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Sample records for gamma prior distribution

  1. Gamma prior distribution selection for Bayesian analysis of failure rate and reliability

    Waler, R.A.; Johnson, M.M.; Waterman, M.S.; Martz, H.F. Jr.

    1977-01-01

    It is assumed that the phenomenon under study is such that the time-to-failure may be modeled by an exponential distribution with failure-rate parameter, lambda. For Bayesian analyses of the assumed model, the family of gamma distributions provides conjugate prior models for lambda. Thus, an experimenter needs to select a particular gamma model to conduct a Bayesian reliability analysis. The purpose of this paper is to present a methodology which can be used to translate engineering information, experience, and judgment into a choice of a gamma prior distribution. The proposed methodology assumes that the practicing engineer can provide percentile data relating to either the failure rate or the reliability of the phenomenon being investigated. For example, the methodology will select the gamma prior distribution which conveys an engineer's belief that the failure rate, lambda, simultaneously satisfies the probability statements, P(lambda less than 1.0 x 10 -3 ) = 0.50 and P(lambda less than 1.0 x 10 -5 ) = 0.05. That is, two percentiles provided by an engineer are used to determine a gamma prior model which agrees with the specified percentiles. For those engineers who prefer to specify reliability percentiles rather than the failure-rate percentiles illustrated above, one can use the induced negative-log gamma prior distribution which satisfies the probability statements, P(R(t 0 ) less than 0.99) = 0.50 and P(R(t 0 ) less than 0.99999) = 0.95 for some operating time t 0 . Also, the paper includes graphs for selected percentiles which assist an engineer in applying the methodology

  2. Gamma prior distribution selection for Bayesian analysis of failure rate and reliability

    Waller, R.A.; Johnson, M.M.; Waterman, M.S.; Martz, H.F. Jr.

    1976-07-01

    It is assumed that the phenomenon under study is such that the time-to-failure may be modeled by an exponential distribution with failure rate lambda. For Bayesian analyses of the assumed model, the family of gamma distributions provides conjugate prior models for lambda. Thus, an experimenter needs to select a particular gamma model to conduct a Bayesian reliability analysis. The purpose of this report is to present a methodology that can be used to translate engineering information, experience, and judgment into a choice of a gamma prior distribution. The proposed methodology assumes that the practicing engineer can provide percentile data relating to either the failure rate or the reliability of the phenomenon being investigated. For example, the methodology will select the gamma prior distribution which conveys an engineer's belief that the failure rate lambda simultaneously satisfies the probability statements, P(lambda less than 1.0 x 10 -3 ) equals 0.50 and P(lambda less than 1.0 x 10 -5 ) equals 0.05. That is, two percentiles provided by an engineer are used to determine a gamma prior model which agrees with the specified percentiles. For those engineers who prefer to specify reliability percentiles rather than the failure rate percentiles illustrated above, it is possible to use the induced negative-log gamma prior distribution which satisfies the probability statements, P(R(t 0 ) less than 0.99) equals 0.50 and P(R(t 0 ) less than 0.99999) equals 0.95, for some operating time t 0 . The report also includes graphs for selected percentiles which assist an engineer in applying the procedure. 28 figures, 16 tables

  3. Accommodating Uncertainty in Prior Distributions

    Picard, Richard Roy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vander Wiel, Scott Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-01-19

    A fundamental premise of Bayesian methodology is that a priori information is accurately summarized by a single, precisely de ned prior distribution. In many cases, especially involving informative priors, this premise is false, and the (mis)application of Bayes methods produces posterior quantities whose apparent precisions are highly misleading. We examine the implications of uncertainty in prior distributions, and present graphical methods for dealing with them.

  4. Bayesian Prior Probability Distributions for Internal Dosimetry

    Miller, G.; Inkret, W.C.; Little, T.T.; Martz, H.F.; Schillaci, M.E

    2001-07-01

    The problem of choosing a prior distribution for the Bayesian interpretation of measurements (specifically internal dosimetry measurements) is considered using a theoretical analysis and by examining historical tritium and plutonium urine bioassay data from Los Alamos. Two models for the prior probability distribution are proposed: (1) the log-normal distribution, when there is some additional information to determine the scale of the true result, and (2) the 'alpha' distribution (a simplified variant of the gamma distribution) when there is not. These models have been incorporated into version 3 of the Bayesian internal dosimetric code in use at Los Alamos (downloadable from our web site). Plutonium internal dosimetry at Los Alamos is now being done using prior probability distribution parameters determined self-consistently from population averages of Los Alamos data. (author)

  5. Finding a minimally informative Dirichlet prior distribution using least squares

    Kelly, Dana; Atwood, Corwin

    2011-01-01

    In a Bayesian framework, the Dirichlet distribution is the conjugate distribution to the multinomial likelihood function, and so the analyst is required to develop a Dirichlet prior that incorporates available information. However, as it is a multiparameter distribution, choosing the Dirichlet parameters is less straightforward than choosing a prior distribution for a single parameter, such as p in the binomial distribution. In particular, one may wish to incorporate limited information into the prior, resulting in a minimally informative prior distribution that is responsive to updates with sparse data. In the case of binomial p or Poisson λ, the principle of maximum entropy can be employed to obtain a so-called constrained noninformative prior. However, even in the case of p, such a distribution cannot be written down in the form of a standard distribution (e.g., beta, gamma), and so a beta distribution is used as an approximation in the case of p. In the case of the multinomial model with parametric constraints, the approach of maximum entropy does not appear tractable. This paper presents an alternative approach, based on constrained minimization of a least-squares objective function, which leads to a minimally informative Dirichlet prior distribution. The alpha-factor model for common-cause failure, which is widely used in the United States, is the motivation for this approach, and is used to illustrate the method. In this approach to modeling common-cause failure, the alpha-factors, which are the parameters in the underlying multinomial model for common-cause failure, must be estimated from data that are often quite sparse, because common-cause failures tend to be rare, especially failures of more than two or three components, and so a prior distribution that is responsive to updates with sparse data is needed.

  6. Dose Distribution of Gamma Irradiators

    Park, Seung Woo; Shin, Sang Hun; Son, Ki Hong; Lee, Chang Yeol; Kim, Kum Bae; Jung, Hai Jo; Ji, Young Hoon

    2010-01-01

    Gamma irradiator using Cs-137 have been widely utilized to the irradiation of cell, blood, and animal, and the dose measurement and education. The Gamma cell 3000 Elan (Nordion International, Kanata, Ontario, Canada) irradiator was installed in 2003 with Cs-137 and dose rate of 3.2 Gy/min. And the BioBeam 8000 (Gamma-Service Medical GmbH, Leipzig, Germany) irradiator was installed in 2008 with Cs-137 and dose rate of 3.5 Gy/min. Our purpose was to evaluate the practical dosimetric problems associated with inhomogeneous dose distribution within the irradiated volume in open air state using glass dosimeter and Gafchromic EBT film dosimeter for routine Gamma irradiator dosimetry applications at the KIRAMS and the measurements were compared with each other. In addition, an user guideline for useful utilization of the device based on practical dosimetry will be prepared. The measurement results of uniformity of delivered dose within the device showed variation more than 14% between middle point and the lowest position at central axis. Therefore, to maintain dose variation within 10%, the criteria of useful dose distribution, for research radiation effects, the irradiated specimen located at central axis of the container should be placed within 30 mm from top and bottom surface, respectively. In addition, for measurements using the film, the variations of dose distribution were more then 50% for the case of less than 10 second irradiation, mostly within 20% for the case of more than 20 second irradiation, respectively. Therefore, the irradiation experiments using the BioBeam 8000 irradiator are recommended to be used for specimen required at least more than 20 second irradiation time.

  7. Acquisition of multiple prior distributions in tactile temporal order judgment

    Yasuhito eNagai

    2012-08-01

    Full Text Available The Bayesian estimation theory proposes that the brain acquires the prior distribution of a task and integrates it with sensory signals to minimize the effect of sensory noise. Psychophysical studies have demonstrated that our brain actually implements Bayesian estimation in a variety of sensory-motor tasks. However, these studies only imposed one prior distribution on participants within a task period. In this study, we investigated the conditions that enable the acquisition of multiple prior distributions in temporal order judgment (TOJ of two tactile stimuli across the hands. In Experiment 1, stimulation intervals were randomly selected from one of two prior distributions (biased to right hand earlier and biased to left hand earlier in association with color cues (green and red, respectively. Although the acquisition of the two priors was not enabled by the color cues alone, it was significant when participants shifted their gaze (above or below in response to the color cues. However, the acquisition of multiple priors was not significant when participants moved their mouths (opened or closed. In Experiment 2, the spatial cues (above and below were used to identify which eye position or retinal cue position was crucial for the eye-movement-dependent acquisition of multiple priors in Experiment 1. The acquisition of the two priors was significant when participants moved their gaze to the cues (i.e., the cue positions on the retina were constant across the priors, as well as when participants did not shift their gazes (i.e., the cue positions on the retina changed according to the priors. Thus, both eye and retinal cue positions were effective in acquiring multiple priors. Based on previous neurophysiological reports, we discuss possible neural correlates that contribute to the acquisition of multiple priors.

  8. Finding a Minimally Informative Dirichlet Prior Distribution Using Least Squares

    Kelly, Dana; Atwood, Corwin

    2011-01-01

    In a Bayesian framework, the Dirichlet distribution is the conjugate distribution to the multinomial likelihood function, and so the analyst is required to develop a Dirichlet prior that incorporates available information. However, as it is a multiparameter distribution, choosing the Dirichlet parameters is less straight-forward than choosing a prior distribution for a single parameter, such as p in the binomial distribution. In particular, one may wish to incorporate limited information into the prior, resulting in a minimally informative prior distribution that is responsive to updates with sparse data. In the case of binomial p or Poisson, the principle of maximum entropy can be employed to obtain a so-called constrained noninformative prior. However, even in the case of p, such a distribution cannot be written down in closed form, and so an approximate beta distribution is used in the case of p. In the case of the multinomial model with parametric constraints, the approach of maximum entropy does not appear tractable. This paper presents an alternative approach, based on constrained minimization of a least-squares objective function, which leads to a minimally informative Dirichlet prior distribution. The alpha-factor model for common-cause failure, which is widely used in the United States, is the motivation for this approach, and is used to illustrate the method. In this approach to modeling common-cause failure, the alpha-factors, which are the parameters in the underlying multinomial aleatory model for common-cause failure, must be estimated from data that is often quite sparse, because common-cause failures tend to be rare, especially failures of more than two or three components, and so a prior distribution that is responsive to updates with sparse data is needed.

  9. Image Denoising via Bayesian Estimation of Statistical Parameter Using Generalized Gamma Density Prior in Gaussian Noise Model

    Kittisuwan, Pichid

    2015-03-01

    The application of image processing in industry has shown remarkable success over the last decade, for example, in security and telecommunication systems. The denoising of natural image corrupted by Gaussian noise is a classical problem in image processing. So, image denoising is an indispensable step during image processing. This paper is concerned with dual-tree complex wavelet-based image denoising using Bayesian techniques. One of the cruxes of the Bayesian image denoising algorithms is to estimate the statistical parameter of the image. Here, we employ maximum a posteriori (MAP) estimation to calculate local observed variance with generalized Gamma density prior for local observed variance and Laplacian or Gaussian distribution for noisy wavelet coefficients. Evidently, our selection of prior distribution is motivated by efficient and flexible properties of generalized Gamma density. The experimental results show that the proposed method yields good denoising results.

  10. A Noninformative Prior on a Space of Distribution Functions

    Alexander Terenin

    2017-07-01

    Full Text Available In a given problem, the Bayesian statistical paradigm requires the specification of a prior distribution that quantifies relevant information about the unknowns of main interest external to the data. In cases where little such information is available, the problem under study may possess an invariance under a transformation group that encodes a lack of information, leading to a unique prior—this idea was explored at length by E.T. Jaynes. Previous successful examples have included location-scale invariance under linear transformation, multiplicative invariance of the rate at which events in a counting process are observed, and the derivation of the Haldane prior for a Bernoulli success probability. In this paper we show that this method can be extended, by generalizing Jaynes, in two ways: (1 to yield families of approximately invariant priors; and (2 to the infinite-dimensional setting, yielding families of priors on spaces of distribution functions. Our results can be used to describe conditions under which a particular Dirichlet Process posterior arises from an optimal Bayesian analysis, in the sense that invariances in the prior and likelihood lead to one and only one posterior distribution.

  11. Reliability for some bivariate gamma distributions

    Nadarajah Saralees

    2005-01-01

    Full Text Available In the area of stress-strength models, there has been a large amount of work as regards estimation of the reliability R=Pr( Xdistributions when X and Y are independent random variables belonging to the same univariate family. In this paper, we consider forms of R when ( X,Y follows a bivariate distribution with dependence between X and Y . In particular, we derive explicit expressions for R when the joint distribution is bivariate gamma. The calculations involve the use of special functions.

  12. Isotropic gates in large gamma detector arrays versus angular distributions

    Iacob, V.E.; Duchene, G.

    1997-01-01

    The quality of the angular distribution information extracted from high-fold gamma-gamma coincidence events is analyzed. It is shown that a correct quasi-isotropic gate setting, available at the modern large gamma-ray detector arrays, essentially preserves the quality of the angular information. (orig.)

  13. Gamma-ray angular distribution and correlation measurement. II

    Twin, P.J.

    1975-01-01

    Angular correlations of γ-rays following nuclear reactions depend, in general, on some alignment of the γ-emitting initial state. The methods of alignment are briefly discussed and then the techniques and experimental methods associated with direct angular distributions, particle-gamma correlations, gamma-gamma correlations and linear polarization correlations are dealt with. Finally the inherent ambiguities which arise when different spin and delta values give identical correlations are discussed for the simple direct and particle-gamma correlations together with the question whether the larger information content of gamma-gamma and linear polarization correlations can resolve these ambiguities. (Auth.)

  14. A method to describe inelastic gamma field distribution in neutron gamma density logging.

    Zhang, Feng; Zhang, Quanying; Liu, Juntao; Wang, Xinguang; Wu, He; Jia, Wenbao; Ti, Yongzhou; Qiu, Fei; Zhang, Xiaoyang

    2017-11-01

    Pulsed neutron gamma density logging (NGD) is of great significance for radioprotection and density measurement in LWD, however, the current methods have difficulty in quantitative calculation and single factor analysis for the inelastic gamma field distribution. In order to clarify the NGD mechanism, a new method is developed to describe the inelastic gamma field distribution. Based on the fast-neutron scattering and gamma attenuation, the inelastic gamma field distribution is characterized by the inelastic scattering cross section, fast-neutron scattering free path, formation density and other parameters. And the contribution of formation parameters on the field distribution is quantitatively analyzed. The results shows the contribution of density attenuation is opposite to that of inelastic scattering cross section and fast-neutron scattering free path. And as the detector-spacing increases, the density attenuation gradually plays a dominant role in the gamma field distribution, which means large detector-spacing is more favorable for the density measurement. Besides, the relationship of density sensitivity and detector spacing was studied according to this gamma field distribution, therefore, the spacing of near and far gamma ray detector is determined. The research provides theoretical guidance for the tool parameter design and density determination of pulsed neutron gamma density logging technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Homogeneity and scale testing of generalized gamma distribution

    Stehlik, Milan

    2008-01-01

    The aim of this paper is to derive the exact distributions of the likelihood ratio tests of homogeneity and scale hypothesis when the observations are generalized gamma distributed. The special cases of exponential, Rayleigh, Weibull or gamma distributed observations are discussed exclusively. The photoemulsion experiment analysis and scale test with missing time-to-failure observations are present to illustrate the applications of methods discussed

  16. Retrospective analysis of 'gamma distribution' based IMRT QA criteria

    Wen, C.; Chappell, R.A.

    2010-01-01

    Full text: IMRT has been implemented into clinical practice at Royal Hobart Hospital (RHH) since mid 2006 for treating patients with Head and Neck (H and N) or prostate tumours. A local quality assurance (QA) acceptance criteria based on 'gamma distribution' for approving IMRT plan was developed and implemented in early 2007. A retrospective analysis of such criteria over 194 clinical cases will be presented. The RHH IMRT criteria was established with assumption that gamma distribution obtained through inter-comparison of 2 D dose maps between planned and delivered was governed by a positive-hail' normal distribution. A commercial system-MapCheck was used for 2 D dose map comparison with a built-in gamma analysis tool. Gamma distribution histogram was generated and recorded for all cases. By retrospectively analysing those distributions using curve fitting technique, a statistical gamma distribution can be obtained and evaluated. This analytical result can be used for future IMRT planing and treatment delivery. The analyses indicate that gamma distribution obtained through MapCheckTM is well under the normal distribution, particularly for prostate cases. The applied pass/fail criteria is not overly sensitive to identify 'false fails' but can be further tighten-up for smaller field while for larger field found in both H and N and prostate cases, the criteria was correctly applied. Non-uniform distribution of detectors in MapCheck and experience level of planners are two major factors to variation in gamma distribution among clinical cases. This criteria derived from clinical statistics is superior and more accurate than single-valued criteria for lMRT QA acceptance procedure. (author)

  17. Mathematical simulation of gamma-radiation angle distribution measurements

    Batij, V.G.; Batij, E.V.; Egorov, V.V.; Fedorchenko, D.V.; Kochnev, N.A.

    2008-01-01

    We developed mathematical model of the facility for gamma-radiation angle distribution measurement and calculated response functions for gamma-radiation intensities. We developed special software for experimental data processing, the 'Shelter' object radiation spectra unfolding and Sphere detector (ShD) angle resolution estimation. Neuronet method using for detection of the radiation directions is given. We developed software based on the neuronet algorithm, that allows obtaining reliable distribution of gamma-sources that make impact on the facility detectors at the measurement point. 10 refs.; 15 figs.; 4 tab

  18. Forecasting economy with Bayesian autoregressive distributed lag model: choosing optimal prior in economic downturn

    Bušs, Ginters

    2009-01-01

    Bayesian inference requires an analyst to set priors. Setting the right prior is crucial for precise forecasts. This paper analyzes how optimal prior changes when an economy is hit by a recession. For this task, an autoregressive distributed lag (ADL) model is chosen. The results show that a sharp economic slowdown changes the optimal prior in two directions. First, it changes the structure of the optimal weight prior, setting smaller weight on the lagged dependent variable compared to varia...

  19. Parameter estimation of multivariate multiple regression model using bayesian with non-informative Jeffreys’ prior distribution

    Saputro, D. R. S.; Amalia, F.; Widyaningsih, P.; Affan, R. C.

    2018-05-01

    Bayesian method is a method that can be used to estimate the parameters of multivariate multiple regression model. Bayesian method has two distributions, there are prior and posterior distributions. Posterior distribution is influenced by the selection of prior distribution. Jeffreys’ prior distribution is a kind of Non-informative prior distribution. This prior is used when the information about parameter not available. Non-informative Jeffreys’ prior distribution is combined with the sample information resulting the posterior distribution. Posterior distribution is used to estimate the parameter. The purposes of this research is to estimate the parameters of multivariate regression model using Bayesian method with Non-informative Jeffreys’ prior distribution. Based on the results and discussion, parameter estimation of β and Σ which were obtained from expected value of random variable of marginal posterior distribution function. The marginal posterior distributions for β and Σ are multivariate normal and inverse Wishart. However, in calculation of the expected value involving integral of a function which difficult to determine the value. Therefore, approach is needed by generating of random samples according to the posterior distribution characteristics of each parameter using Markov chain Monte Carlo (MCMC) Gibbs sampling algorithm.

  20. Estimation of photon energy distribution in gamma calibration field

    Takahashi, Fumiaki; Shimizu, Shigeru; Yamaguchi, Yasuhiro

    1997-03-01

    Photon survey instruments used for radiation protection are usually calibrated at gamma radiation fields, which are traceable to the national standard with regard to exposure. Whereas scattered radiations as well as primary gamma-rays exit in the calibration field, no consideration for the effect of the scattered radiations on energy distribution is given in routine calibration works. The scattered radiations can change photon energy spectra in the field, and this can result in misinterpretations of energy-dependent instrument responses. Construction materials in the field affect the energy distribution and magnitude of the scattered radiations. The geometric relationship between a gamma source and an instrument can determine the energy distribution at the calibration point. Therefore, it is essential for the assurance of quality calibration to estimate the energy spectra at the gamma calibration fields. Then, photon energy distributions at some fields in the Facility of Radiation Standard of the Japan Atomic Energy Research Institute (JAERI) were estimated by measurements using a NaI(Tl) detector and Monte Carlo calculations. It was found that the use of collimator gives a different feature in photon energy distribution. The origin of scattered radiations and the ratio of the scattered radiations to the primary gamma-rays were obtained. The results can help to improve the calibration of photon survey instruments in the JAERI. (author)

  1. Estimation of neutron energy distributions from prompt gamma emissions

    Panikkath, Priyada; Udupi, Ashwini; Sarkar, P. K.

    2017-11-01

    A technique of estimating the incident neutron energy distribution from emitted prompt gamma intensities from a system exposed to neutrons is presented. The emitted prompt gamma intensities or the measured photo peaks in a gamma detector are related to the incident neutron energy distribution through a convolution of the response of the system generating the prompt gammas to mono-energetic neutrons. Presently, the system studied is a cylinder of high density polyethylene (HDPE) placed inside another cylinder of borated HDPE (BHDPE) having an outer Pb-cover and exposed to neutrons. The emitted five prompt gamma peaks from hydrogen, boron, carbon and lead can be utilized to unfold the incident neutron energy distribution as an under-determined deconvolution problem. Such an under-determined set of equations are solved using the genetic algorithm based Monte Carlo de-convolution code GAMCD. Feasibility of the proposed technique is demonstrated theoretically using the Monte Carlo calculated response matrix and intensities of emitted prompt gammas from the Pb-covered BHDPE-HDPE system in the case of several incident neutron spectra spanning different energy ranges.

  2. The log S -log N distribution of gamma ray brust

    Yamagami, Takamasa; Nishimura, Jun; Fujii, Masami

    1982-01-01

    The relation between the size S and the frequency N of gamma ray burst has been studied. This relation may be determined from the celestial distribution of gamma ray burst sources. The present analysis gives that the log S - log N relation for any direction is determined by the celestial distribution of gamma ray burst sources. The observed bursts were analyzed. The celestial distribution of gamma ray burst sources was observed by the satellites of USSR. The results showed that the distribution seemed to be isotropic. However, the calculated log S - log N relation based on the isotropic distribution wasF in disagreement with the observed ones. As the result of analysis, it was found that the observed bursts missed low energy part because of the threshold of detectors. The levels of discrimination of detection were not clear. When a proper threshold level is set for each type of burst, and the size of bursts is determined, the above mentioned discrepancy will be deleted regardless of luminosity and the spatial distribution of bursts. (Kato, T.)

  3. Spatial distribution of reflected gamma rays by Monte Carlo simulation

    Jehouani, A.; Merzouki, A.; Boutadghart, F.; Ghassoun, J.

    2007-01-01

    In nuclear facilities, the reflection of gamma rays of the walls and metals constitutes an unknown origin of radiation. These reflected gamma rays must be estimated and determined. This study concerns reflected gamma rays on metal slabs. We evaluated the spatial distribution of the reflected gamma rays spectra by using the Monte Carlo method. An appropriate estimator for the double differential albedo is used to determine the energy spectra and the angular distribution of reflected gamma rays by slabs of iron and aluminium. We took into the account the principal interactions of gamma rays with matter: photoelectric, coherent scattering (Rayleigh), incoherent scattering (Compton) and pair creation. The Klein-Nishina differential cross section was used to select direction and energy of scattered photons after each Compton scattering. The obtained spectra show peaks at 0.511 * MeV for higher source energy. The Results are in good agreement with those obtained by the TRIPOLI code [J.C. Nimal et al., TRIPOLI02: Programme de Monte Carlo Polycinsetique a Trois dimensions, CEA Rapport, Commissariat a l'Energie Atomique.

  4. Estimation of expected value for lognormal and gamma distributions

    White, G.C.

    1978-01-01

    Concentrations of environmental pollutants tend to follow positively skewed frequency distributions. Two such density functions are the gamma and lognormal. Minimum variance unbiased estimators of the expected value for both densities are available. The small sample statistical properties of each of these estimators were compared for its own distribution, as well as the other distribution to check the robustness of the estimator. Results indicated that the arithmetic mean provides an unbiased estimator when the underlying density function of the sample is either lognormal or gamma, and that the achieved coverage of the confidence interval is greater than 75 percent for coefficients of variation less than two. Further Monte Carlo simulations were conducted to study the robustness of the above estimators by simulating a lognormal or gamma distribution with the expected value of a particular observation selected from a uniform distribution before the lognormal or gamma observation is generated. Again, the arithmetic mean provides an unbiased estimate of expected value, and the coverage of the confidence interval is greater than 75 percent for coefficients of variation less than two

  5. Gamma-distribution and wealth inequality

    the higher end of the distribution of wealth f(x) follows a power-law ... involved; services like public health and education are also counted in, and often ... between wealth inequality and economic growth, and hence the study of wealth.

  6. Gamma-distribution and wealth inequality

    This in turn allows one to quantify the inequalities observed in the wealth distributions and suggests that their origin should be traced back to very general underlying mechanisms, for instance, the fact that smaller the fraction of the relevant quantity (e.g. wealth) that agent can exchange during an interaction, the closer the ...

  7. Bayesian Analysis of two Censored Shifted Gompertz Mixture Distributions using Informative and Noninformative Priors

    Tabassum Naz Sindhu

    2017-03-01

    Full Text Available This study deals with Bayesian analysis of shifted Gompertz mixture model under type-I censored samples assuming both informative and noninformative priors. We have discussed the Bayesian estimation of parameters of shifted Gompertz mixture model under the uniform, and gamma priors assuming three loss functions. Further, some properties of the model with some graphs of the mixture density are discussed. These properties include Bayes estimators, posterior risks and reliability function under simulation scheme. Bayes estimates are obtained considering two cases: (a when the shape parameter is known and (b when all parameters are unknown. We analyzed some simulated sets in order to investigate the effect of prior belief, loss functions, and performance of the proposed set of estimators of the mixture model parameters.

  8. Eliciting hyperparameters of prior distributions for the parameters of paired comparison models

    Nasir Abbas

    2013-02-01

    Full Text Available Normal 0 false false false EN-US X-NONE AR-SA In the study of paired comparisons (PC, items may be ranked or issues may be prioritized through subjective assessment of certain judges. PC models are developed and then used to serve the purpose of ranking. The PC models may be studied through classical or Bayesian approach. Bayesian inference is a modern statistical technique used to draw conclusions about the population parameters. Its beauty lies in incorporating prior information about the parameters into the analysis in addition to current information (i.e. data. The prior and current information are formally combined to yield a posterior distribution about the population parameters, which is the work bench of the Bayesian statisticians. However, the problems the Bayesians face correspond to the selection and formal utilization of prior distribution. Once the type of prior distribution is decided to be used, the problem of estimating the parameters of the prior distribution (i.e. elicitation still persists. Different methods are devised to serve the purpose. In this study an attempt is made to use Minimum Chi-square (hence forth MCS for the elicitation purpose. Though it is a classical estimation technique, but is used here for the election purpose. The entire elicitation procedure is illustrated through a numerical data set.

  9. Likelihood Estimation of Gamma Ray Bursts Duration Distribution

    Horvath, Istvan

    2005-01-01

    Two classes of Gamma Ray Bursts have been identified so far, characterized by T90 durations shorter and longer than approximately 2 seconds. It was shown that the BATSE 3B data allow a good fit with three Gaussian distributions in log T90. In the same Volume in ApJ. another paper suggested that the third class of GRBs is may exist. Using the full BATSE catalog here we present the maximum likelihood estimation, which gives us 0.5% probability to having only two subclasses. The MC simulation co...

  10. Virtuality Distributions in application to gamma gamma* to pi^0 Transition Form Factor at Handbag Level

    Radyushkin, Anatoly V. [ODU, JLAB

    2014-07-01

    We outline basics of a new approach to transverse momentum dependence in hard processes. As an illustration, we consider hard exclusive transition process gamma*gamma -> to pi^0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O(0,z)) describing a hadron with momentum p. Treated as functions of (pz) and z^2, they are parametrized through a virtuality distribution amplitude (VDA) Phi (x, sigma), with x being Fourier-conjugate to (pz) and sigma Laplace-conjugate to z^2. For intervals with z^+=0, we introduce transverse momentum distribution amplitude (TMDA) Psi (x, k_\\perp), and write it in terms of VDA Phi (x, \\sigma). The results of covariant calculations, written in terms of Phi (x sigma) are converted into expressions involving Psi (x, k_\\perp. Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor. We also discuss how one can generate high-k_\\perp tails from primordial soft distributions.

  11. The McDonald exponentiated gamma distribution and its statistical properties

    Al-Babtain, Abdulhakim A; Merovci, Faton; Elbatal, Ibrahim

    2015-01-01

    Abstract In this paper, we propose a five-parameter lifetime model called the McDonald exponentiated gamma distribution to extend beta exponentiated gamma, Kumaraswamy exponentiated gamma and exponentiated gamma, among several other models. We provide a comprehensive mathematical treatment of this distribution. We derive the moment generating function and the rth moment. We discuss estimation of the parameters by maximum likelihood and provide the information matrix. AMS Subject Classificatio...

  12. Conditional maximum-entropy method for selecting prior distributions in Bayesian statistics

    Abe, Sumiyoshi

    2014-11-01

    The conditional maximum-entropy method (abbreviated here as C-MaxEnt) is formulated for selecting prior probability distributions in Bayesian statistics for parameter estimation. This method is inspired by a statistical-mechanical approach to systems governed by dynamics with largely separated time scales and is based on three key concepts: conjugate pairs of variables, dimensionless integration measures with coarse-graining factors and partial maximization of the joint entropy. The method enables one to calculate a prior purely from a likelihood in a simple way. It is shown, in particular, how it not only yields Jeffreys's rules but also reveals new structures hidden behind them.

  13. Simulated and measured neutron/gamma light output distribution for poly-energetic neutron/gamma sources

    Hosseini, S. A.; Zangian, M.; Aghabozorgi, S.

    2018-03-01

    In the present paper, the light output distribution due to poly-energetic neutron/gamma (neutron or gamma) source was calculated using the developed MCNPX-ESUT-PE (MCNPX-Energy engineering of Sharif University of Technology-Poly Energetic version) computational code. The simulation of light output distribution includes the modeling of the particle transport, the calculation of scintillation photons induced by charged particles, simulation of the scintillation photon transport and considering the light resolution obtained from the experiment. The developed computational code is able to simulate the light output distribution due to any neutron/gamma source. In the experimental step of the present study, the neutron-gamma discrimination based on the light output distribution was performed using the zero crossing method. As a case study, 241Am-9Be source was considered and the simulated and measured neutron/gamma light output distributions were compared. There is an acceptable agreement between the discriminated neutron/gamma light output distributions obtained from the simulation and experiment.

  14. Use on non-conjugate prior distributions in compound failure models. Final technical report

    Shultis, J.K.; Johnson, D.E.; Milliken, G.A.; Eckhoff, N.D.

    1981-12-01

    Several theoretical and computational techniques are presented for compound failure models in which the failure rate or failure probability for a class of components is considered to be a random variable. Both the failure-on-demand and failure-rate situation are considered. Ten different prior families are presented for describing the variation or uncertainty of the failure parameter. Methods considered for estimating values for the prior parameters from a given set of failure data are (1) matching data moments to those of the prior distribution, (2) matching data moments to those of the compound marginal distribution, and (3) the marginal maximum likelihood method. Numerical methods for computing the parameter estimators for all ten prior families are presented, as well as methods for obtaining estimates of the variances and covariance of the parameter estimators, it is shown that various confidence, probability, and tolerance intervals can be evaluated. Finally, to test the resulting failure models against the given failure data, generalized chi-squage and Kolmogorov-Smirnov goodness-of-fit tests are proposed together with a test to eliminate outliers from the failure data. Computer codes based on the results presented here have been prepared and are presented in a companion report

  15. A Variance Distribution Model of Surface EMG Signals Based on Inverse Gamma Distribution.

    Hayashi, Hideaki; Furui, Akira; Kurita, Yuichi; Tsuji, Toshio

    2017-11-01

    Objective: This paper describes the formulation of a surface electromyogram (EMG) model capable of representing the variance distribution of EMG signals. Methods: In the model, EMG signals are handled based on a Gaussian white noise process with a mean of zero for each variance value. EMG signal variance is taken as a random variable that follows inverse gamma distribution, allowing the representation of noise superimposed onto this variance. Variance distribution estimation based on marginal likelihood maximization is also outlined in this paper. The procedure can be approximated using rectified and smoothed EMG signals, thereby allowing the determination of distribution parameters in real time at low computational cost. Results: A simulation experiment was performed to evaluate the accuracy of distribution estimation using artificially generated EMG signals, with results demonstrating that the proposed model's accuracy is higher than that of maximum-likelihood-based estimation. Analysis of variance distribution using real EMG data also suggested a relationship between variance distribution and signal-dependent noise. Conclusion: The study reported here was conducted to examine the performance of a proposed surface EMG model capable of representing variance distribution and a related distribution parameter estimation method. Experiments using artificial and real EMG data demonstrated the validity of the model. Significance: Variance distribution estimated using the proposed model exhibits potential in the estimation of muscle force. Objective: This paper describes the formulation of a surface electromyogram (EMG) model capable of representing the variance distribution of EMG signals. Methods: In the model, EMG signals are handled based on a Gaussian white noise process with a mean of zero for each variance value. EMG signal variance is taken as a random variable that follows inverse gamma distribution, allowing the representation of noise superimposed onto this

  16. Statistical Distributions of Optical Flares from Gamma-Ray Bursts

    Yi, Shuang-Xi; Yu, Hai; Wang, F. Y.; Dai, Zi-Gao

    2017-01-01

    We statistically study gamma-ray burst (GRB) optical flares from the Swift /UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the timescales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time, and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin, and both of them are possibly related to central engine activities.

  17. Statistical Distributions of Optical Flares from Gamma-Ray Bursts

    Yi, Shuang-Xi [College of Physics and Engineering, Qufu Normal University, Qufu 273165 (China); Yu, Hai; Wang, F. Y.; Dai, Zi-Gao, E-mail: fayinwang@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2017-07-20

    We statistically study gamma-ray burst (GRB) optical flares from the Swift /UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the timescales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time, and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin, and both of them are possibly related to central engine activities.

  18. The distribution and abundance of gamma emitting radionuclides in Lake Ontario sediments

    McKinley, R.S.

    1985-03-01

    The distribution of gamma emitting radionuclides in Lake Ontario sediments was investigated. Samples were collected using a systematic design in the vicinity of Pickering and Darlington, and supplemented by lakewide offshore samples. Naturally occurring 40 K was the predominant source of gamma activity. 60 Co was the only potentially CANDU released radionuclide which showed a distributional association with the Pickering 'A' NGS discharge

  19. Novel Radiobiological Gamma Index for Evaluation of 3-Dimensional Predicted Dose Distribution

    Sumida, Iori, E-mail: sumida@radonc.med.osaka-u.ac.jp [Department of Radiation Oncology, Osaka University Graduate School of Medicine, Osaka (Japan); Yamaguchi, Hajime; Kizaki, Hisao; Aboshi, Keiko; Tsujii, Mari; Yoshikawa, Nobuhiko; Yamada, Yuji [Department of Radiation Oncology, NTT West Osaka Hospital, Osaka (Japan); Suzuki, Osamu; Seo, Yuji [Department of Radiation Oncology, Osaka University Graduate School of Medicine, Osaka (Japan); Isohashi, Fumiaki [Department of Radiation Oncology, NTT West Osaka Hospital, Osaka (Japan); Yoshioka, Yasuo [Department of Radiation Oncology, Osaka University Graduate School of Medicine, Osaka (Japan); Ogawa, Kazuhiko [Department of Radiation Oncology, NTT West Osaka Hospital, Osaka (Japan)

    2015-07-15

    Purpose: To propose a gamma index-based dose evaluation index that integrates the radiobiological parameters of tumor control (TCP) and normal tissue complication probabilities (NTCP). Methods and Materials: Fifteen prostate and head and neck (H&N) cancer patients received intensity modulated radiation therapy. Before treatment, patient-specific quality assurance was conducted via beam-by-beam analysis, and beam-specific dose error distributions were generated. The predicted 3-dimensional (3D) dose distribution was calculated by back-projection of relative dose error distribution per beam. A 3D gamma analysis of different organs (prostate: clinical [CTV] and planned target volumes [PTV], rectum, bladder, femoral heads; H&N: gross tumor volume [GTV], CTV, spinal cord, brain stem, both parotids) was performed using predicted and planned dose distributions under 2%/2 mm tolerance and physical gamma passing rate was calculated. TCP and NTCP values were calculated for voxels with physical gamma indices (PGI) >1. We propose a new radiobiological gamma index (RGI) to quantify the radiobiological effects of TCP and NTCP and calculate radiobiological gamma passing rates. Results: The mean RGI gamma passing rates for prostate cases were significantly different compared with those of PGI (P<.03–.001). The mean RGI gamma passing rates for H&N cases (except for GTV) were significantly different compared with those of PGI (P<.001). Differences in gamma passing rates between PGI and RGI were due to dose differences between the planned and predicted dose distributions. Radiobiological gamma distribution was visualized to identify areas where the dose was radiobiologically important. Conclusions: RGI was proposed to integrate radiobiological effects into PGI. This index would assist physicians and medical physicists not only in physical evaluations of treatment delivery accuracy, but also in clinical evaluations of predicted dose distribution.

  20. Gamma-ray multiplicity distribution in ternary fission of {sup 252}Cf

    Jandel, M [Department of Nuclear Physics, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava (Slovakia); Kliman, J [Department of Nuclear Physics, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava (Slovakia); Krupa, L [Department of Nuclear Physics, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava (Slovakia); Morhac, M [Department of Nuclear Physics, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava (Slovakia); Hamilton, J H [Department of Physics, Vanderbilt University, Nashville, TN (United States); Kormicki, J [Department of Physics, Vanderbilt University, Nashville, TN (United States); Ramayya, A V [Department of Physics, Vanderbilt University, Nashville, TN (United States); Hwang, J K [Department of Physics, Vanderbilt University, Nashville, TN (United States); Luo, Y X [Department of Physics, Vanderbilt University, Nashville, TN (United States); Fong, D [Department of Physics, Vanderbilt University, Nashville, TN (United States); Gore, P [Department of Physics, Vanderbilt University, Nashville, TN (United States); Akopian, G M Ter; Oganessian, Yu Ts; Rodin, A M; Fomichev, A S; Popeko, G S; Daniel, A V [Flerov Laboratory for Nuclear Reactions, Joint Institute for Nuclear Research, Dubna (Russian Federation); Rasmussen, J O; Macchiavelli, A O [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Stoyer, M A [Lawrence Livermore National Laboratory, Livermore, CA (United States); Donangelo, R [Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21945-970 Rio de Janeiro (Brazil); Cole, J D [Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (United States)

    2002-12-01

    From multiparameter data obtained at Lawrence Berkeley National Laboratory, the integral characteristics of the prompt {gamma}-ray emission were extracted for tripartition of {sup 252}Cf with He, Be and C being the third light charged particle. We used multifold {gamma}-ray coincidence spectra for the determination of {gamma}-ray multiplicities assuming a Gaussian distribution for {gamma}-ray multiplicity. The multiplicity distribution characteristics, i.e. mean multiplicity and its dispersion were obtained by minimizing with respect to the calculated values of probabilities of multifold {gamma}-ray coincidences using a combinatoric method. Comparison with the known experimental data from binary fission was made. Further, we investigated dependencies of the mean {gamma}-ray multiplicity on the kinetic energy of the light charged particle. The mean {gamma}-ray multiplicity for He ternary fission is found to increase rapidly with increasing kinetic energy of He in the region less than 11 MeV and then decrease slowly with increasing kinetic energy of He. The anomalous behaviour of {gamma}-ray emission is discussed. The mean {gamma}-ray multiplicity was determined for the first time for Be and C ternary fission. For Be, the {gamma}-ray multiplicity as a function of kinetic energy was obtained as well.

  1. Slow neutrons and secondary gamma ray distributions in concrete shields followed by reflecting layers

    Makarious, A.S.; Swilem, Y.I.; Awwad, Z.; Bayomy, T.

    1993-01-01

    Slow neutrons and secondary gamma ray distributions in concrete shields with and without a reflecting layer behind layer behind the concrete shield have been investigated first in case of using a bare reactor beam and then on using a B-4 C filtered beam. The total and capture secondary gamma ray coefficient (B gamma and B gamma C ), the ratio of the reflected thermal neutron (gamma) the ratio of the secondary gamma rays caused by reflected neutrons to those caused transmitted neutrons (Th I gamma/F I gamma) and the effect of inserting a blocking layer (a B-4 C layer) between the concrete shield and the reflector on the suppression of the produced secondary gamma rays have been investigated. It was found that the presence of the reflector layer behind the concrete shield reflects some thermal neutrons back to the concrete shields and so it increases the number of thermal neutrons at the interface between the concrete shield and the reflector. Also the capture secondary gamma rays was increased at the interface between the two medii due to the capture of the reflected thermal neutrons in the concrete shields. It was shown that B-gamma is higher than and that B g amma B gamma C and I gamma T h/ I gamma i f for the different concrete types is higher in case of using the graphite reflector than that in using either water or paraffin reflectors. Putting a blocking layer (B 4 C layer) between the concrete shield and the reflector decreases the produced secondary gamma rays due to the absorption of the reflected thermal neutrons. 17 figs

  2. Demonstration of a collimated in situ method for determining depth distributions using gamma-ray spectrometry

    Benke, R R

    2002-01-01

    In situ gamma-ray spectrometry uses a portable detector to quantify radionuclides in materials. The main shortcoming of in situ gamma-ray spectrometry has been its inability to determine radionuclide depth distributions. Novel collimator designs were paired with a commercial in situ gamma-ray spectrometry system to overcome this limitation for large area sources. Positioned with their axes normal to the material surface, the cylindrically symmetric collimators limited the detection of un attenuated gamma-rays from a selected range of polar angles (measured off the detector axis). Although this approach does not alleviate the need for some knowledge of the gamma-ray attenuation characteristics of the materials being measured, the collimation method presented in this paper represents an absolute method that determines the depth distribution as a histogram, while other in situ methods require a priori knowledge of the depth distribution shape. Other advantages over previous in situ methods are that this method d...

  3. An improved in situ method for determining depth distributions of gamma-ray emitting radionuclides

    Benke, R.R.; Kearfott, K.J.

    2001-01-01

    In situ gamma-ray spectrometry determines the quantities of radionuclides in some medium with a portable detector. The main limitation of in situ gamma-ray spectrometry lies in determining the depth distribution of radionuclides. This limitation is addressed by developing an improved in situ method for determining the depth distributions of gamma-ray emitting radionuclides in large area sources. This paper implements a unique collimator design with conventional radiation detection equipment. Cylindrically symmetric collimators were fabricated to allow only those gamma-rays emitted from a selected range of polar angles (measured off the detector axis) to be detected. Positioned with its axis normal to surface of the media, each collimator enables the detection of gamma-rays emitted from a different range of polar angles and preferential depths. Previous in situ methods require a priori knowledge of the depth distribution shape. However, the absolute method presented in this paper determines the depth distribution as a histogram and does not rely on such assumptions. Other advantages over previous in situ methods are that this method only requires a single gamma-ray emission, provides more detailed depth information, and offers a superior ability for characterizing complex depth distributions. Collimated spectrometer measurements of buried area sources demonstrated the ability of the method to yield accurate depth information. Based on the results of actual measurements, this method increases the potential of in situ gamma-ray spectrometry as an independent characterization tool in situations with unknown radionuclide depth distributions

  4. Calculating the Prior Probability Distribution for a Causal Network Using Maximum Entropy: Alternative Approaches

    Michael J. Markham

    2011-07-01

    Full Text Available Some problems occurring in Expert Systems can be resolved by employing a causal (Bayesian network and methodologies exist for this purpose. These require data in a specific form and make assumptions about the independence relationships involved. Methodologies using Maximum Entropy (ME are free from these conditions and have the potential to be used in a wider context including systems consisting of given sets of linear and independence constraints, subject to consistency and convergence. ME can also be used to validate results from the causal network methodologies. Three ME methods for determining the prior probability distribution of causal network systems are considered. The first method is Sequential Maximum Entropy in which the computation of a progression of local distributions leads to the over-all distribution. This is followed by development of the Method of Tribus. The development takes the form of an algorithm that includes the handling of explicit independence constraints. These fall into two groups those relating parents of vertices, and those deduced from triangulation of the remaining graph. The third method involves a variation in the part of that algorithm which handles independence constraints. Evidence is presented that this adaptation only requires the linear constraints and the parental independence constraints to emulate the second method in a substantial class of examples.

  5. Clustering and Bayesian hierarchical modeling for the definition of informative prior distributions in hydrogeology

    Cucchi, K.; Kawa, N.; Hesse, F.; Rubin, Y.

    2017-12-01

    In order to reduce uncertainty in the prediction of subsurface flow and transport processes, practitioners should use all data available. However, classic inverse modeling frameworks typically only make use of information contained in in-situ field measurements to provide estimates of hydrogeological parameters. Such hydrogeological information about an aquifer is difficult and costly to acquire. In this data-scarce context, the transfer of ex-situ information coming from previously investigated sites can be critical for improving predictions by better constraining the estimation procedure. Bayesian inverse modeling provides a coherent framework to represent such ex-situ information by virtue of the prior distribution and combine them with in-situ information from the target site. In this study, we present an innovative data-driven approach for defining such informative priors for hydrogeological parameters at the target site. Our approach consists in two steps, both relying on statistical and machine learning methods. The first step is data selection; it consists in selecting sites similar to the target site. We use clustering methods for selecting similar sites based on observable hydrogeological features. The second step is data assimilation; it consists in assimilating data from the selected similar sites into the informative prior. We use a Bayesian hierarchical model to account for inter-site variability and to allow for the assimilation of multiple types of site-specific data. We present the application and validation of the presented methods on an established database of hydrogeological parameters. Data and methods are implemented in the form of an open-source R-package and therefore facilitate easy use by other practitioners.

  6. Evaluation of dose distributions in gamma chamber using glass plate detector

    Narayan Pradeep

    2008-01-01

    Full Text Available A commercial glass plate of thickness 1.75 mm has been utilized for evaluation of dose distributions inside the irradiation volume of gamma chamber using optical densitometry technique. The glass plate showed linear response in the dose range 0.10 Kilo Gray (kGy to 10 kGy of cobalt-60 gamma radiation with optical sensitivity 0.04 Optical Density (OD /kGy. The change in the optical density at each identified spatial dose matrix on the glass plate in relation to the position in the irradiation volume has been presented as dose distributions inside the gamma chamber. The optical density changes have been graphically plotted in the form of surface diagram of color washes for different percentage dose rate levels as isodose distributions in gamma chamber. The variation in dose distribution inside the gamma chamber unit, GC 900, BRIT India make, using this technique has been observed within ± 15%. This technique can be used for routine quality assurances and dose distribution validation of any gamma chamber during commissioning and source replacement. The application of commercial glass plate for dose mapping in gamma chambers has been found very promising due to its wider dose linearity, quick measurement, and lesser expertise requirement in application of the technique.

  7. Neuronal model with distributed delay: analysis and simulation study for gamma distribution memory kernel.

    Karmeshu; Gupta, Varun; Kadambari, K V

    2011-06-01

    A single neuronal model incorporating distributed delay (memory)is proposed. The stochastic model has been formulated as a Stochastic Integro-Differential Equation (SIDE) which results in the underlying process being non-Markovian. A detailed analysis of the model when the distributed delay kernel has exponential form (weak delay) has been carried out. The selection of exponential kernel has enabled the transformation of the non-Markovian model to a Markovian model in an extended state space. For the study of First Passage Time (FPT) with exponential delay kernel, the model has been transformed to a system of coupled Stochastic Differential Equations (SDEs) in two-dimensional state space. Simulation studies of the SDEs provide insight into the effect of weak delay kernel on the Inter-Spike Interval(ISI) distribution. A measure based on Jensen-Shannon divergence is proposed which can be used to make a choice between two competing models viz. distributed delay model vis-á-vis LIF model. An interesting feature of the model is that the behavior of (CV(t))((ISI)) (Coefficient of Variation) of the ISI distribution with respect to memory kernel time constant parameter η reveals that neuron can switch from a bursting state to non-bursting state as the noise intensity parameter changes. The membrane potential exhibits decaying auto-correlation structure with or without damped oscillatory behavior depending on the choice of parameters. This behavior is in agreement with empirically observed pattern of spike count in a fixed time window. The power spectral density derived from the auto-correlation function is found to exhibit single and double peaks. The model is also examined for the case of strong delay with memory kernel having the form of Gamma distribution. In contrast to fast decay of damped oscillations of the ISI distribution for the model with weak delay kernel, the decay of damped oscillations is found to be slower for the model with strong delay kernel.

  8. Equipment for automatic measurement of gamma activity distribution in a column

    Kalincak, M.; Machan, V.; Vilcek, S.; Balkovsky, K.

    1978-01-01

    The design of a device for stepwise scanning of gamma activity distributions along chromatographic columns is described. In connection with a single-channel gamma spectrometer and a counting ratemeter with a recorder this device permits the resolution of a number of gamma emitters on the column, the determination of the gamma nuclide content in different chemical forms in the sample by means of column separation methods - Gel Chromatography Columns Scanning Method - and the determination of gamma nuclide distribution along the columns. The device permits the scanning of columns of up to 20 mm in diameter and 700 mm in length and continual scanning over a 450 mm column length with one clamping. With minor adaptations it is possible to scan columns up to 30 mm in diameter. The length of the scanned sections is 5 or 10 mm, the scanning time setting is arbitrary and variable activity levels and radiation energies may be measured. (author)

  9. On k-Gamma and k-Beta Distributions and Moment Generating Functions

    Gauhar Rahman

    2014-01-01

    Full Text Available The main objective of the present paper is to define k-gamma and k-beta distributions and moments generating function for the said distributions in terms of a new parameter k>0. Also, the authors prove some properties of these newly defined distributions.

  10. PREFERENCE OF PRIOR FOR BAYESIAN ANALYSIS OF THE MIXED BURR TYPE X DISTRIBUTION UNDER TYPE I CENSORED SAMPLES

    Tabassum Naz Sindhu

    2014-05-01

    Full Text Available The paper is concerned with the preference of prior for the Bayesian analysis of the shape parameter of the mixture of Burr type X distribution using the censored data. We modeled the heterogeneous population using two components mixture of the Burr type X distribution. A comprehensive simulation scheme, through probabilistic mixing, has been followed to highlight the properties and behavior of the estimates in terms of sample size, corresponding risks and the proportion of the component of the mixture. The Bayes estimators of the parameters have been evaluated under the assumption of informative and non-informative priors using symmetric and asymmetric loss functions. The model selection criterion for the preference of the prior has been introduced. The hazard rate function of the mixture distribution has been discussed. The Bayes estimates under exponential prior and precautionary loss function exhibit the minimum posterior risks with some exceptions.

  11. The Study on Radioactive Nuclide Distributions within a Fuel Rod by Tomographic Gamma Scanning Method

    Quanhu, Zhang; Lee, H. K.; Hong, K. P.; Choo, Y. S.; Kim, D. S.

    2005-06-01

    Based on the specified need of the IMEF, the feasibility of Tomographic Gamma Scanning (TGS) technique has been investigated for its potential for non-destructive gamma scanning measurements of irradiated fuel rods. TGS technique has been developed for determining some radioactive isotopes' distributions of a fuel rod in hot cell. The results obtained from the simulation model extracting from real gamma scanning experimental condition in this work by new developed computer simulation codes confirmed that the gamma emission TGS technique has potential for determination of radioactive isotopes' distributions of a fuel rod. In order to verify the simulation codes, we have designed several computation schemes for both 3 by 3 and 10 by 10 fuel rod model under present situation at M1 hot cell in IMEF. The results which relative errors are less than 10% show that we have simulated and implemented determination of radioactive isotopes' distributions on simulated fuel rod by TGS technique successfully

  12. Distributed Attention Is Implemented through Theta-Rhythmic Gamma Modulation.

    Landau, Ayelet Nina; Schreyer, Helene Marianne; van Pelt, Stan; Fries, Pascal

    2015-08-31

    When subjects monitor a single location, visual target detection depends on the pre-target phase of an ∼8 Hz brain rhythm. When multiple locations are monitored, performance decrements suggest a division of the 8 Hz rhythm over the number of locations, indicating that different locations are sequentially sampled. Indeed, when subjects monitor two locations, performance benefits alternate at a 4 Hz rhythm. These performance alternations were revealed after a reset of attention to one location. Although resets are common and important events for attention, it is unknown whether, in the absence of resets, ongoing attention samples stimuli in alternation. Here, we examined whether spatially specific attentional sampling can be revealed by ongoing pre-target brain rhythms. Visually induced gamma-band activity plays a role in spatial attention. Therefore, we hypothesized that performance on two simultaneously monitored stimuli can be predicted by a 4 Hz modulation of gamma-band activity. Brain rhythms were assessed with magnetoencephalography (MEG) while subjects monitored bilateral grating stimuli for a unilateral target event. The corresponding contralateral gamma-band responses were subtracted from each other to isolate spatially selective, target-related fluctuations. The resulting lateralized gamma-band activity (LGA) showed opposite pre-target 4 Hz phases for detected versus missed targets. The 4 Hz phase of pre-target LGA accounted for a 14.5% modulation in performance. These findings suggest that spatial attention is a theta-rhythmic sampling process that is continuously ongoing, with each sampling cycle being implemented through gamma-band synchrony. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. GammaCHI: a package for the inversion and computation of the gamma and chi-square cumulative distribution functions (central and noncentral)

    A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)

    2015-01-01

    textabstractA Fortran 90 module GammaCHI for computing and inverting the gamma and chi-square cumulative distribution functions (central and noncentral) is presented. The main novelty of this package is the reliable and accurate inversion routines for the noncentral cumulative distribution

  14. A simulation study on the dose distribution for a single beam of the gamma knife

    Chen, Chin-cheng; Jiang, Shiang-Huei; Lee, Chung-chi; Shiau, Cheng-Ying

    2000-01-01

    The purpose of this study is to evaluate the impact of the tissue heterogeneity on the dose distribution for a single beam of the gamma knife. The EGS4 Monte Carlo code was used to simulate both depth and radial profiles of the radiation dose in homogeneous and heterogeneous phantoms, respectively. The results are compared with the dose distribution calculated using the mathematical model of Gamma Plan, the treatment planning system of the gamma knife. The skull and sinus heterogeneity were simulated by a Teflon shell and an air shell, respectively. It was found that the tissue heterogeneity caused significant perturbation on the absolute depth dose at the focus as well as on the depth-dose distribution near the phantom surface and/or at the interface but little effect on the radial dose distribution. The effect of the beam aperture on the depth-dose distribution was also investigated in this study. (author)

  15. Measurement of californium-252 gamma photons depth dose distribution in tissue equivalent material. Vol. 4

    Fadel, M A; El-Fiki, M A; Eissa, H M; Abdel-Hafez, A; Naguib, S H [National Institute of Standards, Cairo (Egypt)

    1996-03-01

    Phantom of tissue equivalent material with and without bone was used measuring depth dose distribution of gamma-rays from californium-252 source. The source was positioned at center of perspex walled phantom. Depth dose measurements were recorded for X, Y and Z planes at different distances from source. TLD 700 was used for measuring the dose distribution. Results indicate that implantation of bone in tissue equivalent medium cause changes in the gamma depth dose distribution which varies according to variation in bone geometry. 9 figs.

  16. Isodose distributions and dose uniformity in the Portuguese gamma irradiation facility calculated using the MCNP code

    Oliveira, C

    2001-01-01

    A systematic study of isodose distributions and dose uniformity in sample carriers of the Portuguese Gamma Irradiation Facility was carried out using the MCNP code. The absorbed dose rate, gamma flux per energy interval and average gamma energy were calculated. For comparison purposes, boxes filled with air and 'dummy' boxes loaded with layers of folded and crumpled newspapers to achieve a given value of density were used. The magnitude of various contributions to the total photon spectra, including source-dependent factors, irradiator structures, sample material and other origins were also calculated.

  17. Energy distribution of 0. 279 MeV gamma rays Compton scattered from bound electrons

    Singh, B; Singh, P; Singh, G; Ghumman, B S

    1984-11-01

    Energy and intensity distribution of 0.279 MeV gamma rays Compton scattered from K-shell electrons of tantalum is measured at scattering angle of 70deg. The experimental results are compared with the available theoretical data. Spectral distribution is also obtained as a function of scatterer thickness to account for the contribution of false events. 13 refs.

  18. Extraction of gold and mercury from sea water with bismuth diethyldithiocarbamate prior to neutron activation-. gamma. -spectrometry

    Yu, J.C.; Lo, J.M.; Wai, C.M. (Idaho Univ. Moscow (USA). Dept. of Chemistry)

    1983-11-01

    Gold and mercury in sea water can be selectively extracted by bismuth diethyldithiocarbamate into chloroform at pH <= 1. The matrix species and many other trace elements in the system are effectively removed during extraction. When neutron activation-..gamma..-spectrometry is used, the detection limits for gold and mercury are 0.001 and 0.01 ..mu..g l/sup -1/, respectively. The relative precision is 9% for gold and 13% for mercury.

  19. Radiochemical separation of {sup 231}Pa from siliceous cake prior to its determination by gamma ray spectrometry

    Dalvi, Aditi A. [Bhabha Atomic Research Centre, Mumbai (India). Analytical Chemistry Div.; Homi Bhabha National Institute, Mumbai (India); Verma, Rakesh

    2017-07-01

    A simple and fast radiochemical method for the separation of protactinium ({sup 231}Pa) from siliceous cake for its determination by gamma ray spectrometry is described. The method involves (a) a novel approach, the fusion of the siliceous cake with sodium peroxide, (b) the dissolution of the fused mass in nitric acid and (c) the co-precipitation of {sup 231}Pa with manganese dioxide formed in-situ by the addition of solid manganous sulfate and potassium permanganate to the solution. The fusion, effected in a single step, is simpler and highly effective in comparison to methods reported hitherto in literature. The radiochemical yield of {sup 231}Pa, determined using 311.9 keV gamma ray of {sup 233}Pa radiotracer is quantitative (∝90%). The decontamination factors calculated using gamma ray spectrometry and energy dispersive X-ray fluorescence measurements show that the separation from the interfering radionuclides is high whereas separation from major and minor elements is good. Separation by ion-exchange method in hydrochloric acid, hydrofluoric acid and oxalic acid media have comparatively much lower yields. The concentration of {sup 231}Pa in the siliceous cake measured using interference-free 283.6 keV gamma ray was found to be (6.4 ± 0.33) μg kg{sup -1}. The measured concentration of {sup 231}Pa was well above the limit of quantitation whereas the coefficient of variation was ∝5%. The improvement in the limit of detection was due to the reduction in spectral background. Systematic evaluation of various uncertainty parameters showed that the major contributors to the combined uncertainty were efficiency of the high purity germanium detector and the counting statistics. The present sample decomposition and separation methods are robust, simple to perform and can be effectively used for the determination and hence source prospecting of protactinium.

  20. An overview of multivariate gamma distributions as seen from a (multivariate) matrix exponential perspective

    Bladt, Mogens; Nielsen, Bo Friis

    2012-01-01

    Laplace transform. In a longer perspective stochastic and statistical analysis for MVME will in particular apply to any of the previously defined distributions. Multivariate gamma distributions have been used in a variety of fields like hydrology, [11], [10], [6], space (wind modeling) [9] reliability [3......Numerous definitions of multivariate exponential and gamma distributions can be retrieved from the literature [4]. These distribtuions belong to the class of Multivariate Matrix-- Exponetial Distributions (MVME) whenever their joint Laplace transform is a rational function. The majority...... of these distributions further belongs to an important subclass of MVME distributions [5, 1] where the multivariate random vector can be interpreted as a number of simultaneously collected rewards during sojourns in a the states of a Markov chain with one absorbing state, the rest of the states being transient. We...

  1. Time Evolving Fission Chain Theory and Fast Neutron and Gamma-Ray Counting Distributions

    Kim, K. S.; Nakae, L. F.; Prasad, M. K.; Snyderman, N. J.; Verbeke, J. M.

    2015-01-01

    Here, we solve a simple theoretical model of time evolving fission chains due to Feynman that generalizes and asymptotically approaches the point model theory. The point model theory has been used to analyze thermal neutron counting data. This extension of the theory underlies fast counting data for both neutrons and gamma rays from metal systems. Fast neutron and gamma-ray counting is now possible using liquid scintillator arrays with nanosecond time resolution. For individual fission chains, the differential equations describing three correlated probability distributions are solved: the time-dependent internal neutron population, accumulation of fissions in time, and accumulation of leaked neutrons in time. Explicit analytic formulas are given for correlated moments of the time evolving chain populations. The equations for random time gate fast neutron and gamma-ray counting distributions, due to randomly initiated chains, are presented. Correlated moment equations are given for both random time gate and triggered time gate counting. There are explicit formulas for all correlated moments are given up to triple order, for all combinations of correlated fast neutrons and gamma rays. The nonlinear differential equations for probabilities for time dependent fission chain populations have a remarkably simple Monte Carlo realization. A Monte Carlo code was developed for this theory and is shown to statistically realize the solutions to the fission chain theory probability distributions. Combined with random initiation of chains and detection of external quanta, the Monte Carlo code generates time tagged data for neutron and gamma-ray counting and from these data the counting distributions.

  2. A rapid dissolution procedure to aid initial nuclear forensics investigations of chemically refractory compounds and particles prior to gamma spectrometry

    Reading, David G., E-mail: d.reading@noc.soton.ac.uk [GAU-Radioanalytical Laboratories, Ocean and Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH (United Kingdom); Croudace, Ian W.; Warwick, Phillip E. [GAU-Radioanalytical Laboratories, Ocean and Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH (United Kingdom); Britton, Richard [AWE plc, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom)

    2015-11-05

    A rapid and effective preparative procedure has been evaluated for the accurate determination of low-energy (40–200 keV) gamma-emitting radionuclides ({sup 210}Pb, {sup 234}Th, {sup 226}Ra, {sup 235}U) in uranium ores and uranium ore concentrates (UOCs) using high-resolution gamma ray spectrometry. The measurement of low-energy gamma photons is complicated in heterogeneous samples containing high-density mineral phases and in such situations activity concentrations will be underestimated. This is because attenuation corrections, calculated based on sample mean density, do not properly correct where dense grains are dispersed within a less dense matrix (analogous to a nugget effect). The current method overcomes these problems using a lithium tetraborate fusion that readily dissolves all components including high-density, self-attenuating minerals/compounds. This is the ideal method for dissolving complex, non-volatile components in soils, rocks, mineral concentrates, and other materials where density reduction is required. Lithium borate fusion avoids the need for theoretical efficiency corrections or measurement of matrix matched calibration standards. The resulting homogeneous quenched glass produced can be quickly dissolved in nitric acid producing low-density solutions that can be counted by gamma spectrometry. The effectiveness of the technique is demonstrated using uranium-bearing Certified Reference Materials and provides accurate activity concentration determinations compared to the underestimated activity concentrations derived from direct measurements of a bulk sample. The procedure offers an effective solution for initial nuclear forensic studies where complex refractory minerals or matrices exist. It is also significantly faster, safer and simpler than alternative approaches. - Highlights: • Low energy gamma photons (<200 keV) are attenuated in U-bearing compounds. • Corrections based on bulk density do not yield accurate activity

  3. Study on dose distribution of therapeutic proton beams with prompt gamma measurement

    Kim, J. W. [National Cancer Center, Seoul (Korea, Republic of); Min, C. H.; Kim, C. H.; Kim, D. K.; Yoon, M. Y. [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of)

    2007-03-15

    The proton beam has an advantage of the sharp dose falloff in dose distribution called Bragg peak while conventional radiation therapy modalities such as photons exhibit considerable amount of exit dose. To take advantage of this property it is important to know the exact location of the distal dose falloff. An error can cause overdose to the normal tissue or underdose to the tumor volume. The only way of finding out the dose distribution in-situ in particle therapy is to measure the gammas produced by nuclear reactions with tissue materials. Two kinds of gammas can be used: one is prompt gamma and the other is coincident gamma from the positron-emission isotopes. We chose to detect prompt gammas, and developed a prompt gamma scanning system (PGS). The proton beams of the proton therapy facility at National Cancer Center were used. The gamma distribution was compared to the dose distribution measured by an ionization chamber at three different energies of 100, 150, 200 MeV's. The two distributions were well correlated within 1-2 mm. The effect of high-energy neutron appeared as blurred distribution near the distal dose falloff at the energy of 200 MeV. We then tested the PGS shielding design by adding additional layer of paraffin plates outside of the PGS, and found that fast neutrons significantly affect the background level. But the location of the dose fall-off was nearly coincident. The analysis of gamma energy spectrum showed that cut-off energy in gamma counting can be adjusted to enhance the signal to noise ratio. Further the ATOM phantom, which has similar tissue structure to human, was used to investigate the gamma distribution for the case of inhomogeneous matter. The location of dose falloff region was found to be well defined as for water phantom. Next an actual therapy beam, which was produced by the double scattering method, was used, for which the dose falloff by the gamma distribution was completely wiped out by background neutrons. It is not

  4. Study of time variation of terrestrial gamma radiation due to depth distribution of soil moisture content

    Yoshioka, Katsuhiro

    1994-01-01

    An empirical equation was deduced from studies of time variations of terrestrial gamma exposure rate and soil moisture content with depth distribution in the surface layer. It was definitely suggested that the variation of terrestrial gamma exposure rate is most strongly influenced by the change of soil moisture content at 5 cm depth. The seasonal variation with a relative maximum in early autumn and a relative minimum in early spring was clearly obtained in the consequence of long time measurements of terrestrial gamma exposure rate and degree of soil dryness. The diurnal change and phase difference due to the effect of depth were also obtained in the dynamic characteristics of soil moisture content at 3 different depths. From the comparison between measured terrestrial gamma exposure rate and that evaluated from soil moisture content using the empirical equation, it was seen that seasonal variations of the both agreed fairly well as a whole. (author)

  5. Statistical measurement of the gamma-ray source-count distribution as a function of energy

    Zechlin, H.-S.; Cuoco, A.; Donato, F.; Fornengo, N.; Regis, M.

    2017-01-01

    Photon counts statistics have recently been proven to provide a sensitive observable for characterizing gamma-ray source populations and for measuring the composition of the gamma-ray sky. In this work, we generalize the use of the standard 1-point probability distribution function (1pPDF) to decompose the high-latitude gamma-ray emission observed with Fermi-LAT into: (i) point-source contributions, (ii) the Galactic foreground contribution, and (iii) a diffuse isotropic background contribution. We analyze gamma-ray data in five adjacent energy bands between 1 and 171 GeV. We measure the source-count distribution dN/dS as a function of energy, and demonstrate that our results extend current measurements from source catalogs to the regime of so far undetected sources. Our method improves the sensitivity for resolving point-source populations by about one order of magnitude in flux. The dN/dS distribution as a function of flux is found to be compatible with a broken power law. We derive upper limits on further possible breaks as well as the angular power of unresolved sources. We discuss the composition of the gamma-ray sky and capabilities of the 1pPDF method.

  6. Quantitative Cs-137 distributions from airborne gamma ray data

    Oberlercher, G.; Seiberl, W.

    1997-01-01

    The Chernobyl reactor accident caused in Austria Cs-137 activities up to 180 kBq/m 2 . The following paper explains how airborne NaJ-spectroscopy, originally designed for geological surveys, was used as an accurate method to obtain the ground activity of Cs-137 in certain regions of Austria. To retrieve the net count rate in a Cs-137 window it is necessary to subtract all background contributions from the peak, including the Compton continuum and the contribution of overlapping peaks. Therefore the measurement of Cs-137 with a NaJ detector system must take into account radioactive elements with gamma-ray lines near the peak energy of Cs-137 at 662 keV. In regions with higher concentrations of the natural radioactive elements uranium and thorium a peak near 600 keV is found, containing the 609 keV line of Bi-214 and the 585 keV line of TI-208. Additionally a Cs-134 line is located at 604 keV. Because of the poor energy resolution of NaJ detectors it is not possible to find a clear separation between these peaks and the Cs-137 peak. The following section describes the method that was used to obtain accurate quantified Cs-137 activity values. (author)

  7. SPATIAL AND SPECTRAL MODELING OF THE GAMMA-RAY DISTRIBUTION IN THE LARGE MAGELLANIC CLOUD

    Foreman, Gary; Chu, You-Hua; Gruendl, Robert; Fields, Brian; Ricker, Paul [Department of Astronomy, University of Illinois, 1002 W. Green St., Urbana, IL 61801 (United States); Hughes, Annie, E-mail: gforema2@illinois.edu [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2015-07-20

    We perform spatial and spectral analyses of the LMC gamma-ray emission collected over 66 months by the Fermi Gamma-ray Space Telescope. In our spatial analysis, we model the LMC cosmic-ray distribution and gamma-ray production using observed maps of the LMC interstellar medium, star formation history, interstellar radiation field, and synchrotron emission. We use bootstrapping of the data to quantify the robustness of spatial model performance. We model the LMC gamma-ray spectrum using fitting functions derived from the physics of π{sup 0} decay, Bremsstrahlung, and inverse Compton scattering. We find the integrated gamma-ray flux of the LMC from 200 MeV to 20 GeV to be 1.37 ± 0.02 × 10{sup −7} ph cm{sup −2} s{sup −1}, of which we attribute about 6% to inverse Compton scattering and 44% to Bremsstrahlung. From our work, we conclude that the spectral index of the LMC cosmic-ray proton population is 2.4 ± 0.2, and we find that cosmic-ray energy loss through gamma-ray production is concentrated within a few 100 pc of acceleration sites. Assuming cosmic-ray energy equipartition with magnetic fields, we estimate LMC cosmic rays encounter an average magnetic field strength ∼3 μG.

  8. A novel time dependent gamma evaluation function for dynamic 2D and 3D dose distributions

    Podesta, Mark; Persoon, Lucas CGG; Verhaegen, Frank

    2014-01-01

    Modern external beam radiotherapy requires detailed verification and quality assurance so that confidence can be placed on both the delivery of a single treatment fraction and on the consistency of delivery throughout the treatment course. To verify dose distributions, a comparison between prediction and measurement must be made. Comparisons between two dose distributions are commonly performed using a Gamma evaluation which is a calculation of two quantities on a pixel by pixel basis; the dose difference, and the distance to agreement. By providing acceptance criteria (e.g. 3%, 3 mm), the function will find the most appropriate match within its two degrees of freedom. For complex dynamic treatments such as IMRT or VMAT it is important to verify the dose delivery in a time dependent manner and so a gamma evaluation that includes a degree of freedom in the time domain via a third parameter, time to agreement, is presented here. A C++ (mex) based gamma function was created that could be run on either CPU and GPU computing platforms that would allow a degree of freedom in the time domain. Simple test cases were created in both 2D and 3D comprising of simple geometrical shapes with well-defined boundaries varying over time. Changes of varying magnitude in either space or time were introduced and repeated gamma analyses were performed varying the criteria. A clinical VMAT case was also included, artificial air bubbles of varying size were introduced to a patient geometry, along with shifts of varying magnitude in treatment time. For all test cases where errors in distance, dose or time were introduced, the time dependent gamma evaluation could accurately highlight the errors. The time dependent gamma function presented here allows time to be included as a degree of freedom in gamma evaluations. The function allows for 2D and 3D data sets which are varying over time to be compared using appropriate criteria without penalising minor offsets of subsequent radiation

  9. Evaluation of angular distributions and production cross-sections for discrete gamma lines in iron

    Savin, M.V.; Livke, A.V.; Zvenigorodskij, A.G.

    2001-01-01

    The experimental data were compiled and the angular distributions and production cross-sections for the E γ = 846.8, 1238.3 and 1810.8 keV discrete gamma-lines evaluated. The Legendre polynomial coefficients describing the angular distributions in the energy range up to E n = 14.0 MeV and cross-section values in the E n = 0.85-19.0 MeV range were evaluated. (author)

  10. Influence of a CIDR prior to bull breeding on pregnancy rates and subsequent calving distribution.

    Lamb, G C; Dahlen, C R; Vonnahme, K A; Hansen, G R; Arseneau, J D; Perry, G A; Walker, R S; Clement, J; Arthington, J D

    2008-11-01

    We determined whether insertion of a CIDR for 7 days prior to the breeding season enhanced pregnancy rates and altered the date of conception in suckled beef cows mated naturally. Suckled beef cows (n=2033) from 15 locations were randomly assigned to one of two treatments: (1) cows received a CIDR 7 days prior to the breeding season for 7 days (CIDR; n=999); (2) cows received no treatment (Control; n=1034). On the first day of the breeding season bulls were introduced to herds at a rate of 15-25 cows per yearling bull or 20-30 cows per mature bull. Pregnancy status and the date of conception were determined via transrectal ultrasonography at 56 and 120 days after initiation of the breeding season. Overall pregnancy rates ranged from 59.3 to 98.9% among the 15 locations. The percentage of cows becoming pregnant during the first 30 days of the breeding season was similar between CIDR (68.2%) and Control (66.7%) cows, and overall pregnancy rates were similar between CIDR (88.9%) and Control (88.6%) cows. The average day of conception after initiation of the breeding season was shorter (Pbody condition score and nor parity affected pregnancy rates or days to conception, whereas pregnancy rates and days to conception were affected (Pconception were greater for cows that calved within 40 days (31.6+/-1.2 days) of initiation of the breeding season compared to cows calving between 40 and 50 days (25.3+/-1.2 days) prior to initiation of the breeding season, which were greater than those cows calving between 50-60 days (20.0+/-0.8 days) and 60-70 days (21.3+/-1.0 days) prior to initiation of the breeding season. Cows calving greater than 70 days (17.3+/-1.5 days) from initiation of the breeding season had the shortest interval to conception. We concluded that insertion of a CIDR prior to the breeding season failed to increase overall pregnancy rates, but did influence the average day of conception.

  11. Hybrid ATDL-gamma distribution model for predicting area source acid gas concentrations

    Jakeman, A J; Taylor, J A

    1985-01-01

    An air quality model is developed to predict the distribution of concentrations of acid gas in an urban airshed. The model is hybrid in character, combining reliable features of a deterministic ATDL-based model with statistical distributional approaches. The gamma distribution was identified from a range of distributional models as the best model. The paper shows that the assumptions of a previous hybrid model may be relaxed and presents a methodology for characterizing the uncertainty associated with model predictions. Results are demonstrated for the 98-percentile predictions of 24-h average data over annual periods at six monitoring sites. This percentile relates to the World Health Organization goal for acid gas concentrations.

  12. Isotropic gates and large gamma detector arrays versus angular distributions

    Iacob, V.E.; Duchene, G.

    1997-01-01

    Angular information extracted from in-beam γ ray measurements are of great importance for γ ray multipolarity and nuclear spin assignments. In our days large Ge detector arrays became available allowing the measurements of extremely weak γ rays in almost 4π sr solid angle (e.g., EUROGAM detector array). Given the high detector efficiency it is common for the mean suppressed coincidence multiplicity to reach values as high as 4 to 6. Thus, it is possible to gate on particular γ rays in order to enhance the relative statistics of a definite reaction channel and/or a definite decaying path in the level scheme of the selected residual nucleus. As compared to angular correlations, the conditioned angular distribution spectra exhibit larger statistics because in the latter the gate-setting γ ray may be observed by all the detectors in the array, relaxing somehow the geometrical restrictions of the angular correlations. Since the in-beam γ ray emission is anisotropic one could inquire that gate setting as mentioned above, based on anisotropic γ ray which would perturb the angular distributions in the unfolded events. As our work proved, there is no reason to worry about this if the energy gate runs over the whole solid angle in an ideal 4π sr detector, i.e., if the gate is isotropic. In real quasi 4π sr detector arrays the corresponding quasi isotropic gate preserves the angular properties of the unfolded data, too. However extraction of precise angular distribution coefficient especially a 4 , requires the consideration of the deviation of the quasi isotropic gate relative to the (ideal) isotropic gate

  13. Imaging phase holdup distribution of three phase flow systems using dual source gamma ray tomography

    Varma, Rajneesh; Al-Dahhan, Muthanna; O'Sullivan, Joseph

    2008-01-01

    Full text: Multiphase reaction and process systems are used in abundance in the chemical and biochemical industry. Tomography has been successfully employed to visualize the hydrodynamics of multiphase systems. Most of the tomography methods (gamma ray, x-ray and electrical capacitance and resistance) have been successfully implemented for two phase dynamic systems. However, a significant number of chemical and biochemical systems consists of dynamic three phases. Research effort directed towards the development of tomography techniques to image such dynamic system has met with partial successes for specific systems with applicability to limited operating conditions. A dual source tomography scanner has been developed that uses the 661 keV and 1332 keV photo peaks from the 137 Cs and 60 Co for imaging three phase systems. A new approach has been developed and applied that uses the polyenergetic Alternating Minimization (A-M) algorithm, developed by O'Sullivan and Benac (2007), for imaging the holdup distribution in three phases' dynamic systems. The new approach avoids the traditional post image processing approach used to determine the holdup distribution where the attenuation images of the mixed flow obtained from gamma ray photons of two different energies are used to determine the holdup of three phases. In this approach the holdup images are directly reconstructed from the gamma ray transmission data. The dual source gamma ray tomography scanner and the algorithm were validated using a three phase phantom. Based in the validation, three phase holdup studies we carried out in slurry bubble column containing gas liquid and solid phases in a dynamic state using the dual energy gamma ray tomography. The key results of the holdup distribution studies in the slurry bubble column along with the validation of the dual source gamma ray tomography system would be presented and discussed

  14. On the Efficient Simulation of the Distribution of the Sum of Gamma-Gamma Variates with Application to the Outage Probability Evaluation Over Fading Channels

    Ben Issaid, Chaouki

    2016-06-01

    The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion, a well-desired property characterizing the robustness of importance sampling schemes, for both identically and non-identically independent distributed cases. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.

  15. On the Efficient Simulation of the Distribution of the Sum of Gamma-Gamma Variates with Application to the Outage Probability Evaluation Over Fading Channels

    Ben Issaid, Chaouki; Ben Rached, Nadhir; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul

    2016-01-01

    The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion, a well-desired property characterizing the robustness of importance sampling schemes, for both identically and non-identically independent distributed cases. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.

  16. Catalogue of response spectra for unfolding in situ gamma-ray pulse-height distributions

    Dymke, N.

    1982-01-01

    To unfold in situ gamma-ray pulse-height distributions by means of a response matrix technique, the matrix must be in keeping with the measurement geometry, detector size, and energy range to be covered by the measurements. A methodology has been described for determination of standard gamma-ray spectra needed in deriving response matrices and a spectrum catalogue compiled containing graphs and data for the 0-3 MeV (4 x 4 in. NaI(Tl)) and 0-8 MeV (1.5 x 1.5 in. NaI(Tl)) ranges. (author)

  17. Bayesian Estimation of Two-Parameter Weibull Distribution Using Extension of Jeffreys' Prior Information with Three Loss Functions

    Chris Bambey Guure

    2012-01-01

    Full Text Available The Weibull distribution has been observed as one of the most useful distribution, for modelling and analysing lifetime data in engineering, biology, and others. Studies have been done vigorously in the literature to determine the best method in estimating its parameters. Recently, much attention has been given to the Bayesian estimation approach for parameters estimation which is in contention with other estimation methods. In this paper, we examine the performance of maximum likelihood estimator and Bayesian estimator using extension of Jeffreys prior information with three loss functions, namely, the linear exponential loss, general entropy loss, and the square error loss function for estimating the two-parameter Weibull failure time distribution. These methods are compared using mean square error through simulation study with varying sample sizes. The results show that Bayesian estimator using extension of Jeffreys' prior under linear exponential loss function in most cases gives the smallest mean square error and absolute bias for both the scale parameter α and the shape parameter β for the given values of extension of Jeffreys' prior.

  18. Gamma processes and peaks-over-threshold distributions for time-dependent reliability

    Noortwijk, J.M. van; Weide, J.A.M. van der; Kallen, M.J.; Pandey, M.D.

    2007-01-01

    In the evaluation of structural reliability, a failure is defined as the event in which stress exceeds a resistance that is liable to deterioration. This paper presents a method to combine the two stochastic processes of deteriorating resistance and fluctuating load for computing the time-dependent reliability of a structural component. The deterioration process is modelled as a gamma process, which is a stochastic process with independent non-negative increments having a gamma distribution with identical scale parameter. The stochastic process of loads is generated by a Poisson process. The variability of the random loads is modelled by a peaks-over-threshold distribution (such as the generalised Pareto distribution). These stochastic processes of deterioration and load are combined to evaluate the time-dependent reliability

  19. Gamma-ray scanning of neutron activated geological sediments for studying elemental profile distributions

    Ellinger, M.; Janghorbani, M.; Starke, K.

    1976-01-01

    Gamma-ray scanning for application to elemental profile studies of geological samples was studied with a neutron activated Baltic Shield sediment. Profile distribution of seven elements were measured. The capabilities and limitations of gamma-ray scanning are discussed by comparing the results with profiles obtained after the mechanical subdivision of the sample and the activation of the appropriately sized separates. With respect to the merits and limitations of scanning gamma-ray spectrometry applied to activated complex matrices the following conclusions were drawn. Qualitatively, the scanning method yields the same information as the much more laborious method of mechanical sudbisubdivision. Quantitatively, it is significantly less accurate. The scanning method has the significant advantage of allowing preservation of the sample. This could be important for such speciments as lunar and archeological materials. The method reduces sample preparation time and the possibility of sample contamination. (T.G.)

  20. Neutron star radii, universal relations, and the role of prior distributions

    Steiner, A.W. [University of Tennessee, Department of Physics and Astronomy, Knoxville, TN (United States); Oak Ridge National Laboratory, Physics Division, Oak Ridge, TN (United States); Lattimer, J.M. [Stony Brook University, Dept. of Physics and Astronomy, Stony Brook, NY (United States); Brown, E.F. [Michigan State University, Department of Physics and Astronomy, East Lansing, MI (United States); Michigan State University, The Joint Institute for Nuclear Astrophysics-Center for the Evolution of the Elements, East Lansing, MI (United States); Michigan State University, National Superconducting Cyclotron Laboratory, East Lansing, MI (United States)

    2016-02-15

    We investigate constraints on neutron star structure arising from the assumptions that neutron stars have crusts, that recent calculations of pure neutron matter limit the equation of state of neutron star matter near the nuclear saturation density, that the high-density equation of state is limited by causality and the largest high-accuracy neutron star mass measurement, and that general relativity is the correct theory of gravity. We explore the role of prior assumptions by considering two classes of equation of state models. In a first, the intermediate- and high-density behavior of the equation of state is parameterized by piecewise polytropes. In the second class, the high-density behavior of the equation of state is parameterized by piecewise continuous line segments. The smallest density at which high-density matter appears is varied in order to allow for strong phase transitions above the nuclear saturation density. We critically examine correlations among the pressure of matter, radii, maximum masses, the binding energy, the moment of inertia, and the tidal deformability, paying special attention to the sensitivity of these correlations to prior assumptions about the equation of state. It is possible to constrain the radii of 1.4M {sub CircleDot} neutron stars to be larger than 10 km, even without consideration of additional astrophysical observations, for example, those from photospheric radius expansion bursts or quiescent low-mass X-ray binaries. We are able to improve the accuracy of known correlations between the moment of inertia and compactness as well as the binding energy and compactness. We also demonstrate the existence of a correlation between the neutron star binding energy and the moment of inertia. (orig.)

  1. The Truncated Lognormal Distribution as a Luminosity Function for SWIFT-BAT Gamma-Ray Bursts

    Lorenzo Zaninetti

    2016-11-01

    Full Text Available The determination of the luminosity function (LF in Gamma ray bursts (GRBs depends on the adopted cosmology, each one characterized by its corresponding luminosity distance. Here, we analyze three cosmologies: the standard cosmology, the plasma cosmology and the pseudo-Euclidean universe. The LF of the GRBs is firstly modeled by the lognormal distribution and the four broken power law and, secondly, by a truncated lognormal distribution. The truncated lognormal distribution fits acceptably the range in luminosity of GRBs as a function of the redshift.

  2. Interchromosomal distribution of gamma ray-induced chromatid aberrations in Chinese hamster ovary cells

    Martinez-Lopez, Wilner; Porro, Valentina; Folle, Gustavo A.; Mendez-Acuna, Leticia; Obe, Guenter; Savage, John R.K.

    2000-01-01

    Inter chromosomal distributions of breakpoints from chromatid-type aberrations induced by gamma rays in Chinese hamster ovary cells were analyzed. In most chromosomes the distribution was as expected from chromosome lengths for simple breaks or the respective relative corrected length in case of exchanges. There were deviations from expectation in a few chromosomes for chromatid breaks, interchanges, intra-arm intra changes and inter-arm intra changes. Especially interesting are the results concerning chromosomes 2 and 8, which were more often involved in exchanges than expected. An 'exchange phenotype' for these chromosomes is proposed and possible explanations for the nonrandom distribution of chromosome breakpoints are presented. (author)

  3. Distribution and characteristics of gamma and cosmic ray dose rate in living environment

    Nagaoka, Toshi; Moriuchi, Shigeru

    1991-01-01

    A series of environmental radiation surveys was carried out from the viewpoint of characterizing the natural radiation dose rate distribution in the living environment, including natural and artificial ones. Through the analysis of the data obtained at numbers of places, several aspects of the radiation field in living environments were clarified. That is the gamma ray dose rate varies due to the following three dominant causes: 1) the radionuclide concentration of surrounding materials acting as gamma ray sources, 2) the spatial distribution of surrounding materials, and 3) the geometrical and shielding conditions between the natural gamma ray sources and the measured point; whereas, the cosmic ray dose rate varies due to the thickness of upper shielding materials. It was also suggested that the gamma ray dose rate generally shows an upward tendency, and the cosmic ray dose rate a downward one in artificial environment. This kind of knowledge is expected to serve as fundamental information for accurate and realistic evaluation of the collective dose in the living environment. (author)

  4. On the Efficient Simulation of the Distribution of the Sum of Gamma-Gamma Variates with Application to the Outage Probability Evaluation Over Fading Channels

    Ben Issaid, Chaouki

    2017-01-26

    The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverberation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is related to the difficult question of analyzing the statistics of a sum of Gamma- Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of Gamma-Gamma variates. More specifically, we propose robust importance sampling schemes that efficiently evaluates the outage probability of diversity receivers over Gamma-Gamma fading channels. The proposed estimators satisfy the well-known bounded relative error criterion for both maximum ratio combining and equal gain combining cases. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.

  5. Spatial distribution of the gamma-ray bursts at very high redshift

    Mészáros, Attila

    2018-05-01

    The author - with his collaborators - already in years 1995-96 have shown - purely from the analyses of the observations - that the gamma-ray bursts (GRBs) can be till redshift 20. Since that time several other statistical studies of the spatial distribution of GRBs were provided. Remarkable conclusions concerning the star-formation rate and the validity of the cosmological principle were obtained about the regions of the cosmic dawn. In this contribution these efforts are surveyed.

  6. A method for exploring the distribution of radioelements at depth using gamma-ray spectrometric data

    Li Qingyang

    1997-01-01

    Based on the inherent relation between radioelements and terrestrial heat flow, theoretically shows the possibility of exploring the distribution of radioelements at depth using gamma-ray spectrometric data, and a data-processing and synthesizing method has been adopted to deduce the calculation formula. The practical application in the uranium mineralized area No. 2801 in Yunnan Province proves that this method is of practical value, and it has been successfully applied to the data processing and good results have been obtained

  7. Directional Stand-off Detection of Fast Neutrons and Gammas Using Angular Scattering Distributions

    Vanier P. e.; Dioszegi, I.; Salwen, C.; Forman, L.

    2009-10-25

    We have investigated the response of a DoubleScatter Neutron Spectrometer (DSNS) for sources at long distances (gr than 200 meters). We find that an alternative method for analyzing double scatter data avoids some uncertainties introduced by amplitude measurements in plastic scintillators.Time of flight is used to discriminate between gamma and neutron events, and the kinematic distributions of scattering angles are assumed to apply. Non-relativistic neutrons are most likely to scatter at 45°, while gammas with energies greater than 2 MeV are most likely to be forward scattered. The distribution of scattering angles of fission neutrons arriving from a distant point source generates a 45° cone, which can be back-projected to give the source direction. At the same time, the distribution of Compton-scattered gammas has a maximum in the forward direction, and can be made narrower by selecting events that deposit minimal energy in the first scattering event. We have further determined that the shape of spontaneous fission neutron spectra at ranges gr than 110 m is still significantly different from thecosmic ray background.

  8. A method for determining the analytical form of a radionuclide depth distribution using multiple gamma spectrometry measurements

    Dewey, Steven Clifford, E-mail: sdewey001@gmail.com [United States Air Force School of Aerospace Medicine, Occupational Environmental Health Division, Health Physics Branch, Radiation Analysis Laboratories, 2350 Gillingham Drive, Brooks City-Base, TX 78235 (United States); Whetstone, Zachary David, E-mail: zacwhets@umich.edu [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States); Kearfott, Kimberlee Jane, E-mail: kearfott@umich.edu [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States)

    2011-06-15

    When characterizing environmental radioactivity, whether in the soil or within concrete building structures undergoing remediation or decommissioning, it is highly desirable to know the radionuclide depth distribution. This is typically modeled using continuous analytical expressions, whose forms are believed to best represent the true source distributions. In situ gamma ray spectroscopic measurements are combined with these models to fully describe the source. Currently, the choice of analytical expressions is based upon prior experimental core sampling results at similar locations, any known site history, or radionuclide transport models. This paper presents a method, employing multiple in situ measurements at a single site, for determining the analytical form that best represents the true depth distribution present. The measurements can be made using a variety of geometries, each of which has a different sensitivity variation with source spatial distribution. Using non-linear least squares numerical optimization methods, the results can be fit to a collection of analytical models and the parameters of each model determined. The analytical expression that results in the fit with the lowest residual is selected as the most accurate representation. A cursory examination is made of the effects of measurement errors on the method. - Highlights: > A new method for determining radionuclide distribution as a function of depth is presented. > Multiple measurements are used, with enough measurements to determine the unknowns in analytical functions that might describe the distribution. > The measurements must be as independent as possible, which is achieved through special collimation of the detector. > Although the effects of measurements errors may be significant on the results, an improvement over other methods is anticipated.

  9. Differential Pair Distribution Function Study of the Structure of Arsenate Adsorbed on Nanocrystalline [gamma]-Alumina

    Li, Wei; Harrington, Richard; Tang, Yuanzhi; Kubicki, James D.; Aryanpour, Masoud; Reeder, Richard J.; Parise, John B.; Phillips, Brian L. (SBU); (Penn)

    2012-03-15

    Structural information is important for understanding surface adsorption mechanisms of contaminants on metal (hydr)oxides. In this work, a novel technique was employed to study the interfacial structure of arsenate oxyanions adsorbed on {gamma}-alumina nanoparticles, namely, differential pair distribution function (d-PDF) analysis of synchrotron X-ray total scattering. The d-PDF is the difference of properly normalized PDFs obtained for samples with and without arsenate adsorbed, otherwise identically prepared. The real space pattern contains information on atomic pair correlations between adsorbed arsenate and the atoms on {gamma}-alumina surface (Al, O, etc.). PDF results on the arsenate adsorption sample on {gamma}-alumina prepared at 1 mM As concentration and pH 5 revealed two peaks at 1.66 {angstrom} and 3.09 {angstrom}, corresponding to As-O and As-Al atomic pair correlations. This observation is consistent with those measured by extended X-ray absorption fine structure (EXAFS) spectroscopy, which suggests a first shell of As-O at 1.69 {+-} 0.01 {angstrom} with a coordination number of 4 and a second shell of As-Al at 3.13 {+-} 0.04 {angstrom} with a coordination number of 2. These results are in agreement with a bidentate binuclear coordination environment to the octahedral Al of {gamma}-alumina as predicted by density functional theory (DFT) calculation.

  10. Angular distribution of 662keV multiply-Compton scattered gamma rays in copper

    Singh, Manpreet; Singh, Gurvinderjit; Sandhu, B.S.; Singh, Bhajan

    2007-01-01

    The angular distribution of multiple Compton scattering of 662keV gamma photons, obtained from six Curie 137 Cs source, incident on copper scatterer of varying thickness is studied experimentally in both the forward and backward hemispheres. The scattered photons are detected by a 51mmx51mm NaI(Tl) scintillation detector. The full-energy peak corresponding to singly scattered events is reconstructed analytically. We observe that the numbers of multiply scattered events, having same energy as in the singly scattered distribution, first increases with increase in target thickness and then saturate. The optimum thickness at which the multiply scattered events saturate is determined at different scattering angles

  11. Prior selection for Gumbel distribution parameters using multiple-try metropolis algorithm for monthly maxima PM10 data

    Amin, Nor Azrita Mohd; Adam, Mohd Bakri; Ibrahim, Noor Akma

    2014-09-01

    The Multiple-try Metropolis (MTM) algorithm is the new alternatives in the field of Bayesian extremes for summarizing the posterior distribution. MTM produce efficient estimation scheme for modelling extreme data in term of the convergence and small burn-in periods. The main objective is to explore the accuracy of the parameter estimation to the change of priors and compare the results with a classical likelihood-based analysis. Focus is on modelling the extreme data based on block maxima approach using Gumbel distribution. The comparative study between MTM and MLE is shown by the numerical problems. Several goodness of fit tests are compute for selecting the best model. The application is on the monthly maxima PM10 data for Johor state.

  12. Determination of the distal dose edge in a human phantom by measuring the prompt gamma distribution: a Monte Carlo study

    Min, Chul Hee; Lee, Han Rim; Yeom, Yeon Su; Cho, Sung Koo; Kim, Chan Hyeong [Hanyang University, Seoul (Korea, Republic of)

    2010-06-15

    The close relationship between the proton dose distribution and the distribution of prompt gammas generated by proton-induced nuclear interactions along the path of protons in a water phantom was demonstrated by means of both Monte Carlo simulations and limited experiments. In order to test the clinical applicability of the method for determining the distal dose edge in a human body, a human voxel model, constructed based on a body-composition-approximated physical phantom, was used, after which the MCNPX code was used to analyze the energy spectra and the prompt gamma yields from the major elements composing the human voxel model; finally, the prompt gamma distribution, generated from the voxel model and measured by using an array-type prompt gamma detection system, was calculated and compared with the proton dose distribution. According to the results, effective prompt gammas were produced mainly by oxygen, and the specific energy of the prompt gammas, allowing for selective measurement, was found to be 4.44 MeV. The results also show that the distal dose edge in the human phantom, despite the heterogeneous composition and the complicated shape, can be determined by measuring the prompt gamma distribution with an array-type detection system.

  13. Two Dimensional Verification of the Dose Distribution of Gamma Knife Model C using Monte Carlo Simulation with a Virtual Source

    Kim, Tae-Hoon; Kim, Yong-Kyun; Lee, Cheol Ho; Son, Jaebum; Lee, Sangmin; Kim, Dong Geon; Choi, Joonbum; Jang, Jae Yeong [Hanyang University, Seoul (Korea, Republic of); Chung, Hyun-Tai [Seoul National University, Seoul (Korea, Republic of)

    2016-10-15

    Gamma Knife model C contains 201 {sup 60}Co sources located on a spherical surface, so that each beam is concentrated on the center of the sphere. In the last work, we simulated the Gamma Knife model C through Monte Carlo simulation code using Geant4. Instead of 201 multi-collimation system, we made one single collimation system that collects source parameter passing through the collimator helmet. Using the virtual source, we drastically reduced the simulation time to transport 201 gamma circle beams to the target. Gamma index has been widely used to compare two dose distributions in cancer radiotherapy. Gamma index pass rates were compared in two calculated results using the virtual source method and the original method and measured results obtained using radiocrhomic films. A virtual source method significantly reduces simulation time of a Gamma Knife Model C and provides equivalent absorbed dose distributions as that of the original method showing Gamma Index pass rate close to 100% under 1mm/3% criteria. On the other hand, it gives a little narrow dose distribution compared to the film measurement showing Gamma Index pass rate of 94%. More accurate and sophisticated examination on the accuracy of the simulation and film measurement is necessary.

  14. Using gamma distribution to determine half-life of rotenone, applied in freshwater

    Rohan, Maheswaran, E-mail: mrohan@aut.ac.nz [Department of Biostatistics and Epidemiology, Auckland University of Technology, Auckland (New Zealand); Fairweather, Alastair; Grainger, Natasha [Science and Capability, Department of Conservation, Hamilton (New Zealand)

    2015-09-15

    Following the use of rotenone to eradicate invasive pest fish, a dynamic first-order kinetic model is usually used to determine the half-life and rate at which rotenone dissipated from the treated waterbody. In this study, we investigate the use of a stochastic gamma model for determining the half-life and rate at which rotenone dissipates from waterbodies. The first-order kinetic and gamma models produced similar values for the half-life (4.45 days and 5.33 days respectively) and days to complete dissipation (51.2 days and 52.48 days respectively). However, the gamma model fitted the data better and was more flexible than the first-order kinetic model, allowing us to use covariates and to predict a possible range for the half-life of rotenone. These benefits are particularly important when examining the influence that different environmental factors have on rotenone dissipation and when trying to predict the rate at which rotenone will dissipate during future operations. We therefore recommend that in future the gamma distribution model is used when calculating the half-life of rotenone in preference to the dynamic first-order kinetics model. - Highlights: • We investigated the use of the gamma model to calculate the half-life of rotenone. • Physical and environmental variables can be incorporated into the model. • A method for calculating the range around a mean half-life is presented. • The model is more flexible than the traditionally used first-order kinetic model.

  15. Multiwire proportional gamma camera for imaging /sup 99/Tcsup(m) radionuclide distributions

    Bateman, J E; Connolly, J F [Science Research Council, Chilton (UK). Rutherford Lab.

    1978-05-01

    A gamma camera made of multiple multiwire proportional chambers with thin converter foils has been evaluated for clinical application. Results are presented from a small prototype (10 cm x 10 cm) showing good imaging of /sup 99/Tcsup(m) radionuclide distributions and confirming the predictions of the theory regarding quantum efficiency and spatial resolution. The technique is especially aimed at creating a gamma camera with an active area > approximately 3 1m/sup 2/, a quantum efficiency of 15% and a spatial resolution approximately 3 mm, whole body scanning and tomographic applications. The results generated by the current prototype indicate that the above requirements can be met using relatively cheap mass production techniques from the electronics industry. This apparatus is covered by patent application number 26595/77.

  16. Distributions of neutron and gamma doses in phantom under a mixed field

    Beraud-Sudreau, E.

    1982-06-01

    A calculation program, based on Monte Carlo method, allowed to estimate the absorbed doses relatives to the reactor primary radiation, in a water cubic phantom and in cylindrical phantoms modelized from tissue compositions. This calculation is a theoretical approach of gamma and neutron dose gradient study in an animal phantom. PIN junction dosimetric characteristics have been studied experimentally. Air and water phantom radiation doses measured by PIN junction and lithium 7 fluoride, in reactor field have been compared to doses given by dosimetry classical techniques as tissue equivalent plastic and aluminium ionization chambers. Dosimeter responses have been employed to evaluate neutron and gamma doses in plastinaut (tissue equivalent plastic) and animal (piglet). Dose repartition in the piglet bone medulla has been also determined. This work has been completed by comparisons with Doerschell, Dousset and Brown results and by neutron dose calculations; the dose distribution related to lineic energy transfer in Auxier phantom has been also calculated [fr

  17. A multiwire proportional gamma camera for imaging 99Tcsup(m) radionuclide distributions

    Bateman, J.E.; Connolly, J.F.

    1978-01-01

    A gamma camera made of multiple multiwire proportional chambers with thin converter foils has been evaluated for clinical application. Results are presented from a small prototype (10 cm x 10 cm) showing good imaging of 99 Tcsup(m) radionuclide distributions and confirming the predictions of the theory regarding quantum efficiency and spatial resolution. The technique is especially aimed at creating a gamma camera with an active area > approximately 3 1m 2 , a quantum efficiency of 15% and a spatial resolution approximately 3 mm, whole body scanning and tomographic applications. The results generated by the current prototype indicate that the above requirements can be met using relatively cheap mass production techniques from the electronics industry. This apparatus is covered by patent application number 26595/77. (author)

  18. A distribution-free test for anomalous gamma-ray spectra

    Chan, Kung-sik; Li, Jinzheng; Eichinger, William; Bai, Er-Wei

    2014-01-01

    Gamma-ray spectra are increasingly acquired in monitoring cross-border traffic, or in an area search for lost or orphan special nuclear material (SNM). The signal in such data is generally weak, resulting in poorly resolved spectra, thereby making it hard to detect the presence of SNM. We develop a new test for detecting anomalous spectra by characterizing the complete shape change in a spectrum from background radiation; the proposed method may serve as a tripwire for routine screening for SNM. We show that, with increasing detection time, the limiting distribution of the test is given by some functional of the Brownian bridge. The efficacy of the proposed method is illustrated by simulations. - Highlights: • We develop a new non-parametric test for detecting anomalous gamma-ray spectra. • The proposed test has good empirical power for detecting weak signals. • It can serve as an effective tripwire for invoking more thorough scrutiny of the source

  19. Liver polyribosome distribution in intact and adrenalectomized rats exposed to. gamma. radiation

    Yatvin, M B; Abdel-Halim, M N [Wisconsin Univ., Madison (USA). Dept. of Radiology; Wisconsin Univ., Madison (USA). Dept. of Human Oncology)

    1978-06-01

    The mechanism(s) by which gamma radiation influences liver polyribosome distribution was studied in groups of intact and adrenalectomized male rats. A shift from light to heavy aggregates occurred in the polyribosomes of both intact and adrenalectomized rats after they were exposed to gamma rays. In irradiated adrenalectomized rats, however, the shift to heavier aggregates was not as great as that which occurred in irradiated adrenal-intact animals. Subcutaneous injection of cortisone acetate (10 mg/100 g body weight) also altered the liver polyribosome patterns of both intact and adrenalectomized rats within 8 hours of its administration. The shift which occurred following cortisone administration, however, was less striking than that seen after irradiation only. Thus, although adrenal glucocorticoids contribute to the radiation-indu ied shift in liver polyribosomes in adrenal-intact rats, other factors appear to be involved, since the shift is also obtained in adrenalectomized animals.

  20. Dose rate distribution of the GammaBeam: 127 irradiator using MCNPX code

    Gual, Maritza Rodriguez; Batista, Adriana de Souza Medeiros; Pereira, Claubia; Faria, Luiz O. de; Grossi, Pablo Andrade

    2013-01-01

    The GammaBeam - 127 Irradiator is widely used for biological, chemical and medical applications of the gamma irradiation technology using Cobalt 60 radioactive at the Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil. The source has maximum activity of 60.000Ci, which is composed by 16 double encapsulated radioactive pencils placed in a rack. The facility is classified by the IAEA as Category II (dry storage facility). The aim of this work is to present a modelling developed to evaluate the dose rates at the irradiation room and the dose distribution at the irradiated products. In addition, the simulations could be used as a predictive tool of dose evaluation in the irradiation facility helping benchmark experiments in new similar facilities. The MCNPX simulated results were compared and validated with radiometric measurements using Fricke and TLDs dosimeters along several positions inside the irradiation room. (author)

  1. Measurements of angular and energy distributions of gamma-rays resulting from neutron interactions in shielding barriers

    Makarious, A.S.; Maayouf, R.M.A.; Megahid, R.

    1978-01-01

    Measurements of both angular and energy distributions of secondary gamma resulting from interactions of neutrons emerging from one of the ET-RR-1 reactor beam holes, in barriers from iron, lead and water are reported. The measurements were carried out, both with a bare neutron beam and with the beam being transmitted through a B4C. Filter, using a stilbene crystal gamma spectrometer. The spectrometer applies discrimination between neutrons and gammas according to the difference in decay times of the scintillations produced by them in stilbene. The described angular distributions resulted from measurements made at different angles of neutron incidence and with three different thicknesses of each sample

  2. Constrained noninformative priors

    Atwood, C.L.

    1994-10-01

    The Jeffreys noninformative prior distribution for a single unknown parameter is the distribution corresponding to a uniform distribution in the transformed model where the unknown parameter is approximately a location parameter. To obtain a prior distribution with a specified mean but with diffusion reflecting great uncertainty, a natural generalization of the noninformative prior is the distribution corresponding to the constrained maximum entropy distribution in the transformed model. Examples are given

  3. Testing the anisotropy in the angular distribution of Fermi/GBM gamma-ray bursts

    Tarnopolski, M.

    2017-12-01

    Gamma-ray bursts (GRBs) were confirmed to be of extragalactic origin due to their isotropic angular distribution, combined with the fact that they exhibited an intensity distribution that deviated strongly from the -3/2 power law. This finding was later confirmed with the first redshift, equal to at least z = 0.835, measured for GRB970508. Despite this result, the data from CGRO/BATSE and Swift/BAT indicate that long GRBs are indeed distributed isotropically, but the distribution of short GRBs is anisotropic. Fermi/GBM has detected 1669 GRBs up to date, and their sky distribution is examined in this paper. A number of statistical tests are applied: nearest neighbour analysis, fractal dimension, dipole and quadrupole moments of the distribution function decomposed into spherical harmonics, binomial test and the two-point angular correlation function. Monte Carlo benchmark testing of each test is performed in order to evaluate its reliability. It is found that short GRBs are distributed anisotropically in the sky, and long ones have an isotropic distribution. The probability that these results are not a chance occurrence is equal to at least 99.98 per cent and 30.68 per cent for short and long GRBs, respectively. The cosmological context of this finding and its relation to large-scale structures is discussed.

  4. An Estimation of the Gamma-Ray Burst Afterglow Apparent Optical Brightness Distribution Function

    Akerlof, Carl W.; Swan, Heather F.

    2007-12-01

    By using recent publicly available observational data obtained in conjunction with the NASA Swift gamma-ray burst (GRB) mission and a novel data analysis technique, we have been able to make some rough estimates of the GRB afterglow apparent optical brightness distribution function. The results suggest that 71% of all burst afterglows have optical magnitudes with mRa strong indication that the apparent optical magnitude distribution function peaks at mR~19.5. Such estimates may prove useful in guiding future plans to improve GRB counterpart observation programs. The employed numerical techniques might find application in a variety of other data analysis problems in which the intrinsic distributions must be inferred from a heterogeneous sample.

  5. Constraints on the galactic distribution of cosmic rays from the COS-B gamma-ray data

    1985-08-01

    The velocity information of the HI and CO observations is used as a distance indicator to ascertain the spatial distribution of the interstellar gas. Using this distance information, the galacto-centric distribution of the gamma-ray emissivity (the production rate per H atom) is determined for three gamma-ray energy ranges from a correlation study of the gamma-ray intensity maps and the gas-tracer maps for selected galacto-centric distance intervals, taking into account the expected IC contribution and pointlike gamma-ray sources. On the assumption that unresolved gamma-ray point sources do not contribute significantly to the observed gamma-ray emission, the gamma-ray emissivity is proportional to the Cosmic ray density and, more specifically, the energy dependence can be used to study separately the distribution of Cosmic ray electrons and nuclei: whereas the emission for the 300 MeV - 5 GeV range is dominated by π 0 -decay, the 70 MeV - 150 MeV range has a large electron bremsstrahlung contribution

  6. Dose Distribution Calculation Using MCNPX Code in the Gamma-ray Irradiation Cell

    Kim, Yong Ho

    1991-02-01

    60 Co-gamma irradiators have long been used for foods sterilization, plant mutation and development of radio-protective agents, radio-sensitizers and other purposes. The Applied Radiological Science Research Institute of Cheju National University has a multipurpose gamma irradiation facility loaded with a MDS Nordin standard 60 Co source (C188), of which the initial activity was 400 TBq (10,800 Ci) on February 19, 2004. This panoramic gamma irradiator is designed to irradiate in all directions various samples such as plants, cultured cells and mice to administer given radiation doses. In order to give accurate doses to irradiation samples, appropriate methods of evaluating, both by calculation and measurement, the radiation doses delivered to the samples should be set up. Computational models have been developed to evaluate the radiation dose distributions inside the irradiation chamber and the radiation doses delivered to typical biolological samples which are frequently irradiated in the facility. The computational models are based on using the MCNPX code. The horizontal and vertical dose distributions has been calculated inside the irradiation chamber and compared the calculated results with measured data obtained with radiation dosimeters to verify the computational models. The radiation dosimeters employed are a Famer's type ion chamber and MOSFET dosimeters. Radiation doses were calculated by computational models, which were delivered to cultured cell samples contained in test tubes and to a mouse fixed in a irradiation cage, and compared the calculated results with the measured data. The computation models are also tested to see if they can accurately simulate the case where a thick lead shield is placed between the source and detector. Three tally options of the MCNPX code, F4, F5 and F6, are alternately used to see which option produces optimum results. The computation models are also used to calculate gamma ray energy spectra of a BGO scintillator at

  7. Analysis of nonlocal neural fields for both general and gamma-distributed connectivities

    Hutt, Axel; Atay, Fatihcan M.

    2005-04-01

    This work studies the stability of equilibria in spatially extended neuronal ensembles. We first derive the model equation from statistical properties of the neuron population. The obtained integro-differential equation includes synaptic and space-dependent transmission delay for both general and gamma-distributed synaptic connectivities. The latter connectivity type reveals infinite, finite, and vanishing self-connectivities. The work derives conditions for stationary and nonstationary instabilities for both kernel types. In addition, a nonlinear analysis for general kernels yields the order parameter equation of the Turing instability. To compare the results to findings for partial differential equations (PDEs), two typical PDE-types are derived from the examined model equation, namely the general reaction-diffusion equation and the Swift-Hohenberg equation. Hence, the discussed integro-differential equation generalizes these PDEs. In the case of the gamma-distributed kernels, the stability conditions are formulated in terms of the mean excitatory and inhibitory interaction ranges. As a novel finding, we obtain Turing instabilities in fields with local inhibition-lateral excitation, while wave instabilities occur in fields with local excitation and lateral inhibition. Numerical simulations support the analytical results.

  8. Gamma-ray Burst Formation Environment: Comparison of Redshift Distributions of GRB Afterglows

    Sung-Eun Kim

    2005-12-01

    Full Text Available Since gamma-ray bursts(GRBs have been first known to science societites in 1973, many scientists are involved in their studies. Observations of GRB afterglows provide us with much information on the environment in which the observed GRBs are born. Study of GRB afterglows deals with longer timescale emissions in lower energy bands (e.g., months or even up to years than prompt emissions in gamma-rays. Not all the bursts accompany afterglows in whole ranges of wavelengths. It has been suggested as a reason for that, for instance, that radio and/or X-ray afterglows are not recorded mainly due to lower sensitivity of detectors, and optical afterglows due to extinctions in intergalactic media or self-extinctions within a host galaxy itself. Based on the idea that these facts may also provide information on the GRB environment, we analyze statistical properties of GRB afterglows. We first select samples of the redshift-known GRBs according to the wavelength of afterglow they accompanied. We then compare their distributions as a function of redshift, using statistical methods. As a results, we find that the distribution of the GRBs with X-ray afterglows is consistent with that of the GRBs with optical afterglows. We, therefore, conclude that the lower detection rate of optical afterglows is not due to extinctions in intergalactic media.

  9. Pricing the property claim service (PCS) catastrophe insurance options using gamma distribution

    Noviyanti, Lienda; Soleh, Achmad Zanbar; Setyanto, Gatot R.

    2017-03-01

    The catastrophic events like earthquakes, hurricanes or flooding are characteristics for some areas, a properly calculated annual premium would be closely as high as the loss insured. From an actuarial perspective, such events constitute the risk that are not insurable. On the other hand people living in such areas need protection. In order to securitize the catastrophe risk, futures or options based on a loss index could be considered. Chicago Board of Trade launched a new class of catastrophe insurance options based on new indices provided by Property Claim Services (PCS). The PCS-option is based on the Property Claim Service Index (PCS-Index). The index are used to determine and payout in writing index-based insurance derivatives. The objective of this paper is to price PCS Catastrophe Insurance Option based on PCS Catastrophe index. Gamma Distribution is used to estimate PCS Catastrophe index distribution.

  10. Parameter Estimations and Optimal Design of Simple Step-Stress Model for Gamma Dual Weibull Distribution

    Hamdy Mohamed Salem

    2018-03-01

    Full Text Available This paper considers life-testing experiments and how it is effected by stress factors: namely temperature, electricity loads, cycling rate and pressure. A major type of accelerated life tests is a step-stress model that allows the experimenter to increase stress levels more than normal use during the experiment to see the failure items. The test items are assumed to follow Gamma Dual Weibull distribution. Different methods for estimating the parameters are discussed. These include Maximum Likelihood Estimations and Confidence Interval Estimations which is based on asymptotic normality generate narrow intervals to the unknown distribution parameters with high probability. MathCAD (2001 program is used to illustrate the optimal time procedure through numerical examples.

  11. Spatial distribution of {gamma} emissivity and fast ions during ({sup 3}He)D ICRF heating experiments on JET

    Start, D F.H. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Righi, E [Imperial Coll. of Science and Technology, London (United Kingdom); Warrick, C [UKAEA Culham Lab., Abingdon (United Kingdom)

    1994-07-01

    A model is presented that can simulate the {gamma} emissivity in the poloidal cross-section during ({sup 3}He)D ICRF heated discharges in JET plasmas, by merging information obtained from the fast ion distribution and from nuclear reactions producing the observed {gamma} emissivity (production of {gamma} photons during {sup 3}He-{sup 9}Be reactions). This technique can play an important role in the identification of plasma instabilities that affect the redistribution of the fast ions in the plasma, like the TAE modes and the ripple in the tokamak magnetic field. 9 refs., 4 figs., 1 tab.

  12. Modified model of neutron resonance widths distribution. Results of total gamma-widths approximation

    Sukhovoj, A.M.; Khitrov, V.A.

    2011-01-01

    Functional dependences of probability to observe given Γ n 0 value and algorithms for determination of the most probable magnitudes of the modified model of resonance parameter distributions were used for analysis of the experimental data on the total radiative widths of neutron resonances. As in the case of neutron widths, precise description of the Γ γ spectra requires a superposition of three and more probability distributions for squares of the random normally distributed values with different nonzero average and nonunit dispersion. This result confirms the preliminary conclusion obtained earlier at analysis of Γ n 0 that practically in all 56 tested sets of total gamma widths there are several groups noticeably differing from each other by the structure of their wave functions. In addition, it was determined that radiative widths are much more sensitive than the neutron ones to resonance wave functions structure. Analysis of early obtained neutron reduced widths distribution parameters for 157 resonance sets in the mass region of nuclei 35 ≤ A ≤ 249 was also performed. It was shown that the experimental values of widths can correspond with high probability to superposition of several expected independent distributions with their nonzero mean values and nonunit dispersion

  13. Malaria prevalence, anemia and baseline intervention coverage prior to mass net distributions in Abia and Plateau States, Nigeria.

    Noland, Gregory S; Graves, Patricia M; Sallau, Adamu; Eigege, Abel; Emukah, Emmanuel; Patterson, Amy E; Ajiji, Joseph; Okorofor, Iheanyichi; Oji, Oji Uka; Umar, Mary; Alphonsus, Kal; Damen, James; Ngondi, Jeremiah; Ozaki, Masayo; Cromwell, Elizabeth; Obiezu, Josephine; Eneiramo, Solomon; Okoro, Chinyere; McClintic-Doyle, Renn; Oresanya, Olusola; Miri, Emmanuel; Emerson, Paul M; Richards, Frank O

    2014-03-26

    Nigeria suffers the world's largest malaria burden, with approximately 51 million cases and 207,000 deaths annually. As part of the country's aim to reduce by 50% malaria-related morbidity and mortality by 2013, it embarked on mass distribution of free long-lasting insecticidal nets (LLINs). Prior to net distribution campaigns in Abia and Plateau States, Nigeria, a modified malaria indicator survey was conducted in September 2010 to determine baseline state-level estimates of Plasmodium prevalence, childhood anemia, indoor residual spraying (IRS) coverage and bednet ownership and utilization. Overall age-adjusted prevalence of Plasmodium infection by microscopy was similar between Abia (36.1%, 95% CI: 32.3%-40.1%; n = 2,936) and Plateau (36.6%, 95% CI: 31.3%-42.3%; n = 4,209), with prevalence highest among children 5-9 years. P. malariae accounted for 32.0% of infections in Abia, but only 1.4% of infections in Plateau. More than half of children ≤10 years were anemic, with anemia significantly higher in Abia (76.9%, 95% CI: 72.1%-81.0%) versus Plateau (57.1%, 95% CI: 50.6%-63.4%). Less than 1% of households in Abia (n = 1,305) or Plateau (n = 1,335) received IRS in the 12 months prior to survey. Household ownership of at least one bednet of any type was 10.1% (95% CI: 7.5%-13.4%) in Abia and 35.1% (95% CI: 29.2%-41.5%) in Plateau. Ownership of two or more bednets was 2.1% (95% CI: 1.2%-3.7%) in Abia and 14.5% (95% CI: 10.2%-20.3%) in Plateau. Overall reported net use the night before the survey among all individuals, children Abia and 14.7%, 19.1% and 21.0%, respectively in Plateau. Among households owning nets, 34.4% of children Abia used a net, compared to 52.6% of children and 62.7% of pregnant women in Plateau. These results reveal high Plasmodium prevalence and childhood anemia in both states, low baseline coverage of IRS and LLINs, and sub-optimal net use-especially among age groups with highest observed malaria burden.

  14. Lithium formate EPR dosimetry for verifications of planned dose distributions prior to intensity-modulated radiation therapy

    Gustafsson, H.; Lund, E.; Olsson, S.

    2008-09-01

    The objective of the present investigation was to evaluate lithium formate electron paramagnetic resonance (EPR) dosimetry for measurement of dose distributions in phantoms prior to intensity-modulated radiation therapy (IMRT). Lithium formate monohydrate tablets were carefully prepared, and blind tests were performed in clinically relevant situations in order to determine the precision and accuracy of the method. Further experiments confirmed that within the accuracy of the current method, the dosimeter response was independent of beam energies and dose rates used for IMRT treatments. The method was applied to IMRT treatment plans, and the dose determinations were compared to ionization chamber measurements. The experiments showed that absorbed doses above 3 Gy could be measured with an uncertainty of less than 2.5% of the dose (coverage factor k = 1.96). Measurement time was about 15 min using a well-calibrated dosimeter batch. The conclusion drawn from the investigation was that lithium formate EPR dosimetry is a promising new tool for absorbed dose measurements in external beam radiation therapy, especially for doses above 3 Gy.

  15. Lithium formate EPR dosimetry for verifications of planned dose distributions prior to intensity-modulated radiation therapy

    Gustafsson, H; Lund, E [Department of Medical and Health Sciences, Radiation Physics, Faculty of Health Sciences, Linkoeping University, S-581 85 Linkoeping (Sweden); Olsson, S [Division of Radiation Physics, Linkoeping University Hospital, S-581 85 Linkoeping (Sweden)], E-mail: hakgu@imv.liu.se

    2008-09-07

    The objective of the present investigation was to evaluate lithium formate electron paramagnetic resonance (EPR) dosimetry for measurement of dose distributions in phantoms prior to intensity-modulated radiation therapy (IMRT). Lithium formate monohydrate tablets were carefully prepared, and blind tests were performed in clinically relevant situations in order to determine the precision and accuracy of the method. Further experiments confirmed that within the accuracy of the current method, the dosimeter response was independent of beam energies and dose rates used for IMRT treatments. The method was applied to IMRT treatment plans, and the dose determinations were compared to ionization chamber measurements. The experiments showed that absorbed doses above 3 Gy could be measured with an uncertainty of less than 2.5% of the dose (coverage factor k = 1.96). Measurement time was about 15 min using a well-calibrated dosimeter batch. The conclusion drawn from the investigation was that lithium formate EPR dosimetry is a promising new tool for absorbed dose measurements in external beam radiation therapy, especially for doses above 3 Gy.

  16. Distribution characteristics of natural gamma background levels around the capital city Shillong, Meghalaya (India)

    Kukreti, B.M.; Sharma, G.K.; Rao, M.S.; Ramabhadraih, T.; Bhaskar Rao, Arjun; Bhuphang, A.

    2012-01-01

    Onsite measurement of natural gamma radiation around the capital city Shillong in Meghalaya, has been carried out using GPS device and environmental survey meter. Each referenced insitu data point was validated at the site by means of simultaneous measurements of radiation levels (at 1.0 mts height) through handheld dosimeters. Collected data points on natural background levels, have been analysed and quantified in the context of preparing reference background levels in the city in order to deal with any radiological emergency that may arise in the public domain. Study reveals Gaussian distributed mean annual gamma dose of 0.77 mSv (n=53) in the range of 0.38 to 1.51 mSv. The study area, bound by the coordinates N (25.50°-25.66°, and E (91.82°-91.96°) indicates few pockets of higher average background levels, particularly towards the eastern side of study area, namely Nongmynsong, NEIGRIMS and Happy Valley. However, from the radiological safety aspects in public domain, all these reported levels are within the safety limits of prevailing environmental background. (author)

  17. Calculation of the secondary gamma radiation by the Monte Carlo method at displaced sampling from distributed sources

    Petrov, Eh.E.; Fadeev, I.A.

    1979-01-01

    A possibility to use displaced sampling from a bulk gamma source in calculating the secondary gamma fields by the Monte Carlo method is discussed. The algorithm proposed is based on the concept of conjugate functions alongside the dispersion minimization technique. For the sake of simplicity a plane source is considered. The algorithm has been put into practice on the M-220 computer. The differential gamma current and flux spectra in 21cm-thick lead have been calculated. The source of secondary gamma-quanta was assumed to be a distributed, constant and isotropic one emitting 4 MeV gamma quanta with the rate of 10 9 quanta/cm 3 xs. The calculations have demonstrated that the last 7 cm of lead are responsible for the whole gamma spectral pattern. The spectra practically coincide with the ones calculated by the ROZ computer code. Thus the algorithm proposed can be offectively used in the calculations of secondary gamma radiation transport and reduces the computation time by 2-4 times

  18. Spectral distribution of the radiochemiluminescence from gamma-irradiated humic acid

    Goraczko, W.; Slawinski, J.; Staninski, K.

    2008-01-01

    This study was conducted to investigate radiochemiluminescence (RCL) spectra (340-650 nm), kinetics and absorption spectra of humic acids (HA) after their exposure of gamma-radiation (absorbed doses of 1-10 kGy, 60 Co) in model systems. The kinetics and spectral distribution of RCL were measured using the single photon counting method (SPC) and cut-off filters. Absorption spectra (range 240-800 nm) of irradiated solutions indicated that post-radiative degradation/polymerization processes take place in the HA changing their macromolecule or properties. The intensity of the delayed RCL was nonlinearly and suggested that complex radical formation mechanisms were still involved in the post-radiative reactions. (author)

  19. Spectral distribution of the radiochemiluminescence from gamma-irradiated humic acid

    Goraczko, W [Poznan University of Technology, Poznan (Poland). Faculty of Chemical Technology, Radio- and Photochemistry Department; Slawinski, J [Institute of Ecotechnology, Gniezno (Poland). State High Vocational School; Staninski, K [Adam Mickiewicz University, Poznan (Poland). Faculty of Chemistry, Department of Rare Earths

    2008-09-15

    This study was conducted to investigate radiochemiluminescence (RCL) spectra (340-650 nm), kinetics and absorption spectra of humic acids (HA) after their exposure of gamma-radiation (absorbed doses of 1-10 kGy, {sup 60}Co) in model systems. The kinetics and spectral distribution of RCL were measured using the single photon counting method (SPC) and cut-off filters. Absorption spectra (range 240-800 nm) of irradiated solutions indicated that post-radiative degradation/polymerization processes take place in the HA changing their macromolecule or properties. The intensity of the delayed RCL was nonlinearly and suggested that complex radical formation mechanisms were still involved in the post-radiative reactions. (author)

  20. mrpy: Renormalized generalized gamma distribution for HMF and galaxy ensemble properties comparisons

    Murray, Steven G.; Robotham, Aaron S. G.; Power, Chris

    2018-02-01

    mrpy calculates the MRP parameterization of the Halo Mass Function. It calculates basic statistics of the truncated generalized gamma distribution (TGGD) with the TGGD class, including mean, mode, variance, skewness, pdf, and cdf. It generates MRP quantities with the MRP class, such as differential number counts and cumulative number counts, and offers various methods for generating normalizations. It can generate the MRP-based halo mass function as a function of physical parameters via the mrp_b13 function, and fit MRP parameters to data in the form of arbitrary curves and in the form of a sample of variates with the SimFit class. mrpy also calculates analytic hessians and jacobians at any point, and allows the user to alternate parameterizations of the same form via the reparameterize module.

  1. Extended q -Gaussian and q -exponential distributions from gamma random variables

    Budini, Adrián A.

    2015-05-01

    The family of q -Gaussian and q -exponential probability densities fit the statistical behavior of diverse complex self-similar nonequilibrium systems. These distributions, independently of the underlying dynamics, can rigorously be obtained by maximizing Tsallis "nonextensive" entropy under appropriate constraints, as well as from superstatistical models. In this paper we provide an alternative and complementary scheme for deriving these objects. We show that q -Gaussian and q -exponential random variables can always be expressed as a function of two statistically independent gamma random variables with the same scale parameter. Their shape index determines the complexity q parameter. This result also allows us to define an extended family of asymmetric q -Gaussian and modified q -exponential densities, which reduce to the standard ones when the shape parameters are the same. Furthermore, we demonstrate that a simple change of variables always allows relating any of these distributions with a beta stochastic variable. The extended distributions are applied in the statistical description of different complex dynamics such as log-return signals in financial markets and motion of point defects in a fluid flow.

  2. Stereotactic radiosurgery with the gamma knife. Possibilities of dose distribution optimizations

    Stuecklschweiger, G.

    1995-01-01

    On April 1992, the first stereotactic radiosurgical procedure using the gamma knife was performed at the University Medical School Graz, Department of Neurosurgery. Accurate dose optimization is the foundation of a convenient and responsible utilization of this modality. But there are limits, because the final collimation is only achieved by 1 of the 4 special helm collimators. The possibilities of dose optimization and its influence on the dose distributions were investigated and partly compared with results of film densitometry measurements. In detail, the technique, which uses the same isocenter, but different sized collimators was studied. The influence of these optimization techniques on the resulting dose distributions and the dose gradient at the edge of the treatment planning volume was analyzed. Also the visions for an effective dose optimization are discussed. With 2 shots of different diameters, located at the same target coordinates and different weighting of time any collimator size between the 4 mm and 18 mm can be achieved. Because of that, a combination of more than 2 collimators is not meaningful. With the combined shots the dose fall gradient was less than that of either of the single shots involved in the combination. With the available physical and technical possibilities only a limited, very time consuming optimization is practicable. The quality control of isodose distributions requires optimizations in hard-and software, that enable CT- or MRT-based 3-dimensional visualization and dose volume analysis. (orig./MG) [de

  3. A clinical trial design using the concept of proportional time using the generalized gamma ratio distribution.

    Phadnis, Milind A; Wetmore, James B; Mayo, Matthew S

    2017-11-20

    Traditional methods of sample size and power calculations in clinical trials with a time-to-event end point are based on the logrank test (and its variations), Cox proportional hazards (PH) assumption, or comparison of means of 2 exponential distributions. Of these, sample size calculation based on PH assumption is likely the most common and allows adjusting for the effect of one or more covariates. However, when designing a trial, there are situations when the assumption of PH may not be appropriate. Additionally, when it is known that there is a rapid decline in the survival curve for a control group, such as from previously conducted observational studies, a design based on the PH assumption may confer only a minor statistical improvement for the treatment group that is neither clinically nor practically meaningful. For such scenarios, a clinical trial design that focuses on improvement in patient longevity is proposed, based on the concept of proportional time using the generalized gamma ratio distribution. Simulations are conducted to evaluate the performance of the proportional time method and to identify the situations in which such a design will be beneficial as compared to the standard design using a PH assumption, piecewise exponential hazards assumption, and specific cases of a cure rate model. A practical example in which hemorrhagic stroke patients are randomized to 1 of 2 arms in a putative clinical trial demonstrates the usefulness of this approach by drastically reducing the number of patients needed for study enrollment. Copyright © 2017 John Wiley & Sons, Ltd.

  4. EGSnrc calculated and MRI-polymer gel dosimeter measured dose distribution of gamma knife in presence of inhomogeneities

    Allahverdi Pourfallah, T.; Allahverdi, M.; Riahi Alam, N.; Ay, M.; Zahmatkesh, M.; Ibbott, J.S.

    2008-01-01

    Stereotactic gamma-knife radiosurgery plays an important role in managing small intracranial brain lesions. Currently, polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. polymer gel dosimeters are tissue equivalent and can act as a phantom material. In this study effects of inhomogeneities on those distributions have been investigated using both EGSnrc calculation and PAGAT polymer gel dosimeter. (author)

  5. A Monte Carlo Method for the Analysis of Gamma Radiation Transport from Distributed Sources in Laminated Shields

    Leimdoerfer, M.

    1964-02-01

    A description is given of a method for calculating the penetration and energy deposition of gamma radiation, based on Monte Carlo techniques. The essential feature is the application of the exponential transformation to promote the transport of penetrating quanta and to balance the steep spatial variations of the source distributions which appear in secondary gamma emission problems. The estimated statistical errors in a number of sample problems, involving concrete shields with thicknesses up to 500 cm, are shown to be quite favorable, even at relatively short computing times. A practical reactor shielding problem is also shown and the predictions compared with measurements

  6. A Monte Carlo Method for the Analysis of Gamma Radiation Transport from Distributed Sources in Laminated Shields

    Leimdoerfer, M

    1964-02-15

    A description is given of a method for calculating the penetration and energy deposition of gamma radiation, based on Monte Carlo techniques. The essential feature is the application of the exponential transformation to promote the transport of penetrating quanta and to balance the steep spatial variations of the source distributions which appear in secondary gamma emission problems. The estimated statistical errors in a number of sample problems, involving concrete shields with thicknesses up to 500 cm, are shown to be quite favorable, even at relatively short computing times. A practical reactor shielding problem is also shown and the predictions compared with measurements.

  7. Calculation of angular distribution of 662 keV gamma rays by Monte Carlo method in copper medium

    Kahraman, A.; Ozmutlu, E.N.; Gurler, O.; Yalcin, S.; Kaynak, G.; Gundogdu, O.

    2009-01-01

    This paper presents results on the angular distribution of Compton scattering of 662 keV gamma photons in both forward and backward hemispheres in copper medium. The number of scattered events graph has been determined for scattered gamma photons in both the forward and backward hemispheres and theoretical saturation thicknesses have been obtained using these results. Furthermore, response function of a 51x51 mm NaI(Tl) detector at 60 deg. angle with incoming photons scattered from a 10 mm thick copper layer has been determined using Monte Carlo method.

  8. Calculation of angular distribution of 662 keV gamma rays by Monte Carlo method in copper medium

    Kahraman, A.; Ozmutlu, E.N. [Physics Department, Faculty of Arts and Sciences, Uludag University, Gorukle Campus, 16059 Bursa (Turkey); Gurler, O. [Physics Department, Faculty of Arts and Sciences, Uludag University, Gorukle Campus, 16059 Bursa (Turkey)], E-mail: ogurler@uludag.edu.tr; Yalcin, S. [Kastamonu University, Education Faculty, 37200 Kastamonu (Turkey); Kaynak, G. [Physics Department, Faculty of Arts and Sciences, Uludag University, Gorukle Campus, 16059 Bursa (Turkey); Gundogdu, O. [NCCPM, Medical Physics, Royal Surrey County, Hospital, GU2 7XX (United Kingdom); University of Kocaeli, Umuttepe Campus, 41100 Kocaeli (Turkey)

    2009-12-15

    This paper presents results on the angular distribution of Compton scattering of 662 keV gamma photons in both forward and backward hemispheres in copper medium. The number of scattered events graph has been determined for scattered gamma photons in both the forward and backward hemispheres and theoretical saturation thicknesses have been obtained using these results. Furthermore, response function of a 51x51 mm NaI(Tl) detector at 60 deg. angle with incoming photons scattered from a 10 mm thick copper layer has been determined using Monte Carlo method.

  9. Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy

    Moss, C.E.; Lucas, M.C.; Tisinger, E.W.; Hamm, M.E.

    1984-01-01

    Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the work of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry

  10. The probability distribution of maintenance cost of a system affected by the gamma process of degradation: Finite time solution

    Cheng, Tianjin; Pandey, Mahesh D.; Weide, J.A.M. van der

    2012-01-01

    The stochastic gamma process has been widely used to model uncertain degradation in engineering systems and structures. The optimization of the condition-based maintenance (CBM) policy is typically based on the minimization of the asymptotic cost rate. In the financial planning of a maintenance program, however, a more accurate prediction interval for the cost is needed for prudent decision making. The prediction interval cannot be estimated unless the probability distribution of cost is known. In this context, the asymptotic cost rate has a limited utility. This paper presents the derivation of the probability distribution of maintenance cost, when the system degradation is modelled as a stochastic gamma process. A renewal equation is formulated to derive the characteristic function, then the discrete Fourier transform of the characteristic function leads to the complete probability distribution of cost in a finite time setting. The proposed approach is useful for a precise estimation of prediction limits and optimization of the maintenance cost.

  11. Investigation of dose distribution in mixed neutron-gamma field of boron neutron capture therapy using N isopropylacrylamide gel

    Bavarmegin, Elham; Sadremomtaz, Alireza [Nuclear Science and Technology Research Institute (NSTRI), Tehran (Iran, Islamic Republic of); Khalafi, Hossein; Kasesaz, Yaser [Dept. of Physics, University of Guilan, Rasht (Iran, Islamic Republic of); Khajeali, Azim [Medical Education Research Center, Tabriz (Iran, Islamic Republic of)

    2017-02-15

    Gel dosimeters have unique advantages in comparison with other dosimeters. Until now, these gels have been used in different radiotherapy techniques as a reliable dosimetric tool. Because dose distribution measurement is an important factor for appropriate treatment planning in different radiotherapy techniques, in this study, we evaluated the ability of the N-isopropylacrylamide (NIPAM) polymer gel to record the dose distribution resulting from the mixed neutron-gamma field of boron neutron capture therapy (BNCT). In this regard, a head phantom containing NIPAM gel was irradiated using the Tehran Research Reactor BNCT beam line, and then by a magnetic resonance scanner. Eventually, the R2 maps were obtained in different slices of the phantom by analyzing T2-weighted images. The results show that NIPAM gel has a suitable potential for recording three-dimensional dose distribution in mixed neutron-gamma field dosimetry.

  12. Computer aided collimation gamma (Cacao): a new approach in measuring and visualizing the distribution of X and gamma ray emitters in contaminate wounds

    Douiri, A.; Jeanguillaume, C.; Franck, D.; Carlan, L. de; Quartuccio, M.; Begot, S.

    2003-01-01

    The treatment of contaminated wounds can be greatly improved by visualizing the distribution of the radioactivity that is present. The low sensitivity of the conventional Anger camera means that it can only be used where there is a high level of activity. Moreover, these gamma cameras cannot make full use of the recent progress made in high spatial resolution semi-conductor detectors. In order to increase sensitivity while at the same time maintaining a sufficient resolution of the reconstructed image, the principle of the Computer aided collimation gamma camera (CACAO in French) was proposed as a possible means of using gamma cameras in intern dosimetry. This principle is based on the combined use of collimators with holes that are wider- than the intrinsic resolution of the detector, circular and linear scanning movements, a detector sensitive to the source depth and a specific reconstruction algorithm. This article presents the recent developments of the CACAO system and illustrates by a theoretical and experimental study, its performances compared with the classic tomography system. We start with a general overview of the CACAO system and its reconstruction algorithm. First of all, the superiority of the CACAO system is demonstrated by a simulation ,study. Then, an experimental bench was developed using an implanted silicon pixel detector specifically designed to allow the visualization of a subject contaminated with low energy X and gamma emitters. The study presented here shows images obtained from a phantom composed of three sources of Americium 341 Am. Although the comparison between the conventional and CACAO approaches were not carried out with optimal parameters, especially for CACAO, the initial results show that CACAO has an improved sensitivity and a superior resolution. Finally, the transposition of this system to the practical study of contaminated wounds is discussed. (authors)

  13. Elimination, distribution and metabolism of lindane (gamma Hexachloro cyclohexane) in male goat

    Elozargani, Gaafar A.; Elfahal, Rihab Ali

    2001-01-01

    Elimination, distribution in tissues and metabolic degradation of lindane insecticide (gamma hexachlorocyclohexane) were studied in male Nubian goat (Cappara aegagrus Hircus). The goat was dosed orally with 262.76 mg 14 C-lindane equivalent to one fourth of its lethal dose (LD50). Urine and faeces were collected for two weeks following the application date and the radioactivity was measured in order to determine the rate of the insecticide elimination from the animal body. Lindane elimination was found to be initially fairly rapid, principally via urine (19.6% of the applied dose was detected in urine and 3.1% in faeces). However, it was observed that total recovery of the insecticide via faeces and urine is low. After two weeks, the animal was sacrificed and samples of the brain, liver, kidneys, heart, lungs, legs muscles, and abdominal fat were collected. The percentage of the total radioactivity detected in all tissue sample was 0.29% of the applied radioactive Lindane. The fat contained 48.25% of this percentage, 29.78% was detected in the liver, 9.05% in the lungs and 8.72% in the heart. Smaller percentages were detected in the other tissues. Urine and faeces extracted, analysed and their contents of lindane metabolites were Identified using autoradiography. It was found that 23% of the labeled lindane detected in urine was extracted unchanged. A nonpolar compound possibly a trichlorophenol represented 26% of the radioactivity detected in urine, while 51% was represented in highly polar compound and conjugates

  14. An asymmetric distribution of positrons in the Galactic disk revealed by {gamma}-rays

    Weidenspointner, G; Skinner, G; Jean, P; Knoedlseder, J; Von Ballmoos, P; Bignami, G [UPS, CNRS, Ctr Etud Spatiale Rayonnements, Toulouse 4, (France); Weidenspointner, G; Diehl, R; Strong, A [Max Planck Inst Extraterr Phys, D-85741 Garching, (Germany); Weidenspointner, G [MPI Halbleiterlab, D-81739 Munich, (Germany); Skinner, G [NASA, CRESST, Greenbelt, MD 20771 (United States); Skinner, G [NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 (United States); Skinner, G [Univ Maryland, Dept Astron, College Pk, MD 20742 (United States); Cordier, B; Schanne, S [CEA Saclay, DSM, DAPNIA, SAp, F-91191 Gif Sur Yvette, (France); Winkler, Ch [ESA, ESTEC, SCI SA, NL-2201 AZ Noordwijk, (Netherlands); Bignami, G [IUSS, I-27100 Pavia, (Italy)

    2008-07-01

    Gamma-ray line radiation at 511 keV is the signature of electron positron annihilation. Such radiation has been known for 30 years to come from the general direction of the Galactic Centre, but the origin of the positrons has remained a mystery. Stellar nucleosynthesis, accreting compact objects, and even the annihilation of exotic dark-matter particles have all been suggested. Here we report a distinct asymmetry in the 511 keV line emission coming from the inner Galactic disk ({approx} 10-50 degrees from the Galactic Centre). This asymmetry resembles an asymmetry in the distribution of low mass X-ray binaries with strong emission at photon energies {>=}20 keV ('hard' LMXBs), indicating that they may be the dominant origin of the positrons. Although it had long been suspected that electron-positron pair plasmas may exist in X-ray binaries, it was not evident that many of the positrons could escape to lose energy and ultimately annihilate with electrons in the interstellar medium and thus lead to the emission of a narrow 511 keV line. For these models, our result implies that up to a few times 10{sup 41} positrons escape per second from a typical hard LMXB. Positron production at this level from hard LMXBs in the Galactic bulge would reduce (and possibly eliminate) the need for more exotic explanations, such as those involving dark matter. (authors)

  15. Multisite stochastic simulation of daily precipitation from copula modeling with a gamma marginal distribution

    Lee, Taesam

    2018-05-01

    Multisite stochastic simulations of daily precipitation have been widely employed in hydrologic analyses for climate change assessment and agricultural model inputs. Recently, a copula model with a gamma marginal distribution has become one of the common approaches for simulating precipitation at multiple sites. Here, we tested the correlation structure of the copula modeling. The results indicate that there is a significant underestimation of the correlation in the simulated data compared to the observed data. Therefore, we proposed an indirect method for estimating the cross-correlations when simulating precipitation at multiple stations. We used the full relationship between the correlation of the observed data and the normally transformed data. Although this indirect method offers certain improvements in preserving the cross-correlations between sites in the original domain, the method was not reliable in application. Therefore, we further improved a simulation-based method (SBM) that was developed to model the multisite precipitation occurrence. The SBM preserved well the cross-correlations of the original domain. The SBM method provides around 0.2 better cross-correlation than the direct method and around 0.1 degree better than the indirect method. The three models were applied to the stations in the Nakdong River basin, and the SBM was the best alternative for reproducing the historical cross-correlation. The direct method significantly underestimates the correlations among the observed data, and the indirect method appeared to be unreliable.

  16. Distribution of microorganisms in spices and their decontamination by gamma-irradiation

    Muhamad Lebai Juri; Ito, Hitoshi; Watanabe, Hiroshi; Tamura, Naoyuki

    1986-01-01

    The distribution of microorganisms in 15 samples of selected spices and the effects of irradiation of them were studied. The total aerobic bacteria in black pepper, white pepper, turmeric, rosemary and basil were determined to be 3 x 10 3 to 5 x 10 7 per gram. Coliforms were also determined in 8 samples to be 2 x 10 2 to 2 x 10 6 per gram. The main aerobic-spore-formers were identified as Bacillus pumilus and B. subtilis. Molds were determined in 10 samples to be 1 x 10 2 to 2 x 10 4 per gram which consisted mainly of the Aspergillus glaucus, A. restrictus, A. flavus, A. fumigatus, A. niger groups and Penicillium. A study on the inactivation of microorganisms in spices showed that gamma-irradiation doses of 1.2 to 1.5 Mrad were required to reduce the total aerobic bacteria to below a detectable level, while doses of below 1.0 Mrad were required to decrease the spore-forming bacteria to below 10 3 per gram, the Japanese hygenic standard. Coliforms were eliminated with 0.4 to 1.0 Mrad irradiation. In the storage study, at humidity levels higher than 84 % at 30 or 35 0 C, mold counts increased more than 10 6 per gram in many kinds of powdered spices in polyethylene pouches during 1 to 2 months of storage, while samples subjected to 0.4 Mrad irradiation were free from molds. (author)

  17. DOSKMF2, Dose Rate Distribution in Co60 Gamma Irradiation Plants

    Remer, M.

    1988-01-01

    1 - Description of program or function: The DOSKMF2 code calculates dose rate distributions in gamma irradiation facilities with 60 Co sources. It has been developed as a tool for the evaluation of research units for the characterization, modification and optimization as well as for the simulation, planning design and evaluation of pilot and industrial facilities. 2 - Method of solution: The basic model of DOSKMF2 contains the computation of the exposure rate, which is dependent on a system of radiation sources (line and/or point sources) at one point of the radiation field. The geometric conditions are described by two coordinate systems. The first is used to arrange the radiation sources and tubes; the second is used to describe the shielding layers in the form of concentric circles. The build-up factor is approximated by Taylor coefficients, also in the case of multi-layer configurations. Calculations of radiation fields in complex irradiation facilities are made by many organizational variants based on the basic model. The interpretation of the results is supported by some statistical calculations. It is possible to store the calculated dose rate values for further processing. 3 - Restrictions on the complexity of the problem: The DOSKMF2 code is presently limited to 40 irradiation tubes and 10 crossed shielding layers. This can be increased by changing dimension statements and input organization

  18. Seasonal distribution and uptake of gamma emitting radionuclides at the test reactor area leaching ponds

    Millard, J.B.

    1986-01-01

    Radioactive leaching ponds adjacent to the Test Reactor Area (TRA) located on the Idaho National Engineering Laboratory (INEL) site were investigated to determine the seasonal distribution and ecological behavior of gamma emitting radionuclides in various pond compartments. The physical, chemical and biological properties of the TRA ponds were documented including basic morphometry, water chemistry and species identification. Penetrating radiation exposure rates at the ponds ranged from 35 to 65 mR/d at the water surface and up to 3400 mR/d one meter above bottom sediments. Seasonal concentrations and concentration ratios were determined for 16 principle radionuclides in filtered water, sediment, seston, zooplankton, net plankton, nannoplankton, periphyton, macrophytes, thistle, speedwell and willow. Seston and nannoplankton had the highest concentration ratios with substantial decreases observed for higher trophic level compartments. Significant (P < 0.01 to P < 0.001) seasonal effects wee found for concentration ratios. Radionuclides without nutrient analogs had the highest ratios in spring for periphyton, macrophytes and littoral plants. Concentration ratios were highest in summer, fall or winter for radionuclides with nutrient analogs

  19. ON THE DISTRIBUTION OF STELLAR MASSES IN GAMMA-RAY BURST HOST GALAXIES

    Castro Ceron, J. M.; Michalowski, M. J.; Hjorth, J.; Malesani, D.; Watson, D.; Fynbo, J. P. U.; Gorosabel, J.; Morales Calderon, M.

    2010-01-01

    We analyze Spitzer images of 30 long-duration gamma-ray burst (GRB) host galaxies. We estimate their total stellar masses (M * ) based on the rest-frame K-band luminosities (L K rest ) and constrain their star formation rates (SFRs; not corrected for dust extinction) based on the rest-frame UV continua. Further, we compute a mean M * /L K rest = 0.45 M sun /L sun . We find that the hosts are low M * , star-forming systems. The median M * in our sample ((M * ) = 10 9.7 M sun ) is lower than that of 'field' galaxies (e.g., Gemini Deep Deep Survey). The range spanned by M * is 10 7 M sun * 11 M sun , while the range spanned by the dust-uncorrected UV SFR is 10 -2 M sun yr -1 sun yr -1 . There is no evidence for intrinsic evolution in the distribution of M * with redshift. We show that extinction by dust must be present in at least 25% of the GRB hosts in our sample and suggest that this is a way to reconcile our finding of a relatively lower UV-based, specific SFR (φ ≡ SFR/M * ) with previous claims that GRBs have some of the highest φ values. We also examine the effect that the inability to resolve the star-forming regions in the hosts has on φ.

  20. Distribution of iron and titanium on the lunar surface from lunar prospector gamma ray spectra

    Prettyman, T.H.; Feldman, W.C.; Lawrence, David J.; Elphic, R.C.; Gasnault, O.M.; Maurice, S.; Moore, K.R.; Binder, A.B.

    2001-01-01

    Gamma ray pulse height spectra acquired by the Lunar Prospector (LP) Gamma-Ray Spectrometer (GRS) contain information on the abundance of major elements in the lunar surface, including O, Si, Ti, Al, Fe, Mg, Ca, K, and Th. With the exception of Th and K, prompt gamma rays produced by cosmic ray interactions with surface materials are used to determine elemental abundance. Most of these gamma rays are produced by inelastic scattering of fast neutrons and by neutron capture. The production of neutron-induced gamma rays reaches a maximum deep below the surface (e.g. ∼140 g/cm 2 for inelastic scattering and ∼50 g/cm 2 for capture). Consequently, gamma rays sense the bulk composition of lunar materials, in contrast to optical methods (e.g. Clementine Spectral Reflectance (CSR)), which only sample the top few microns. Because most of the gamma rays are produced deep beneath the surface, few escape unscattered and the continuum of scattered gamma rays dominates the spectrum. In addition, due to the resolution of the spectrometer, there are few well-isolated peaks and peak fitting algorithms must be used to deconvolve the spectrum in order to determine the contribution of individual elements.

  1. Innovative research reactor core designed. Estimation and analysis of gamma heating distribution

    Setiyanto

    2014-01-01

    The Gamma heating value is an important factor needed for safety analysis of each experiments that will be realized on research reactor core. Gamma heat is internal heat source occurs in each irradiation facilities or any material irradiated in reactor core. This value should be determined correctly because of the safety related problems. The gamma heating value is in general depend on. reactor core characteristics, different one and other, and then each new reactor design should be completed by gamma heating data. The Innovative Research Reactor is one of the new reactor design that should be completed with any safety data, including the gamma heating value. For this reasons, calculation and analysis of gamma heating in the hole of reactor core and irradiation facilities in reflector had been done by using of modified and validated Gamset computer code. The result shown that gamma heating value of 11.75 W/g is the highest value at the center of reactor core, higher than gamma heating value of RSG-GAS. However, placement of all irradiation facilities in reflector show that safety characteristics for irradiation facilities of innovative research reactor more better than RSG-GAS reactor. Regarding the results obtained, and based on placement of irradiation facilities in reflector, can be concluded that innovative research reactor more safe for any irradiation used. (author)

  2. Angular Distribution of Gamma Rays from the Fission of {sup 235}U Induced by 14-Mev Neutrons

    Jeki, L.; Kluge, Gy.; Lajtai, A. [Central Research Institute for Physics, Hungarian Academy of Sciences (Hungary)

    1969-12-15

    Experiments are reported which were performed to study the angular distribution of the gamma radiation following fast-neutron-induced nuclear fission. The investigations were, in particular, focussed on the influence which the angular momentum imparted to the compound nucleus by the fast neutrons has on the angular distribution of the {gamma}-rays. The fission of {sup 235}U is induced by 14-MeV-energy neutrons from the T(d, n) {alpha} reaction. The fission fragments are detected by a gas-scintillation counter filled with a mixture of Ar and Ni gases, the {gamma}-rays by 5 cm x 5 cm Nal(Tl) crystal with an energy threshold of 120 keV. The intensity of the {gamma}-rays is measured at 90 Degree-Sign and 174 Degree-Sign to the direction of fragment motion. The flight times of fission neutrons and {gamma}-rays are measured with a 20-ns overlap-type time-to-pulse height converter while the background was covered simultaneously with another converter delayed with respect to the former. The signals from both converters are analysed by a multichannel analyser with divisible memory. The flight path, which is chosen to be about 70 cm, makes it possible to separate the neutron from the gamma counts. The geometry is designed to keep the direction of the outflying fission fragments nearly the same as that of the incident fast neutrons. In this way the angular momenta of the fast neutrons are normal to the flight path of the fragments. The measured gamma intensities are extrapolated to 180 Degree-Sign on a computer using Strutinski's formula n( Greek-Theta-Symbol ) {approx}1 + B sin Greek-Theta-Symbol . On transformation of the measured data from the laboratory system to the system of fragments the anisotropy is found to be A = 1(180 Degree-Sign )/l (90 Degree-Sign ) = 1.33 {+-} 0.05. The main angular momentum of fission fragments is calculated from the anisotropy as 15 h units. As compared with the thermal-neutron-induced fission the present results indicate an additional

  3. Angular distribution of gamma rays from the fission of {sup 235}U induced by 14-MeV neutrons

    Jeki, L; Kluge, G; Lajtai, A [Central Research Institute for Physics, Hungarian Academy of Sciences (Hungary)

    1969-12-15

    Experiments are reported which were performed to study the angular distribution of the gamma radiation following fast-neutron-induced nuclear fission. The investigations were, in particular, focussed on the influence which the angular momentum imparted to the compound nucleus by the fast neutrons has on the angular distribution of the {gamma}-rays. The fission of {sup 235}U is induced by 14-MeV-energy neutrons from the T(d, n) {alpha} reaction. The fission fragments are detected by a gas-scintillation counter filled with a mixture of Ar and Ni gases, the {gamma}-rays by 5 cm x 5 cm Nal(Tl) crystal with an energy threshold of 120 keV. The intensity of the {gamma}-rays is measured at 90 deg. and 174 deg. to the direction of fragment motion. The flight times of fission neutrons and {gamma}-rays are measured with a 20-ns overlap-type time-to-pulse height converter while the background was covered simultaneously with another converter delayed with respect to the former. The signals from both converters are analysed by a multichannel analyser with divisible memory. The flight path, which is chosen to be about 70 cm, makes it possible to separate the neutron from the gamma counts. The geometry is designed to keep the direction of the outflying fission fragments nearly the same as that of the incident fast neutrons. In this way the angular momenta of the fast neutrons are normal to the flight path of the fragments. The measured gamma intensities are extrapolated to 180 deg on a computer using Strutinski's formula n({theta}) {approx} 1 + B sin {theta}. On transformation of the measured data from the laboratory system to the system of fragments the anisotropy is found to be A = I(180 deg.)/I (90 deg.) = 1.33 {+-} 0.05. The main angular momentum of fission fragments is calculated from the anisotropy as 15 (h/2{pi}) units. As compared with the thermal-neutron-induced fission the present results indicate an additional contribution from the angular momentum of the compound

  4. Extracting Prior Distributions from a Large Dataset of In-Situ Measurements to Support SWOT-based Estimation of River Discharge

    Hagemann, M.; Gleason, C. J.

    2017-12-01

    The upcoming (2021) Surface Water and Ocean Topography (SWOT) NASA satellite mission aims, in part, to estimate discharge on major rivers worldwide using reach-scale measurements of stream width, slope, and height. Current formalizations of channel and floodplain hydraulics are insufficient to fully constrain this problem mathematically, resulting in an infinitely large solution set for any set of satellite observations. Recent work has reformulated this problem in a Bayesian statistical setting, in which the likelihood distributions derive directly from hydraulic flow-law equations. When coupled with prior distributions on unknown flow-law parameters, this formulation probabilistically constrains the parameter space, and results in a computationally tractable description of discharge. Using a curated dataset of over 200,000 in-situ acoustic Doppler current profiler (ADCP) discharge measurements from over 10,000 USGS gaging stations throughout the United States, we developed empirical prior distributions for flow-law parameters that are not observable by SWOT, but that are required in order to estimate discharge. This analysis quantified prior uncertainties on quantities including cross-sectional area, at-a-station hydraulic geometry width exponent, and discharge variability, that are dependent on SWOT-observable variables including reach-scale statistics of width and height. When compared against discharge estimation approaches that do not use this prior information, the Bayesian approach using ADCP-derived priors demonstrated consistently improved performance across a range of performance metrics. This Bayesian approach formally transfers information from in-situ gaging stations to remote-sensed estimation of discharge, in which the desired quantities are not directly observable. Further investigation using large in-situ datasets is therefore a promising way forward in improving satellite-based estimates of river discharge.

  5. Near threshold angular distributions for the H-2(gamma,I >)X reaction

    Beckford, B.; Bydžovský, Petr; Chiba, A.; Doi, D.; Fujii, T.; Fujii, Y.; Futatsukawa, K.; Gogami, T.; Hashimoto, O.; Han, Y. C.; Hirose, K.; Honda, R.; Hosomi, K.; Ishikawa, T.; Kanda, H.; Kaneta, M.; Kaneko, Y.; Kato, S.; Kawama, D.; Kimura, C.; Kiyokawa, S.; Koike, T.; Maeda, K.; Makabe, K.; Matsubara, M.; Miwa, K.; Nagao, S.; Nakamura, S. N.; Okuyama, A.; Shirotori, K.; Sugihara, K.; Suzuki, K.; Tamae, T.; Tamura, H.; Tsukada, K.; Yamamoto, F.; Yamamoto, T.; Yonemoto, F.; Yamazaki, H.

    2016-01-01

    Roč. 2016, č. 6 (2016), 063D01 ISSN 2050-3911 Institutional support: RVO:61389005 Keywords : neutral Kaon photoproduction * electromagnetic production * gamma Subject RIV: BE - Theoretical Physics Impact factor: 2.039, year: 2016

  6. Transformation and Self-Similarity Properties of Gamma and Weibull Fragment Size Distributions

    2015-12-01

    the spatial dimension ( 31 m ). For classic aerosols with nearly-spherical droplets, 3m and 6/s . Alternatively, Wittel et. al. (2006...which come from the definitions of )(DFM , )(MFM , )(DF , and )(MF . The fourth transformation equation is as follows: )(~)( DfDDf mM... dimension defined by Equation (2), )(x is the gamma function, and ),( xs is the upper incomplete gamma function. Table 1a. Rosin-Rammler (a.k.a

  7. Measurements of the gamma-quanta angular distributions emitted from neutron inelastic scattering on 28Si

    Fedorov, N. A.; Grozdanov, D. N.; Bystritskiy, V. M.; Kopach, Yu. N.; Ruskov, I. N.; Skoy, V. R.; Tretyakova, T. Yu.; Zamyatin, N. I.; Wang, D.; Aliev, F. A.; Hramco, C.; Gandhi, A.; Kumar, A.; Dabylova, S.; Bogolubov, E. P.; Barmakov, Yu. N.

    2018-04-01

    The characteristic gamma radiation from the interaction of 14.1 MeV neutrons with a natural silicon sample is investigated with Tagged Neutron Method (TNM). The anisotropy of gamma-ray emission of 1.779 MeV was measured at 11 azimuth angles with a step of ∠15°. The present results are in good agreement with some recent experimental data.

  8. A GIS model-based assessment of the environmental distribution of gamma-hexachlorocyclohexane in European soils and waters.

    Vizcaíno, P; Pistocchi, A

    2010-10-01

    The MAPPE GIS based multimedia model is used to produce a quantitative description of the behaviour of gamma-hexachlorocyclohexane (gamma-HCH) in Europe, with emphasis on continental surface waters. The model is found to reasonably reproduce gamma-HCH distributions and variations along the years in atmosphere and soil; for continental surface waters, concentrations were reasonably well predicted for year 1995, when lindane was still used in agriculture, while for 2005, assuming severe restrictions in use, yields to substantial underestimation. Much better results were yielded when same mode of release as in 1995 was considered, supporting the conjecture that for gamma-HCH, emission data rather that model structure and parameterization can be responsible for wrong estimation of concentrations. Future research should be directed to improve the quality of emission data. Joint interpretation of monitoring and modelling results, highlights that lindane emissions in Europe, despite the marked decreasing trend, persist beyond the provisions of existing legislation. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  9. SOILD: A computer model for calculating the effective dose equivalent from external exposure to distributed gamma sources in soil

    Chen, S.Y.; LePoire, D.; Yu, C.; Schafetz, S.; Mehta, P.

    1991-01-01

    The SOLID computer model was developed for calculating the effective dose equivalent from external exposure to distributed gamma sources in soil. It is designed to assess external doses under various exposure scenarios that may be encountered in environmental restoration programs. The models four major functional features address (1) dose versus source depth in soil, (2) shielding of clean cover soil, (3) area of contamination, and (4) nonuniform distribution of sources. The model is also capable of adjusting doses when there are variations in soil densities for both source and cover soils. The model is supported by a data base of approximately 500 radionuclides. 4 refs

  10. Performance analysis of a threshold-based parallel multiple beam selection scheme for WDM-based systems for Gamma-Gamma distributions

    Nam, Sung Sik

    2017-03-02

    In this paper, we statistically analyze the performance of a threshold-based parallel multiple beam selection scheme (TPMBS) for Free-space optical (FSO) based system with wavelength division multiplexing (WDM) in cases where a pointing error has occurred for practical consideration over independent identically distributed (i.i.d.) Gamma-Gamma fading conditions. Specifically, we statistically analyze the characteristics in operation under conventional heterodyne detection (HD) scheme for both adaptive modulation (AM) case in addition to non-AM case (i.e., coherentnon-coherent binary modulation). Then, based on the statistically derived results, we evaluate the outage probability (CDF) of a selected beam, the average spectral efficiency (ASE), the average number of selected beams (ANSB), and the average bit error rate (BER). Some selected results shows that we can obtain the higher spectral efficiency and simultaneously reduce the potential increasing of the complexity of implementation caused by applying the selection based beam selection scheme without a considerable performance loss.

  11. Performance Analysis of Polarization Modulated DirectDetection Optical CDMA Systems over Turbulent FSO LinksModeled by the Gamma-Gamma Distribution

    Fan Bai

    2015-01-01

    Full Text Available This paper proposes a theoretical study to characterize the transmission of optical code division multiple access (CDMA systems deploying polarization shift keying (PolSK over a free space optical (FSO link under the impact of atmospheric turbulence. In our analysis, a novel transceiver architecture for atmospheric OCDMA FSO systems based on polarization modulation with direct detection is proposed and discussed. A detailed analytical model for PolSK-OCDMA systems over a turbulent FSO link is provided. Further, we derive a closed-form bit error ratio (BER and outage probability expressions, taking into account the multiple-access interference (MAI, optical noise and the atmospheric turbulence effect on the FSO link modeled by the Gamma-Gamma distribution. Finally, the results of this study show the most significant parameters that degrade the transmission performance of the PolSK-OCDMA signal over FSO links and indicate that the proposed approach offers improved bit error ratio (BER performances compared to the on-off-keying (OOK modulation scheme in the presence of turbulence.

  12. Spatial distribution and polarization of {gamma}-rays generated via Compton backscattering in the Duke/OK-4 storage ring FEL

    Park, S.H. E-mail: shpark@nanum.kaeri.re.kr; Litvinenko, V.N.; Tornow, W.; Montgomery, C

    2001-12-21

    Beams of nearly monochromatic {gamma}-rays are produced via intracavity Compton backscattering in the OK-4/Duke storage ring FEL, the high-intensity {gamma}-ray source (HI{gamma}S). Presently, HI{gamma}S generates {gamma}-ray beams with an energy tunable from 2 to 58 MeV and a maximum flux of 5x10{sup 7} {gamma}-rays per second. The {gamma}-rays are linearly polarized with a degree of polarization close to 100% (V.N. Litvinenko, et al., Predictions and expected performance for the VUV OK-5/Duke Storage Ring FEL with variable polarization, Nucl. Instr. and Meth. A, to be published in this proceeding) and they are collimated to pencil-like semi-monoenergetic beams with RMS energy spreads as low as 0.2%. The detailed theoretical and experimental studies of the {gamma}-ray beam quality were conducted during the last two years (S.H. Park, Thesis, Duke University, Durham, NC, USA, 2000). In this paper, we present the theoretical analysis and the experimental results on the spatial distribution and polarization of {gamma}-rays from the HI{gamma}S facility.

  13. On the Efficient Simulation of the Distribution of the Sum of Gamma-Gamma Variates with Application to the Outage Probability Evaluation Over Fading Channels

    Ben Issaid, Chaouki; Rached, Nadhir B.; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul

    2017-01-01

    the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is related to the difficult question of analyzing the statistics of a sum of Gamma- Gamma random variables

  14. Mapping the spatial distribution and activity of "2"2"6Ra at legacy sites through Machine Learning interpretation of gamma-ray spectrometry data

    Varley, Adam; Tyler, Andrew; Smith, Leslie; Dale, Paul; Davies, Mike

    2016-01-01

    Radium ("2"2"6Ra) contamination derived from military, industrial, and pharmaceutical products can be found at a number of historical sites across the world posing a risk to human health. The analysis of spectral data derived using gamma-ray spectrometry can offer a powerful tool to rapidly estimate and map the activity, depth, and lateral distribution of "2"2"6Ra contamination covering an extensive area. Subsequently, reliable risk assessments can be developed for individual sites in a fraction of the timeframe compared to traditional labour-intensive sampling techniques: for example soil coring. However, local heterogeneity of the natural background, statistical counting uncertainty, and non-linear source response are confounding problems associated with gamma-ray spectral analysis. This is particularly challenging, when attempting to deal with enhanced concentrations of a naturally occurring radionuclide such as "2"2"6Ra. As a result, conventional surveys tend to attribute the highest activities to the largest total signal received by a detector (Gross counts): an assumption that tends to neglect higher activities at depth. To overcome these limitations, a methodology was developed making use of Monte Carlo simulations, Principal Component Analysis and Machine Learning based algorithms to derive depth and activity estimates for "2"2"6Ra contamination. The approach was applied on spectra taken using two gamma-ray detectors (Lanthanum Bromide and Sodium Iodide), with the aim of identifying an optimised combination of detector and spectral processing routine. It was confirmed that, through a combination of Neural Networks and Lanthanum Bromide, the most accurate depth and activity estimates could be found. The advantage of the method was demonstrated by mapping depth and activity estimates at a case study site in Scotland. There the method identified significantly higher activity ( 0.4 m), that conventional gross counting algorithms failed to identify. It was

  15. Mapping the spatial distribution and activity of {sup 226}Ra at legacy sites through Machine Learning interpretation of gamma-ray spectrometry data

    Varley, Adam, E-mail: a.l.varley@stir.ac.uk [Department of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA (United Kingdom); Tyler, Andrew [Department of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA (United Kingdom); Smith, Leslie [Department of Computing Science and Mathematics, University of Stirling, Stirling FK9 4LA (United Kingdom); Dale, Paul [Scottish Environmental Protection Agency, Radioactive Substances, Strathallan House, Castle Business Park, Stirling FK9 4TZ (United Kingdom); Davies, Mike [Nuvia Limited, The Library, Eight Street, Harwell Oxford, Didcot, Oxfordshire OX11 0RL (United Kingdom)

    2016-03-01

    Radium ({sup 226}Ra) contamination derived from military, industrial, and pharmaceutical products can be found at a number of historical sites across the world posing a risk to human health. The analysis of spectral data derived using gamma-ray spectrometry can offer a powerful tool to rapidly estimate and map the activity, depth, and lateral distribution of {sup 226}Ra contamination covering an extensive area. Subsequently, reliable risk assessments can be developed for individual sites in a fraction of the timeframe compared to traditional labour-intensive sampling techniques: for example soil coring. However, local heterogeneity of the natural background, statistical counting uncertainty, and non-linear source response are confounding problems associated with gamma-ray spectral analysis. This is particularly challenging, when attempting to deal with enhanced concentrations of a naturally occurring radionuclide such as {sup 226}Ra. As a result, conventional surveys tend to attribute the highest activities to the largest total signal received by a detector (Gross counts): an assumption that tends to neglect higher activities at depth. To overcome these limitations, a methodology was developed making use of Monte Carlo simulations, Principal Component Analysis and Machine Learning based algorithms to derive depth and activity estimates for {sup 226}Ra contamination. The approach was applied on spectra taken using two gamma-ray detectors (Lanthanum Bromide and Sodium Iodide), with the aim of identifying an optimised combination of detector and spectral processing routine. It was confirmed that, through a combination of Neural Networks and Lanthanum Bromide, the most accurate depth and activity estimates could be found. The advantage of the method was demonstrated by mapping depth and activity estimates at a case study site in Scotland. There the method identified significantly higher activity (< 3 Bq g{sup −1}) occurring at depth (> 0.4 m), that conventional gross

  16. Distribution of microorganisms in herb medicines and their decontamination by gamma-irradiation

    Ito, Hitoshi

    1999-01-01

    Herb medicines are traditional medicine in Japan and have been used for medical treatment. These herb medicines are contaminating frequently by microorganisms which has possibility to cause opportunistic diseases. Recently, hygienic standard of herb medicines become more strict than before, and it needs to decontaminate microorganisms by some treatments. However, chemical treatments such as by ethylene oxide fumigation leave toxic residues in the herbs while steam sterilization decease medicinal components. From study on the distribution of microorganisms in 31 samples of selected herb medicines, colony forming units of total aerobic bacteria were determined to be l.9 x 10 2 to l.4 x 10 8 per gram in 30 samples. Coliforms were also determined to be 6.9 x 10 2 to 4.3 x 10 6 per gram in 16 samples. The main aerobic bacteria were identified as Bacillus pumilus, B. circulans, B. megaterium, Erwinia, Enterobacter and Acinetobacter, whereas consisted mainly of Enterobacter in coliform counts. Molds were determined to be 6.3 x 10 1 to 1.9 x 10 5 per gram which consisted mainly Aspergillus glaucus group, A. restrictus group, A. flavus group, A. ostianus, A. phoenicis, Penicillium, Tricoderma, Rhizopus and Alternaria in 25 samples. A study on the inactivation of microorganisms at sample No. S18 showed that a gamma-irradiation dose of 20 kGy was required to reduce the total aerobic bacteria and the coliforms below a detectable level, while radiation-resistant bacteria were survived at high doses more than 10 kGy consisted with Acinetobacter and Enterobacter. Molds were inactivated below 8 kGy except Alternaria. However, a dose of 10 kGy should be effective for the sample No. S18 to reduce the spore-forming bacteria, the fecal coliforms and the molds below a detectable level per gram. On the study of inactivation of microorganisms in many samples except the No. 18, all kinds of microorganism were inactivated below a detectable level at 10 kGy irradiation. (author)

  17. Distribution of microorganisms in herb medicines and their decontamination by gamma-irradiation

    Ito, Hitoshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Kamakura, Hiroyuki; Sekita, Setuko [National Institute of Health Sciences, Kamiyoga, Tokyo (Japan)

    1999-09-01

    Herb medicines are traditional medicine in Japan and have been used for medical treatment. These herb medicines are contaminating frequently by microorganisms which has possibility to cause opportunistic diseases. Recently, hygienic standard of herb medicines become more strict than before, and it needs to decontaminate microorganisms by some treatments. However, chemical treatments such as by ethylene oxide fumigation leave toxic residues in the herbs while steam sterilization decease medicinal components. From study on the distribution of microorganisms in 31 samples of selected herb medicines, colony forming units of total aerobic bacteria were determined to be l.9 x 10{sup 2} to l.4 x 10{sup 8} per gram in 30 samples. Coliforms were also determined to be 6.9 x 10{sup 2} to 4.3 x 10{sup 6} per gram in 16 samples. The main aerobic bacteria were identified as Bacillus pumilus, B. circulans, B. megaterium, Erwinia, Enterobacter and Acinetobacter, whereas consisted mainly of Enterobacter in coliform counts. Molds were determined to be 6.3 x 10{sup 1} to 1.9 x 10{sup 5} per gram which consisted mainly Aspergillus glaucus group, A. restrictus group, A. flavus group, A. ostianus, A. phoenicis, Penicillium, Tricoderma, Rhizopus and Alternaria in 25 samples. A study on the inactivation of microorganisms at sample No. S18 showed that a gamma-irradiation dose of 20 kGy was required to reduce the total aerobic bacteria and the coliforms below a detectable level, while radiation-resistant bacteria were survived at high doses more than 10 kGy consisted with Acinetobacter and Enterobacter. Molds were inactivated below 8 kGy except Alternaria. However, a dose of 10 kGy should be effective for the sample No. S18 to reduce the spore-forming bacteria, the fecal coliforms and the molds below a detectable level per gram. On the study of inactivation of microorganisms in many samples except the No. 18, all kinds of microorganism were inactivated below a detectable level at 10 k

  18. Hemlock Alkaloids in Aloes. Occurrence and Distribution of gamma-Coniceine.

    Dring, J V; Nash, R J; Roberts, M F; Reynolds, T

    1984-10-01

    The hemlock alkaloid gamma-coniceine was identified in a number of ALOE species, namely A. GILLILANDII, Reynolds A. BALLYI Reynolds, A. RUSPOLIANA Baker, A. IBITIENSIS Perrier and A. DELTOIDEODONTA Baker. Coniine was identified in A. VIGUIERI Perrier. The levels of gamma-coniceine are higher than those found in CONIUM MACULATUM L. Some species also contained trace amounts of conhydrinone and pseudoconhydrin. Three of the species are Madagascan endemics, one is restricted to Arabia, while the rest are remote from each other in East Africa. Some of the species are loosely related but there is no overall taxonomic affinity between them.

  19. Analysis on the gamma dose distribution by major corrosion products during preventive maintenance period in nuclear power plant

    Ha, Wi Ho

    2006-02-01

    The information on dose distribution inside the containment building is an essential requirement to make a reduction of radiation exposure as well as effective operation and design of nuclear power plant. After reactor shutdown, radiation exposure to workers mainly occurs during preventive maintenance period due to inspection or repair works of major components. During that period, gamma doses are induced by major corrosion products in the primary coolant system. The radiation exposure to workers has been assessed by using the measurements. The measurements are, of course, a basic and reliable assessment. But the measurement has defect such as limitation of detecting area. In order to improve the defect of the measurements, system for assessment of gamma dose distribution during preventive maintenance period by using computational code was suggested in this study. First, activity of major corrosion products was calculated by using modified CRUDSIM code. Original CRUDSIM code was modified to add evaluation of other major corrosion products besides cobalt isotopes. Modeling of containment building for YGN Unit 3 was then performed. Gamma dose distribution by major corrosion products inside the containment building was calculated by using MCNPX code. Finally, the calculations were mapped for whole space inside the containment building and were compared with the measurements. As a result of this study, the defect of the measurement are supplemented by using computational calculation system, and it is expected that workers can make an effective work plan through providing dose distribution inside the containment building in advance. In addition, this study can be applied to technology development to make an effective containment shielding design of the next generation reactor as well as an improvement of the safety for workers in nuclear power plant

  20. Sets of priors reflecting prior-data conflict and agreement

    Walter, G.M.; Coolen, F.P.A.; Carvalho, J.P.; Lesot, M.-J.; Kaymak, U.; Vieira, S.; Bouchon-Meunier, B.; Yager, R.R.

    2016-01-01

    Bayesian inference enables combination of observations with prior knowledge in the reasoning process. The choice of a particular prior distribution to represent the available prior knowledge is, however, often debatable, especially when prior knowledge is limited or data are scarce, as then

  1. Planar Cell Polarity Breaks the Symmetry of PAR Protein Distribution prior to Mitosis in Drosophila Sensory Organ Precursor Cells.

    Besson, Charlotte; Bernard, Fred; Corson, Francis; Rouault, Hervé; Reynaud, Elodie; Keder, Alyona; Mazouni, Khalil; Schweisguth, François

    2015-04-20

    During development, cell-fate diversity can result from the unequal segregation of fate determinants at mitosis. Polarization of the mother cell is essential for asymmetric cell division (ACD). It often involves the formation of a cortical domain containing the PAR complex proteins Par3, Par6, and atypical protein kinase C (aPKC). In the fly notum, sensory organ precursor cells (SOPs) divide asymmetrically within the plane of the epithelium and along the body axis to generate two distinct cells. Fate asymmetry depends on the asymmetric localization of the PAR complex. In the absence of planar cell polarity (PCP), SOPs divide with a random planar orientation but still asymmetrically, showing that PCP is dispensable for PAR asymmetry at mitosis. To study when and how the PAR complex localizes asymmetrically, we have used a quantitative imaging approach to measure the planar polarization of the proteins Bazooka (Baz, fly Par3), Par6, and aPKC in living pupae. By using imaging of functional GFP-tagged proteins with image processing and computational modeling, we find that Baz, Par6, and aPKC become planar polarized prior to mitosis in a manner independent of the AuroraA kinase and that PCP is required for the planar polarization of Baz, Par6, and aPKC during interphase. This indicates that a "mitosis rescue" mechanism establishes asymmetry at mitosis in PCP mutants. This study therefore identifies PCP as the initial symmetry-breaking signal for the planar polarization of PAR proteins in asymmetrically dividing SOPs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Misfolded SOD1 associated with motor neuron mitochondria alters mitochondrial shape and distribution prior to clinical onset.

    Christine Vande Velde

    Full Text Available Mutations in superoxide dismutase (SOD1 are causative for inherited amyotrophic lateral sclerosis. A proportion of SOD1 mutant protein is misfolded onto the cytoplasmic face of mitochondria in one or more spinal cord cell types. By construction of mice in which mitochondrially targeted enhanced green fluorescent protein is selectively expressed in motor neurons, we demonstrate that axonal mitochondria of motor neurons are primary in vivo targets for misfolded SOD1. Mutant SOD1 alters axonal mitochondrial morphology and distribution, with dismutase active SOD1 causing mitochondrial clustering at the proximal side of Schmidt-Lanterman incisures within motor axons and dismutase inactive SOD1 producing aberrantly elongated axonal mitochondria beginning pre-symptomatically and increasing in severity as disease progresses. Somal mitochondria are altered by mutant SOD1, with loss of the characteristic cylindrical, networked morphology and its replacement by a less elongated, more spherical shape. These data indicate that mutant SOD1 binding to mitochondria disrupts normal mitochondrial distribution and size homeostasis as early pathogenic features of SOD1 mutant-mediated ALS.

  3. On the change points of mean residual life and failure rate functions for some generalized gamma type distributions

    Parsa M.

    2014-01-01

    Full Text Available Mean residual life and failure rate functions are ubiquitously employed in reliability analysis. The term of useful period of lifetime distributions of bathtub-shaped failure rate functions is referred to the flat rigion of this function and has attracted authors and researchers in reliability, actuary, and survival analysis. In recent years, considering the change points of mean residual life and failure rate functions has been extensively utelized in determining the optimum burn-in time. In this paper we investigate the difference between the change points of failure rate and mean residual life functions of some generalized gamma type distributions due to the capability of these distributions in modeling various bathtub-shaped failure rate functions.

  4. Spatial distribution and polarization of gamma-rays generated via Compton backscattering in the Duke/OK-4 storage ring FEL

    Park, S H; Tornow, W; Montgomery, C

    2001-01-01

    Beams of nearly monochromatic gamma-rays are produced via intracavity Compton backscattering in the OK-4/Duke storage ring FEL, the high-intensity gamma-ray source (HI gamma S). Presently, HI gamma S generates gamma-ray beams with an energy tunable from 2 to 58 MeV and a maximum flux of 5x10 sup 7 gamma-rays per second. The gamma-rays are linearly polarized with a degree of polarization close to 100% (V.N. Litvinenko, et al., Predictions and expected performance for the VUV OK-5/Duke Storage Ring FEL with variable polarization, Nucl. Instr. and Meth. A, to be published in this proceeding) and they are collimated to pencil-like semi-monoenergetic beams with RMS energy spreads as low as 0.2%. The detailed theoretical and experimental studies of the gamma-ray beam quality were conducted during the last two years (S.H. Park, Thesis, Duke University, Durham, NC, USA, 2000). In this paper, we present the theoretical analysis and the experimental results on the spatial distribution and polarization of gamma-rays fro...

  5. Finding A Minimally Informative Dirichlet Prior Using Least Squares

    Kelly, Dana

    2011-01-01

    In a Bayesian framework, the Dirichlet distribution is the conjugate distribution to the multinomial likelihood function, and so the analyst is required to develop a Dirichlet prior that incorporates available information. However, as it is a multiparameter distribution, choosing the Dirichlet parameters is less straightforward than choosing a prior distribution for a single parameter, such as p in the binomial distribution. In particular, one may wish to incorporate limited information into the prior, resulting in a minimally informative prior distribution that is responsive to updates with sparse data. In the case of binomial p or Poisson λ, the principle of maximum entropy can be employed to obtain a so-called constrained noninformative prior. However, even in the case of p, such a distribution cannot be written down in the form of a standard distribution (e.g., beta, gamma), and so a beta distribution is used as an approximation in the case of p. In the case of the multinomial model with parametric constraints, the approach of maximum entropy does not appear tractable. This paper presents an alternative approach, based on constrained minimization of a least-squares objective function, which leads to a minimally informative Dirichlet prior distribution. The alpha-factor model for common-cause failure, which is widely used in the United States, is the motivation for this approach, and is used to illustrate the method. In this approach to modeling common-cause failure, the alpha-factors, which are the parameters in the underlying multinomial model for common-cause failure, must be estimated from data that are often quite sparse, because common-cause failures tend to be rare, especially failures of more than two or three components, and so a prior distribution that is responsive to updates with sparse data is needed.

  6. Dose distribution close to metal implants in Gamma Knife Radiosurgery: A Monte Carlo study

    Cheung, Joel Y.C.; Yu, K.N.; Chan, Josie F.K.; Ho, Robert T.K.; Yu, C.P.

    2003-01-01

    Materials with high atomic numbers favor the occurrence of the photoelectric effect when they are irradiated with gamma rays. Therefore, the photoelectric effects of metal implants within the target regions in Gamma Knife Radiosurgery are worth studying. In the present work, Monte Carlo simulations using EGS4 were employed to investigate the resulting dose enhancements. A dose enhancement as high as 10% was observed close to a platinum implant along the x and y axes, while no significant dose enhancements were observed for silver, stainless steel 301, and titanium ones. A dose enhancement as high as 20% was observed close to the platinum implant along the z axis at the superior position of the metal-phantom interface and was 10% higher for other metal implants

  7. Distributed control and data acquisition for the EUROGAM gamma ray spectrometer

    Owen, E.C.G.

    1992-01-01

    EUROGAM is an Anglo/French Gamma Ray Detector which will alternate between the Tandem Van der Graaf at Daresbury and the Vivitron at Strasbourg. Because of the need to conform to the standards of Laboratories in two different countries, and the very sensitive nature of electronics for Germanium Gamma Ray telescopes, the newly emerging VXlbus (VMEbus EXtensions for Instrumentation) was chosen as the basis for control and data acquisition. This entailed a major programme of development for both the signal processing front end modules for Germanium and Bismuth Germanate detectors, and also for the hardware and software management of resources from within the VXI environment. The paper will concentrate mainly on the latter areas. (author)

  8. EARLY AFTERGLOWS OF GAMMA-RAY BURSTS IN A STRATIFIED MEDIUM WITH A POWER-LAW DENSITY DISTRIBUTION

    Yi, Shuang-Xi; Dai, Zi-Gao; Wu, Xue-Feng

    2013-01-01

    A long-duration gamma-ray burst (GRB) has been widely thought to arise from the collapse of a massive star, and it has been suggested that its ambient medium is a homogenous interstellar medium (ISM) or a stellar wind. There are two shocks when an ultra-relativistic fireball that has been ejected during the prompt gamma-ray emission phase sweeps up the circumburst medium: a reverse shock that propagates into the fireball, and a forward shock that propagates into the ambient medium. In this paper, we investigate the temporal evolution of the dynamics and emission of these two shocks in an environment with a general density distribution of n∝R –k (where R is the radius) by considering thick-shell and thin-shell cases. A GRB afterglow with one smooth onset peak at early times is understood to result from such external shocks. Thus, we can determine the medium density distribution by fitting the onset peak appearing in the light curve of an early optical afterglow. We apply our model to 19 GRBs and find that their k values are in the range of 0.4-1.4, with a typical value of k ∼ 1, implying that this environment is neither a homogenous ISM with k = 0 nor a typical stellar wind with k = 2. This shows that the progenitors of these GRBs might have undergone a new mass-loss evolution

  9. Simulations of a spectral gamma-ray logging tool response to a surface source distribution on the borehole wall

    Wilson, R.D.; Conaway, J.G.

    1991-01-01

    We have developed Monte Carlo and discrete ordinates simulation models for the large-detector spectral gamma-ray (SGR) logging tool in use at the Nevada Test Site. Application of the simulation models produced spectra for source layers on the borehole wall, either from potassium-bearing mudcakes or from plate-out of radon daughter products. Simulations show that the shape and magnitude of gamma-ray spectra from sources distributed on the borehole wall depend on radial position with in the air-filled borehole as well as on hole diameter. No such dependence is observed for sources uniformly distributed in the formation. In addition, sources on the borehole wall produce anisotropic angular fluxes at the higher scattered energies and at the source energy. These differences in borehole effects and in angular flux are important to the process of correcting SGR logs for the presence of potassium mudcakes; they also suggest a technique for distinguishing between spectral contributions from formation sources and sources on the borehole wall. These results imply the existence of a standoff effect not present for spectra measured in air-filled boreholes from formation sources. 5 refs., 11 figs

  10. Performance Analysis of Multi-Hop Heterodyne FSO Systems over Malaga Turbulent Channels with Pointing Error Using Mixture Gamma Distribution

    Alheadary, Wael Ghazy

    2017-11-16

    This work investigates the end-to-end performance of a free space optical amplify-and-forward relaying system using heterodyne detection over Malaga turbulence channels at the presence of pointing error. In order to overcome the analytical difficulties of the proposed composite channel model, we employed the mixture Gamma (MG) distribution. The proposed model shows a high accurate and tractable approximation just by adjusting some parameters. More specifically, we derived new closed-form expression for average bit error rate employing rectangular quadrature amplitude modulation in term of MG distribution and generalized power series of the Meijer\\'s G- function. The closed-form has been validated numerically and asymptotically at high signal to noise ratio.

  11. On the null distribution of Bayes factors in linear regression

    We show that under the null, the 2 log (Bayes factor) is asymptotically distributed as a weighted sum of chi-squared random variables with a shifted mean. This claim holds for Bayesian multi-linear regression with a family of conjugate priors, namely, the normal-inverse-gamma prior, the g-prior, and...

  12. Dosimetric and Clinical Analysis of Spatial Distribution of the Radiation Dose in Gamma Knife Radiosurgery for Vestibular Schwannoma

    Massager, Nicolas; Lonneville, Sarah; Delbrouck, Carine; Benmebarek, Nadir; Desmedt, Françoise; Devriendt, Daniel

    2011-01-01

    Objectives: We investigated variations in the distribution of radiation dose inside (dose inhomogeneity) and outside (dose falloff) the target volume during Gamma Knife (GK) irradiation of vestibular schwannoma (VS). We analyzed the relationship between some parameters of dose distribution and the clinical and radiological outcome of patients. Methods and Materials: Data from dose plans of 203 patients treated for a vestibular schwannoma by GK C using same prescription dose (12 Gy at the 50% isodose) were collected. Four different dosimetric indexes were defined and calculated retrospectively in all plannings on the basis of dose–volume histograms: Paddick conformity index (PI), gradient index (GI), homogeneity index (HI), and unit isocenter (UI). The different measures related to distribution of the radiation dose were compared with hearing and tumor outcome of 203 patients with clinical and radiological follow-up of minimum 2 years. Results: Mean, median, SD, and ranges of the four indexes of dose distribution analyzed were calculated; large variations were found between dose plans. We found a high correlation between the target volume and PI, GI, and UI. No significant association was found between the indexes of dose distribution calculated in this study and tumor control, tumor volume shrinkage, hearing worsening, loss of functional hearing, or complete hearing loss at last follow-up. Conclusions: Parameters of distribution of the radiation dose during GK radiosurgery for VS can be highly variable between dose plans. The tumor and hearing outcome of patients treated is not significantly related to these global indexes of dose distribution inside and around target volume. In GK radiosurgery for VS, the outcome seems more to be influenced by local radiation dose delivered to specific structures or volumes than by global dose gradients.

  13. Effect of Gamma Irradiation and Coagualtion on the Molegular Weight Distribution of Soluble Organic Substances in Paper Mill Effluent

    Shijun, He; Jianlong, Wang [Institute of Nuclear and New Energy Technology (INET), Tsinghua University, Beijing 100084 (China); Jianxin, Wan; Mengmeng, Sun [Institute of Nuclear and New Energy Technology (INET), Tsinghua University, Beijing 100084 (China); School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070 (China); Longfei, Ye [Institute of Nuclear and New Energy Technology (INET), Tsinghua University, Beijing 100084 (China); College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082 (China)

    2012-07-01

    In order to look into the insights of the influence of gamma irradiation and coagulation on the molecular weight distribution (MWD) of soluble organic substances in real paper mill effluent, various parameters of wastewater samples before and after treated were investigated, including chemical oxygen demand (COD), biochemical oxygen demand (BOD{sub 5}), dissolved organic carbon (DOC) and absorbance at 254 nm wavelength (UV{sub 254}) as well. In addition, the effects of irradiation on oxygen uptake and on acute toxicity were also presented. The results showed that irradiation alone cannot promote the biodegradability and oxygen uptake as originally expected. The whole acute toxicity of samples was reduced after gamma irradiation. On the other side, coagulation can not only effectively eliminate the sectors with high molecular weight (MW>3000 Dalton, in short HMW), but also improve the capacity of ionizing irradiation initiated the transformation of medium molecular weight (1000 Dalton

  14. Effect of Gamma Irradiation and Coagualtion on the Molegular Weight Distribution of Soluble Organic Substances in Paper Mill Effluent

    He Shijun; Wang Jianlong; Wan Jianxin; Sun Mengmeng; Ye Longfei

    2012-01-01

    In order to look into the insights of the influence of gamma irradiation and coagulation on the molecular weight distribution (MWD) of soluble organic substances in real paper mill effluent, various parameters of wastewater samples before and after treated were investigated, including chemical oxygen demand (COD), biochemical oxygen demand (BOD 5 ), dissolved organic carbon (DOC) and absorbance at 254 nm wavelength (UV 254 ) as well. In addition, the effects of irradiation on oxygen uptake and on acute toxicity were also presented. The results showed that irradiation alone cannot promote the biodegradability and oxygen uptake as originally expected. The whole acute toxicity of samples was reduced after gamma irradiation. On the other side, coagulation can not only effectively eliminate the sectors with high molecular weight (MW>3000 Dalton, in short HMW), but also improve the capacity of ionizing irradiation initiated the transformation of medium molecular weight (1000 Dalton< MW<3000 Dalton, in short MMW) into low molecular weight (MW<1000 Dalton, in short LWM), which is readily degraded by the subsequently activated sludge process. (author)

  15. Incorporation and distribution of dihomo-gamma-linolenic acid, arachidonic acid, and eicosapentaenoic acid in cultured human keratinocytes

    Punnonen, K.; Puustinen, T.; Jansen, C.T.

    1986-01-01

    Human keratinocytes in culture were labelled with 14 C-dihomo-gamma-linolenic acid, 14 C-arachidonic acid or 14 C-eicosapentaenoic acid. All three eicosanoid precursor fatty acids were effectively incorporated into the cells. In phospholipids most of the radioactivity was recovered, in neutral lipids a substantial amount, and as free unesterified fatty acids only a minor amount. Most of the radioactivity was found in phosphatidylethanolamine which was also the major phospholipid as measured by phosphorous assay. The incorporation of dihomo-gamma-linolenic acid and arachidonic acid into lipid subfractions was essentially similar. Eicosapentaenoic acid was, however, much less effectively incorporated into phosphatidylinositol + phosphatidylserine and, correspondingly, more effectively into triacylglycerols as compared to the two other precursor fatty acids. Once incorporated, the distribution of all three precursor fatty acids was relatively stable, and only minor amounts of fatty acids were released into the culture medium during short term culture (two days). Our study demonstrates that eicosanoid precursor fatty acids are avidly taken up by human keratinocytes and esterified into membrane lipids. The clinical implication of this finding is that dietary manipulations might be employed to cause changes in the fatty acid composition of keratinocytes

  16. Measurement of density distribution of a cracking catalyst in experimental riser with a sampling procedure for gamma ray tomography

    Dantas, C.C.; Melo, S.B.; Oliveira, E.F.; Simoes, F.P.M.; Santos, M.G. dos; Santos, V.A. dos

    2008-01-01

    By scanning a riser the number of the gamma ray trajectories and the beam width involve temporal, spatial and density resolutions as they are closely correlated parameters. Therefore, evaluation of parameters and their interaction quantification, certainly, are required in the imaging process. Measuring the density distribution of the catalyst from the FCC - fluid cracking catalytic process in an experimental riser in single beam tomographic system, density resolution is evaluated and correlated with spatial resolution. The beam width Δs inside riser is measured and a criterion for determining spatial resolution is proposed. Experiments are carried out to demonstrate resolution effects of three Δs values: 3.30 x 10 -3 , 6.20 x 10 -3 and 12.00 x 10 -3 m. The gamma beam profile is modeled and a sampling rate according to Nyquist criterion is analyzed. The 4.3%, 8.1% and 15.6% ratios of Δs/R to internal riser radius are correlated to counting time in the sampling procedure. Results are discussed by comparison with values from literature

  17. The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

    Perley, D. A.; Kruhler, T.; Schulze, S.; Postigo, A. De Ugarte; Hjorth, J.; Berger, E.; Cenko, S. B.; Chary, R.; Cucchiara, A.; Ellis, R.; hide

    2016-01-01

    We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey (SHOALS), a multi-observatory high redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst (GRB) hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly deep, multicolor optical/near-IR photometry, plus spectroscopy of events without preexisting redshifts. Our optimized selection cuts combined with host galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust obscured, and at most 2% originate from z > 5.5. Using this sample, we estimate the redshift-dependent GRB rate density, showing it to peak at z approx. 2.5 and fall by at least an order of magnitude toward low (z = 0) redshift, while declining more gradually toward high (z approx. 7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star formation occurring in undetectable galaxies at all redshifts.

  18. Simulation of a method for determining one-dimensional {sup 137}Cs distribution using multiple gamma spectroscopic measurements with an adjustable cylindrical collimator and center shield

    Whetstone, Z.D.; Dewey, S.C. [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States); Kearfott, K.J., E-mail: kearfott@umich.ed [Radiological Health Engineering Laboratory, Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, 1906 Cooley Building, Ann Arbor, MI 48109-2104 (United States)

    2011-05-15

    With multiple in situ gamma spectroscopic measurements obtained with an adjustable cylindrical collimator and a circular shield, the arbitrary one-dimensional distribution of radioactive material can be determined. The detector responses are theoretically calculated, field measurements obtained, and a system of equations relating detector response to measurement geometry and activity distribution solved to estimate the distribution. This paper demonstrates the method by simulating multiple scenarios and providing analysis of the system conditioning.

  19. Vaginal distribution and retention of a multiparticulate drug delivery system, assessed by gamma scintigraphy and magnetic resonance imaging.

    Mehta, Samata; Verstraelen, Hans; Peremans, Kathelijne; Villeirs, Geert; Vermeire, Simon; De Vos, Filip; Mehuys, Els; Remon, Jean Paul; Vervaet, Chris

    2012-04-15

    For any new vaginal dosage form, the distribution and retention in the vagina has to be assessed by in vivo evaluation. We evaluated the vaginal distribution and retention of starch-based pellets in sheep as live animal model by gamma scintigraphy (using Indium-111 DTPA as radiolabel) and in women via magnetic resonance imaging (MRI, using a gadolinium chelate as contrast agent). A conventional cream formulation was used as reference in both studies. Cream and pellets were administered to sheep (n=6) in a two period-two treatment study and to healthy female volunteers (n=6) via a randomized crossover trial. Pellets (filled into hard gelatin capsule) and cetomacrogol cream, both labeled with Indium-111 DTPA (for gamma scintigraphy) or with gadolinium chelate (for MRI) were evaluated for their intravaginal distribution and retention over a 24h period. Spreading in the vagina was assessed based on the part of the vagina covered with formulation (expressed in relation to the total vaginal length). Vaginal retention of the formulation was quantified based on the radioactivity remaining in the vaginal area (sheep study), or qualitatively evaluated (women study). Both trials indicated a rapid distribution of the cream within the vagina as complete coverage of the vaginal mucosa was seen 1h after dose administration. Clearance of the cream was rapid: about 10% activity remained in the vaginal area of the sheep 12h post-administration, while after 8h only a thin layer of cream was detected on the vaginal mucosa of women. After disintegration of the hard gelatin capsule, the pellet formulation gradually distributed over the entire vaginal mucosa. Residence time of the pellets in the vagina was longer compared to the semi-solid formulation: after 24h 23 ± 7% radioactivity was detected in the vaginal area of the sheep, while in women the pellet formulation was still detected throughout the vagina. A multi-particulate system containing starch-based pellets was identified as a

  20. The Microstructure and Gamma Prime Distributions in Inertia Friction Welded Joint of P/M Superalloy FGH96

    Zhang, Chi; Shen, Wenfei; Zhang, Liwen; Xia, Yingnan; Li, Ruiqin

    2017-04-01

    A gamma prime ( γ') precipitation ( 35% in volume)-hardened powder metallurgy (P/M) superalloy FGH96 was welded using inertia friction welding (IFW). The microstructure and γ' distributions in the joints in two conditions, hot isostatic pressed state and solution-treated and aged state, were characterized. The recrystallization of grains, the dissolution and re-precipitation of γ' in the joints were discussed in terms of the temperature evolutions which were calculated by finite element model analysis. Regardless of the initial states, fully recrystallized fine grain structure formed at welded zone. Meanwhile, very fine γ' precipitations were re-precipitated at the welded zone. These recrystallized grain structure and fine re-precipitated γ' resulted in increasing hardness of IFW joint while making the hardness dependent on the microstructure and γ' precipitation.

  1. Distribution of gamma-ray dose rate in Fukushima prefecture by a car-borne survey method

    Sugihara, Shinji; Momoshima, Noriyuki; Maekawa, Akihiro; Ichikawa, Ryohei; Kawamura, Hidehisa

    2013-01-01

    The Tohoku Pacific Earthquake and Tsunami on March 11, 2011, caused severe damage to the TEPCO Fukushima Dai-ichi NPP. This was followed by a nuclear accident at an unprecedented scale, and huge amounts of radioactive material were released into the environment. The distributions of the gamma-ray dose rate in Fukushima prefecture were measured using a NaI(Tl) scintillation survey meter as part of a car-borne survey method on April 18-21, June 20-22, October 18-21, 2011, and on April 9-11 and July 30 - August 1, 2012. The dose rate near TEPCO Fukushima Dai-ichi NPP and at Iitate-mura, Fukushima-city was high (1 to >30 μSv/h). (author)

  2. Sensitivity of the LHC isolated-gamma+jet data to the parton distribution functions of the proton

    Carminati, L.; D'Enterria, D.; Koletsou, I.; Marchiori, G.; Rojo, J.; Stockton, M.; Tartarelli, F.

    2013-01-01

    We study the impact of differential isolated-photon+jet cross sections measured in proton-proton collisions at a center-of-mass energy of sqrt{s} = 7 TeV on the parton distribution functions (PDF) of the proton. Next-to-leading order perturbative QCD (pQCD) calculations complemented with the NNPDF2.1 parton densities, and a Bayesian PDF reweighting method are employed. We find that although the current data provide only mild constraints to the parton densities, future gamma-jet measurements with reduced experimental uncertainties can improve our knowledge of the gluon density over a wide range of parton fractional momenta x as well as of the quarks at low-x.

  3. Evaluation of absorbed dose-distribution in the X-ray or gamma-irradiator for blood products

    Moriyama, Satoshi; Kurihara, Katsuhiko; Yokokawa, Nobuhiko; Satake, Masahiro; Juji, Takeo

    2001-01-01

    Irradiation of blood products abrogates the proliferation of lymphocytes present in cellular component, which is currently the only accepted methodology to prevent transfusion-associated graft versus host disease (TA-GVHD). A range of irradiation dose levels between 15 Gy and 50 Gy is being used, but the majority of facilities are employing 15 Gy. It should, however, be recognized that the delivered dose in the instrument canister might differ from the actual dose absorbed by the blood bag. This study have evaluated the actual dose distribution under practical conditions where a container was loaded with blood products or water bags, or filled with distilled water. This approach provides data that the maximum attenuation occurred when the container was completely filled with a blood-compatible material. Thus, an error of approximately 20 percent should be considered in the dose measured in the in-air condition. A dose calibration in an in-air condition may lead to substantial underexposure of the blood products. A dose distribution study using adequately prearranged exposure period verified that the absorbed dose of 15 Gy was attained at any point in the container for both linear accelerator and gamma-irradiator. The maximal difference in the absorbed dose between measured points was 1.5- and 1.6-fold for linear accelerator and gamma-irradiator, respectively. In conclusion, using blood-compatible materials, a careful dose calibration study should be employed in which the absorbed dose of 15 Gy is obtained at the point where the lowest dose could be expected. (author)

  4. Distribution of bacteria in frozen shrimps and their decontamination by gamma irradiation

    Ito, Hitoshi; Adulyatham, P.; Ishigaki, Isao

    1987-11-01

    Six samples of frozen shrimps were obtained through importing company mainly from South-east Asian countries. Five samples of frozen shrimps contained 1.5 x 10/sup 5/ to 6.2 x 10/sup 6/ per gram of total aerobic bacteria, and 4 samples contained 1.4 x 10/sup 2/ to 2.2 x 10/sup 3/ per gram of coliforms, which are higher contamination than Japanese standard of hygenic level for frozen food products (total counts below 10/sup 5/ per gram and no coliforms). The dominant bacteria in total counts were consisted with psychrotrophic Moraxella, Arthrobacter, Micrococcus, Acinetobacter, Flavobacterium, Corynebacterium, Pseudomonas and etc, in all kinds of frozen shrimps. Salmonellae or enteric Vibrio were could not isolated by ordinary isolation methods, and there were isolated many strains of Proteus mirabilis instead of these bacteria. Necessary dose of gamma irradiation for decontamination of bacteria to hygenic level was decided as 3 approx. 5 kGy from the inactivation curves of total bacteria, coliforms, Proteus mirabilis and Salmonella typhymurium in frozen shrimps. Off-odor was suppressed by frozen condition of irradiation.

  5. Distribution of bacteria in frozen shrimps and their decontamination by gamma irradiation

    Ito, Hitoshi; Adulyatham, P.; Ishigaki, Isao

    1987-01-01

    Six samples of frozen shrimps were obtained through importing company mainly from South-east Asian countries. Five samples of frozen shrimps contained 1.5 x 10 5 to 6.2 x 10 6 per gram of total aerobic bacteria, and 4 samples contained 1.4 x 10 2 to 2.2 x 10 3 per gram of coliforms, which are higher contamination than Japanese standard of hygenic level for frozen food products (total counts below 10 5 per gram and no coliforms). The dominant bacteria in total counts were consisted with psychrotrophic Moraxella, Arthrobacter, Micrococcus, Acinetobacter, Flavobacterium, Corynebacterium, Pseudomonas and etc, in all kinds of frozen shrimps. Salmonellae or enteric Vibrio were could not isolated by ordinary isolation methods, and there were isolated many strains of Proteus mirabilis instead of these bacteria. Necessary dose of gamma irradiation for decontamination of bacteria to hygenic level was decided as 3 ∼ 5 kGy from the inactivation curves of total bacteria, coliforms, Proteus mirabilis and Salmonella typhymurium in frozen shrimps. Off-odor was suppressed by frozen condition of irradiation. (author)

  6. Effect of source angular distribution on the evaluation of gamma-ray skyshine

    Sheu, R.D.; Jiang, S.H. [Dept. of Engineering and System Science, National Tsing Hua Univ., Taiwan (China); Chang, B.J.; Chen, I.J. [Division of Health Physics, Inst. of Nuclear Energy Research, Taiwan (China)

    2000-03-01

    The effect of the angular distribution of the equivalent point source on the analysis of the skyshine dose rates was investigated in detail. The dedicated skyshine codes SKYDOSE and McSKY were revised to include the capability of dealing with the anisotropic source. It was found that a replace of the cosine-distributed source by an isotropic source will overestimate the skyshine dose rates for large roof-subtended angles and cause underestimation for small roof-subtended angles. For building with roof shielding, however, replacing the cosine-distributed source by an isotropic source will always underestimate the skyshine dose rates. The skyshine dose rates from a volume source calculated by the dedicated skyshine code agree very well with those of the MCNP Monte Carlo calculation. (author)

  7. Measurement of the relative power density distribution of the IPEN/MB-01 reactor, using a fuel rod gamma scanning technique

    Carneiro, Alvaro Luiz Guimaraes

    1996-01-01

    This work presents a measurement methodology for determination of radial and axial relative power density distribution of the IPEN/MB-01 Reactor core by means of the fuel rod gamma scanning. The methodology is based on the proportionality between gamma activity emitted by the radioactive decay of the fission products and power density. The scanning technique consists of counting gamma radiation above 0,6 MeV along the active area of the fuel rod, getting a distribution profile. The experimental results will be used as a benchmark for qualification and to establish possible deviations for the calculational methodology currently used at IPEN. The comparison of the calculated and measured results showed good agreement. (author)

  8. Gamma-ray burst afterglows as probes of environment and blast wave physics. II. The distribution of p and structure of the circumburst medium

    Starling, R.L.C.; van der Horst, A.J.; Rol, E.; Wijers, R.A.M.J.; Kouveliotou, C.; Wiersema, K.; Curran, P.A.; Weltevrede, P.

    2008-01-01

    We constrain blast wave parameters and the circumburst media of a subsample of 10 BeppoSAX gamma-ray bursts (GRBs). For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral

  9. Magnetic interaction of positronium atoms measured by perturbed angular distribution in 3 gamma annihilation decay

    Ivanov, E.; Vata, I.; Plostinaru, D.; Catana, D.; Dudu, D.; Constantinescu, O.

    2003-01-01

    The Time Differential Perturbed Angular Distribution (TDPAD) method in connection with long-lived Positron Life-Time Spectroscopy (PLTS) have been used to observe 'quantum beat' spin oscillations of positronium atom in an external magnetic field. Our results offer an encouraging hint toward a new method of condensed matter investigation by PLTS. Similarities with Muonium Spin Rotation (μSR) method are suggested. (authors)

  10. Measuring the plutonium distribution in fuel elements by the gamma scanning method

    Gorobets, A.K.; Leshchenko, Yu.I.; Semenov, A.L.

    1982-01-01

    An on-line system designed for measuring Pu distribution in the length of fresh fuel elements with vibrocompacted UO 2 -PuO 2 fuel rods by the γ-scanning method is described. An algorithm for measurement result processing and the procedure of determination of calibration parameters necessary for the valid signal separat.ion by means of a two-channel analyzer and for evaluation of the self-absorption effect are considered. The device scanning unit consists of two NaI(Tl) detectors simultaneously detecting γ-radiation from the opposite sides of a measured fuel rod section. The cesium source with Esub(γ)=660 keV is used for fuel scanning. On the base of the analysis of the results obtained when studying the BOR-60 experimental fuel elements with fuel rods of 400 mm long by means of the described device clusion is made that fuel element scanning during 20 min (scanning step is 4 mm, measuring time at each step is 10 s) makes it possible to determine Pu distribution with the error less than +-4% at the confidence probability of 0.68

  11. Correlation of gamma spectrometer measurements at surface with concentrations and distributions of subsurface radium contamination: Development, verification and application of methodology

    McCallum, B.A.; Clement, C.H.; Huffman, D.; Stager, R.H.

    2000-01-01

    This work is a step forward in the investigation of data gathering principles and analysis tools for improved estimates of subsurface radium contamination concentrations and distributions using surface gamma radiation spectra. Techniques to solve the inverse problem of estimating surface gamma radiation spectra given a fully known subsurface radium distribution have been investigated and applied with success. These techniques fell into three broad categories: empirical (using laboratory and field data), analytical (using mathematical derivations of relationships), and computer simulation (using Monte-Carlo photon transport simulation methods). Methods of analyzing surface spectra to estimate certain source parameters have been studied. The most fully developed methods are those involving the ratio of the areas of two peaks of differing energy from the same radionuclide to determine the source depth. For a point source of radium and its progeny, these techniques are able to reliably estimate the source depth from a single gamma radiation spectrum taken at the surface directly above the source. The only significant uncertainties in this case are the soil density and uncertainties introduced as a result of counting statistics. Further work remains to fully achieve the goals of the larger project: to develop a comprehensive suite of tools for the improved interpretation of surface gamma radiation spectra from subsurface distributions of radium contaminated soil. (author)

  12. High-resolution studies of momentum distributions using perfect crystal gamma diffractometry

    Krexner, G.; Bischof, G.; Jentschel, M.; Boerner, H.

    2006-01-01

    Full text: Positron annihilation spectroscopy has turned out to be highly successful in the investigation of Fermi surfaces, electronic structures and various kinds of defects. On the other hand, algorithms based on density functional theory have made enormous progress in recent years and calculations for the contributions of both delocalized and core electrons in a rapidly increasing number of systems is either already feasible today or to be expected in the near future. By comparison, over the last decades there has been little improvement in the experimental limitations which are still set by the energy resolution of germanium detectors (slightly above 1 keV for annihilation photons close to 500 keV) and the angular resolution in ACAR studies (superior by about one order of magnitude). In addition, coincidence techniques are hampered by low count rates. An alternative is suggested by the fact that, in principle, Bragg diffraction techniques using perfect single crystals provide a way for the precise determination of wavelengths corresponding to energies in the MeV range. The single crystal analyzer instrument PN3 at the Institute Laue-Langevin (Grenoble, France) offers the unique possibility to determine the energy of annihilation photons with an accuracy close to about 1 eV, i.e. an improvement of up to three orders of magnitude in comparison to conventional semiconductor detectors. We discuss possible applications of this spectrometer in high-resolution studies of momentum distributions for both delocalized and core electrons. (author)

  13. Distribution of microorganisms in medical devices and their inactivation effects by gamma-irradiation

    Ito, Hitoshi; Ishigaki, Isao

    1986-01-01

    Radiation treatment is getting important position for sterilizing medical devices and for packaging films of foods. Recently, survey of bioburden is an important technique for evaluation of sterility doses for medical devices. However, many studies have been done mainly on the irradiation effects of spore-forming bacteria in medical devices. In this study, radiation sensitivity of spore-forming bacteria and fungi were examined after the survey on distribution of microorganisms in several kinds of medical devices. The main contaminant in disposable syringes, needles and conical flasks were consisted of Bacillus, with lesser amount of Micrococcus, Pseudomonas, Peptococcaceae and fungi as positive of 5 - 60 % in the medical devices which cultivated in thioglycolate broth. Bacillus group were identified as B. pumilus, B. sphaericus, B. coagulans, B. megaterium and etc. Fungi were isolated a lesser amounts compared with spore-forming bacteria and identified as Blastomyces, Penicillium, Haplosporangium, Euricoa and Audeobasidium. Peptococaceae were not isolated after irradiation with a dose of 0.1 Mrad even the samples were contaminated with high percentage. The D 10 values of dryed endospores of Bacillus-isolates which attached to the filter paper with pepton-glycerin were obtained to be 0.11 - 0.19 Mrad. The D 10 values of many isolates of fungi in dry condition were obtained below 0.08 Mrad. However, the isolate of Aureobasidium is radiation-resistant, and it's D 10 values was obtained as 0.28 Mrad under aerobic and anaerobic dry condition. (author)

  14. Factorization, the light-cone distribution amplitude of the B-meson and the radiative decay $B \\to \\gamma l \

    Descotes-Genon, S

    2003-01-01

    We study the radiative decay B -> gamma l nu_l in the framework of QCD factorization. We demonstrate explicitly that, in the heavy-quark limit and at one-loop order in perturbation theory, the amplitude does factorize, i.e. that it can be written as a convolution of a perturbatively calculable hard-scattering amplitude with the (non-perturbative) light-cone distribution amplitude of the B-meson. We evaluate the hard-scattering amplitude at one-loop order and verify that the large logarithms are those expected from a study of the b->u transition in the Soft-Collinear Effective Theory. Assuming that this is also the case at higher orders, we resum the large logarithms and perform an exploratory phenomenological analysis. The questions addressed in this study are also relevant for the applications of the QCD factorization formalism to two-body non-leptonic B-decays, in particular to the component of the amplitude arising from hard spectator interactions.

  15. The Pattern of Distribution of Peroxidase and H2O2 in Hypocotyls of Pumpkin irradiated with Gamma Ray

    Wi, Seung Gon; Chung, Byung Yeoup; Kim, Jae Sung; Kim, Jin Hong; Lee, Ju Woon; Baek, Myung Hwa; Chae, Hyo Seok

    2005-01-01

    Gamma radiation, one of ionizing radiations, has been reported to affect the morphological, anatomical, biochemical and physiological changes of plants at different dose levels. These effects at high level include inhibition in plant growth. Peroxidases (PODs) are mainly participations the process of lignification on the cell wall and protect the cell organelles in cytosol against the oxidative stresses by ROS (reactive oxygen species). Hydrogen peroxide (ROS) is normal metabolite in aerobic cells and the physiological steady concentrations (between 10 -7 and 10 -9 ) are not particularly cytotoxic. When these concentrations are increased by ionizing radiation, they lead to cell lethality. Thus radiation-induced H 2 O 2 may appear as an important agent causing cell damage. In this study, a polyclonal antibody against peroxidase and cerium chloride as a trapping agent for H 2 O 2 were used to obtain for better information on the occurrence and distribution of POD and H 2 O 2 in the cytoplasm and walls of vascular bundle in hypocotyls of pumpkin

  16. A new method for the determination of radionuclide distribution in the soil by in situ gamma-ray spectrometry

    Zombori, P.; Andrasi, A.; Nemeth, I.

    1995-01-01

    In case of major nuclear accidents when larger amount of radioactive material is released into the atmosphere vast areas can become contaminated by the nuclear fallout. The deposited radioactivity penetrates the soil in a complex manner: dry and wet deposition lead to different initial distribution patterns which are further modified by the later transport processes in the upper layers of the soil. The distribution is influenced by various factors (physico-chemical characteristics of the radioisotopes, soil type, weather conditions, environment etc.), the resulting soil profile is hardly predictable. An important lesson we learned from the Chernobyl reactor accident is the great variability of the contamination both in the extent of the deposition and in the penetration features. In recent years - following the reactor accident in Chernobyl - an increased interest for rapid methods of monitoring environmental radioactivity was expressed. The International Atomic Energy Agency initiated a research project to co-ordinate the activities carried out in various laboratories aiming at the development of rapid monitoring procedures. The Co-ordinated Research Project (CRP) G6 10 01 under the title Rapid Instrumental and Separation Methods for Monitoring Radionuclides in Food and the Environment has given a frame for 11 research programs. The Health Physics Department of the KFKI Institute for Atomic Energy Research (the former Central Research Institute for Physics) has taken a part in this CRP with a project titled: Rapid In Situ Gamma Spectrometric Determination of Fallout Radioactivity in the Environment. The main objective of our study was to find a method to estimate the penetration characteristics of the fallout radioactivity by using only spectral information obtained by the in situ spectrometric measurement thus avoiding the need for a long and tiresome sampling and sample analysis procedure

  17. Effects of bone- and air-tissue inhomogeneities on the dose distributions of the Leksell Gamma Knife (registered) calculated with PENELOPE

    Al-Dweri, Feras M O; Rojas, E Leticia; Lallena, Antonio M

    2005-01-01

    Monte Carlo simulation with PENELOPE (version 2003) is applied to calculate Leksell Gamma Knife (registered) dose distributions for heterogeneous phantoms. The usual spherical water phantom is modified with a spherical bone shell simulating the skull and an air-filled cube simulating the frontal or maxillary sinuses. Different simulations of the 201 source configuration of the Gamma Knife have been carried out with a simplified model of the geometry of the source channel of the Gamma Knife recently tested for both single source and multisource configurations. The dose distributions determined for heterogeneous phantoms including the bone- and/or air-tissue interfaces show non-negligible differences with respect to those calculated for a homogeneous one, mainly when the Gamma Knife isocentre approaches the separation surfaces. Our findings confirm an important underdosage (∼10%) nearby the air-tissue interface, in accordance with previous results obtained with the PENELOPE code with a procedure different from ours. On the other hand, the presence of the spherical shell simulating the skull produces a few per cent underdosage at the isocentre wherever it is situated

  18. Characterization of fuel distribution in the Three Mile Island Unit 2 (TMI-2) reactor system by neutron and gamma-ray dosimetry

    Gold, R.; Roberts, J.H.; Ruddy, F.H.; Preston, C.C.; McNeece, J.P.; Kaiser, B.J.; McElroy, W.N.

    1984-01-01

    Neutron and gamma-ray dosimetry are being used for nondestructive assessment of the fuel distribution throughout the Three Mile Island Unit 2 (TMI-2) reactor core region and primary cooling system. The fuel content of TMI-2 makeup and purification Demineralizer A has been quantified with Si(Li) continuous gamma-ray spectrometry and solid-state track recorder (SSTR) neutron dosimetry. For fuel distribution characterization in the core region, results from SSTR neutron dosimetry exposures in the TMI-2 reactor cavity are presented. These SSTR results are consistent with the presence of a significant amount of fuel debris, equivalent to several fuel assemblies or more, lying at the bottom of the reactor vessel. (Auth.)

  19. Gamma-ray application to the measurement of a media distribution at the catalyst cooler of a residue fluid catalytic cracking unit (RFCCU) in the petrochemical industry

    Kim, Jin Seop; Jung, Sung Hee; Kim, Jong Bum

    2006-01-01

    The dynamic behavior of the process media in the petrochemical industry can hardly be observed during its operation. Because the information on the process media is directly related to the processes efficiency, therefore it is necessary to establish what is actually happening inside the process unit. For this purpose, a field experiment was performed to study the fluidized catalyst patterns and confirm the internal conditions by using a sealed gamma-ray source. From the results, the areas showing a different pattern from the surrounding vicinity were found successfully. Especially at the upper part of the connection point at which the pipeline from are generator was joined, a relatively low amount of catalyst was distributed. Sealed gamma-ray application to the catalyst cooler is considered as a worthwhile technique for a measurement of the catalyst distribution at the RFCCU.

  20. Gamma-ray application to the measurement of a media distribution at the catayst cooler of a residue fluid catalytic cracking unit (RFCCU) in the petrochemical industry

    Kim, Jin Seop; Jung, Sung Hee; Kim, Jong Bum

    2006-01-01

    The dynamic behavior of the process media in the petrochemical industry can hardly be observed during its operation. Because the information on the process media is directly related to the processes efficiency, therefore it is necessary to establish what is actually happening inside the process unit. For this purpose, a field experiment was performed to study the fluidized catalyst patterns and confirm the internal conditions by using a sealed gamma-ray source. From the results, the areas showing a different pattern from the surrounding vicinity were found successfully. Especially at the upper part of the connection point at which the pipeline from are generator was joined, a relatively low amount of catalyst was distributed. Sealed gamma-ray application to the catalyst cooler is considered as a worthwhile technique for a measurement of the catalyst distribution at the RFCCU.

  1. Relative distribution and abundance of fishes and crayfish in 2010 and 2014 prior to saltcedar (Tamarix ssp.) removal in the Amargosa River Canyon, southeastern California

    Hereford, Mark E.

    2016-07-22

    The Amargosa River Canyon, located in the Mojave Desert of southeastern California, contains the longest perennial reach of the Amargosa River. Because of its diverse flora and fauna, it has been designated as an Area of Critical Environmental Concern and a Wild and Scenic River by the Bureau of Land Management. A survey of fishes conducted in summer 2010 indicated that endemic Amargosa River pupfish (Cyprinodon nevadensis amargosae) and speckled dace (Rhinichthys osculus spp.) were abundant and occurred throughout the Amargosa River Canyon. The 2010 survey reported non-native red swamp crayfish (Procambarus clarkii) and western mosquitofish (Gambusia affinis) captures were significantly higher, whereas pupfish captures were lower, in areas dominated by non-native saltcedar (Tamarix ssp.). Based on the 2010 survey, it was hypothesized that the invasion of saltcedar could result in a decrease in native species. In an effort to maintain and enhance native fish populations, the Bureau of Land Management removed saltcedar from a 1,550 meter reach of stream on the Amargosa River in autumn 2014 and autumn 2015. Prior to the removal of saltcedar, a survey of fishes and crayfish using baited minnow traps was conducted in the treatment reach to serve as a baseline for future comparisons with post-saltcedar removal surveys. During the 2014 survey, 1,073 pupfish and 960 speckled dace were captured within the treatment reach. Catch per unit effort of pupfish and speckled dace in the treatment reach was less in 2014 than in 2010, although differences could be owing to seasonal variation in capture probability. Non-native mosquitofish catch per unit effort decreased from 2010 to 2014; however, the catch per unit effort of crayfish increased from 2010 to 2014. Future monitoring efforts of this reach should be conducted at the same time period to account for potential seasonal fluctuations of abundance and distribution of fishes and crayfish. A more robust study design that

  2. Spatial and energy distributions of skyshine neutron and gamma radiation from nuclear reactors on the ground-air boundary

    Orlov, Y.; Netecha, M.E.; Vasiliev, A.P.; Avaev, V.N.; Vasiliev, G.A. [Research and Development Institute of Power Engineering, Moscow (Russian Federation); Zelensky, D.I.; Istomin, Y.L.; Cherepnin, Y.S. [Institute of Atomic Energy of the National Nuclear Center of the Republic of Kazakhstan, Semipalatinsk-21 (Kazakhstan); Nomura, Y. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2000-03-01

    A set of measurements on skyshine radiation was conducted at two special research reactors. A broad range of detectors was used in the measurements to record neutron and gamma radiations. Dosimetric and radiometric field measurements of the neutrons and gamma quanta of the radiation scattered in the air were performed at distances of 50 to 1000 m from the reactor during different weather conditions. The neutron spectra in the energy range of 1 eV to 10 MeV and the gamma quanta spectra in the range of 0.1-10 MeV were measured. (author)

  3. Search for CP violation in K/sup + -/. --> pi. /sup + -/. pi. /sup 0/. gamma. decays. [Charge asymmetry, rates, Dalitz plot distribution, 55 to 90 MeV

    Smith, K M [Glasgow Univ. (UK). Dept. of Natural Philosophy; Booth, P S.L.; Renshall, H R [Liverpool Univ. (UK); Jones, P B; Salmon, G L; Williams, W S.C. [Oxford Univ. (UK). Nuclear Physics Lab.; Duke, P J; Evans, W M; Hill, R E; Holley, W R

    1976-06-21

    A search has been made for a charge asymmetry in the decay rates for K/sup + -/..--> pi../sup + -/..pi../sup 0/..gamma.., which would indicate a CP violating transition. No asymmetry has been found in the Dalitz plot distribution for the decay, nor has any asymmetry been found in the decay rate for the charged pion kinetic energy range 55 to 90 MeV, to a precision of +-2.9%.

  4. Gross Mal distribution Identification and Effect of Inlet Distributor on the Phase Holdup in a Trickle Bed Reactor Using Gamma-Ray Densitometry (GRD)

    Mohd Fitri Abdul Rahman; Alexander, V.; Al-Dahhan, M.

    2016-01-01

    Local liquid and gas mal distribution and their holdups in a packed column are difficult to identify due to multiphase properties and other design factors. Good liquid and gas flow distribution important to determine to get high performance of Trickle Bed Reactor (TBR). Gross mal distribution indicates some faulty or bad flow distribution of liquid and gas. In this work, gross mal distribution of phases has been identified using Gamma Ray Densitometry (GRD) technique with three types of inlet distributors (single inlet towards the wall, single inlet at the center, and proper shower) by measuring line average diameter profile of phases (Liquid, Gas, and Solids) holdups. Gamma-ray densitometry is a non-invasive technique which can be implemented at the laboratory, pilot plant, and industrial scales reactors. Experiments were performed on 0.14 m diameter reactor made of Plexiglas filled with 0.003 m glass bead which acts as the solid. The superficial velocities for both gas and liquid were in the range 0.03 m/s to 0.27 m/s and 0.004 m/s to 0.014 m/s respectively. Proper shower distributor showed early liquid spreading than compared with other distributors. The effect of superficial gas velocity on liquid spread was seen to be non-significant, and liquid distribution is found to be almost uniform at the center region of the catalyst bed. (author)

  5. Reliability assessment based on small samples of normal distribution

    Ma Zhibo; Zhu Jianshi; Xu Naixin

    2003-01-01

    When the pertinent parameter involved in reliability definition complies with normal distribution, the conjugate prior of its distributing parameters (μ, h) is of normal-gamma distribution. With the help of maximum entropy and the moments-equivalence principles, the subjective information of the parameter and the sampling data of its independent variables are transformed to a Bayesian prior of (μ,h). The desired estimates are obtained from either the prior or the posterior which is formed by combining the prior and sampling data. Computing methods are described and examples are presented to give demonstrations

  6. Monte Carlo simulation of dose distribution in water around {sup 57}Fe{sub 3}O{sub 4} magnetite nanoparticle in the nuclear gamma resonance condition

    Gabbasov, R.; Polikarpov, M. [National Research Centre Kurchatov Institute (Russian Federation); Safronov, V. [Shubnikov Institute of Crystallography, Research Center Space Materials Science (Russian Federation); Sozontov, E.; Yurenya, A., E-mail: antonyurenya@gmail.com; Panchenko, V. [National Research Centre Kurchatov Institute (Russian Federation)

    2016-12-15

    In this work was proposed a new radiotherapy enhancement method consisting of the administration of magnetic nanoparticles into the cells with further irradiation with a gamma-ray beam. As a result, adjusting the energy distribution of a gamma-ray beam and {sup 57}Fe abundance it is possible to achieve an extremely intensive electron emission because of a nuclear resonance. The produced conversion and Auger electrons can be used as an effective tool for DNA lesions production. We developed a Monte Carlo model for an electron and gamma emission by {sup 57}Fe nucleus using the Geant4 program package. The parameters of a resonant absorption were taken from Mössbauer spectra of magnetite nanoparticles synthesized for the administration into live cells. The space distribution of the radiation dose showed an increase in the dose of 2–2.5 times in the case of the natural abundance and more than 50 times in the case of the 66 % enrichment of the nanoparticles.

  7. Development of a computer program to determine the pulse-height distribution in a gamma-ray detector from an arbitrary geometry source -feasibility study

    Currie, G.D.; Marshall, M.

    1989-03-01

    The feasibility of developing a computer program suitable for evaluating the pulse-height spectrum in a gamma-ray detector from a complex geometry source has been examined. A selection of relevant programs, Monte Carlo radiation transport codes, have been identified and their applicability to this study discussed. It is proposed that the computation be performed in two parts: the evaluation of the photon fluence at the detector using a photon transport code, and calculation of the pulse-height distribution from this spectrum using response functions determined with an electron-photon transport code. The two transport codes selected to perform this procedure are MCNP (Monte Carlo Neutron Photon code), and EGS4 (Electron Gamma Shower code). (Author)

  8. Quantitative analysis of the fission product distribution in a damaged fuel assembly using gamma-spectrometry and computed tomography for the Phébus FPT3 test

    Biard, B.

    2013-01-01

    Highlights: • The FP quantitative distribution in the fuel bundle is measured by gamma-spectrometry. • The FP location is obtained with emission tomograms and other experiment results. • X-ray tomograms provide the material and density mapping of the degraded bundle. • The self-attenuation may then be computed for each isotope at its key line energy. • Results are consistent with other FPT3 measurements, with acceptable uncertainties. -- Abstract: The international Phébus FP programme, initiated in 1988 by the French “Institut de Radioprotection et de Sûreté Nucléaire” (IRSN), in cooperation with the European Commission (EC) and with financial support from USNRC, Canada, PSI/HSK (Switzerland), Japan and Korea, was aimed at studying severe accident phenomena: the fuel degradation, the release of fission products (FPs) and their transport through the reactor coolant system to the containment building. The FPT3 test, conducted in 2004, was the last of the five light water reactor core meltdown accident tests performed on irradiated fuel rods. After the experiment, the test device was recovered and analysed through a full set of non-destructive examinations performed over the fuel bundle zone, including gamma-scanning, gamma emission tomography, X-ray radiography and X-ray transmission tomography. The gamma-scanning was specifically devoted to the location, identification and amount quantification of the FPs remaining in the bundle. Since the fuel bundle became highly degraded during the experiment, the geometry was different at each level examined, and did not correspond to the well-known initial state. The self-attenuation of the test device and consequently the efficiency correction could then not be estimated by classical means that need to know the geometry of the object. Using the results of the other non-destructive examinations, specific computational tools and methods have therefore been developed to compute the self-attenuation of the bundle

  9. Quantitative analysis of the fission product distribution in a damaged fuel assembly using gamma-spectrometry and computed tomography for the Phébus FPT3 test

    Biard, B., E-mail: bruno.biard@irsn.fr

    2013-09-15

    Highlights: • The FP quantitative distribution in the fuel bundle is measured by gamma-spectrometry. • The FP location is obtained with emission tomograms and other experiment results. • X-ray tomograms provide the material and density mapping of the degraded bundle. • The self-attenuation may then be computed for each isotope at its key line energy. • Results are consistent with other FPT3 measurements, with acceptable uncertainties. -- Abstract: The international Phébus FP programme, initiated in 1988 by the French “Institut de Radioprotection et de Sûreté Nucléaire” (IRSN), in cooperation with the European Commission (EC) and with financial support from USNRC, Canada, PSI/HSK (Switzerland), Japan and Korea, was aimed at studying severe accident phenomena: the fuel degradation, the release of fission products (FPs) and their transport through the reactor coolant system to the containment building. The FPT3 test, conducted in 2004, was the last of the five light water reactor core meltdown accident tests performed on irradiated fuel rods. After the experiment, the test device was recovered and analysed through a full set of non-destructive examinations performed over the fuel bundle zone, including gamma-scanning, gamma emission tomography, X-ray radiography and X-ray transmission tomography. The gamma-scanning was specifically devoted to the location, identification and amount quantification of the FPs remaining in the bundle. Since the fuel bundle became highly degraded during the experiment, the geometry was different at each level examined, and did not correspond to the well-known initial state. The self-attenuation of the test device and consequently the efficiency correction could then not be estimated by classical means that need to know the geometry of the object. Using the results of the other non-destructive examinations, specific computational tools and methods have therefore been developed to compute the self-attenuation of the bundle

  10. Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

    Krupička, Jan; Matoušek, Václav

    2014-01-01

    Roč. 62, č. 2 (2014), s. 126-132 ISSN 0042-790X R&D Projects: GA ČR GA103/09/0383 Institutional support: RVO:67985874 Keywords : two-phase flow * gamma radiometry * computational tomography * slurry flow experiment Subject RIV: BK - Fluid Dynamics Impact factor: 1.486, year: 2014

  11. Altered cellular distribution and subcellular sorting of gamma-tubulin in diffuse astrocytic gliomas and human glioblastoma cell lines

    Katsetos, C.; Path, M.; Reddy, G.; Dráberová, Eduarda; Šmejkalová, Barbora; Del Valle, L.; Asfraf, Q.; Tadevosyan, A.; Yelin, K.; Maraziotis, T.; Mörk, S.; Mishra, O.; Legido, A.; Nissanov, J.; Baas, P.; De Chadarevian, J.; Dráber, Pavel

    2006-01-01

    Roč. 65, č. 5 (2006), s. 465-477 ISSN 0022-3069 Institutional research plan: CEZ:AV0Z50520514; CEZ:AV0Z5052915 Keywords : anaplastic changes * glioblastoma * gamma tubulin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.371, year: 2006

  12. Determination of solar flare accelerated ion angular distributions from SMM gamma ray and neutron measurements and determination of the He-3/H ratio in the solar photosphere from SMM gamma ray measurements

    Lingenfelter, Richard E.

    1989-01-01

    Comparisons of Solar Maximum Mission (SMM) observations of gamma-ray line and neutron emission with theoretical calculation of their expected production by flare accelerated ion interactions in the solar atmosphere have led to significant advances in the understanding of solar flare particle acceleration and interaction, as well as the flare process itself. These comparisons have enabled the determination of, not only the total number and energy spectrum of accelerated ions trapped at the sun, but also the ion angular distribution as they interact in the solar atmosphere. The Monte Carlo program was modified to include in the calculations of ion trajectories the effects of both mirroring in converging magnetic fields and of pitch angle scattering. Comparing the results of these calculations with the SMM observations, not only the angular distribution of the interacting ions can be determined, but also the initial angular distribution of the ions at acceleration. The reliable determination of the solar photospheric He-3 abundance is of great importance for understanding nucleosynthesis in the early universe and its implications for cosmology, as well as for the study of the evolution of the sun. It is also essential for the determinations of the spectrum and total number of flare accelerated ions from the SMM/GRS gamma-ray line measurements. Systematic Monte Carlo calculations of the time dependence were made as a function of the He-3 abundance and other variables. A new series of calculations were compared for the time-dependent flux of 2.223 MeV neutron capture line emission and the ratio of the time-integrated flux in the 2.223 MeV line to that in the 4.1 to 6.4 MeV nuclear deexcitation band.

  13. Vertical distribution of elements in non-polluted estuarine sediments determined by neutron induced prompt gamma-ray and instrumental neutron activation analyses

    Kuno, A.; Sampei, K.; Matsuo, M.; Sawahata, H.

    1999-01-01

    Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments. (author)

  14. Study of the heterogeneities effect in the dose distributions of Leksell Gamma Knife (R), through Monte Carlo simulation

    Rojas C, E.L.; Al-Dweri, F.M.O.; Lallena R, A.M.

    2005-01-01

    In this work they are studied, by means of Monte Carlo simulation, the effects that take place in the dose profiles that are obtained with the Leksell Gamma Knife (R), when they are kept in account heterogeneities. The considered heterogeneities simulate the skull and the spaces of air that are in the head, like they can be the nasal breasts or the auditory conduits. The calculations were made using the Monte Carlo Penelope simulation code (v. 2003). The geometry of each one of the 201 sources that this instrument is composed, as well as of the corresponding channels of collimation of the Gamma Knife (R), it was described by means of a simplified model of geometry that has been recently studied. The obtained results when they are kept in mind the heterogeneities they present non worthless differences regarding those obtained when those are not considered. These differences are maximum in the proximities of the interfaces among different materials. (Author)

  15. Isotopic distributions, element ratios, and element mass fractions from enrichment-meter-type gamma-ray measurements of MOX

    Close, D.A.; Parker, J.L.; Haycock, D.L.; Dragnev, T.

    1991-01-01

    The gamma-ray spectra from ''infinitely'' thick mixed oxide samples have been measured. The plutonium isotopics, the U/Pu ratio, the high-Z mass fractions (assuming only plutonium, uranium, and americium), and the low-Z mass fraction (assuming the matrix is only oxygen) can be determined by carefully analyzing the data. The results agree well with the chemical determination of these parameters. 8 refs., 3 figs., 3 tabs

  16. TLD-300 detectors for separate measurement of total and gamma absorbed dose distributions of single, multiple, and moving-field neutron treatments

    Rassow, J.

    1984-01-01

    Fast neutron therapy requirements, because of the poor depth dose characteristic of present therapeutical sources, are at least as complex in treatment plans as photon therapy. The physical part of the treatment planning is very important; however, it is much more complicated than for photons or electrons owing to the need for: Separation of total and gamma absorbed dose distributions (Dsub(T) and Dsub(G)); and more stringent tissue-equivalence conditions of phantoms than in photon therapy. Therefore, methods of clinical dosimetry for the separate determination of total and gamma absorbed dose distributions in irregularly shaped (inhomogeneous) phantoms are needed. A method using TLD-300 (CaF 2 :Tm) detectors is described, which is able to give an approximate solution of the above-mentioned dosimetric requirements. The two independent doses, Dsub(T) and Dsub(G), can be calculated by an on-line computer analysis of the digitalized glow curve of TLD-300 detectors, irradiated with d(14)+Be neutrons of the cyclotron isocentric neutron therapy facility CIRCE in Essen. Results are presented for depth and lateral absorbed dose distributions (Dsub(T) and Dsub(G)) for fixed neutron beams of different field sizes compared with measurements by standard procedures (TE-TE ionization chamber, GM counter) in an A-150 phantom. The TLD-300 results for multiple and moving-field treatments (with and without wedge filters) in a patient simulating irregularly shaped (inhomogeneous) phantoms, are shown together with computer calculations of these dose distributions. The probable causes for some systematic deviations are discussed, which lead to open problems for further investigations owing to features of the detector material and the evaluation method, but mainly to differences in the composition of phantom materials used for the calculations (standard dose distributions) and TLD-300 measurements. (author)

  17. BURST FLUENCE DISTRIBUTIONS OF SOFT GAMMA REPEATERS 1806–20 AND 1900+14 IN THE ROSSI X-RAY TIMING EXPLORER PCA ERA

    Prieskorn, Zachary; Kaaret, Philip

    2012-01-01

    We study the fluence distributions of over 3040 bursts from SGR 1806–20 and over 1963 bursts from SGR 1900+14 using the complete set of observations available from the Rossi X-Ray Timing Explorer/Proportional Counter Array through 2011 March. Cumulative event distributions are presented for both sources and are fitted with single and broken power laws as well as an exponential cutoff. The distributions are best fitted by a broken power law with exponential cutoff; however the statistical significance of the cutoff is not high and the upper portion of the broken power law can be explained as the expected number of false bursts due to random noise fluctuations. Event distributions are also examined in high and low burst rate regimes and power-law indices are found to be consistent, independent of the burst rate. The contribution function of the event fluence is calculated. This distribution shows that the energy released in the soft gamma repeater (SGR) bursts is dominated by the most powerful events for both sources. The power-law nature of these distributions combined with the dominant energy dissipation of the system occurring in the large, less frequent bursts is indicative of a self-organized critical system, as suggested by Goğus et al. in 1999.

  18. Wealth of the world's richest publicly traded companies per industry and per employee: Gamma, Log-normal and Pareto power-law as universal distributions?

    Soriano-Hernández, P.; del Castillo-Mussot, M.; Campirán-Chávez, I.; Montemayor-Aldrete, J. A.

    2017-04-01

    Forbes Magazine published its list of leading or strongest publicly-traded two thousand companies in the world (G-2000) based on four independent metrics: sales or revenues, profits, assets and market value. Every one of these wealth metrics yields particular information on the corporate size or wealth size of each firm. The G-2000 cumulative probability wealth distribution per employee (per capita) for all four metrics exhibits a two-class structure: quasi-exponential in the lower part, and a Pareto power-law in the higher part. These two-class structure per capita distributions are qualitatively similar to income and wealth distributions in many countries of the world, but the fraction of firms per employee within the high-class Pareto is about 49% in sales per employee, and 33% after averaging on the four metrics, whereas in countries the fraction of rich agents in the Pareto zone is less than 10%. The quasi-exponential zone can be adjusted by Gamma or Log-normal distributions. On the other hand, Forbes classifies the G-2000 firms in 82 different industries or economic activities. Within each industry, the wealth distribution per employee also follows a two-class structure, but when the aggregate wealth of firms in each industry for the four metrics is divided by the total number of employees in that industry, then the 82 points of the aggregate wealth distribution by industry per employee can be well adjusted by quasi-exponential curves for the four metrics.

  19. Calculation of noninformative prior of reliability parameter and initiating event frequency with Jeffreys method

    He Jie; Zhang Binbin

    2013-01-01

    In the probabilistic safety assessment (PSA) of nuclear power plants, there are few historical records on some initiating event frequencies or component failures in industry. In order to determine the noninformative priors of such reliability parameters and initiating event frequencies, the Jeffreys method in Bayesian statistics was employed. The mathematical mechanism of the Jeffreys prior and the simplified constrained noninformative distribution (SCNID) were elaborated in this paper. The Jeffreys noninformative formulas and the credible intervals of the Gamma-Poisson and Beta-Binomial models were introduced. As an example, the small break loss-of-coolant accident (SLOCA) was employed to show the application of the Jeffreys prior in determining an initiating event frequency. The result shows that the Jeffreys method is an effective method for noninformative prior calculation. (authors)

  20. Attrition resistant gamma-alumina catalyst support

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  1. In situ gamma-ray spectrometric analysis of radionuclide distributions at a commercial shallow land burial site

    Kirby, L.J.; Campbell, R.M.

    1984-10-01

    Gamma-ray spectrometric analysis conducted at the Maxey Flats, Kentucky (USA) shallow land burial site confirmed that the waste radionuclides have been retained largely within the restricted area of the burial site. Concentrations of 137 Cs and 60 Co were comparable with those originating from global fallout and lower than concentrations measured in several other areas having similar rainfall. In-situ spectrometric analyses, corroborated by soil sample and vegetation analyses, indicate that the site has influenced 60 Co levels slightly in the west drainage channel, but 137 Cs did not originate from the site. Concentrations of 60 Co, 90 Sr and 137 Cs determined in subsurface soils by well logging techniques confirmed that subsurface migration of waste-derived radionuclides to points outside the restricted area has not been a significant source of contamination of the environs adjacent to the site. 8 references, 8 figures

  2. Compton scattering study of electron momentum distribution in lithium fluoride using 662 keV gamma radiations

    Vijayakumar, R.; Shivaramu; Ramamurthy, N.; Ford, M. J.

    2008-12-01

    Here we report the first ever 137Cs Compton spectroscopy study of lithium fluoride. The spherical average Compton profiles of lithium fluoride are deduced from Compton scattering measurements on poly crystalline sample at gamma ray energy of 662 keV. To compare the experimental data, we have computed the spherical average Compton profiles using self-consistent Hartree-Fock wave functions employed on linear combination of atomic orbital (HF-LCAO) approximation. The directional Compton profiles and their anisotropic effects are also calculated using the same HF-LCAO approximation. The experimental spherical average profiles are found to be in good agreement with the corresponding HF-LCAO calculations and in qualitative agreement with Hartree-Fock free atom values. The present experimental isotropic and calculated directional profiles are also compared with the available experimental isotropic and directional Compton profiles using 59.54 and 159 keV γ-rays.

  3. Ultraviolet B irradiation induces changes in the distribution and release of arachidonic acid, dihomo-gamma-linolenic acid, and eicosapentaenoic acid in human keratinocytes in culture

    Punnonen, K.; Puustinen, T.; Jansen, C.T.

    1987-01-01

    There is increasing evidence that derivatives of 20-carbon polyunsaturated fatty acids, the eicosanoids, play an important role in the inflammatory responses of the human skin. To better understand the metabolic fate of fatty acids in the skin, the effect of ultraviolet B (UVB) irradiation (280-320 nm) on the distribution and release of 14 C-labeled arachidonic acid, dihomo-gamma-linolenic acid, and eicosapentaenoic acid in human keratinocytes in culture was investigated. Ultraviolet B irradiation induced the release of all three 14 C-labeled fatty acids from the phospholipids, especially from phosphatidylethanolamine, and this was accompanied by increased labeling of the nonphosphorus lipids. This finding suggests that UVB induces a significant liberation of eicosanoid precursor fatty acids from cellular phospholipids, but the liberated fatty acids are largely reincorporated into the nonphosphorus lipids. In conclusion, the present study suggests that not only arachidonic acid but also dihomo-gamma-linolenic acid, and eicosapentaenoic acid might be involved in the UVB irradiation-induced inflammatory reactions of human skin

  4. Impact of gamma irradiation on porosity and pore distribution of poly [ethylene-oxide] films: correlation with dielectric and microstructural properties

    Saha, Mou; Mukhopadhyay, Madhumita; Ray, Ruma

    2018-03-01

    The structure and morphology of polymers are significantly altered upon exposure to high energy gamma irradiation either through bond breakage i.e. scission or cross-linkage. The present article reports the influence of gamma radiation (1-20 kGy) on the distribution of molecular weight and porosity of the films prepared using irradiated and unirradiated poly-[ethylene oxide] (PEO) powder. The PEO films exhibit pore dimension in the range of 20-500 nm. Selective irradiation is capable of tailoring the pore-size and reducing the multimodal trait to uni-or bimodal upon high energy perturbation. The porosity of PEO films is determined from both 2D-pore surface calculation from SEM images and compared with 3D-BET porosity. Correlation is established among dielectric constant (ɛ') and porosity. The magnitude of ɛ' increases sharply towards low frequency due to electrode polarization effects. Relaxation time is found to be highest and comparable for 1 and 10 KGy. With increase in irradiation dose, scission is predominant, owing to which smaller polymer fragments are produced which are able to follow fast frequency regime and thereby relax at lesser time.

  5. Computer aided collimation gamma (Cacao): a new approach in measuring and visualizing the distribution of X and gamma ray emitters in contaminate wounds; Cacao (camera a collimation assistee par ordinateur): une nouvelle approche pour reconstruire et visualiser des contaminations d'emetteurs X et gamma dans les blessures

    Douiri, A. [Hopital Pitie-Salpetriere (LENA), 75 - Paris (France); Jeanguillaume, C. [Centre Hospitalier Universitaire de Larrey, Service de Medecine Nucleaire, 49 - Angers (France); Franck, D.; Carlan, L. de [Institut de Radioprotection et de Surete Nucleaire, IRSN, Dept. de Protection de la Sante de l' Homme et de Dosimetrie, 92 - Fontenay aux Roses (France); Quartuccio, M.; Begot, S. [Faculte des Sciences d' Orsay (LPS), 91 - Orsay (France)

    2003-07-01

    The treatment of contaminated wounds can be greatly improved by visualizing the distribution of the radioactivity that is present. The low sensitivity of the conventional Anger camera means that it can only be used where there is a high level of activity. Moreover, these gamma cameras cannot make full use of the recent progress made in high spatial resolution semi-conductor detectors. In order to increase sensitivity while at the same time maintaining a sufficient resolution of the reconstructed image, the principle of the Computer aided collimation gamma camera (CACAO in French) was proposed as a possible means of using gamma cameras in intern dosimetry. This principle is based on the combined use of collimators with holes that are wider- than the intrinsic resolution of the detector, circular and linear scanning movements, a detector sensitive to the source depth and a specific reconstruction algorithm. This article presents the recent developments of the CACAO system and illustrates by a theoretical and experimental study, its performances compared with the classic tomography system. We start with a general overview of the CACAO system and its reconstruction algorithm. First of all, the superiority of the CACAO system is demonstrated by a simulation ,study. Then, an experimental bench was developed using an implanted silicon pixel detector specifically designed to allow the visualization of a subject contaminated with low energy X and gamma emitters. The study presented here shows images obtained from a phantom composed of three sources of Americium {sup 341}Am. Although the comparison between the conventional and CACAO approaches were not carried out with optimal parameters, especially for CACAO, the initial results show that CACAO has an improved sensitivity and a superior resolution. Finally, the transposition of this system to the practical study of contaminated wounds is discussed. (authors)

  6. The Kolmogorov-Smirnov test for three redshift distributions of long gamma-ray bursts in the Swift Era

    Dong Yunming; Lu Tan

    2009-01-01

    We investigate redshift distributions of three long burst samples, with the first sample containing 131 long bursts with observed redshifts, the second including 220 long bursts with pseudo-redshifts calculated by the variability-luminosity relation, and the third including 1194 long bursts with pseudo-redshifts calculated by the lag-luminosity relation, respectively. In the redshift range 0-1 the Kolmogorov-Smirnov probability of the observed redshift distribution and that of the variability-luminosity relation is large. In the redshift ranges 1-2, 2-3, 3-6.3 and 0-37, the Kolmogorov-Smirnov probabilities of the redshift distribution from lag-luminosity relation and the observed redshift distribution are also large. For the GRBs, which appear both in the two pseudo-redshift burst samples, the KS probability of the pseudo-redshift distribution from the lag-luminosity relation and the observed reshift distribution is 0.447, which is very large. Based on these results, some conclusions are drawn: i) the V-L iso relation might be more believable than the τ-L iso relation in low redshift ranges and the τ-L iso relation might be more real than the V-Liso relation in high redshift ranges; ii) if we do not consider the redshift ranges, the τ-L iso relation might be more physical and intrinsical than the V-L i so relation. (research papers)

  7. Gamma-Ray Burst Afterglows as Probes of Environment and Blast Wave Physics. II. The Distribution of rho and Structure of the Circumburst Medium

    Starling, R. L. C.; vanderHorst, A. J.; Rol, E.; Wijers, R. A. M. J.; Kouveliotou, C.; Wiersema, K.; Curran, P. A.; Weltervrede, P.

    2008-01-01

    We constrain blast wave parameters and the circumburst media ofa subsample of 10 BeppoSAX gamma-ray bursts (GRBs). For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral fits to their X-ray, optical, and NIR afterglow data. The spectral fits have been done in count space and include the effects ofmetallicity, and are compared with the previously reported optical and X-ray temporal behavior. Using the blast wave model and some assumptions which include on-axis viewing and standard jet structure, constant blast wave energy, and no evolution of the microphysical parameters, we find a mean value ofp for the sample as a whole of 9.... oa -0.003.0" 2 a_ statistical analysis of the distribution demonstrates that the p-values in this sample are inconsistent with a single universal value forp at the 3 _ level or greater, which has significant implications for particle acceleration models. This approach provides us with a measured distribution ofcircumburst density structures rather than considering only the cases of k ----0 (homogeneous) and k - 2 (windlike). We find five GRBs for which k can be well constrained, and in four of these cases the circumburst medium is clearly windlike. The fifth source has a value of 0 medium.

  8. Gamma-Ray Burst Afterglows as Probes of Environment and Blastwave Physics II: The Distribution of p and Structure of the Circumburst Medium

    Starling, R. L. C.; vanderHorst, A. J.; Rol, E.; Wijers, R. A. M. J.; Kouveliotou, C.; Wiersema, K.; Curran, P. A.; Weltevrede, P.

    2007-01-01

    We constrain blastwave parameters and the circumburst media of a subsample of BeppoSAX Gamma-Ray Bursts. For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral fits to their X-ray, optical and nIR afterglow data. The spectral fits have been done in count space and include the effects of metallicity, and are compared with the previously reported optical and X-ray temporal behaviour. Assuming the fireball model, we can find a mean value of p for the sample as a whole of 2.035. A statistical analysis Of the distribution demonstrates that the p values in this sample are inconsistent with a single universal value for p at the 3sigma level or greater. This approach provides us with a measured distribution of circumburst density structures rather than considering only the cases of k = 0 (homogeneous) and k = 2 (wind-like). We find five GRBs for which k can be well constrained, and in four of these cases the circumburst medium is clearly wind-like. The fifth source has a value of 0 less than or equal to k less than or equal to 1, consistent with a homogeneous circumburst medium.

  9. Electron-density distribution in cubic SrTiO{sub 3}: a comparative {gamma}-ray diffraction study

    Jauch, W. [Hahn-Meitner-Inst., Berlin (Germany); Reehuis, M. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2005-07-01

    The electron density and atomic displacements in the perovskite SrTiO{sub 3} have been studied using extensive and accurate {gamma}-ray diffraction data ({lambda}=0.0392 Aa) at room temperature. The six strongest low-order structure factors have been determined under extinction-free conditions. Gram-Charlier series expansion of the thermal parameters have revealed no evidence for anharmonicity. The population of the 3d subshell on Ti is found to be close to zero, in agreement with the observed magnetic behaviour. The electronic properties at the bond critical points indicate ionic Ti-O and Sr-O interactions of different strengths, which is corroborated by the net charges of the atomic basins [q(Sr)=1.18 vertical stroke e vertical stroke, q(Ti)=3.10 vertical stroke e vertical stroke, q(O)=1.42 vertical stroke e vertical stroke ]. A critical comparison is made with earlier experimental results from laboratory X-ray, synchrotron X-ray, electron and neutron diffraction studies. Agreement and discrepancies are identified and resolved. (orig.)

  10. Ambient radiation dose to the population of the city of Sao Paulo-Brazil: indoor gamma distribution

    Otsubo, Sergio M.; Yoshimura, Elizabeth M.

    2001-01-01

    The objective of this work is to present results of indoor ambient dose equivalent rate (H * (10)) in the city of Sao Paulo. Studies show that people of industrialized cities spend indoor approximately 80% of their time, and that there are great variations of the rate of H * (10) all over the world. Values of environmental radiation are important base to epidemiological studies, or analyses of consequences and effects of radioactive or nuclear accidents and also to assist research on biological effects of low doses, a very controversial subject in the literature. There are no reports in the literature about environmental radiation in the city of Sao Paulo, showing the important of this study. Environmental radiation exists everywhere in the planet, so the human beings are exposed to it at any time or place, being indoor or outdoor. Three types of commercial indoor ambient with large flow of the population were analyzed: bank offices, shops in the neighborhood of the banks, and shopping centers. A gamma ray portable spectrometer was used, composed by a crystal of NaI (Tl). The mean value of the H * (10) rate obtained was 173,8(17) nSv/h. The results analyzed by commerce type and by the health divisions of the city are also presented. (author)

  11. Gamow-Teller strength distribution in the beta-decay of 100Ag from total-absorption gamma spectrometry

    Batist, L.; Bykov, A.; Moroz, F.; Wittmann, V.; Alkhazov, G.D.; Keller, H.; Kirchner, R.; Klepper, O.; Roeckl, E.; Huyse, M.; Duppen, P. van; Reusen, G.; Plochocki, A.; Pfuetzner, M.; Rykaczewski, K.; Szerypo, J.; Zylicz, J.; Brown, B.A.

    1994-10-01

    The EC/β + -decay of the odd-odd nucleus 100 Ag was studied by means of total absorption γ-ray spectrometry. Most of the Gamow-Teller strength was found to be concentrated at an excitation energy of 5.6 MeV in 100 Pd, the FWHM of this resonance being 1.5 MeV. The measured strength distribution which is interpreted within the BCS approximation as being due to the dominant population of four-quasiparticle excitations, resembles the distribution predicted by an advanced shell-model calculation for the 98 Ag→ 98 Cd decay. (orig.)

  12. Generalized Bayesian inference with sets of conjugate priors for dealing with prior-data conflict : course at Lund University

    Walter, G.

    2015-01-01

    In the Bayesian approach to statistical inference, possibly subjective knowledge on model parameters can be expressed by so-called prior distributions. A prior distribution is updated, via Bayes’ Rule, to the so-called posterior distribution, which combines prior information and information from

  13. A new gamma-ray diagnostic for energetic ion distributions - The Compton tail on the neutron capture line

    Vestrand, W.T.

    1990-01-01

    This paper presents a new radiation diagnostic for assaying the energy spectrum and the angular distribution of energetic ions incident on thick hydrogen-rich thermal targets. This diagnostic compares the number of emergent photons in the narrow neutron capture line at 2.223 MeV to the number of Compton scattered photons that form a low-energy tail on the line. It is shown that the relative strength of the tail can be used as a measure of the hardness of the incident ion-energy spectrum. Application of this diagnostic to solar flare conditions is the main thrust of the work presented here. It is examined how the strength of the Compton tail varies with flare viewing angle and the angular distribution of the flare-accelerated particles. Application to compact X-ray binary systems is also briefly discussed. 39 refs

  14. Aerial gamma spectrometry of the uranium province of Lagoa Real (Caetite, BA, Brazil): go environmental aspects and distribution of the absorbed dose in the air

    Santos, Esau Francisco Sena

    2006-01-01

    In the present study, it was analyzed the surface concentrations of the natural radioelements K, U and Th, as well as the absorbed dose rate in air caused by gamma radiation from the Lagoa Real uranium province, which is located at the center southern portion of Bahia State and comprises an area of approximately 4.600 Km 2 . Data from the airborne gamma ray spectrometric survey of the region (Sao Timoeo Project) carried out in 1979, was used in this study. Besides, recent data of U, Th and absorbed dose rates from the Environmental Monitoring Program of the uranium concentration plant (URA), operated in the region by the Brazilian Nuclear Industries (INB), were used with the aim of inter compare the sampling points in the same geo referenced area. Imaging geo processing software's give support to frame maps of surface concentrations and ternary maps, as well as allow the integration of these with other themes (e.g. hydrology, geology, pedology) favouring the interpretation of geo environmental process from the radioactive cartography. Considering the whole study area, it was obtained the following mean values: absorbed dose rate in air (61,08 nGy.h -1 ), Potassium (1,65 % K) , Uranium (3,02 ppm eU) and thorium (18,26 ppm eTh). The geological unities bounding the uranium anomalies were placed in the areas characterized by the highest values of radioelements and, as expected, the major dose levels. The use of ternary maps coupled with the geology and hydrology allowed distinguishing the relationship between the surface distribution of natural radioelements and the geo environmental aspects, including the influence of the catchment in their transport and migration. (author)

  15. MCNPX calculations of dose rate distribution inside samples treated in the research gamma irradiating facility at CTEx

    Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G., E-mail: tiagorusin@ime.eb.b, E-mail: rebello@ime.eb.b, E-mail: vellozo@cbpf.b, E-mail: renatoguedes@ime.eb.b [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Nuclear; Vital, Helio C., E-mail: vital@ctex.eb.b [Centro Tecnologico do Exercito (CTEx), Rio de Janeiro, RJ (Brazil); Silva, Ademir X., E-mail: ademir@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear

    2011-07-01

    A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)

  16. MCNPX calculations of dose rate distribution inside samples treated in the research gamma irradiating facility at CTEx

    Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G.; Silva, Ademir X.

    2011-01-01

    A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)

  17. Gamma Knife

    ... News Physician Resources Professions Site Index A-Z Gamma Knife Gamma Knife® is a radiation therapy that uses computerized ... If you're scheduled for radiation therapy using Gamma Knife®, a treatment team consisting of a radiation ...

  18. Penalised Complexity Priors for Stationary Autoregressive Processes

    Sø rbye, Sigrunn Holbek; Rue, Haavard

    2017-01-01

    The autoregressive (AR) process of order p(AR(p)) is a central model in time series analysis. A Bayesian approach requires the user to define a prior distribution for the coefficients of the AR(p) model. Although it is easy to write down some prior, it is not at all obvious how to understand and interpret the prior distribution, to ensure that it behaves according to the users' prior knowledge. In this article, we approach this problem using the recently developed ideas of penalised complexity (PC) priors. These prior have important properties like robustness and invariance to reparameterisations, as well as a clear interpretation. A PC prior is computed based on specific principles, where model component complexity is penalised in terms of deviation from simple base model formulations. In the AR(1) case, we discuss two natural base model choices, corresponding to either independence in time or no change in time. The latter case is illustrated in a survival model with possible time-dependent frailty. For higher-order processes, we propose a sequential approach, where the base model for AR(p) is the corresponding AR(p-1) model expressed using the partial autocorrelations. The properties of the new prior distribution are compared with the reference prior in a simulation study.

  19. Penalised Complexity Priors for Stationary Autoregressive Processes

    Sørbye, Sigrunn Holbek

    2017-05-25

    The autoregressive (AR) process of order p(AR(p)) is a central model in time series analysis. A Bayesian approach requires the user to define a prior distribution for the coefficients of the AR(p) model. Although it is easy to write down some prior, it is not at all obvious how to understand and interpret the prior distribution, to ensure that it behaves according to the users\\' prior knowledge. In this article, we approach this problem using the recently developed ideas of penalised complexity (PC) priors. These prior have important properties like robustness and invariance to reparameterisations, as well as a clear interpretation. A PC prior is computed based on specific principles, where model component complexity is penalised in terms of deviation from simple base model formulations. In the AR(1) case, we discuss two natural base model choices, corresponding to either independence in time or no change in time. The latter case is illustrated in a survival model with possible time-dependent frailty. For higher-order processes, we propose a sequential approach, where the base model for AR(p) is the corresponding AR(p-1) model expressed using the partial autocorrelations. The properties of the new prior distribution are compared with the reference prior in a simulation study.

  20. Reproducing kernel Hilbert spaces of Gaussian priors

    Vaart, van der A.W.; Zanten, van J.H.; Clarke, B.; Ghosal, S.

    2008-01-01

    We review definitions and properties of reproducing kernel Hilbert spaces attached to Gaussian variables and processes, with a view to applications in nonparametric Bayesian statistics using Gaussian priors. The rate of contraction of posterior distributions based on Gaussian priors can be described

  1. Estimation of the Vertical Distribution of Radiocesium in Soil on the Basis of the Characteristics of Gamma-Ray Spectra Obtained via Aerial Radiation Monitoring Using an Unmanned Helicopter.

    Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi; Hamamoto, Shoichiro; Nishimura, Taku; Sanada, Yukihisa

    2017-08-17

    After the Fukushima Daiichi Nuclear Power Plant accident, the vertical distribution of radiocesium in soil has been investigated to better understand the behavior of radiocesium in the environment. The typical method used for measuring the vertical distribution of radiocesium is troublesome because it requires collection and measurement of the activity of soil samples. In this study, we established a method of estimating the vertical distribution of radiocesium by focusing on the characteristics of gamma-ray spectra obtained via aerial radiation monitoring using an unmanned helicopter. The estimates are based on actual measurement data collected at an extended farm. In this method, the change in the ratio of direct gamma rays to scattered gamma rays at various depths in the soil was utilized to quantify the vertical distribution of radiocesium. The results show a positive correlation between the abovementioned and the actual vertical distributions of radiocesium measured in the soil samples. A vertical distribution map was created on the basis of this ratio using a simple equation derived from the abovementioned correlation. This technique can provide a novel approach for effective selection of high-priority areas that require decontamination.

  2. Estimation of the Vertical Distribution of Radiocesium in Soil on the Basis of the Characteristics of Gamma-Ray Spectra Obtained via Aerial Radiation Monitoring Using an Unmanned Helicopter

    Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi; Sanada, Yukihisa

    2017-01-01

    After the Fukushima Daiichi Nuclear Power Plant accident, the vertical distribution of radiocesium in soil has been investigated to better understand the behavior of radiocesium in the environment. The typical method used for measuring the vertical distribution of radiocesium is troublesome because it requires collection and measurement of the activity of soil samples. In this study, we established a method of estimating the vertical distribution of radiocesium by focusing on the characteristics of gamma-ray spectra obtained via aerial radiation monitoring using an unmanned helicopter. The estimates are based on actual measurement data collected at an extended farm. In this method, the change in the ratio of direct gamma rays to scattered gamma rays at various depths in the soil was utilized to quantify the vertical distribution of radiocesium. The results show a positive correlation between the abovementioned and the actual vertical distributions of radiocesium measured in the soil samples. A vertical distribution map was created on the basis of this ratio using a simple equation derived from the abovementioned correlation. This technique can provide a novel approach for effective selection of high-priority areas that require decontamination. PMID:28817098

  3. A new method for the determination of radionuclide distribution in the soil by in situ gamma-ray spectrometry

    Zombori, P.; Andrasi, A.; Nemeth, I.

    1992-06-01

    A method was searched for to estimate the penetration characteristics of fallout radioactivity, using only spectral information obtained by in situ spectrometric measurements, and avoiding the need for long and tiresome sampling and sample analysis procedures. To speed up the analysis for depth distribution determination of fallout radioactivity in soil, an instrumental method based on the shape of spectra was developed. The ratio of peak to valley (the region between the photopeak and Compton edge) depends on the penetration of radionuclides in soil, providing an estimation of depth profile. These ratios were calculated and the method was tested by actual measurements. (R.P.) 7 refs.; 14 figs.; 2 tabs

  4. Population distribution of flexible molecules from maximum entropy analysis using different priors as background information: application to the Φ, Ψ-conformational space of the α-(1-->2)-linked mannose disaccharide present in N- and O-linked glycoproteins.

    Säwén, Elin; Massad, Tariq; Landersjö, Clas; Damberg, Peter; Widmalm, Göran

    2010-08-21

    The conformational space available to the flexible molecule α-D-Manp-(1-->2)-α-D-Manp-OMe, a model for the α-(1-->2)-linked mannose disaccharide in N- or O-linked glycoproteins, is determined using experimental data and molecular simulation combined with a maximum entropy approach that leads to a converged population distribution utilizing different input information. A database survey of the Protein Data Bank where structures having the constituent disaccharide were retrieved resulted in an ensemble with >200 structures. Subsequent filtering removed erroneous structures and gave the database (DB) ensemble having three classes of mannose-containing compounds, viz., N- and O-linked structures, and ligands to proteins. A molecular dynamics (MD) simulation of the disaccharide revealed a two-state equilibrium with a major and a minor conformational state, i.e., the MD ensemble. These two different conformation ensembles of the disaccharide were compared to measured experimental spectroscopic data for the molecule in water solution. However, neither of the two populations were compatible with experimental data from optical rotation, NMR (1)H,(1)H cross-relaxation rates as well as homo- and heteronuclear (3)J couplings. The conformational distributions were subsequently used as background information to generate priors that were used in a maximum entropy analysis. The resulting posteriors, i.e., the population distributions after the application of the maximum entropy analysis, still showed notable deviations that were not anticipated based on the prior information. Therefore, reparameterization of homo- and heteronuclear Karplus relationships for the glycosidic torsion angles Φ and Ψ were carried out in which the importance of electronegative substituents on the coupling pathway was deemed essential resulting in four derived equations, two (3)J(COCC) and two (3)J(COCH) being different for the Φ and Ψ torsions, respectively. These Karplus relationships are denoted

  5. Measurement of the weak mixing angle and the spin of the gluon from angular distributions in the reaction pp{yields} Z/{gamma}*+X{yields}{mu}{sup +}{mu}{sup -}+X with ATLAS

    Schmieden, Kristof

    2013-04-15

    The measurement of the effective weak mixing angle with the ATLAS experiment at the LHC is presented. It is extracted from the forward-backward asymmetry in the polar angle distribution of the muons originating from Z boson decays in the reaction pp{yields}Z/{gamma}{sup *}+X{yields} {mu}{sup +}{mu}{sup -}+X. In total 4.7 fb{sup -1} of proton-proton collisions at {radical}(s)=7 TeV are analysed. In addition, the full polar and azimuthal angular distributions are measured as a function of the transverse momentum of the Z/{gamma}{sup *} system and are compared to several simulations as well as recent results obtained in p anti p collisions. Finally, the angular distributions are used to confirm the spin of the gluon using the Lam-Tung relation.

  6. Diversity and distribution of entomopathogenic nematodes (Nematoda: Steinernematidae, Heterorhabditidae) and their bacterial symbionts (gamma-Proteobacteria: Enterobacteriaceae) in Jordan.

    Stock, S Patricia; Al Banna, Luma; Darwish, Rula; Katbeh, Ahmad

    2008-06-01

    Until now, only a few systematic surveys of entomopathogenic nematodes (EPN) have been conducted in Middle Eastern countries. Many of the recovered EPN species in this region have shown to own distinctive qualities that enable their survival in unique environments, such as high temperatures and low moisture levels tolerance. These new species and strains, with unique environmental tolerances, are more suitable for their consideration in pest management programs in xerophytic regions. With this background in mind, we recently conducted a survey of EPN in Jordan. This study records for the first time the diversity and distribution of these nematodes and their bacterial symbionts in this country. Jordan's three geographic regions: (1) the highlands, (2) Jordan valley and (3) the desert region were sampled. Within each region, natural habitats and agricultural regions characteristic to each region were considered for sampling purposes. Four EPN species including three Steinernema and one Heterorhabditis were recovered. Nematodes were identified using a combination of molecular markers and classic morphological diagnostic tools. Bacterial symbionts were identified by analysis of 16S rRNA sequences. Abiotic characteristics such as soil type, soil pH, and elevation were also recorded. We herein report the diversity of EPN species in Jordan and discuss their potential in Biocontrol and IPM programs for this country.

  7. The Pattern of Distribution of Peroxidase and H{sub 2}O{sub 2} in Hypocotyls of Pumpkin irradiated with Gamma Ray

    Wi, Seung Gon; Chung, Byung Yeoup; Kim, Jae Sung; Kim, Jin Hong; Lee, Ju Woon; Baek, Myung Hwa; Chae, Hyo Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2005-07-01

    Gamma radiation, one of ionizing radiations, has been reported to affect the morphological, anatomical, biochemical and physiological changes of plants at different dose levels. These effects at high level include inhibition in plant growth. Peroxidases (PODs) are mainly participations the process of lignification on the cell wall and protect the cell organelles in cytosol against the oxidative stresses by ROS (reactive oxygen species). Hydrogen peroxide (ROS) is normal metabolite in aerobic cells and the physiological steady concentrations (between 10{sup -7} and 10{sup -9}) are not particularly cytotoxic. When these concentrations are increased by ionizing radiation, they lead to cell lethality. Thus radiation-induced H{sub 2}O{sub 2} may appear as an important agent causing cell damage. In this study, a polyclonal antibody against peroxidase and cerium chloride as a trapping agent for H{sub 2}O{sub 2} were used to obtain for better information on the occurrence and distribution of POD and H{sub 2}O{sub 2} in the cytoplasm and walls of vascular bundle in hypocotyls of pumpkin.

  8. The Prior-project

    Engerer, Volkmar Paul; Roued-Cunliffe, Henriette; Albretsen, Jørgen

    digitisation of Arthur Prior’s Nachlass kept in the Bodleian Library, Oxford. The DH infrastructure in question is the Prior Virtual Lab (PVL). PVL was established in 2011 in order to provide researchers in the field of temporal logic easy access to the papers of Arthur Norman Prior (1914-1969), and officially......In this paper, we present a DH research infrastructure which relies heavily on a combination of domain knowledge with information technology. The general goal is to develop tools to aid scholars in their interpretations and understanding of temporal logic. This in turn is based on an extensive...

  9. Survival Bayesian Estimation of Exponential-Gamma Under Linex Loss Function

    Rizki, S. W.; Mara, M. N.; Sulistianingsih, E.

    2017-06-01

    This paper elaborates a research of the cancer patients after receiving a treatment in cencored data using Bayesian estimation under Linex Loss function for Survival Model which is assumed as an exponential distribution. By giving Gamma distribution as prior and likelihood function produces a gamma distribution as posterior distribution. The posterior distribution is used to find estimatior {\\hat{λ }}BL by using Linex approximation. After getting {\\hat{λ }}BL, the estimators of hazard function {\\hat{h}}BL and survival function {\\hat{S}}BL can be found. Finally, we compare the result of Maximum Likelihood Estimation (MLE) and Linex approximation to find the best method for this observation by finding smaller MSE. The result shows that MSE of hazard and survival under MLE are 2.91728E-07 and 0.000309004 and by using Bayesian Linex worths 2.8727E-07 and 0.000304131, respectively. It concludes that the Bayesian Linex is better than MLE.

  10. Arthur Prior and 'Now'

    Blackburn, Patrick Rowan; Jørgensen, Klaus Frovin

    2016-01-01

    ’s search led him through the work of Castañeda, and back to his own work on hybrid logic: the first made temporal reference philosophically respectable, the second made it technically feasible in a modal framework. With the aid of hybrid logic, Prior built a bridge from a two-dimensional UT calculus...

  11. Prior Knowledge Assessment Guide

    2014-12-01

    assessment in a reasonable amount of time. Hands-on assessments can be extremely diverse in makeup and administration depending on the subject matter...DEVELOPING AND USING PRIOR KNOWLEDGE ASSESSMENTS TO TAILOR TRAINING D-3 ___ Brush and scrub ___ Orchards ___ Rice

  12. Bayesian inference from count data using discrete uniform priors.

    Federico Comoglio

    Full Text Available We consider a set of sample counts obtained by sampling arbitrary fractions of a finite volume containing an homogeneously dispersed population of identical objects. We report a Bayesian derivation of the posterior probability distribution of the population size using a binomial likelihood and non-conjugate, discrete uniform priors under sampling with or without replacement. Our derivation yields a computationally feasible formula that can prove useful in a variety of statistical problems involving absolute quantification under uncertainty. We implemented our algorithm in the R package dupiR and compared it with a previously proposed Bayesian method based on a Gamma prior. As a showcase, we demonstrate that our inference framework can be used to estimate bacterial survival curves from measurements characterized by extremely low or zero counts and rather high sampling fractions. All in all, we provide a versatile, general purpose algorithm to infer population sizes from count data, which can find application in a broad spectrum of biological and physical problems.

  13. Equipment for x- and gamma ray radiography

    Abd Nasir Ibrahim; Azali Muhammad; Ab Razak Hamzah; Abd Aziz Mohamed; Mohammad Pauzi Ismail

    2004-01-01

    The following topics related to the equipment for x - and gamma ray radiography are discussed in this chapter. The topics are x-ray source for Industrial Radiography: properties of x-ray, generation of x-ray, mechanism of x-ray production, x-ray equipment, power supply, distribution of x-ray intensity along the tube: gamma ray source for Industrial Radiography: properties of gamma rays, gamma ray sources, gamma ray projectors on cameras, source changing. Care of Radiographic Equipments: Merits and Demerits of x and Gamma Rays

  14. Dynamic gamma knife radiosurgery

    Luan Shuang; Swanson, Nathan; Chen Zhe; Ma Lijun

    2009-01-01

    Gamma knife has been the treatment of choice for various brain tumors and functional disorders. Current gamma knife radiosurgery is planned in a 'ball-packing' approach and delivered in a 'step-and-shoot' manner, i.e. it aims to 'pack' the different sized spherical high-dose volumes (called 'shots') into a tumor volume. We have developed a dynamic scheme for gamma knife radiosurgery based on the concept of 'dose-painting' to take advantage of the new robotic patient positioning system on the latest Gamma Knife C(TM) and Perfexion(TM) units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical 'paintbrush', and treatment planning reduces to finding the best route of this 'paintbrush' to 'paint' a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are more conformal than step-and-shoot plans and can maintain a steep dose gradient (around 13% per mm) between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (4) With dynamic gamma knife radiosurgery, one can obtain a family of plans representing a tradeoff between the delivery time and

  15. Dynamic gamma knife radiosurgery

    Luan Shuang; Swanson, Nathan; Chen Zhe [Department of Computer Science, University of New Mexico, Albuquerque, NM 87131 (United States); Ma Lijun [Department of Radiation Oncology, University of California San Francisco, San Francisco, CA 94143 (United States)], E-mail: sluan@cs.unm.edu, E-mail: nate@cs.unm.edu, E-mail: zchen@cs.unm.edu, E-mail: lijunma@radonc.ucsf.edu

    2009-03-21

    Gamma knife has been the treatment of choice for various brain tumors and functional disorders. Current gamma knife radiosurgery is planned in a 'ball-packing' approach and delivered in a 'step-and-shoot' manner, i.e. it aims to 'pack' the different sized spherical high-dose volumes (called 'shots') into a tumor volume. We have developed a dynamic scheme for gamma knife radiosurgery based on the concept of 'dose-painting' to take advantage of the new robotic patient positioning system on the latest Gamma Knife C(TM) and Perfexion(TM) units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical 'paintbrush', and treatment planning reduces to finding the best route of this 'paintbrush' to 'paint' a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are more conformal than step-and-shoot plans and can maintain a steep dose gradient (around 13% per mm) between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (4) With dynamic gamma knife radiosurgery, one can

  16. External Prior Guided Internal Prior Learning for Real-World Noisy Image Denoising

    Xu, Jun; Zhang, Lei; Zhang, David

    2018-06-01

    Most of existing image denoising methods learn image priors from either external data or the noisy image itself to remove noise. However, priors learned from external data may not be adaptive to the image to be denoised, while priors learned from the given noisy image may not be accurate due to the interference of corrupted noise. Meanwhile, the noise in real-world noisy images is very complex, which is hard to be described by simple distributions such as Gaussian distribution, making real noisy image denoising a very challenging problem. We propose to exploit the information in both external data and the given noisy image, and develop an external prior guided internal prior learning method for real noisy image denoising. We first learn external priors from an independent set of clean natural images. With the aid of learned external priors, we then learn internal priors from the given noisy image to refine the prior model. The external and internal priors are formulated as a set of orthogonal dictionaries to efficiently reconstruct the desired image. Extensive experiments are performed on several real noisy image datasets. The proposed method demonstrates highly competitive denoising performance, outperforming state-of-the-art denoising methods including those designed for real noisy images.

  17. A simple neutron-gamma discriminating system

    Liu Zhongming; Xing Shilin; Wang Zhongmin

    1986-01-01

    A simple neutron-gamma discriminating system is described. A detector and a pulse shape discriminator are suitable for the neutron-gamma discriminating system. The influence of the constant fraction discriminator threshold energy on the neutron-gamma resolution properties is shown. The neutron-gamma timing distributions from an 241 Am-Be source, 2.5 MeV neutron beam and 14 MeV neutron beam are presented

  18. Varying prior information in Bayesian inversion

    Walker, Matthew; Curtis, Andrew

    2014-01-01

    Bayes' rule is used to combine likelihood and prior probability distributions. The former represents knowledge derived from new data, the latter represents pre-existing knowledge; the Bayesian combination is the so-called posterior distribution, representing the resultant new state of knowledge. While varying the likelihood due to differing data observations is common, there are also situations where the prior distribution must be changed or replaced repeatedly. For example, in mixture density neural network (MDN) inversion, using current methods the neural network employed for inversion needs to be retrained every time prior information changes. We develop a method of prior replacement to vary the prior without re-training the network. Thus the efficiency of MDN inversions can be increased, typically by orders of magnitude when applied to geophysical problems. We demonstrate this for the inversion of seismic attributes in a synthetic subsurface geological reservoir model. We also present results which suggest that prior replacement can be used to control the statistical properties (such as variance) of the final estimate of the posterior in more general (e.g., Monte Carlo based) inverse problem solutions. (paper)

  19. Study of the heterogeneities effect in the dose distributions of Leksell Gamma Knife (R), through Monte Carlo simulation; Estudio del efecto de las heterogeneidades en las distribuciones de dosis del Leksell GammaKnife (R), mediante simulacion Monte Carlo

    Rojas C, E.L. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Al-Dweri, F.M.O.; Lallena R, A.M. [Universidad de Granada, Granada (Spain)]. e-mail: elrc@nuclear.inin.mx

    2005-07-01

    In this work they are studied, by means of Monte Carlo simulation, the effects that take place in the dose profiles that are obtained with the Leksell Gamma Knife (R), when they are kept in account heterogeneities. The considered heterogeneities simulate the skull and the spaces of air that are in the head, like they can be the nasal breasts or the auditory conduits. The calculations were made using the Monte Carlo Penelope simulation code (v. 2003). The geometry of each one of the 201 sources that this instrument is composed, as well as of the corresponding channels of collimation of the Gamma Knife (R), it was described by means of a simplified model of geometry that has been recently studied. The obtained results when they are kept in mind the heterogeneities they present non worthless differences regarding those obtained when those are not considered. These differences are maximum in the proximities of the interfaces among different materials. (Author)

  20. Prior indigenous technological species

    Wright, Jason T.

    2018-01-01

    One of the primary open questions of astrobiology is whether there is extant or extinct life elsewhere the solar system. Implicit in much of this work is that we are looking for microbial or, at best, unintelligent life, even though technological artefacts might be much easier to find. Search for Extraterrestrial Intelligence (SETI) work on searches for alien artefacts in the solar system typically presumes that such artefacts would be of extrasolar origin, even though life is known to have existed in the solar system, on Earth, for eons. But if a prior technological, perhaps spacefaring, species ever arose in the solar system, it might have produced artefacts or other technosignatures that have survived to present day, meaning solar system artefact SETI provides a potential path to resolving astrobiology's question. Here, I discuss the origins and possible locations for technosignatures of such a prior indigenous technological species, which might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus or a wet Mars. In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived Gyr ago. Remaining indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer solar system.

  1. Distribution

    John R. Jones

    1985-01-01

    Quaking aspen is the most widely distributed native North American tree species (Little 1971, Sargent 1890). It grows in a great diversity of regions, environments, and communities (Harshberger 1911). Only one deciduous tree species in the world, the closely related Eurasian aspen (Populus tremula), has a wider range (Weigle and Frothingham 1911)....

  2. Gamma astronomy

    Cesarsky, C.; Cesarsky, J.P.

    1986-01-01

    This article overviews the gamma astronomy research. Sources already observed, and what causes to give to them; the galactic radiation and its interpretation; techniques already used and current projects [fr

  3. Gamma Spectroscopy

    Niemantsverdriet, J.W.; Butz, Tilman; Ertl, G.; Knözinger, H.; Schüth, F.

    2008-01-01

    No abstract. The sections in this article are 1 Introduction 2 Mössbauer Spectroscopy 3 Time-Differential Perturbed Angular Correlations (TDPAC) 4 Conclusions and Outlook Keywords: Mössbauer spectroscopy; gamma spectroscopy; perturbed angular correlation; TDPAC

  4. Prior processes and their applications nonparametric Bayesian estimation

    Phadia, Eswar G

    2016-01-01

    This book presents a systematic and comprehensive treatment of various prior processes that have been developed over the past four decades for dealing with Bayesian approach to solving selected nonparametric inference problems. This revised edition has been substantially expanded to reflect the current interest in this area. After an overview of different prior processes, it examines the now pre-eminent Dirichlet process and its variants including hierarchical processes, then addresses new processes such as dependent Dirichlet, local Dirichlet, time-varying and spatial processes, all of which exploit the countable mixture representation of the Dirichlet process. It subsequently discusses various neutral to right type processes, including gamma and extended gamma, beta and beta-Stacy processes, and then describes the Chinese Restaurant, Indian Buffet and infinite gamma-Poisson processes, which prove to be very useful in areas such as machine learning, information retrieval and featural modeling. Tailfree and P...

  5. Gamma spectrometry on MANITU 271-01 gamma scan wires

    Dassel, G.; Buurveld, H.A.; Minkema, J.

    1994-08-01

    A series of irradiation experiments (271-series) is being performed of the sustain programme for material development and characterization of the NET (Next European Torus). In the framework of the first irradiation experiment 271-01, with irradiation up to 0.2 dpa, four gamma scan wires have been examined by gamma scanning. The purpose of the gamma scan wires (GSW) is to get information about the neutron fluence distribution in the capsules during irradiation. In the stainless steel wires the nuclides Co-58, Mu-54, Fe-59 and Co-60 are produced, are characteristic for fast and thermal neutron reactions. (orig./HP)

  6. Observation of galactic gamma radiation

    Paul, J.A.

    1982-09-01

    A complete and deep survey of the galactic high-energy gamma radiation is now available, thanks to the gamma-ray telescopes on board of the SAS-2 and COS-B spacecrafts. A comparison of the COS-B gamma-ray survey with a fully sampled CO survey together with an Hsub(I) survey is used to show that a simple model, in which uniformly distributed cosmic rays interact with the interstellar gas, can account for almost all the gamma-ray emission observed in the first galactic quadrant. At medium galactic latitudes, it is shown that a relationship exists between the gamma radiation and the interstellar absorption derived from galaxy counts. Therefore gamma rays from the local galactic environment can be used as a valuable probe of the content and structure of the local interstellar medium. The large scale features of the local interstellar gas are revealed, in particular wide concentrations of nearby molecular hydrogen. On a smaller scale, the detection of numerous localized gamma-ray sources focuses the attention on some particular phases of clusters of young and massive stars where diffuse processes of gamma-ray emission may also be at work

  7. Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar

    Clark, Colin J.; Pletsch, Holger J.; Wu, Jason; Guillemot, Lucas; Kerr, Matthew; Johnson, Tyrel J.; Camilo, Fernando; Salvetti, David; Allen, Bruce; Anderson, David; Aulbert, Carsten; Beer, Christian; Bock, Oliver; Cuéllar, Andres; Eggenstein, Heinz-Bernd; Fehrmann, Henning; Kramer, Michael; Kwang, Shawn A.; Machenschalk, Bernd; Nieder, Lars; Ackermann, Markus; Ajello, Marco; Baldini, Luca; Ballet, Jean; Barbiellini, Guido; Bastieri, Denis; Bellazzini, Ronaldo; Bissaldi, Elisabetta; Blandford, Roger D.; Bloom, Elliott D.; Bonino, Raffaella; Bottacini, Eugenio; Brandt, Terri J.; Bregeon, Johan; Bruel, Philippe; Buehler, Rolf; Burnett, Toby H.; Buson, Sara; Cameron, Rob A.; Caputo, Regina; Caraveo, Patrizia A.; Cavazzuti, Elisabetta; Cecchi, Claudia; Charles, Eric; Chekhtman, Alexandre; Ciprini, Stefano; Cominsky, Lynn R.; Costantin, Denise; Cutini, Sara; D’Ammando, Filippo; De Luca, Andrea; Desiante, Rachele; Di Venere, Leonardo; Di Mauro, Mattia; Di Lalla, Niccolò; Digel, Seth W.; Favuzzi, Cecilia; Ferrara, Elizabeth C.; Franckowiak, Anna; Fukazawa, Yasushi; Funk, Stefan; Fusco, Piergiorgio; Gargano, Fabio; Gasparrini, Dario; Giglietto, Nico; Giordano, Francesco; Giroletti, Marcello; Gomez-Vargas, Germán A.; Green, David; Grenier, Isabelle A.; Guiriec, Sylvain; Harding, Alice K.; Hewitt, John W.; Horan, Deirdre; Jóhannesson, Guðlaugur; Kensei, Shiki; Kuss, Michael; La Mura, Giovanni; Larsson, Stefan; Latronico, Luca; Li, Jian; Longo, Francesco; Loparco, Francesco; Lovellette, Michael N.; Lubrano, Pasquale; Magill, Jeffrey D.; Maldera, Simone; Manfreda, Alberto; Mazziotta, Mario N.; McEnery, Julie E.; Michelson, Peter F.; Mirabal, Nestor; Mitthumsiri, Warit; Mizuno, Tsunefumi; Monzani, Maria Elena; Morselli, Aldo; Moskalenko, Igor V.; Nuss, Eric; Ohsugi, Takashi; Omodei, Nicola; Orienti, Monica; Orlando, Elena; Palatiello, Michele; Paliya, Vaidehi S.; de Palma, Francesco; Paneque, David; Perkins, Jeremy S.; Persic, Massimo; Pesce-Rollins, Melissa; Porter, Troy A.; Principe, Giacomo; Rainò, Silvia; Rando, Riccardo; Ray, Paul S.; Razzano, Massimiliano; Reimer, Anita; Reimer, Olaf; Romani, Roger W.; Saz Parkinson, Pablo M.; Sgrò, Carmelo; Siskind, Eric J.; Smith, David A.; Spada, Francesca; Spandre, Gloria; Spinelli, Paolo; Thayer, Jana B.; Thompson, David J.; Torres, Diego F.; Troja, Eleonora; Vianello, Giacomo; Wood, Kent; Wood, Matthew

    2018-01-01

    Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population. PMID:29503868

  8. Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar.

    Clark, Colin J; Pletsch, Holger J; Wu, Jason; Guillemot, Lucas; Kerr, Matthew; Johnson, Tyrel J; Camilo, Fernando; Salvetti, David; Allen, Bruce; Anderson, David; Aulbert, Carsten; Beer, Christian; Bock, Oliver; Cuéllar, Andres; Eggenstein, Heinz-Bernd; Fehrmann, Henning; Kramer, Michael; Kwang, Shawn A; Machenschalk, Bernd; Nieder, Lars; Ackermann, Markus; Ajello, Marco; Baldini, Luca; Ballet, Jean; Barbiellini, Guido; Bastieri, Denis; Bellazzini, Ronaldo; Bissaldi, Elisabetta; Blandford, Roger D; Bloom, Elliott D; Bonino, Raffaella; Bottacini, Eugenio; Brandt, Terri J; Bregeon, Johan; Bruel, Philippe; Buehler, Rolf; Burnett, Toby H; Buson, Sara; Cameron, Rob A; Caputo, Regina; Caraveo, Patrizia A; Cavazzuti, Elisabetta; Cecchi, Claudia; Charles, Eric; Chekhtman, Alexandre; Ciprini, Stefano; Cominsky, Lynn R; Costantin, Denise; Cutini, Sara; D'Ammando, Filippo; De Luca, Andrea; Desiante, Rachele; Di Venere, Leonardo; Di Mauro, Mattia; Di Lalla, Niccolò; Digel, Seth W; Favuzzi, Cecilia; Ferrara, Elizabeth C; Franckowiak, Anna; Fukazawa, Yasushi; Funk, Stefan; Fusco, Piergiorgio; Gargano, Fabio; Gasparrini, Dario; Giglietto, Nico; Giordano, Francesco; Giroletti, Marcello; Gomez-Vargas, Germán A; Green, David; Grenier, Isabelle A; Guiriec, Sylvain; Harding, Alice K; Hewitt, John W; Horan, Deirdre; Jóhannesson, Guðlaugur; Kensei, Shiki; Kuss, Michael; La Mura, Giovanni; Larsson, Stefan; Latronico, Luca; Li, Jian; Longo, Francesco; Loparco, Francesco; Lovellette, Michael N; Lubrano, Pasquale; Magill, Jeffrey D; Maldera, Simone; Manfreda, Alberto; Mazziotta, Mario N; McEnery, Julie E; Michelson, Peter F; Mirabal, Nestor; Mitthumsiri, Warit; Mizuno, Tsunefumi; Monzani, Maria Elena; Morselli, Aldo; Moskalenko, Igor V; Nuss, Eric; Ohsugi, Takashi; Omodei, Nicola; Orienti, Monica; Orlando, Elena; Palatiello, Michele; Paliya, Vaidehi S; de Palma, Francesco; Paneque, David; Perkins, Jeremy S; Persic, Massimo; Pesce-Rollins, Melissa; Porter, Troy A; Principe, Giacomo; Rainò, Silvia; Rando, Riccardo; Ray, Paul S; Razzano, Massimiliano; Reimer, Anita; Reimer, Olaf; Romani, Roger W; Saz Parkinson, Pablo M; Sgrò, Carmelo; Siskind, Eric J; Smith, David A; Spada, Francesca; Spandre, Gloria; Spinelli, Paolo; Thayer, Jana B; Thompson, David J; Torres, Diego F; Troja, Eleonora; Vianello, Giacomo; Wood, Kent; Wood, Matthew

    2018-02-01

    Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.

  9. Gamma radiation in apartments

    Grindborg, J.-E.

    1983-05-01

    This investigation forms the basis for the description of methods for the detection of gamma radiation. The aim is to control that the dose limit will not exceed 50 μR/h in a room where people reside. The distribution of dose rates in different rooms has been calculated and the results have been compared with experimental data. Various instruments have been calibrated and their specifications are discussed. (G.B.)

  10. Gamma camera

    Berninger, W.H.

    1975-01-01

    The light pulse output of a scintillator, on which incident collimated gamma rays impinge, is detected by an array of photoelectric tubes each having a convexly curved photocathode disposed in close proximity to the scintillator. Electronic circuitry connected to outputs of the phototubes develops the scintillation event position coordinate electrical signals with good linearity and with substantial independence of the spacing between the scintillator and photocathodes so that the phototubes can be positioned as close to the scintillator as is possible to obtain less distortion in the field of view and improved spatial resolution as compared to conventional planar photocathode gamma cameras

  11. Notes on the gamma kernel

    Barndorff-Nielsen, Ole E.

    The density function of the gamma distribution is used as shift kernel in Brownian semistationary processes modelling the timewise behaviour of the velocity in turbulent regimes. This report presents exact and asymptotic properties of the second order structure function under such a model......, and relates these to results of von Karmann and Horwath. But first it is shown that the gamma kernel is interpretable as a Green’s function....

  12. Prior Elicitation, Assessment and Inference with a Dirichlet Prior

    Michael Evans

    2017-10-01

    Full Text Available Methods are developed for eliciting a Dirichlet prior based upon stating bounds on the individual probabilities that hold with high prior probability. This approach to selecting a prior is applied to a contingency table problem where it is demonstrated how to assess the prior with respect to the bias it induces as well as how to check for prior-data conflict. It is shown that the assessment of a hypothesis via relative belief can easily take into account what it means for the falsity of the hypothesis to correspond to a difference of practical importance and provide evidence in favor of a hypothesis.

  13. Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

    Adrian H.

    2017-12-01

    Full Text Available Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

  14. Observation of a new coherent transient in NMR - nutational two-pulse stimulated echo in the angular distribution of gamma-radiation from oriented nuclei

    Shakhmuratova, L.N.; Hutchison, W.D.; Isbister, D.J.; Chaplin, D.H. [University of New South Wales, Australian Defence Force Academy, School of Physics, University College (Australia)

    1997-07-15

    A new coherent transient in pulsed NMR, the two-pulse nutational stimulated echo, is reported for the ferromagnetic system {sup 60}CoFe using resonant perturbations on the directional emission of anisotropic gamma-radiation from thermally oriented nuclei. The new spin echo is a result of non-linear nuclear spin dynamics due to large Larmor inhomogeneity active during radiofrequency pulse application. It is made readily observable through the gross detuning between NMR radiofrequency excitation and gamma radiation detection, and inhomogeneity in the Rabi frequency caused by metallic skin-effect. The method of concatenation of perturbation factors in a statistical tensor formalism is quantitatively applied to successfully predict and then fit in detail the experimental time-domain data.

  15. Observation of a new coherent transient in NMR - nutational two-pulse stimulated echo in the angular distribution of gamma-radiation from oriented nuclei

    Shakhmuratova, L.N.; Hutchison, W.D.; Isbister, D.J.; Chaplin, D.H.

    1997-01-01

    A new coherent transient in pulsed NMR, the two-pulse nutational stimulated echo, is reported for the ferromagnetic system 60 CoFe using resonant perturbations on the directional emission of anisotropic gamma-radiation from thermally oriented nuclei. The new spin echo is a result of non-linear nuclear spin dynamics due to large Larmor inhomogeneity active during radiofrequency pulse application. It is made readily observable through the gross detuning between NMR radiofrequency excitation and gamma radiation detection, and inhomogeneity in the Rabi frequency caused by metallic skin-effect. The method of concatenation of perturbation factors in a statistical tensor formalism is quantitatively applied to successfully predict and then fit in detail the experimental time-domain data

  16. Modeling the irradiation facility in the Deir Al-Hajar area to calculate the spatial gamma dose distribution using the MCNP code

    Khattab, K.; Bush, M; Kassery, H.

    2009-03-01

    A 3-D model for the irradiation plant which belongs to the Atomic Energy Commission, Department of Radiation Technology in the Deir Al-Hajar area near Damascus, is presented in this work using the MCNP-4C code. This model is used to calculate the spatial gamma ray dose in the (x, y, z) coordinate. Good agreements are noticed between the measured and the calculated results. (author)

  17. Gamma camera

    Tschunt, E.; Platz, W.; Baer, Ul; Heinz, L.

    1978-01-01

    A gamma camera has a plurality of exchangeable collimators, one of which is replaceably mounted in the ray inlet opening of the camera, while the others are placed on separate supports. Supports are swingably mounted upon a column one above the other

  18. Gamma camera

    Schlosser, P.A.; Steidley, J.W.

    1980-01-01

    The design of a collimation system for a gamma camera for use in nuclear medicine is described. When used with a 2-dimensional position sensitive radiation detector, the novel system can produce superior images than conventional cameras. The optimal thickness and positions of the collimators are derived mathematically. (U.K.)

  19. Transformation of Bayesian posterior distribution into a basic analytical distribution

    Jordan Cizelj, R.; Vrbanic, I.

    2002-01-01

    Bayesian estimation is well-known approach that is widely used in Probabilistic Safety Analyses for the estimation of input model reliability parameters, such as component failure rates or probabilities of failure upon demand. In this approach, a prior distribution, which contains some generic knowledge about a parameter is combined with likelihood function, which contains plant-specific data about the parameter. Depending on the type of prior distribution, the resulting posterior distribution can be estimated numerically or analytically. In many instances only a numerical Bayesian integration can be performed. In such a case the posterior is provided in the form of tabular discrete distribution. On the other hand, it is much more convenient to have a parameter's uncertainty distribution that is to be input into a PSA model to be provided in the form of some basic analytical probability distribution, such as lognormal, gamma or beta distribution. One reason is that this enables much more convenient propagation of parameters' uncertainties through the model up to the so-called top events, such as plant system unavailability or core damage frequency. Additionally, software tools used to run PSA models often require that parameter's uncertainty distribution is defined in the form of one among the several allowed basic types of distributions. In such a case the posterior distribution that came as a product of Bayesian estimation needs to be transformed into an appropriate basic analytical form. In this paper, some approaches on transformation of posterior distribution to a basic probability distribution are proposed and discussed. They are illustrated by an example from NPP Krsko PSA model.(author)

  20. PCR nuclear composition at 1-20 PeV according to lateral distributions of all EAS and EAS accompanied high-energy-gamma rays and hadrons in EC at Tien-Shan level

    Nesterova, N.M.; Pavlyuchenko, V.P.; Chubenko, A.P.; Shaulov, S.B.

    2003-01-01

    The Tien-Shan array Adron data are presented on electron-photon component lateral distributions (age parameter S) of extensive air showers of cosmic rays. The data are given as a dependence on the electron size N e for all showers and for showers accompanied by high-energy gamma rays and hadrons in X-ray films. N e characterizes the energy of primary-cosmic-ray nuclei E 0 . Later events are generated by primary photons chiefly. That allows judging on the proton role with E 0 change. S distributions point to the considerable part of light nuclei, protons mainly, at the region above knee of the spectrum at N e > 10 6 up to N e = 5 x 10 6 (E 0 ∼ 10 PeV) at least [ru

  1. Cosmic gamma-ray burst

    Yamagami, Takamasa

    1985-01-01

    Ballon experiments for searching gamma-ray burst were carried out by employing rotating-cross modulation collimators. From a very long observation of total 315 hours during 1975 to 1979, three gamma-ray intensity anomalies were observed which were speculated as a gamma-ray burst. As for the first gamma-ray intensity anomaly observed in 1975, the burst source could be located precisely but the source, heavenly body, could not be specified. Gamma-ray burst source estimation was made by analyzing distribution of burst source in the celestial sphere, burst size distribution, and burst peak. Using the above-mentioned data together with previously published ones, apparent inconsistency was found between the observed results and the adopted theory that the source was in the Galaxy, and this inconsistency was found due to the different time profiles of the burst observed with instruments of different efficiency. It was concluded by these analysis results that employment of logN - logP (relation between burst frequency and burst count) was better than that of logN - logS (burst size) in the examination of gamma-ray burst because the former was less uncertain than the latter. Analyzing the author's observed gamma-ray burst data and the related published data, it was clarified that the burst distribution was almost P -312 for the burst peak value larger than 10 -6 erg/cm 2 .sec. The author could indicate that the calculated celestial distribution of burst source was consistent with the observed results by the derivation using the logN - logP relationship and that the burst larger than 10 -6 erg/cm 2 .sec happens about one thousand times a year, about ten times of the previous value. (Takagi, S.)

  2. The Prior Can Often Only Be Understood in the Context of the Likelihood

    Andrew Gelman

    2017-10-01

    Full Text Available A key sticking point of Bayesian analysis is the choice of prior distribution, and there is a vast literature on potential defaults including uniform priors, Jeffreys’ priors, reference priors, maximum entropy priors, and weakly informative priors. These methods, however, often manifest a key conceptual tension in prior modeling: a model encoding true prior information should be chosen without reference to the model of the measurement process, but almost all common prior modeling techniques are implicitly motivated by a reference likelihood. In this paper we resolve this apparent paradox by placing the choice of prior into the context of the entire Bayesian analysis, from inference to prediction to model evaluation.

  3. Gamma-Gompertz life expectancy at birth

    Trifon I. Missov

    2013-01-01

    BACKGROUND The gamma-Gompertz multiplicative frailty model is the most common parametric modelapplied to human mortality data at adult and old ages. The resulting life expectancy hasbeen calculated so far only numerically. OBJECTIVE Properties of the gamma-Gompertz distribution have not been thoroughly studied. The focusof the paper is to shed light onto its first moment or, demographically speaking, characterizelife expectancy resulting from a gamma-Gompertz force of mortality. The paperprov...

  4. Gamma-ray Output Spectra from 239 Pu Fission

    Ullmann, John

    2015-01-01

    Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239 Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution

  5. Dose distribution in the area of the operative cicatrice and the problem of local reccurences during postoperative external beam gamma therapy of breast cancer

    Todorov, Y.; Ivanova, K.; Penchev, V.

    1982-01-01

    Five-year experience is recorded with treatment of 503 patients with breast cancer, who received postoperative external beam gamma therapy, and the developement of local reccurences. Results are reported of dosimetric studies in the irradiated area, especially the thoracic wall, where total focal doses of 50 had been realized. The clinical results of treatment are discussed on this basis. Comparison is made with data available in the literature on the incidence, localization and time of development of local reccurences and the methods of treatment of the basic disease. The need of postoperative radiation treatment, particularly in the later stages of the disease, is pointed out. (authors)

  6. Gamma camera

    Reiss, K.H.; Kotschak, O.; Conrad, B.

    1976-01-01

    A gamma camera with a simplified setup as compared with the state of engineering is described permitting, apart from good localization, also energy discrimination. Behind the usual vacuum image amplifier a multiwire proportional chamber filled with trifluorine bromium methane is connected in series. Localizing of the signals is achieved by a delay line, energy determination by means of a pulse height discriminator. With the aid of drawings and circuit diagrams, the setup and mode of operation are explained. (ORU) [de

  7. Gamma irradiator

    Simonet, G.

    1986-09-01

    Fiability of devices set around reactors depends on material resistance under irradiation noticeably joints, insulators, which belongs to composition of technical, safety or physical incasurement devices. The irradiated fuel elements, during their desactivation in a pool, are an interesting gamma irradiation device to simulate damages created in a nuclear environment. The existing facility at Osiris allows to generate an homogeneous rate dose in an important volume. The control of the element distances to irradiation box allows to control this dose rate [fr

  8. Gamma teletopography

    Simonet, G.

    1987-06-01

    The mapping of gamma sources radiation emission in a nuclear plant is an important safety point. A remote gamma ray mapping process was developed in SPS/CEA/SACLAY. It uses the ''pinhole camera'' principle, precursor of photography. It mainly consists of a radiation proof box, with a small orifice, containing sensitive emulsions at the opposite. A first conventional photographic type emulsion photographs the area. A second photographic emulsion shows up the gamma radiations. The superim position of the two shots gives immediate informations of the precise location of each source of radiation in the observed area. To make easier the presentation and to improve the accuracy of the results for radiation levels mapping, the obtained films are digitally processed. The processing assigns a colours scale to the various levels of observed radiations. Taking account physical data and standard parameters, it gets possible to estimate the dose rate. The device is portable. Its compactness and fully independent nature make it suitable for use anywhere. It can be adapted to a remote automatic handling system, robot... so as to avoid all operator exposure when the local dose rate is too high [fr

  9. On the prior probabilities for two-stage Bayesian estimates

    Kohut, P.

    1992-01-01

    The method of Bayesian inference is reexamined for its applicability and for the required underlying assumptions in obtaining and using prior probability estimates. Two different approaches are suggested to determine the first-stage priors in the two-stage Bayesian analysis which avoid certain assumptions required for other techniques. In the first scheme, the prior is obtained through a true frequency based distribution generated at selected intervals utilizing actual sampling of the failure rate distributions. The population variability distribution is generated as the weighed average of the frequency distributions. The second method is based on a non-parametric Bayesian approach using the Maximum Entropy Principle. Specific features such as integral properties or selected parameters of prior distributions may be obtained with minimal assumptions. It is indicated how various quantiles may also be generated with a least square technique

  10. The Prior Internet Resources 2017

    Engerer, Volkmar Paul; Albretsen, Jørgen

    2017-01-01

    The Prior Internet Resources (PIR) are presented. Prior’s unpublished scientific manuscripts and his wast letter correspondence with fellow researchers at the time, his Nachlass, is now subject to transcription by Prior-researchers worldwide, and form an integral part of PIR. It is demonstrated...

  11. The Importance of Prior Knowledge.

    Cleary, Linda Miller

    1989-01-01

    Recounts a college English teacher's experience of reading and rereading Noam Chomsky, building up a greater store of prior knowledge. Argues that Frank Smith provides a theory for the importance of prior knowledge and Chomsky's work provided a personal example with which to interpret and integrate that theory. (RS)

  12. Genome position specific priors for genomic prediction

    Brøndum, Rasmus Froberg; Su, Guosheng; Lund, Mogens Sandø

    2012-01-01

    casual mutation is different between the populations but affects the same gene. Proportions of a four-distribution mixture for SNP effects in segments of fixed size along the genome are derived from one population and set as location specific prior proportions of distributions of SNP effects...... for the target population. The model was tested using dairy cattle populations of different breeds: 540 Australian Jersey bulls, 2297 Australian Holstein bulls and 5214 Nordic Holstein bulls. The traits studied were protein-, fat- and milk yield. Genotypic data was Illumina 777K SNPs, real or imputed Results...

  13. A DETAILED STUDY OF THE MOLECULAR AND ATOMIC GAS TOWARD THE {gamma}-RAY SUPERNOVA REMNANT RX J1713.7-3946: SPATIAL TeV {gamma}-RAY AND INTERSTELLAR MEDIUM GAS CORRESPONDENCE

    Fukui, Y.; Sano, H.; Sato, J.; Torii, K.; Horachi, H.; Hayakawa, T.; Inutsuka, S.; Kawamura, A.; Yamamoto, H.; Okuda, T.; Mizuno, N.; Onishi, T. [Department of Physics and Astrophysics, Nagoya University, Nagoya, Aichi 464-8601 (Japan); McClure-Griffiths, N. M. [CSIRO Astronomy and Space Science, Epping NSW 1710 (Australia); Rowell, G. [School of Chemistry and Physics, University of Adelaide, Adelaide 5005 (Australia); Inoue, T. [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 (Japan); Mizuno, A. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi 464-8601 (Japan); Ogawa, H., E-mail: fukui@a.phys.nagoya-u.ac.jp [Department of Astrophysics, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

    2012-02-10

    RX J1713.7-3946 is the most remarkable TeV {gamma}-ray supernova remnant (SNR) that emits {gamma}-rays in the highest energy range. We have made a new combined analysis of CO and H I in the SNR and derived the total protons in the interstellar medium (ISM). We have found that the inclusion of the H I gas provides a significantly better spatial match between the TeV {gamma}-rays and ISM protons than the H{sub 2} gas alone. In particular, the southeastern rim of the {gamma}-ray shell has a counterpart only in the H I. The finding shows that the ISM proton distribution is consistent with the hadronic scenario that cosmic-ray (CR) protons react with ISM protons to produce the {gamma}-rays. This provides another step forward for the hadronic origin of the {gamma}-rays by offering one of the necessary conditions missing in the previous hadronic interpretations. We argue that the highly inhomogeneous distribution of the ISM protons is crucial in the origin of the {gamma}-rays. Most of the neutral gas was likely swept up by the stellar wind of an OB star prior to the supernova (SN) explosion to form a low-density cavity and a swept-up dense wall. The cavity explains the low-density site where the diffusive shock acceleration of charged particles takes place with suppressed thermal X-rays, whereas the CR protons can reach the target protons in the wall to produce the {gamma}-rays. The present finding allows us to estimate the total CR proton energy to be {approx}10{sup 48} erg, 0.1% of the total energy of the SN explosion.

  14. Determination of solar flare accelerated ion angular distributions from SMM gamma ray and neutron measurements and determination of the He-3/H ratio in the solar photosphere from SMM gamma ray measurements. Final technical report, 1 July 1987-31 August 1989

    Lingenfelter, R.E.

    1989-08-01

    Comparisons of Solar Maximum Mission (SMM) observations of gamma-ray line and neutron emission with theoretical calculation of their expected production by flare accelerated ion interactions in the solar atmosphere have led to significant advances in the understanding of solar flare particle acceleration and interaction, as well as the flare process itself. These comparisons have enabled the determination of, not only the total number and energy spectrum of accelerated ions trapped at the sun, but also the ion angular distribution as they interact in the solar atmosphere. The Monte Carlo program was modified to include in the calculations of ion trajectories the effects of both mirroring in converging magnetic fields and of pitch angle scattering. Comparing the results of these calculations with the SMM observations, not only the angular distribution of the interacting ions can be determined, but also the initial angular distribution of the ions at acceleration. The reliable determination of the solar photospheric He-3 abundance is of great importance for understanding nucleosynthesis in the early universe and its implications for cosmology, as well as for the study of the evolution of the sun. It is also essential for the determinations of the spectrum and total number of flare accelerated ions from the SMM/GRS gamma-ray line measurements. Systematic Monte Carlo calculations of the time dependence were made as a function of the He-3 abundance and other variables. A new series of calculations were compared for the time-dependent flux of 2.223 MeV neutron capture line emission and the ratio of the time-integrated flux in the 2.223 MeV line to that in the 4.1 to 6.4 MeV nuclear deexcitation band

  15. Utilization of thermoluminescent dosemeters for determination of exposure or absorbed dose in a radiation gamma or X radiation field with unknown spectral distribution

    Rosa, L.A.R. da.

    1981-06-01

    Having in view the choice of the best pair of dosemeters to be used in the 'Tandem' method, the main response characteristics of LiF:Mg, Ti, Li 2 B 4 O 7 :Mn, CaSO 4 Dy, CaF 2 :Mn and CaF 2 :Dy thermoluminescent dosemeters and also some critical parameters in their calibration and evaluation processes were studied. Three different physical forms of TLD's were investigated: hot pressed chips, disc teflon dosemeters and glass mini TLD's. Their calibration factors were obtained for the energy of Cobalt-60 gamma rays. Their energy dependences normalized to 60 Co radiation were determined using spectral width as parameter. 'Tandens' formed by all TLD's evaluated were compaired. (E.G.) [pt

  16. Induction of inherited sterility and sex ratio distribution due to exposure to substerilising doses of gamma radiation in cotton bollworm Earias vittella fabricius

    Tamhankar, A.J.; Shantharam, K.

    2005-01-01

    Substerilising doses of gamma radiation induced inherited sterility and sex ratio distortion in the cotton bollworm Earias vittella fabricius. Adults irradiated with 75 Gy and self-crossed, provided sterile F 1 adults, suitable for direct use in sterile insect technique (SIT). In case of 50 Gy, the F 1 adults, when backcrossed, produced F 2 progeny with sex ratio in favour of females (1: >3). With 25 Gy, a sex ratio distortion was recorded in F 1 (1 male: 2.25 females) and self-crossing of F 1 resulted in progeny with a sex ratio of 3:1. Backcrossing of the F 1 female produced F 2 progeny with a sex ratio of 1:5. These results have implications in improving cost/benefit ratio of SIT for this species. (author)

  17. Gamma teletopography

    Simonet, G.

    1986-09-01

    To set the gamma activity cartography is an important element of safety in numerous cases: intervention in hot cell, search of a radioactive source, examination of radioactive waste circuit followed by a reprocessing definition of decontamination and decommissioning processes and for all other accidents. The device presented here is like a ''black box'' with an aperture and an emulsion photosensitive to the opposite; a classical film takes photography of the place; a X-ray type emulsion gives a spot more or less contrasted and extensive corresponding to each source. Images can be processed with a microprocessor [fr

  18. The distribution of cosmic rays in the galaxy and their dynamics as deduced from recent gamma ray observations. [noting maximum in toroidal region between 4 and 5 kpc from galactic center

    Puget, J. L.; Stecker, F. W.

    1974-01-01

    Data from SAS-2 on the galactic gamma ray line flux as a function of longitude is examined. It is shown that the gamma ray emissivity varies with galactocentric distance and is about an order of magnitude higher than the local value in a toroidal region between 4 and 5 kpc from the galactic center. This enhancement is accounted for in part by first-order Fermi acceleration, compression, and trapping of cosmic rays consistent with present ideas of galactic dynamics and galactic structure theory. Calculations indicate that cosmic rays in the 4 to 5 kpc region are trapped and accelerated over a mean time of the order of a few million years or about 2 to 4 times the assumed trapping time in the solar region of the galaxy on the assumption that only an increased cosmic ray flux is responsible for the observed emission. Cosmic ray nucleons, cosmic ray electrons, and ionized hydrogen gas were found to have a strikingly similar distribution in the galaxy according to both the observational data and the theoretical model discussed.

  19. Bayesian road safety analysis: incorporation of past evidence and effect of hyper-prior choice.

    Miranda-Moreno, Luis F; Heydari, Shahram; Lord, Dominique; Fu, Liping

    2013-09-01

    This paper aims to address two related issues when applying hierarchical Bayesian models for road safety analysis, namely: (a) how to incorporate available information from previous studies or past experiences in the (hyper) prior distributions for model parameters and (b) what are the potential benefits of incorporating past evidence on the results of a road safety analysis when working with scarce accident data (i.e., when calibrating models with crash datasets characterized by a very low average number of accidents and a small number of sites). A simulation framework was developed to evaluate the performance of alternative hyper-priors including informative and non-informative Gamma, Pareto, as well as Uniform distributions. Based on this simulation framework, different data scenarios (i.e., number of observations and years of data) were defined and tested using crash data collected at 3-legged rural intersections in California and crash data collected for rural 4-lane highway segments in Texas. This study shows how the accuracy of model parameter estimates (inverse dispersion parameter) is considerably improved when incorporating past evidence, in particular when working with the small number of observations and crash data with low mean. The results also illustrates that when the sample size (more than 100 sites) and the number of years of crash data is relatively large, neither the incorporation of past experience nor the choice of the hyper-prior distribution may affect the final results of a traffic safety analysis. As a potential solution to the problem of low sample mean and small sample size, this paper suggests some practical guidance on how to incorporate past evidence into informative hyper-priors. By combining evidence from past studies and data available, the model parameter estimates can significantly be improved. The effect of prior choice seems to be less important on the hotspot identification. The results show the benefits of incorporating prior

  20. Gamma scanning of the irradiated HANARO fuels

    Hong, Kwon Pyo; Lee, K. S.; Park, D. G.; Baik, S. Y.; Song, W. S.; Kim, T. Y.; Seo, C. K.

    1997-02-01

    To conform the burnup state of the fuels, we have transported the irradiated HANARO fuels from the reactor to IMEF (Irradiated Material Examination Facility), and executed gamma scanning for the fuels. By measuring the gamma-rays from the irradiated fuels we could see the features of the relative burnup distributions in the fuel bundles. All of 17 fuel bundles were taken in and out between HANARO and IMEF from March till August in 1996, and we carried out the related regulations. Longitudinal gamma scanning and angular gamma scanning are done for each fuel bundle without dismantlement of the bundles. (author). 5 tabs., 25 figs

  1. Distribution and dynamics of radionuclides and stable elements in the coastal waters off Rokkasho Village, Japan, prior to the opening of a nuclear reprocessing facility. Part 3. Concentration levels of radionuclides in seawater off Rokkasho Village

    Kondo, K.; Kawabata, H.; Ueda, S.; Akata, N.; Inaba, J.; Ohmomo, Y.; Mitamura, O.; Seike, Y.

    2003-01-01

    A survey was conducted to determine the concentration levels of 3 H, 137 Cs, 90 Sr, 238,239+240 Pu, and 234,235,238 U in seawater off Rokkasho Village, Japan, before the start-up of a nuclear-fuel reprocessing plant. The level, fluctuation range and distribution characteristics of each radionuclide was determined. (author)

  2. Sampling Polya-Gamma random variates: alternate and approximate techniques

    Windle, Jesse; Polson, Nicholas G.; Scott, James G.

    2014-01-01

    Efficiently sampling from the P\\'olya-Gamma distribution, ${PG}(b,z)$, is an essential element of P\\'olya-Gamma data augmentation. Polson et. al (2013) show how to efficiently sample from the ${PG}(1,z)$ distribution. We build two new samplers that offer improved performance when sampling from the ${PG}(b,z)$ distribution and $b$ is not unity.

  3. Gamma knife

    Kawamoto, Shunsuke; Takakura, Kintomo

    1991-01-01

    As to the gamma knife which is the radiation surgery device developed in Sweden a quarter century ago, its principle, structure, treatment techniques, already established clinical effect and the problems being left for hereafter are described. This treatment means supplements the operation under microscopes, and at present it takes the important position in neurosurgery, but hereafter, by the interdisciplinary cooperation of neurosurgery and clinical radiobiology, the more development can be expected. The method of irradiating the radiation of high dose selectively to a target region and breaking its tissue is called radiosurgery, and the device developed for this purpose is the gamma knife. First, it was applied to functional diseases, but good results were obtained by its application to auditory nerve and brain blood vessels, and it establishes the position as the safe treatment method of the morbid state in the deep part of brains, which is difficult to reach by operation. Accompanying the recent progress of the operation of skull base part, attention is paid to its application to various tumors in skull base. On the other hand, the radiosurgery combining a cyclotron or a linear accelerator with stereotaxic brain surgery is actively tried mainly to the deformation of brain blood vessels. (K.I.)

  4. Gamma irradiation devices

    Foeldiak, Gabor; Stenger, Vilmos.

    1983-01-01

    The main parameters and the preparation procedures of the gamma radiation sources frequently applied for irradiation purposes are discussed. In addition to 60 Co and 137 Cs sources also the nuclear power plants offer further opportunities: spent fuel elements and products of certain (n,γ) reactions can serve as irradiation sources. Laboratory scale equipments, pilot plant facilities for batch or continuous operation, continuous industrial irradiators and special multipurpose, mobile and panorama type facilities are reviewed including those in Canada, USA, India, the Soviet Union, Hungary, UK, Japan and Australia. For irradiator design the source geometry dependence of the spatial distribution of dose rates can be calculated. (V.N.)

  5. Gamma-Gompertz life expectancy at birth

    Trifon I. Missov

    2013-02-01

    Full Text Available BACKGROUND The gamma-Gompertz multiplicative frailty model is the most common parametric modelapplied to human mortality data at adult and old ages. The resulting life expectancy hasbeen calculated so far only numerically. OBJECTIVE Properties of the gamma-Gompertz distribution have not been thoroughly studied. The focusof the paper is to shed light onto its first moment or, demographically speaking, characterizelife expectancy resulting from a gamma-Gompertz force of mortality. The paperprovides an exact formula for gamma-Gompertz life expectancy at birth and a simplerhigh-accuracy approximation that can be used in practice for computational convenience.In addition, the article compares actual (life-table to model-based (gamma-Gompertzlife expectancy to assess on aggregate how many years of life expectancy are not captured(or overestimated by the gamma-Gompertz mortality mechanism. COMMENTS A closed-form expression for gamma-Gomeprtz life expectancy at birth contains a special(the hypergeometric function. It aids assessing the impact of gamma-Gompertz parameterson life expectancy values. The paper shows that a high-accuracy approximation canbe constructed by assuming an integer value for the shape parameter of the gamma distribution.A historical comparison between model-based and actual life expectancy forSwedish females reveals a gap that is decreasing to around 2 years from 1950 onwards.Looking at remaining life expectancies at ages 30 and 50, we see this gap almost disappearing.

  6. The topological filtration of gamma-structures

    Li, Thomas; Reidys, Christian

    2013-01-01

    In this paper we study gamma-structures filtered by topological genus. gamma-structures are a class of RNA pseudoknot structures that plays a key role in the context of polynomial time folding of RNA pseudoknot structures. A gamma-structure is composed by specific building blocks, that have...... topological genus less than or equal to gamma, where composition means concatenation and nesting of such blocks. Our main results are the derivation of a new bivariate generating function for gamma-structures via symbolic methods, the singularity analysis of the solutions and a central limit theorem...... for the distribution of topological genus in gamma-structures of given length. In our derivation specific bivariate polynomials play a central role. Their coefficients count particular motifs of fixed topological genus and they are of relevance in the context of genus recursion and novel folding algorithms....

  7. Bayesian optimal experimental design for priors of compact support

    Long, Quan

    2016-01-01

    to account for the bounded domain of the uniform prior pdf of the parameters. The underlying Gaussian distribution is obtained in the spirit of the Laplace method, more precisely, the mode is chosen as the maximum a posteriori (MAP) estimate

  8. Observations of gamma-ray bursts

    Strong, I.B.; Klebesadel, R.W.; Evans, W.D.

    1975-01-01

    Observational data on gamma-ray bursts are reviewed. Information is grouped into temporal properties, energy fluxes and spectral properties, and directions and distributions of the sources in space. (BJG)

  9. Exclusive production of pion pairs in {gamma}*{gamma} collisions at Large Q{sup 2}

    Diehl, M.

    2000-03-15

    The authors perform a QCD analysis of the exclusive production of two mesons in {gamma}*{gamma} collisions in the kinematical domain of large photon virtuality Q and small hadronic invariant mass W. This reaction is dominated by a scale invariant mechanism which factorizes into a perturbative subprocess, {gamma}*{gamma} {r{underscore}arrow} q{anti q} or {gamma}*{gamma} {r{underscore}arrow} gg, and a generalized two-meson distribution amplitude. The authors develop in detail the phenomenology of this process at e{sup +}e{sup {minus}} colliders. Using a simple model for the two-pion distribution amplitude, based on its general properties, the authors estimate the cross section for the kinematics accessible at BABAR, BELLE, CLEO and LEP.

  10. About cosmic gamma ray lines

    Diehl, Roland

    2017-06-01

    Gamma ray lines from cosmic sources convey the action of nuclear reactions in cosmic sites and their impacts on astrophysical objects. Gamma rays at characteristic energies result from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. The gamma-ray line from the annihilation of positrons at 511 keV falls into the same energy window, although of different origin. We present here the concepts of cosmic gamma ray spectrometry and the corresponding instruments and missions, followed by a discussion of recent results and the challenges and open issues for the future. Among the lessons learned are the diffuse radioactive afterglow of massive-star nucleosynthesis in 26Al and 60Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae; large interstellar cavities and superbubbles have been recognised to be of key importance here. Also, constraints on the complex processes making stars explode as either thermonuclear or core-collapse supernovae are being illuminated by gamma-ray lines, in this case from shortlived radioactivities from 56Ni and 44Ti decays. In particular, the three-dimensionality and asphericities that have recently been recognised as important are enlightened in different ways through such gamma-ray line spectroscopy. Finally, the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity disctribution is measured through spatially-resolved spectra, which indicate that annihilation conditions may differ in different parts of our Galaxy. But it is now understood that a variety of sources may feed positrons into the interstellar medium, and their characteristics largely get lost during slowing down and propagation of positrons before annihilation; a recent microquasar flare was caught as an opportunity to see positrons annihilate at a source.

  11. Recruiting for Prior Service Market

    2008-06-01

    perceptions, expectations and issues for re-enlistment • Develop potential marketing and advertising tactics and strategies targeted to the defined...01 JUN 2008 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Recruiting for Prior Service Market 5a. CONTRACT NUMBER 5b. GRANT...Command First Handshake to First Unit of Assignment An Army of One Proud to Be e e to Serve Recruiting for Prior Service Market MAJ Eric Givens / MAJ Brian

  12. Gamma-scintigraphy as a novel method to study the distribution and clearance rate of different muco adhesive nasal delivery systems

    Tofaghodi, M.; Zakavi, R.; Sajadi Tabasi, A.; Jaafari, M.R.

    2002-01-01

    Nasal route has a high potential for drug delivery. One important limiting factor for nasal drug delivery is the rapid clearance of drugs from the nasal cavity. Several nasal drug delivery systems including different kinds of microspheres and liposomes have been tried for encapsulation of drugs and increasing the residence time in nasal cavity. In this study clearance rate of three kinds of microspheres (Alginate, PLGA and Dextran) and four kinds of liposomes (neutral, cationic, fusogenic and cationic-fusogenic) was determined. Lactose powder was used as negative control. Technetium pertechnetate labeling and gamma scintigraphy was used for precise and quantitative measurement of clearance rate of these delivery system. 99 mTc labeled microspheres and liposomes were prepared using technetium pertechnetate in the presence of a potent reducing agent, st annus chloride. The labeling procedure was set in a manner that each 150 micro litter of liposome suspensions and each 3-5 mg of microspheres contained 2 MBq of radioactivity. Labeling efficiency was calculated by paper chromatography using acetone as mobile phase. Each delivery system containing 2 MBq of activity was sprayed into right nostril of four healthy volunteers and immediately after spraying, anterior view of nasal cavity was measured by a large field gamma camera equipped with a low-energy high resolution parallel collimator. One minute static views were repeated each half hour until 4 hours. Clearance rates were compared using two ROI; the initial site of deposition of sprays, and all of nasal cavity to nasopharynx. Clearance rate of each one of microspheres and liposomes was calculated after applying the physical decay corrections. The labeling efficiency for liposomes and microspheres calculated as 41.2% and 60.7% respectively. The cleared percent of delivery systems after 4 hours was determined as follows: neutral liposomes 18.7±3.9% cationic liposomes 43.7±2.1%; fusogenic liposomes 32.8±2

  13. Effect of Gamma Rays on the Distribution of Toxigenic Fusarium Moulds and Chemical Changes in Whole and Dry Milled Fractions of Wheat

    Mahrous, S.R.

    2008-01-01

    The influence of gamma-irradiation on Fusarium-mycotoxins and the chemical composition of whole and dry-milled fractions of wheat grains was investigated. Wheat samples collected from the Egyptian markets were found to be heavily contaminated by, Fusarium graminearum (70-100%), F. moniliforme (40-60%) and F.subglutinilils (10-30%). Fusarium counts in wheat fractions were 1.1-2.7 x 10 1 CFU/g in flour; 1.1 x 10 3 to 3.7 X 10 4 CFU/g in bran and 1.4 x 10 2 to 1.6 X 10 3 in shorts. The levels of deoxynivalenol (DON) and zearalenone were generally highest in the bran and lowest in the flour. The levels of DON and zearalenone. in whole wheat samples were generally lower than the levels in the bran and shorts. Irradiation at a dose 5.0 kGy reduced the Fusarium moulds growth greatly relative to unirradiated controls and there was no growth at 7.0 kGy. Application of radiation at 15.0 kGy reduced the levels of DON and zearalenon by less than 1 ppm and Fusarium toxins were eliminated at 20.0 kGy. The chemical composition of the raw and irradiated whole and dry- milled fractions of-wheat grains up to 20.0 kGy was similar

  14. Polynomial reconstruction of radial catalyst concentration distribution in an experimental type FCC riser for a low number of transversal projections in gamma ray tomography

    Melo, Silvio B.; Simoes, Francisco P.M.; Oliveira, Eric F. de; Santos, Maria das Gracas dos; Dantas, Carlos C.

    2007-01-01

    In the FCC - Fluid Catalytic Cracking process the Riser is an opaque cylinder, so that, in order to investigate the catalyst concentration inside, a gamma- ray based tomography is employed. Each section is submitted to a parallel beam and by means of the Beer-Lambert transmission is calculated. This tomography session is repeated from different angles, in manual tomographic experiments where the source/detector pair is rotated, producing in each direction what we called a transversal projection. In order to reconstruct the concentration of the present catalyst in a given moment some methods use successfully the inverse Radon transform through the filtered back-projection algorithm. The results are fully satisfactory for a large number of projections, widely seen as better than those produced by the algebraic methods. For a low number of projections, however, the algebraic methods become more competitive. In practice, simple experimental set-ups work with less than 10 projections, due to the time taken by the whole process. In this work, we present an investigation of polynomial reconstructions by using Bezier surfaces of arbitrary degree, adjusted to the experimental data through a least squares method. A computational algorithm was developed to implement the mathematical reconstruction for the 3D graphics presentation. (author)

  15. Gamma camera

    Tschunt, E.; Platz, W.; Baer, U.; Heinz, L.

    1978-01-01

    A gamma camera has a plurality of exchangeable collimators, one of which is mounted in the ray inlet opening of the camera, while the others are placed on separate supports. The supports are swingably mounted upon a column one above the other through about 90 0 to a collimator exchange position. Each of the separate supports is swingable to a vertically aligned position, with limiting of the swinging movement and positioning of the support at the desired exchange position. The collimators are carried on the supports by means of a series of vertically disposed coil springs. Projections on the camera are movable from above into grooves of the collimator at the exchange position, whereupon the collimator is turned so that it is securely prevented from falling out of the camera head

  16. Prior Sensitivity Analysis in Default Bayesian Structural Equation Modeling.

    van Erp, Sara; Mulder, Joris; Oberski, Daniel L

    2017-11-27

    Bayesian structural equation modeling (BSEM) has recently gained popularity because it enables researchers to fit complex models and solve some of the issues often encountered in classical maximum likelihood estimation, such as nonconvergence and inadmissible solutions. An important component of any Bayesian analysis is the prior distribution of the unknown model parameters. Often, researchers rely on default priors, which are constructed in an automatic fashion without requiring substantive prior information. However, the prior can have a serious influence on the estimation of the model parameters, which affects the mean squared error, bias, coverage rates, and quantiles of the estimates. In this article, we investigate the performance of three different default priors: noninformative improper priors, vague proper priors, and empirical Bayes priors-with the latter being novel in the BSEM literature. Based on a simulation study, we find that these three default BSEM methods may perform very differently, especially with small samples. A careful prior sensitivity analysis is therefore needed when performing a default BSEM analysis. For this purpose, we provide a practical step-by-step guide for practitioners to conducting a prior sensitivity analysis in default BSEM. Our recommendations are illustrated using a well-known case study from the structural equation modeling literature, and all code for conducting the prior sensitivity analysis is available in the online supplemental materials. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  17. Adaptive Detectors for Two Types of Subspace Targets in an Inverse Gamma Textured Background

    Ding Hao

    2017-06-01

    Full Text Available Considering an inverse Gamma prior distribution model for texture, the adaptive detection problems for both first order Gaussian and second order Gaussian subspace targets are researched in a compound Gaussian sea clutter. Test statistics are derived on the basis of the two-step generalized likelihood ratio test. From these tests, new adaptive detectors are proposed by substituting the covariance matrix with estimation results from the Sample Covariance Matrix (SCM, normalized SCM, and fixed point estimator. The proposed detectors consider the prior distribution model for sea clutter during the design stage, and they model parameters that match the working environment during the detection stage. Analysis and validation results indicate that the detection performance of the proposed detectors out performs existing AMF (Adaptive Matched Filter, AMF and ANMF (Adaptive Normalized Matched Filter, ANMF detectors.

  18. Dose mapping role in gamma irradiation industry

    Noriah Mod Ali; John Konsoh Sangau; Mazni Abd Latif

    2002-01-01

    In this studies, the role of dosimetry activity in gamma irradiator was discussed. Dose distribution in the irradiator, which is a main needs in irradiator or chamber commissioning. This distribution data were used to confirm the dosimetry parameters i.e. exposure time, maximum and minimum dose map/points, and dose distribution - in which were used as guidelines for optimum product irradiation. (Author)

  19. Crowdsourcing prior information to improve study design and data analysis.

    Jeffrey S Chrabaszcz

    Full Text Available Though Bayesian methods are being used more frequently, many still struggle with the best method for setting priors with novel measures or task environments. We propose a method for setting priors by eliciting continuous probability distributions from naive participants. This allows us to include any relevant information participants have for a given effect. Even when prior means are near-zero, this method provides a principle way to estimate dispersion and produce shrinkage, reducing the occurrence of overestimated effect sizes. We demonstrate this method with a number of published studies and compare the effect of different prior estimation and aggregation methods.

  20. LiF thermoluminescence dosimetry for mapping absorbed dose distributions in the gamma ray disinfection of machine-baled sheep wool

    Dexi Jiang

    1985-01-01

    The measurement of absorbed dose distributions of 60 Co γ-rays in machine-baled sheep wool, which is disinfected of certain parasitic bacteria (e.g. Brucella bacilli) by γ-ray treatment, is summarized. The preparation and main physical properties of the LiF-TLD are described, as well as the shape, structure and the activity of the 60 Co source and typical dose distributions measured around the source in free air. The results of dose distributions measured by the LiF-TLD agreed within +-5% with those given by a calibrated ionization chamber. The exposure rates (units R/min) at three typical measurement points inside a bale of sheep's wool were found to be quite uniform: centre 3.8x10 3 (+-2.1%); upper region 3.9x10 3 (+-2.4%); lower region 3.9x10 3 (+-1.9%). (author)

  1. Background gamma radiation mapping in forest ecosystem of Bangladesh: A study on the radioactivity distribution in the national reserve forest of Gazipur

    Sheikh Shariful Islam

    2017-01-01

    Full Text Available Natural and artificial radioactivity appears to be different in different geological regions. Moreover, the radionuclides may migrate to the deeper region of the earth after deposition, and the depth profile of a radionuclide reveals information on the rate of migration. Countrywide background gamma radiation mapping program has been initiated in Bangladesh by dividing the whole country primarily into ~2 km × ~2 km (1' ×1' in Global Positioning System scale systematic square grids to formulate the radioactivity profile. About 28 km × 30 km area of forest land of Gazipur district called the “BhawalGahr” including the Bhawal National Park was selected for sampling. Soil samples from 0 to 5 cm, 5 to 15, cm and 15 to 30 cm depth were collected from the 27 grid node points of the square grids. A total of 81 samples were collected for the current study. The samples were subjected to elemental and radioactivity analyses. The elements found in the samples were in decreasing order as Fe>K>Ti>Ca>Co>Mn>V>Cr>Ni. The calculated activity concentration of natural radionuclides 226Ra, 232Th, and 40K for surface soil samples (0–5 cm depth ranged from 44.2 ± 5.7 to 84.5 ± 10.2 Bq/kg, 75.6 ± 8.3 to 126.5 ± 8.3 Bq/kg, and 263.7 ± 92.3 to 606.7 ± 107.9 Bq/kg, respectively and there is no significant variation for other depths. The radiological hazard indices such as radium equivalent activity, radiation external hazard index, absorbed dose rate, and annual effective dose were also estimated from the calculated values of activity concentrations.

  2. Adaptive estimation of multivariate functions using conditionally Gaussian tensor-product spline priors

    Jonge, de R.; Zanten, van J.H.

    2012-01-01

    We investigate posterior contraction rates for priors on multivariate functions that are constructed using tensor-product B-spline expansions. We prove that using a hierarchical prior with an appropriate prior distribution on the partition size and Gaussian prior weights on the B-spline

  3. Testability evaluation using prior information of multiple sources

    Wang Chao

    2014-08-01

    Full Text Available Testability plays an important role in improving the readiness and decreasing the life-cycle cost of equipment. Testability demonstration and evaluation is of significance in measuring such testability indexes as fault detection rate (FDR and fault isolation rate (FIR, which is useful to the producer in mastering the testability level and improving the testability design, and helpful to the consumer in making purchase decisions. Aiming at the problems with a small sample of testability demonstration test data (TDTD such as low evaluation confidence and inaccurate result, a testability evaluation method is proposed based on the prior information of multiple sources and Bayes theory. Firstly, the types of prior information are analyzed. The maximum entropy method is applied to the prior information with the mean and interval estimate forms on the testability index to obtain the parameters of prior probability density function (PDF, and the empirical Bayesian method is used to get the parameters for the prior information with a success-fail form. Then, a parametrical data consistency check method is used to check the compatibility between all the sources of prior information and TDTD. For the prior information to pass the check, the prior credibility is calculated. A mixed prior distribution is formed based on the prior PDFs and the corresponding credibility. The Bayesian posterior distribution model is acquired with the mixed prior distribution and TDTD, based on which the point and interval estimates are calculated. Finally, examples of a flying control system are used to verify the proposed method. The results show that the proposed method is feasible and effective.

  4. Testability evaluation using prior information of multiple sources

    Wang Chao; Qiu Jing; Liu Guanjun; Zhang Yong

    2014-01-01

    Testability plays an important role in improving the readiness and decreasing the life-cycle cost of equipment. Testability demonstration and evaluation is of significance in measuring such testability indexes as fault detection rate (FDR) and fault isolation rate (FIR), which is useful to the producer in mastering the testability level and improving the testability design, and helpful to the consumer in making purchase decisions. Aiming at the problems with a small sample of testabil-ity demonstration test data (TDTD) such as low evaluation confidence and inaccurate result, a test-ability evaluation method is proposed based on the prior information of multiple sources and Bayes theory. Firstly, the types of prior information are analyzed. The maximum entropy method is applied to the prior information with the mean and interval estimate forms on the testability index to obtain the parameters of prior probability density function (PDF), and the empirical Bayesian method is used to get the parameters for the prior information with a success-fail form. Then, a parametrical data consistency check method is used to check the compatibility between all the sources of prior information and TDTD. For the prior information to pass the check, the prior credibility is calculated. A mixed prior distribution is formed based on the prior PDFs and the corresponding credibility. The Bayesian posterior distribution model is acquired with the mixed prior distribution and TDTD, based on which the point and interval estimates are calculated. Finally, examples of a flying control system are used to verify the proposed method. The results show that the proposed method is feasible and effective.

  5. On the maximum and minimum of two modified Gamma-Gamma variates with applications

    Al-Quwaiee, Hessa; Ansari, Imran Shafique; Alouini, Mohamed-Slim

    2014-01-01

    on these new results to present the performance analysis of (i) a dual-branch free-space optical selection combining diversity undergoing independent but not necessarily identically distributed Gamma-Gamma fading under the impact of pointing errors and of (ii

  6. Gamma ray astronomy from satellites and balloons

    Schoenfelder, V.

    1986-01-01

    A survey is given of gamma ray astronomy topics presented at the Cosmic Ray Conference. The major conclusions at the Cosmic Ray Conference in the field of gamma ray astronomy are given. (1) MeV-emission of gamma-ray bursts is a common feature. Variations in duration and energy spectra from burst to burst may explain the discrepancy between the measured log N - log S dependence and the observed isotropy of bursts. (2) The gamma-ray line at 1.809 MeV from Al(26) is the first detected line from a radioactive nucleosynthesis product. In order to understand its origin it will be necessary to measure its longitude distribution in the Milky Way. (3) The indications of a gamma-ray excess found from the direction of Loop I is consistent with the picture that the bulk of cosmic rays below 100 GeV is produced in galactic supernova remnants. (4) The interpretation of the large scale distribution of gamma rays in the Milky Way is controversial. At present an extragalactic origin of the cosmic ray nuclei in the GeV-range cannot be excluded from the gamma ray data. (5) The detection of MeV-emission from Cen A is a promising step towards the interesting field of extragalactic gamma ray astronomy

  7. Gamma camera

    Conrad, B.; Heinzelmann, K.G.

    1975-01-01

    A gamma camera is described which obviates the distortion of locating signals generally caused by the varied light conductive capacities of the light conductors in that the flow of light through each light conductor may be varied by means of a shutter. A balancing of the flow of light through each of the individual light conductors, in effect, collective light conductors may be balanced on the basis of their light conductive capacities or properties, so as to preclude a distortion of the locating signals caused by the varied light conductive properties of the light conductors. Each light conductor has associated therewith two, relative to each other, independently adjustable shutters, of which one forms a closure member and the other an adjusting shutter. In this embodiment of the invention it is thus possible to block all of the light conductors leading to a photoelectric transducer, with the exception of those light conductors which are to be balanced. The balancing of the individual light conductors may then be obtained on the basis of the output signals of the photoelectric transducer. (auth)

  8. Gamma ray generator

    Firestone, Richard B; Reijonen, Jani

    2014-05-27

    An embodiment of a gamma ray generator includes a neutron generator and a moderator. The moderator is coupled to the neutron generator. The moderator includes a neutron capture material. In operation, the neutron generator produces neutrons and the neutron capture material captures at least some of the neutrons to produces gamma rays. An application of the gamma ray generator is as a source of gamma rays for calibration of gamma ray detectors.

  9. Genomic sequences of murine gamma B- and gamma C-crystallin-encoding genes: promoter analysis and complete evolutionary pattern of mouse, rat and human gamma-crystallins.

    Graw, J; Liebstein, A; Pietrowski, D; Schmitt-John, T; Werner, T

    1993-12-22

    The murine genes, gamma B-cry and gamma C-cry, encoding the gamma B- and gamma C-crystallins, were isolated from a genomic DNA library. The complete nucleotide (nt) sequences of both genes were determined from 661 and 711 bp, respectively, upstream from the first exon to the corresponding polyadenylation sites, comprising more than 2650 and 2890 bp, respectively. The new sequences were compared to the partial cDNA sequences available for the murine gamma B-cry and gamma C-cry, as well as to the corresponding genomic sequences from rat and man, at both the nt and predicted amino acid (aa) sequence levels. In the gamma B-cry promoter region, a canonical CCAAT-box, a TATA-box, putative NF-I and C/EBP sites were detected. An R-repeat is inserted 366 bp upstream from the transcription start point. In contrast, the gamma C-cry promoter does not contain a CCAAT-box, but some other putative binding sites for transcription factors (AP-2, UBP-1, LBP-1) were located by computer analysis. The promoter regions of all six gamma-cry from mouse, rat and human, except human psi gamma F-cry, were analyzed for common sequence elements. A complex sequence element of about 70-80 bp was found in the proximal promoter, which contains a gamma-cry-specific and almost invariant sequence (crygpel) of 14 nt, and ends with the also invariant TATA-box. Within the complex sequence element, a minimum of three further features specific for the gamma A-, gamma B- and gamma D/E/F-cry genes can be defined, at least two of which were recently shown to be functional. In addition to these four sequence elements, a subtype-specific structure of inverted repeats with different-sized spacers can be deduced from the multiple sequence alignment. A phylogenetic analysis based on the promoter region, as well as the complete exon 3 of all gamma-cry from mouse, rat and man, suggests separation of only five gamma-cry subtypes (gamma A-, gamma B-, gamma C-, gamma D- and gamma E/F-cry) prior to species separation.

  10. Random template placement and prior information

    Roever, Christian

    2010-01-01

    In signal detection problems, one is usually faced with the task of searching a parameter space for peaks in the likelihood function which indicate the presence of a signal. Random searches have proven to be very efficient as well as easy to implement, compared e.g. to searches along regular grids in parameter space. Knowledge of the parameterised shape of the signal searched for adds structure to the parameter space, i.e., there are usually regions requiring to be densely searched while in other regions a coarser search is sufficient. On the other hand, prior information identifies the regions in which a search will actually be promising or may likely be in vain. Defining specific figures of merit allows one to combine both template metric and prior distribution and devise optimal sampling schemes over the parameter space. We show an example related to the gravitational wave signal from a binary inspiral event. Here the template metric and prior information are particularly contradictory, since signals from low-mass systems tolerate the least mismatch in parameter space while high-mass systems are far more likely, as they imply a greater signal-to-noise ratio (SNR) and hence are detectable to greater distances. The derived sampling strategy is implemented in a Markov chain Monte Carlo (MCMC) algorithm where it improves convergence.

  11. Equipment to determine the total gamma activity and/or the geometrical distribution of radiation sources in a body with four detectors in near-cruciform arrangement

    Morsy, S.M.; Pohlit, W.; Stahlhofen, W.; Werner, E.

    1979-01-01

    This appliance serves for detection of the spatial distribution of airborne radioactive substances or aerosols which incorporated or inhaled in the pulmonary-respiratory tract. In order to determine the activities irrespective of their positions in the investigated body cross-section, the collimator cases of the four detectors, two of them being situated over and two under the carrying apparatus for men, have rectangular cross-sections. The detectors themselves can be removed within the collimator cases realtive to the axis of symmetry. (DG) [de

  12. An analysis of the distribution and dose response of chromosome aberrations in human lymphocytes after in vitro exposure to 137cesium gamma radiation

    Doggett, N.A.; McKenzie, W.H.

    1983-01-01

    The chromosome aberration yield for human lymphocytes exposed in vitro to various doses of 137 Cesium has been studied. Dicentric, total acentric, and excess acentric data were seen to follow a Possion distribution. Calculated total hits demonstrated over-dispersion which could possibly be accounted for by a greater occurrence of single-hit phenomena being repaired than two-hit exchange processes. The resulting distribution generally contained an under-representation of cells with odd numbers of hits and an over-representation of zero-and even-hit classes as compared with Poisson predicted values. The relationship between dicentric yield and dose received in rads was fitted to the linear-quadratic formula Y=αD+βD 2 for dicentrics, yielding values of (20.1+-3.8)x10 -4 (aberrations/cell)/rad and (1.89+-0.75)x10 -6 (aberrations/cell)/rad 2 for α and β respectively. A plot of percent ''normal'' cells versus the dose in rads resembled cell survival curves and was fitted to the relation P(D)=100 esup(-Y) where Y=αD+αD 2 with α=(23+-11)x10 -4 rad -1 and β=(8.3+-2.5)x10 -6 rad -2 . A possible use of scoring ''normal'' cells for purposes of biological dosimetry is presented. (orig.)

  13. Quantum steganography using prior entanglement

    Mihara, Takashi

    2015-01-01

    Steganography is the hiding of secret information within innocent-looking information (e.g., text, audio, image, video, etc.). A quantum version of steganography is a method based on quantum physics. In this paper, we propose quantum steganography by combining quantum error-correcting codes with prior entanglement. In many steganographic techniques, embedding secret messages in error-correcting codes may cause damage to them if the embedded part is corrupted. However, our proposed steganography can separately create secret messages and the content of cover messages. The intrinsic form of the cover message does not have to be modified for embedding secret messages. - Highlights: • Our steganography combines quantum error-correcting codes with prior entanglement. • Our steganography can separately create secret messages and the content of cover messages. • Errors in cover messages do not have affect the recovery of secret messages. • We embed a secret message in the Steane code as an example of our steganography

  14. Quantum steganography using prior entanglement

    Mihara, Takashi, E-mail: mihara@toyo.jp

    2015-06-05

    Steganography is the hiding of secret information within innocent-looking information (e.g., text, audio, image, video, etc.). A quantum version of steganography is a method based on quantum physics. In this paper, we propose quantum steganography by combining quantum error-correcting codes with prior entanglement. In many steganographic techniques, embedding secret messages in error-correcting codes may cause damage to them if the embedded part is corrupted. However, our proposed steganography can separately create secret messages and the content of cover messages. The intrinsic form of the cover message does not have to be modified for embedding secret messages. - Highlights: • Our steganography combines quantum error-correcting codes with prior entanglement. • Our steganography can separately create secret messages and the content of cover messages. • Errors in cover messages do not have affect the recovery of secret messages. • We embed a secret message in the Steane code as an example of our steganography.

  15. Prior information in structure estimation

    Kárný, Miroslav; Nedoma, Petr; Khailova, Natalia; Pavelková, Lenka

    2003-01-01

    Roč. 150, č. 6 (2003), s. 643-653 ISSN 1350-2379 R&D Projects: GA AV ČR IBS1075102; GA AV ČR IBS1075351; GA ČR GA102/03/0049 Institutional research plan: CEZ:AV0Z1075907 Keywords : prior knowledge * structure estimation * autoregressive models Subject RIV: BC - Control Systems Theory Impact factor: 0.745, year: 2003 http://library.utia.cas.cz/separaty/historie/karny-0411258.pdf

  16. Measurement of the reaction {gamma}d {yields}pn{pi}{sup +}{pi}{sup -} at SAPHIR and investigation of the decay angular distribution of the {Delta}{sup ++}(1232) resonance; Messung der Reaktion {gamma}d {yields}pn{pi}{sup +}{pi}{sup -} an SAPHIR und Untersuchung der Zerfallswinkelverteilung der {Delta}{sup ++}(1232)-Resonanz

    Schuetz, P.

    1993-03-01

    SAPHIR, a new experiment at the Bonn electron stretcher ring ELSA, started taking data in spring 1992. It was set up for the investigation of photon induced reactions with multiparticle final states. In the first part of this paper the special design of the target is described. It can be operated with liquefied hydrogen or deuterium and is placed in the middle of the central drift chamber. To project the surrounding chamber in case of a fracture of the target cell as safety system is installed. In addition two independent methods of monitoring the cell are procided. The first measurement was performed with a deuterium target at a photon energy range of E{sub {gamma}} = 500-700 MeV. In the second part of this paper first results of an analysis of the decay angular distribution of the {Delta}{sup ++}(1232) in the reaction {gamma}d {yields} n{Delta}{sup ++}{pi}{sup -} are presented. They are compared to old data from a hydrogen bubble chamber experiment and are discussed on the basis of a spectator model. (orig.) [Deutsch] Im Rahmen dieser Arbeit ist der Aufbau eines Fluessiggas-Targets beschrieben worden, das speziell fuer den Einsatz im SAPHIR-Detektor entwickelt worden ist. Es wurden Funktionen zur Ueberwachung der Targetzelle vorgestellt und ein Sicherheitssystem zum Schutz der zentralen Driftkammer, die das Target unmittelbar umgibt. Weiterhin ist in Simulationsrechnungen untersucht worden, welchen Einfluss die Konstruktion des Targetstreutopfes auf die Messung unterschiedlicher Reaktionen haben kann. Dabei sind bei 50% bis 70% der Ereignisse Treffer in den Aluminiumstuetzen des Targetstreutopfes aufgetreten. Diese starke Beeintraechtigung kann durch eine Neukonstruktion des Streutopfes und der Verwendung von z.B. Rohazell als Streutopffenster vermieden werden. Rohazell zeichnet sich durch eine hohe Festigkeit und grosse Strahlungslaenge aus. An der Neukonstruktion des Streutopfes wird z.Z. gearbeitet. Der zweite Teil der Arbeit beschreibt eine der ersten

  17. Estimating Functions with Prior Knowledge, (EFPK) for diffusions

    Nolsøe, Kim; Kessler, Mathieu; Madsen, Henrik

    2003-01-01

    In this paper a method is formulated in an estimating function setting for parameter estimation, which allows the use of prior information. The main idea is to use prior knowledge of the parameters, either specified as moments restrictions or as a distribution, and use it in the construction of a...... of an estimating function. It may be useful when the full Bayesian analysis is difficult to carry out for computational reasons. This is almost always the case for diffusions, which is the focus of this paper, though the method applies in other settings.......In this paper a method is formulated in an estimating function setting for parameter estimation, which allows the use of prior information. The main idea is to use prior knowledge of the parameters, either specified as moments restrictions or as a distribution, and use it in the construction...

  18. The Three-dimensional Spatial Distribution of Interstellar Gas in the Milky Way: Implications for Cosmic Rays and High-energy Gamma-ray Emissions

    Jóhannesson, Guđlaugur; Porter, Troy A.; Moskalenko, Igor V.

    2018-03-01

    Direct measurements of cosmic ray (CR) species combined with observations of their associated γ-ray emissions can be used to constrain models of CR propagation, trace the structure of the Galaxy, and search for signatures of new physics. The spatial density distribution of interstellar gas is a vital element for all these studies. So far, models have employed the 2D cylindrically symmetric geometry, but their accuracy is well behind that of the available data. In this paper, 3D spatial density models for neutral and molecular hydrogen are constructed based on empirical model fitting to gas line-survey data. The developed density models incorporate spiral arms and account for the warping of the disk, and the increasing gas scale height with radial distance from the Galactic center. They are employed together with the GALPROP CR propagation code to investigate how the new 3D gas models affect calculations of CR propagation and high-energy γ-ray intensity maps. The calculations reveal non-trivial features that are directly related to the new gas models. The best-fit values for propagation model parameters employing 3D gas models are presented and they differ significantly from those derived with the 2D gas density models that have been widely used. The combination of 3D CR and gas density models provide a more realistic basis for the interpretation of non-thermal emissions from the Galaxy.

  19. An assessment of the natural radioactivity distribution and radiation hazard in soil samples from Qatar using high-resolution gamma-ray spectrometry

    Al-Sulaiti, Huda; Al Mugren, K. S.; Bradley, D. A.; Regan, P. H.; Santawamaitre, T.; Malain, D.; Habib, A.; Nasir, Tabassum; Alkhomashi, N.; Al-Dahan, N.; Al-Dosari, M.; Bukhari, S.

    2017-11-01

    We establish baseline measurements for radioactivity concentration in the soil samples collected from the Qatarian peninsula. The work focused on the naturally occurring and technically enhanced levels of radiation associated with 235,8U and 232Th natural decay chains and the long-lived naturally occurring radionuclide 40K in 129 soil samples collected across the landscape of the State of Qatar. Three radiological distribution maps showing the activity concentrations of 226Ra, 232Th and 40K were constructed. Two soil samples were found to be elevated to the favour of 226Ra concentration and significantly above the average and global values. Notably, these samples were collected from an area within an oil field (NW Dukhan). The mean values of activity concentrations of 226Ra, 232Th and 40K for the full cohort of samples were found to be 17.2±1.6, 6.38±0.26 and 169±5 Bq/kg, respectively. These values lie within the expected range relative to the world average values in soil samples of 30, 35 and 400 Bq/kg, respectively.

  20. Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination

    2016-06-01

    Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination Distribution Statement A. Approved for public release; distribution is...Final Technical Report BRBAA08-Per5-Y-1-2-0030 Title: “Gadolinium-Based GaN for Neutron Detection with Gamma Discrimination ” Grant...Analysis  .............................................................................................  23   6.   Gamma-ray Discrimination

  1. An assessment of the natural radioactivity distribution and radiation hazard in soil samples from Qatar using high-resolution gamma-ray spectrometry

    Al-Sulaiti, Huda; Al Mugren, K.S.; Bradley, D.A.; Regan, P.H.; Santawamaitre, T.; Malain, D.; Habib, A.; Nasir, Tabassum; Alkhomashi, N.; Al-Dahan, N.; Al-Dosari, M.; Bukhari, S.

    2017-01-01

    We establish baseline measurements for radioactivity concentration in the soil samples collected from the Qatarian peninsula. The work focused on the naturally occurring and technically enhanced levels of radiation associated with 235,8 U and 232 Th natural decay chains and the long-lived naturally occurring radionuclide 40 K in 129 soil samples collected across the landscape of the State of Qatar. Three radiological distribution maps showing the activity concentrations of 226 Ra, 232 Th and 40 K were constructed. Two soil samples were found to be elevated to the favour of 226 Ra concentration and significantly above the average and global values. Notably, these samples were collected from an area within an oil field (NW Dukhan). The mean values of activity concentrations of 226 Ra, 232 Th and 40 K for the full cohort of samples were found to be 17.2±1.6, 6.38±0.26 and 169±5 Bq/kg, respectively. These values lie within the expected range relative to the world average values in soil samples of 30, 35 and 400 Bq/kg, respectively. - Highlights: • This study aimed to establish a baseline for soil radioactivity in Qatar. • The work focused on measurement of NORM levels in 129 samples using HPGe detector. • The mean values lie within the range relative to the world average values. • The Ac of Dukhan soil samples were elevated. • The mean of D, Ra eq , H ex and AEDE had all normal levels of radiation.

  2. Part I. Development of a concept inventory addressing students' beliefs and reasoning difficulties regarding the greenhouse effect, Part II. Distribution of chlorine measured by the Mars Odyssey Gamma Ray Spectrometer

    Keller, John Michael

    chlorine on Mars measured by the Mars Odyssey Gamma Ray Spectrometer (GRS). The distribution of chlorine is heterogeneous across the surface, with a concentration of high chlorine centered over the Medusa Fossae Formation. The distribution of chlorine correlates positively with hydrogen and negatively with silicon and thermal inertia. Four mechanisms (aeolian, volcanic, aqueous, and hydrothermal) are discussed as possible factors influencing the distribution of chlorine measured within the upper few tens of centimeters of the surface.

  3. Cosmic gamma bursts

    Ehstulin, I.V.

    1980-01-01

    A brief consideration is being given to the history of cosmic gamma burst discovery and modern knowledge of their properties. The time dependence of gamma bursts is described and their possible sources are discussed

  4. Gamma ray astronomy

    Broomhead, Laurent.

    1980-01-01

    The nuclear gamma astronomy is presented, in particular the Gamma Ray Observatory, an enormous eight tonnes machine fitted with gamma telescopes, scheduled for launching around 1985. It is thereby hoped to study the natural nuclear reactions which occur when stars explode [fr

  5. Reactor gamma spectrometry: status

    Gold, R.; Kaiser, B.J.

    1979-01-01

    Current work is described for Compton Recoil Gamma-Ray Spectrometry including developments in experimental technique as well as recent reactor spectrometry measurements. The current status of the method is described concerning gamma spectromoetry probe design and response characteristics. Emphasis is given to gamma spectrometry work in US LWR and BR programs. Gamma spectrometry in BR environments are outlined by focussing on start-up plans for the Fast Test Reactor (FTR). Gamma spectrometry results are presented for a LWR pressure vessel mockup in the Poolside Critical Assembly (PCA) at Oak Ridge National Laboratory

  6. GammaWorkshops Proceedings

    Ramebaeck, H.; Straelberg, E.; Klemola, S.; Nielsen, Sven P.; Palsson, S.E.

    2012-01-01

    Due to a sparse interaction during the last years between practioners in gamma ray spectrometry in the Nordic countries, a NKS activity was started in 2009. This GammaSem was focused on seminars relevant to gamma spectrometry. A follow up seminar was held in 2010. As an outcome of these activities it was suggested that the 2011 meeting should be focused on practical issues, e.g. different corrections needed in gamma spectrometric measurements. This three day's meeting, GammaWorkshops, was held in September at Risoe-DTU. Experts on different topics relevant for gamma spectrometric measurements were invited to the GammaWorkshops. The topics included efficiency transfer, true coincidence summing corrections, self-attenuation corrections, measurement of natural radionuclides (natural decay series), combined measurement uncertainty calculations, and detection limits. These topics covered both lectures and practical sessions. The practical sessions included demonstrations of tools for e.g. corrections and calculations of the above meantioned topics. (Author)

  7. Chromosomal differences between acute nonlymphocytic leukemia in patients with prior solid tumors and prior hematologic malignancies. A study of 14 cases with prior breast cancer

    Mamuris, Z.; Dumont, J.; Dutrillaux, B.; Aurias, A.

    1989-01-01

    A cytogenetic study of 14 patients with secondary acute nonlymphocytic leukemia (S-ANLL) with prior treatment for breast cancer is reported. The chromosomes recurrently involved in numerical or structural anomalies are chromosomes 7, 5, 17, and 11, in decreasing order of frequency. The distribution of the anomalies detected in this sample of patients is similar to that observed in published cases with prior breast or other solid tumors, though anomalies of chromosome 11 were not pointed out, but it significantly differs from that of the S-ANLL with prior hematologic malignancies. This difference is principally due to a higher involvement of chromosome 7 in patients with prior hematologic malignancies and of chromosomes 11 and 17 in patients with prior solid tumors. A genetic determinism involving abnormal recessive alleles located on chromosomes 5, 7, 11, and 17 uncovered by deletions of the normal homologs may be a cause of S-ANLL. The difference between patients with prior hematologic malignancies or solid tumors may be explained by different constitutional mutations of recessive genes in the two groups of patients

  8. Identification of subsurface structures using electromagnetic data and shape priors

    Tveit, Svenn, E-mail: svenn.tveit@uni.no [Uni CIPR, Uni Research, Bergen 5020 (Norway); Department of Mathematics, University of Bergen, Bergen 5020 (Norway); Bakr, Shaaban A., E-mail: shaaban.bakr1@gmail.com [Department of Mathematics, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Uni CIPR, Uni Research, Bergen 5020 (Norway); Lien, Martha, E-mail: martha.lien@octio.com [Uni CIPR, Uni Research, Bergen 5020 (Norway); Octio AS, Bøhmergaten 44, Bergen 5057 (Norway); Mannseth, Trond, E-mail: trond.mannseth@uni.no [Uni CIPR, Uni Research, Bergen 5020 (Norway); Department of Mathematics, University of Bergen, Bergen 5020 (Norway)

    2015-03-01

    We consider the inverse problem of identifying large-scale subsurface structures using the controlled source electromagnetic method. To identify structures in the subsurface where the contrast in electric conductivity can be small, regularization is needed to bias the solution towards preserving structural information. We propose to combine two approaches for regularization of the inverse problem. In the first approach we utilize a model-based, reduced, composite representation of the electric conductivity that is highly flexible, even for a moderate number of degrees of freedom. With a low number of parameters, the inverse problem is efficiently solved using a standard, second-order gradient-based optimization algorithm. Further regularization is obtained using structural prior information, available, e.g., from interpreted seismic data. The reduced conductivity representation is suitable for incorporation of structural prior information. Such prior information cannot, however, be accurately modeled with a gaussian distribution. To alleviate this, we incorporate the structural information using shape priors. The shape prior technique requires the choice of kernel function, which is application dependent. We argue for using the conditionally positive definite kernel which is shown to have computational advantages over the commonly applied gaussian kernel for our problem. Numerical experiments on various test cases show that the methodology is able to identify fairly complex subsurface electric conductivity distributions while preserving structural prior information during the inversion.

  9. Gamma camera system

    Miller, D.W.; Gerber, M.S.

    1982-01-01

    The invention provides a composite solid state detector for use in deriving a display, by spatial coordinate information, of the distribution or radiation emanating from a source within a region of interest, comprising several solid state detector components, each having a given surface arranged for exposure to impinging radiation and exhibiting discrete interactions therewith at given spatially definable locations. The surface of each component and the surface disposed opposite and substantially parallel thereto are associated with impedence means configured to provide for each opposed surface outputs for signals relating the given location of the interactions with one spatial coordinate parameter of one select directional sense. The detector components are arranged to provide groupings of adjacently disposed surfaces mutually linearly oriented to exhibit a common directional sense of the spatial coordinate parameter. Means interconnect at least two of the outputs associated with each of the surfaces within a given grouping for collecting the signals deriving therefrom. The invention also provides a camera system for imaging the distribution of a source of gamma radiation situated within a region of interest

  10. The Hankel transform of causal distributions

    Manuel A. Aguirre T.

    2012-03-01

    Full Text Available In this note we evaluate the unidimensional distributional Hankel transform of \\dfrac{x^{\\alpha-1}_{+}}{\\Gamma^{\\alpha}},\\dfrac{x^{\\alpha-1}_{-}}{\\Gamma^{\\alpha}},dfrac{|x|^{\\alpha-1}}{\\Gamma^{\\frac{\\alpha}{2}}},dfrac{|x|^{\\alpha-1}sgn(x}{\\Gamma^{\\frac{\\alpha +1}{2}}} and (x± i0^{\\alpha-1} and then we extend the formulae to certain kinds of n-dimensional distributions calles "causal" and "anti-causal" distributions. We evaluate the distributional Handel transform of \\dfrac{(m^2+P^{\\alpha -1}_{-}}{\\Gamma^{(\\alpha} }, \\dfrac{|m^2+P|^{\\alpha -1}_{-}}{\\Gamma^{(\\frac{\\alpha}{2}}}, \\dfrac{|m^2+P|^{\\alpha -1}sgn(m^2+P}{\\Gamma (\\frac{\\alpha +1}{2 }} and (m^2+P±i0^{\\alpha-1}

  11. The Dependence of Cirrus Gamma Size Distributions Expressed as Volumes in N(sub 0)-Lambda-Mu Phase Space and Bulk Cloud Properties on Environmental Conditions: Results from the Small Ice Particles in Cirrus Experiment (SPARTICUS)

    Jackson, Robert C.; McFarquhar, Greg M.; Fridlind, Ann M.; Atlas, Rachel

    2015-01-01

    The variability of cirrus ice microphysical properties is investigated using observations obtained during the Small Particles in Cirrus (SPARTICUS) campaign. An existing approach that represents a size distribution (SD) as a single gamma function using an ellipsoid of equally realizable solutions in (N(sub 0), lambda, mu) phase space is modified to automatically identify multiple modes in SDs and characterize each mode by such an ellipsoid. The modified approach is applied to ice crystals with maximum dimension D greater than15 micrometers collected by the 2-D stereo and 2-D precipitation probes on the Stratton Park Engineering Company Learjet. The dependencies of N(sub 0), mu, and lambda from each mode, total number concentration, bulk extinction, ice water content (IWC), and mass median maximum dimension D(sub mm) as a function of temperature T and cirrus type are then analyzed. The changes in the observed codependencies between N(sub 0), mu, and lambda, bulk extinction, IWC, and D(sub mm) with environmental conditions indicate that particles were larger at higher T during SPARTICUS. At most two modes were observed in any SD during SPARTICUS, with the average boundary between them at 115 micrometers, similar to past studies not using probes with shatter mitigating tips and artifact removal algorithms. The bimodality of the SDs increased with T. This and the differences in N(sub 0), mu, and lambda between the modes suggest that particles with smaller D nucleated more recently than particles with larger D, which grew via vapor deposition and aggregation. Because smaller crystals, whose concentrations are uncertain, make marginal contributions to higher order moments, the use of higher moments for evaluating model fields is suggested.

  12. On Bayesian reliability analysis with informative priors and censoring

    Coolen, F.P.A.

    1996-01-01

    In the statistical literature many methods have been presented to deal with censored observations, both within the Bayesian and non-Bayesian frameworks, and such methods have been successfully applied to, e.g., reliability problems. Also, in reliability theory it is often emphasized that, through shortage of statistical data and possibilities for experiments, one often needs to rely heavily on judgements of engineers, or other experts, for which means Bayesian methods are attractive. It is therefore important that such judgements can be elicited easily to provide informative prior distributions that reflect the knowledge of the engineers well. In this paper we focus on this aspect, especially on the situation that the judgements of the consulted engineers are based on experiences in environments where censoring has also been present previously. We suggest the use of the attractive interpretation of hyperparameters of conjugate prior distributions when these are available for assumed parametric models for lifetimes, and we show how one may go beyond the standard conjugate priors, using similar interpretations of hyper-parameters, to enable easier elicitation when censoring has been present in the past. This may even lead to more flexibility for modelling prior knowledge than when using standard conjugate priors, whereas the disadvantage of more complicated calculations that may be needed to determine posterior distributions play a minor role due to the advanced mathematical and statistical software that is widely available these days

  13. Form of prior for constrained thermodynamic processes with uncertainty

    Aneja, Preety; Johal, Ramandeep S.

    2015-05-01

    We consider the quasi-static thermodynamic processes with constraints, but with additional uncertainty about the control parameters. Motivated by inductive reasoning, we assign prior distribution that provides a rational guess about likely values of the uncertain parameters. The priors are derived explicitly for both the entropy-conserving and the energy-conserving processes. The proposed form is useful when the constraint equation cannot be treated analytically. The inference is performed using spin-1/2 systems as models for heat reservoirs. Analytical results are derived in the high-temperatures limit. An agreement beyond linear response is found between the estimates of thermal quantities and their optimal values obtained from extremum principles. We also seek an intuitive interpretation for the prior and the estimated value of temperature obtained therefrom. We find that the prior over temperature becomes uniform over the quantity kept conserved in the process.

  14. Gamma-rays from decaying dark matter

    Bertone, G. [Paris-6 Univ., 75 (France). Inst. d' Astrophysique; Buchmueller, W.; Covi, L.; Ibarra, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2007-10-15

    We study the prospects for detecting gamma-rays from decaying Dark Matter (DM), focusing in particular on gravitino DM in R-parity breaking vacua. Given the substantially different angular distribution of the predicted gamma-ray signal with respect to the case of annihilating DM, and the relatively poor (of order 0.1 ) angular resolution of gamma-ray detectors, the best strategy for detection is in this case to look for an exotic contribution to the gamma-ray flux at high galactic latitudes, where the decaying DM contribution would resemble an astrophysical extragalactic component, similar to the one inferred by EGRET observations. Upcoming experiments such as GLAST and AMS-02 may identify this exotic contribution and discriminate it from astrophysical sources, or place significant constraints on the mass and lifetime of DM particles. (orig.)

  15. Galactic structure and gamma radiation

    Casse, Michel; Cesarsky, Catherine; Paul Jacques

    1977-01-01

    A model of spiral structure of the Galaxy is outlined from radiosynchrotron and gamma observations. The most interesting observations in the galactic context, obtained by the SAS II American satellite are concerned with the distribution of the γ photoemission at energies higher than 10 8 eV, along the galactic equator. The model proposed is in quantitative agreement with the present ideas on the spiral structure of the Galaxy, the galactic magnetic field, and the confinement of cosmic rays by the magnetic field and of the magnetic field by matter. Following the American era, the European COS-B satellite opens the European phase towards an identification of the discrete gamma radiation sources [fr

  16. Learning priors for Bayesian computations in the nervous system.

    Max Berniker

    Full Text Available Our nervous system continuously combines new information from our senses with information it has acquired throughout life. Numerous studies have found that human subjects manage this by integrating their observations with their previous experience (priors in a way that is close to the statistical optimum. However, little is known about the way the nervous system acquires or learns priors. Here we present results from experiments where the underlying distribution of target locations in an estimation task was switched, manipulating the prior subjects should use. Our experimental design allowed us to measure a subject's evolving prior while they learned. We confirm that through extensive practice subjects learn the correct prior for the task. We found that subjects can rapidly learn the mean of a new prior while the variance is learned more slowly and with a variable learning rate. In addition, we found that a Bayesian inference model could predict the time course of the observed learning while offering an intuitive explanation for the findings. The evidence suggests the nervous system continuously updates its priors to enable efficient behavior.

  17. Multiplicity and correlated energy of gamma rays emitted in the spontaneous fission of Californium-252

    Brunson, G.S. Jr.

    1982-06-01

    An array of eight high-speed plastic scintillation detectors has been used to infer a mathematical model for the emission multipliciy of prompt gammas in the spontaneous fission of 252 Cf. Exceptional time resolution and coincidence capability permitted the separation of gammas from fast neutrons over a flight path of approximately 10 cm. About 20 different distribution models were tested. The average energy of the prompt gammas is inversely related to the number emitted; however, this inverse relationship is not strong and the total gamma energy does increase with increasing gamma number. An extension of the experiment incorporated a lithium-drifted germanium gamma spectrometer that resolved nearly 100 discrete gammas associated with fission. Of these gammas, some were preferentially associated with fission in which few gammas were emitted. Certain others were more frequent when many gammas were emitted. Results are presented

  18. Possible galactic origin of. gamma. -ray bursts

    Manchanda, R K; Ramsden, D [Southampton Univ. (UK). Dept. of Physics

    1977-03-31

    It is stated that extragalactic models for the origin of non-solar ..gamma..-ray bursts include supernova bursts in remote galaxies, and the collapse of the cores of active stars, whilst galactic models are based on flare stars, thermonuclear explosions in neutron stars and the sudden accretion of cometary gas on to neutron stars. The acceptability of any of these models may be tested by the observed size spectrum of the ..gamma..-ray bursts. The extragalactic models predict a power law spectrum with number index -1.5, whilst for the galactic models the number index will be -1. Experimental data on ..gamma..-ray bursts is, however, still meagre, and so far only 44 confirmed events have been recorded by satellite-borne instruments. The number spectrum of the observed ..gamma..-ray bursts indicates that the observed distribution for events with an energy < 10/sup -4/ erg/cm/sup 2/ is flat; this makes the choice of any model completely arbitrary. An analysis of the observed ..gamma..-ray events is here presented that suggests very interesting possibilities for their origin. There appears to be a preferred mean energy for ..gamma..-ray bursts; some 90% of the recorded events show a mean energy between 5 x 10/sup -5/ and 5 x 10/sup -4/ erg/cm/sup 2/, contrary to the predicted characteristics of the number spectrum of various models. A remarkable similarity is found between the distribution of ..gamma..-ray bursts and that of supernova remnants, suggesting a genetic relationship between the two and the galactic origin of the ..gamma..-ray bursts, and the burst source could be identified with completely run down neutron stars, formed during supernova explosions.

  19. Bayesian genomic selection: the effect of haplotype lenghts and priors

    Villumsen, Trine Michelle; Janss, Luc

    2009-01-01

    Breeding values for animals with marker data are estimated using a genomic selection approach where data is analyzed using Bayesian multi-marker association models. Fourteen model scenarios with varying haplotype lengths, hyper parameter and prior distributions were compared to find the scenario ...

  20. Bayesian nonparametric system reliability using sets of priors

    Walter, G.M.; Aslett, L.J.M.; Coolen, F.P.A.

    2016-01-01

    An imprecise Bayesian nonparametric approach to system reliability with multiple types of components is developed. This allows modelling partial or imperfect prior knowledge on component failure distributions in a flexible way through bounds on the functioning probability. Given component level test

  1. Investigation of {sup 136} Ba gamma-Transitions in the (n,n` gamma) Reaction

    Sergiwa, S M [University of Garyuonis, Benghazi, (Libyan Arab Jamahiriya); Rateb, G M; Zleetni, S M; dufani, M M; Shermit, A M; Al Hamidi, M M [Tajoura Nuclear Research Center, Tripoli, (Libyan Arab Jamahiriya); El-Ahrash, M S [7th of April University, Zawia, (Libyan Arab Jamahiriya)

    1995-10-01

    Using the reactor fast neutron beam, angular distribution and linear polarization of gamma-rays emitted from the {sup 136} Ba (n,n` gamma) reaction were measured. From these measurements, a decay scheme of {sup 1}36{sup B}a has been constructed. New spin and parity (J{pi}) assignments as well as resolving ambiguities in previous assignments for some levels were done. In addition, multipole mixing rations ({delta} - values, important for model comparison) have been unambiguously determined for many gamma-transitions. 1 fig., 2 tabs.

  2. Gamma Splines and Wavelets

    Hannu Olkkonen

    2013-01-01

    Full Text Available In this work we introduce a new family of splines termed as gamma splines for continuous signal approximation and multiresolution analysis. The gamma splines are born by -times convolution of the exponential by itself. We study the properties of the discrete gamma splines in signal interpolation and approximation. We prove that the gamma splines obey the two-scale equation based on the polyphase decomposition. to introduce the shift invariant gamma spline wavelet transform for tree structured subscale analysis of asymmetric signal waveforms and for systems with asymmetric impulse response. Especially we consider the applications in biomedical signal analysis (EEG, ECG, and EMG. Finally, we discuss the suitability of the gamma spline signal processing in embedded VLSI environment.

  3. Gamma ray bursts: Current status of observations and theory

    Meegan, C.A.

    1990-04-01

    Gamma ray bursts display a wide range of temporal and spectral characteristics, but typically last several seconds and emit most of their energy in a low energy, gamma ray region. The burst sources appear to be isotropically distributed on the sky. Several lines of evidence suggest magnetic neutron stars as sources for bursts. A variety of energy sources and emission mechanisms are proposed

  4. Structure and content of the galaxy and galactic gamma rays

    1976-01-01

    The conference included papers on ..gamma..-ray pulsars, galactic diffuse flux and surveys, radio surveys of external galaxies, galactic distribution of pulsars, and galactic gamma emission. Galactic structure drawing on all branches of galactic astronomy is discussed. New and unpublished material is included. (JFP)

  5. A new approach to the evaluation of peripheral vascular disease using the gamma camera

    Gerritsen, H.A.M.

    1976-01-01

    To estimate the degree of impaired perfusion in legs, and the extent of improvement after treatment, a functional test was developed using a gamma camera to follow the perfusion of intravenously injected sup(99m)Tc-pertechnetate. An analysis is given of normal and pathologic curve patterns. The influence of the severity of occlusive arterial disease on the arrival and distribution of radioactivity in the leg is demonstrated. After vascular surgery, changes in the curve pattern and the imaging of activity distribution reflected the function of the inserted bypass grafts. The test proved to be useful in the differentiation between patients with false claudication complaints due to non-arterial disease and patients with true claudication. It is concluded that the technique presented in this thesis can serve as a useful, non-invasive, screening test prior to arteriography and as a functional assessment of vascular reconstruction

  6. Bayesian Estimation of the Scale Parameter of Inverse Weibull Distribution under the Asymmetric Loss Functions

    Farhad Yahgmaei

    2013-01-01

    Full Text Available This paper proposes different methods of estimating the scale parameter in the inverse Weibull distribution (IWD. Specifically, the maximum likelihood estimator of the scale parameter in IWD is introduced. We then derived the Bayes estimators for the scale parameter in IWD by considering quasi, gamma, and uniform priors distributions under the square error, entropy, and precautionary loss functions. Finally, the different proposed estimators have been compared by the extensive simulation studies in corresponding the mean square errors and the evolution of risk functions.

  7. Gamma ray astronomy

    Fichtel, C.E.

    1975-01-01

    The first certain detection of celestial high energy gamma rays came from a satellite experiment flown on the third Orbiting Solar Observatory (OSO-111). A Gamma ray spark chamber telescope with substantively greater sensitivity and angular resolution (a few degrees) flown on the second Small Astronomy Satellite (SAS-II) has now provided a better picture of the gamma ray sky, and particularly the galactic plane and pulsars. This paper will summarize the present picture of gamma ray astronomy as it has developed at this conference from measurements made with experiments carried out on balloons, those remaining on the ground, and ones flown on satellites. (orig.) [de

  8. Gamma sensitivity of the Eberline PCM-1

    Blanton, J.D.

    1988-01-01

    This paper reports that normally, alarm setpoints for the Eberline PCM-1 series personnel contamination monitors are calculated based upon efficiencies measured using 100-cm 2 or larger beta or mixed beta-gamma sources. This simulates the type of contamination most frequently encountered on personnel and clothing--low-level, distributed beta-gamma emitters. In most circumstances, the PCM-1's sensitivity to the other type of contamination encountered in nuclear plant work--hot particles--would be expected to be the same as, or better than, its sensitivity to distributed contamination. However, particles that are deposited on skin or clothing can be partially shielded from the view of the PCM-1's detectors. In these situations, the PCm-1's sensitivity to gamma radiation may be more relevant than its sensitivity to betas

  9. New Riemannian Priors on the Univariate Normal Model

    Salem Said

    2014-07-01

    Full Text Available The current paper introduces new prior distributions on the univariate normal model, with the aim of applying them to the classification of univariate normal populations. These new prior distributions are entirely based on the Riemannian geometry of the univariate normal model, so that they can be thought of as “Riemannian priors”. Precisely, if {pθ ; θ ∈ Θ} is any parametrization of the univariate normal model, the paper considers prior distributions G( θ - , γ with hyperparameters θ - ∈ Θ and γ > 0, whose density with respect to Riemannian volume is proportional to exp(−d2(θ, θ - /2γ2, where d2(θ, θ - is the square of Rao’s Riemannian distance. The distributions G( θ - , γ are termed Gaussian distributions on the univariate normal model. The motivation for considering a distribution G( θ - , γ is that this distribution gives a geometric representation of a class or cluster of univariate normal populations. Indeed, G( θ - , γ has a unique mode θ - (precisely, θ - is the unique Riemannian center of mass of G( θ - , γ, as shown in the paper, and its dispersion away from θ - is given by γ.  Therefore, one thinks of members of the class represented by G( θ - , γ as being centered around θ - and  lying within a typical  distance determined by γ. The paper defines rigorously the Gaussian distributions G( θ - , γ and describes an algorithm for computing maximum likelihood estimates of their hyperparameters. Based on this algorithm and on the Laplace approximation, it describes how the distributions G( θ - , γ can be used as prior distributions for Bayesian classification of large univariate normal populations. In a concrete application to texture image classification, it is shown that  this  leads  to  an  improvement  in  performance  over  the  use  of  conjugate  priors.

  10. Divergent Priors and well Behaved Bayes Factors

    R.W. Strachan (Rodney); H.K. van Dijk (Herman)

    2011-01-01

    textabstractDivergent priors are improper when defined on unbounded supports. Bartlett's paradox has been taken to imply that using improper priors results in ill-defined Bayes factors, preventing model comparison by posterior probabilities. However many improper priors have attractive properties

  11. Application of conventional laser technology to gamma-gamma colliders

    Clayton, C.E.; Kurnit, N.A.; Meyerhofer, D.D.

    1995-01-01

    A future e - e + (electron-positron) linear collider can be configured with perhaps minimal modification to serve as an γ-γ (gamma-gamma) or a e - -γ collider. This is accomplished by Compton-backscattering low energy photons (from a laser source) off of the high-energy electron beams prior to the crossing of the electron beams. However, to be competitive with the e - e + configuration, the luminosity cannot be compromised in the process. This requires that the laser source deliver a sufficient number of photons per pulse with a pulse format and rate matching that of the electron beams. As it turns out, this requires an average optical power of 5 to 15 kW from the laser which is beyond the current state of the art. In this paper, the authors address how to generate the required pulse format and how the high average power requirement can be met with conventional laser technology. They also address concerns about the survivability of mirrors located near the interaction point. Finally, they list a program of research and development which addresses some of the unknowns in such a system

  12. Neutrino mass priors for cosmology from random matrices

    Long, Andrew J.; Raveri, Marco; Hu, Wayne; Dodelson, Scott

    2018-02-01

    Cosmological measurements of structure are placing increasingly strong constraints on the sum of the neutrino masses, Σ mν, through Bayesian inference. Because these constraints depend on the choice for the prior probability π (Σ mν), we argue that this prior should be motivated by fundamental physical principles rather than the ad hoc choices that are common in the literature. The first step in this direction is to specify the prior directly at the level of the neutrino mass matrix Mν, since this is the parameter appearing in the Lagrangian of the particle physics theory. Thus by specifying a probability distribution over Mν, and by including the known squared mass splittings, we predict a theoretical probability distribution over Σ mν that we interpret as a Bayesian prior probability π (Σ mν). Assuming a basis-invariant probability distribution on Mν, also known as the anarchy hypothesis, we find that π (Σ mν) peaks close to the smallest Σ mν allowed by the measured mass splittings, roughly 0.06 eV (0.1 eV) for normal (inverted) ordering, due to the phenomenon of eigenvalue repulsion in random matrices. We consider three models for neutrino mass generation: Dirac, Majorana, and Majorana via the seesaw mechanism; differences in the predicted priors π (Σ mν) allow for the possibility of having indications about the physical origin of neutrino masses once sufficient experimental sensitivity is achieved. We present fitting functions for π (Σ mν), which provide a simple means for applying these priors to cosmological constraints on the neutrino masses or marginalizing over their impact on other cosmological parameters.

  13. Incorporating prior knowledge induced from stochastic differential equations in the classification of stochastic observations.

    Zollanvari, Amin; Dougherty, Edward R

    2016-12-01

    In classification, prior knowledge is incorporated in a Bayesian framework by assuming that the feature-label distribution belongs to an uncertainty class of feature-label distributions governed by a prior distribution. A posterior distribution is then derived from the prior and the sample data. An optimal Bayesian classifier (OBC) minimizes the expected misclassification error relative to the posterior distribution. From an application perspective, prior construction is critical. The prior distribution is formed by mapping a set of mathematical relations among the features and labels, the prior knowledge, into a distribution governing the probability mass across the uncertainty class. In this paper, we consider prior knowledge in the form of stochastic differential equations (SDEs). We consider a vector SDE in integral form involving a drift vector and dispersion matrix. Having constructed the prior, we develop the optimal Bayesian classifier between two models and examine, via synthetic experiments, the effects of uncertainty in the drift vector and dispersion matrix. We apply the theory to a set of SDEs for the purpose of differentiating the evolutionary history between two species.

  14. Drilling azimuth gamma embedded design

    Zhou Yi Ren

    2016-01-01

    Full Text Available Embedded drilling azimuth gamma design, the use of radioactive measuring principle embedded gamma measurement while drilling a short section analysis. Monte Carlo method, in response to the density of horizontal well logging numerical simulation of 16 orientation, the orientation of horizontal well analysed, calliper, bed boundary location, space, different formation density, formation thickness, and other factors inclined strata dip the impact by simulating 137Cs sources under different formation conditions of the gamma distribution, to determine the orientation of drilling density tool can detect window size and space, draw depth of the logging methods. The data 360° azimuth imaging, image processing method to obtain graph, display density of the formation, dip and strata thickness and other parameters, the logging methods obtain real-time geo-steering. To establish a theoretical basis for the orientation density logging while drilling method implementation and application of numerical simulation in-depth study of the MWD azimuth and density log response factors of horizontal wells.

  15. Iterated random walks with shape prior

    Pujadas, Esmeralda Ruiz; Kjer, Hans Martin; Piella, Gemma

    2016-01-01

    the parametric probability density function. Then, random walks is performed iteratively aligning the prior with the current segmentation in every iteration. We tested the proposed approach with natural and medical images and compared it with the latest techniques with random walks and shape priors......We propose a new framework for image segmentation using random walks where a distance shape prior is combined with a region term. The shape prior is weighted by a confidence map to reduce the influence of the prior in high gradient areas and the region term is computed with k-means to estimate....... The experiments suggest that this method gives promising results for medical and natural images....

  16. Thermodynamics and long-range order of nitrogen in gamma'-Fe4N1-x

    Kooi, BJ; Somers, MAJ; Mittemeijer, EJ

    Models are given for the description of the chemical potential of nitrogen in gamma'-Fe4N1-x. In previous work, gamma'-Fe4N1-x was treated as a (sub)regular solution, thereby assuming that the N atoms are distributed randomly on the sites of their own sublattice. However, in gamma'-Fe4N1-x,

  17. Higher-order multipole amplitude measurement in psi ' -> gamma chi(c2)

    Ablikim, M.; Achasov, M. N.; Alberto, D.; An, F. F.; An, Q.; An, Z. H.; Bai, J. Z.; Baldini, R.; Ban, Y.; Becker, J.; Berger, N.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Calcaterra, A. C.; Cao, G. F.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, Y.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denysenko, I.; Destefanis, M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Han, Y. L.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, B.; Huang, G. M.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jia, L. K.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Kuehn, W.; Lai, W.; Lange, J. S.; Leung, J. K. C.; Li, C. H.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, Lei; Li, N. B.; Li, Q. J.; Li, S. L.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, X. T.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H.; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K.; Liu, K. Y.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. H.; Liu, Y. B.; Liu, Y. W.; Liu, Yong; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X.; Ma, X. Y.; Maggiora, M.; Malik, Q. A.; Mao, H.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Muchnoi, N. Yu; Nefedov, Y.; Nikolaev, I. B.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Park, J. W.; Pelizaeus, M.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pun, C. S. J.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. D.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tian, H. L.; Toth, D.; Varner, G. S.; Wang, B.; Wang, B. Q.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, Q. J.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Q. J.; Xu, X. P.; Xu, Y.; Xu, Z. R.; Xu, Z. Z.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, T.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, S. P.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, S. H.; Zhang, T. R.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. S.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhao, Z. L.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zheng, Z. P.; Zhong, B.; Zhong, J.; Zhong, L.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, X. W.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Zuo, J. X.

    2011-01-01

    Using 106 x 10(6) psi' events collected with the BESIII detector at the BEPCII storage ring, the higher-order multipole amplitudes in the radiative transition psi' -> gamma chi(c2) -> gamma pi(+)pi(-)/gamma K+K- are measured. A fit to the chi(c2) production and decay angular distributions yields M2

  18. Neutron gamma competition in fast fission

    Frehaut, J.

    1989-01-01

    In the present paper we analyse the data we have obtained on the distribution of the gamma-ray energy per fission, as well as on the average energy E-barγ released per fission for the neutron induced fission of several isotopes, in the energy range up to 15 MeV. 6 refs, 9 figs

  19. Synthesis of graphene using gamma radiations

    Considering the advantages of radiolytic synthesis such as the absence of toxic chemical as a reducing agent, uniform distribution of reducing agent and high purity of product, the synthesis of graphene (rGO) from graphene oxide (GO) by the gamma irradiation technique using a relatively low dose rate of 0.24 kGy h−1 has ...

  20. Prior knowledge processing for initial state of Kalman filter

    Suzdaleva, Evgenia

    2010-01-01

    Roč. 24, č. 3 (2010), s. 188-202 ISSN 0890-6327 R&D Projects: GA ČR(CZ) GP201/06/P434 Institutional research plan: CEZ:AV0Z10750506 Keywords : Kalman filtering * prior knowledge * state-space model * initial state distribution Subject RIV: BC - Control Systems Theory Impact factor: 0.729, year: 2010 http://library.utia.cas.cz/separaty/2009/AS/suzdaleva-prior knowledge processing for initial state of kalman filter.pdf

  1. Inactivation of rabies diagnostic reagents by gamma radiation

    Gamble, W.C.; Chappell, W.A.; George, E.H.

    1980-01-01

    Treatment of CVS-11 rabies adsorbing suspensions and street rabies infected mouse brains with gamma radiation resulted in inactivated reagents that are safer to distribute and use. These irradiated reagents were as sensitive and reactive as the nonirradiated control reagents

  2. Gamma tomography apparatus

    Span, F.J.

    1988-01-01

    The patent concerns a gamma tomography apparatus for medical diagnosis. The apparatus comprises a gamma scintillation camera head and a suspension system for supporting and positioning the camera head with respect for the patient. Both total body scanning and single photon emission tomography can be carried out with the apparatus. (U.K.)

  3. Gamma-sterilization

    Lindgren, E.

    1974-01-01

    The author makes a survey of his experience in sterilization and sterility control of medical products. At present three different methods are used, steamsterilization, gassterilizing and gammasterilizing. The investments and costs for gamma radiation is presented and a comparison of the costs for gamma- and gassterilization including sterility control is made. (M.S.)

  4. Gamma-ray sources

    Hermsen, W.

    1980-01-01

    Results are presented from an analysis of the celestial gamma-ray fine-scale structure based on over half of the data which may ultimately be available from the COS-B satellite. A catalogue consisting of 25 gamma-ray sources measured at energies above 100 MeV is presented. (Auth.)

  5. Gamma ray astronomy

    Hillier, R.

    1984-01-01

    The book reviews the development of gamma ray astronomy over the past twenty five years. A large section of the book is devoted to the problems of background radiation and the design of detectors. Gamma rays from the sun, the galactic disc, the galaxy, and extra galactic sources; are also discussed. (U.K.)

  6. Gamma spectroscopy in water cooled reactors

    Persault, M.

    1977-10-01

    Gamma spectroscopy analysis of spent fuels in power reactors; study of two typical cases: determination of the power distribution by the mean of the activity of a low periodic element (Lanthanum 140) and determination of the burnup absolute rate by examining the ratio of Cesium 134 and Cesium 137 activities. Measures were realized on fuel solutions and on fuel assemblies. Development of a power distribution map of the assemblies and comparison with the results of a three dimensional calculation of core evolution [fr

  7. Gamma motes for detection of radioactive materials in shipping containers

    Harold McHugh; William Quam; Stephan Weeks; Brendan Sever

    2007-01-01

    Shipping containers can be effectively monitored for radiological materials using gamma (and neutron) motes in distributed mesh networks. The mote platform is ideal for collecting data for integration into operational management systems required for efficiently and transparently monitoring international trade. Significant reductions in size and power requirements have been achieved for room-temperature cadmium zinc telluride (CZT) gamma detectors. Miniaturization of radio modules and microcontroller units are paving the way for low-power, deeply-embedded, wireless sensor distributed mesh networks

  8. Comparison of the effects of gamma irradiation and steam sterilization on Southern pine sapwood

    Simon Curling; Jerrold E. Winandy

    2008-01-01

    Gamma irradiation is a commonly used method of sterilization of wood specimens prior to decay testing. As part of a larger series of studies, an investigation was made into the effects of gamma irradiation on flexural bending strength properties and its corresponding relationship to changes in lignin and hemicellulosic contents of wood after exposure to various dose...

  9. Fitting and Analyzing Randomly Censored Geometric Extreme Exponential Distribution

    Muhammad Yameen Danish

    2016-06-01

    Full Text Available The paper presents the Bayesian analysis of two-parameter geometric extreme exponential distribution with randomly censored data. The continuous conjugate prior of the scale and shape parameters of the model does not exist while computing the Bayes estimates, it is assumed that the scale and shape parameters have independent gamma priors. It is seen that the closed-form expressions for the Bayes estimators are not possible; we suggest the Lindley’s approximation to obtain the Bayes estimates. However, the Bayesian credible intervals cannot be constructed while using this method, we propose Gibbs sampling to obtain the Bayes estimates and also to construct the Bayesian credible intervals. Monte Carlo simulation study is carried out to observe the behavior of the Bayes estimators and also to compare with the maximum likelihood estimators. One real data analysis is performed for illustration.

  10. Maximum Likelihood Estimates of Parameters in Various Types of Distribution Fitted to Important Data Cases.

    HIROSE,Hideo

    1998-01-01

    TYPES OF THE DISTRIBUTION:13;Normal distribution (2-parameter)13;Uniform distribution (2-parameter)13;Exponential distribution ( 2-parameter)13;Weibull distribution (2-parameter)13;Gumbel Distribution (2-parameter)13;Weibull/Frechet Distribution (3-parameter)13;Generalized extreme-value distribution (3-parameter)13;Gamma distribution (3-parameter)13;Extended Gamma distribution (3-parameter)13;Log-normal distribution (3-parameter)13;Extended Log-normal distribution (3-parameter)13;Generalized ...

  11. Cumulative Poisson Distribution Program

    Bowerman, Paul N.; Scheuer, Ernest M.; Nolty, Robert

    1990-01-01

    Overflow and underflow in sums prevented. Cumulative Poisson Distribution Program, CUMPOIS, one of two computer programs that make calculations involving cumulative Poisson distributions. Both programs, CUMPOIS (NPO-17714) and NEWTPOIS (NPO-17715), used independently of one another. CUMPOIS determines cumulative Poisson distribution, used to evaluate cumulative distribution function (cdf) for gamma distributions with integer shape parameters and cdf for X (sup2) distributions with even degrees of freedom. Used by statisticians and others concerned with probabilities of independent events occurring over specific units of time, area, or volume. Written in C.

  12. Migration patterns of dendritic cells in the rat: comparison of the effects of gamma and UV-B irradiation on the migration of dendritic cells and lymphocytes

    Oluwole, S.F.; Engelstad, K.; De Rosa, C.; Wang, T.S.; Fawwaz, R.A.; Reemtsma, K.; Hardy, M.A. (Columbia Univ., New York, NY (USA))

    1991-04-01

    To further define the underlying mechanisms of immune suppression induced by UV-B irradiation, we have examined the kinetics of homing patterns of in vitro UV-B-irradiated and gamma-irradiated-thoracic duct lymphocytes (TDL) compared to dendritic cells (DC). Our findings show that {sup 111}In-oxine-labeled TDL specifically home to the spleen, liver, lymph nodes, and bone marrow with subsequent recirculation of a large number of cells from the spleen to lymph nodes. In contrast, DC preferentially migrate to the spleen and liver with a relatively insignificant distribution to lymph nodes and an absence of subsequent recirculation. Splenectomy prior to cell injection significantly diverts the spleen-seeking DC to the liver but not to the lymph nodes, while the homing of TDL to lymph nodes is significantly increased. In vitro exposure of 111In-oxine labeled TDL to gamma irradiation does not significantly impair immediate homing to lymphoid tissues but inhibits cell recirculation between 3 and 24 hr. In contrast, gamma irradiation does not affect the tissue distribution of labeled DC, suggesting that DC are more radioresistant to gamma irradiation than TDL. Unlike the findings in animals injected with gamma-irradiated cells, UV-B irradiation virtually abolished the homing of TDL to lymph nodes and significantly reduced the homing of the spleen-seeking DC to the splenic compartment while a large number of cells were sequestered in the liver. The results of in vitro cell binding assay show that TDL, unlike DC, have the capacity to bind to high endothelial venules (HEV) within lymph node frozen sections while gamma and UV-B irradiation significantly inhibit the binding of TDL to lymph node HEV.

  13. Inverse problems with non-trivial priors: efficient solution through sequential Gibbs sampling

    Hansen, Thomas Mejer; Cordua, Knud Skou; Mosegaard, Klaus

    2012-01-01

    Markov chain Monte Carlo methods such as the Gibbs sampler and the Metropolis algorithm can be used to sample solutions to non-linear inverse problems. In principle, these methods allow incorporation of prior information of arbitrary complexity. If an analytical closed form description of the prior...... is available, which is the case when the prior can be described by a multidimensional Gaussian distribution, such prior information can easily be considered. In reality, prior information is often more complex than can be described by the Gaussian model, and no closed form expression of the prior can be given....... We propose an algorithm, called sequential Gibbs sampling, allowing the Metropolis algorithm to efficiently incorporate complex priors into the solution of an inverse problem, also for the case where no closed form description of the prior exists. First, we lay out the theoretical background...

  14. On the maximum and minimum of two modified Gamma-Gamma variates with applications

    Al-Quwaiee, Hessa

    2014-04-01

    In this work, we derive the statistical characteristics of the maximum and the minimum of two modified1 Gamma-Gamma variates in closed-form in terms of Meijer\\'s G-function and the extended generalized bivariate Meijer\\'s G-function. Then, we rely on these new results to present the performance analysis of (i) a dual-branch free-space optical selection combining diversity undergoing independent but not necessarily identically distributed Gamma-Gamma fading under the impact of pointing errors and of (ii) a dual-hop free-space optical relay transmission system. Computer-based Monte-Carlo simulations verify our new analytical results.

  15. GammaWorkshops Proceedings

    Ramebaeck, H. (ed.) (Swedish Defence Research Agency (Sweden)); Straalberg, E. (Institute for Energy Technology, Kjeller (Norway)); Klemola, S. (Radiation and Nuclear Safety Authority, STUK (Finland)); Nielsen, Sven P. (Technical Univ. of Denmark. Risoe National Lab. for Sustainable Energy, Roskilde (Denmark)); Palsson, S.E. (Icelandic Radiation Safety Authority (Iceland))

    2012-01-15

    Due to a sparse interaction during the last years between practioners in gamma ray spectrometry in the Nordic countries, a NKS activity was started in 2009. This GammaSem was focused on seminars relevant to gamma spectrometry. A follow up seminar was held in 2010. As an outcome of these activities it was suggested that the 2011 meeting should be focused on practical issues, e.g. different corrections needed in gamma spectrometric measurements. This three day's meeting, GammaWorkshops, was held in September at Risoe-DTU. Experts on different topics relevant for gamma spectrometric measurements were invited to the GammaWorkshops. The topics included efficiency transfer, true coincidence summing corrections, self-attenuation corrections, measurement of natural radionuclides (natural decay series), combined measurement uncertainty calculations, and detection limits. These topics covered both lectures and practical sessions. The practical sessions included demonstrations of tools for e.g. corrections and calculations of the above meantioned topics. (Author)

  16. The gamma function

    Artin, Emil

    2015-01-01

    This brief monograph on the gamma function was designed by the author to fill what he perceived as a gap in the literature of mathematics, which often treated the gamma function in a manner he described as both sketchy and overly complicated. Author Emil Artin, one of the twentieth century's leading mathematicians, wrote in his Preface to this book, ""I feel that this monograph will help to show that the gamma function can be thought of as one of the elementary functions, and that all of its basic properties can be established using elementary methods of the calculus."" Generations of teachers

  17. Basics of Gamma Ray Detection

    Stinnett, Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Venkataraman, Ram [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-13

    The objective of this training is to explain the origin of x-rays and gamma rays, gamma ray interactions with matter, detectors and electronics used in gamma ray-spectrometry, and features of a gamma-ray spectrum for nuclear material that is safeguarded.

  18. Analysis of Extracting Prior BRDF from MODIS BRDF Data

    Hu Zhang; Ziti Jiao; Yadong Dong; Peng Du; Yang Li; Yi Lian; Tiejun Cui

    2016-01-01

    Many previous studies have attempted to extract prior reflectance anisotropy knowledge from the historical MODIS Bidirectional Reflectance Distribution Function (BRDF) product based on land cover or Normalized Difference Vegetation Index (NDVI) data. In this study, the feasibility of the method is discussed based on MODIS data and archetypal BRDFs. The BRDF is simplified into six archetypal BRDFs that represent different reflectance anisotropies. Five-year time series of MODIS BRDF data over ...

  19. Dosimetry for terrestrial gamma-ray sources

    Abdullah, S.A.; Dickson, H.W.; Kerr, G.D.; Miah, M.F.K.; Perdue, P.T.

    1975-01-01

    Dose rates from natural radionuclides and 137 Cs in soils of the Oak Ridge area have been determined from in situ and core sample measurements. Information on soil composition, density, and moisture content and on the distribution of cesium in the soil was obtained from the core samples. Measurements of radionuclide concentrations in the samples were made with a 4 x 4 in. NaI detector. Gamma-ray spectroscopy using a lithium-drifted germanium (GeLi) detector has been applied to the determination of radionuclide concentrations in soil and the associated gamma dose rates above the earth plane. An unshielded GeLi detector placed about 1 m above the earth detects gamma radiation from an area of about 100 m 2 . The equipment and data processing procedure are briefly described

  20. Environmental gamma radiation measurements in Bangladeshi houses

    Idrish Miah, M.

    2002-01-01

    The indoor gamma dose rate in air measured using TLDs in the Dhaka district is not wide ranging and follows a normal distribution with an arithmetic mean of 1.54±0.26 mGy.y -1 . The result has been compared with those found by other investigators for different locations of the world. Measurements were made on a monthly basis for a year period, and a sinusoidal variation of monthly indoor gamma radiation of the type: d = 160 + 65 cos p/6 (m -1 ), where d is the indoor dose rate (nGy.h -1 ) and m the month, was observed. This might be due to seasonally varied air exchange rates of the houses. The average annual effective dose and the collective dose equivalent for the residents were estimated to be 0.86 mSv and 172.20 man-Sv respectively based on the indoor gamma exposure. (author)

  1. Environmental gamma radiation measurements in Bangladeshi houses

    Miah, M.I.

    2004-01-01

    Indoor gamma dose rate in air measured using TLDs in the Dhaka district is not wide ranging and follows a normal distribution with an arithmetic mean of 1.54±0.26 mGy y -1 . The result has been compared with those found by other investigators for different locations of the world. Measurements were made on a monthly basis for a year period, and a sinusoidal variation of monthly indoor gamma radiation of the type: d=160+65 cos π/6 (m-1), where d is the indoor dose rate (nGy h -1 ) and m the month. This might be due to the seasonally varied air exchange rates of the houses. The average annual effective dose and the collective dose equivalent for the residents were estimated to be 0.86 mSv and 172.20 man-Sv, respectively, based on the indoor gamma exposure

  2. Environmental gamma radiation measurements in Bangladeshi houses

    Miah, M.I. E-mail: idrish_physics@yahoo.com

    2004-06-01

    Indoor gamma dose rate in air measured using TLDs in the Dhaka district is not wide ranging and follows a normal distribution with an arithmetic mean of 1.54{+-}0.26 mGy y{sup -1}. The result has been compared with those found by other investigators for different locations of the world. Measurements were made on a monthly basis for a year period, and a sinusoidal variation of monthly indoor gamma radiation of the type: d=160+65 cos {pi}/6 (m-1), where d is the indoor dose rate (nGy h{sup -1}) and m the month. This might be due to the seasonally varied air exchange rates of the houses. The average annual effective dose and the collective dose equivalent for the residents were estimated to be 0.86 mSv and 172.20 man-Sv, respectively, based on the indoor gamma exposure.

  3. Gate Simulation of a Gamma Camera

    Abidi, Sana; Mlaouhi, Zohra

    2008-01-01

    Medical imaging is a very important diagnostic because it allows for an exploration of the internal human body. The nuclear imaging is an imaging technique used in the nuclear medicine. It is to determine the distribution in the body of a radiotracers by detecting the radiation it emits using a detection device. Two methods are commonly used: Single Photon Emission Computed Tomography (SPECT) and the Positrons Emission Tomography (PET). In this work we are interested on modelling of a gamma camera. This simulation is based on Monte-Carlo language and in particular Gate simulator (Geant4 Application Tomographic Emission). We have simulated a clinical gamma camera called GAEDE (GKS-1) and then we validate these simulations by experiments. The purpose of this work is to monitor the performance of these gamma camera and the optimization of the detector performance and the the improvement of the images quality. (Author)

  4. Impact of image noise on gamma index calculation

    Chen, M; Mo, X; Parnell, D; Olivera, G; Galmarini, D; Lu, W

    2014-01-01

    Purpose: The Gamma Index defines an asymmetric metric between the evaluated image and the reference image. It provides a quantitative comparison that can be used to indicate sample-wised pass/fail on the agreement of the two images. The Gamma passing/failing rate has become an important clinical evaluation tool. However, the presence of noise in the evaluated and/or reference images may change the Gamma Index, hence the passing/failing rate, and further, clinical decisions. In this work, we systematically studied the impact of the image noise on the Gamma Index calculation. Methods: We used both analytic formulation and numerical calculations in our study. The numerical calculations included simulations and clinical images. Three different noise scenarios were studied in simulations: noise in reference images only, in evaluated images only, and in both. Both white and spatially correlated noises of various magnitudes were simulated. For clinical images of various noise levels, the Gamma Index of measurement against calculation, calculation against measurement, and measurement against measurement, were evaluated. Results: Numerical calculations for both the simulation and clinical data agreed with the analytic formulations, and the clinical data agreed with the simulations. For the Gamma Index of measurement against calculation, its distribution has an increased mean and an increased standard deviation as the noise increases. On the contrary, for the Gamma index of calculation against measurement, its distribution has a decreased mean and stabilized standard deviation as the noise increases. White noise has greater impact on the Gamma Index than spatially correlated noise. Conclusions: The noise has significant impact on the Gamma Index calculation and the impact is asymmetric. The Gamma Index should be reported along with the noise levels in both reference and evaluated images. Reporting of the Gamma Index with switched roles of the images as reference and

  5. Impact of Image Noise on Gamma Index Calculation

    Chen, M.; Mo, X.; Parnell, D.; Olivera, G.; Galmarini, D.; Lu, W.

    2014-03-01

    Purpose: The Gamma Index defines an asymmetric metric between the evaluated image and the reference image. It provides a quantitative comparison that can be used to indicate sample-wised pass/fail on the agreement of the two images. The Gamma passing/failing rate has become an important clinical evaluation tool. However, the presence of noise in the evaluated and/or reference images may change the Gamma Index, hence the passing/failing rate, and further, clinical decisions. In this work, we systematically studied the impact of the image noise on the Gamma Index calculation. Methods: We used both analytic formulation and numerical calculations in our study. The numerical calculations included simulations and clinical images. Three different noise scenarios were studied in simulations: noise in reference images only, in evaluated images only, and in both. Both white and spatially correlated noises of various magnitudes were simulated. For clinical images of various noise levels, the Gamma Index of measurement against calculation, calculation against measurement, and measurement against measurement, were evaluated. Results: Numerical calculations for both the simulation and clinical data agreed with the analytic formulations, and the clinical data agreed with the simulations. For the Gamma Index of measurement against calculation, its distribution has an increased mean and an increased standard deviation as the noise increases. On the contrary, for the Gamma index of calculation against measurement, its distribution has a decreased mean and stabilized standard deviation as the noise increases. White noise has greater impact on the Gamma Index than spatially correlated noise. Conclusions: The noise has significant impact on the Gamma Index calculation and the impact is asymmetric. The Gamma Index should be reported along with the noise levels in both reference and evaluated images. Reporting of the Gamma Index with switched roles of the images as reference and

  6. GammaWorkshops Proceedings

    Strålberg, Elisabeth; Klemola, Seppo; Nielsen, Sven Poul

    to the GammaWorkshops. The topics included efficiency transfer, true coincidence summing corrections, self-attenuation corrections, measurement of natural radionuclides (natural decay series), combined measurement uncertainty calculations, and detection limits. These topics covered both lectures and practical...

  7. FTR europia gamma heating

    Ward, J.T. Jr.

    1975-01-01

    Calculated and experimental gamma heating rates of europia in the Engineering Mockup Critical Assembly (EMC) were correlated. A calculated to experimental (C/E) ratio of 1.086 was established in validating the theoretical approach and computational technique applied in the calculations. Gamma heat deposition rates in the FTR with Eu 2 O 3 control absorbers were determined from three-dimensional calculations. Maximum gamma heating was found to occur near the tip of a half-inserted row 5 control rod assembly--12.8 watts/gm of europia. Gamma heating profiles were established for a single half-inserted europia absorber assembly. Local heat peaking was found not to alter significantly heating rates computed in the FTR core model, where larger mesh interval sizes precluded examination of spatially-limited heating gradients. These computations provide the basis for thermal-hydraulic analyses to ascertain temperature profiles in the FTR under europia control

  8. Beta and Gamma Gradients

    Løvborg, Leif; Gaffney, C. F.; Clark, P. A.

    1985-01-01

    Experimental and/or theoretical estimates are presented concerning, (i) attenuation within the sample of beta and gamma radiation from the soil, (ii) the gamma dose within the sample due to its own radioactivity, and (iii) the soil gamma dose in the proximity of boundaries between regions...... of differing radioactivity. It is confirmed that removal of the outer 2 mm of sample is adequate to remove influence from soil beta dose and estimates are made of the error introduced by non-removal. Other evaluations include variation of the soil gamma dose near the ground surface and it appears...... that the present practice of avoiding samples above a depth of 0.3 m may be over-cautious...

  9. Gamma spectrometry today

    Hemingway, J.

    1990-01-01

    This paper reviews the important advances in gamma spectroscopy made in recent years. Improvements in detectors and other components and the addition of on-line computer control systems is discussed. (UK)

  10. Improving Open Access through Prior Learning Assessment

    Yin, Shuangxu; Kawachi, Paul

    2013-01-01

    This paper explores and presents new data on how to improve open access in distance education through using prior learning assessments. Broadly there are three types of prior learning assessment (PLAR): Type-1 for prospective students to be allowed to register for a course; Type-2 for current students to avoid duplicating work-load to gain…

  11. Quantitative Evidence Synthesis with Power Priors

    Rietbergen, C.|info:eu-repo/dai/nl/322847796

    2016-01-01

    The aim of this thesis is to provide the applied researcher with a practical approach for quantitative evidence synthesis using the conditional power prior that allows for subjective input and thereby provides an alternative tgbgo deal with the difficulties as- sociated with the joint power prior

  12. IMEF gamma scanning system

    Baek, Sang Yeol; Park, Dae Kyu; Ahn, Sang Bok; Ju, Yong Sun; Jeon, Yong Bum

    1997-06-01

    The gamma scanning system which is installed in IMEF is the equipment obtaining the gamma ray spectrum from irradiated fuels. This equipment could afford the useful data relating spent fuels like as burn-up measurements. We describe the specifications of the equipment and its accessories, and also described its operation procedure so that an operator can use this report as the operation procedure. (author). 1 tab., 11 figs., 11 refs.

  13. IMEF gamma scanning system

    Baek, Sang Yeol; Park, Dae Kyu; Ahn, Sang Bok; Ju, Yong Sun; Jeon, Yong Bum.

    1997-06-01

    The gamma scanning system which is installed in IMEF is the equipment obtaining the gamma ray spectrum from irradiated fuels. This equipment could afford the useful data relating spent fuels like as burn-up measurements. We describe the specifications of the equipment and its accessories, and also described its operation procedure so that an operator can use this report as the operation procedure. (author). 1 tab., 11 figs., 11 refs

  14. On the sum of Gamma-Gamma variates with application to the fast outage probability evaluation over fading channels

    Ben Issaid, Chaouki; Rached, Nadhir B.; Kammoun, Abla; Alouini, Mohamed-Slim; Tempone, Raul

    2017-01-01

    The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of independent and identically distributed Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.

  15. On the sum of Gamma-Gamma variates with application to the fast outage probability evaluation over fading channels

    Ben Issaid, Chaouki

    2017-04-01

    The Gamma-Gamma distribution has recently emerged in a number of applications ranging from modeling scattering and reverbation in sonar and radar systems to modeling atmospheric turbulence in wireless optical channels. In this respect, assessing the outage probability achieved by some diversity techniques over this kind of channels is of major practical importance. In many circumstances, this is intimately related to the difficult question of analyzing the statistics of a sum of Gamma-Gamma random variables. Answering this question is not a simple matter. This is essentially because outage probabilities encountered in practice are often very small, and hence the use of classical Monte Carlo methods is not a reasonable choice. This lies behind the main motivation of the present work. In particular, this paper proposes a new approach to estimate the left tail of the sum of independent and identically distributed Gamma-Gamma variates. More specifically, we propose a mean-shift importance sampling scheme that efficiently evaluates the outage probability of L-branch maximum ratio combining diversity receivers over Gamma-Gamma fading channels. The proposed estimator satisfies the well-known bounded relative error criterion. We show the accuracy and the efficiency of our approach compared to naive Monte Carlo via some selected numerical simulations.

  16. Evaluation of the neutron and gamma-ray production cross-sections for 55Mn

    Takahashi, H.

    1974-11-01

    The evaluation of neutron and gamma production cross sections for manganese-55 from 1.0 (10) -5 eV to 20.0 MeV for ENDF/ B-IV is summarized. Included are resonance parameters, neutron cross sections, angular and energy distribution of secondary neutrons, gamma multiplicities and transition probability array, gamma angular and energy distributions, nuclear model calculations, uncertainty estimates of cross sections, and evaluated cross sections. (U.S.)

  17. Terrestrial gamma radiation dose rate in Ryukyu Islands, subtropical region of Japan

    Furukawa, M.; Shiroma, M.; Motomura, D.; Fujioka, S.; Kawakami, T.; Yasuda, Y.; Arakawa, K.; Fukahori, K.; Jyunicho, M.; Ishikawa, S.; Ohomoto, T.; Kina, S.; Shiroma, Y.; Masuda, N.; Hiraoka, H.; Shingaki, R.; Akata, N.; Zhuo, W.; Tokonami, S.

    2015-01-01

    In order to explain the distribution of natural radiation level in the Asia, in situ measurements of dose rate in air due to terrestrial gamma radiation have been conducted in a total of 21 islands that belong to Ryukyu Islands (Ryukyu Archipelago), subtropical rejoin of southwest Japan. Car-borne surveys have also been carried out in Okinawa-jima, the biggest island of the archipelago. Based on the results for these measurements, arithmetic mean, the maximum and the minimum of the dose rates at 1 m in height from the unpaved soil ground in the archipelago were estimated to be 47, 165 and 8 nGy h -1 , respectively. A comparative study of car-borne data obtained prior to and subsequent to the 2011 Fukushima nuclear accident, as for Okinawa-jima, indicated that the nuclear accident has no impact on the environmental radiation at the present time. (authors)

  18. Gamma scanning of mixed carbide and oxide fuel pins irradiated in FBTR

    Jayaraj, V.V.; Padalakshmi, M.; Ulaganathan, T.; Venkiteswaran, C.N.; Divakar, R.; Joseph, Jojo; Bhaduri, A.K.

    2016-01-01

    Fission in nuclear fuels results in a number of fission products that are gamma emitters in the energy range of 100 keV to 3 MeV. The gamma emitting fission products are therefore amenable for detection by gamma detectors. Assessment of the fission product distribution and their migration behavior through gamma scanning is important for characterizing the in reactor behavior of the fuel. Gamma scanning is an important non destructive technique used to evaluate the behavior of irradiated fuels. As a part of Post Irradiation Examinations (PIE), axial gamma scanning has been carried out on selected fuel pins of the FBTR Mark I mixed carbide fuel sub-assemblies and PFBR MOX test fuel sub-assembly irradiated in FBTR. This paper covers the results of gamma scanning and correlation of gamma scanning results with other PIE techniques

  19. Terminology for pregnancy loss prior to viability

    Kolte, A M; Bernardi, L A; Christiansen, O B

    2015-01-01

    Pregnancy loss prior to viability is common and research in the field is extensive. Unfortunately, terminology in the literature is inconsistent. The lack of consensus regarding nomenclature and classification of pregnancy loss prior to viability makes it difficult to compare study results from...... different centres. In our opinion, terminology and definitions should be based on clinical findings, and when possible, transvaginal ultrasound. With this Early Pregnancy Consensus Statement, it is our goal to provide clear and consistent terminology for pregnancy loss prior to viability....

  20. 3D reconstruction for partial data electrical impedance tomography using a sparsity prior

    Garde, Henrik; Knudsen, Kim

    2015-01-01

    of the conductivity is used to improve reconstructions for the partial data problem with Cauchy data measured only on a subset of the boundary. A sparsity prior is enforced using the ℓ1 norm in the penalty term of a Tikhonov functional, and spatial prior information is incorporated by applying a spatially distributed...

  1. Maximum entropy reconstruction of spin densities involving non uniform prior

    Schweizer, J.; Ressouche, E.; Papoular, R.J.; Zheludev, A.I.

    1997-01-01

    Diffraction experiments give microscopic information on structures in crystals. A method which uses the concept of maximum of entropy (MaxEnt), appears to be a formidable improvement in the treatment of diffraction data. This method is based on a bayesian approach: among all the maps compatible with the experimental data, it selects that one which has the highest prior (intrinsic) probability. Considering that all the points of the map are equally probable, this probability (flat prior) is expressed via the Boltzman entropy of the distribution. This method has been used for the reconstruction of charge densities from X-ray data, for maps of nuclear densities from unpolarized neutron data as well as for distributions of spin density. The density maps obtained by this method, as compared to those resulting from the usual inverse Fourier transformation, are tremendously improved. In particular, any substantial deviation from the background is really contained in the data, as it costs entropy compared to a map that would ignore such features. However, in most of the cases, before the measurements are performed, some knowledge exists about the distribution which is investigated. It can range from the simple information of the type of scattering electrons to an elaborate theoretical model. In these cases, the uniform prior which considers all the different pixels as equally likely, is too weak a requirement and has to be replaced. In a rigorous bayesian analysis, Skilling has shown that prior knowledge can be encoded into the Maximum Entropy formalism through a model m(rvec r), via a new definition for the entropy given in this paper. In the absence of any data, the maximum of the entropy functional is reached for ρ(rvec r) = m(rvec r). Any substantial departure from the model, observed in the final map, is really contained in the data as, with the new definition, it costs entropy. This paper presents illustrations of model testing

  2. Investigation of zones with increased ground surface gamma radiation

    Butkus, D.V.; Morkunas, G.S.; Styro, B.I.

    1989-01-01

    Measurements of the increased gamma radiation zones of soils were conducted in the South-Western part of the Litvinian. The shores of lakes in the north-eastern part of the Suduva high land were investigated. the maximum values of the gamma radiation dose rates were distributed along the lake shores at a distance of 1 m from the water surface, while farther than 1.5 m from it the dose rate was close to the natural value. The increased gamma radiation intensity zones on the ground surface were found only at the northern (Lake Reketija) or the western shore (other lakes under investigation). The highest values of the gamma radiation dose 200-600 μR/h (0.5-1.5 nGy/s) were observed in the comparatively small areas (up to several square metres). The gamma radiation intensity of soil surface increased strongly moving towards the point where the maximum intensity was obsered. 10 figs

  3. Efficient gamma index calculation using fast Euclidean distance transform

    Chen Mingli; Lu Weiguo; Chen Quan; Ruchala, Kenneth; Olivera, Gustavo [TomoTherapy Inc., 1240 Deming Way, Madison, WI 53717 (United States)], E-mail: wlu@tomotherapy.com

    2009-04-07

    The gamma index is a tool for dose distribution comparison. It combines both dose difference (DD) and distance to agreement (DTA) into a single quantity. Though it is an effective measure, making up for the inadequacy of DD or DTA alone, its calculation can be very time-consuming. For a k-D space with N quantization levels in each dimension, the complexity of the exhaustive search is O(N{sup 2k}). In this work, we proposed an efficient method that reduces the complexity from O(N{sup 2k}) to O(N{sup k}M), where M is the number of discretized dose values and is comparable to N. More precisely, by embedding the reference dose distribution in a (k+1)-D spatial-dose space, we can use fast Euclidean distance transform with linear complexity to obtain a table of gamma indices evaluated over a range of the (k+1)-D spatial-dose space. Then, to obtain gamma indices for the test dose distribution, it requires only table lookup with complexity O(N{sup k}). Such a table can also be used for other test dose distributions as long as the reference dose distribution is the same. Simulations demonstrated the efficiency of our proposed method. The speedup for 3D gamma index calculation is expected to be on the order of tens of thousands (from O(N{sup 6}) to O(N{sup 3}M)) if N is a few hundreds, which makes clinical usage of the 3D gamma index feasible. A byproduct of the gamma index table is that the gradient of the gamma index with respect to either the spatial or dose dimension can be easily derived. The gradient can be used to identify the main causes of the discrepancy from the reference distribution at any dose point in the test distribution or incorporated in treatment planning and machine parameter optimization.

  4. A Simulation of Pell Grant Awards and Costs Using Prior-Prior Year Financial Data

    Kelchen, Robert; Jones, Gigi

    2015-01-01

    We examine the likely implications of switching from a prior year (PY) financial aid system, the current practice in which students file the Free Application for Federal Student Aid (FAFSA) using income data from the previous tax year, to prior-prior year (PPY), in which data from two years before enrollment is used. While PPY allows students to…

  5. Prior Authorization of PMDs Demonstration - Status Update

    U.S. Department of Health & Human Services — CMS implemented a Prior Authorization process for scooters and power wheelchairs for people with Fee-For-Service Medicare who reside in seven states with high...

  6. Short Report Biochemical derangements prior to emergency ...

    MMJ VOL 29 (1): March 2017. Biochemical derangements prior to emergency laparotomy at QECH 55. Malawi Medical Journal 29 (1): March 2017 ... Venepuncture was performed preoperatively for urgent cases, defined as those requiring.

  7. An Adaptively Accelerated Bayesian Deblurring Method with Entropy Prior

    Yong-Hoon Kim

    2008-05-01

    Full Text Available The development of an efficient adaptively accelerated iterative deblurring algorithm based on Bayesian statistical concept has been reported. Entropy of an image has been used as a “prior” distribution and instead of additive form, used in conventional acceleration methods an exponent form of relaxation constant has been used for acceleration. Thus the proposed method is called hereafter as adaptively accelerated maximum a posteriori with entropy prior (AAMAPE. Based on empirical observations in different experiments, the exponent is computed adaptively using first-order derivatives of the deblurred image from previous two iterations. This exponent improves speed of the AAMAPE method in early stages and ensures stability at later stages of iteration. In AAMAPE method, we also consider the constraint of the nonnegativity and flux conservation. The paper discusses the fundamental idea of the Bayesian image deblurring with the use of entropy as prior, and the analytical analysis of superresolution and the noise amplification characteristics of the proposed method. The experimental results show that the proposed AAMAPE method gives lower RMSE and higher SNR in 44% lesser iterations as compared to nonaccelerated maximum a posteriori with entropy prior (MAPE method. Moreover, AAMAPE followed by wavelet wiener filtering gives better result than the state-of-the-art methods.

  8. Gamma-Ray Treatment of Echinococcus Protoscoleces prior to Implantation in Mice Reduces Echinococcosis.

    Yuan, Qing; Li, Bo; Jiang, Shiping; Zhao, Qiang; Duo, Ji; Huang, Xiang

    2016-01-01

    Echinococcosis is a serious parasitic disease caused by Echinococcus tapeworms. Protoscoleces are sometimes released during surgical treatment for hydatid cysts, causing the recurrence of echinococcosis. Protoscoleces may be susceptible to radiation therapy. In this study Echinococcus protoscoleces were cultured in vitro and then divided into four different γ-ray irradiation dose groups (10 Gy, 20 Gy, 40 Gy, and 80 Gy) and a blank group. The protoscoleces were then implanted into the abdominal cavity of mice. Four months later, we observed that the incidence and weight of cysts declined with the increase of irradiation dose. γ-ray irradiation can suppress the generation of Echinococcus originated from protoscolex, the reason of which is due to the damaging to the structure of Echinococcus. Irradiation may prevent echinococcosis recurrence after surgical removal of hydatid cysts.

  9. Gamma-Ray Treatment of Echinococcus Protoscoleces prior to Implantation in Mice Reduces Echinococcosis

    Qing Yuan

    2016-01-01

    Full Text Available Echinococcosis is a serious parasitic disease caused by Echinococcus tapeworms. Protoscoleces are sometimes released during surgical treatment for hydatid cysts, causing the recurrence of echinococcosis. Protoscoleces may be susceptible to radiation therapy. In this study Echinococcus protoscoleces were cultured in vitro and then divided into four different γ-ray irradiation dose groups (10 Gy, 20 Gy, 40 Gy, and 80 Gy and a blank group. The protoscoleces were then implanted into the abdominal cavity of mice. Four months later, we observed that the incidence and weight of cysts declined with the increase of irradiation dose. γ-ray irradiation can suppress the generation of Echinococcus originated from protoscolex, the reason of which is due to the damaging to the structure of Echinococcus. Irradiation may prevent echinococcosis recurrence after surgical removal of hydatid cysts.

  10. Order-Constrained Reference Priors with Implications for Bayesian Isotonic Regression, Analysis of Covariance and Spatial Models

    Gong, Maozhen

    Selecting an appropriate prior distribution is a fundamental issue in Bayesian Statistics. In this dissertation, under the framework provided by Berger and Bernardo, I derive the reference priors for several models which include: Analysis of Variance (ANOVA)/Analysis of Covariance (ANCOVA) models with a categorical variable under common ordering constraints, the conditionally autoregressive (CAR) models and the simultaneous autoregressive (SAR) models with a spatial autoregression parameter rho considered. The performances of reference priors for ANOVA/ANCOVA models are evaluated by simulation studies with comparisons to Jeffreys' prior and Least Squares Estimation (LSE). The priors are then illustrated in a Bayesian model of the "Risk of Type 2 Diabetes in New Mexico" data, where the relationship between the type 2 diabetes risk (through Hemoglobin A1c) and different smoking levels is investigated. In both simulation studies and real data set modeling, the reference priors that incorporate internal order information show good performances and can be used as default priors. The reference priors for the CAR and SAR models are also illustrated in the "1999 SAT State Average Verbal Scores" data with a comparison to a Uniform prior distribution. Due to the complexity of the reference priors for both CAR and SAR models, only a portion (12 states in the Midwest) of the original data set is considered. The reference priors can give a different marginal posterior distribution compared to a Uniform prior, which provides an alternative for prior specifications for areal data in Spatial statistics.

  11. Attentional and Contextual Priors in Sound Perception.

    Wolmetz, Michael; Elhilali, Mounya

    2016-01-01

    Behavioral and neural studies of selective attention have consistently demonstrated that explicit attentional cues to particular perceptual features profoundly alter perception and performance. The statistics of the sensory environment can also provide cues about what perceptual features to expect, but the extent to which these more implicit contextual cues impact perception and performance, as well as their relationship to explicit attentional cues, is not well understood. In this study, the explicit cues, or attentional prior probabilities, and the implicit cues, or contextual prior probabilities, associated with different acoustic frequencies in a detection task were simultaneously manipulated. Both attentional and contextual priors had similarly large but independent impacts on sound detectability, with evidence that listeners tracked and used contextual priors for a variety of sound classes (pure tones, harmonic complexes, and vowels). Further analyses showed that listeners updated their contextual priors rapidly and optimally, given the changing acoustic frequency statistics inherent in the paradigm. A Bayesian Observer model accounted for both attentional and contextual adaptations found with listeners. These results bolster the interpretation of perception as Bayesian inference, and suggest that some effects attributed to selective attention may be a special case of contextual prior integration along a feature axis.

  12. Modeling the Broad-Band Emission from the Gamma-Ray Emitting Narrow-Line Seyfert-1 Galaxies 1H 0323+342 and B2 0954+25A

    Arrieta-Lobo, Maialen; Boisson, Catherine; Zech, Andreas

    2017-01-01

    Prior to the Fermi-LAT era, only two classes of Active Galactic Nuclei (AGN) were thought to harbor relativistic jets that radiate up to gamma-ray energies: blazars and radio galaxies. The detection of variable gamma-ray emission from Narrow Line Seyfert 1 (NLSy1) galaxies has put them on the spotlight as a new class of gamma-ray emitting AGN. In this respect, gamma-ray emitting NLSy1s seem to be situated between blazars (dominated by non-thermal emission) and Seyferts (accretion disc dominated). In this work, we model the Spectral Energy Distribution (SED) of two gamma-loud NLSy1s, 1H 0323+342 and B2 0954+25A, during quiescent and flaring episodes via a multi-component radiative model that features a relativistic jet and external photon fields from the torus, disc, corona and Broad Line Region (BLR). We find that the interpretation of the high-energy emission of jetted NLSy1s requires taking into account Inverse Compton emission from particles in the relativistic jet that interact with external photon fields. Minimal changes are applied to the model parameters to transition from average to flaring states. In this scenario, the observed variability is explained mainly by means of changes in the jet density and Doppler factor.

  13. Modeling the Broad-Band Emission from the Gamma-Ray Emitting Narrow-Line Seyfert-1 Galaxies 1H 0323+342 and B2 0954+25A

    Arrieta-Lobo, Maialen; Boisson, Catherine; Zech, Andreas, E-mail: maialen.arrieta@obspm.fr [Laboratoire Univers et Theories, Observatoire de Paris, CNRS, Université Paris-Diderot, PSL Research University, Meudon (France)

    2017-12-08

    Prior to the Fermi-LAT era, only two classes of Active Galactic Nuclei (AGN) were thought to harbor relativistic jets that radiate up to gamma-ray energies: blazars and radio galaxies. The detection of variable gamma-ray emission from Narrow Line Seyfert 1 (NLSy1) galaxies has put them on the spotlight as a new class of gamma-ray emitting AGN. In this respect, gamma-ray emitting NLSy1s seem to be situated between blazars (dominated by non-thermal emission) and Seyferts (accretion disc dominated). In this work, we model the Spectral Energy Distribution (SED) of two gamma-loud NLSy1s, 1H 0323+342 and B2 0954+25A, during quiescent and flaring episodes via a multi-component radiative model that features a relativistic jet and external photon fields from the torus, disc, corona and Broad Line Region (BLR). We find that the interpretation of the high-energy emission of jetted NLSy1s requires taking into account Inverse Compton emission from particles in the relativistic jet that interact with external photon fields. Minimal changes are applied to the model parameters to transition from average to flaring states. In this scenario, the observed variability is explained mainly by means of changes in the jet density and Doppler factor.

  14. Numerical study on determining formation porosity using a boron capture gamma ray technique and MCNP.

    Liu, Juntao; Zhang, Feng; Wang, Xinguang; Han, Fei; Yuan, Zhelong

    2014-12-01

    Formation porosity can be determined using the boron capture gamma ray counting ratio with a near to far detector in a pulsed neutron-gamma element logging tool. The thermal neutron distribution, boron capture gamma spectroscopy and porosity response for formations with different water salinity and wellbore diameter characteristics were simulated using the Monte Carlo method. We found that a boron lining improves the signal-to-noise ratio and that the boron capture gamma ray counting ratio has a higher sensitivity for determining porosity than total capture gamma. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Quarkonium+{gamma} production in coherent hadron-hadron interactions at LHC energies

    Goncalves, V.P. [Universidade Federal de Pelotas, Instituto de Fisica e Matematica, Caixa Postal 354, Pelotas, RS (Brazil); Machado, M.M. [IF - Farroupilha, Instituto Federal de Educacao, Ciencia e Tecnologia, Sao Borja, RS (Brazil)

    2012-11-15

    In this paper we study the H+{gamma} (H=J/{Psi} and and upsilon;) production in coherent hadron-hadron interactions at LHC energies. Considering the ultrarelativistic protons as a source of photons, we estimate the {gamma}+p{yields}H+{gamma}+X cross section using the non-relativistic QCD (NRQCD) factorization formalism and considering different sets of values for the matrix elements. Our results for the total p+p{yields}p+H+{gamma}+X cross sections and rapidity distributions at {radical}(s) = 7 and 14 TeV demonstrate that the experimental analysis of the J/{Psi}+{gamma} production at LHC is feasible. (orig.)

  16. Examination of irradiated fuel elements using gamma scanning technique

    Ichim, O.; Mincu, M.; Man, I.; Stanica, M.

    2016-01-01

    The purpose of this paper is to validate the gamma scanning technique used to calculate the activity of gamma fission products from CANDU/TRIGA irradiated fuel elements. After a short presentation of the equipments used and their characteristics, the paper describes the calibration technique for the devices and how computed tomography reconstruction is done. Following the previously mentioned steps is possible to obtain the axial and radial profiles and the computed tomography reconstruction for calibration sources and for the irradiated fuel elements. The results are used to validate the gamma scanning techniques as a non-destructive examination method. The gamma scanning techniques will be used to: identify the fission products in the irradiated CANDU/TRIGA fuel elements, construct the axial and radial distributions of fission products, get the distribution in cross section through computed tomography reconstruction, and determine the nuclei number and the fission products activity of the irradiated CANDU/TRIGA fuel elements. (authors)

  17. System for gamma-gamma formation density logging while drilling

    Paske, W.C.

    1991-01-01

    The patent relates to a system for logging subterranean formations for the determination of formation density by using gamma radiation. Gamma ray source and detection means are disposed within a housing adapted for positioning within a borehole for the emission and detection of gamma rays propagating through earth formations and borehole drilling fluid. The gamma ray detection means comprises first and second gamma radiation sensors geometrically disposed within the housing, the same longitudinal distance from the gamma ray source and diametrically opposed in a common plane. A formation matrix density output signal is produced in proportion to the output signal from each of the gamma ray sensors and in conjunction with certain constants established by the geometrical configuration of the sensors relative to the gamma ray source and the borehole diameter. Formation density is determined without regard to the radial position of the logging probe within the borehole in a measuring while drilling mode. 6 figs

  18. Microscopic beta and gamma data for decay-heat needs

    Dickens, J.K.

    1983-01-01

    Microscopic beta and gamma data for decay-heat needs are defined as absolute-intensity spectral distributions of beta and gamma rays following radioactive decay of radionuclides created by, or following, the fission process. Four well-known evaluated data files, namely the US ENDF/B-V, the UK UKFPDD-2, the French BDN (for fission products), and the Japanese JNDC Nuclear Data Library, are reviewed. Comments regarding the analyses of experimental data (particularly gamma-ray data) are given; the need for complete beta-ray spectral measurements is emphasized. Suggestions on goals for near-term future experimental measurements are presented. 34 references

  19. Gamma histograms for radiotherapy plan evaluation

    Spezi, Emiliano; Lewis, D. Geraint

    2006-01-01

    Background and purpose: The technique known as the 'γ evaluation method' incorporates pass-fail criteria for both distance-to-agreement and dose difference analysis of 3D dose distributions and provides a numerical index (γ) as a measure of the agreement between two datasets. As the γ evaluation index is being adopted in more centres as part of treatment plan verification procedures for 2D and 3D dose maps, the development of methods capable of encapsulating the information provided by this technique is recommended. Patients and methods: In this work the concept of γ index was extended to create gamma histograms (GH) in order to provide a measure of the agreement between two datasets in two or three dimensions. Gamma area histogram (GAH) and gamma volume histogram (GVH) graphs were produced using one or more 2D γ maps generated for each slice of the irradiated volume. GHs were calculated for IMRT plans, evaluating the 3D dose distribution from a commercial treatment planning system (TPS) compared to a Monte Carlo (MC) calculation used as reference dataset. Results: The extent of local anatomical inhomogenities in the plans under consideration was strongly correlated with the level of difference between reference and evaluated calculations. GHs provided an immediate visual representation of the proportion of the treated volume that fulfilled the γ criterion and offered a concise method for comparative numerical evaluation of dose distributions. Conclusions: We have introduced the concept of GHs and investigated its applications to the evaluation and verification of IMRT plans. The gamma histogram concept set out in this paper can provide a valuable technique for quantitative comparison of dose distributions and could be applied as a tool for the quality assurance of treatment planning systems

  20. Application of Bayesian Decision Theory Based on Prior Information in the Multi-Objective Optimization Problem

    Xia Lei

    2010-12-01

    Full Text Available General multi-objective optimization methods are hard to obtain prior information, how to utilize prior information has been a challenge. This paper analyzes the characteristics of Bayesian decision-making based on maximum entropy principle and prior information, especially in case that how to effectively improve decision-making reliability in deficiency of reference samples. The paper exhibits effectiveness of the proposed method using the real application of multi-frequency offset estimation in distributed multiple-input multiple-output system. The simulation results demonstrate Bayesian decision-making based on prior information has better global searching capability when sampling data is deficient.

  1. Modular gamma systems

    Millegan, D.R.; Nixon, K.V.

    1982-01-01

    Nuclear safeguards requires sensitive, easily operated instruments for rapid inspection of personnel and vehicles to ensure that no uranium or plutonium is being diverted. Two portable gamma-ray detection systems have been developed. The Modular Gamma System (MGS) is very sensitive and two or more systems can be connected for even better performance. The multiunit configuration can be deployed by motor vehicle for search of large areas too extensive to search on foot. The Programmable Rate Monitor (PRM) is less sensitive but much smaller and therefore is more suitable for search of vehicles, personnel, or smaller areas. The PRM is programmable, which implements measurement and alarm algorithms for individual applications

  2. Proprioceptive evoked gamma oscillations

    Arnfred, S.M.; Hansen, Lars Kai; Parnas, J.

    2007-01-01

    A proprioceptive stimulus consisting of a weight change of a handheld load has recently been shown to elicit an evoked potential. Previously, somatosensory gamma oscillations have only been evoked by electrical stimuli. We conjectured that a natural proprioceptive stimulus also would be able...... to evoke gamma oscillations. EEG was recorded using 64 channels in 14 healthy subjects. In each of three runs a stimulus of 100 g load increment in each hand was presented in 120 trials. Data were wavelet transformed and runs collapsed. Inter-trial phase coherence (ITPC) was computed as the best measure...

  3. Gamma-Ray Bursts

    Pellizza, L. J.

    Gamma-ray bursts are the brightest transient sources in the gamma-ray sky. Since their discovery in the late 1960s, the investigation of the astrophysical sys- tems in which these phenomena take place, and the physical mechanisms that drive them, has become a vast and prolific area of modern astrophysics. In this work I will briefly describe the most relevant observations of these sources, and the models that describe their nature, emphasizing on the in- vestigations about the progenitor astrophysical systems. FULL TEXT IN SPANISH

  4. Gamma Ray Bursts

    Gehrels, Neil; Meszaros, Peter

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day ,last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

  5. Quarkonium +{gamma} production in coherent interactions at LHC

    Goncalves, V. P. [Instituto de Fisica e Matematica, Universidade Federal de Pelotas Caixa Postal 354, CEP 96010-900, Pelotas, RS (Brazil); Machado, M. M. [Instituto Federal de Educacao, Ciencia e Tecnologia, IF - Farroupilha, Campus Sao Borja Rua Otaviano Castilho Mendes, 355, CEP 97670-000 - Sao Borja, RS (Brazil)

    2013-04-15

    The quarkonium plus photon production in coherent hadron - hadron interactions at LHC is studied using the non-relativistic QCD (NRQCD) factorization formalism. Considering different sets of NRQCD matrix elements we estimate the rapidity distribution and total cross section for H+{gamma} (H=J/{Psi} and {gamma}) production. Our results demonstrate that the experimental analysis of this process is feasible and that it can be used to constrain the matrix elements.

  6. Bayesian Image Segmentations by Potts Prior and Loopy Belief Propagation

    Tanaka, Kazuyuki; Kataoka, Shun; Yasuda, Muneki; Waizumi, Yuji; Hsu, Chiou-Ting

    2014-12-01

    This paper presents a Bayesian image segmentation model based on Potts prior and loopy belief propagation. The proposed Bayesian model involves several terms, including the pairwise interactions of Potts models, and the average vectors and covariant matrices of Gauss distributions in color image modeling. These terms are often referred to as hyperparameters in statistical machine learning theory. In order to determine these hyperparameters, we propose a new scheme for hyperparameter estimation based on conditional maximization of entropy in the Potts prior. The algorithm is given based on loopy belief propagation. In addition, we compare our conditional maximum entropy framework with the conventional maximum likelihood framework, and also clarify how the first order phase transitions in loopy belief propagations for Potts models influence our hyperparameter estimation procedures.

  7. Interferon Gamma-1b Injection

    Interferon gamma-1b injection is used to reduce the frequency and severity of serious infections in people with chronic ... severe, malignant osteopetrosis (an inherited bone disease). Interferon gamma-1b is in a class of medications called ...

  8. Gamma knife surgery for craniopharyngioma

    Prasad, D.; Steiner, M.; Steiner, L.

    1995-01-01

    We present our results of Gamma Knife surgery for craniopharyngioma in nine patients. The current status of surgery, radiation therapy, intracavitary instillation of radionuclides and Gamma Knife surgery in the management of craniopharyngiomas is discussed. (author)

  9. CKM angle $\\gamma$ from LHCb

    Smith, Jackson

    2015-01-01

    Results of the latest $\\gamma$ combination from LHCb are presented, along with the six LHCb measurements used as inputs. In addition, the anticipated precision attainable for measuring $\\gamma$ after the LHCb Upgrade is outlined

  10. Penalising Model Component Complexity: A Principled, Practical Approach to Constructing Priors

    Simpson, Daniel

    2017-04-06

    In this paper, we introduce a new concept for constructing prior distributions. We exploit the natural nested structure inherent to many model components, which defines the model component to be a flexible extension of a base model. Proper priors are defined to penalise the complexity induced by deviating from the simpler base model and are formulated after the input of a user-defined scaling parameter for that model component, both in the univariate and the multivariate case. These priors are invariant to repa-rameterisations, have a natural connection to Jeffreys\\' priors, are designed to support Occam\\'s razor and seem to have excellent robustness properties, all which are highly desirable and allow us to use this approach to define default prior distributions. Through examples and theoretical results, we demonstrate the appropriateness of this approach and how it can be applied in various situations.

  11. Penalising Model Component Complexity: A Principled, Practical Approach to Constructing Priors

    Simpson, Daniel; Rue, Haavard; Riebler, Andrea; Martins, Thiago G.; Sø rbye, Sigrunn H.

    2017-01-01

    In this paper, we introduce a new concept for constructing prior distributions. We exploit the natural nested structure inherent to many model components, which defines the model component to be a flexible extension of a base model. Proper priors are defined to penalise the complexity induced by deviating from the simpler base model and are formulated after the input of a user-defined scaling parameter for that model component, both in the univariate and the multivariate case. These priors are invariant to repa-rameterisations, have a natural connection to Jeffreys' priors, are designed to support Occam's razor and seem to have excellent robustness properties, all which are highly desirable and allow us to use this approach to define default prior distributions. Through examples and theoretical results, we demonstrate the appropriateness of this approach and how it can be applied in various situations.

  12. Heuristics as Bayesian inference under extreme priors.

    Parpart, Paula; Jones, Matt; Love, Bradley C

    2018-05-01

    Simple heuristics are often regarded as tractable decision strategies because they ignore a great deal of information in the input data. One puzzle is why heuristics can outperform full-information models, such as linear regression, which make full use of the available information. These "less-is-more" effects, in which a relatively simpler model outperforms a more complex model, are prevalent throughout cognitive science, and are frequently argued to demonstrate an inherent advantage of simplifying computation or ignoring information. In contrast, we show at the computational level (where algorithmic restrictions are set aside) that it is never optimal to discard information. Through a formal Bayesian analysis, we prove that popular heuristics, such as tallying and take-the-best, are formally equivalent to Bayesian inference under the limit of infinitely strong priors. Varying the strength of the prior yields a continuum of Bayesian models with the heuristics at one end and ordinary regression at the other. Critically, intermediate models perform better across all our simulations, suggesting that down-weighting information with the appropriate prior is preferable to entirely ignoring it. Rather than because of their simplicity, our analyses suggest heuristics perform well because they implement strong priors that approximate the actual structure of the environment. We end by considering how new heuristics could be derived by infinitely strengthening the priors of other Bayesian models. These formal results have implications for work in psychology, machine learning and economics. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  13. The early X-ray afterglows of optically bright and dark Gamma-Ray Bursts

    Lin, Yi-Qing

    2006-01-01

    A systematical study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift has been presented. Our sample includes 25 GRBs. Among them 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes ($F_{X}$), the gamma-ray fluxes ($S_{\\gamma}$), and the ratio ($R_{\\gamma, X}$) for both the D-GRBs and B-GRBs are similar. The differences of these distributions for the two kinds of GRBs shoul...

  14. Offending prior to first psychiatric contact

    Stevens, H; Agerbo, E; Dean, K

    2012-01-01

    There is a well-established association between psychotic disorders and subsequent offending but the extent to which those who develop psychosis might have a prior history of offending is less clear. Little is known about whether the association between illness and offending exists in non-psychot......-psychotic disorders. The aim of this study was to determine whether the association between mental disorder and offending is present prior to illness onset in psychotic and non-psychotic disorders.......There is a well-established association between psychotic disorders and subsequent offending but the extent to which those who develop psychosis might have a prior history of offending is less clear. Little is known about whether the association between illness and offending exists in non...

  15. GENERAL ASPECTS REGARDING THE PRIOR DISCIPLINARY RESEARCH

    ANDRA PURAN (DASCĂLU

    2012-05-01

    Full Text Available Disciplinary research is the first phase of the disciplinary action. According to art. 251 paragraph 1 of the Labour Code no disciplinary sanction may be ordered before performing the prior disciplinary research.These regulations provide an exception: the sanction of written warning. The current regulations in question, kept from the old regulation, provides a protection for employees against abuses made by employers, since sanctions are affecting the salary or the position held, or even the development of individual employment contract. Thus, prior research of the fact that is a misconduct, before a disciplinary sanction is applied, is an essential condition for the validity of the measure ordered. Through this study we try to highlight some general issues concerning the characteristics, processes and effects of prior disciplinary research.

  16. Ultrasonography X gamma radiography

    Mello Campos, A.M. de

    1989-01-01

    The accumulated experience in the last ten years of substitution to essays by gamma radiography to essay by ultrasonography, starting of the systematic comparison and tabulation of the results obtained by both essays applied in welding joints, in field, in steel pipelines of the SABESP. (V.R.B.)

  17. Gamma knife radiosurgery

    Kobayashi, Tatsuya; Mori, Yohsimasa; Kida, Yoshihisa

    2003-01-01

    Gamma knife radiosurgery has become a new treatment modality in the field of neurosurgery since the first gamma knife was brought into Japan in 1990. Advances in applications of new indications and long-term results have been continued to evolve during the past 12 years. Based on the experience of more than 4,500 cases treated by gamma knife at Komaki City Hospital, long-term results of arteriovenous malformations (AVMs), metastatic brain tumors, acoustic neurinomas, meningiomas and trigeminal neuralgias are presented. Radiosurgery has become a novel treatment modality, especially for AVM, acoustic neurinoma and meningioma, which were once only treatable by conventional surgery, and shows a high cure rate in AVM cases and high control rate in benign tumors without major complications. The effects of radiosurgery for metastatic brain tumors have been thought to be superior to fractionated radiotherapy due to high response and control rates, and patients showed improved quality of life although no prolongation of the life span was obtained. Gamma knife treatment for trigeminal neuralgia has been shown to be effective and less invasive than microvascular decompression, and is useful for cases resistant to conventional therapies and as an initial treatment as well. (author)

  18. Automated gamma counters

    Regener, M.

    1977-01-01

    This is a report on the most recent developments in the full automation of gamma counting in RIA, in particular by Messrs. Kontron. The development targets were flexibility in sample capacity and shape of test tubes, the possibility of using different radioisotopes for labelling due to an optimisation of the detector system and the use of microprocessers to substitute software for hardware. (ORU) [de

  19. Gamma cardio 82

    Itti, R.

    1982-01-01

    New trends in nuclear cardiology are briefly presented supported by a large bibliography. The following topics are reviewed: new tracers of myocardial perfusion and metabolism; quantitative analysis of cardiac function; nuclear stethoscope; gamma emission tomography; diagnostic value of cardiac dynamic tests (at rest and during exercise), pharmacological tests; new clinical applications of cardiovascular nuclear medicine [fr

  20. Marine gamma spectrometric survey

    Kostoglodov, V.V.

    1979-01-01

    Presented are theoretical problems physical and geochemical prerequisites and possibilities of practical application of the method of continuous submarine gamma-spectrometric survey and radiometric survey destined for rapid study of the surface layer of marine sediments. Shown is high efficiency and advantages of this method in comparison with traditional and widely spread in marine geology methods of bottom sediments investigation

  1. Industrial radiography. Gamma radiography

    Menetrier, J.

    1975-01-01

    Informations are given on gamma radiodefectology regulations, entire references and main dispositions applicable to each state of the European Economic Community. The content includes previous arrangements for source acquisition, holding and use of the sources, transport, accidents, civil liability of the source holder, person insurance against radiation hazards and contamination, property insurance, penal liability of the source holder

  2. Introscopy using gamma sources

    Gromov, Yu.V.; Leonov, B.I.; Najorov, A.N.; Smirnov, N.N.; Firstov, V.G.

    1978-01-01

    A method is described of working with standard 170 Tm, 75 Se, 192 Ir, 137 Cs and 60 Co sources at the activity of 1-4000 Ci, during television gamma introscopy of steel products. Experiments involving the RI-10T introscope are carried out to determine prospects of using various radiation sources. The results of using X-ray instruments for control of steel products are also shown for comparison. In introscopy of X-rayed steel products over 25 mm thick, spreading of the edge of the detected groove image is shown to be comparable when using X radiation and gamma radiation of standard sources. Sensitivity of control by fluorographic introscope in X-raying and gamma irradiation of products over 25 mm thick will presumably be the same owing to the detector storage capacity. The use of commercial gamma flaw detecting instruments together with a television introscope permits to reliably reveal defects of 0.5-2.0 mm in size, eliminating possible instability of operation of X-ray instruments, particularly in field conditions

  3. Gamma apparatuses for radiotherapy

    Sul'kin, A.G.

    1986-01-01

    Scientific and technical achievements in development and application of gamma therapeutic apparatuses for external and intracavity irradiations are generalized. Radiation-physical parameters of apparatuses providing usability of progressive methods in radiotherapy of onclogical patients are given. Optimization of main apparatus elements, ensurance of its operation reliability, reduction of errors of irradiation plan reproduction are considered. Attention is paid to radiation safety

  4. Gamma ray calibration system

    Rosauer, P.J.; Flaherty, J.J.

    1981-01-01

    This invention is in the field of gamma ray inspection devices for tubular products and the like employing an improved calibrating block which prevents the sensing system from being overloaded when no tubular product is present, and also provides the operator with a means for visually detecting the presence of wall thicknesses which are less than a required minimum. (author)

  5. New nuclear medicine gamma camera systems

    Villacorta, Edmundo V.

    1997-01-01

    The acquisition of the Open E.CAM and DIACAM gamma cameras by Makati Medical Center is expected to enhance the capabilities of its nuclear medicine facilities. When used as an aid to diagnosis, nuclear medicine entails the introduction of a minute amount of radioactive material into the patient; thus, no reaction or side-effect is expected. When it reaches the particular target organ, depending on the radiopharmaceutical, a lesion will appear as a decrease (cold) area or increase (hot) area in the radioactive distribution as recorded byu the gamma cameras. Gamma camera images in slices or SPECT (Single Photon Emission Computer Tomography), increase the sensitivity and accuracy in detecting smaller and deeply seated lesions, which otherwise may not be detected in the regular single planar images. Due to the 'open' design of the equipment, claustrophobic patients will no longer feel enclosed during the procedure. These new gamma cameras yield improved resolution and superb image quality, and the higher photon sensitivity shortens imaging acquisition time. The E.CAM, which is the latest generation gamma camera, is featured by its variable angle dual-head system, the only one available in the Philipines, and the excellent choice for Myocardial Perfusion Imaging (MPI). From the usual 45 minutes, the acquisition time for gated SPECT imaging of the heart has now been remarkably reduced to 12 minutes. 'Gated' infers snap-shots of the heart in selected phases of its contraction and relaxation as triggered by ECG. The DIACAM is installed in a room with access outside the main entrance of the department, intended specially for bed-borne patients. Both systems are equipped with a network of high performance Macintosh ICOND acquisition and processing computers. Added to the hardware is the ICON processing software which allows total simultaneous acquisition and processing capabilities in the same operator's terminal. Video film and color printers are also provided. Together

  6. On the use of prior information in modelling metabolic utilization of energy in growing pigs

    Strathe, Anders Bjerring; Jørgensen, Henry; Fernández, José Adalberto

    2011-01-01

    Construction of models that provide a realistic representation of metabolic utilization of energy in growing animals tend to be over-parameterized because data generated from individual metabolic studies are often sparse. In the Bayesian framework prior information can enter the data analysis......, PD and LD) made on a given pig at a given time followed a multivariate normal distribution. Two different equation systems were adopted from Strathe et al. (2010), generating the expected values in the multivariate normal distribution. Non-informative prior distributions were assigned for all model......, kp and kf, respectively. Utilizing both sets of priors showed that the maintenance component was sensitive to the statement of prior belief and, hence, that the estimate of 0.91 MJkg0.60d1 (95% CI: 0.78; 1.09) should be interpreted with caution. It was shown that boars were superior in depositing...

  7. Gamma factors of an ambulatory source; Factores gamma de una fuente ambulatoria

    Arcos P, A; Vega C, H R; Manzanares A, E; Salas L, M A; Hernandez D, V M [Unidades Academicas de Estudios Nucleares e Ingenieria Electrica, Universidad Autonoma de Zacatecas, C. Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Barquero, R [Hospital Universitario del Rio Hortega, E-47010 Valladolid (Spain)

    2007-07-01

    Some of the procedures for diagnostic or treatment used in the medicine use radioactive materials as the I{sup 131}. By means of Monte Carlo methods were calculated the doses in the internal organs of a woman, with three months of pregnancy, due to the radioiodine captured by her thyroid, as well as to 1 meter of the gland. A three-dimensional mathematical model of the body of a woman was used and by means of Monte Carlo, the radioiodine photons were transported isotropically from the thyroid toward the whole body and was calculated the absorbed dose by their internal organs, also the Kerma in air (K) was determined and the environmental equivalent dose (H{sup *}(10)) at 1 m of the gland. Two activity factors at dose were determined, Gamma Factors that it allows to estimate the dose that the patient produces to people to its around. Of the gamma radiation that emits the I{sup 131} in the thyroid was found that the thymus receives the biggest dose while the uterus is the organ that smaller dose receives. The determined gamma factors were: {gamma}{sub KAire} = 56 {mu}Gy-m{sup 2}-h{sup -1}-GBq{sup -1}, and {gamma}{sub H}{sup *}{sub (10)} = 73 {mu}Sv-m{sup 2}-h{sup -1}-GBq{sup -1}. The distribution of the absorbed dose by the internal organs is attributed to the relative distance among the thyroid and the other organs, to the inter-organs shielding, its size and to its elementary composition. The {gamma}{sub KAire} and {gamma}{sub H}{sup *}{sub (10)} factors allow to estimate the exposure that the patient produces on the personnel to its around. With this, the nuclear medicus, the medical physicist or the one responsible of the radiological safety in the hospital can give more precise indications on the behavior of people around the patient. (Author)

  8. Can natural selection encode Bayesian priors?

    Ramírez, Juan Camilo; Marshall, James A R

    2017-08-07

    The evolutionary success of many organisms depends on their ability to make decisions based on estimates of the state of their environment (e.g., predation risk) from uncertain information. These decision problems have optimal solutions and individuals in nature are expected to evolve the behavioural mechanisms to make decisions as if using the optimal solutions. Bayesian inference is the optimal method to produce estimates from uncertain data, thus natural selection is expected to favour individuals with the behavioural mechanisms to make decisions as if they were computing Bayesian estimates in typically-experienced environments, although this does not necessarily imply that favoured decision-makers do perform Bayesian computations exactly. Each individual should evolve to behave as if updating a prior estimate of the unknown environment variable to a posterior estimate as it collects evidence. The prior estimate represents the decision-maker's default belief regarding the environment variable, i.e., the individual's default 'worldview' of the environment. This default belief has been hypothesised to be shaped by natural selection and represent the environment experienced by the individual's ancestors. We present an evolutionary model to explore how accurately Bayesian prior estimates can be encoded genetically and shaped by natural selection when decision-makers learn from uncertain information. The model simulates the evolution of a population of individuals that are required to estimate the probability of an event. Every individual has a prior estimate of this probability and collects noisy cues from the environment in order to update its prior belief to a Bayesian posterior estimate with the evidence gained. The prior is inherited and passed on to offspring. Fitness increases with the accuracy of the posterior estimates produced. Simulations show that prior estimates become accurate over evolutionary time. In addition to these 'Bayesian' individuals, we also

  9. Gamma rays from the interstellar medium

    Bloemen, J.B.G.M.

    1985-01-01

    This thesis describes new gamma-ray views on cosmic rays and the interstellar medium. The author describes the COS-B data base and the pre-launch and in-flight calibration data used for all analyses. Diffuse galactic gamma radiation (> 50 MeV) may be either a result of cosmic-ray-matter interactions, or of the cosmic-ray electrons with the interstellar radiation field (mainly at optical and infrared wavelengths), through the inverse-Compton process. A detailed comparison between the gamma-ray observations of the large complex of interstellar clouds in Orion and Monoceros and the CO and HI surveys of this region is given. It gives insight into the cloud penetration of cosmic rays and in the relation between CO detections and molecular hydrogen column densities. Next, the radial distribution of gamma rays in the Galaxy is studied, as well as the galactic centre (more precisely, the central 400 pc), which contains a large concentration of CO molecules. The H 2 /CO abundance and the cosmic-ray density in the galactic centre are discussed and compared to the findings for the galactic disk. In various analyses in this thesis a likelihood-ratio method is applied for parameter estimation and hypothesis testing. A general description of this method is added as an appendix. (Auth.)

  10. Variable code gamma ray imaging system

    Macovski, A.; Rosenfeld, D.

    1979-01-01

    A gamma-ray source distribution in the body is imaged onto a detector using an array of apertures. The transmission of each aperture is modulated using a code such that the individual views of the source through each aperture can be decoded and separated. The codes are chosen to maximize the signal to noise ratio for each source distribution. These codes determine the photon collection efficiency of the aperture array. Planar arrays are used for volumetric reconstructions and circular arrays for cross-sectional reconstructions. 14 claims

  11. Development of gallium arsenide gamma spectrometric detector

    Kobayashi, T.; Kuru, I.

    1975-03-01

    GaAs semiconductor material has been considered to be a suitable material for gamma-ray spectrometer operating at room temperature since it has a wid-band gap, larger than that of silicon and germanium. The basic objective of this work is to develop a GaAs gamma-ray spectrometric detector which could be used for gamma spectrometric measurement of uranium and plutonium in nuclear fuel safeguards. Liquid phase epitaxial techniques using iron (Fe) as dopant have been developed in making high purity GaAs crystals suitable for gamma-ray spectrometer operating at room temperature. Concentration of Fe in the epitaxial crystal was controlled by initial growth temperature. The best quality epitaxial crystal was obtained under the following conditions: starting temperature is about 800degC, the proportion of Fe to Ga solvent is 1 to 300. Carrier concentration of epitaxial crystals grown distributed in the ranges of 10 12 cm -3 to 10 14 cm -3 at room temperature. The thickness of the crystals ranged from 38 μm to 120 μm. Au-GaAs surface barrier detector was made of epitaxial crystal. Some of the detector were encapsulated in a can with a 50 μm Be window by welding a can to the detector holder. The detector with high energy resolution and good charge collecting characteristics was selected by alpha spectrometry at room temperature. Energy resolution of the detector for gamma-rays up to about 200 keV was very good at room temperature operation. The best energy resolutions taken with a GaAs detector were 3 keV (fwhm) and 3.8 keV for 241 Am 59.6 keV and 57 Co 122 keV, respectively, at room temperature. In order to study the applicability of the detector for nuclear safeguards, the measurements of 235 U gamma-ray spectrum have been carried out at room temperature. It was clarified that the gamma-ray spectrum of enriched U sample could be measured in high resolution with GaAs detector at room temperature, and that the content of 235 U in enriched U sources could be determined by

  12. Calibrated birth-death phylogenetic time-tree priors for bayesian inference.

    Heled, Joseph; Drummond, Alexei J

    2015-05-01

    Here we introduce a general class of multiple calibration birth-death tree priors for use in Bayesian phylogenetic inference. All tree priors in this class separate ancestral node heights into a set of "calibrated nodes" and "uncalibrated nodes" such that the marginal distribution of the calibrated nodes is user-specified whereas the density ratio of the birth-death prior is retained for trees with equal values for the calibrated nodes. We describe two formulations, one in which the calibration information informs the prior on ranked tree topologies, through the (conditional) prior, and the other which factorizes the prior on divergence times and ranked topologies, thus allowing uniform, or any arbitrary prior distribution on ranked topologies. Although the first of these formulations has some attractive properties, the algorithm we present for computing its prior density is computationally intensive. However, the second formulation is always faster and computationally efficient for up to six calibrations. We demonstrate the utility of the new class of multiple-calibration tree priors using both small simulations and a real-world analysis and compare the results to existing schemes. The two new calibrated tree priors described in this article offer greater flexibility and control of prior specification in calibrated time-tree inference and divergence time dating, and will remove the need for indirect approaches to the assessment of the combined effect of calibration densities and tree priors in Bayesian phylogenetic inference. © The Author(s) 2014. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.

  13. Optimal design of priors constrained by external predictors

    Quinn, A.; Kárný, Miroslav; Guy, Tatiana Valentine

    2017-01-01

    Roč. 84, č. 1 (2017), s. 150-158 ISSN 0888-613X R&D Projects: GA ČR(CZ) GA16-09848S Institutional support: RVO:67985556 Keywords : Fully probabilistic design * Parameter prior * External predictive distribution * Bayesian transfer learning * Kullback–Leibler divergence Subject RIV: BC - Control Systems Theory OBOR OECD: Computer sciences, information science, bioinformathics (hardware development to be 2.2, social aspect to be 5.8) Impact factor: 2.845, year: 2016 http://library.utia.cas.cz/separaty/2017/AS/guy-0473911.pdf

  14. Collimatorless imaging of gamma rays with help of gamma-ray tracking

    Marel, J V D

    2001-01-01

    In many gamma-ray detector systems that are built for imaging purposes Compton scattered photons are suppressed as much as possible. However, the information from photons that scattered inside a detector system can be used to reconstruct the tracks of the photons with help of gamma-ray tracking. Estimates of the incident directions of the photons can be made and an image can be created. Examples of potential applications for this technique are the use as a gamma-camera in medical imaging (e.g. SPECT) or as a detector for PET. Due to the omission of collimators, much higher detection efficiencies can be achieved, reducing the doses required for an image. A gamma-ray tracking method, called backtracking, has been developed for nuclear spectroscopy. The method tracks gamma-rays originating from a point source in the center of a spherical detector system consisting of position-sensitive germanium detectors. This method can also be used as a tracking technique for imaging of an unknown source distribution. With he...

  15. A gamma beam profile imager for ELI-NP Gamma Beam System

    Cardarelli, P.; Paternò, G.; Di Domenico, G.; Consoli, E.; Marziani, M.; Andreotti, M.; Evangelisti, F.; Squerzanti, S.; Gambaccini, M.; Albergo, S.; Cappello, G.; Tricomi, A.; Veltri, M.; Adriani, O.; Borgheresi, R.; Graziani, G.; Passaleva, G.; Serban, A.; Starodubtsev, O.; Variola, A.; Palumbo, L.

    2018-06-01

    The Gamma Beam System of ELI-Nuclear Physics is a high brilliance monochromatic gamma source based on the inverse Compton interaction between an intense high power laser and a bright electron beam with tunable energy. The source, currently being assembled in Magurele (Romania), is designed to provide a beam with tunable average energy ranging from 0.2 to 19.5 MeV, rms energy bandwidth down to 0.5% and flux of about 108 photons/s. The system includes a set of detectors for the diagnostic and complete characterization of the gamma beam. To evaluate the spatial distribution of the beam a gamma beam profile imager is required. For this purpose, a detector based on a scintillator target coupled to a CCD camera was designed and a prototype was tested at INFN-Ferrara laboratories. A set of analytical calculations and Monte Carlo simulations were carried out to optimize the imager design and evaluate the performance expected with ELI-NP gamma beam. In this work the design of the imager is described in detail, as well as the simulation tools used and the results obtained. The simulation parameters were tuned and cross-checked with the experimental measurements carried out on the assembled prototype using the beam from an x-ray tube.

  16. Estimating the changes in the distribution of energy efficiency in the U.S. automobile assembly industry

    Boyd, Gale A.

    2014-01-01

    This paper describes the EPA's voluntary ENERGY STAR program and the results of the automobile manufacturing industry's efforts to advance energy management as measured by the updated ENERGY STAR Energy Performance Indicator (EPI). A stochastic single-factor input frontier estimation using the gamma error distribution is applied to separately estimate the distribution of the electricity and fossil fuel efficiency of assembly plants using data from 2003 to 2005 and then compared to model results from a prior analysis conducted for the 1997–2000 time period. This comparison provides an assessment of how the industry has changed over time. The frontier analysis shows a modest improvement (reduction) in “best practice” for electricity use and a larger one for fossil fuels. This is accompanied by a large reduction in the variance of fossil fuel efficiency distribution. The results provide evidence of a shift in the frontier, in addition to some “catching up” of poor performing plants over time. - Highlights: • A non-public dataset of U.S. auto manufacturing plants is compiled. • A stochastic frontier with a gamma distribution is applied to plant level data. • Electricity and fuel use are modeled separately. • Comparison to prior analysis reveals a shift in the frontier and “catching up”. • Results are used by ENERGY STAR to award energy efficiency plant certifications

  17. Cosmical sources of gamma radiation

    Kuchowicz, B [Warsaw Univ. (Poland)

    1974-01-01

    A brief historical outline of the X-ray and ..gamma..-ray astronomies is given first, then a summary of the recent status of X-ray astronomy follows. Further chapters include information on ..gamma..-ray sources in the solar system, in our Galaxy, and beyond it. In discussing linear gamma spectra attention is paid to the possibility of studying explosive nucleo-synthesis by observation of gamma lines from supernova remnants, etc. Questions of the isotropic gamma background are discussed at the end of the survey.

  18. Recognition of Prior Learning: The Participants' Perspective

    Miguel, Marta C.; Ornelas, José H.; Maroco, João P.

    2016-01-01

    The current narrative on lifelong learning goes beyond formal education and training, including learning at work, in the family and in the community. Recognition of prior learning is a process of evaluation of those skills and knowledge acquired through life experience, allowing them to be formally recognized by the qualification systems. It is a…

  19. Validity in assessment of prior learning

    Wahlgren, Bjarne; Aarkrog, Vibe

    2015-01-01

    , the article discusses the need for specific criteria for assessment. The reliability and validity of the assessment procedures depend on whether the competences are well-defined, and whether the teachers are adequately trained for the assessment procedures. Keywords: assessment, prior learning, adult...... education, vocational training, lifelong learning, validity...

  20. PET reconstruction via nonlocal means induced prior.

    Hou, Qingfeng; Huang, Jing; Bian, Zhaoying; Chen, Wufan; Ma, Jianhua

    2015-01-01

    The traditional Bayesian priors for maximum a posteriori (MAP) reconstruction methods usually incorporate local neighborhood interactions that penalize large deviations in parameter estimates for adjacent pixels; therefore, only local pixel differences are utilized. This limits their abilities of penalizing the image roughness. To achieve high-quality PET image reconstruction, this study investigates a MAP reconstruction strategy by incorporating a nonlocal means induced (NLMi) prior (NLMi-MAP) which enables utilizing global similarity information of image. The present NLMi prior approximates the derivative of Gibbs energy function by an NLM filtering process. Specially, the NLMi prior is obtained by subtracting the current image estimation from its NLM filtered version and feeding the residual error back to the reconstruction filter to yield the new image estimation. We tested the present NLMi-MAP method with simulated and real PET datasets. Comparison studies with conventional filtered backprojection (FBP) and a few iterative reconstruction methods clearly demonstrate that the present NLMi-MAP method performs better in lowering noise, preserving image edge and in higher signal to noise ratio (SNR). Extensive experimental results show that the NLMi-MAP method outperforms the existing methods in terms of cross profile, noise reduction, SNR, root mean square error (RMSE) and correlation coefficient (CORR).

  1. Prior learning assessment and quality assurance practice ...

    The use of RPL (Recognition of Prior Learning) in higher education to assess RPL candidates for admission into programmes of study met with a lot of criticism from faculty academics. Lecturers viewed the possibility of admitting large numbers of under-qualified adult learners, as a threat to the institution's reputation, or an ...

  2. Action priors for learning domain invariances

    Rosman, Benjamin S

    2015-04-01

    Full Text Available behavioural invariances in the domain, by identifying actions to be prioritised in local contexts, invariant to task details. This information has the effect of greatly increasing the speed of solving new problems. We formalise this notion as action priors...

  3. Development of the computer code to monitor gamma radiation in the nuclear facility environment

    Akhmad, Y. R.; Pudjiyanto, M.S.

    1998-01-01

    Computer codes for gamma radiation monitoring in the vicinity of nuclear facility which have been developed could be introduced to the commercial potable gamma analyzer. The crucial stage of the first year activity was succeeded ; that is the codes have been tested to transfer data file (pulse high distribution) from Micro NOMAD gamma spectrometer (ORTEC product) and the convert them into dosimetry and physics quantities. Those computer codes are called as GABATAN (Gamma Analyzer of Batan) and NAGABAT (Natural Gamma Analyzer of Batan). GABATAN code can isable to used at various nuclear facilities for analyzing gamma field up to 9 MeV, while NAGABAT could be used for analyzing the contribution of natural gamma rays to the exposure rate in the certain location

  4. Measurement of gamma radiation doses in nuclear power plant environment

    Bochvar, I.A.; Keirim-Markus, I.B.; Sergeeva, N.A.

    1976-01-01

    Considered are the problems of measuring gamma radiation dose values and the dose distribution in the nuclear power plant area with the aim of estimating the extent of their effect on the population. Presented are the dosimeters applied, their distribution throughout the controlled area, time of measurement. The distribution of gamma radiation doses over the controlled area and the dose alteration with the increase of the distance from the release source are shown. The results of measurements are investigated. The conclusion is made that operating nuclear power plants do not cause any increase in the gamma radiation dose over the area. Recommendations for clarifying the techniques for using dose-meters and decreasing measurement errors are given [ru

  5. Precise measurement of {gamma}(K{yields}e {nu}({gamma}))/{gamma}(K{yields}{mu} {nu}({gamma})) and study of K{yields}e {nu} {gamma}

    Ambrosino, F.; Massarotti, P.; Meola, S.; Napolitano, M. [Dipartimento di Scienze Fisiche dell' Universita ' ' Federico II' ' , Napoli (Italy); INFN Sezione di Napoli, Napoli (Italy); Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bloise, C.; Bossi, F.; Capon, G.; Capussela, T.; Ciambrone, P.; De Lucia, E.; De Simone, P.; Dreucci, M.; Felici, G.; Gatti, C.; Giovannella, S.; Jacewicz, M.; Lanfranchi, G.; Miscetti, S.; Moulson, M.; Murtas, F.; Palutan, M.; Santangelo, P.; Sciascia, B.; Sibidanov, A.; Spadaro, T.; Venanzoni, G. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Archilli, F. [Dipartimento di Fisica dell' Universita ' ' Tor Vergata' ' , Rome (Italy); INFN Sezione di Roma Tor Vergata, Rome (Italy); Beltrame, P.; Denig, A.; Mueller, S. [Johannes Gutenberg-Universitaet, Institut fuer Kernphysik, Mainz (Germany); Bini, C.; De Santis, A.; De Zorzi, G.; Di Domenico, A.; Fiore, S.; Franzini, P.; Gauzzi, P. [Dipartimento di Fisica dell' Universita ' ' La Sapienza' ' , Rome (Italy); INFN Sezione di Roma, Rome (Italy); Bocchetta, S.; Ceradini, F.; Di Micco, B.; Nguyen, F. [Dipartimento di Fisica dell' Universita ' ' Roma Tre' ' , Rome (Italy); INFN Sezione di Roma Tre, Rome (Italy); Branchini, P.; Graziani, E.; Passeri, A.; Tortora, L. [INFN Sezione di Roma Tre, Rome (Italy); Capriotti, D. [Dipartimento di Fisica dell' Universita ' ' Roma Tre' ' , Rome (Italy); Di Donato, C. [INFN Sezione di Napoli, Napoli (Italy); Kulikov, V. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Lee-Franzini, J. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); State University of New York, Physics Department, Stony Brook (United States); Martini, M.; Patera, V.; Versaci, R. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dipartimento di Energetica dell' Universita ' ' La Sapienza' ' , Rome (Italy); Valente, P. [INFN Sezione di Roma, Rome (Italy)

    2009-12-15

    We present a precise measurement of the ratio R{sub K}={gamma}(K{yields}e{nu}({gamma}))/{gamma}(K{yields}{mu}{nu}({gamma})) and a study of the radiative process K{yields}e{nu}{gamma}, performed with the KLOE detector. The results are based on data collected at the Frascati e{sup +}e{sup -} collider DA {phi}NE for an integrated luminosity of 2.2 fb{sup -1}. We find R{sub K}=(2.493{+-}0.025{sub stat}{+-}0.019{sub syst}) x 10{sup -5}, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate d {gamma}(K{yields}e{nu}{gamma})/dE{sub {gamma}} for photon energies 10gamma}}<250 MeV. Results are compared with predictions from theory. (orig.)

  6. A Single Image Dehazing Method Using Average Saturation Prior

    Zhenfei Gu

    2017-01-01

    Full Text Available Outdoor images captured in bad weather are prone to yield poor visibility, which is a fatal problem for most computer vision applications. The majority of existing dehazing methods rely on an atmospheric scattering model and therefore share a common limitation; that is, the model is only valid when the atmosphere is homogeneous. In this paper, we propose an improved atmospheric scattering model to overcome this inherent limitation. By adopting the proposed model, a corresponding dehazing method is also presented. In this method, we first create a haze density distribution map of a hazy image, which enables us to segment the hazy image into scenes according to the haze density similarity. Then, in order to improve the atmospheric light estimation accuracy, we define an effective weight assignment function to locate a candidate scene based on the scene segmentation results and therefore avoid most potential errors. Next, we propose a simple but powerful prior named the average saturation prior (ASP, which is a statistic of extensive high-definition outdoor images. Using this prior combined with the improved atmospheric scattering model, we can directly estimate the scene atmospheric scattering coefficient and restore the scene albedo. The experimental results verify that our model is physically valid, and the proposed method outperforms several state-of-the-art single image dehazing methods in terms of both robustness and effectiveness.

  7. The search for Infrared radiation prior to major earthquakes

    Ouzounov, D.; Taylor, P.; Pulinets, S.

    2004-12-01

    This work describes our search for a relationship between tectonic stresses and electro-chemical and thermodynamic processes in the Earth and increases in mid-IR flux as part of a possible ensemble of electromagnetic (EM) phenomena that may be related to earthquake activity. Recent analysis of continuous ongoing long- wavelength Earth radiation (OLR) indicates significant and anomalous variability prior to some earthquakes. The cause of these anomalies is not well understood but could be the result of a triggering by an interaction between the lithosphere-hydrosphere and atmospheric related to changes in the near surface electrical field and gas composition prior to the earthquake. The OLR anomaly covers large areas surrounding the main epicenter. We have use the NOAA IR data to differentiate between the global and seasonal variability and these transient local anomalies. Indeed, on the basis of a temporal and spatial distribution analysis, an anomaly pattern is found to occur several days prior some major earthquakes. The significance of these observations was explored using data sets of some recent worldwide events.

  8. Generalized species sampling priors with latent Beta reinforcements

    Airoldi, Edoardo M.; Costa, Thiago; Bassetti, Federico; Leisen, Fabrizio; Guindani, Michele

    2014-01-01

    Many popular Bayesian nonparametric priors can be characterized in terms of exchangeable species sampling sequences. However, in some applications, exchangeability may not be appropriate. We introduce a novel and probabilistically coherent family of non-exchangeable species sampling sequences characterized by a tractable predictive probability function with weights driven by a sequence of independent Beta random variables. We compare their theoretical clustering properties with those of the Dirichlet Process and the two parameters Poisson-Dirichlet process. The proposed construction provides a complete characterization of the joint process, differently from existing work. We then propose the use of such process as prior distribution in a hierarchical Bayes modeling framework, and we describe a Markov Chain Monte Carlo sampler for posterior inference. We evaluate the performance of the prior and the robustness of the resulting inference in a simulation study, providing a comparison with popular Dirichlet Processes mixtures and Hidden Markov Models. Finally, we develop an application to the detection of chromosomal aberrations in breast cancer by leveraging array CGH data. PMID:25870462

  9. Natural priors, CMSSM fits and LHC weather forecasts

    Allanach, Benjamin C.; Cranmer, Kyle; Lester, Christopher G.; Weber, Arne M.

    2007-01-01

    Previous LHC forecasts for the constrained minimal supersymmetric standard model (CMSSM), based on current astrophysical and laboratory measurements, have used priors that are flat in the parameter tan β, while being constrained to postdict the central experimental value of M Z . We construct a different, new and more natural prior with a measure in μ and B (the more fundamental MSSM parameters from which tan β and M Z are actually derived). We find that as a consequence this choice leads to a well defined fine-tuning measure in the parameter space. We investigate the effect of such on global CMSSM fits to indirect constraints, providing posterior probability distributions for Large Hadron Collider (LHC) sparticle production cross sections. The change in priors has a significant effect, strongly suppressing the pseudoscalar Higgs boson dark matter annihilation region, and diminishing the probable values of sparticle masses. We also show how to interpret fit information from a Markov Chain Monte Carlo in a frequentist fashion; namely by using the profile likelihood. Bayesian and frequentist interpretations of CMSSM fits are compared and contrasted

  10. Distinguishing 'Higgs' spin hypotheses using $\\gamma \\gamma$ and $W W^*$ decays

    Ellis, John; Hwang, Dae Sung; Sanz, Veronica; You, Tevong

    2013-01-01

    The new particle X recently discovered by the ATLAS and CMS Collaborations in searches for the Higgs boson has been observed to decay into gamma gamma, ZZ* and WW*, but its spin and parity, J^P, remain a mystery, with J^P = 0^+ and 2^+ being open possibilities. We use PYTHIA and Delphes to simulate an analysis of the angular distribution of gg to X to gamma gamma decays in a full 2012 data set, including realistic background levels. We show that this angular distribution should provide strong discrimination between the possibilities of spin zero and spin two with graviton-like couplings: ~ 3 sigma if a conservative symmetric interpretation of the log-likelihood ratio (LLR) test statistic is used, and ~ 6 sigma if a less conservative asymmetric interpretation is used. The WW and ZZ couplings of the Standard Model Higgs boson and of a 2^+ particle with graviton-like couplings are both expected to exhibit custodial symmetry. We simulate the present ATLAS and CMS search strategies for X to WW* using PYTHIA and De...

  11. Performance of informative priors skeptical of large treatment effects in clinical trials: A simulation study.

    Pedroza, Claudia; Han, Weilu; Thanh Truong, Van Thi; Green, Charles; Tyson, Jon E

    2018-01-01

    One of the main advantages of Bayesian analyses of clinical trials is their ability to formally incorporate skepticism about large treatment effects through the use of informative priors. We conducted a simulation study to assess the performance of informative normal, Student- t, and beta distributions in estimating relative risk (RR) or odds ratio (OR) for binary outcomes. Simulation scenarios varied the prior standard deviation (SD; level of skepticism of large treatment effects), outcome rate in the control group, true treatment effect, and sample size. We compared the priors with regards to bias, mean squared error (MSE), and coverage of 95% credible intervals. Simulation results show that the prior SD influenced the posterior to a greater degree than the particular distributional form of the prior. For RR, priors with a 95% interval of 0.50-2.0 performed well in terms of bias, MSE, and coverage under most scenarios. For OR, priors with a wider 95% interval of 0.23-4.35 had good performance. We recommend the use of informative priors that exclude implausibly large treatment effects in analyses of clinical trials, particularly for major outcomes such as mortality.

  12. Bayesian image reconstruction in SPECT using higher order mechanical models as priors

    Lee, S.J.; Gindi, G.; Rangarajan, A.

    1995-01-01

    While the ML-EM (maximum-likelihood-expectation maximization) algorithm for reconstruction for emission tomography is unstable due to the ill-posed nature of the problem, Bayesian reconstruction methods overcome this instability by introducing prior information, often in the form of a spatial smoothness regularizer. More elaborate forms of smoothness constraints may be used to extend the role of the prior beyond that of a stabilizer in order to capture actual spatial information about the object. Previously proposed forms of such prior distributions were based on the assumption of a piecewise constant source distribution. Here, the authors propose an extension to a piecewise linear model--the weak plate--which is more expressive than the piecewise constant model. The weak plate prior not only preserves edges but also allows for piecewise ramplike regions in the reconstruction. Indeed, for the application in SPECT, such ramplike regions are observed in ground-truth source distributions in the form of primate autoradiographs of rCBF radionuclides. To incorporate the weak plate prior in a MAP approach, the authors model the prior as a Gibbs distribution and use a GEM formulation for the optimization. They compare quantitative performance of the ML-EM algorithm, a GEM algorithm with a prior favoring piecewise constant regions, and a GEM algorithm with the weak plate prior. Pointwise and regional bias and variance of ensemble image reconstructions are used as indications of image quality. The results show that the weak plate and membrane priors exhibit improved bias and variance relative to ML-EM techniques

  13. QCD factorizations in {gamma}*{gamma}*->{rho}{sub L}{sup 0}{rho}{sub L}{sup 0}

    Pire, B. [CPHT, Unite mixte 7644 du CNRS, Ecole Polytechnique, 91128 Palaiseau (France)]. E-mail: pire@cpht.polytechnique.fr; Segond, M. [LPT, Unite mixte 8627 du CNRS, Universite Paris-Sud, 91405 Orsay (France); Szymanowski, L. [LPT, Unite mixte 8627 du CNRS, Universite Paris-Sud, 91405 Orsay (France); Universite de Liege, B-4000 Liege (Belgium); Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Wallon, S. [LPT, Unite mixte 8627 du CNRS. , Universite Paris-Sud, 91405 Orsay (France)

    2006-08-24

    We calculate the lowest order QCD amplitude, i.e. the quark exchange contribution, to the forward production amplitude of a pair of longitudinally polarized {rho} mesons in the scattering of two virtual photons {gamma}*(Q{sub 1}){gamma}*(Q{sub 2})->{rho}{sub L}{sup 0}{rho}{sub L}{sup 0}. We show that the scattering amplitude simultaneously factorizes in two quite different ways: the part with transverse photons is described by the QCD factorization formula involving the generalized distribution amplitude of two final {rho} mesons, whereas the part with longitudinally polarized photons takes the QCD factorized form with the {gamma}{sub L}*->{rho}{sub L}{sup 0} transition distribution amplitude. Perturbative expressions for these, in general, non-perturbative functions are obtained in terms of the {rho}-meson distribution amplitude.

  14. Measurement and Calculation of Gamma Radiation from HWZPR Reactor

    Jalali, Majid

    2006-01-01

    HWZPR is a research reactor with natural uranium fuel, D 2 O moderator and graphite reflector with maximum power of 100 W. It is a suitable means for theoretical research and heavy water reactor experiments. Neutrons from the core participate in different nuclear reactions by interactions with fuel, moderator, graphite and the concrete around the reactor. The results of these interactions are the production of prompt gammas in the environment. Useful information is gained by the reactor gamma spectrum measurement from point of view of relative quantity and energy distribution of direct and scattered radiations. Reactor gamma ray spectrum has been gathered in different places around the reactor by HPGe detector. In analysis of these spectra, 1 H(n,γ) 2 H, 16 O(n,n'γ) 16 O, 2 H(n,γ) 3 H and 238 U(n,γ) 239 U reactions occurring in reactor moderator and fuel, are important. The measured spectrum has been primarily estimated by the MCNP code. There is agreement between the code and the experiments in some points. The scattered gamma rays from 27 Al (n,γ) 28 Al reaction in the reactor tank, are the most among the gammas scattered in the reactor environment. Also the dose calculations by MCNP code show that 72% of gamma dose belongs to the energy range 3-11 MeV from reactor gamma spectrum and the danger of exposure from the reactor high-energy photons is serious. (author)

  15. Bayesian analysis of general failure data from an ageing distribution: advances in numerical methods

    Procaccia, H.; Villain, B.; Clarotti, C.A.

    1996-01-01

    EDF and ENEA carried out a joint research program for developing the numerical methods and computer codes needed for Bayesian analysis of component-lives in the case of ageing. Early results of this study were presented at ESREL'94. Since then the following further steps have been gone: input data have been generalized to the case that observed lives are censored both on the right and on the left; allowable life distributions are Weibull and gamma - their parameters are both unknown and can be statistically dependent; allowable priors are histograms relative to different parametrizations of the life distribution of concern; first-and-second-order-moments of the posterior distributions can be computed. In particular the covariance will give some important information about the degree of the statistical dependence between the parameters of interest. An application of the code to the appearance of a stress corrosion cracking in a tube of the PWR Steam Generator system is presented. (authors)

  16. PC based simulation of gamma camera for training of operating and maintenance staff

    Singh, B.; Kataria, S.K.; Samuel, A.M.

    2000-01-01

    Gamma camera- a sophisticated imaging system is used for functional assessment of biological subsystems/organs in nuclear medicine. The radioactive tracer attached to the native substance is injected into the patient. The distribution of radioactivity in the patient is imaged by the gamma camera. This report describes a PC based package for simulation of gamma cameras and effect of malfunctioning of its subsystems on images of different phantoms

  17. Gamma counter calibration system

    1977-01-01

    A method and apparatus are described for the calibration of a gamma radiation measurement instrument to be used over any of a number of different absolute energy ranges. The method includes the steps of adjusting the overall signal gain associated with pulses which are derived from detected gamma rays, until the instrument is calibrated for a particular absolute energy range; then storing parameter settings corresponding to the adjusted overall signal gain, and repeating the process for other desired absolute energy ranges. The stored settings can be subsequently retrieved and reapplied so that test measurements can be made using a selected one of the absolute energy ranges. Means are provided for adjusting the overall signal gain and a specific technique is disclosed for making coarse, then fine adjustments to the signal gain, for rapid convergence of the required calibration settings. (C.F.)

  18. Gamma-ray bursts

    Wijers, Ralph A M J; Woosley, Stan

    2012-01-01

    Cosmic gamma ray bursts (GRBs) have fascinated scientists and the public alike since their discovery in the late 1960s. Their story is told here by some of the scientists who participated in their discovery and, after many decades of false starts, solved the problem of their origin. Fourteen chapters by active researchers in the field present a detailed history of the discovery, a comprehensive theoretical description of GRB central engine and emission models, a discussion of GRB host galaxies and a guide to how GRBs can be used as cosmological tools. Observations are grouped into three sets from the satellites CGRO, BeppoSAX and Swift, and followed by a discussion of multi-wavelength observations. This is the first edited volume on GRB astrophysics that presents a fully comprehensive review of the subject. Utilizing the latest research, Gamma-ray Bursts is an essential desktop companion for graduate students and researchers in astrophysics.

  19. Gamma ray camera

    Wang, S.-H.; Robbins, C.D.

    1979-01-01

    An Anger gamma ray camera is improved by the substitution of a gamma ray sensitive, proximity type image intensifier tube for the scintillator screen in the Anger camera. The image intensifier tube has a negatively charged flat scintillator screen, a flat photocathode layer, and a grounded, flat output phosphor display screen, all of which have the same dimension to maintain unit image magnification; all components are contained within a grounded metallic tube, with a metallic, inwardly curved input window between the scintillator screen and a collimator. The display screen can be viewed by an array of photomultipliers or solid state detectors. There are two photocathodes and two phosphor screens to give a two stage intensification, the two stages being optically coupled by a light guide. (author)

  20. Imaging capabilities of germanium gamma cameras

    Steidley, J.W.

    1977-01-01

    Quantitative methods of analysis based on the use of a computer simulation were developed and used to investigate the imaging capabilities of germanium gamma cameras. The main advantage of the computer simulation is that the inherent unknowns of clinical imaging procedures are removed from the investigation. The effects of patient scattered radiation were incorporated using a mathematical LSF model which was empirically developed and experimentally verified. Image modifying effects of patient motion, spatial distortions, and count rate capabilities were also included in the model. Spatial domain and frequency domain modeling techniques were developed and used in the simulation as required. The imaging capabilities of gamma cameras were assessed using low contrast lesion source distributions. The results showed that an improvement in energy resolution from 10% to 2% offers significant clinical advantages in terms of improved contrast, increased detectability, and reduced patient dose. The improvements are of greatest significance for small lesions at low contrast. The results of the computer simulation were also used to compare a design of a hypothetical germanium gamma camera with a state-of-the-art scintillation camera. The computer model performed a parametric analysis of the interrelated effects of inherent and technological limitations of gamma camera imaging. In particular, the trade-off between collimator resolution and collimator efficiency for detection of a given low contrast lesion was directly addressed. This trade-off is an inherent limitation of both gamma cameras. The image degrading effects of patient motion, camera spatial distortions, and low count rate were shown to modify the improvements due to better energy resolution. Thus, based on this research, the continued development of germanium cameras to the point of clinical demonstration is recommended