer has been used to detect attogram quantities of aqueous rhodamine 6G by laser-induced fluorescence analysis. A detection limit of 28 attograms (35,000 molecules) was obtained, nearly two orders of magnitude better than earlier measurements. The detection limit in concentration units was 1.4 x 10/sup -13/ mole per liter. During the 1-second measurement period, the total volume sampled was 0.42 microliter. On average, only half a rhodamine 6G molecule was present in the 6-picoliter probed volume.

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

    PubMed Central

    Heald, Steve M.

    2015-01-01

    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 1013 photons s−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 107 Hz. Detection schemes with better energy resolution can help at the largest dilutions if their collection efficiency and count rate limits can be improved. PMID:25723945

  17. 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.

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

    DOE PAGESBeta

    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

  19. 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.

  20. 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.

  1. 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.

  2. Calculation of the detection limit in radiation measurements with systematic uncertainties

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, J. M.; Russ, W.; Venkataraman, R.; Young, B. M.

    2015-06-01

    The detection limit (LD) or Minimum Detectable Activity (MDA) is an a priori evaluation of assay sensitivity intended to quantify the suitability of an instrument or measurement arrangement for the needs of a given application. Traditional approaches as pioneered by Currie rely on Gaussian approximations to yield simple, closed-form solutions, and neglect the effects of systematic uncertainties in the instrument calibration. These approximations are applicable over a wide range of applications, but are of limited use in low-count applications, when high confidence values are required, or when systematic uncertainties are significant. One proposed modification to the Currie formulation attempts account for systematic uncertainties within a Gaussian framework. We have previously shown that this approach results in an approximation formula that works best only for small values of the relative systematic uncertainty, for which the modification of Currie's method is the least necessary, and that it significantly overestimates the detection limit or gives infinite or otherwise non-physical results for larger systematic uncertainties where such a correction would be the most useful. We have developed an alternative approach for calculating detection limits based on realistic statistical modeling of the counting distributions which accurately represents statistical and systematic uncertainties. Instead of a closed form solution, numerical and iterative methods are used to evaluate the result. Accurate detection limits can be obtained by this method for the general case.

  3. 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.

  4. Absolute optical instruments without spherical symmetry

    NASA Astrophysics Data System (ADS)

    Tyc, Tomáš; Dao, H. L.; Danner, Aaron J.

    2015-11-01

    Until now, the known set of absolute optical instruments has been limited to those containing high levels of symmetry. Here, we demonstrate a method of mathematically constructing refractive index profiles that result in asymmetric absolute optical instruments. The method is based on the analogy between geometrical optics and classical mechanics and employs Lagrangians that separate in Cartesian coordinates. In addition, our method can be used to construct the index profiles of most previously known absolute optical instruments, as well as infinitely many different ones.

  5. The absolute path command

    Energy Science and Technology Software Center (ESTSC)

    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 canmore » provide the absolute path to a relative directory from the current working directory.« less

  6. 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.

  7. 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.

  8. 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.

  9. True detection limits in an experimental linearly heteroscedastic system.. Part 2

    NASA Astrophysics Data System (ADS)

    Voigtman, Edward; Abraham, Kevin T.

    2011-11-01

    Despite much different processing of the experimental fluorescence detection data presented in Part 1, essentially the same estimates were obtained for the true theoretical Currie decision levels ( YC and XC) and true Currie detection limits ( YD and XD). The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.0 mV, YD = 125. mV, XC = 0.132 μg/mL and XD = 0.293 μg/mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158 . mV and XD = 0.371 μg/mL. Furthermore, by using bootstrapping methodology on the experimental data for the standards and the analytical blank, it was possible to validate previously published experimental domain expressions for the decision levels ( yC and xC) and detection limits ( yD and xD). This was demonstrated by testing the generated decision levels and detection limits for their performance in regard to false positives and false negatives. In every case, the obtained numbers of false negatives and false positives were as specified a priori.

  10. 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.

  11. Direct detection of neutral metal atoms in electron-stimulated desorption: Al from CH{sub 3}O/Al(111) - velocity distribution and absolute yield

    SciTech Connect

    Whitten, J.E.; Young, C.E.; Pellin, M.J.; Gruen, D.M.; Jones, P.L.

    1994-06-01

    Electron-stimulated desorption of neutral aluminum from the system CH{sub 3}O/Al(111) has been directly monitored via quasiresonant photoionization with 193 nm excimer laser light and confirmed by two-step resonant ionization, utilizing the Al 3d {sup 2}D manifold. Velocity distribution measurements for the neutral Al peak at {approximately} 800 m/s for 1 keV incident electron energy. An absolute yield of 3.2 x 10{sup {minus}6} Al atoms/electron was determined by comparison with sputtering measurements in the same apparatus. This is the first observation of electron-stimulated metal desorption from adsorbate-covered metallic surfaces.

  12. Absolute detection efficiency of a microchannel plate detector to X rays in the 1-100 KeV energy range

    NASA Astrophysics Data System (ADS)

    Burginyon, Gary A.; Jacoby, Barry A.; Wobser, James K.; Ernst, Richard; Ancheta, Dione S.; Tirsell, Kenneth G.

    1993-02-01

    There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K(subscript (alpha) ) x rays) to convert x rays to electrons, an MCP to amplify the electrons, and a fast In:CdS phosphor that converts the electron's kinetic energy to light. The phosphor is coated on a fiber-optic faceplate to transmit the light out of the vacuum system. Electrostatic focusing electrodes compress the electron current out of the MCP in one dimension while preserving spatial resolution in the other. The calibration geometry, dictated by a recent experiment, required grazing incidence x rays (15.6 degree(s)) onto the MCP detector in order to maximize deliverable current. The experiment also used a second detector made up of 0.071 in. thick BC422 plastic scintillator material from the Bicron Corporation. We compare the absolute efficiencies of these two detectors in units of optical W/cm(superscript 2) into 4 (pi) per x ray W/cm(superscript 2) incident. At 7.47 keV and 900 volts MCP bias, the MCP detector delivers approximately 1400 times more light than the scintillator detector.

  13. 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

  14. 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.

  15. Detection of expiratory flow limitation in COPD using the forced oscillation technique.

    PubMed

    Dellacà, R L; Santus, P; Aliverti, A; Stevenson, N; Centanni, S; Macklem, P T; Pedotti, A; Calverley, P M A

    2004-02-01

    Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease. PMID:14979497

  16. 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

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

    PubMed

    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

  18. Microfluidic means of achieving attomolar detection limits with molecular beacon probes.

    PubMed

    Puleo, Christopher M; Wang, Tza-Huei

    2009-04-21

    We used inline, micro-evaporators to concentrate and transport DNA targets to a nanoliter single molecule fluorescence detection chamber for subsequent molecular beacon probe hybridization and analysis. This use of solvent removal as a unique means of target transport in a microanalytical platform led to a greater than 5000-fold concentration enhancement and detection limits that pushed below the femtomolar barrier commonly reported using confocal fluorescence detection. This simple microliter-to-nanoliter interconnect for single molecule counting analysis resolved several common limitations, including the need for excessive fluorescent probe concentrations at low target levels and inefficiencies in direct handling of highly dilute biological samples. In this report, the hundreds of bacteria-specific DNA molecules contained in approximately 25 microliters of a 50 aM sample were shuttled to a four nanoliter detection chamber through micro-evaporation. Here, the previously undetectable targets were enhanced to the pM regime and underwent probe hybridization and highly-efficient fluorescent event analysis via microfluidic recirculation through the confocal detection volume. This use of microfluidics in a single molecule detection (SMD) platform delivered unmatched sensitivity and introduced compliment technologies that may serve to bring SMD to more widespread use in replacing conventional methodologies for detecting rare target biomolecules in both research and clinical labs. PMID:19350088

  19. 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.

  20. Increasing Capacity: Practice Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew

    2011-01-01

    In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…

  1. Maximum likelihood ratio tests for comparing the discriminatory ability of biomarkers subject to limit of detection.

    PubMed

    Vexler, Albert; Liu, Aiyi; Eliseeva, Ekaterina; Schisterman, Enrique F

    2008-09-01

    In this article, we consider comparing the areas under correlated receiver operating characteristic (ROC) curves of diagnostic biomarkers whose measurements are subject to a limit of detection (LOD), a source of measurement error from instruments' sensitivity in epidemiological studies. We propose and examine the likelihood ratio tests with operating characteristics that are easily obtained by classical maximum likelihood methodology. PMID:18047527

  2. Chiroptical signal enhancement in quasi-null-polarization-detection geometry: Intrinsic limitations

    NASA Astrophysics Data System (ADS)

    Rhee, Hanju; Eom, Intae; Ahn, Sung-Hyun; Song, Ki-Hee; Cho, Minhaeng

    2015-05-01

    Despite its unique capability of distinguishing molecular handedness, chiroptical spectroscopy suffers from the weak-signal problem, which has restricted more extensive applications. The quasi-null-polarization-detection (QNPD) method has been shown to be useful for enhancing the chiroptical signal. Here, the underlying enhancement mechanism in the QNPD method combined with a heterodyne detection scheme is elucidated. It is experimentally demonstrated that the optical rotatory dispersion signal can be amplified by a factor of ˜400, which is the maximum enhancement effect achievable with our femtosecond laser setup. The upper limit of the QNPD enhancement effect of chiroptical measurements could, in practice, be limited by imperfection of the polarizer and finite detection sensitivity. However, we show that there exists an intrinsic limit in the enhancement with the QNPD method due to the weak but finite contribution from the homodyne chiroptical signal. This is experimentally verified by measuring the optical rotation of linearly polarized light with the QNPD scheme. We further provide discussions on the connection between this intrinsic limitation in the QNPD scheme for enhanced detection of weak chiroptical signals and those in optical enantioselectivity and Raman optical activity with a structured chiral field. We anticipate that the present work could be useful in further developing time-resolved nonlinear chiroptical spectroscopy.

  3. 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...

  4. 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. PMID:19137842

  5. 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. PMID:12647952

  6. 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. PMID:25496031

  7. Guidelines for Improving the Lower Detection Limit of Ion-Selective Electrodes: A Systematic Approach

    SciTech Connect

    Radu, Aleksandar; Peper, Shane M.; Bakker, Eric; Diamond, Dermot

    2007-01-01

    Zero-current membrane fluxes are the principal source of bias that has prohibited researchers from obtaining true, thermodynamic selectivity coefficients for membrane-based ion selective electrodes (ISEs). They are also responsible for the mediocre detection limits historically seen with these types of potentiometric sensors. By choosing an experimental protocol that suppresses these fluxes, it becomes possible to obtain unbiased thermodynamic selectivity coefficients that are needed to produce ISEs with greatly improved detection limits. In this work, a Cs+-selective electrode based on calix[6]arene-hexaacetic acid hexaethyl ester (Cs I) is used to systematically demonstrate how unbiased selectivity coefficients can be obtained, and how they can be used to optimize inner filling solutions for low detection limit measurements. A comparison of biased selectivity methods (e.g., classical separate solution method (SSM), fixed interference method (FIM), matched potential method (MPM)) with the unbiased modified separate solution method (MSSM) found that selectivity coefficients were underestimated in several cases by more than 4 orders of magnitude. The importance of key experimental parameters, including diffusion coefficients and diffusion layer thicknesses in the aqueous and organic phases, on the minimization of ion fluxes and the improvement of lower detection limits is also described. A dramatic reduction of membrane fluxes by the covalent attachment of a Ca2+-selective ionophore to a methyl methacrylate-decyl methacrylate copolymer matrix is also demonstrated. The ionophore-immobilized ISE exhibited no super-Nernstian response and yielded a detection limit of 40 ppt with an inner filling solution of 1 x 10-3 M KCl. Finally, a set of guidelines for experimental protocols leading to obtaining unbiased selectivity coefficients and producing ISEs for trace level analyses is given.

  8. Absolute quantification of Medicago truncatula sucrose synthase isoforms and N-metabolism enzymes in symbiotic root nodules and the detection of novel nodule phosphoproteins by mass spectrometry

    PubMed Central

    Wienkoop, Stefanie; Larrainzar, Estíbaliz; Glinski, Mirko; González, Esther M.; Arrese-Igor, Cesar; Weckwerth, Wolfram

    2008-01-01

    Mass spectrometry (MS) has become increasingly important for tissue specific protein quantification at the isoform level, as well as for the analysis of protein post-translational regulation mechanisms and turnover rates. Thanks to the development of high accuracy mass spectrometers, peptide sequencing without prior knowledge of the amino acid sequence—de novo sequencing—can be performed. In this work, absolute quantification of a set of key enzymes involved in carbon and nitrogen metabolism in Medicago truncatula ‘Jemalong A17’ root nodules is presented. Among them, sucrose synthase (SuSy; EC 2.4.1.13), one of the central enzymes in sucrose cleavage in root nodules, has been further characterized and the relative phosphorylation state of the three most abundant isoforms has been quantified. De novo sequencing provided sequence information of a so far unidentified peptide, most probably belonging to SuSy2, the second most abundant isoform in M. truncatula root nodules. TiO2-phosphopeptide enrichment led to the identification of not only a phosphorylation site at Ser11 in SuSy1, but also of several novel phosphorylation sites present in other root nodule proteins such as alkaline invertase (AI; EC 3.2.1.26) and an RNA-binding protein. PMID:18772307

  9. 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

    2012-01-01

    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%. PMID:22843069

  10. Radiographic detectability limits for seeded voids in sintered silicon carbide and silicon nitride

    NASA Technical Reports Server (NTRS)

    Baaklini, G. Y.; Kiser, J. D.; Roth, D. J.

    1984-01-01

    Conventional and microfocus X-radiographic techniques were compared to determine relative detectability limits for voids in green and sintered SiC and Si3N4. The relative sensitivity of the techniques was evaluated by comparing their ability to detect voids that were artificially introduced by a seeding process. For projection microfocus radiography the sensitivity of void detection at a 90/95 probability of detection/confidence level is 1.5% of specimen thickness in sintered SiC and Si3N4. For conventional contact radiography the sensitivity is 2.5% of specimen thickness. It appears that microfocus projection radiography is preferable to conventional contact radiography in cases where increased sensitivity is required and where the additional complexity of the technique can be tolerated.

  11. 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.

  12. True detection limits in an experimental linearly heteroscedastic system. Part 1

    NASA Astrophysics Data System (ADS)

    Voigtman, Edward; Abraham, Kevin T.

    2011-11-01

    Using a lab-constructed laser-excited filter fluorimeter deliberately designed to exhibit linearly heteroscedastic, additive Gaussian noise, it has been shown that accurate estimates may be made of the true theoretical Currie decision levels ( YC and XC) and true Currie detection limits ( YD and XD) for the detection of rhodamine 6 G tetrafluoroborate in ethanol. The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.1 mV, YD = 125. mV, XC = 0.132 μg /mL and XD = 0.294 μg /mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158. mV and XD = 0.372 μg /mL. These decision levels and corresponding detection limits were shown to pass the ultimate test: they resulted in observed probabilities of false positives and false negatives that were statistically equivalent to the a priori specified values.

  13. 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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. A Method Detection Limit for Bacillus anthracis Spores in Water Using an Automated Waterborne Pathogen Concentrator.

    PubMed

    Humrighouse, Ben; Pemberton, Adin; Gallardo, Vicente; Lindquist, H D Alan; LaBudde, Robert

    2015-01-01

    The method detection limit (MDL, 99% chance of detecting a positive result in a single replicate), as per the United States Code of Federal Regulations, was determined for a protocol using an ultrafiltration based automated waterborne pathogen concentration device. Bacillus anthracis Sterne strain spores were seeded at low levels into 100 L reagent water samples. Suspect colonies were confirmed through morphological, chemical, and genetic tests. Samples of 100 L (n=14) of reagent water were seeded with five B. anthracis CFUs each. To confirm the estimated detection limit, a second set (n=19) of 100 L reagent water samples were seeded at a higher level (7 CFUs). The second estimate of the MDL could not be pooled with the first, due to significant difference in variance. A third trial (n=7) seeded with 10 CFUs produced an estimate of the MDL that could be pooled with the higher previous estimate. Another trial consisting of eight 100 L samples of tap water were seeded with approximately 7 CFUs. Recovery in these samples was not significantly different from the pooled MDL. Theoretically a concentration of 4.6 spores/100 L would be required for detection 95% of the time, based on a Poisson distribution. The calculated pooled MDL, based on experimental data was approximately 6 B. anthracis CFU/100 L (95% confidence interval 4.8 to 8.4). Detection at this level was achieved in municipal water samples. PMID:26268983

  17. Effects of data limitations on heartbeat detection in the method of constant stimuli.

    PubMed

    Brener, J; Ring, C; Liu, X

    1994-05-01

    In the method of constant stimuli applied to measuring heartbeat detection, subjects judge the simultaneity of heartbeats and exteroceptive comparison stimuli presented at various intervals after the R-wave (0, 100, 200, 300, 400, and 500 ms). Using versions of this procedure, investigators have found that between 20% (Yates, Jones, Marie, & Hogben, 1985) and 54% (Brener, Liu, & Ring, 1993) of subjects can detect heartbeat sensations. Whereas Yates et al. used a single comparison stimulus on each trial and Brener et al. used 10, the present study examined whether this disparity in heartbeat detection performance could be attributed to the number of comparison stimuli presented on each trial. In each of 360 trials, 30 subjects judged the simultaneity of heartbeat sensations and tones following 1, 5, or 10 comparison stimulus presentations. Significantly fewer subjects met the criterion for heartbeat detection with 1 tone presentation (13%) than with either 5 (43%) or 10 (47%) tone presentations. It is concluded that a single stimulus presentation imposes data limitations that result in underestimation of the accuracy of heartbeat detection. The presentation of at least 5 stimuli in each trial alleviates this limitation. PMID:8008794

  18. Synthesis of Electron Energy Loss Spectra for the Quantification of Detection Limits

    NASA Astrophysics Data System (ADS)

    Menon, Nanda K.; Krivanek, Ondrej L.

    2002-06-01

    We describe a method for predicting detection limits of minority elements in electron energy loss spectroscopy (EELS), and its implementation as a software package that gives quantitative predictions for user-specified materials and experimental conditions. The method is based on modeling entire energy loss spectra, including shot noise as well as instrumental noise, and taking into account all the relevant experimental parameters. We describe the steps involved in modeling the entire spectrum, from the zero loss up to inner shell edges, and pay particular attention to the contributions to the pre-edge background. The predicted spectra are used to evaluate the signal-to-noise ratios (SNRs) for inner shell edges from user-specified minority elements. The software also predicts the minimum detectable mass (MDM) and minimum mass fraction (MMF). It can be used to ascertain whether an element present at a particular concentration should be detectable for given experimental conditions, and also to quickly and quantitatively explore ways of optimizing the experimental conditions for a particular EELS analytical task. We demonstrate the usefulness of the software by confirming the recent empirical observation of single atom detection using EELS of phosphorus in thin carbon films, and show the effect on the SNR of varying the acquisition parameters. The case of delta-doped semiconductors is also considered as an important example from materials science where low detection limits and high spatial resolution are essential, and the feasibility of such characterization using EELS is assessed.

  19. Evaluation of the limit of detection of the BD Veritor™ system flu A+B test and two rapid influenza detection tests for influenza virus.

    PubMed

    Peters, Timothy R; Blakeney, Elizabeth; Vannoy, Lauren; Poehling, Katherine A

    2013-02-01

    We evaluated the limits of detection of 3 rapid influenza diagnostic tests-BD Veritor™ System for Flu A+B, Binax NOW® Influenza A+B, and QuickVue® Influenza-for influenza strains circulating in 2010-2012. Limits of detection varied by influenza strain, with Veritor™ Flu A+B test showing the lowest limit of detection for all strains. PMID:23219228

  20. Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

    PubMed

    Dellacà, R L; Duffy, N; Pompilio, P P; Aliverti, A; Koulouris, N G; Pedotti, A; Calverley, P M A

    2007-02-01

    The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative. PMID:17079262

  1. 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.

  2. 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.

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

    SciTech Connect

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

    2010-12-15

    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.

  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. 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.

  6. Ultralow detection limits for an organic dye determined by fluorescence spectroscopy with laser diode excitation

    SciTech Connect

    Johnson, P.A.; Barber, T.E.; Smith, B.W.; Winefordner, J.D. )

    1989-04-15

    Fluorescence of IR-140, a laser dye in methanol solution, is excited by a semiconductor laser diode. Analytical figures of merit are compared for three different instrumental configurations, with the dye measured in a cuvette, a liquid jet, and a compact instrument. The best limit of detection, 46,000 molecules, was achieved with a liquid jet. Linear dynamic range was 6 orders of magnitude. The laser diode operates in the near-infrared region, resulting in low background fluorescence.

  7. Polychromatic excitation improves detection limits in total reflection X-ray fluorescence analysis compared with monochromatic excitation.

    PubMed

    Kunimura, Shinsuke; Kawai, Jun

    2010-08-01

    Detection limits obtained by a portable total reflection X-ray fluorescence (TXRF) spectrometer with or without a monochromator are compared. A 1 W X-ray tube (tube voltage: 20 kV) is used in this spectrometer. Polychromatic excitation improves the detection limits in TXRF analysis with the low power X-ray tube compared with monochromatic excitation. A detection limit of 26 pg is achieved for Co when using the weak polychromatic X-rays. PMID:20535410

  8. 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.

  9. 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

  10. Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

    PubMed Central

    Lifson, Mark A.; Roy, Dhrubajyoti Basu; Miller, Benjamin L.

    2014-01-01

    Nanoscale biosensors have remarkable theoretical sensitivities, but often suffer from sub-optimal limits of detection in practice. This is in part because the sensing area of nanoscale sensors is orders of magnitude smaller than the total device substrate. Current strategies to immobilize probes (capture molecules) functionalize both sensing and non-sensing regions, leading to target depletion and diminished limits of detection. The difference in topography between these regions on nanoscale biosensors offers a way to selectively address only the sensing area. We developed a bottom-up, topographically selective approach employing self-assembled poly(N-isopropylacrylamide) (PNIPAM) hydrogel nanoparticles as a mask to preferentially bind target to only the active sensing region of a photonic crystal (PhC) biosensor. This led to over one order of magnitude improvement in the limit of detection for the device, in agreement with finite element simulations. Since the sensing elements in many nanoscale sensors are topographically distinct, this approach should be widely applicable. PMID:24372197

  11. [Molecular techniques for detection and identification of pathogens in food: advantages and limitations].

    PubMed

    Palomino-Camargo, Carolina; González-Muñoz, Yuniesky

    2014-01-01

    Foodborne diseases, caused by pathogenic microorganisms, are a major public health problem worldwide. Microbiological methods commonly used in the detection of these foodborne pathogens are laborious and time consuming. This situation, coupled with the demand for immediate results and with technological advances, has led to the development of a wide range of rapid methods in recent decades. On this basis, this review describes the advantages and limitations of the main molecular methods used in detection and identification of foodborne pathogens. To this end, we considered how recent the information was published, the objective analysis of the topic and its scope. Recent literature reports a significant number of alternative, sensitive and selective molecular techniques for detection, enumeration and identification of pathogenic microorganisms in food. Polymerase chain reaction (PCR) is the most popular platform, while high performance sequencing is emerging as a technique of wide applicability for the future. However, even with all the advantages of these new methodologies, their limitations should not be overlooked. For example, molecular methods are not standardized protocols, which hinders its use in some cases. For this reason, hard work should be done to overcome these limitations and improve the application of these techniques in complex matrices such as food systems. PMID:25418655

  12. Evaluation of in vivo and in vitro dose detection limits for different radionuclides and measurement techniques.

    PubMed

    Bitar, A; Maghrabi, M; Doubal, A W

    2016-07-01

    Personal monitoring programs for workers handling radioactive materials are influenced by numerous factors as the measurements of radioactivity in tissues or/and in excreta can be carried out using different techniques. This paper summaries the basic procedures needed for accurate and fast measurement of different radionuclides like (235)U, (234)U, (238)U, (226)Ra, (210)Po, (131)I, (99m)Tc, (134)Cs, (137)Cs, (57)Co, (58)Co, and (60)Co. Overviews of in vitro and in vivo monitoring methods are provided as well as methods used to calculate detection limits and internal radiation dose. For the radionuclides of interest, in vivo and in vitro detection limits were converted into committed effective doses to evaluate the applicability and limitations of the systems used at the laboratory. The results proved that the systems' sensitivity is suitable for use in routine monitoring of workers subject to risk of internal exposure from such radionuclides. Consequently, monitoring programs suggested by the Syrian internal dosimetry laboratory are suitable to detect committed effective doses even below 1mSv in most cases. PMID:27108068

  13. An adaptive confidence limit for periodic non-steady conditions fault detection

    NASA Astrophysics Data System (ADS)

    Wang, Tianzhen; Wu, Hao; Ni, Mengqi; Zhang, Milu; Dong, Jingjing; Benbouzid, Mohamed El Hachemi; Hu, Xiong

    2016-05-01

    System monitoring has become a major concern in batch process due to the fact that failure rate in non-steady conditions is much higher than in steady ones. A series of approaches based on PCA have already solved problems such as data dimensionality reduction, multivariable decorrelation, and processing non-changing signal. However, if the data follows non-Gaussian distribution or the variables contain some signal changes, the above approaches are not applicable. To deal with these concerns and to enhance performance in multiperiod data processing, this paper proposes a fault detection method using adaptive confidence limit (ACL) in periodic non-steady conditions. The proposed ACL method achieves four main enhancements: Longitudinal-Standardization could convert non-Gaussian sampling data to Gaussian ones; the multiperiod PCA algorithm could reduce dimensionality, remove correlation, and improve the monitoring accuracy; the adaptive confidence limit could detect faults under non-steady conditions; the fault sections determination procedure could select the appropriate parameter of the adaptive confidence limit. The achieved result analysis clearly shows that the proposed ACL method is superior to other fault detection approaches under periodic non-steady conditions.

  14. Energy-filtering TEM at high magnification: spatial resolution and detection limits.

    PubMed

    Grogger, Werner; Schaffer, Bernhard; Krishnan, Kannan M; Hofer, Ferdinand

    2003-09-01

    Energy-filtering TEM (EFTEM) has turned out to be a very efficient and rapid tool for the chemical characterization of a specimen on a nanometer and even subnanometer length scale. Especially, the detection and measurement of very thin layers has become a great application of this technique in many materials science fields, e.g. semiconductors and hard disk technology. There, the reliability of compositional profiles is an important issue. However, the experimentally obtainable spatial resolution strongly influences the appearance of a thin layer in an EFTEM image, when dimensions reach subnanometer levels, which mainly leads to a broadening of the layer in the image. This fact has to be taken into account, when measuring the thickness of such a thin layer. Additionally, the convolution decreases contrast which makes the layer less visible in the image and finally determines the detection limit. In this work we present a systematic study on specifically designed Mn/PdMn multilayer test specimens to explore the practical aspects of spatial resolution and detection limits in EFTEM. Although specific to the ionization edges used, we will present general conclusions about the practical limitations in terms of EFTEM spatial resolution. Additionally, work will be shown about low energy-loss imaging of thin oxide layers, where delocalization is the main factor responsible for broadening. PMID:12871810

  15. 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

  16. Microfluidic-SERS devices for one shot limit-of-detection.

    PubMed

    Kim, Donghyuk; Campos, Antonio R; 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

    2014-07-01

    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

  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. PMID:23202333

  18. Doppler velocity detection limitations in spectrometer-based versus swept-source optical coherence tomography

    PubMed Central

    Hendargo, Hansford C.; McNabb, Ryan P.; Dhalla, Al-Hafeez; Shepherd, Neal; Izatt, Joseph A.

    2011-01-01

    Recent advances in Doppler techniques have enabled high sensitivity imaging of biological flow to measure blood velocities and vascular perfusion. Here we compare spectrometer-based and wavelength-swept Doppler OCT implementations theoretically and experimentally, characterizing the lower and upper observable velocity limits in each configuration. We specifically characterize the washout limit for Doppler OCT, the velocity at which signal degradation results in loss of flow information, which is valid for both quantitative and qualitative flow imaging techniques. We also clearly differentiate the washout effect from the separate phenomenon of phase wrapping. We demonstrate that the maximum detectable Doppler velocity is determined by the fringe washout limit and not phase wrapping. Both theory and experimental results from phantom flow data and retinal blood flow data demonstrate the superiority of the swept-source technique for imaging vessels with high flow rates. PMID:21833356

  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. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  1. Optimized Signal-To Ratio with Shot Noise Limited Detection in Stimulated Raman Scattering Microscopy

    NASA Astrophysics Data System (ADS)

    Moester, M. J. B.; Ariese, F.; de Boer, J. F.

    2015-04-01

    We describe our set-up for Stimulated Raman Scattering (SRS) microscopy with shot noise limited detection for a broad window of biologically relevant laser powers. This set-up is used to demonstrate that the highest signal-to-noise ratio (SNR) in SRS with shot noise limited detection is achieved with a time-averaged laser power ratio of 1:2 of the unmodulated and modulated beam. In SRS, two different coloured laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy can be transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometre resolution. Recent technological advances have resulted in an improvement of the sensitivity of SRS applications, but few show shot noise limited detection. The dominant noise source in this SRS microscope is the shot noise of the unmodulated, detected beam. Under the assumption that photodamage is linear with the total laser power, the optimal SNR shifts away from equal beam powers, where the most signal is generated, to a 1:2 power ratio. Under these conditions the SNR is maximized and the total laser power that could induce photodamage is minimized. Compared to using a 1:1 laser power ratio, we show improved image quality and a signal-to-noise ratio improvement of 8 % in polystyrene beads and C. Elegans worms. Including a non-linear damage mechanism in the analysis, we find that the optimal power ratio converges to a 1:1 ratio with increasing order of the non-linear damage mechanism.

  2. 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.

  3. 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.

  4. 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.

  5. A reusable microfluidic device provides continuous measurement capability and improves the detection limit of digital biology.

    PubMed

    Araci, I Emre; Robles, Michael; Quake, Stephen R

    2016-04-26

    Current digital biology platforms lack the ability to perform continuous measurements for transient analysis. A fundamental challenge is to perform complex fluidic manipulation processes such as washing and mixing in individual reaction volumes. Here, we present a reusable digital biology platform where the reaction compartmentalization and commencement are controlled by micromechanical valves fabricated in high density through microfluidic very large scale integration (mVLSI) technology. Background noise correction enabled by the platform improves signal-to-noise ratio and thus eliminates the need for sophisticated imaging technologies. We have used the detection platform for probing single molecules of the β-galactosidase enzyme. The measurements were repeated hundreds of times at concentrations as low as 0.8 fM (resulting in a theoretical detection limit of 3 aM). We have also demonstrated multiple TNF-α measurements with a magnetic bead based digital ELISA assay. The assay showed that the average number of enzymes per magnetic bead is 0.55 for 10 pM TNF-α (compared to 0.08 for negative control). This automated and reusable digital platform allows on-chip assay preparation and continuous measurements; as a result, it will enable single cell/enzyme studies and clinical diagnostic tests (i.e. digital ELISA) to be performed in shorter time scales and with lower detection limits. PMID:27072314

  6. Evolutionary divergence and limits of conserved non-coding sequence detection in plant genomes

    PubMed Central

    Reineke, Anna R.; Bornberg-Bauer, Erich; Gu, Jenny

    2011-01-01

    The discovery of regulatory motifs embedded in upstream regions of plants is a particularly challenging bioinformatics task. Previous studies have shown that motifs in plants are short compared with those found in vertebrates. Furthermore, plant genomes have undergone several diversification mechanisms such as genome duplication events which impact the evolution of regulatory motifs. In this article, a systematic phylogenomic comparison of upstream regions is conducted to further identify features of the plant regulatory genomes, the component of genomes regulating gene expression, to enable future de novo discoveries. The findings highlight differences in upstream region properties between major plant groups and the effects of divergence times and duplication events. First, clear differences in upstream region evolution can be detected between monocots and dicots, thus suggesting that a separation of these groups should be made when searching for novel regulatory motifs, particularly since universal motifs such as the TATA box are rare. Second, investigating the decay rate of significantly aligned regions suggests that a divergence time of ∼100 mya sets a limit for reliable conserved non-coding sequence (CNS) detection. Insights presented here will set a framework to help identify embedded motifs of functional relevance by understanding the limits of bioinformatics detection for CNSs. PMID:21470961

  7. Detection limits of CDNC and albedo changes by Marine Cloud Brightening

    NASA Astrophysics Data System (ADS)

    N, Aswathy V.; Quaas, Johannes; Mülmenstädt, Johannes

    2015-04-01

    Marine cloud brightening (MCB) is one of the proposed futuristic climate engineering techniques. MCB aims in seeding marine stratocumulus clouds with cloud condensation nuclei which might increase the cloud droplet number concentration(CDNC) and thereby increasing the albedo of the clouds. Clouds are highly variable, complex and inhomogeneous in nature. Detecting the signals of climate engineering in the high natural variability of clouds is essential to prove the efficiency of climate engineering. Objective of this work is to perform a detection limit for the albedo change induced by MCB climate engineering. We thus provide a top-down approach reducing the extent in region and time period required to provide a statistically significant change in albedo due to MCB climate engineering. Study involve satellite observations from MODIS and CERES. We evaluate the change in low could cover albedo with change in CDNC, which is derived from MODIS data. Study aim to provide a map of the detection limits for different regions in terms of CDNC increment as well as albedo change. We intend to provide a quantitative solution for otherwise obvious queries such as how large? how long? and how much intense? the MCB experiment should be to provide a statistically significant signal from the noisy natural variability. We also try to use signatures easier to identify in cloud properties, like temporally as well as spatially changing pattern in modification.

  8. 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

  9. 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.

  10. 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...

  11. Properties and Detection Limits of Planetary Caustic Perturbation Induced by a Wide-separation Planet

    NASA Astrophysics Data System (ADS)

    Ryu, Yoon-Hyun; Chung, Sun-Ju; Lee, Ki-Won; Kim, Han-Seek; Han, Du-Hwan

    2016-03-01

    Microlensing experiments are entering a next generation of survey types to monitor a wide field of view continuously with a frequent sampling. The theoretically predicted sensitivity of a planet detection on the lensing parameters can be used for the establishment of observational strategies for maximal planet detections. Hence, we investigate the detection condition of planetary signals caused by the planetary caustic. We calculate the deviation area induced by the planetary caustic for various lensing parameters and find that the deviation area generally increases according to the increase of the source radius. However, after the normalized source radius approaches a certain value the deviation area rapidly decreases and disappears at the same normalized source radius, regardless of the mass ratio and the separation between the planet and its host star. We find a simple relation between the normalized source radius and the deviation threshold for the largest and smallest deviation areas. From this relation we also find an analytic condition for the detection limit of the planetary signal as the function of the source radius and the deviation threshold. In addition, we compare the deviation areas and the light curves between the planetary caustic perturbation and a free-floating planet. We find that the planetary caustic perturbation can be approximated by the single-lensing light curve of the planet itself perturbed by the planetary caustic. Finally, we can expect to find a low-mass planet with the Earth’s mass or even that of the Earth's moon from the detection condition and conclude that our findings may help for maximal planet detections considering the source type and the photometric accuracy.

  12. 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

  13. Limiter-discriminator detection of Continuous Phase Modulation (CPM) Tomlinson filtering

    NASA Astrophysics Data System (ADS)

    Trachtman, Ayal; Kalet, Irving; Shamai, Shlomo

    1994-02-01

    Limiter-discriminator detection of Continuous Phase Modulation (CPM) partial response signals is of special importance in system in which phase coherence is very difficult to establish and/or maintain (e.g., mobile communications systems). We propose a Tomlinson-based approach which copes with the intersymbol interference (ISI) introduced by the baseband partial response frequency modulating pulses of the CPM schemes, (e.g., GTFM, GMSK, Raised Cosin (RC)). In this approach, the ISI equalization is divided between the transmitter and the receiver. We investigate, through simulation, the detectability performance and spectral properties of a number of CPM signals and receiver structures with special emphasis on the Tomlinson approach. It is shown that this novel application of the Tomlinson configuration allows the use of relatively simple receivers which exhibit almost the same performance as more complex Viterbi structured receivers.

  14. Galileo PPR observations of Europa: Hotspot detection limits and surface thermal properties

    NASA Astrophysics Data System (ADS)

    Rathbun, Julie A.; Rodriguez, Nathaniel J.; Spencer, John R.

    2010-12-01

    The Galileo photopolarimeter-radiometer (PPR) made over 100 observations of Europa's surface temperature. We have used these data to constrain a diurnal thermal model and, thus, map the thermal inertia and bolometric albedo over 20% of the surface. We find an increased thermal inertia at mid-latitudes that is widespread in longitude and does not appear to correlate with geology, albedo, or other observables. Our derived thermophysical properties can be used to predict volatile stability across the surface over the course of a day and in planning of infrared instruments on future missions. Furthermore, while observations in the thermal infrared can and have been used to find endogenic activity, no such activity was detected at Europa. We have calculated the detection limits of these PPR observations and find that 100 km 2 hotspots with temperatures of 116-1200 K could exist undetected on the surface, depending on the location.

  15. A radiographic study of the detection limits of bone-cement remnants in total joint arthroplasty.

    PubMed

    Rauh, Michael A; Bayers-Thering, Mary; Madanagopal, Sudhakar; Krackow, Kenneth A

    2002-12-01

    Management of an infected hip prosthesis typically requires that all associated cement be removed. In the absence of gross mantle loosening, the surgeon frequently resorts to intraoperative radiographs to assess the completeness of removal. For this reason, we undertook a study to determine limits of detection of retained cement by routine radiography. Polymethyl methacrylate bone-cement beads (Simplex-P; Stryker-Howmedica-Osteonics, Allendale, NJ) were fashioned into graduated sizes and placed within cadaver medullary canals using 2 different methods. Standard radiographic images were obtained. Individually and independently, we viewed these images and proposed the limit of resolution to be 2.4 to 3.2 mm. It is difficult to remove all cement based on radiographs alone. These results suggest a need to use techniques that permit visualization of the canal to ensure adequate cement removal. PMID:12478508

  16. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  17. Using C₆₀⁺ Sputtering to Improve Detection Limit of Nitrogen in Zinc Oxide

    SciTech Connect

    Zhu, Zihua; Shutthanandan, V.; Nachimuthu, Ponnusamy

    2010-05-11

    C₆₀⁺ sputtering was firstly used to determine depth profile of nitrogen in zinc oxide materials by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Compared to traditional Cs+ sputtering depth profiling, the C₆₀⁺ sputtering provides over 200 times of effective signal intensity and the detection limit is about 10 times better. In addition, our X-ray photoelectron spectroscopy (XPS) results show that sputtering zinc oxide materials by 10 keV C₆₀⁺ leads to very weak carbon deposition at bottom of the sputter crater.

  18. Limiter-discriminator detection performance of Manchester and NRZ coded FSK

    NASA Technical Reports Server (NTRS)

    Cartier, D. E.

    1977-01-01

    The theory of limiter-discriminator detection of a frequency shift keyed (FSK) carrier is reviewed and this theory is used to predict the bit error probability performance of Manchester coded and nonreturn-to-zero (NRZ) coded data. A major result of the study is that the predetection time bandwidth product BT and the deviation ratio h needed to give optimum performance for Manchester coding are seen to be larger than optimum NRZ FSK. Specifically, BT of about 2 and h of about 1 will result in Manchester performance about 2 dB worse than optimum NRZ.

  19. A revisited hemolytic assay for palytoxin detection: Limitations for its quantitation in mussels.

    PubMed

    Brovedani, Valentina; Sosa, Silvio; Poli, Mark; Forino, Martino; Varello, Katia; Tubaro, Aurelia; Pelin, Marco

    2016-09-01

    Palytoxin (PLTX) and its analogues have been detected as seafood contaminants associated with a series of human foodborne poisonings. Due to a number of fatalities ascribed to the ingestion of PLTX-contaminated marine organisms, the development of methods for its detection in seafood has been recommended by the European Food Safety Authority (EFSA). Due to its feasibility, the spectrophotometric hemolytic assay is widely used to detect PLTX in different matrices, even though a standardized protocol is still lacking. Thus, on the basis of available assay procedures, a new standardized protocol was set up using purified human erythrocytes exposed to PLTX (working range: 3.9 × 10(-10)-2.5 × 10(-8) M) in a K(+)-free phosphate buffered saline solution, employing a 5 h incubation at 41 °C. An intra-laboratory characterization demonstrated its sensitivity (limit of detection, LOD = 1.4 × 10(-10) M and quantitation, LOQ = 3.4 × 10(-10) M), accuracy (bias = -0.8%), repeatability (RSDr = 15% and 6% for intra- and inter-day repeatability, respectively) and specificity. However, the standardized method seems not to be suitable for PLTX quantitation in complex matrices, such as mussel (Mytilus galloprovincialis) extracts, at least below the limit suggested by EFSA (30 μg PLTXs/Kg shellfish meat). Thus, the hemolytic assay for PLTX quantitation in seafood should be used only after a careful evaluation of the specific matrix effects. PMID:27343702

  20. Detecting limited health literacy in Brazil: development of a multidimensional screening tool.

    PubMed

    Apolinario, Daniel; Mansur, Leticia Lessa; Carthery-Goulart, Maria Teresa; Brucki, Sonia Maria Dozzi; Nitrini, Ricardo

    2014-03-01

    Screening questions have been proposed as practical tools for detecting limited functional health literacy, but have achieved only moderate accuracy in previous studies. We hypothesized that a combination of screening questions and demographic characteristics could better predict a patient's functional health literacy. Three hundred and twenty-two hospital users from São Paulo, Brazil, were interviewed for demographic information and answered questions about literacy habits and perceived difficulties. The Short Test of Functional Health Literacy in Adults was used to classify individuals as having adequate or limited functional health literacy. Of the 322 participants, 102 (31.7%) presented limited functional health literacy. The final logistic model included six predictors. The three demographic variables were educational attainment, mother's educational attainment and major lifetime occupation (manual or non-manual). The three questions concerned 'frequency of use of computers', 'difficulty with writing that have precluded the individual from getting a better job' and 'difficulty reading the subtitles while watching a foreign movie'. A simple score was derived to constitute a practical tool we named the Multidimensional Screener of Functional Health Literacy (MSFHL). The sensitivity of the MSFHL in detecting limited functional health literacy was 81.4% and the specificity was 87.7%, with an area under receiver operating characteristic (ROC) curve of 0.93 (95% CI 0.89-0.95). The MSFHL was better than educational attainment in accurately classifying functional health literacy status (p = 0.0018). We have developed a screening tool based on three demographic characteristics and three simple questions which provides an accurate prediction of a patient's functional health literacy level. PMID:24179154

  1. 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.

  2. Sensitivity, Prediction Uncertainty, and Detection Limit for Artificial Neural Network Calibrations.

    PubMed

    Allegrini, Franco; Olivieri, Alejandro C

    2016-08-01

    With the proliferation of multivariate calibration methods based on artificial neural networks, expressions for the estimation of figures of merit such as sensitivity, prediction uncertainty, and detection limit are urgently needed. This would bring nonlinear multivariate calibration methodologies to the same status as the linear counterparts in terms of comparability. Currently only the average prediction error or the ratio of performance to deviation for a test sample set is employed to characterize and promote neural network calibrations. It is clear that additional information is required. We report for the first time expressions that easily allow one to compute three relevant figures: (1) the sensitivity, which turns out to be sample-dependent, as expected, (2) the prediction uncertainty, and (3) the detection limit. The approach resembles that employed for linear multivariate calibration, i.e., partial least-squares regression, specifically adapted to neural network calibration scenarios. As usual, both simulated and real (near-infrared) spectral data sets serve to illustrate the proposal. PMID:27363813

  3. 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.

  4. Detection limits of four antimicrobial residue screening tests for beta-lactams in goat's milk.

    PubMed

    Sierra, D; Sánchez, A; Contreras, A; Luengo, C; Corrales, J C; Morales, C T; de la Fe, C; Guirao, I; Gonzalo, C

    2009-08-01

    This study was conducted to compare the detection limits (DL) of several antibiotic residue screening tests with the maximum residue limits (MRL) authorized by the EU according to the guidance for the standardized evaluation of microbial inhibitor tests of the International Dairy Federation. Composite antibiotic-free milk samples from 30 primiparous Murciano-Granadina goats in good health condition were used to prepare test samples spiked with different concentrations of each antimicrobial. In total, 5,760 analytical determinations of 10 beta-lactam antibiotics (penicillin-G, ampicillin, amoxicillin, cloxacillin, oxacillin, dicloxacillin, cefadroxyl, cefalexin, cefoperazone, and cefuroxime) were performed using 4 antibiotic residue screening tests: the brilliant black reduction test BRT AiM (AiM-Analytik in Milch Produktions-und Vertriebs GmbH, München, Germany), Delvotest MCS (DSM Food Specialties, Delft, the Netherlands), Eclipse 100 (ZEU-Inmunotec SL, Zaragoza, Spain), and the Copan Milk Test (CMT; Copan Italia SpA, Brescia, Italy). For each method, we estimated the detection limits of the antimicrobial agents using a logistic regression model. Using the CMT and Delvotest on samples spiked with the 8 antibiotics for which MRL were available, DL were at or below the MRL. The BRT test provided DL at or below the MRL for all of the agents except cefalexin, whereas the Eclipse 100 method failed to detect 4 antibiotics (ampicillin, amoxicillin, cloxacillin, and cefoperazone) at MRL or below. Logistic regression-determined levels of agreement were highest for the CMT method (98.6 to 100%) and lowest for Eclipse 100 (66.3 to 100%). In general, agreement levels indicated good correlation between observed results and those predicted by logistic regression. The lowest b values (closely related to test sensitivity) were recorded for the cephalosporins (0.074 to 0.430) and highest for penicillin G, ampicillin, and amoxicillin (11.270 to 11.504). Delvotest and CMT best

  5. Novel techniques for detection and imaging of spin related phenomena: Towards sub-diffraction limited resolution

    NASA Astrophysics Data System (ADS)

    Wolfe, Christopher Stuart

    The idea that the spin degree of freedom of particles can be used to store and transport information has revolutionized the data storage industry and inspired a huge amount of research activity. Spin electronics, or spintronics, provides a plethora of potential improvements to conventional charge electronics that include increased functionality and energy efficiency. Scientists studying spintronics will need a multitude of characterization tools to sensitively detect spins in new materials and devices. There are already a handful of powerful techniques to image spin-related phenomena, but each has limitations. Magnetic resonance force microscopy, for example, offers sensitive detection of spin moments that are localized or nearly so but requires a high vacuum, cryogenic environment. Magnetometry based on nitrogen vacancy centers in diamond is a powerful approach, but requires the nitrogen vacancy center to be in very close contact to the spin system being studied to be able to measure the field generated by the system. Spin-polarized scanning tunneling microscopy provides perhaps the best demonstrated spatial resolution, but typically requires ultrahigh vacuum conditions and is limited to studying the surface of a sample. Traditional optical techniques such as Faraday or Kerr microscopy are limited in spatial resolution by the optical diffraction limit. In this dissertation I will present three new techniques we have developed to address some of these issues and to provide the community with new tools to help push forward spintronics and magnetism related research. I will start by presenting the first experimental demonstration of scanned spin-precession microscopy. This technique has the potential to turn any spin-sensitive detection technique into an imaging platform by providing the groundwork for incorporating a magnetic field gradient with that technique, akin to magnetic resonance imaging, and the mathematical tools to analyze the data and extract the local

  6. Detection limits of thin layer coulometry with ionophore based ion-selective membranes.

    PubMed

    Shvarev, Alexey; Neel, Bastien; Bakker, Eric

    2012-09-18

    We report here on a significant improvement in lowering the low detection limit of thin layer coulometric sensors based on liquid ion-selective membranes, using a potassium-selective system as a model example. Various possible processes that may result in an elevated residual current reading after electrolysis were eliminated. Self-dissolution of AgCl on the Ag/AgCl inner element may result in a residual ion flux that could adversely affect the lower detection limit. It was here replaced with an Ag/AgI inner pseudoreference electrode where the self-dissolution equilibrium is largely suppressed. Possible residual currents originating from a direct contact between inner element and ion-selective membranes were eliminated by introducing an inert PVDF separator of 50 μm diameter that was coiled around the inner element by a custom-made instrument. Finally, the influence of electrolyte fluxes from the outer solution across the membrane into the sample was evaluated by altering its lipophilic nature and reducing its concentration. It was found that this last effect is most likely responsible for the observed residual current for the potassium-selective membranes studied here. For the optimized conditions, the calibration curves demonstrated a near zero intercept, thereby paving the way to the coulometric calibration-free sensing of ionic species. A linear calibration curve for the coulometric cell with valinomycin potassium-selective membrane was obtained in the range of 100 nM to 10 μM potassium in the presence of a 10 μM sodium background. In the presence of a higher (100 μM) concentration of sodium, a reliable detection of 1-100 μM of potassium was achieved. PMID:22917023

  7. Fine Structure ENA Sources Beyond the Termination Shock: Observational Constraints and Detection Limits

    NASA Astrophysics Data System (ADS)

    Demajistre, R.; Janzen, P. H.; Allegrini, F.; Dayeh, M. A.; McComas, D. J.; Schwadron, N.

    2015-12-01

    High spatial resolution maps from the IBEX mission (McComas et al, Science, 2009) suggest the presence of "fine structure" in the signal from beyond the termination shock. That is, areas of enhanced ENA emission that span less than a degree in the IBEX sky map. If confirmed, this would suggest very concentrated areas of emission from sources with scales of a few AU embedded in the outer heliosphere (or proportionally larger if they are located beyond the heliopause). This, in turn, would require the presence of unanticipated structures (plasma or neutral) beyond the termination shock for which the physics is poorly defined. It is therefore crucial to confirm the presence of these structures through careful analysis, or to establish the detection limits if the data taken to date is not sufficient for such a confirmation. In this work, we use 5 years worth of IBEX data to examine the statistical significance of these enhancements. We examine correlations in time, ENA energy and coincidence type for evidence of these small-scale spatial structures. Then, using the known spatial response of the IBEX instrument, establish the conditions under which such structure, if present, would be detectable. This detection threshold analysis is fully applicable future measurements, such as those planned for IMAP.

  8. 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.

  9. Noninvasive detection of expiratory flow limitation in COPD patients during nasal CPAP.

    PubMed

    Dellacà, R L; Rotger, M; Aliverti, A; Navajas, D; Pedotti, A; Farré, R

    2006-05-01

    The difference between mean inspiratory and expiratory respiratory reactance (delta(rs)) measured with forced oscillation technique (FOT) at 5 Hz allows the detection of expiratory flow limitation (EFL) in chronic obstructive pulmonary disease (COPD) patients breathing spontaneously. This aim of this study was to evaluate whether this approach can be applied to COPD patients during noninvasive pressure support. Delta(rs) was measured in seven COPD patients subjected to nasal continuous positive airway pressure (CPAP) at 0, 4, 8 and 12 cmH2O in sitting and supine positions. Simultaneous recording of oesophageal pressure and the Mead and Whittenberger (M-W) method provided a reference for scoring each breath as flow-limited (FL), non-flow-limited (NFL) or indeterminate (I). For each patient, six consecutive breaths were analysed for each posture and CPAP level. According to M-W scoring, 47 breaths were FL, 166 NFL and 51 I. EFL scoring using FOT coincided with M-W in 94.8% of the breaths. In the four patients who were FL in at least one condition, delta(rs) was reduced with increasing CPAP. These data suggest that the forced oscillation technique may be useful in chronic obstructive pulmonary disease patients on nasal pressure support by identifying continuous positive airway pressure levels that support breathing without increasing lung volume, which in turn increase the work of breathing and reduce muscle effectiveness and efficiency. PMID:16446315

  10. Combined Use of Absolute and Differential Seismic Arrival Time Data to Improve Absolute Event Location

    NASA Astrophysics Data System (ADS)

    Myers, S.; Johannesson, G.

    2012-12-01

    Arrival time measurements based on waveform cross correlation are becoming more common as advanced signal processing methods are applied to seismic data archives and real-time data streams. Waveform correlation can precisely measure the time difference between the arrival of two phases, and differential time data can be used to constrain relative location of events. Absolute locations are needed for many applications, which generally requires the use of absolute time data. Current methods for measuring absolute time data are approximately two orders of magnitude less precise than differential time measurements. To exploit the strengths of both absolute and differential time data, we extend our multiple-event location method Bayesloc, which previously used absolute time data only, to include the use of differential time measurements that are based on waveform cross correlation. Fundamentally, Bayesloc is a formulation of the joint probability over all parameters comprising the multiple event location system. The Markov-Chain Monte Carlo method is used to sample from the joint probability distribution given arrival data sets. The differential time component of Bayesloc includes scaling a stochastic estimate of differential time measurement precision based the waveform correlation coefficient for each datum. For a regional-distance synthetic data set with absolute and differential time measurement error of 0.25 seconds and 0.01 second, respectively, epicenter location accuracy is improved from and average of 1.05 km when solely absolute time data are used to 0.28 km when absolute and differential time data are used jointly (73% improvement). The improvement in absolute location accuracy is the result of conditionally limiting absolute location probability regions based on the precise relative position with respect to neighboring events. Bayesloc estimates of data precision are found to be accurate for the synthetic test, with absolute and differential time measurement

  11. 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

    2014-09-01

    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

  12. 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.

  13. 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

  14. 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…

  15. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  16. Effectiveness of limited cone-beam computed tomography in the detection of horizontal root fracture.

    PubMed

    Kamburoğlu, Kivanç; Ilker Cebeci, A R; Gröndahl, Hans Göran

    2009-06-01

    To compare the diagnostic accuracy of conventional film radiography, charge coupled device (CCD) and photostimulable phosphor plate (PSP) digital images and limited cone-beam computed tomography in detecting simulated horizontal root fracture. Root fractures were created in the horizontal plane in 18 teeth by a mechanical force and fragments were relocated. Another 18 intact teeth with no horizontal root fracture served as a control group. Thirty-six teeth were placed in the respective empty maxillary anterior sockets of a human dry skull in groups three by three. Intraoral radiographs were obtained in three different vertical views by utilizing Eastman Kodak E-speed film, CCD sensor, RVG 5.0 Trophy and a PSP sensor Digora, Optime. Cone beam CT images were taken with a unit (3D Accuitomo; J Morita MFG. Corp, Kyoto, Japan). Three dental radiologists separately examined the intraoral film, PSP, CCD and cone beam CT images for the presence of horizontal root fracture. Specificity and sensitivity for each radiographic technique were calculated. Kappa statistics was used for assessing the agreement between observers. Chi-square statistics was used to determine whether there were differences between the systems. Results were considered significant at P < 0.05. Cone beam CT images revealed significantly higher sensitivities (P < 0.05) than the intraoral systems between which no significant differences were found. Specificities did not show any statistically significant differences between any of the four systems. The kappa values for inter-observer agreement between observers (four pairs) ranged between 0.82-0.90 for the 3DX evaluations and between 0.63-0.71 for the different types of intraoral images. Limited cone beam CT, outperformed the two-dimensional intraoral, conventional as well as digital, radiographic methods in detecting simulated horizontal root fracture. PMID:19583573

  17. 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

  18. Investigations into modeling and further estimation of detection limits of the liquid electrode dielectric barrier discharge.

    PubMed

    Krähling, Tobias; Michels, Antje; Geisler, Sebastian; Florek, Stefan; Franzke, Joachim

    2014-06-17

    The liquid electrode dielectric barrier discharge (LE-DBD) is a miniaturized atmospheric pressure plasma as emission excitation source for elemental determination with pulsed behavior. Metals dissolved in liquids are detectable in flow systems with low flow rates of 20 μL min(-1) by means of optical emission spectrometry using a simple portable spectrometer. Time-resolved determination of the hydrogen excitation temperature Tαβ indicates that the LE-DBD does not reach a stable state during a burning phase, whereat the maximum and minimum Tαβ is independent of the flow rate. Adding dissolved metals to the liquid electrode does not influence the minimum Tαβ at the end of a burning phase. With the help of measured doubly charged lanthanum lines and spatially resolved measurements, the mechanism of the liquid transfer into the plasma will be clarified. Emissions from metal oxides indicate a thermal evaporation transfer mechanism, but only an additional electrospray-like transfer mechanism can explain the observed La III emissions and nonhomogeneous spatial distribution of exited species. The reaction pathways for electrosprayed hydrated metal ions are discussed for triply and doubly charged ions. The analytical performance is evaluated for 23 elements from the categories of alkali, alkaline earth, transition, and poor metals. The achieved detection limits are between 0.016 mg L(-1) for Li and 41 mg L(-1) for Bi. PMID:24831065

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

    PubMed

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

    2014-12-13

    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

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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

    2016-08-01

    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. PMID:27377477

  5. 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.

  6. Improving HST Pointing & Absolute Astrometry

    NASA Astrophysics Data System (ADS)

    Lallo, Matthew; Nelan, E.; Kimmer, E.; Cox, C.; Casertano, S.

    2007-05-01

    Accurate absolute astrometry is becoming increasingly important in an era of multi-mission archives and virtual observatories. Hubble Space Telescope's (HST's) Guidestar Catalog II (GSC2) has reduced coordinate error to around 0.25 arcsecond, a factor 2 or more compared with GSC1. With this reduced catalog error, special attention must be given to calibrate and maintain the Fine Guidance Sensors (FGSs) and Science Instruments (SIs) alignments in HST to a level well below this in order to ensure that the accuracy of science product's astrometry keywords and target positioning are limited only by the catalog errors. After HST Servicing Mission 4, such calibrations' improvement in "blind" pointing accuracy will allow for more efficient COS acquisitions. Multiple SIs and FGSs each have their own footprints in the spatially shared HST focal plane. It is the small changes over time in primarily the whole-body positions & orientations of these instruments & guiders relative to one another that is addressed by this work. We describe the HST Cycle 15 program CAL/OTA 11021 which, along with future variants of it, determines and maintains positions and orientations of the SIs and FGSs to better than 50 milli- arcseconds and 0.04 to 0.004 degrees of roll, putting errors associated with the alignment sufficiently below GSC2 errors. We present recent alignment results and assess their errors, illustrate trends, and describe where and how the observer sees benefit from these calibrations when using HST.

  7. 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.

  8. 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

  9. A Shadowing Problem in the Detection of Overlapping Communities: Lifting the Resolution Limit through a Cascading Procedure

    PubMed Central

    Young, Jean-Gabriel; Allard, Antoine; Hébert-Dufresne, Laurent; Dubé, Louis J.

    2015-01-01

    Community detection is the process of assigning nodes and links in significant communities (e.g. clusters, function modules) and its development has led to a better understanding of complex networks. When applied to sizable networks, we argue that most detection algorithms correctly identify prominent communities, but fail to do so across multiple scales. As a result, a significant fraction of the network is left uncharted. We show that this problem stems from larger or denser communities overshadowing smaller or sparser ones, and that this effect accounts for most of the undetected communities and unassigned links. We propose a generic cascading approach to community detection that circumvents the problem. Using real and artificial network datasets with three widely used community detection algorithms, we show how a simple cascading procedure allows for the detection of the missing communities. This work highlights a new detection limit of community structure, and we hope that our approach can inspire better community detection algorithms. PMID:26461919

  10. IUPAC-consistent approach to the limit of detection in partial least-squares calibration.

    PubMed

    Allegrini, Franco; Olivieri, Alejandro C

    2014-08-01

    There is currently no well-defined procedure for providing the limit of detection (LOD) in multivariate calibration. Defining an estimator for the LOD in this scenario has shown to be more complex than intuitively extending the traditional univariate definition. For these reasons, although many attempts have been made to arrive at a reasonable convention, additional effort is required to achieve full agreement between the univariate and multivariate LOD definitions. In this work, a novel approach is presented to estimate the LOD in partial least-squares (PLS) calibration. Instead of a single LOD value, an interval of LODs is provided, which depends on the variation of the background composition in the calibration space. This is in contrast with previously proposed univariate extensions of the LOD concept. With the present definition, the LOD interval becomes a parameter characterizing the overall PLS calibration model, and not each test sample in particular, as has been proposed in the past. The new approach takes into account IUPAC official recommendations, and also the latest developments in error-in-variables theory for PLS calibration. Both simulated and real analytical systems have been studied for illustrating the properties of the new LOD concept. PMID:25008998

  11. 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. PMID:12083275

  12. 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. PMID:25616701

  13. [Geriatrics: an absolute necessity].

    PubMed

    Oostvogel, F J

    1982-02-01

    The medical care for elderly people could be greatly improved. If no specific attention is paid immediately, namely through the various training courses and by way of further and part-time schooling, then this medical care will remain unsatisfactory. This situation worsens continually due to the growing number of elderly people and, within this group, a much higher rate of very aged people. Increasing the care in institutions is altogether unsatisfactory. The problem should be dealt with structurally and the emphasis placed upon prevention and early-diagnosis. There is an urgent need for an integrated method, keeping in mind the limits of the elderly person, from the physical, psychological and social aspects. This demands teamwork in a multidisciplinary system inside as well as outside the institutions. It demands a thorough knowledge of geriatrics based upon gerontology. Geriatricians are urgently needed in this development together with doctors in nursing homes, general practitioners and specialists, so that the necessary care may be established as quickly as possible. PMID:7101393

  14. 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.

  15. 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.

  16. Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner.

    PubMed

    El-Sharkawy, Abdel-Monem M; Sotiriadis, Paul P; Bottomley, Paul A; Atalar, Ergin

    2006-11-01

    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

  17. Detection of Nitric Oxide in the Lower Atmosphere of Venus and Upper Limit for Mars

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V. A.

    2006-05-01

    High-resolution spectra of Venus and Mars at the NO fundamental band at 5.3 μm with resolving power ν/δν = 76,000 were acquired using the TEXES spectrograph at NASA IRTF on Mauna Kea, Hawaii. The observed spectrum of Venus covered three NO lines of the P-branch. One of the lines is strongly contaminated, and the other two lines reveal NO in the lower atmosphere at a detection level of 9 sigma. A simple photochemical model for NO and N at 50 to 112 km was coupled with a radiative transfer code to simulate the observed equivalent widths of the NO and some CO2 lines. The derived NO mixing ratio is 5.5 ± 1.5 ppb below 60 km and its flux is (6 ± 2)×107 cm-2s-1. Predissociation of NO at the (0-0) 191 nm and (1-0) 183 nm bands of the δ-system and the reaction with N are the only important loss processes for NO in the lower atmosphere of Venus. The photochemical impact of the measured NO abundance is significant and should be taken into account in photochemical modeling of the Venus atmosphere. Lightning is the only known source of NO in the lower atmosphere of Venus, and the detection of NO is a convincing and independent proof of lightning on Venus. The required flux of NO is corrected for the production of NO and N by the cosmic ray ionization and corresponds to the lightning energy deposition of 0.19 ± 0.06 erg cm-2s-1. For a flash energy on Venus similar to that on the Earth (~109 J), the global flashing rate is ~90 s-1 and ~6 km-2y-1 which is in reasonable agreement with the existing optical observations. The observed spectrum of Mars covered three NO lines of the R-branch. Two of these lines are contaminated by CO2 lines, and the line at 1900.076 cm-1 is clean and shows some excess over the continuum. Some photochemical reactions may result in a significant excitation of NO (v = 1) in the lowest 20 km on Mars. However, quenching of NO (v = 1) by CO2 is very effective below 40 km. Excitation of NO (v = 1) in the collisions with atomic oxygen is weak because

  18. 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

  19. Limits of detection and quantification in comprehensive multidimensional separations. 1. A theoretical look.

    PubMed

    de la Mata, A Paulina; Harynuk, James J

    2012-08-01

    Comprehensive multidimensional separations (e.g., GC×GC, LC×LC, etc.) are increasingly popular tools for the analysis of complex samples, due to their many advantages, such as vastly increased peak capacity, and improvements in sensitivity. The most well-established of these techniques, GC×GC, has revolutionized analytical separations in fields as diverse as petroleum, environmental research, food and flavors, and metabolic profiling. Using multidimensional approaches, analytes can be quantified at levels substantially lower than those possible by one-dimensional techniques. However, it has also been shown that the modulation process introduces a new source of error to the measurement. In this work, we present the results of a study into the limits of quantification and detection (LOQ and LOD) in comprehensive multidimensional separations using GC×GC and the more popular "two-step" integration algorithm as an example. Simulation of chromatographic data permits precise control of relevant parameters of peak geometry and modulation phase. Results are expressed in terms of the dimensionless parameter of signal-to-noise ratio of the base peak (S/N(BP)) making them transportable to any result where quantification is performed using a two-step algorithm. Based on these results, the LOD is found to depend upon the modulation ratio used for the experiment and vary between a S/N(BP) of 10-17, while the LOQ depends on both the modulation ratio and the phase of the modulation for the peak and ranges from a S/N(BP) of 10 to 50, depending on the circumstances. PMID:22813213

  20. 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

    2016-06-01

    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. PMID:27188210

  1. Intrinsic limitation of cavity-enhanced Faraday detection of spin noise in quantum wells and quantum dots

    NASA Astrophysics Data System (ADS)

    Scalbert, D.

    2016-04-01

    Spin noise spectroscopy is a quite attractive experimental tool for studying unperturbed spin dynamics and magnetic resonance in semiconductor nanostructures. However in some cases its practical interest maybe severely limited by the weakness of the spin noise signal to be detected. In this paper we examine by how much the detection of spin noise of magnetic atoms or of nuclei, in quantum wells or quantum dots, can be improved by making use of cavity-enhanced Faraday rotation. The conditions for optimized cavities are first determined. In reflection geometry it corresponds to tune the cavity to the critical point of impedance matching. It is shown that even for optimized cavities the enhancement in spin noise detection is intrinsically limited by absorption. It turns out that the cavity effect improves the spin noise detection only when the inhomogeneous broadening of the involved optical resonance is large compared to its radiative broadening.

  2. 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.

  3. Absolute dosimetry for extreme-ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Berger, Kurt W.; Campiotti, Richard H.

    2000-06-01

    The accurate measurement of an exposure dose reaching the wafer on an extreme ultraviolet (EUV) lithographic system has been a technical challenge directly applicable to the evaluation of candidate EUV resist materials and calculating lithography system throughputs. We have developed a dose monitoring sensor system that can directly measure EUV intensities at the wafer plane of a prototype EUV lithographic system. This sensor system, located on the wafer stage adjacent to the electrostatic chuck used to grip wafers, operates by translating the sensor into the aerial image, typically illuminating an 'open' (unpatterned) area on the reticle. The absolute signal strength can be related to energy density at the wafer, and thus used to determine resist sensitivity, and the signal as a function of position can be used to determine illumination uniformity at the wafer plane. Spectral filtering to enhance the detection of 13.4 nm radiation was incorporated into the sensor. Other critical design parameters include the packaging and amplification technologies required to place this device into the space and vacuum constraints of a EUV lithography environment. We describe two approaches used to determine the absolute calibration of this sensor. The first conventional approach requires separate characterization of each element of the sensor. A second novel approach uses x-ray emission from a mildly radioactive iron source to calibrate the absolute response of the entire sensor system (detector and electronics) in a single measurement.

  4. 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

  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. PMID:25914379

  6. Unveiling the Gamma-Ray Source Count Distribution Below the Fermi Detection Limit with Photon Statistics

    NASA Astrophysics Data System (ADS)

    Zechlin, Hannes-S.; Cuoco, Alessandro; Donato, Fiorenza; Fornengo, Nicolao; Vittino, Andrea

    2016-08-01

    The source-count distribution as a function of their flux, {dN}/{dS}, is one of the main quantities characterizing gamma-ray source populations. 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| ≥slant 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 6 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× {10}-11 {{cm}}-2 {{{s}}}-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}-1.3+1.0× {10}-8 {{cm}}-2 {{{s}}}-1. The power-law index {n}1={3.1}-0.5+0.7 for bright sources above the break hardens to {n}2=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× {10}-11 {{cm}}-2 {{{s}}}-1 at 95% confidence level. 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.

  7. 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

  8. 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. PMID:25628612

  9. 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

    2015-10-01

    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. PMID:26302058

  10. 40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Definition and Procedure for the Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL..., G.D., Quave, S.A., and Budde, W.L., “Trace Analysis for Wastewaters,” Environmental Science...

  11. 40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Definition and Procedure for the Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL..., G.D., Quave, S.A., and Budde, W.L., “Trace Analysis for Wastewaters,” Environmental Science...

  12. 40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Definition and Procedure for the Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL..., G.D., Quave, S.A., and Budde, W.L., “Trace Analysis for Wastewaters,” Environmental Science...

  13. 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

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Definition and Procedure for the Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL..., G.D., Quave, S.A., and Budde, W.L., “Trace Analysis for Wastewaters,” Environmental Science...

  14. LIMITS OF DETECTION AND ARTIFACT FORMATION OF SULFATES AND NITRATES COLLECTED WITH A TRIPLE-PATH DENUDER

    EPA Science Inventory

    Ammonium sulfate and nitrate aerosols were generated and sampled on Teflon (PTFE) filters in a triple-path denuder (TPD) at the Research Triangle Institute. ower limits of detection and quantitative analysis of the resulting samples were completed by X-ray diffraction at the Sout...

  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 parts per billion by volume (ppbv), as cited in Method TO-15, to ...

  16. 40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL... CATEGORY Pt. 425, App. C Appendix C to Part 425—Definition and Procedure for the Determination of the... reagent water. (c) The concentration value that corresponds to the region of the standard curve...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The limit of detection (LOD) for qPCR-based analyses is not consistently defined or determined in studies on waterborne pathogens. Moreover, the LODs reported often reflect the qPCR assay rather than the entire sample process. Our objective was to develop a method to determine the 95% LOD (lowest co...

  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 ppbv, as cited in Method TO-15, to much lower concentrations. R...

  19. 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.

  20. 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

  1. 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

  2. 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.-

  3. 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).

  4. Limits on Surface Gravities of Kepler Planet-candidate Host Stars from Non-detection of Solar-like Oscillations

    NASA Astrophysics Data System (ADS)

    Campante, T. L.; Chaplin, W. J.; Lund, M. N.; Huber, D.; Hekker, S.; García, R. A.; Corsaro, E.; Handberg, R.; Miglio, A.; Arentoft, T.; Basu, S.; Bedding, T. R.; Christensen-Dalsgaard, J.; Davies, G. R.; Elsworth, Y. P.; Gilliland, R. L.; Karoff, C.; Kawaler, S. D.; Kjeldsen, H.; Lundkvist, M.; Metcalfe, T. S.; Silva Aguirre, V.; Stello, D.

    2014-03-01

    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.

  5. 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.

  6. 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.

  7. 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.

  8. A microfluidic platform with digital readout and ultra-low detection limit for quantitative point-of-care diagnostics.

    PubMed

    Li, Ying; Xuan, Jie; Song, Yujun; Wang, Ping; Qin, Lidong

    2015-08-21

    Quantitative assays are of great importance for point-of-care (POC) diagnostics because they can offer accurate information on the analytes. However, current POC devices often require an accessory instrument to give quantitative readouts for protein biomarkers, especially for those at very low concentration levels. Here, we report a microfluidic platform, the digital volumetric bar-chart chip (DV-chip), for quantitative POC diagnostics with ultra-low detection limits that are readable with the naked eye. Requiring no calibration, the DV-chip presents a digital ink bar chart (representing multiple bits composed of 0 and 1) for the target biomarker based on direct competition between O2 generated by the experimental and control samples. The bar chart clearly and accurately defines target concentration, allowing identification of disease status. For the standard PtNP solutions, the detection limit of the platform is approximately 0.1 pM and the dynamic range covers four orders of magnitude from 0.1 to 1000 pM. CEA samples with concentrations of 1 ng mL(-1) and 1.5 ng mL(-1) could be differentiated by the device. We also performed the ELISA assay for B-type natriuretic peptide (BNP) in 20 plasma samples from heart failure patients and the obtained on-chip data were in agreement with the clinical results. In addition, BNP was detectable at concentrations of less than 5 pM, which is three orders of magnitude lower than the detection limit of the previously reported readerless digital methods. By the integration of gas competition, volumetric bar chart, and digital readout, the DV-chip possesses merits of portability, visible readout, and ultra-low detection limit, which should offer a powerful platform for quantitative POC diagnostics in clinical settings and personalized detection. PMID:26170154

  9. Activity induced detection limits for Earth-sized planets from radial velocity studies

    NASA Astrophysics Data System (ADS)

    Korhonen, Heidi; Gråe Jørgensen, Uffe; Andersen, Jan Marie

    2015-08-01

    The detection of exoplanets using any method is prone to confusion due to the intrinsic variability of the host star. We have recently investigated the effect of cool starspots on the detectability of exoplanets around solar-like stars and M dwarfs using the radial velocity method. Our methods use full radiative transfer, known stellar atomic and molecular lines, different surface spot configurations, and an added planetary signal. In this talk we present our methods, and apply them to studying the detectability of small planets, and especially the case of alpha Centauri B planet.

  10. 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.

  11. Prediction of the limits of detection of hazardous vapors by passive infrared with the use of modtran.

    PubMed

    Flanigan, D F

    1996-10-20

    Passive infrared remote detection of hazardous gases, vapors, and aerosols is based on the difference, Δ 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 Δ 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 Δ T with angle of elevation (AOE). PMID:21127625

  12. 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.

  13. 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.

  14. 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

  15. The Frog-Boiling Attack: Limitations of Anomaly Detection for Secure Network Coordinate Systems

    NASA Astrophysics Data System (ADS)

    Chan-Tin, Eric; Feldman, Daniel; Hopper, Nicholas; Kim, Yongdae

    A network coordinate system assigns Euclidean “virtual” coordinates to every node in a network to allow easy estimation of network latency between pairs of nodes that have never contacted each other. These systems have been implemented in a variety of applications, most notably the popular Azureus/Vuze BitTorrent client. Zage and Nita-Rotaru (CCS 2007) and independently, Kaafar et al. (SIGCOMM 2007), demonstrated that several widely-cited network coordinate systems are prone to simple attacks, and proposed mechanisms to defeat these attacks using outlier detection to filter out adversarial inputs. We propose a new attack, Frog-Boiling, that defeats anomaly-detection based defenses in the context of network coordinate systems, and demonstrate empirically that Frog-Boiling is more disruptive than the previously known attacks. Our results suggest that a new approach is needed to solve this problem: outlier detection alone cannot be used to secure network coordinate systems.

  16. Absolute calibration of optical flats

    DOEpatents

    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.

  17. Limitations of a localized surface plasmon resonance sensor on Salmonella detection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  18. Absolute instability of a viscous hollow jet

    NASA Astrophysics Data System (ADS)

    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.

  19. 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.

  20. 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

    2015-03-01

    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. PMID:26262665

  1. 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.

  2. 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

  3. The influence of nondestructive inspection parameters on the preproof and postproof fatigue crack detection limits for fracture mechanics applications

    NASA Technical Reports Server (NTRS)

    Pettit, D. E.; Hoeppner, D. W.

    1973-01-01

    The results of a preliminary NDI program to examine the variability of flaw size detection limits in terms of specimen thickness and NDI procedures is reviewed and reanalyzed in terms of the variables involved. Penetrant, X-ray, eddy current, and ultrasonic methods developed independently at three separate laboratories were used to examine specimens having a range of thickness. The results are discussed in terms of the variables of thickness and NDI procedures.

  4. 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

  5. Detection limits for close eclipsing and transiting substellar and planetary companions to white dwarfs in the WASP survey

    NASA Astrophysics Data System (ADS)

    Faedi, F.; West, R. G.; Burleigh, M. R.; Goad, M. R.; Hebb, L.

    2011-01-01

    We have performed extensive simulations to explore the possibility of detecting eclipses and transits of close, substellar and planetary companions to white dwarfs in WASP (the UK Wide-Angle Search for Planets) light curves. Our simulations cover companions ˜0.3 < Rpl < 12 R? and orbital periods 2 < P < 15 d, equivalent to orbital radii 0.003 < a < 0.1 au. For Gaussian random noise, WASP is sensitive to transits by companions as small as the Moon orbiting a V≃ 12 white dwarf. For fainter white dwarfs, WASP is sensitive to increasingly larger radius bodies. However, in the presence of correlated noise structure in the light curves, the sensitivity drops, although Earth-sized companions remain detectable, in principle, even in low signal-to-noise data. Mars-sized, and even Mercury-sized, bodies yield reasonable detection rates in high-quality light curves with little residual noise. We searched for eclipses and transit signals in long-term light curves of a sample of 194 white dwarfs resulting from a cross-correlation of the McCook & Sion catalogue and the WASP archive. No evidence for eclipsing or transiting substellar and planetary companions was found. We used this non-detection and results from our simulations to place tentative upper limits to the frequency of such objects in close orbits at white dwarfs. While only weak limits can be placed on the likely frequency of Earth-sized or smaller companions, brown dwarfs and gas giants (radius ≈Rjup) with periods <0.1-0.2 d must certainly be rare (<10 per cent). More stringent constraints likely require 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 optimized for planetary transits of main-sequence stars.

  6. 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.

  7. 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

  8. 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.

  9. Detection of Stimulus Displacements Across Saccades is Capacity-Limited and Biased in Favor of the Saccade Target

    PubMed Central

    Irwin, David E.; Robinson, Maria M.

    2015-01-01

    Retinal image displacements caused by saccadic eye movements are generally unnoticed. Recent theories have proposed that perceptual stability across saccades depends on a local evaluation process centered on the saccade target object rather than on remapping and evaluating the positions of all objects in a display. In three experiments, we examined whether objects other than the saccade target also influence perceptual stability by measuring displacement detection thresholds across saccades for saccade targets and a variable number of non-saccade objects. We found that the positions of multiple objects are maintained across saccades, but with variable precision, with the saccade target object having priority in the perception of displacement, most likely because it is the focus of attention before the saccade and resides near the fovea after the saccade. The perception of displacement of objects that are not the saccade target is affected by acuity limitations, attentional limitations, and limitations on memory capacity. Unlike previous studies that have found that a postsaccadic blank improves the detection of displacement direction across saccades, we found that postsaccadic blanking hurt the detection of displacement per se by increasing false alarms. Overall, our results are consistent with the hypothesis that visual working memory underlies the perception of stability across saccades. PMID:26640430

  10. 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.

  11. An ultra-low detection-limit optofluidic biosensor based on all glass Fabry-Perot cavity.

    PubMed

    Wu, Haibo; Huang, Hui; Bai, Min; Liu, Pengbo; Chao, Ming; Hu, Jie; Hao, Jian; Cao, Tun

    2014-12-29

    An all glass optofludic biosensor with high quality-factor Fabry-Perot cavity (FPC) channel was reported. The all glass sandwich structure can completely eliminate the etching roughness of the channel surface, and can extend the operating wavelength to visible and ultraviolet regions compared with that of Si-based sensor. The quality-factor of the FPC channel is 875, and the system noise can be reduced to 1.2 nV by combining optical differential detection with phase lock-in detection. A detection limit of 15ng/mL for glucose solution, which corresponds to a refractive index unit of 2.0 × 10-9, was experimentally demonstrated. The all glass FPC sensor features low cost and robust compared with surface-plasmon-resonance sensor and ring-resonator sensor. PMID:25607165

  12. 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.

  13. The detection limit of a Gd3+-based T1 agent is substantially reduced when targeted to a protein microdomain

    PubMed Central

    Hanaoka, Kenjiro; Lubag, Angelo Josue M.; Castillo-Muzquiz, Aminta; Kodadek, Thomas; Sherry, A. Dean

    2008-01-01

    Simple low MW chelates of Gd3+ such as those currently used in clinical MR imaging are considered too insensitive for most molecular imaging applications. Here, we evaluated the detection limit of a molecularly targeted, low MW Gd3+-based, T1 agent in a model where the receptor concentration was precisely known. The data demonstrate that receptors clustered together to form a microdomain of high local concentration can be imaged successfully even when the bulk concentration of the receptor is quite low. A GdDO3A-peptide identified by phage display to target the anti-FLAG antibody was synthesized, purified and characterized. T1 weighted MR images were compared with the agent bound to antibody in bulk solution and with the agent bound to the antibody localized on agarose beads. Fluorescence competition binding assays show that the agent has a high binding affinity (KD = 150 nM) for the antibody while the fully bound relaxivity of the GdDO3A-peptide:anti-FLAG antibody in solution was a relatively modest 17 mM−1s−1. The agent:antibody complex was MR silent at concentrations below ~9 µM but was detectable down to 4 µM bulk concentrations when presented to antibody clustered together on the surface of agarose beads. These results provided an estimate of the detection limits for other T1-based agents with higher fully bound relaxivities or multimeric structures bound to clustered receptor molecules. The results demonstrate that the sensitivity of molecularly-targeted contrast agents depends on the local microdomain concentration of the target protein and the molecular relaxivity of the bound complex. A model is presented which predicts that for a molecularly targeted agent consisting of a single Gd3+ complex with bound relaxivity of 100 mM−1s−1 or, more reasonably, four tethered Gd3+ complexes each having a bound relaxivity of 25 mM−1s−1, the detection limit of a protein microdomain is ~690 nM at 9.4T. These experimental and extrapolated detection limits are

  14. 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.

  15. Information Limited Oligonucleotide Amplification Assay for Affinity-Based, Parallel Detection Studies

    PubMed Central

    Bokkasam, Harish; Ott, Albrecht

    2016-01-01

    Molecular communication systems encounter similar constraints as telecommunications. In either case, channel crosstalk at the receiver end will result in information loss that statistical analysis cannot compensate. This is because in any communication channel there is a physical limit to the amount of information that can be transmitted. We present a novel and simple modified end amplification (MEA) technique to generate reduced and defined amounts of specific information in form of short fragments from an oligonucleotide source that also contains unrelated and redundant information. Our method can be a valuable tool to investigate information overflow and channel capacity in biomolecular recognition systems. PMID:26978653

  16. 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.

  17. 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.

  18. 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.

  19. SQUID-detected MRI in the limit of zero static field

    NASA Astrophysics Data System (ADS)

    Kelso, Nathan Dean

    The magnetic gradient fields used in magnetic resonance imaging (MRI) have a component which is parallel to the uniform field B0 = B0ẑ, as well as a component perpendicular to B0. The component parallel to B0 is used in spatial encoding. The component perpendicular to B0, called the "concomitant gradient," causes image distortions (by altering the magnitude and direction of the total field) if its magnitude approaches B0 at any point in the field of view (FOV). In a conventional imaging sequence, the presence of the concomitant gradients limits the maximum gradient that can be used with a given B0 field or, conversely, limits the minimum B0 field that can be used with a given gradient field. This thesis describes an implementation of the so-called "zero-field MRI" (ZFMRI) pulse sequence, which allows for imaging in an arbitrarily low B0 field. The ZFMRI sequence created an effective unidirectional gradient field by using a train of pi pulses to average out the concomitant gradient components during encoding. The signals were acquired using a low-transition temperature dc Superconducting QUantum Interference Device (low-Tc dc SQUID) coupled to a first-order axial gradiometer. The experiments were carried out in a liquid helium dewar which was magnetically shielded with a single-layer mu-metal can around the outside and a superconducting Pb can contained within the helium space. We increased the filling factor of the custom-made, double-walled Pyrex insert by placing the liquid alcohol sample, at a temperature of approximately -50°C, at the center of one loop of the superconducting gradiometer, which was immersed in the helium bath. Using the aforementioned sequence and apparatus, images were acquired in the limit of zero static field, using gradients of up to 100 muT/m over a 23 mm FOV. The change in field magnitude over the FOV due to gradients was up to 10 times larger than the magnitude of any static field present in the dewar (static fields arose from

  20. 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.

  1. 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. PMID:26475963

  2. The AFGL absolute gravity program

    NASA Technical Reports Server (NTRS)

    Hammond, J. A.; Iliff, R. L.

    1978-01-01

    A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.

  3. Study of minimum detection limit of TLD personnel monitoring system in India.

    PubMed

    Sneha, C; Pradhan, S M; Adtani, M M

    2010-09-01

    Personnel monitoring of radiation workers in India is carried out using a thermoluminescence dosemeter (TLD) system based on CaSO(4):Dy Teflon TLD disc. The dose due to occupational exposure for a majority of radiation workers is very small and hence is reported as zero. In view of this the detection of low levels of occupational dose over and above a variable background assumes great importance. The present values of reporting levels are based on the standard deviations of annealed dosemeters and therefore are fixed irrespective of period of use and background radiation levels. The validity of these levels is investigated under laboratory conditions. The laboratory values of standard deviations cannot be used as an indication of the imprecision that occurs during service. Therefore, the validity of the reporting levels is also investigated for control dosemeters used in routine service. PMID:20511403

  4. 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.

  5. 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. PMID:25907667

  6. Protein biomarkers on tissue as imaged via MALDI mass spectrometry: A systematic approach to study the limits of detection.

    PubMed

    van de Ven, Stephanie M W Y; Bemis, Kyle D; Lau, Kenneth; Adusumilli, Ravali; Kota, Uma; Stolowitz, Mark; Vitek, Olga; Mallick, Parag; Gambhir, Sanjiv S

    2016-06-01

    MALDI mass spectrometry imaging (MSI) is emerging as a tool for protein and peptide imaging across tissue sections. Despite extensive study, there does not yet exist a baseline study evaluating the potential capabilities for this technique to detect diverse proteins in tissue sections. In this study, we developed a systematic approach for characterizing MALDI-MSI workflows in terms of limits of detection, coefficients of variation, spatial resolution, and the identification of endogenous tissue proteins. Our goal was to quantify these figures of merit for a number of different proteins and peptides, in order to gain more insight in the feasibility of protein biomarker discovery efforts using this technique. Control proteins and peptides were deposited in serial dilutions on thinly sectioned mouse xenograft tissue. Using our experimental setup, coefficients of variation were <30% on tissue sections and spatial resolution was 200 μm (or greater). Limits of detection for proteins and peptides on tissue were in the micromolar to millimolar range. Protein identification was only possible for proteins present in high abundance in the tissue. These results provide a baseline for the application of MALDI-MSI towards the discovery of new candidate biomarkers and a new benchmarking strategy that can be used for comparing diverse MALDI-MSI workflows. PMID:26970438

  7. Short communication: Detection limits of non-beta-lactam antibiotics in goat's milk by microbiological residues screening tests.

    PubMed

    Sierra, D; Contreras, A; Sánchez, A; Luengo, C; Corrales, J C; Morales, C T; de la Fe, C; Guirao, I; Gonzalo, C

    2009-09-01

    This study compares the performance of 4 antimicrobial residue screening tests [brilliant black reduction test AiM (Analytik in Milch Produktions- und Vertriebs GmbH, München, Germany), Delvotest MCS (DSM Food Specialties, Delft, the Netherlands), Eclipse 100 test (ZEU-Inmunotec SL, Zaragoza, Spain), and Copan Milk Test (Copan Italia S.p.a., Brescia, Italy)] used to detect 20 antimicrobial agents (aminoglycosides, macrolides, tetracyclines, sulfonamides, and quinolones) in goat's milk, according to International Dairy Federation guidelines. Composite milk samples from 30 antibiotic-free goats were used to prepare spiked milk samples and 11,520 analytical determinations were carried out. According to a logistic regression model, agreement coefficients were greater than 98% for most of the antibiotics, with higher b values obtained for macrolides. Neither tetracyclines nor quinolones were detected at European Union maximum residue limits. Only the Copan Milk Test and the Delvotest MCS were able to detect 3 antimicrobials below their maximum residue limits (neomycin, tylosin, and sulfadimethoxine). Given that these tests are used in control programs for goat's milk, our results indicate their sensitivity would need to be improved to guarantee safety for consumers. PMID:19700680

  8. Multifrequency continuous wave terahertz spectroscopy for absolute thickness determination

    SciTech Connect

    Scheller, Maik; Baaske, Kai; Koch, Martin

    2010-04-12

    We present a tunable multifrequency continuous wave terahertz spectrometer based on two laser diodes, photoconductive antennas, and a coherent detection scheme. The system is employed to determine the absolute thickness of samples utilizing a proposed synthetic difference frequency method to circumvent the 2pi uncertainty known from conventional photomixing systems while preserving a high spatial resolution.

  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. 40 CFR Table I-10 to Subpart I of... - Maximum Field Detection Limits Applicable to Fluorinated GHG Concentration Measurements for Stack...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Maximum Field Detection Limits Applicable to Fluorinated GHG Concentration Measurements for Stack Systems I Table I-10 to Subpart I of Part... Subpart I of Part 98—Maximum Field Detection Limits Applicable to Fluorinated GHG...

  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. Improved Detection Limit in Rapid Detection of Human Enterovirus 71 and Coxsackievirus A16 by a Novel Reverse Transcription–Isothermal Multiple-Self-Matching-Initiated Amplification Assay

    PubMed Central

    Ding, Xiong; Nie, Kai; Shi, Lei; Zhang, Yong; Guan, Li; Zhang, Dan

    2014-01-01

    Rapid detection of human enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) is important in the early phase of hand-foot-and-mouth disease (HFMD). In this study, we developed and evaluated a novel reverse transcription–isothermal multiple-self-matching-initiated amplification (RT-IMSA) assay for the rapid detection of EV71 and CVA16 by use of reverse transcriptase, together with a strand displacement DNA polymerase. Real-time RT-IMSA assays using a turbidimeter and visual RT-IMSA assays to detect EV71 and CVA16 were established and completed in 1 h, and the reported corresponding real-time reverse transcription–loop-mediated isothermal amplification (RT-LAMP) assays targeting the same regions of the VP1 gene were adopted as parallel tests. Through testing VP1 RNAs transcribed in vitro, the real-time RT-IMSA assays exhibited better linearity of quantification, with R2 values of 0.952 (for EV71) and 0.967 (for CVA16), than the real-time RT-LAMP assays, which had R2 values of 0.803 (for EV71) and 0.904 (for CVA16). Additionally, the detection limits of the real-time RT-IMSA assays (approximately 937 for EV71 and 67 for CVA16 copies/reaction) were higher than those of real-time RT-LAMP assays (approximately 3,266 for EV71 and 430 for CVA16 copies/reaction), and similar results were observed in the visual RT-IMSA assays. The new approaches also possess high specificities for the corresponding targets, with no cross-reactivity observed. In clinical assessment, compared to commercial reverse transcription-quantitative PCR (qRT-PCR) kits, the diagnostic sensitivities of the real-time RT-IMSA assays (96.4% for EV71 and 94.6% for CVA16) were higher than those of the real-time RT-LAMP assays (91.1% for EV71 and 90.8% for CVA16). The visual RT-IMSA assays also exhibited the same results. In conclusion, this proof-of-concept study suggests that the novel RT-IMSA assay is superior to the RT-LAMP assay in terms of detection limit and has the potential to rapidly detect EV71

  13. Apparent Stellar Wobble by a Planet in a Circumstellar Disk: Limitations on Planet Detection by Astrometry

    NASA Technical Reports Server (NTRS)

    Takeuchi, Taku; Velusamy, T.; Lin, D. N. C.

    2005-01-01

    Astrometric detection of a stellar wobble on the plane of the sky will provide us the next breakthrough in searching for extrasolar planets. The Space Interferometry Mission (SIM) is expected to achieve high-precision astrometry as accurate as 1 (mu)as, which is precise enough to discover a newborn Jupiter mass planet around a pre-main-sequence (PMS) star in the Taurus-Auriga star-forming region. PMS stars, however, have circumstellar disks that may be obstacles to the precise measurement of the stellar position.We present results on disk influences on the stellar wobble. The density waves excited by a planet move both the disk's mass center and the photocenter. The motion of the disk mass center induces an additional wobble of the stellar position, and the motion of the disk photocenter causes a contamination in the measurement of the stellar position. We show that the additional stellar motion dynamically caused by the disk's gravity is always negligible but that the contamination by the disk light can interfere with the precise measurement of the stellar position if the planet's mass is smaller than approximately 10MJ. The motion of the disk photocenter is sensitive to a slight change in the wave pattern and the disk properties. Measurements by interferometers are generally insensitive to extended sources such as disks. Because of this property, SIM will not suffer significant contamination by the disk light, even if the planet's mass is as small as 1M(sub J).

  14. A Direct Detection of Gas Accretion: The Lyman Limit System in 3C 232

    NASA Astrophysics Data System (ADS)

    Stocke, John T.; Keeney, Brian A.; Danforth, Charles W.

    2010-06-01

    The gas added to and removed from galaxies over cosmic time greatly affects their stellar populations and star formation rates. QSO absorption line studies in close QSO/galaxy pairs create a unique opportunity to study the physical conditions and kinematics of this gas. Here we present new Hubble Space Telescope (HST) images of the QSO/galaxy pair, 3C 232/NGC 3067. The quasar spectrum contains a Lyman limit (NHi = 1 × 1020 cm-2) absorption system (LLS) at cz = 1421 km s-1 that is associated with the nearby Sab galaxy NGC 3067. Previous work identifies this absorber as a high-velocity cloud (HVC) in NGC 3067 but the kinematics of the absorbing gas, infalling or outflowing, were uncertain. The HST images presented here establish the orientation of NGC 3067 and so establish that the LLS/HVC is infalling. Using this system as a prototype, we extend these results to higher-z Mgii/LLS to suggest that Mgii/LLSs are a sightline sampling of the so-called `cold mode accretion' (CMA) infalling onto luminous galaxies. To match the observed Mgii absorber statistics, the CMA must be more highly ionised at higher redshifts. The key observations needed to further the study of low-z LLSs is HST UV spectroscopy, for which a new instrument, the Cosmic Origins Spectrograph, has just been installed greatly enhancing our observational capabilities.

  15. 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

  16. 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.

  17. 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.

  18. An accurate and inexpensive color-based assay for detecting severe anemia in a limited-resource setting.

    PubMed

    McGann, Patrick T; Tyburski, Erika A; de Oliveira, Vysolela; Santos, Brigida; Ware, Russell E; Lam, Wilbur A

    2015-12-01

    Severe anemia is an important cause of morbidity and mortality among children in resource-poor settings, but laboratory diagnostics are often limited in these locations. To address this need, we developed a simple, inexpensive, and color-based point-of-care (POC) assay to detect severe anemia. The purpose of this study was to evaluate the accuracy of this novel POC assay to detect moderate and severe anemia in a limited-resource setting. The study was a cross-sectional study conducted on children with sickle cell anemia in Luanda, Angola. The hemoglobin concentrations obtained by the POC assay were compared to reference values measured by a calibrated automated hematology analyzer. A total of 86 samples were analyzed (mean hemoglobin concentration 6.6 g/dL). There was a strong correlation between the hemoglobin concentrations obtained by the POC assay and reference values obtained from an automated hematology analyzer (r=0.88, P<0.0001). The POC assay demonstrated excellent reproducibility (r=0.93, P<0.0001) and the reagents appeared to be durable in a tropical setting (r=0.93, P<0.0001). For the detection of severe anemia that may require blood transfusion (hemoglobin <5 g/dL), the POC assay had sensitivity of 88.9% and specificity of 98.7%. These data demonstrate that an inexpensive (<$0.25 USD) POC assay accurately estimates low hemoglobin concentrations and has the potential to become a transformational diagnostic tool for severe anemia in limited-resource settings. PMID:26317494

  19. Detection Limit of Smectite by Chemin IV Laboratory Instrument: Preliminary Implications for Chemin on the Mars Science Laboratory Mission

    NASA Technical Reports Server (NTRS)

    Archilles, Cherie; Ming, D. W.; Morris, R. V.; Blake, D. F.

    2011-01-01

    The CheMin instrument on the Mars Science Laboratory (MSL) is an miniature X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of detecting the mineralogical and elemental compositions of rocks, outcrops and soils on the surface of Mars. CheMin uses a microfocus-source Co X-ray tube, a transmission sample cell, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. CRISM and OMEGA have identified the presence of phyllosilicates at several locations on Mars including the four candidate MSL landing sites. The objective of this study was to conduct preliminary studies to determine the CheMin detection limit of smectite in a smectite/olivine mixed mineral system.

  20. A STUDY OF FUNDAMENTAL LIMITATIONS TO STATISTICAL DETECTION OF REDSHIFTED H I FROM THE EPOCH OF REIONIZATION

    SciTech Connect

    Thyagarajan, Nithyanandan; Udaya Shankar, N.; Subrahmanyan, Ravi; Arcus, Wayne; Emrich, David; Herne, David; Bernardi, Gianni; Greenhill, Lincoln J.; Bowman, Judd D.; Briggs, Frank; Gaensler, Bryan M.; Bunton, John D.; DeSouza, Ludi; Cappallo, Roger J.; Corey, Brian E.; Goeke, Robert F.; Hewitt, Jacqueline N.; Hazelton, Bryna J.; Johnston-Hollitt, Melanie; Kaplan, David L.; and others

    2013-10-10

    In this paper, we explore for the first time the relative magnitudes of three fundamental sources of uncertainty, namely, foreground contamination, thermal noise, and sample variance, in detecting the H I power spectrum from the epoch of reionization (EoR). We derive limits on the sensitivity of a Fourier synthesis telescope to detect EoR based on its array configuration and a statistical representation of images made by the instrument. We use the Murchison Widefield Array (MWA) configuration for our studies. Using a unified framework for estimating signal and noise components in the H I power spectrum, we derive an expression for and estimate the contamination from extragalactic point-like sources in three-dimensional k-space. Sensitivity for EoR H I power spectrum detection is estimated for different observing modes with MWA. With 1000 hr of observing on a single field using the 128 tile MWA, EoR detection is feasible (S/N >1 for k ∼< 0.8 Mpc{sup –1}). Bandpass shaping and refinements to the EoR window are found to be effective in containing foreground contamination, which makes the instrument tolerant to imaging errors. We find that for a given observing time, observing many independent fields of view does not offer an advantage over a single field observation when thermal noise dominates over other uncertainties in the derived power spectrum.

  1. 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. PMID:19429546

  2. 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.

  3. Recovery Efficiency and Limit of Detection of Aerosolized Bacillus anthracis Sterne from Environmental Surface Samples ▿

    PubMed Central

    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.

    2009-01-01

    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 cm2). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm2) or wipe or vacuum (929 cm2) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm2) 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 cm2 for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm2 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. PMID:19429546

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

    PubMed

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

    2016-06-01

    The limit of detection (LOD) for qPCR-based analyses is not consistently defined or determined in studies on waterborne pathogens. Moreover, the LODs reported often reflect the qPCR assay alone rather than the entire sample process. Our objective was to develop an approach to determine the 95% LOD (lowest concentration at which 95% of positive samples are detected) for the entire process of waterborne pathogen detection. We began by spiking the lowest concentration that was consistently positive at the qPCR step (based on its standard curve) into each procedural step working backwards (i.e., extraction, secondary concentration, primary concentration), which established a concentration that was detectable following losses of the pathogen from processing. Using the fraction of positive replicates (n = 10) at this concentration, we selected and analyzed a second, and then third, concentration. If the fraction of positive replicates equaled 1 or 0 for two concentrations, we selected another. We calculated the LOD using probit analysis. To demonstrate our approach we determined the 95% LOD for Salmonella enterica serovar Typhimurium, adenovirus 41, and vaccine-derived poliovirus Sabin 3, which were 11, 12, and 6 genomic copies (gc) per reaction (rxn), respectively (equivalent to 1.3, 1.5, and 4.0 gc L(-1) assuming the 1500 L tap-water sample volume prescribed in EPA Method 1615). This approach limited the number of analyses required and was amenable to testing multiple genetic targets simultaneously (i.e., spiking a single sample with multiple microorganisms). An LOD determined this way can facilitate study design, guide the number of required technical replicates, aid method evaluation, and inform data interpretation. PMID:27023926

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

    USGS Publications Warehouse

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

    2016-01-01

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

  6. Extending the Sensitivity to the Detection of WIMP Dark Matter with an Improved Understanding of the Limiting Neutron Backgrounds

    SciTech Connect

    Kamat, Sharmila

    2005-01-01

    The Cryogenic Dark Matter Search (CDMS) uses position-sensitive Germanium and Silicon crystals in the direct detection of Weakly Interacting Massive Particles (WIMPs) believed to constitute most of the dark matter in the Universe. WIMP interactions with matter being rare, identifying and eliminating known backgrounds is critical for detection. Event-by-event discrimination by the detectors rejects the predominant gamma and beta backgrounds while Monte Carlo simulations help estimate, and subtract, the contribution from the neutrons. This thesis describes the effort to understand neutron backgrounds as seen in the two stages of the CDMS search for WIMPs. The first stage of the experiment was at a shallow site at the Stanford Underground Facility where the limiting background came from high-energy neutrons produced by cosmic-ray muon interactions in the rock surrounding the cavern. Simulations of this background helped inform the analysis of data from an experimental run at this site and served as input for the background reduction techniques necessary to set new exclusion limits on the WIMP-nucleon cross-section, excluding new parameter space for WIMPs of masses 8-20 GeV/c{sup 2}. This thesis considers the simulation methods used as well as how various event populations in the data served as checks on the simulations to allow them to be used in the interpretation of the WIMP-search data. The studies also confirmed the presence of a limiting neutron background at the shallow site, necessitating the move to the 713-meter deep Soudan Underground Facility. Similar computer-based studies helped quantify the neutron background seen at the deeper site and informed the analysis of the data emerging from the first physics run of the experiment at Soudan. In conjunction with the WIMP-search and calibration data, the simulations confirmed that increased depth considerably reduced the neutron backgrounds seen, greatly improving the sensitivity to WIMP detection. The data run

  7. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  8. Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source.

    PubMed

    Tiedtke, K; Sorokin, A A; Jastrow, U; Juranić, P; Kreis, S; Gerken, N; Richter, M; Arp, U; Feng, Y; Nordlund, D; Soufli, R; Fernández-Perea, M; Juha, L; Heimann, P; Nagler, B; Lee, H J; Mack, S; Cammarata, M; Krupin, O; Messerschmidt, M; Holmes, M; Rowen, M; Schlotter, W; Moeller, S; Turner, J J

    2014-09-01

    This paper reports novel measurements of x-ray optical radiation on an absolute scale from the intense and ultra-short radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the detection principle for radiation measurements which was specifically adapted for this photon energy range. We present data characterizing the soft x-ray instrument at the Linac Coherent Light Source (LCLS) with respect to the radiant power output and transmission by using an absolute detector temporarily placed at the downstream end of the instrument. This provides an estimation of the reflectivity of all x-ray optical elements in the beamline and provides the absolute photon number per bandwidth per pulse. This parameter is important for many experiments that need to understand the trade-offs between high energy resolution and high flux, such as experiments focused on studying materials via resonant processes. Furthermore, the results are compared with the LCLS diagnostic gas detectors to test the limits of linearity, and observations are reported on radiation contamination from spontaneous undulator radiation and higher harmonic content. PMID:25321502

  9. Silver nanoparticles for SERS-based ultrasensitive chemical detection in aqueous solutions: Role of binding affinity and surface oxidation in the detection limit

    NASA Astrophysics Data System (ADS)

    Erol, Melek

    Surface-enhanced Raman spectroscopy (SERS) in the presence of noble metal nanostructures holds significant promise for sensing and molecular fingerprinting down to single molecule level. This dissertation explores the effect of binding affinity and surface oxidation of Ag nanoparticles on SERS detection sensitivity of SO42-, CN-, SCN-, ClO4- and nitro-aromatic compounds in water. Specifically positively charged Ag nanoparticles (Ag [+]) were synthesized by UV-assisted reduction of silver nitrate using branched polyethyleneimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) solutions. Both primary amino and amide groups on the surface of Ag [+] allowed strong binding affinity with anions, critical for sensitive SERS measurements. For substrates with immobilized Ag [+] (30 nanoparticles/mum2), SERS sensitivity increased in the order of SO42- < CN- < SCN- ≈ ClO4 -, with respective binding constants of 105, 3.3 x 105, and 107 (for both SCN- and ClO4-) M-1. Significantly, substrates with Ag [+] exhibited limit of detection values of 8.0 x 10-8 M (8 ppb) and 2.7 x 10-7 M (7 ppb) for ClO 4- and CN-, respectively. We revealed for the first time that oxidation of negatively charged Ag nanoparticles (Ag [-]) produced by a modified Lee and Meisel procedure drastically altered adsorption and orientation of nitro-aromatic molecules and increased their SERS detection limit. This observation can be attributed to the hinderance of Ag-to-aromatic ring charge transfer by the resultant oxide layer. SERS detection of p-nitrophenol at 1 ppt was achieved through inhibition of oxidation of Ag [-] in argon gas. Finally, to extend our work for potential biosensing applications, we showed that BPEI coatings of high molecular weight were unique in their ability to provide avidin-resistant surfaces at physiological conditions due to steric hindrance from the branched architecture of adsorbed polymer chains. BPEI coated surfaces were also effective for suppression of

  10. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  11. Resistance of lichens to simulated galactic cosmic radiation: limits of survival capacity and biosignature detection

    NASA Astrophysics Data System (ADS)

    de la Torre Noetzel, Rosa; Miller, Ana Z.; Cubero, Beatriz; Raguse, Marina; Meessen, Joachim

    2016-04-01

    Space constitutes an extremely harmful environment for survival of terrestrial organisms. Amongst extremophiles on Earth, lichens are one of the most resistant organisms to harsh terrestrial environments, as well as some species of microorganisms, such as bacteria (Moeller et al., 2010), criptoendolithic cyanobacteria and lithic fungi (de los Ríos et al. 2004). To study the survival capacity of lichens to the harmful radiation environment of space, we have selected the lichen Circinaria gyrosa, an astrobiological model defined by its high capacity of resistance to space conditions (De la Torre et al. 2010) and to a simulated Mars environment (Sanchez et al., 2012). Samples were irradiated with four types of space-relevant ionizing radiation in the STARLIFE campaign: helium and iron ion doses (up to 2,000 Gy), X-ray doses (up to 5,000 Gy) and ultra-high γ-ray doses (from 6 to 113 kGy). Results on resistance of C. gyrosa to space-relevant ionizing radiation and its post-irradiation viability were obtained by: (i) chlorophyll a fluorescence of photosystem II (PS II); (ii) epifluorescence microscopy; (iii) confocal laser-scanning microscopy (CLSM), and (iv) field emission scanning electron microscopy (FESEM). Results of photosynthetic activity and epifluorescence showed no significant changes on the viability of C. gyrosa with increasing doses of helium and iron ions as well as X-rays. In contrast, γ-irradiation elicited significant dose-correlated effects as revealed by all applied techniques. Relevant is the presence of whewellite-like crystals, detected by FESEM on C. gyrosa thalli after high irradiation doses, which has been also identified in previous Mars simulation studies (Böttcher et al., 2014). These studies contribute to the better understanding of the adaptability of extremophile organisms to harsh environments, as well as to estimate the habitability of a planet's surface, like Mars; they will be important for planning experiments on the search of life

  12. Application limit of Landsat ETM images to detect Saxaul plant community in desert ecosystems

    NASA Astrophysics Data System (ADS)

    Sepehry, Adel; Hassanzadeh, Hassan

    2004-02-01

    band) and 16 derivative images related to 53 sampling units were extracted for statistical analysis. Principal Component Analysis and Correlation Analysis showed no meaningful correlation between canopy cover percentage classes of Saxaul and DN values of all ETM bands as well as 16 derivative images. To examine capability of ETM bands and their 16 derivative images to differentiate between Saxaul sites having more than %75 of canopy cover and sites with bare soil, discrimination of the two sites were tested via Student T test. A series of unsupervised classification was also performed on FCC image with 2, 3, 16 and unlimited number of classes using ISODATA clustering method to find if Saxaul plantation could be classified as a distinct class. Results showed no distinction between the two sites. Visual investigation of all images proved the statistical results. Despite the fact that the image was acquired in a season with highest Saxaul greenness and LAI, It was found that ETM images are unable to detect Saxaul plant community. It seems, inability of ETM to discriminate Saxaul plant community from surrounding bare soil is due to Saxaul prevailing bark percentage comparing to its LAI, its reduced leaf surface area as well as its pubescent leaf structure which seems to let beneath soil reflectance prevail upper plant cover reflectance.

  13. Electroweak absolute, meta-, and thermal stability in neutrino mass models

    NASA Astrophysics Data System (ADS)

    Lindner, Manfred; Patel, Hiren H.; Radovčić, Branimir

    2016-04-01

    We analyze the stability of the electroweak vacuum in neutrino mass models containing right-handed neutrinos or fermionic isotriplets. In addition to considering absolute stability, we place limits on the Yukawa couplings of new fermions based on metastability and thermal stability in the early Universe. Our results reveal that the upper limits on the neutrino Yukawa couplings can change significantly when the top quark mass is allowed to vary within the experimental range of uncertainty in its determination.

  14. Limits of detection and artifact formation of sulfates and nitrates collected with a triple-path denuder

    NASA Astrophysics Data System (ADS)

    Davis, Briant L.; Deng, Yun; Anderson, Darcy J.; Johnson, L. Ronald; Detwiler, Andrew G.; Hodson, Laura L.; Sickles, Joseph E.

    Ammonium sulfate and nitrate aerosols were generated and sampled on Teflon (PTFE) filters in a triple-path denuder (TPD) at the Research Triangle Institute. Lower limits of detection and quantitative analysis of the resulting samples were completed by X-ray diffraction at the South Dakota School of Mines and Technology. Denuder coatings included oxalic acid for removal of ammonia, and NaCl for capture of nitric acid; a third path was left uncoated. Primary aerosol concentrations of 17 and 79 μg m -3 for (NH 4) 2SO 4 (mascagnite), and 10 μg m -3 for NH 4NO 3 were generated by a nebulizer and introduced to the instrument's PM 10 sampling inlet under a Tedlar chamber. Monitoring of generated species during collection at RTI was conducted using ion chromatography. Lower limits of detection (LLD, as wt%) for the sulfate and nitrate collections on the filters varied from 0.9 to (as high as) 22 for extremely light filter loadings. Spalling of the oxalic acid coating along denuder A and contamination of the aerosol in the collection cassette resulted in an initially rapid but decaying rate of artifact reaction of the mascagnite to letovicite (NH 4) 3H(SO 4) 2 over several months of laboratory storage. No analogous reaction was observed for the NH 4NO 3 aerosol samples.

  15. Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction.

    PubMed

    Rupp, Simone; Off, Andreas; Seitz-Moskaliuk, Hendrik; James, Timothy M; Telle, Helmut H

    2015-01-01

    Raman spectroscopy for low-pressure or trace gas analysis is rather challenging, in particular in process control applications requiring trace detection and real-time response; in general, enhancement techniques are required. One possible enhancement approach which enjoys increasing popularity makes use of an internally-reflective capillary as the gas cell. However, in the majority of cases, such capillary systems were often limited in their achievable sensitivity by a significant fluorescence background, which is generated as a consequence of interactions between the laser light and optical glass components in the setup. In order to understand and counteract these problems we have investigated a range of fluorescence-reducing measures, including the rearrangement of optical elements, and the replacement of glass components--including the capillary itself--by metal alternatives. These studies now have led to a capillary setup in which fluorescence is practically eliminated and substantial signal enhancement over standard Raman setups is achieved. With this improved (prototype) setup, detection limits of well below 1 mbar could be obtained in sub-second acquisition times, demonstrating the potential of capillary Raman spectroscopy for real-time, in situ gas sensing and process control applications, down to trace level concentrations. PMID:26378545

  16. Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction

    PubMed Central

    Rupp, Simone; Off, Andreas; Seitz-Moskaliuk, Hendrik; James, Timothy M.; Telle, Helmut H.

    2015-01-01

    Raman spectroscopy for low-pressure or trace gas analysis is rather challenging, in particular in process control applications requiring trace detection and real-time response; in general, enhancement techniques are required. One possible enhancement approach which enjoys increasing popularity makes use of an internally-reflective capillary as the gas cell. However, in the majority of cases, such capillary systems were often limited in their achievable sensitivity by a significant fluorescence background, which is generated as a consequence of interactions between the laser light and optical glass components in the setup. In order to understand and counteract these problems we have investigated a range of fluorescence-reducing measures, including the rearrangement of optical elements, and the replacement of glass components—including the capillary itself—by metal alternatives. These studies now have led to a capillary setup in which fluorescence is practically eliminated and substantial signal enhancement over standard Raman setups is achieved. With this improved (prototype) setup, detection limits of well below 1 mbar could be obtained in sub-second acquisition times, demonstrating the potential of capillary Raman spectroscopy for real-time, in situ gas sensing and process control applications, down to trace level concentrations. PMID:26378545

  17. A Control Allocation System for Automatic Detection and Compensation of Phase Shift Due to Actuator Rate Limiting

    NASA Technical Reports Server (NTRS)

    Yildiz, Yidiray; Kolmanovsky, Ilya V.; Acosta, Diana

    2011-01-01

    This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

  18. INTERPRETATION OF THE ARCADE 2 ABSOLUTE SKY BRIGHTNESS MEASUREMENT

    SciTech Connect

    Seiffert, M.; Levin, S. M.; Fixsen, D. J.; Kogut, A.; Wollack, E.; Limon, M.; Lubin, P. M.; Mirel, P.; Singal, J.; Villela, T.; Wuensche, C. A.

    2011-06-10

    We use absolutely calibrated data between 3 and 90 GHz from the 2006 balloon flight of the ARCADE 2 instrument, along with previous measurements at other frequencies, to constrain models of extragalactic emission. Such emission is a combination of the cosmic microwave background (CMB) monopole, Galactic foreground emission, the integrated contribution of radio emission from external galaxies, any spectral distortions present in the CMB, and any other extragalactic source. After removal of estimates of foreground emission from our own Galaxy, and an estimated contribution of external galaxies, we present fits to a combination of the flat-spectrum CMB and potential spectral distortions in the CMB. We find 2{sigma} upper limits to CMB spectral distortions of {mu} < 6 x 10{sup -4} and |Y{sub ff}| < 1 x 10{sup -4}. We also find a significant detection of a residual signal beyond that, which can be explained by the CMB plus the integrated radio emission from galaxies estimated from existing surveys. This residual signal may be due to an underestimated galactic foreground contribution, an unaccounted for contribution of a background of radio sources, or some combination of both. The residual signal is consistent with emission in the form of a power law with amplitude 18.4 {+-} 2.1 K at 0.31 GHz and a spectral index of -2.57 {+-} 0.05.

  19. Limited Streamer Tube System for Detecting Contamination in the Gas Used in the BaBar Instrumented Flux Return

    SciTech Connect

    Huntley, L.I.; /Franklin - Marshall Coll.

    2006-08-30

    The Resistive Plate Chambers (RPCs) initially installed in the Instrumented Flux Return (IFR) of the BABAR particle detector have proven unreliable and inefficient for detecting muons and neutral hadrons. In the summer of 2004, the BABAR Collaboration began replacing the RPCs with Limited Streamer Tubes (LSTs). LST operation requires a mixture of very pure gases and an operating voltage of 5500 V to achieve maximum efficiency. In the past, the gas supplies obtained by the BABAR Collaboration have contained contaminants that caused the efficiency of the IFR LSTs to drop from approximately 90% to approximately 60%. Therefore, it was necessary to develop a method for testing this gas for contaminants. An LST test system was designed and built using two existing LSTs, one placed 1 cm above the other. These LSTs detect cosmic muons in place of particles created during the BABAR experiment. The effect of gas contamination was mimicked by reducing the operating voltage of the test system in order to lower the detection efficiency. When contaminated gas was simulated, the coincidence rate and the percent coincidence between the LSTs in the test system dropped off significantly, demonstrating that test system can be used as an indicator of gas purity. In the fall of 2006, the LST test system will be installed in the gas storage area near the BABAR facility for the purpose of testing the gas being sent to the IFR.

  20. THE FIRM REDSHIFT LOWER LIMIT OF THE MOST DISTANT TeV-DETECTED BLAZAR PKS 1424+240

    SciTech Connect

    Furniss, A.; Williams, D. A.; Primack, J.; Danforth, C.; Stocke, J.; Fumagalli, M.; Prochaska, J. X.; Filippenko, A. V.; Neely, W.

    2013-05-10

    We present the redshift lower limit of z {>=} 0.6035 for the very high energy (VHE; E {>=} 100 GeV) emitting blazar PKS 1424+240 (PG 1424+240). This limit is inferred from Ly{beta} and Ly{gamma} absorption observed in the far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph. No VHE-detected blazar has shown solid spectroscopic evidence of being more distant. At this distance, VHE observations by VERITAS are shown to sample historically large gamma-ray opacity values at 500 GeV, extending beyond {tau} = 4 for low-level models of the extragalactic background light (EBL) and beyond {tau} = 5 for high levels. The majority of the z = 0.6035 absorption-corrected VHE spectrum appears to exhibit a lower flux than an extrapolation of the contemporaneous Large Area Telescope power-law fit beyond 100 GeV. However, the highest energy VERITAS point is the only point showing agreement with this extrapolation, possibly implying the overestimation of the gamma-ray opacity or the onset of an unexpected VHE spectral feature. A curved log parabola is favored when fitting the full range of gamma-ray data (0.5-500 GeV). While fitting the absorption-corrected VHE data alone results in a harder differential power law than that from the full range, the indices derived using three EBL models are consistent with the physically motivated limit set by Fermi acceleration processes.

  1. A LIMIT ON THE NUMBER OF ISOLATED NEUTRON STARS DETECTED IN THE ROSAT ALL-SKY-SURVEY BRIGHT SOURCE CATALOG

    SciTech Connect

    Turner, Monica L.; Rutledge, Robert E.; Letcavage, Ryan; Shevchuk, Andrew S. H.; Fox, Derek B. E-mail: rutledge@physics.mcgill.c E-mail: ahs148@psu.ed

    2010-05-10

    Using new and archival observations made with the Swift satellite and other facilities, we examine 147 X-ray sources selected from the ROSAT All-Sky-Survey Bright Source Catalog (RASS/BSC) to produce a new limit on the number of isolated neutron stars (INSs) in the RASS/BSC, the most constraining such limit to date. Independent of X-ray spectrum and variability, the number of INSs is {<=}48 (90% confidence). Restricting attention to soft (kT{sub eff} < 200 eV), non-variable X-ray sources-as in a previous study-yields an all-sky limit of {<=}31 INSs. In the course of our analysis, we identify five new high-quality INS candidates for targeted follow-up observations. A future all-sky X-ray survey with eROSITA, or another mission with similar capabilities, can be expected to increase the detected population of X-ray-discovered INSs from the 8-50 in the BSC, to (for a disk population) 240-1500, which will enable a more detailed study of neutron star population models.

  2. Absolute determination of the neutron source yield using melamine as a neutron detector

    NASA Astrophysics Data System (ADS)

    Ciechanowski, M.; Bolewski, A., Jr.; Kreft, A.

    2015-01-01

    A new approach to absolute determination of the neutron source yield is presented. It bases on the application of melamine (C3H6N6) to neutron detection combined with Monte Carlo simulations of neutron transport. Melamine has the ability to detect neutrons via 14N(n, p)14C reaction and subsequent determination of 14C content. A cross section for this reaction is relatively high for thermal neutrons (1.827 b) and much lower for fast neutrons. A concentration of 14C nuclei created in the irradiated sample of melamine can be reliably measured with the aid of the accelerator mass spectrometry (AMS). The mass of melamine sufficient for this analysis is only 10 mg. Neutron detection is supported by Monte Carlo simulations of neutron transport carried out with the use of MCNP-4C code. These simulations are aimed at computing the probability of 14C creation in the melamine sample per the source neutron. The result of AMS measurements together with results of MCNP calculations enable us to determine the number of neutrons emitted from the source during the irradiation of melamine. The proposed method was applied for determining the neutron emission from a commercial 252Cf neutron source which was independently calibrated. The measured neutron emission agreed with the certified one within uncertainty limits. The relative expanded uncertainty (k=2) of the absolute neutron source yield determination was estimated at 2.6%. Apart from calibration of radionuclide neutron sources the proposed procedure could facilitate absolute yield measurements for more complex sources. Potential applications of this methodology as it is further developed include diagnostics of inertial confinement fusion and plasma-focus experiments, calibration of neutron measurement systems at tokamaks and accelerator-based neutron sources as well as characterization of neutron fields generated in large particle detectors during collisions of hadron beams.

  3. Evaluating Detection Limits of Next-Generation Sequencing for the Surveillance and Monitoring of International Marine Pests

    PubMed Central

    Pochon, Xavier; Bott, Nathan J.; Smith, Kirsty F.; Wood, Susanna A.

    2013-01-01

    Most surveillance programmes for marine invasive species (MIS) require considerable taxonomic expertise, are laborious, and are unable to identify species at larval or juvenile stages. Therefore, marine pests may go undetected at the initial stages of incursions when population densities are low. In this study, we evaluated the ability of the benchtop GS Junior™ 454 pyrosequencing system to detect the presence of MIS in complex sample matrices. An initial in-silico evaluation of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear small subunit ribosomal DNA (SSU) genes, found that multiple primer sets (targeting a ca. 400 base pair region) would be required to obtain species level identification within the COI gene. In contrast a single universal primer set was designed to target the V1–V3 region of SSU, allowing simultaneous PCR amplification of a wide taxonomic range of MIS. To evaluate the limits of detection of this method, artificial contrived communities (10 species from 5 taxonomic groups) were created using varying concentrations of known DNA samples and PCR products. Environmental samples (water and sediment) spiked with one or five 160 hr old Asterias amurensis larvae were also examined. Pyrosequencing was able to recover DNA/PCR products of individual species present at greater than 0.64% abundance from all tested contrived communities. Additionally, single A. amurensis larvae were detected from both water and sediment samples despite the co-occurrence of a large array of environmental eukaryotes, indicating an equivalent sensitivity to quantitative PCR. NGS technology has tremendous potential for the early detection of marine invasive species worldwide. PMID:24023913

  4. Evaluating detection limits of next-generation sequencing for the surveillance and monitoring of international marine pests.

    PubMed

    Pochon, Xavier; Bott, Nathan J; Smith, Kirsty F; Wood, Susanna A

    2013-01-01

    Most surveillance programmes for marine invasive species (MIS) require considerable taxonomic expertise, are laborious, and are unable to identify species at larval or juvenile stages. Therefore, marine pests may go undetected at the initial stages of incursions when population densities are low. In this study, we evaluated the ability of the benchtop GS Junior™ 454 pyrosequencing system to detect the presence of MIS in complex sample matrices. An initial in-silico evaluation of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear small subunit ribosomal DNA (SSU) genes, found that multiple primer sets (targeting a ca. 400 base pair region) would be required to obtain species level identification within the COI gene. In contrast a single universal primer set was designed to target the V1-V3 region of SSU, allowing simultaneous PCR amplification of a wide taxonomic range of MIS. To evaluate the limits of detection of this method, artificial contrived communities (10 species from 5 taxonomic groups) were created using varying concentrations of known DNA samples and PCR products. Environmental samples (water and sediment) spiked with one or five 160 hr old Asterias amurensis larvae were also examined. Pyrosequencing was able to recover DNA/PCR products of individual species present at greater than 0.64% abundance from all tested contrived communities. Additionally, single A. amurensis larvae were detected from both water and sediment samples despite the co-occurrence of a large array of environmental eukaryotes, indicating an equivalent sensitivity to quantitative PCR. NGS technology has tremendous potential for the early detection of marine invasive species worldwide. PMID:24023913

  5. Absolute oral bioavailability of ciprofloxacin.

    PubMed

    Drusano, G L; Standiford, H C; Plaisance, K; Forrest, A; Leslie, J; Caldwell, J

    1986-09-01

    We evaluated the absolute bioavailability of ciprofloxacin, a new quinoline carboxylic acid, in 12 healthy male volunteers. Doses of 200 mg were given to each of the volunteers in a randomized, crossover manner 1 week apart orally and as a 10-min intravenous infusion. Half-lives (mean +/- standard deviation) for the intravenous and oral administration arms were 4.2 +/- 0.77 and 4.11 +/- 0.74 h, respectively. The serum clearance rate averaged 28.5 +/- 4.7 liters/h per 1.73 m2 for the intravenous administration arm. The renal clearance rate accounted for approximately 60% of the corresponding serum clearance rate and was 16.9 +/- 3.0 liters/h per 1.73 m2 for the intravenous arm and 17.0 +/- 2.86 liters/h per 1.73 m2 for the oral administration arm. Absorption was rapid, with peak concentrations in serum occurring at 0.71 +/- 0.15 h. Bioavailability, defined as the ratio of the area under the curve from 0 h to infinity for the oral to the intravenous dose, was 69 +/- 7%. We conclude that ciprofloxacin is rapidly absorbed and reliably bioavailable in these healthy volunteers. Further studies with ciprofloxacin should be undertaken in target patient populations under actual clinical circumstances. PMID:3777908

  6. Absolute Instability in Coupled-Cavity TWTs

    NASA Astrophysics Data System (ADS)

    Hung, D. M. H.; Rittersdorf, I. M.; Zhang, Peng; Lau, Y. Y.; Simon, D. H.; Gilgenbach, R. M.; Chernin, D.; Antonsen, T. M., Jr.

    2014-10-01

    This paper will present results of our analysis of absolute instability in a coupled-cavity traveling wave tube (TWT). The structure mode at the lower and upper band edges are respectively approximated by a hyperbola in the (omega, k) plane. When the Briggs-Bers criterion is applied, a threshold current for onset of absolute instability is observed at the upper band edge, but not the lower band edge. The nonexistence of absolute instability at the lower band edge is mathematically similar to the nonexistence of absolute instability that we recently demonstrated for a dielectric TWT. The existence of absolute instability at the upper band edge is mathematically similar to the existence of absolute instability in a gyroton traveling wave amplifier. These interesting observations will be discussed, and the practical implications will be explored. This work was supported by AFOSR, ONR, and L-3 Communications Electron Devices.

  7. Methods for automatized detection of rapid changes in lateral boundary condition fields for NWP limited area models

    NASA Astrophysics Data System (ADS)

    Tudor, M.

    2015-08-01

    Three-hourly temporal resolution of lateral boundary data for limited area models (LAMs) can be too infrequent to resolve rapidly moving storms. This problem is expected to be worse with increasing horizontal resolution. In order to detect intensive disturbances in surface pressure moving rapidly through the model domain, a filtered surface pressure field (MCUF) is computed operationally in the ARPEGE global model of Météo France. The field is distributed in the coupling files along with conventional meteorological fields used for lateral boundary conditions (LBCs) for the operational forecast using limited area model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) in the Meteorological and Hydrological Service of Croatia (DHMZ). Here an analysis is performed of the MCUF field for the LACE coupling domain for the period from 23 January 2006, when it became available, until 15 November 2014. The MCUF field is a good indicator of rapidly moving pressure disturbances (RMPDs). Its spatial and temporal distribution can be associated with the usual cyclone tracks and areas known to be supporting cyclogenesis. An alternative set of coupling files from the IFS operational run in the European Centre for Medium-Range Weather Forecasts (ECMWF) is also available operationally in DHMZ with 3-hourly temporal resolution, but the MCUF field is not available. Here, several methods are tested that detect RMPDs in surface pressure a posteriori from the IFS model fields provided in the coupling files. MCUF is computed by running ALADIN on the coupling files from IFS. The error function is computed using one-time-step integration of ALADIN on the coupling files without initialization, initialized with digital filter initialization (DFI) or scale-selective DFI (SSDFI). Finally, the amplitude of changes in the mean sea level pressure is computed from the fields in the coupling files. The results are compared to the MCUF field of ARPEGE and the results of same

  8. Absolute negative mobility of interacting Brownian particles

    NASA Astrophysics Data System (ADS)

    Ou, Ya-li; Hu, Cai-tian; Wu, Jian-chun; Ai, Bao-quan

    2015-12-01

    Transport of interacting Brownian particles in a periodic potential is investigated in the presence of an ac force and a dc force. From Brownian dynamic simulations, we find that both the interaction between particles and the thermal fluctuations play key roles in the absolute negative mobility (the particle noisily moves backwards against a small constant bias). When no the interaction acts, there is only one region where the absolute negative mobility occurs. In the presence of the interaction, the absolute negative mobility may appear in multiple regions. The weak interaction can be helpful for the absolute negative mobility, while the strong interaction has a destructive impact on it.

  9. On the precision of absolute sensitivity calibration and specifics of spectroscopic quantities interpretation in tokamaks.

    PubMed

    Naydenkova, D I; Weinzettl, V; Stockel, J; Matějíček, J

    2014-12-01

    Typical situations, which can be met during the process of absolute calibration, are shown in the case of a visible light observation system for the COMPASS tokamak. Technical issues and experimental limitations of absolute measurements connected with tokamak operation are discussed. PMID:25607972

  10. A Fast EM Algorithm for Fitting Joint Models of a Binary Response and Multiple Longitudinal Covariates Subject to Detection Limits

    PubMed Central

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

    2014-01-01

    Joint modeling techniques have become a popular strategy for studying the association between a response and one or more longitudinal covariates. Motivated by the GenIMS study, where it is of interest to model the event of survival using censored longitudinal biomarkers, a joint model is proposed for describing the relationship between a binary outcome and multiple longitudinal covariates subject to detection limits. A fast, approximate EM algorithm is developed that reduces the dimension of integration in the E-step of the algorithm to one, regardless of the number of random effects in the joint model. Numerical studies demonstrate that the proposed approximate EM algorithm leads to satisfactory parameter and variance estimates in situations with and without censoring on the longitudinal covariates. The approximate EM algorithm is applied to analyze the GenIMS data set. PMID:25598564

  11. NiO/graphene nanocomposite for determination of H2O2 with a low detection limit.

    PubMed

    Yu, Zhiyuan; Li, Hejun; Zhang, Xinmeng; Liu, Ningkun; Zhang, Xv

    2015-11-01

    In this study, we have reported the preparation of NiO/graphene (NiO/GR) nanocomposite for determination of H2O2 via a convenient solid reaction. The electrocatalytic behaviors towards H2O2 are investigated by cyclic voltammetry and chronoamperometry in alkaline aqueous solution. Electrochemical results indicate that the NiO/GR nanocomposite exhibits a high peak current towards the oxidation of H2O2. Moreover, high electrocatalytic activity toward the oxidation of H2O2 is observed with a low detection limit of 0.7664 μM, high sensitivity of 591 μA mM(-1) cm(-2), a wide linear range of 0.25-4.75 mM (R(2)=0.9971). Besides, the sensor presents many attractive features such as high stability and reproducibility. PMID:26452784

  12. Taking single virus detection and sizing to the limit with molecular sensitivity: the birth of nanoplasmonic-microcavity hybrid sensors

    NASA Astrophysics Data System (ADS)

    Arnold, S.

    2013-03-01

    The BioPhotonics community is buzzing at the prospect that ulta-small bio-nanoparticles such as Polio virus and protein can be detected label-free in their native state and sized one at a time. As the awareness that the claim of label-free single protein sensing through the frequency shift of a bare microcavity by A.M. Armani et al in Science in 2007 fades from lack of independent experimental confirmation or a viable physical mechanism to account for the magnitude of the reported wavelength shifts, a new approach has captured the community's interest. It is a product of a marriage between nano-optics and micro-photonics, and is poised to take label-free sensing to the limit.

  13. Limitations on the detection rate of high-risk HPV by hybrid capture 2 methodology in high grade intraepithelial (HSIL) or atypical squamous cells-cannot exclude HSIL (ASC-H) cytological lesions with proved CIN2.

    PubMed

    Noël, Jean-Christophe; Simon, Philippe

    2015-01-01

    Recent literature data suggest that the high-risk human papillomaviruses (HR-HPVs) testing with several molecular techniques could be an alternative to cytology in the detection of cervical intraepithelial neoplasias of grade 2 or worse (CIN2+). However, any molecular techniques have its own limits and may give false negative results which must be clearly known before undertaking a primary HPV screening. This study aims to evaluate the performance of the high-risk HPV hybrid capture II detection kit (HCII) which is considered as a "gold standard technique" in a series of 100 women having proved both cytological lesions of atypical squamous cells-cannot exclude an HSIL (ASC-H) or high-grade squamous intraepithelial lesion (HSIL) and histological lesions of CIN2+. The clinical sensitivity of HCII in women with a cytological diagnosis of ASC-H/HSIL and a diagnosis of CIN2+ is high but not absolute and estimated at 96% (95,6% and 100% of women with a diagnosis of CIN2/3 or invasive squamous cell carcinoma, resp.). These data although they are infrequent must be clearly referred before to start an HPV primary screening of CIN2+ especially with HCII methodology. PMID:26421258

  14. On the importance of direct detection combined limits for spin independent and spin dependent dark matter interactions

    NASA Astrophysics Data System (ADS)

    Marcos, Cristina; Peiró, Miguel; Robles, Sandra

    2016-03-01

    In this work we show how the inclusion of dark matter (DM) direct detection upper bounds in a theoretically consistent manner can affect the allowed parameter space of a DM model. Traditionally, the limits from DM direct detection experiments on the elastic scattering cross section of DM particles as a function of their mass are extracted under simplifying assumptions. Relaxing the assumptions related to the DM particle nature, such as the neutron to proton ratio of the interactions, or the possibility of having similar contributions from the spin independent (SI) and spin dependent (SD) interactions can vary significantly the upper limits. Furthermore, it is known that astrophysical and nuclear uncertainties can also affect the upper bounds. To exemplify the impact of properly including all these factors, we have analysed two well motivated and popular DM scenarios: neutralinos in the NMSSM and a Z' portal with Dirac DM. We have found that the allowed parameter space of these models is subject to important variations when one includes both the SI and SD interactions at the same time, realistic neutron to proton ratios, as well as using different self-consistent speed distributions corresponding to popular DM halo density profiles, and distinct SD structure functions. Finally, we provide all the necessary information to include the upper bounds of SuperCDMS and LUX taking into account all these subtleties in the investigation of any particle physics model. The data for each experiment and example codes are available at this site http://goo.gl/1CDFYi, and their use is detailed in the appendices of this work.

  15. A new approach for decreasing the detection limit for a ketamine(I) ion-selective electrode.

    PubMed

    Abu Shawish, Hazem M; Tamous, Hassan; Saadeh, Salman M; Abed-Almonem, Khalid I; Al Khalili, Osama

    2015-04-01

    Our endeavors of lowering the detection limit for a ketamine(I) ion-selective electrode were described. The paper stresses the electrode which showed best results for determination of ketamine ion. The present electrode incorporates ketamine-phosphomolybdate (KT-PM) as ion-exchanger combined with the lipophilic anionic additive (Na-TPB) dissolved in dibutyl phthalate (DBP) as a plasticizer. The characteristics of the electrode were elaborately measured and its performance was tested in various samples and urine. It has favorable features as it provides measurements of the potential with a near-Nernstian slope of 56.6±0.3mV/decade over the concentration range of 1.5×10(-6)-1.0×10(-2)M over the pH range 3.0-6.8 in a short response time (7s). Importantly, it has a low detection limit of 1.2×10(-7)M and its life-span is 22days. Moreover, it displayed notable selectivity for ketamine ion over other species such as inorganic and organic cations and different excipients which may be present in pharmaceutical preparations. The sensor was applied for determination of KT ions in urine and pharmaceutical preparations using potentiometric determination, standard addition and the calibration curve methods. The standard deviation computed on the results indicated excellent repeatability of the measurements. Overall, it showed satisfactory results with excellent percentage recovery comparable to and sometimes better than those obtained by other routine methods for the assay. PMID:25686971

  16. Absolute quantum cutting efficiency of Tb{sup 3+}-Yb{sup 3+} co-doped glass

    SciTech Connect

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

    2013-12-07

    The absolute quantum cutting efficiency of Tb{sup 3+}-Yb{sup 3+} co-doped glass was quantitatively measured by an integrating sphere detection system, which is independent of the excitation power. As the Yb{sup 3+} 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 Tb{sup 3+} (<61%) and significant cross-relaxation nonradiative loss between Yb{sup 3+} ions.

  17. Quantifying Efficacy and Limits of Unmanned Aerial Vehicle (UAV) Technology for Weed Seedling Detection as Affected by Sensor Resolution

    PubMed Central

    Peña, José M.; Torres-Sánchez, Jorge; Serrano-Pérez, Angélica; de Castro, Ana I.; López-Granados, Francisca

    2015-01-01

    In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early detection of weed seedlings. The ability to discriminate weeds was significantly affected by the imagery spectral (type of camera), spatial (flight altitude) and temporal (the date of the study) resolutions. The colour-infrared images captured at 40 m and 50 days after sowing (date 2), when plants had 5–6 true leaves, had the highest weed detection accuracy (up to 91%). At this flight altitude, the images captured before date 2 had slightly better results than the images captured later. However, this trend changed in the visible-light images captured at 60 m and higher, which had notably better results on date 3 (57 days after sowing) because of the larger size of the weed plants. Our results showed the requirements on spectral and spatial resolutions needed to generate a suitable weed map early in the growing season, as well as the best moment for the UAV image acquisition, with the ultimate objective of applying site-specific weed management operations. PMID:25756867

  18. Shot-noise Limited Faraday Rotation Spectroscopy for Detection of Nitric Oxide Isotopes in Breath, Urine, and Blood

    PubMed Central

    Wang, Yin; Nikodem, Michal; Zhang, Eric; Cikach, Frank; Barnes, Jarrod; Comhair, Suzy; Dweik, Raed A.; Kao, Christina; Wysocki, Gerard

    2015-01-01

    Measurement of NO and/or its metabolites in the various body compartments has transformed our understanding of biology. The inability of the current NO measurement methods to account for naturally occurring and experimental NO isotopes, however, has prevented the scientific community from fully understating NO metabolism in vivo. Here we present a mid-IR Faraday rotation spectrometer (FRS) for detection of NO isotopes. The instrument utilizes a novel dual modulation/demodulation (DM) FRS method which exhibits noise performance at only 2 times the fundamental quantum shot-noise level and provides the record sensitivity in its class. This is achieved with a system that is fully autonomous, robust, transportable, and does not require cryogenic cooling. The DM-FRS enables continuous monitoring of nitric oxide isotopes with the detection limits of 3.72 ppbv/Hz1/2 to14NO and 0.53 ppbv/Hz1/2 to15NO using only 45 cm active optical path. This DM-FRS measurement method can be used to improve the performance of conventional FRS sensors targeting other radical species. The feasibility of the instrument to perform measurements relevant to studies of NO metabolism in humans is demonstrated. PMID:25767064

  19. Shot-noise Limited Faraday Rotation Spectroscopy for Detection of Nitric Oxide Isotopes in Breath, Urine, and Blood

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Nikodem, Michal; Zhang, Eric; Cikach, Frank; Barnes, Jarrod; Comhair, Suzy; Dweik, Raed A.; Kao, Christina; Wysocki, Gerard

    2015-03-01

    Measurement of NO and/or its metabolites in the various body compartments has transformed our understanding of biology. The inability of the current NO measurement methods to account for naturally occurring and experimental NO isotopes, however, has prevented the scientific community from fully understating NO metabolism in vivo. Here we present a mid-IR Faraday rotation spectrometer (FRS) for detection of NO isotopes. The instrument utilizes a novel dual modulation/demodulation (DM) FRS method which exhibits noise performance at only 2 times the fundamental quantum shot-noise level and provides the record sensitivity in its class. This is achieved with a system that is fully autonomous, robust, transportable, and does not require cryogenic cooling. The DM-FRS enables continuous monitoring of nitric oxide isotopes with the detection limits of 3.72 ppbv/Hz1/2 to14NO and 0.53 ppbv/Hz1/2 to15NO using only 45 cm active optical path. This DM-FRS measurement method can be used to improve the performance of conventional FRS sensors targeting other radical species. The feasibility of the instrument to perform measurements relevant to studies of NO metabolism in humans is demonstrated.

  20. Quantifying efficacy and limits of unmanned aerial vehicle (UAV) technology for weed seedling detection as affected by sensor resolution.

    PubMed

    Peña, José M; Torres-Sánchez, Jorge; Serrano-Pérez, Angélica; de Castro, Ana I; López-Granados, Francisca

    2015-01-01

    In order to optimize the application of herbicides in weed-crop systems, accurate and timely weed maps of the crop-field are required. In this context, this investigation quantified the efficacy and limitations of remote images collected with an unmanned aerial vehicle (UAV) for early detection of weed seedlings. The ability to discriminate weeds was significantly affected by the imagery spectral (type of camera), spatial (flight altitude) and temporal (the date of the study) resolutions. The colour-infrared images captured at 40 m and 50 days after sowing (date 2), when plants had 5-6 true leaves, had the highest weed detection accuracy (up to 91%). At this flight altitude, the images captured before date 2 had slightly better results than the images captured later. However, this trend changed in the visible-light images captured at 60 m and higher, which had notably better results on date 3 (57 days after sowing) because of the larger size of the weed plants. Our results showed the requirements on spectral and spatial resolutions needed to generate a suitable weed map early in the growing season, as well as the best moment for the UAV image acquisition, with the ultimate objective of applying site-specific weed management operations. PMID:25756867

  1. Advantages and Limitations of Androgen Receptor-Based Methods for Detecting Anabolic Androgenic Steroid Abuse as Performance Enhancing Drugs

    PubMed Central

    Bailey, Kathy; Yazdi, Tahmineh; Masharani, Umesh; Tyrrell, Blake; Butch, Anthony; Schaufele, Fred

    2016-01-01

    Testosterone (T) and related androgens are performance enhancing drugs (PEDs) abused by some athletes to gain competitive advantage. To monitor unauthorized androgen abuse, doping control programs use mass spectrometry (MS) to detect androgens, synthetic anabolic-androgenic steroids (AASs) and their metabolites in an athlete’s urine. AASs of unknown composition will not be detected by these procedures. Since AASs achieve their anabolic effects by activating the Androgen Receptor (AR), cell-based bioassays that measure the effect of a urine sample on AR activity are under investigation as complementary, pan-androgen detection methods. We evaluated an AR BioAssay as a monitor for androgen activity in urine pre-treated with glucuronidase, which releases T from the inactive T-glucuronide that predominates in urine. AR BioAssay activity levels were expressed as ‘T-equivalent’ concentrations by comparison to a T dose response curve. The T-equivalent concentrations of androgens in the urine of hypogonadal participants supplemented with T (in whom all androgenic activity should arise from T) were quantitatively identical to the T measurements conducted by MS at the UCLA Olympic Analytical Laboratory (0.96 ± 0.22). All 17 AASs studied were active in the AR BioAssay; other steroids were inactive. 12 metabolites of 10 commonly abused AASs, which are used for MS monitoring of AAS doping because of their prolonged presence in urine, had reduced or no AR BioAssay activity. Thus, the AR BioAssay can accurately and inexpensively monitor T, but its ability to monitor urinary AASs will be limited to a period immediately following doping in which the active AASs remain intact. PMID:26998755

  2. Advantages and Limitations of Androgen Receptor-Based Methods for Detecting Anabolic Androgenic Steroid Abuse as Performance Enhancing Drugs.

    PubMed

    Bailey, Kathy; Yazdi, Tahmineh; Masharani, Umesh; Tyrrell, Blake; Butch, Anthony; Schaufele, Fred

    2016-01-01

    Testosterone (T) and related androgens are performance enhancing drugs (PEDs) abused by some athletes to gain competitive advantage. To monitor unauthorized androgen abuse, doping control programs use mass spectrometry (MS) to detect androgens, synthetic anabolic-androgenic steroids (AASs) and their metabolites in an athlete's urine. AASs of unknown composition will not be detected by these procedures. Since AASs achieve their anabolic effects by activating the Androgen Receptor (AR), cell-based bioassays that measure the effect of a urine sample on AR activity are under investigation as complementary, pan-androgen detection methods. We evaluated an AR BioAssay as a monitor for androgen activity in urine pre-treated with glucuronidase, which releases T from the inactive T-glucuronide that predominates in urine. AR BioAssay activity levels were expressed as 'T-equivalent' concentrations by comparison to a T dose response curve. The T-equivalent concentrations of androgens in the urine of hypogonadal participants supplemented with T (in whom all androgenic activity should arise from T) were quantitatively identical to the T measurements conducted by MS at the UCLA Olympic Analytical Laboratory (0.96 ± 0.22). All 17 AASs studied were active in the AR BioAssay; other steroids were inactive. 12 metabolites of 10 commonly abused AASs, which are used for MS monitoring of AAS doping because of their prolonged presence in urine, had reduced or no AR BioAssay activity. Thus, the AR BioAssay can accurately and inexpensively monitor T, but its ability to monitor urinary AASs will be limited to a period immediately following doping in which the active AASs remain intact. PMID:26998755

  3. Computer-based bioassay for evaluation of sensory irritation of airborne chemicals and its limit of detection.

    PubMed

    Alarie, Y

    1998-04-01

    We expanded a previously described rule-based computerized method to recognize the sensory irritating effect of airborne chemicals. Using 2-chlorobenzylchloride (CBC) as a sensory irritant, characteristic modifications of the normal breathing pattern of exposed mice were evaluated by measuring the duration of braking (TB) after inspiration and the resulting decrease in breathing frequency. From the measurement of TB, each breath was then classified as normal (N) or sensory irritation (S). Using increasing exposure concentrations, the classification S increased from < or = 2% (equivalent to sham-exposure) to 100% within a narrow exposure concentration range. The potency of CBC was then evaluated by calculating the concentration necessary to produce 50% of the breaths classified as S, i.e., S50. This approach is easier to use than obtaining RD50 (decrease in respiratory frequency by 50%) when high exposure concentrations are difficult to achieve. Detection limits were also established for this bioassay and experiments were conducted to obtain a level of response just around these limits, in order to delineate the practicality of using this bioassay at low exposure concentrations. Using this approach, sensory irritation was the only effect induced by CBC at low exposure concentrations. However, bronchoconstriction and pulmonary irritation were superimposed on this effect at higher exposure concentrations. PMID:9630013

  4. [Study on limit detection of flavones in diterpene ginkgolides meglumine injection materials by LC-MS and HPLC-DAD].

    PubMed

    Bi, Sen; Li, Yan-jing; Huang, Wen-zhe; Kang, Dan-yu; Ding, Gang; Xiao, Wei

    2015-08-01

    Limit test of flavones in diterpene ginkgolides meglumine injection materials by UV-Vis and HPLC-DAD method was studied in this essay. The HPLC-DAD method has lower LOD (about 1% of the UV-Vis), that is, the sensitivity is higher than UV-Vis method. Through the analysis of the kinds of flavonoids ingredients in the samples by LC-MS, the three compounds with highest contents are kaempferol, quercetin and isorhamnetin. Kaempferol, quercetin and isorhamnetin were chosen as reference compounds for HPLC analysis, and the HPLC separation analysis was carried on an Agilent Eclipse plus C18 column (4.6 mm x 250 mm, 5 μm) with methanol and water containing 0.4% phosphoric acid (50: 50) as mobile phase, and the flow rate was 1.0 mL x min(-1). The detection wavelength was set at 360 nm. This method has good specificity, precision and reproducibility. The LODs of quercetin, kaempferide and isorhamnetin were 27.6, 22.3, 29.5 μg x L(-1). The average recovery was 87.9% (RSD 3.3%), 91.7% (RSD 3.1%), 88.3 (RSD 1.3%) for quercetin, kaempferide and isorhamnetin, respectively. Based on the 10 batches of sample results and sensitivity of different HPLC, the content of total flavonoids ingredients of diterpene ginkgolides meglumine injection materials was limited no more than 2 x 10(-5). This method is simple, quick and has good maneuverability, and could be used to the limit test of flavonoids in the diterpene ginkgolides meglumine injection materials. PMID:26790294

  5. Inequalities, Absolute Value, and Logical Connectives.

    ERIC Educational Resources Information Center

    Parish, Charles R.

    1992-01-01

    Presents an approach to the concept of absolute value that alleviates students' problems with the traditional definition and the use of logical connectives in solving related problems. Uses a model that maps numbers from a horizontal number line to a vertical ray originating from the origin. Provides examples solving absolute value equations and…

  6. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  7. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  8. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  9. Investigating Absolute Value: A Real World Application

    ERIC Educational Resources Information Center

    Kidd, Margaret; Pagni, David

    2009-01-01

    Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…

  10. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  11. Camera-based speckle noise reduction for 3-D absolute shape measurements.

    PubMed

    Zhang, Hao; Kuschmierz, Robert; Czarske, Jürgen; Fischer, Andreas

    2016-05-30

    Simultaneous position and velocity measurements enable absolute 3-D shape measurements of fast rotating objects for instance for monitoring the cutting process in a lathe. Laser Doppler distance sensors enable simultaneous position and velocity measurements with a single sensor head by evaluating the scattered light signals. The superposition of several speckles with equal Doppler frequency but random phase on the photo detector results in an increased velocity and shape uncertainty, however. In this paper, we present a novel image evaluation method that overcomes the uncertainty limitations due to the speckle effect. For this purpose, the scattered light is detected with a camera instead of single photo detectors. Thus, the Doppler frequency from each speckle can be evaluated separately and the velocity uncertainty decreases with the square root of the number of camera lines. A reduction of the velocity uncertainty by the order of one magnitude is verified by the numerical simulations and experimental results, respectively. As a result, the measurement uncertainty of the absolute shape is not limited by the speckle effect anymore. PMID:27410133

  12. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  13. Estimation of absolute protein quantities of unlabeled samples by selected reaction monitoring mass spectrometry.

    PubMed

    Ludwig, Christina; Claassen, Manfred; Schmidt, Alexander; Aebersold, Ruedi

    2012-03-01

    For many research questions in modern molecular and systems biology, information about absolute protein quantities is imperative. This information includes, for example, kinetic modeling of processes, protein turnover determinations, stoichiometric investigations of protein complexes, or quantitative comparisons of different proteins within one sample or across samples. To date, the vast majority of proteomic studies are limited to providing relative quantitative comparisons of protein levels between limited numbers of samples. Here we describe and demonstrate the utility of a targeting MS technique for the estimation of absolute protein abundance in unlabeled and nonfractionated cell lysates. The method is based on selected reaction monitoring (SRM) mass spectrometry and the "best flyer" hypothesis, which assumes that the specific MS signal intensity of the most intense tryptic peptides per protein is approximately constant throughout a whole proteome. SRM-targeted best flyer peptides were selected for each protein from the peptide precursor ion signal intensities from directed MS data. The most intense transitions per peptide were selected from full MS/MS scans of crude synthetic analogs. We used Monte Carlo cross-validation to systematically investigate the accuracy of the technique as a function of the number of measured best flyer peptides and the number of SRM transitions per peptide. We found that a linear model based on the two most intense transitions of the three best flying peptides per proteins (TopPep3/TopTra2) generated optimal results with a cross-correlated mean fold error of 1.8 and a squared Pearson coefficient R(2) of 0.88. Applying the optimized model to lysates of the microbe Leptospira interrogans, we detected significant protein abundance changes of 39 target proteins upon antibiotic treatment, which correlate well with literature values. The described method is generally applicable and exploits the inherent performance advantages of SRM

  14. Absolute decay width measurements in 16O

    NASA Astrophysics Data System (ADS)

    Wheldon, C.; Ashwood, N. I.; Barr, M.; Curtis, N.; Freer, M.; Kokalova, Tz; Malcolm, J. D.; Spencer, S. J.; Ziman, V. A.; Faestermann, Th; Krücken, R.; Wirth, H.-F.; Hertenberger, R.; Lutter, R.; Bergmaier, A.

    2012-09-01

    The reaction 126C(63Li, d)168O* at a 6Li bombarding energy of 42 MeV has been used to populate excited states in 16O. The deuteron ejectiles were measured using the high-resolution Munich Q3D spectrograph. A large-acceptance silicon-strip detector array was used to register the recoil and break-up products. This complete kinematic set-up has enabled absolute α-decay widths to be measured with high-resolution in the 13.9 to 15.9 MeV excitation energy regime in 16O; many for the first time. This energy region spans the 14.4 MeV four-α breakup threshold. Monte-Carlo simulations of the detector geometry and break-up processes yield detection efficiencies for the two dominant decay modes of 40% and 37% for the α+12C(g.s.) and a+12C(2+1) break-up channels respectively.

  15. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  16. Diagnostic Application of Absolute Neutron Activation Analysis in Hematology

    SciTech Connect

    Zamboni, C.B.; Oliveira, L.C.; Dalaqua, L. Jr.

    2004-10-03

    The Absolute Neutron Activation Analysis (ANAA) technique was used to determine element concentrations of Cl and Na in blood of healthy group (male and female blood donators), select from Blood Banks at Sao Paulo city, to provide information which can help in diagnosis of patients. This study permitted to perform a discussion about the advantages and limitations of using this nuclear methodology in hematological examinations.

  17. SERS activity with tenfold detection limit optimization on a type of nanoporous AAO-based complex multilayer substrate

    NASA Astrophysics Data System (ADS)

    Sui, Chaofan; Wang, Kaige; Wang, Shuang; Ren, Junying; Bai, Xiaohong; Bai, Jintao

    2016-03-01

    Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 107) and detection limit (10-10 M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm-1 in 5 × 5 μm2 area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the electromagnetic field distribution. In addition, this SERS substrate is proposed for applications within the field of chemical and biochemical analyses.Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 107) and detection limit (10-10 M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm-1 in 5 × 5 μm2 area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the

  18. On the methodological limitations of detecting oxidative stress: effects of paraquat on measures of oxidative status in greenfinches.

    PubMed

    Meitern, Richard; Sild, Elin; Kilk, Kalle; Porosk, Rando; Hõrak, Peeter

    2013-07-15

    Oxidative stress (OS) is widely believed to be responsible for the generation of trade-offs in evolutionary ecology by means of constraining investment into a number of components of fitness. Yet, progress in understanding the true role of OS in ecology and evolution has remained elusive. Interpretation of current findings is particularly hampered by the scarcity of experiments demonstrating which of the many available parameters of oxidative status respond most sensitively to and are relevant for measuring OS. We addressed these questions in wild-caught captive greenfinches (Carduelis chloris) by experimental induction of OS by administration of the pro-oxidant compound paraquat with drinking water. Treatment induced 50% mortality, a significant drop in body mass and an increase in oxidative DNA damage and glutathione levels in erythrocytes among the survivors of the high paraquat (0.2 g l(-1) over 7 days) group. Samples taken 3 days after the end of paraquat treatment showed no effect on the peroxidation of lipids (plasma malondialdehyde), carbonylation of proteins (in erythrocytes), parameters of plasma antioxidant protection (total antioxidant capacity and oxygen radical absorbance), uric acid or carotenoids. Our findings of an increase in one marker of damage and one marker of protection from the multitude of measured variables indicate that detection of OS is difficult even under the most stringent experimental induction of oxidative insult. We hope that this study highlights the need for reconsideration of over-simplistic models of OS and draws attention to the limitations of detection of OS due to time-lagged and hormetic upregulation of protective mechanisms. This study also underpins the diagnostic value of measurement of oxidative damage to DNA bases and assessment of erythrocyte glutathione levels. PMID:23580720

  19. Study of the art: canine olfaction used for cancer detection on the basis of breath odour. Perspectives and limitations.

    PubMed

    Jezierski, Tadeusz; Walczak, Marta; Ligor, Tomasz; Rudnicka, Joanna; Buszewski, Bogusław

    2015-06-01

    Experimental studies using trained dogs to identify breath odour markers of human cancer, published in the recent decade, have been analyzed and compared with the authors' own results. Particular published studies differ as regards the experimental setup, kind of odour samples (breath, urine, tumor tissue, serum), sample collection methods, dogs' characteristics and dog training methods as well as in results presented in terms of detection sensitivity and specificity. Generally it can be stated that trained dogs are able to distinguish breath odour samples typical for patients with lung cancer and other cancers from samples typical for healthy humans at a 'better than by chance' rate. Dogs' indications were positively correlated with content of 2-pentanone and ethyl acetate (r = 0.97 and r = 0.85 respectively) and negatively correlated with 1-propanol and propanal in breath samples (r = -0.98 and -0.87 respectively). The canine method has some advantages as a potential cancer-screening method, due to its non-invasiveness, simplicity of odour sampling and storage, ease of testing and interpretation of results and relatively low costs. Disadvantages and limitations of this method are related to the fact that it is still not known exactly to which chemical compounds and/or their combinations the dogs react. So far it could not be confirmed that dogs are able to sniff out early preclinical cancer stages with approximately the same accuracy as already diagnosed cases. The detection accuracy may vary due to failure in conditioning of dogs, decreasing motivation or confounding factors. The dogs' performance should be systematically checked in rigorous double-blind procedures. Recommendations for methodological standardization have been proposed. PMID:25944810

  20. Youden Index and Optimal Cut-Point Estimated from Observations Affected by a Lower Limit of Detection

    PubMed Central

    Ruopp, Marcus D.; Perkins, Neil J.; Whitcomb, Brian W.; Schisterman, Enrique F.

    2008-01-01

    Summary The receiver operating characteristic (ROC) curve is used to evaluate a biomarker’s ability for classifying disease status. The Youden Index (J), the maximum potential effectiveness of a biomarker, is a common summary measure of the ROC curve. In biomarker development, levels may be unquantifiable below a limit of detection (LOD) and missing from the overall dataset. Disregarding these observations may negatively bias the ROC curve and thus J. Several correction methods have been suggested for mean estimation and testing; however, little has been written about the ROC curve or its summary measures. We adapt non-parametric (empirical) and semi-parametric (ROC-GLM [generalized linear model]) methods and propose parametric methods (maximum likelihood (ML)) to estimate J and the optimal cut-point (c*) for a biomarker affected by a LOD. We develop unbiased estimators of J and c* via ML for normally and gamma distributed biomarkers. Alpha level confidence intervals are proposed using delta and bootstrap methods for the ML, semi-parametric, and non-parametric approaches respectively. Simulation studies are conducted over a range of distributional scenarios and sample sizes evaluating estimators’ bias, root-mean square error, and coverage probability; the average bias was less than one percent for ML and GLM methods across scenarios and decreases with increased sample size. An example using polychlorinated biphenyl levels to classify women with and without endometriosis illustrates the potential benefits of these methods. We address the limitations and usefulness of each method in order to give researchers guidance in constructing appropriate estimates of biomarkers’ true discriminating capabilities. PMID:18435502

  1. Geometrical configurations of unphased diffraction-limited antennas in passive millimetre-wave imaging systems for concealed weapon detection

    NASA Astrophysics Data System (ADS)

    Serenelli, Roberto

    2004-12-01

    This paper analyzes simple imaging configurations to scan a human body, suitable as passive or active millimetre-wave imaging systems for concealed weapon detection (CWD). The first cylindrical configuration allows a 360 degrees scan: N unphased diffraction-limited antennas each of size L are placed on a circular support surrounding the subject (allowing scanning in the horizontal plane with N non-overlapping independent beams), and this circle is mechanically displaced over the whole body height. An analytical formula gives the maximum obtainable spatial resolution for different dimensions of the circular scanning device and operating frequencies, and the number of receivers achieving this optimal resolution. Constraints to be taken into account are diffraction, the usable total length of the circle, and the full coverage by the N beams over the subject, which is modelled as a cylinder with variable radius, coaxial with the scanning circle. Numerical calculations of system resolution are shown for different operating microwave (MW) and millimetre-wave (MMW) frequencies; in order to study off-axis performances, situations where the subject is not coaxial with the scanning device are also considered. For the case of a parallelepiped to be imaged instead of a cylinder, a linear array configuration is analyzed similarly to the circular one. A theoretical study is carried out to design other curved arrays, filled with unphased diffraction-limited antennas, for the imaging of linear subjects with finer resolution. Finally, the application of such configurations is considered for the design of active imaging systems, and different system architectures are discussed.

  2. Improved limit of detection and quantitation development and validation procedure for quantification of zinc in Insulin by atomic absorption spectrometry.

    PubMed

    Qadir, Muhammad Abdul; Ahmed, Mahmood; Haq, Iftikharul; Ahmed, Saghir

    2015-05-01

    A simple and expeditious analytical method for determination of zinc in human insulin isophane suspension by flame atomic absorption spectrophotometer (FAAS) was validated. The method was carried out on atomic absorption spectrometer with 0.4 nm bandwidth, 1.0 filter factor on deuterium (D2) background correction. The integration time was set at 3.0 second with 5.0 mA lamp current. The parameters of method validation showed adequate linearity, efficiency and relative standard deviation values were between 0.64%-1.69% (n=7), 1.31%-1.58% (n=10) for repeatability and intermediate precision respectively. The limit of detection 0.0032 μg/mL, 0.0173 μg/mL, 0.0231 μg/mL and limit of quantitation 0.0107μg/mL, 0.0578 μg/mL, 0.0694 μg/mL based on signal to noise (SN), calibration curve method (CCM) and fortification of blank (FB) were obtained respectively. The percentages of recovery for low, medium and high spiked concentration levels of zinc in human insulin were 99.38 ± 0.04 to 100.3 ± 0.03, 98.45 ± 0.38 to 100.3 ± 0.07 and 99.42 ± 0.03 to 99.42 ± 0.08 respectively. With the use of this method, five samples from each vial of human insulin isophane suspension were analyzed and the zinc content was determined. The zinc content were 22.1 ± 0.025 μg/mL and 24.3 ± 0.028 μg/mL which compliance the British Pharmacopoeia standard. PMID:26004720

  3. Invalid phase values removal method for absolute phase recovery.

    PubMed

    Lu, Jin; Mo, Rong; Sun, Huibin; Chang, Zhiyong; Zhao, Xiaxia

    2016-01-10

    A novel approach is presented for more effectively removing invalid phase values in absolute phase recovery. The approach is based on a detailed study involving the types and cases of invalid phase values. Meanwhile, some commonalities of the existing removal algorithms also are thoroughly analyzed. It is well known that rough absolute phase and fringe order maps can very easily be obtained by temporal phase unwrapping techniques. After carefully analyzing the components and fringe order distribution of the rough fringe order map, the proposed method chiefly adopts an entirely new strategy to refine a pure fringe order map. The strategy consists of three parts: (1) the square of an image gradient, (2) subregion areas of the binary image, and (3) image decomposition and composition. In combination with the pure fringe order map and a removal criterion, the invalid phase values can be identified and filtered out from the rough absolute phase map. This new strategy not only gets rid of the limitations of traditional removal methods but also has a two-fold function. The paper also offers different metrics from the experiment to evaluate the quality of the final absolute phase. In contrast with other removal methods, experimental results have verified the feasibility, effectiveness, and superiority of the proposed method. PMID:26835776

  4. Metal Stable Isotope Tagging: Renaissance of Radioimmunoassay for Multiplex and Absolute Quantification of Biomolecules.

    PubMed

    Liu, Rui; Zhang, Shixi; Wei, Chao; Xing, Zhi; Zhang, Sichun; Zhang, Xinrong

    2016-05-17

    The unambiguous quantification of biomolecules is of great significance in fundamental biological research as well as practical clinical diagnosis. Due to the lack of a detectable moiety, the direct and highly sensitive quantification of biomolecules is often a "mission impossible". Consequently, tagging strategies to introduce detectable moieties for labeling target biomolecules were invented, which had a long and significant impact on studies of biomolecules in the past decades. For instance, immunoassays have been developed with radioisotope tagging by Yalow and Berson in the late 1950s. The later languishment of this technology can be almost exclusively ascribed to the use of radioactive isotopes, which led to the development of nonradioactive tagging strategy-based assays such as enzyme-linked immunosorbent assay, fluorescent immunoassay, and chemiluminescent and electrochemiluminescent immunoassay. Despite great success, these strategies suffered from drawbacks such as limited spectral window capacity for multiplex detection and inability to provide absolute quantification of biomolecules. After recalling the sequences of tagging strategies, an apparent question is why not use stable isotopes from the start? A reasonable explanation is the lack of reliable means for accurate and precise quantification of stable isotopes at that time. The situation has changed greatly at present, since several atomic mass spectrometric measures for metal stable isotopes have been developed. Among the newly developed techniques, inductively coupled plasma mass spectrometry is an ideal technique to determine metal stable isotope-tagged biomolecules, for its high sensitivity, wide dynamic linear range, and more importantly multiplex and absolute quantification ability. Since the first published report by our group, metal stable isotope tagging has become a revolutionary technique and gained great success in biomolecule quantification. An exciting research highlight in this area

  5. Evaluation of the odd-even effect in limits of detection for electron microprobe analysis of natural minerals.

    PubMed

    Verma, Surendra P; Pandarinath, Kailasa; Velasco-Tapia, Fernando; Rodríguez-Ríos, Rodolfo

    2009-04-13

    Limit of detection (LOD), being a fundamental quality parameter for analytical techniques, has been recently investigated and a systematic behavior has been observed for most odd-even element pairs for many techniques. However, to the best of our knowledge very few LOD data are available in published literature for electron microprobe analysis; these consist of three papers, two being on rare-earth elements and the third covering a large number of elements of atomic number between 21 and 92. These data confirm the systematic behavior of LODs for many odd-even pairs. To initiate to full this gap, we determined LODs for several major rock-forming chemical elements from Na to Fe with atomic numbers between 11 and 26, during the microprobe analysis of common minerals (olivine, plagioclase, pyroxene, amphibole, quartz, and opaques) in volcanic rocks. The odd-even effect of nuclear stability seems to be present in LOD data for most odd-even pairs investigated. Nevertheless, the experimental strategy concerning the reference materials, calibration procedure, and blank measurements, should be substantially modified to better evaluate the systematic behavior of LOD values in microprobe analysis. PMID:19327450

  6. SERS activity with tenfold detection limit optimization on a type of nanoporous AAO-based complex multilayer substrate.

    PubMed

    Sui, Chaofan; Wang, Kaige; Wang, Shuang; Ren, Junying; Bai, Xiaohong; Bai, Jintao

    2016-03-21

    Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 10(7)) and detection limit (10(-10) M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm(-1) in 5 × 5 μm(2) area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the electromagnetic field distribution. In addition, this SERS substrate is proposed for applications within the field of chemical and biochemical analyses. PMID:26911325

  7. Multiplex real-time quantitative PCR, microscopy and rapid diagnostic immuno-chromatographic tests for the detection of Plasmodium spp: performance, limit of detection analysis and quality assurance

    PubMed Central

    2009-01-01

    Background Accurate laboratory diagnosis of malaria species in returning travelers is paramount in the treatment of this potentially fatal infectious disease. Materials and methods A total of 466 blood specimens from returning travelers to Africa, Asia, and South/Central America with suspected malaria infection were collected between 2007 and 2009 at the reference public health laboratory. These specimens were assessed by reference microscopy, multipex real-time quantitative polymerase chain reaction (QPCR), and two rapid diagnostic immuno-chromatographic tests (ICT) in a blinded manner. Key clinical laboratory parameters such as limit of detection (LOD) analysis on clinical specimens by parasite stage, inter-reader variability of ICTs, staffing implications, quality assurance and cost analysis were evaluated. Results QPCR is the most analytically sensitive method (sensitivity 99.41%), followed by CARESTART (sensitivity 88.24%), and BINAXNOW (sensitivity 86.47%) for the diagnosis of malaria in returning travelers when compared to reference microscopy. However, microscopy was unable to specifically identify Plasmodia spp. in 18 out of 170 positive samples by QPCR. Moreover, the 17 samples that were negative by microscopy and positive by QPCR were also positive by ICTs. Quality assurance was achieved for QPCR by exchanging a blinded proficiency panel with another reference laboratory. The Kappa value of inter-reader variability among three readers for BINAXNOW and CARESTART was calculated to be 0.872 and 0.898 respectively. Serial dilution studies demonstrated that the QPCR cycle threshold correlates linearly with parasitemia (R2 = 0.9746) in a clinically relevant dynamic range and retains a LOD of 11 rDNA copies/μl for P. falciparum, which was several log lower than reference microscopy and ICTs. LOD for QPCR is affected not only by parasitemia but the parasite stage distribution of each clinical specimen. QPCR was approximately 6-fold more costly than reference

  8. An electrically detected magnetic resonance study of performance limiting defects in SiC metal oxide semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Cochrane, C. J.; Lenahan, P. M.; Lelis, A. J.

    2011-01-01

    SDR detected EDMR at other biases. Part of this inverted phase spectrum involves two narrow lines which are separated by ≈10.5 G. Since the center responsible for this spectrum is almost certainly in the SiO2, it is likely due to the so called 10.4 G doublet center, an unpaired electron residing on an oxygen deficient silicon atom coupled to a hydrogen in SiO2. The likely presence of one oxygen deficient silicon defect suggests that other oxygen deficient silicon atom defect sites in the oxide may also be important in SiC/SiO2 devices. Oxygen deficient silicon defects in SiO2 are typically called E' centers. Our results collectively demonstrate considerable complexity in both the chemical composition and physical distribution of performance limiting defects in SiC transistors, with defects observed on both sides of the SiC/SiO2 interface. Our results most strongly indicate that fairly high densities of intrinsic deep-level defects, likely due to a Si vacancy or a closely related defect, extend into the bulk of the SiC in all but one of the devices prepared utilizing a fairly wide range of processing parameters.

  9. Absolute magnitudes of trans-neptunian objects

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.

    2015-10-01

    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.

  10. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  11. Changes in respiratory function impairment following the treatment of severe pulmonary tuberculosis – limitations for the underlying COPD detection

    PubMed Central

    Radovic, Milan; Ristic, Lidija; Ciric, Zorica; Dinic-Radovic, Violeta; Stankovic, Ivana; Pejcic, Tatjana; Rancic, Milan; Bogdanovic, Dragan

    2016-01-01

    Background During the treatment phase of active pulmonary tuberculosis (PTB), respiratory function impairment is usually restrictive. This may become obstructive, as a PTB-associated airflow obstruction (AFO) or as a later manifestation of underlying COPD. Purpose The aim of the study was to examine the potential causes and risks for AFO development in PTB by exploring the aspects of spirometry limitations and clinical implications for the underlying COPD detection, taking into account various confounding factors. Patients and methods Prospective, nest case–control study on 40 new cases of PTB with initial restrictive respiratory function impairment, diagnosed and treated according to the directly observed treatment short course (DOTS) strategy. Results From all observed patients, 37.5% of them developed AFO upon the completion of PTB treatment, with significantly increased average of forced vital capacity (%) (P<0.01). Their changes in forced expiratory volume in the first second (%) during the PTB treatment were strongly associated with the air pollution exposure in living (0.474%–20.971% for 95% confidence interval [CI]; P=0.041) and working environments (3.928%–20.379% for 95% CI; P=0.005), initial radiological extent of PTB lesions (0.018%–0.700% for 95% CI; P=0.047), leukocyte count (0.020%–1.328% for 95% CI; P=0.043), and C-reactive protein serum level (0.046%–0.205% for 95% CI; P=0.003) compared to the other patients. The multivariate logistic regression analysis model shows initial radiological extent of pulmonary tuberculosis lesions (OR 1.01–1.05 for 95% CI; P=0.02) and sputum conversion rate on culture (OR 1.02–1.68 for 95% CI; P=0.04) as the most significant predictors for the risk of AFO development. Conclusion AFO upon PTB treatment is a common manifestation of underlying COPD, which mostly occurs later, during the reparative processes in active PTB, even in the absence of major risk factors, such as cigarette smoking and biomass fuel

  12. Absolute Efficiency Calibration of a Beta-Gamma Detector

    SciTech Connect

    Cooper, Matthew W.; Ely, James H.; Haas, Derek A.; Hayes, James C.; McIntyre, Justin I.; Lidey, Lance S.; Schrom, Brian T.

    2013-04-10

    Abstract- Identification and quantification of nuclear events such as the Fukushima reactor failure and nuclear explosions rely heavily on the accurate measurement of radioxenon releases. One radioxenon detection method depends on detecting beta-gamma coincident events paired with a stable xenon measurement to determine the concentration of a plume. Like all measurements, the beta-gamma method relies on knowing the detection efficiency for each isotope measured. Several methods are commonly used to characterize the detection efficiency for a beta-gamma detector. The most common method is using a NIST certified sealed source to determine the efficiency. A second method determines the detection efficiencies relative to an already characterized detector. Finally, a potentially more accurate method is to use the expected sample to perform an absolute efficiency calibration; in the case of a beta-gamma detector, this relies on radioxenon gas samples. The complication of the first method is it focuses only on the gamma detectors and does not offer a solution for determining the beta efficiency. The second method listed is not similarly constrained, however it relies on another detector to have a well-known efficiency calibration. The final method using actual radioxenon samples to make an absolute efficiency determination is the most desirable, but until recently it was not possible to produce all four isotopically pure radioxenon. The production, by University of Texas (UT), of isotopically pure radioxenon has allowed the beta-gamma detectors to be calibrated using the absolute efficiency method. The first four radioxenon isotope calibration will be discussed is this paper.

  13. Comb-calibrated frequency-modulated continuous-wave ladar for absolute distance measurements.

    PubMed

    Baumann, Esther; Giorgetta, Fabrizio R; Coddington, Ian; Sinclair, Laura C; Knabe, Kevin; Swann, William C; Newbury, Nathan R

    2013-06-15

    We demonstrate a comb-calibrated frequency-modulated continuous-wave laser detection and ranging (FMCW ladar) system for absolute distance measurements. The FMCW ladar uses a compact external cavity laser that is swept quasi-sinusoidally over 1 THz at a 1 kHz rate. The system simultaneously records the heterodyne FMCW ladar signal and the instantaneous laser frequency at sweep rates up to 3400 THz/s, as measured against a free-running frequency comb (femtosecond fiber laser). Demodulation of the ladar signal against the instantaneous laser frequency yields the range to the target with 1 ms update rates, bandwidth-limited 130 μm resolution and a ~100 nm accuracy that is directly linked to the counted repetition rate of the comb. The precision is <100 nm at the 1 ms update rate and reaches ~6 nm for a 100 ms average. PMID:23938965

  14. Interaction of cosmic ray muons with spent nuclear fuel dry casks and determination of lower detection limit

    NASA Astrophysics Data System (ADS)

    Chatzidakis, S.; Choi, C. K.; Tsoukalas, L. H.

    2016-08-01

    The potential non-proliferation monitoring of spent nuclear fuel sealed in dry casks interacting continuously with the naturally generated cosmic ray muons is investigated. Treatments on the muon RMS scattering angle by Moliere, Rossi-Greisen, Highland and, Lynch-Dahl were analyzed and compared with simplified Monte Carlo simulations. The Lynch-Dahl expression has the lowest error and appears to be appropriate when performing conceptual calculations for high-Z, thick targets such as dry casks. The GEANT4 Monte Carlo code was used to simulate dry casks with various fuel loadings and scattering variance estimates for each case were obtained. The scattering variance estimation was shown to be unbiased and using Chebyshev's inequality, it was found that 106 muons will provide estimates of the scattering variances that are within 1% of the true value at a 99% confidence level. These estimates were used as reference values to calculate scattering distributions and evaluate the asymptotic behavior for small variations on fuel loading. It is shown that the scattering distributions between a fully loaded dry cask and one with a fuel assembly missing initially overlap significantly but their distance eventually increases with increasing number of muons. One missing fuel assembly can be distinguished from a fully loaded cask with a small overlapping between the distributions which is the case of 100,000 muons. This indicates that the removal of a standard fuel assembly can be identified using muons providing that enough muons are collected. A Bayesian algorithm was developed to classify dry casks and provide a decision rule that minimizes the risk of making an incorrect decision. The algorithm performance was evaluated and the lower detection limit was determined.

  15. Application and Limitations of GPS Radio Occultation (GPS-RO) Data for Atmospheric Boundary Layer Height Detection over the Arctic.

    NASA Astrophysics Data System (ADS)

    Ganeshan, M.; Wu, D. L.

    2014-12-01

    Due to recent changes in the Arctic environment, it is important to monitor the atmospheric boundary layer (ABL) properties over the Arctic Ocean, especially to explore the variability in ABL clouds (such as sensitivity and feedback to sea ice loss). For example, radiosonde and satellite observations of the Arctic ABL height (and low-cloud cover) have recently suggested a positive response to sea ice loss during October that may not occur during the melt season (June-September). Owing to its high vertical and spatiotemporal resolution, an independent ABL height detection algorithm using GPS Radio Occultation (GPS-RO) refractivity in the Arctic is explored. Similar GPS-RO algorithms developed previously typically define the level of the most negative moisture gradient as the ABL height. This definition is favorable for subtropical oceans where a stratocumulus-topped ABL is often capped by a layer of sharp moisture lapse rate (coincident with the temperature inversion). The Arctic Ocean is also characterized by stratocumulus cloud cover, however, the specific humidity does not frequently decrease in the ABL capping inversion. The use of GPS-RO refractivity for ABL height retrieval therefore becomes more complex. During winter months (December-February), when the total precipitable water in the troposphere is a minimum, a fairly straightforward algorithm for ABL height retrieval is developed. The applicability and limitations of this method for other seasons (Spring, Summer, Fall) is determined. The seasonal, interannual and spatial variability in the GPS-derived ABL height over the Arctic Ocean, as well as its relation to the underlying surface (ice vs. water), is investigated. The GPS-RO profiles are also explored for the evidence of low-level moisture transport in the cold Arctic environment.

  16. Determination of absolute internal conversion coefficients using the SAGE spectrometer

    NASA Astrophysics Data System (ADS)

    Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.

    2016-03-01

    A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.

  17. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed. PMID:19831037

  18. In situ TDLAS measurement of absolute acetylene concentration profiles in a non-premixed laminar counter-flow flame

    NASA Astrophysics Data System (ADS)

    Wagner, S.; Klein, M.; Kathrotia, T.; Riedel, U.; Kissel, T.; Dreizler, A.; Ebert, V.

    2012-06-01

    Acetylene (C2H2), as an important precursor for chemiluminescence species, is a key to understand, simulate and model the chemiluminescence and the related reaction paths. Hence we developed a high resolution spectrometer based on direct Tunable Diode Laser Absorption Spectroscopy (TDLAS) allowing the first quantitative, calibration-free and spatially resolved in situ C2H2 measurement in an atmospheric non-premixed counter-flow flame supported on a Tsuji burner. A fiber-coupled distributed feedback diode laser near 1535 nm was used to measure several absolute C2H2 concentration profiles (peak concentrations up to 9700 ppm) in a laminar non-premixed CH4/air flame ( T up to 1950 K) supported on a modified Tsuji counter-flow burner with N2 purge slots to minimize end flames. We achieve a fractional optical resolution of up to 5×10-5 OD (1 σ) in the flame, resulting in temperature-dependent acetylene detection limits for the P17e line at 6513 cm-1 of up to 2.1 ppmṡm. Absolute C2H2 concentration profiles were obtained by translating the burner through the laser beam using a DC motor with 100 μm step widths. Intercomparisons of the experimental C2H2 profiles with simulations using our new hydrocarbon oxidation mechanisms show excellent agreement in position, shape and in the absolute C2H2 values.

  19. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  20. 40 CFR Appendix B to Part 136 - Definition and Procedure for the Determination of the Method Detection Limit-Revision 1.11

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 23 2014-07-01 2014-07-01 false Definition and Procedure for the Determination of the Method Detection Limit-Revision 1.11 B Appendix B to Part 136 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS (CONTINUED) GUIDELINES ESTABLISHING TEST PROCEDURES FOR THE ANALYSIS OF POLLUTANTS...

  1. Absolute isotopic abundances of TI in meteorites

    NASA Astrophysics Data System (ADS)

    Niederer, F. R.; Papanastassiou, D. A.; Wasserburg, G. J.

    1985-03-01

    The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46Ti/48Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. The authors provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components.

  2. Molecular iodine absolute frequencies. Final report

    SciTech Connect

    Sansonetti, C.J.

    1990-06-25

    Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

  3. Stimulus probability effects in absolute identification.

    PubMed

    Kent, Christopher; Lamberts, Koen

    2016-05-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record PMID:26478959

  4. Absolute Performance of AUSGeoid09 in Mountainous Regions

    NASA Astrophysics Data System (ADS)

    Sussanna, Vittorio; Janssen, Volker; Gibbings, Peter

    2014-09-01

    The Australian Height Datum (AHD) is the current national vertical datum for Australia, and AUSGeoid09 is the latest quasigeoid model used to compute (normal-orthometric)AHDheights fromGlobalNavigation Satellite System (GNSS) derived ellipsoidal heights. While previous studies have evaluated the AUSGeoid09 model across Australia, such studies have not focused on mountainous regions in particular. This paper investigates the performance of AUSGeoid09 in an absolute sense in the Mid Hunter and Snowy Mountains regions of New South Wales. Absolute (i.e. single point) comparisons were undertaken between AUSGeoid09-derived heights and published AHD heights. The performance of AUSGeoid09 was evaluated relative to its predecessor AUSGeoid98. In both study areas, an overall improvement is evident when applying AUSGeoid09 to compute AHD heights in an absolute sense. In the MidHunter, AUSGeoid09 provided a substantial improvement over its predecessor, clearly demonstrating the benefits of its new geometric component on GNSS-derived AHD height determination. In the Snowy Mountains, moderate improvement over AUSGeoid98 was evident. However, a slope was detected for AUSGeoid09 residuals, and it appears that the geometric component may have overcompensated for sea surface topography in this area. While this appraisal of AUSGeoid09 performance in mountainous regions is encouraging, it has been shown that some discrepancies still remain between AUSGeoid09-derived heights and AHD. Eventually, a new vertical datum will be necessary to ensure homogeneity across Australia.

  5. Precise Measurement of the Absolute Fluorescence Yield

    NASA Astrophysics Data System (ADS)

    Ave, M.; Bohacova, M.; Daumiller, K.; Di Carlo, P.; di Giulio, C.; San Luis, P. Facal; Gonzales, D.; Hojvat, C.; Hörandel, J. R.; Hrabovsky, M.; Iarlori, M.; Keilhauer, B.; Klages, H.; Kleifges, M.; Kuehn, F.; Monasor, M.; Nozka, L.; Palatka, M.; Petrera, S.; Privitera, P.; Ridky, J.; Rizi, V.; D'Orfeuil, B. Rouille; Salamida, F.; Schovanek, P.; Smida, R.; Spinka, H.; Ulrich, A.; Verzi, V.; Williams, C.

    2011-09-01

    We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources--the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

  6. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed. PMID:26022836

  7. Sample-morphology effects on x-ray photoelectron peak intensities. II. Estimation of detection limits for thin-film materials

    SciTech Connect

    Powell, Cedric J.; Werner, Wolfgang S. M.; Smekal, Werner

    2014-09-01

    The authors show that the National Institute of Standards and Technology database for the simulation of electron spectra for surface analysis (SESSA) can be used to determine detection limits for thin-film materials such as a thin film on a substrate or buried at varying depths in another material for common x-ray photoelectron spectroscopy (XPS) measurement conditions. Illustrative simulations were made for a W film on or in a Ru matrix and for a Ru film on or in a W matrix. In the former case, the thickness of a W film at a given depth in the Ru matrix was varied so that the intensity of the W 4d{sub 5/2} peak was essentially the same as that for a homogeneous RuW{sub 0.001} alloy. Similarly, the thickness of a Ru film at a selected depth in the W matrix was varied so that the intensity of the Ru 3p{sub 3/2} peak matched that from a homogeneous WRu{sub 0.01} alloy. These film thicknesses correspond to the detection limits of each minor component for measurement conditions where the detection limits for a homogeneous sample varied between 0.1 at. % (for the RuW{sub 0.001} alloy) and 1 at. % (for the WRu{sub 0.01} alloy). SESSA can be similarly used to convert estimates of XPS detection limits for a minor species in a homogeneous solid to the corresponding XPS detection limits for that species as a thin film on or buried in the chosen solid.

  8. Absolute partial photoionization cross sections of ozone.

    SciTech Connect

    Berkowitz, J.; Chemistry

    2008-04-01

    Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

  9. Solving Absolute Value Equations Algebraically and Geometrically

    ERIC Educational Resources Information Center

    Shiyuan, Wei

    2005-01-01

    The way in which students can improve their comprehension by understanding the geometrical meaning of algebraic equations or solving algebraic equation geometrically is described. Students can experiment with the conditions of the absolute value equation presented, for an interesting way to form an overall understanding of the concept.

  10. Teaching Absolute Value Inequalities to Mature Students

    ERIC Educational Resources Information Center

    Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea

    2011-01-01

    This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…

  11. On Relative and Absolute Conviction in Mathematics

    ERIC Educational Resources Information Center

    Weber, Keith; Mejia-Ramos, Juan Pablo

    2015-01-01

    Conviction is a central construct in mathematics education research on justification and proof. In this paper, we claim that it is important to distinguish between absolute conviction and relative conviction. We argue that researchers in mathematics education frequently have not done so and this has lead to researchers making unwarranted claims…

  12. Absolute Points for Multiple Assignment Problems

    ERIC Educational Resources Information Center

    Adlakha, V.; Kowalski, K.

    2006-01-01

    An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…

  13. Nonequilibrium equalities in absolutely irreversible processes

    NASA Astrophysics Data System (ADS)

    Murashita, Yuto; Funo, Ken; Ueda, Masahito

    2015-03-01

    Nonequilibrium equalities have attracted considerable attention in the context of statistical mechanics and information thermodynamics. Integral nonequilibrium equalities reveal an ensemble property of the entropy production σ as = 1 . Although nonequilibrium equalities apply to rather general nonequilibrium situations, they break down in absolutely irreversible processes, where the forward-path probability vanishes and the entropy production diverges. We identify the mathematical origins of this inapplicability as the singularity of probability measure. As a result, we generalize conventional integral nonequilibrium equalities to absolutely irreversible processes as = 1 -λS , where λS is the probability of the singular part defined based on Lebesgue's decomposition theorem. The acquired equality contains two physical quantities related to irreversibility: σ characterizing ordinary irreversibility and λS describing absolute irreversibility. An inequality derived from the obtained equality demonstrates the absolute irreversibility leads to the fundamental lower bound on the entropy production. We demonstrate the validity of the obtained equality for a simple model.

  14. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  15. Precision absolute positional measurement of laser beams.

    PubMed

    Fitzsimons, Ewan D; Bogenstahl, Johanna; Hough, James; Killow, Christian J; Perreur-Lloyd, Michael; Robertson, David I; Ward, Henry

    2013-04-20

    We describe an instrument which, coupled with a suitable coordinate measuring machine, facilitates the absolute measurement within the machine frame of the propagation direction of a millimeter-scale laser beam to an accuracy of around ±4 μm in position and ±20 μrad in angle. PMID:23669658

  16. Effects of Kapton Sample Cell Windows on the Detection Limit of Smectite: Implications for CheMin on the Mars Science Laboratory Mission

    NASA Technical Reports Server (NTRS)

    Achilles, C. N.; Ming, Douglas W.; Morris, R. V.; Blake, D. F.

    2012-01-01

    The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity is an X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of providing the mineralogical and chemical compositions of rocks and soils on the surface of Mars. CheMin uses a microfocus X-ray tube with a Co target, transmission geometry, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. CheMin has two different window materials used for sample cells -- Mylar and Kapton. Instrument details are provided elsewhere. Fe/Mg-smectite (e.g., nontronite) has been identified in Gale Crater, the MSL future landing site, by CRISM spectra. While large quantities of phyllosilicate minerals will be easily detected by CheMin, it is important to establish detection limits of such phases to understand capabilities and limitations of the instrument. A previous study indicated that the (001) peak of smectite at 15 Ang was detectable in a mixture of 1 wt.% smectite with olivine when Mylar is the window material for the sample cell. Complications arise when Kapton is the window material because Kapton itself also has a diffraction peak near 15 Ang (6.8 deg 2 Theta). This study presents results of mineral mixtures of smectite and olivine to determine smectite detection limits for Kapton sample cells. Because the intensity and position of the smectite (001) peak depends on the hydration state, we also analyzed mixtures with "hydrated" and "dehydrated"h smectite to examine the effects of hydration state on detection limits.

  17. Enhancement of laser-induced breakdown spectroscopy (LIBS) Detection limit using a low-pressure and short-pulse laser-induced plasma process.

    PubMed

    Wang, Zhen Zhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Yan, Jun Jie; Liu, Ji Ping

    2013-11-01

    Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process. PMID:24160875

  18. Picoliter Well Array Chip-Based Digital Recombinase Polymerase Amplification for Absolute Quantification of Nucleic Acids

    PubMed Central

    Li, Zhao; Liu, Yong; Wei, Qingquan; Liu, Yuanjie; Liu, Wenwen; Zhang, Xuelian; Yu, Yude

    2016-01-01

    Absolute, precise quantification methods expand the scope of nucleic acids research and have many practical applications. Digital polymerase chain reaction (dPCR) is a powerful method for nucleic acid detection and absolute quantification. However, it requires thermal cycling and accurate temperature control, which are difficult in resource-limited conditions. Accordingly, isothermal methods, such as recombinase polymerase amplification (RPA), are more attractive. We developed a picoliter well array (PWA) chip with 27,000 consistently sized picoliter reactions (314 pL) for isothermal DNA quantification using digital RPA (dRPA) at 39°C. Sample loading using a scraping liquid blade was simple, fast, and required small reagent volumes (i.e., <20 μL). Passivating the chip surface using a methoxy-PEG-silane agent effectively eliminated cross-contamination during dRPA. Our creative optical design enabled wide-field fluorescence imaging in situ and both end-point and real-time analyses of picoliter wells in a 6-cm2 area. It was not necessary to use scan shooting and stitch serial small images together. Using this method, we quantified serial dilutions of a Listeria monocytogenes gDNA stock solution from 9 × 10-1 to 4 × 10-3 copies per well with an average error of less than 11% (N = 15). Overall dRPA-on-chip processing required less than 30 min, which was a 4-fold decrease compared to dPCR, requiring approximately 2 h. dRPA on the PWA chip provides a simple and highly sensitive method to quantify nucleic acids without thermal cycling or precise micropump/microvalve control. It has applications in fast field analysis and critical clinical diagnostics under resource-limited settings. PMID:27074005

  19. Picoliter Well Array Chip-Based Digital Recombinase Polymerase Amplification for Absolute Quantification of Nucleic Acids.

    PubMed

    Li, Zhao; Liu, Yong; Wei, Qingquan; Liu, Yuanjie; Liu, Wenwen; Zhang, Xuelian; Yu, Yude

    2016-01-01

    Absolute, precise quantification methods expand the scope of nucleic acids research and have many practical applications. Digital polymerase chain reaction (dPCR) is a powerful method for nucleic acid detection and absolute quantification. However, it requires thermal cycling and accurate temperature control, which are difficult in resource-limited conditions. Accordingly, isothermal methods, such as recombinase polymerase amplification (RPA), are more attractive. We developed a picoliter well array (PWA) chip with 27,000 consistently sized picoliter reactions (314 pL) for isothermal DNA quantification using digital RPA (dRPA) at 39°C. Sample loading using a scraping liquid blade was simple, fast, and required small reagent volumes (i.e., <20 μL). Passivating the chip surface using a methoxy-PEG-silane agent effectively eliminated cross-contamination during dRPA. Our creative optical design enabled wide-field fluorescence imaging in situ and both end-point and real-time analyses of picoliter wells in a 6-cm(2) area. It was not necessary to use scan shooting and stitch serial small images together. Using this method, we quantified serial dilutions of a Listeria monocytogenes gDNA stock solution from 9 × 10(-1) to 4 × 10(-3) copies per well with an average error of less than 11% (N = 15). Overall dRPA-on-chip processing required less than 30 min, which was a 4-fold decrease compared to dPCR, requiring approximately 2 h. dRPA on the PWA chip provides a simple and highly sensitive method to quantify nucleic acids without thermal cycling or precise micropump/microvalve control. It has applications in fast field analysis and critical clinical diagnostics under resource-limited settings. PMID:27074005

  20. A Day in the Life of Millisecond Pulsar J1713+0747: Limits on Timing Precision Over 24 Hours and Implications for Gravitational Wave Detection

    NASA Astrophysics Data System (ADS)

    Dolch, Timothy; Bailes, M.; Bassa, C.; Bhat, R.; Bhattacharyya, B.; Champion, D.; Chatterjee, S.; Cognard, I.; Cordes, J. M.; Crowter, K.; Demorest, P.; Finn, L. S.; Fonseca, E.; Hessels, J.; Hobbs, G.; Janssen, G.; Jones, G.; Jordan, C.; Karuppusamy, R.; Keith, M.; Kramer, M.; Kraus, A.; Lam, M. T.; Lazarus, P.; Lazio, J.; Lee, K.; Levin, L.; Liu, K.; Lorimer, D.; Manchester, R. N.; McLaughlin, M.; Palliyaguru, N.; Perrodin, D.; Petroff, E.; Rajwade, K.; Rankin, J. M.; Ransom, S. M.; Rosenblum, J.; Roy, J.; Shannon, R.; Stappers, B.; Stinebring, D.; Stovall, K.; Teixeira, M.; van Leeuwen, J.; van Straten, W.; Verbiest, J.; Zhu, W.

    2014-01-01

    A 24-hour global observation of millisecond radio pulsar J1713+0747 was undertaken by the International Pulsar Timing Array (IPTA) collaboration as an effort to better quantify sources of noise in this object, which is regularly timed for the purpose of detecting gravitational waves (GWs). Given an 8-year timing RMS of 30ns, it is regarded as one of the best precision clocks in the PTA. However, sources of timing noise visible on timescales longer than the usual 20-30min biweekly observation may nonetheless be present. Data from the campaign were taken contiguously with the Parkes, Arecibo, Green Bank, GMRT, LOFAR, Effelsberg, WSRT, Lovell, and Nancay radio telescopes. The combined pulse times-of-arrival provide an estimate of the absolute noise floor, in other words, what unaccounted sources of timing noise impede an otherwise simple sqrt(N) improvement in timing precision, where N is the number of pulses in a single observing session. We present first results of specific phenomena probed on the unusual timescale of tens of hours, in particular interstellar scattering (ISS), and discuss the degree to which ISS affects precision timing. Finally, we examine single pulse information during selected portions of the observation and determine the degree to which the pulse jitter of J1713+0747 varies throughout the course of the day-long dataset.

  1. Water vapour emission in vegetable fuel: absorption cell measurements and detection limits of our CO II Dial system

    NASA Astrophysics Data System (ADS)

    Bellecci, C.; De Leo, L.; Gaudio, P.; Gelfusa, M.; Lo Feudo, T.; Martellucci, S.; Richetta, M.

    2006-09-01

    Forest fires can be the cause of serious environmental and economic damages. For this reason a considerable effort has been directed toward the forest protection and fire fighting. In the early forest fire detection, Lidar technique present considerable advantages compared to the passive detection methods based on infrared cameras currently in common use, due its higher sensitivity and ability to accurately locate the fire. The combustion phase of the vegetable matter causes a great amount of water vapour emission, thus the water molecule behaviour will be studied to obtain a fire detection system ready and efficient also before the flame propagation. A first evaluation of increment of the water vapour concentration compared to standard one will be estimated by a numerical simulation. These results will be compared with the experimental measurements carried out into a cell with a CO II Dial system, burning different kinds of vegetable fuel. Our results and their comparison will be reported in this paper.

  2. Behavior of Multiclass Pesticide Residue Concentrations during the Transformation from Rose Petals to Rose Absolute.

    PubMed

    Tascone, Oriane; Fillâtre, Yoann; Roy, Céline; Meierhenrich, Uwe J

    2015-05-27

    This study investigates the concentrations of 54 multiclass pesticides during the transformation processes from rose petal to concrete and absolute using roses spiked with pesticides as a model. The concentrations of the pesticides were followed during the process of transforming the spiked rose flowers from an organic field into concrete and then into absolute. The rose flowers, the concrete, and the absolute, as well as their transformation intermediates, were analyzed for pesticide content using gas chromatography/tandem mass spectrometry. We observed that all the pesticides were extracted and concentrated in the absolute, with the exception of three molecules: fenthion, fenamiphos, and phorate. Typical pesticides were found to be concentrated by a factor of 100-300 from the rose flowers to the rose absolute. The observed effect of pesticide enrichment was also studied in roses and their extracts from four classically phytosanitary treated fields. Seventeen pesticides were detected in at least one of the extracts. Like the case for the spiked samples in our model, the pesticides present in the rose flowers from Turkey were concentrated in the absolute. Two pesticides, methidathion and chlorpyrifos, were quantified in the rose flowers at approximately 0.01 and 0.01-0.05 mg kg(-1), respectively, depending on the treated field. The concentrations determined for the corresponding rose absolutes were 4.7 mg kg(-1) for methidathion and 0.65-27.25 mg kg(-1) for chlorpyrifos. PMID:25942486

  3. Detection of Microbial Water Quality Indicators and Fecal Waterborne Pathogens in Environmental Waters: A Review of Methods, Applications, and Limitations

    EPA Science Inventory

    Environmental waters are important reservoirs of pathogenic microorganisms, many of which are of fecal origin. In most cases, the presence of pathogens is determined using surrogate bacterial indicators. In other cases, direct detection of the pathogen in question is required. M...

  4. Markov dynamics as a zooming lens for multiscale community detection: non clique-like communities and the field-of-view limit.

    PubMed

    Schaub, Michael T; Delvenne, Jean-Charles; Yaliraki, Sophia N; Barahona, Mauricio

    2012-01-01

    In recent years, there has been a surge of interest in community detection algorithms for complex networks. A variety of computational heuristics, some with a long history, have been proposed for the identification of communities or, alternatively, of good graph partitions. In most cases, the algorithms maximize a particular objective function, thereby finding the 'right' split into communities. Although a thorough comparison of algorithms is still lacking, there has been an effort to design benchmarks, i.e., random graph models with known community structure against which algorithms can be evaluated. However, popular community detection methods and benchmarks normally assume an implicit notion of community based on clique-like subgraphs, a form of community structure that is not always characteristic of real networks. Specifically, networks that emerge from geometric constraints can have natural non clique-like substructures with large effective diameters, which can be interpreted as long-range communities. In this work, we show that long-range communities escape detection by popular methods, which are blinded by a restricted 'field-of-view' limit, an intrinsic upper scale on the communities they can detect. The field-of-view limit means that long-range communities tend to be overpartitioned. We show how by adopting a dynamical perspective towards community detection [1], [2], in which the evolution of a Markov process on the graph is used as a zooming lens over the structure of the network at all scales, one can detect both clique- or non clique-like communities without imposing an upper scale to the detection. Consequently, the performance of algorithms on inherently low-diameter, clique-like benchmarks may not always be indicative of equally good results in real networks with local, sparser connectivity. We illustrate our ideas with constructive examples and through the analysis of real-world networks from imaging, protein structures and the power grid, where a

  5. Markov Dynamics as a Zooming Lens for Multiscale Community Detection: Non Clique-Like Communities and the Field-of-View Limit

    PubMed Central

    Schaub, Michael T.; Delvenne, Jean-Charles; Yaliraki, Sophia N.; Barahona, Mauricio

    2012-01-01

    In recent years, there has been a surge of interest in community detection algorithms for complex networks. A variety of computational heuristics, some with a long history, have been proposed for the identification of communities or, alternatively, of good graph partitions. In most cases, the algorithms maximize a particular objective function, thereby finding the ‘right’ split into communities. Although a thorough comparison of algorithms is still lacking, there has been an effort to design benchmarks, i.e., random graph models with known community structure against which algorithms can be evaluated. However, popular community detection methods and benchmarks normally assume an implicit notion of community based on clique-like subgraphs, a form of community structure that is not always characteristic of real networks. Specifically, networks that emerge from geometric constraints can have natural non clique-like substructures with large effective diameters, which can be interpreted as long-range communities. In this work, we show that long-range communities escape detection by popular methods, which are blinded by a restricted ‘field-of-view’ limit, an intrinsic upper scale on the communities they can detect. The field-of-view limit means that long-range communities tend to be overpartitioned. We show how by adopting a dynamical perspective towards community detection [1], [2], in which the evolution of a Markov process on the graph is used as a zooming lens over the structure of the network at all scales, one can detect both clique- or non clique-like communities without imposing an upper scale to the detection. Consequently, the performance of algorithms on inherently low-diameter, clique-like benchmarks may not always be indicative of equally good results in real networks with local, sparser connectivity. We illustrate our ideas with constructive examples and through the analysis of real-world networks from imaging, protein structures and the power grid

  6. Absolute and relative quantification of RNA modifications via biosynthetic isotopomers

    PubMed Central

    Kellner, Stefanie; Ochel, Antonia; Thüring, Kathrin; Spenkuch, Felix; Neumann, Jennifer; Sharma, Sunny; Entian, Karl-Dieter; Schneider, Dirk; Helm, Mark

    2014-01-01

    In the resurging field of RNA modifications, quantification is a bottleneck blocking many exciting avenues. With currently over 150 known nucleoside alterations, detection and quantification methods must encompass multiple modifications for a comprehensive profile. LC–MS/MS approaches offer a perspective for comprehensive parallel quantification of all the various modifications found in total RNA of a given organism. By feeding 13C-glucose as sole carbon source, we have generated a stable isotope-labeled internal standard (SIL-IS) for bacterial RNA, which facilitates relative comparison of all modifications. While conventional SIL-IS approaches require the chemical synthesis of single modifications in weighable quantities, this SIL-IS consists of a nucleoside mixture covering all detectable RNA modifications of Escherichia coli, yet in small and initially unknown quantities. For absolute in addition to relative quantification, those quantities were determined by a combination of external calibration and sample spiking of the biosynthetic SIL-IS. For each nucleoside, we thus obtained a very robust relative response factor, which permits direct conversion of the MS signal to absolute amounts of substance. The application of the validated SIL-IS allowed highly precise quantification with standard deviations <2% during a 12-week period, and a linear dynamic range that was extended by two orders of magnitude. PMID:25129236

  7. Absolute Quantification of Norovirus Capsid Protein in Food, Water, and Soil Using Synthetic Peptides with Electrospray and MALDI Mass Spectrometry

    PubMed Central

    Hartmann, Erica M.; Colquhoun, David R.; Schwab, Kellogg J.; Halden, Rolf U.

    2015-01-01

    Norovirus infections are one of the most prominent public health problems of microbial origin in the U.S. and other industrialized countries. Surveillance is necessary to prevent secondary infection, confirm successful cleanup after outbreaks, and track the causative agent. Quantitative mass spectrometry, based on absolute quantitation with stable-isotope labeled peptides, is a promising tool for norovirus monitoring because of its speed, sensitivity, and robustness in the face of environmental inhibitors. In the current study, we present two new methods for the detection of the norovirus genogroup I capsid protein using electrospray and matrixassisted laser desorption/ionization (MALDI) mass spectrometry. The peptide TLDPIEVPLEDVR was used to quantify norovirus-like particles down to 500 attomoles with electrospray and 100 attomoles with MALDI. With MALDI, we also demonstrate a detection limit of 1 femtomole and a quantitative dynamic range of 5 orders of magnitude in the presence of an environmental matrix effect. Due to the rapid processing time and applicability to a wide range of environmental sample types (bacterial lysate, produce, milk, soil, and groundwater), mass spectrometry-based absolute quantitation has a strong potential for use in public health and environmental sciences. PMID:25603302

  8. Absolute quantification of norovirus capsid protein in food, water, and soil using synthetic peptides with electrospray and MALDI mass spectrometry.

    PubMed

    Hartmann, Erica M; Colquhoun, David R; Schwab, Kellogg J; Halden, Rolf U

    2015-04-01

    Norovirus infections are one of the most prominent public health problems of microbial origin in the U.S. and other industrialized countries. Surveillance is necessary to prevent secondary infection, confirm successful cleanup after outbreaks, and track the causative agent. Quantitative mass spectrometry, based on absolute quantitation with stable-isotope labeled peptides, is a promising tool for norovirus monitoring because of its speed, sensitivity, and robustness in the face of environmental inhibitors. In the current study, we present two new methods for the detection of the norovirus genogroup I capsid protein using electrospray and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The peptide TLDPIEVPLEDVR was used to quantify norovirus-like particles down to 500 attomoles with electrospray and 100 attomoles with MALDI. With MALDI, we also demonstrate a detection limit of 1 femtomole and a quantitative dynamic range of 5 orders of magnitude in the presence of an environmental matrix effect. Due to the rapid processing time and applicability to a wide range of environmental sample types (bacterial lysate, produce, milk, soil, and groundwater), mass spectrometry-based absolute quantitation has a strong potential for use in public health and environmental sciences. PMID:25603302

  9. Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them

    PubMed Central

    Trofimov, Vyacheslav A.; Varentsova, Svetlana A.

    2016-01-01

    Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with a thick paper bag as well as with Si-based semiconductors under laboratory conditions. In fact, standard THz spectroscopy leads to false detection of hazardous substances in neutral samples, which do not contain them. This disadvantage of the THz TDS method can be overcome by using time-dependent THz pulse spectrum analysis. For a quality assessment of the standard substance spectral features presence in the signal under analysis, one may use time-dependent integral correlation criteria. PMID:27070617

  10. Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them.

    PubMed

    Trofimov, Vyacheslav A; Varentsova, Svetlana A

    2016-01-01

    Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with a thick paper bag as well as with Si-based semiconductors under laboratory conditions. In fact, standard THz spectroscopy leads to false detection of hazardous substances in neutral samples, which do not contain them. This disadvantage of the THz TDS method can be overcome by using time-dependent THz pulse spectrum analysis. For a quality assessment of the standard substance spectral features presence in the signal under analysis, one may use time-dependent integral correlation criteria. PMID:27070617

  11. Absolute far-ultraviolet spectrophotometry of hot subluminous stars from Voyager

    SciTech Connect

    Holberg, J.B.; Ali, B.; Carone, T.E.; Polidan, R.S. NASA, Goddard Space Flight Center, Greenbelt, MD )

    1991-07-01

    Observations, obtained with the Voyager ultraviolet spectrometers, are presented of absolute fluxes for two well-known hot subluminous stars: BD + 28 deg 4211, an sdO, and G191 - B2B, a hot DA white dwarf. Complete absolute energy distributions for these two stars, from the Lyman limit at 912 A to 1 micron, are given. For BD + 28 deg 4211, a single power law closely represents the entire observed energy distribution. For G191 - B2B, a pure hydrogen model atmosphere provides an excellent match to the entire absolute energy distribution. Voyager absolute fluxes are discussed in relation to those reported from various sounding rocket experiments, including a recent rocket observation of BD + 28 deg 4211. 43 refs.

  12. Detection and differentiation of herpes simplex viruses by use of the viper platform: advantages, limitations, and concerns.

    PubMed

    Lang, Amanda L S; Roberts, Catherine; Mazzulli, Tony; Hatchette, Todd F; LeBlanc, Jason J

    2014-06-01

    The Viper HSV-Q(x) assay was evaluated for the detection of herpes simplex virus 1 (HSV-1) and HSV-2 in specimens from oral, anogenital, and other miscellaneous sites. The HSV-Q(x) assay was found to be highly sensitive and accurate; however, a gray zone may be required for specimens with values falling between 50 and 800 maximum relative fluorescence units. PMID:24696023

  13. Absolute and relative dosimetry for ELIMED

    SciTech Connect

    Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F.; Carpinelli, M.; Presti, D. Lo; Raffaele, L.; Tramontana, A.; Cirio, R.; Sacchi, R.; Monaco, V.; Marchetto, F.; Giordanengo, S.

    2013-07-26

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  14. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  15. Absolute radiometry and the solar constant

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1974-01-01

    A series of active cavity radiometers (ACRs) are described which have been developed as standard detectors for the accurate measurement of irradiance in absolute units. It is noted that the ACR is an electrical substitution calorimeter, is designed for automatic remote operation in any environment, and can make irradiance measurements in the range from low-level IR fluxes up to 30 solar constants with small absolute uncertainty. The instrument operates in a differential mode by chopping the radiant flux to be measured at a slow rate, and irradiance is determined from two electrical power measurements together with the instrumental constant. Results are reported for measurements of the solar constant with two types of ACRs. The more accurate measurement yielded a value of 136.6 plus or minus 0.7 mW/sq cm (1.958 plus or minus 0.010 cal/sq cm per min).

  16. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  17. Absolute calibration of TFTR helium proportional counters

    SciTech Connect

    Strachan, J.D.; Diesso, M.; Jassby, D.; Johnson, L.; McCauley, S.; Munsat, T.; Roquemore, A.L.; Barnes, C.W. |; Loughlin, M. |

    1995-06-01

    The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 msec and 50 msec depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments.

  18. Absolute enantioselective separation: optical activity ex machina.

    PubMed

    Bielski, Roman; Tencer, Michal

    2005-11-01

    The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. PMID:16342798

  19. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  20. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  1. Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity

    NASA Astrophysics Data System (ADS)

    Jensen, Kasper; Budvytyte, Rima; Thomas, Rodrigo A.; Wang, Tian; Fuchs, Annette M.; Balabas, Mikhail V.; Vasilakis, Georgios; Mosgaard, Lars D.; Stærkind, Hans C.; Müller, Jörg H.; Heimburg, Thomas; Olesen, Søren-Peter; Polzik, Eugene S.

    2016-07-01

    Magnetic fields generated by human and animal organs, such as the heart, brain and nervous system carry information useful for biological and medical purposes. These magnetic fields are most commonly detected using cryogenically-cooled superconducting magnetometers. Here we present the first detection of action potentials from an animal nerve using an optical atomic magnetometer. Using an optimal design we are able to achieve the sensitivity dominated by the quantum shot noise of light and quantum projection noise of atomic spins. Such sensitivity allows us to measure the nerve impulse with a miniature room-temperature sensor which is a critical advantage for biomedical applications. Positioning the sensor at a distance of a few millimeters from the nerve, corresponding to the distance between the skin and nerves in biological studies, we detect the magnetic field generated by an action potential of a frog sciatic nerve. From the magnetic field measurements we determine the activity of the nerve and the temporal shape of the nerve impulse. This work opens new ways towards implementing optical magnetometers as practical devices for medical diagnostics.

  2. Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity.

    PubMed

    Jensen, Kasper; Budvytyte, Rima; Thomas, Rodrigo A; Wang, Tian; Fuchs, Annette M; Balabas, Mikhail V; Vasilakis, Georgios; Mosgaard, Lars D; Stærkind, Hans C; Müller, Jörg H; Heimburg, Thomas; Olesen, Søren-Peter; Polzik, Eugene S

    2016-01-01

    Magnetic fields generated by human and animal organs, such as the heart, brain and nervous system carry information useful for biological and medical purposes. These magnetic fields are most commonly detected using cryogenically-cooled superconducting magnetometers. Here we present the first detection of action potentials from an animal nerve using an optical atomic magnetometer. Using an optimal design we are able to achieve the sensitivity dominated by the quantum shot noise of light and quantum projection noise of atomic spins. Such sensitivity allows us to measure the nerve impulse with a miniature room-temperature sensor which is a critical advantage for biomedical applications. Positioning the sensor at a distance of a few millimeters from the nerve, corresponding to the distance between the skin and nerves in biological studies, we detect the magnetic field generated by an action potential of a frog sciatic nerve. From the magnetic field measurements we determine the activity of the nerve and the temporal shape of the nerve impulse. This work opens new ways towards implementing optical magnetometers as practical devices for medical diagnostics. PMID:27417378

  3. Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity

    PubMed Central

    Jensen, Kasper; Budvytyte, Rima; Thomas, Rodrigo A.; Wang, Tian; Fuchs, Annette M.; Balabas, Mikhail V.; Vasilakis, Georgios; Mosgaard, Lars D.; Stærkind, Hans C.; Müller, Jörg H.; Heimburg, Thomas; Olesen, Søren-Peter; Polzik, Eugene S.

    2016-01-01

    Magnetic fields generated by human and animal organs, such as the heart, brain and nervous system carry information useful for biological and medical purposes. These magnetic fields are most commonly detected using cryogenically-cooled superconducting magnetometers. Here we present the first detection of action potentials from an animal nerve using an optical atomic magnetometer. Using an optimal design we are able to achieve the sensitivity dominated by the quantum shot noise of light and quantum projection noise of atomic spins. Such sensitivity allows us to measure the nerve impulse with a miniature room-temperature sensor which is a critical advantage for biomedical applications. Positioning the sensor at a distance of a few millimeters from the nerve, corresponding to the distance between the skin and nerves in biological studies, we detect the magnetic field generated by an action potential of a frog sciatic nerve. From the magnetic field measurements we determine the activity of the nerve and the temporal shape of the nerve impulse. This work opens new ways towards implementing optical magnetometers as practical devices for medical diagnostics. PMID:27417378

  4. Finnigan ion trap mass spectrometer detection limits and thermal energy analyzer interface status report and present capabilities

    SciTech Connect

    Alcaraz, A.; Andresen, B.; Martin, W.

    1990-10-18

    A new Finnigan ion trap mass spectrometer was purchased and installed at LLNL. Over a period of several months the instrument was tested under a variety of conditions utilizing a capillary gas chromatography interface which allowed separated organic compounds to be carried directly into the ion source of the mass spectrometer. This direct interface allowed maximum analytical sensitivity. A variety of critical tests were performed in order to optimize the sensitivity of the system under a variety of analysis conditions. These tests altered the critical time cycles of the ionization, ion trapping, and detection. Various carrier gas pressures were also employed in order to ascertain the overall sensitivity of the instrument. In addition we have also interfaced a thermal energy analyzer (TEA) to the gas chromatograph in order to simultaneously detect volatile nitrogen containing compounds while mass spectral data is being acquired. This is the first application at this laboratory of simultaneous ultra-trace detections while utilizing two orthogonal analytical techniques. In particular, explosive-related compound and/or residues are of interest to the general community in water, soil and gas sampler. In this paper are highlighted a few examples of the analytical power of this new GC-TEA-ITMS technology.

  5. Electrochemical immunosensor for detection of epidermal growth factor reaching lower detection limit: toward oxidized glutathione as a more efficient blocking reagent for the antibody functionalized silver nanoparticles and antigen interaction.

    PubMed

    Lin, Yuqing; Liu, Kangyu; Wang, Chao; Li, Linbo; Liu, Yuxin

    2015-08-18

    Blocking reagent is of vital importance for an immunosensor because it ensures the antifouling of the sensing interface and thus selective determination of the target. This Letter investigates a small inactive peptide, oxidized glutathione (GSSG), to replace the commonly used bovine serum albumin (BSA) as blocking reagent for immunosensor fabrication to lower the detection limit of electrochemical immunosensors. The EGF (epidermal growth factor) detection as an example is used here to compare the blocking effects from GSSG and BSA, respectively. The relatively big size of BSA sterically hinders EGF and antibody functionalized silver nanoparticles (Ab-AgNPs) binding. By comparison, GSSG cannot hinder EGF and Ab-AgNPs binding since it is much smaller than EGF, verified by scanning electron microscopy (SEM) results. The established GSSG blocking-based immunosensor for EGF reaches a very low detection limit of 0.01 pM, exhibits wide linearity range between 0.1 pM and 0.1 μM and is more sensitive than the BSA blocking strategy. The proposed GSSG-blocking strategy in the immunoassay paves an attractive platform for other biomolecules to reach a lower detection limit. PMID:26204199

  6. Long range surface plasmon resonance with ultra-high penetration depth for self-referenced sensing and ultra-low detection limit using diverging beam approach

    SciTech Connect

    Isaacs, Sivan Abdulhalim, Ibrahim

    2015-05-11

    Using an insulator-metal-insulator structure with dielectric having refractive index (RI) larger than the analyte, long range surface plasmon (SP) resonance exhibiting ultra-high penetration depth is demonstrated for sensing applications of large bioentities at wavelengths in the visible range. Based on the diverging beam approach in Kretschmann-Raether configuration, one of the SP resonances is shown to shift in response to changes in the analyte RI while the other is fixed; thus, it can be used as a built in reference. The combination of the high sensitivity, high penetration depth and self-reference using the diverging beam approach in which a dark line is detected of the high sensitivity, high penetration depth, self-reference, and the diverging beam approach in which a dark line is detected using large number of camera pixels with a smart algorithm for sub-pixel resolution, a sensor with ultra-low detection limit is demonstrated suitable for large bioentities.

  7. Limitations to the detection of deception: true and false recollections are poorly distinguished using an event-related potential procedure.

    PubMed

    Allen, John J B; Mertens, Ralf

    2009-01-01

    The utility of using indices of neural function to identify deception relies on finding highly reliable and valid approaches that adequately identify the guilty and exonerate the innocent. A class of approaches, based on the guilty knowledge technique (GKT), assume that guilty individuals will recognize specific crime-relevant details, whereas innocent individuals will not. Memory distortions, however, may limit the accuracy of such procedures. To investigate these limits, two studies were conducted to examine whether brain electrical activity could differentiate true from false recollections elicited by the Deese-Roediger-McDermott (DRM) paradigm. The design of each study maximized the opportunity of finding electrocortical differences between true and false recognition. Each study found very high rates of false recognition, with little evidence that brain electrical activity could differentiate true from false memories. Results suggested that under certain conditions both true and false recollections can produce a pattern of brain activity indicative of recognition. PMID:18633842

  8. Metallic Magnetic Calorimeters for Absolute Activity Measurement

    NASA Astrophysics Data System (ADS)

    Loidl, M.; Leblanc, E.; Rodrigues, M.; Bouchard, J.; Censier, B.; Branger, T.; Lacour, D.

    2008-05-01

    We present a prototype of metallic magnetic calorimeters that we are developing for absolute activity measurements of low energy emitting radionuclides. We give a detailed description of the realization of the prototype, containing an 55Fe source inside the detector absorber. We present the analysis of first data taken with this detector and compare the result of activity measurement with liquid scintillation counting. We also propose some ways for reducing the uncertainty on the activity determination with this new technique.

  9. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1985-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  10. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  11. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  12. Blood pressure targets and absolute cardiovascular risk.

    PubMed

    Odutayo, Ayodele; Rahimi, Kazem; Hsiao, Allan J; Emdin, Connor A

    2015-08-01

    In the Eighth Joint National Committee guideline on hypertension, the threshold for the initiation of blood pressure-lowering treatment for elderly adults (≥60 years) without chronic kidney disease or diabetes mellitus was raised from 140/90 mm Hg to 150/90 mm Hg. However, the committee was not unanimous in this decision, particularly because a large proportion of adults ≥60 years may be at high cardiovascular risk. On the basis of Eighth Joint National Committee guideline, we sought to determine the absolute 10-year risk of cardiovascular disease among these adults through analyzing the National Health and Nutrition Examination Survey (2005-2012). The primary outcome measure was the proportion of adults who were at ≥20% predicted absolute cardiovascular risk and above goals for the Seventh Joint National Committee guideline but reclassified as at target under the Eighth Joint National Committee guideline (reclassified). The Framingham General Cardiovascular Disease Risk Score was used. From 2005 to 2012, the surveys included 12 963 adults aged 30 to 74 years with blood pressure measurements, of which 914 were reclassified based on the guideline. Among individuals reclassified as not in need of additional treatment, the proportion of adults 60 to 74 years without chronic kidney disease or diabetes mellitus at ≥20% absolute risk was 44.8%. This corresponds to 0.8 million adults. The proportion at high cardiovascular risk remained sizable among adults who were not receiving blood pressure-lowering treatment. Taken together, a sizable proportion of reclassified adults 60 to 74 years without chronic kidney disease or diabetes mellitus was at ≥20% absolute cardiovascular risk. PMID:26056340

  13. Relative errors can cue absolute visuomotor mappings.

    PubMed

    van Dam, Loes C J; Ernst, Marc O

    2015-12-01

    When repeatedly switching between two visuomotor mappings, e.g. in a reaching or pointing task, adaptation tends to speed up over time. That is, when the error in the feedback corresponds to a mapping switch, fast adaptation occurs. Yet, what is learned, the relative error or the absolute mappings? When switching between mappings, errors with a size corresponding to the relative difference between the mappings will occur more often than other large errors. Thus, we could learn to correct more for errors with this familiar size (Error Learning). On the other hand, it has been shown that the human visuomotor system can store several absolute visuomotor mappings (Mapping Learning) and can use associated contextual cues to retrieve them. Thus, when contextual information is present, no error feedback is needed to switch between mappings. Using a rapid pointing task, we investigated how these two types of learning may each contribute when repeatedly switching between mappings in the absence of task-irrelevant contextual cues. After training, we examined how participants changed their behaviour when a single error probe indicated either the often-experienced error (Error Learning) or one of the previously experienced absolute mappings (Mapping Learning). Results were consistent with Mapping Learning despite the relative nature of the error information in the feedback. This shows that errors in the feedback can have a double role in visuomotor behaviour: they drive the general adaptation process by making corrections possible on subsequent movements, as well as serve as contextual cues that can signal a learned absolute mapping. PMID:26280315

  14. Absolute distance measurements by variable wavelength interferometry

    NASA Astrophysics Data System (ADS)

    Bien, F.; Camac, M.; Caulfield, H. J.; Ezekiel, S.

    1981-02-01

    This paper describes a laser interferometer which provides absolute distance measurements using tunable lasers. An active feedback loop system, in which the laser frequency is locked to the optical path length difference of the interferometer, is used to tune the laser wavelengths. If the two wavelengths are very close, electronic frequency counters can be used to measure the beat frequency between the two laser frequencies and thus to determine the optical path difference between the two legs of the interferometer.

  15. Surface modification of alignment layer by ultraviolet irradiation to dramatically improve the detection limit of liquid-crystal-based immunoassay for the cancer biomarker CA125.

    PubMed

    Su, Hui-Wen; Lee, Mon-Juan; Lee, Wei

    2015-05-01

    Liquid crystal (LC)-based biosensing has attracted much attention in recent years. We focus on improving the detection limit of LC-based immunoassay techniques by surface modification of the surfactant alignment layer consisting of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP). The cancer biomarker CA125 was detected with an array of anti-CA125 antibodies immobilized on the ultraviolet (UV)-modified DMOAP monolayer. Compared with a pristine counterpart, UV irradiation enhanced the binding affinity of the CA125 antibody and reproducibility of immunodetection in which a detection limit of 0.01 ng∕ml for the cancer biomarker CA125 was achieved. Additionally, the optical texture observed under a crossed polarized microscope was correlated with the analyte concentration. In a proof-of-concept experiment using CA125-spiked human serum as the analyte, specific binding between the CA125 antigen and the anti-CA125 antibody resulted in a distinct and concentration-dependent optical response despite the high background caused by nonspecific binding of other biomolecules in the human serum. Results from this study indicate that UVmodification of the alignment layer, as well as detection with LCs of large birefringence, contributes to the enhanced performance of the label-free LC-based immunodetection, which may be considered a promising alternative to conventional label-based methods. PMID:26000796

  16. Surface modification of alignment layer by ultraviolet irradiation to dramatically improve the detection limit of liquid-crystal-based immunoassay for the cancer biomarker CA125

    NASA Astrophysics Data System (ADS)

    Su, Hui-Wen; Lee, Mon-Juan; Lee, Wei

    2015-05-01

    Liquid crystal (LC)-based biosensing has attracted much attention in recent years. We focus on improving the detection limit of LC-based immunoassay techniques by surface modification of the surfactant alignment layer consisting of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP). The cancer biomarker CA125 was detected with an array of anti-CA125 antibodies immobilized on the ultraviolet (UV)-modified DMOAP monolayer. Compared with a pristine counterpart, UV irradiation enhanced the binding affinity of the CA125 antibody and reproducibility of immunodetection in which a detection limit of 0.01 ng/ml for the cancer biomarker CA125 was achieved. Additionally, the optical texture observed under a crossed polarized microscope was correlated with the analyte concentration. In a proof-of-concept experiment using CA125-spiked human serum as the analyte, specific binding between the CA125 antigen and the anti-CA125 antibody resulted in a distinct and concentration-dependent optical response despite the high background caused by nonspecific binding of other biomolecules in the human serum. Results from this study indicate that UV modification of the alignment layer, as well as detection with LCs of large birefringence, contributes to the enhanced performance of the label-free LC-based immunodetection, which may be considered a promising alternative to conventional label-based methods.

  17. How to calculate dark matter direct detection exclusion limits that are consistent with gamma rays from annihilation in the Milky Way halo

    NASA Astrophysics Data System (ADS)

    Cerdeño, David G.; Fornasa, Mattia; Green, Anne M.; Peiró, Miguel

    2016-08-01

    When comparing constraints on the weakly interacting massive particle (WIMP) properties from direct and indirect detection experiments it is crucial that the assumptions made about the dark matter (DM) distribution are realistic and consistent. For instance, if the Fermi-LAT Galactic center GeV gamma-ray excess was due to WIMP annihilation, its morphology would be incompatible with the standard halo model that is usually used to interpret data from direct detection experiments. In this article, we calculate exclusion limits from direct detection experiments using self-consistent velocity distributions, derived from mass models of the Milky Way where the DM halo has a generalized Navarro-Frenk-White profile. We use two different methods to make the mass model compatible with a DM interpretation of the Galactic center gamma-ray excess. First, we fix the inner slope of the DM density profile to the value that best fits the morphology of the excess. Second, we allow the inner slope to vary and include the morphology of the excess in the data sets used to constrain the gravitational potential of the Milky Way. The resulting direct detection limits differ significantly from those derived using the standard halo model, in particular for light WIMPs, due to the differences in both the local DM density and velocity distribution.

  18. Conductance and Absolutely Continuous Spectrum of 1D Samples

    NASA Astrophysics Data System (ADS)

    Bruneau, L.; Jakšić, V.; Last, Y.; Pillet, C.-A.

    2016-06-01

    We characterize the absolutely continuous spectrum of the one-dimensional Schrödinger operators {h = -Δ + v} acting on {ℓ^2(mathbb{Z}_+)} in terms of the limiting behaviour of the Landauer-Büttiker and Thouless conductances of the associated finite samples. The finite sample is defined by restricting h to a finite interval {[1, L] \\cap mathbb{Z}_+} and the conductance refers to the charge current across the sample in the open quantum system obtained by attaching independent electronic reservoirs to the sample ends. Our main result is that the conductances associated to an energy interval {I} are non-vanishing in the limit {L to infty} iff {sp_ac(h) \\cap I neq emptyset}. We also discuss the relationship between this result and the Schrödinger Conjecture (Avila, J Am Math Soc 28:579-616, 2015; Bruneau et al., Commun Math Phys 319:501-513, 2013).

  19. Sparse aperture masking at the VLT. I. Faint companion detection limits for the two debris disk stars HD 92945 and HD 141569

    NASA Astrophysics Data System (ADS)

    Lacour, S.; Tuthill, P.; Amico, P.; Ireland, M.; Ehrenreich, D.; Huelamo, N.; Lagrange, A.-M.

    2011-08-01

    Aims: Observational data on companion statistics around young stellar systems is needed to flesh out the formation pathways for extrasolar planets and brown dwarfs. Aperture masking is a new technique that is able to address an important part of this discovery space. Methods: We observed the two debris disk systems HD 92945 and HD 141569 with sparse aperture masking (SAM), a new mode offered on the NaCo instrument at the VLT. A search for faint companions was performed using a detection strategy based on the analysis of closure phases recovered from interferograms recorded on the Conica camera. Results: Our results demonstrate that SAM is a very competitive mode in the field of companion detection. We obtained 5σ high-contrast detection limits at λ/D of 2.5 × 10-3 (ΔL' = 6.5) for HD 92945 and 4.6 × 10-3 (ΔL' = 5.8) for HD 141569. According to brown dwarf evolutionary models, our data impose an upper mass boundary for any companion for the two stars to, respectively, 18 and 22 Jupiter masses at minimum separations of 1.5 and 7 AU. The detection limits is mostly independent of angular separation, until reaching the diffraction limit of the telescope. Conclusions: We have placed upper limits on the existence of companions to our target systems that fall close to the planetary mass regime. This demonstrates the potential for SAM mode to contribute to studies of faint companions. We furthermore show that the final dynamic range obtained is directly proportional to the error on the closure phase measurement. At the present performance levels of 0.28 degree closure phase error, SAM is among the most competitive techniques for recovering companions at scales of one to several times the diffraction limit of the telescope. Further improvements to the detection threshold can be expected with more accurate phase calibration. Based on observations collected at the European Southern Observatory (ESO) during runs 084.C-755 (A) and 085.C-277 (A).

  20. The detection limits for estimates of infection intensity in schistosomiasis mansoni established by a study in non-human primates.

    PubMed

    Alan Wilson, R; van Dam, Govert J; Kariuki, Thomas M; Farah, Idle O; Deelder, André M; Coulson, Patricia S

    2006-10-01

    In human schistosomiasis mansoni, it is impossible to directly determine worm burden and hence infection intensity, so surrogates must be used. Studies on non-human primates revealed a linear relationship between worm burden and three surrogates, faecal egg output, circulating anodic and circulating cathodic antigens. By regression, the thresholds of detection were determined as 40, 24 and 47 worms, respectively. These observations provide a quantitative basis for the contention that low intensity infections in humans are being missed. The significance for estimates of disease prevalence, evaluation of the effects of chemotherapy and the implementation of vaccine trials is emphasised. PMID:16930605

  1. Gap Detection and Temporal Modulation Transfer Function as Behavioral Estimates of Auditory Temporal Acuity Using Band-Limited Stimuli in Young and Older Adults

    PubMed Central

    Shen, Yi

    2015-01-01

    Purpose Gap detection and the temporal modulation transfer function (TMTF) are 2 common methods to obtain behavioral estimates of auditory temporal acuity. However, the agreement between the 2 measures is not clear. This study compares results from these 2 methods and their dependencies on listener age and hearing status. Method Gap detection thresholds and the parameters that describe the TMTF (sensitivity and cutoff frequency) were estimated for young and older listeners who were naive to the experimental tasks. Stimuli were 800-Hz-wide noises with upper frequency limits of 2400 Hz, presented at 85 dB SPL. A 2-track procedure (Shen & Richards, 2013) was used for the efficient estimation of the TMTF. Results No significant correlation was found between gap detection threshold and the sensitivity or the cutoff frequency of the TMTF. No significant effect of age and hearing loss on either the gap detection threshold or the TMTF cutoff frequency was found, while the TMTF sensitivity improved with increasing hearing threshold and worsened with increasing age. Conclusion Estimates of temporal acuity using gap detection and TMTF paradigms do not seem to provide a consistent description of the effects of listener age and hearing status on temporal envelope processing. PMID:25087722

  2. Variation in the limit-of-detection of the ProSpecT Campylobacter microplate enzyme immunoassay in stools spiked with emerging Campylobacter species.

    PubMed

    Bojanić, Krunoslav; Midwinter, Anne Camilla; Marshall, Jonathan Craig; Rogers, Lynn Elizabeth; Biggs, Patrick Jon; Acke, Els

    2016-08-01

    Campylobacter enteritis in humans is primarily associated with C. jejuni/coli infection. The impact of other Campylobacter spp. is likely to be underestimated due to the bias of culture methods towards Campylobacter jejuni/coli diagnosis. Stool antigen tests are becoming increasingly popular and appear generally less species-specific. A review of independent studies of the ProSpecT® Campylobacter Microplate enzyme immunoassay (EIA) developed for C. jejuni/coli showed comparable diagnostic results to culture methods but the examination of non-jejuni/coli Campylobacter spp. was limited and the limit-of-detection (LOD), where reported, varied between studies. This study investigated LOD of EIA for Campylobacter upsaliensis, Campylobacter hyointestinalis and Campylobacter helveticus spiked in human stools. Multiple stools and Campylobacter isolates were used in three different concentrations (10(4)-10(9)CFU/ml) to reflect sample heterogeneity. All Campylobacter species evaluated were detectable by EIA. Multivariate analysis showed LOD varied between Campylobacter spp. and faecal consistency as fixed effects and individual faecal samples as random effects. EIA showed excellent performance in replicate testing for both within and between batches of reagents, in agreement between visual and spectrophotometric reading of results, and returned no discordance between the bacterial concentrations within independent dilution test runs (positive results with lower but not higher concentrations). This study shows how limitations in experimental procedures lead to an overestimation of consistency and uniformity of LOD for EIA that may not hold under routine use in diagnostic laboratories. Benefits and limitations for clinical practice and the influence on estimates of performance characteristics from detection of multiple Campylobacter spp. by EIA are discussed. PMID:27317896

  3. Testing the discrimination and detection limits of WorldView-2 imagery on a challenging invasive plant target

    NASA Astrophysics Data System (ADS)

    Robinson, T. P.; Wardell-Johnson, G. W.; Pracilio, G.; Brown, C.; Corner, R.; van Klinken, R. D.

    2016-02-01

    Invasive plants pose significant threats to biodiversity and ecosystem function globally, leading to costly monitoring and management effort. While remote sensing promises cost-effective, robust and repeatable monitoring tools to support intervention, it has been largely restricted to airborne platforms that have higher spatial and spectral resolutions, but which lack the coverage and versatility of satellite-based platforms. This study tests the ability of the WorldView-2 (WV2) eight-band satellite sensor for detecting the invasive shrub mesquite (Prosopis spp.) in the north-west Pilbara region of Australia. Detectability was challenged by the target taxa being largely defoliated by a leaf-tying biological control agent (Gelechiidae: Evippe sp. #1) and the presence of other shrubs and trees. Variable importance in the projection (VIP) scores identified bands offering greatest capacity for discrimination were those covering the near-infrared, red, and red-edge wavelengths. Wavelengths between 400 nm and 630 nm (coastal blue, blue, green, yellow) were not useful for species level discrimination in this case. Classification accuracy was tested on three band sets (simulated standard multispectral, all bands, and bands with VIP scores ≥1). Overall accuracies were comparable amongst all band-sets (Kappa = 0.71-0.77). However, mesquite omission rates were unacceptably high (21.3%) when using all eight bands relative to the simulated standard multispectral band-set (9.5%) and the band-set informed by VIP scores (11.9%). An incremental cover evaluation on the latter identified most omissions to be for objects <16 m2. Mesquite omissions reduced to 2.6% and overall accuracy significantly improved (Kappa = 0.88) when these objects were left out of the confusion matrix calculations. Very high mapping accuracy of objects >16 m2 allows application for mapping mesquite shrubs and coalesced stands, the former not previously possible, even with 3 m resolution hyperspectral

  4. Using European travellers as an early alert to detect emerging pathogens in countries with limited laboratory resources

    PubMed Central

    Guerin, Philippe J; Grais, Rebecca Freeman; Rottingen, John Arne; Valleron, Alain Jacques

    2007-01-01

    Background The volume, extent and speed of travel have dramatically increased in the past decades, providing the potential for an infectious disease to spread through the transportation network. By collecting information on the suspected place of infection, existing surveillance systems in industrialized countries may provide timely information for areas of the world without adequate surveillance currently in place. We present the results of a case study using reported cases of Shigella dysenteriae serotype 1 (Sd1) in European travellers to detect "events" of Sd1, related to either epidemic cases or endemic cases in developing countries. Methods We identified papers from a Medline search for reported events of Sd1 from 1940 to 2002. We requested data on shigella infections reported to the responsible surveillance entities in 17 European countries. Reports of Sd1 from the published literature were then compared with Sd1 notified cases among European travellers from 1990 to 2002. Results Prior to a large epidemic in 1999–2000, no cases of Sd1 had been identified in West Africa. However, if travellers had been used as an early warning, Sd1 could have been identified in this region as earlier as 1992. Conclusion This project demonstrates that tracking diseases in European travellers could be used to detect emerging disease in developing countries. This approach should be further tested with a view to the continuous improvement of national health surveillance systems and existing European networks, and may play a significant role in aiding the international public health community to improve infectious disease control. PMID:17239228

  5. Limits of detections for the determination of mono- and dicarboxylic acids using gas and liquid chromatographic methods coupled with mass spectrometry

    PubMed Central

    Št’ávová, Jana; Beránek, Josef; Nelson, Eric P.; Diep, Bonnie A.; Kubátová, Alena

    2011-01-01

    The chromatographic separation and instrumental limits of detection (LODs) were obtained for a broad range of C1-C18 monocarboxylic (MCAs) and C2-C14 dicarboxylic acids (DCAs) employing either chemical derivatization followed by gas chromatography-mass spectrometry and flame ionization detection (GC-MS/FID) or direct analysis with liquid chromatography high resolution MS and tandem MS (LC-MS). Suitability, efficiency and stability of reaction products for several derivatization agents used for esterification (BF3/butanol), and trimethysilylation, including trimethylsilyl-N-N-dimethylcarbamate (TMSDMC) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were evaluated. The lowest limits of detection for the majority of compounds below 10 pg (with the exception of acetic acid) were obtained for derivatization with BF3/butanol followed by GC-MS in the total ion current (TIC) mode. Further improvements were achieved when applying either selected ion monitoring (SIM), which decreased the LODs to 1–4 pg or a combination of SIM and TIC (SITI) (2–5 pg). GC-FID provided LODs comparable to those obtained by GC-MS TIC. Both trimethylsilylation (followed by GC-MS) and direct LC-MS/MS analysis yielded LODs of 5– 40 pg for most of the acids. For volatile acids the LODs were higher, e.g., 25 and 590 ng for TMSDMC and BSTFA derivatized formic acid, respectively whereas the LC-MS methods did not allow for the analysis of formic acid at all. PMID:21185238

  6. Limited proteolysis and peptide mapping for comparability of biopharmaceuticals: An evaluation of repeatability, intra-assay precision and capability to detect structural change.

    PubMed

    Perrin, Camille; Burkitt, Will; Perraud, Xavier; O'Hara, John; Jone, Carl

    2016-05-10

    The use of limited proteolysis followed by peptide mapping for the comparability of the higher-order structure of biopharmaceuticals was investigated. In this approach the proteolysis is performed under non-reducing and non-denaturing conditions, and the resulting peptide map is determined by the samples primary and higher order structures. This allows comparability of biopharmaceuticals to be made in terms of their higher order structure, using a method that is relatively simple to implement. The digestion of a monoclonal antibody under non-denaturing conditions was analyzed using peptide mapping, circular dichroism (CD) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This allowed an optimal digestion time to be chosen. This method was then assessed for its ability to detect structural change using a monoclonal antibody, which had been subjected to a range of stresses; deglycosylation, mild denaturation and a batch that had failed specifications due to in-process reduction. The repeatability and inter-assay precision were assessed. It was demonstrated that the limited proteolysis peptide maps of the three stressed samples were significantly different to control samples and that the differences observed were consistent between the occasions when the assays were run. A combination of limited proteolysis and CD or SDS-PAGE analysis was shown to enhance the capacity of these techniques to detect structural change, which otherwise would not have been observed. PMID:26918895

  7. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  8. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  9. The National Geodetic Survey absolute gravity program

    NASA Astrophysics Data System (ADS)

    Peter, George; Moose, Robert E.; Wessells, Claude W.

    1989-03-01

    The National Geodetic Survey absolute gravity program will utilize the high precision afforded by the JILAG-4 instrument to support geodetic and geophysical research, which involves studies of vertical motions, identification and modeling of other temporal variations, and establishment of reference values. The scientific rationale of these objectives is given, the procedures used to collect gravity and environmental data in the field are defined, and the steps necessary to correct and remove unwanted environmental effects are stated. In addition, site selection criteria, methods of concomitant environmental data collection and relative gravity observations, and schedule and logistics are discussed.

  10. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  11. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  12. Absolute angular positioning in ultrahigh vacuum

    SciTech Connect

    Schief, H.; Marsico, V.; Kern, K.

    1996-05-01

    Commercially available angular resolvers, which are routinely used in machine tools and robotics, are modified and adapted to be used under ultrahigh-vacuum (UHV) conditions. They provide straightforward and reliable measurements of angular positions for any kind of UHV sample manipulators. The corresponding absolute reproducibility is on the order of 0.005{degree}, whereas the relative resolution is better than 0.001{degree}, as demonstrated by high-resolution helium-reflectivity measurements. The mechanical setup and possible applications are discussed. {copyright} {ital 1996 American Institute of Physics.}

  13. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  14. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  15. Absolute analytical prediction of photonic crystal guided mode resonance wavelengths

    SciTech Connect

    Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron L. C.; Kristensen, Anders

    2014-08-18

    A class of photonic crystal resonant reflectors known as guided mode resonant filters are optical structures that are widely used in the field of refractive index sensing, particularly in biosensing. For the purposes of understanding and design, their behavior has traditionally been modeled numerically with methods such as rigorous coupled wave analysis. Here it is demonstrated how the absolute resonance wavelengths of such structures can be predicted by analytically modeling them as slab waveguides in which the propagation constant is determined by a phase matching condition. The model is experimentally verified to be capable of predicting the absolute resonance wavelengths to an accuracy of within 0.75 nm, as well as resonance wavelength shifts due to changes in cladding index within an accuracy of 0.45 nm across the visible wavelength regime in the case where material dispersion is taken into account. Furthermore, it is demonstrated that the model is valid beyond the limit of low grating modulation, for periodically discontinuous waveguide layers, high refractive index contrasts, and highly dispersive media.

  16. Absolute Quantification of Selected Proteins in the Human Osteoarthritic Secretome

    PubMed Central

    Peffers, Mandy J.; Beynon, Robert J.; Clegg, Peter D.

    2013-01-01

    Osteoarthritis (OA) is characterized by a loss of extracellular matrix which is driven by catabolic cytokines. Proteomic analysis of the OA cartilage secretome enables the global study of secreted proteins. These are an important class of molecules with roles in numerous pathological mechanisms. Although cartilage studies have identified profiles of secreted proteins, quantitative proteomics techniques have been implemented that would enable further biological questions to be addressed. To overcome this limitation, we used the secretome from human OA cartilage explants stimulated with IL-1β and compared proteins released into the media using a label-free LC-MS/MS-based strategy. We employed QconCAT technology to quantify specific proteins using selected reaction monitoring. A total of 252 proteins were identified, nine were differentially expressed by IL-1 β stimulation. Selected protein candidates were quantified in absolute amounts using QconCAT. These findings confirmed a significant reduction in TIMP-1 in the secretome following IL-1β stimulation. Label-free and QconCAT analysis produced equivocal results indicating no effect of cytokine stimulation on aggrecan, cartilage oligomeric matrix protein, fibromodulin, matrix metalloproteinases 1 and 3 or plasminogen release. This study enabled comparative protein profiling and absolute quantification of proteins involved in molecular pathways pertinent to understanding the pathogenesis of OA. PMID:24132152

  17. Study of boron detection limit using the in-air PIGE set-up at LAMFI-USP

    NASA Astrophysics Data System (ADS)

    Moro, M. V.; Silva, T. F.; Trindade, G. F.; Added, N.; Tabacniks, M. H.

    2014-11-01

    The quantification of small amounts of boron in materials is of extreme importance in different areas of materials science. Boron is an important contaminant and also a silicon dopant in the semiconductor industry. Boron is also extensively used in nuclear power plants, either for neutron shielding or for safety control and boron is an essential nutrient for life, either vegetable or animal. The production of silicon solar cells, by refining metallurgical-grade silicon (MG-Si) requires the control and reduction of several silicon contaminants to very low concentration levels. Boron is one of the contaminants of solar-grade silicon (SG-Si) that must be controlled and quantified at sub-ppm levels. In the metallurgical purification, boron quantification is usually made by Inductive Coupled Plasma Mass Spectrometry, (ICP-MS) but the results need to be verified by an independent analytical method. In this work we present the results of the analysis of silicon samples by Particle Induced Gamma-Ray Emission (PIGE) aiming the quantification of low concentrations of boron. PIGE analysis was carried out using the in-air external beam line of the Laboratory for Materials Analysis with Ion Beans (LAMFI-USP) by the 10B ( p ,αγ(7Be nuclear reaction, and measuring the 429 keV γ-ray. The in-air PIGE measurements at LAMFI have a quantification limit of the order of 1016 at/cm2.

  18. Study of boron detection limit using the in-air PIGE set-up at LAMFI-USP

    SciTech Connect

    Moro, M. V.; Silva, T. F.; Trindade, G. F.; Added, N.; Tabacniks, M. H.

    2014-11-11

    The quantification of small amounts of boron in materials is of extreme importance in different areas of materials science. Boron is an important contaminant and also a silicon dopant in the semiconductor industry. Boron is also extensively used in nuclear power plants, either for neutron shielding or for safety control and boron is an essential nutrient for life, either vegetable or animal. The production of silicon solar cells, by refining metallurgical-grade silicon (MG-Si) requires the control and reduction of several silicon contaminants to very low concentration levels. Boron is one of the contaminants of solar-grade silicon (SG-Si) that must be controlled and quantified at sub-ppm levels. In the metallurgical purification, boron quantification is usually made by Inductive Coupled Plasma Mass Spectrometry, (ICP-MS) but the results need to be verified by an independent analytical method. In this work we present the results of the analysis of silicon samples by Particle Induced Gamma-Ray Emission (PIGE) aiming the quantification of low concentrations of boron. PIGE analysis was carried out using the in-air external beam line of the Laboratory for Materials Analysis with Ion Beams (LAMFI-USP) by the {sup 10}B(p,αγ({sup 7}Be nuclear reaction, and measuring the 429 keV γ-ray. The in-air PIGE measurements at LAMFI have a quantification limit of the order of 10{sup 16} at/cm{sup 2}.

  19. Fluids with competing interactions. I. Decoding the structure factor to detect and characterize self-limited clustering

    NASA Astrophysics Data System (ADS)

    Bollinger, Jonathan A.; Truskett, Thomas M.

    2016-08-01

    We use liquid state theory and computer simulations to gain insights into the shape of the structure factor for fluids of particles interacting via a combination of short-range attractions and long-range repulsions. Such systems can reversibly morph between homogeneous phases and states comprising compact self-limiting clusters. We first highlight trends with respect to the presence and location of the intermediate-range order (IRO) pre-peak in the structure factor, which is commonly associated with clustering, for wide ranges of the tunable parameters that control interparticle interactions (e.g., Debye screening length). Next, for approximately 100 different cluster phases at various conditions (where aggregates range in size from six to sixty monomers), we quantitatively relate the shape of the structure factor to physical characteristics including intercluster distance and cluster size. We also test two previously postulated criteria for identifying the emergence of clustered phases that are based on IRO peak-height and -width, respectively. We find that the criterion based on peak-width, which encodes the IRO thermal correlation length, is more robust across a wide range of conditions and interaction strengths but nonetheless approximate. Ultimately, we recommend a hybrid heuristic drawing on both pre-peak height and width for positively identifying the emergence of clustered states.

  20. Limitations of Vegetation Indices For Detecting Pasture Degradation: A Case Study of Montane Pastoral Systems in Central Asia

    NASA Astrophysics Data System (ADS)

    Eddy, I. M. S.; Gergel, S. E.

    2015-12-01

    Grazing is the most extensive land use on Earth. Widespread consequences of overgrazing pastures include long-term decreases in plant biomass and limited recovery of vegetation. Remotely-sensed vegetation indices linked to biomass (e.g. NDVI) are routinely used to monitor pasture health over broad areas to track pasture degradation and recovery over time. Unfortunately, overgrazing can impact vegetation in various other ways not easily evaluated using satellite imagery, such as by altering species composition. Furthermore, the response of vegetation to grazing may be influenced by underlying terrain and topographic gradients. We examined multi-decadal trends in pasture condition in Kyrgyzstan, a country where pasture degradation is of serious concern. Using a chronosequence of Moderate-Resolution Imaging Spectroradiometer (MODIS) imagery, we compared fifteen-year trends in NDVI with contemporary field-based measurements of pasture health in thirty 1-km 2 sites. Multivariate regression was used to discern the relationship between long-term NDVI trends and pasture health in pastures of differing terrain (areas of varying topographic wetness index and solar insolation). Preliminary results suggest that pasture degradation can be correlated with either positive or negative changes in NDVI depending upon the topographic position of the pasture. Furthermore, terrain characteristics explained a considerable portion of the observed variance in NDVI trends across the region. Improving our understanding of grazing impacts in montane systems is critical given their vulnerability to impending climate change.

  1. Determination of the absolute contours of optical flats

    NASA Technical Reports Server (NTRS)

    Primak, W.

    1969-01-01

    Emersons procedure is used to determine true absolute contours of optical flats. Absolute contours of standard flats are determined and a comparison is then made between standard and unknown flats. Contour differences are determined by deviation of Fizeau fringe.

  2. Absolute and Trend Accuracy of a New Regional Oximeter in Healthy Volunteers During Controlled Hypoxia

    PubMed Central

    Paidy, Samata; Kashif, Faisal

    2014-01-01

    BACKGROUND: Traditional patient monitoring may not detect cerebral tissue hypoxia, and typical interventions may not improve tissue oxygenation. Therefore, monitoring cerebral tissue oxygen status with regional oximetry is being increasingly used by anesthesiologists and perfusionists during surgery. In this study, we evaluated absolute and trend accuracy of a new regional oximetry technology in healthy volunteers. METHODS: A near-infrared spectroscopy sensor connected to a regional oximetry system (O3TM, Masimo, Irvine, CA) was placed on the subject’s forehead, to provide continuous measurement of regional oxygen saturation (rSo2). Reference blood samples were taken from the radial artery and internal jugular bulb vein, at baseline and after a series of increasingly hypoxic states induced by altering the inspired oxygen concentration while maintaining normocapnic arterial carbon dioxide pressure (Paco2). Absolute and trend accuracy of the regional oximetry system was determined by comparing rSo2 against reference cerebral oxygen saturation (Savo2), that is calculated by combining arterial and venous saturations of oxygen in the blood samples. RESULTS: Twenty-seven subjects were enrolled. Bias (test method mean error), standard deviation of error, standard error of the mean, and root mean square accuracy (ARMS) of rSo2 compared to Savo2 were 0.4%, 4.0%, 0.3%, and 4.0%, respectively. The limits of agreement were 8.4% (95% confidence interval, 7.6%–9.3%) to −7.6% (95% confidence interval, −8.4% to −6.7%). Trend accuracy analysis yielded a relative mean error of 0%, with a standard deviation of 2.1%, a standard error of 0.1%, and an ARMS of 2.1%. Multiple regression analysis showed that age and skin color did not affect the bias (all P > 0.1). CONCLUSIONS: Masimo O3 regional oximetry provided absolute root-mean-squared error of 4% and relative root-mean-squared error of 2.1% in healthy volunteers undergoing controlled hypoxia. PMID:25405692

  3. Silicon photomultiplier (SPM) detection of low-level bioluminescence for the development of deployable whole-cell biosensors: possibilities and limitations.

    PubMed

    Li, Huaqing; Lopes, Nicholas; Moser, Scott; Sayler, Gary; Ripp, Steven

    2012-03-15

    Whole-cell bacterial bioreporters await miniaturized photon counting modules with high sensitivity and robust compatible hardware to fulfill their promise of versatile, on-site biosensor functionality. In this study, we explore the photon counting readout properties of the silicon photomultiplier (SPM) with a thermoelectric cooler and the possibilities of detecting low-level bioluminescent signals. Detection performance was evaluated through a simulated LED light source and the bioluminescence produced by the genetically engineered Pseudomonas fluorescens bacterial bioreporter 5RL. Compared with the conventional photomultiplier tube (PMT), the results revealed that the cooled SPM exhibits a wider linear response to inducible substrate concentrations (salicylate) ranging from 250 to 5000 ppb. Although cooling of the SPM lowered dark count rates and improved the minimum detectable signal, and the application of a digital filter enhanced the signal-to-noise ratio, the detection of very low light signals is still limited and remains a challenge in the design of compact photon counting systems. PMID:22305444

  4. The Capabilities and Limitation of Remote Visual Methods to Detect Service-Induced Cracks in Reactor Components

    SciTech Connect

    Cumblidge, Stephen E.; Doctor, Steven R.; Anderson, Michael T.

    2006-11-01

    detect cracks of various widths under ideal conditions.

  5. Lower limits of spin detection efficiency for two-parameter two-qubit (TPTQ) states with non-ideal ferromagnetic detectors

    NASA Astrophysics Data System (ADS)

    Majd, Nayereh; Ghasemi, Zahra

    2016-07-01

    We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell's inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.

  6. Calibrating the absolute amplitude scale for air showers measured at LOFAR

    NASA Astrophysics Data System (ADS)

    Nelles, A.; Hörandel, J. R.; Karskens, T.; Krause, M.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Erdmann, M.; Falcke, H.; Haungs, A.; Hiller, R.; Huege, T.; Krause, R.; Link, K.; Norden, M. J.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Scholten, O.; Schröder, F. G.; ter Veen, S.; Thoudam, S.; Trinh, T. N. G.; Weidenhaupt, K.; Wijnholds, S. J.; Anderson, J.; Bähren, L.; Bell, M. E.; Bentum, M. J.; Best, P.; Bonafede, A.; Bregman, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Carbone, D.; Ciardi, B.; de Gasperin, F.; Duscha, S.; Eislöffel, J.; Fallows, R. A.; Frieswijk, W.; Garrett, M. A.; van Haarlem, M. P.; Heald, G.; Hoeft, M.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kohler, J.; Kondratiev, V. I.; Kuniyoshi, M.; Kuper, G.; van Leeuwen, J.; Maat, P.; McFadden, R.; McKay-Bukowski, D.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Schwarz, D.; Serylak, M.; Sluman, J.; Smirnov, O.; Tasse, C.; Toribio, M. C.; Vermeulen, R.; van Weeren, R. J.; Wijers, R. A. M. J.; Wucknitz, O.; Zarka, P.

    2015-11-01

    Air showers induced by cosmic rays create nanosecond pulses detectable at radio frequencies. These pulses have been measured successfully in the past few years at the LOw-Frequency ARray (LOFAR) and are used to study the properties of cosmic rays. For a complete understanding of this phenomenon and the underlying physical processes, an absolute calibration of the detecting antenna system is needed. We present three approaches that were used to check and improve the antenna model of LOFAR and to provide an absolute calibration of the whole system for air shower measurements. Two methods are based on calibrated reference sources and one on a calibration approach using the diffuse radio emission of the Galaxy, optimized for short data-sets. An accuracy of 19% in amplitude is reached. The absolute calibration is also compared to predictions from air shower simulations. These results are used to set an absolute energy scale for air shower measurements and can be used as a basis for an absolute scale for the measurement of astronomical transients with LOFAR.

  7. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  8. Absolute rates of hole transfer in DNA.

    PubMed

    Senthilkumar, Kittusamy; Grozema, Ferdinand C; Guerra, Célia Fonseca; Bickelhaupt, F Matthias; Lewis, Frederick D; Berlin, Yuri A; Ratner, Mark A; Siebbeles, Laurens D A

    2005-10-26

    Absolute rates of hole transfer between guanine nucleobases separated by one or two A:T base pairs in stilbenedicarboxamide-linked DNA hairpins were obtained by improved kinetic analysis of experimental data. The charge-transfer rates in four different DNA sequences were calculated using a density-functional-based tight-binding model and a semiclassical superexchange model. Site energies and charge-transfer integrals were calculated directly as the diagonal and off-diagonal matrix elements of the Kohn-Sham Hamiltonian, respectively, for all possible combinations of nucleobases. Taking into account the Coulomb interaction between the negative charge on the stilbenedicarboxamide linker and the hole on the DNA strand as well as effects of base pair twisting, the relative order of the experimental rates for hole transfer in different hairpins could be reproduced by tight-binding calculations. To reproduce quantitatively the absolute values of the measured rate constants, the effect of the reorganization energy was taken into account within the semiclassical superexchange model for charge transfer. The experimental rates could be reproduced with reorganization energies near 1 eV. The quantum chemical data obtained were used to discuss charge carrier mobility and hole-transport equilibria in DNA. PMID:16231945

  9. Transient absolute robustness in stochastic biochemical networks.

    PubMed

    Enciso, German A

    2016-08-01

    Absolute robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the dynamical behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, absolutely robust behaviour corresponding to the deterministic case. This result contrasts with the long-term dynamics of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic dynamics. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485

  10. Sentinel-2/MSI absolute calibration: first results

    NASA Astrophysics Data System (ADS)

    Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.

    2015-10-01

    Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.

  11. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  12. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  13. Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding

    ERIC Educational Resources Information Center

    Ponce, Gregorio A.

    2008-01-01

    Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…

  14. 20 CFR 404.1205 - Absolute coverage groups.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Absolute coverage groups. 404.1205 Section... INSURANCE (1950- ) Coverage of Employees of State and Local Governments What Groups of Employees May Be Covered § 404.1205 Absolute coverage groups. (a) General. An absolute coverage group is a...

  15. Method and apparatus for making absolute range measurements

    DOEpatents

    Earl, Dennis D [Knoxville, TN; Allison, Stephen W [Knoxville, TN; Cates, Michael R [Oak Ridge, TN; Sanders, Alvin J [Knoxville, TN

    2002-09-24

    This invention relates to a method and apparatus for making absolute distance or ranging measurements using Fresnel diffraction. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through a screen at least partially opaque at the wavelength. The screen has an aperture sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector spaced some distance from the screen. The detector detects the central intensity of the beam as well as a set of intensities displaced from a center of the aperture. The distance from the source to the target can then be calculated based upon the known wavelength, aperture radius, and beam intensity.

  16. Absolute properties of the eclipsing binary star IM Persei

    SciTech Connect

    Lacy, Claud H. Sandberg; Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W.; Southworth, John E-mail: gtorres@cfa.harvard.edu E-mail: matthew1@coe.tsuniv.edu

    2015-01-01

    IM Per is a detached A7 eccentric eclipsing binary star. We have obtained extensive measurements of the light curve (28,225 differential magnitude observations) and radial velocity curve (81 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.7831 ± 0.0094 and 1.7741 ± 0.0097 solar masses, and radii of 2.409 ± 0.018 and 2.366 ± 0.017 solar radii. The orbital period is 2.25422694(15) days and the eccentricity is 0.0473(26). A faint third component was detected in the analysis of the light curves, and also directly observed in the spectra. The observed rate of apsidal motion is consistent with theory (U = 151.4 ± 8.4 year). We determine a distance to the system of 566 ± 46 pc.

  17. Absolute Radiation Measurements in Earth and Mars Entry Conditions

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.

    2014-01-01

    This paper reports on the measurement of radiative heating for shock heated flows which simulate conditions for Mars and Earth entries. Radiation measurements are made in NASA Ames' Electric Arc Shock Tube at velocities from 3-15 km/s in mixtures of N2/O2 and CO2/N2/Ar. The technique and limitations of the measurement are summarized in some detail. The absolute measurements will be discussed in regards to spectral features, radiative magnitude and spatiotemporal trends. Via analysis of spectra it is possible to extract properties such as electron density, and rotational, vibrational and electronic temperatures. Relaxation behind the shock is analyzed to determine how these properties relax to equilibrium and are used to validate and refine kinetic models. It is found that, for some conditions, some of these values diverge from non-equilibrium indicating a lack of similarity between the shock tube and free flight conditions. Possible reasons for this are discussed.

  18. Absolute stellar photometry on moderate-resolution FPA images

    USGS Publications Warehouse

    Stone, T.C.

    2009-01-01

    An extensive database of star (and Moon) images has been collected by the ground-based RObotic Lunar Observatory (ROLO) as part of the US Geological Survey program for lunar calibration. The stellar data are used to derive nightly atmospheric corrections for the observations from extinction measurements, and absolute calibration of the ROLO sensors is based on observations of Vega and published reference flux and spectrum data. The ROLO telescopes were designed for imaging the Moon at moderate resolution, thus imposing some limitations for the stellar photometry. Attaining accurate stellar photometry with the ROLO image data has required development of specialized processing techniques. A key consideration is consistency in discriminating the star core signal from the off-axis point spread function. The analysis and processing methods applied to the ROLO stellar image database are described. ?? 2009 BIPM and IOP Publishing Ltd.

  19. Sub-nanometer periodic nonlinearity error in absolute distance interferometers.

    PubMed

    Yang, Hongxing; Huang, Kaiqi; Hu, Pengcheng; Zhu, Pengfei; Tan, Jiubin; Fan, Zhigang

    2015-05-01

    Periodic nonlinearity which can result in error in nanometer scale has become a main problem limiting the absolute distance measurement accuracy. In order to eliminate this error, a new integrated interferometer with non-polarizing beam splitter is developed. This leads to disappearing of the frequency and/or polarization mixing. Furthermore, a strict requirement on the laser source polarization is highly reduced. By combining retro-reflector and angel prism, reference and measuring beams can be spatially separated, and therefore, their optical paths are not overlapped. So, the main cause of the periodic nonlinearity error, i.e., the frequency and/or polarization mixing and leakage of beam, is eliminated. Experimental results indicate that the periodic phase error is kept within 0.0018°. PMID:26026510

  20. An Alpha-Gamma Counter for Absolute Neutron Flux Measurement

    NASA Astrophysics Data System (ADS)

    Yue, A.; Greene, G.; Dewey, M.; Gilliam, D.; Nico, J.; Laptev, A.

    2012-03-01

    An alpha-gamma counter was used to measure the absolute neutron flux of a monochromatic cold neutron beam to sub-0.1,% precision. Simultaneously, the counter was used to calibrate a thin neutron flux monitor based on neutron absorption on ^6Li to the same precision. This monitor was used in the most precise beam-based measurement of the neutron lifetime, where the limiting systematic effect was the uncertainty in the neutron counting efficiency (0.3,%). The counter uses a thick target of ^10B-enriched boron carbide to completely absorb the beam. The rate of absorbed neutrons is determined by counting 478 keV gamma rays from neutron capture on ^10B with calibrated high-purity germanium detectors. The calibration results and the implications for the neutron lifetime will be discussed.