Bootstrap Sequential Determination of the Co-integration Rank in VAR Models
DEFF Research Database (Denmark)
Guiseppe, Cavaliere; Rahbæk, Anders; Taylor, A.M. Robert
empirical rejection frequencies often very much in excess of the nominal level. As a consequence, bootstrap versions of these tests have been developed. To be useful, however, sequential procedures for determining the co-integrating rank based on these bootstrap tests need to be consistent, in the sense...... we fill this gap in the literature by proposing a bootstrap sequential algorithm which we demonstrate delivers consistent cointegration rank estimation for general I(1) processes. Finite sample Monte Carlo simulations show the proposed procedure performs well in practice....
Bootstrap Sequential Determination of the Co-integration Rank in VAR Models
DEFF Research Database (Denmark)
Cavaliere, Giuseppe; Rahbek, Anders; Taylor, A. M. Robert
empirical rejection frequencies often very much in excess of the nominal level. As a consequence, bootstrap versions of these tests have been developed. To be useful, however, sequential procedures for determining the co-integrating rank based on these bootstrap tests need to be consistent, in the sense...... that the probability of selecting a rank smaller than (equal to) the true co-integrating rank will converge to zero (one minus the marginal significance level), as the sample size diverges, for general I(1) processes. No such likelihood-based procedure is currently known to be available. In this paper...... we fill this gap in the literature by proposing a bootstrap sequential algorithm which we demonstrate delivers consistent cointegration rank estimation for general I(1) processes. Finite sample Monte Carlo simulations show the proposed procedure performs well in practice....
Bootstrap determination of the cointegration rank in heteroskedastic VAR models
DEFF Research Database (Denmark)
Cavaliere, Guiseppe; Rahbæk, Anders; Taylor, A.M. Robert
2014-01-01
In a recent paper Cavaliere et al. (2012) develop bootstrap implementations of the (pseudo-) likelihood ratio (PLR) co-integration rank test and associated sequential rank determination procedure of Johansen (1996). The bootstrap samples are constructed using the restricted parameter estimates of...... the underlying vector autoregressive (VAR) model which obtain under the reduced rank null hypothesis. They propose methods based on an independent and individual distributed (i.i.d.) bootstrap resampling scheme and establish the validity of their proposed bootstrap procedures in the context of a co......-integrated VAR model with i.i.d. innovations. In this paper we investigate the properties of their bootstrap procedures, together with analogous procedures based on a wild bootstrap resampling scheme, when time-varying behavior is present in either the conditional or unconditional variance of the innovations. We...
Bootstrap confidence intervals in a complex situation: A sequential paired clinical trial
International Nuclear Information System (INIS)
This paper considers the problem of determining a confidence interval for the difference between two treatments in a simplified sequential paired clinical trial, which is analogous to setting an interval for the drift of a random walk subject to a parabolic stopping boundary. Three bootstrap methods of construction are applied: Efron's accelerated bias-covered, the DiCiccio-Romano, and the bootstrap-t. The results are compared with a theoretical approximate interval due to Siegmund. Difficulties inherent in the use of these bootstrap methods in a complex situations are illustrated. The DiCiccio-Romano method is shown to be the easiest to apply and to work well. 13 refs
Bootstrap Determination of the Co-Integration Rank in Heteroskedastic VAR Models
DEFF Research Database (Denmark)
Cavaliere, Giuseppe; Rahbek, Anders; Taylor, A. M. Robert
In a recent paper Cavaliere et al. (2012) develop bootstrap implementations of the (pseudo-) likelihood ratio [PLR] co-integration rank test and associated sequential rank determination procedure of Johansen (1996). The bootstrap samples are constructed using the restricted parameter estimates of...... the underlying VAR model which obtain under the reduced rank null hypothesis. They propose methods based on an i.i.d. bootstrap re-sampling scheme and establish the validity of their proposed bootstrap procedures in the context of a co-integrated VAR model with i.i.d. innovations. In this paper we...... investigate the properties of their bootstrap procedures, together with analogous procedures based on a wild bootstrap re-sampling scheme, when time-varying behaviour is present in either the conditional or unconditional variance of the innovations. We show that the bootstrap PLR tests are asymptotically...
Bootstrap Determination of the Co-integration Rank in Heteroskedastic VAR Models
DEFF Research Database (Denmark)
Cavaliere, Giuseppe; Rahbek, Anders; Taylor, A.M.Robert
In a recent paper Cavaliere et al. (2012) develop bootstrap implementations of the (pseudo-) likelihood ratio [PLR] co-integration rank test and associated sequential rank determination procedure of Johansen (1996). The bootstrap samples are constructed using the restricted parameter estimates of...... the underlying VAR model which obtain under the reduced rank null hypothesis. They propose methods based on an i.i.d. bootstrap re-sampling scheme and establish the validity of their proposed bootstrap procedures in the context of a co-integrated VAR model with i.i.d. innovations. In this paper we...... investigate the properties of their bootstrap procedures, together with analogous procedures based on a wild bootstrap re-sampling scheme, when time-varying behaviour is present in either the conditional or unconditional variance of the innovations. We show that the bootstrap PLR tests are asymptotically...
Varouchakis, Emmanouil; Hristopulos, Dionissios
2015-04-01
Space-time geostatistical approaches can improve the reliability of dynamic groundwater level models in areas with limited spatial and temporal data. Space-time residual Kriging (STRK) is a reliable method for spatiotemporal interpolation that can incorporate auxiliary information. The method usually leads to an underestimation of the prediction uncertainty. The uncertainty of spatiotemporal models is usually estimated by determining the space-time Kriging variance or by means of cross validation analysis. For de-trended data the former is not usually applied when complex spatiotemporal trend functions are assigned. A Bayesian approach based on the bootstrap idea and sequential Gaussian simulation are employed to determine the uncertainty of the spatiotemporal model (trend and covariance) parameters. These stochastic modelling approaches produce multiple realizations, rank the prediction results on the basis of specified criteria and capture the range of the uncertainty. The correlation of the spatiotemporal residuals is modeled using a non-separable space-time variogram based on the Spartan covariance family (Hristopulos and Elogne 2007, Varouchakis and Hristopulos 2013). We apply these simulation methods to investigate the uncertainty of groundwater level variations. The available dataset consists of bi-annual (dry and wet hydrological period) groundwater level measurements in 15 monitoring locations for the time period 1981 to 2010. The space-time trend function is approximated using a physical law that governs the groundwater flow in the aquifer in the presence of pumping. The main objective of this research is to compare the performance of two simulation methods for prediction uncertainty estimation. In addition, we investigate the performance of the Spartan spatiotemporal covariance function for spatiotemporal geostatistical analysis. Hristopulos, D.T. and Elogne, S.N. 2007. Analytic properties and covariance functions for a new class of generalized Gibbs
Energy Technology Data Exchange (ETDEWEB)
Niehof, Jonathan T.; Morley, Steven K.
2012-01-01
We review and develop techniques to determine associations between series of discrete events. The bootstrap, a nonparametric statistical method, allows the determination of the significance of associations with minimal assumptions about the underlying processes. We find the key requirement for this method: one of the series must be widely spaced in time to guarantee the theoretical applicability of the bootstrap. If this condition is met, the calculated significance passes a reasonableness test. We conclude with some potential future extensions and caveats on the applicability of these methods. The techniques presented have been implemented in a Python-based software toolkit.
Bootstrap, Wild Bootstrap and Generalized Bootstrap
Mammen, Enno
1995-01-01
Some modifications and generalizations of the bootstrap procedurehave been proposed. In this note we will consider the wild bootstrap and the generalized bootstrap and we will give two arguments why it makes sense touse these modifications instead of the original bootstrap. The firstargument is that there exist examples where generalized and wild bootstrapwork, but where the original bootstrap fails and breaks down. The secondargument will be based on higher order considerations. We will show...
Dynamics of bootstrap percolation
Indian Academy of Sciences (India)
Prabodh Shukla
2008-08-01
Bootstrap percolation transition may be first order or second order, or it may have a mixed character where a first-order drop in the order parameter is preceded by critical fluctuations. Recent studies have indicated that the mixed transition is characterized by power-law avalanches, while the continuous transition is characterized by truncated avalanches in a related sequential bootstrap process. We explain this behaviour on the basis of an analytical and numerical study of the avalanche distributions on a Bethe lattice.
Niska, Christoffer
2014-01-01
Practical and instruction-based, this concise book will take you from understanding what Bootstrap is, to creating your own Bootstrap theme in no time! If you are an intermediate front-end developer or designer who wants to learn the secrets of Bootstrap, this book is perfect for you.
Bootstrapping heteroskedastic regression models: wild bootstrap vs. pairs bootstrap
Flachaire, Emmanuel
2005-01-01
International audience In regression models, appropriate bootstrap methods for inference robust to heteroskedasticity of unknown form are the wild bootstrap and the pairs bootstrap. The finite sample performance of a heteroskedastic-robust test is investigated with Monte Carlo experiments. The simulation results suggest that one specific version of the wild bootstrap outperforms the other versions of the wild bootstrap and of the pairs bootstrap. It is the only one for which the bootstrap ...
Echeverri, Alejandro Castedo; Serone, Marco
2016-01-01
We study the numerical bounds obtained using a conformal-bootstrap method - advocated in ref. [1] but never implemented so far - where different points in the plane of conformal cross ratios $z$ and $\\bar z$ are sampled. In contrast to the most used method based on derivatives evaluated at the symmetric point $z=\\bar z =1/2$, we can consistently "integrate out" higher-dimensional operators and get a reduced simpler, and faster to solve, set of bootstrap equations. We test this "effective" bootstrap by studying the 3D Ising and $O(n)$ vector models and bounds on generic 4D CFTs, for which extensive results are already available in the literature. We also determine the scaling dimensions of certain scalar operators in the $O(n)$ vector models, with $n=2,3,4$, which have not yet been computed using bootstrap techniques.
Survey bootstrap and bootstrap weights
Stas Kolenikov
2008-01-01
In this presentation, I will review the bootstrap for complex surveys with designs featuring stratification, clustering, and unequal probability weights. I will present the Stata module bsweights, which creates the bootstrap weights for designs specified through and supported by svy. I will also provide simple demonstrations highlighting the use of the procedure and its syntax. I will discuss various tuning parameters and their impact on the performance of the procedure, and I will give argum...
Bengoubou-Valerius, Mendy,; Gibert, Dominique
2013-01-01
We consider some practical issues of the determination of the b-value of sequences of magnitudes with the bootstrap method for short series of length L and various quantization levels Dm of the magnitude. Preliminary Monte Carlo tests performed with Dm ¼ 0 demonstrate the superiority of the maximum likelihood estimator bMLE, and the inconsistency of the, yet often used, bLR estimator defined as the least-squares slope of the experimental Gutenberg-Richter curve. The Monte Carlo tests are also...
Wild Bootstrap Versus Moment-Oriented Bootstrap
Sommerfeld, Volker
1997-01-01
We investigate the relative merits of a “moment-oriented” bootstrap method of Bunke (1997) in comparison with the classical wild bootstrap of Wu (1986) in nonparametric heteroscedastic regression situations. The “moment-oriented” bootstrap is a wild bootstrap based on local estimators of higher order error moments that are smoothed by kernel smoothers. In this paper we perform an asymptotic comparison of these two dierent bootstrap procedures. We show that the moment-oriented bootstrap is in ...
Pfiffner, H. J.
1969-01-01
Circuit can sample a number of transducers in sequence without drawing from them. This bootstrap unloader uses a differential amplifier with one input connected to a circuit which is the equivalent of the circuit to be unloaded, and the other input delivering the proper unloading currents.
Bhaumik, Snig
2015-01-01
If you are a web developer who designs and develops websites and pages using HTML, CSS, and JavaScript, but have very little familiarity with Bootstrap, this is the book for you. Previous experience with HTML, CSS, and JavaScript will be helpful, while knowledge of jQuery would be an extra advantage.
A Bootstrap Cointegration Rank Test for Panels of VAR Models
Callot, Laurent
2010-01-01
This paper proposes a sequential procedure to determine the common cointegration rank of panels of cointegrated VARs. It shows how a panel of cointegrated VARs can be transformed in a set of independent individual models. The likelihood function of the transformed panel is the sum of the likelihood functions of the individual Cointegrated VARs (CVAR) models. A bootstrap based procedure is used to compute empirical distributions of the trace test statistics for these individual models. From th...
The Bootstrap Approach for Testing Skewness Persistence
Krishnamurty Muralidhar
1993-01-01
This study presents a new methodology for testing changes in skewness between time periods (or samples) using the bootstrap method. A Monte Carlo simulation experiment was conducted to compare the effectiveness of the bootstrap method with the method suggested by Lau, Wingender and Lau (1989) to test skewness persistence. The results show the bootstrap method to be more powerful than the other method. The bootstrap method was also used to determine the persistence of skewness in stock returns...
Beran, Rudolf
1994-01-01
This essay is organized around the theoretical and computationalproblem of constructing bootstrap confidence sets, with forays into relatedtopics. The seven section headings are: Introduction; The Bootstrap World;Bootstrap Confidence Sets; Computing Bootstrap Confidence Sets; Quality ofBootstrap Confidence Sets; Iterated and Two-step Boostrap; Further Resources.
MacKinnon, James G.
2007-01-01
This paper surveys bootstrap and Monte Carlo methods for testing hypotheses in econometrics. Several different ways of computing bootstrap P values are discussed, including the double bootstrap and the fast double bootstrap. It is emphasized that there are many different procedures for generating bootstrap samples for regression models and other types of model. As an illustration, a simulation experiment examines the performance of several methods of bootstrapping the supF test for structural...
Sequential determination of actinides in a variety of matrices
International Nuclear Information System (INIS)
A large number of analytical procedures for the actinides have been published, each catering for a specific need. Due to the bioassay programme in our laboratory, a need arose for a method to determine natural (Th and U) and anthropogenic actinides (Np, Pu and Am/Cm) together in a variety of samples. The method would have to be suitable for routine application: simple, inexpensive, rapid and robust. In some cases, the amount of material available is not sufficient for the determination of separate groups of actinides, and a sequential separation and measurement of the analytes would therefore be required. The types of matrices vary from aqueous samples to radiological surveillance (urine and faeces) to environmental studies (soil, sediment and fish), but the separation procedure should be able to service all of these. The working range of the method would have to cater for lower levels of the transuranium actinides in particular sample types containing higher levels of the natural actinides (U and Th). The first analytical problem to be discussed, is how to get the different sample types into the same loading solution required by a single separation approach. This entails sample dissolution or decomposition in some cases, and pre-concentration or pre-separation in others. A separation scheme is presented for the clean separation of all the actinides in a form suitable for alpha spectrometry. The development of a single column separation of the analytes of interest are looked at, as well as observations made during the development of the separation scheme, such as concentration effects. Results for test samples and certified reference materials are be presented. (author)
Poland, David; Simmons-Duffin, David
2016-06-01
The conformal bootstrap was proposed in the 1970s as a strategy for calculating the properties of second-order phase transitions. After spectacular success elucidating two-dimensional systems, little progress was made on systems in higher dimensions until a recent renaissance beginning in 2008. We report on some of the main results and ideas from this renaissance, focusing on new determinations of critical exponents and correlation functions in the three-dimensional Ising and O(N) models.
Magno, Alexandre
2013-01-01
A practical, step-by-step tutorial on developing websites for mobile using Bootstrap.This book is for anyone who wants to get acquainted with the new features available in Bootstrap 3 and who wants to develop websites with the mobile-first feature of Bootstrap. The reader should have a basic knowledge of Bootstrap as a frontend framework.
Bootstrap inference in econometrics
James G. MacKinnon
2002-01-01
The astonishing increase in computer performance over the past two decades has made it possible for economists to base many statistical inferences on simulated, or bootstrap, distributions rather than on distributions obtained from asymptotic theory. In this paper, I review some of the basic ideas of bootstrap inference. I discuss Monte Carlo tests, several types of bootstrap test, and bootstrap confidence intervals. Although bootstrapping often works well, it does not do so in every case.
Kozak, Joanna; Wójtowicz, Marzena; Gawenda, Nadzieja; Kościelniak, Paweł
2011-06-15
An automatic sequential injection system, combining monosegmented flow analysis, sequential injection analysis and sequential injection titration is proposed for acidity determination. The system enables controllable sample dilution and generation of standards of required concentration in a monosegmented sequential injection manner, sequential injection titration of the prepared solutions, data collecting, and handling. It has been tested on spectrophotometric determination of acetic, citric and phosphoric acids with sodium hydroxide used as a titrant and phenolphthalein or thymolphthalein (in the case of phosphoric acid determination) as indicators. Accuracy better than |4.4|% (RE) and repeatability better than 2.9% (RSD) have been obtained. It has been applied to the determination of total acidity in vinegars and various soft drinks. The system provides low sample (less than 0.3 mL) consumption. On average, analysis of a sample takes several minutes. PMID:21641455
Bootstrap Methods in Econometrics
MacKinnon, James G.
2006-01-01
There are many bootstrap methods that can be used for econometric analysis. In certain circumstances, such as regression models with independent and identically distributed error terms, appropriately chosen bootstrap methods generally work very well. However, there are many other cases, such as regression models with dependent errors, in which bootstrap methods do not always work well. This paper discusses a large number of bootstrap methods that can be useful in econometrics. Applications to...
Mitterpach, Róbert
2012-01-01
Aim of this thesis is to introduce the reader to the basic bootstrap techniques used in econometrics, to present their variations and importance. Results of the ordinary least squares model, residual bootstrap and case resampling bootstrap will be presented and compared on cross-sectional data and time series from small numbered random subsample from the available data. Bootstrap was shown to improve numerical performance of ordinary least squares model.
Balogh, József; Morris, Robert
2011-01-01
Graph bootstrap percolation is a deterministic cellular automaton which was introduced by Bollob\\'as in 1968, and is defined as follows. Given a graph $H$, and a set $G \\subset E(K_n)$ of initially `infected' edges, we infect, at each time step, a new edge $e$ if there is a copy of $H$ in $K_n$ such that $e$ is the only not-yet infected edge of $H$. We say that $G$ percolates in the $H$-bootstrap process if eventually every edge of $K_n$ is infected. The extremal questions for this model, when $H$ is the complete graph $K_r$, were solved (independently) by Alon, Kalai and Frankl almost thirty years ago. In this paper we study the random questions, and determine the critical probability $p_c(n,K_r)$ for the $K_r$-process up to a poly-logarithmic factor. In the case $r = 4$ we prove a stronger result, and determine the threshold for $p_c(n,K_4)$.
Ganesh, S; Khan, Fahmida; Ahmed, M K; Pandey, S K
2011-08-15
A simple potentiometric method for the determination of free acidity in presence of hydrolysable ions and sequential determination of hydrazine is developed and described. Both free acid and hydrazine are estimated from the same aliquot. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 1.2% relative standard deviation. Hydrazine content has also been determined in the same aliquot with a recovery of nitric acid is 99% with 2% relative standard deviation. The major advantage of the method is that generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal. PMID:21726724
Rubin, Donald B.
1981-01-01
The Bayesian bootstrap is the Bayesian analogue of the bootstrap. Instead of simulating the sampling distribution of a statistic estimating a parameter, the Bayesian bootstrap simulates the posterior distribution of the parameter; operationally and inferentially the methods are quite similar. Because both methods of drawing inferences are based on somewhat peculiar model assumptions and the resulting inferences are generally sensitive to these assumptions, neither method should be applied wit...
Nonparametric bootstrap prediction
Fushiki, Tadayoshi; Komaki, Fumiyasu; Aihara, Kazuyuki
2005-01-01
Ensemble learning has recently been intensively studied in the field of machine learning. `Bagging' is a method of ensemble learning and uses bootstrap data to construct various predictors. The required prediction is then obtained by averaging the predictors. Harris proposed using this technique with the parametric bootstrap predictive distribution to construct predictive distributions, and showed that the parametric bootstrap predictive distribution gives asymptotically better prediction tha...
Bootstrapping Macroeconometric Models
2001-01-01
This paper outlines a bootstrapping approach to the estimation and analysis of macroeconometric models. It integrates for dynamic, nonlinear, simultaneous equation models the bootstrapping approach to evaluating estimators initiated by Efron (1979) and the stochastic simulation approach to evaluating models' properties initiated by Adelman and Adelman (1959). It also estimates for a particular model the gain in coverage accuracy from using bootstrap confidence intervals over asymptotic confid...
Sequential extraction separation for determination of technetium-99 in radwastes by ICP-MS
International Nuclear Information System (INIS)
An approach based on sequential extraction separation and the subsequent ICP-MS measurement was introduced to determine 99Tc in radioactive wastes. The radwastes were firstly alkaline-fused and the 99Tc was separated by a sequential solvent extraction prior to ICP-MS measurement. NaDDC was selected as a chelation reagent in the solvent extraction processes. The influence of HCl and matrix concentration on the recovery yield and the effectiveness of removing isobar and unwanted radionuclides, such as 137Cs, 54Mn, 60Co and 110mAg, were evaluated. The designed sequential extraction procedure was optimized by an extraction experiment. The proposed technique is proven to be a simple and practical alternative for 99Tc determination in low-level radioactive wastes; chemical separation of 99Tc can be simplified and preconcentration such as precipitation and/or ion exchange, before the solvent extraction, can be excluded. (author)
Collier, Scott; Yin, Xi
2016-01-01
We constrain the spectrum of two-dimensional unitary, compact conformal field theories with central charge c > 1 using modular bootstrap. Upper bounds on the gap in the dimension of primary operators of any spin, as well as in the dimension of scalar primaries, are computed numerically as functions of the central charge using semi-definite programming. Our bounds refine those of Hellerman and Friedan-Keller, and are in some cases saturated by known CFTs. In particular, we show that unitary CFTs with c < 8 must admit relevant deformations, and that a nontrivial bound on the gap of scalar primaries exists for c < 25. We also study bounds on the dimension gap in the presence of twist gaps, bounds on the degeneracy of operators, and demonstrate how "extremal spectra" which maximize the degeneracy at the gap can be determined numerically.
The Local Fractional Bootstrap
DEFF Research Database (Denmark)
Bennedsen, Mikkel; Hounyo, Ulrich; Lunde, Asger;
new resampling method, the local fractional bootstrap, relies on simulating an auxiliary fractional Brownian motion that mimics the fine properties of high frequency differences of the Brownian semistationary process under the null hypothesis. We prove the first order validity of the bootstrap method...
Oliveira, Sara M.; Lopes, Teresa I. M. S.; Rangel, António O. S. S.
2007-01-01
A sequential injection system for the determination of nitrate (NO3 2) in vegetables was developed to automate this determination, allowing for substantially reduced reagent consumption and generated waste using low-cost equipment. After extraction with water and filtration, the extracted nitrate is reduced inline to nitrite in a copperized cadmium (Cd) column and determined as nitrite. According to the Griess–Ilosvay reaction, nitrate is diazotized with sulfanilamide and coupled wit...
A model study in hadron statistical bootstrap
Hagedorn, Rolf
1973-01-01
In the framework of the statistical bootstrap the decay of a fireball is considered as an exact inverse of its statistical composition. This assumption leads to a bootstrap formulated in terms of integral equations for all kinds of distributions of the fireball's decay products. Solutions of the equations are obtained in terms of power series and of K-transforms and determine in the general case their asymptotic behaviour for large fireball mass. Relations to a thermodynamical description are established and illustrated by effective temperatures. The approach to the asymptotic limits is easy to investigate in a simplified linear bootstrap where the K-transforms can be more explicitly calculated. (30 refs).
Bootstrap confidence intervals
Thomas J. DiCiccio; Efron, Bradley
1996-01-01
This article surveys bootstrap methods for producing good approximate confidence intervals. The goal is to improve by an order of magnitude upon the accuracy of the standard intervals $\\hat{\\theta} \\pm z^{(\\alpha)} \\hat{\\sigma}$, in a way that allows routine application even to very complicated problems. Both theory and examples are used to show how this is done. The first seven sections provide a heuristic overview of four bootstrap confidence interval procedures: $BC_a$, bootstrap-t , ABC a...
A test of sequential extractions for determining metal speciation in sewage sludge-amended soils
International Nuclear Information System (INIS)
Sequential extraction procedures are widely used to estimate the quantity of trace metals bound to different solid fractions in contaminated soils. However, reliability of speciation of trace metals by these procedures remains largely unexamined. In the present study, the selectivity of each extraction step was tested by observing the effect of reversing the extraction order in the procedure. Two different sequential extraction methods and their reversed modes were used for metal fractionation in sewage sludge-amended soils. Significantly increased amounts of extractable metals (Cd, Cu, Pb and Zn) were evident in the sludge-amended soils compared to control soil by all extraction schemes; however, the amounts of metals extracted by each step were strongly dependent on the order of extraction, the type of reagents and the nature of the individual metals. Caution is advised in deducing the forms of soil metals from sequential extraction results from metal-contaminated soils. - Sequential extraction methods are of questionable accuracy for determining the chemical forms of certain trace metals in soils
Bootstrap percolation with inhibition
Einarsson, Hafsteinn; Lengler, Johannes; Panagiotou, Konstantinos; Mousset, Frank; Steger, Angelika
2014-01-01
Bootstrap percolation is a prominent framework for studying the spreading of activity on a graph. We begin with an initial set of active vertices. The process then proceeds in rounds, and further vertices become active as soon as they have a certain number of active neighbors. A recurring feature in bootstrap percolation theory is an `all-or-nothing' phenomenon: either the size of the starting set is so small that the process stops very soon, or it percolates (almost) completely. Motivated by...
Wild cluster bootstrap confidence intervals
MacKinnon, James G.
2014-01-01
Confidence intervals based on cluster-robust covariance matrices can be constructed in many ways. In addition to conventional intervals obtained by inverting Wald (t) tests, the paper studies intervals obtained by inverting LM tests, studentized bootstrap intervals based on the wild cluster bootstrap, and restricted bootstrap intervals obtained by inverting bootstrap Wald and LM tests. It also studies the choice of an auxiliary distribution for the wild bootstrap, a modified covariance matrix...
Breakdown theory for bootstrap quantiles
Singh, Kesar
1998-01-01
A general formula for computing the breakdown point in robustness for the $t$th bootstrap quantile of a statistic $T_n$ is obtained. The answer depends on $t$ and the breakdown point of $T_n$. Since the bootstrap quantiles are vital ingredients of bootstrap confidence intervals, the theory has implications pertaining to robustness of bootstrap confidence intervals. For certain $L$ and $M$ estimators, a robustification of bootstrap is suggested via the notion of Winsorization.
DEFF Research Database (Denmark)
Liu, Xuezhu; Hansen, Elo Harald
1996-01-01
A sequential injection analysis system is described that incorporates a nylon tubular reactor containing immobilised glucose oxidase, allowing determination of D-glucose by means of subsequent luminol chemiluminescence detection of the hydrogen peroxide generated in the enzymatic reaction. The...... operating parameters were optimised by fractional factorial screening and response surface modelling. The linear range of D-glucose determination was 30-600 mu M, With a detection limit of 15 mu M using a photodiode detector. The sampling frequency was 54 h(-1). Lower LOD (0.5 mu M D-glucose) could be...
International Nuclear Information System (INIS)
Two separation methods for the sequential determination of Am and Pu radionuclides are presented and the results obtained are compared. Analysis involves leaching the sample with concentrated nitric acid (HNO3), followed by radiochemical separation using extraction chromatographic resins (UTEVA, TRU) and anion exchange. Sources for alpha spectrometry were prepared by micro-precipitation on neodymium fluoride (NdF3). The chemical recoveries were determined using 242Pu and 243Am tracers. The methods were tested on reference materials and on two sediments. All the results were in good agreement with the reference values. The evaluation of uncertainty is also included
Toral, M Inés; Paine, Maximiliano; Leyton, Patricio; Richter, Pablo
2004-01-01
A new method for the sequential determination of attapulgite and nifuroxazide in pharmaceutical formulations by first- and second-derivative spectrophotometry, respectively, has been developed. In order to obtain the optimal conditions for nifuroxazide stability, studies of solvent, light, and temperature effects were performed. The results show that a previous hydrolysis of 2 h in 1.0 x 10(-1)M NaOH solution is necessary in order to obtain stable compounds for analytical purposes. Subsequently, the first- and second-derivative spectra were evaluated directly in the same samples. The sequential determination of the drugs can be performed using the zero-crossing method; the attapulgite determination was carried out using the first derivative at 278.0 nm and the nifuroxazide determination, using the second derivative at 282.0 nm. The determination ranges were 5.7 x 10(-6)-1.0 x 10(-4) and 3.7 x 10(-8) -1.2 x 10(-4)M for attapulgite and nifuroxazide, respectively. Repeatability (relative standard deviation) values of 1.2 and 3.0% were observed for attapulgite and nifuroxazide, respectively. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets. Further, infrared spectroscopy and cyclic voltammetry studies were carried out in order to obtain knowledge of the decomposition products of nifuroxazide. PMID:15675443
Temperature Corrected Bootstrap Algorithm
Comiso, Joey C.; Zwally, H. Jay
1997-01-01
A temperature corrected Bootstrap Algorithm has been developed using Nimbus-7 Scanning Multichannel Microwave Radiometer data in preparation to the upcoming AMSR instrument aboard ADEOS and EOS-PM. The procedure first calculates the effective surface emissivity using emissivities of ice and water at 6 GHz and a mixing formulation that utilizes ice concentrations derived using the current Bootstrap algorithm but using brightness temperatures from 6 GHz and 37 GHz channels. These effective emissivities are then used to calculate surface ice which in turn are used to convert the 18 GHz and 37 GHz brightness temperatures to emissivities. Ice concentrations are then derived using the same technique as with the Bootstrap algorithm but using emissivities instead of brightness temperatures. The results show significant improvement in the area where ice temperature is expected to vary considerably such as near the continental areas in the Antarctic, where the ice temperature is colder than average, and in marginal ice zones.
DETERMINATION OF STOPPING DISTANCE OF UNPOWERED ROLLING STOCK BY METHOD OF SEQUENTIAL BRAKING
Directory of Open Access Journals (Sweden)
O. H. Reidemeister
2015-09-01
Full Text Available Purpose. In the paper it is necessary to estimate the determination accuracy of a car stopping distance during the test by the method of sequential braking. The method of sequential braking is applied for experimental evaluation of the stopping distances. Unlike the abandonment method when a sample car is disconnected from the tractive connection and they record the stopping distance of a single car from the moment of uncoupling to the moment of stop, the method of sequential braking involves stopping distance measurement of the tractive connection, the integrity of which in the course of the test is not affected, but its set (locomotive, locomotive with the track test car or with a sample car at the different stages of the test is changed. Direct measuring of the stopping distance of a sample car is not possible using this way, it requires calculating of the stopping distance values of the tractive connection. This adversely affects the accuracy of the result, but it can increase the safety level of the test. Methodology. To evaluate the accuracy researches have conducted the numerical experiment, which simulated experimental processing of stopping distance values. An error was found by giving disturbance of basic data (stopping distance of tractive connection of different configuration and analyzing the resulted scatter of readings (stopping distance of a single car. Findings. The study proved: 1 the relative error of car stopping distances value, with relative error of basic data 1%, made 3.3-19.7% (depending on the tractive connection variant. 2 the proposed ways of error reduction (without track test car, less-weighed-locomotive use allowed declining the error to 2.15-5.1%. Originality. The methodology of error estimation of car stopping distances determination under tests by the method of sequential braking was proposed. Practical value. Work results make it possible to replace the running brake tests by the abandonment method, under which
Rejon-Barrera, Fernando; Robbins, Daniel
2016-01-01
We work out all of the details required for implementation of the conformal bootstrap program applied to the four-point function of two scalars and two vectors in an abstract conformal field theory in arbitrary dimension. This includes a review of which tensor structures make appearances, a construction of the projectors onto the required mixed symmetry representations, and a computation of the conformal blocks for all possible operators which can be exchanged. These blocks are presented as differential operators acting upon the previously known scalar conformal blocks. Finally, we set up the bootstrap equations which implement crossing symmetry. Special attention is given to the case of conserved vectors, where several simplifications occur.
DEFF Research Database (Denmark)
Qiao, Jixin; Hou, Xiaolin; Roos, Per;
2013-01-01
An analytical method was developed for simultaneous determination of ultratrace level plutonium (Pu) and neptunium (Np) using iron hydroxide coprecipitation in combination with automated sequential injection extraction chromatography separation and accelerator mass spectrometry (AMS) measurement...
Introduction to the Bootstrap World
Boos, Dennis D.
2003-01-01
The bootstrap has made a fundamental impact on how we carry out statistical inference in problems without analytic solutions. This fact is illustrated with examples and comments that emphasize the parametric bootstrap and hypothesis testing.
Metastability threshold for anisotropic bootstrap percolation in three dimensions
van Enter, Aernout
2011-01-01
In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability threshold for a fairly general class of models. In our proofs we use an adaptation of the technique of dimensional reduction. We find that the order of the metastability threshold is generally determined by the "easiest growth direction" in the model. In contrast to the anisotropic bootstrap percolation in two dimensions, in three dimensions the order of the metatstability threshold for anisotropic bootstrap percolation can be equal to that of isotropic bootstrap percolation.
Generalized bootstrap for estimating equations
Chatterjee, Snigdhansu; Bose, Arup
2005-01-01
We introduce a generalized bootstrap technique for estimators obtained by solving estimating equations. Some special cases of this generalized bootstrap are the classical bootstrap of Efron, the delete-d jackknife and variations of the Bayesian bootstrap. The use of the proposed technique is discussed in some examples. Distributional consistency of the method is established and an asymptotic representation of the resampling variance estimator is obtained.
The bootstrap and Bayesian bootstrap method in assessing bioequivalence
International Nuclear Information System (INIS)
Parametric method for assessing individual bioequivalence (IBE) may concentrate on the hypothesis that the PK responses are normal. Nonparametric method for evaluating IBE would be bootstrap method. In 2001, the United States Food and Drug Administration (FDA) proposed a draft guidance. The purpose of this article is to evaluate the IBE between test drug and reference drug by bootstrap and Bayesian bootstrap method. We study the power of bootstrap test procedures and the parametric test procedures in FDA (2001). We find that the Bayesian bootstrap method is the most excellent.
Il bootstrap. Un'applicazione informatica per un problema di ricampionamento
Morana, Maria Teresa; Porcu, Mariano
2002-01-01
The aim of this paper is to give a simple introduction to the bootstrap techniques showing a basic computer algorithm. The algorithm displays, step by step, how to determinate a bootstrap confidence interval.
Bootstrap Percolation on Random Geometric Graphs
Bradonjić, Milan
2012-01-01
Bootstrap percolation has been used effectively to model phenomena as diverse as emergence of magnetism in materials, spread of infection, diffusion of software viruses in computer networks, adoption of new technologies, and emergence of collective action and cultural fads in human societies. It is defined on an (arbitrary) network of interacting agents whose state is determined by the state of their neighbors according to a threshold rule. In a typical setting, bootstrap percolation starts by random and independent "activation" of nodes with a fixed probability $p$, followed by a deterministic process for additional activations based on the density of active nodes in each neighborhood ($\\th$ activated nodes). Here, we study bootstrap percolation on random geometric graphs in the regime when the latter are (almost surely) connected. Random geometric graphs provide an appropriate model in settings where the neighborhood structure of each node is determined by geographical distance, as in wireless {\\it ad hoc} ...
USEFULNESS OF BOOTSTRAPPING IN PORTFOLIO MANAGEMENT
Directory of Open Access Journals (Sweden)
Boris Radovanov
2012-12-01
Full Text Available This paper contains a comparison of in-sample and out-of-sample performances between the resampled efficiency technique, patented by Richard Michaud and Robert Michaud (1999, and traditional Mean-Variance portfolio selection, presented by Harry Markowitz (1952. Based on the Monte Carlo simulation, data (samples generation process determines the algorithms by using both, parametric and nonparametric bootstrap techniques. Resampled efficiency provides the solution to use uncertain information without the need for constrains in portfolio optimization. Parametric bootstrap process starts with a parametric model specification, where we apply Capital Asset Pricing Model. After the estimation of specified model, the series of residuals are used for resampling process. On the other hand, nonparametric bootstrap divides series of price returns into the new series of blocks containing previous determined number of consecutive price returns. This procedure enables smooth resampling process and preserves the original structure of data series.
Bootstrap percolation in high dimensions
Balogh, Jozsef; Morris, Robert
2009-01-01
In r-neighbour bootstrap percolation on a graph G, a set of initially infected vertices A \\subset V(G) is chosen independently at random, with density p, and new vertices are subsequently infected if they have at least r infected neighbours. The set A is said to percolate if eventually all vertices are infected. Our aim is to understand this process on the grid, [n]^d, for arbitrary functions n = n(t), d = d(t) and r = r(t), as t -> infinity. The main question is to determine the critical probability p_c([n]^d,r) at which percolation becomes likely, and to give bounds on the size of the critical window. In this paper we study this problem when r = 2, for all functions n and d satisfying d \\gg log n. The bootstrap process has been extensively studied on [n]^d when d is a fixed constant and 2 \\le r \\le d, and in these cases p_c([n]^d,r) has recently been determined up to a factor of 1 + o(1) as n -> infinity. At the other end of the scale, Balogh and Bollobas determined p_c([2]^d,2) up to a constant factor, and...
Discharges with high bootstrap current fraction on Tore Supra
International Nuclear Information System (INIS)
This document deals with bootstrap current non-inductively driving a fraction of the total current. Non-inductive current density profile is determined on Tore Supra and high bootstrap current fraction regimes in Tore Supra are analysed. (TEC). 11 refs., 3 figs
Automated IR determination of petroleum products in water based on sequential injection analysis.
Falkova, Marina; Vakh, Christina; Shishov, Andrey; Zubakina, Ekaterina; Moskvin, Aleksey; Moskvin, Leonid; Bulatov, Andrey
2016-02-01
The simple and easy performed automated method for the IR determination of petroleum products (PP) in water using extraction-chromatographic cartridges has been developed. The method assumes two stages: on-site extraction of PP during a sampling by using extraction-chromatographic cartridges and subsequent determination of the extracted PP using sequential injection analysis (SIA) with IR detection. The appropriate experimental conditions for extraction of the dissolved in water PP and for automated SIA procedure were investigated. The calibration plot constructed using the developed procedure was linear in the range of 3-200 μg L(-1). The limit of detection (LOD), calculated from a blank test based on 3σ was 1 µg L(-1). The sample volume was 1L. The system throughput was found to be 12 h(-1). PMID:26653498
Determination of plutonium and uranium in mixed oxide fuels by sequential redox titration.
Chadwick, P H; McGowan, I R
1972-11-01
The use of a sequential determination of uranium and plutonium in a single sample solution results in a saving in analysis time and apparatus requirements. The method starts with U(IV) and Pu(in) in a mixture of sulphuric and nitric adds. Titration with dichromate, using amperometry at a pair of polarizable electrodes, produces two well-defined end-points corresponding to the sequential oxidation of U(IV) to U(VI) and Pu(III) to Pu(IV). The quantitative oxidation of U(IV) to U(VI) is achieved via the action of Pu(IV) as intermediate, and is dependent upon establishing conditions which favour rapid reaction between U(IV) and Pu(IV). The method is precise and accurate. With Pu-U mixtures containing between 15 and 30% plutonium the precision (3sigma) of the Pu: U ratio results is +/-0.6% on samples containing 100-120 mg of plutonium plus uranium. Iron and vanadium interfere quantitatively with plutonium, copper interferes non-quantitatively with uranium, and gross amounts of molybdenum mask the uranium end-point. PMID:18961189
FWEH induced high bootstrap current on Tore Supra
International Nuclear Information System (INIS)
Bootstrap current is regarded as a good candidate to sustain a large fraction of the plasma current, in the so-called open-quotes advancedclose quotes regimes of a tokamak reactor. It is thus important to study the stability of such discharges and to control them. By means of fast wave electron heating (FWEH, up to 9.5 MW), stationary high bootstrap discharges (during 5 seconds, ∼40%) were routinely obtained on Tore Supra. The bootstrap profile is computed with a matrix formulation (1,2) and is directly compared to the experimental determination of the non-inductive current. The simulation of the loop voltage either with the code CRONOS (1D current diffusion code) using the profile of bootstrap current, or with the knowledge of the resistivity, allows also a self consistent determination of the bootstrap current. The bootstrap induced by the FWEH is mainly due to the central pressure electron gradient (the central power deposition strongly peaks the electronic temperature). A 0D study shows that the bootstrap current (Ibs) varies linearly with the poloidal beta (Ibs/Ip∼Cbsβp). The effect of various plasma parameters (toroidal field Bt, line-integrated density nl, ion and electron temperature, plasma current Ip) on the bootstrap profile, and fraction are analysed. copyright 1997 American Institute of Physics
International Nuclear Information System (INIS)
The fractionation of the eight metals Pb, Ni, Zn, Co, Cr, Mn, Fe and Cd in Yarmouk River were determined by applying a sequential extraction procedure. The potential environmental impacts of the metals estimated through the five extraction categories, that's exchangeable, bound to carbonate, bound to Fe/Mn oxides, bound to organic matter and the residual. The results show that the sediments of the Yarmouk River would be moderately to heavily polluted fluvial systems in the region. The observed metal distribution patterns in the different sediment fractions, however, indicated that the major proportions of most metals seemed to be associated with the residual fraction which consists essentially of detrital silicate minerals, resistant sulfides, and a small quantity of refractory organic material that could therefore be classified to be of geochemical origin. (Author's) 14 refs., 4 tabs., 4 figs
Directory of Open Access Journals (Sweden)
José Luiz Rufino
2011-01-01
Full Text Available This work proposes a sequential injection analysis (SIA system for the spectrophotometric determination of norfloxacin (NOR and ciprofloxacin (CIP in pharmaceutical formulations. The methodology was based on the reaction of these drugs with p-(dimethylaminocinnamaldehyde in micellar medium, producing orange colored products (λmax = 495 nm. Beer´s law was obeyed in the concentration range from 2.75x10-5 to 3.44x10-4 mol L-1 and 3.26x10-5 to 3.54x10-4 mol L-1 for NOR and CIP, respectively and sampling rate was 25 h-1. Commercial samples were analyzed and results obtained through the proposed method were in good agreement with those obtained using the reference procedure for a 95% confidence level.
Bootstrap and Wild Bootstrap for High Dimensional Linear Models
Mammen, Enno
1993-01-01
In this paper two bootstrap procedures are considered for the estimation of the distribution of linear contrasts and of F-test statistics in high dimensional linear models. An asymptotic approach will be chosen where the dimension p of the model may increase for sample size $n\\rightarrow\\infty$. The range of validity will be compared for the normal approximation and for the bootstrap procedures. Furthermore, it will be argued that the rates of convergence are different for the bootstrap proce...
Sequential determination of uranium (IV), free acidity and hydrazine in a single aliquot
International Nuclear Information System (INIS)
A simple analytical procedure for the sequential determination of uranium (IV), free acidity and hydrazine in presence of hydrolysable ions is developed and described. In this method, first, uranium (IV) is determined using fiber optic aided spectrophotometry then same solution is used for determination of free acidity and hydrazine. Free acid is titrated with standard sodium carbonate solution after uranium (IV) is masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. The overall recovery of uranium (IV), nitric acid and hydrazine is 98% with 3% relative standard deviation respectively. The major advantage of the method is that it uses sodium carbonate a primary standard as titrant and generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal. (author)
Bootstrap current due to shear of magnetic field stochasticity
International Nuclear Information System (INIS)
The 'bootstrap' current is a fundamental effect in toroidal magnetic confinement. It is shown that the electron current in stochastic magnetic field causes not only anomalous electron heat transport, but also novel currents, termed 'anomalous bootstrap' in order to bring up the analogy with the well-known effect in the neoclassical theory. Due to the magnetic fluctuations an additional bootstrap current appears. Its value is proportional to the derivative of square of the magnetic fluctuations, the radial electric field and ratio of streaming velocity to thermal one for collisionless case. The obtained bootstrap current can be comparable with the Ohmic current. In the collisional case, in contrast to the collisionless case, the value of bootstrap current does not depend on the magnitude of the averaged velocity, but its direction is determined by the streaming velocity sign. (J.P.N.)
Convex and Monotonic Bootstrapped Kriging
Kleijnen, Jack P.C.; Mehdad, E.; Beers, W.C.M. van
2012-01-01
Abstract: Distribution-free bootstrapping of the replicated responses of a given discreteevent simulation model gives bootstrapped Kriging (Gaussian process) metamodels; we require these metamodels to be either convex or monotonic. To illustrate monotonic Kriging, we use an M/M/1 queueing simulation with as output either the mean or the 90% quantile of the transient-state waiting times, and as input the traffic rate. In this example, monotonic bootstrapped Kriging enables better sensitivity a...
Bo E. Honoré; Hu, Luojia
2015-01-01
The bootstrap is a convenient tool for calculating standard errors of the parameters of complicated econometric models. Unfortunately, the fact that these models are complicated often makes the bootstrap extremely slow or even practically infeasible. This paper proposes an alternative to the bootstrap that relies only on the estimation of one-dimensional parameters. The paper contains no new difficult math. But we believe that it can be useful.
Detrending bootstrap unit root tests
Smeekes, S.
2009-01-01
The role of detrending in bootstrap unit root tests is investigated. When bootstrapping, detrending must not only be done for the construction of the test statistic, but also in the first step of the bootstrap algorithm. It is argued that the two points should be treated separately. Asymptotic validity of sieve bootstrap ADF unit root tests is shown for test statistics based on full sample and recursive OLS and GLS detrending. It is also shown that the detrending method in the first step of t...
Pragourpun, Kraivinee; Sakee, Uthai; Fernandez, Carlos; Kruanetr, Senee
2015-05-01
We present for the first time the use of deferiprone as a non-toxic complexing agent for the determination of iron by sequential injection analysis in pharmaceuticals and food samples. The method was based on the reaction of Fe(III) and deferiprone in phosphate buffer at pH 7.5 to give a Fe(III)-deferiprone complex, which showed a maximum absorption at 460 nm. Under the optimum conditions, the linearity range for iron determination was found over the range of 0.05-3.0 μg mL-1 with a correlation coefficient (r2) of 0.9993. The limit of detection and limit of quantitation were 0.032 μg mL-1 and 0.055 μg mL-1, respectively. The relative standard deviation (%RSD) of the method was less than 5.0% (n = 11), and the percentage recovery was found in the range of 96.0-104.0%. The proposed method was satisfactorily applied for the determination of Fe(III) in pharmaceuticals, water and food samples with a sampling rate of 60 h-1.
Chester, Shai M
2016-01-01
We initiate the conformal bootstrap study of Quantum Electrodynamics in $2+1$ space-time dimensions (QED$_{3}$) with $N$ flavors of charged fermions by focusing on the 4-point function of four monopole operators with the lowest unit of topological charge. We obtain upper bounds on the scaling dimension of the doubly-charged monopole operator, with and without assuming other gaps in the operator spectrum. Intriguingly, we find a (gap-dependent) kink in these bounds that comes reasonably close to the large $N$ extrapolation of the scaling dimensions of the singly-charged and doubly-charged monopole operators down to $N=4$ and $N=6$.
Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran
2016-03-01
We study the conformal bootstrap for a 4-point function of fermions in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ × ψ OPE, and also on the central charge C T . We observe features in our bounds that coincide with scaling dimensions in the GrossNeveu models at large N . We also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.
Sequential determination of free acidity and hydrazine in presence of hydrolysable ions
International Nuclear Information System (INIS)
A simple method for the sequential determination of free acidity and hydrazine in presence of hydrolysable ions is developed and described. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 3% relative standard deviation. The major advantage of the method is that it uses sodium carbonate a primary standard as titrant and generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal. (orig.)
Chinvongamorn, Chakorn; Pinwattana, Kulwadee; Praphairaksit, Narong; Imato, Toshihiko; Chailapakul, Orawon
2008-01-01
A gas diffusion sequential injection system with amperometric detection using a boron-doped diamond electrode was developed for the determination of sulfite. A gas diffusion unit (GDU) was used to prevent interference from sample matrices for the electrochemical measurement. The sample was mixed with an acid solution to generate gaseous sulfur dioxide prior to its passage through the donor channel of the GDU. The sulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1M phosphate buffer (pH 8)/0.1% sodium dodecyl sulfate in the acceptor channel of the GDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell and detected directly by amperometry using the boron-doped diamond electrode at 0.95 V (versus Ag/AgCl). Sodium dodecyl sulfate was added to the carrier solution to prevent electrode fouling. This method was applicable in the concentration range of 0.2-20 mg SO32−/L and a detection limit (S/N = 3) of 0.05 mg SO32−/L was achieved. This method was successfully applied to the determination of sulfite in wines and the analytical results agreed well with those obtained by iodimetric titration. The relative standard deviations for the analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was 65 h−1.
Directory of Open Access Journals (Sweden)
Orawon Chailapakul
2008-03-01
Full Text Available A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1 M phosphate buffer (pH 8/0.1% sodium dodecyl sulfate in the acceptor channel of theGDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell anddetected directly by amperometry using the boron-doped diamond electrode at 0.95 V(versus Ag/AgCl. Sodium dodecyl sulfate was added to the carrier solution to preventelectrode fouling. This method was applicable in the concentration range of 0.2-20 mgSO32Ã¢ÂˆÂ’/L and a detection limit (S/N = 3 of 0.05 mg SO32Ã¢ÂˆÂ’/L was achieved. This method wassuccessfully applied to the determination of sulfite in wines and the analytical resultsagreed well with those obtained by iodimetric titration. The relative standard deviations forthe analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was65 hÃ¢ÂˆÂ’1.
International Nuclear Information System (INIS)
A sequential injection analysis (SIA) with chemiluminescence detection has been proposed for the determination of the antibiotic gemifloxacin mesylate (GFX). The developed method is based on the enhancement effect of silver nanoparticles (Ag NPs) on the chemiluminescence (CL) signal of luminol-potassium ferricyanide reaction in alkaline medium. The introduction of gemifloxacin in this system produced a significant decrease in the CL intensity in presence of (Ag NPs). The optimum conditions for CL emission were investigated. Linear relationship between the decrease in CL intensity and concentration was obtained in the range 0.01-1000 ng mL-1, (r = 0.9997) with detection limit of 2.0 pg mL-1 and quantification limit of 0.01 pg mL-1. The relative standard deviation was 1.3 %. The proposed method was employed for the determination of gemifloxacin in bulk drug, in its pharmaceutical dosage forms and biological fluids such as human serum and urine. The interference of some common additive compounds such as glucose, lactose, starch, talc and magnesium stearate was investigated, and no interference was found from these excipients. The obtained SIA results were statistically compared with those obtained from a reported method and did not show any significant difference at confidence level 95%. (author)
Bootstrapping structured page segmentation
Ma, Huanfeng; Doermann, David S.
2003-01-01
In this paper, we present an approach to the bootstrap learning of a page segmentation model. The idea evolves from attempts to segment dictionaries that often have a consistent page structure, and is extended to the segmentation of more general structured documents. In cases of highly regular structure, the layout can be learned from examples of only a few pages. The system is first trained using a small number of samples, and a larger test set is processed based on the training result. After making corrections to a selected subset of the test set, these corrected samples are combined with the original training samples to generate bootstrap samples. The newly created samples are used to retrain the system, refine the learned features and resegment the test samples. This procedure is applied iteratively until the learned parameters are stable. Using this approach, we do not need to initially provide a large set of training samples. We have applied this segmentation to many structured documents such as dictionaries, phone books, spoken language transcripts, and obtained satisfying segmentation performance.
Calibration of parallel kinematic devices using sequential determination of kinematic parameters
Energy Technology Data Exchange (ETDEWEB)
JOKIEL JR.,BERNHARD; BIEG,LOTHAR F.; ZIEGERT,JOHN C.
2000-04-06
In PKM Machines, the Cartesian position and orientation of the tool point carried on the platform is obtained from a kinematic model of the particular machine. Accurate positioning of these machines relies on the accurate knowledge of the parameters of the kinematic model unique to the particular machine. The parameters in the kinematic model include the spatial locations of the joint centers on the machine base and moving platform, the initial strut lengths, and the strut displacements. The strut displacements are readily obtained from sensors on the machine. However, the remaining kinematic parameters (joint center locations, and initial strut lengths) are difficult to determine when these machines are in their fully assembled state. The size and complexity of these machines generally makes it difficult and somewhat undesirable to determine the remaining kinematic parameters by direct inspection such as in a coordinate measuring machine. In order for PKMs to be useful for precision positioning applications, techniques must be developed to quickly calibrate the machine by determining the kinematic parameters without disassembly of the machine. A number of authors have reported techniques for calibration of PKMs (Soons, Masory, Zhuang et. al., Ropponen). In two other papers, the authors have reported on work recently completed by the University of Florida and Sandia National Laboratories on calibration of PKMs, which describes a new technique to sequentially determine the kinematic parameters of an assembled parallel kinematic device. The technique described is intended to be used with a spatial coordinate measuring device such as a portable articulated CMM measuring arm (Romer, Faro, etc.), a Laser Ball Bar (LBB), or a laser tracker (SMX< API, etc.). The material to be presented is as follows: (1) methods to identify the kinematic parameters of 6--6 variant Stewart platform manipulators including joint center locations relative to the workable and spindle nose
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
On the basis of oxidative decoloration of bromopyrogallol red(BPR) with H2O2, catalyzed by horseradish peroxidase(HRP), and the sequential injection renewable surface technique(SI-RST), a highly sensitive optical-fiber sensor spectrophotometric method for the enzymatic determination of hydrogen peroxide was proposed. By coupling with a glucose oxidase(GOD) -catalyzed reaction, the method was used to determine glucose in human serum. The considerations in system and flow cell design, and factors that influence the determination performance are discussed. With 100 μL of sample loaded and 0. 6 mg of bead trapped, the linear response range from 5.0 × 10-8 to 5. 2 × 10-6mol/L BPR with a detection limit(3σ) of 2. 5 × 10 -8 mol/L BPR, and a precision of 1.1% RSD(n = 11) and a throughput of a 80 samples per hour can be achieved. Under the conditions of a 8. 7 × 10-6 mol/L BPR substrate,0.04 unit/mL HRP, 600 s reaction time and a reaction temperature of 37 ℃, the linear response range for H2O2 was from 5.0 × 10-8 to 7.0 × 10-6 mol/L with a detection limit(3σ) of 1.0 × 10-8 mol/L and a precision of 3.7% RSD(n=11). The linear response range by coupling with a GOD-catalyzed reaction was from 1.0 ×10-7 to 1.0 × 10-5mol/L. The method was directly applied to determine glucose in human serum. Glucose contents obtained by the proposed procedure were compared with those obtained by using the phenol-4-AAP method, the error was found to be less than 3%.
Applications of the Fast Double Bootstrap
MacKinnon, James G.
2006-01-01
The fast double bootstrap, or FDB, is a procedure for calculating bootstrap P values that is much more computationally efficient than the double bootstrap itself. In many cases, it can provide more accurate results than ordinary bootstrap tests. For the fast double bootstrap to be valid, the test statistic must be asymptotically independent of the random parts of the bootstrap data generating process. This paper presents simulation evidence on the performance of FDB tests in three cases of in...
Breakdown Point Theory for Implied Probability Bootstrap
Lorenzo Camponovo; Taisuke Otsu
2011-01-01
This paper studies robustness of bootstrap inference methods under moment conditions. In particular, we compare the uniform weight and implied probability bootstraps by analyzing behaviors of the bootstrap quantiles when outliers take arbitrarily large values, and derive the breakdown points for those bootstrap quantiles. The breakdown point properties characterize the situation where the implied probability bootstrap is more robust than the uniform weight bootstrap against outliers. Simulati...
The bootstrap fraction in TFTR
International Nuclear Information System (INIS)
The TRANSP plasma analysis code is used to calculate the bootstrap current generated during neutral beam injection and ion cyclotron resonance frequency heating for a wide variety of TFTR discharges. An empirical scaling relation is given for the bootstrap current fraction using the ratio of the peakednesses of the thermal pressure and of the total current density. copyright 1997 American Institute of Physics
On sieve bootstrap prediction intervals.
Andrés M. Alonso; Peña, Daniel; Romo Urroz, Juan
2003-01-01
In this paper we consider a sieve bootstrap method for constructing nonparametric prediction intervals for a general class of linear processes. We show that the sieve bootstrap provides consistent estimators of the conditional distribution of future values given the observed data.
Ultrafast Approximation for Phylogenetic Bootstrap
Bui Quang Minh, [No Value; Nguyen, Thi; von Haeseler, Arndt
2013-01-01
Nonparametric bootstrap has been a widely used tool in phylogenetic analysis to assess the clade support of phylogenetic trees. However, with the rapidly growing amount of data, this task remains a computational bottleneck. Recently, approximation methods such as the RAxML rapid bootstrap (RBS) and
Explorations in Statistics: the Bootstrap
Curran-Everett, Douglas
2009-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fourth installment of Explorations in Statistics explores the bootstrap. The bootstrap gives us an empirical approach to estimate the theoretical variability among possible values of a sample statistic such as the…
Second Thoughts on the Bootstrap
Efron, Bradley
2003-01-01
This brief review article is appearing in the issue of Statistical Science that marks the 25th anniversary of the bootstrap. It concerns some of the theoretical and methodological aspects of the bootstrap and how they might influence future work in statistics.
Lima, M.J. Reis; Fernandes, Sílvia M.V.; Rangel, António O.S.S.
2006-01-01
A sequential injection analysis (SIA) system for the spectrophotometric determination of nitrate in dairy samples was developed. A test portion was aspirated into a carrier solution containing ethylendiaminetetracetic acid (EDTA) and ammonium buffer, which flowed into a copperized cadmium reduction column installed in-line for the determination of the nitrate plus nitrite contents of samples. For the nitrite determination, another test portion of sample was aspirated and directly sen...
International Nuclear Information System (INIS)
The study of the chemical forms of heavy metals in sediments (Solid Speciation) was done by sequential extractions. A process of 3 stages sequential extraction from Almendares River sediments was applied, to determine the specification of Cd, Cu, Ni, Pb and Zn following a protocol proposed by the Bureau Community of Reference (BCR) The relation between the percentage of metal extracted in each fraction and the contents of carbonates, manganese and iron oxides, and organic matter and silice is studied. The extracts were analyzed by flame AAE. No any matrix interference were observed
Li, Songqing; Gao, Peng; Zhang, Jiaheng; Li, Yubo; Peng, Bing; Gao, Haixiang; Zhou, Wenfeng
2012-12-01
A novel dispersive liquid-liquid microextraction (DLLME) method followed by HPLC analysis, termed sequential DLLME, was developed for the preconcentration and determination of aryloxyphenoxy-propionate herbicides (i.e. haloxyfop-R-methyl, cyhalofop-butyl, fenoxaprop-P-ethyl, and fluazifop-P-butyl) in aqueous samples. The method is based on the combination of ultrasound-assisted DLLME with in situ ionic liquid (IL) DLLME into one extraction procedure and achieved better performance than widely used DLLME procedures. Chlorobenzene was used as the extraction solvent during the first extraction. Hydrophilic IL 1-octyl-3-methylimidazolium chloride was used as a dispersive solvent during the first extraction and as an extraction solvent during the second extraction after an in situ chloride exchange by bis[(trifluoromethane)sulfonyl]imide. Several experimental parameters affecting the extraction efficiency were studied and optimized with the design of experiments using MINITAB® 16 software. Under the optimized conditions, the extractions resulted in analyte recoveries of 78-91%. The correlation coefficients of the calibration curves ranged from 0.9994 to 0.9997 at concentrations of 10-300, 15-300, and 20-300 μg L(-1). The relative SDs (n = 5) ranged from 2.9 to 5.4%. The LODs for the four herbicides were between 1.50 and 6.12 μg L(-1). PMID:23109344
International Nuclear Information System (INIS)
This works reports the development of a pulsed flow sequential injection analysis (SIA) system based on the utilisation of pulse generating solenoid micro-pumps, which replace the conventional solutions propelling units commonly used in SIA systems. The influence on sample/reagent zones interpenetration and reaction zone formation of the reproducible pulsed flow produced by micro-pumps operation, which is characterised by a chaotic solutions movement, was comparatively evaluated with the typical laminar flow conditions of conventional SIA systems. The enhanced sample/reagent mixing provided by the controlled pulsed flow was favourably applied in the implementation of a SIA methodology for the fluorimetric determination of indomethacin in pharmaceutical preparations upon alkaline hydrolysis in micellar medium. Linear calibration plots were obtained for indomethacin concentrations up to 10-5 mol l-1 with a 3σ detection limit of about 1.6 x 10-8 mol l-1. The obtained results complied with those furnished by the reference procedure (RD ≤ 2.3%) and exhibited good reproducibility (RSD < 1.2%, n = 15). Sampling rate was about 30 samples per hour
International Nuclear Information System (INIS)
A sequential chemical extraction method for the determination of the geochemical fractionation of Am, Pu, and U was evaluated rigorously on a single marine sediment standard (IAEA-135). Partitioning of actinides was operationally defined for five reagent fractions and stable element analyses (Al, Ca, Fe, Mn, Ti, etc.) were performed to assist in establishing the phase specificity of the extractions. The method produces, in general, results that agree to within a one standard deviation interval for replicate measurements for each fraction. Actinide readsorption, examined by a double-spiking technique, was found to be significant in some cases. Ethylenediamine-tetraacetic acid (EDTA) was examined as a hold-back reagent to lessen the effect of readsorption but seriously compromised the phase selectivity of the extractants. In addition, the use of NaOCl for the destruction of organic matter was found to dissolve carbonates out of sequence and is not recommended for carbonate-bearing materials. (Copyright (c) 1988 Elsevier Science B.V., Amsterdam. All rights reserved.)
Sequential and rapid determination of Po-210, Bi-210 and Pb-210 in natural waters.
Tokieda, T; Narita, H; Harada, K; Tsunogai, S
1994-12-01
A sequential and rapid separation method for the determination of radon daughter nuclides, Pb-210, Bi-210 and Po-210 has been developed for application to natural waters. Rapid separation is attained by the use of the same hydrochloric acid solution. After isolation of the three radionuclides from the sample by co-precipitation with added Fe(3+), polonium isotopes are first spontaneously deposited onto a silver disc from a 0.5N hydrochloric acid solution. Next, bismuth isotopes are electrodeposited onto a platinum net cathode coupled with a platinum coil anode at 1.2 V. Finally, lead isotopes are electrodeposited onto a platinum net cathode at 1.8 V from the remaining solution by adding hydroxylamine hydrochloride as an anodic depolarizer. This method can be applied to meteorological precipitation samples where these three nuclides are separated within 10 hr after the sampling with chemical yields of more than 80% for Po-210 and Bi-210 and more than 70% for Pb-210. This method is applicable to other environmental water samples. PMID:18966174
Michel, H; Levent, D; Barci, V; Barci-Funel, G; Hurel, C
2008-02-15
A new sequential method for the determination of both natural (U, Th) and anthropogenic (Sr, Cs, Pu, Am) radionuclides has been developed for application to soil and sediment samples. The procedure was optimised using a reference sediment (IAEA-368) and reference soils (IAEA-375 and IAEA-326). Reference materials were first digested using acids (leaching), 'total' acids on hot plate, and acids in microwave in order to compare the different digestion technique. Then, the separation and purification were made by anion exchange resin and selective extraction chromatography: transuranic (TRU) and strontium (SR) resins. Natural and anthropogenic alpha radionuclides were separated by uranium and tetravalent actinide (UTEVA) resin, considering different acid elution medium. Finally, alpha and gamma semiconductor spectrometer and liquid scintillation spectrometer were used to measure radionuclide activities. The results obtained for strontium-90, cesium-137, thorium-232, uranium-238, plutonium-239+240 and americium-241 isotopes by the proposed method for the reference materials provided excellent agreement with the recommended values and good chemical recoveries. Plutonium isotopes in alpha spectrometry planchet deposits could be also analysed by ICPMS. PMID:18371813
Henkel, Susann; Kasten, Sabine; Poulton, Simon W.; Michael STAUBWASSER
2016-01-01
Reactive iron (oxyhydr)oxide minerals preferentially undergo early diagenetic redox cycling which can result in the production of dissolved Fe(II), the adsorption of Fe(II) onto particle surfaces, and the formation of authigenic Fe minerals. The partitioning of iron in sediments has traditionally been studied by applying sequential extractions that target operationally-defined iron phases. Here, we complement an existing sequential leaching method by developing a sample processing protocol fo...
The bootstrap current in tokamaks
International Nuclear Information System (INIS)
The properties of the Hirshman equation for the bootstrap in the tokamak and the difference between it and the simpler Hinton-Hazeltine equation are discussed. The Hirshman model, which takes into account finite-aspect-ratio effects, is used to calculate the bootstrap current in the plasma in a circular cross section with Te = Ti. Approximate upper and lower bounds on the bootstrap current are obtained. These restrict the range of variation of the current as the temperature and density profiles vary. 16 refs., 9 figs
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo-environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10% (at 95% confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1% and 98.4% , respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.
The wild tapered block bootstrap
DEFF Research Database (Denmark)
Hounyo, Ulrich
In this paper, a new resampling procedure, called the wild tapered block bootstrap, is introduced as a means of calculating standard errors of estimators and constructing confidence regions for parameters based on dependent heterogeneous data. The method consists in tapering each overlapping block......-of-the-art block-based method in terms of asymptotic accuracy of variance estimation and distribution approximation. For stationary time series, the asymptotic validity, and the favorable bias properties of the new bootstrap method are shown in two important cases: smooth functions of means, and M-estimators. The...... estimator for the sample mean is shown to be robust against heteroskedasticity of the wild tapered block bootstrap. This easy to implement alternative bootstrap method works very well even for moderate sample sizes....
Linear algebra and bootstrap percolation
Balogh, József; Morris, Robert; Riordan, Oliver
2011-01-01
In $\\HH$-bootstrap percolation, a set $A \\subset [n]$ of initially `infected' vertices spreads by infecting vertices which are the only uninfected vertex in an edge of the hypergraph $\\HH \\subset \\P(n)$. A particular case of this is the $H$-bootstrap process, in which $\\HH$ encodes copies of $H$ in a graph $G$. We find the minimum size of a set $A$ that leads to complete infection when $G$ is a power of a complete graph and $H$ is a hypercube. The proof uses linear algebra, a technique that is new in bootstrap percolation, although standard in the study of weakly saturated graphs, which are equivalent to (edge) $H$-bootstrap percolation on a complete graph.
Rossi, Elena; Mitnitski, Arnold; Feldman, Anatol G
2002-01-15
studies, together with the present finding that the trunk only begins to contribute to the hand displacement at peak hand velocity, imply that the central commands that determine the contributions of the arm and the trunk to the transport of the hand are generated sequentially, even though the arm and trunk move in parallel. PMID:11790827
Energy Technology Data Exchange (ETDEWEB)
Urbanski, P.; Kowalska, E.
1997-12-31
The principle of the bootstrap methodology applied for the assessment of parameters and prediction ability of the linear regression models was presented. Application of this method was shown on the example of calibration of the radioisotope sulphuric acid concentration gauge. The bootstrap method allows to determine not only the numerical values of the regression coefficients, but also enables to investigate their distributions. (author). 11 refs, 12 figs, 3 tabs.
Bootstrapping Realized Multivariate Volatility Measures.
Donovon, Prosper; Goncalves, Silvia; Meddahi, Nour
2013-01-01
We study bootstrap methods for statistics that are a function of multivariate high frequency returns such as realized regression coefficients and realized covariances and correlations. For these measures of covariation, the Monte Carlo simulation results of Barndorff-Nielsen and Shephard (2004) show that finite sample distortions associated with their feasible asymptotic theory approach may arise if sampling is not too frequent. This motivates our use of the bootstrap as an altern...
Deep Exploration via Bootstrapped DQN
Osband, Ian; Blundell, Charles; Pritzel, Alexander; Van Roy, Benjamin
2016-01-01
Efficient exploration in complex environments remains a major challenge for reinforcement learning. We propose bootstrapped DQN, a simple algorithm that explores in a computationally and statistically efficient manner through use of randomized value functions. Unlike dithering strategies such as epsilon-greedy exploration, bootstrapped DQN carries out temporally-extended (or deep) exploration; this can lead to exponentially faster learning. We demonstrate these benefits in complex stochastic ...
Bootstrap current in a tokamak
Energy Technology Data Exchange (ETDEWEB)
Kessel, C.E.
1994-03-01
The bootstrap current in a tokamak is examined by implementing the Hirshman-Sigmar model and comparing the predicted current profiles with those from two popular approximations. The dependences of the bootstrap current profile on the plasma properties are illustrated. The implications for steady state tokamaks are presented through two constraints; the pressure profile must be peaked and {beta}{sub p} must be kept below a critical value.
Bootstrap current in a tokamak
International Nuclear Information System (INIS)
The bootstrap current in a tokamak is examined by implementing the Hirshman-Sigmar model and comparing the predicted current profiles with those from two popular approximations. The dependences of the bootstrap current profile on the plasma properties are illustrated. The implications for steady state tokamaks are presented through two constraints; the pressure profile must be peaked and βp must be kept below a critical value
Bootstrap percolation on spatial networks
Jian Gao; Tao Zhou; Yanqing Hu
2015-01-01
Bootstrap percolation is a general representation of some networked activation process, which has found applications in explaining many important social phenomena, such as the propagation of information. Inspired by some recent findings on spatial structure of online social networks, here we study bootstrap percolation on undirected spatial networks, with the probability density function of long-range links’ lengths being a power law with tunable exponent. Setting the size of the giant active...
Bootstrap Dynamical Symmetry Breaking
Directory of Open Access Journals (Sweden)
Wei-Shu Hou
2013-01-01
Full Text Available Despite the emergence of a 125 GeV Higgs-like particle at the LHC, we explore the possibility of dynamical electroweak symmetry breaking by strong Yukawa coupling of very heavy new chiral quarks Q . Taking the 125 GeV object to be a dilaton with suppressed couplings, we note that the Goldstone bosons G exist as longitudinal modes V L of the weak bosons and would couple to Q with Yukawa coupling λ Q . With m Q ≳ 700 GeV from LHC, the strong λ Q ≳ 4 could lead to deeply bound Q Q ¯ states. We postulate that the leading “collapsed state,” the color-singlet (heavy isotriplet, pseudoscalar Q Q ¯ meson π 1 , is G itself, and a gap equation without Higgs is constructed. Dynamical symmetry breaking is affected via strong λ Q , generating m Q while self-consistently justifying treating G as massless in the loop, hence, “bootstrap,” Solving such a gap equation, we find that m Q should be several TeV, or λ Q ≳ 4 π , and would become much heavier if there is a light Higgs boson. For such heavy chiral quarks, we find analogy with the π − N system, by which we conjecture the possible annihilation phenomena of Q Q ¯ → n V L with high multiplicity, the search of which might be aided by Yukawa-bound Q Q ¯ resonances.
Bootstrapping quarks and gluons
International Nuclear Information System (INIS)
Dual topological unitarization (DTU) - the approach to S-matrix causality and unitarity through combinatorial topology - is reviewed. Amplitudes associated with triangulated spheres are shown to constitute the core of particle physics. Each sphere is covered by triangulated disc faces corresponding to hadrons. The leading current candidate for the hadron-face triangulation pattern employs 3-triangle basic subdiscs whose orientations correspond to baryon number and topological color. Additional peripheral triangles lie along the hadron-face perimeter. Certain combinations of peripheral triangles with a basic-disc triangle can be identified as quarks, the flavor of a quark corresponding to the orientation of its edges that lie on the hadron-face perimeter. Both baryon number and flavor are additively conserved. Quark helicity, which can be associated with triangle-interior orientation, is not uniformly conserved and interacts with particle momentum, whereas flavor does not. Three different colors attach to the 3 quarks associated with a single basic subdisc, but there is no additive physical conservation law associated with color. There is interplay between color and quark helicity. In hadron faces with more than one basic subdisc, there may occur pairs of adjacent flavorless but colored triangles with net helicity +-1 that are identifiable as gluons. Broken symmetry is an automatic feature of the bootstrap. T, C and P symmetries, as well as up-down flavor symmetry, persist on all orientable surfaces
Bootstrapping Time Dilation Decoherence
Gooding, Cisco; Unruh, William G.
2015-10-01
We present a general relativistic model of a spherical shell of matter with a perfect fluid on its surface coupled to an internal oscillator, which generalizes a model recently introduced by the authors to construct a self-gravitating interferometer (Gooding and Unruh in Phys Rev D 90:044071, 2014). The internal oscillator evolution is defined with respect to the local proper time of the shell, allowing the oscillator to serve as a local clock that ticks differently depending on the shell's position and momentum. A Hamiltonian reduction is performed on the system, and an approximate quantum description is given to the reduced phase space. If we focus only on the external dynamics, we must trace out the clock degree of freedom, and this results in a form of intrinsic decoherence that shares some features with a proposed "universal" decoherence mechanism attributed to gravitational time dilation (Pikovski et al in Nat Phys, 2015). We note that the proposed decoherence remains present in the (gravity-free) limit of flat spacetime, emphasizing that the effect can be attributed entirely to proper time differences, and thus is not necessarily related to gravity. Whereas the effect described in (Pikovski et al in Nat Phys, 2015) vanishes in the absence of an external gravitational field, our approach bootstraps the gravitational contribution to the time dilation decoherence by including self-interaction, yielding a fundamentally gravitational intrinsic decoherence effect.
Filter and modified stepwedge bootstrap sensitometry in medical radiography
Energy Technology Data Exchange (ETDEWEB)
Yoshida, Akira
1988-05-01
Two new bootstrap methods for determining characteristic curves of radiographic screen/film systems are presented : filter bootstrap sensitometry and modified stepwedge bootstrap sensitometry. Both are intensity-scale sensitometries since the radiation intensity can be varied through use of a combination of inverse square and metal filters. Characteristic curves obtained by these methods are compared with those from screen/film systems using inverse square sensitometry as a reference standard of accuracy. The precision of all three methods is better than +- 2 % with agreement among generally being within 3 % over the useful density range. By these bootstrap methods, it is possible to obtain characteristic curves agreeing well with those using the inverse square method for a relatively short distance, and make radiographic sensitometry practical and convenient at most medical institutions.
Extremal bootstrapping: go with the flow
El-Showk, Sheer
2016-01-01
The extremal functional method determines approximate solutions to the constraints of crossing symmetry, which saturate bounds on the space of unitary CFTs. We show that such solutions are characterized by extremality conditions, which may be used to flow continuously along the boundaries of parameter space. Along the flow there is generically no further need for optimization, which dramatically reduces computational requirements, bringing calculations from the realm of computing clusters to laptops. Conceptually, extremality sheds light on possible ways to bootstrap without positivity, extending the method to non-unitary theories, and implies that theories saturating bounds, and especially those sitting at kinks, have unusually sparse spectra. We discuss several applications, including the first high-precision bootstrap of a non-unitary CFT.
Double-bootstrap methods that use a single double-bootstrap simulation
Chang, Jinyuan; Hall, Peter
2014-01-01
We show that, when the double bootstrap is used to improve performance of bootstrap methods for bias correction, techniques based on using a single double-bootstrap sample for each single-bootstrap sample can be particularly effective. In particular, they produce third-order accuracy for much less computational expense than is required by conventional double-bootstrap methods. However, this improved level of performance is not available for the single double-bootstrap methods that have been s...
Institute of Scientific and Technical Information of China (English)
DONGDe－ming; FANGChun－sheng; 等
2002-01-01
Sequential chemical extraction procedure has been widely used to partition particulate trace metals into vari-ous fractions and to describe the distribution and the statue of trace metals in geo-environment.One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils.The experiment was designed with quality controlling concept in order to show sampling and analytical error.Experimental results obtained on duplicate analy-sis of all soil samples demonstrated that the precision was less than 10%(at 95% confidence level).The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions.The recovery of Mn from SRM1 and SRM2 was 94.1% and 98.4%,respectively.The detection limit,accuracy and precision of the sequential chemical extraction procedure were discussed in detailed.All the results suggest that the trueness of the analytical method is satisfactory.
International Nuclear Information System (INIS)
A radiochemical sequential extraction procedure has been developed in our laboratory to determine 226Ra and 234,238U by alpha spectrometry in environmental samples. This method has been validated for both radionuclides by comparing in selected samples the values obtained through its application with the results obtained by applying alternative procedures. Recoveries obtained, counting periods applied and background levels found in the alpha spectra give suitable detection limits to allow the Ra and U determination in operational forms defined in riverbed contaminated sediments. Results obtained in these speciation studies show that 226Ra and 234,238U contamination tend to be associated to precipitated forms of the sediments. (author)
On variance estimation and a goodness-of-fit test using the bootstrap method
Amiri, Saeid
2009-01-01
This thesis deals with the study of variance estimation using the bootstrap method, including the problem of choosing between nonparametric and parametric bootstrap methods. Paper I compares the two approaches, determines which method is preferable and analyses the accuracy of the approximations. The underlying concept of parametric bootstrap is based on the assumption of correct choice of parametric distribution. Paper II therefore considers goodness-of-fit tests and presents a new test base...
Sequential determination of fat- and water-soluble vitamins in green leafy vegetables during storage
Santos, Joana; Mendiola, J. A.; Oliveira, M.B.P.P.; Ibáñez, Elena; Herrero, Miguel
2012-01-01
The simultaneous analysis of fat- and water-soluble vitamins from foods is a difficult task considering the wide range of chemical structures involved. In this work, a new procedure based on a sequential extraction and analysis of both types of vitamins is presented. The procedure couples several simple extraction steps to LC–MS/MS and LC–DAD in order to quantify the free vitamins contents in fresh-cut vegetables before and after a 10-days storage period. The developed method allows the corre...
Lee, Jin-Ho; Kim, Dong-Jin; Ahn, Byung-Koo
2015-06-01
The objectives of this study were to investigate the distribution of thallium in soils collected near suspected areas such as cement plants, active and closed mines, and smelters and to examine the extraction of thallium in the soils using 19 single chemical and sequential chemical extraction procedures. Thallium concentrations in soils near cement plants were distributed between 1.20 and 12.91 mg kg(-1). However, soils near mines and smelters contained relatively low thallium concentrations ranging from 0.18 to 1.09 mg kg(-1). Thallium extractability with 19 single chemical extractants from selected soils near cement plants ranged from 0.10% to 8.20% of the total thallium concentration. In particular, 1.0 M NH4Cl, 1.0 M (NH4)2SO4, and 1.0 M CH3COONH4 extracted more thallium than other extractants. Sequential fractionation results of thallium from different soils such as industrially and artificially contaminated soils varied with the soil properties, especially soil pH and the duration of thallium contamination. PMID:25836266
Determination of sequential extracted uranium speciation in geological samples with HR-ICP-MS method
International Nuclear Information System (INIS)
This paper presents a method of determing uranium speciation in geological samples by means of sequential extraction procedure with HR-ICP-MS and its application to sandstone uranium exploration. The extraction chemical procedure is modified from Tessier, uranium in sample is classified into five speclarion: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to sulfide-organic matter, and residual. The uranium is extracted respectively and the extractants are measured by the high-resolution inductively coupled mass spectrometry (HR-ICP-MS) with high sensitivity and low background. The extraction procedure has been proved to be satisfactory by means of national reference standard materials, international reference standard materials, and artificial uranium mine sample. Experiment results obtained on replicate samples demonstrate that the relative standard deviation (RSD) of the sequential extraction procedure followed by HR-ICP-MS is 2.6 % for bound to carbonates, 4.0% for bound to sulfide -organic matter, 6.0% for residual, 6.1% bound to Fe-Mn oxides, and 26% for exchangeable fraction. The ratio of uranium in bound to uranium carbonates in residual can be used to indicated the probability of buried uranium deposit. (authors)
Bootstrap data methodology for sequential hybrid model building
Volponi, Allan J. (Inventor); Brotherton, Thomas (Inventor)
2007-01-01
A method for modeling engine operation comprising the steps of: 1. collecting a first plurality of sensory data, 2. partitioning a flight envelope into a plurality of sub-regions, 3. assigning the first plurality of sensory data into the plurality of sub-regions, 4. generating an empirical model of at least one of the plurality of sub-regions, 5. generating a statistical summary model for at least one of the plurality of sub-regions, 6. collecting an additional plurality of sensory data, 7. partitioning the second plurality of sensory data into the plurality of sub-regions, 8. generating a plurality of pseudo-data using the empirical model, and 9. concatenating the plurality of pseudo-data and the additional plurality of sensory data to generate an updated empirical model and an updated statistical summary model for at least one of the plurality of sub-regions.
Bootstrap bias-adjusted GMM estimators
Ramalho, Joaquim J.S.
2005-01-01
The ability of six alternative bootstrap methods to reduce the bias of GMM parameter estimates is examined in an instrumental variable framework using Monte Carlo analysis. Promising results were found for the two bootstrap estimators suggested in the paper.
Analytical bootstrap methods for censored data
Alan D. Hutson
2002-01-01
Analytic bootstrap estimators for the moments of survival quantities are derived. By using these expressions recommendations can be made as to the appropriateness of bootstrap estimation under censored data conditions.
TOKALIOĞLU, Şerife; BİROL, Şenol KARTAL and Gökhan
2003-01-01
A sequential extraction procedure, a three-step protocol proposed by the Standards, Measurements and Testing programme (SM & T--formerly BCR) of the European Union, was applied to soil samples for the determination of metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). This procedure provides measurements of extractable metals from media such as acetic acid (0.11 mol L-1), hydroxylammonium chloride (0.1 mol L-1) and hydrogen peroxide (8.8 mol L-1) plus ammonium acetate (1 mol L - 1), ...
Improving the Reliability of Bootstrap Tests
Russell Davidson; MacKinnon, James G.
2000-01-01
We first propose procedures for estimating the rejection probabilities for bootstrap tests in Monte Carlo experiments without actually computing a bootstrap test for each replication. These procedures are only about twice as expensive as estimating rejection probabilities for asymptotic tersts. We then propose procedures for computing modified bootstrap P values that will often be more accurate than ordinary ones. These procedures are closely related to the double bootstrap, but they are far ...
Unsupervised model compression for multilayer bootstrap networks
ZHANG, XIAO-LEI
2015-01-01
Recently, multilayer bootstrap network (MBN) has demonstrated promising performance in unsupervised dimensionality reduction. It can learn compact representations in standard data sets, i.e. MNIST and RCV1. However, as a bootstrap method, the prediction complexity of MBN is high. In this paper, we propose an unsupervised model compression framework for this general problem of unsupervised bootstrap methods. The framework compresses a large unsupervised bootstrap model into a small model by ta...
Ezoe, Kentaro; Ohyama, Seiichi; Hashem, Md Abul; Ohira, Shin-Ichi; Toda, Kei
2016-02-01
After the Fukushima disaster, power generation from nuclear power plants in Japan was completely stopped and old coal-based power plants were re-commissioned to compensate for the decrease in power generation capacity. Although coal is a relatively inexpensive fuel for power generation, it contains high levels (mgkg(-1)) of selenium, which could contaminate the wastewater from thermal power plants. In this work, an automated selenium monitoring system was developed based on sequential hydride generation and chemiluminescence detection. This method could be applied to control of wastewater contamination. In this method, selenium is vaporized as H2Se, which reacts with ozone to produce chemiluminescence. However, interference from arsenic is of concern because the ozone-induced chemiluminescence intensity of H2Se is much lower than that of AsH3. This problem was successfully addressed by vaporizing arsenic and selenium individually in a sequential procedure using a syringe pump equipped with an eight-port selection valve and hot and cold reactors. Oxidative decomposition of organoselenium compounds and pre-reduction of the selenium were performed in the hot reactor, and vapor generation of arsenic and selenium were performed separately in the cold reactor. Sample transfers between the reactors were carried out by a pneumatic air operation by switching with three-way solenoid valves. The detection limit for selenium was 0.008 mg L(-1) and calibration curve was linear up to 1.0 mg L(-1), which provided suitable performance for controlling selenium in wastewater to around the allowable limit (0.1 mg L(-1)). This system consumes few chemicals and is stable for more than a month without any maintenance. Wastewater samples from thermal power plants were collected, and data obtained by the proposed method were compared with those from batchwise water treatment followed by hydride generation-atomic fluorescence spectrometry. PMID:26653491
Coefficient Omega Bootstrap Confidence Intervals: Nonnormal Distributions
Padilla, Miguel A.; Divers, Jasmin
2013-01-01
The performance of the normal theory bootstrap (NTB), the percentile bootstrap (PB), and the bias-corrected and accelerated (BCa) bootstrap confidence intervals (CIs) for coefficient omega was assessed through a Monte Carlo simulation under conditions not previously investigated. Of particular interests were nonnormal Likert-type and binary items.…
On the Asymptotic Accuracy of Efron's Bootstrap
Singh, Kesar
1981-01-01
In the non-lattice case it is shown that the bootstrap approximation of the distribution of the standardized sample mean is asymptotically more accurate than approximation by the limiting normal distribution. The exact convergence rate of the bootstrap approximation of the distributions of sample quantiles is obtained. A few other convergence rates regarding the bootstrap method are also studied.
The bootstrap and edgeworth expansion
Hall, Peter
1992-01-01
This monograph addresses two quite different topics, in the belief that each can shed light on the other. Firstly, it lays the foundation for a particular view of the bootstrap. Secondly, it gives an account of Edgeworth expansion. Chapter 1 is about the bootstrap, witih almost no mention of Edgeworth expansion; Chapter 2 is about Edgeworth expansion, with scarcely a word about the bootstrap; and Chapters 3 and 4 bring these two themes together, using Edgeworth expansion to explore and develop the properites of the bootstrap. The book is aimed a a graduate level audience who has some exposure to the methods of theoretical statistics. However, technical details are delayed until the last chapter (entitled "Details of Mathematical Rogour"), and so a mathematically able reader without knowledge of the rigorous theory of probability will have no trouble understanding the first four-fifths of the book. The book simultaneously fills two gaps in the literature; it provides a very readable graduate level account of t...
A bootstrap approach to bump hunting
Silverman, B. W.
1982-01-01
An important question in cluster analysis and pattern recognition is the determination of the number of clusters into which a given population should be divided. Frequently, particularly when certain specific clustering methods are being used, the number of clusters is taken to be equal to the number of modes, or local maxima, in the probability density function underlying the given data set. The use of kernal density estimates in mode estimation is discussed. The test statistic to be used is defined and a bootstrap technique for assessing significance is given. An illustrative application is followed by an examination of the asymptotic behavior of the test statistic.
Evaluating Neural Network Predictors by Bootstrapping
Blake LeBaron; Andreas S. Weigend
1994-01-01
We present a new method, inspired by the bootstrap, whose goal it is to determine the quality and reliability of a neural network predictor. Our method leads to more robust forecasting along with a large amount of statistical information on forecast performance that we exploit. We exhibit the method in the context of multi-variate time series prediction on financial data from the New York Stock Exchange. It turns out that the variation due to different resamplings (i.e., splits between traini...
Feti, Andreea; Dudele, Aiga
2012-01-01
Bootstrapping plays a vital role in the life of small and medium-sized enter-prises. By providing a large variety of financing alternatives bootstrapping ensures the existence of entrepreneurship, even though, too less attention is paid to bootstrapping in the specific literature. Therefore, the master thesis strives to eliminate the gaps in the theory by bringing new insights in the field of bootstrapping.The purpose of the master thesis is to investigate the usage of boot-strapping methods ...
Zhang, Zhuomin; Zhao, Cheng; Li, Gongke
2016-07-01
Achieving reproducible signals is a key point to improve the analytical precision and accuracy of surface enhanced Raman scattering (SERS) technique and further expand the application scope of SERS for on-site and rapid analysis of real sample with complex matrice. In this work, a novel Au@hydroxyl-functionalized polystyrene (Au@PS-OH) substrate was prepared by atom transfer radical polymerization and chemical assembly method, which possessed promised potential for the rapid and sequential analysis of multisamples coupling with SERS technique. Au@PS-OH substrate with regular nanoarrayed morphology possessed excellent anti-agglomeration capability even for testing solutions with strong basicity or acidity, mechanic and chemical stability due to the large amount of Au nanoparticles homogeneously and stably fixed on substrate surface. Moreover, excellent hydrophobicity of Au@PS-OH substrate could keep testing droplets of multiple samples stable and uniform spherical shape with similar contact angles to substrate, which guaranteed the reproducible SERS light paths and SERS signals during real sequential analysis. Then, an Au@PS-OH based SERS analytical method was developed and practically applied for the sequential determination of trace 4-aminoazobenzene in various textiles. It was satisfactory that the contents of trace 4-aminoazobenzene in black woolen, green woolen and yellow fiber cloth could be actually found and calculated to be 106.4, 120.9 and 140.8mg/kg with good recoveries of 76.0-118.9% and relative standard deviations of 1.6-5.1%. It is expected that this SERS method is suitable for on-site and rapid analysis of multiple samples in a short period. PMID:27154685
Locality, bulk equations of motion and the conformal bootstrap
Kabat, Daniel
2016-01-01
We develop an approach to construct local bulk operators in a CFT to order 1/N^2. Since 4-point functions are not fixed by conformal invariance we use the OPE to categorize possible forms for a bulk operator. Using previous results on 3-point functions we construct a local bulk operator in each OPE channel. We then impose the condition that the bulk operators constructed in different channels agree, and hence give rise to a well-defined bulk operator. We refer to this condition as the "bulk bootstrap." We argue and explicitly show in some examples that the bulk bootstrap leads to some of the same results as the regular conformal bootstrap. In fact the bulk bootstrap provides an easier way to determine some CFT data, since it does not require knowing the form of the conformal blocks. This analysis clarifies previous results on the relation between bulk locality and the bootstrap for theories with a 1/N expansion, and it identifies a simple and direct way in which OPE coefficients and anomalous dimensions deter...
Chain ladder method: Bayesian bootstrap versus classical bootstrap
Peters, Gareth W.; Mario V. W\\"uthrich; Shevchenko, Pavel V.
2010-01-01
The intention of this paper is to estimate a Bayesian distribution-free chain ladder (DFCL) model using approximate Bayesian computation (ABC) methodology. We demonstrate how to estimate quantities of interest in claims reserving and compare the estimates to those obtained from classical and credibility approaches. In this context, a novel numerical procedure utilising Markov chain Monte Carlo (MCMC), ABC and a Bayesian bootstrap procedure was developed in a truly distribution-free setting. T...
No unitary bootstrap for the fractal Ising model
Golden, John
2015-01-01
We consider the conformal bootstrap for spacetime dimension $1
International Nuclear Information System (INIS)
Determinations of hexamethylene tetramine (HMTA) and urea in the process solutions are required to optimize their concentrations for obtaining high quality ceramic oxide microspheres, for monitoring the washing procedure and for their subsequent recovery, recycling or waste disposal. Determination of urea is the feed solution by conventional procedures is difficult as it contains HMTA. It is more so in the effluent as it contains hydrolytic products like formaldehyde, methylol derivatives of urea, ammonium nitrate and ammonium hydroxide used for washing the gel microspheres. A derivative potentiometric method using a microprocessor-based autotitrator is described. Peaks on the first derivative of the titration plot corresponded to constituents of different basicities. Urea was selectively hydrolyzed at room temperature by the catalytic action of urease enzyme leaving HMTA unaffected. Ammonium hydroxide and ammonium bicarbonate produced from urea and HMTA were sequentially titrated for the analysis of the feed solution to obtain the three corresponding peaks respectively. Two separate titrations were required for the analysis of the effluent solution, which contained free ammonia also. One aliquot was first titrated directly without adding urease (for free ammonia and HMTA) and another aliquot was titrated after treatment with urease. The end points due to the ammonia used for washing and that from urea hydrolysis merged resulting in the appearance of three peaks again. Using this sequential method the relative standard deviations were found to be 0.81% and 1.38% for urea and HMTA, respectively, in eight determinations when the aliquots contained 50 to 75 mg of urea and 75 to 125 mg of HMTA. Feed and effluent solutions of the process stream were analyzed. (author)
Bootstrap Current in Spherical Tokamaks
Institute of Scientific and Technical Information of China (English)
王中天; 王龙
2003-01-01
Variational principle for the neoclassical theory has been developed by including amomentum restoring term in the electron-electron collisional operator, which gives an additionalfree parameter maximizing the heat production rate. All transport coefficients are obtained in-cluding the bootstrap current. The essential feature of the study is that the aspect ratio affects thefunction of the electron-electron collision operator through a geometrical factor. When the aspectratio approaches to unity, the fraction of circulating particles goes to zero and the contribution toparticle flux from the electron-electron collision vanishes. The resulting diffusion coefficient is inrough agreement with Hazeltine. When the aspect ratio approaches to infinity, the results are inagreement with Rosenbluth. The formalism gives the two extreme cases a connection. The theoryis particularly important for the calculation of bootstrap current in spherical tokamaks and thepresent tokamaks, in which the square root of the inverse aspect ratio, in general, is not small.
Bootstrapping N=2 chiral correlators
Lemos, Madalena; Liendo, Pedro
2016-01-01
We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.
Bootstrapping N=2 chiral correlators
Energy Technology Data Exchange (ETDEWEB)
Lemos, Madalena [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Liendo, Pedro [Humboldt-Univ. Berlin (Germany). IMIP
2015-12-15
We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.
Horn, D.
2015-03-01
The quark model emerged from the Gell-Mann-Ne'eman flavor SU(3) symmetry. Its development, in the context of strong interactions, took place in a heuristic theoretical framework, referred to as the Bootstrap Era. Setting the background for the dominant ideas in strong interaction of the early 1960s, we outline some aspects of the constituent quark model. An independent theoretical development was the emergence of hadron duality in 1967, leading to a realization of the Bootstrap idea by relating hadron resonances (in the s-channel) with Regge pole trajectories (in t- and u-channels). The synthesis of duality with the quark-model has been achieved by duality diagrams, serving as a conceptual framework for discussing many aspects of hadron dynamics toward the end of the 1960s.
Conformal Bootstrap in Mellin Space
Gopakumar, Rajesh; Sen, Kallol; Sinha, Aninda
2016-01-01
We propose a new approach towards analytically solving for the dynamical content of Conformal Field Theories (CFTs) using the bootstrap philosophy. This combines the original bootstrap idea of Polyakov with the modern technology of the Mellin representation of CFT amplitudes. We employ exchange Witten diagrams with built in crossing symmetry as our basic building blocks rather than the conventional conformal blocks in a particular channel. Demanding consistency with the operator product expansion (OPE) implies an infinite set of constraints on operator dimensions and OPE coefficients. We illustrate the power of this method in the epsilon expansion of the Wilson-Fisher fixed point by computing operator dimensions and, strikingly, OPE coefficients to higher orders in epsilon than currently available using other analytic techniques (including Feynman diagram calculations). Our results enable us to get a somewhat better agreement of certain observables in the 3d Ising model, with the precise numerical values that...
Bootstrapping N=2 chiral correlators
International Nuclear Information System (INIS)
We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.
On a generalized bootstrap principle
International Nuclear Information System (INIS)
The S-matrices for non-simply-laced affine Toda field theories are considered in the context of a generalized bootstrap principle. The S-matrices, and in particular their poles, depend on a parameter whose range lies between the Coxeter numbers of dual pairs of the corresponding non-simply-laced algebras. It is proposed that only odd order poles in the physical strip with positive coefficients throughout this range should participate in the bootstrap. All other singularities have an explanation in principle in terms of a generalized Coleman-Thun mechanism. Besides the S-matrices introduced by Delius, Grisaru and Zanon, the missing case (F4(1), e6(2)), is also considered and provides many interesting examples of pole generation. (author)
Bootstrap clustering for graph partitioning
Gambette, Philippe; Guénoche, Alain
2011-01-01
Given a simple undirected weighted or unweighted graph, we try to cluster the vertex set into communities and also to quantify the robustness of these clusters. For that task, we propose a new method, called bootstrap clustering which consists in (i) defining a new clustering algorithm for graphs, (ii) building a set of graphs similar to the initial one, (iii) applying the clustering method to each of them, making a profile (set) of partitions, (iv) computing a consensus partition for this pr...
Conformal Bootstrap in Embedding Space
Fortin, Jean-François
2016-01-01
It is shown how to obtain conformal blocks from embedding space with the help of the operator product expansion. The minimal conformal block originates from scalar exchange in a four-point correlation functions of four scalars. All remaining conformal blocks are simple derivatives of the minimal conformal block. With the help of the orthogonality properties of the conformal blocks, the analytic conformal bootstrap can be implemented directly in embedding space, leading to a Jacobi-like definition of conformal field theories.
Conformal bootstrap in embedding space
Fortin, Jean-François; Skiba, Witold
2016-05-01
It is shown how to obtain conformal blocks from embedding space with the help of the operator product expansion. The minimal conformal block originates from scalar exchange in a four-point correlation function of four scalars. All remaining conformal blocks are simple derivatives of the minimal conformal block. With the help of the orthogonality properties of the conformal blocks, the analytic conformal bootstrap can be implemented directly in embedding space, leading to a Jacobi-like definition of conformal field theories.
Bootstrapping High Dimensional Time Series
Zhang, Xianyang; Cheng, Guang
2014-01-01
This article studies bootstrap inference for high dimensional weakly dependent time series in a general framework of approximately linear statistics. The following high dimensional applications are covered: (1) uniform confidence band for mean vector; (2) specification testing on the second order property of time series such as white noise testing and bandedness testing of covariance matrix; (3) specification testing on the spectral property of time series. In theory, we first derive a Gaussi...
Modified Bootstrap Sensitometry In Radiography
Bednarek, Daniel R.; Rudin, Stephen
1981-04-01
A new modified bootstrap approach to sensitometry is presented which provides H and D curves that show almost exact agreement with those obtained using conventional methods. Two bootstrap techniques are described; both involve a combination of inverse-square and stepped-wedge modulation of the radiation field and provide intensity-scale sensitometric curves as appropriate for medical radiography. H and D curves obtained with these modified techniques are compared with those obtained for screen-film combinations using inverse-square sensitometry as well as with those obtained for direct x-ray film using time-scale sensitometry. The stepped wedge of the Wisconsin X-Ray Test Cassette was used in the bootstrap approach since it provides sufficient exposure latitude to encompass the useful density range of medical x-ray film. This approach makes radiographic sensitometry quick and convenient, allowing accurate characteristic curves to be obtained for any screen-film cassette using standard diagnostic x-ray equipment.
Kilovoltage bootstrap sensitometry.
Yester, M V; Barnes, G T; King, M A
1980-09-01
A new method for determining the sensitometric curve of radiographic film/screen combinations is described. The approach employs kVp variation at several mAs values to provide the necessary range of exposures. The method is simple and easy to perform and is presented along with experimental data for illustration. The sources and relative magnitude of errors associated with the technique are also discussed. PMID:7403562
Sequential determination of U and Th isotopes, 226Ra, 228Ra, 210Pb, and 210Po in mushroom
International Nuclear Information System (INIS)
For this study, mushroom samples were collected in Brazil at the Sao Paulo Metropolitan Region and at the Pocos de Caldas Plateau (PC; a region of elevated natural radioactivity, which houses the first Brazilian uranium mine). This paper discusses a sequential methodology to determine natural series radionuclides in mushrooms, such as uranium (238U and 234U) and thorium (232Th, 230Th, and 228Th) isotopes, radium-226, radium-228, as well as lead-210 and polonium-210; using Alpha Spectrometry, Gamma Spectrometry, and Total Alpha and Beta Counting. The method involves total sample dissolution in a closed system in order to avoid loss of Polonium and employment of specific chromatographic resins for radionuclide purification. A subsequent interpretation of the results can provide information on pollutants present in mushrooms and infer possible contamination in the areas sampled as well as allow an association of measured concentrations to radioactive anomalies in the Plateau. (author)
International Nuclear Information System (INIS)
The Brazilian phosphate fertilizer is obtained by wet reaction of igneous phosphate rock with concentrated sulphuric acid, giving as final product phosphoric acid and calcium sulphate (phosphogypsum) as by-product. Phosphoric acid is the starting material for the production of the majors' phosphate fertilizers: triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP) and diammonium phosphate (DAP). The phosphate rock used as raw material is enriched in radionuclides of the U and Th natural series. During the chemical attack these radionuclides are distributed among products and by-products. A sequential procedure was implemented to determine the content of radionuclides alpha emitters (234U, 238U, 230Th, 232Th, 228Th and 226Ra) in samples of phosphate rock, phosphogypsum and phosphate fertilizers produced by the Brazilian industries. The experimental procedure consisted of a chemical attack with strong acids, followed by sequential chromatography extractions in column with ionic resins. Depending upon the conditions of percolation U isotopes are separated, followed by Th isotopes and 226Ra. The solutions containing U and Th are electroplated on stainless steel disks and counted on a surface barrier detector for alpha spectrometry. To the Ra final solution, a BaSO4 seeding suspension was added to allow the formation of a micro precipitated of BaRaSO4. This precipitate is filtered in a polypropylene membrane and counted on the same detector. The precision and accuracy of the method were determined by analyzing reference materials: soil IAEA-326 and sediment IAEA-300. SSP and TSP, which are obtained by reacting phosphoric acid with phosphate rock in different proportions, presented higher concentrations of all studied radionuclides. Brazilian phosphate fertilizers, which are produced directly from phosphoric acid, MAP and DAP, present in their composition low concentrations of radionuclide 226Ra. As for the radionuclides U and Th, the
Sequential Failure Analysis Using Novel Algorithms in Sequence Determination of Petri Nets Firing
Farshad Tooyserkani; Jamshid Parvizian; Abolfazl Doostparast Torshizi
2013-01-01
Failure occurrence in industrial systems can be a result of a sequence of failures leading to a total system failure. Up to now, several methods to determine failure sequences and to calculate probability of such failures have been proposed. These methods primarily focus on modeling aspects of the problem and do not present a certain framework to determine potential failure sequences. In this paper, a novel approach based on Petri net modeling of the systems is proposed and several heuristic ...
International Nuclear Information System (INIS)
A sequential extraction technique was developed allowing the extraction and purification of uranium, thorium, radium, lead and polonium radionuclides from the same sample. Environmental materials such as water, soil, biological materials, can be analyzed for those radionuclides without matrix interferences in the quality of radioelement purification and in the radiochemical yield. The use of isotopic tracers (232U, 229Th, 224Ra, 209Po and stable lead carrier) added to the sample at the beginning of the chemical procedure enables an accurate control of the radiochemical yield for each radioelement. The ion extraction procedure, applied after either complete dissolution of the solid sample with mineral acids or dissolution of MnO2 precipitate for aqueous samples, includes the use of commercially available columns from Eichrom and laboratory prepared anionic and cationic columns, in a total of three chromatography columns. All radioelements are purified and electroplated on stainless steel discs except for polonium which is spontaneously plated on a silver disc. The discs are measured using high resolution silicon surface barrier detectors. 210Pb, a beta emitter, can be measured either through the beta emission of 210Bi, or stored for a few months and determined by alpha spectrometry through the in-growth of 210Po. This sequential extraction chromatography technique was tested and validated by analysis of certified reference materials from IAEA (soil, marine sediment, and fish). Reproducibility was tested through repeated analysis of the same homogeneous material (water sample). Performance, when applied to samples with different matrix, was tested analyzing cabbage, potatoes, fish filet, meat, water, urine, soils and sediments with high yield of recovery and complete separation of radioelements. Precision was tested also through participation in analytical inter laboratory world wide comparisons analysing blind samples (round robin tests) organized by the IAEA and
International Nuclear Information System (INIS)
In this work, a fully automated flow system exploiting the advantages of the association of multi-pumping, multicommutation, binary sampling and merging zones, to accomplish the sequential determination of copper in serum and urine by flame atomic absorption spectrometry, is described. The developed flow system allowed multiple tasks, such as serum samples preparation (samples and standard solutions viscosity adjustment), serum copper (SCu) measurement, urine copper (UCu) pre-concentration and its subsequent elution and measurement, to be carried out sequentially. The implemented flow manifold presented a modular configuration consisting on two quasi-independent modules, each one accountable for a specific sample manipulation and whose combined operation under computer control enabled the determination of copper in a wide concentrations range. Once optimised and with a sample consumption of about 0.250 mL of serum and 7 mL of urine, the developed flow system allowed linear calibration plots up to 5 mg L-1 with a detection limit of 0.035 mg L-1 for SCu and linear calibration plots up to 300 μg L-1 with a detection limit of 0.67 μg L-1 for UCu. The sampling rate varied according to the module employed and was about 360 determinations h-1 (SCu module), 12 determinations h-1 (UCu module) or 24 determinations h-1 (12 urine and 12 serum samples; UCu and SCu modules simultaneously). Repeatability studies (R.S.D.%, n = 10) showed good precision for UCu at concentrations of 25 μg L-1 (2.54%), 50 μg L-1 (0.90%) and 100 μg L-1 (1.62%) as well as for SCu at concentrations of 0.25 mg L-1 (8.11%), 1 mg L-1 (3.11%) and 5 mg L-1 (0.90%). A comparative evaluation showed a good agreement between the results obtained in the analysis of UCu and SCu (n = 18) by both the developed methodology and the reference procedures. Accuracy was further evaluated by means of the analysis of reference samples (SeronormTM Trace Elements Urine and SeronormTM Trace Elements Serum) and the
DEFF Research Database (Denmark)
Liu, Xuezhu; Hansen, Elo Harald
operating parameters were optimised by fractional factorial screening and response surface modelling. The linear range of D-glucose determination was 30-600 mu M, With a detection limit of 15 mu M using a photodiode detector. The sampling frequency was 54 h(-1). Lower LOD (0.5 mu M D-glucose) could be...
International Nuclear Information System (INIS)
A sequential extraction technique was developed and tested for common naturally-occurring radionuclides. This technique allows the extraction and purification of uranium, thorium, radium, lead, and polonium radionuclides from the same sample. Environmental materials such as water, soil, and biological samples can be analyzed for those radionuclides without matrix interferences in the quality of radioelement purification and in the radiochemical yield. The use of isotopic tracers (232U, 229Th, 224Ra, 209Po, and stable lead carrier) added to the sample in the beginning of the chemical procedure, enables an accurate control of the radiochemical yield for each radioelement. The ion extraction procedure, applied after either complete dissolution of the solid sample with mineral acids or co-precipitation of dissolved radionuclide with MnO2 for aqueous samples, includes the use of commercially available pre-packed columns from Eichrom(r) and ion exchange columns packed with Bio-Rad resins, in altogether three chromatography columns. All radioactive elements but one are purified and electroplated on stainless steel discs. Polonium is spontaneously plated on a silver disc. The discs are measured using high resolution silicon surface barrier detectors. 210Pb, a beta emitter, can be measured either through the beta emission of 210Bi, or stored for a few months and determined by alpha spectrometry through the in-growth of 210Po. This sequential extraction chromatography technique was tested and validated with the analysis of certified reference materials from the IAEA. Reproducibility was tested through repeated analysis of the same homogeneous material (water sample). (author)
Matong, Joseph M; Nyaba, Luthando; Nomngongo, Philiswa N
2016-07-01
The main objectives of this study were to determine the concentration of fourteen trace elements and to investigate their distribution as well as a contamination levels in selected agricultural soils. An ultrasonic assisted sequential extraction procedure derived from three-step BCR method was used for fractionation of trace elements. The total concentration of trace elements in soil samples was obtained by total digestion method in soil samples with aqua regia. The results of the extractable fractions revealed that most of the target trace elements can be transferred to the human being through the food chain, thus leading to serious human health. Enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), risk assessment code (RAC) and individual contamination factors (ICF) were used to assess the environmental impacts of trace metals in soil samples. The EF revealed that Cd was enriched by 3.1-7.2 (except in Soil 1). The Igeo results showed that the soils in the study area was moderately contaminated with Fe, and heavily to extremely polluted with Cd. The soil samples from the unplanted field was found to have highest contamination factor for Cd and lowest for Pb. Soil 3 showed a high risk for Tl and Cd with RAC values of greater than or equal to 50%. In addition, Fe, Ni, Cu, V, As, Mo (except Soil 2), Sb and Pb posed low environmental risk. The modified BCR sequential extraction method provided more information about mobility and environmental implication of studied trace elements in the study area. PMID:27058917
Efficient bootstrap with weakly dependent processes
Francesco Bravo; Federico Crudu
2012-01-01
The efficient bootstrap methodology is developed for overidentified moment conditions models with weakly dependent observation. The resulting bootstrap procedure is shown to be asymptotically valid and can be used to approximate the distributions of t-statistics, J statistic for overidentifying restrictions, and Wald, Lagrange multiplier and distance statistics for nonlinear hypotheses. The asymptotic validity of the efficient bootstrap based on a computationally less demanding approximate k-...
The wild bootstrap for multilevel models
Modugno, Lucia; Giannerini, Simone
2015-01-01
In this paper we study the performance of the most popular bootstrap schemes for multilevel data. Also, we propose a modified version of the wild bootstrap procedure for hierarchical data structures. The wild bootstrap does not require homoscedasticity or assumptions on the distribution of the error processes. Hence, it is a valuable tool for robust inference in a multilevel framework. We assess the finite size performances of the schemes through a Monte Carlo study. The results show that for...
Theoretical comparisons of block bootstrap methods
Lahiri, S. N.
1999-01-01
In this paper, we compare the asymptotic behavior of some common block bootstrap methods based on nonrandom as well as random block lengths. It is shown that, asymptotically, bootstrap estimators derived using any of the methods considered in the paper have the same amount of bias to the first order. However, the variances of these bootstrap estimators may be different even in the first order. Expansions for the bias, the variance and the mean-squared error of different bloc...
Determinants of the Internationalization of the Firm: The Accelerated Model vs. the Sequential Model
Luis Ernesto Ocampo Figueroa; Moises Alejandro Alarcon Osuna; Carlos Fong Reynoso
2014-01-01
The aim of this paper is to analyze the internationalization strategies followed by enterprises in the world, distinguishing between big enterprises and other firms (SMEs). In particular, we want to delve into determinants of internationalization and processes that allow companies to perform in international markets according to their resources. We developed an analytical framework based on the resources-based view of the firm and on two internationalization models, the Uppsala and Born-Globa...
DEFF Research Database (Denmark)
Hansen, Elo Harald
Determination of low or trace-level amounts of metals by electrothermal atomic absorption spectrometry (ETAAS) often requires the use of suitable preconcentration and/or separation procedures in order to attain the necessary sensitivity and selectivity. Such schemes are advantageously executed in...... compensated by superior performance and versatility. In fact, two approaches are conceivable: The analyte-loaded ion-exchange beads might either be transported directly into the graphite tube where they are pyrolized and the measurand is atomized and quantified; or the loaded beads can be eluted and the...
International Nuclear Information System (INIS)
Inductively coupled plasma atomic emission spectrometry(ICP/AES) was used for the determination of uranium and thorium in geological materials. Samples were predecomposed by mixed acid digestion technique. The separation of the uranium and thorium was achieved by systematic solvent extraction with TTA(thenoyltrifluoroacetone) and TOA(tri-n-octylamine) and back extraction into HCl. The results for standard rock sample, NIST SRM 278, showed a good agreement with those certified from NIST as well as found values by other non-destructive techniques. Additional purification for extracted portions was carried out by anion exchange chromatography for measurement of several natural radioisotopes of uranium and thorium by alpha spectrometry. (author)
Multiquark hadrons in topological bootstrap
International Nuclear Information System (INIS)
We use the lowest-order topological bootstrap framework to calculate hadron masses by imposing duality on an infinite sum of ladder graphs generated from spherical unitarity. By making a certain simple dynamical approximation, we derive an explicit generic Regge-trajectory formula for any given process. If we then make certain reasonable dynamical assumptions and require simultaneous consistency for entire sets of processes, we are able to calculate the masses of all the lowest meson, baryon and multiquark states involving u and d quarks, and the Regge trajectories associated with each of them. The only arbitrary parameter is the mass of the rho, which merely serves to set the mass scale
Energy Technology Data Exchange (ETDEWEB)
Silva, Sidnei G. [Universidade de Sao Paulo, Instituto de Quimica, Sao Paulo (Brazil); Morales-Rubio, Angel; Guardia, Miguel de la [Universidad de Valencia, Department of Analytical Chemistry, Burjassot, Valencia (Spain); Rocha, Fabio R.P. [Universidade de Sao Paulo, Centro de Energia Nuclear na Agricultura, Piracicaba (Brazil)
2011-07-15
A new procedure for spectrofluorimetric determination of free and total glycerol in biodiesel samples is presented. It is based on the oxidation of glycerol by periodate, forming formaldehyde, which reacts with acetylacetone, producing the luminescent 3,5-diacetyl-1,4-dihydrolutidine. A flow system with solenoid micro-pumps is proposed for solution handling. Free glycerol was extracted off-line from biodiesel samples with water, and total glycerol was converted to free glycerol by saponification with sodium ethylate under sonication. For free glycerol, a linear response was observed from 5 to 70 mg L{sup -1} with a detection limit of 0.5 mg L{sup -1}, which corresponds to 2 mg kg{sup -1} in biodiesel. The coefficient of variation was 0.9% (20 mg L{sup -1}, n = 10). For total glycerol, samples were diluted on-line, and the linear response range was 25 to 300 mg L{sup -1}. The detection limit was 1.4 mg L{sup -1} (2.8 mg kg{sup -1} in biodiesel) with a coefficient of variation of 1.4% (200 mg L{sup -1}, n = 10). The sampling rate was ca. 35 samples h{sup -1} and the procedure was applied to determination of free and total glycerol in biodiesel samples from soybean, cottonseed, and castor beans. (orig.)
Reche, F; Garrigós, M C; Marín, M L; Jiménez, A
2002-11-01
A new method to determine N-nitrosamines in latex products has been developed by combination of supercritical fluids and chemical derivatization. A new design for a liquid trap has been introduced. A factorial fractional design was used in order to evaluate the influence of the different factors affecting the process. Factors such as pressure, temperature, static and dynamic time, restrictor temperature and volume of an hydrobromic acid-acetic anhydride mixture (1:10, v/v) were included in the design. CO2 was used as the extraction fluid. Gas chromatography with nitrogen and phosphorus sensitive detection was employed to achieve good sensitivity attending to the molecular structure of these compounds (N-nitrosamines and their corresponding secondary amines). The obtained results have shown to be useful to increase selectivity and reduce sample handling. PMID:12462622
International Nuclear Information System (INIS)
Solid sample graphite furnace atomic absorption spectroscopy (SS-GFAAS) has been proposed since its appearance as a good alternative to wet methods of analysis in many matrices. Here, we examine the use of SS-GFAAS for total and leachable arsenic determination in sediments from distinct origins. Our direct analysis of seven selected sediments was not always free of spectral matrix interference, but the spectroscopic technique gave very good results for (a) direct arsenic measurement in solid residues from a range of leaching processes, (b) total arsenic determination (HNO3 leaching test) and (c) the evaluation of its potential remobilisation (modified BCR three-step sequential extraction scheme). For the optimised instrumental conditions, the analysis limit was 0.44 mg kg-1 and long-term reproducibility was between 10-15%. The sum of leachable arsenic in HNO3 65% and the residual fraction, gave recoveries from 72 to 118% of total arsenic content. These results are a good alternative to other cumbersome wet methods involving HF
Statistical bootstrap model and annihilations
Möhring, H J
1974-01-01
The statistical bootstrap model (SBM) describes the decay of single, high mass, hadronic states (fireballs, clusters) into stable particles. Coupling constants B, one for each isospin multiplet of stable particles, are the only free parameter of the model. They are related to the maximum temperature parameter T/sub 0/. The various versions of the SMB can be classified into two groups: full statistical bootstrap models and linear ones. The main results of the model are the following: i) All momentum spectra are isotropic; especially the exclusive ones are described by invariant phase space. The inclusive and semi-inclusive single-particle distributions are asymptotically of pure exponential shape; the slope is governed by T /sub 0/ only. ii) The model parameter B for pions has been obtained by fitting the multiplicity distribution in pp and pn at rest, and corresponds to T/sub 0/=0.167 GeV in the full SBM with exotics. The average pi /sup -/ multiplicity for the linear and the full SBM (both with exotics) is c...
The (2, 0) superconformal bootstrap
Beem, Christopher; Lemos, Madalena; Rastelli, Leonardo; van Rees, Balt C.
2016-01-01
We develop the conformal bootstrap program for six-dimensional conformal field theories with (2, 0) supersymmetry, focusing on the universal four-point function of stress tensor multiplets. We review the solution of the superconformal Ward identities and describe the superconformal block decomposition of this correlator. We apply numerical bootstrap techniques to derive bounds on operator product expansion (OPE) coefficients and scaling dimensions from the constraints of crossing symmetry and unitarity. We also derive analytic results for the large spin spectrum using the light cone expansion of the crossing equation. Our principal result is strong evidence that the A1 theory realizes the minimal allowed central charge (c =25 ) for any interacting (2, 0) theory. This implies that the full stress tensor four-point function of the A1 theory is the unique unitary solution to the crossing symmetry equation at c =25 . For this theory, we estimate the scaling dimensions of the lightest unprotected operators appearing in the stress tensor operator product expansion. We also find rigorous upper bounds for dimensions and OPE coefficients for a general interacting (2, 0) theory of central charge c . For large c , our bounds appear to be saturated by the holographic predictions obtained from eleven-dimensional supergravity.
Bootstrap percolation on spatial networks
Gao, Jian; Zhou, Tao; Hu, Yanqing
2015-10-01
Bootstrap percolation is a general representation of some networked activation process, which has found applications in explaining many important social phenomena, such as the propagation of information. Inspired by some recent findings on spatial structure of online social networks, here we study bootstrap percolation on undirected spatial networks, with the probability density function of long-range links’ lengths being a power law with tunable exponent. Setting the size of the giant active component as the order parameter, we find a parameter-dependent critical value for the power-law exponent, above which there is a double phase transition, mixed of a second-order phase transition and a hybrid phase transition with two varying critical points, otherwise there is only a second-order phase transition. We further find a parameter-independent critical value around -1, about which the two critical points for the double phase transition are almost constant. To our surprise, this critical value -1 is just equal or very close to the values of many real online social networks, including LiveJournal, HP Labs email network, Belgian mobile phone network, etc. This work helps us in better understanding the self-organization of spatial structure of online social networks, in terms of the effective function for information spreading.
DEFF Research Database (Denmark)
Qiao, Jixin; Hou, Xiaolin; Roos, Per;
2009-01-01
This article presents an automated method for the rapid determination of 239Pu and 240Pu in various environmental samples. The analytical method involves the in-line separation of Pu isotopes using extraction chromatography (TEVA) implemented in a sequential injection (SI) network followed by det...
DEFF Research Database (Denmark)
Long, Xiangbao; Miró, Manuel; Hansen, Elo Harald
2005-01-01
A new concept is presented for selective and sensitive determination of trace metals via electrothermal atomic absorption spectrometry (ETAAS) based on the principle of bead injection (BI) with renewable reversed-phase surfaces in a sequential injection-lab-on-valve (SI-LOV) mode. The methodology...
A comparison of four different block bootstrap methods
Boris Radovanov; Aleksandra Marcikić
2014-01-01
The paper contains a description of four different block bootstrap methods, i.e., non-overlapping block bootstrap, overlapping block bootstrap (moving block bootstrap), stationary block bootstrap and subsampling. Furthermore, the basic goal of this paper is to quantify relative efficiency of each mentioned block bootstrap procedure and then to compare those methods. To achieve the goal, we measure mean square errors of estimation variance returns. The returns are calculated from 1250 daily ob...
A Bayesian Bootstrap for a Finite Population
Lo, Albert Y.
1988-01-01
A Bayesian bootstrap for a finite population is introduced; its small-sample distributional properties are discussed and compared with those of the frequentist bootstrap for a finite population. It is also shown that the two are first-order asymptotically equivalent.
Coefficient Alpha Bootstrap Confidence Interval under Nonnormality
Padilla, Miguel A.; Divers, Jasmin; Newton, Matthew
2012-01-01
Three different bootstrap methods for estimating confidence intervals (CIs) for coefficient alpha were investigated. In addition, the bootstrap methods were compared with the most promising coefficient alpha CI estimation methods reported in the literature. The CI methods were assessed through a Monte Carlo simulation utilizing conditions…
Bootstrapping Phylogenetic Trees: Theory and Methods
Holmes, Susan
2003-01-01
This is a survey of the use of the bootstrap in the area of systematic and evolutionary biology. I present the current usage by biologists of the bootstrap as a tool both for making inferences and for evaluating robustness, and propose a framework for thinking about these problems in terms of mathematical statistics.
Efficient bootstrap with weakly dependent processes
Bravo, Francesco; Crudu, Federico
2012-01-01
The efficient bootstrap methodology is developed for overidentified moment conditions models with weakly dependent observation. The resulting bootstrap procedure is shown to be asymptotically valid and can be used to approximate the distributions of t-statistics, the J-statistic for overidentifying
Directory of Open Access Journals (Sweden)
Mohtasham MOHAMMADI
2014-03-01
Full Text Available An experiment was conducted to evaluate 295 wheat genotypes in Alpha-Lattice design with two replications. The arithmetic mean and standard deviation of grain yield was 2706 and 950 (kg/ha,respectively. The results of correlation coefficients indicated that grain yield had significant and positive association with plant height, spike length, early growth vigor and agronomic score. Whereas there were negative correlation coefficients between grain yield and days to physiological maturity and canopy temperature before and during anthesis. Path analysis indicated agronomic score and plant height had high positive direct effects on grain yield, while canopy temperature before and during anthesis, and days to maturity, wes another trait having negative direct effect on grain yield. The results of sequential path analysis showed the traits that accounted as a criteria variable for high grain yield were agronomic score, plant height, canopy temperature, spike length, chlorophyll content and early growth vigor, which were determined as first, second and third order variables and had strong effects on grain yield via one or more paths. More important, as canopy temperature, agronomic score and early growth vigor can be evaluated quickly and easily, these traits may be used for evaluation of large populations.
International Nuclear Information System (INIS)
Highlights: • Highly sensitive determination of Hg(II) using SI–ASV-BDD was achieved. • Electrochemical detection of Hg(II) using Cu(II) enhancer was accomplished. • LOD and LOQ were found to be very low at 40.0 ppt and 135.0 ppt. • This method was successfully applied for determination of Hg(II) in real samples. - Abstract: A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection–anodic stripping voltammetry (SI–ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5 M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at −1.0 V (vs. Ag/AgCl, 3 M KCl) for 150 s with a flow rate of 14 μL s−1. An anodic stripping voltammogram was recorded from −0.4 V to 0.25 V using a frequency of 60 Hz, an amplitude of 50 mV, and a step potential of 10 mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at −0.25 V and +0.05 V (vs. Ag/AgCl, 3 M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1–30.0 ng mL−1 and 5.0–60.0 ng mL−1). The limit of detection (S/N = 3) obtained from the experiment was found to be 0.04 ng mL−1. The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20 ng mL−1, respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg(II), according to the paired t-test at a
Energy Technology Data Exchange (ETDEWEB)
Chaiyo, Sudkate [Department of Chemistry, Faculty of Science, Srinakharinwirot University (Thailand); Chailapakul, Orawon [Department of Chemistry, Faculty of Science, Chulalongkorn University (Thailand); Center for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University (Thailand); Siangproh, Weena, E-mail: weena@swu.ac.th [Department of Chemistry, Faculty of Science, Srinakharinwirot University (Thailand)
2014-12-10
Highlights: • Highly sensitive determination of Hg(II) using SI–ASV-BDD was achieved. • Electrochemical detection of Hg(II) using Cu(II) enhancer was accomplished. • LOD and LOQ were found to be very low at 40.0 ppt and 135.0 ppt. • This method was successfully applied for determination of Hg(II) in real samples. - Abstract: A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection–anodic stripping voltammetry (SI–ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5 M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at −1.0 V (vs. Ag/AgCl, 3 M KCl) for 150 s with a flow rate of 14 μL s{sup −1}. An anodic stripping voltammogram was recorded from −0.4 V to 0.25 V using a frequency of 60 Hz, an amplitude of 50 mV, and a step potential of 10 mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at −0.25 V and +0.05 V (vs. Ag/AgCl, 3 M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1–30.0 ng mL{sup −1} and 5.0–60.0 ng mL{sup −1}). The limit of detection (S/N = 3) obtained from the experiment was found to be 0.04 ng mL{sup −1}. The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20 ng mL{sup −1}, respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg
Zhu, Zhenwu; Zhuo, Yuqun; Fan, Yaming; Wang, Zhipeng
2016-05-01
A considerable amount of Hg is retained in flue gas desulfurization (FGD) gypsum from Wet Flue Gas Desulfurization (WFGD) systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition (TPD) and Sequential Chemical Extraction (SCE) were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg2Cl2
Limitations of bootstrap current models
International Nuclear Information System (INIS)
We assess the accuracy and limitations of two analytic models of the tokamak bootstrap current: (1) the well-known Sauter model (1999 Phys. Plasmas 6 2834, 2002 Phys. Plasmas 9 5140) and (2) a recent modification of the Sauter model by Koh et al (2012 Phys. Plasmas 19 072505). For this study, we use simulations from the first-principles kinetic code NEO as the baseline to which the models are compared. Tests are performed using both theoretical parameter scans as well as core-to-edge scans of real DIII-D and NSTX plasma profiles. The effects of extreme aspect ratio, large impurity fraction, energetic particles, and high collisionality are studied. In particular, the error in neglecting cross-species collisional coupling—an approximation inherent to both analytic models—is quantified. Furthermore, the implications of the corrections from kinetic NEO simulations on MHD equilibrium reconstructions is studied via integrated modeling with kinetic EFIT. (paper)
The N=2 superconformal bootstrap
Beem, Christopher; Lemos, Madalena; Liendo, Pedro; Rastelli, Leonardo; van Rees, Balt C.
2016-03-01
In this work we initiate the conformal bootstrap program for N=2 super-conformal field theories in four dimensions. We promote an abstract operator-algebraic viewpoint in order to unify the description of Lagrangian and non-Lagrangian theories, and formulate various conjectures concerning the landscape of theories. We analyze in detail the four-point functions of flavor symmetry current multiplets and of N=2 chiral operators. For both correlation functions we review the solution of the superconformal Ward identities and describe their superconformal block decompositions. This provides the foundation for an extensive numerical analysis discussed in the second half of the paper. We find a large number of constraints for operator dimensions, OPE coefficients, and central charges that must hold for any N=2 superconformal field theory.
Vergé, Christelle; Del Moral, Pierre; Moulines, Eric; Olsson, Jimmy
2014-01-01
Particle island models (Verg\\'e et al., 2013) provide a means of parallelization of sequential Monte Carlo methods, and in this paper we present novel convergence results for algorithms of this sort. In particular we establish a central limit theorem - as the number of islands and the common size of the islands tend jointly to infinity - of the double bootstrap algorithm with possibly adaptive selection on the island level. For this purpose we introduce a notion of archipelagos of weighted is...
Bootstrap Prediction Intervals in Non-Parametric Regression with Applications to Anomaly Detection
Kumar, Sricharan; Srivistava, Ashok N.
2012-01-01
Prediction intervals provide a measure of the probable interval in which the outputs of a regression model can be expected to occur. Subsequently, these prediction intervals can be used to determine if the observed output is anomalous or not, conditioned on the input. In this paper, a procedure for determining prediction intervals for outputs of nonparametric regression models using bootstrap methods is proposed. Bootstrap methods allow for a non-parametric approach to computing prediction intervals with no specific assumptions about the sampling distribution of the noise or the data. The asymptotic fidelity of the proposed prediction intervals is theoretically proved. Subsequently, the validity of the bootstrap based prediction intervals is illustrated via simulations. Finally, the bootstrap prediction intervals are applied to the problem of anomaly detection on aviation data.
Clarkson, B H; Chang, S R; Holland, G R
1998-01-01
Phosphoprotein appears to play an important role in the mineralization of dentin during tooth development and remineralization after demineralization by dental caries. To better understand this role, we describe the extraction and characterization of phosphoprotein from immature, human root apex dentin during and after EDTA demineralization. The extraction procedure included dissociation of the demineralized dentin matrix by guanidine hydrochloride (Gdn.HCl) followed by subsequent digestion with cyanogen bromide (CNBr) and collagenase. Characterization of these extracts included 'Stains-All' staining of SDS polyacrylamide gels (SDS-PAGE) and amino acid, protein and phosphorus analyses. The ability of these matrices to remineralize was determined by TEM and measuring calcium levels in the remineralized tissue by atomic absorption spectroscopy. The staining of SDS-PAGE gels and amino acid analysis showed that an intact phosphophoryn was extracted from the dentin of the immature apices during EDTA demineralization and that it had an apparent Mr approximately 140,000. In the subsequent extracts and digests, the phosphoprotein has a range of molecular weights, some of which may have been degraded products of the intact phosphoprotein. A greater quantity of phosphoprotein was found in the EDTA-demineralized dentin matrices than in dentin after Gdn.HCl, CNBr and collagenase digests. These EDTA-demineralized matrices also remineralized to a greater extent than those dissociated with Gdn.HCl. The differences in both the quantity and the quality, as defined by the amino acid residue profile, of the phosphoprotein in the sequential extracts of the root apex dentin may be important in affecting the ability of this tissue to remineralize. PMID:9701661
Bootstrap current estimate in the ETE Tokamak
International Nuclear Information System (INIS)
First estimates of the bootstrap current in the ETE small aspect ratio tokamak using the Hirshman single ion collisionless model show that we can expect from 25 to 55% of total bootstrap current depending on the optimization level of the plasma parameter profiles. Higher levels of bootstrap current are limited by peaked pressure profiles and βpol values which must be kept under a critical level due to stability conditions. Different methods for the trapped particle fraction calculation are also illustrated in this paper. (author). 7 refs., 5 figs., 1 tab
International Nuclear Information System (INIS)
River Tinto is located in the Huelva province, SW of Spain. This river has been strongly affected by anthropogenic activities in its vicinity such as mining, paper mills or phosphoric acid industries (in fact phosphogypsum deposits, so-called gyp-stacks, are located in the mouth of the Tinto River estuary). The combination of acid water from mines, different industrial effluents and fluvial and sea waters plays a determining role in the evolutionary process of the environmental characteristics of the Tinto River and its estuary. In this context several natural radionuclides as polonium, radium, thorium and uranium isotopes, could be used as markers and/or tracers of several environmental processes. Therefore, environmental matrixes (superficial sediments, waters and suspended matter) have been collected from 12 points along the Tinto River and its estuary. Activity concentrations of natural radionuclides (210Po, 226,228Ra, 230,232Th, 234,238U) have been determined in these samples. Due to sampling conditions, low water volumes and suspended matter masses were collected, so radioactive activities were expected to be close to the mBq order of magnitude. As a consequence, alpha-particle spectrometry was a suitable radiometric technique to perform our wide set of measurements. Then a radiochemical scheme for polonium, radium, thorium and uranium isolation, purification and deposition from these polluted environmental samples was needed. This work will show the sequential radiochemical procedure, originally developed by CSIRO laboratories, adapted to our laboratory conditions and applied for natural radionuclides determination in environmental samples collected from the Tinto River. Hence, and after pretreatment of the sample, polonium was extracted by DDTC and deposited onto silver planchets. Then, after a co-precipitation process, uranium was found in the supernatant whereas radium and thorium were found in the precipitate. Using TBP, uranium was separated and
Wald, Abraham
2013-01-01
In 1943, while in charge of Columbia University's Statistical Research Group, Abraham Wald devised Sequential Design, an innovative statistical inference system. Because the decision to terminate an experiment is not predetermined, sequential analysis can arrive at a decision much sooner and with substantially fewer observations than equally reliable test procedures based on a predetermined number of observations. The system's immense value was immediately recognized, and its use was restricted to wartime research and procedures. In 1945, it was released to the public and has since revolutio
A Comparison of Correlation Coefficients via a Three-Step Bootstrap Approach
2010-01-01
In this article we compare ten correlation coefficients using a three-step bootstrap approach (TSB). A three-step bootstrap is applied to determine the optimal repetitions, $B$, to estimate the standard error of the statistic with certain degree of accuracy. The coefficients in question are Pearson product moment ($r$), Spearman's rho ($\\rho$), Kendall's tau ($\\tau$) , Spearman's Footrule ($F_t$), Symmetric Footrule ($C$), the Greatest deviation ($R_g$), the Top - Down ($r_T$), Weighted Ken...
Improving the Reliability of Bootstrap Tests with the Fast Double Bootstrap
Davidson, Russell; MacKinnon, James
2006-01-01
Two procedures are proposed for estimating the rejection probabilities of bootstrap tests in Monte Carlo experiments without actually computing a bootstrap test for each replication. These procedures are only about twice as expensive (per replication) as estimating rejection probabilities for asymptotic tests. Then a new procedure is proposed for computing bootstrap P values that will often be more accurate than ordinary ones. This “fast double bootstrap” is closely related to the double boot...
The alignment of bootstrap current in tokamak
International Nuclear Information System (INIS)
By calculating the trapped particle fraction, solving the Grand-Shafranov equation describing plasma equilibrium, and using Harris model, the magnitude and alignment of the bootstrap current in tokamak are calculated and analysed under the conventional shear regimes and also the negative central shear regimes. The conclusion authors obtained are: through adjusting the profile parameters of plasma density, temperature and current, and the elongation k and triangularity d which describe the plasma shape, the alignment of bootstrap current profile with the equilibrium current profile can be produced; the negative central shear regimes are advantage ous to produce bootstrap current, and the profile of bootstrap current is well-aligned with the equilibrium current profile. By comparing authors' calculated results, the optimized parameters are obtained under the conventional shear and the negative central shear regimes
iDESWEB: Frameworks CSS: Bootstrap
Yuste Torregrosa, Álvaro; Luján Mora, Sergio
2012-01-01
Framework CSS (herramientas y pautas), frameworks más famosos (BluePrint, 960 Grid System, YUI), Twitter Bootstrap, ejemplo de botones, ejemplo de uso de la rejilla. Sitio web del curso: http://idesweb.es/
T.A. Knoch (Tobias)
2003-01-01
textabstractGenomes are one of the major foundations of life due to their role in information storage, process regulation and evolution. However, the sequential and three-dimensional structure of the human genome in the cell nucleus as well as its interplay with and embedding into the cell and organ
T.A. Knoch (Tobias)
2003-01-01
textabstractGenomes are one of the major foundations of life due to their role in information storage, process regulation and evolution. However, the sequential and three-dimensional structure of the human genome in the cell nucleus as well as its interplay with and embedding into the cell and o
Al-Mudhafar, W. J.
2013-12-01
Precisely prediction of rock facies leads to adequate reservoir characterization by improving the porosity-permeability relationships to estimate the properties in non-cored intervals. It also helps to accurately identify the spatial facies distribution to perform an accurate reservoir model for optimal future reservoir performance. In this paper, the facies estimation has been done through Multinomial logistic regression (MLR) with respect to the well logs and core data in a well in upper sandstone formation of South Rumaila oil field. The entire independent variables are gamma rays, formation density, water saturation, shale volume, log porosity, core porosity, and core permeability. Firstly, Robust Sequential Imputation Algorithm has been considered to impute the missing data. This algorithm starts from a complete subset of the dataset and estimates sequentially the missing values in an incomplete observation by minimizing the determinant of the covariance of the augmented data matrix. Then, the observation is added to the complete data matrix and the algorithm continues with the next observation with missing values. The MLR has been chosen to estimate the maximum likelihood and minimize the standard error for the nonlinear relationships between facies & core and log data. The MLR is used to predict the probabilities of the different possible facies given each independent variable by constructing a linear predictor function having a set of weights that are linearly combined with the independent variables by using a dot product. Beta distribution of facies has been considered as prior knowledge and the resulted predicted probability (posterior) has been estimated from MLR based on Baye's theorem that represents the relationship between predicted probability (posterior) with the conditional probability and the prior knowledge. To assess the statistical accuracy of the model, the bootstrap should be carried out to estimate extra-sample prediction error by randomly
Investigating Mortality Uncertainty Using the Block Bootstrap
Directory of Open Access Journals (Sweden)
Xiaoming Liu
2010-01-01
Full Text Available This paper proposes a block bootstrap method for measuring mortality risk under the Lee-Carter model framework. In order to take account of all sources of risk (the process risk, the parameter risk, and the model risk properly, a block bootstrap is needed to cope with the spatial dependence found in the residuals. As a result, the prediction intervals we obtain for life expectancy are more accurate than the ones obtained from other similar methods.
Theoretical Comparison of Bootstrap Confidence Intervals
Hall, Peter
1988-01-01
We develop a unified framework within which many commonly used bootstrap critical points and confidence intervals may be discussed and compared. In all, seven different bootstrap methods are examined, each being usable in both parametric and nonparametric contexts. Emphasis is on the way in which the methods cope with first- and second-order departures from normality. Percentile-$t$ and accelerated bias-correction emerge as the most promising of existing techniques. Certain other methods are ...
Investigating Mortality Uncertainty Using the Block Bootstrap
Xiaoming Liu; W. John Braun
2010-01-01
This paper proposes a block bootstrap method for measuring mortality risk under the Lee-Carter model framework. In order to take account of all sources of risk (the process risk, the parameter risk, and the model risk) properly, a block bootstrap is needed to cope with the spatial dependence found in the residuals. As a result, the prediction intervals we obtain for life expectancy are more accurate than the ones obtained from other similar methods.
Bootstrapping Reflective Systems: The Case of Pharo
Polito, Guillermo; Ducasse, Stéphane; Fabresse, Luc; Bouraqadi, Noury; Van Ryseghem, Benjamin
2014-01-01
Bootstrapping is a technique commonly known by its usage in language definition by the introduction of a compiler written in the same language it compiles. This process is important to understand and modify the definition of a given language using the same language, taking benefit of the abstractions and expression power it provides. A bootstrap, then, supports the evolution of a language. However, the infrastructure of reflective systems like Smalltalk includes, in addition to a compiler, an...
Bootstrapping the European Gender Wage Gap
Rueckert, Eva
2003-01-01
This paper investigates the gender wage gap in Denmark, the Netherlands, France and Spain by bootstrapping the Oaxaca-Blinder decomposition. The bootstrap method is used to compute confidence intervals and to perform hypothesis tests for the (disaggregated) explained and unexplained components of the national earnings di?erentials between men and women. From the subset of paid employees selected from the European Community Household Panel (ECHP) it is revealed that the respective national gen...
Frentiu, Tiberiu; Pintican, Bogdan Petru; Butaciu, Sanziana; Mihaltan, Alin Ironim; Ponta, Michaela; Frentiu, Maria
2013-01-01
Background The paper presents the evaluation of soil contamination with total, water-available, mobile, semi-mobile and non-mobile Hg fractions in the surroundings of a former chlor-alkali plant in connection with several chemical soil characteristics. Principal Component Analysis and Cluster Analysis were used to evaluate the chemical composition variability of soil and factors influencing the fate of Hg in such areas. The sequential extraction EPA 3200-Method and the determination technique...
A new approach to bootstrap inference in functional coefficient models
Herwartz, Helmut; Xu, Fang
2007-01-01
We introduce a new, factor based bootstrap approach which is robust under heteroskedastic error terms for inference in functional coefficient models. Modeling the functional coefficient parametrically, the bootstrap approximation of an F statistic is shown to hold asymptotically. In simulation studies with both parametric and nonparametric functional coefficients, factor based bootstrap inference outperforms the wild bootstrap and pairs bootstrap approach according to its size features. Apply...
The Bootstrap of Mean for Dependent Heterogeneous Arrays.
GONÇALVES, Silvia; White, Halbert
2001-01-01
Presently, conditions ensuring the validity of bootstrap methods for the sample mean of (possibly heterogeneous) near epoch dependent (NED) functions of mixing processes are unknown. Here we establish the validity of the bootstrap in this context, extending the applicability of bootstrap methods to a class of processes broadly relevant for applications in economics and finance. Our results apply to two block bootstrap methods: the moving blocks bootstrap of Künsch ( 989) and Liu and Singh ( 9...
Maximum Likelihood and the Bootstrap for Nonlinear Dynamic Models
Goncalves, Silvia; White, Halbert
2002-01-01
The bootstrap is an increasingly popular method for performing statistical inference. This paper provides the theoretical foundation for using the bootstrap as a valid tool of inference for quasi-maximum likelihood estimators (QMLE). We provide a unified framework for analyzing bootstrapped extremum estimators of nonlinear dynamic models for heterogeneous dependent stochastic processes. We apply our results to two block bootstrap methods, the moving blocks bootstrap of Künsch (1989) and Liu a...
A Score Based Approach to Wild Bootstrap Inference
Patrick M. Kline; Andres Santos
2010-01-01
We propose a generalization of the wild bootstrap of Wu (1986) and Liu (1988) based upon perturbing the scores of M-estimators. This "score bootstrap" procedure avoids recomputing the estimator in each bootstrap iteration, making it substantially less costly to compute than the conventional nonparametric bootstrap, particularly in complex nonlinear models. Despite this computational advantage, in the linear model, the score bootstrap studentized test statistic is equivalent to that of the con...
Bootstrap current in NBI heated plasmas
International Nuclear Information System (INIS)
The expression for the bootstrap current density due to fast ions produced by NBI is derived in an axisymmetric magnetic field. From this expression the fast-ion-induced bootstrap current density is explicitly calculated in a large aspect ratio tokamak with circular cross-section. This bootstrap current is found to be quite small for parallel injection of neutral beams although it rapidly increases as it approaches perpendicular injection. In addition to the injection angle, this bootstrap current density depends strongly upon the values of the inverse aspect ratio an element of and the ratio υc (critical velocity)/υb (birth velocity). In perpendicular injection the ratio of the fast-ion-induced bootstrap current density to the bulk bootstrap current density is estimated for the typical parameters an element of = 0.1 and υc/υb = 0.5 as 0.09 (δβb/δr)/(δβe/δr), where βb and βe are the values of beta due to fast-ion and electron pressures, respectively. (author). 7 refs, 4 figs
Conformal bootstrap: non-perturbative QFT's under siege
CERN. Geneva
2016-01-01
[Exceptionally in Council Chamber] Originally formulated in the 70's, the conformal bootstrap is the ambitious idea that one can use internal consistency conditions to carve out, and eventually solve, the space of conformal field theories. In this talk I will review recent developments in the field which have boosted this program to a new level. I will present a method to extract quantitative informations in strongly-interacting theories, such as 3D Ising, O(N) vector model and even systems without a Lagrangian formulation. I will explain how these techniques have led to the world record determination of several critical exponents. Finally, I will review exact analytical results obtained using bootstrap techniques.
Directory of Open Access Journals (Sweden)
Miriam Martinez-Biarge
Full Text Available The evolution of non-hemorrhagic white matter injury (WMI based on sequential magnetic resonance imaging (MRI has not been well studied. Our aim was to describe sequential MRI findings in preterm infants with non-hemorrhagic WMI and to develop an MRI classification system for preterm WMI based on these findings.Eighty-two preterm infants (gestation ≤35 weeks were retrospectively included. WMI was diagnosed and classified based on sequential cranial ultrasound (cUS and confirmed on MRI.138 MRIs were obtained at three time-points: early (<2 weeks; n = 32, mid (2-6 weeks; n = 30 and term equivalent age (TEA; n = 76. 63 infants (77% had 2 MRIs during the neonatal period. WMI was non-cystic in 35 and cystic in 47 infants. In infants with cystic-WMI early MRI showed extensive restricted diffusion abnormalities, cysts were already present in 3 infants; mid MRI showed focal or extensive cysts, without acute diffusion changes. A significant reduction in the size and/or extent of the cysts was observed in 32% of the infants between early/mid and TEA MRI. In 4/9 infants previously seen focal cysts were no longer identified at TEA. All infants with cystic WMI showed ≥2 additional findings at TEA: significant reduction in WM volume, mild-moderate irregular ventriculomegaly, several areas of increased signal intensity on T1-weighted-images, abnormal myelination of the PLIC, small thalami.In infants with extensive WM cysts at 2-6 weeks, cysts may be reduced in number or may even no longer be seen at TEA. A single MRI at TEA, without taking sequential cUS data and pre-TEA MRI findings into account, may underestimate the extent of WMI; based on these results we propose a new MRI classification for preterm non-hemorrhagic WMI.
Knoch, Tobias
2003-01-01
textabstractGenomes are one of the major foundations of life due to their role in information storage, process regulation and evolution. However, the sequential and three-dimensional structure of the human genome in the cell nucleus as well as its interplay with and embedding into the cell and organism only arise scarcely from the unknown. To achieve a deeper unterstanding of the human genome the three-dimensional organization of the human cell nucleus, the structural-, scaling- and dynamic p...
Energy Technology Data Exchange (ETDEWEB)
Zdenek Klika; Lenka Ambruzova; Ivana Sykorova; Jana Seidlerova; Ivan Kolomaznik [VSB-Technical University Ostrava, Ostrava (Czech Republic)
2009-10-15
The affinities of Ga and Ge in lignite were determined using sequential extraction (SE) and element affinity calculation (EAC) based on sink-float data. For this study a bulk lignite sample was fractioned into two sets. The first set of samples (A) consisted of the different grain sizes fractions; the second one set (B) was prepared by density fractionation. Sequential extractions (1) were performed on both sets of fractions with very good agreement between determined organic elements affinities (OEA of Ga evaluated from A data is 32%, from B data 35%; OEA of Ge evaluated from A data is 31% and from B data 26%). The data of B lignite fractions were evaluated using two element affinity calculations: (a) EAC (I) of Klika and Kolomaznk (2) and (b) newly prepared subroutine EAC (II) based on quantitative contents of lignite macerals and minerals. There was also good agreement between both methods obtained (OEA of Ga calculated by EAC (I) is 83% and by EAC (II) 77%; OEA of Ge calculated by EAC (I) is 89% and by EAC (II) 97%). The significant differences of organic elements affinities of Ga and Ge evaluated by sequential extraction and by element affinity calculation based on sink-float data are discussed. 34 refs., 7 figs., 6 tabs.
Energy Technology Data Exchange (ETDEWEB)
Lozano, J.C. [Departamento de Fisica Fundamental, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca (Spain); Blanco Rodriguez, P. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz (Spain); Vera Tome, F., E-mail: fvt@unex.es [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz (Spain); Leal-Cidoncha, E. [Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz (Spain)
2012-04-15
In a previous paper the authors proposed a sequential method for the determination of isotopes of uranium, thorium, radium, and lead from environmental samples using alpha-particle spectrometry and LSC techniques. Although the radiochemical yields were suitable when the assays were performed on synthetic samples, application to real environmental samples caused a major decrease in the radiochemical yield, especially for uranium in inorganic samples (soils). A modification of the procedure is described that overcomes this drawback. - Highlights: Black-Right-Pointing-Pointer Sequential methods permit one to obtain the radionuclides from the same aliquot. Black-Right-Pointing-Pointer The proposal method enhances the radiochemical yields. Black-Right-Pointing-Pointer For soil samples, the yields were of (56{+-}2)%, (57{+-}6)%, and (71{+-}4)% for U, Ra, and Pb.
Siriangkhawut, Watsaka; Khanhuathon, Yaowalak; Chantiratikul, Piyanete; Ponhong, Kraingkrai; Grudpan, Kate
2016-01-01
A cost-effective and environmentally friendly approach using a simple sequential injection spectrophotometric system with a non-synthetic reagent from plant extracts was proposed for a green analytical-chemistry methodology. The crude aqueous extracts from heartwood of Ceasalpinia sappan Linn. in acetate buffer pH 5.5 were utilized as an alternative natural reagent for the quantification of aluminium. The extracts contained homoisoflavonoid compounds, brazilin, and brazilein, which reacted with Al(3+) to form reddish complexes with the maximum absorption wavelength at 530 nm. The optimum conditions for the sequential injection parameters, such as sequential profile, sample and reagent volumes, and the pH effect, were investigated. Under the optimum conditions, a linear calibration graph in the range of 0.075 - 1.0 mg L(-1) Al(3+) was obtained with limits of detection and quantification of 0.021 and 0.072 mg L(-1) Al(3+), respectively. Relative standard deviations of 3.2 and 2.4% for 0.1 and 0.25 mg L(-1) Al(3+) (n = 11), respectively, and sampling rate of 128 injections h(-1) were achieved. The developed system was successfully applied to pharmaceutical preparations, water, and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 87 and 104% were obtained. PMID:26960614
Conformal collider physics from the lightcone bootstrap
Li, Daliang; Meltzer, David; Poland, David
2016-02-01
We analytically study the lightcone limit of the conformal bootstrap equations for 4-point functions containing global symmetry currents and the stress tensor in 3d CFTs. We show that the contribution of the stress tensor to the anomalous dimensions of large spin double-twist states is negative if and only if the conformal collider physics bounds are satisfied. In the context of AdS/CFT these results indicate a relation between the attractiveness of AdS gravity and positivity of the CFT energy flux. We also study the contribution of non-Abelian conserved currents to the anomalous dimensions of double- twist operators, corresponding to the gauge binding energy of 2-particle states in AdS. We show that the representation of the double-twist state determines the sign of the gauge binding energy if and only if the coefficients appearing in the current 3-point function satisfies a similar bound, which is equivalent to an upper bound on the charge flux asymmetry of the CFT.
Conformal Collider Physics from the Lightcone Bootstrap
Li, Daliang; Poland, David
2015-01-01
We analytically study the lightcone limit of the conformal bootstrap equations for 4-point functions containing global symmetry currents and the stress tensor in 3d CFTs. We show that the contribution of the stress tensor to the anomalous dimensions of large spin double-twist states is negative if and only if the conformal collider physics bounds are satisfied. In the context of AdS/CFT these results indicate a relation between the attractiveness of AdS gravity and positivity of the CFT energy flux. We also study the contribution of non-Abelian conserved currents to the anomalous dimensions of double-twist operators, corresponding to the gauge binding energy of 2-particle states in AdS. We show that the representation of the double-twist state determines the sign of the gauge binding energy if and only if the coefficient appearing in the current 3-point function satisfies a similar bound, which is equivalent to an upper bound on the charge flux asymmetry of the CFT.
Bootstrap states of the Z-pinch
International Nuclear Information System (INIS)
Steady bootstrap states of a Z-pinch are investigated both in absence and in presence of an imposed axial magnetic field, in terms of MHD theory with classical resistivity. The results indicate that bootstrap operation should become possible for certain classes of plasma profiles and that such operation can lead to higher bootstrap currents in a Z-pinch without axial magnetic field than in a tokamak-like case under similar plasma conditions. The ratio between the latter and the former currents is of the order of the square root of the beta value in the tokamak-like case. A simple numerical example is given on boot-strap operation in the Z-pinch. Neoclassical or anomalous diffusion will increase the diffusion velocity of the plasma but are not expected to affect the main physical features of the present results. This applies also to the kinetic effects in the weak-field region near the axis of the Z-pinch, because these effects can largely be described by MHD-like equations for a steady equilibrium. Bootstrap operation and the technical difficulty in realizing a volume distribution of particle sinks introduce certain constraints on the plasma and current profiles. This has to be taken into account in a stability analysis. The latter cannot only be performed in terms of MHD-like theory but has to be based on kinetic theory including large Larmor radius (LLR) effects. (author)
International Nuclear Information System (INIS)
Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil-containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified by the partitioning of inorganic phosphorus in agricultural soils. The on-line fractionation method capitalises on the accurate metering and sequential exposure of the various extractants to the solid sample by application of programmable flow as precisely coordinated by a syringe pump. Three different soil phase associations for phosphorus, that is, exchangeable, Al- and Fe-bound, and Ca-bound fractions, were elucidated by accommodation in the flow manifold of the three steps of the Hieltjes-Lijklema (HL) scheme involving the use of 1.0 M NH4Cl, 0.1 M NaOH and 0.5 M HCl, respectively, as sequential leaching reagents. The precise timing and versatility of SI for tailoring various operational extraction modes were utilized for investigating the extractability and the extent of phosphorus re-distribution for variable partitioning times. Automatic spectrophotometric determination of soluble reactive phosphorus in soil extracts was performed by a flow injection (FI) analyser based on the Molybdenum Blue (MB) chemistry. The 3σ detection limit was 0.02 mg P L-1 while the linear dynamic range extended up to 20 mg P L-1 regardless of the extracting media. Despite the variable chemical composition of the HL extracts, a single FI set-up was assembled with no need for either manifold re-configuration or modification of chemical composition of reagents. The mobilization of trace elements, such as Cd, often present in grazed pastures as a result of the application of phosphate fertilizers, was also explored in the HL fractions by electrothermal atomic absorption spectrometry
Rogan, Nastja; Dolenec, Tadej; Serafimovski, Todor; Tasev, Goran; Dolenec, Matej
2008-01-01
In this study we examine the distribution of heavy metals (As, Cd, Cu, Pb and Zn) in paddy soil samples from Kočani Field (Macedonia) by ICP-EAS and sequential extraction procedure. Very high concentrations of As (42 mg/kg), Cd (5.6 mg/kg), Cu (99 mg/kg), Pb (892 mg/kg) and Zn (1134 mg/kg) were found in the paddy soil sample from location VII-2 in the western part of Kočani Field, close to the Zletovska River, which drains the untreated effuents of the Pb-Zn mine in Zletovo and is used for th...
DEFF Research Database (Denmark)
Hansen, Elo Harald; Miró, Manuel; Petersen, Roongrat
In recent years sequential injection (SI) analysis and Lab-on-Valve (LOV) approaches have proven themselves as powerful and versatile front ends to implement suitable pre-treatment procedures (separation and pre-concentration) for the assay of low concentrations of metals, as amply reflected....../emission spectrometry (FAAS, ETAAS, ICP-AES, ICP-MS). The lecture will initially give an overview of various automated alternatives for facilitating appropriate SI/LOV-separation and pre-concentration schemes of metals in liquid samples, including examples of solid-phase extraction with permanent columns or renewable...
DEFF Research Database (Denmark)
Hansen, Elo Harald
In recent years sequential injection (SI) analysis and Lab-on-Valve (LOV) approaches have proven themselves as powerful and versatile front ends to implement suitable pre-treatment procedures (separation and pre-concentration) for the assay of low concentrations of metals, as amply reflected....../emission spectrometric devices such as FAAS, ETAAS, AFS, ICP-AES, and ICP-MS. While earlier separation and pre-concentration schemes of metals in liquid samples primarily have been centred on the use solvent extraction, or precipitate/(co)-precipitate collection in incorporated knotted reactors, or permanent columns...
Characteristics of the bootstrap estimate of discrepant data sets
International Nuclear Information System (INIS)
We present in this paper a Bootstrap Method to estimate a best value and its standard deviation for a discrepant set of data. The method is applied to the determination of the half-lives of 137Cs, 90Sr, 252Cf, Tritium, 35S, 55Fe, and 99Mo. The self-consistency of the method and its capability to reject outliers was tested with good results. The application of the method to the determination of covariance matrices was tried, with poor results. (author)
The bootstrap conditions for the gluon Reggeization
International Nuclear Information System (INIS)
Compatibility of gluon Reggeization with s-channel unitarity requires the vertices of the Reggeon interactions to satisfy a series of bootstrap conditions. In order to derive, in the next-to-leading order (NLO), conditions related to the gluon production amplitudes, we calculate the s-channel discontinuities of these amplitudes and compare them with those required by the Reggeization. It turns out that these conditions include the so called strong bootstrap conditions for the kernel and for the impact factors of scattering particles, which were proposed earlier without derivation, and recently were proved to be satisfied. Besides this, there is a new bootstrap condition, which relates a number of Reggeon vertices and the gluon trajectory. (orig.)
Stability of LHD plasmas with bootstrap current
International Nuclear Information System (INIS)
Since a net toroidal current flowing in the direction increasing the rotational transform (t) has a destabilizing contribution in the Mercier criterion in the LHD configuration, two approaches are considered so that the bootstrap current should not flow in the direction. One is the change in the geometry by unbalancing the helical coil currents. The other is the enhancement of the collisionality in the plasma. In both cases, the bootstrap current can flow in the direction where t is decreased, because the geometrical factor in the limit of the 1/ν regime is drastically changed. The enhancement of the bumpiness and the l=1 components in the magnetic field is essential in the change. In these equilibria, the reduction of t by the bootstrap current results in the increase of the Shafranov shift, which leads to the improvement of the Mercier criterion. (author)
Selfconsistent RF driven and bootstrap currents
International Nuclear Information System (INIS)
In order to achieve steady-state high performance regimes in tokamaks, it is important to sustain and control the pressure and magnetic shear profiles in high bootstrap current plasmas. RF waves can be used to achieve such a goal. Then the bootstrap current fraction must be calculated selfconsistently with RF induced currents, taking into account possible synergistic effects resulting from the distortion of the electron velocity-space distribution. Results obtained with a new 3-D code that solves the electron drift kinetic equation to study the synergistic effects are presented. While synergism between bootstrap and LH-driven currents remains modest, it may reach up to 30-40% for the case of EC current drive provided the plasma parameters are properly chosen. (author)
International Nuclear Information System (INIS)
An analytical procedure for determination of As(III) and As(V) in soils using sequential extraction combined with flow injection (FI) hydride generation atomic fluorescence spectrometry (HG-AFS) was presented. The soils were sequentially extracted by water, 0.6 mol l-1 KH2PO4 solution, 1% (v/v) HCl solution and 1% (w/v) NaOH solution. The arsenite (As(III)) in extract was analyzed by HG-AFS in the medium of 0.1 mol l-1 citric acid solution, then the total arsenic in extract was determined by HG-AFS using on-line reduction of arsenate with L-cysteine. The concentration of arsenate (As(V)) was calculated by the difference. The optimum conditions of extraction and determination were studied in detail. The detection limit (3σ) for As(III) and As(V) were 0.11 and 0.07 μg l-1, respectively. The relative standard deviation (R.S.D.) was 1.43% (n=11) at the 10 μg l-1 As level. The method was applied in the determination of As(III) and As(V) of real soils and the recoveries of As(III) and As(V) were in the range of 89.3-118 and 80.4-111%, respectively
DEFF Research Database (Denmark)
Long, Xiangbao; Miró, Manuel; Hansen, Elo Harald
A new sample pretreatment approach is presented for selective and sensitive determination of trace metals via electrothermal atomic absorption spectrometry (ETAAS) based on the principle of bead injection (BI) with renewable reagent-loaded hydrophobic beads in a Sequential Injection...
Bootstrap percolation: a renormalisation group approach
International Nuclear Information System (INIS)
In bootstrap percolation, sites are occupied at random with probability p, but each site is considered active only if at least m of its neighbours are also active. Within an approximate position-space renormalization group framework on a square lattice we obtain the behaviour of the critical concentration p (sub)c and of the critical exponents ν and β for m = 0 (ordinary percolation), 1,2 and 3. We find that the bootstrap percolation problem can be cast into different universality classes, characterized by the values of m. (author)
BOOTSTRAPPING FOR EXTRACTING RELATIONS FROM LARGE CORPORA
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A new approach of relation extraction is described in this paper. It adopts a bootstrapping model with a novel iteration strategy, which generates more precise examples of specific relation. Compared with previous methods, the proposed method has three main advantages: first, it needs less manual intervention; second, more abundant and reasonable information are introduced to represent a relation pattern; third, it reduces the risk of circular dependency occurrence in bootstrapping. Scalable evaluation methodology and metrics are developed for our task with comparable techniques over TianWang 100G corpus. The experimental results show that it can get 90% precision and have excellent expansibility.
Early Stop Criterion from the Bootstrap Ensemble
DEFF Research Database (Denmark)
Hansen, Lars Kai; Larsen, Jan; Fog, Torben L.
1997-01-01
This paper addresses the problem of generalization error estimation in neural networks. A new early stop criterion based on a Bootstrap estimate of the generalization error is suggested. The estimate does not require the network to be trained to the minimum of the cost function, as required by...... other methods based on asymptotic theory. Moreover, in contrast to methods based on cross-validation which require data left out for testing, and thus biasing the estimate, the Bootstrap technique does not have this disadvantage. The potential of the suggested technique is demonstrated on various time...
Conference on Bootstrapping and Related Techniques
Rothe, Günter; Sendler, Wolfgang
1992-01-01
This book contains 30 selected, refereed papers from an in- ternational conference on bootstrapping and related techni- ques held in Trier 1990. Thepurpose of the book is to in- form about recent research in the area of bootstrap, jack- knife and Monte Carlo Tests. Addressing the novice and the expert it covers as well theoretical as practical aspects of these statistical techniques. Potential users in different disciplines as biometry, epidemiology, computer science, economics and sociology but also theoretical researchers s- hould consult the book to be informed on the state of the art in this area.
Bootstrapped models for intrinsic random functions
Energy Technology Data Exchange (ETDEWEB)
Campbell, K.
1988-08-01
Use of intrinsic random function stochastic models as a basis for estimation in geostatistical work requires the identification of the generalized covariance function of the underlying process. The fact that this function has to be estimated from data introduces an additional source of error into predictions based on the model. This paper develops the sample reuse procedure called the bootstrap in the context of intrinsic random functions to obtain realistic estimates of these errors. Simulation results support the conclusion that bootstrap distributions of functionals of the process, as well as their kriging variance, provide a reasonable picture of variability introduced by imperfect estimation of the generalized covariance function.
Karakaseva, Elizabeta; Boev, Blazo; Zajkova-Paneva, Vesna
2012-01-01
The total and extractable forms of Cu, Zn, Pb, Ni, Cr, and Fe in vineyard soils from the valley of Valandovo were analyzed in order to understand the existence of metals in soils and their potential availability to the flora and fauna. The content of metals was determined by ICP-EAS analysis, while metal binding was defined with a sequential extraction procedure. The total content of Cu, Zn, Pb, Ni, Fe and Cr, in almost all soil samples, did not exceed the maximum permissible cont...
The use of the bootstrap in the analysis of case-control studies with missing data
DEFF Research Database (Denmark)
Siersma, Volkert Dirk; Johansen, Christoffer
2004-01-01
nonparametric bootstrap, bootstrap confidence intervals, missing values, multiple imputation, matched case-control study......nonparametric bootstrap, bootstrap confidence intervals, missing values, multiple imputation, matched case-control study...
A Large Sample Study of the Bayesian Bootstrap
Lo, Albert Y.
1987-01-01
An asymptotic justification of the Bayesian bootstrap is given. Large-sample Bayesian bootstrap probability intervals for the mean, the variance and bands for the distribution, the smoothed density and smoothed rate function are also provided.
International Nuclear Information System (INIS)
Highlights: → Sequential injection determination of phosphate in estuarine and freshwaters. → Alternative spectrophotometric flow cells are compared. → Minimization of schlieren effect was assessed. → Proposed method can cope with wide salinity ranges. → Multi-reflective cell shows clear advantages. - Abstract: A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 μM PO43-) is consistent with the requirement of the target water samples, and a wide quantification range (0.024-9.5 μM) was achieved using both detection systems.
Energy Technology Data Exchange (ETDEWEB)
Mesquita, Raquel B.R. [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal); Laboratory of Hydrobiology, Institute of Biomedical Sciences Abel Salazar (ICBAS) and Institute of Marine Research (CIIMAR), Universidade do Porto, Lg. Abel Salazar 2, 4099-003 Porto (Portugal); Ferreira, M. Teresa S.O.B. [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal); Toth, Ildiko V. [REQUIMTE, Departamento de Quimica, Faculdade de Farmacia, Universidade de Porto, Rua Anibal Cunha, 164, 4050-047 Porto (Portugal); Bordalo, Adriano A. [Laboratory of Hydrobiology, Institute of Biomedical Sciences Abel Salazar (ICBAS) and Institute of Marine Research (CIIMAR), Universidade do Porto, Lg. Abel Salazar 2, 4099-003 Porto (Portugal); McKelvie, Ian D. [School of Chemistry, University of Melbourne, Victoria 3010 (Australia); Rangel, Antonio O.S.S., E-mail: aorangel@esb.ucp.pt [CBQF/Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, R. Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal)
2011-09-02
Highlights: {yields} Sequential injection determination of phosphate in estuarine and freshwaters. {yields} Alternative spectrophotometric flow cells are compared. {yields} Minimization of schlieren effect was assessed. {yields} Proposed method can cope with wide salinity ranges. {yields} Multi-reflective cell shows clear advantages. - Abstract: A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 {mu}M PO{sub 4}{sup 3-}) is consistent with the requirement of the target water samples, and a wide quantification range (0.024-9.5 {mu}M) was achieved using both detection systems.
International Nuclear Information System (INIS)
An improved methodology has been developed, based on dissolution by automated fusion followed by extraction chromatography for the detection and quantification of uranium in environmental matrices by mass spectrometry. A rapid fusion protocol (2/LiBr melts were used. The use of a M4 fusion unit also improved repeatability in sample preparation over muffle furnace fusion. Instrumental issues originating from the presence of high salt concentrations in the digestate after lithium metaborate fusion was also mitigated using an extraction chromatography (EXC) protocol aimed at removing lithium and interfering matrix constituants prior to the elution of uranium. The sequential methodology, which can be performed simultaneously on three samples, requires less than 20 min per sample for fusion and separation. It was successfully coupled to inductively coupled plasma mass spectrometry (ICP-MS) achieving detection limits below 100 pg kg-1 for 5-300 mg of sample.
International Nuclear Information System (INIS)
The Oostriku peat bog (central Estonia) has been exposed to metal-rich groundwater discharge over a long period of time and has accumulated high concentrations of Fe (up to 40 wt-%), heavy metals (e.g. Pb, Zn, Mn, Cu), and As. In this study, the peat was characterised with respect to composition and metal content with depth. The peat pore water was analysed and compared to a spring water emerging at the site. Sequential extraction, using a Tessier scheme optimised for iron-rich sediments, was used to understand the relative roles of binding mechanisms involved in the retention of different metals in the peat. Significant difference in depth distribution was found between different metals bound in the peat, which was partly attributed to varying compositions of the peat with depth and different dominant binding mechanisms for different metals. - Sorption and precipitation processes are important in metal retention over a long time
Non-Parametric Data Dependent Bootstrap for Conditional Moment Model
Bruce E. Hansen
2000-01-01
A new non-parametric bootstrap is introduced for dependent data. The bootstrap is based on a weighted empirical-likelihood estimate of the one-step-ahead conditional distribution, imposing the conditional moment restrictions implied by the model. This is the first dependent-data bootstrap procedure which imposes conditional moment restrictions on a bootstrap distribution. The method can be applied to form confidence intervals and p-values from hypothesis tests in Generalized Method of Moments...
Wild bootstrap of the mean in the infinite variance case
Giuseppe Cavaliere; Iliyan Georgiev; Robert Taylor, A. M.
2011-01-01
It is well known that the standard i.i.d. bootstrap of the mean is inconsistent in a location model with infinite variance (alfa-stable) innovations. This occurs because the bootstrap distribution of a normalised sum of infinite variance random variables tends to a random distribution. Consistent bootstrap algorithms based on subsampling methods have been proposed but have the drawback that they deliver much wider confidence sets than those generated by the i.i.d. bootstrap owing to the fact ...
uniform bootstrap confidence bands for bounded influence curve estimators
Härdle, Wolfgang Karl; Ritov, Ya‘acov; Wang, Weining
2013-01-01
We consider theoretical bootstrap "coupling" techniques for nonparametric robust smoothers and quantile regression, and verify the bootstrap improvement. To cope with curse of dimensionality, a variant of "coupling" bootstrap techniques are developed for additive models with both symmetric error distributions and further extension to the quantile regression framework. Our bootstrap method can be used in many situations like constructing con dence intervals and bands. We demonstrate the bootst...
Weak Convergence of Smoothed and Nonsmoothed Bootstrap Quantile Estimates
Falk, M; Reiss, R.-D.
1989-01-01
Under fairly general assumptions on the underlying distribution function, the bootstrap process, pertaining to the sample $q$-quantile, converges weakly in $D_\\mathbb{R}$ to the standard Brownian motion. Furthermore, weak convergence of a smoothed bootstrap quantile estimate is proved which entails that in this particular case the smoothed bootstrap estimate outperforms the nonsmoothed one.
Testing for asymmetry in economic time series using bootstrap methods
Claudio Lupi; Patrizia Ordine
2001-01-01
In this paper we show that phase-scrambling bootstrap offers a natural framework for asymmetry testing in economic time series. A comparison with other bootstrap schemes is also sketched. A Monte Carlo analysis is carried out to evaluate the size and power properties of the phase-scrambling bootstrap-based test.
The bootstrap current and its consequences
International Nuclear Information System (INIS)
The physical mechanism behind the bootstrap current is explained, and the consequences are discussed with the emphasis on the two main objectives of fusion plasma, confinement and MHD stability. For a tokamak reactor that is optimized for good confinement and stability, and that has a limited size, the total plasma current exceeds the bootstrap current by a factor of three to five and therefore almost all the plasma current must be driven through other means. Furthermore, the neoclassical tearing mode which is driven by the bootstrap current is expected to be the limiting MHD instability in these reactors. Raising the fraction of the bootstrap current is not expected to be beneficial for confinement and stability expect when broad pressure profiles (internal transport barriers) can be realized. In stellarators several optimizations are possible, either optimizing the current to zero such that it does not destroy the desired topology, and it does not generate any current-driven instabilities, or using the current to generate some of the poloidal field. (author)
How to Bootstrap a Human Communication System
Fay, Nicolas; Arbib, Michael; Garrod, Simon
2013-01-01
How might a human communication system be bootstrapped in the absence of conventional language? We argue that motivated signs play an important role (i.e., signs that are linked to meaning by structural resemblance or by natural association). An experimental study is then reported in which participants try to communicate a range of pre-specified…
Bootstrapping Density-Weighted Average Derivatives
DEFF Research Database (Denmark)
Cattaneo, Matias D.; Crump, Richard K.; Jansson, Michael
Employing the "small bandwidth" asymptotic framework of Cattaneo, Crump, and Jansson (2009), this paper studies the properties of a variety of bootstrap-based inference procedures associated with the kernel-based density-weighted averaged derivative estimator proposed by Powell, Stock, and Stoker...
Pulling Econometrics Students up by Their Bootstraps
O'Hara, Michael E.
2014-01-01
Although the concept of the sampling distribution is at the core of much of what we do in econometrics, it is a concept that is often difficult for students to grasp. The thought process behind bootstrapping provides a way for students to conceptualize the sampling distribution in a way that is intuitive and visual. However, teaching students to…
A Bootstrap Procedure of Propensity Score Estimation
Bai, Haiyan
2013-01-01
Propensity score estimation plays a fundamental role in propensity score matching for reducing group selection bias in observational data. To increase the accuracy of propensity score estimation, the author developed a bootstrap propensity score. The commonly used propensity score matching methods: nearest neighbor matching, caliper matching, and…
Automatic bootstrapping and tracking of object contours.
Chiverton, John; Xie, Xianghua; Mirmehdi, Majid
2012-03-01
A new fully automatic object tracking and segmentation framework is proposed. The framework consists of a motion-based bootstrapping algorithm concurrent to a shape-based active contour. The shape-based active contour uses finite shape memory that is automatically and continuously built from both the bootstrap process and the active-contour object tracker. A scheme is proposed to ensure that the finite shape memory is continuously updated but forgets unnecessary information. Two new ways of automatically extracting shape information from image data given a region of interest are also proposed. Results demonstrate that the bootstrapping stage provides important motion and shape information to the object tracker. This information is found to be essential for good (fully automatic) initialization of the active contour. Further results also demonstrate convergence properties of the content of the finite shape memory and similar object tracking performance in comparison with an object tracker with unlimited shape memory. Tests with an active contour using a fixed-shape prior also demonstrate superior performance for the proposed bootstrapped finite-shape-memory framework and similar performance when compared with a recently proposed active contour that uses an alternative online learning model. PMID:21908256
El-Zahry, Marwa R; Refaat, Ibrahim H; Mohamed, Horria A; Lendl, Bernhard
2016-07-01
In this contribution, the utility of sequential injection analysis in combination with surface-enhanced Raman spectroscopy (SERS) as a detection technique was investigated for simultaneous determination of aspirin and vitamin C in their pharmaceutical dosage forms and in spiked urine samples. The silver substrate was synthesized in situ by laser-induced photochemical procedure. By focusing the laser on a flow cell at 1 ml/min of continuous flow of 0.5 mM silver nitrate and 5 mM sodium citrate mixture, an active silver spot on the inner wall of the flow cell was prepared in a few seconds. The whole setup is fully computer controlled using ATLAS software to combine the two techniques. The system allows sequential determination of aspirin concentrations ranging from 100 to 500 ng/ml and vitamin C concentrations between 10 and 110 ng/ml with good precision of relative standard deviations (RSDs) of 0.85 and 1.7 %, respectively. A comparison of these results with those of the reported procedures showed excellent results compared with t and F values, indicating good accuracy and precision. The detection limits were 32 and 3 ng/ml for aspirin and vitamin C, respectively. PMID:27108284
International Nuclear Information System (INIS)
Single-drop microextraction (SDME) and sequential injection analysis have been hyphenated for ultratrace metal determination by Electrothermal-Atomic Absorption Spectrometry (ETAAS). The novel method was targeted on extraction of the Cr(VI)-APDC chelate and encompasses the potential of SDME as a miniaturized and virtually solvent-free preconcentration technique, the ability of sequential injection analysis to handle samples and the versatility of furnace autosamplers for introducing microliter samples in ETAAS. The variables influencing the microextraction of Cr(VI) onto an organic solvent drop, i.e., type of organic solvent, microextraction time, stirring rate of the sample solution, drop volume, immersion depth of the drop, salting-out effect, temperature of the sample, concentration of the complexing agent and pH of the sample solution were fully investigated. For a 5 and 20 min microextraction time, the preconcentration factors were 20 and 70, respectively. The detection limit was 0.02 μg/L of Cr(VI) and the repeatability expressed as relative standard deviation was 7%. The SDME-SIA-ETAAS technique was validated against BCR CRM 544 (lyophilized solution) and applied to ultrasensitive determination of Cr(VI) in natural waters
Kokkinos, Christos; Economou, Anastasios; Goddard, Nicholas G; Fielden, Peter R; Baldock, Sara J
2016-06-01
This work reports the development of a sequential injection/stripping analysis method for the determination of trace Pb(II) at injection-moulded electrochemical fluidic cells. Conducting carbon fibre-loaded polystyrene electrodes were integrated within the plastic cells. The flow-through cells were incorporated into a home-made sequential injection analysis (SIA) manifold. Different experimental parameters for the detection of Pb(II) were investigated including the type and concentration of the supporting electrolyte, the conditions of the stripping step, the volume of the sample, the flow rate and the accumulation potential. The LOD for Pb(II) was 0.5μgL(-1), the within-cell % relative standard deviation (n=8) was 3.1% and the between-cell % relative standard deviation (n=5) was 8.9% for 25μgL(-1) Pb(II). The cells were applied to the determination of Pb(II) in tapwater and a phosphate fertilizer sample. PMID:27130105
International Nuclear Information System (INIS)
Highlights: • We develop a HR CS FAAS method for fast sequential multi-elemental analysis. • Major and minor elements are determined in a single run using the same solution. • Less than 10 mL of sample are necessary to determine in triplicate eleven elements. • The method is successfully applied in environmental samples and drinking waters. • The sample consumption is minimal compared to multi-elemental analysis by LS FAAS. - Abstract: The fast sequential multi-element determination of 11 elements present at different concentration levels in environmental samples and drinking waters has been investigated using high-resolution continuum source flame atomic absorption spectrometry. The main lines for Cu (324.754 nm), Zn (213.857 nm), Cd (228.802 nm), Ni (232.003 nm) and Pb (217.001 nm), main and secondary absorption lines for Mn (279.482 and 279.827 nm), Fe (248.327, 248.514 and 302.064 nm) and Ca (422.673 and 239.856 nm), secondary lines with different sensitivities for Na (589.592 and 330.237 nm) and K (769.897 and 404.414 nm) and a secondary line for Mg (202.582 nm) have been chosen to perform the analysis. A flow injection system has been used for sample introduction so sample consumption has been reduced up to less than 1 mL per element, measured in triplicate. Furthermore, the use of multiplets for Fe and the side pixel registration approach for Mg have been studied in order to reduce sensitivity and extend the linear working range. The figures of merit have been calculated and the proposed method was applied to determine these elements in a pine needles reference material (SRM 1575a), drinking and natural waters and soil extracts. Recoveries of analytes added at different concentration levels to water samples and extracts of soils were within 88–115% interval. In this way, the fast sequential multi-element determination of major and minor elements can be carried out, in triplicate, with successful results without requiring additional dilutions of
Al-Masri, M. S.; Al-Kharfan, K.; Al-Shamali, K.
Speciation of three trace elements (Zn, Pb, Cu) in air particulates of two Syrian cities (Tartous and Darya) with different climate conditions and industrial emissions has been studied. Air filters were collected during 2000-2001 and extracted chemically using different selective fluids in an attempt to identify the different forms of trace elements. Approximately 60% of lead in air particulates of both cities was found to be associated with organic materials produced by incomplete burning of vehicles fuels and residential heating; the remaining 40% of lead was as lead oxides and mineral acids soluble compounds. Zinc was found in oxides (28-65%) samples collected in Tartous city, indicating that the Tartous cement factory and phosphate loading cargoes are the main source of emissions. In the Darya filters, zinc associated with organic materials (28-49%) was related to the presence of plastic molding industries and corroding car tires. In addition, copper was also found to be in the form of oxides (19-46%) in both cities in the summer periods, while 13-25% and 35% are associated with organic materials and silicates, respectively. Differences in chemical forms of the studied trace elements in air particulates were found to be related to differences in air pollution sources and differences in human behaviour throughout the year. Therefore, chemical fractionation of trace elements in air particulates using sequential leaching can be used for identification of air pollutions sources in urban and industrial areas.
The cluster bootstrap consistency in generalized estimating equations
Cheng, Guang
2013-03-01
The cluster bootstrap resamples clusters or subjects instead of individual observations in order to preserve the dependence within each cluster or subject. In this paper, we provide a theoretical justification of using the cluster bootstrap for the inferences of the generalized estimating equations (GEE) for clustered/longitudinal data. Under the general exchangeable bootstrap weights, we show that the cluster bootstrap yields a consistent approximation of the distribution of the regression estimate, and a consistent approximation of the confidence sets. We also show that a computationally more efficient one-step version of the cluster bootstrap provides asymptotically equivalent inference. © 2012.
Iterated smoothed bootstrap confidence intervals for population quantiles
Lee, SMS; Ho, YHS
2005-01-01
This paper investigates the effects of smoothed bootstrap iterations on coverage probabilities of smoothed bootstrap and bootstrap-t confidence intervals for population quantiles, and establishes the optimal kernel bandwidths at various stages of the smoothing procedures. The conventional smoothed bootstrap and bootstrap-t methods have been known to yield one-sided coverage errors of orders O(n−1/2) and o(n−2/3), respectively, for intervals based on the sample quantile of a random sample of s...
The Block-block Bootstrap: Improved Asymptotic Refinements
Donald W.K. Andrews
2002-01-01
The asymptotic refinements attributable to the block bootstrap for time series are not as large as those of the nonparametric iid bootstrap or the parametric bootstrap. One reason is that the independence between the blocks in the block bootstrap sample does not mimic the dependence structure of the original sample. This is the join-point problem. In this paper, we propose a method of solving this problem. The idea is not to alter the block bootstrap. Instead, we alter the original sample sta...
A comparison of four different block bootstrap methods
Directory of Open Access Journals (Sweden)
Boris Radovanov
2014-12-01
Full Text Available The paper contains a description of four different block bootstrap methods, i.e., non-overlapping block bootstrap, overlapping block bootstrap (moving block bootstrap, stationary block bootstrap and subsampling. Furthermore, the basic goal of this paper is to quantify relative efficiency of each mentioned block bootstrap procedure and then to compare those methods. To achieve the goal, we measure mean square errors of estimation variance returns. The returns are calculated from 1250 daily observations of Serbian stock market index values BELEX15 from April 2009 to April 2014. Thereby, considering the effects of potential changes in decisions according to variations in the sample length and purposes of the use, this paper introduces stability analysis which contains robustness testing of the different sample size and the different block length. Testing results indicate some changes in bootstrap method efficiencies when altering the sample size or the block length.
International Nuclear Information System (INIS)
A novel automatic sequential injection (SI) single-drop micro-extraction (SDME) system is proposed as versatile approach for on-line metal preconcentration and/or separation. Coupled to electrothermal atomic absorption spectrometry (ETAAS) the potentials of this SI scheme are demonstrated for trace cadmium determination in water samples. A non-charged complex of cadmium with ammonium diethyldithiophosphate (DDPA) was produced and extracted on-line into a 60 μL micro-drop of di-isobutyl ketone (DIBK). The extraction procedure was performed into a newly designed flow-through extraction cell coupled on a sequential injection manifold. As the complex Cd(II)-DDPA flowed continuously around the micro-droplet, the analyte was extracting into the solvent micro-drop. All the critical parameters were optimized and offered good performance characteristics and high preconcentration ratios. For 600 s micro-extraction time, the enhancement factor was 10 and the sampling frequency was 6 h-1. The detection limit was 0.01 μg L-1 and the precision (RSD at 0.1 μg L-1 of cadmium) was 3.9%. The proposed method was evaluated by analyzing certified reference material
International Nuclear Information System (INIS)
Sequential extraction procedures and the high-pressure digestion method were selected to determine the element constituents of fly ash samples. Sequential extraction is one of the most useful methods used to measure the various elements from municipal solid waste incineration ash and contaminated soils. The extract from each step is analyzed using various techniques and equipments, and the results are then evaluated. In this work, a six-step extraction procedure modified from that of Tessier et al. and Wang et al. was performed and applied to the certified reference material BCR 176 (city waste incineration ash). Analyses were carried out by various techniques such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and X-ray powder diffraction (XRPD) to evaluate the characteristics of fly ash. The extraction efficiency of many elements was higher than 80%, and the relative standard deviations (RSD) for recovery of most elements were within 10%. In addition, an H2O2 + HNO3 + HF mixed acid digestion solution processed using a low-temperature evaporation procedure was selected as the optimal process for fly ash digestion. The results of this work provide information on the chemical composition, distribution, and potential mobility of the investigated elements
Bootstrapping phylogenies inferred from rearrangement data
Directory of Open Access Journals (Sweden)
Lin Yu
2012-08-01
Full Text Available Abstract Background Large-scale sequencing of genomes has enabled the inference of phylogenies based on the evolution of genomic architecture, under such events as rearrangements, duplications, and losses. Many evolutionary models and associated algorithms have been designed over the last few years and have found use in comparative genomics and phylogenetic inference. However, the assessment of phylogenies built from such data has not been properly addressed to date. The standard method used in sequence-based phylogenetic inference is the bootstrap, but it relies on a large number of homologous characters that can be resampled; yet in the case of rearrangements, the entire genome is a single character. Alternatives such as the jackknife suffer from the same problem, while likelihood tests cannot be applied in the absence of well established probabilistic models. Results We present a new approach to the assessment of distance-based phylogenetic inference from whole-genome data; our approach combines features of the jackknife and the bootstrap and remains nonparametric. For each feature of our method, we give an equivalent feature in the sequence-based framework; we also present the results of extensive experimental testing, in both sequence-based and genome-based frameworks. Through the feature-by-feature comparison and the experimental results, we show that our bootstrapping approach is on par with the classic phylogenetic bootstrap used in sequence-based reconstruction, and we establish the clear superiority of the classic bootstrap for sequence data and of our corresponding new approach for rearrangement data over proposed variants. Finally, we test our approach on a small dataset of mammalian genomes, verifying that the support values match current thinking about the respective branches. Conclusions Our method is the first to provide a standard of assessment to match that of the classic phylogenetic bootstrap for aligned sequences. Its
Lahiri, S. N.
2005-01-01
Efron [J. Roy. Statist. Soc. Ser. B 54 (1992) 83--111] proposed a computationally efficient method, called the jackknife-after-bootstrap, for estimating the variance of a bootstrap estimator for independent data. For dependent data, a version of the jackknife-after-bootstrap method has been recently proposed by Lahiri [Econometric Theory 18 (2002) 79--98]. In this paper it is shown that the jackknife-after-bootstrap estimators of the variance of a bootstrap quantile are consistent for both de...
[Sensitometry of Mammographic Screen-film System Using Bootstrap Aluminum Step-Wedge.].
Abe, Shinji; Imada, Ryou; Terauchi, Takashi; Fujisaki, Tatsuya; Monma, Masahiko; Nishimura, Katsuyuki; Saitoh, Hidetoshi; Mochizuki, Yasuo
2005-01-01
Recently, a few types of step-wedges for bootstrap sensitometry with a mammographic screen-film system have been proposed. In this study, the bootstrap sensitometry with the mammographic screen-film system was studied for two types of aluminum step-wedges. Characteristic X-ray energy curves were determined using mammographic and general radiographic aluminum step-wedges devised to prevent scattered X-rays generated from one step penetrating into the region of another one, and dependence of the characteristic curves on the wedges was also discussed. No difference was found in the characteristic curves due to the difference in the step-wedges for mammography and general radiography although there was a slight difference in shape at the shoulder portion for the two types of step-wedges. Therefore, it was concluded that aluminum step-wedges for mammography and general radiography could be employed in bootstrap sensitometry with the mammographic screen-film system. PMID:16479054
Bootstrapping ${\\mathcal N}=2$ chiral correlators
Lemos, Madalena
2016-01-01
We apply the numerical bootstrap program to chiral operators in four-dimensional ${\\mathcal N}=2$ SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of ${\\mathcal N}=2$ SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.
The $(2,0)$ superconformal bootstrap
Beem, Christopher; Rastelli, Leonardo; van Rees, Balt C
2016-01-01
We develop the conformal bootstrap program for six-dimensional conformal field theories with $(2,0)$ supersymmetry, focusing on the universal four-point function of stress tensor multiplets. We review the solution of the superconformal Ward identities and describe the superconformal block decomposition of this correlator. We apply numerical bootstrap techniques to derive bounds on OPE coefficients and scaling dimensions from the constraints of crossing symmetry and unitarity. We also derive analytic results for the large spin spectrum using the lightcone expansion of the crossing equation. Our principal result is strong evidence that the $A_1$ theory realizes the minimal allowed central charge $(c=25)$ for any interacting $(2,0)$ theory. This implies that the full stress tensor four-point function of the $A_1$ theory is the unique unitary solution to the crossing symmetry equation at $c=25$. For this theory, we estimate the scaling dimensions of the lightest unprotected operators appearing in the stress tenso...
Bootstrapped models for intrinsic random functions
Energy Technology Data Exchange (ETDEWEB)
Campbell, K.
1987-01-01
The use of intrinsic random function stochastic models as a basis for estimation in geostatistical work requires the identification of the generalized covariance function of the underlying process, and the fact that this function has to be estimated from the data introduces an additional source of error into predictions based on the model. This paper develops the sample reuse procedure called the ''bootstrap'' in the context of intrinsic random functions to obtain realistic estimates of these errors. Simulation results support the conclusion that bootstrap distributions of functionals of the process, as well as of their ''kriging variance,'' provide a reasonable picture of the variability introduced by imperfect estimation of the generalized covariance function.
The Correct Kriging Variance Estimated by Bootstrapping
den Hertog, D.; Kleijnen, J.P.C.; Siem, A.Y.D.
2004-01-01
The classic Kriging variance formula is widely used in geostatistics and in the design and analysis of computer experiments.This paper proves that this formula is wrong.Furthermore, it shows that the formula underestimates the Kriging variance in expectation.The paper develops parametric bootstrapping to estimate the Kriging variance.The new method is tested on several artificial examples and a real-life case study.These results demonstrate that the classic formula underestimates the true Kri...
TASI Lectures on the Conformal Bootstrap
Simmons-Duffin, David
2016-01-01
These notes are from courses given at TASI and the Advanced Strings School in summer 2015. Starting from principles of quantum field theory and the assumption of a traceless stress tensor, we develop the basics of conformal field theory, including conformal Ward identities, radial quantization, reflection positivity, the operator product expansion, and conformal blocks. We end with an introduction to numerical bootstrap methods, focusing on the 2d and 3d Ising models.
Bootstrapping Deep Lexical Resources: Resources for Courses
Baldwin, Timothy
2007-01-01
We propose a range of deep lexical acquisition methods which make use of morphological, syntactic and ontological language resources to model word similarity and bootstrap from a seed lexicon. The different methods are deployed in learning lexical items for a precision grammar, and shown to each have strengths and weaknesses over different word classes. A particular focus of this paper is the relative accessibility of different language resource types, and predicted ``bang for the buck'' associated with each in deep lexical acquisition applications.
Bootstraping the general linear hypothesis test
Delicado, Pedro; Río, Manuel del, 1690-1766
1993-01-01
We discuss the use of bootstrap methodology in hypothesis testing, focusing on the classical F-test for linear hypotheses in the linear model. A modification of the F-statistics which allows for resampling under the null hypothesis is proposed. This approach is specifically considered in the one-way analysis of variance model. A simulation study illustrating the behaviour of our proposal is presented.
Accidental symmetries and the conformal bootstrap
Chester, Shai M.; Giombi, Simone; Iliesiu, Luca V.; Klebanov, Igor R.; Pufu, Silviu S.; Yacoby, Ran
2016-01-01
We study an N=2 supersymmetric generalization of the three-dimensional critical O( N) vector model that is described by N + 1 chiral superfields with superpotential W = g 1 X∑ i Z 1 2 + g 2 X 3. By combining the tools of the conformal bootstrap with results obtained through supersymmetric localization, we argue that this model exhibits a symmetry enhancement at the infrared superconformal fixed point due to g 2 flowing to zero. This example is special in that the existence of an infrared fixed point with g 1 , g 2 ≠ 0, which does not exhibit symmetry enhancement, does not generally lead to any obvious unitarity violations or other inconsistencies. We do show, however, that the F-theorem excludes the models with g 1 , g 2 ≠ 0 for N > 5. The conformal bootstrap provides a stronger constraint and excludes such models for N > 2. We provide evidence that the g 2 = 0 models, which have the enhanced O( N) × U(1) symmetry, come close to saturating the bootstrap bounds. We extend our analysis to fractional dimensions where we can motivate the nonexistence of the g 1 , g 2 ≠ 0 models by studying them perturbatively in the 4 - ɛ expansion.
H. Bunschoten; M. Gore (Milind); I.J.Th.M. Claassen (Ivo); F.G.C.M. Uytdehaag (Fons); B. Dietzschold; W.H. Wunner; A.D.M.E. Osterhaus (Ab)
1989-01-01
textabstractTwo new monoclonal antibodies (MAbs) derived from mice immunized with the Pitman-Moore (PM) strain of rabies virus were used to identify and characterize two unique antigenic determinants on the rabies virus glycoprotein. One of the determinants, which defined an additional antigenic sit
DEFF Research Database (Denmark)
Qiao, Jixin; Hou, Xiaolin; Roos, Per;
2010-01-01
This paper reports an automated analytical method for rapid and simultaneous determination of plutonium isotopes (239Pu and 240Pu) and neptunium (237Np) in environmental samples. An extraction chromatographic column packed with TrisKem TEVA® resin was incorporated in a sequential injection (SI......) system for the isolation of plutonium and neptunium from matrix elements and interfering nuclides. Valence adjustment is a crucial step to ensure the same chemical behavior of plutonium and neptunium onto the TEVA column and consequently to accomplish their simultaneous separation and detection. Distinct...... procedures were investigated and compared for the adjustment of oxidation states of plutonium and neptunium to Pu(IV) and Np(IV), respectively. A two-step protocol using sulfite and concentrated nitric acid as redox reagents was proven to be the most effective method. The analytical results for both...
DEFF Research Database (Denmark)
Long, Xiangbao; Miró, Manuel; Hansen, Elo Harald
2005-01-01
A new concept is presented for selective and sensitive determination of trace metals via electrothermal atomic absorption spectrometry (ETAAS) based on the principle of bead injection (BI) with renewable reversed-phase surfaces in a sequential injection-lab-on-valve (SI-LOV) mode. The methodology...... involves the use of poly(styrene-divinylbenzene) beads containing pendant octadecyl moieties (C18-PS/DVB), which are preimpregnated with a selective organic metal chelating agent prior to the automatic manipulation of the beads in the microbore conduits of the LOV unit. By adapting this approach, the...... immobilization of the most suitable chelating agent can be effected irrespective of the kinetics involved, optimal reaction conditions can be used for implementing the chelating reaction of the target metal analyte with the immobilized reagent, and an added degree of freedom is offered in selecting the most...
DEFF Research Database (Denmark)
Shi, Keliang; Qiao, Jixin; Wu, Wangsuo;
2012-01-01
An automated method was developed for rapid determination of 99Tc in large volume seawater samples. The analytical procedure involves preconcentration of technetium with coprecipitation, online separation using extraction chromatography (two TEVA columns) implemented in a sequential injection setup...... also acidity (or concentration of H+) of the loading or eluting solution affect the adsorption and desorption of TcO4– on TEVA resin. Decontamination factors of more than 1 × 106 for ruthenium and 5 × 105 for molybdenum are achieved. Chemical yields of technetium in the overall procedure range from 60......% to 75% depending on the sample volumes, and a detection limit of 7.5 mBq/m3 (or 11.5 pg/m3) for 200 L of seawater was obtained. Compared with the conventional analytical procedure, the developed method significantly reduces analytical time. A batch of samples (n > 4) can be analyzed within 24 h. The...
Meeravali, Noorbasha N; Madhavi, K; Manjusha, R; Kumar, Sunil Jai
2014-01-01
A sequential extraction procedure is developed for the separation of trace levels of hexachloroplatinate, cisplatin and carboplatin from soil, which are then, pre-concentrated using a vesicular coacervative cloud point extraction method prior to their determination as platinum by continuum source ETAAS. Sequential extraction of carboplatin, cisplatin and hexachloroplatinate from a specific red soil is achieved by using the 20% HCl, aqua regia at room temperature and by combination of aqua regia and HF with microwave digestion, respectively. The pre-concentration of these species from the extracted solutions is based on the formation of extractable hydrophobic complexes of PtCl₆(2-) anionic species with free cationic head groups solubilizing sites of the Triton X-114 co-surfactant stabilized TOMAC (tri-octyl methyl ammonium chloride) vesicles through electrostatic attraction. This process separates the platinum from bulk aqueous solution into a small vesicular rich phase. The parameters affecting the extraction procedures are optimized. Under the optimized conditions, the achieved pre-concentration factor is 20 and detection limit is 0.5 ng g(-1) for soil and 0.02 ng mL(-1) for water samples. The spiked recoveries of hexachloroplatinate, cisplatin and carboplatin in water and soil extracts in the vesicular coacervative extraction are in the range of 96-102% at 0.5-1 ng mL(-1) with relative standard deviation of 1-3%. The accuracy of the method for platinum determination is evaluated by analyzing CCRMP PTC-1a copper-nickel sulfide concentrate and BCR 723 road dust certified reference materials and the obtained results agreed with the certified values with 95% confidence level of student t-test. The results were also compared to mixed-micelle (MM)-CPE method reported in the literature. PMID:24274268
Bootstrap current for small aspect ratio TOKAMAK equilibria
International Nuclear Information System (INIS)
Full text. We present equilibrium features of the very small ratio tokamak, TBR-2 E, with the aspect ratio of 1.6, which is being designed in Brazil - a joint project with the participation of the University of Sao Paulo, the State University of Campinas, and the National Institute for Space Research. The equilibria have been studied by using the SELENE-J code developed at JAERI, Japan, by Tokuda et al. We have concentrated our study on the determination of the stability limit by using the critical pressure criterion for ballooning stability and Mercier criterion for other MHD modes. The β-limit values were calculated for the case of the non-inductive current and found that its maximum lies at elongation of 1.7. Increasing the triangularity, the β-limit values increase, but the maximum continues to stay at the same value of elongation. We have also studied the effect of the neo-classical transport properties by changing the plasma temperature (or β values). In particular, we have studied the trapped particles and bootstrap current. We have found that at temperatures as low as 600 eV the transport is already in banana regime and that the bootstrap current may account for a significant part of the total plasma current. (author)
Chu, Ning; Fan, Shihua
2009-12-01
A new analytical method was developed for the simultaneous kinetic spectrophotometric determination of a quaternary carbamate pesticide mixture consisting of carbofuran, propoxur, metolcarb and fenobucarb using sequential injection analysis (SIA). The procedure was based upon the different kinetic properties between the analytes reacted with reagent in flow system in the non-stopped-flow mode, in which their hydrolysis products coupled with diazotized p-nitroaniline in an alkaline medium to form the corresponding colored complexes. The absorbance data from SIA peak time profile were recorded at 510 nm and resolved by the use of back-propagation-artificial neural network (BP-ANN) algorithms for multivariate quantitative analysis. The experimental variables and main network parameters were optimized and each of the pesticides could be determined in the concentration range of 0.5-10.0 μg mL -1, at a sampling frequency of 18 h -1. The proposed method was compared to other spectrophotometric methods for simultaneous determination of mixtures of carbamate pesticides, and it was proved to be adequately reliable and was successfully applied to the simultaneous determination of the four pesticide residues in water and fruit samples, obtaining the satisfactory results based on recovery studies (84.7-116.0%).
DEFF Research Database (Denmark)
Long, Xiangbao; Chomchoei, Roongrat; Hansen, Elo Harald;
2004-01-01
an external packed column and in a sequential injection lab-on-valve (SI-LOV) system. Employed for the determination of cadmium(II), complexed with diethyldithiophosphate (DDPA), and detection by electrothermal atomic absorption spectrometry (ETAAS), its performance was compared to that of a...
International Nuclear Information System (INIS)
The development of mercury-free electroanalytical systems for in-field analysis of pollutants requires a foundation on the electrochemical behaviour of the chosen electrode material in the target sample matrices. In this work, the behaviour of gold working electrodes in the media employed in the BCR sequential extraction protocol, for the fractionation of metals in solid environmental matrices, is reported. All three of the BCR sequential extraction media are redox active, on the basis of acidity and oxygen content as well as the inherent reducing or oxidising nature of some of the reagents employed: 0.11 M acetic acid, 0.1 M hydroxylammonium chloride (adjusted to pH 2) and 1 M ammonium acetate (adjusted to pH 2) with added trace hydrogen peroxide. The available potential ranges together with the demonstrated detection of target metals in these media are presented. Stripping voltammetry of copper or lead in the BCR extract media solutions reveal a multi-peak behaviour due to the stripping of both bulk metal and underpotential metal deposits. A procedure based on underpotential deposition-stripping voltammetry (UPD-SV) was evaluated for application to determination of copper in 0.11 M acetic acid soil extracts. A preliminary screening step in which different deposition times are applied to the sample enables a deposition time commensurate with UPD-SV to be selected so that no bulk deposition or stripping occurs thus simplifying the shape and features of the resulting voltammograms. Choice of the suitable deposition time is then followed by standards addition calibration. The method was validated by the analysis of a number of BCR 0.11 M acetic acid soil extracts. Good agreement was obtained been the UPD-SV method and atomic spectroscopic results
Stationary bootstrapping realized volatility under market microstructure noise
Hwang, Eunju; Shin, Dong Wan
2013-01-01
Large-sample validity is proved for stationary bootstrapping of a bias-corrected realized volatility under market microstructure noise, which enables us to construct a bootstrap confidence interval of integrated volatility. A finite-sample simulation shows that the stationary bootstrapping confidence interval outperforms existing ones which are constructed ignoring market microstructure noise or using asymptotic normality for the bias-corrected realized volatility.
Model Based Bootstrap Methods for Interval Censored Data
Sen, Bodhisattva; Xu, Gongjun
2013-01-01
We investigate the performance of model based bootstrap methods for constructing point-wise confidence intervals around the survival function with interval censored data. We show that bootstrapping from the nonparametric maximum likelihood estimator of the survival function is inconsistent for both the current status and case 2 interval censoring models. A model based smoothed bootstrap procedure is proposed and shown to be consistent. In addition, simulation studies are conducted to illustra...
Change-point in stochastic design regression and the bootstrap
Seijo, Emilio; Sen, Bodhisattva
2011-01-01
In this paper we study the consistency of different bootstrap procedures for constructing confidence intervals (CIs) for the unique jump discontinuity (change-point) in an otherwise smooth regression function in a stochastic design setting. This problem exhibits nonstandard asymptotics and we argue that the standard bootstrap procedures in regression fail to provide valid confidence intervals for the change-point. We propose a version of smoothed bootstrap, illustrate its remarkable finite sa...
Is Bootstrap Really Helpful in Point Process Statistics?
Snethlage, Martin
2000-01-01
There are some papers which describe the use of bootstrap techniques in point process statistics. The aim of the present paper is to show that the form in which bootstrap is used there is dubious. In case of variance estimation of pair correlation function estimators the used bootstrap techniques lead to results which can be obtained simpler without simulation; furthermore, they differ from the desired results. The problem to obtain confidence regions for the intensity function of inhomogeneo...
A PARAMETRIC BOOTSTRAP USING THE FIRST FOURMOMENTS OF THE RESIDUALS
Pierre-Eric Treyens
2007-01-01
We consider linear regression models and we suppose that disturbances are either Gaussian or non Gaussian. Until now, within the framework of the bootstrap, we thought that the error in rejection probability (ERP) had the same rate of convergence with the parametric bootstrap or the nonparametric bootstrap. For linear data generating processes (DGP) we show in this paper that this assertion is false if skewness and/or kurtosis coefficients of the distribution of the disturbances are nonnull. ...
Improving Coverage Accuracy of Block Bootstrap Confidence Intervals
Lee, Stephen M. S.; Lai, P. Y.
2008-01-01
The block bootstrap confidence interval based on dependent data can outperform the computationally more convenient normal approximation only with non-trivial Studentization which, in the case of complicated statistics, calls for highly specialist treatment. We propose two different approaches to improving the accuracy of the block bootstrap confidence interval under very general conditions. The first calibrates the coverage level by iterating the block bootstrap. The second calculates Student...
Nava-Júnior, I. S.; Aucelio, R. Q.
2009-03-01
The selective determination of norfloxacin in mixtures with other fluorquinolones was achieved by synchronous scanning solid surface room-temperature phosphorimetry (SSRTP) and Th(NO 3) 4 as selective phosphorescence inducer. The method also allowed the determination of levofloxacin in a sequential way. The optimization of experimental conditions was made through an univariate approach, in order to find the best conditions for norfloxacin phosphorescence, followed by a 2 3 factorial design in order to verify interaction among relevant variables, to check robustness for each variable and to perform final adjustment of parameters. Absolute limit of detection (ALOD) for norfloxacin was 12 ng with a linear signal response extending up to 400 ng. Under the same experimental conditions set for norfloxacin, the ALOD for levofloxacin was 13 ng with linear signal response up to 450 ng. Accuracy of the method, using Th (IV) as selective phosphorescence inducer, was evaluated through the analysis of commercial and simulated pharmaceutical formulations with recoveries between 94.4 and 101% for norfloxacin and 95.9 and 103.8% for levofloxacin. The use of Cd (II), a traditional phosphorescence inducer for fluorquinolones, did not allow selective determination of norfloxacin. Further studies indicated the potential application of the method in urine samples.
International Nuclear Information System (INIS)
Since 2004, IAEA activities related to the terrestrial environment have aimed at the development of a set of procedures to determine radionuclides in environmental samples. Reliable, comparable and ‘fit for purpose’ results are an essential requirement for any decision based on analytical measurements. For the analyst, tested and validated analytical procedures are extremely important tools for the production of analytical data. For maximum utility, such procedures should be comprehensive, clearly formulated and readily available for reference to both the analyst and the customer. This publication describes a combined procedure for the sequential determination of 90Sr, 241Am and Pu radioisotopes in environmental samples. The method is based on the chemical separation of strontium, americium and plutonium using ion exchange chromatography, extraction chromatography and precipitation followed by alpha spectrometric and liquid scintillation counting detection. The method was tested and validated in terms of repeatability and trueness in accordance with International Organization for Standardization (ISO) guidelines using reference materials and proficiency test samples. Reproducibility tests were performed later at the IAEA Terrestrial Environment Laboratory. The calculations of the massic activity, uncertainty budget, decision threshold and detection limit are also described in this publication. The procedure is introduced for the determination of 90Sr, 241Am and Pu radioisotopes in environmental samples such as soil, sediment, air filter and vegetation samples. It is expected to be of general use to a wide range of laboratories, including the Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) network for routine environmental monitoring purposes
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A short sequential extraction procedure(SSEP) was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed: Cd＜Cu＜Zn, and samples S1,S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and resi-dual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.
Bootstrap confidence intervals for the process capability index under half-logistic distribution
Wararit Panichkitkosolkul
2012-01-01
This study concerns the construction of bootstrap confidence intervals for theprocess capability index in the case of half-logistic distribution. The bootstrap confidence intervals applied consist of standard bootstrap confidence interval, percentile bootstrap confidence interval and bias-corrected percentile bootstrap confidence interval. Using Monte Carlo simulations, the estimated coverage probabilities and average widths ofbootstrap confidence intervals are compared, with results showing ...
DEFF Research Database (Denmark)
Buanuam, Janya; Miró, Manuel; Hansen, Elo Harald;
2006-01-01
Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified by the pa...... electrothermal atomic absorption spectrometry....
Bootstrap current fraction scaling for a tokamak reactor design study
International Nuclear Information System (INIS)
Highlights: • New bootstrap current fraction scalings for systems codes were derived by solving the Hirshman–Sigmar model. • Nine self-consistent MHD equilibria were constructed in order to compare the bootstrap current fraction values. • Wilson formula most successfully predicted the bootstrap current fraction, but it requires current density profile index. • The new scaling formulas and IPDG accurately estimated the fBS values for the normal and weakly reversed shear tokamaks. - Abstract: We have derived new bootstrap current fraction scalings for systems codes by solving the Hirshman–Sigmar model, which is valid for arbitrary aspect ratios and collision conditions. The bootstrap current density calculation module in the ACCOME code was used with the matrix inversion method without the large aspect ratio assumption. Nine self-consistent MHD equilibria, which cover conventional, advanced and spherical tokamaks with normal or reversed shear, were constructed using numerical calculations in order to compare the bootstrap current fraction values with those of the new model and all six existing models. The Wilson formula successfully predicted the bootstrap current fraction, but it requires current density profile index for the calculation. The new scaling formulas and IPDG accurately estimated the bootstrap current fraction for the normal and weakly reversed shear tokamaks, regardless of the aspect ratio. However, none of the existing models except the Wilson formula can accurately estimate the bootstrap current fraction for the reversed shear tokamaks, which is promising for the advanced tokamak operation mode
International Nuclear Information System (INIS)
A procedure is described by which plutonium and americium can be determined in environmental samples. The sample is leached with nitric acid and hydrogen peroxide, and the two elements are co-precipitated with ferric hydroxide and calcium oxalate. The calcium oxalate is incinerated at 4500 and the ash is dissolved in nitric acid. Plutonium is extracted with tri-n-octylamine solution in xylene from 4M nitric acid and stripped with ammonium iodide/hydrochloric acid. Americium is extracted with thenoyltrifluoroacetone solution in xylene at pH 4 together with rare-earth elements and stripped with 1M nitric acid. Americium and the rare-earth elements thus separated are sorbed on Dowex 1 x 4 resin from 1M nitric acid in 93% methanol, the rare-earth elements are eluted with 0.1M hydrochloric acid/0.5M ammonium thiocyanate/80% methanol and the americium is finally eluted with 1.5M hydrochloric acid in 86% methanol. Plutonium and americium in each fraction are electro-deposited and determined by alpha-spectrometry. Overall average recoveries are 81% for plutonium and 59% for americium. (author)
de Santana, Fernanda A; Portugal, Lindomar A; Serra, Antonio M; Ferrer, Laura; Cerdà, Víctor; Ferreira, Sergio L C
2016-08-15
This paper proposed a multisyringe flow injection analysis (MSFIA) system for antimony, arsenic and selenium determination in peanut samples by hydride generation atomic fluorescence spectrometry (HG-AFS). The optimization step of the hydride generation was performed using a two-level full factorial design involving the parameters: hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations. So, using the chemical conditions optimized, this method allows the determination of these elements employing the external calibration technique using aqueous standards with limits of detection and quantification of 0.04 and 0.14µgL(-1) for antimony, 0.04 and 0.14µgL(-1) for arsenic and 0.14 and 0.37µgL(-1) for selenium, respectively. Additionally, the effect of vanadium, chromium, cobalt, nickel, zinc, copper, iron and molybdenum on the generation of chemical vapour was also studied. The precision expressed as relative standard deviation varied from 1.2 to 3.6% for antimony, 1.8-3.9% for arsenic and 1.8-2% for selenium. The accuracy for arsenic and selenium was confirmed using the certified peach leaves reference material SRM 1547 produced by National Institute of Standard and Technology. The proposed method showed 45 injection throughput (h(-1)) using 1.6mL sample volume for each element, 0.8mL NaBH4 0.5% (w/v) containing NaOH 0.05% (w/v), 0.8mL HCl 5M and 0.4mL KI 14% (w/v) containing L-ascorbic acid 2.5% (w/v). The method was applied to the determination of antimony, arsenic and selenium in peanut samples, which were firstly lyophilized and afterward digested using microwave assisted radiation. Six samples were analyzed and the contents of the elements found were: 28.7-41.3µgkg(-1) for arsenic, 86.4-480.1µgkg(-1) for selenium and 32.6-52.4µgkg(-1) for antimony. Addition/recovery tests were also performed to confirm the method accuracy for the three elements. PMID:27260431
Confidence Intervals for the Mean: To Bootstrap or Not to Bootstrap
Calzada, Maria E.; Gardner, Holly
2011-01-01
The results of a simulation conducted by a research team involving undergraduate and high school students indicate that when data is symmetric the student's "t" confidence interval for a mean is superior to the studied non-parametric bootstrap confidence intervals. When data is skewed and for sample sizes n greater than or equal to 10, the results…
International Nuclear Information System (INIS)
Radiation dose for various techniques have been derived from the literature and are presented in a table (equivalent dose for kidney, whole body, ovary, thyroid of mother and fetus). Calculation of the increase in the gentically significant dose to all pregnant women in 1977 produces a value of 0.196 mrem/year for the D.D.R.. In our opinion this could be reduced to 20% if the indications for the examination are strictly defined by the gynaecologists. Compared with X-ray diagnostic irradiation, the increase in the gentically significant dose of 0.0392 mrem/year would then be very small. This confirms that suitable methods for determining disturbances of renal function can be used during the pregnancy if the risk of failing to make a diagnosis is balanced against the risk of the radiation. (orig.)
International Nuclear Information System (INIS)
A novel diffusion method was used for preparation of NH4+- and NO3--N samples from soil extracts for 15N determination. Ammonium, and nitrate following reduction to ammonia, are allowed to diffuse to an acid-wetted glass filter enclosed in polytetrafluoroethylene tape. The method was evaluated with simulated soil extracts obtained using 50 ml of 2 M potassium chloride solution containing 130 μg of NH4=-N (2.3 atom% 15N) and 120 μg of NO3--N (natural 15N abundance). No cross-over in the 15N abundances of NH4+-N and NO3--N was observed, indicating a quantitative diffusion process (72 h, 25 deg C). Owing to the presence of inorganic nitrogen impurities in the potassium chloride, the 15N enrichments should be corrected for the blank nitrogen content. (author). 8 refs.; 1 tab
Naghshineh, Mahsa; Larsen, Jan; Georgiou, Constantinos; Olsen, Karsten
2016-08-01
A novel method for automated determination pectin degree of esterification (DE) using micro sequential injection lab-on-valve (μSI-LOV) system is developed. A face-centered central composite response surface methodology (RSM) was used to optimise system parameters. A calibration graph for determination of non-esterified galacturonic acid (GalA) content in pectin solutions with linear range of 0.08-0.34% (w/v) and the limit of detection (LOD) of 0.057% (w/v) under optimal condition was achieved. The difference between concentrations (w/v, %) of total GalA and non-esterified GalA was applied to estimate DE (%) of pectin samples. Results indicated a good agreement (tstat
Peña-Vázquez, E.; Barciela-Alonso, M. C.; Pita-Calvo, C.; Domínguez-González, R.; Bermejo-Barrera, P.
2015-09-01
The objective of this work is to develop a method for the determination of metals in saline matrices using high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Module SFS 6 for sample injection was used in the manual mode, and flame operating conditions were selected. The main absorption lines were used for all the elements, and the number of selected analytical pixels were 5 (CP±2) for Cd, Cu, Fe, Ni, Pb and Zn, and 3 pixels for Mn (CP±1). Samples were acidified (0.5% (v/v) nitric acid), and the standard addition method was used for the sequential determination of the analytes in diluted samples (1:2). The method showed good precision (RSD(%) < 4%, except for Pb (6.5%)) and good recoveries. Accuracy was checked after the analysis of an SPS-WW2 wastewater reference material diluted with synthetic seawater (dilution 1:2), showing a good agreement between certified and experimental results.
International Nuclear Information System (INIS)
Highlights: ► Drop-in-plug micro-extraction based on SI-LAV platform for metal preconcentration. ► Automatic liquid phase micro-extraction coupled with FAAS. ► Organic solvents with density higher than water are used. ► Lead determination in environmental water and urine samples. -- Abstract: A novel automatic on-line liquid phase micro-extraction method based on drop-in-plug sequential injection lab-at-valve (LAV) platform was proposed for metal preconcentration and determination. A flow-through micro-extraction chamber mounted at the selection valve was adopted without the need of sophisticated lab-on-valve components. Coupled to flame atomic absorption spectrometry (FAAS), the potential of this lab-at-valve scheme is demonstrated for trace lead determination in environmental and biological water samples. A hydrophobic complex of lead with ammonium pyrrolidine dithiocarbamate (APDC) was formed on-line and subsequently extracted into an 80 μL plug of chloroform. The extraction procedure was performed by forming micro-droplets of aqueous phase into the plug of the extractant. All critical parameters that affect the efficiency of the system were studied and optimized. The proposed method offered good performance characteristics and high preconcentration ratios. For 10 mL sample consumption an enhancement factor of 125 was obtained. The detection limit was 1.8 μg L−1 and the precision expressed as relative standard deviation (RSD) at 50.0 μg L−1 of lead was 2.9%. The proposed method was evaluated by analyzing certified reference materials and applied for lead determination in natural waters and urine samples
顺序注射尿碘测定仪的研制及应用%Sequential Injection Instrument for Determination of Urine Iodine
Institute of Scientific and Technical Information of China (English)
刘颖; 张榕; 布伟静; 唐洁冰; 陈珊; 刘立侠
2009-01-01
An iodine analysis instrument with sequential injection of urine samples was developed. A method for measurement of urine iodine was also developed by combining sequential injection and catalysis kinetics,and making use of catalysis facilitation of the iodine in the redox reaction of As~(3+) and Ce~(4+) . The sequential injection and stopped-flow stabilization determination were made possible by the program-controlled injector with controlled flow rate and the 16-hole program-controlled selection valves. The arsenic-cerium reaction with iodine-catalyzed at constant temperature state might proceed with the constant temperature flow cell. Using the syringes with program-controlled velocity,pushing and suction,Using the digital connected circuit and micro-iodine determination software,the reaction temperature of (32.0±0.1)℃,injection time of 45 s,stabilization time of 60 s,detection time of 20 s,injection volume of 400μL,linear range of 15 -600μg/L,detecting limitation of 5.01 μg/L(n=11) and recovery rate of 94. 1 % - 105. 1 % were obtained. With this method,the detecting result of the National Standard Reference (GBW09109 and GBW09110) materials was within a given standard range. Through this method,the detecting results had no significant differences comparing with those by standard method of National Health Service(P >0.05).%研制了一种顺序注射尿碘分析仪,将顺序注射技术与催化动力学分析相结合,利用碘对砷-铈氧化还原反应的催化作用,建立了顺序注射尿碘测定方法.采用流速和推吸可控的程控注射器及16孔程控选择阀,实现了顺序注射进样和停留稳态测量.恒温流动池使碘催化的砷-铈反应可以在恒温状态下进行.应用自行设计的微机接口电路和尿碘测定的应用软件,控制反应温度(32.0±0.1)℃,流动配送时间45 s,停流稳定时间60 s,停流检测时间20 s,进样量400 μL.本方法线性范围为15～600 μg/L,检出限为5.01 μg/L(n=11),
High βp bootstrap tokamak reactor
International Nuclear Information System (INIS)
Basic characteristics of a steady state tokamak fusion reactor is presented. The minimum required energy multiplication factor Q is found to be 20 to 30 for the feasibility of the fusion reactor. Such a high Q steady state tokamak operation is possible, within our present knowledge of the operational constraints and the current drive physics, when a large fraction of the plasma current is carried by the bootstrap current. Operation at high βp (≥2.0) and high qψ (=4-5) with relatively small εβp (3) and fusion output power (2.5 GW) and is consistent with the present knowledges of the plasma physics of the tokamak, namely the Troyon limit, the energy confinement scalings, the bootstrap current, the current drive efficiency (NB current drive with the total power of 70 MW and the beam energy of 1 MeV) with a favorable aspect on the formation of the cold and dense diverter plasma-condition. From the economical aspect of the tokamak fusion reactor, a more compact reactor is favorable. The use of the high field magnet with Bmax = 16T (for example Ti-doped Nb3Sn conductor) enables to reduce the total machine size to 50% of the above-described conventional design, namely Rp = 7m, Vp = 760m-3, PF = 2.8 GW. (author)
Physics issues of high bootstrap current tokamaks
International Nuclear Information System (INIS)
Physics issues of a tokamak plasma with a hollow current profile produced by a large bootstrap current are discussed based on experiments in JT-60U. An internal transport barrier for both ions and electrons was obtained just inside the radius of zero magnetic shear in JT-60U. Analysis of the toroidal ITG microinstability by toroidal particle simulation shows that weak and negative shear reduces the toroidal coupling and suppresses the ITG mode. A hard beta limit was observed in JT-60U negative shear experiments. Ideal MHD mode analysis shows that the n = 1 pressure-driven kink mode is a plausible candidate. One of the methods to improve the beta limit against the kink mode is to widen the negative shear region, which can induce a broader pressure profile resulting in a higher beta limit. The TAE mode for the hollow current profile is less unstable than that for the monotonic current profile. The reason is that the continuum gaps near the zero shear region are not aligned when the radius of qmin is close to the region of high ∇ne. Finally, a method for stable start-up for a plasma with a hollow current profile is describe, and stable sustainment of a steady-state plasma with high bootstrap current is discussed. (Author)
Boundary and Interface CFTs from the Conformal Bootstrap
Gliozzi, F; Meineri, M; Rago, A
2015-01-01
We explore some consequences of the crossing symmetry for defect conformal field theories, focusing on codimension one defects like flat boundaries or interfaces. We study surface transitions of the 3d Ising and other O(N) models through numerical solutions to the crossing equations with the method of determinants. In the extraordinary transition, where the low-lying spectrum of the surface operators is known, we use the bootstrap equations to obtain information on the bulk spectrum of the theory. In the ordinary transition the knowledge of the low-lying bulk spectrum allows to calculate the scale dimension of the relevant surface operator, which compares well with known results of two-loop calculations in 3d. Estimates of various OPE coefficients are also obtained. We also analyze in 4-epsilon dimensions the renormalization group interface between the O(N) model and the free theory and check numerically the results in 3d.
International Nuclear Information System (INIS)
A sequential analytical method for the determination of U-238, U-234, Th-232, Th-230, Th-228, Ra-226 and Ra-228 in environmental samples and applied to the analysis of mineral waters is studied. Thorium isotopes are coprecipitated with lanthanium fluoride before counting in alpha spectrometer, the uranium isotopes are determined by alpha spectrometry following extraction with TOPO onto a polymenic membrane. Radium-226 is determined with the radom emanation technique. (M.J.C.)
DEFF Research Database (Denmark)
Long, Xiangbao; Hansen, Elo Harald; Miró, Manuel
2005-01-01
The analytical performance of an on-line sequential injection lab-on-valve (SI-LOV) system using chelating Sepharose beads as sorbent material for the determination of ultra trace levels of Cd(II), Pb(II) and Ni(II) by electrothermal atomic absorption spectrometry (ETAAS) is described and discussed...
MHD stability of ITER H-mode confinement with pedestal bootstrap current effects taken into account
Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.; Mahajan, S. M.; Hatch, D.; Liu, X.
2015-11-01
We have shown that the bootstrap current can have significant effects both on tokamak equilibrium and stability (Nucl. Fusion 53, 063009 (2013)). For ITER H-mode discharges pedestal density is low and consequently bootstrap current is large. We reconstruct numerically ITER equilibria with bootstrap current taken into account. Especially, we have considered a more realistic scenario in which density and temperature profiles can be different. The direct consequence of bootstrap current effects on equilibrium is the modification of local safety factor profile at pedestal. This results in a dramatic change of MHD mode behavior. The stability of ITER numerical equilibria is investigated with AEGIS code. Both low-n and peeling-ballooning modes are investigated. Note that pressure gradient at pedestal is steep. High resolution computation is needed. Since AEGIS code is an adaptive code, it can well handle this problem. Also, the analytical continuation technique based on the Cauchy-Riemann condition of dispersion relation is applied, so that the marginal stability conditions can be determined. Both numerical scheme and results will be presented. The effects of different density and temperature profiles on ITER H-mode discharges will be discussed. This research is supported by U. S. Department of Energy, Office of Fusion Energy Science: Grant No. DE-FG02-04ER-54742.
On the Bootstrap of $U$ and $V$ Statistics
Arcones, Miguel A.; Gine, Evarist
1992-01-01
Bootstrap distributional limit theorems for $U$ and $V$ statistics are proved. They hold a.s., under weak moment conditions and without restrictions on the bootstrap sample size (as long as it tends to $\\infty$), regardless of the degree of degeneracy of $U$ and $V$. A testing procedure based on these results is outlined.
MHD equilibrium property with bootstrap current in heliotron plasmas
International Nuclear Information System (INIS)
We study the properties of MHD equilibrium with self-consistent bootstrap current for a heliotron type device. We show the possibility that MHD equilibrium beta limit with consistent bootstrap current might significantly decrease in the low collisional regime comparing with currentless case depending on the vertical field control methods in finite beta and magnetic configurations. (author)
On bootstrap sample size in extreme value theory
J.L. Geluk (Jaap); L.F.M. de Haan (Laurens)
2002-01-01
textabstractIt has been known for a long time that for bootstrapping the probability distribution of the maximum of a sample consistently, the bootstrap sample size needs to be of smaller order than the original sample size. See Jun Shao and Dongsheng Tu (1995), Ex. 3.9,p. 123. We show that the same
Bootstrap Estimates of Standard Errors in Generalizability Theory
Tong, Ye; Brennan, Robert L.
2007-01-01
Estimating standard errors of estimated variance components has long been a challenging task in generalizability theory. Researchers have speculated about the potential applicability of the bootstrap for obtaining such estimates, but they have identified problems (especially bias) in using the bootstrap. Using Brennan's bias-correcting procedures…
Using Commonly Available Software for Conducting Bootstrap Analyses.
Fan, Xitao
Bootstrap analysis, both for nonparametric statistical inference and for describing sample results stability and replicability, has been gaining prominence among quantitative researchers in educational and psychological research. Procedurally, however, it is often quite a challenge for quantitative researchers to implement bootstrap analysis in…
Unbiased Estimates of Variance Components with Bootstrap Procedures
Brennan, Robert L.
2007-01-01
This article provides general procedures for obtaining unbiased estimates of variance components for any random-model balanced design under any bootstrap sampling plan, with the focus on designs of the type typically used in generalizability theory. The results reported here are particularly helpful when the bootstrap is used to estimate standard…
Bootstrapping and Bartlett corrections in the cointegrated VAR model
P.H. Omtzigt; S. Fachin
2003-01-01
The small sample properties of tests on long-run coefficients in cointegrated systems are still a matter of concern to applied econometricians. We compare the performance of the Bartlett correction, the bootstrap and the fast double bootstrap for tests on ccointegration parameters in the maximum lik
A nonparametric hypothesis test via the Bootstrap resampling
Temel, Tugrul
2011-01-01
This paper adapts an already existing nonparametric hypothesis test to the bootstrap framework. The test utilizes the nonparametric kernel regression method to estimate a measure of distance between the models stated under the null hypothesis. The bootstraped version of the test allows to approximate errors involved in the asymptotic hypothesis test. The paper also develops a Mathematica Code for the test algorithm.
Learning web development with Bootstrap and AngularJS
Radford, Stephen
2015-01-01
Whether you know a little about Bootstrap or AngularJS, or you're a complete beginner, this book will enhance your capabilities in both frameworks and you'll build a fully functional web app. A working knowledge of HTML, CSS, and JavaScript is required to fully get to grips with Bootstrap and AngularJS.
International Nuclear Information System (INIS)
An automated sequential injection (SI) method for the determination of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in freshwaters is presented. For DIC measurement on-line sample acidification (sulphuric acid, pH 2 which subsequently diffused through a PTFE membrane into a basic, cresol red acceptor stream. The CO2 increased the concentration of the acidic form of the cresol red indicator, with a resultant decrease in absorbance at 570 nm being directly proportional to DIC concentration. DIC + DOC was determined after on-line sample irradiation (15 W low power UV lamp) coupled with acid-peroxydisulfate digestion, with the subsequent detection of CO2 as described above. DOC was determined by subtraction of DIC from (DIC + DOC). Analytical figures of merit were linear ranges of 0.05-5.0 mg C L-1 for both DIC and DIC + DOC, with typical R.S.D.s of less than 7% (0.05 mg C L-1-5.3% for DIC and 6.6% for DIC + DOC; 4.0 mg C L-1-2.6% for DIC and 2.4% for DIC + DOC, n = 3) and an LOD (blank + 3S.D.) of 0.05 mg C L-1. Sample throughput for the automated system was 8 h-1 for DIC and DOC with low reagent consumption (acid/peroxydisulfate 200 μL per DIC + DOC analysis). A range of model carbon compounds and Tamar River (Plymouth, UK) samples were analysed for DIC and DOC and the results showed good agreement with a high temperature catalytic oxidation (HTCO) reference method (t-test, P = 0.05)
Qiao, Jixin; Hou, Xiaolin; Roos, Per; Miró, Manuel
2009-10-01
This article presents an automated method for the rapid determination of 239Pu and 240Pu in various environmental samples. The analytical method involves the in-line separation of Pu isotopes using extraction chromatography (TEVA) implemented in a sequential injection (SI) network followed by detection of isolated analytes with inductively coupled plasma mass spectrometry (ICP-MS). The method has been devised for the determination of Pu isotopes at environmentally relevant concentrations, whereby it has been successfully applied to the analyses of large volumes/amounts of samples, for example, 100-200 g of soil and sediment, 20 g of seaweed, and 200 L of seawater following analyte preconcentration. The investigation of the separation capability of the assembled SI system revealed that up to 200 g of soil or sediment can be treated using a column containing about 0.70 g of TEVA resin. The analytical results of Pu isotopes in the reference materials showed good agreement with the certified or reference values at the 0.05 significance level. Chemical yields of Pu ranged from 80 to 105%, and the decontamination factors for uranium, thorium, mercury and lead were all above 10(4). The duration of the in-line extraction chromatographic run was <1.5 h, and the proposed setup was able to handle up to 20 samples (14 mL each) in a fully automated mode using a single chromatographic column. The SI manifold is thus suitable for rapid and automated determination of Pu isotopes in environmental risk assessment and emergency preparedness scenarios. PMID:19722516
Lu, Dasheng; Lin, Yuanjie; Feng, Chao; Wang, Dongli; Qiu, Xinlei; Jin, Yu'e; Xiong, Libei; Jin, Ying; Wang, Guoquan
2014-01-15
A new method was developed to determine polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in fishery and aquaculture products. Samples were extracted by an accelerated solvent extraction system and cleaned up by sequential solid phase extraction (SPE) including dispersive SPE (D-SPE) and tandem SPE. PBDEs and PCBs were analyzed by a large-volume injection gas chromatography triple quadrupole mass spectrometry (LVI-GC-QqQ-MS/MS). Good linearity (R(2)≥0.9958) was achieved. Method detection limits (MDLs) were 0.16-3.3pgg(-1) (wet weight, ww) for PBDEs and 0.13-0.97pgg(-1)ww for PCBs. Mean recoveries were 60-140% with relative standard deviations (RSDs) of less than 20% in weever fish, scallop and shrimp samples spiked at a lower level of 13-31pgg(-1)ww and a higher level of 50-125pgg(-1)ww. Certified reference materials were analyzed with acceptable results. The method reduced solvent consumption, analytical time and labor, and is suitable for the routine analysis of PBDEs and PCBs in fishery and aquaculture products. PMID:24321764
International Nuclear Information System (INIS)
A new sequential method for the determination of both natural (U, Th) and anthropogenic (Sr, Cs, Pu, Am) radionuclides has been developed for application to soil and sediment samples. The procedure was optimised using a reference sediment (IAEA-368) and reference soils (IAEA-375 and IAEA-326). Reference materials were first digested using acids (leaching), 'total' acids on hot plate, and acids in microwave in order to compare the different digestion technique. Then, the separation and purification were made by anion exchange resin and selective extraction chromatography: Transuranic (TRU) and Strontium (SR) resins. Natural and anthropogenic alpha radionuclides were separated by Uranium and Tetravalent Actinide (UTEVA) resin, considering different acid elution medium. Finally, alpha and gamma semiconductor spectrometer and liquid scintillation spectrometer were used to measure radionuclide activities. The results obtained for strontium-90, cesium-137, thorium-232, uranium- 238, plutonium-239+240 and americium-241 isotopes by the proposed method for the reference materials provided excellent agreement with the recommended values and good chemical recoveries. (authors)
Ding, Jun; Mao, Li-Jing; Guo, Ning; Yu, Lei; Feng, Yu-Qi
2016-05-13
In this study, a sequential magnetic solid phase extraction followed by in situ derivatization/desorption method was proposed for the fast, selective and sensitive determination of brassinosteroids (BRs) in plant tissues. Magnetic sorbent for quick, easy, cheap, effective, rugged and safe method (mQuEChERS) and polymer(4-vinylphenylboronic acid-co-ethylene glycol dimethacrylate) coated Fe3O4@SiO2 (p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2) were prepared and characterized. Using them as sorbents, pigments and hydrophilic interferents were firstly removed from plant extract by mQuEChERS, and then endogenous BRs were selectively enriched by p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 through boronate affinity interaction. After loading BRs on p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2, instead of directly eluting free BRs, the adsorbed BRs were released by adding 4-(N,N-dimethyamino)phenylboronic acid (4-DMAPBA) solution for in situ derivatizaiton/desorption of BRs based on a transesterification reaction between the boronate moieties of p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 and 4-DMAPBA, finally the resultant solution was submitted to LC-MS/MS for quantification. The whole procedure of the sequential MSPE could be accomplished within 1h, and the matrix effect to MS signal after the sample pretreatment was estimated to be in the range of 93.0-97.4%. The established method provided broad linear dynamics ranges (1.0-100.0pg/mL) with correlation coefficients (R) >0.9978, substantial sensitivity (limits of detection ranged from 0.27 to 1.29pg/mL), high reproducibility (intra-day and inter-day relative standard deviations (RSDs) less than 14.8%) and satisfactory accuracy (recoveries ranged from 74.0%-116.6%). Furthermore, endogenous BRs were successfully detected in one flower of Brassica napus L. (22.5-542.7pg/g fresh weight) and other plant tissues (13.7-289.8pg/g fresh weight). PMID:27072523
Change-point in stochastic design regression and the bootstrap
Seijo, Emilio
2011-01-01
In this paper we study the consistency of different bootstrap procedures for constructing confidence intervals (CIs) for the unique jump discontinuity (change-point) in an otherwise smooth regression function in a stochastic design setting. This problem exhibits nonstandard asymptotics and we argue that the standard bootstrap procedures in regression fail to provide valid confidence intervals for the change-point. We propose a version of smoothed bootstrap, illustrate its remarkable finite sample performance in our simulation study, and prove the consistency of the procedure. The $m$ out of $n$ bootstrap procedure is also considered and shown to be consistent. We also provide sufficient conditions for any bootstrap procedure to be consistent in this scenario.
Hilmer, Christiana E.; Holt, Matthew T.
2000-01-01
This paper compares the finite sample performance of subsample bootstrap and subsample jackknife techniques to the traditional bootstrap method when parameters are constrained to be on some boundary. To assess how these three methods perform in an empirical application, a negative semi-definite translog cost function is estimated using U.S. manufacturing data.
Energy Technology Data Exchange (ETDEWEB)
Injang, Uthaitip; Noyrod, Peeyanun [Sensor Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Siangproh, Weena [Department of Chemistry, Faculty of Science, Srinakharinwirot University, Sukumvit 23 Rd., Wattana, Bangkok 10110 (Thailand); Dungchai, Wijitar [Sensor Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Motomizu, Shoji [Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530 (Japan); Chailapakul, Orawon, E-mail: corawon@chula.ac.th [Sensor Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand)
2010-05-23
A method for the simultaneous determination of Pb(II), Cd(II), and Zn(II) at low {mu}g L{sup -1} concentration levels by sequential injection analysis-anodic stripping voltammetry (SIA-ASV) using screen-printed carbon nanotubes electrodes (SPCNTE) was developed. A bismuth film was prepared by in situ plating of bismuth on the screen-printed carbon nanotubes electrode. Operational parameters such as ratio of carbon nanotubes to carbon ink, bismuth concentration, deposition time and flow rate during preconcentration step were optimized. Under the optimal conditions, the linear ranges were found to be 2-100 {mu}g L{sup -1} for Pb(II) and Cd(II), and 12-100 {mu}g L{sup -1} for Zn(II). The limits of detection (S{sub bl}/S = 3) were 0.2 {mu}g L{sup -1} for Pb(II), 0.8 {mu}g L{sup -1} for Cd(II) and 11 {mu}g L{sup -1} for Zn(II). The measurement frequency was found to be 10-15 stripping cycle h{sup -1}. The present method offers high sensitivity and high throughput for on-line monitoring of trace heavy metals. The practical utility of our method was also demonstrated with the determination of Pb(II), Cd(II), and Zn(II) by spiking procedure in herb samples. Our methodology produced results that were correlated with ICP-AES data. Therefore, we propose a method that can be used for the automatic and sensitive evaluation of heavy metals contaminated in herb items.
Thorn, Graeme J; King, John R
2016-01-01
The Gram-positive bacterium Clostridium acetobutylicum is an anaerobic endospore-forming species which produces acetone, butanol and ethanol via the acetone-butanol (AB) fermentation process, leading to biofuels including butanol. In previous work we looked to estimate the parameters in an ordinary differential equation model of the glucose metabolism network using data from pH-controlled continuous culture experiments. Here we combine two approaches, namely the approximate Bayesian computation via an existing sequential Monte Carlo (ABC-SMC) method (to compute credible intervals for the parameters), and the profile likelihood estimation (PLE) (to improve the calculation of confidence intervals for the same parameters), the parameters in both cases being derived from experimental data from forward shift experiments. We also apply the ABC-SMC method to investigate which of the models introduced previously (one non-sporulation and four sporulation models) have the greatest strength of evidence. We find that the joint approximate posterior distribution of the parameters determines the same parameters as previously, including all of the basal and increased enzyme production rates and enzyme reaction activity parameters, as well as the Michaelis-Menten kinetic parameters for glucose ingestion, while other parameters are not as well-determined, particularly those connected with the internal metabolites acetyl-CoA, acetoacetyl-CoA and butyryl-CoA. We also find that the approximate posterior is strongly non-Gaussian, indicating that our previous assumption of elliptical contours of the distribution is not valid, which has the effect of reducing the numbers of pairs of parameters that are (linearly) correlated with each other. Calculations of confidence intervals using the PLE method back this up. Finally, we find that all five of our models are equally likely, given the data available at present. PMID:26561777
International Nuclear Information System (INIS)
Full text: This paper presents an automated analytical method for the rapid and simultaneous determination of Pu and Np in the environmental samples. Anion exchange chromatographic column was incorporated in a sequential injection system to actualize the automated separation of Pu isotpes along with 237Np from the matrix elements and interfering radionuclides. K2S2O5-conc. HNO3 was applied as redox reagents for the valence adjustment and stabilization of Pu(IV) and Np(IV). 242Pu preformed well as a tracer for both Pu isotopes and 237Np. It was observed that the cross-link and particle size of the resins had significant effluence on the separation efficiency and anion exchange resin Bio-Rad AG 1 x 4 with the particle size of 100-200 mesh was chosen as the optimum. The investigation on the capacity showed small-sized column packed with 2mL resin sufficed up to 50g of soil sample, which provides an advantage of low consumption of the resin and low generation of acid waste after the column washing. The analytical results for Pu and Np in three reference materials showed good agreement with the certified or reference values at the 0.05 significance level. Chemical yields of Pu and Np equally range from 80% to 100%, and the decontamination factors for uranium, thorium and lead were in the range of 103 to 104. The total time of separation for a single sample was < 2.5 hours, which extremely improve the analysis efficiency and reduces the labor intensity, as well as enables a rapid determination of Pu and Np in emergency situations. (author)
Sequential tests for failure detection
International Nuclear Information System (INIS)
The problem of constructing sequential tests for fault detection methods that are based on the concept of Mahalanobis distance is addressed. First the distribution of the Mahalanobis distance that belongs to the degraded (alternative) state of a multivariate system is determined. Then three sequential tests are constructed and their performance investigated for fault detection. For each test, the average sample number and an upper limit for the number of samples necessary so that the test will terminate with a given probability are calculated. (author)
Bootstrap performance profiles in stochastic algorithms assessment
International Nuclear Information System (INIS)
Optimization with stochastic algorithms has become a relevant research field. Due to its stochastic nature, its assessment is not straightforward and involves integrating accuracy and precision. Performance profiles for the mean do not show the trade-off between accuracy and precision, and parametric stochastic profiles require strong distributional assumptions and are limited to the mean performance for a large number of runs. In this work, bootstrap performance profiles are used to compare stochastic algorithms for different statistics. This technique allows the estimation of the sampling distribution of almost any statistic even with small samples. Multiple comparison profiles are presented for more than two algorithms. The advantages and drawbacks of each assessment methodology are discussed
Conformal bootstrap, universality and gravitational scattering
Directory of Open Access Journals (Sweden)
Steven Jackson
2015-12-01
Full Text Available We use the conformal bootstrap equations to study the non-perturbative gravitational scattering between infalling and outgoing particles in the vicinity of a black hole horizon in AdS. We focus on irrational 2D CFTs with large c and only Virasoro symmetry. The scattering process is described by the matrix element of two light operators (particles between two heavy states (BTZ black holes. We find that the operator algebra in this regime is (i universal and identical to that of Liouville CFT, and (ii takes the form of an exchange algebra, specified by an R-matrix that exactly matches the scattering amplitude of 2+1 gravity. The R-matrix is given by a quantum 6j-symbol and the scattering phase by the volume of a hyperbolic tetrahedron. We comment on the relevance of our results to scrambling and the holographic reconstruction of the bulk physics near black hole horizons.
On Bootstrap Percolation in Living Neural Networks
Amini, Hamed
2009-01-01
Recent experimental studies of living neural networks reveal that their global activation induced by electrical stimulation can be explained using the concept of bootstrap percolation on a directed random network. The experiment consists in activating externally an initial random fraction of the neurons and observe the process of firing until its equilibrium. The final portion of neurons that are active depends in a non linear way on the initial fraction. The main result of this paper is a theorem which enables us to find the asymptotic of final proportion of the fired neurons in the case of random directed graphs with given node degrees as the model for interacting network. This gives a rigorous mathematical proof of a phenomena observed by physicists in neural networks.
Vélez, J I; Chandrasekharappa, S C; Henao, E; Martinez, A F; Harper, U; Jones, M.; Solomon, B D; Lopez, L.; G. Garcia; Aguirre-Acevedo, D C; Acosta-Baena, N; Correa, J C; Lopera-Gómez, C M; Jaramillo-Elorza, M C; Rivera, D.
2012-01-01
The literature on GWAS (genome-wide association studies) data suggests that very large sample sizes (for example, 50,000 cases and 50,000 controls) may be required to detect significant associations of genomic regions for complex disorders such as Alzheimer's disease (AD). Because of the challenges of obtaining such large cohorts, we describe here a novel sequential strategy that combines pooling of DNA and bootstrapping (pbGWAS) in order to significantly increase the statistical power and ex...
Bootstrap consistency for general semiparametric M-estimation
Cheng, Guang
2010-10-01
Consider M-estimation in a semiparametric model that is characterized by a Euclidean parameter of interest and an infinite-dimensional nuisance parameter. As a general purpose approach to statistical inferences, the bootstrap has found wide applications in semiparametric M-estimation and, because of its simplicity, provides an attractive alternative to the inference approach based on the asymptotic distribution theory. The purpose of this paper is to provide theoretical justifications for the use of bootstrap as a semiparametric inferential tool. We show that, under general conditions, the bootstrap is asymptotically consistent in estimating the distribution of the M-estimate of Euclidean parameter; that is, the bootstrap distribution asymptotically imitates the distribution of the M-estimate. We also show that the bootstrap confidence set has the asymptotically correct coverage probability. These general onclusions hold, in particular, when the nuisance parameter is not estimable at root-n rate, and apply to a broad class of bootstrap methods with exchangeable ootstrap weights. This paper provides a first general theoretical study of the bootstrap in semiparametric models. © Institute of Mathematical Statistics, 2010.
Anthemidis, Aristidis N; Ioannou, Kallirroy-Ioanna G
2009-06-30
A simple, sensitive and powerful on-line sequential injection (SI) dispersive liquid-liquid microextraction (DLLME) system was developed as an alternative approach for on-line metal preconcentration and separation, using extraction solvent at microlitre volume. The potentials of this novel schema, coupled to flame atomic absorption spectrometry (FAAS), were demonstrated for trace copper and lead determination in water samples. The stream of methanol (disperser solvent) containing 2.0% (v/v) xylene (extraction solvent) and 0.3% (m/v) ammonium diethyldithiophosphate (chelating agent) was merged on-line with the stream of sample (aqueous phase), resulting a cloudy mixture, which was consisted of fine droplets of the extraction solvent dispersed entirely into the aqueous phase. By this continuous process, metal chelating complexes were formed and extracted into the fine droplets of the extraction solvent. The hydrophobic droplets of organic phase were retained into a microcolumn packed with PTFE-turnings. A portion of 300 microL isobutylmethylketone was used for quantitative elution of the analytes, which transported directly to the nebulizer of FAAS. All the critical parameters of the system such as type of extraction solvent, flow-rate of disperser and sample, extraction time as well as the chemical parameters were studied. Under the optimum conditions the enhancement factor for copper and lead was 560 and 265, respectively. For copper, the detection limit and the precision (R.S.D.) were 0.04 microg L(-1) and 2.1% at 2.0 microg L(-1) Cu(II), respectively, while for lead were 0.54 microg L(-1) and 1.9% at 30.0 microg L(-1) Pb(II), respectively. The developed method was evaluated by analyzing certified reference material and applied successfully to the analysis of environmental water samples. PMID:19376348
International Nuclear Information System (INIS)
In order to investigate the behavior and distribution of metallic elements including rare earth elements(REEs), thorium(Th) and uranium(U) in the agricultural field, these elements in agricultural soils were partitioned into 6 fractions by a sequential extraction procedure: water soluble(F1), exchangeable(F2), bound to inorganic matter(F3), bound to organic matter(F4), bound to free oxides(F5) and residual(F6) fractions, and determined for each fraction as well as for total amount. Soil samples were collected from the agricultural field (paddy and upland field) and non-agricultural field in Sakata City (from 2005 to 2010) and Murayama City (from 2008 to 2010) in Yamagata Prefecture, and Sekikawa Village, Iwafune District (from 2007 to 2010) in Niigata Prefecture. Consequently, the following matters have been mainly clarified. (1) The distribution proportion of metallic elements among six fractions of the soils are varied depending on elements and soil utilization(i.e., paddy, upland or no plow). Among REEs, the tendency that the proportion of F5 of heavy-REE(HREE) is generally larger than that of light-REE(LREE) or in middle-REE(MREE) can be found. (2) The differences of REEs concentrations(or REE pattern) of soils are observed among sampling points. It can be related to the nature of soil including the content of Fe-Mn oxides or organic carbon (i.e., the affinity for free oxides or organic matter). (3) The distribution proportion as well as total concentrations of metallic elements in soils are not greatly varied regardless of sampling period(i.e., spring or autumn). (author)
Terol, Javier; Mascarell, Rosario; Fernandez-Pedrosa, Victoria; Pérez-Alonso, Manuel
2002-02-27
Sequencing of the mitochondrial cytochrome b gene has been used to differentiate three tuna species: Thunnus albacares (yellowfin tuna), Thunnus obesus (bigeye tuna), and Katsuwonus pelamis (skipjack). A PCR amplified 528 bp fragment from 30 frozen samples and a 171 bp fragment from 26 canned samples of the three species were analyzed to determine the intraspecific variation and the positions with diagnostic value. Polymorphic sites between the species that did not present intraspecific variation were given a diagnostic value. The genetic distance between the sequences was calculated, and a phylogenetic tree was constructed, showing that the sequences belonging to the same species clustered together. The bootstrap test of confidence was used to determine the statistical validation of the species assignation, allowing for the first time a quantification of the certainty of the species assignation. The bootstrap values obtained from these results indicate that the sequencing of the cytochrome b fragments allows a correct species assignation with a probability > or =95%. PMID:11853465
Properties of bootstrap tests for N-of-1 studies
Lin, Sharon Xiaowen; Morrison, Leanne; Smith, Peter; Hargood, Charlie; Weal, Mark; Yardley, Lucy
2016-01-01
N-of-1 study designs involve the collection and analysis of repeated measures data from an individual not using an intervention and using an intervention. This study explores the use of semi-parametric and parametric bootstrap tests in the analysis of N-of-1 studies under a single time series framework in the presence of autocorrelation. When the Type I error rates of bootstrap tests are compared to Wald tests, our results show that the bootstrap tests have more desirable properties. We compa...
Nonparametric confidence intervals based on extreme bootstrap percentiles
Lee, SMS
2000-01-01
Monte Carlo approximation of standard bootstrap confidence intervals relies on the drawing of a large number, B say, of bootstrap resamples. Conventional choice of B is often made on the order of 1,000. While this choice may prove to be more than sufficient for some cases, it may be far from adequate for others. A new approach is suggested to construct confidence intervals based on extreme bootstrap percentiles and an adaptive choice of B. It economizes on the computational effort in a proble...
International Nuclear Information System (INIS)
Different bootstrap current formulations are implemented in a self-consistent equilibrium calculation obtained from a direct variational technique in fixed boundary tokamak plasmas. The total plasma current profile is supposed to have contributions of the diamagnetic, Pfirsch-Schlueter, and the neoclassical Ohmic and bootstrap currents. The Ohmic component is calculated in terms of the neoclassical conductivity, compared here among different expressions, and the loop voltage determined consistently in order to give the prescribed value of the total plasma current. A comparison among several bootstrap current models for different viscosity coefficient calculations and distinct forms for the Coulomb collision operator is performed for a variety of plasma parameters of the small aspect ratio tokamak ETE (Experimento Tokamak Esferico) at the Associated Plasma Laboratory of INPE, in Brazil. We have performed this comparison for the ETE tokamak so that the differences among all the models reported here, mainly regarding plasma collisionality, can be better illustrated. The dependence of the bootstrap current ratio upon some plasma parameters in the frame of the self-consistent calculation is also analysed. We emphasize in this paper what we call the Hirshman-Sigmar/Shaing model, valid for all collisionality regimes and aspect ratios, and a fitted formulation proposed by Sauter, which has the same range of validity but is faster to compute than the previous one. The advantages or possible limitations of all these different formulations for the bootstrap current estimate are analysed throughout this work. (author)
Energy Technology Data Exchange (ETDEWEB)
Andrade, Maria Celia Ramos; Ludwig, Gerson Otto [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: mcr@plasma.inpe.br
2004-07-01
Different bootstrap current formulations are implemented in a self-consistent equilibrium calculation obtained from a direct variational technique in fixed boundary tokamak plasmas. The total plasma current profile is supposed to have contributions of the diamagnetic, Pfirsch-Schlueter, and the neoclassical Ohmic and bootstrap currents. The Ohmic component is calculated in terms of the neoclassical conductivity, compared here among different expressions, and the loop voltage determined consistently in order to give the prescribed value of the total plasma current. A comparison among several bootstrap current models for different viscosity coefficient calculations and distinct forms for the Coulomb collision operator is performed for a variety of plasma parameters of the small aspect ratio tokamak ETE (Experimento Tokamak Esferico) at the Associated Plasma Laboratory of INPE, in Brazil. We have performed this comparison for the ETE tokamak so that the differences among all the models reported here, mainly regarding plasma collisionality, can be better illustrated. The dependence of the bootstrap current ratio upon some plasma parameters in the frame of the self-consistent calculation is also analysed. We emphasize in this paper what we call the Hirshman-Sigmar/Shaing model, valid for all collisionality regimes and aspect ratios, and a fitted formulation proposed by Sauter, which has the same range of validity but is faster to compute than the previous one. The advantages or possible limitations of all these different formulations for the bootstrap current estimate are analysed throughout this work. (author)
Double bootstrap confidence intervals in the two-stage DEA approach
Chronopoulos, D.K.; Girardone, C.; Nankervis, J.C.
2015-01-01
Contextual factors usually assume an important role in determining firms' productive efficiencies. Nevertheless, identifying them in a regression framework might be complicated. The problem arises from the efficiencies being correlated with each other when estimated by Data Envelopment Analysis, rendering standard inference methods invalid. Simar and Wilson (2007) suggest the use of bootstrap algorithms that allow for valid statistical inference in this context. This article extends their wor...
On a Second-Order Asymptotic Property of the Bayesian Bootstrap Mean
Weng, Chung-Sing
1989-01-01
It is shown that the Bayesian bootstrap approximation to the posterior distribution of the unknown mean (with respect to a Dirichlet process prior) is more accurate than both the standard normal approximation and the bootstrap approximation. It is also shown that the Bayesian bootstrap approximation to the sampling distribution of the sample average is not as accurate as the bootstrap approximation.
Einecke, Sabrina; Bissantz, Nicolai; Clevermann, Fabian; Rhode, Wolfgang
2016-01-01
Astroparticle experiments such as IceCube or MAGIC require a deconvolution of their measured data with respect to the response function of the detector to provide the distributions of interest, e.g. energy spectra. In this paper, appropriate uncertainty limits that also allow to draw conclusions on the geometric shape of the underlying distribution are determined using bootstrap methods, which are frequently applied in statistical applications. Bootstrap is a collective term for resampling methods that can be employed to approximate unknown probability distributions or features thereof. A clear advantage of bootstrap methods is their wide range of applicability. For instance, they yield reliable results, even if the usual normality assumption is violated. The use, meaning and construction of uncertainty limits to any user-specific confidence level in the form of confidence intervals and levels are discussed. The precise algorithms for the implementation of these methods, applicable for any deconvolution algor...
Bootstrap current of fast ions in neutral beam injection heating
International Nuclear Information System (INIS)
The bootstrap current of fast ions produced by the neutral beam injection is investigated in a large aspect ratio tokamak with circular cross-section under specific parameters. The bootstrap current density distribution and the total bootstrap current are figured out. In addition, the beam bootstrap current always accompanies the electron return current due to the parallel momentum transfer from fast ions. With the electron return current considered, the net current density obviously decreases due to electron return current, at the same time the peak of current moves towards the centre plasma. Numerical results show that the value of the net current depends sensitively not only on the angle of the neutral beam injection but also on the ratio of the velocity of fast ions to the critical velocity: the value of net current is small for the neutral beam parallel injection but increases multipliedly for perpendicular injection, and increases with beam energy increasing. (authors)
Bootstrap current of fast ions in neutral beam injection heating
International Nuclear Information System (INIS)
The bootstrap current of fast ions produced by neutral beam injection (NBI) is investigated in a large-aspect-ratio tokamak with circular cross-section under specific parameters. The bootstrap current density distribution and the total bootstrap current are reported. In addition, the beam bootstrap current always accompanies the electron return current due to the parallel momentum transfer from fast ions. With the electron return current taken into consideration, the net current density obviously decreases; at the same time, the peak of the current moves towards the central plasma. Numerical results show that the value of the net current depends sensitively not only on the angle of the NBI but also on the ratio of the velocity of fast ions to the critical velocity: the value of the net current is small for neutral beam parallel injection, but increases severalfold for perpendicular injection, and increases with increasing beam energy. (paper)
Variance estimation in neutron coincidence counting using the bootstrap method
International Nuclear Information System (INIS)
In the study, we demonstrate the implementation of the “bootstrap” method for a reliable estimation of the statistical error in Neutron Multiplicity Counting (NMC) on plutonium samples. The “bootstrap” method estimates the variance of a measurement through a re-sampling process, in which a large number of pseudo-samples are generated, from which the so-called bootstrap distribution is generated. The outline of the present study is to give a full description of the bootstrapping procedure, and to validate, through experimental results, the reliability of the estimated variance. Results indicate both a very good agreement between the measured variance and the variance obtained through the bootstrap method, and a robustness of the method with respect to the duration of the measurement and the bootstrap parameters
Variance estimation in neutron coincidence counting using the bootstrap method
Energy Technology Data Exchange (ETDEWEB)
Dubi, C., E-mail: chendb331@gmail.com [Physics Department, Nuclear Research Center of the Negev, P.O.B. 9001 Beer Sheva (Israel); Ocherashvilli, A.; Ettegui, H. [Physics Department, Nuclear Research Center of the Negev, P.O.B. 9001 Beer Sheva (Israel); Pedersen, B. [Nuclear Security Unit, Institute for Transuranium Elements, Via E. Fermi, 2749 JRC, Ispra (Italy)
2015-09-11
In the study, we demonstrate the implementation of the “bootstrap” method for a reliable estimation of the statistical error in Neutron Multiplicity Counting (NMC) on plutonium samples. The “bootstrap” method estimates the variance of a measurement through a re-sampling process, in which a large number of pseudo-samples are generated, from which the so-called bootstrap distribution is generated. The outline of the present study is to give a full description of the bootstrapping procedure, and to validate, through experimental results, the reliability of the estimated variance. Results indicate both a very good agreement between the measured variance and the variance obtained through the bootstrap method, and a robustness of the method with respect to the duration of the measurement and the bootstrap parameters.
Bootstrapping pre-averaged realized volatility under market microstructure noise
DEFF Research Database (Denmark)
Hounyo, Ulrich; Goncalves, Sílvia; Meddahi, Nour
The main contribution of this paper is to propose a bootstrap method for inference on integrated volatility based on the pre-averaging approach of Jacod et al. (2009), where the pre-averaging is done over all possible overlapping blocks of consecutive observations. The overlapping nature of the pre......-averaged returns implies that these are kn-dependent with kn growing slowly with the sample size n. This motivates the application of a blockwise bootstrap method. We show that the "blocks of blocks" bootstrap method suggested by Politis and Romano (1992) (and further studied by Bühlmann and Künsch (1995)) is...... valid only when volatility is constant. The failure of the blocks of blocks bootstrap is due to the heterogeneity of the squared pre-averaged returns when volatility is stochastic. To preserve both the dependence and the heterogeneity of squared pre-averaged returns, we propose a novel procedure that...
'Bootstrap' Configuration for Multistage Pulse-Tube Coolers
Nguyen, Bich; Nguyen, Lauren
2008-01-01
A bootstrap configuration has been proposed for multistage pulse-tube coolers that, for instance, provide final-stage cooling to temperatures as low as 20 K. The bootstrap configuration supplants the conventional configuration, in which customarily the warm heat exchangers of all stages reject heat at ambient temperature. In the bootstrap configuration, the warm heat exchanger, the inertance tube, and the reservoir of each stage would be thermally anchored to the cold heat exchanger of the next warmer stage. The bootstrapped configuration is superior to the conventional setup, in some cases increasing the 20 K cooler's coefficient of performance two-fold over that of an otherwise equivalent conventional layout. The increased efficiency could translate into less power consumption, less cooler mass, and/or lower cost for a given amount of cooling.
On the range of validity of the autoregressive sieve bootstrap
Kreiss, Jens-Peter; Politis, Dimitris N; 10.1214/11-AOS900
2012-01-01
We explore the limits of the autoregressive (AR) sieve bootstrap, and show that its applicability extends well beyond the realm of linear time series as has been previously thought. In particular, for appropriate statistics, the AR-sieve bootstrap is valid for stationary processes possessing a general Wold-type autoregressive representation with respect to a white noise; in essence, this includes all stationary, purely nondeterministic processes, whose spectral density is everywhere positive. Our main theorem provides a simple and effective tool in assessing whether the AR-sieve bootstrap is asymptotically valid in any given situation. In effect, the large-sample distribution of the statistic in question must only depend on the first and second order moments of the process; prominent examples include the sample mean and the spectral density. As a counterexample, we show how the AR-sieve bootstrap is not always valid for the sample autocovariance even when the underlying process is linear.
Monotonicity-preserving bootstrapped kriging metamodels for expensive simulations
Kleijnen, Jack P.C.; Beers, W.C.M. van
2013-01-01
Kriging (Gaussian process, spatial correlation) metamodels approximate the Input/Output (I/O) functions implied by the underlying simulation models; such metamodels serve sensitivity analysis and optimization, especially for computationally expensive simulations. In practice, simulation analysts often know that the I/O function is monotonic. To obtain a Kriging metamodel that preserves this known shape, this article uses bootstrapping (or resampling). Parametric bootstrapping assuming normali...
Bootstrapped Multinomial Logistic Regression on Apnea Detection Using ECG Data
Sanabila, Hadaiq R.; Fanany, Mohamad Ivan; Jatmiko, Wisnu; Arymurthy, Aniati Murni
2010-01-01
In designing a classification system, one of the most important considerations is how optimal the classifier will adapt and give best generalization when it is given data from unknown model distribution. Unlike linear regression, logistic regression has no simple formula to assess its generalization ability. In such cases, bootstrapping offers an advantage over analytical methods thanks to its simplicity. This paper presents an analysis of bootstrapped multinomial logistic regression appli...
Bootstrap transition to high beta equilibrium in helical system
International Nuclear Information System (INIS)
It is shown theoretically and computationally that helical magnetic field, produced by continuous winding helical coils and without the toroidal coil, can sustain MHD stable high beta plasma. Pressure driven toroidal current (bootstrap current) cancels the external magnetic field and reduces the MHD potential energy, depending on the plasma beta values. Ramp-up of heating power input induces bootstrap transition to higher beta plasmas with flat-top pressure profiles. Helical pitch parameter dependence of MHD stability is analyzed. (author)
Bootstrap current for tokamak plasma with anisotropic electron temperature
International Nuclear Information System (INIS)
The neoclassical bootstrap current for an anisotropic plasma has been studied in a large aspect-ratio tokamak. The enhancement factor due to the temperature anisotropy in the equilibrium electron distribution function is explicitly calculated, and is shown to reach to about 1.5 when the perpendicular temperature is twice as large as the parallel temperature. This bootstrap current is also predicted to have the component proportional to the radial electric field even in an axisymmetric magnetic field. (author)
Bootstrapping the statistical uncertainties of NN scattering data
International Nuclear Information System (INIS)
We use the Monte Carlo bootstrap as a method to simulate pp and np scattering data below pion production threshold from an initial set of over 6700 experimental mutually 3σ consistent data. We compare the results of the bootstrap, with 1020 statistically generated samples of the full database, with the standard covariance matrix method of error propagation. No significant differences in scattering observables and phase shifts are found. This suggests alternative strategies for propagating errors of nuclear forces in nuclear structure calculations
Generalized bootstrap equations and possible implications for the NLO Odderon
Energy Technology Data Exchange (ETDEWEB)
Bartels, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Vacca, G.P. [INFN, Sezione di Bologna (Italy)
2013-07-15
We formulate and discuss generalized bootstrap equations in nonabelian gauge theories. They are shown to hold in the leading logarithmic approximation. Since their validity is related to the self-consistency of the Steinmann relations for inelastic production amplitudes they can be expected to be valid also in NLO. Specializing to the N=4 SYM, we show that the validity in NLO of these generalized bootstrap equations allows to find the NLO Odderon solution with intercept exactly at one.
Bootstrap tests in linear models with many regressors
Patrick Richard
2014-01-01
This paper is concerned with bootstrap hypothesis testing in high dimensional linear regression models. Using a theoretical framework recently introduced by Anatolyev (2012), we show that bootstrap F, LR and LM tests are asymptotically valid even when the numbers of estimated parameters and tested restrictions are not asymptotically negligible fractions of the sample size. These results are derived for models with iid error terms, but Monte Carlo evidence suggests that they extend to the wild...
Bootstrapping and Bartlett corrections in the cointegrated VAR model
Omtzigt, P.H.; Fachin, S.
2002-01-01
The small sample properties of tests on long-run coefficients in cointegrated systems are still a matter of concern to applied econometricians. We compare the performance of the Bartlett correction, the bootstrap and the fast double bootstrap for tests on ccointegration parameters in the maximum likelihood framework. We show by means of a theoretical result and simulations that all three procedures should be based on the unrestricted estimate of the cointegration vectors. The fast double boot...
Spectrum of local boundary operators from boundary form factor bootstrap
Szots, M
2007-01-01
Using the recently introduced boundary form factor bootstrap equations, we map the complete space of their solutions for the boundary version of the scaling Lee-Yang model and sinh-Gordon theory. We show that the complete space of solutions, graded by the ultraviolet behaviour of the form factors can be brought into correspondence with the spectrum of local boundary operators expected from boundary conformal field theory, which is a major evidence for the correctness of the boundary form factor bootstrap framework.
BOOTSTRAP-BASED STATISTICAL THRESHOLDING FOR MEG SOURCE RECONSTRUCTION IMAGES
Sekihara, Kensuke; Sahani, Maneesh; Nagarajan, Srikantan S.
2004-01-01
This paper proposes a bootstrap-based statistical method for extracting target source activities from MEG/EEG source reconstruction results. The method requires measurements in a control condition, which contains only non-target source activities. The method derives, at each pixel location, an empirical probability distribution of the non-target source activity using bootstrapped reconstruction obtained from the control period. The statistical threshold that can extract the target source acti...
On the range of validity of the autoregressive sieve bootstrap
Kreiss, Jens-Peter; Paparoditis, Efstathios; Politis, Dimitris N.
2012-01-01
We explore the limits of the autoregressive (AR) sieve bootstrap, and show that its applicability extends well beyond the realm of linear time series as has been previously thought. In particular, for appropriate statistics, the AR-sieve bootstrap is valid for stationary processes possessing a general Wold-type autoregressive representation with respect to a white noise; in essence, this includes all stationary, purely nondeterministic processes, whose spectral density is everywhere positive....
An Algebraic Approach to the Analytic Bootstrap
Alday, Luis F
2015-01-01
We develop an algebraic approach to the analytic bootstrap in CFTs. By acting with the Casimir operator on the crossing equation we map the problem of doing large spin sums to any desired order to the problem of solving a set of recursion relations. We compute corrections to the anomalous dimension of large spin operators due to the exchange of a primary and its descendants in the crossed channel and show that this leads to a Borel-summable expansion. We analyse higher order corrections to the microscopic CFT data in the direct channel and its matching to infinite towers of operators in the crossed channel. We apply this method to the critical $O(N)$ model. At large $N$ we reproduce the first few terms in the large spin expansion of the known two-loop anomalous dimensions of higher spin currents in the traceless symmetric representation of $O(N)$ and make further predictions. At small $N$ we present the results for the truncated large spin expansion series of anomalous dimensions of higher spin currents.
Bootstrap inference longitudinal semiparametric regression model
Pane, Rahmawati; Otok, Bambang Widjanarko; Zain, Ismaini; Budiantara, I. Nyoman
2016-02-01
Semiparametric regression contains two components, i.e. parametric and nonparametric component. Semiparametric regression model is represented by yt i=μ (x˜'ti,zt i)+εt i where μ (x˜'ti,zt i)=x˜'tiβ ˜+g (zt i) and yti is response variable. It is assumed to have a linear relationship with the predictor variables x˜'ti=(x1 i 1,x2 i 2,…,xT i r) . Random error εti, i = 1, …, n, t = 1, …, T is normally distributed with zero mean and variance σ2 and g(zti) is a nonparametric component. The results of this study showed that the PLS approach on longitudinal semiparametric regression models obtain estimators β˜^t=[X'H(λ)X]-1X'H(λ )y ˜ and g˜^λ(z )=M (λ )y ˜ . The result also show that bootstrap was valid on longitudinal semiparametric regression model with g^λ(b )(z ) as nonparametric component estimator.
Remarks on bootstrap percolation in metric networks
International Nuclear Information System (INIS)
We examine bootstrap percolation in d-dimensional, directed metric graphs in the context of recent measurements of firing dynamics in 2D neuronal cultures. There are two regimes depending on the graph size N. Large metric graphs are ignited by the occurrence of critical nuclei, which initially occupy an infinitesimal fraction, f* → 0, of the graph and then explode throughout a finite fraction. Smaller metric graphs are effectively random in the sense that their ignition requires the initial ignition of a finite, unlocalized fraction of the graph, f* > 0. The crossover between the two regimes is at a size N* which scales exponentially with the connectivity range λ like N* ∼ exp λd. The neuronal cultures are finite metric graphs of size N ≅ 105 - 106, which, for the parameters of the experiment, is effectively random since N *. This explains the seeming contradiction in the observed finite f* in these cultures. Finally, we discuss the dynamics of the firing front
Quantum bootstrapping via compressed quantum Hamiltonian learning
International Nuclear Information System (INIS)
A major problem facing the development of quantum computers or large scale quantum simulators is that general methods for characterizing and controlling are intractable. We provide a new approach to this problem that uses small quantum simulators to efficiently characterize and learn control models for larger devices. Our protocol achieves this by using Bayesian inference in concert with Lieb–Robinson bounds and interactive quantum learning methods to achieve compressed simulations for characterization. We also show that the Lieb–Robinson velocity is epistemic for our protocol, meaning that information propagates at a rate that depends on the uncertainty in the system Hamiltonian. We illustrate the efficiency of our bootstrapping protocol by showing numerically that an 8 qubit Ising model simulator can be used to calibrate and control a 50 qubit Ising simulator while using only about 750 kilobits of experimental data. Finally, we provide upper bounds for the Fisher information that show that the number of experiments needed to characterize a system rapidly diverges as the duration of the experiments used in the characterization shrinks, which motivates the use of methods such as ours that do not require short evolution times. (fast track communication)
Bootstrapping Object Coreferencing on the Semantic Web
Institute of Scientific and Technical Information of China (English)
Wei Hu; Yu-Zhong Qu; Xing-Zhi Sun
2011-01-01
An object on the Semantic Web is likely to be denoted with several URIs by different parties.Object coreferencing is a process to identify "equivalent" URIs of objects for achieving a better Data Web.In this paper,we propose a bootstrapping approach for object coreferencing on the Semantic Web.For an object URI,we firstly establish a kernel that consists of semantically equivalent URIs from the same-as,(inverse) functional properties and (max-)cardinalities,and then extend the kernel with respect to the textual descriptions (e.g.,labels and local names) of URIs.We also propose a trustworthiness-based method to rank the coreferent URIs in the kernel as well as a similarity-based method for ranking the URIs in the extension of the kernel.We implement the proposed approach,called ObjectCoref,on a large-scale dataset that contains 76 million URIs collected by the Falcons search engine until 2008.The evaluation on precision,relative recall and response time demonstrates the feasibility of our approach.Additionally,we apply the proposed approach to investigate the popularity of the URI alias phenomenon on the current Semantic Web.
Tie the straps: Uniform bootstrap con fidence bands for bounded influence curve estimators
Härdle, Wolfgang Karl; Ritov, Ya'Acov; Wang, Weining
2013-01-01
We consider theoretical bootstrap coupling techniques for nonparametric robust smoothers and quantile regression, and verify the bootstrap improvement. To cope with curse of dimensionality, a variant of coupling bootstrap techniques are developed for additive models with both symmetric error distributions and further extension to the quantile regression framework. Our bootstrap method can be used in many situations like constructing con dence intervals and bands. We demonstrate the bootstrap ...
Control of bootstrap current in the pedestal region of tokamaks
International Nuclear Information System (INIS)
The high confinement mode (H-mode) plasmas in the pedestal region of tokamaks are characterized by steep gradient of the radial electric field, and sonic poloidal Up,m flow that consists of poloidal components of the E×B flow and the plasma flow velocity that is parallel to the magnetic field B. Here, E is the electric field. The bootstrap current that is important for the equilibrium, and stability of the pedestal of H-mode plasmas is shown to have an expression different from that in the conventional theory. In the limit where ‖Up,m‖≫ 1, the bootstrap current is driven by the electron temperature gradient and inductive electric field fundamentally different from that in the conventional theory. The bootstrap current in the pedestal region can be controlled through manipulating Up,m and the gradient of the radial electric. This, in turn, can control plasma stability such as edge-localized modes. Quantitative evaluations of various coefficients are shown to illustrate that the bootstrap current remains finite when ‖Up,m‖ approaches infinite and to provide indications how to control the bootstrap current. Approximate analytic expressions for viscous coefficients that join results in the banana and plateau-Pfirsch-Schluter regimes are presented to facilitate bootstrap and neoclassical transport simulations in the pedestal region
Control of bootstrap current in the pedestal region of tokamaks
Energy Technology Data Exchange (ETDEWEB)
Shaing, K. C. [Institute for Space and Plasma Sciences, National Cheng Kung University, Tainan City 70101, Taiwan (China); Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53796 (United States); Lai, A. L. [Institute for Space and Plasma Sciences, National Cheng Kung University, Tainan City 70101, Taiwan (China)
2013-12-15
The high confinement mode (H-mode) plasmas in the pedestal region of tokamaks are characterized by steep gradient of the radial electric field, and sonic poloidal U{sub p,m} flow that consists of poloidal components of the E×B flow and the plasma flow velocity that is parallel to the magnetic field B. Here, E is the electric field. The bootstrap current that is important for the equilibrium, and stability of the pedestal of H-mode plasmas is shown to have an expression different from that in the conventional theory. In the limit where ‖U{sub p,m}‖≫ 1, the bootstrap current is driven by the electron temperature gradient and inductive electric field fundamentally different from that in the conventional theory. The bootstrap current in the pedestal region can be controlled through manipulating U{sub p,m} and the gradient of the radial electric. This, in turn, can control plasma stability such as edge-localized modes. Quantitative evaluations of various coefficients are shown to illustrate that the bootstrap current remains finite when ‖U{sub p,m}‖ approaches infinite and to provide indications how to control the bootstrap current. Approximate analytic expressions for viscous coefficients that join results in the banana and plateau-Pfirsch-Schluter regimes are presented to facilitate bootstrap and neoclassical transport simulations in the pedestal region.
The sharp threshold for bootstrap percolation in all dimensions
Balogh, József; Duminil-Copin, Hugo; Morris, Robert
2010-01-01
In r-neighbour bootstrap percolation on a graph G, a (typically random) set A of initially 'infected' vertices spreads by infecting (at each time step) vertices with at least r already-infected neighbours. This process may be viewed as a monotone version of the Glauber dynamics of the Ising model, and has been extensively studied on the d-dimensional grid $[n]^d$. The elements of the set A are usually chosen independently, with some density p, and the main question is to determine $p_c([n]^d,r)$, the density at which percolation (infection of the entire vertex set) becomes likely. In this paper we prove, for every pair $d \\ge r \\ge 2$, that there is a constant L(d,r) such that $p_c([n]^d,r) = [(L(d,r) + o(1)) / log_(r-1) (n)]^{d-r+1}$ as $n \\to \\infty$, where $log_r$ denotes an r-times iterated logarithm. We thus prove the existence of a sharp threshold for percolation in any (fixed) number of dimensions. Moreover, we determine L(d,r) for every pair (d,r).
Funatsuki, Atsushi; Takaoka, Masaki; Oshita, Kazuyuki; Takeda, Nobuo
2012-01-01
Understanding the chemical state of lead in fly ash generated from a waste thermal treatment is important, since the toxicity and solubility of the element depends on its chemical state. This study identified three potential methods for obtaining quantitative information regarding the chemical state of lead in fly ash: X-ray absorption near edge structure (XANES) analysis, extended X-ray absorption fine structure (EXAFS) analysis, and the sequential extraction procedure. The result of this pr...
A Bootstrap Approach to Martian Manufacturing
Dorais, Gregory A.
2004-01-01
In-Situ Resource Utilization (ISRU) is an essential element of any affordable strategy for a sustained human presence on Mars. Ideally, Martian habitats would be extremely massive to allow plenty of room to comfortably live and work, as well as to protect the occupants from the environment. Moreover, transportation and power generation systems would also require significant mass if affordable. For our approach to ISRU, we use the industrialization of the U.S. as a metaphor. The 19th century started with small blacksmith shops and ended with massive steel mills primarily accomplished by blacksmiths increasing their production capacity and product size to create larger shops, which produced small mills, which produced the large steel mills that industrialized the country. Most of the mass of a steel mill is comprised of steel in simple shapes, which are produced and repaired with few pieces of equipment also mostly made of steel in basic shapes. Due to this simplicity, we expect that the 19th century manufacturing growth can be repeated on Mars in the 21st century using robots as the primary labor force. We suggest a "bootstrap" approach to manufacturing on Mars that uses a "seed" manufacturing system that uses regolith to create major structural components and spare parts. The regolith would be melted, foamed, and sintered as needed to fabricate parts using casting and solid freeform fabrication techniques. Complex components, such as electronics, would be brought from Earth and integrated as needed. These parts would be assembled to create additional manufacturing systems, which can be both more capable and higher capacity. These subsequent manufacturing systems could refine vast amounts of raw materials to create large components, as well as assemble equipment, habitats, pressure vessels, cranes, pipelines, railways, trains, power generation stations, and other facilities needed to economically maintain a sustained human presence on Mars.
Assessment of bootstrap resampling performance for PET data
International Nuclear Information System (INIS)
Bootstrap resampling has been successfully used for estimation of statistical uncertainty of parameters such as tissue metabolism, blood flow or displacement fields for image registration. The performance of bootstrap resampling as applied to PET list-mode data of the human brain and dedicated phantoms is assessed in a novel and systematic way such that: (1) the assessment is carried out in two resampling stages: the ‘real world’ stage where multiple reference datasets of varying statistical level are generated and the ‘bootstrap world’ stage where corresponding bootstrap replicates are generated from the reference datasets. (2) All resampled datasets were reconstructed yielding images from which multiple voxel and regions of interest (ROI) values were extracted to form corresponding distributions between the two stages. (3) The difference between the distributions from both stages was quantified using the Jensen–Shannon divergence and the first four moments. It was found that the bootstrap distributions are consistently different to the real world distributions across the statistical levels. The difference was explained by a shift in the mean (up to 33% for voxels and 14% for ROIs) being proportional to the inverse square root of the statistical level (number of counts). Other moments were well replicated by the bootstrap although for very low statistical levels the estimation of the variance was poor. Therefore, the bootstrap method should be used with care when estimating systematic errors (bias) and variance when very low statistical levels are present such as in early time frames of dynamic acquisitions, when the underlying population may not be sufficiently represented. (paper)
Xu, Kuan-Man
2006-01-01
A new method is proposed to compare statistical differences between summary histograms, which are the histograms summed over a large ensemble of individual histograms. It consists of choosing a distance statistic for measuring the difference between summary histograms and using a bootstrap procedure to calculate the statistical significance level. Bootstrapping is an approach to statistical inference that makes few assumptions about the underlying probability distribution that describes the data. Three distance statistics are compared in this study. They are the Euclidean distance, the Jeffries-Matusita distance and the Kuiper distance. The data used in testing the bootstrap method are satellite measurements of cloud systems called cloud objects. Each cloud object is defined as a contiguous region/patch composed of individual footprints or fields of view. A histogram of measured values over footprints is generated for each parameter of each cloud object and then summary histograms are accumulated over all individual histograms in a given cloud-object size category. The results of statistical hypothesis tests using all three distances as test statistics are generally similar, indicating the validity of the proposed method. The Euclidean distance is determined to be most suitable after comparing the statistical tests of several parameters with distinct probability distributions among three cloud-object size categories. Impacts on the statistical significance levels resulting from differences in the total lengths of satellite footprint data between two size categories are also discussed.
DEFF Research Database (Denmark)
Wang, Jianhua; Hansen, Elo Harald
2001-01-01
A sequential injection system for on-line ion-exchange separation and preconcentration of trace-level amounts of metal ions with ensuing detection by electrothermal atomic absorption spectrometry (ETAAS) is described. Based on the use of a renewable microcolumn incorporated within an integrated l...... the determination of 2.0 mug/l Bi (n = 7). The procedure was validated by determination of bismuth in a certified reference material CRM 320 (river sediment), and by bismuth spike recoveries in two human urine samples....
Improving reliability of genomic predictions for Jersey sires using bootstrap aggregation sampling.
Mikshowsky, Ashley A; Gianola, Daniel; Weigel, Kent A
2016-05-01
Genomic selection has revolutionized the dairy genetics industry and enhanced the rate of response to selection for most economically important traits. All young bulls are now genotyped using commercially available single nucleotide polymorphism arrays to compute genomic predicted transmitting ability (GPTA) and reliability (REL) values. Decisions regarding the purchasing, marketing, and culling of dairy bulls are based on GPTA until roughly 5 yr of age, when milk-recorded offspring become available. At that time, daughter yield deviations (DYD) can be used to assess the accuracy of the GPTA computed several years earlier. Although agreement between predictions and DYD is often good, the DYD of some bulls differ widely from corresponding GPTA, and published REL are of limited value in identifying such bulls. A method of bootstrap aggregation sampling (bagging) using genomic BLUP (GBLUP) was implemented to predict the GPTA of 379, 379, and 342 young Jersey bulls for protein yield, somatic cell score, and daughter pregnancy rate, respectively. For each trait, 50 bootstrap samples from a reference population consisting of 2011 DYD of 1,738, 1,616, and 1,551 older Jersey bulls were used, and correlations between bagged GBLUP predictions and 2014 DYD were lower than GBLUP predictions derived from the full reference population. Although the bagged GBLUP approach did not improve the predictive correlations, it allowed computation of bootstrap predictive reliabilities across random samples of the reference population. The bootstrap predictive reliabilities could be a useful diagnostic tool for assessing genome-enabled prediction systems or evaluating the composition of a reference population. Our main objective was to determine if bagging GBLUP of young Jersey bulls could lead to measures of reliability that would be a useful alternative to published REL values. The standard deviations of bagged GBLUP predictions were found to weakly improve our ability to identify bulls
Institute of Scientific and Technical Information of China (English)
王晖; 刘大有; 等
1994-01-01
In this paper we consider the problem of sequential processing and present a sequential model based on the back-propagation algorithm.This model is intended to deal with intrinsically sequential problems,such as word recognition,speech recognition,natural language understanding.This model can be used to train a network to learn the sequence of input patterns,in a fixed order or a random order.Besides,this model is open- and partial-associative,characterized as “resognizing while accumulating”, which, as we argue, is mental cognition process oriented.
Non-abelian binding energies from the lightcone bootstrap
Li, Daliang; Meltzer, David; Poland, David
2016-02-01
We analytically study the lightcone limit of the conformal bootstrap for 4-point functions containing scalars charged under global symmetries. We show the existence of large spin double-twist operators in various representations of the global symmetry group. We then compute their anomalous dimensions in terms of the central charge C T , current central charge C J , and the OPE coefficients of low dimension scalars. In AdS, these results correspond to the binding energy of two-particle states arising from the exchange of gravitons, gauge bosons, and light scalar fields. Using unitarity and crossing symmetry, we show that gravity is universal and attractive among different types of two-particle states, while the gauge binding energy can have either sign as determined by the representation of the two-particle state, with universal ratios fixed by the symmetry group. We apply our results to 4D {N}=1 SQCD and the 3D O( N) vector models. We also show that in a unitary CFT, if the current central charge C J stays finite when the global symmetry group becomes infinitely large, such as the N → ∞ limit of the O( N) vector model, then the theory must contain an infinite number of higher spin currents.
Non-Abelian Binding Energies from the Lightcone Bootstrap
Li, Daliang; Poland, David
2015-01-01
We analytically study the lightcone limit of the conformal bootstrap for 4-point functions containing scalars charged under global symmetries. We show the existence of large spin double-twist operators in various representations of the global symmetry group. We then compute their anomalous dimensions in terms of the central charge $C_T$, current central charge $C_J$, and the OPE coefficients of low dimension scalars. In AdS, these results correspond to the binding energy of two-particle states arising from the exchange of gravitons, gauge bosons, and light scalar fields. Using unitarity and crossing symmetry, we show that gravity is universal and attractive among different types of two-particle states, while the gauge binding energy can have either sign as determined by the representation of the two-particle state, with universal ratios fixed by the symmetry group. We apply our results to 4D $\\mathcal{N}=1$ SQCD and the 3D O(N) vector models. We also show that in a unitary CFT, if the current central charge $...
More on analytic bootstrap for O( N) models
Dey, Parijat; Kaviraj, Apratim; Sen, Kallol
2016-06-01
This note is an extension of a recent work on the analytical bootstrapping of O( N) models. An additonal feature of the O( N) model is that the OPE contains trace and antisymmetric operators apart from the symmetric-traceless objects appearing in the OPE of the singlet sector. This in addition to the stress tensor ( T μν ) and the ϕ i ϕ i scalar, we also have other minimal twist operators as the spin-1 current J μ and the symmetric-traceless scalar in the case of O( N). We determine the effect of these additional objects on the anomalous dimensions of the corresponding trace, symmetric-traceless and antisymmetric operators in the large spin sector of the O( N) model, in the limit when the spin is much larger than the twist. As an observation, we also verified that the leading order results for the large spin sector from the ɛ-expansion are an exact match with our n = 0 case. A plausible holographic setup for the special case when N = 2 is also mentioned which mimics the calculation in the CFT.
International Nuclear Information System (INIS)
A modified three-step sequential extraction procedure proposed by the Commission of European Communities Bureau of Reference (BCR) was applied to certified reference materials of three different soil groups (rendzina, luvisol, cambisol) and sewage sludge of different composition originating from a municipal water treatment plant in order to assess potential mobility and the distribution of vanadium in the resulting fractions. Analysis of the extracts was carried out by electrothermal atomic absorption spectrometry with Zeeman background correction using transversely heated graphite atomizers. Extracts showed significant matrix interferences which were overcome by the standard addition technique. The original soil and sludge certified reference materials (CRMs) and the extraction residue from the sequential extraction were decomposed by a mixture of HNO3-HClO4-HF in an open system. The content of V determined after decomposition of the samples was in very good agreement with the certified total values. The accuracy of the sequential extraction procedure was checked by comparing the sum of the vanadium contents in the three fractions and in the extraction residue with the certified total content of V. The amounts of vanadium leached were in good correlation with the certified total contents of V in the CRMs of soils and sewage sludge. In the soils examined, vanadium was present almost entirely in the mineral lattice, while in the sewage sludge samples 9-14% was found in the oxidizable and almost 25% in the reducible fractions. The recovery ranged from 93-106% and the precision (RSD) was below 10%
High bootstrap current in RF-heated discharges
International Nuclear Information System (INIS)
Purely non-inductive steady-state discharges in tokamak reactors will require a large bootstrap current, Ibtot, in order to minimize the amounts of power in external current drive systems. In present day tokamaks, high bootstrap current discharges are produced under various conditions. It has been demonstrated that the on-axis RF heatings are good candidates for producing a large bootstrap current, especially the fast magnetosonic wave direct electron heating (FWEH), for which power deposition is centrally peaked. Moreover, the heating and current drive methods using RF waves could be used as external sources to optimize Iboot through the current profile control. In this paper, the dependence of Iboot on the profiles of the plasma density, temperature, pressure and current density is analysed using a theoretical approach with a matrix formulation. Examples of quasi-steady-state discharges with large bootstrap current fraction using FWEH on Tore Supra are given. Examples of high bootstrap current fractions on reverse shear discharges (TFTR, DIII-D, ...) are also mentioned. Purely non-inductive discharges with improved confinement by combination of FWEH and lower hybrid current drive are analysed and the extrapolation to the so-called 'Tore Supra CIEL phase' is reported. (author)
A bootstrap estimation scheme for chemical compositional data with nondetects
Palarea-Albaladejo, J; Martín-Fernández, J.A; Olea, Ricardo A.
2014-01-01
The bootstrap method is commonly used to estimate the distribution of estimators and their associated uncertainty when explicit analytic expressions are not available or are difficult to obtain. It has been widely applied in environmental and geochemical studies, where the data generated often represent parts of whole, typically chemical concentrations. This kind of constrained data is generically called compositional data, and they require specialised statistical methods to properly account for their particular covariance structure. On the other hand, it is not unusual in practice that those data contain labels denoting nondetects, that is, concentrations falling below detection limits. Nondetects impede the implementation of the bootstrap and represent an additional source of uncertainty that must be taken into account. In this work, a bootstrap scheme is devised that handles nondetects by adding an imputation step within the resampling process and conveniently propagates their associated uncertainly. In doing so, it considers the constrained relationships between chemical concentrations originated from their compositional nature. Bootstrap estimates using a range of imputation methods, including new stochastic proposals, are compared across scenarios of increasing difficulty. They are formulated to meet compositional principles following the log-ratio approach, and an adjustment is introduced in the multivariate case to deal with nonclosed samples. Results suggest that nondetect bootstrap based on model-based imputation is generally preferable. A robust approach based on isometric log-ratio transformations appears to be particularly suited in this context. Computer routines in the R statistical programming language are provided.
Genetic Sequential Dynamical Systems
Avino-Diaz, Maria A.; Ortiz, Humberto; Moreno, Oscar
2006-01-01
The whole complex process to obtain a protein encoded by a gene is difficult to include in a mathematical model. There are many models for describing different aspects of a genetic network. Finding a better model is one of the most important and interesting questions in computational biology. Sequential dynamical systems have been developed for a theory of computer simulation, and in this paper, a genetic sequential dynamical system is introduced. A gene is considered to be a function which c...
Deep Sequential Neural Network
Denoyer, Ludovic; Gallinari, Patrick
2014-01-01
Neural Networks sequentially build high-level features through their successive layers. We propose here a new neural network model where each layer is associated with a set of candidate mappings. When an input is processed, at each layer, one mapping among these candidates is selected according to a sequential decision process. The resulting model is structured according to a DAG like architecture, so that a path from the root to a leaf node defines a sequence of transformations. Instead of c...
Institute of Scientific and Technical Information of China (English)
Fang-Ling Tao; Shi-Fan Min; Wei-Jian Wu; Guang-Wen Liang; Ling Zeng
2008-01-01
Taking a published natural population life table office leaf roller, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), as an example, we estimated the population trend index,I, via re-sampling methods (jackknife and bootstrap), determined its statistical properties and illustrated the application of these methods in determining the control effectiveness of bio-agents and chemical insecticides. Depending on the simulation outputs, the smoothed distribution pattern of the estimates of I by delete-1 jackknife is visually distinguishable from the normal density, but the smoothed pattern produced by delete-d jackknife, and logarithm-transformed smoothed patterns produced by both empirical and parametric bootstraps,matched well the corresponding normal density. Thus, the estimates of I produced by delete-1 jackknife were not used to determine the suppressive effect of wasps and insecticides. The 95% percent confidence intervals or the narrowest 95 percentiles and Z-test criterion were employed to compare the effectiveness of Trichogrammajaponicum Ashmead and insecti-cides (powder, 1.5% mevinphos + 3% alpha-hexachloro cyclohexane) against the rice leaf roller based on the estimates of I produced by delete-d jackknife and bootstrap techniques.At α= 0.05 level, there were statistical differences between wasp treatment and control, and between wasp and insecticide treatments, if the normality is ensured, or by the narrowest 95 percentiles. However, there is still no difference between insecticide treatment and control.By Z-test criterion, wasp treatment is better than control and insecticide treatment with P-value＜0.01. Insecticide treatment is similar to control with P-value ＞ 0.2 indicating that 95% confidence intervals procedure is more conservative. Although similar conclusions may be drawn by re-sampling techniques, such as the delta method, about the suppressive effect of trichogramma and insecticides, the normality of the estimates can be checked and guaranteed
Implementation of bootstrap current effects in the PIES code
International Nuclear Information System (INIS)
The PIES code (Princeton Iterative Equilibrium Solver) has been modified to take into account the effects of bootstrap current. A simple bootstrap current model, applicable to tokamaks, is presently being employed. Pressure flattening, caused by the evolution of islands, has an important effect on the bootstrap current, which in turn has an important large effect on the island width. Analytic models have shown that the overall result of this interaction is, for negative shear, a destabilization of the islands. Recently, Chang et al., has shown that good agreement exists between the analytic expression proposed by reference and experiments on TFTR. Approximations used in this analytic expression, such as the expressions for Δ'(w), axe avoided in the calculations done with the PIES code. A comparison of the two results will be presented
Point Set Denoising Using Bootstrap-Based Radial Basis Function
Ramli, Ahmad; Abd. Majid, Ahmad
2016-01-01
This paper examines the application of a bootstrap test error estimation of radial basis functions, specifically thin-plate spline fitting, in surface smoothing. The presence of noisy data is a common issue of the point set model that is generated from 3D scanning devices, and hence, point set denoising is one of the main concerns in point set modelling. Bootstrap test error estimation, which is applied when searching for the smoothing parameters of radial basis functions, is revisited. The main contribution of this paper is a smoothing algorithm that relies on a bootstrap-based radial basis function. The proposed method incorporates a k-nearest neighbour search and then projects the point set to the approximated thin-plate spline surface. Therefore, the denoising process is achieved, and the features are well preserved. A comparison of the proposed method with other smoothing methods is also carried out in this study. PMID:27315105
A Bootstrap Algebraic Multilevel method for Markov Chains
Bolten, M; Brannick, J; Frommer, A; Kahl, K; Livshits, I
2010-01-01
This work concerns the development of an Algebraic Multilevel method for computing stationary vectors of Markov chains. We present an efficient Bootstrap Algebraic Multilevel method for this task. In our proposed approach, we employ a multilevel eigensolver, with interpolation built using ideas based on compatible relaxation, algebraic distances, and least squares fitting of test vectors. Our adaptive variational strategy for computation of the state vector of a given Markov chain is then a combination of this multilevel eigensolver and associated multilevel preconditioned GMRES iterations. We show that the Bootstrap AMG eigensolver by itself can efficiently compute accurate approximations to the state vector. An additional benefit of the Bootstrap approach is that it yields an accurate interpolation operator for many other eigenmodes. This in turn allows for the use of the resulting AMG hierarchy to accelerate the MLE steps using standard multigrid correction steps. The proposed approach is applied to a rang...
Addressing the P2P Bootstrap Problem for Small Networks
Wolinsky, David Isaac; Boykin, P Oscar; Figueiredo, Renato
2010-01-01
P2P overlays provide a framework for building distributed applications consisting of few to many resources with features including self-configuration, scalability, and resilience to node failures. Such systems have been successfully adopted in large-scale services for content delivery networks, file sharing, and data storage. In small-scale systems, they can be useful to address privacy concerns and for network applications that lack dedicated servers. The bootstrap problem, finding an existing peer in the overlay, remains a challenge to enabling these services for small-scale P2P systems. In large networks, the solution to the bootstrap problem has been the use of dedicated services, though creating and maintaining these systems requires expertise and resources, which constrain their usefulness and make them unappealing for small-scale systems. This paper surveys and summarizes requirements that allow peers potentially constrained by network connectivity to bootstrap small-scale overlays through the use of e...
Design and Implementation of a Bootstrap Trust Chain
Institute of Scientific and Technical Information of China (English)
YU Fajiang; ZHANG Huanguo
2006-01-01
The chain of trust in bootstrap process is the basis of whole system trust in the trusted computing group (TCG) definition. This paper presents a design and implementation of a bootstrap trust chain in PC based on the Windows and today' commodity hardware, merely depends on availability of an embedded security module (ESM). ESM and security enhanced BIOS is the root of trust, PMBR (Pre-MBR) checks the integrity of boot data and Windows kernel, which is a checking agent stored in ESM. In the end, the paper analyzed the mathematic expression of the chain of trust and the runtime performance compared with the common booting process. The trust chain bootstrap greatly strengthens the security of personal computer system, and affects the runtime performance with only adding about 12% booting time.
Investigations of dipole localization accuracy in MEG using the bootstrap.
Darvas, F; Rautiainen, M; Pantazis, D; Baillet, S; Benali, H; Mosher, J C; Garnero, L; Leahy, R M
2005-04-01
We describe the use of the nonparametric bootstrap to investigate the accuracy of current dipole localization from magnetoencephalography (MEG) studies of event-related neural activity. The bootstrap is well suited to the analysis of event-related MEG data since the experiments are repeated tens or even hundreds of times and averaged to achieve acceptable signal-to-noise ratios (SNRs). The set of repetitions or epochs can be viewed as a set of independent realizations of the brain's response to the experiment. Bootstrap resamples can be generated by sampling with replacement from these epochs and averaging. In this study, we applied the bootstrap resampling technique to MEG data from somatotopic experimental and simulated data. Four fingers of the right and left hand of a healthy subject were electrically stimulated, and about 400 trials per stimulation were recorded and averaged in order to measure the somatotopic mapping of the fingers in the S1 area of the brain. Based on single-trial recordings for each finger we performed 5000 bootstrap resamples. We reconstructed dipoles from these resampled averages using the Recursively Applied and Projected (RAP)-MUSIC source localization algorithm. We also performed a simulation for two dipolar sources with overlapping time courses embedded in realistic background brain activity generated using the prestimulus segments of the somatotopic data. To find correspondences between multiple sources in each bootstrap, sample dipoles with similar time series and forward fields were assumed to represent the same source. These dipoles were then clustered by a Gaussian Mixture Model (GMM) clustering algorithm using their combined normalized time series and topographies as feature vectors. The mean and standard deviation of the dipole position and the dipole time series in each cluster were computed to provide estimates of the accuracy of the reconstructed source locations and time series. PMID:15784414
Beam-driven and bootstrap currents in JT-60 upgrade
International Nuclear Information System (INIS)
We recently performed beam-driven current-drive experiments with a low fraction of bootstrap currents in a wide range of plasma parameters in JT-60 upgrade. The evidence of current profile modification by the beam-driven current with tangential neutral beam injectors. A high βN, high βp and ELMy H-mode plasma with possibly fully non-inductive current-drive by beam-driven and bootstrap currents was maintained for a considerably long duration with the combined injection of quasi-perpendicular and co-tangential beams. (author) 4 refs., 7 figs
Generalized bootstrap equations and possible implications for the NLO odderon
International Nuclear Information System (INIS)
We formulate and discuss generalized bootstrap equations in nonabelian gauge theories. They are shown to hold in the leading logarithmic approximation. Since their validity is related to the self-consistency of the Steinmann relations for inelastic production amplitudes they can be expected to be valid also in NLO. Specializing to the N=4 SYM, we show that the validity in NLO of these generalized bootstrap equations allows to find the NLO odderon solution with intercept exactly at one, a result which is valid also for the planar limit of QCD. (orig.)
Experimental evidence for the bootstrap current in a tokamak
International Nuclear Information System (INIS)
The bootstrap current is a plasma current associated with trapped particles in a toroidal plasma. Magnetic measurements, such as the surface voltage, the internal inductance, and the Faraday rotation, are consistent with the existence of the neoclassical bootstrap current in tokamaks. The neoclassical trapped-particle correction to the electrical conductivity is also systematically validated against experiments. These results support the assertion that the generalized Ohm's law along the magnetic field is valid, as predicted by the neoclassical transport theory, while the perpendicular transport deviates from the neoclassical transport theory. (Author)
Bootstrap current increment after siliconization on the HT-7 tokamak
International Nuclear Information System (INIS)
The authors present some results for the estimation of the bootstrap current after siliconization on the HT-7 tokamak. After siliconization, the plasma pressure gradient and the electron temperature near the boundary are larger than before siliconization. These factors influence the ratio of the bootstrap current to the total plasma current which increases from several per cent to above 10%. The results are expected to explain the previous experimental phenomena that, after siliconization, the plasma current profile is broadened and the higher current can be obtained easily on the HT-7 tokamak experiment
Modelos alternativos de simulación Bootstrap
Pino Mejías, Rafael
1992-01-01
Se describen las características fundamentales de los métodos Bootstrap. Se analizan diversas problemáticas que presentan tales métodos, por lo que se presentan dos métodos alternativos dentro del método Bootstrap basado en la simulación de muestras (método II de Efron). En el primero se presenta un método, que a partir de un estudio de las propiedades algebraicas y estadísticas del conjunto de posibles muestras, utiliza un criterio probabilístico para detectar muestras "outliers". En el segu...
Bootstrapped efficiency measures of oil blocks in Angola
International Nuclear Information System (INIS)
This paper investigates the technical efficiency of Angola oil blocks over the period 2002-2007. A double bootstrap data envelopment analysis (DEA) model is adopted composed in the first stage of a DEA-variable returns to scale (VRS) model and then followed in the second stage by a bootstrapped truncated regression. Results showed that on average, the technical efficiency has fluctuated over the period of study, but deep and ultradeep oil blocks have generally maintained a consistent efficiency level. Policy implications are derived.
Bootstrapping Critical Ising Model on Three Dimensional Real Projective Space
Nakayama, Yu
2016-04-01
Given conformal data on a flat Euclidean space, we use crosscap conformal bootstrap equations to numerically solve the Lee-Yang model as well as the critical Ising model on a three dimensional real projective space. We check the rapid convergence of our bootstrap program in two dimensions from the exact solutions available. Based on the comparison, we estimate that our systematic error on the numerically solved one-point functions of the critical Ising model on a three dimensional real projective space is less than 1%. Our method opens up a novel way to solve conformal field theories on nontrivial geometries.
PyCFTBoot: A flexible interface for the conformal bootstrap
Behan, Connor
2016-01-01
We introduce PyCFTBoot, a wrapper designed to reduce the barrier to entry in conformal bootstrap calculations that require semidefinite programming. Symengine and SDPB are used for the most intensive symbolic and numerical steps respectively. After reviewing the built-in algorithms for conformal blocks, we explain how to use the code through a number of examples that verify past results. As an application, we show that the multi-correlator bootstrap still appears to single out the Wilson-Fisher fixed points as special theories in dimensions between 3 and 4 despite the recent proof that they violate unitarity.
International Nuclear Information System (INIS)
A simple and rapid method of the sequential determination of radionuclides 239,240Pu, 238 Pu, 241 Am and 90Sr in radioactive sludge from the NPP Bohunice A1 with high radiochemical yields and efficient removal of interfering components from a matrix was developed. Separation method combines SPE sorbents Analig Pu02, AnaLig Sr01 made by IBC Advanced Technologies and TRU Resin (Eichrom Technologies) placed in tandem. Advantage of a single-stage column located on the vacuum box with a rapid flow is an effective pre-concentration and separation of radionuclides and minimization of sample separation time. (authors)
Bootstrap Tests and Confidence Regions for Functions of a Covariance Matrix
Beran, Rudolf; Srivastava, Muni S.
1985-01-01
Bootstrap tests and confidence regions for functions of the population covariance matrix have the desired asymptotic levels, provided model restrictions, such as multiple eigenvalues in the covariance matrix, are taken into account in designing the bootstrap algorithm.
International Nuclear Information System (INIS)
We are developing the NIST standard sequential extraction protocol for identifying the fractionation of radioactive elements in soils and sediments. The procedure is designed to partition a soil or sediment sample into six operationally-defined fractions. A full-factorial experimental design/data analysis methodology was used to establish the optimum conditions for the first of these six fractions, called 'exchangeables'. Reaction time, reagent concentration and reaction temperature were chosen as experimental variables. The criteria for choosing optimum conditions were the maximum extraction of 238U combined with a minimum dissolution of non-targeted geochemical phases. Reagent concentration (i.e. ionic strength) is shown to be the controlling factor in the extraction of exchangeable 238U. The optimum (exchangeable) conditions, based on these experiments are: time=1 h; temperature=25 deg. C and concentration=0.4 M MgCl2
A new resampling method for sampling designs without replacement: the doubled half bootstrap
Antal, Erika; Tillé, Yves
2016-01-01
A new and very fast method of bootstrap for sampling without replacement from a finite population is proposed. This method can be used to estimate the variance in sampling with unequal inclusion probabilities and does not require artificial populations or utilization of bootstrap weights. The bootstrap samples are directly selected from the original sample. The bootstrap procedure contains two steps: in the first step, units are selected once with Poisson sampling using the same inclusion pro...
A frequency domain bootstrap for ratio statistics in time series analysis
Dahlhaus, R.; Janas, D.
1996-01-01
The asymptotic properties of the bootstrap in the frequency domain based on Studentized periodogram ordinates are studied. It is proved that this bootstrap approximation is valid for ratio statistics such as autocorrelations. By using Edgeworth expansions it is shown that the bootstrap approximation even outperforms the normal approximation. The results carry over to Whittle estimates. In a simulation study the behavior of the bootstrap is studied for empirical correlations and Whittle estima...
Siana Halim; Herman Mallian
2006-01-01
The Bootstrap is a lively research area. A lot Of ideas are around and have let to quiet different proposals. In this paper we sketch briefly some Bootstrap methods for independent and dependent data. Finally we give an Bootstrap example for constructing confidence interval in the forecasting for stationer data. Abstract in Bahasa Indonesia : Bootstrap merupakan area penelitian yang terus berkembang. Ada banyak ide dan proposal-proposal yang berbeda telah diberikan oleh para peneliti. Namun d...
First and second order analysis for periodic random arrays using block bootstrap methods
Dudek, Anna E.
2016-01-01
In the paper row-wise periodically correlated triangular arrays are considered. The period length is assumed to grow in time. The Fourier decomposition of the mean and autocovariance functions for each row of the matrix is presented. To construct bootstrap estimators of the Fourier coefficients two block bootstrap techniques are used. These are the circular version of the Generalized Seasonal Block Bootstrap and the Circular Block Bootstrap. Consistency results for both methods are presented....
Sequential stochastic optimization
Cairoli, Renzo
1996-01-01
Sequential Stochastic Optimization provides mathematicians and applied researchers with a well-developed framework in which stochastic optimization problems can be formulated and solved. Offering much material that is either new or has never before appeared in book form, it lucidly presents a unified theory of optimal stopping and optimal sequential control of stochastic processes. This book has been carefully organized so that little prior knowledge of the subject is assumed; its only prerequisites are a standard graduate course in probability theory and some familiarity with discrete-paramet
Normal Limits, Nonnormal Limits, and the Bootstrap for Quantiles of Dependent Data
Sharipov, O. Sh.; Wendler, M.
2012-01-01
We will show under very weak conditions on differentiability and dependence that the central limit theorem for quantiles holds and that the block bootstrap is weakly consistent. Under slightly stronger conditions, the bootstrap is strongly consistent. Without the differentiability condition, quantiles might have a non-normal asymptotic distribution and the bootstrap might fail.
Spinella, Sarah
2011-01-01
As result replicability is essential to science and difficult to achieve through external replicability, the present paper notes the insufficiency of null hypothesis statistical significance testing (NHSST) and explains the bootstrap as a plausible alternative, with a heuristic example to illustrate the bootstrap method. The bootstrap relies on…
Noncentral limit theorem and the bootstrap for quantiles of dependent data
Sharipov, Olimjon S.; Wendler, Martin
2012-01-01
We will show under minimal conditions on differentiability and dependence that the central limit theorem for quantiles holds and that the block bootstrap is weakly consistent. Under slightly stronger conditions, the bootstrap is strongly consistent. Without the differentiability condition, quantiles might have a non-normal asymptotic distribution and the bootstrap might fail.
RANDOM QUADRATIC-FORMS AND THE BOOTSTRAP FOR U-STATISTICS
DEHLING, H; MIKOSCH, T
1994-01-01
We study the bootstrap distribution for U-statistics with special emphasis on the degenerate case. For the Efron bootstrap we give a short proof of the consistency using Mallows' metrics. We also study the i.i.d. weighted bootstrap [GRAPHICS] where (X(i)) and (xi(i)) are two i.i.d. sequences, indepe
Sidecoin: a snapshot mechanism for bootstrapping a blockchain
Krug, Joseph; Peterson, Jack
2015-01-01
Sidecoin is a mechanism that allows a snapshot to be taken of Bitcoin's blockchain. We compile a list of Bitcoin's unspent transaction outputs, then use these outputs and their corresponding balances to bootstrap a new blockchain. This allows the preservation of Bitcoin's economic state in the context of a new blockchain, which may provide new features and technical innovations.
Automatic bootstrapping of a morphable face model using multiple components
Haar, F.B. ter; Veltkamp, R.C.
2009-01-01
We present a new bootstrapping algorithm to automatically enhance a 3D morphable face model with new face data. Our algorithm is based on a morphable model fitting method that uses a set of predefined face components. This fitting method produces accurate model fits to 3D face data with noise and ho
Application of bootstrap to detecting chaos in financial time series
Brzozowska-Rup, Katarzyna; Orłowski, Arkadiusz
2004-12-01
A moving blocks bootstrap procedure is used to investigate the dynamics of nominal exchange rates and the return rates of the US Dollar against the Polish Zloty. The problem if these financial time series exhibit chaotic behavior is undertaken. A possibility of detecting the presence of a positive Lyapunov exponent is studied.
Generalized Bootstrap Method for Assessment of Uncertainty in Semivariogram Inference
Olea, R.A.; Pardo-Iguzquiza, E.
2011-01-01
The semivariogram and its related function, the covariance, play a central role in classical geostatistics for modeling the average continuity of spatially correlated attributes. Whereas all methods are formulated in terms of the true semivariogram, in practice what can be used are estimated semivariograms and models based on samples. A generalized form of the bootstrap method to properly model spatially correlated data is used to advance knowledge about the reliability of empirical semivariograms and semivariogram models based on a single sample. Among several methods available to generate spatially correlated resamples, we selected a method based on the LU decomposition and used several examples to illustrate the approach. The first one is a synthetic, isotropic, exhaustive sample following a normal distribution, the second example is also a synthetic but following a non-Gaussian random field, and a third empirical sample consists of actual raingauge measurements. Results show wider confidence intervals than those found previously by others with inadequate application of the bootstrap. Also, even for the Gaussian example, distributions for estimated semivariogram values and model parameters are positively skewed. In this sense, bootstrap percentile confidence intervals, which are not centered around the empirical semivariogram and do not require distributional assumptions for its construction, provide an achieved coverage similar to the nominal coverage. The latter cannot be achieved by symmetrical confidence intervals based on the standard error, regardless if the standard error is estimated from a parametric equation or from bootstrap. ?? 2010 International Association for Mathematical Geosciences.
Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions
Van Enter, A.C.D.; Fey, A.
2012-01-01
In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the orde
A Bootstrap Cointegration Rank Test for Panels of VAR Models
DEFF Research Database (Denmark)
Callot, Laurent
functions of the individual Cointegrated VARs (CVAR) models. A bootstrap based procedure is used to compute empirical distributions of the trace test statistics for these individual models. From these empirical distributions two panel trace test statistics are constructed. The satisfying small sample...
A Statistical Mechanics Approach to Approximate Analytical Bootstrap Averages
DEFF Research Database (Denmark)
Malzahn, Dorthe; Opper, Manfred
2003-01-01
We apply the replica method of Statistical Physics combined with a variational method to the approximate analytical computation of bootstrap averages for estimating the generalization error. We demonstrate our approach on regression with Gaussian processes and compare our results with averages...
Metastability thresholds for anisotropic bootstrap percolation in three dimensions
Van Enter, A.C.D.; Fey, A.
2012-01-01
In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the orde
More on analytic bootstrap for O(N) models
Dey, Parijat; Sen, Kallol
2016-01-01
This note is an extension of a recent work on the analytical bootstrapping of $O(N)$ models. An additonal feature of the $O(N)$ model is that the OPE contains trace and antisymmetric operators apart from the symmetric-traceless objects appearing in the OPE of the singlet sector. This in addition to the stress tensor $(T_{\\mu\
Bootstrapping rapidity anomalous dimension for transverse-momentum resummation
Li, Ye
2016-01-01
Soft function relevant for transverse-momentum resummation for Drell-Yan or Higgs production at hadron colliders are computed through to three loops in the expansion of strong coupling, with the help of bootstrap technique and supersymmetric decomposition. The corresponding rapidity anomalous dimension is extracted. An intriguing relation between anomalous dimensions for transverse-momentum resummation and threshold resummation is found.
Bootstrapping Rapidity Anomalous Dimension for Transverse-Momentum Resummation
Energy Technology Data Exchange (ETDEWEB)
Li, Ye [Fermilab; Zhu, Hua Xing [MIT, Cambridge, CTP
2016-04-05
Soft function relevant for transverse-momentum resummation for Drell-Yan or Higgs production at hadron colliders are computed through to three loops in the expansion of strong coupling, with the help of bootstrap technique and supersymmetric decomposition. The corresponding rapidity anomalous dimension is extracted. An intriguing relation between anomalous dimensions for transverse-momentum resummation and threshold resummation is found.
A neural network based reputation bootstrapping approach for service selection
Wu, Quanwang; Zhu, Qingsheng; Li, Peng
2015-10-01
With the concept of service-oriented computing becoming widely accepted in enterprise application integration, more and more computing resources are encapsulated as services and published online. Reputation mechanism has been studied to establish trust on prior unknown services. One of the limitations of current reputation mechanisms is that they cannot assess the reputation of newly deployed services as no record of their previous behaviours exists. Most of the current bootstrapping approaches merely assign default reputation values to newcomers. However, by this kind of methods, either newcomers or existing services will be favoured. In this paper, we present a novel reputation bootstrapping approach, where correlations between features and performance of existing services are learned through an artificial neural network (ANN) and they are then generalised to establish a tentative reputation when evaluating new and unknown services. Reputations of services published previously by the same provider are also incorporated for reputation bootstrapping if available. The proposed reputation bootstrapping approach is seamlessly embedded into an existing reputation model and implemented in the extended service-oriented architecture. Empirical studies of the proposed approach are shown at last.
Sequential memory: Binding dynamics
Afraimovich, Valentin; Gong, Xue; Rabinovich, Mikhail
2015-10-01
Temporal order memories are critical for everyday animal and human functioning. Experiments and our own experience show that the binding or association of various features of an event together and the maintaining of multimodality events in sequential order are the key components of any sequential memories—episodic, semantic, working, etc. We study a robustness of binding sequential dynamics based on our previously introduced model in the form of generalized Lotka-Volterra equations. In the phase space of the model, there exists a multi-dimensional binding heteroclinic network consisting of saddle equilibrium points and heteroclinic trajectories joining them. We prove here the robustness of the binding sequential dynamics, i.e., the feasibility phenomenon for coupled heteroclinic networks: for each collection of successive heteroclinic trajectories inside the unified networks, there is an open set of initial points such that the trajectory going through each of them follows the prescribed collection staying in a small neighborhood of it. We show also that the symbolic complexity function of the system restricted to this neighborhood is a polynomial of degree L - 1, where L is the number of modalities.
Synthetic Aperture Sequential Beamforming
DEFF Research Database (Denmark)
Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke
2008-01-01
A synthetic aperture focusing (SAF) technique denoted Synthetic Aperture Sequential Beamforming (SASB) suitable for 2D and 3D imaging is presented. The technique differ from prior art of SAF in the sense that SAF is performed on pre-beamformed data contrary to channel data. The objective is to...
BOOTSTRAP WAVELET IN THE NONPARAMETRIC REGRESSION MODEL WITH WEAKLY DEPENDENT PROCESSES
Institute of Scientific and Technical Information of China (English)
林路; 张润楚
2004-01-01
This paper introduces a method of bootstrap wavelet estimation in a nonparametric regression model with weakly dependent processes for both fixed and random designs. The asymptotic bounds for the bias and variance of the bootstrap wavelet estimators are given in the fixed design model. The conditional normality for a modified version of the bootstrap wavelet estimators is obtained in the fixed model. The consistency for the bootstrap wavelet estimator is also proved in the random design model. These results show that the bootstrap wavelet method is valid for the model with weakly dependent processes.
International Nuclear Information System (INIS)
The classical use of a generalized χ2-distance to determine the evaluated cross section uncertainty requires the values of the experimental cross sections covariance matrix. The usual propagation error method to estimate the covariances is hardly usable and the lack of data prevents from using the direct empirical estimator. Thus we present an alternative which exploits a regression model of the experimental cross section to generate pseudo-measurements and thereby allows an estimation of experimental covariances. The problem of assessing the quality of the estimate still remains. In our approach, we propose to determine the estimation quality through the means of the bootstrap method. We show on numerical examples that the bootstrap allows to have an order of magnitude of the estimation quality through a matrix norm. All the results are illustrated with a toy model (where all quantities are known) and also with real cross-section data measurements. (authors)
A Grammatical Inference Sequential Mining Algorithm for Protein Fold Recognition
Taysir Hassan A.Soliman; Ahmed Sharaf Eldin; Marwa M. Ghareeb; Mohammed E. Marie
2014-01-01
Protein fold recognition plays an important role in computational protein analysis since it can determine protein function whose structure is unknown. In this paper, a Classified Sequential Pattern mining technique for Protein Fold Recognition (CSPF) is proposed. CSPF technique consists of two main phases: the sequential mining pattern phase and the fold recognition phase. In the sequential mining pattern phase, Mix & Test algorithm is developed based on Grammatical Inference, which is used a...
International Nuclear Information System (INIS)
The characteristic difference of neoclassical bootstrap current and its effects on MHD equilibria are described for the CHS heliotron/torsatron and the CHS-qa quasi-axisymmetric stellarator. The direction of bootstrap current strongly depends on collisionality in CHS, whereas it does not in CHS-qa because of quasi-axisymmetry. In the CHS configuration, it appears that enhanced bumpy (B01) and sideband components of helical ripple (B11) play an important role in reducing the magnetic geometrical factor, which is a key factor in evaluating the value of bootstrap current, and determining its polarity. The bootstrap current in CHS-qa is theoretically predicted to be larger than that in CHS and produces significant effects on the resulting rotational transform and magnetic shear. In the finite β plasmas, the magnetic well becomes deeper in both CHS and CHS-qa and its region is expanded in CHS. The existence of co-flowing bootstrap current makes the magnetic well shallow in comparison with that in currentless equilibrium. (author)
Application of the bootstrap method to radiolabeled antibody dosimetry from planar images
International Nuclear Information System (INIS)
Full text: Planar imaging dosimetry of radiolabeled antibody treatment uses the MIRD schema to compute dose to an organ from the calculated activity in that and other organs. The calculated activity in an organ is a function of the average count rates in the organ, a standard and an appropriate background measurement. The geometric mean of conjugate averages, together with an attenuation factor is used to provide an approximate attenuation correction. It is sometimes desirable to know the variance of the activity in an organ in order to apply weighted least squares regression to the data. This is particularly important when incorporating more accurate data from autoradiography of biopsied tissue into the analysis, but is also useful when some data points have low signal. While the geometric mean image can be used to calculate the variance of an organ's count rate. It is difficult to calculate the variance of the activity, since the organ in question, the standard and the background all contribute to it. Bootstrap methods are Monte Carlo techniques that can be used to estimate parameters from data and to determine the accuracy of the estimation. By bootstrapping pixel values in the organ, background and standard ROIs, it is possible to calculate many realisations of the organ activity and calculate its variance. As an example, bootstrapping is applied to the pharmacodynamic analysis of 131I-huA33 in colon. The data includes planar whole body images, and autoradiographs and planar images of a resected colon. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc
Study of EC current drive efficiency and bootstrap current by power modulation experiments
International Nuclear Information System (INIS)
In Stellarators, the absence of a strong 'obscuring' Ohmic component permits the experimental investigation of small non-inductive currents with a precision difficult to be obtained in an equivalent Tokamak. In the W7-AS Stellarator (R = 2 m, ≤0.18 m, PECRH ≤ 800 kW) we have performed a systematic study of Electron Cyclotron Current Drive. Uncertainties in the measurements of the ECCD efficiency, ηECCD, are introduced by the unavoidable presence of the bootstrap current (and, eventually, an Ohmic one) and by the strong coupling between confinement properties and rotational transform, which is typical for low-shear vacuum magnetic field configurations, as W7-AS. To improve the accuracy, we have applied a new perturbative procedure for the determination of ηECCD. The method is based on the independent launch of two microwave beams. While one of the two beams is launched with a toroidal angle of injection corresponding to co-current drive (with respect to the bootstrap current direction) the second one is injected in the opposite direction (counter-current drive). In absence of effects perturbing the symmetry (e.g., strong E|| as in Tokamaks, or strong anisotropic electron distribution functions as in presence of LHCD) the two r.f. beams are equivalently absorbed and the two driven currents compensate. Through a modulation of the powers in both beam with same amplitude but opposite phase, the modulated ECCD contribution can be discriminated from the unaffected bootstrap and Ohmic ones. Furthermore, the time delay between the modulated power and the response of the loop voltage contains information about the radial localization of the modulated ECCD-current. (author) 6 refs., 5 figs
Deng, Nina; Allison, Jeroan J; Fang, Hua Julia; Ash, Arlene S.; Ware, John E.
2013-01-01
Background Relative validity (RV), a ratio of ANOVA F-statistics, is often used to compare the validity of patient-reported outcome (PRO) measures. We used the bootstrap to establish the statistical significance of the RV and to identify key factors affecting its significance. Methods Based on responses from 453 chronic kidney disease (CKD) patients to 16 CKD-specific and generic PRO measures, RVs were computed to determine how well each measure discriminated across clinically-defined groups ...
Sequential measurements of conjugate observables
Energy Technology Data Exchange (ETDEWEB)
Carmeli, Claudio [Dipartimento di Fisica, Universita di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Heinosaari, Teiko [Department of Physics and Astronomy, Turku Centre for Quantum Physics, University of Turku, 20014 Turku (Finland); Toigo, Alessandro, E-mail: claudio.carmeli@gmail.com, E-mail: teiko.heinosaari@utu.fi, E-mail: alessandro.toigo@polimi.it [Dipartimento di Matematica ' Francesco Brioschi' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)
2011-07-15
We present a unified treatment of sequential measurements of two conjugate observables. Our approach is to derive a mathematical structure theorem for all the relevant covariant instruments. As a consequence of this result, we show that every Weyl-Heisenberg covariant observable can be implemented as a sequential measurement of two conjugate observables. This method is applicable both in finite- and infinite-dimensional Hilbert spaces, therefore covering sequential spin component measurements as well as position-momentum sequential measurements.
Forced Sequence Sequential Decoding
DEFF Research Database (Denmark)
Jensen, Ole Riis
In this thesis we describe a new concatenated decoding scheme based on iterations between an inner sequentially decoded convolutional code of rate R=1/4 and memory M=23, and block interleaved outer Reed-Solomon codes with non-uniform profile. With this scheme decoding with good performance is...... of computational overflow. Analytical results for the probability that the first Reed-Solomon word is decoded after C computations are presented. This is supported by simulation results that are also extended to other parameters....... possible as low as Eb/No=0.6 dB, which is about 1.7 dB below the signal-to-noise ratio that marks the cut-off rate for the convolutional code. This is possible since the iteration process provides the sequential decoders with side information that allows a smaller average load and minimizes the probability...
Jofre-Bonet, M; Pesendorfer, M.
2014-01-01
Sequential sealed first-price and open descending-price procurement auctions are studied. We examine which procurement auction rule achieves the low procurement cost. We show that the answer to this policy question depends on whether the items are complements or substitutes. With substitutes, the first-price procurement auction is preferred, while with complements, the open descending-price procurement auction is preferred. We also illustrate the procurement cost minimizing auction and the au...
Sequential cloning of chromosomes
Energy Technology Data Exchange (ETDEWEB)
Lacks, S.A.
1991-12-31
A method for sequential cloning of chromosomal DNA and chromosomal DNA cloned by this method are disclosed. The method includes the selection of a target organism having a segment of chromosomal DNA to be sequentially cloned. A first DNA segment, having a first restriction enzyme site on either side. homologous to the chromosomal DNA to be sequentially cloned is isolated. A first vector product is formed by ligating the homologous segment into a suitably designed vector. The first vector product is circularly integrated into the target organism`s chromosomal DNA. The resulting integrated chromosomal DNA segment includes the homologous DNA segment at either end of the integrated vector segment. The integrated chromosomal DNA is cleaved with a second restriction enzyme and ligated to form a vector-containing plasmid, which is replicated in a host organism. The replicated plasmid is then cleaved with the first restriction enzyme. Next, a DNA segment containing the vector and a segment of DNA homologous to a distal portion of the previously isolated DNA segment is isolated. This segment is then ligated to form a plasmid which is replicated within a suitable host. This plasmid is then circularly integrated into the target chromosomal DNA. The chromosomal DNA containing the circularly integrated vector is treated with a third, retrorestriction enzyme. The cleaved DNA is ligated to give a plasmid that is used to transform a host permissive for replication of its vector. The sequential cloning process continues by repeated cycles of circular integration and excision. The excision is carried out alternately with the second and third enzymes.
The Index of Biological Integrity and the bootstrap revisited: an example from Minnesota streams
Dolph, Christine L.; Sheshukov, Aleksey Y.; Chizinski, Christopher J.; Vondracek, Bruce C.; Wilson, Bruce
2010-01-01
Multimetric indices, such as the Index of Biological Integrity (IBI), are increasingly used by management agencies to determine whether surface water quality is impaired. However, important questions about the variability of these indices have not been thoroughly addressed in the scientific literature. In this study, we used a bootstrap approach to quantify variability associated with fish IBIs developed for streams in two Minnesota river basins. We further placed this variability into a management context by comparing it to impairment thresholds currently used in water quality determinations for Minnesota streams. We found that 95% confidence intervals ranged as high as 40 points for IBIs scored on a 0–100 point scale. However, on average, 90% of IBI scores calculated from bootstrap replicate samples for a given stream site yielded the same impairment status as the original IBI score. We suggest that sampling variability in IBI scores is related to both the number of fish and the number of rare taxa in a field collection. A comparison of the effects of different scoring methods on IBI variability indicates that a continuous scoring method may reduce the amount of bias in IBI scores.
Forced Sequence Sequential Decoding
DEFF Research Database (Denmark)
Jensen, Ole Riis; Paaske, Erik
1998-01-01
We describe a new concatenated decoding scheme based on iterations between an inner sequentially decoded convolutional code of rate R=1/4 and memory M=23, and block interleaved outer Reed-Solomon (RS) codes with nonuniform profile. With this scheme decoding with good performance is possible as low...... as Eb/N0=0.6 dB, which is about 1.25 dB below the signal-to-noise ratio (SNR) that marks the cutoff rate for the full system. Accounting for about 0.45 dB due to the outer codes, sequential decoding takes place at about 1.7 dB below the SNR cutoff rate for the convolutional code. This is possible...... since the iteration process provides the sequential decoders with side information that allows a smaller average load and minimizes the probability of computational overflow. Analytical results for the probability that the first RS word is decoded after C computations are presented. These results are...
Five dimensional O(N)-symmetric CFTs from conformal bootstrap
International Nuclear Information System (INIS)
We investigate the conformal bootstrap approach to O(N) symmetric CFTs in five dimensions with particular emphasis on the lower bound on the current central charge. The bound has a local minimum for all N>1, and in the large N limit we propose that the minimum is saturated by the critical O(N) vector model at the UV fixed point, the existence of which has been recently argued by Fei, Giombi, and Klebanov. The location of the minimum is generically different from the minimum of the lower bound of the energy–momentum tensor central charge when it exists for smaller N. To better understand the situation, we examine the lower bounds of the current central charge of O(N) symmetric CFTs in three dimensions to compare. We find the similar agreement in the large N limit but the discrepancy for smaller N with the other sectors of the conformal bootstrap
A proof of fulfillment of the strong bootstrap condition
International Nuclear Information System (INIS)
It is shown that the kernel of the BFKL equation for the octet color state of two Reggeized gluons satisfies the strong bootstrap condition in the next-to-leading order. This condition is much more restrictive than the one obtained from the requirement of the Reggeized form for the elastic scattering amplitudes in the next-to-leading approximation. It is necessary, however, for self-consistency of the assumption of the Reggeized form of the production amplitudes in multi-Regge kinematics, which are used in the derivation of the BFKL equation. The fulfillment of the strong bootstrap condition for the kernel opens the way to a rigorous proof of the BFKL equation in the next-to-leading approximation. (orig.)
Self-consistent ECCD calculations with bootstrap current
International Nuclear Information System (INIS)
To achieve high performance, steady-state operation in tokamaks, it is increasingly important to find the appropriate means for modifying and sustaining the pressure and magnetic shear profiles in the plasma. In such advanced scenarios, especially in the vicinity of internal transport barrier, RF induced currents have to be calculated self-consistently with the bootstrap current, thus taking into account possible synergistic effects resulting from the momentum space distortion of the electron distribution function fe. Since RF waves can cause the distribution of electrons to become non-Maxwellian, the associated changes in parallel diffusion of momentum between trapped and passing particles can be expected to modify the bootstrap current fraction; conversely, the bootstrap current distribution function can enhance the current driven by RF waves. For this purpose, a new, fast and fully implicit solver has been recently developed to carry out computations including new and detailed evaluations of the interactions between bootstrap current (BC) and Electron Cyclotron current drive (ECCD). Moreover, Ohkawa current drive (OKCD) appears to be an efficient method for driving current when the fraction of trapped particles is large. OKCD in the presence of BC is also investigated. Here, results are illustrated around projected tokamak parameters in high performance scenarios of AlcatorC-MOD. It is shown that by increasing n//, the EC wave penetration into the bulk of the electron distribution is greater, and since the resonance extends up to high p// values, this situation is the usual ECCD based on the Fisch-Boozer mechanism concerning passing particles. However, because of the close vicinity of the trapped boundary at r/a=0.7, this process is counterbalanced by the Ohkawa effect, possibly leading to a negative net current. Therefore, by injecting the EC wave in the opposite toroidal direction (n// RF by OKCD may be 70% larger than that of ECCD, with a choice of EC wave
Combined RF current drive and bootstrap current in tokamaks
International Nuclear Information System (INIS)
By calculating radio frequency current drive (RFCD) and the bootstrap current in a consistent kinetic manner, we find synergistic effects in the total noninductive current density in tokamaks [1]. We include quasilinear diffusion in the Drift Kinetic Equation (DKE) in order to generalize neoclassical theory to highly non-Maxwellian electron distributions due to RFCD. The parallel plasma current is evaluated numerically with the help of the FASTEP Fokker-Planck code [2]. Current drive efficiency is found to be significantly affected by neoclassical effects, even in cases where only circulating electrons interact with the waves. Predictions of the current drive efficiency are made for lower hybrid and electron cyclotron wave current drive scenarios in the presence of bootstrap current. (c) 1999 American Institute of Physics
Thermal energy and bootstrap current in fusion reactor plasmas
International Nuclear Information System (INIS)
For DT fusion reactors with prescribed alpha particle heating power Pα, plasma volume V and burn temperature i> ∼ 10 keV specific relations for the thermal energy content, bootstrap current, central plasma pressure and other quantities are derived. It is shown that imposing Pα and V makes these relations independent of the magnitudes of the density and temperature, i.e. they only depend on Pα, V and shape factors or profile parameters. For model density and temperature profiles analytic expressions for these shape factors and for the factor Cbs in the bootstrap current formula Ibs ∼ Cbs(a/R)1/2βpIp are given. In the design of next-step devices and fusion reactors, the fusion power is a fixed quantity. Prescription of the alpha particle heating power and plasma volume results in specific relations which can be helpful for interpreting computer simulations and for the design of fusion reactors. (author) 5 refs
Bootstrap bound for conformal multi-flavor QCD on lattice
Nakayama, Yu
2016-07-01
The recent work by Iha et al. shows an upper bound on mass anomalous dimension γ m of multi-flavor massless QCD at the renormalization group fixed point from the conformal bootstrap in SU( N F ) V symmetric conformal field theories under the assumption that the fixed point is realizable with the lattice regularization based on staggered fermions. We show that the almost identical but slightly stronger bound applies to the regularization based on Wilson fermions (or domain wall fermions) by studying the conformal bootstrap in SU( N f ) L × SU( N f ) R symmetric conformal field theories. For N f = 8, our bound implies γ m < 1 .31 to avoid dangerously irrelevant operators that are not compatible with the lattice symmetry.
A bootstrap lunar base: Preliminary design review 2
1987-01-01
A bootstrap lunar base is the gateway to manned solar system exploration and requires new ideas and new designs on the cutting edge of technology. A preliminary design for a Bootstrap Lunar Base, the second provided by this contractor, is presented. An overview of the work completed is discussed as well as the technical, management, and cost strategies to complete the program requirements. The lunar base design stresses the transforming capabilities of its lander vehicles to aid in base construction. The design also emphasizes modularity and expandability in the base configuration to support the long-term goals of scientific research and profitable lunar resource exploitation. To successfully construct, develop, and inhabit a permanent lunar base, however, several technological advancements must first be realized. Some of these technological advancements are also discussed.
Bootstrap bound for conformal multi-flavor QCD on lattice
Nakayama, Yu
2016-01-01
The recent work by Iha et al shows an upper bound on mass anomalous dimension $\\gamma_m$ of multi-flavor massless QCD at the renormalization group fixed point from the conformal bootstrap in $SU(N_F)_V$ symmetric conformal field theories under the assumption that the fixed point is realizable with the lattice regularization based on staggered fermions. We show that the almost identical but slightly stronger bound applies to the regularization based on Wilson fermions (or domain wall fermions) by studying the conformal bootstrap in $SU(N_f)_L \\times SU(N_f)_R$ symmetric conformal field theories. For $N_f=8$, our bound implies $\\gamma_m < 1.31$ to avoid dangerously irrelevant operators that are not compatible with the lattice symmetry.
Bootstrapping a Five-Loop Amplitude from Steinmann Relations
Caron-Huot, Simon; McLeod, Andrew; von Hippel, Matt
2016-01-01
The analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.
Directed rigidity and bootstrap percolation in (1+1) dimensions
de Menezes, Marcio Argollo; Moukarzel, Cristian F.
1999-01-01
We study directed rigidity percolation (equivalent to directed bootstrap percolation) on three different lattices: square, triangular, and augmented triangular. The first two of these display a first-order transition at p=1, while the augmented triangular lattice shows a continuous transition at a non-trivial p_c. On the augmented triangular lattice we find, by extensive numerical simulation, that the directed rigidity percolation transition belongs to the same universality class as directed ...
Bootstrapping an empty repertoire of experience: the design case
Saliou, Philippe; Ribaud, Vincent
2009-01-01
Performing good design is a difficult task. To take up this challenge, practitioners rely on their repertoire of experience. Students, however, do not have any such repertoire. We propose an approach aimed at bootstrapping the repertoire. The approach is generally accomplished in two steps: tailoring the activity - acquiring a minimal structure through a deductive approach, then initializing the repertoire through an inductive approach; and performing the activity - to begin filling the reper...
Educational efficiency in a dea-bootstrap approach
Francesca Giambona; Erasmo Vassallo; Elli Vassiliadis
2010-01-01
We use the PISA 2006 results to analyse the students' proficiencies in 24 European Countries with regard to two indexes that represent the educational resources available at home and the family background of students. Many factors affect the proficiencies and therefore, using a DEA-bootstrap method, we intend to measure the efficiency of the European educational systems as capability to ensure high students' competencies despite adverse conditions about the educational resources available in ...
'Bootstrap' charging of surfaces composed of multiple materials
Stannard, P. R.; Katz, I.; Parks, D. E.
1981-01-01
The paper examines the charging of a checkerboard array of two materials, only one of which tends to acquire a negative potential alone, using the NASA Charging Analyzer Program (NASCAP). The influence of the charging material's field causes the otherwise 'non-charging' material to acquire a negative potential due to the suppression of its secondary emission ('bootstrap' charging). The NASCAP predictions for the equilibrium potential difference between the two materials are compared to results based on an analytical model.
Higgs Critical Exponents and Conformal Bootstrap in Four Dimensions
DEFF Research Database (Denmark)
Antipin, Oleg; Mølgaard, Esben; Sannino, Francesco
2015-01-01
We investigate relevant properties of composite operators emerging in nonsupersymmetric, four-dimensional gauge-Yukawa theories with interacting conformal fixed points within a precise framework. The theories investigated in this work are structurally similar to the standard model of particle int...... bootstrap results are then compared to precise four dimensional conformal field theoretical results. To accomplish this, it was necessary to calculate explicitly the crossing symmetry relations for the global symmetry group SU($N$)$\\times$SU($N$)....
Spectrum of local boundary operators from boundary form factor bootstrap
Szots, M.; Takacs, G.
2007-01-01
Using the recently introduced boundary form factor bootstrap equations, we map the complete space of their solutions for the boundary version of the scaling Lee-Yang model and sinh-Gordon theory. We show that the complete space of solutions, graded by the ultraviolet behaviour of the form factors can be brought into correspondence with the spectrum of local boundary operators expected from boundary conformal field theory, which is a major evidence for the correctness of the boundary form fact...
Bootstrap and the physical values of $\\pi N$ resonance parameters
Semenov-Tian-Shansky, Kirill M.; Vereshagin, Alexander V.; Vereshagin, Vladimir V.
2007-01-01
This is the 6th paper in the series developing the formalism to manage the effective scattering theory of strong interactions. Relying on the theoretical scheme suggested in our previous publications we concentrate here on the practical aspect and apply our technique to the elastic pion-nucleon scattering amplitude. We test numerically the pion-nucleon spectrum sum rules that follow from the tree level bootstrap constraints. We show how these constraints can be used to estimate the tensor and...
Study and Integrate Bootstrap 3 for OpixManager
Tapani, Zhejia
2010-01-01
ABSTRACT This bachelor thesis is about how to study and integrate Bootstrap 3 into OpixManager. The purpose is to improve user interface of OpixManager application. OpixManager is constructed by using CodeIgniter and Model-View-Controller (MVC) framework. OpixManager application is for project management. It includes staff augmentation, customer management, report management and so on. It is to support both scrum and traditional software development process. There are two major parts...
Bootstrap-Based Regularization for Low-Rank Matrix Estimation
Josse, Julie; Wager, Stefan
2014-01-01
We develop a flexible framework for low-rank matrix estimation that allows us to transform noise models into regularization schemes via a simple bootstrap algorithm. Effectively, our procedure seeks an autoencoding basis for the observed matrix that is stable with respect to the specified noise model; we call the resulting procedure a stable autoencoder. In the simplest case, with an isotropic noise model, our method is equivalent to a classical singular value shrinkage estimator. For non-iso...
Addressing the P2P Bootstrap Problem for Small Networks
Wolinsky, David Isaac; Juste, Pierre St.; Boykin, P. Oscar; Figueiredo, Renato
2010-01-01
P2P overlays provide a framework for building distributed applications consisting of few to many resources with features including self-configuration, scalability, and resilience to node failures. Such systems have been successfully adopted in large-scale services for content delivery networks, file sharing, and data storage. In small-scale systems, they can be useful to address privacy concerns and for network applications that lack dedicated servers. The bootstrap problem, finding an existi...
A conformal bootstrap approach to critical percolation in two dimensions
Picco, Marco; Santachiara, Raoul
2016-01-01
We study four-point functions of critical percolation in two dimensions, and more generally of the Potts model. We propose an exact ansatz for the spectrum: an infinite, discrete and non-diagonal combination of representations of the Virasoro algebra. Based on this ansatz, we compute four-point functions using a numerical conformal bootstrap approach. The results agree with Monte-Carlo computations of connectivities of random clusters.
Bootstrapping Security Policies for Wearable Apps Using Attributed Structural Graphs
González-Tablas, Ana I.; Tapiador, Juan E.
2016-01-01
We address the problem of bootstrapping security and privacy policies for newly-deployed apps in wireless body area networks (WBAN) composed of smartphones, sensors and other wearable devices. We introduce a framework to model such a WBAN as an undirected graph whose vertices correspond to devices, apps and app resources, while edges model structural relationships among them. This graph is then augmented with attributes capturing the features of each entity together with user-defined tags. We...
Current profile control for high bootstrap current operation in ITER
International Nuclear Information System (INIS)
For the achievement of steady-state fusion power plant, non-inductively current-driven plasma operation should be maintained in tokamak fusion reactors. Total non-inductive current is a summation of bootstrap current proportional to the plasma pressure gradient and externally driven non-inductive current such as neutral beam driven current. Especially in order to establish a commercial reactor, it is necessary to reduce the amount of external current-drive power and to maintain the majority of the plasma current with bootstrap current. Burning plasma has high autonomy, so the change in current density profile including changes in particle and heat transports should be checked. In this study time-evolution analysis of the current density profile for burning plasmas in the ITER machine has been conducted by using 2.0-dimensional equilibrium, 1.5-dimensional-transport code (TOTAL code). Here current-diffusive ballooning mode model was adopted as a heat transport model. It is concluded that external current-drive is required both in the center and near the periphery of the plasma in order to maintain steady-state profiles of temperature and density with high bootstrap current fraction. (author)
Quantitative evaluation of PET image using event information bootstrap
Song, Hankyeol; Kwak, Shin Hye; Kim, Kyeong Min; Kang, Joo Hyun; Chung, Yong Hyun; Woo, Sang-Keun
2016-04-01
The purpose of this study was to enhance the effect in the PET image quality according to event bootstrap of small animal PET data. In order to investigate the time difference condition, realigned sinograms were generated from randomly sampled data set using bootstrap. List-mode data was obtained from small animal PET scanner for Ge-68 30 sec, Y-90 20 min and Y-90 60 min. PET image was reconstructed by Ordered Subset Expectation Maximization(OSEM) 2D with the list-mode format. Image analysis was investigated by Signal to Noise Ratio(SNR) of Ge-68 and Y-90 image. Non-parametric resampled PET image SNR percent change for the Ge-68 30 sec, Y-90 60 min, and Y-90 20 min was 1.69 %, 7.03 %, and 4.78 %, respectively. SNR percent change of non-parametric resampled PET image with time difference condition was 1.08 % for the Ge-68 30 sec, 6.74 % for the Y-90 60 min and 10.94 % for the Y-90 29 min. The result indicated that the bootstrap with time difference condition had a potential to improve a noisy Y-90 PET image quality. This method should be expected to reduce Y-90 PET measurement time and to enhance its accuracy.
Truncatable bootstrap equations in algebraic form and critical surface exponents
Gliozzi, Ferdinando
2016-01-01
We describe examples of drastic truncations of conformal bootstrap equations encoding much more information than that obtained by a direct numerical approach. A three-term truncation of the four point function of a free scalar in any space dimensions provides algebraic identities among conformal block derivatives which generate the exact spectrum of the infinitely many primary operators contributing to it. In boundary conformal field theories, we point out that the appearance of free parameters in the solutions of bootstrap equations is not an artifact of truncations, rather it reflects a physical property of permeable conformal interfaces which are described by the same equations. Surface transitions correspond to isolated points in the parameter space. We are able to locate them in the case of 3d Ising model, thanks to a useful algebraic form of 3d boundary bootstrap equations. It turns out that the low-lying spectra of the surface operators in the ordinary and the special transitions of 3d Ising model form...
Comparison Of Modified Bootstrap And Conventional Sensitometry In Medical Radiography
Bednarek, Daniel R.; Rudin, Stephen
1980-08-01
A new modified bootstrap approach to sensitometry is presented which provides H and D curves that show almost exact agreement with those obtained using conventional methods. Two bootstrap techniques are described; both involve a combination of inverse-square and step-ped wedge modulation of the radiation field and provide intensity-scale sensitometric curves as appropriate for medical radiography. H and D curves obtained with these modified techniques are compared with those obtained for screen-film combinations using inverse-square sensitometry as well as with those obtained for direct x-ray film using time-scale sensitometry. The stepped-wedge of the Wisconsin X-Ray Test Cassette was used in the boot-strap approach since it provides sufficient exposure latitude to encompass the useful den-sity range of medical x-ray film. This approach makes radiographic sensitometry quick and convenient, allowing accurate characteristic curves to be obtained for any screen-film cassette using standard diagnostic equipment.
DEFF Research Database (Denmark)
Hansen, Elo Harald
2005-01-01
Despite their excellent analytical chemical capacities for determination of low levels of metal species, electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry often require suitable pretreatment (separation and preconcentration) of the sample material to...
DEFF Research Database (Denmark)
Hansen, Elo Harald; Miró, Manuel; Long, Xiangbao;
2006-01-01
The determination of trace level concentrations of elements, such as metal species, in complex matrices by atomic absorption or emission spectrometric methods often require appropriate pretreatments comprising separation of the analyte from interfering constituents and analyte preconcentration...
Using minimum bootstrap support for splits to construct confidence regions for trees
Directory of Open Access Journals (Sweden)
Edward Susko
2006-01-01
Full Text Available Many of the estimated topologies in phylogenetic studies are presented with the bootstrap support for each of the splits in the topology indicated. If phylogenetic estimation is unbiased, high bootstrap support for a split suggests that there is a good deal of certainty that the split actually is present in the tree and low bootstrap support suggests that one or more of the taxa on one side of the estimated split might in reality be located with taxa on the other side. In the latter case the follow-up questions about how many and which of the taxa could reasonably be incorrectly placed as well as where they might alternatively be placed are not addressed through the presented bootstrap support. We present here an algorithm that finds the set of all trees with minimum bootstrap support for their splits greater than some given value. The output is a ranked list of trees, ranked according to the minimum bootstrap supports for splits in the trees. The number of such trees and their topologies provides useful supplementary information in bootstrap analyses about the reasons for low bootstrap support for splits. We also present ways of quantifying low bootstrap support by considering the set of all topologies with minimum bootstrap greater than some quantity as providing a confidence region of topologies. Using a double bootstrap we are able to choose a cutoff so that the set of topologies with minimum bootstrap support for a split greater than that cutoff gives an approximate 95% confidence region. As with bootstrap support one advantage of the methods is that they are generally applicable to the wide variety of phylogenetic estimation methods.
A bootstrapping soft shrinkage approach for variable selection in chemical modeling.
Deng, Bai-Chuan; Yun, Yong-Huan; Cao, Dong-Sheng; Yin, Yu-Long; Wang, Wei-Ting; Lu, Hong-Mei; Luo, Qian-Yi; Liang, Yi-Zeng
2016-02-18
In this study, a new variable selection method called bootstrapping soft shrinkage (BOSS) method is developed. It is derived from the idea of weighted bootstrap sampling (WBS) and model population analysis (MPA). The weights of variables are determined based on the absolute values of regression coefficients. WBS is applied according to the weights to generate sub-models and MPA is used to analyze the sub-models to update weights for variables. The optimization procedure follows the rule of soft shrinkage, in which less important variables are not eliminated directly but are assigned smaller weights. The algorithm runs iteratively and terminates until the number of variables reaches one. The optimal variable set with the lowest root mean squared error of cross-validation (RMSECV) is selected. The method was tested on three groups of near infrared (NIR) spectroscopic datasets, i.e. corn datasets, diesel fuels datasets and soy datasets. Three high performing variable selection methods, i.e. Monte Carlo uninformative variable elimination (MCUVE), competitive adaptive reweighted sampling (CARS) and genetic algorithm partial least squares (GA-PLS) are used for comparison. The results show that BOSS is promising with improved prediction performance. The Matlab codes for implementing BOSS are freely available on the website: http://www.mathworks.com/matlabcentral/fileexchange/52770-boss. PMID:26826688
Kinetic effects on a tokamak pedestal ion flow, ion heat transport and bootstrap current
International Nuclear Information System (INIS)
We consider the effects of a finite radial electric field on ion orbits in a subsonic pedestal. Using a procedure that makes a clear distinction between a transit average and a flux surface average we are able to solve the kinetic equation to retain the modifications due to finite E-vector x B-vector drift orbit departures from flux surfaces. Our approach properly determines the velocity space localized, as well as the nonlocal, portion of the ion distribution function in the banana and plateau regimes in the small aspect ratio limit. The rapid variation of the poloidal ion flow coefficient and the electrostatic potential in the total energy modify previous banana regime evaluations of the ion flow, the bootstrap current, and the radial ion heat flux in a subsonic pedestal. In the plateau regime, the rapid variation of the poloidal flow coefficient alters earlier results for the ion flow and bootstrap current, while leaving the ion heat flux unchanged since the rapid poloidal variation of the total energy was properly retained. (paper)
Robust parametric bootstrap test with MOM estimator: An alternative to independent sample t-test
Harun, Nurul Hanis; Yusof, Zahayu Md
2014-12-01
Normality and homogeneity are two major assumptions that need to be fulfilled when using independent sample t-test. However, not all data encompassed with these assumptions. Consequently, the result produced by independent sample t-test becomes invalid. Therefore, the alternative is to use robust statistical procedure in handling the problems of nonnormality and variances heterogeneity. This study proposed to use Parametric Bootstrap test with popular robust estimators, MADn and Tn which empirically determines the amount of trimming. The Type I error rates produced by each procedure were examined and compared with classical parametric test and nonparametric test namely independent sample t-test and Mann Whitney test, respectively. 5000 simulated data sets are used in this study in order to generate the Type I error for each procedure. The findings of this study indicate that the Parametric Bootstrap test with MADn and Tn produces the best Type I error control compared to the independent sample t-test and the Mann Whitney test under nonnormal distribution, heterogeneous variances and unbalanced design. Then, the performance of each procedure was demonstrated using real data.
Bootstrap inversion for Pn wave velocity in North-Western Italy
Directory of Open Access Journals (Sweden)
C. Eva
1997-06-01
Full Text Available An inversion of Pn arrival times from regional distance earthquakes (180-800 km, recorded by 94 seismic stations operating in North-Western Italy and surrounding areas, was carried out to image lateral variations of P-wave velocity at the crust-mantle boundary, and to estimate the static delay time at each station. The reliability of the obtained results was assessed using both synthetic tests and the bootstrap Monte Carlo resampling technique. Numerical simulations demonstrated the existence of a trade-off between cell velocities and estimated station delay times along the edge of the model. Bootstrap inversions were carried out to determine the standard deviation of velocities and time terms. Low Pn velocity anomalies are detected beneath the outer side of the Alps (-6% and the Western Po plain (-4% in correspondence with two regions of strong crustal thickening and negative Bouguer anomaly. In contrast, high Pn velocities are imaged beneath the inner side of the Alps (+4% indicating the presence of high velocity and density lower crust-upper mantle. The Ligurian sea shows high Pn velocities close to the Ligurian coastlines (+3% and low Pn velocities (-1.5% in the middle of the basin in agreement with the upper mantle velocity structure revealed by seismic refraction profiles.
Bootstrapping the Three-Loop Hexagon
International Nuclear Information System (INIS)
We consider the hexagonal Wilson loop dual to the six-point MHV amplitude in planar N = 4 super Yang-Mills theory. We apply constraints from the operator product expansion in the near-collinear limit to the symbol of the remainder function at three loops. Using these constraints, and assuming a natural ansatz for the symbol's entries, we determine the symbol up to just two undetermined constants. In the multi-Regge limit, both constants drop out from the symbol, enabling us to make a non-trivial confirmation of the BFKL prediction for the leading-log approximation. This result provides a strong consistency check of both our ansatz for the symbol and the duality between Wilson loops and MHV amplitudes. Furthermore, we predict the form of the full three-loop remainder function in the multi-Regge limit, beyond the leading-log approximation, up to a few constants representing terms not detected by the symbol. Our results confirm an all-loop prediction for the real part of the remainder function in multi-Regge 3 → 3 scattering. In the multi-Regge limit, our result for the remainder function can be expressed entirely in terms of classical polylogarithms. For generic six-point kinematics other functions are required.
Bootstrapping the Three-Loop Hexagon
Energy Technology Data Exchange (ETDEWEB)
Dixon, Lance J.; /CERN /SLAC; Drummond, James M.; /CERN /Annecy, LAPTH; Henn, Johannes M.; /Humboldt U., Berlin /Santa Barbara, KITP
2011-11-08
We consider the hexagonal Wilson loop dual to the six-point MHV amplitude in planar N = 4 super Yang-Mills theory. We apply constraints from the operator product expansion in the near-collinear limit to the symbol of the remainder function at three loops. Using these constraints, and assuming a natural ansatz for the symbol's entries, we determine the symbol up to just two undetermined constants. In the multi-Regge limit, both constants drop out from the symbol, enabling us to make a non-trivial confirmation of the BFKL prediction for the leading-log approximation. This result provides a strong consistency check of both our ansatz for the symbol and the duality between Wilson loops and MHV amplitudes. Furthermore, we predict the form of the full three-loop remainder function in the multi-Regge limit, beyond the leading-log approximation, up to a few constants representing terms not detected by the symbol. Our results confirm an all-loop prediction for the real part of the remainder function in multi-Regge 3 {yields} 3 scattering. In the multi-Regge limit, our result for the remainder function can be expressed entirely in terms of classical polylogarithms. For generic six-point kinematics other functions are required.
Optimization of bootstrap current in a large helical system with L = 2
International Nuclear Information System (INIS)
Neoclassical bootstrap currents in the banana and plateau regions are evaluated for an L = 2 large helical system with the major radius of 5 m. Various vacuum magnetic field configurations are invoked to optimize the bootstrap current. In the banana region shifting the magnetic axis and shaping magnetic surfaces have remarkable effects on the bootstrap current and it is clarified that a small outward shift of the magnetic axis and vertically elongated magnetic surfaces are favourable to reduce the bootstrap current. On the contrary, the bootstrap current in the plateau region depends strongly on the toroidal pitch number of helical winding coils but shifting the axis and shaping magnetic surfaces are not effective. The magnitude of bootstrap current is estimated for plasmas in the large helical system predicted by a one dimensional transport code. (author)
Better confidence intervals for left censored data using bias corrected bootstrap method
International Nuclear Information System (INIS)
Estimation of the 95% confidence intervals of the population parameters of small sized (say <= 30) environmental data samples under conventional statistical methodologies are error prone because the probability density function associated with the specified data sets, most of the times, is questionable. Therefore, in instances when the distribution of a statistic is unknown, nonparametric methods such as bootstrap override the conventional ones. The nonparametric (percentile) bootstrap method has been used to evaluate the confidence intervals of the mean. This paper describes the application of bias-corrected percentile bootstrap method that yields better confidence intervals than the percentile bootstrap method. An inter-comparative study of the two methods is also carried out. A case study with air activity data recorded from a specific Indian nuclear power plant is presented to support the superiority of bias corrected bootstrap method over the percentile bootstrap method and the conventional students -t method. (author)
Asal Bileşenler Analizine Bootstrap Yaklaşımı
AKTÜKÜN, Dr. Aylin
2011-01-01
Bu çalışmada, bootstrap yöntemlerin asal bileşenler analizine uygulanma sürecini sunduk. Hipotetik bir veri ile asal bileşenler analizinde başvurulan bazı güven aralıklarının bootstrap yöntemlerle nasıl gerçekleştirilebileceğini gösterdik. Makaledeki tüm bootstrap süreçleri Mathematica dilinde yazdığımız bir programla gerçekleştirdik. Anahtar Kelimeler: Asal bileşenler analizi, Bootstrap, Bootstrap kantiller, Bootstrap Güven Aralıkları, Mathematica. ABSRACT In this paper, we apply ...
International Nuclear Information System (INIS)
The simultaneous determination of actinides in air filter and water samples around the WIPP site have been demonstrated. The analytical method is based on the selective separation and purification by anion exchange and Eichrome-TEVA, TRU and DGA-resin followed by determination of actinides by alpha spectrometry. Counting sources for alpha spectrometric measurements were prepared by microcoprecipitation on neodymium fluoride (NdF3). Radiochemical yields were determined using 242Pu, 229Th, 243Am and 232U as tracers. The validation of the method is performed through the analysis of reference materials or participating in laboratory intercomparison programs. The plutonium concentrations in aerosols varied seasonally, being highest in spring and summer due to the spring-time enhanced wind-storm transportation of radioactive aerosols from the stratosphere to the troposphere. The 238Pu/239+240Pu activity ratio in the aerosol samples is typically close to that of global fallout from historic above-ground nuclear weapons testing. The results presented here indicate that the source of plutonium in the WIPP environment results mainly from global nuclear fallout and there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP. (author)
Transport simulation of a large-bootstrap-current Tokamak plasma driven by the ohmic seed current
International Nuclear Information System (INIS)
A large-bootstrap-current tokamak plasma driven by the ohmic seed current has been studied for inductively-operated ultra-long-pulse tokamak fusion reactors. The safety factor profile with the negative magnetic shear has been demonstrated only by the combination of the ohmic and bootstrap currents, by adjusting the density profile, and the bootstrap current fraction more than 80% is realized with the help of the increased q(0) value. 7 refs., 4 figs., 1 tab
Full Hirshman-Sigmar model for bootstrap current estimate in the ETE small aspect ratio Tokamak
International Nuclear Information System (INIS)
An estimate of the bootstrap current through the full Hirshman-Sigmar model, which is the most accurate available for thermal plasmas up to now, will be carried out the ETE tokamak. These results will be compared to previous calculations performed with the single-ion collisionless Hirshman model in order to check possible limitations imposed by this model on the bootstrap current estimate. The dependences of the bootstrap current profile upon the plasma parameters will also be briefly illustrated. (author)
Performance of the bootstrap for DEA estimators and iterating the principle
Simar, Léopold; Wilson, Paul
2000-01-01
This paper further examines the bootstrap method proposed by Simar and Wilson (1998) for DEA efficiency estimators. Some simplifications are provided, and we provide Monte Carlo evidence on the coverage probabilities of confidence intervals estimated by the method. In addition, we provide similar evidence for confidence intervals estimate with the so-called naive bootstrap, which is known to be inconsistent in the DEA setting. Finally, we propose an interated version of the bootstrap which ma...
Higher-order accuracy of multiscale-double bootstrap for testing regions
Shimodaira, Hidetoshi
2013-01-01
We consider hypothesis testing for the null hypothesis being represented as an arbitrary-shaped region in the parameter space. We compute an approximate p-value by counting how many times the null hypothesis holds in bootstrap replicates. This frequency, known as bootstrap probability, is widely used in evolutionary biology, but often reported as biased in the literature. Based on the asymptotic theory of bootstrap confidence intervals, there have been some new attempts for adjusting the bias...
A PARAMETRIC BOOTSTRAP USING THE FIRST FOUR
MOMENTS OF THE RESIDUALS
Treyens, Pierre-Eric
2007-01-01
We consider linear regression models and we suppose that disturbances are either Gaussian or non Gaussian. Until now, within the framework of the bootstrap, we thought that the error in rejection probability (ERP) had the same rate of convergence with the parametric bootstrap or the nonparametric bootstrap. For linear data generating processes (DGP) we show in this paper that this assertion is false if skewness and/or kurtosis coefficients of the distribution of the disturbances are nonnull. ...
Bootstrap Co-integration Rank Testing: The Effect of Bias-Correcting Parameter Estimates
Cavaliere, Giuseppe; Taylor, A. M. Robert; Trenkler, Carsten
2013-01-01
In this paper we investigate bootstrap-based methods for bias-correcting the first-stage parameter estimates used in some recently developed bootstrap implementations of the co-integration rank tests of Johansen (1996). In order to do so we adapt the framework of Kilian (1998) which estimates the bias in the original parameter estimates using the average bias in the corresponding parameter esti- mates taken across a large number of auxiliary bootstrap replications. A number of possible imp...
Building Confidence Intervals with Block Bootstraps for the Variance Ratio Test of Predictability
Eduardo José Araújo Lima; Benjamin Miranda Tabak
2007-01-01
This paper compares different versions of the multiple variance ratio test based on bootstrap techniques for the construction of empirical distributions. It also analyzes the crucial issue of selecting optimal block sizes when block bootstrap procedures are used, by applying the methods developed by Hall et al. (1995) and by Politis and White (2004). By comparing the results of the different methods using Monte Carlo simulations, we conclude that methodologies using block bootstrap methods pr...
On the Impact of Bootstrap in Survey Sampling and Small-Area Estimation
Lahiri, P.
2003-01-01
Development of valid bootstrap procedures has been a challenging problem for survey samplers for the last two decades. This is due to the fact that in surveys we constantly face various complex issues such as complex correlation structure induced by the survey design, weighting, imputation, small-area estimation, among others. In this paper, we critically review various bootstrap methods developed to deal with these challenging issues. We discuss two applications where the bootstrap has been ...
First estimate of bootstrap current in the ETE small aspect ratio tokamak
International Nuclear Information System (INIS)
A first estimate of the bootstrap current in the ETE (Experimento Tokamak Esferico) small aspect ratio tokamak using the Hirshman single-ion collisionless model shows that we can expect a ratio of 15 to 30% of total bootstrap current in relation to the total equilibrium current depending on the optimization level of the plasma profile parameters. Bootstrap current levels basically depend on the βp values which must be kept under a critical level due to stability conditions and current alignment requirements. Preliminary studies of Shaing's predictions regarding bootstrap current calculations in collisional plasmas are briefly described and different methods for the trapped particle fraction calculation are also illustrated. (Author)
Dale Poirier
2008-01-01
This paper provides Bayesian rationalizations for White’s heteroskedastic consistent (HC) covariance estimator and various modifications of it. An informed Bayesian bootstrap provides the statistical framework.
Santos, Inês C; Mesquita, Raquel B R; Rangel, António O S S
2015-09-01
This work describes the development of a solid phase spectrophotometry method in a μSI-LOV system for cadmium, zinc, and copper determination in freshwaters. NTA (Nitrilotriacetic acid) beads with 60-160 μm diameter were packed in the flow cell of the LOV for a μSPE column of 1 cm length. The spectrophotometric determination is based on the colourimetric reaction between dithizone and the target metals, previously retained on NTA resin. The absorbance of the coloured product formed is measured, at 550 nm, on the surface of the NTA resin beads in a solid phase spectrophotometry approach. The developed method presented preconcentration factors in the range of 11-21 for the metal ions. A LOD of 0.23 μg L(-1) for cadmium, 2.39 μg L(-1) for zinc, and 0.11 μg L(-1) for copper and a sampling rate of 12, 13, and 15 h(-1) for cadmium, zinc, and copper were obtained, respectively. The proposed method was successfully applied to freshwater samples. PMID:26388376
Alcaide-Molina, Miguel; Priego-Capote, Feliciano; Luque de Castro, María Dolores
2013-02-15
A dual method is proposed for the determination of metabolites involved in the shikimate pathway which are biomarkers of the effects of glyphosate action on plants exposed to this herbicide. Extraction of the target metabolites (phenylalanine, tryptophan, tyrosine and shikimic acid) from a wheat model plant was accelerated by ultrasound energy. After centrifugation and micro-filtration, 1 μL of extract was injected into the chromatograph in an isocratic regime for 4 min to determine shikimate by absorption at 254 nm. In the mean time, a 130 μL aliquot of extract was subjected to derivatization with o-phthaldialdehyde and 2-mercaptoethanol for 1 min, the reaction stopped and 1 μL of the solution chromatographied in a gradient regime prior to laser-induced fluorescence detection of the derivatized amino acids. The characterization of the dual method provided limits of detection around 0.03 μg mL(-1) for the aromatic amino acids and 1.52 μg mL(-1) for shikimate, whereas the limits of quantitation ranged between 0.084 and 0.093 μg mL(-1) for amino acids and was of 4.56 μg mL(-1) for shikimate. The suitability of the method was checked by application to Triticum aestivum (wheat) plants grown under controlled conditions, sprayed with different doses of glyphosate and collected at different times after exposition to the herbicide. PMID:23598041
Directory of Open Access Journals (Sweden)
Frantisek Cacho
2012-01-01
Full Text Available Flow-through stripping chronopotentiometry with a gold wire electrode was used for the determination of total arsenic and cadmium in cadmium sulphate solutions for cadmium production. The analysis is based on the online separation of arsenic as arsenate anion from cadmium cations by means of a cation exchanger. On measuring arsenate in the effluent, the trapped cadmium is eluted by sodium chloride solution and determined in a small segment of the effluent by making use of the same electrode. The elaborated protocol enables a full automatic measurement of both species in the same sample solution. The accuracy of the results was confirmed by atomic absorption spectrometry. The LOD and LOQ for Arsenic were found to be 0.9 μg dm-3 and 2.7 μg dm-3, respectively. A linear response range was observed in the concentration range of 1 to 300 μg dm-3 for sample volumes of 4 mL. The repeatability and reproducibility were found to be 2.9% and 5.2%, respectively. The linear response range for cadmium was found to be 0.5 to 60 g/L. The method was tested on samples from a cadmium production plant.
DEFF Research Database (Denmark)
Sørensen, P.; Jensen, E.S.
A novel diffusion method was used for preparation of NH4+- and NO3--N samples from soil extracts for N-15 determination. Ammonium, and nitrate following reduction to ammonia, are allowed to diffuse to an acid-wetted glass filter enclosed in polytetrafluoroethylene tape. The method was evaluated...... with simulated soil extracts obtained using 50 ml of 2 M potassium chloride solution containing 130-mu-g of NH4+-N (2.3 atom% N-15) and 120-mu-g of NO3--N (natural N-15 abundance). No cross-over in the N-15 abundances of NH4+-N and NO3--N was observed, indicating a quantitative diffusion process (72 h......, 25-degrees-C). Owing to the presence of inorganic nitrogen impurities in the potassium chloride, the N-15 enrichments should be corrected for the blank nitrogen content....
A Bootstrap Approach to an Affordable Exploration Program
Oeftering, Richard C.
2011-01-01
This paper examines the potential to build an affordable sustainable exploration program by adopting an approach that requires investing in technologies that can be used to build a space infrastructure from very modest initial capabilities. Human exploration has had a history of flight programs that have high development and operational costs. Since Apollo, human exploration has had very constrained budgets and they are expected be constrained in the future. Due to their high operations costs it becomes necessary to consider retiring established space facilities in order to move on to the next exploration challenge. This practice may save cost in the near term but it does so by sacrificing part of the program s future architecture. Human exploration also has a history of sacrificing fully functional flight hardware to achieve mission objectives. An affordable exploration program cannot be built when it involves billions of dollars of discarded space flight hardware, instead, the program must emphasize preserving its high value space assets and building a suitable permanent infrastructure. Further this infrastructure must reduce operational and logistics cost. The paper examines the importance of achieving a high level of logistics independence by minimizing resource consumption, minimizing the dependency on external logistics, and maximizing the utility of resources available. The approach involves the development and deployment of a core suite of technologies that have minimum initial needs yet are able expand upon initial capability in an incremental bootstrap fashion. The bootstrap approach incrementally creates an infrastructure that grows and becomes self sustaining and eventually begins producing the energy, products and consumable propellants that support human exploration. The bootstrap technologies involve new methods of delivering and manipulating energy and materials. These technologies will exploit the space environment, minimize dependencies, and
Two novel applications of bootstrap currents: snakes and jitter stabilization
International Nuclear Information System (INIS)
Both neoclassical theory and certain turbulence theories of particle transport in tokamaks predict the existence of bootstrap (i.e., pressure-driven) currents. Two new applications of this form of non-inductive current are considered in this work. The first is an explanation of the 'snake' phenomenon observed in JET based on steady-state nonlinear tearing theory. The second is an active method of dynamic stabilization of the m=1 mode using the 'jitter' approach suggested by Thyagaraja et al in a recent paper. (author) 11 refs
Microcanonical statistics of black holes and bootstrap condition
Huang, Wung-Hong
2000-01-01
The microcanonical statistics of the Schwarzschild black holes as well as the Reissner-Nordstr$\\sf \\ddot{o}$m black holes are analyzed. In both cases we set up the inequalities in the microcanonical density of states. These are then used to show that the most probable configuration in the gases of black holes is that one black hole acquires all of the mass and all of the charge at high energy limit. Thus the black holes obey the statistical bootstrap condition and, in contrast to the other in...
The S-matrix Bootstrap II: Two Dimensional Amplitudes
Paulos, Miguel F; Toledo, Jonathan; van Rees, Balt C; Vieira, Pedro
2016-01-01
We consider constraints on the S-matrix of any gapped, Lorentz invariant quantum field theory in 1 + 1 dimensions due to crossing symmetry and unitarity. In this way we establish rigorous bounds on the cubic couplings of a given theory with a fixed mass spectrum. In special cases we identify interesting integrable theories saturating these bounds. Our analytic bounds match precisely with numerical bounds obtained in a companion paper where we consider massive QFT in an AdS box and study boundary correlators using the technology of the conformal bootstrap.
Bootstrapped Oblivious Transfer and Secure Two-Party Function Computation
Wang, Ye
2009-01-01
We propose an information theoretic framework for the secure two-party function computation (SFC) problem and introduce the notion of SFC capacity. We study and extend string oblivious transfer (OT) to sample-wise OT. We propose an efficient, perfectly private OT protocol utilizing the binary erasure channel or source. We also propose the bootstrap string OT protocol which provides disjoint (weakened) privacy while achieving a multiplicative increase in rate, thus trading off security for rate. Finally, leveraging our OT protocol, we construct a protocol for SFC and establish a general lower bound on SFC capacity of the binary erasure channel and source.
Bootstrap framework : web-suunnittelun työkaluna
Peltomäki, Veera
2014-01-01
Pienen näytön omaavat mobiililaitteet kasvattavat suosiotaan Internetin selaamisessa. Samaan aikaan modernit pelikonsolit ja SmartTV:t yleistyvät kuluttajien keskuudessa, jolloin Internetiä voi selata suuren näyttötarkkuuden omaavilla laitteilla. Responsiivinen web-suunnittelu vastaa nykypäivän vaatimuksiin, jossa käyttäjät odottavat sivustoilta yhdenmukaista käyttökokemusta, päätelaitteesta riippumatta. Tämä opinnäytetyö käsittelee responsiivisen Bootstrap frameworkin valintaa web-suunni...
Convergence rates of empirical block length selectors for block bootstrap
Nordman, Daniel J.; Lahiri, Soumendra N.
2014-01-01
We investigate the accuracy of two general non-parametric methods for estimating optimal block lengths for block bootstraps with time series – the first proposed in the seminal paper of Hall, Horowitz and Jing (Biometrika 82 (1995) 561–574) and the second from Lahiri et al. (Stat. Methodol. 4 (2007) 292–321). The relative performances of these general methods have been unknown and, to provide a comparison, we focus on rates of convergence for these block length selectors for the moving block ...
Comparing groups randomization and bootstrap methods using R
Zieffler, Andrew S; Long, Jeffrey D
2011-01-01
A hands-on guide to using R to carry out key statistical practices in educational and behavioral sciences research Computing has become an essential part of the day-to-day practice of statistical work, broadening the types of questions that can now be addressed by research scientists applying newly derived data analytic techniques. Comparing Groups: Randomization and Bootstrap Methods Using R emphasizes the direct link between scientific research questions and data analysis. Rather than relying on mathematical calculations, this book focus on conceptual explanations and the use of statistica
A survey of bootstrap methods in finite population sampling
Directory of Open Access Journals (Sweden)
Zeinab Mashreghi
2016-03-01
Full Text Available We review bootstrap methods in the context of survey data where the effect of the sampling design on the variability of estimators has to be taken into account. We present the methods in a unified way by classifying them in three classes: pseudo-population, direct, and survey weights methods. We cover variance estimation and the construction of confidence intervals for stratified simple random sampling as well as some unequal probability sampling designs. We also address the problem of variance estimation in presence of imputation to compensate for item non-response.