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1

SDI: setting the record straight  

SciTech Connect

After a few introductory remarks, Mr. Adelman first discusses Soviet propaganda against SDI. He then poses and answers questions regarding the following: SDI and the ABM Treaty; SDI and US arms control objectives; and the ethics of SDI. The final portion of the address reviews US nonproliferation efforts.

Adelman, K.L.

1985-01-01

2

Dangers of limited SDI  

SciTech Connect

Recent efforts to redefine the Strategic Defense Initiative (SDI) are mostly aimed at building support for a system to defend US land-based missiles. This is thought to be a more feasible goal than President Reagan's dream of an impregnable shield to defend the US population against ballistic missiles. But a feasible idea is not necessarily a good one. While chasing the population-defense fantasy would destroy the existing arms control regime and waste the national treasure of money and talent, defending land-based missiles would be dangerous and destabilizing. Defense Secretary Caspar Weinberger held fast to the idea of population defense in January, when he told the Senate Armed Services Committee that even early deployments of SDI systems that could be developed in the near future should be the first phase of a system that would protect the continent. But such statements may reflect the administration's determination to do away with the 1972 Anti-Ballistic Missile Treaty more than its belief that population defense is a reasonable goal. The author notes that, to those longstanding problems of defense decision making, they must now add the pressures of SDI. Furthermore, whatever the motives of those who advocate redirecting SDI, it is clear that concerns about the vulnerability of land-based missiles could be addressed in more sensible ways. 5 references.

Marsh, G.E.

1987-03-01

3

Sdi and arms control  

SciTech Connect

President Reagan's Strategic Defense Initiative, or SDI, and the pursuit of defenses to protect against ballistic missile attack are issues of significant debate. Some praise the proposal, first made in a presidential address to the nation on 23 March 1983, as a grand vision that will abolish nuclear blackmail by adopting a totally defensive posture. Others condemn it as being destabilizing, a Pandora's box of strategic transition that could precipitate armed conflict.

DeWolf, H.G.

1989-11-01

4

STATISTICAL PROPERTIES OF DYNAMICAL CHAOS  

Microsoft Academic Search

This study presents a survey of the results obtained by the au- thors on statistical description of dynamical chaos and the eect of noise on dynamical regimes. We deal with nearly hyperbolic and nonhyperbolic chaotic attractors and discuss methods of diagnosing the type of an attractor. We consider regularities of the relaxation to an invariant probability measure for dieren t

Vadim S. Anishchenko; Tatjana E. Vadivasova; Galina I. Strelkova; George A. Okrokvertskhov

2004-01-01

5

Statistical physics of social dynamics  

Microsoft Academic Search

Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide list of topics are reviewed ranging from opinion and cultural and language dynamics to crowd behavior,

Claudio Castellano; Santo Fortunato; Vittorio Loreto

2009-01-01

6

Building SDI Bridges for Catchment Management  

Microsoft Academic Search

This research paper discusses the importance of spatial data and Spatial Data Infra- structure (SDI) for catchment management. It reviews four SDI theories including hier- archical spatial theory, diffusion theory, evolution theory and principal-agent (P-A) the- ory and discusses their characteristics and potential utilisation for catchment manage- ment. As catchment management issues are characterised by multi-level stakeholder participation in SDI

Dev Raj Paudyal; Kevin McDougall; Armando Apan

2009-01-01

7

Application of SDI technology in space propulsion  

NASA Astrophysics Data System (ADS)

Numerous technologies developed by the DOD within the SDI program are now available for adaptation to the requirements of commercial spacecraft; SDI has accordingly organized the Technology Applications Information System data base, which contains nearly 2000 nonproprietary abstracts on SDI technology. Attention is here given to such illustrative systems as hydrogen arcjets, ammonia arcjets, ion engines, SSTO launch vehicles, gel propellants, lateral thrusters, pulsed electrothermal thrusters, laser-powered rockets, and nuclear propulsion.

Klein, Allen J.

8

Statistical Hypotheses in Stellar Dynamics  

Microsoft Academic Search

This paper starts with a short review of the usual methods of stellar dynamics and analyzes the underlying hypotheses. The most successful approach to stellar dynamics has been the one which neglects interactions between nearby stars (because they are weak) and takes into consideration the motion of stars in a smooth field of force only, produced by the smeared-out mass

Herbert Jehle

1946-01-01

9

SDI FOR CONSERVING WATER IN CORN PRODUCTION  

Microsoft Academic Search

On-farm water savings of 20-25% can be obtained with subsurface drip irrigation (SDI) for corn production on the deep silt loam soils of the semi-arid Great Plains (United States) through a combination of reducing non-beneficial water balance components and better usage of precipitation. The conjunctive use of SDI with appropriate nitrogen fertigation strategies resulted in optimization of corn yield, nitrogen

Freddie R. Lamm

10

Statistical dynamics of religion evolutions  

NASA Astrophysics Data System (ADS)

A religion affiliation can be considered as a “degree of freedom” of an agent on the human genre network. A brief review is given on the state of the art in data analysis and modelization of religious “questions” in order to suggest and if possible initiate further research, after using a “statistical physics filter”. We present a discussion of the evolution of 18 so-called religions, as measured through their number of adherents between 1900 and 2000. Some emphasis is made on a few cases presenting a minimum or a maximum in the investigated time range—thereby suggesting a competitive ingredient to be considered, besides the well accepted “at birth” attachment effect. The importance of the “external field” is still stressed through an Avrami late stage crystal growth-like parameter. The observed features and some intuitive interpretations point to opinion based models with vector, rather than scalar, like agents.

Ausloos, M.; Petroni, F.

2009-10-01

11

Statistical Kinetics of Macromolecular Dynamics  

PubMed Central

Fluctuations in biochemical processes can provide insights into the underlying kinetics beyond what can be gleaned from studies of average rates alone. Historically, analysis of fluctuating transmembrane currents supplied information about ion channel conductance states and lifetimes before single-channel recording techniques emerged. More recently, fluctuation analysis has helped to define mechanochemical pathways and coupling ratios for the motor protein kinesin as well as to probe the contributions of static and dynamic disorder to the kinetics of single enzymes. As growing numbers of assays are developed for enzymatic or folding behaviors of single macromolecules, the range of applications for fluctuation analysis increases. To evaluate specific biochemical models against experimental data, one needs to predict analytically the distribution of times required for completion of each reaction pathway. Unfortunately, using traditional methods, such calculations can be challenging for pathways of even modest complexity. Here, we derive an exact expression for the distribution of completion times for an arbitrary pathway with a finite number of states, using a recursive method to solve algebraically for the appropriate moment-generating function. To facilitate comparisons with experiments on processive motor proteins, we develop a theoretical formalism for the randomness parameter, a dimensionless measure of the variance in motor output. We derive the randomness for motors that take steps of variable sizes or that move on heterogeneous substrates, and then discuss possible applications to enzymes such as RNA polymerase, which transcribes varying DNA sequences, and to myosin V and cytoplasmic dynein, which may advance by variable increments.

Shaevitz, Joshua W.; Block, Steven M.; Schnitzer, Mark J.

2005-01-01

12

Statistical Ensembles, Dynamical Ensembles and Hybrid Ensembles  

NASA Astrophysics Data System (ADS)

It is now appreciated that information concerning the uncertainty of a forecast should be an intrinsic part of any forecasting product. It is still not clear, however, what the best way of estimating forecast uncertainty is. In the context of ``traditional'' best guess forecasts, one approach is to estimate error statistics using historical forecasts. Statistical ensembles can then be generated from these error statistics but such ensembles do not capture the state dependence of predictability. Seasonal and state dependence of the error statistics can be incorporated into the error models, but the number of parameters required can then outstrip the amount of data available. In recent years dynamical ensembles, i.e. ensembles of forecasts, each generated using a NWP model, have become a standard part of operational forecasting procedure. Dynamical ensembles attempt to quantify the uncertainty in a forecast due to initial condition error, and also, through stochastic parameterizations and multi-model approaches, the uncertainty due to model error. Dynamical ensembles are capable of reflecting state dependence predictability. The primary disadvantages of dynamical ensembles is their small size, which is determined by computational expense, and the fact that they do not reflect uncertainty due to residual errors. We present a combined approach. The basic concept is very simple; ``dress'' each member of a dynamical ensemble with its own statistical ``daughter'' ensemble. This results in ``hyperensembles'' which both capture the state dependent nature of predictability, and contain information on residual errors determined using historical forecasts. The error statistics for the daughter ensembles should be the statistics of the errors of the best members of the ensembles. While the is idea simple, we show that estimating the best member error statistics for an individual ensemble member has pitfalls. Specifically, attempting to identify the best member of an ensemble in a space with too low a dimensional will lead to suboptimal results.

Roulston, M. S.; Smith, L. A.

2001-12-01

13

MEDLINE SDI services: how do they compare?*  

PubMed Central

Introduction: Selective dissemination of information (SDI) services regularly alert users to new information on their chosen topics. This type of service can increase a user's ability to keep current and may have a positive impact on efficiency and productivity. Currently, there are many venues available where users can establish, store, and automatically run MEDLINE searches. Purpose: To describe, evaluate, and compare SDI services for MEDLINE. Resources: The following SDI services were selected for this study: PubMed Cubby, BioMail, JADE, PubCrawler, OVID, and ScienceDirect. Methodology: Identical searches were established in four of the six selected SDI services and were run on a weekly basis over a period of two months. Eight search strategies were used in each system to test performance under various search conditions. The PubMed Cubby system was used as the baseline against which the other systems were compared. Other aspects were evaluated in all six services and include ease of use, frequency of results, ability to use MeSH, ability to access and edit existing search strategies, and ability to download to a bibliographic management program. Results: Not all MEDLINE SDI services retrieve identical results, even when identical search strategies are used. This study also showed that the services vary in terms of features and functions offered.

Shultz, Mary; De Groote, Sandra L.

2003-01-01

14

Exact statistics of chaotic dynamical systems.  

PubMed

We present an inverse method to construct large classes of chaotic invariant sets together with their exact statistics. The associated dynamical systems are characterized by a probability distribution and a two-form. While our emphasis is on classical systems, we briefly speculate about possible applications to quantum field theory, in the context of generalizations of stochastic quantization. PMID:19045452

Guralnik, Zachary

2008-09-01

15

Teaching the principles of statistical dynamics.  

PubMed

We describe a simple framework for teaching the principles that underlie the dynamical laws of transport: Fick's law of diffusion, Fourier's law of heat flow, the Newtonian viscosity law, and the mass-action laws of chemical kinetics. In analogy with the way that the maximization of entropy over microstates leads to the Boltzmann distribution and predictions about equilibria, maximizing a quantity that E. T. Jaynes called "caliber" over all the possible microtrajectories leads to these dynamical laws. The principle of maximum caliber also leads to dynamical distribution functions that characterize the relative probabilities of different microtrajectories. A great source of recent interest in statistical dynamics has resulted from a new generation of single-particle and single-molecule experiments that make it possible to observe dynamics one trajectory at a time. PMID:23585693

Ghosh, Kingshuk; Dill, Ken A; Inamdar, Mandar M; Seitaridou, Effrosyni; Phillips, Rob

2006-02-01

16

SDI Effectiveness from the User Perspective  

Microsoft Academic Search

Definitions of spatial data infrastructure (SDI), and claims about its value, emphasise applications that solve real societal issues as the ultimate benefit. While it may be premature to expect that those benefits show up in many SDIs (if in any, by now), preparing for systematic evaluation is timely. Initiatives like the Spatial Data Interest Community on Monitoring and Reporting, in

Zorica Nedovi?-Budi?; Jeffrey K. Pinto; Nama Raj Budhathoki

17

SDI (Strategic Defense Initiative): a policy analysis  

SciTech Connect

Contents include -- Foundations of Deterrence; A Model for Stability; Analysis of SDI/Stability; Related Issues; Treatment of Implementation Factors; Historical Evolution and Trends; The Strategic Choices and Flexible Response; The Planners' Perspective; The Impact of Strategic Defense on a Strategy of Flexible Response; Synthesis.

Fought, S.O.

1987-01-01

18

Statistical physics approaches to neuronal network dynamics.  

PubMed

We review a statistical physics approach for reduced descriptions of neuronal network dynamics. From a network of all-to-all coupled, excitatory integrate-and-fire neurons, we derive a (2+1)-D advection-diffusion equation for a probability distribution function, which describes neuronal population dynamics. We further show how to derive a (1+1)-D kinetic equation, using a moment closure scheme, without introducing any new parameters to the system. We demonstrate the numerical accuracy of our kinetic theory by comparing its results to Monte Carlo simulations of the full integrate-and-fire neuronal network. PMID:22002236

Cai, David; Tao, Louis

2011-10-25

19

ASTROPHYSICAL FLUID DYNAMICS VIA DIRECT STATISTICAL SIMULATION  

SciTech Connect

In this paper, we introduce the concept of direct statistical simulation for astrophysical flows. This technique may be appropriate for problems in astrophysical fluids where the instantaneous dynamics of the flows are of secondary importance to their statistical properties. We give examples of such problems including mixing and transport in planets, stars, and disks. The method is described for a general set of evolution equations, before we consider the specific case of a spectral method optimized for problems on a spherical surface. The method is illustrated for the simplest non-trivial example of hydrodynamics and magnetohydrodynamics on a rotating spherical surface. We then discuss possible extensions of the method both in terms of computational methods and the range of astrophysical problems that are of interest.

Tobias, S. M. [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom); Dagon, K.; Marston, J. B., E-mail: smt@maths.leeds.ac.uk [Department of Physics, Brown University, Providence, RI 02912-1843 (United States)

2011-02-01

20

Statistical dynamics of interacting kinks I  

NASA Astrophysics Data System (ADS)

A statistical-mechanical theory is developed for a gas of kinks (or one-dimensional domain walls) interacting with exponential attractive forces, which models long-time behaviors of the bistable TDGL field equation. Employing a factorization approximation in the BBGKY-like hierarchical equations for the size distribution functions of consecutive domains, we obtain a kinetic equation for the size distribution function of a single domain. The scaling solution of thr latter yields the logarithmic growth law of domain sizes with the coefficient related to the width of the size distribution. Scattering structure function is also obtained. The results are compared with those of molecular dynamics and experiments on layered magnets.

Kawasaki, Kyozi; Nagai, Tatsuzo

1983-08-01

21

The origins of SDI, 1944--1983  

SciTech Connect

The most distinctive and important contribution of this new book on the Strategic Defense Initiative is that it ends where most other studies begin, with President Ronald Reagan's famous (or infamous, depending on one's perspective) March 1983 speech that introduced the Star Wars concept. In taking this approach, Donald R. Baucom - a former Air Force historian who has been the official historian who has been the official historian of the Strategic Defense Initiative Organization since May 1987 - helps to correct the common misperception that US efforts in strategic defense began and ended with the SDI. Although Baucom tells us that The Origins of SDI is a significantly revised version of an SDIO study he completed in 1989, representing his own views and not those of the SDIO, the reader should be warned that the book reads like an official history. It is often dry or too episodic and offers little that is new in the way of analysis or interpretation.

Baucom, D.R.

1992-01-01

22

STATISTICAL TOOLS FOR CLASSIFYING GALAXY GROUP DYNAMICS  

SciTech Connect

The dynamical state of galaxy groups at intermediate redshifts can provide information about the growth of structure in the universe. We examine three goodness-of-fit tests, the Anderson-Darling (A-D), Kolmogorov, and {chi}{sup 2} tests, in order to determine which statistical tool is best able to distinguish between groups that are relaxed and those that are dynamically complex. We perform Monte Carlo simulations of these three tests and show that the {chi}{sup 2} test is profoundly unreliable for groups with fewer than 30 members. Power studies of the Kolmogorov and A-D tests are conducted to test their robustness for various sample sizes. We then apply these tests to a sample of the second Canadian Network for Observational Cosmology Redshift Survey (CNOC2) galaxy groups and find that the A-D test is far more reliable and powerful at detecting real departures from an underlying Gaussian distribution than the more commonly used {chi}{sup 2} and Kolmogorov tests. We use this statistic to classify a sample of the CNOC2 groups and find that 34 of 106 groups are inconsistent with an underlying Gaussian velocity distribution, and thus do not appear relaxed. In addition, we compute velocity dispersion profiles (VDPs) for all groups with more than 20 members and compare the overall features of the Gaussian and non-Gaussian groups, finding that the VDPs of the non-Gaussian groups are distinct from those classified as Gaussian.

Hou, Annie; Parker, Laura C.; Harris, William E. [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Wilman, David J. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)], E-mail: houa2@physics.mcmaster.ca, E-mail: lparker@physics.mcmaster.ca, E-mail: harris@physics.mcmaster.ca, E-mail: dwilman@mpe.mpg.de

2009-09-10

23

A statistical description of neural ensemble dynamics.  

PubMed

The growing use of multi-channel neural recording techniques in behaving animals has produced rich datasets that hold immense potential for advancing our understanding of how the brain mediates behavior. One limitation of these techniques is they do not provide important information about the underlying anatomical connections among the recorded neurons within an ensemble. Inferring these connections is often intractable because the set of possible interactions grows exponentially with ensemble size. This is a fundamental challenge one confronts when interpreting these data. Unfortunately, the combination of expert knowledge and ensemble data is often insufficient for selecting a unique model of these interactions. Our approach shifts away from modeling the network diagram of the ensemble toward analyzing changes in the dynamics of the ensemble as they relate to behavior. Our contribution consists of adapting techniques from signal processing and Bayesian statistics to track the dynamics of ensemble data on time-scales comparable with behavior. We employ a Bayesian estimator to weigh prior information against the available ensemble data, and use an adaptive quantization technique to aggregate poorly estimated regions of the ensemble data space. Importantly, our method is capable of detecting changes in both the magnitude and structure of correlations among neurons missed by firing rate metrics. We show that this method is scalable across a wide range of time-scales and ensemble sizes. Lastly, the performance of this method on both simulated and real ensemble data is used to demonstrate its utility. PMID:22319486

Long, John D; Carmena, Jose M

2011-11-28

24

Statistical analysis of undersampled dynamic displacement measurements  

NASA Astrophysics Data System (ADS)

The Lutrive highway bridges are two twin bridges built in 1972 by the cantilever method with mid-span articulations. The bridge deck consists of a box girder of variable depth. In 1997 this bridge was instrumented with 30 SOFO fiber optic deformation sensors installed inside the box girder. This sensor network is mainly aimed at measuring the short- and long-term spatial displacements of one of the spans. This includes the displacement resulting from the daily variations of temperature and the long-term creep effects. It was found that these same sensors could also be used to capture the quasi-static part of the dynamic deformation of the bridge under traffic load. Although the measurement system can acquire measurements only at intervals a few seconds apart, it was found that these 'snapshots' could give interesting information about the low frequency quasi-static deformations of the bridge. The data from pair of sensors was combined to obtain information about the instantaneous curvature variations of the bridge. This curvature data was then analyzed statistically to extract information about the dynamic traffic loads. This measurement and analysis method was validated in a fatigue test on a concrete slab.

Inaudi, Daniele; Conte, Joel P.; Perregaux, Nicholas; Vurpillot, Samuel

1998-06-01

25

Grumman and SDI-related technology  

SciTech Connect

The application of Grumman Corporation's aerospace and nuclear fusion technology to the Strategic Defense Initiative (SDI) program has taken place in at least five major areas. These include infrared boost surveillance and tracking to detect intercontinental ballistic missiles just after launch, space-based radar, neutral particle beam platforms, nuclear electric power and propulsion units in space, and battle management systems. The author summarizes developments in each of these areas to illustrate how Grumman has responded to the request that the scientific and industrial communities pursue innovative, high-risk concepts involving materials, structures, space power, space physics, and kinetic energy weapon concepts. 3 figures.

Lewis, B.

1985-01-01

26

Surface drip irrigation (SDI): Status of the technology in 2010  

Technology Transfer Automated Retrieval System (TEKTRAN)

Subsurface drip irrigation (SDI), although a much smaller fraction of the microirrigated land area than surface drip irrigation, is growing at a much faster rate and is the subject of considerable research and educational efforts in the United States. This paper will discuss the growth in SDI, highl...

27

Investigating strategies to improve crop germination when using SDI  

Technology Transfer Automated Retrieval System (TEKTRAN)

As the nation's population increases and available irrigation water decreases, new technologies are being developed to maintain or increase production on fewer acres. One of these advancements has been the use of subsurface drip irrigation (SDI) on field crops. Research has shown that SDI is the m...

28

Dynamic multivariate statistical process control using subspace identification  

Microsoft Academic Search

In this article, the monitoring of continuous processes using linear dynamic models is presented. It is outlined that dynamic extensions to conventional multivariate statistical process control (MSPC) models may lead to the inclusion of large numbers of variables in the condition monitor. To prevent this, a new dynamic monitoring scheme, based on subspace identification, is introduced, which can (1) determine

Richard J. Treasure; Uwe Kruger; Jonathan E. Cooper

2004-01-01

29

Multifragmentation: New dynamics or old statistics?  

SciTech Connect

The understanding of the fission process as it has developed over the last fifty years has been applied to multifragmentation. Two salient aspects have been discovered: 1) a strong decoupling of the entrance and exit channels with the formation of well-characterized sources: 2) a statistical competition between two-, three-, four-, five-, ... n-body decays.

Moretto, L.G.; Delis, D.N.; Wozniak, G.J.

1993-10-01

30

Statistical Mechanical Interpretation of the Inverse Scattering Method: Level Dynamics for Exclusion Statistics  

NASA Astrophysics Data System (ADS)

Considered is the relationship between the level dynamics and the integrable differential-difference equation. By applying the inverse scattering method to the Bogoyavlensky lattice, which is an extension of the Volterra model, the role of the exclusion statistics is clarified. Each dynamical variable is identified with an energy level. Briefly discussed is a generalization of the Yangian symmetric system, and the ``Gentile'' statistics is revealed.

Hikami, Kazuhiro

1998-05-01

31

Improving Dynamic Calibration through Statistical Process Control  

Microsoft Academic Search

Dynamic calibration (DC), presented by the authors in previous works has proved to be a flexible approach for massive maintenance software project estimation, able to recalibrate an estimation model in use according to relevant process performance changes pointed out by the project manager. Nevertheless, it results quite subjective in its application and tightly based on manager experience. In this work

Maria Teresa Baldassarre; Nicola Boffoli; Danilo Caivano; Giuseppe Visaggio

2005-01-01

32

Segmenting Dynamic Human Action via Statistical Structure  

ERIC Educational Resources Information Center

|Human social, cognitive, and linguistic functioning depends on skills for rapidly processing action. Identifying distinct acts within the dynamic motion flow is one basic component of action processing; for example, skill at segmenting action is foundational to action categorization, verb learning, and comprehension of novel action sequences. Yet…

Baldwin, Dare; Andersson, Annika; Saffran, Jenny; Meyer, Meredith

2008-01-01

33

Dynamic Test Compression Using Statistical Coding  

Microsoft Academic Search

Test compression\\/decompression is an efficient method for reducing the test application cost. In this paper we propose a test generation method for obtaining test-patterns suitable to test compression by statistical coding. In general, an ATPG generates a test-pattern that includes don't-care values. In our method, such don't-care values are specified based on an estimation of the final probability of 0\\/1

Hideyuki Ichihara; Atsuhiro Ogawa; Tomoo Inoue; Akio Tamura

2001-01-01

34

SDI and/or arms control  

SciTech Connect

A frame of reference is established which relates U.S. policies regarding both strategic defense and arms control to the deterrence of aggression and the limiting of damage should deterrence fail. Early deployment of an extensive but only partially effective strategic defense system could actually reduce security. However, strategic defense, if deployed in such a way that it did not damage the deterrent effect of assured retaliation, can make a profound contribution to national survival if deterrence failed and nuclear weapons were launched by accident or against all reason. Assured national survival, a more modest goal than perfect population defense, still presents problems of technical feasibility and possible destabilization if engaged in unilaterally. The U.S. should plan on the continued need for cooperation with the U.S.S.R. and for arms control. Policy implications include: (1) the need to reverse the erosion of the ABM treaty; (2) the desirability of enacting the 50 percent reduction negotiated in Reykjavik; and (3) during arms negotiations, the U.S. should maintain a vigorous strategic defense initiative (SDI) technology program.

Ochmanek, D.A.

1987-08-01

35

Statistical dynamics of religions and adherents  

NASA Astrophysics Data System (ADS)

Religiosity is one of the most important sociological aspects of populations. All religions may evolve in their beliefs and adapt to the society developments. A religion is a social variable, like a language or wealth, to be studied like any other organizational parameter. Several questions can be raised, as considered in this study; e.g.: i) From a "macroscopic" point of view: How many religions exist at a given time? ii) From a "microscopic" viewpoint: How many adherents belong to one religion? Does the number of adherents increase or not, and how? No need to say that if quantitative answers and mathematical laws are found, agent-based models can be imagined to describe such non-equilibrium processes. It is found that empirical laws can be deduced and related to preferential attachment processes, like on an evolving network; we propose two different algorithmic models reproducing as well the data. Moreover, a population growth-death equation is shown to be a plausible modeling of evolution dynamics in a continuous-time framework. Differences with language dynamic competition are emphasized.

Ausloos, M.; Petroni, F.

2007-02-01

36

SDI-Based Groundwater Information Interoperability  

NASA Astrophysics Data System (ADS)

Though groundwater data are important inputs to hydrologic decision-making, they are highly distributed and heterogeneous, and thus difficult to access in a coordinated manner. The Geological Survey of Canada (GSC) is developing an information system for coordinated groundwater data access, using the standards and technologies of Spatial Data Infrastructures (SDI). In mid-stage development, the system is designed to manage and disseminate data produced by GSC scientists, as well as potentially disseminate data produced by other groundwater agencies. The system involves a typical three-tiered, mediator-wrapper architecture that includes a data tier, a mediator tier, and an applications tier. At the data tier local data sources are wrapped by OGC web services (WFS, WMS), which deliver diversely structured data to the mediator tier. The mediator tier acts as: (1) a central registry for the distributed data and other services; (2) a translator of the local data to the standard data format, GroundWater Markup Language; and (3) a consistent set of OGC web services that enable users to access the distributed data as one source. The applications tier involves both GSC and third-party web applications, such as analysis tools or on-line atlases, that provide user interfaces to the system. Apart from the data format standards used to achieve schematic interoperability, the system also deploys some light-weight data content standards to move toward semantic interoperability. These content standards include the definition of common categories for datasets such as standard subject classifications and map layers. A demonstration of the working prototype will be available, as well as discussion of the architecture of the system and the impacts on interoperability. The intent of the development is to grow the system into a national enterprise with a broad range of contributors and users.

Brodaric, B.; Boisvert, E.

2007-12-01

37

Statistical Analysis of Molecular Dynamics Simulations  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the specification and analysis of stochastic models of molecular motion and interaction in simple liquids. Basic chemical terminology is introduced and a brief description is given of the technique of molecular dynamics simulation. Stochastic process theory, in so far as it is relevant to the modelling of molecular trajectories and chemical reaction, is reviewed. First passage densities are shown to be important in the analysis of diffusion controlled chemical reaction. The relationship between first passage densities and flux or flow across the absorbing boundary is given. A formula proposed by Durbin is discussed and shown to be valid for diffusion processes under certain regularity conditions. The simplest integrated diffusion, integrated Brownian motion, is considered and a detailed derivation of McKean's half-winding formula is given. An explicit expression for the return-time density is derived, from which the large time asymptotics can be deduced. Goldman's formula for the density of the hitting-time of positive levels is extended to all real values and a simple intuitive derivation is given. Similar arguments enable the results of Gor'kov to be extended to a wider class of integrated diffusions. First passage time densities are computed numerically using the extension of Goldman's formula and compared with approximations which have been suggested by Hesse. Small drift asymptotics are derived for the escape probability of integrated Brownian motion with drift. A number of results are obtained for the integrated Ornstein -Uhlenbeck process, by using martingale methods. Finally, the empirical observations of Lynden-Bell, Hutchinson and Doyle are analysed. A stochastic model of single-particle motion based on the velocity autocorrelation function is proposed and shown to be in excellent agreement with the computer generated data.

Atkinson, R. A.

38

Statistical coarse-graining of molecular dynamics into peridynamics.  

SciTech Connect

This paper describes an elegant statistical coarse-graining of molecular dynamics at finite temperature into peridynamics, a continuum theory. Peridynamics is an efficient alternative to molecular dynamics enabling dynamics at larger length and time scales. In direct analogy with molecular dynamics, peridynamics uses a nonlocal model of force and does not employ stress/strain relationships germane to classical continuum mechanics. In contrast with classical continuum mechanics, the peridynamic representation of a system of linear springs and masses is shown to have the same dispersion relation as the original spring-mass system.

Silling, Stewart Andrew; Lehoucq, Richard B.

2007-10-01

39

Applying GPS to ERIS and other SDI applications  

NASA Astrophysics Data System (ADS)

The necessity of adapting GPS technology to SDI program requirements is demonstrated. Basic measurement techniques for direct hit, near miss, and miss situations are described. It is concluded that GPS is far superior to tracking radars for time, space, and position information (TSPI) applications in the SDI test and evaluation program of the future. It is noted that in the case of ground launched interceptors such as ERIS or HEDI, GPS frequency translators would be used both in the interceptors and in the reentry vehicle targets.

Hoefener, C. E.; Clark, J.

40

Smooth Dynamics and New Theoretical Ideas in Nonequilibrium Statistical Mechanics  

Microsoft Academic Search

This paper reviews various applications of the theory of smooth dynamical systems to conceptual problems of nonequilibrium statistical mecanics. We adopt a new point of view which has emerged progressively in recent years, and which takes seriously into account the chaotic character of the microscopic time evolution. The emphasis is on nonequilibrium steady states rather than the traditional approach to

David Ruelle

1999-01-01

41

Statistical analysis of the dynamic voltage electrical breakdown in nitrogen  

Microsoft Academic Search

The statistical analysis of the electrical breakdown in nitrogen at p=20 mbar using dynamic method is presented in this paper. The analysis was performed for the working voltage increase rates 50, 150, and 300 Vs-1. For each working, voltage increase rate a 1000 measurements were done. It was shown that results are lined up accidentally without any systematic trend. New

M. K. Radovic; Cedomir A. Maluckov

2001-01-01

42

INVITED ARTICLE: Nonlinear dynamics and statistical physics of DNA  

Microsoft Academic Search

DNA is not only an essential object of study for biologists---it also raises very interesting questions for physicists. This paper discuss its nonlinear dynamics, its statistical mechanics, and one of the experiments that one can now perform at the level of a single molecule and which leads to a non-equilibrium transition at the molecular scale. After a review of experimental

Michel Peyrard

2004-01-01

43

Soviet SDI Rhetoric: The "Evil Empire" Vision of Mikhail Gorbachev.  

ERIC Educational Resources Information Center

The symbolic presence of Ronald Reagan's Strategic Defense Initiative (SDI) has been and continues to be the pivot point in all summitry rhetoric between the American President and Soviet General Secretary Mikhail Gorbachev. To examine some of the rhetorical choices made by Gorbachev to dramatize his vision of why Ronald Reagan refuses to…

Kelley, Colleen E.

44

SDI: O, what a tangled web we weave  

SciTech Connect

The ghost of the Strategic Defense Initiative (SDI) still haunts the Pentagon. The recent relevation that the highly publicized 1984 intercept of a mock Soviet reentry vehicle (RV) was rigged - as part of a highly secret deception plan to mislead the Soviet Union - has raised questions about the integrity and wisdom of defense development and policy processes.

Keeny, S.M. Jr.

1993-11-01

45

Dynamic computation of network statistics via updating schema.  

PubMed

Given a large network, computing statistics such as clustering coefficient, or modularity, is costly for large networks. When one more edge or vertex is added, traditional methods require that the full (expensive) computation be redone on this slightly modified graph. Alternatively, we introduce here a new approach: under modification to the graph, we update the statistics instead of computing them from scratch. In this paper we provide update schemes for a number of popular statistics, to include degree distribution, clustering coefficient, assortativity, and modularity. Our primary aim is to reduce the computational complexity needed to track the evolving behavior of large networks. As an important consequence, this approach provides efficient methods which may support modeling the evolution of dynamic networks to identify and understand critical transitions. Using the updating scheme, the network statistics can be computed much faster than re-calculating each time that the network evolves. We also note that the update formula can be used to determine which edge or node will lead to the extremal change of network statistics, providing a way of predicting or designing network evolution rules that would optimize some chosen statistic. We present our evolution methods in terms of a network statistics differential notation. PMID:19392027

Sun, Jie; Bagrow, James P; Bollt, Erik M; Skufca, Joseph D

2009-03-30

46

Algorithm development for SDI weapons system allocation. Final report, December 1987-May 1989  

SciTech Connect

While several SDI weapons systems can provide adequate defense in a one-on-one basis, a coordinated attack by several enemy missiles launched over a substantial volume will be difficult to resist without an efficient command and control system for warfare coordination. This study of weapons allocation - coordination algorithms, is based on dynamical models for the missile/decoy systems including noise effects and uncertainties in the model parameters. Performance of the weapons targeting system may be measured in terms of the expected number of targets eliminated in a given interval (phase of operations) or the expected time to eliminate all the targets in a given region. Scheduling weapons deployment is a problem of constrained optimal (weapons) and state variables. The selection of weapons deployment tactics is based on solution of a complex optimization problem. We have conducted an investigation of advanced modeling, stochastic control, and scheduling methodologies for aspects of the SDI weapons allocation problem - several platforms with assets of different character defending against a diverse collection of targets. The models for such scenarios lead to stochastic scheduling problems that can not be handled by conventional analytical methods. The authors describe several different analytical approaches that have the potential for synthesis of effective engagement algorithms.

Blankenship, G.L.; Bennett, W.

1989-06-01

47

SDI (Strategic Defense Initiative) software technology program plan. Final report  

SciTech Connect

This paper was prepared in response to a request from the Battle Management C3 office within the Strategic Defense Initiative Organization (SDIO) of the Department of Defense (DoD). The request was for a software-technology program plan to define software research and development (RandD) efforts required by the SDI, and to provide the basis for integrating the SDIO software technology program with ongoing non-SDIO programs. The paper emphasizes reviewing the ongoing software programs and plans within the DoD and academia. The reviews identify critical software technology areas required to meet the unique SDI requirements, and indicate priorities among the software technologies to meet attainability, productivity, and reliability goals, as well as functional performance objectives.

Linn, C.J.; Redwine, S.T.; Bloom, M.I.; Brykczynski, B.; Chludzinski, J.

1987-06-01

48

SDI performance and START constraints: Modeling Phase-1 defense engagements  

SciTech Connect

My interest has been the performance of near-term Strategic Defense Initiative (SDI) systems rather than the kinds of questions discussed at this Workshop (e.g., implications of US force structure). It is clear, though, that the two issues are closely related. Arms control along with treaties that impact the force structure of the Soviet Union will greatly affect the performance of SDI systems. Similarly, the US intention to pursue SDI will be a driver in arms control negotiations, as well it should be. Indeed, the implications of SDI for Strategic Arms Reduction Treaty (START)-constrained Soviet forces are the focus of my discussion. To put this in some context, I will begin with the premises underlying my results: the United States and the Soviet Union reach an arms control agreement limiting strategic forces below current levels. The United States decides to pursue defense deployments to limit damage to the US and, eventually, to provide robust protection against ballistic missile attack. The Soviet Union responds by improving its forces within the numerical bounds of the treaty. My basic calculations are: Under START and in the absence of defenses, the offenses has sufficient weapons to attack 10,000 targets with strong value contrast. START constraints are severely limiting against an adaptive preferential defense, even with adaptive targeting. The adaptive preferential defense may contain a random-subtractive SBI tier. PBV redesign alone is insufficient to stress the SBI. Offload penalties to defeat endoatmospheric interceptors appear significant. Despite increased flexibility to modernize, a small attacking force is vulnerable to a small defense. 6 figs., 2 tabs.

Cunningham, C.

1991-03-20

49

Role of SdiA in Salmonella enterica serovar Typhimurium physiology and virulence  

Microsoft Academic Search

sdiA in Salmonella enterica serovar Typhimurium encodes a protein belonging to the LuxR family of transcriptional regulators. Initial computer analysis revealed the presence of a fur box 19 bp upstream of the start codon of the sdiA gene and a helix-turn-helix motif in the carboxy-terminal part of the SdiA protein typical for transcriptional regulators. Deletion of the fur box resulted

Jiri Volf; Mojmir Sevcik; Hana Havlickova; Frantisek Sisak; Jiri Damborsky; Ivan Rychlik

2002-01-01

50

Statistical Dynamics of Clustering in the Genome Structure  

NASA Astrophysics Data System (ADS)

Clustering and long-range correlations in the nucleotide sequences of different categories of organisms are studied. As a result of clustering, the size distribution of coding and non-coding DNA regions is estimated analytically using the Generalised Central Limit Theorem.The alternation of coding regions (which follow a short range size distribution) with non-coding regions (which follow a long range size distribution in higher organisms) leads to DNA structures which have a striking resemblance to random Cantor Fractals. For lower organisms (such as viruses, procaryotes etc.) long-range correlations are sporadically observed and the DNA structures do not present fractality.Statistical models are proposed based on biologically motivated dynamical mechanisms (such as aggregation of oligonucleotides, influx and DNA length reduction), which can account for the above statistical features.

Provata, A.; Almirantis, Y.

2000-10-01

51

Recurrence time statistics in chaotic dynamics. I. Discrete time maps  

NASA Astrophysics Data System (ADS)

The dynamics of transitions between the cells of a finite-phase-space partition in a variety of systems giving rise to chaotic behavior is analyzed, with special emphasis on the statistics of recurrence times. In the case of one-dimensional piecewise Markow maps the recurrence problem is cast into a-renewal process. In the presence of intermittency, transitions between cells define a non-Markovian, non-renewal process reflected in the presence of power-law probability distributions and of divergent variances and mean values.

Balakrishnan, V.; Nicolis, G.; Nicolis, C.

1997-01-01

52

Hydrological responses to dynamically and statistically downscaled climate model output  

USGS Publications Warehouse

Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis. A distributed hydrological model was then applied to the downscaled data. Relative to raw NCEP output, downscaled climate variables provided more realistic stimulations of basin scale hydrology. However, the results highlight the sensitivity of modeled processes to the choice of downscaling technique, and point to the need for caution when interpreting future hydrological scenarios.

Wilby, R. L.; Hay, L. E.; Gutowski, Jr. , W. J.; Arritt, R. W.; Takle, E. S.; Pan, Z.; Leavesley, G. H.; Clark, M. P.

2000-01-01

53

Statistical Molecular Dynamics study of displacement energies in diamond  

NASA Astrophysics Data System (ADS)

Molecular Dynamics simulations in bulk diamond using AIREBO potential have been used to calculate minimum displacement energy. A statistical approach has been applied calculating displacement probability curves along the main crystallographic directions. With these curves a minimum displacement energy of around 30 eV can be obtained, and a weighted average energy of around 70 eV. This value has been estimated as more accurate for its use in BCA displacement equations to obtain Frenkel pairs at moderate temperatures. This work also includes a study of defect states whose analysis reveals interesting results concerning the evolution of primary damage at higher PKA energies.

Delgado, Diego; Vila, Rafael

2011-12-01

54

Neutral dynamics and cluster statistics in a tropical forest.  

PubMed

The neutral theory of biodiversity attributes community structure to the effects of chance alone, assuming that all species and individuals are demographically equivalent. Here we present a spatially explicit version of the neutral theory and test it against the Barro Colorado Island (BCI) data. Monitoring the dynamics of clusters, we show that the effect of local heterogeneities (e.g., microtopography) is weak, making a spatially homogenous model plausible. We then compare the cluster statistics of the three most frequent species with the patterns obtained from neutral dynamics, examining two families of recruitment kernels: one that interpolates between a limited distance and panmictic dispersal (local-global) and one that assumes a scale-free Cauchy kernel. The results rule out the local-global dispersal model and show that the spatial patterns fit very nicely those obtained from the fat-tailed kernel. Our work emphasizes the importance of spatiotemporal cluster dynamics as an instrument for detecting the factors that govern community assembly. PMID:23149409

Seri, Efrat; Maruvka, Yosef E; Shnerb, Nadav M

2012-10-30

55

Extreme value statistics for dynamical systems with noise  

NASA Astrophysics Data System (ADS)

We study the distribution of maxima (extreme value statistics) for sequences of observables computed along orbits generated by random transformations. The underlying, deterministic, dynamical system can be regular or chaotic. In the former case, we show that, by perturbing rational or irrational rotations with additive noise, an extreme value law appears, regardless of the intensity of the noise, while unperturbed rotations do not admit such limiting distributions. In the case of deterministic chaotic dynamics, we will consider observables specially designed to study the recurrence properties in the neighbourhood of periodic points. Hence, the exponential limiting law for the distribution of maxima is modified by the presence of the extremal index, a positive parameter not larger than one, whose inverse gives the average size of the clusters of extreme events. The theory predicts that such a parameter is unitary when the system is perturbed randomly. We perform sophisticated numerical tests to assess how strong the impact of noise level is when finite time series are considered. We find agreement with the asymptotic theoretical results but also non-trivial behaviour in the finite range. In particular, our results suggest that, in many applications where finite datasets can be produced or analysed, one must be careful in assuming that the smoothing nature of noise prevails over the underlying deterministic dynamics.

Faranda, Davide; Milhazes Freitas, Jorge; Lucarini, Valerio; Turchetti, Giorgio; Vaienti, Sandro

2013-09-01

56

Spatial and Dynamical Biases in Velocity Statistics of Galaxies  

NASA Astrophysics Data System (ADS)

We present velocity statistics of galaxies and their biases inferred from the statistics of the underlying dark matter using a cosmological hydrodynamic simulation of galaxy formation in low-density and spatially flat (?0=0.3 and ?0=0.7) cold dark matter cosmogony. Our simulation is based on a particle-particle-particle-mesh (P3M) N-body Poisson solver and smoothed particle hydrodynamics. Galaxies in our simulation are identified as clumps of cold and dense gas particles and classified as young and old galaxies according to their formation epochs. We find that the pairwise velocity dispersion (PVD) of all galaxies is significantly lower than that of the dark matter particles and that the PVD of the young galaxies is lower than that of the old types, and even of all galaxies together, especially at small separations. These results are in reasonable agreement with the recent measurements of PVDs in the Las Campanas redshift survey, the IRAS Point Source Catalogue Redshift Survey, and the Sloan Digital Sky Survey data. We also find that the low PVD of young galaxies is due to the effects of dynamical friction as well as the different spatial distribution, while the difference in the PVD between all galaxies and dark matter can be mostly ascribed to their different spatial distributions. We also consider the mean infall velocity and the POTENT density reconstruction that are often used to measure the cosmological parameters, and investigate the effects of spatial bias and dynamical friction. In our simulation, the mean infall velocity of young galaxies is significantly lower than that of all the galaxies or of the old galaxies, and the dynamical bias becomes important on scales less than 3h-1Mpc. The mass density field reconstructed from the velocity field of young galaxies using the POTENT-style method suffers in accuracy from both the spatial bias and the dynamical friction on the smoothing scale of Rs=8h-1Mpc. On the other hand, in the case of Rs=12h-1Mpc, which is typically adopted in the actual POTENT analysis, the density reconstruction based on various tracers of galaxies is reasonably accurate. We also analyze the motions of central galaxies and the velocity dispersion of galaxies within halos and discuss their implications for the motion of cD galaxies and the determination of the mass of galaxy groups.

Yoshikawa, Kohji; Jing, Y. P.; Börner, Gerhard

2003-06-01

57

Evaluation of the Selective Dissemination of Information (SDI) Program for the Aerospace Materials Information Center.  

ERIC Educational Resources Information Center

|The Aerospace Materials Information Center (AMIC) Selective Dissemination of Information (SDI) program was evaluated by an interview technique after one year of operation. The data base for the SDI consists of the periodic document index records input to the AMIC system. The users are 63 engineers, scientists, and technical administrators at the…

Scheffler, F. L.; March, J. F.

58

SELECTIVE DISSEMINATION OF INFORMATION IN PRACTICE, SURVEY OF OPERATIONAL AND EXPERIMENTAL SDI PROGRAMS.  

ERIC Educational Resources Information Center

|AN OVERVIEW OF THE OPERATIONAL AND EXPERIMENTAL SYSTEMS ESTABLISHED FOR THE SELECTIVE DISSEMINATION OF SCIENTIFIC AND TECHNICAL INFORMATION (SDI) IS PRESENTED. AN ATTEMPT HAS ALSO BEEN MADE TO IDENTIFY THE TRENDS WHICH MAY SHAPE THE FUTURE DEVELOPMENT OF THE SELECTIVE DISSEMINATION PROCEDURES. THE REPORT IS BASED IN PART ON THE EXISTING SDI

DOWNIE, CURRIE S.; HOSHOVSKY, ALEXANDER G.

59

COMPARISON OF SDI, LEPA, AND SPRAY IRRIGATION PERFORMANCE FOR GRAIN SORGHUM  

Microsoft Academic Search

Subsurface drip irrigation (SDI), lowenergy precision application (LEPA), and spray irrigation can be very efficient by minimizing water losses, but relative performance may vary for different irrigation system capacities, soils, crops, and climates. A threeyear study was conducted at Bushland, Texas, in the Southern High Plains to compare SDI, LEPA, and spray irrigation for grain sorghum on a slowly permeable

P. D. Colaizzi; A. D. Schneider; S. R. Evett; T. A. Howell

60

Forecasting: it is not about statistics, it is about dynamics.  

PubMed

In 1963, the mathematician and meteorologist Edward Lorenz published a paper (Lorenz 1963 J. Atmos. Sci. 20, 130-141) that changed the way scientists think about the prediction of geophysical systems, by introducing the ideas of chaos, attractors, sensitivity to initial conditions and the limitations to forecasting nonlinear systems. Three years earlier, the mathematician and engineer Rudolf Kalman had published a paper (Kalman 1960 Trans. ASME Ser. D, J. Basic Eng. 82, 35-45) that changed the way engineers thought about prediction of electronic and mechanical systems. Ironically, in recent years, geophysicists have become increasingly interested in Kalman filters, whereas engineers have become increasingly interested in chaos. It is argued that more often than not the tracking and forecasting of nonlinear systems has more to do with the nonlinear dynamics that Lorenz considered than it has to do with statistics that Kalman considered. A position with which both Lorenz and Kalman would appear to agree. PMID:19948555

Judd, Kevin; Stemler, Thomas

2010-01-13

61

Path planning for mobile vehicles within dynamic worlds using statistical data  

Microsoft Academic Search

This paper proposes a new path planning approach based on statistical information, like the occupancy probability of partly or completely dynamic obstacles and\\/or the statistical flow of dynamic obstacles. With this new approach it is possible to integrate the expected behavior of moving obstacles into the preplanning of paths without knowing the individual movement of these dynamic obstacles. As the

R. Gutsche; C. Laloni; F. M. Wahl

1994-01-01

62

Statistical mechanics and dynamics of two supported stacked lipid bilayers.  

PubMed

The statistical physics and dynamics of double supported bilayers are studied theoretically. The main goal in designing double supported lipid bilayers is to obtain model systems of biomembranes: the upper bilayer is meant to be almost freely floating, the substrate being screened by the lower bilayer. The fluctuation-induced repulsion between membranes and between the lower membrane and the wall are explicitly taken into account using a Gaussian variational approach. It is shown that the variational parameters, the "effective" adsorption strength, and the average distance to the substrate, depend strongly on temperature and membrane elastic moduli, the bending rigidity, and the microscopic surface tension, which is a signature of the crucial role played by membrane fluctuations. The range of stability of these supported membranes is studied, showing a complex dependence on bare adsorption strengths. In particular, the experimental conditions of having an upper membrane slightly perturbed by the lower one and still bound to the surface are found. Included in the theoretical calculation of the damping rates associated with membrane normal modes are hydrodynamic friction by the wall and hydrodynamic interactions between both membranes. PMID:20000797

Manghi, Manoel; Destainville, Nicolas

2010-03-16

63

SDI and the lawyers: Evolving interpretations of international arms control accords  

SciTech Connect

This note surveys international agreements that SDI may violate and discusses the policies underlying these potential legal and diplomatic conflicts. Part I provides an overview of the ABM Treaty, with emphasis on the provisions involved in the present interpretation controversy. Part II considers five other international covenants containing provisions upon which SDI may ultimately encroach. Part III evaluates several policy proposals that would permit SDI to proceed consistently with American international diplomatic commitments. This part also examines how an outright abrogation of the ABM Treaty or other agreements might affect American credibility and the arms-control process.

Kaman, E.J.; Loprest, F.J. Jr.; Pisano, N.A.; Steiner, R.W.

1989-01-01

64

Particle bed reactor central to SDI nuclear rocket project  

SciTech Connect

A classified SDI project designated 'Timberwind' and funded with an estimated $7-8 billion over the project's life is charged with the development and flight testing of nuclear reactor-powered rockets. Timberwind's novel 'particle-bed reactor' technology will employ small pellets of reactor fuel to heat a low molecular weight working fluid, such as hydrogen. The fuel pellets would be 0.5 mm in diameter and may be composed of a kernel of fissionable U together with a carbon alloy, coated by layers of carbon and a sealant. A covering of zirconium carbide would prevent chemical degradation of the pellets by the hydrogen working fluid. Performace projection comparisons are conducted for Timberwind, an advanced Atlas-Centaur, and an advanced Titan launch vehicle.

Asker, J.R.

1991-04-01

65

Application of High Resolution Dynamical-Numerical Models as a Tool to Infer Climate Statistics.  

National Technical Information Service (NTIS)

The grant The Application of High Resolution Dynamical-Numerical Models as a Tool to Infer Climate Statistics was designed to investigate the use of dynamical-numerical models as a tool for the inference of climate statistics. In addition this grant would...

C. E. Graves J. Zack

1998-01-01

66

Comparison of the Eagleson statistical-dynamical water balance model with numerical simulations  

Microsoft Academic Search

With minor modification an existing analytic model employing a simple statistical description of soil moisture dynamics is found to give accurate estimates of the mean water balance partitioning; comparisons are made to a Monte Carlo numerical simulation of unsaturated moisture flow in a soil column. In the statistical-dynamical model the complex temporal and spatial characteristics of the soil moisture profile

Guido Daniel Salvucci; Dara Entekhabi

1994-01-01

67

Comparison of grain sorghum, soybean, and cotton production under spray, LEPA, and SDI  

Technology Transfer Automated Retrieval System (TEKTRAN)

Crop production was compared under subsurface drip irrigation (SDI), low energy precision applicators (LEPA), low elevation spray applicators (LESA), and mid elevation spray applicators (MESA) at the USDA-Agricultural Research Service Conservation and Production Research Laboratory, Bushland, Tex., ...

68

CONSIDERATIONS FOR THE DESIGN AND INSTALLATION OF SDI SYSTEMS IN HUMID AREAS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Humid areas, such as the southeastern and midsouthern United States, have particular climate, topography, soils, cropping systems, and water sources that require special consideration when considering and implementing a subsurface drip irrigation (SDI) system. Design criteria, are generally the sam...

69

Intermittency and Statistics of Single Biomolecule Reaction Dynamics  

NASA Astrophysics Data System (ADS)

The statistics of individual activated events in slowly fluctuating environments such as biomolecules exhibits intermittency where rare activation events mostly dominate and may not always obey Poisson's law. Intermittency maybe characterized by high order statistics of the population. We used a path integral method to study the statistics of the populations. It is found that at short times, high order moments are of the same order to the corresponding power of the average survival probability. For long times, the high order moments decay much more slowly than the Poisson statistics indicate.

Wang, Jin; Wolynes, Peter

1998-03-01

70

IRRIGATION CAPACITY AND PLANT POPULATION EFFECTS ON CORN PRODUCTION USING SDI  

Microsoft Academic Search

Corn was grown with subsurface drip irrigation (SDI) under 6 different irrigation capacities (0, 0.10, 0.13, 0.17, 0.20 and 0.25 inches\\/day) and 4 different plant populations (33100, 29900, 26800, and 23700 plants\\/acre). Daily SDI application of even small amounts of water (0.10 inches) doubled corn grain yields in 2000. Results suggest an irrigation capacity of 0.17 inches\\/day might be adequate

Freddie R. Lamm; Todd P. Trooien

71

Control system design for dynamical systems with statistical model uncertainty  

Microsoft Academic Search

This dissertation is devoted to the study of control systems for which the plant models are uncertain. The plant model uncertainty considered is of statistical nature. The model uncertainty is assumed to be given in terms of first- and second-order statistics of random model parameters, or alternatively, by a joint probability distribution. The first problem is the characterization of the

Ruben Tarsicio Huerta-Ochoa

2000-01-01

72

Simulation for Statistical Inference in Dynamic Network Models  

Microsoft Academic Search

Actor-oriented models are proposed for the statistical analysis of longitudinal social network data. These models are implemented as simulation models, and the statis- tical evaluation is based on the method of moments and the Robbins-Monro process applied to computer simulation outcomes. In this approach, the calculations that are required for statistical inference are too complex to be carried out analytically,

Tom Snijders; Marijtje van Duijn

1997-01-01

73

Statistical Modeling of Dynamic Multivariate Process Using Canonical Variate Analysis  

Microsoft Academic Search

For quality control or statistical process monitoring in an industrial process, the valid models are necessary. While the mechanical modeling is a time-consuming and difficult task, the statistical modeling is adopted in many industrial continuous. But most of these processes always have a large number of process variables and are usually operated under closed-loop control, yielding process measurements that are

Juan Lu; Fei Liu

2006-01-01

74

Statistical methods for estimating the dynamical parameters of manipulators  

Microsoft Academic Search

The determination of the dynamical parameters of robot manipulators is crucial in many applications where model based control architectures are needed to match stringent performance requirements. Unfortunately only the kinematic model of the robot is usually available whereas the dynamical parameters are unknown and very difficult to compute by first principle or CAD analysis. In the last decades several algorithms

Riccardo Muradore; Roberto Foroncelli; Paolo Fiorini

2009-01-01

75

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics  

SciTech Connect

Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen-Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Renyi divergence.

Crooks, Gavin; Sivak, David

2011-06-03

76

A path-stack algorithm for optimizing dynamic regimes in a statistical hidden dynamic model of speech  

Microsoft Academic Search

In this paper we report our recent research whose goal is to improve the performance of a novel speech recognizer based on an underlying statistical hidden dynamic model of phonetic reduction in the production of conversational speech. We have developed a path-stack search algorithm which efficiently computes the likelihood of any observation utterance while optimizing the dynamic regimes in the

Jeff Z. Ma; Li Deng

2000-01-01

77

Non-extensive statistics, relativistic kinetic theory and fluid dynamics  

NASA Astrophysics Data System (ADS)

Experimental particle spectra can be successfully described by power law tailed energy distributions characteristic to canonical equilibrium distributions associated to Rényi's or Tsallis' entropy formula --over a wide range of energies, colliding system sizes, and produced hadron sorts. In order to derive its evolution one needs a corresponding dynamical description of the system which results in such final state observables. The equations of relativistic fluid dynamics are obtained from a non-extensive Boltzmann equation consistent with Tsallis' non-extensive q-entropy formula. The transport coefficients like shear viscosity, bulk viscosity, and heat conductivity are evaluate based on a linearized collision integral.

Biró, T. S.; Molnár, E.

2012-11-01

78

Statistical and dynamical assessment of vegetation feedbacks on climate over the boreal forest  

Microsoft Academic Search

Vegetation feedbacks over Asiatic Russia are assessed through a combined statistical and dynamical approach in a fully coupled\\u000a atmosphere–ocean–land model, FOAM-LPJ. The dynamical assessment is comprised of initial value ensemble experiments in which\\u000a the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response\\u000a is determined. The statistical feedback approach, adopted from

Michael Notaro; Zhengyu Liu

2008-01-01

79

Statistical analysis of nanoparticle dosing in a dynamic cellular system  

NASA Astrophysics Data System (ADS)

The delivery of nanoparticles into cells is important in therapeutic applications and in nanotoxicology. Nanoparticles are generally targeted to receptors on the surfaces of cells and internalized into endosomes by endocytosis, but the kinetics of the process and the way in which cell division redistributes the particles remain unclear. Here we show that the chance of success or failure of nanoparticle uptake and inheritance is random. Statistical analysis of nanoparticle-loaded endosomes indicates that particle capture is described by an over-dispersed Poisson probability distribution that is consistent with heterogeneous adsorption and internalization. Partitioning of nanoparticles in cell division is random and asymmetric, following a binomial distribution with mean probability of 0.52-0.72. These results show that cellular targeting of nanoparticles is inherently imprecise due to the randomness of nature at the molecular scale, and the statistical framework offers a way to predict nanoparticle dosage for therapy and for the study of nanotoxins.

Summers, Huw D.; Rees, Paul; Holton, Mark D.; Rowan Brown, M.; Chappell, Sally C.; Smith, Paul J.; Errington, Rachel J.

2011-03-01

80

New Dynamical-Statistical Techniques for Wind Power Prediction  

NASA Astrophysics Data System (ADS)

The increased use of renewable energy sources, and especially of wind power, has revealed the significance of accurate environmental and wind power predictions over wind farms that critically affect the integration of the produced power in the general grid. This issue is studied in the present paper by means of high resolution physical and statistical models. Two numerical weather prediction (NWP) systems namely SKIRON and RAMS are used to simulate the flow characteristics in selected wind farms in Greece. The NWP model output is post-processed by utilizing Kalman and Kolmogorov statistics in order to remove systematic errors. Modeled wind predictions in combination with available on-site observations are used for estimation of the wind power potential by utilizing a variety of statistical power prediction models based on non-linear and hyperbolic functions. The obtained results reveal the strong dependence of the forecasts uncertainty on the wind variation, the limited influence of previously recorded power values and the advantages that nonlinear - non polynomial functions could have in the successful control of power curve characteristics. This methodology is developed at the framework of the FP7 projects WAUDIT and MARINA PLATFORM.

Stathopoulos, C.; Kaperoni, A.; Galanis, G.; Kallos, G.

2012-04-01

81

Comparison of the Eagleson statistical-dynamical water balance model with numerical simulations  

Microsoft Academic Search

With minor modification an existing analytic model employing a simple statistical description of soil moisture dynamics is found to give accurate estimates of the mean water balance partioning; comparisons are made to a Monte Carlo numerical simulation of unsaturated moisture flow in a soil column. In the statistical-dynamicl model the complex temporal and spatial characteristics of the soil moisture profile

Guido Daniel Salvucci; Dara Entekhabi

1994-01-01

82

Minimal Agent Based Model for Financial Markets II: Statistical Properties of the Linear and Multiplicative Dynamics  

Microsoft Academic Search

We present a detailed study of the statistical properties of an Agent Based Model and of its generalization to the multiplicative dynamics. The aim of the model is to consider the minimal elements for the understanding of the origin of the Stylized Facts and their Self-Organization. The key elements are fundamentalist agents, chartist agents, herding dynamics and price behavior. The

V. Alfi; M. Cristelli; L. Pietronero; A. Zaccaria

2008-01-01

83

Introduction to Focus Issue: statistical mechanics and billiard-type dynamical systems.  

PubMed

Dynamical systems of the billiard type are of fundamental importance for the description of numerous phenomena observed in many different fields of research, including statistical mechanics, Hamiltonian dynamics, nonlinear physics, and many others. This Focus Issue presents the recent progress in this area with contributions from the mathematical as well as physical stand point. PMID:22757560

Leonel, Edson D; Beims, Marcus W; Bunimovich, Leonid A

2012-06-01

84

Introduction to Focus Issue: Statistical mechanics and billiard-type dynamical systems  

NASA Astrophysics Data System (ADS)

Dynamical systems of the billiard type are of fundamental importance for the description of numerous phenomena observed in many different fields of research, including statistical mechanics, Hamiltonian dynamics, nonlinear physics, and many others. This Focus Issue presents the recent progress in this area with contributions from the mathematical as well as physical stand point.

Leonel, Edson D.; Beims, Marcus W.; Bunimovich, Leonid A.

2012-06-01

85

Accuracy analysis of statistical linearization methods applied to nonlinear dynamical systems  

Microsoft Academic Search

The purpose of this paper is to present the accuracy analysis of statistical linearization methods applied to dynamical systems described by nonlinear integral equations defined over locally compact Abelian groups. Nonstationary dynamical systems are considered as well as stationary ones. The technique of generalized harmonic analysis of noncommutativc causal operators from L1(G; L(Rn, Rn)) is used to analyse special Banach

Jerzy Skrzypczyk

1995-01-01

86

Dynamic Cartographic Methods for Visualisation of Health Statistics  

Microsoft Academic Search

\\u000a The article deals with interdisciplinary research on health status data analysis and so-called ‘health cartography’ mapping\\u000a approaches. In the first part existing cognitive studies and recommendations on map design are discussed.\\u000a \\u000a \\u000a The following part describes current trends in cartographic visualisation and non-traditional methods for exploratory cartography.\\u000a Examples and possibilities of modern cartographic tools for dynamic presentation, publication, and analysis of

Radim Stampach; Milan Konecny; Petr Kubicek; Edvard Geryk

87

Reconfiguring the Quorum-Sensing Regulator SdiA of Escherichia coli To Control Biofilm Formation via Indole and N-Acylhomoserine Lactones  

Microsoft Academic Search

SdiA is a homolog of quorum-sensing regulators that detects N-acylhomoserine lactone (AHL) signals from other bacteria. Escherichia coli uses SdiA to reduce its biofilm formation in the presence of both AHLs and its own signal indole. Here we reconfigured SdiA (240 amino acids) to control biofilm formation using protein engineering. Four SdiA variants were obtained with altered biofilm formation, including

Jintae Lee; Toshinari Maeda; Seok Hoon Hong; Thomas K. Wood

2009-01-01

88

Dynamical analogy between epileptic seizures and seismogenic electromagnetic emissions by means of nonextensive statistical mechanics  

NASA Astrophysics Data System (ADS)

The field of study of complex systems considers that the dynamics of complex systems are founded on universal principles that may be used to describe a great variety of scientific and technological approaches of different types of natural, artificial, and social systems. Several authors have suggested that earthquake dynamics and neurodynamics can be analyzed within similar mathematical frameworks. Recently, authors have shown that a dynamical analogy supported by scale-free statistics exists between seizures and earthquakes, analyzing populations of different seizures and earthquakes, respectively. The purpose of this paper is to suggest a shift in emphasis from the large to the small scale: our analyses focus on a single epileptic seizure generation and the activation of a single fault (earthquake) and not on the statistics of sequences of different seizures and earthquakes. We apply the concepts of the nonextensive statistical physics to support the suggestion that a dynamical analogy exists between the two different extreme events, seizures and earthquakes. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg–Richter distribution of event sizes and the distribution of the waiting time until the next event). The performed analysis confirms the existence of a dynamic analogy between earthquakes and seizures, which moreover follow the dynamics of magnetic storms and solar flares.

Eftaxias, Konstantinos; Minadakis, George; Potirakis, Stelios. M.; Balasis, Georgios

2013-02-01

89

Statistical Physics Approaches to Respiratory Dynamics and Lung Structure  

NASA Astrophysics Data System (ADS)

The lung consists of a branching airway tree embedded in viscoelastic tissue and provides life-sustaining gas exchange to the body. In diseases, its structure is damaged and its function is compromised. We review two recent works about lung structure and dynamics and how they change in disease. 1) We introduced a new acoustic imaging approach to study airway structure. When airways in a collapsed lung are inflated, they pop open in avalanches. A single opening emits a sound package called crackle consisting of an initial spike (s) followed by ringing. The distribution n(s) of s follows a power law and the exponent of n(s) can be used to calculate the diameter ratio d defined as the ratio of the diameters of an airway to that of its parent averaged over all bifurcations. To test this method, we measured crackles in dogs, rabbits, rats and mice by inflating collapsed isolated lungs with air or helium while recording crackles with a microphone. In each species, n(s) follows a power law with an exponent that depends on species, but not on gas in agreement with theory. Values of d from crackles compare well with those calculated from morphometric data suggesting that this approach is suitable to study airway structure in disease. 2) Using novel experiments and computer models, we studied pulmonary emphysema which is caused by cigarette smoking. In emphysema, the elastic protein fibers of the tissue are actively remodeled by lung cells due to the chemicals present in smoke. We measured the mechanical properties of tissue sheets from normal and emphysematous lungs and imaged its structure which appears as a heterogeneous hexagonal network of fibers. We found evidence that during uniaxial stretching, the collagen and elastin fibers in emphysematous tissue can fail at a critical stress generating holes of various sizes (h). We developed network models of the failure process. When the failure is governed by mechanical forces, the distribution n(h) of h is a power law which compares well with Computed Tomographic images of patients. These results suggest that the progressive nature of emphysema may be due to a complex breakdown process initiated by chemicals in the smoke and maintained by mechanical failure of the remodeled fiber network.

Suki, Bela

2004-03-01

90

Measuring dynamical randomness of quantum chaos by statistics of Schmidt eigenvalues  

NASA Astrophysics Data System (ADS)

We study statistics of entanglement generated by quantum chaotic dynamics. Using an ensemble of the very large number (?107) of quantum states obtained from the temporally evolving coupled kicked tops, we verify that the estimated one-body distribution of the squared Schmidt eigenvalues for the quantum chaotic dynamics can agree surprisingly well with the analytical one for the universality class of the random matrices described by the fixed trace ensemble (FTE). In order to quantify this agreement, we introduce the L1 norm of the difference between the one-body distributions for the quantum chaos and FTE and use it as an indicator of the dynamical randomness. As we increase the scaled coupling constant, the L1 difference decreases. When the effective Planck constant is not small enough, the decrease saturates, which implies quantum suppression of dynamical randomness. On the other hand, when the effective Planck constant is small enough, the decrease of the L1 difference continues until it is masked by statistical fluctuation due to finiteness of the ensemble. Furthermore, we carry out two statistical analyses, the ?2 goodness of fit test and an autocorrelation analysis, on the difference between the distributions to seek for dynamical remnants buried under the statistical fluctuation. We observe that almost all fluctuating deviations are statistical. However, even for well-developed quantum chaos, unexpectedly, we find a slight nonstatistical deviation near the largest Schmidt eigenvalue. In this way, the statistics of Schmidt eigenvalues enables us to measure dynamical randomness of quantum chaos with reference to the random matrix theory of FTE.

Kubotani, Hiroto; Adachi, Satoshi; Toda, Mikito

2013-06-01

91

An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models  

Microsoft Academic Search

This study used statistical simulation to calculate differential statistical power in dynamic structural equation models with groups (as in McArdle & Prindle, 2008). Patterns of between-group differences were simulated to provide insight into how model parameters influence power approximations. Chi-square and root mean square error of approximation (RMSEA) power approximation procedures were used to compare the effects of parameter manipulations

John J. Prindle; John J. McArdle

2012-01-01

92

Liberty Development and Production Plan Ultra Extended Reach Drilling from Endicott - Satellite Drilling Island (SDI).  

National Technical Information Service (NTIS)

A detailed description of the proposed Liberty (SDI) Project may be found in the Liberty DPP, and the EIA is an attachment to the DPP. Following is a summary of the project. The Liberty prospect is located about 5.5 miles offshore in about 20 feet of wate...

2007-01-01

93

Understanding the Motivations and Capacity for SDI Development from the Local Level  

Microsoft Academic Search

Local government is a rich source of accurate and detailed spatial information which is utilised not only at the local level but increasingly at other levels of government. To build the spatial data infrastructure (SDI) at a state and national level, the role of local governments and their motivation to participate in the sharing of spatial information must be better

Ian WILLIAMSON

94

Social Development in Hong Kong: Development Issues Identified by Social Development Index (SDI)  

ERIC Educational Resources Information Center

|Surviving the aftermaths of the Asian Financial Crisis and SARS in 2003, Hong Kong's economy has re-gained its momentum and its economic growth has been quite remarkable too in recent few years. Nevertheless, as reflected by the Social Development Index (SDI), economic growth in Hong Kong does not seem to have benefited the people of the city at…

Chua, Hoi-wai; Wong, Anthony K. W.; Shek, Daniel T. L.

2010-01-01

95

Beyond SDI: Integrating Science and Communities to Create Environmental Policies for the Sustainability of the Amazon  

Microsoft Academic Search

In this paper will explore ways to go beyond the traditional SDI (spatial data infrastructures) in the direction of the Digital Earth, with the objective of supporting environmental policies that will lead to sustainability. We use the Amazon region as a starting point for the discussion. Environmental policy making for a place such as the Amazon has to take into

Clodoveu A. Davis Jr; Frederico T. Fonseca; Gilberto Câmara

96

SDI Report, A Review of Developments in the Strategic Defense Initiative Program.  

National Technical Information Service (NTIS)

The SDI report No. 41 from the Heritage Foundation issued a Review of Developments in the strategic defense Initiative Program. On March 23 Ronald Reagan called for a research and development program to begin to achieve our ultimate goal of eliminating th...

J. P. Kosminsky

1992-01-01

97

Dynamics of statistical distance: Quantum limits for two-level clocks  

SciTech Connect

We study the evolution of statistical distance on the Bloch sphere under unitary and nonunitary dynamics. This corresponds to studying the limits to clock precision for a clock constructed from a two-state system. We find that the initial motion away from pure states under nonunitary dynamics yields the greatest accuracy for a one-tick'' clock; in this case the clock's precision is not limited by the largest frequency of the system.

Braunstein, S.L. (Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100 (Israel)); Milburn, G.J. (Department of Physics, University of Queensland, St. Lucia 4072 (Australia))

1995-03-01

98

ExpI and PhzI Are Descendants of the Long Lost Cognate Signal Synthase for SdiA  

PubMed Central

SdiA of E. coli and Salmonella is a LuxR homolog that detects N-acyl homoserine lactones (AHLs). Most LuxR homologs function together with a cognate AHL synthase (a LuxI homolog), but SdiA does not. Instead, SdiA detects AHLs produced by other bacterial species. In this report, we performed a phylogenetic analysis of SdiA. The results suggest that one branch of the Enterobacteriaceae obtained a rhlR/rhlI pair by horizontal transfer. The Erwinia and Pantoea branches still contain the complete pair where it is known as expR/expI and phzR/phzI, respectively. A deletion event removed the luxI homolog from the remainder of the group, leaving just the luxR homolog known as sdiA. Thus ExpR and PhzR are SdiA orthologs and ExpI and PhzI are descendants of the long lost cognate signal synthase of SdiA.

Sabag-Daigle, Anice; Ahmer, Brian M. M.

2012-01-01

99

Statistically accurate low-order models for uncertainty quantification in turbulent dynamical systems  

PubMed Central

A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra.

Sapsis, Themistoklis P.; Majda, Andrew J.

2013-01-01

100

Statistically accurate low-order models for uncertainty quantification in turbulent dynamical systems.  

PubMed

A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398

Sapsis, Themistoklis P; Majda, Andrew J

2013-08-05

101

Pseudo-dynamic source modeling with 1-point and 2-point statistics of earthquake source parameters  

NASA Astrophysics Data System (ADS)

Dynamic rupture modeling considers physical processes during fault rupture, by incorporating conservation laws of continuum mechanics, the constitutive behavior of rocks on the fault plane, and the state of stress in the Earth crust. This approach has been successfully adopted for physics-based source and ground motion simulations in the last couple of decades. However, dynamic rupture calculations are still computationally expensive, especially for large events. Moreover, the required input parameters of stress and frictional properties are generally not well constrained. Therefore, pseudo-dynamic source modeling has been introduced (Guatteri et al, 2004), by combining strengths from both dynamic and kinematic modeling approaches i.e., keeping computational efficiency with kinematic source modeling, but trying to emulate the physics of the source process inferred from rupture dynamics and data observations. Song and Somerville (2010) propose a pseudo-dynamic source modeling method based on cross-correlation structures between kinematic source parameters, including both zero- and nonzero-offset correlations, which thus define a 2-point statistics of source parameters. In this study, we extend previous studies in the following ways: 1) The concept of 1-point statistics is included in both source characterization and modeling, 2) A new stochastic source modeling tool, based on the Cholesky factorization, is implemented, in addition to the previously proposed sequential Gaussian simulation with kriging method, 3) Ground motions are computed using both full- and pseudo-dynamic modeling methods, and then compared quantitatively. Our preliminary source and ground motion modeling results show that we can successfully capture the main characteristics of dynamic rupture models by applying 1-point and 2-point statistics, and hence also reproduce the main characteristics of ground motions generated by full dynamic rupture modeling.

Song, Seok Goo; Mai, Paul Martin; Dalguer, Luis Angel

2013-04-01

102

Remote Impact on Tropical Atlantic Climate Variability: Statistical Assessment and Dynamic Assessment  

Microsoft Academic Search

The remote impact of tropical Pacific and North Atlantic climate forcing on the tropical Atlantic sea surface temperature variability is assessed using both a traditional statistical correlation method and a model-aided dynamic method. Consistently, both assessment methods suggest that the remote impact contributes to nearly half of the variance of the tropical Atlantic sea surface temperature variability at interannual and

Z. Liu; Q. Zhang; L. Wu

2004-01-01

103

An Evaluation of Statistical and Dynamical Techniques for Downscaling Local Climate  

Microsoft Academic Search

An assessment is made of downscaling estimates of screen temperature and precipitation observed at 976 European stations during 1983-94. A statistical downscaling technique, in which local values are inferred from observed atmospheric predictor variables, is compared against two dynamical downscaling techniques, based on the use of the screen temperature or precipitation simulated at the nearest grid point in integrations of

James Murphy

1999-01-01

104

Statistical-Dynamical Approach for Streamflow Modeling at Malakal, Sudan, on the White Nile River  

Microsoft Academic Search

The upper White Nile Basin above Malakal, Sudan, is considered to be one of the most complicated and diverse hydrologic settings on Earth. Accurately depicting and predicting the streamflow at Malakal is essential for water managers considering Nile Basin-wide initiatives and potential large-scale projects. Dynamical, statistical, and combination models are assessed for their ability to predict monthly streamflow at Malakal.

Paul Block; Balaji Rajagopalan

2010-01-01

105

Statistical and dynamical assessment of vegetation feedbacks on climate over the boreal forest  

NASA Astrophysics Data System (ADS)

Vegetation feedbacks over Asiatic Russia are assessed through a combined statistical and dynamical approach in a fully coupled atmosphere-ocean-land model, FOAM-LPJ. The dynamical assessment is comprised of initial value ensemble experiments in which the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response is determined. The statistical feedback approach, adopted from previous studies of ocean-atmosphere interactions, is applied to compute the feedback of forest cover on subsequent temperature and precipitation in the control simulation. Both methodologies indicate a year-round positive feedback on temperature and precipitation, strongest in spring and moderately substantial in summer. Reduced boreal forest cover enhances the surface albedo, leading to an extended snow season, lower air temperatures, increased atmospheric stability, and enhanced low cloud cover. Changes in the hydrological cycle include diminished transpiration and moisture recycling, supporting a reduction in precipitation. The close agreement in sign and magnitude between the statistical and dynamical feedback assessments testifies to the reliability of the statistical approach. An additional statistical analysis of monthly vegetation feedbacks over Asiatic Russia reveals a robust positive feedback on air temperature of similar quantitative strength in two coupled models, FOAM-LPJ and CAM3-CLM3, and the observational record.

Notaro, Michael; Liu, Zhengyu

2008-11-01

106

Statistical–dynamical modeling of the cloud-to-ground lightning activity in Portugal  

NASA Astrophysics Data System (ADS)

The present study employs a dataset of cloud-to-ground discharges over Portugal, collected by the Portuguese lightning detection network in the period of 2003–2009, to identify dynamically coherent lightning regimes in Portugal and to implement a statistical–dynamical modeling of the daily discharges over the country. For this purpose, the high-resolution MERRA reanalysis is used. Three lightning regimes are then identified for Portugal: WREG, WREM and SREG. WREG is a typical cold-core cut-off low. WREM is connected to strong frontal systems driven by remote low pressure systems at higher latitudes over the North Atlantic. SREG is a combination of an inverted trough and a mid-tropospheric cold-core nearby Portugal. The statistical–dynamical modeling is based on logistic regressions (statistical component) developed for each regime separately (dynamical component). It is shown that the strength of the lightning activity (either strong or weak) for each regime is consistently modeled by a set of suitable dynamical predictors (65–70% of efficiency). The difference of the equivalent potential temperature in the 700–500 hPa layer is the best predictor for the three regimes, while the best 4-layer lifted index is still important for all regimes, but with much weaker significance. Six other predictors are more suitable for a specific regime. For the purpose of validating the modeling approach, a regional-scale climate model simulation is carried out under a very intense lightning episode.

Sousa, J. F.; Fragoso, M.; Mendes, S.; Corte-Real, J.; Santos, J. A.

2013-10-01

107

Energy dependent dynamics of the O(1D) + HCl reaction: a quantum, quasiclassical and statistical study.  

PubMed

The dynamics of the reaction O((1)D) + HCl ? ClO + H, OH + Cl has been investigated in detail by means of a time-dependent wave packet (TDWP) method in comparison with quasiclassical trajectory (QCT) and statistical approaches on the ground potential energy surface by Martínez et al. [Phys. Chem. Chem. Phys., 2000, 2, 589]. Fully coupled quantum mechanical (QM) reaction probabilities for high values of the total angular momentum (J? 50) are reported for the first time. At the low collision energy regime (E(c)? 0.4 eV) the TDWP probabilities are well reproduced by the QCT and statistical results for the ClO forming product channel, but for the OH + Cl arrangement, only QCT probabilities are found to agree with the QM values. The good accordance found between the rigorous statistical models and the dynamical QM and QCT calculations for the O + HCl ? ClO + H process underpins the assumption that the reaction pathway leading to ClO is predominantly governed by a complex-forming mechanism. In addition, to further test the statistical character of this reaction channel, the laboratory angular distribution and time-of-flight spectra obtained in a crossed molecular beam study by Balucani et al. [Chem. Phys. Lett. 1991, 180, 34] at a collision energy as high as 0.53 eV have been simulated using the state resolved differential cross section obtained with the statistical approaches yielding a satisfactory agreement with the experimental results. For the other channel, O + HCl ? OH + Cl, noticeable differences between the statistical results and those found with the QCT calculation suggest that the dynamics of the reaction are controlled by a direct mechanism. The comparison between the QCT and QM-TDWP results in the whole range of collision energies lends credence to the QCT description of the dynamics of this reaction. PMID:21431209

Bargueño, P; Jambrina, P G; Alvariño, J M; Menéndez, M; Verdasco, E; Hankel, M; Smith, S C; Aoiz, F J; González-Lezana, T

2011-03-23

108

Indole is an inter-species biofilm signal mediated by SdiA  

PubMed Central

Background As a stationary phase signal, indole is secreted in large quantities into rich medium by Escherichia coli and has been shown to control several genes (e.g., astD, tnaB, gabT), multi-drug exporters, and the pathogenicity island of E. coli; however, its impact on biofilm formation has not been well-studied. Results Through a series of global transcriptome analyses, confocal microscopy, isogenic mutants, and dual-species biofilms, we show here that indole is a non-toxic signal that controls E. coli biofilms by repressing motility, inducing the sensor of the quorum sensing signal autoinducer-1 (SdiA), and influencing acid resistance (e.g., hdeABD, gadABCEX). Isogenic mutants showed these associated proteins are directly related to biofilm formation (e.g., the sdiA mutation increased biofilm formation 50-fold), and SdiA-mediated transcription was shown to be influenced by indole. The reduction in motility due to indole addition results in the biofilm architecture changing from scattered towers to flat colonies. Additionally, there are 12-fold more E. coli cells in dual-species biofilms grown in the presence of Pseudomonas cells engineered to express toluene o-monooxygenase (TOM, which converts indole to an insoluble indigoid) than in biofilms with pseudomonads that do not express TOM due to a 22-fold reduction in extracellular indole. Also, indole stimulates biofilm formation in pseudomonads. Further evidence that the indole effects are mediated by SdiA and homoserine lactone quorum sensing is that the addition of N-butyryl-, N-hexanoyl-, and N-octanoyl-L-homoserine lactones repress E. coli biofilm formation in the wild-type strain but not with the sdiA mutant. Conclusion Indole is an interspecies signal that decreases E. coli biofilms through SdiA and increases those of pseudomonads. Indole may be manipulated to control biofilm formation by oxygenases of bacteria that do not synthesize it in a dual-species biofilm. Furthermore, E. coli changes its biofilm in response to signals it cannot synthesize (homoserine lactones), and pseudomonads respond to signals they do not synthesize (indole).

Lee, Jintae; Jayaraman, Arul; Wood, Thomas K

2007-01-01

109

Structure and evolution of protein interaction networks: a statistical model for link dynamics and gene duplications  

PubMed Central

Background The structure of molecular networks derives from dynamical processes on evolutionary time scales. For protein interaction networks, global statistical features of their structure can now be inferred consistently from several large-throughput datasets. Understanding the underlying evolutionary dynamics is crucial for discerning random parts of the network from biologically important properties shaped by natural selection. Results We present a detailed statistical analysis of the protein interactions in Saccharomyces cerevisiae based on several large-throughput datasets. Protein pairs resulting from gene duplications are used as tracers into the evolutionary past of the network. From this analysis, we infer rate estimates for two key evolutionary processes shaping the network: (i) gene duplications and (ii) gain and loss of interactions through mutations in existing proteins, which are referred to as link dynamics. Importantly, the link dynamics is asymmetric, i.e., the evolutionary steps are mutations in just one of the binding parters. The link turnover is shown to be much faster than gene duplications. Both processes are assembled into an empirically grounded, quantitative model for the evolution of protein interaction networks. Conclusions According to this model, the link dynamics is the dominant evolutionary force shaping the statistical structure of the network, while the slower gene duplication dynamics mainly affects its size. Specifically, the model predicts (i) a broad distribution of the connectivities (i.e., the number of binding partners of a protein) and (ii) correlations between the connectivities of interacting proteins, a specific consequence of the asymmetry of the link dynamics. Both features have been observed in the protein interaction network of S. cerevisiae.

Berg, Johannes; Lassig, Michael; Wagner, Andreas

2004-01-01

110

Simple Example of an SADMT SDI-(Strategic Defense Initiative) Architecture Dataflow Modeling Technique) Architecture Specification. Version 1.5.  

National Technical Information Service (NTIS)

This IDA Paper P-2036 presents a simple architecture specification in the SDI Architecture Dataflow Modeling Technique (SADMT). The example code is given in the SADMT Generator (SAGEN) Language. This simple architecture includes (1) an informal descriptio...

C. J. Linn J. L. Linn S. H. Edwards M. R. Kappel C. D. Ardoin

1988-01-01

111

Joint Statistical and Dynamical Assessment of Simulated Vegetation Feedbacks on Climate Over the Boreal Forests  

NASA Astrophysics Data System (ADS)

Vegetation feedbacks over Asiatic Russia are assessed through a combined statistical and dynamical approach in a fully coupled atmosphere-ocean-land model, FOAM-LPJ. The dynamical assessment is comprised of initial value ensemble experiments in which the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response is determined. The statistical feedback approach, adopted from previous studies of ocean-atmosphere interactions, is applied to compute the feedback of forest cover on subsequent temperature and precipitation in the control simulation. Both methodologies indicate a year-round positive feedback on temperature and precipitation, strongest in spring and moderately substantial in summer. Reduced boreal forest cover enhances the surface albedo, leading to an extended snow season, lower air temperatures, increased atmospheric stability, and enhanced low cloud cover. Changes in the hydrological cycle include diminished transpiration and moisture recycling, supporting a reduction in precipitation. The close agreement in sign and magnitude between the statistical and dynamical feedback assessments testifies to the reliability of the statistical approach. This study supports the previous finding of a strong positive vegetation feedback on air temperature over Asiatic Russia in the observational record.

Notaro, M.; Liu, Z.

2007-12-01

112

Modified statistical dynamical diffraction theory: analysis of model SiGe heterostructures  

PubMed Central

A modified version of the statistical dynamical diffraction theory (mSDDT) permits full-pattern fitting of high-resolution X-ray diffraction scans from thin-film systems across the entire range from fully dynamic to fully kinematic scattering. The mSDDT analysis has been applied to a set of model SiGe/Si thin-film samples in order to define the capabilities of this approach. For defect-free materials that diffract at the dynamic limit, mSDDT analyses return structural information that is consistent with commercial dynamical diffraction simulation software. As defect levels increase and the diffraction characteristics shift towards the kinematic limit, the mSDDT provides new insights into the structural characteristics of these materials.

Shreeman, P. K.; Dunn, K. A.; Novak, S. W.; Matyi, R. J.

2013-01-01

113

SDI-based business processes: A territorial analysis web information system in Spain  

NASA Astrophysics Data System (ADS)

Spatial Data Infrastructures (SDIs) provide access to geospatial data and operations through interoperable Web services. These data and operations can be chained to set up specialized geospatial business processes, and these processes can give support to different applications. End users can benefit from these applications, while experts can integrate the Web services in their own business processes and developments. This paper presents an SDI-based territorial analysis Web information system for Spain, which gives access to land cover, topography and elevation data, as well as to a number of interoperable geospatial operations by means of a Web Processing Service (WPS). Several examples illustrate how different territorial analysis business processes are supported. The system has been established by the Spanish National SDI (Infraestructura de Datos Espaciales de España, IDEE) both as an experimental platform for geoscientists and geoinformation system developers, and as a mechanism to contribute to the Spanish citizens knowledge about their territory.

Béjar, Rubén; Latre, Miguel Á.; Lopez-Pellicer, Francisco J.; Nogueras-Iso, Javier; Zarazaga-Soria, F. J.; Muro-Medrano, Pedro R.

2012-09-01

114

Dynamic length-scale characterization and nonequilibrium statistical mechanics of transport in open-cell foams.  

PubMed

Nuclear magnetic resonance measurements of scale dependent dynamics in a random solid open-cell foam reveal a characteristic length scale for transport processes in this novel type of porous medium. These measurements and lattice Boltzmann simulations for a model foam structure indicate dynamical behavior analogous to lower porosity consolidated granular porous media, despite extremely high porosity in solid cellular foams. Scaling by the measured characteristic length collapses data for different foam structures as well as consolidated granular media. The nonequilibrium statistical mechanics theory of preasymptotic dispersion, developed for hierarchical porous media, is shown to model the hydrodynamic dispersive transport in a foam structure. PMID:20366068

Brosten, Tyler R; Codd, Sarah L; Maier, Robert S; Seymour, Joseph D

2009-11-20

115

WFP SPATIAL DATA INFRASTRUCTURE (SDI) IMPLEMENTATION IN SUPPORT OF EMERGENCY MANAGEMENT  

Microsoft Academic Search

a , O. Terzo b ABSTRACT: Short-term emergency response capacities, long-term risk reduction, development and environmental protection activities are sector where a Spatial Data Infrastructure (SDI) may strongly improve efficiency, facilitating access to geographically-related information using a minimum set of standard practices, protocols, and specifications. The production and use of geospatial information within the United Nations has been accomplished historically

A. Ajmar; F. Perez

116

Fitting the dynamic model PCLake to a multi-lake survey through Bayesian Statistics  

Microsoft Academic Search

A method is presented for the regression of dynamic lake ecosystem models on multi-lake data. The method draws upon Bayesian Statistics as the main inference engine, as outlined by Box and Draper (1965), M.J. Box (1971) and Box and Tiao (1973\\/1992). The Bayesian approach allows the calculation of the uncertainty of parameters and predictions both before and after the model

T. Aldenberg; J. H. Janse; P. R. G. Kramer

1995-01-01

117

Stability, capacity, and statistical dynamics of second-order bidirectional associative memory  

Microsoft Academic Search

The stability, capacity and statistical dynamics of second-order bidirectional associative memory (BAM) are presented here. We first use an example to illustrate that the state of second-order BAR I may converge to limited cycles. When error in the retrieved pairs is not allowed, a lower bound of memory capacity is derived. That is O(min(n 2\\/(log n),p2\\/(log p))) where n and

Chi-Sing Leung; Lai-Wan Chan; Edmund Lai

1995-01-01

118

Extrema statistics in the dynamics of a non-Gaussian random field.  

PubMed

When the equations that govern the dynamics of a random field are nonlinear, the field can develop with time non-Gaussian statistics even if its initial condition is Gaussian. Here, we provide a general framework for calculating the effect of the underlying nonlinear dynamics on the relative densities of maxima and minima of a two-dimensional field. Using this simple geometrical probe, we can identify the size of the non-Gaussian contributions in the random field, or alternatively the magnitude of the nonlinear terms in the underlying equations of motion. We demonstrate our approach by applying it to an initially Gaussian field that evolves according to the deterministic KPZ equation, which models surface growth and shock dynamics. PMID:23496494

Beuman, T H; Turner, A M; Vitelli, V

2013-02-26

119

Mechanical-statistical modeling in ecology: from outbreak detections to pest dynamics.  

PubMed

Knowledge about large-scale and long-term dynamics of (natural) populations is required to assess the efficiency of control strategies, the potential for long-term persistence, and the adaptability to global changes such as habitat fragmentation and global warming. For most natural populations, such as pest populations, large-scale and long-term surveys cannot be carried out at a high resolution. For instance, for population dynamics characterized by irregular abundance explosions, i.e., outbreaks, it is common to report detected outbreaks rather than measuring the population density at every location and time event. Here, we propose a mechanical-statistical model for analyzing such outbreak occurrence data and making inference about population dynamics. This spatio-temporal model contains the main mechanisms of the dynamics and describes the observation process. This construction enables us to account for the discrepancy between the phenomenon scale and the sampling scale. We propose the Bayesian method to estimate model parameters, pest densities and hidden factors, i.e., variables involved in the dynamics but not observed. The model was specified and used to learn about the dynamics of the European pine sawfly (Neodiprion sertifer Geoffr., an insect causing major defoliation of pines in northern Europe) based on Finnish sawfly data covering the years 1961-1990. In this application, a dynamical Beverton-Holt model including a hidden regime variable was incorporated into the model to deal with large variations in the population densities. Our results gave support to the idea that pine sawfly dynamics should be studied as metapopulations with alternative equilibria. The results confirmed the importance of extreme minimum winter temperatures for the occurrence of European pine sawfly outbreaks. The strong positive connection between the ratio of lake area over total area and outbreaks was quantified for the first time. PMID:18843520

Soubeyrand, S; Neuvonen, S; Penttinen, A

2008-10-09

120

Statistical and dynamic aspects of the fissionability description as applied to preactinide and actinide nuclei  

NASA Astrophysics Data System (ADS)

A wide range of problems related to description of preactinide nuclei fissionability are considered—the dependence of the rotational level density enhancement on the excitation energy and deformation of nuclei, emission of neutrons into the second well of the potential deformation energy, dynamic effects, etc. Taking them into account allowed elimination of drawbacks of earlier analysis and improving fission barriers values in the region 160 ? A ? 215, which serves to test the phenomenological models of nuclear mass and energy. Statistical analysis of the experimental data on fissionability and angular anisotropy of fragments from symmetric and asymmetric nuclear fission in the region of Ra yields results confirming theoretical predictions of their difference in thresholds and symmetry of saddle forms. Cross sections for fission of actinide nuclei induced by neutrons with the energy E n up to 20 MeV were described within the statistical theory using the deformation energy and level density of excited nuclei calculated on the basis of realistic spectra of singleparticle states. Dynamic effects are considered at high neutron energies E n > 20 MeV. Allowance for nuclear friction in the calculation of the fission cross section results in a change in its value and chance structure as compared with the statistical description.

Svirin, M. I.

2010-03-01

121

Dynamic whole-body PET parametric imaging: II. Task-oriented statistical estimation  

NASA Astrophysics Data System (ADS)

In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (˜15-20 cm) of a single-bed position and have not been translated to the whole-body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of whole-body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical 18F-deoxyglucose patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of whole-body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ˜30 min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, whole-body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection.

Karakatsanis, Nicolas A.; Lodge, Martin A.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman

2013-10-01

122

Dynamic whole-body PET parametric imaging: II. Task-oriented statistical estimation.  

PubMed

In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (?15-20 cm) of a single-bed position and have not been translated to the whole-body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of whole-body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical (18)F-deoxyglucose patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of whole-body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ?30 min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, whole-body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection. PMID:24080994

Karakatsanis, Nicolas A; Lodge, Martin A; Zhou, Y; Wahl, Richard L; Rahmim, Arman

2013-09-30

123

Quantum particle statistics on the holographic screen leads to modified Newtonian dynamics  

NASA Astrophysics Data System (ADS)

Employing a thermodynamic interpretation of gravity based on the holographic principle and assuming underlying particle statistics, fermionic or bosonic, for the excitations of the holographic screen leads to modified Newtonian dynamics (MOND). A connection between the acceleration scale a0 appearing in MOND and the Fermi energy of the holographic fermionic degrees of freedom is obtained. In this formulation the physics of MOND results from the quantum-classical crossover in the fermionic specific heat. However, due to the dimensionality of the screen, the formalism is general and applies to two-dimensional bosonic excitations as well. It is shown that replacing the assumption of the equipartition of energy on the holographic screen by a standard quantum-statistical-mechanics description wherein some of the degrees of freedom are frozen out at low temperatures is the physical basis for the MOND interpolating function ?˜. The interpolating function ?˜ is calculated within the statistical mechanical formalism and compared to the leading phenomenological interpolating functions, most commonly used. Based on the statistical mechanical view of MOND, its cosmological implications are reinterpreted: the connection between a0 and the Hubble constant is described as a quantum uncertainty relation; and the relationship between a0 and the cosmological constant is better understood physically.

Pazy, E.; Argaman, N.

2012-05-01

124

Statistical modelling of subdiffusive dynamics in the cytoplasm of living cells: A FARIMA approach  

NASA Astrophysics Data System (ADS)

Golding and Cox (Phys. Rev. Lett., 96 (2006) 098102) tracked the motion of individual fluorescently labelled mRNA molecules inside live E. coli cells. They found that in the set of 23 trajectories from 3 different experiments, the automatically recognized motion is subdiffusive and published an intriguing microscopy video. Here, we extract the corresponding time series from this video by image segmentation method and present its detailed statistical analysis. We find that this trajectory was not included in the data set already studied and has different statistical properties. It is best fitted by a fractional autoregressive integrated moving average (FARIMA) process with the normal-inverse Gaussian (NIG) noise and the negative memory. In contrast to earlier studies, this shows that the fractional Brownian motion is not the best model for the dynamics documented in this video.

Burnecki, K.; Muszkieta, M.; Sikora, G.; Weron, A.

2012-04-01

125

Statistics of voltage drop in distribution circuits: a dynamic programming approach  

SciTech Connect

We analyze a power distribution line with high penetration of distributed generation and strong variations of power consumption and generation levels. In the presence of uncertainty the statistical description of the system is required to assess the risks of power outages. In order to find the probability of exceeding the constraints for voltage levels we introduce the probability distribution of maximal voltage drop and propose an algorithm for finding this distribution. The algorithm is based on the assumption of random but statistically independent distribution of loads on buses. Linear complexity in the number of buses is achieved through the dynamic programming technique. We illustrate the performance of the algorithm by analyzing a simple 4-bus system with high variations of load levels.

Turitsyn, Konstantin S [Los Alamos National Laboratory

2010-01-01

126

Disseminating sexually transmitted infections diagnostics information: the SDI web publication review series  

PubMed Central

Objectives The World Health Organization Sexually Transmitted Diseases Diagnostics Initiative (SDI) website publication review seeks to provide health care providers in all geographic and economic settings with timely, critical, and concise information concerning new developments in laboratory and field diagnosis of sexually transmitted infections (STI). Methods Since 2003, the website (www.who.int/std_diagnostics/literature_reviews) has disseminated information in the form of annotated abstracts and commentaries on articles covering studies of STI laboratory?based and rapid assays that are commercially available or under development. Articles identified through searches of PubMed, specific journals, and by referrals from Editorial Board members are selected for inclusion if they meet pre?specified criteria. The objectives, methods, results, and conclusions for each article are summarised and board members are invited to prepare commentaries addressing study design and applicability of findings to end users. Results Currently, 91 STI diagnostics experts from 17 countries on six continents serve on the Editorial Board. Twelve quarterly issues have been posted that include summaries of 214 original and 17 review articles published from January 2002 through March 2005, with expert commentaries on 153 articles. Interest in the site has increased every year. In 2005, over 36?700 unique visitors from more than 100 countries viewed over 75?000 pages of information. Conclusions The SDI Publication Review series has the potential to contribute to SDI's goal of improving care for patients with STI by increasing knowledge and awareness of STI diagnostics. Given the proliferation of internet?based STI testing services, this website may be broadened to meet the needs of a wider range of users.

Kuypers, J; Tam, M R; Holmes, K K; Peeling, R W

2006-01-01

127

Probabilistic estimates of future changes in California temperature and precipitation using statistical and dynamical downscaling  

NASA Astrophysics Data System (ADS)

Sixteen global general circulation models were used to develop probabilistic projections of temperature (T) and precipitation (P) changes over California by the 2060s. The global models were downscaled with two statistical techniques and three nested dynamical regional climate models, although not all global models were downscaled with all techniques. Both monthly and daily timescale changes in T and P are addressed, the latter being important for a range of applications in energy use, water management, and agriculture. The T changes tend to agree more across downscaling techniques than the P changes. Year-to-year natural internal climate variability is roughly of similar magnitude to the projected T changes. In the monthly average, July temperatures shift enough that that the hottest July found in any simulation over the historical period becomes a modestly cool July in the future period. Januarys as cold as any found in the historical period are still found in the 2060s, but the median and maximum monthly average temperatures increase notably. Annual and seasonal P changes are small compared to interannual or intermodel variability. However, the annual change is composed of seasonally varying changes that are themselves much larger, but tend to cancel in the annual mean. Winters show modestly wetter conditions in the North of the state, while spring and autumn show less precipitation. The dynamical downscaling techniques project increasing precipitation in the Southeastern part of the state, which is influenced by the North American monsoon, a feature that is not captured by the statistical downscaling.

Pierce, David W.; Das, Tapash; Cayan, Daniel R.; Maurer, Edwin P.; Miller, Norman L.; Bao, Yan; Kanamitsu, M.; Yoshimura, Kei; Snyder, Mark A.; Sloan, Lisa C.; Franco, Guido; Tyree, Mary

2013-02-01

128

Statistical analysis of nonlinear dynamical systems using differential geometric sampling methods  

PubMed Central

Mechanistic models based on systems of nonlinear differential equations can help provide a quantitative understanding of complex physical or biological phenomena. The use of such models to describe nonlinear interactions in molecular biology has a long history; however, it is only recently that advances in computing have allowed these models to be set within a statistical framework, further increasing their usefulness and binding modelling and experimental approaches more tightly together. A probabilistic approach to modelling allows us to quantify uncertainty in both the model parameters and the model predictions, as well as in the model hypotheses themselves. In this paper, the Bayesian approach to statistical inference is adopted and we examine the significant challenges that arise when performing inference over nonlinear ordinary differential equation models describing cell signalling pathways and enzymatic circadian control; in particular, we address the difficulties arising owing to strong nonlinear correlation structures, high dimensionality and non-identifiability of parameters. We demonstrate how recently introduced differential geometric Markov chain Monte Carlo methodology alleviates many of these issues by making proposals based on local sensitivity information, which ultimately allows us to perform effective statistical analysis. Along the way, we highlight the deep link between the sensitivity analysis of such dynamic system models and the underlying Riemannian geometry of the induced posterior probability distributions.

Calderhead, Ben; Girolami, Mark

2011-01-01

129

Dynamical study of metallic clusters using the statistical method of time series clustering  

NASA Astrophysics Data System (ADS)

We perform common neighbor analysis on the long-time series data generated by isothermal Brownian-type molecular dynamics simulations to study the thermal and dynamical properties of metallic clusters. In our common neighbor analysis, we introduce the common neighbor label (CNL) which is a group of atoms of a smaller size (than the cluster) designated by four numeric digits. The CNL thus describes topologically smaller size atomic configurations and is associated an abundance value which is the number of "degenerate" four digits all of which characterize the same CNL. When the cluster is in its lowest energy state, it has a fixed number of CNLs and hence abundances. At nonzero temperatures, the cluster undergoes different kinds of atomic activities such as vibrations, migrational relocation, permutational and topological isomer transitions, etc. depending on its lowest energy structure. As a result, the abundances of CNLs at zero temperature will change and new CNLs with their respective new abundances are created. To understand the temperature dependence of the CNL dynamics, and hence shed light on the cluster dynamics itself, we employ a novel method of statistical time series analysis. In this method, we perform statistical clustering at two time scales. First, we examine, at given temperature, the signs of abundance changes at a short-time scale, and assign CNLs to two short-time clusters. Quasi-periodic features can be seen in the time evolution of these short-time clusters, based on which we choose a long-time scale to compute the long-time correlations between CNL pairs. We then exploit the separation of correlation levels seen in these long-time correlations to extract strongly-correlated collections of CNLs, which we will identify as effective variables for the long-time cluster dynamics. It is found that certain effective variables show subtleties in their temperature dependences and these thermal traits bear a delicate relation to prepeaks and main peaks seen in clusters Ag14, Cu14 and Cu13Au1. We therefore infer from the temperature changes of effective variables and locate the temperatures at which these prepeaks and principal peaks appear, and they are evaluated by comparing with those deduced from the specific heat data.

Lai, S. K.; Lin, Yu-Ting; Hsu, P. J.; Cheong, S. A.

2011-04-01

130

Salmonella typhimurium Encodes an SdiA Homolog, a Putative Quorum Sensor of the LuxR Family, That Regulates Genes on the Virulence Plasmid  

PubMed Central

Quorum sensing is a phenomenon in which bacteria sense and respond to their own population density by releasing and sensing pheromones. In gram-negative bacteria, quorum sensing is often performed by the LuxR family of transcriptional regulators, which affect phenotypes as diverse as conjugation, bioluminescence, and virulence gene expression. The gene encoding one LuxR family member, named sdiA (suppressor of cell division inhibition), is present in the Escherichia coli genome. In this report, we have cloned the Salmonella typhimurium homolog of SdiA and performed a systematic screen for sdiA-regulated genes. A 4.4-kb fragment encoding the S. typhimurium sdiA gene was sequenced and found to encode the 3? end of YecC (homologous to amino acid transporters of the ABC family), all of SdiA and SirA (Salmonella invasion regulator), and the 5? end of UvrC. This gene organization is conserved between E. coli and S. typhimurium. We determined that the S. typhimurium sdiA gene was able to weakly complement the E. coli sdiA gene for activation of ftsQAZ at promoter 2 and for suppression of filamentation caused by an ftsZ(Ts) allele. To better understand the function of sdiA in S. typhimurium, we screened 10,000 random lacZY transcriptional fusions (MudJ transposon mutations) for regulation by sdiA. Ten positively regulated fusions were isolated. Seven of the fusions were within an apparent operon containing ORF8, ORF9, rck (resistance to complement killing), and ORF11 of the S. typhimurium virulence plasmid. The three ORFs have now been named srgA, srgB, and srgC (for sdiA-regulated gene), respectively. The DNA sequence adjacent to the remaining three fusions shared no similarity with previously described genes.

Ahmer, Brian M. M.; van Reeuwijk, Jeroen; Timmers, Cynthia D.; Valentine, Peter J.; Heffron, Fred

1998-01-01

131

A comparison of dynamical and statistical downscaling methods for regional wave climate projections along French coastlines.  

NASA Astrophysics Data System (ADS)

Wave climate forecasting is a major issue for numerous marine and coastal related activities, such as offshore industries, flooding risks assessment and wave energy resource evaluation, among others. Generally, there are two main ways to predict the impacts of the climate change on the wave climate at regional scale: the dynamical and the statistical downscaling of GCM (Global Climate Model). In this study, both methods have been applied on the French coast (Atlantic , English Channel and North Sea shoreline) under three climate change scenarios (A1B, A2, B1) simulated with the GCM ARPEGE-CLIMAT, from Météo-France (AR4, IPCC). The aim of the work is to characterise the wave climatology of the 21st century and compare the statistical and dynamical methods pointing out advantages and disadvantages of each approach. The statistical downscaling method proposed by the Environmental Hydraulics Institute of Cantabria (Spain) has been applied (Menendez et al., 2011). At a particular location, the sea-state climate (Predictand Y) is defined as a function, Y=f(X), of several atmospheric circulation patterns (Predictor X). Assuming these climate associations between predictor and predictand are stationary, the statistical approach has been used to project the future wave conditions with reference to the GCM. The statistical relations between predictor and predictand have been established over 31 years, from 1979 to 2009. The predictor is built as the 3-days-averaged squared sea level pressure gradient from the hourly CFSR database (Climate Forecast System Reanalysis, http://cfs.ncep.noaa.gov/cfsr/). The predictand has been extracted from the 31-years hindcast sea-state database ANEMOC-2 performed with the 3G spectral wave model TOMAWAC (Benoit et al., 1996), developed at EDF R&D LNHE and Saint-Venant Laboratory for Hydraulics and forced by the CFSR 10m wind field. Significant wave height, peak period and mean wave direction have been extracted with an hourly-resolution at 110 coastal locations along the French coast. The model, based on the BAJ parameterization of the source terms (Bidlot et al, 2007) was calibrated against ten years of GlobWave altimeter observations (2000-2009) and validated through deep and shallow water buoy observations. The dynamical downscaling method has been performed with the same numerical wave model TOMAWAC used for building ANEMOC-2. Forecast simulations are forced by the 10m wind fields of ARPEGE-CLIMAT (A1B, A2, B1) from 2010 to 2100. The model covers the Atlantic Ocean and uses a spatial resolution along the French and European coast of 10 and 20 km respectively. The results of the model are stored with a time resolution of one hour. References: Benoit M., Marcos F., and F. Becq, (1996). Development of a third generation shallow-water wave model with unstructured spatial meshing. Proc. 25th Int. Conf. on Coastal Eng., (ICCE'1996), Orlando (Florida, USA), pp 465-478. Bidlot J-R, Janssen P. and Adballa S., (2007). A revised formulation of ocean wave dissipation and its model impact, technical memorandum ECMWF n°509. Menendez, M., Mendez, F.J., Izaguirre,C., Camus, P., Espejo, A., Canovas, V., Minguez, R., Losada, I.J., Medina, R. (2011). Statistical Downscaling of Multivariate Wave Climate Using a Weather Type Approach, 12th International Workshop on Wave Hindcasting and Forecasting and 3rd Coastal Hazard Symposium, Kona (Hawaii).

Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Mendez, Fernando

2013-04-01

132

Statistical analysis of a new European Cloud Dynamics and Radiation Database  

NASA Astrophysics Data System (ADS)

Physically-based algorithms for the retrieval of precipitation from satellite-borne microwave (MW) radiometers, make use of Cloud Radiation Databases (CRD's) that are composed of thousands of detailed microphysical cloud profiles, obtained from Cloud Resolving Model (CRM) simulations, coupled with the corresponding brightness temperatures (TB's), calculated by applying Radiative Transfer (RT) schemes to the CRM outputs. Usually, CRD's are generated on the basis of CRM simulations of past precipitation events and then utilized for the analysis of satellite observations of new events. Notably, retrieval precision and accuracy is strictly related to the appropriate generation of the cloud profile datasets associated to the typologies of the observed precipitation events more than to an a-posteriori statistical treatment of uncertainties. In essence, the retrieval performance can be improved by generating a statistically significant CRD by means of a large number of different CRM simulations representing all precipitation regimes that are of interest for the zone(s) and season(s) under investigation. In addition, it should be noted that despite some reasonable successes with the CRD and the Bayesian approach, there is a considerable reservoir of potential information available that has not been yet tapped. This ancillary information exists in the knowledge of the "synoptic situation" of the considered event and the geographical and temporal location of the event. This knowledge renders some entries into the CRD more relevant than others by virtue of how similar the circumstances of the simulated events are to those of the event for which the database is applied. We can capture this information in the form of "dynamical tags" which can be used to link a satellite-observed event to a subset of the entire CRD using an independent estimate of these tags. To accomplish this, we have expanded the CRD approach so as to include these "dynamical tags" and have developed a new passive MW precipitation retrieval algorithm which employs these tags in addition to the upwelling TB's. We call these the Cloud Dynamics and Radiation Database (CDRD) approach and the CDRD Algorithm, respectively. Recently, we have generated a CDRD database for Europe using a large amount of CRM simulations of precipitating systems over this area by means of the "University of Wisconsin - Non-hydrostatic Modeling System" (UW-NMS). In our presentation, we will briefly review the main design features of the CDRD approach and will show an analysis of the statistical properties of this highly-populated European CDRD database. Finally, we will compare its radiative characteristics with an equivalent set of MW radiometric measurements from polar satellites.

Casella, D.; Formenton, M.; Leung, W.-Y.; Mugnai, A.; Sanò, P.; Smith, E. A.; Tripoli, G. J.

2009-04-01

133

Assessment of prediction skill of intraseasonal variation from dynamical, statistical, and combined models  

NASA Astrophysics Data System (ADS)

We consider intraseasonal variation (ISV) prediction by statistical and dynamical models. For the fair comparison, the real-time multivariate Madden-Julian Oscillation (MJO) (RMM) index for the boreal winter is used as a predictand. The statistical prediction results are compared by reassessing the multi linear regression (MLR), wavelet, and singular spectrum analysis (SSA) model. The correlation score for RMM1 (RMM2) falls away to 0.5 between 16-17 (15-16) days for MLR, 7-8 (9-10) days for wavelet, and 8-9 (9-10) days for SSA model. As both wavelet and SSA model have a discontinuity at the boundary of data, the skill of the real-time forecast shows a steep decrease at the beginning of the forecasts. To examine the skill of dynamical prediction, serial integration is performed with Seoul National University AGCM and CGCM over the entire boreal winter period. The ocean-atmosphere coupling acts to improve the simulation ability of MJO variability, the eastward propagation, and the phase relationship between convection and SST. The skill score of RMM1 (RMM2) falls out to 0.5 at 18-19 (22-23), 15-16 (17-18), and 16-17 (15-16) for CGCM, AGCM, and MLR. This result demonstrates that dynamical prediction does not lag statistical prediction in skill and is even better when ocean-atmosphere coupling is included. The dependency of prediction skill on the initial phase and amplitude of the MJO is investigated. The score is better when the MJO is initialized during an active period than during a quiescent period for both systems. Based on different characteristics of prediction skill for each phase and amplitude and for individual models, predictions are combined using available information extracted using the better of the two predictions. By simple selection, the prediction skill is clearly improved in strong MJO cases. Using another combination process based on Bayesian concepts, two independent predictions are combined by minimizing the forecast error that is known from historical information. It shows the superior to both of the predictions over the entire forecast lead days.

Kim, H.; Kang, I.; Webster, P. J.

2008-12-01

134

Application of statistical and dynamics models for snow avalanche hazard assessment in mountain regions of Russia  

NASA Astrophysics Data System (ADS)

The estimation of extreme avalanche runout distances, flow velocities, impact pressures and volumes is an essential part of snow engineering in mountain regions of Russia. It implies the avalanche hazard assessment and mapping. Russian guidelines accept the application of different avalanche models as well as approaches for the estimation of model input parameters. Consequently different teams of engineers in Russia apply various dynamics and statistical models for engineering practice. However it gives more freedom to avalanche practitioners and experts but causes lots of uncertainties in case of serious limitations of avalanche models. We discuss these problems by presenting the application results of different well known and widely used statistical (developed in Russia) and avalanche dynamics models for several avalanche test sites in the Khibini Mountains (The Kola Peninsula) and the Caucasus. The most accurate and well-documented data from different powder and wet, big rare and small frequent snow avalanche events is collected from 1960th till today in the Khibini Mountains by the Avalanche Safety Center of "Apatit". This data was digitized and is available for use and analysis. Then the detailed digital avalanche database (GIS) was created for the first time. It contains contours of observed avalanches (ESRI shapes, more than 50 years of observations), DEMs, remote sensing data, description of snow pits, photos etc. Thus, the Russian avalanche data is a unique source of information for understanding of an avalanche flow rheology and the future development and calibration of the avalanche dynamics models. GIS database was used to analyze model input parameters and to calibrate and verify avalanche models. Regarding extreme dynamic parameters the outputs using different models can differ significantly. This is unacceptable for the engineering purposes in case of the absence of the well-defined guidelines in Russia. The frequency curves for the runout distance in different avalanche sites were constructed using the field data. It allowed us to assess the probability (return period) of the calculated extreme runout distances using obtained frequency curves. Avalanche zoning is not yet used by land planning authorities to prevent construction in avalanche hazard zones in Russia. Our approach can be used for the future development of avalanche zoning in Russia.

Turchaninova, A.

2012-04-01

135

Kinematic and dynamic collision statistics of cloud droplets from high-resolution simulations  

NASA Astrophysics Data System (ADS)

We study the dynamic and kinematic collision statistics of cloud droplets for a range of flow Taylor microscale Reynolds numbers (up to 500), using a highly scalable hybrid direct numerical simulation approach. Accurate results of radial relative velocity (RRV) and radial distribution function (RDF) at contact have been obtained by taking advantage of their power-law scaling at short separation distances. Three specific but inter-related questions have been addressed in a systematic manner for geometric collisions of same-size droplets (of radius from 10 to 60 ?m) in a typical cloud turbulence (dissipation rate at 400 cm2 s-3). Firstly, both deterministic and stochastic forcing schemes were employed to test the sensitivity of the simulation results on the large-scale driving mechanism. We found that, in general, the results are quantitatively similar, with the deterministic forcing giving a slightly larger RDF and collision kernel. This difference, however, is negligible for droplets of radius less than 30 ?m. Secondly, we have shown that the dependence of pair statistics on the flow Reynolds number R? or larger scale fluid motion is of secondary importance, with a tendency for this effect to saturate at high enough R? leading to R?-independent results. Both DNS results and theoretical arguments show that the saturation happens at a smaller R? for smaller droplets. Finally, since most previous studies of turbulent collision of inertial particles concerned non-sedimenting particles, we have specifically addressed the role of gravity on collision statistics, by simultaneously simulating collision statistics with and without gravity. It is shown that the collision statistics is not affected by gravity when a < ac, where the critical droplet radius ac is found to be around 30 ?m for the RRV, and around 20 ?m for the RDF. For larger droplets, gravity alters the particle-eddy interaction time and significantly reduces the RRV. The effect of gravity on the RDF is rather complex: gravity reduces the RDF for intermediate-sized droplets but enhances the RDF for larger droplets. In addition, we have studied the scaling exponents of both RDF and RRV, and found that gravity modifies the RDF scaling exponents for both intermediate and large particles, in a manner very similar to the effect of gravity on the RDF at contact. Gravity is shown to cause the scaling exponents for RDF and RRV to level off for large droplets, in contrast to diminishing exponents for non-sedimenting particles.

Rosa, Bogdan; Parishani, Hossein; Ayala, Orlando; Grabowski, Wojciech W.; Wang, Lian-Ping

2013-04-01

136

Extreme Wind Gusts within European Winter Storms estimated from Dynamical and Statistical Downscaling  

NASA Astrophysics Data System (ADS)

Extreme winter wind storms are major natural catastrophes leading to enormous socio-economic impacts in Europe. The impact of a single events depends on the severity and extent of the event itself but also on the region hit by the storm, combined with its specific exposure of values and vulnerability. The spatial distribution of exposed values and their vulnerability is highly heterogeneous. Therefore, it is necessary to analyze extremes of surface wind speeds within winter wind storms with high spatial resolution. This study analyzes if rather simple linear regression methods are suitable for estimating extreme surface wind gusts of high spatial resolution, using different coarse resolution predictors. The statistical relationships between coarse resolution predictors from ECMWF reanalysis data and high resolution (~7km x 7km) predictands, i.e. the maximum gusts, are derived from dynamical simulations of extreme historical events performed with the German Weather Service (DWD) model chain GME—COSMO-EU. Validation of the results of the statistical downscaling confirms the high skill of linear regressions for different European sub-regions. Hence, the application of these methods to more extensive datasets in order to estimate extreme wind gusts and their exceedance probabilities or return periods is justified.

Kruschke, T.; Lorenz, P.; Osinski, R.; Voigt, M.; Leckebusch, G. C.; Ulbrich, U.

2012-04-01

137

Hydraulic management in a soil moisture controlled SDI wastewater dispersal system in an Alabama black belt soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

An experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial in a Vertisol in the Alabama Black Belt region for two years. The system was designed to start hydraulic dosing only when field moisture was below field capacity. Results sho...

138

Hydraulic management of a soil moisture controlled SDI wastewater dispersal system in an Alabama Black Belt soil  

Microsoft Academic Search

Rural areas represent approximately 95% of the 14000 km2 Alabama Black Belt, an area of widespread Vertisols dominated by clayey, smectitic, shrink–swell soils. These soils are unsuitable for conventional onsite wastewater treatment systems (OWTS) which are nevertheless widely used in this region. In order to provide an alternative wastewater dosing system, an experimental field moisture controlled subsurface drip irrigation (SDI) system

Jiajie He; Mark Dougherty; Joey Shaw; John Fulton; Francisco Arriaga

2011-01-01

139

Neocortical dynamics at multiple scales: EEG standing waves, statistical mechanics, and physical analogs.  

PubMed

The dynamic behavior of scalp potentials (EEG) is apparently due to some combination of global and local processes with important top-down and bottom-up interactions across spatial scales. In treating global mechanisms, we stress the importance of myelinated axon propagation delays and periodic boundary conditions in the cortical-white matter system, which is topologically close to a spherical shell. By contrast, the proposed local mechanisms are multiscale interactions between cortical columns via short-ranged non-myelinated fibers. A mechanical model consisting of a stretched string with attached nonlinear springs demonstrates the general idea. The string produces standing waves analogous to large-scale coherent EEG observed in some brain states. The attached springs are analogous to the smaller (mesoscopic) scale columnar dynamics. Generally, we expect string displacement and EEG at all scales to result from both global and local phenomena. A statistical mechanics of neocortical interactions (SMNI) calculates oscillatory behavior consistent with typical EEG, within columns, between neighboring columns via short-ranged non-myelinated fibers, across cortical regions via myelinated fibers, and also derives a string equation consistent with the global EEG model. PMID:21167841

Ingber, Lester; Nunez, Paul L

2010-12-16

140

Statistical and dynamical analysis of RNA structures and complexes with applications to nanodevice design  

NASA Astrophysics Data System (ADS)

This dissertation combines rigid body motion kinematics and statistical analysis techniques to extract information from detailed dynamic simulations and large databases of biomolecular structures. This information is then used to quantify and elucidate structural patterns that could be used to design functional nano-structures or provide new targets for ligand-based drug design. In this regard, three particular classes of problems are examined. First, we propose new methods for estimating the stiffness of continuum filament models of helical nucleic acid structures. In this work, molecular dynamics is used to sample RNA helices consisting of several base-pairs fluctuating about an equilibrium position. At equilibrium, each base-pair has a tightly clustered probability distribution and so we can describe the rigid body motion of the helix as the convolution of highly concentrated probability densities on SE(3). Second, the structure and dynamics of a common RNA non-helical motif is classified. We examine several RNA bulges with varying sequences and helix curvature, and establish degrees of similarity (and dissimilarity) in the bulge motif according to the nucleic acid type of the bulge and surrounding base-pairs. Both the "static" X-ray-crystal and NMR structures and the dynamics generated from molecular dynamics simulations are used to quantify the flexibility and conservative aspects of the motif. The resulting classification scheme provides bulge motifs that could be included in a toolbox of "nanostructures" where one could pick the pieces to design a structure that has the needed shape and desired behavior. Finally, we analyze a large collection of adenosine binding sites, focusing on the functional region of the binding site. We provide a new analysis tool that finds spatial patterns in adenosine binding pockets by examining the relative pose (position and orientation) between the adenosine ligand and the amino acids at each binding site. The similarities of the numerous adenosine binding pockets are calculated according to the pose similarity and homogeny of the structures. We show that correlations between the binding pockets are multifaceted and illustrate our findings using similarity plots and multiple correlation calculations for a comprehensive analysis.

Hastings, Whitney Allen

141

Inactivation of the Transcriptional Regulator-Encoding Gene sdiA Enhances Rice Root Colonization and Biofilm Formation in Enterobacter cloacae GS1  

PubMed Central

Enterobacter cloacae GS1 is a plant growth-promoting bacterium which colonizes rice roots. In the rhizosphere environment, N-acyl homoserine lactone (NAHL)-like quorum-sensing signals are known to be produced by host plants and other microbial inhabitants. E. cloacae GS1 was unable to synthesize NAHL quorum-sensing signals but had the NAHL-dependent transcriptional regulator-encoding gene sdiA. This study was aimed at understanding the effects of SdiA and NAHL-dependent cross talk in rice root colonization by E. cloacae GS1. Pleiotropic effects of sdiA inactivation included substantial increases in root colonization and biofilm formation, suggesting a negative role for SdiA in bacterial adhesion. We provide evidence that sdiA inactivation leads to elevated levels of biosynthesis of curli, which is involved in cellular adhesion. Extraneous addition of NAHLs had a negative effect on root colonization and biofilm formation. However, the sdiA mutant of E. cloacae GS1 was insensitive to NAHLs, suggesting that this NAHL-induced inhibition of root colonization and biofilm formation is SdiA dependent. Therefore, it is proposed that NAHLs produced by both plant and microbes in the rice rhizosphere act as cross-kingdom and interspecies signals to negatively impact cellular adhesion and, thereby, root colonization in E. cloacae GS1.

Shankar, Manoharan; Ponraj, Paramasivan; Illakkiam, Devaraj; Rajendhran, Jeyaprakash

2013-01-01

142

SdiA, an N-Acylhomoserine Lactone Receptor, Becomes Active during the Transit of Salmonella enterica through the Gastrointestinal Tract of Turtles  

PubMed Central

Background LuxR-type transcription factors are typically used by bacteria to determine the population density of their own species by detecting N-acylhomoserine lactones (AHLs). However, while Escherichia and Salmonella encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species. Methodology/Principal Findings In this report, we tested the hypothesis that SdiA detects the AHL-production of other bacterial species within the animal host. SdiA did not detect AHLs during the transit of Salmonella through the gastrointestinal tract of a guinea pig, a rabbit, a cow, 5 mice, 6 pigs, or 12 chickens. However, SdiA was activated during the transit of Salmonella through turtles. All turtles examined were colonized by the AHL-producing species Aeromonas hydrophila. Conclusions/Significance We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals.

Soares, Jitesh A.; Ellermeier, Craig D.; Altier, Craig; Lawhon, Sara D.; Adams, L. Garry; Konjufca, Vjollca; Curtiss, Roy; Slauch, James M.; Ahmer, Brian M. M.

2008-01-01

143

Groundwater dynamic in a coastal aquifer using statistical analysis and geochemical modeling  

NASA Astrophysics Data System (ADS)

Coastal aquifers are natural environments particularly vulnerable and seriously threatened. Coastal areas are densely populated and this leads to a massive withdrawal of groundwater. These conditions may induce a salinization process of groundwater, due to the change of the balances that govern the coexistence between fresh and salt water. Hydrochemical data from well water samples collected during a year of monitoring in Palo Laziale area are used to evaluate water quality and to determine processes that control water chemistry. Geochemical ratios (EC vs rCl; Na vs Cl; rCl/rBr vs Cl) give information about mixing, cation exchange and salinity acquisition process. Multivariate statistical approach and geochemical modeling are adopted to assist the interpretation of the geochemical data, particularly cluster analysis and Principal Component Analysis. Software PHREEQC was used for geochemical modeling and data processing. In add to determining chemical components and some chemical-physical properties (T, pH,electrical conductivity, TDS) the studied provided following: statistical analysis of data, thermodynamic equilibrium of aquifer with quantitative analysis of the saturation index and the speciation of trace and minor elements. According to statistical analysis is possible to identify two different groups of water: typical of domestic wells in Palo SIC area and external wells. PCA analysis suggests that Palo Laziale SIC is located in an area of interface between fresh and salt water and there is a significant amount of water recharge (the monitoring of the area occurred in a year particularly rainy). Calculation of saturation indices (SI) for primary minerals (aragonite, calcite a dolomite-d) was carried out to obtain a quantitative estimate of the instability of these phases. The result of the calculation of saturation indices allow to define a sequence of instability of minerals: calcite > dolomite > aragonite. The order of solubility indicates that during the leaching process, calcite and aragonite are characterized by a kinetics faster than the dissolution of dolomite. A combination of statistic and geochemical techniques proved to be a reliable tool in the interpretation of hydrogeochemical dynamic of a coastal area.

Garone, A.; Battistel, M.; Barbieri, M.; Parisse, B.

2012-04-01

144

A multinational SDI-based system to facilitate disaster risk management in the Andean Community  

NASA Astrophysics Data System (ADS)

A useful strategy for improving disaster risk management is sharing spatial data across different technical organizations using shared information systems. However, the implementation of this type of system requires a large effort, so it is difficult to find fully implemented and sustainable information systems that facilitate sharing multinational spatial data about disasters, especially in developing countries. In this paper, we describe a pioneer system for sharing spatial information that we developed for the Andean Community. This system, called SIAPAD (Andean Information System for Disaster Prevention and Relief), integrates spatial information from 37 technical organizations in the Andean countries (Bolivia, Colombia, Ecuador, and Peru). SIAPAD was based on the concept of a thematic Spatial Data Infrastructure (SDI) and includes a web application, called GEORiesgo, which helps users to find relevant information with a knowledge-based system. In the paper, we describe the design and implementation of SIAPAD together with general conclusions and future directions which we learned as a result of this work.

Molina, Martin; Bayarri, Salvador

2011-09-01

145

The linked ArcView 2.1 and XGobi environment—GIS, dynamic statistical graphics, and spatial data  

Microsoft Academic Search

This paper reports on research into interactive, dynamic statistical graphics (DSG) applied to spatial data maintained within a geo- graphic information system (GIS). We developed a bidirectional link between ArcView 2.1 , a GIS, and XGobi, a DSG program. Multivariate data, collected at geographic locations, is passed from ArcView to XGobi and can be dynamically analyzed. The relation between the

Jiirgen Symanzik; James J. Majure; Dianne Cook

1996-01-01

146

The scientists' opposition to SDI: How political views affect technical analysis  

SciTech Connect

This study examines the scientists' opposition to President Reagan's Strategic Defense Initiative (1983-1989) with a focus on the relationship between the scientists' political and strategic opposition to ballistic missile defenses (BMD) and their technical doubts about BMD technologies. The study begins with a review of the scientists' increased influence in United State's national security decision making because of the development of atomic weapons. The study then examines the scientists' role in developing and promoting a theory of arms control based upon mutual societal vulnerability. Because of this theory, a large segment of the American scientific community came to believe that the development of ballistic missile defenses would destabilize the strategic balance and therefore took the lead in arguing against BMD deployments. These background chapters conclude with an analysis of the scientists' involvement in the political campaign to stop the proposed Sentinel and Safeguard Anti-Ballistic Missile defense. The study then turns to the contemporary scientific opposition to BMD deployments and the SDI research program. After examining the polls and petitions that identify the scientists opposed to SDI, the study analyzes the tactics that three scientists use in their political effort to prevent BMD deployments. Next, an examination of the political and strategic assumptions behind the scientists' opposition to BMD reveals that a belief in the arms control process and deterrence by punishment, especially Assured Destruction deterrence, with a fear of an action-reaction arms race inspires much of the contemporary opposition to BMD. Finally, the scientists' technical doubts about BMD technologies are analyzed through the prism of peer critique. These critiques show that the scientists opposed to BMD deployments us pessimistic and unrealistic assumptions to skew their technical analysis of BMD technologies.

Tait, G.E.

1989-01-01

147

Statistical mechanics and dynamics of solvable models with long-range interactions  

NASA Astrophysics Data System (ADS)

For systems with long-range interactions, the two-body potential decays at large distances as V(r)˜1/r, with ??d, where d is the space dimension. Examples are: gravitational systems, two-dimensional hydrodynamics, two-dimensional elasticity, charged and dipolar systems. Although such systems can be made extensive, they are intrinsically non additive: the sum of the energies of macroscopic subsystems is not equal to the energy of the whole system. Moreover, the space of accessible macroscopic thermodynamic parameters might be non convex. The violation of these two basic properties of the thermodynamics of short-range systems is at the origin of ensemble inequivalence. In turn, this inequivalence implies that specific heat can be negative in the microcanonical ensemble, and temperature jumps can appear at microcanonical first order phase transitions. The lack of convexity allows us to easily spot regions of parameter space where ergodicity may be broken. Historically, negative specific heat had been found for gravitational systems and was thought to be a specific property of a system for which the existence of standard equilibrium statistical mechanics itself was doubted. Realizing that such properties may be present for a wider class of systems has renewed the interest in long-range interactions. Here, we present a comprehensive review of the recent advances on the statistical mechanics and out-of-equilibrium dynamics of solvable systems with long-range interactions. The core of the review consists in the detailed presentation of the concept of ensemble inequivalence, as exemplified by the exact solution, in the microcanonical and canonical ensembles, of mean-field type models. Remarkably, the entropy of all these models can be obtained using the method of large deviations. Long-range interacting systems display an extremely slow relaxation towards thermodynamic equilibrium and, what is more striking, the convergence towards quasi-stationary states. The understanding of such unusual relaxation process is obtained by the introduction of an appropriate kinetic theory based on the Vlasov equation. A statistical approach, founded on a variational principle introduced by Lynden-Bell, is shown to explain qualitatively and quantitatively some features of quasi-stationary states. Generalizations to models with both short and long-range interactions, and to models with weakly decaying interactions, show the robustness of the effects obtained for mean-field models.

Campa, Alessandro; Dauxois, Thierry; Ruffo, Stefano

2009-09-01

148

Statistical mechanics and molecular dynamics in evaluating thermodynamic properties of biomolecular recognition  

PubMed Central

Molecular recognition plays a central role in biochemical processes. Although well studied, understanding the mechanisms of recognition is inherently difficult due to the range of potential interactions, the molecular rearrangement associated with binding, and the time and length scales involved. Computational methods have the potential for not only complementing experiments that have been performed, but also in guiding future ones through their predictive abilities. In this review, we discuss how molecular dynamics (MD) simulations may be used in advancing our understanding of the thermodynamics that drive biomolecular recognition. We begin with a brief review of the statistical mechanics that form a basis for these methods. This is followed by a description of some of the most commonly used methods: thermodynamic pathways employing alchemical transformations and potential of mean force calculations, along with end-point calculations for free energy differences, and harmonic and quasi-harmonic analysis for entropic calculations. Finally, a few of the fundamental findings that have resulted from these methods are discussed, such as the role of configurational entropy and solvent in intermolecular interactions, along with selected results of the model system T4 lysozyme to illustrate potential and current limitations of these methods.

Wereszczynski, Jeff; McCammon, J. Andrew

2012-01-01

149

Statistical mechanics and molecular dynamics in evaluating thermodynamic properties of biomolecular recognition.  

PubMed

Molecular recognition plays a central role in biochemical processes. Although well studied, understanding the mechanisms of recognition is inherently difficult due to the range of potential interactions, the molecular rearrangement associated with binding, and the time and length scales involved. Computational methods have the potential for not only complementing experiments that have been performed, but also in guiding future ones through their predictive abilities. In this review, we discuss how molecular dynamics (MD) simulations may be used in advancing our understanding of the thermodynamics that drive biomolecular recognition. We begin with a brief review of the statistical mechanics that form a basis for these methods. This is followed by a description of some of the most commonly used methods: thermodynamic pathways employing alchemical transformations and potential of mean force calculations, along with end-point calculations for free energy differences, and harmonic and quasi-harmonic analysis for entropic calculations. Finally, a few of the fundamental findings that have resulted from these methods are discussed, such as the role of configurational entropy and solvent in intermolecular interactions, along with selected results of the model system T4 lysozyme to illustrate potential and current limitations of these methods. PMID:22082669

Wereszczynski, Jeff; McCammon, J Andrew

2011-11-15

150

Combined dynamical and statistical approach to describing induced fission of heavy nuclei  

NASA Astrophysics Data System (ADS)

A combined dynamical and statistical approach to describing induced fission of heavy nuclei is proposed. This approach takes into account the nuclear-dissipation phenomenon and the double-humped structure of the fission barrier. A method that is intended for calculating the angular distribution of fission fragments and which is applicable over a broad range of excitation energies is discussed. The potential of the approach is demonstrated by addressing the problems of self-consistently describing experimental data on fission probabilities for plutonium and americium isotopes, the yields of shape isomers in the ?+238U reaction at alpha-particle energies in the range E ? = 20-32 MeV and the d+242,240Pu reactions at deuteron energies in the range E d = 20-30 MeV, fission times in the ? + 238U reaction at alpha-particle energies in the range E ? = 20-32 MeV, and angular distributions of fission fragments in the ? + 238U, 237Np reactions at alpha-particle energies in the range E ? = 20-100 MeV.

Eremenko, D. O.; Dermenev, A. A.; Drozdov, V. A.; Platonov, S. Yu.; Fotina, O. V.; Yuminov, O. A.

2009-10-01

151

A Statistical-Dynamical Parameterization of Interception and Land Surface-Atmosphere Interactions.  

NASA Astrophysics Data System (ADS)

At a local scale, the interception capacity of the canopy depends on a variety of climatic and canopy factors. Of particular importance is the intensity of rainfall-interception capacity varies inversely with rainfall intensity. At a field or regional scale, like the scale of global climate models, the spatially averaged interception also depends significantly on the spatial variability of rainfall intensity and total precipitation depth.A new parameterization of canopy interception is developed. In the new parameterization, the spatial average of actual interception is obtained as a function of rainfall intensity and total precipitation depth, and of an interception capacity, which depends on the characteristics of the leaf surface and of the vegetation cover. In a statistical-dynamical framework, the new parameterization also accounts for the subgrid-scale spatial variability of rainfall intensity and total precipitation depth.The implications of accounting for the dependence of interception capacity on rainfall characteristics are examined by assessing the consequent responses of the energy and the water fluxes at the land surface. This is accomplished by incorporating the new parameterization into a soil-plant-atmosphere column model that is fundamentally based on the physical parameterizations of NCAR's Community Climate Model.

Ramírez, Jorge A.; Senarath, Sharika U. S.

2000-11-01

152

Statistical Analysis of Ion Mobility Spectrometry. I. Unbiased and Guided Replica-Exchange Molecular Dynamics  

NASA Astrophysics Data System (ADS)

Achieving (bio)macromolecular structural assignment from the interpretation of ion mobility spectrometry (IMS) experiments requires successful comparison with computer modeling. Replica-exchange molecular dynamics simulations with suitable force fields not only offer a convenient framework to locate relevant conformations, especially in the case of multiple-funnel energy landscapes, but they are also well suited to statistical analyses. In the present paper, we discuss two extensions of the method used to improve its efficiency in the context of IMS. Two doubly-protonated polyalanines [RA4XA4K + 2H]2+ with X = V and D appear as favorable cases for which the calculated collision cross-section distributions naturally agree with the measurements, providing reliable candidate structures. For these compounds, a careful consideration of other order parameters based on the weighted histogram method resolves several otherwise hidden underlying conformational families. In the case of a much larger peptide exhibiting bistability, assignment is more difficult but could be achieved by guiding the sampling with an umbrella potential using the square gyration radius as the biasing coordinate. Applied to triply protonated bradykinine, the two presented methods indicate that different conformations compatible with the measurements are very close in energy.

Chirot, Fabien; Calvo, Florent; Albrieux, Florian; Lemoine, Jérôme; Tsybin, Yury O.; Dugourd, Philippe

2012-02-01

153

Statistical analysis of ion mobility spectrometry. I. Unbiased and guided replica-exchange molecular dynamics.  

PubMed

Achieving (bio)macromolecular structural assignment from the interpretation of ion mobility spectrometry (IMS) experiments requires successful comparison with computer modeling. Replica-exchange molecular dynamics simulations with suitable force fields not only offer a convenient framework to locate relevant conformations, especially in the case of multiple-funnel energy landscapes, but they are also well suited to statistical analyses. In the present paper, we discuss two extensions of the method used to improve its efficiency in the context of IMS. Two doubly-protonated polyalanines [RA(4)XA(4)K + 2H](2+) with X=V and D appear as favorable cases for which the calculated collision cross-section distributions naturally agree with the measurements, providing reliable candidate structures. For these compounds, a careful consideration of other order parameters based on the weighted histogram method resolves several otherwise hidden underlying conformational families. In the case of a much larger peptide exhibiting bistability, assignment is more difficult but could be achieved by guiding the sampling with an umbrella potential using the square gyration radius as the biasing coordinate. Applied to triply protonated bradykinine, the two presented methods indicate that different conformations compatible with the measurements are very close in energy. PMID:22131226

Chirot, Fabien; Calvo, Florent; Albrieux, Florian; Lemoine, Jérôme; Tsybin, Yury O; Dugourd, Philippe

2011-12-01

154

Dynamical and statistical behavior of discrete combustion waves: a theoretical and numerical study.  

PubMed

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius' macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius' microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism. PMID:23679470

Bharath, Naine Tarun; Rashkovskiy, Sergey A; Tewari, Surya P; Gundawar, Manoj Kumar

2013-04-03

155

Dynamical and statistical behavior of discrete combustion waves: A theoretical and numerical study  

NASA Astrophysics Data System (ADS)

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius’ macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius’ microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.

Bharath, Naine Tarun; Rashkovskiy, Sergey A.; Tewari, Surya P.; Gundawar, Manoj Kumar

2013-04-01

156

Global Aspects of the Dissipative Dynamical Systems. I Statistical Identification and Fractal Properties of the Lorenz Chaos  

Microsoft Academic Search

Several empirical concepts which become practically necessary to characterize the ergodic motion in the dissipative systems are explained concretely by carrying out with the Lorenz model. Chaotic motions are characterized not only by the geometrical features in the phase space but also by the statistical aspects in the time series of the dynamical variables. These global aspects are understood in

Yoji Aizawa

1982-01-01

157

p21Waf1\\/Cip1\\/Sdi1 induces permanent growth arrest with markers of replicative senescence in human tumor cells lacking functional p53  

Microsoft Academic Search

We have shown previously that wild type p53 can rapidly induce replicative senescence in EJ human bladder carcinoma cells lacking functional p53. A major effector of p53 functions is p21Waf1\\/Cip1\\/Sdi1, a potent cyclin-dependent kinase inhibitor. p21Waf1\\/Cip1\\/Sdi1 has been shown to be involved in both p53 dependent and independent control of cell proliferation, differentiation and death. To directly investigate the effects

Li Fang; Makoto Igarashi; Jennifer Leung; Mary M Sugrue; Sam W Lee; Stuart A Aaronson

1999-01-01

158

Statistical Software.  

ERIC Educational Resources Information Center

|This buyer's guide to seven major types of statistics software packages for microcomputers reviews Edu-Ware Statistics 3.0; Financial Planning; Speed Stat; Statistics with DAISY; Human Systems Dynamics package of Stats Plus, ANOVA II, and REGRESS II; Maxistat; and Moore-Barnes' MBC Test Construction and MBC Correlation. (MBR)|

Callamaras, Peter

1983-01-01

159

The sexually dimorphic on the Y-chromosome gene (sdY) is a conserved male-specific Y-chromosome sequence in many salmonids  

PubMed Central

All salmonid species investigated to date have been characterized with a male heterogametic sex-determination system. However, as these species do not share any Y-chromosome conserved synteny, there remains a debate on whether they share a common master sex-determining gene. In this study, we investigated the extent of conservation and evolution of the rainbow trout (Oncorhynchus mykiss) master sex-determining gene, sdY (sexually dimorphic on the Y-chromosome), in 15 different species of salmonids. We found that the sdY sequence is highly conserved in all salmonids and that sdY is a male-specific Y-chromosome gene in the majority of these species. These findings demonstrate that most salmonids share a conserved sex-determining locus and also strongly suggest that sdY may be this conserved master sex-determining gene. However, in two whitefish species (subfamily Coregoninae), sdY was found both in males and females, suggesting that alternative sex-determination systems may have also evolved in this family. Based on the wide conservation of sdY as a male-specific Y-chromosome gene, efficient and easy molecular sexing techniques can now be developed that will be of great interest for studying these economically and environmentally important species.

Yano, Ayaka; Nicol, Barbara; Jouanno, Elodie; Quillet, Edwige; Fostier, Alexis; Guyomard, Rene; Guiguen, Yann

2013-01-01

160

Salmonella SdiA recognizes N-acyl homoserine lactone signals from Pectobacterium carotovorum in vitro, but not in a bacterial soft rot.  

PubMed

Genomes of Salmonella enterica isolates, including those linked to outbreaks of produce-associated gastroenteritis, contain sdiA, which encodes a receptor of N-acyl homoserine lactones (AHL). AHL are the quorum-sensing signals used by bacteria to coordinately regulate gene expression within -their populations. Because S. enterica does not produce its own AHL, SdiA is hypothesized to function in the interspecies cross-talk with AHL-producing bacteria. Under laboratory conditions, S. enterica responded to AHL from phytobacteria by upregulating expression of srgE. AHL-dependent expression of srgE required a functional sdiA. Essentially, no sdiA-dependent resolution of the srgE recombinase-based (RIVET) reporter was observed inside a soft rot formed on a tomato by an AHL-producing strain of Pectobacterium carotovorum. The results of the control experiments suggest that sdiA is not expressed inside tomato, pepper, green onion, or carrot affected by the soft rot, and the lack of sdiA expression in planta prevents Salmonella spp. from responding to AHL. Despite its inability to detect and respond to AHL during colonization of soft rots, S. enterica reached higher final cell numbers inside a tomato soft rot compared with its growth in intact tomato fruit. The synergistic effect was the strongest under the conditions that are typical for the Florida fall/winter production season. PMID:20121449

Noel, J T; Joy, J; Smith, J N; Fatica, M; Schneider, K R; Ahmer, B M M; Teplitski, M

2010-03-01

161

Polymer statistics under confinement and multiple scattering theory for polymer dynamics and elasticity  

NASA Astrophysics Data System (ADS)

In this dissertation we report new theoretical results-both analytical and numerical-concerning a variety of polymeric systems. Applying path-integral and differentiable manifolds techniques, we have obtained original results concerning the statistics of a Gaussian polymer embedded on a sphere, a cylinder, a cone and a torus. Generally, we found that the curvature of the surfaces induces a geometrical localization area. Next we employ field theoretical (instanton calculus) and differential equations techniques (Darboux method) to obtain approximate and exact new results regarding the average size and the Green function of a Gaussian, one- dimensional polymer chain subjected to a multi-stable potential (the tunnel effect in polymer physics). Extending the multiple scattering formalism, we have investigated the steady-state dynamics of suspensions of spheres and Gaussian polymer chains without excluded volume interactions. We have calculated the self- diffusion and friction coefficients for probe objects (sphere and polymer chain) and the shear viscosity of the suspensions. At certain values of the concentration of the ambient medium, motion of probe objects freezes. Deviation from the Stokes-Einstein behavior is observed and interpreted. Next, we have calculated the diffusion coefficient and the change in the viscosity of a dilute solution of freely translating and rotating diblock, Gaussian copolymers. Regimes that lead to increasing the efficiency of separation processes have been identified. The parallel between Navier-Stokes and Lamé equations was exploited to extend the effective medium formalism to the computation of the effective shear and Young moduli and the Poisson ratio of a composite material containing rigid, monodispersed, penetrable spheres. Our approach deals efficiently with the high concentration regime of inclusions.

Mondescu, Radu Paul

1999-08-01

162

Hydrologic Implications of Dynamical and Statistical Approaches to Downscaling Climate Model Outputs  

SciTech Connect

Six approaches for downscaling climate model outputs for use in hydrologic simulation were evaluated, with particular emphasis on each method's ability to produce precipitation and other variables used to drive a macroscale hydrology model applied at much higher spatial resolution than the climate model. Comparisons were made on the basis of a twenty-year retrospective (1975–1995) climate simulation produced by the NCAR-DOE Parallel Climate Model (PCM), and the implications of the comparison for a future (2040–2060) PCM climate scenario were also explored. The six approaches were made up of three relatively simple statistical downscaling methods – linear interpolation (LI), spatial disaggregation (SD), and bias-correction and spatial disaggregation (BCSD) – each applied to both PCM output directly (at T42 spatial resolution), and after dynamical downscaling via a Regional Climate Model (RCM – at ½-degree spatial resolution), for downscaling the climate model outputs to the ?-degree spatial resolution of the hydrological model. For the retrospective climate simulation, results were compared to an observed gridded climatology of temperature and precipitation, and gridded hydrologic variables resulting from forcing the hydrologic model with observations. The most significant findings are that the BCSD method was successful in reproducing the main features of the observed hydrometeorology from the retrospective climate simulation, when applied to both PCM and RCM outputs. Linear interpolation produced better results using RCM output than PCM output, but both methods (PCM-LI and RCM-LI) lead to unacceptably biased hydrologic simulations. Spatial disaggregation of the PCM output produced results similar to those achieved with the RCM interpolated output; nonetheless, neither PCM nor RCM output was useful for hydrologic simulation purposes without a bias-correction step. For the future climate scenario, only the BCSD-method (using PCM or RCM) was able to produce hydrologically plausible results. With the BCSD method, the RCM-derived hydrology was more sensitive to climate change than the PCM-derived hydrology.

Wood, Andrew W.; Leung, Lai R.; Sridhar, V.; Lettenmaier, D. P.

2004-01-01

163

Sensitivity properties of a biosphere model based on BATS and a statistical-dynamical climate model  

SciTech Connect

A biosphere model based on the Biosphere-Atmosphere Transfer Scheme (BATS) and the Saltzman-Vernekar (SV) statistical-dynamical climate model is developed. Some equations of BATS are adopted either intact or with modifications, some are conceptually modified, and still others are replaced with equations of the SV model. The model is designed so that it can be run independently as long as the parameters related to the physiology and physiognomy of the vegetation, the atmospheric conditions, solar radiation, and soil conditions are given. With this stand-alone biosphere model, a series of sensitivity investigations, particularly the model sensitivity to fractional area of vegetation cover, soil surface water availability, and solar radiation for different types of vegetation, were conducted as a first step. These numerical experiments indicate that the presence of a vegetation cover greatly enhances the exchanges of momentum, water vapor, and energy between the atmosphere and the surface of the earth. An interesting result is that a dense and thick vegetation cover tends to serve as an environment conditioner or, more specifically, a thermostat and a humidistat, since the soil surface temperature, foliage temperature, and temperature and vapor pressure of air within the foliage are practically insensitive to variation of soil surface water availability and even solar radiation within a wide range. An attempt is also made to simulate the gradual deterioration of environment accompanying gradual degradation of a tropical forest to grasslands. Comparison with field data shows that this model can realistically simulate the land surface processes involving biospheric variations. 46 refs., 10 figs., 6 tabs.

Zhang, T. (Yale Univ., New Haven, CT (United States))

1994-06-01

164

A statistical-dynamical climate model applied to trace gas transport and chemistry in the troposphere  

NASA Astrophysics Data System (ADS)

A zonally averaged statistical-dynamical climate model, representing a single hemisphere from 1000 to 240 mb, is used to provide a mean circulation and eddy transfer coefficients for trace gas transport experiments. The annual mean model is highly parameterized for relevant physical processes. The model is first adapted for seasonally varying climate integrations, which fail catastrophically. A positive feedback mechanism between Hadley Cell and latent heating is found to be responsible and averted by the addition of tropical eddy transfers of water vapor. Though stabilized, the model's seasonal temperature variation is extreme. Exploratory integrations reveal a tendency for the model's component radiation fields to mutually adjust to preserve an unrealistic net radiation distribution, and so too, temperature. A simple two box, energy balance model is considered to establish the mechanism. This temperature feedback in a freely responding, highly parameterized model implies such features may also be hidden in more specified models. The annual gross exchange rate of air between stratosphere and troposphere in the Northern Hemisphere is estimated to be 2.5(+ or - 2) x 10 (exp 17) kg year(exp -1) from trace gas budgets. Assuming a tropopause folding mechanism for the exchange, this flux is distributed with latitude and time to give an upper boundary condition for the trace gas transport model. Annual mean and seasonal experiments concerning the transfer of stratospheric ozone to the troposphere, and its subsequent fate, are performed with the zonally averaged model. A hypothetical troposphere with no potential for photochemical ozone formation is considered. The sinks of ozone represented are surface deposition and a photochemical sink through photolysis, and subsequent reaction of singlet oxygen with water vapor. The net annual flux of ozone from stratosphere to troposphere, for this system, is estimated to be 1.7 x 10(exp 11) kg.

Follows, Michael John

165

a Statistical-Dynamical Climate Model Applied to Trace Gas Transport and Chemistry in the Troposphere  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. A zonally averaged statistical-dynamical climate model, representing a single hemisphere from 1000 to 240 mb, is used to provide a mean circulation and eddy transfer coefficients for trace gas transport experiments. The annual mean model is highly parameterised for relevant physical processes. The model is first adapted for seasonally varying climate intergrations, which fail catastrophically. A positive feedback mechanism between Hadley Cell and latent heating is found to be responsible and averted by the addition of tropical eddy transfers of water vapour. Though stabilised, the model's seasonal temperature variation is extreme. Exploratory integrations reveal a tendency for the model's component radiation fields to mutually adjust to preserve an unrealistic net radiation distribution, and so too, temperature. A simple two box, energy balance model is considered to establish the mechanism. This temperature feedback in a freely responding, highly parameterised model implies such features may also be hidden in more specified models. The annual gross exchange rate of air between stratosphere and troposphere in the Northern Hemisphere is estimated to be 2.5(+/-2) * 10 ^{17} kg year^ {-1} from trace gas budgets. Assuming a tropopause folding mechanism for the exchange, this flux is distributed with latitude and time to give an upper boundary condition for the trace gas transport model. Annual mean and seasonal experiments concerning the transfer of stratospheric ozone to the troposphere, and its subsequent fate, are performed with the zonally averaged model. A hypothetical troposphere with no potential for photochemical ozone formation is considered. The sinks of ozone represented are surface deposition and a photochemical sink through photolysis, and subsequent reaction of singlet oxygen with water vapour. The net annual flux of ozone from stratosphere to troposphere, for this system, is estimated to be 1.7 * 10^{11} kg.

Follows, Michael John

1990-01-01

166

Comparison of dynamically and statistically downscaled seasonal climate forecasts for the cold season over the United States  

NASA Astrophysics Data System (ADS)

This study compares two approaches, dynamical and statistical downscaling, for their potential to improve regional seasonal forecasts for the United States (U.S.) during the cold season. In the MultiRCM Ensemble Downscaling (MRED) project, seven regional climate models (RCMs) are used to dynamically downscale the Climate Forecast System (CFS) seasonal prediction over the conterminous U.S. out to 5 months for the period of 1982-2003. The simulations cover December to April of next year with 10 ensemble members from each RCM with different initial and boundary conditions from the corresponding ensemble members. These dynamically downscaled forecasts are compared with statistically downscaled forecasts produced by two bias correction methods applied to both the CFS and RCM forecasts. Results of the comparison suggest that the RCMs add value in seasonal prediction application, but the improvements largely depend on location, forecast lead time, variables, and skill metrics used for evaluation. Generally, more improvements are found over the Northwest and North Central U.S. for the shorter lead times. The comparison results also suggest a hybrid forecast system that combines both dynamical and statistical downscaling methods have the potential to maximize prediction skill.

Yoon, Jin-Ho; Ruby Leung, L.; Correia, James

2011-11-01

167

Comparison of dynamically and statistically downscaled seasonal climate forecasts for the cold season over the United States  

NASA Astrophysics Data System (ADS)

This study compares two approaches, dynamical and statistical downscaling, for their potential to improve regional seasonal forecasts for the United States (U.S.) during the cold season. In the MultiRCM Ensemble Downscaling (MRED) project, seven regional climate models (RCMs) are used to dynamically downscale the Climate Forecast System (CFS) seasonal prediction over the conterminous U.S. out to 5 months for the period of 1982-2003. The simulations cover December to April of next year with 10 ensemble members from each RCM with different initial and boundary conditions from the corresponding ensemble members. These dynamically downscaled forecasts are compared with statistically downscaled forecasts produced by two bias correction methods applied to both the CFS and RCM forecasts. Results of the comparison suggest that the RCMs add value in seasonal prediction application, but the improvements largely depend on location, forecast lead time, variables, and skill metrics used for evaluation. Generally, more improvements are found over the Northwest and North Central U.S. for the shorter lead times. The comparison results also suggest a hybrid forecast system that combines both dynamical and statistical downscaling methods have the potential to maximize prediction skill.

Yoon, Jin-Ho; Ruby Leung, L.; Correia, James, Jr.

2012-11-01

168

An in-house alternative to traditional SDI services at Argonne National Laboratory  

SciTech Connect

Selective Dissemination of Information (SDIs) are based on automated, well-defined programs that regularly produce precise, relevant bibliographic information. Librarians have typically turned to information vendors such as Dialog or STN international to design and implement these searches for their users in business, academia, and the science community. Because Argonne National Laboratory (ANL) purchases the Institute for Scientific Information (ISI) Current Contents tapes (all subject areas excluding Humanities). ANL scientists enjoy the benefit of in-house developments with BASISplus software programming and no longer need to turn to outside companies for reliable SDI service. The database and its customized services are known as ACCESS (Argonne Current Contents Electronic Search Service). Through collaboration with librarians on Boolean logic and selection of terms, users can now design their own personal profiles to comb the new data, thereby avoiding service fees from outside providers. Based on the feedback from scientists, it seems that this new service can help transform the ANL distributed libraries into more efficient central functioning entities that better serve the users. One goal is to eliminate the routing of paper copies of many new journal issues to different library locations for users to browse; instead users may be expected to rely more on electronic dissemination of both table of contents and customized SDIs for new scientific and technical information.

Noel, R.E.; Dominiak, R.R.

1997-02-20

169

A review of gas-cooled reactor concepts for SDI (Strategic Defense Initiative) applications  

SciTech Connect

We have completed a review of multimegawatt gas-cooled reactor concepts proposed for SDI applications. Our study concluded that the principal reason for considering gas-cooled reactors for burst-mode operation was the potential for significant system mass savings over closed-cycle systems if open-cycle gas-cooled operation (effluent exhausted to space) is acceptable. The principal reason for considering gas-cooled reactors for steady-state operation is that they may represent a lower technology risk than other approaches. In the review, nine gas-cooled reactor concepts were compared to identify the most promising. For burst-mode operation, the NERVA (Nuclear Engine for Rocket Vehicle Application) derivative reactor concept emerged as a strong first choice since its performance exceeds the anticipated operational requirements and the technology has been demonstrated and is retrievable. Although the NERVA derivative concepts were determined to be the lead candidates for the Multimegawatt Steady-State (MMWSS) mode as well, their lead over the other candidates is not as great as for the burst mode. 90 refs., 2 figs., 10 tabs.

Marshall, A.C.

1989-08-01

170

Nuclear magnetic resonance measurement of hydrodynamic dispersion in porous media: preasymptotic dynamics, structure and nonequilibrium statistical mechanics  

NASA Astrophysics Data System (ADS)

Measurement of displacement time and length scale dependent dynamics by pulsed gradient spin echo nuclear magnetic resonance in porous media directly provides the preasymptotic hydrodynamic dispersion coefficient. This allows for comparison with nonequilibrium statistical mechanics models of hydrodynamics dispersion in porous media. Preasymptotic dispersion data and models provide characterization of porous media structure length scales relevant to transport and are related to the permeability and sample heterogeneity.

Codd, S. L.; Seymour, J. D.

2012-11-01

171

Effects of temporal modeling on the statistical uncertainty of spatiotemporal distributions estimated directly from dynamic SPECT projections  

SciTech Connect

Artifacts can result when reconstructing a dynamic image sequence from inconsistent single photon emission computed tomography (SPECT) projections acquired by a slowly rotating gantry. The artifacts can lead to biases in kinetic parameters estimated from time-activity curves generated by overlaying volumes of interest on the images. To overcome these biases in conventional image based dynamic data analysis, we have been investigating the estimation of time-activity curves and kinetic model parameters directly from dynamic SPECT projection data by modeling the spatial and temporal distribution of the radiopharmaceutical throughout the projected field of view. In previous work we developed computationally efficient methods for fully four-dimensional (4-D) direct estimation of spatiotemporal distributions [1] and their statistical uncertainties [2] from dynamic SPECT projection data, using a spatial segmentation and temporal B-splines. In addition, we studied the bias that results from modeling various orders of temporal continuity and using various time samplings [1]. In the present work, we use the methods developed in [1, 2] and Monte Carlo simulations to study the effects of the temporal modeling on the statistical variability of the reconstructed distributions.

Reutter, Bryan W.; Gullberg, Grant T.; Huesman, Ronald H.

2001-04-30

172

Universality in solar flare, magnetic storm and earthquake dynamics using Tsallis statistical mechanics  

Microsoft Academic Search

The universal character of the dynamics of various extreme phenomena is an outstanding scientific challenge. We show that X-ray flux and Dst time series during powerful solar flares and intense magnetic storms, respectively, obey a nonextensive energy distribution function for earthquake dynamics with similar values for the Tsallis entropic index q. Thus, evidence for universality in solar flares, magnetic storms

Georgios Balasis; Ioannis A. Daglis; Anastasios Anastasiadis; Constantinos Papadimitriou; Mioara Mandea; Konstantinos Eftaxias

2011-01-01

173

Statistical mechanics of coarse graining: estimating dynamical speedups from excess entropies.  

PubMed

The excess entropy of fluids has been shown to play a decisive role in the determination of dynamical properties [Y. Rosenfeld, Phys. Rev. A 15, 2545 (1977)]. We argue that it could play an equally important role in connecting dynamical properties of atomistic and coarse-grained models of molecular fluid systems. Molecular dynamics simulations for an atomistic and a coarse-grained model of water confirm the validity of this conjecture, showing that the sizable enhancement of the diffusion rate upon coarse-graining is a simple function of the difference in the excess entropy of the two models. This empirical observation could ease the way to a first-principles prediction of the relation of dynamical properties estimated from models at different resolution. PMID:22462870

Armstrong, J A; Chakravarty, C; Ballone, P

2012-03-28

174

Statistics and kinetics of single-molecule electron transfer dynamics in complex environments: A simulation model study  

SciTech Connect

Dynamics of the environments of complex systems such as biomolecules, polar solvents, and glass plays an important role in controlling electron transfer reactions. The kinetics is determined by the nature of a complex multidimensional landscape. By quantifying the mean and high-order statistics of the first-passage time and the associated ratios, the dynamics in electron transfer reactions controlled by the environments can be revealed. We consider real experimental conditions with finite observation time windows. At high temperatures, exponential kinetics is observed and there are multiple kinetic paths leading to the product state. At and below an intermediate temperature, nonexponential kinetics starts to appear, revealing the nature of the distribution of local traps on the landscape. Discrete kinetic paths emerge. At very low temperatures, nonexponential kinetics continues to be observed. We point out that the size of the observational time window is crucial in revealing the intrinsic nature of the real kinetics. The mean first-passage time is defined as a characteristic time. Only when the observational time window is significantly larger than this characteristic time does one have the opportunity to collect enough statistics to capture rare statistical fluctuations and characterize the kinetics accurately.

Paula, Luciana C. [Departamento de Fisica, Instituto de Biociencias Letras e Ciencias Exatas, Universidade Estadual Paulista, Sao Jose do Rio Preto, Sao Paulo 15054-000 (Brazil); Departamento de Estudos Basicos e Instrumentais, Universidade Estadual do Sudoeste da Bahia, Itapetinga, Bahia 45700-000 (Brazil); Wang Jin [Department of Chemistry, Physics and Applied Mathematics, State University of New York at Stony Brook, Stony Brook, New York 11794-3800 (United States); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry of Chinese Academy of Sciences, Changchun 130022 (China); Leite, Vitor B. P. [Departamento de Fisica, Instituto de Biociencias Letras e Ciencias Exatas, Universidade Estadual Paulista, Sao Jose do Rio Preto, Sao Paulo 15054-000 (Brazil)

2008-12-14

175

Fractional-dimensional Fock spaces, second quantization, and dynamical interaction of particles with Haldane's exclusion statistics  

NASA Astrophysics Data System (ADS)

We propose that the notion of Haldane's dimension and the corresponding statistics be treated in a probabilistic spirit. Motivated by the experience of dimensional regularization, the dimension of a space is defined as a trace of a diagonal ``unit operator'' where the diagonal matrix elements are not in unity in general but are probabilities to find a system in a given state. These probabilities are then uniquely defined by the rules of Haldane's statistics. The partition function for an ideal gas of the particles, a state-counting procedure, the entropy and a distribution function for this probabilistic definition are investigated and compared with previous works in the context of g particles. The corresponding creation and annihilation operators are introduced and Hamiltonians for interacting g particles are constructed. The stability of the thermodynamical properties of a gas of particles with exclusion statistics under the influence of hopping (or scattering) between states is investigated.

Ilinski, K. N.; Gunn, J. M. F.; Ilinskaia, A. V.

1996-02-01

176

Statistical properties, dynamic conditional correlation and scaling analysis: Evidence from Dow Jones and Nasdaq high-frequency data  

NASA Astrophysics Data System (ADS)

This paper investigates statistical properties of high-frequency intraday stock returns across various frequencies. Both time series and panel data are utilized to explore the properties of probability distribution, dynamic conditional correlations, and scaling analysis in Dow Jones Industrial Average (DJIA) and Nasdaq intraday returns across 10-min, 30-min, 60-min, 120-min, and 390-min frequencies. The evidence shows that both returns and volatility (standard deviation) increase with the increasing scaling from 10-min to 390-min intervals. By fitting an AR(1)-GARCH(1,1) model to intraday data, we find that AR(1) coefficients are negative for DJIA returns and positive for Nasdaq, exhibiting a positive and negative feedback strategy in DJIA and Nasdaq, respectively. The evidence also shows that these coefficients are statistically significant for either including or excluding opening returns for the 10-min and 30-min frequencies. By examining the dynamic conditional correlation between the DJIA and the Nasdaq across different frequencies, a positive correlation ranging from 0.6 to 0.8 was found. In addition, the variance of the dynamic correlation coefficients is decreasing and appears to be stable for the 2001-2003 period. Finally, both returns on DJIA and Nasdaq satisfy the stable Lévy distributions, implying that both markets can converge to equilibrium by self-governing mechanism after shocks. Results of this work provide relevant implications for investors and policy makers.

Chiang, Thomas C.; Yu, Hai-Chin; Wu, Ming-Chya

2009-04-01

177

On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes - Part 1: Statistical models and spatial fingerprints of atmospheric dynamics and chemistry  

NASA Astrophysics Data System (ADS)

We use statistical models for mean and extreme values of total column ozone to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes on grid cell basis. At each grid cell, the r-largest order statistics method is used for the analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively), and an autoregressive moving average (ARMA) model is used for the corresponding mean value analysis. In order to describe the dynamical and chemical state of the atmosphere, the statistical models include important atmospheric covariates: the solar cycle, the Quasi-Biennial Oscillation (QBO), ozone depleting substances (ODS) in terms of equivalent effective stratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the Antarctic Oscillation (AAO), the El Niño/Southern Oscillation (ENSO), and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the statistical distribution of ozone, respectively described by mean values and EHOs/ELOs. While results for the solar cycle, QBO, and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates. Column ozone is enhanced over Labrador/Greenland, the North Atlantic sector and over the Norwegian Sea, but is reduced over Europe, Russia and the Eastern United States during the positive NAO phase, and vice-versa during the negative phase. The NAO's southern counterpart, the AAO, strongly influences column ozone at lower southern mid-latitudes, including the southern parts of South America and the Antarctic Peninsula, and the central southern mid-latitudes. Results for both NAO and AAO confirm the importance of atmospheric dynamics for ozone variability and changes from local/regional to global scales.

Frossard, L.; Rieder, H. E.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.

2013-01-01

178

Statistical tests for discriminating inaccurate input functions in dynamic mouse microPET studies  

Microsoft Academic Search

Image-derived input functions (EDIF) are desirable for quantifying biological functions in mouse microPET studies. Due to difficulties in taking many blood samples from each mouse, conventional IDIF validation method of comparing blood samples with IDIF in a single animal is not applicable. A new approach that requires statistical testing on data of multiple animals has been conceived and investigated for

Sung-Cheng Huang; Hsiao-Ming Wu; Kooresh Shoghi-Jadid; David Stout; Arion Chatziioannou

2003-01-01

179

Convergence to Equilibrium and Critical Slowing Down of Dynamical Models in Statistical Mechanics  

Microsoft Academic Search

The convergence properties of Monte Carlo and Langevin simulations for classical lattice systems are studied. For the kinetic Ising model, it is shown that the time-dependent correlation functions have an infinite volume limit, which decays exponentially in time for high temperatures. Unlike previous investigations, the methods used are similar to those in equilibrium statistical mechanics, e.g. correlation inequalities, reduction to

Steven Hiroshi Adachi

1987-01-01

180

DYNAMICS OF INTERPERSONAL INTERACTION, A STUDY OF CONSULTATION AMONG GRADUATE STUDENTS IN A BEGINNING STATISTICS COURSE.  

ERIC Educational Resources Information Center

|SELF-REPORTS OF INTERACTION AMONG 100 GRADUATE STUDENTS IN TWO SECTIONS OF A FIVE-WEEK SUMMER SESSION COURSE IN ELEMENTARY STATISTICS WERE ANALYZED IN AN ATTEMPT TO INCREASE UNDERSTANDING OF SOCIAL ASSOCIATION AMONG HIGHLY SPECIALIZED PERSONS. SUMMARIES WERE COMPILED FOR 1203 INSTANCES OF INTERACTION--408 OF MUTUAL STUDY-HELP, 388 OF HELP GIVEN…

PIERCE, DOUGLAS R.

181

A Unified Description of the Statistics of Radar and Gauge Rainfall Data in terms of a Stochastic Dynamical Model  

NASA Astrophysics Data System (ADS)

Rainfall varies in space and time in a highly irregular manner that calls for a probabilistic description. A characteristic feature of rainfall statistics is that they depend strongly on the space-time scales over which rain rate data are averaged. A spectral model of precipitation has been developed based on a linear stochastic dynamical equation for the point rain rate that allows a concise description of the second moment statistics of rain at any prescribed space-time averaging scale. The model is thus capable of providing a unified description of the statistics of both radar and rain gauge data representing rainfall measurement in two distinct regimes — near-instantaneous rain rate spatially averaged over a large area and time-averaged rain rate at a point. The postulated form of the model spectrum gives it adequate flexibility to capture the subtle interplay between the spatial and temporal scales of variability of rain but at the same time strongly constrains the predicted statistical behavior as function of the averaging length and times scales. We test the model by tuning its parameters to fit radar and gauge data (TRMM standard products 2A53 and 2A56) collected contemporaneously at the NASA TRMM ground validation site near Melbourne, Florida.

Kundu, P. K.; Travis, J.

2010-12-01

182

A new statistical dynamic analysis on vegetation patterns in land ecosystems  

NASA Astrophysics Data System (ADS)

As complex self-adaptive systems, land ecosystems usually tend to produce intricate vegetation patterns under specific environmental constraints, which have ever puzzled us for decades. In this paper, a universal principle on pattern formation of land ecosystems is highlighted as: a land ecosystem always tries to find an optimal process to acquire maximized flux under a certain constraint or price. The underlying microscopic dynamic mechanism that induces complex vegetation patterns in land ecosystems is then revealed. Based on the Holdridge life zone system, evolutionary dynamic processes and structural classifications of several typical vegetation patterns are then simulated and discussed. Good agreements between theoretical analyses and numerical results are found. This paper demonstrates that the new theoretical analyses and simulation technique can be possibly applied to the whole land ecosystem, not only benefiting academic study on the formation and dynamics of vegetation patterns, but also providing implications for vegetation classification, vegetation protection and soil erosion control.

Feng, Qing Yi; Chai, Li He

2008-06-01

183

Statistical analysis of polychaete population diversity: hyperbolic extremes and species dynamics  

NASA Astrophysics Data System (ADS)

The objective of this work is to characterise the dynamics of four diverse polychaete populations based on long-term benthic surveys of shallow fine sand communities in the Bay of Morlaix (Western English Channel) and in Gravelines (South of the North Sea), France. The abundance and species richness of these populations display high variability, which we analysed using scaling approaches. We found that population density had heavy tailed probability density functions. We analysed the dynamics of relative species abundance in a community of trophically similar species, by estimating a diffusion coefficient which characterises its temporal fluctuations. We conclude on the necessity of using new tools to approach and model such highly variable population dynamics in coastal marine ecosystems.

Quiroz Martinez, Benjamin; Schmitt, François G.; Dauvin, Jean-Claude; Dewarumez, Jean-Marie

2010-05-01

184

Structure-based virtual screening for plant-derived SdiA-selective ligands as potential antivirulent agents against uropathogenic Escherichia coli.  

PubMed

The uropathogenic Escherichia coli pathogenecity is affected by quorum sensing transcriptional regulator SdiA. In this study, in vitro characterization of the active principles that could potentially antagonize with SdiA from the Melia dubia bark extracts has been described. After in vitro assays carried out to evaluate the inhibitory activities against the uropathogenic E. coli, the ethanolic extract (30 mg/ml) which showed the strongest suppression of haemolysis, swarming motility, hydrophobicity and biofilm formation, was subjected to GC-MS analysis and an array of 40 unrelated compounds was identified. Docking studies was conducted to screen for plant-based SdiA inhibitors. Five hits were assessed for their binding profiles and 7-(1-bromoethyl)-3, 3-dimethyl-bicyclo [4.1.0]heptan-2-one showed 66.95% binding ability with respect to C(8)HSL. PMID:22209416

Ravichandiran, Vinothkannan; Shanmugam, Karthi; Anupama, K; Thomas, Sabu; Princy, Adline

2011-12-16

185

Hydrodynamics from statistical mechanics: combined dynamical-NEMD and conditional sampling to relax an interface between two immiscible liquids.  

PubMed

We present a method to study hydrodynamic phenomena from atomistic simulations. In statistical mechanics, these fields are computed as the ensemble average over the time dependent probability density function corresponding to the time evolution of an initial conditional probability density function consistent with some initial conditions. These initial conditions typically consist in constraints on some macroscopic fields, e.g. the density field. We show how these processes can be studied by combining the dynamical approach to non-equilibrium molecular dynamics with the restrained simulation approach. As an illustration of our method, we study the relaxation to the equilibrium of an interface between two immiscible liquids. We show that, at a variance with the local time average method, the standard atomistic approach used in this field, our method is able to produce (macroscopic) fields satisfying the symmetry conditions of the problem. PMID:21698337

Orlandini, Sergio; Meloni, Simone; Ciccotti, Giovanni

2011-06-23

186

[Validation of the Tekscan system for statistic and dynamic pressure measurements of the human femorotibial joint].  

PubMed

In vitro dynamic pressure measurements in the healthy and pathologically altered knee joint help to improve our understanding of the loading pattern on femorotibial surfaces. The aim of the study was to evaluate a piezoresistive pressure measuring system. A human cadaveric knee was mounted in a material-testing machine (Bionix 858) using a specially designed knee-holding device. Axial loading of the knee, flexed at 20o, at 500 N, 1000N and 1500 N was then carried out. For the static investigations, the piezoresistive measuring system (Tekscan), was compared with the FUJI measuring system. In addition, dynamic measurements were also performed with the Tekscan System. With the exception of the lateral compartment at a load of 1500 N, no differences in maximum pressures were observed between the two systems. Nor were there any differences with regard to contact surfaces, either in the medial or lateral compartment (p > 0.05). However, the reproducibility of the data was significantly higher with the Tekscan System (p < 0.01). Dynamic pressure measurements obtained with the knee flexed 20 to 90o showed that the lateral contact area shifted from anterior to posterior, while the medial contact area remained virtually unchanged. The Tekscan System proved to be more reliable than the FUJI System, and permits simultaneous measurements in both compartments. The Tekscan System is suitable for dynamic measurement of the femorotibial joint, and permits measurements to be made under more physiological conditions. PMID:12201014

Wirz, D; Becker, R; Li, S Feng; Friederich, N F; Müller, W

187

Statistical dynamics of dislocations in simple models of plastic deformation: Phase transitions and related phenomena  

Microsoft Academic Search

Dislocation assemblies in crystalline substrates are a beautiful example of the broad class of systems that are governed by the presence of kinematical constraints induced by interactions, geometry, and\\/or disorder. The interactions between dislocation lines of different type together with the dynamic constraints which tie the motion of the dislocations to their slip planes lead to the possibility of forming

Michael Zaiserb; A. Moro

188

Statistical dynamics of dislocations in simple models of plastic deformation: Phase transitions and related phenomena  

Microsoft Academic Search

Dislocation assemblies in crystalline substrates are a beautiful example of the broad class of systems that are governed by the presence of kinematical constraints induced by interactions, geometry, and\\/or disorder. The interactions between dislocation lines of different type together with the dynamic constraints which tie the motion of the dislocations to their slip planes lead to the possibility of forming

M.-Carmen Miguel; Paolo Moretti; Michael Zaiser; Stefano Zapperi

2005-01-01

189

Hierarchical statistical modelling of influenza epidemic dynamics in space and time  

Microsoft Academic Search

SUMMARY An infectious disease typically spreads via contact between infected and susceptible individuals. Since the small-scale movements and contacts between people are generally not recorded, available data regarding infectious disease are often aggregations in space and time, yielding small-area counts of the number infected during successive, regular time intervals. In this paper, we develop a spatially descriptive, temporally dynamic hierarchical

Andrew S. Mugglin; Noel Cressie; Islay Gemmell

2002-01-01

190

An investigation of the transfer dynamics of quantum teleportation by weak measurement statistics  

NASA Astrophysics Data System (ADS)

We explore the mechanism of quantum teleportation by analyzing the weak measurement statistics post-selected by the result of the Bell measurement for the joint system composed of the input A and the spatially separated output B. It is shown that the weak measurement statistics observed before the Bell measurement includes correlations which relate every physical property in the input A to a corresponding physical property in the output B. The Bell measurement thus identifies the accidental relation between A and B already present in the quantum fluctuations of the input state. Significantly, this relation applies to all physical properties equally, and is completely independent of the input state. Teleportation therefore copies all physical properties of input system A to output system B, irrespective of whether the input state is an eigenstate of the property or not.

Hiroishi, Masanori; Hofmann, Holger F.

2013-06-01

191

Statistical occurrence and dynamics of the Harang discontinuity during steady magnetospheric convection  

NASA Astrophysics Data System (ADS)

Harang discontinuity is a longitudinally extended ionospheric signature near midnight of flow reversal from westward to eastward with decreasing latitude. Its occurrence indicates enhanced convection in the magnetotail that requires an upward field-aligned current from the ionosphere due to diamagnetic ion drift. Previous reports using event studies have been conflicting as to the occurrence of the Harang discontinuity during a mode of enhanced magnetotail response called steady magnetospheric convection (SMC). With a comprehensive list of SMC events from 1997 through 2007, we utilize data from the Super Dual Auroral Radar Network and a novel spatial superposition technique to statistically examine the occurrence of the Harang discontinuity during SMC events. We find that the statistical signature of the Harang discontinuity begins before SMC starts and strengthens as the SMC events progress. We also detail the typical size and strength of the Harang discontinuity and find that it is more pronounced during interplanetary magnetic field +By conditions.

Kissinger, J.; Wilder, F. D.; McPherron, R. L.; Hsu, T.-S.; Baker, J. B. H.; Kepko, L.

2013-08-01

192

Earthquake statistics in a Block Slider Model and a fully dynamic Fault Model  

NASA Astrophysics Data System (ADS)

We examine the event statistics obtained from two differing simplified models for earthquake faults. The first model is a reproduction of the Block-Slider model of Carlson et al. (1991), a model often employed in seismicity studies. The second model is an elastodynamic fault model based upon the Lattice Solid Model (LSM) of Mora and Place (1994). We performed simulations in which the fault length was varied in each model and generated synthetic catalogs of event sizes and times. From these catalogs, we constructed interval event size distributions and inter-event time distributions. The larger, localised events in the Block-Slider model displayed the same scaling behaviour as events in the LSM however the distribution of inter-event times was markedly different. The analysis of both event size and inter-event time statistics is an effective method for comparative studies of differing simplified models for earthquake faults.

Weatherley, D.; Abe, S.

2004-11-01

193

Statistical dynamic image reconstruction in state-of-the-art high-resolution PET  

Microsoft Academic Search

Modern high-resolution PET is now more than ever in need of scrutiny into the nature and limitations of the imaging modality itself as well as image reconstruction techniques. In this work, we have reviewed, analysed and addressed the following three considerations within the particular context of state-of-the-art dynamic PET imaging: (i) the typical average numbers of events per line-of-response (LOR)

Arman Rahmim; Ju-Chieh Cheng; Stephan Blinder; Maurie-Laure Camborde; Vesna Sossi

2005-01-01

194

Overpopulation of Omega; in pp collisions: a way to distinguish statistical hadronization from string dynamics.  

PubMed

The Omega/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies ( E(lab) = 160 GeV). The antiomega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions. PMID:12005560

Bleicher, M; Liu, F M; Keränen, A; Aichelin, J; Bass, S A; Becattini, F; Redlich, K; Werner, K

2002-05-01

195

Optimization and Statistical Analysis of Evolutionary Dynamics in the SK Spin Glass Model  

NASA Astrophysics Data System (ADS)

In this work we perform a statistical analysis of the evolutionary events in a modified version of the Sherrigton-Kirkpatrick model that takes into account the neutrality effect in the landscape. The evolutionary events correspond to abrupt changes in the fitness of the population after long period of stasis. The distribution of these events and its dependence on the set of parameters of the model are investigated. We also examine the performance of the optimization process looking at the temporal evolution of average and maximum fitness in the population.

Campos, Paulo R. A.; de Oliveira, Viviane M.

196

Statistical versus dynamical downscaling over the mountainous regions in France: a performance evaluation and comparison of several scenarios  

NASA Astrophysics Data System (ADS)

Over the mountainous areas, several mesoscale features and precipitation processes are combined with a complex orography that makes it difficult to evaluate the consequences of global warming. Precipitation over these areas is also an important component of the hydrological cycle, since it influences the water resources, agriculture, forestry, floods, land management, etc. The future climate scenarios provided directly by the General Circulation Models (GCMs) are inadequate to evaluate the impacts of global warming over the mountainous areas, since they operate at very coarse horizontal resolution that cannot resolve mesoscale processes. Consequently, several techniques have been developed to downscale the GCMs' information to regional scales. In this work, two downscaling methods have been implemented to study climate change over the mountainous areas in France (Alps, Pyrenees, Corsica). The first method consists of dynamical downscaling carried out by the Météo-France Regional Climate Model (RCM) ALADIN (Radu et al. 2008) using a 12 km grid-mesh over France. The second method consists of a statistical downscaling model that combines the weather regimes and an analogues approach (Boé and Terray, 2008). The statistical downscaling provides outputs over the entire France at an 8 km resolution. These two methods are first compared over the present climate for the period 1961-1999. Then, three different SRES scenarios (A1B, B1, A2) have been downscaled using both dynamical and statistical methods. A comparison of the methodologies will be shown, accompanied by an evaluation of some uncertainties aspects of climate change over different parameters. Boé, J. and L. Terray, 2008: A Weather-Type Approach to Analyzing Winter Precipitation in France: Twentieth-Century Trends and the Role of Anthropogenic Forcing. J. Climate, 21 (13), 3118. Radu R., Déqué M. and Somot S., 2008: Spectral nudging in a spectral regional climate model, Tellus A, 60, 898-910.

Sanchezgomez, E.; Page, C.; Deque, M.; Terray, L.

2010-12-01

197

Precipitation and temperature space-time variability and extremes in the Mediterranean region: evaluation of dynamical and statistical downscaling methods  

NASA Astrophysics Data System (ADS)

This study evaluates how statistical and dynamical downscaling models as well as combined approach perform in retrieving the space-time variability of near-surface temperature and rainfall, as well as their extremes, over the whole Mediterranean region. The dynamical downscaling model used in this study is the Weather Research and Forecasting (WRF) model with varying land-surface models and resolutions (20 and 50 km) and the statistical tool is the Cumulative Distribution Function-transform (CDF-t). To achieve a spatially resolved downscaling over the Mediterranean basin, the European Climate Assessment and Dataset (ECA&D) gridded dataset is used for calibration and evaluation of the downscaling models. In the frame of HyMeX and MED-CORDEX international programs, the downscaling is performed on ERA-I reanalysis over the 1989-2008 period. The results show that despite local calibration, CDF-t produces more accurate spatial variability of near-surface temperature and rainfall with respect to ECA&D than WRF which solves the three-dimensional equation of conservation. This first suggests that at 20-50 km resolutions, these three-dimensional processes only weakly contribute to the local value of temperature and precipitation with respect to local one-dimensional processes. Calibration of CDF-t at each individual grid point is thus sufficient to reproduce accurately the spatial pattern. A second explanation is the use of gridded data such as ECA&D which smoothes in part the horizontal variability after data interpolation and damps the added value of dynamical downscaling. This explains partly the absence of added-value of the 2-stage downscaling approach which combines statistical and dynamical downscaling models. The temporal variability of statistically downscaled temperature and rainfall is finally strongly driven by the temporal variability of its forcing (here ERA-Interim or WRF simulations). CDF-t is thus efficient as a bias correction tool but does not show any added-value regarding the time variability of the downscaled field. Finally, the quality of the reference observation dataset is a key issue. Comparison of CDF-t calibrated with ECA&D dataset and WRF simulations to local measurements from weather stations not assimilated in ECA&D, shows that the temporal variability of the downscaled data with respect to the local observations is closer to the local measurements than to ECA&D data. This highlights the strong added-value of dynamical downscaling which improves the temporal variability of the atmospheric dynamics with regard to the driving model. This article highlights the benefits and inconveniences emerging from the use of both downscaling techniques for climate research. Our goal is to contribute to the discussion on the use of downscaling tools to assess the impact of climate change on regional scales.

Flaounas, Emmanouil; Drobinski, Philippe; Vrac, Mathieu; Bastin, Sophie; Lebeaupin-Brossier, Cindy; Stéfanon, Marc; Borga, Marco; Calvet, Jean-Christophe

2012-10-01

198

A simple statistical-dynamical downscaling scheme based on weather types and conditional resampling  

NASA Astrophysics Data System (ADS)

A multivariate statistical downscaling methodology is implemented to generate local precipitation and temperature series at different sites based on the results from a variable resolution general circulation model. It starts from regional climate properties to establish discriminating weather types for the chosen local variable, precipitation in this case. Intratype variations of the relevant forcing parameters are then taken into account by multivariate regression using the distances of a given day to the different weather types as predictors. The final step consists of conditional resampling. The methodology is evaluated in the Seine basin in France. Using reanalysis fields as predictors, satisfying results are obtained at daily timescale and concerning low-frequency variations, both for temperature and precipitation. The use of model results as predictors gives a realistic representation of regional climate properties. Nevertheless, as the validation of a statistical downscaling algorithm for present day climate conditions does not necessarily imply the validity of its climate change projections, the plausibility of the downscaled climate projections is assessed by verifying the consistency between spatially averaged downscaled results and direct model outputs for two climate change scenarios. Despite some discrepancies for precipitation with the more extreme scenario, the consistency is good for both local variables. This result reinforces the confidence in the use of the downscaling scheme in altered climates. Finally, it is shown that the intertype variations of the atmospheric circulation represent only a fraction of the climate change signal for the local variables. Thus a downscaling methodology based on weather typing should incorporate information concerning intratype modifications.

Boé, J.; Terray, L.; Habets, F.; Martin, E.

2006-12-01

199

DYNAMIC COMPARISON OF SYSTEMS FOR IRRIGATION AND EFFLUENT APPLICATION  

Microsoft Academic Search

This study compares subsurface drip irrigation and sprinkler irrigation with respect to expected returns, aquifer life, nutrient utilization and accumulation in the production of irrigated corn using swine effluent and fresh groundwater from a depleting aquifer in the Oklahoma Panhandle. The results of the Dynamic Programming model indicate that SDI outperforms center pivot sprinkler irrigation in terms of NPV of

Rita I. Carreira; Arthur L. Stoecker; Jeffory A. Hattey; Michael A. Kizer

2004-01-01

200

A statistical-dynamical approach to parameterize subgrid-scale land-surface heterogeneity in climate models  

NASA Astrophysics Data System (ADS)

Land surface interacts strongly with the atmosphere at all scales. This has a considerable impact on the hydrologic cycle and the climate. Therefore, in order to produce realistic simulations with climate models, their land-surface processes must be parameterized accurately. Because continental surfaces are usually extremely heterogeneous over the resolvable scales considered in these models, surface parameterizations based on the ‘big leaf-big stoma’ approach (that assume grid-scale homogeneity) fail to represent the land-atmosphere interactions that occur at much smaller scales. A parameterization based on a statistical-dynamical approach is suggested here. With this approach, each surface grid element of the numerical model is divided into homogeneous land patches (i.e., patches with similar internal heterogeneity). Assuming that horizontal fluxes between the different patches within a grid element are small as compared to the vertical fluxes, patches of the same type located at different places in the grid can be regrouped into one subgrid surface class. Then, for each one of the subgrid surface classes, probability density functions (pdf) are used to characterize the variability of the different parameters of the soil-plant-atmosphere system. These pdf are combined with the equations of the model that describe the dynamic and the energy and mass conservations in the atmosphere. The potential application of this statistical-dynamical parameterization is illustrated by simulating (i) the development of an agricultural area in an arid region and (ii) the process of deforestation in a tropical region. Both cases emphasize the importance of land-atmosphere interactions on regional hydrologic processes and climate.

Avissar, Roni

1991-03-01

201

Network Self-Organization Explains the Statistics and Dynamics of Synaptic Connection Strengths in Cortex  

PubMed Central

The information processing abilities of neural circuits arise from their synaptic connection patterns. Understanding the laws governing these connectivity patterns is essential for understanding brain function. The overall distribution of synaptic strengths of local excitatory connections in cortex and hippocampus is long-tailed, exhibiting a small number of synaptic connections of very large efficacy. At the same time, new synaptic connections are constantly being created and individual synaptic connection strengths show substantial fluctuations across time. It remains unclear through what mechanisms these properties of neural circuits arise and how they contribute to learning and memory. In this study we show that fundamental characteristics of excitatory synaptic connections in cortex and hippocampus can be explained as a consequence of self-organization in a recurrent network combining spike-timing-dependent plasticity (STDP), structural plasticity and different forms of homeostatic plasticity. In the network, associative synaptic plasticity in the form of STDP induces a rich-get-richer dynamics among synapses, while homeostatic mechanisms induce competition. Under distinctly different initial conditions, the ensuing self-organization produces long-tailed synaptic strength distributions matching experimental findings. We show that this self-organization can take place with a purely additive STDP mechanism and that multiplicative weight dynamics emerge as a consequence of network interactions. The observed patterns of fluctuation of synaptic strengths, including elimination and generation of synaptic connections and long-term persistence of strong connections, are consistent with the dynamics of dendritic spines found in rat hippocampus. Beyond this, the model predicts an approximately power-law scaling of the lifetimes of newly established synaptic connection strengths during development. Our results suggest that the combined action of multiple forms of neuronal plasticity plays an essential role in the formation and maintenance of cortical circuits.

Zheng, Pengsheng; Dimitrakakis, Christos; Triesch, Jochen

2013-01-01

202

Financial price dynamics and pedestrian counterflows: A comparison of statistical stylized facts  

NASA Astrophysics Data System (ADS)

We propose and document the evidence for an analogy between the dynamics of granular counterflows in the presence of bottlenecks or restrictions and financial price formation processes. Using extensive simulations, we find that the counterflows of simulated pedestrians through a door display eight stylized facts observed in financial markets when the density around the door is compared with the logarithm of the price. Finding so many stylized facts is very rare indeed among all agent-based models of financial markets. The stylized properties are present when the agents in the pedestrian model are assumed to display a zero-intelligent behavior. If agents are given decision-making capacity and adapt to partially follow the majority, periods of herding behavior may additionally occur. This generates the very slow decay of the autocorrelation of absolute return due to an intermittent dynamics. Our findings suggest that the stylized facts in the fluctuations of the financial prices result from a competition of two groups with opposite interests in the presence of a constraint funneling the flow of transactions to a narrow band of prices with limited liquidity.

Parisi, Daniel R.; Sornette, Didier; Helbing, Dirk

2013-01-01

203

Dynamical phase transition for current statistics in a simple driven diffusive system  

NASA Astrophysics Data System (ADS)

We consider fluctuations of the time-averaged current in the one-dimensional weakly asymmetric exclusion process on a ring. The optimal density profile which sustains a given fluctuation exhibits an instability for low enough currents, where it becomes time dependent. This instability corresponds to a dynamical phase transition in the system fluctuation behavior: while typical current fluctuations result from the sum of weakly correlated local events and are still associated with the flat, steady-state density profile, for currents below a critical threshold, the system self-organizes into a macroscopic jammed state in the form of a coherent traveling wave, which hinders transport of particles and thus facilitates a time-averaged current fluctuation well below the average current. We analyze in detail this phenomenon using advanced Monte Carlo simulations, and work out macroscopic fluctuation theory predictions, finding very good agreement in all cases. In particular, we study not only the current large-deviation function, but also the critical current threshold, the associated optimal density profiles, and the traveling-wave velocity, analyzing in depth finite-size effects and hence providing a detailed characterization of the dynamical transition.

Espigares, Carlos P.; Garrido, Pedro L.; Hurtado, Pablo I.

2013-03-01

204

Delayed Ionization and Fragmentation EN Route to Thermionic Emission: Statistics and Dynamics  

NASA Astrophysics Data System (ADS)

Thermionic emission is discussed as a long time (microseconds) decay mode of energy-rich large molecules, metallic and metcar clusters, and fullerenes. We review what is known and consider the many experiments, systems, and theoretical and computational studies that still need to be done. We conclude with a wish list for future work. Particular attention is given to the experimental signatures, such as the dependence on the mode of energy acquisition, and theoretical indications of a not-quite-statistical delayed ionization and to the competition of electron emission with other decay modes, such as fragmentation or radiative cooling. Coupling of the electronic and nuclear modes can be a bottleneck and quite long time-delayed ionization can be observed, as in the decay of high Rydberg states probed by ZEKE spectroscopy, before the onset of complete energy partitioning.

Campbell, E. E. B.; Levine, R. D.

2000-10-01

205

Statistical Properties and Multifractal Behaviors of Market Returns by Ising Dynamic Systems  

NASA Astrophysics Data System (ADS)

An interacting-agent model of speculative activity explaining price formation in financial markets is considered in the present paper, which based on the stochastic Ising model and the mean field theory. The model describes the interaction strength among the agents as well as an external field, and the corresponding random logarithmic price return process is investigated. According to the empirical research of the model, the time series formed by this Ising model exhibits the bursting typical of volatility clustering, the fat-tail phenomenon, the power-law distribution tails and the long-time memory. The statistical properties of the returns of Hushen 300 Index, Shanghai Stock Exchange (SSE) Composite Index and Shenzhen Stock Exchange (SZSE) Component Index are also studied for comparison between the real time series and the simulated ones. Further, the multifractal detrended fluctuation analysis is applied to investigate the time series returns simulated by Ising model have the distribution multifractality as well as the correlation multifractality.

Fang, Wen; Wang, Jun

206

Avalanche statistics and time-resolved grain dynamics for a driven heap  

NASA Astrophysics Data System (ADS)

We probe the dynamics of intermittent avalanches caused by steady addition of grains to a quasi-two-dimensional heap. To characterize the time-dependent average avalanche flow speed v(t) , we image the top free surface. To characterize the grain fluctuation speed ?v(t) , we use speckle-visibility spectroscopy. During an avalanche, we find that the fluctuation speed is approximately one-tenth the average flow speed, ?v?0.1v , and that these speeds are largest near the beginning of an event. We also find that the distribution of event durations is peaked, and that event sizes are correlated with the time interval since the end of the previous event. At high rates of grain addition, where successive avalanches merge into smooth continuous flow, the relationship between average and fluctuation speeds changes to ??v1/2 .

Abate, A. R.; Katsuragi, H.; Durian, D. J.

2007-12-01

207

A statistical and dynamical analysis of some Winter and Summer temperature extremes in Europe  

NASA Astrophysics Data System (ADS)

Over the last decades Europe has been facing strong extreme events, particularly temperature extremes, with foremost influence on economy, agriculture, water management and society in general. The study of the large-scale atmospheric mechanisms linked to their occurrence is thus significant and is going to be discussed for the winter and summer seasons in this region for 50 years (1961-2010). Additionally, a canonical correlation analysis, coupled with a principal component analysis (BPCCA), is applied between the monthly mean sea level pressure fields and the monthly occurrences of four temperature extreme indices (TN10p - cold nights, TN90p - warm nights, and TX90p - warm days, TX10p - cold days) within a large Euro-Atlantic sector. Each co-variability mode represents a large-scale forcing on the occurrence of those extremes. North Atlantic Oscillation-like patterns and strong anomalies in the atmospheric flow westwards of the British Isles are leading couplings between large-scale atmospheric circulation and wintertime occurrences of both cold (warm) nights and warm (cold) days in Europe. Although summer couplings show lower coherence between warm and cold events, their key driving mechanisms are significant to explain their atmospheric anomalies. In order to get a better insight for both seasons of these extremes, the main features of the statistical distributions of the minima (TNn and TXn) and maxima (TXx and TNx) are also analyzed. Moreover, statistically significant downward (upward) trends are detected in the cold nights and days (warm nights and days) occurrences over the period 1961-2010 throughout Europe for the winters. These tendencies can also be found in summer for the cold nights and warm days, which is in clear agreement with the overall warming. For the summer warm nights and cold days these tendencies are weaker and its signal is geographically dependent. This work is supported by European Union Funds (FEDER/COMPETE - Operational Competitiveness Programme) and by national funds (FCT - Portuguese Foundation for Science and Technology) under the project FCOMP-01-0124-FEDER-022692.

Andrade, Cristina; Santos, João

2013-04-01

208

Enterohemorrhagic Escherichia coli O157:H7 requires quorum sensing transcriptional regulators QseA and SdiA for colonization and persistence in the bovine intestinal tract  

Technology Transfer Automated Retrieval System (TEKTRAN)

QseA and SdiA are two of several transcriptional regulators that regulate virulence gene expression of enterohemorrhagic Escherichia coli (EHEC) O157:H7 via quorum sensing (QS). QseA regulates the expression of the locus of enterocyte effacement (LEE). LEE encodes for a type III secretion (T3S) sys...

209

Evaluation of an S.D.I. System Based on "Nuclear Science Abstracts" and the Performance of Matching by Words in Titles Compared With Indexing Terms.  

ERIC Educational Resources Information Center

|A selective dissemination of information service based on computer scanning of Nuclear Science Abstracts tapes has operated at the Atomic Energy Research Establishment, Harwell, England since October, 1968. The performance of the mechanized SDI service has been compared with that of the pre-existing current awareness service which is based on…

Olive, G.; And Others

210

Kinetics, statistics, and energetics of lipid membrane electroporation studied by molecular dynamics simulations.  

PubMed

Membrane electroporation is the method to directly transfer bioactive substances such as drugs and genes into living cells, as well as preceding electrofusion. Although much information on the microscopic mechanism has been obtained both from experiment and simulation, the existence and nature of possible intermediates is still unclear. To elucidate intermediates of electropore formation by direct comparison with measured prepore formation kinetics, we have carried out 49 atomistic electroporation simulations on a palmitoyl-oleoyl-phosphatidylcholine bilayer for electric field strengths between 0.04 and 0.7 V/nm. A statistical theory is developed to facilitate direct comparison of experimental (macroscopic) prepore formation kinetics with the (single event) preporation times derived from the simulations, which also allows us to extract an effective number of lipids involved in each pore formation event. A linear dependency of the activation energy for prepore formation on the applied field is seen, with quantitative agreement between experiment and simulation. The distribution of preporation times suggests a four-state pore formation model. The model involves a first intermediate characterized by a differential tilt of the polar lipid headgroups on both leaflets, and a second intermediate (prepore), where a polar chain across the bilayer is formed by 3-4 lipid headgroups and several water molecules, thereby providing a microscopic explanation for the polarizable volume derived previously from the measured kinetics. An average pore radius of 0.47 +/- 0.15 nm is seen, in favorable agreement with conductance measurements and electrooptical experiments of lipid vesicles. PMID:18469089

Böckmann, Rainer A; de Groot, Bert L; Kakorin, Sergej; Neumann, Eberhard; Grubmüller, Helmut

2008-05-09

211

Structural, thermodynamic, and kinetic properties of Gramicidin analogue GS6 studied by molecular dynamics simulations and statistical mechanics.  

PubMed

Gramicidin S (GS) analogues belong to an important class of cyclic peptides, characterized by an antiparallel double-stranded beta-sheet structure with Type II' beta-turns. Such compounds can be used as model systems to understand the folding/unfolding process of beta-hairpins and more in general of beta-structures. In the present study, we specifically investigate the folding/unfolding behavior of the hexameric Gramicidin S analogue GS6 by using all-atoms molecular dynamics (MD) simulations at different temperatures, coupled to a statistical mechanical model based on the Quasi Gaussian Entropy theory. Such an approach permits to describe the structural, thermodynamic, and kinetic properties of the peptide and to quantitatively characterize its folding/unfolding transitions. PMID:19396809

Zanetti-Polzi, Laura; Anselmi, Massimiliano; D'Alessandro, Maira; Amadei, Andrea; Di Nola, Alfredo

2009-12-01

212

Benefits from using combined dynamical-statistical downscaling approaches - lessons from a case study in the Mediterranean region  

NASA Astrophysics Data System (ADS)

Various downscaling techniques have been developed to bridge the scale gap between global climate models (GCMs) and finer scales required to assess hydrological impacts of climate change. Such techniques may be grouped into two downscaling approaches: the deterministic dynamical downscaling (DD) and the statistical downscaling (SD). Although SD has been traditionally seen as an alternative to DD, recent works on statistical downscaling have aimed to combine the benefits of these two approaches. The overall objective of this study is to assess whether a DD processing performed before the SD permits to obtain more suitable climate scenarios for basin scale hydrological applications starting from GCM simulations. The case study presented here focuses on the Apulia region (South East of Italy, surface area about 20 000 km2), characterised by a typical Mediterranean climate; the monthly cumulated precipitation and monthly mean of daily minimum and maximum temperature distribution were examined for the period 1953-2000. The fifth-generation ECHAM model from the Max-Planck-Institute for Meteorology was adopted as GCM. The DD was carried out with the Protheus system (ENEA), while the SD was performed through a monthly quantile-quantile correction. The SD resulted efficient in reducing the mean bias in the spatial distribution at both annual and seasonal scales, but it was not able to correct the miss-modelled non-stationary components of the GCM dynamics. The DD provided a partial correction by enhancing the spatial heterogeneity of trends and the long-term time evolution predicted by the GCM. The best results were obtained through the combination of both DD and SD approaches.

Guyennon, N.; Romano, E.; Portoghese, I.; Salerno, F.; Calmanti, S.; Petrangeli, A. B.; Tartari, G.; Copetti, D.

2013-02-01

213

Molecular structure and elastic properties of thermotropic liquid crystals: Integrated molecular dynamics--Statistical mechanical theory vs molecular field approach  

NASA Astrophysics Data System (ADS)

The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4'-n-pentyloxy-4-cyanobiphenyl and 4'-n-heptyloxy-4-cyanobiphenyl. Both methods yield K3(bend) >K1 (splay) >K2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio.

Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.

2013-03-01

214

Global statistical predictor model for characteristic adsorption energy of organic vapors-solid interaction: use in dynamic process simulation.  

PubMed

Adsorption of Volatile Organic Compounds (VOCs) is one of the best remediation techniques for controlling industrial air pollution. In this paper, a quantitative predictor model for the characteristic adsorption energy (E) of the Dubinin-Radushkevich (DR) isotherm model has been established with R(2) value of 0.94. A predictor model for characteristic adsorption energy (E) has been established by using Multiple Linear Regression (MLR) analysis in a statistical package MINITAB. The experimental value of characteristic adsorption energy was computed by modeling the isotherm equilibrium data (which contain 120 isotherms involving five VOCs and eight activated carbons at 293, 313, 333, and 353 K) with the Gauss-Newton method in a statistical package R-STAT. The MLR model has been validated with the experimental equilibrium isotherm data points, and it will be implemented in the dynamic adsorption simulation model PROSIM. By implementing this model, it predicts an enormous range of 1200 isotherm equilibrium coefficients of DR model at different temperatures such as 293, 313, 333, and 353K (each isotherm has 10 equilibrium points by changing the concentration) just by a simple MLR characteristic energy model without any experiments. PMID:22503987

Ramalingam, Shivaji G; Hamon, Lomig; Pré, Pascaline; Giraudet, Sylvain; Le Coq, Laurence; Le Cloirec, Pierre

2012-04-02

215

Molecular dynamics study of network statistics in lithium disilicate: Qn distribution and the pressure-volume diagram  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have been performed to study the structures along the pressure-volume diagram of network-glasses and melts exemplified by the lithium disilicate system. Experimentally, densification of the disilicate glass by elevated pressure is known and this feature is reasonably reproduced by the simulations. During the process of densification or decompression of the system, the statistics of Qn (i.e., SiO4 tetrahedron unit with n bridging oxygen linked to the silicon atom where n = 0, 1, 2, 3, or 4) change, and the percentage of the Q3 structures show the maximum value near atmospheric pressure at around Tg. Changes of Qn distribution are driven by the changes of volume (or pressure) and are explained by the different volumes of structural units. Furthermore, some pairs of network structures with equi-volume, but having different distributions of Qn (or different heterogeneity), are found. Therefore, for molecular dynamics simulations of the Qn distributions, it is important to take into account the complex phase behavior including poly-structures with different heterogeneities as well as the position of the system in the P-V-T diagram.

Habasaki, J.; Ngai, K. L.

2013-08-01

216

Intramolecular Distances and Dynamics from the Combined Photon Statistics of Single-Molecule FRET and Photoinduced Electron Transfer.  

PubMed

Single-molecule Förster resonance energy transfer (FRET) and photoinduced electron transfer (PET) have developed into versatile and complementary methods for probing distances and dynamics in biomolecules. Here we show that the two methods can be combined in one molecule to obtain both accurate distance information and the kinetics of intramolecular contact formation. In a first step, we show that the fluorescent dyes Alexa 488 and Alexa 594, which are frequently used as a donor and acceptor for single-molecule FRET, are also suitable as PET probes with tryptophan as a fluorescence quencher. We then performed combined FRET/PET experiments with FRET donor- and acceptor-labeled polyproline peptides. The placement of a tryptophan residue into the polyglycylserine tail incorporated in the peptides allowed us to measure both FRET efficiencies and the nanosecond dynamics of contact formation between one of the fluorescent dyes and the quencher. Variation of the linker length between the polyproline and the Alexa dyes and in the position of the tryptophan residue demonstrates the sensitivity of this approach. Modeling of the combined photon statistics underlying the combined FRET and PET process enables the accurate analysis of both the resulting transfer efficiency histograms and the nanosecond fluorescence correlation functions. This approach opens up new possibilities for investigating single biomolecules with high spatial and temporal resolution. PMID:23718771

Haenni, Dominik; Zosel, Franziska; Reymond, Luc; Nettels, Daniel; Schuler, Benjamin

2013-05-29

217

Space-time Dynamics of Depositional Systems: Experimental Evidence for Heavy-tailed Statistics and Theoretical Modeling  

NASA Astrophysics Data System (ADS)

In depositional systems, channels migrate from one location to another causing erosion and deposition at any given point in the domain. The durations of depositional and erosional events, as well as their magnitudes control the structure of the stratigraphic record. In this study, we use high-resolution temporal surface elevation data from a controlled experiment to quantify the probability distributions of the processes that govern the evolution of depositional deltaic systems. Heavy-tailed statistics of erosional and depositional events are documented indicating that a small, but significant chance exists for the occurrence of extreme events. We show that periods of inactivity, when neither deposition nor erosion occurs, follow a truncated Pareto distribution whose truncation scale is set by the mean characteristic avulsion time scale in the system. Further, we show that the heavy tails in the magnitudes of the erosional and depositional events are not preserved in the stratigraphic record thicknesses. It is also shown that the temporal evolution of surface elevation exhibits self-similarity with a nonlinear spectrum of scaling exponents (multi-fractality) quantifying the complex dynamics of the system. Finally, some preliminary thoughts on modeling of surface dynamics and surface elevation growth of stratigraphic columns using the tools of fractional calculus are presented.

Ganti, V. K.; Straub, K. M.; Foufoula-Georgiou, E.; Paola, C.

2010-12-01

218

An analytical comparison of three spatio-temporal regularization methods for dynamic linear inverse problems in a common statistical framework  

NASA Astrophysics Data System (ADS)

Dynamic inverse problems, which occur in medical imaging and other fields, are inverse problems in which the quantities to be reconstructed vary in time, although they are related to the measurements through spatial operators only. Traditional methods solve these problems by frame-by-frame reconstruction, then extract temporal behaviour of the objects or regions of interest through curve fitting and other image-based processing. These approaches solve the inverse problem while exploiting only the spatial relationship between the object and the measurement data at each time instant, without using any temporal dynamics of the underlying process, and thus are not optimal unless the solution is temporally uncorrelated. If the spatial operators are linear, and if one, by contrast, solves the whole spatio-temporal process jointly, it falls into the category of general linear least-squares problems. Such approaches are generally difficult, both due to the challenge of modelling the temporal dynamics appropriately as well as to the high dimensionality of the associated large linear system. Several recent reports have approached this problem in different ways, making different prior assumptions on the spatial and temporal behaviour. In this paper we discuss three such approaches, which have been introduced from different points of view, in a common statistical regularization framework, and illuminate their relationships. The three methods are a state-space model, the separability condition and a multiple constraints model. The key result is that there is a clear relationship among the three methods; specifically, the inverse of the spatio-temporal autocovariance matrix has a block tri-diagonal form, a Kronecker product form or a Kronecker sum form, respectively. Some simple simulation examples are presented to illustrate the theoretical analysis.

Zhang, Yiheng; Ghodrati, Alireza; Brooks, Dana H.

2005-02-01

219

Statistics Revelations  

ERIC Educational Resources Information Center

|The use, and misuse, of statistics is commonplace, yet in the printed format data representations can be either over simplified, supposedly for impact, or so complex as to lead to boredom, supposedly for completeness and accuracy. In this article the link to the video clip shows how dynamic visual representations can enliven and enhance the…

Chicot, Katie; Holmes, Hilary

2012-01-01

220

ERK mediates anti-apoptotic effect through phosphorylation and cytoplasmic localization of p21Waf1/Cip1/Sdi in response to DNA damage in normal human embryonic fibroblast (HEF) cells.  

PubMed

Since anti-apoptotic effect of ERK has not been elucidated clearly in DNA-damage-induced cell death, the role of ERK was examined in normal HEF cells treated with mild DNA damage using etoposide or camptothecin. ERK was activated by DNA damage in HEF cells. PD98059 increased apoptosis and reduced DNA-damage-induced p21Waf1/Cip1/Sdi level. Depletion of p21Waf1/Cip1/Sdi induced cell death and PD98059 induced additional cell death. DNA-damage-induced increase in cytoplasmic localization and phosphorylation of threonine residues of p21Waf1/Cip1/Sdi was reversed by PD98059. Thus, the results suggest that ERK pathway mediates anti-apoptotic effects through phosphorylation and cytoplasmic localization of p21Waf1/Cip1/Sdi in response to mild DNA damage. PMID:21110119

Heo, Jee-In; Oh, Soo-Jin; Kho, Yoon-Jung; Kim, Jeong-Hyeon; Kang, Hong-Joon; Park, Seong-Hoon; Kim, Hyun-Seok; Shin, Jong-Yeon; Kim, Min-Ju; Kim, Sung Chan; Park, Jae-Bong; Kim, Jaebong; Lee, Jae-Yong

2010-11-26

221

The Farey series devil's staircase: Connection to dynamical-systems, statistical physics, music theory and music perception?  

NASA Astrophysics Data System (ADS)

Some time ago two apparently dissimilar presentations were given at the 2007 Helmholtz Workshop in Berlin. One by J. Douthett and R. Krantz focused on the commonality between the mathematical descriptions of musical scales and the long-ranged, one-dimensional, anti-ferromagnetic Ising model of statistical physics. The other by J. Cartwright, D. Gonzalez, and O. Piro articulated a nonlinear dynamical model of pitch perception. Both approaches lead to a Farey series devil's staircase structure. In the first case, the ground state magnetic phase diagram of the Ising model is a Farey series devil's staircase. In the second case, the ear is modeled as a nonlinear system leading to a three-frequency resonant pitch perception model of the auditory system that exhibits a devil's staircase phase-locked structure. In this poster we present a summary of each of these works side-by-side to illuminate the link between these two seemingly disparate systems. Adapted from JMM Vol. 4, No. 1, 57, Mar. 2010.

Krantz, Richard; Douthett, Jack; Cartwright, Julyan; Gonzalez, Diego; Piro, Oreste

2010-10-01

222

Effects of biomass burning in Amazonia on climate: A numerical experiment with a statistical-dynamical model  

NASA Astrophysics Data System (ADS)

Chou and Suarez's solar and infrared radiation models are incorporated in a statistical-dynamical model with biosphere and atmosphere interaction in order to study the climatic effects due to biomass burning in Amazonian forest. In the control experiment the mean annual zonally averaged climate is well simulated by the model when compared with observed data. Biomass burning plays an important role on the earth's radiative balance and climate through the release of large amounts of greenhouse gases and aerosols in the atmosphere and the alteration of the land surface characteristics. For investigating the relative importance of these changes five experiments are performed: (1) degradation of the surface, (2) change in the smoke aerosols concentration, (3) change in the CO2 concentration, (4) change in CH4 concentration, and (5) all the changes together. The results show that biomass burning in Amazonian forest causes a reduction in the absorbed solar radiation and net radiation fluxes at the surface in the perturbed region and an increase in the air surface temperature and the net thermal infrared radiation flux at the surface. Also there is a decrease in the latent and sensible heat fluxes, evapotranspiration and precipitation compared to the control case. In general, the greater changes in the radiative balance and climate are due mainly to the changes in the land surface characteristics, followed by those caused by the large amounts of smoke aerosols released in the atmosphere. The changes due to the greenhouse gases CO2 and CH4 are small.

Moraes, Elisabete C.; Franchito, Sergio H.; Brahmananda Rao, V.

2004-03-01

223

From food-dependent statistics to metabolic parameters, a practical guide to the use of dynamic energy budget theory.  

PubMed

The standard model of the dynamic energy budget theory for metabolic organisation has variables and parameters that can be quantified using indirect methods only. We present new methods (and software) to extract food-independent parameter values of the energy budget from food-dependent quantities that are easy to observe, and so facilitate the practical application of the theory to enhance predictability and extrapolation. A natural sequence of 10 steps is discussed to obtain some compound parameters first, then the primary parameters, then the composition parameters and finally the thermodynamic parameters; this sequence matches a sequence of required data of increasing complexity which is discussed in detail. Many applications do not require knowledge of all parameters, and we discuss methods to extrapolate parameters from one species to another. The conversion of mass, volume and energy measures of biomass is discussed; these conversions are not trivial because biomass can change in chemical composition in particular ways thanks to different forms of homeostasis. We solve problems like "What would be the ultimate reproduction rate and the von Bertalanffy growth rate at a specific food level, given that we have measured these statistics at abundant food?" and "What would be the maximum incubation time, given the parameters of the von Bertalanffy growth curve?". We propose a new non-destructive method for quantifying the chemical potential and entropy of living reserve and structure, that can potentially change our ideas on the thermodynamic properties of life. We illustrate the methods using data on daphnids and molluscs. PMID:19016672

Kooijman, S A L M; Sousa, T; Pecquerie, L; van der Meer, J; Jager, T

2008-11-01

224

Space-time dynamics of depositional systems: Experimental evidence and theoretical modeling of heavy-tailed statistics  

NASA Astrophysics Data System (ADS)

In depositional systems, channels migrate from one location to another, causing erosion and deposition at any given point in the domain. The durations of depositional and erosional events, as well as their magnitudes, control the structure of the stratigraphic record. In this study, we use high-resolution temporal surface elevation data from a controlled experiment to quantify the probability distributions of the processes that govern the evolution of depositional deltaic systems. Heavy-tailed statistics of erosional and depositional events are documented, indicating that a small but significant chance exists for the occurrence of extreme events. We show that the periods of inactivity, when neither deposition nor erosion occurs, follow a truncated Pareto distribution whose truncation scale is set by the mean characteristic avulsion time scale in the system. Further, we show that the heavy tails in the magnitudes of the erosional and depositional events are not preserved in the stratigraphic record, resulting instead in an exponential distribution for the bed sediment thickness. It is also shown that the temporal evolution of surface elevation exhibits self-similarity with a nonlinear spectrum of scaling exponents (multifractality) quantifying the complex dynamics of the system. Finally, we show how the results of this study can lead to improved diffusional models for surface evolution using the tools of fractional calculus.

Ganti, Vamsi; Straub, Kyle M.; Foufoula-Georgiou, Efi; Paola, Chris

2011-06-01

225

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

Microsoft Academic Search

The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using

J. P. Kochendorfer; J. A. Ramírez

2008-01-01

226

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

Microsoft Academic Search

The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using

J. P. Kochendorfer; J. A. Ramírez

2010-01-01

227

Evaluation of inherent gray-level dynamic range in a digital image using the runs test and join-count statistics.  

PubMed

The dynamic range of the gray level of a digital image is limited by the noise it contains. Two statistical methods called "runs test" and "join-count statistic" are used to measure the noise level in a digital image. A residual image is formed by subtracting an original image from its smoothed version. Theoretically, the noise level in the residual image should be identical to that in the original image. The noise level is determined by examining each bit plane of the residual image individually starting from the least significant bit up to the bit plane whose statistic does not show a random pattern. Images from three digital modalities: computerized tomography, magnetic resonance, and computed radiography are used to evaluate the gray-level dynamic range. Both methods are easy to implement and fast to perform. PMID:8455510

Chuang, K S; Huang, H K

228

Effects of p21Waf1\\/Cip1\\/Sdi1 on cellular gene expression: Implications for carcinogenesis, senescence, and age-related diseases  

Microsoft Academic Search

Induction of cyclin-dependent kinase inhibitor p21Waf1\\/Cip1\\/Sdi1 triggers cell growth arrest associated with senescence and damage response. Overexpression of p21 from an inducible promoter in a human cell line induces growth arrest and phenotypic features of senescence. cDNA array hybridization showed that p21 expression selectively inhibits a set of genes involved in mitosis, DNA replication, segregation, and repair. The kinetics of

Bey-Dih Chang; Keiko Watanabe; Eugenia V. Broude; Jing Fang; Jason C. Poole; Tatiana V. Kalinichenko; Igor B. Roninson

2000-01-01

229

Synthesis of N-Acyl Homoserine Lactone Analogues Reveals Strong Activators of SdiA, the Salmonella enterica Serovar Typhimurium LuxR Homologue  

Microsoft Academic Search

N-Acyl homoserine lactones (AHLs) are molecules that are synthesized and detected by many gram-negative bacteria to monitor the population density, a phenomenon known as quorum sensing. Salmonella enterica serovar Typhimurium is an exceptional species since it does not synthesize its own AHLs, while it does encode a LuxR homologue, SdiA, which enables this bacterium to detect AHLs that are produced

Joost C. A. Janssens; Kristine Metzger; Ruth Daniels; Dave Ptacek; Tine Verhoeven; Lothar W. Habel; Jos Vanderleyden; Dirk E. De Vos; Sigrid C. J. De Keersmaecker

2007-01-01

230

The mammalian Cut homeodomain protein functions as a cell-cycle-dependent transcriptional repressor which downmodulates p21WAF1/CIP1/SDI1 in S phase.  

PubMed Central

Cut is a homeodomain transcription factor which has the unusual property of containing several DNA-binding domains: three regions called Cut repeats and the Cut homeodomain. Genetic studies in Drosophila melanogaster indicate that cut plays important roles in the determination and maintenance of cell-type specificity. In the present study, we show that mammalian Cut proteins may yet play another biological role, specifically in proliferating cells. We found that the binding of Cut to a consensus binding site varies during the cell cycle. Binding was virtually undetectable in G0 and early G1, but became very strong as cells reached S phase. This was shown to result both from an increase in Cut expression and dephosphorylation of the Cut homeodomain by the Cdc25A phosphatase. We also show that the increase in Cut activity coincides with a decrease in p21WAF1/CIP1/SDI1 mRNAs. In co-transfection experiments, Cut proteins repressed p21WAF1/CIP1/SDI1 gene expression through binding to a sequence that overlaps the TATA box. Moreover, p21WAF1/CIP1/SDI1 expression was repressed equally well by either Cdc25A or Cut. Altogether, these results suggest a model by which Cdc25A activates the Cut repressor which then downregulates transcription of p21WAF1/CIP1/SDI1 in S phase. Thus, in addition to their role during cellular differentiation, Cut proteins also serve as cell-cycle-dependent transcriptional factors in proliferating cells.

Coqueret, O; Berube, G; Nepveu, A

1998-01-01

231

Mean-field calculations of chain packing and conformational statistics in lipid bilayers: comparison with experiments and molecular dynamics studies.  

PubMed Central

A molecular, mean-field theory of chain packing statistics in aggregates of amphiphilic molecules is applied to calculate the conformational properties of the lipid chains comprising the hydrophobic cores of dipalmitoyl-phosphatidylcholine (DPPC), dioleoyl-phosphatidylcholine (DOPC), and palmitoyl-oleoyl-phosphatidylcholine (POPC) bilayers in their fluid state. The central quantity in this theory, the probability distribution of chain conformations, is evaluated by minimizing the free energy of the bilayer assuming only that the segment density within the hydrophobic region is uniform (liquidlike). Using this distribution we calculate chain conformational properties such as bond orientational order parameters and spatial distributions of the various chain segments. The lipid chains, both the saturated palmitoyl (-(CH2)14-CH3) and the unsaturated oleoyl (-(CH2)7-CH = CH-(CH2)7-CH3) chains are modeled using rotational isomeric state schemes. All possible chain conformations are enumerated and their statistical weights are determined by the self-consistency equations expressing the condition of uniform density. The hydrophobic core of the DPPC bilayer is treated as composed of single (palmitoyl) chain amphiphiles, i.e., the interactions between chains originating from the same lipid headgroup are assumed to be the same as those between chains belonging to different molecules. Similarly, the DOPC system is treated as a bilayer of oleoyl chains. The POPC bilayer is modeled as an equimolar mixture of palmitoyl and oleoyl chains. Bond orientational order parameter profiles, and segment spatial distributions are calculated for the three systems above, for several values of the bilayer thickness (or, equivalently, average area/headgroup) chosen, where possible, so as to allow for comparisons with available experimental data and/or molecular dynamics simulations. In most cases the agreement between the mean-field calculations, which are relatively easy to perform, and the experimental and simulation data is very good, supporting their use as an efficient tool for analyzing a variety of systems subject to varying conditions (e.g., bilayers of different compositions or thicknesses at different temperatures).

Fattal, D R; Ben-Shaul, A

1994-01-01

232

STAtistical and Regional dynamical Downscaling of EXtremes for European regions: some preliminary results from the STARDEX project  

NASA Astrophysics Data System (ADS)

STARDEX will provide a rigorous and systematic inter-comparison and evaluation of statistical and dynamical downscaling methods for the construction of scenarios of extremes. The more robust techniques will be identified and used to produce scenarios for European case-study regions for the end of the 21st century. During the first year of the project, work has focused on the following objectives, for which preliminary results will be presented: 1. To focus on an agreed, standard set of daily temperature extremes (e.g., percentiles of daily max./min. temperature, frost severity and duration indices and a heatwave duration index) and daily precipitation extremes (e.g., max. length of dry/wet spells, magnitude of the 90th percentile, percentage of rain falling on days with amounts above the 90th percentile) together with derived indices/parameters (e.g., thermal discomfort and fire hazard indices). 2. To focus on specific regions of Europe, ensuring that the case-study regions reflect the range of European climatic regimes and that the size/location of each region is appropriate for the extreme being studied (the selected regions encompass the British Isles, the Alps, the Mediterranean, Scandinavia and Germany). 3. To use a consistent approach (in terms of regions, data inputs, variables and statistics studied and time periods) for all analyses and case studies in order to allow rigorous and systematic evaluation and direct inter-comparison of the results. 4. To analyse observed data series for the second half of the 20th century from specific regions of Europe and for Europe as a whole in order to identify trends in the magnitude and frequency of occurrence of extremes (and, for specific events, their losses in life and financial costs) and to investigate whether these changes are related to changes in other climatic variables (i.e., potential predictor variables derived primarily from NCEP Reanalysis data, such as large-scale and regional objective circulation indices and patterns, including the North Atlantic Oscillation, measures of atmospheric humidity and stability and sea surface temperatures). 5. To analyse output from GCMs and RCMs, focusing on their ability to simulate extremes (including their magnitude, frequency of occurrence and trends) and potential predictor variables (including their relationships with surface climate). Acknowledgements: STARDEX (http://www.cru.uea.ac.uk/projects/stardex/) is supported by the European Commission under the Framework V Thematic Programme 'Energy, Environment and Sustainable Development', 2002-2005.

Goodess, C. M.; Haylock, M. R.; Jones, P. D.; Bardossy, A.; Frei, C.; Schmith, T.

2003-04-01

233

Evaluation of surface air temperature change due to the greenhouse gases increase with a statistical-dynamical model  

NASA Astrophysics Data System (ADS)

A statistical-dynamical climate model is used for investigating the relative contribution of the changes in the radiation budget and surface air temperature due to the increase of the anthropogenic greenhouse gases predicted for 2100 on the basis of IPCC SRES A1FI (the highest greenhouse level scenario). Five experiments are performed considering the changes in concentrations of (1) CO2, (2) CH4, (3) N2O, (4) tropospheric O3, and (5) all the changes together. The results show that the mean global planetary absorbed solar radiation increases in response to the predicted conditions according to the scenario A1FI for year 2100 (A1FI-2100). This is due to the effect of O3 absorptions. This increase leads to a decrease in the mean global planetary net thermal infrared radiation emitted to space by the Earth-atmosphere system to space and to an increase in mean global planetary net radiation. These changes are controlled mainly by the increase in CO2 concentration. The changes in the radiation budget due to N2O and CH4 are small. The mean global surface air temperature response to the predicted conditions for A1FI-2100 was +0.59°C. The change in CO2 concentration is responsible for an increase of +0.49°C. The higher increases occur in the polar regions: +2.15°C (at 85°S) and +1.55°C (at 85°N) in the case of the predicted conditions for A1FI-2100. Additional experiments indicate that the changes in surface air temperature are similar in the cases of the predicted conditions for A1FI-2100 and 4 × CO2, 2 × CO2 and 4 × N2O, and in 2 × N2O and 4 × CH4.

Moraes, Elisabete C.; Franchito, Sergio H.; Rao, V. Brahmananda

2005-12-01

234

Studies of succinate dehydrogenase inhibition (SDI) test with cisplatin encapsulated liposome against cancer cells.  

PubMed

In the present study, by means of encapsulating into liposome, cisplatin was made a soluble capsule, and augmentation of the antitumor effect through the cell affinity of liposome was investigated by chemosensitivity test for cancer cells. Augmentation of the antitumor effect by collaboration of the cell affinity of liposome with the diffusion by concentration gradient was expected. However, although a difference in absorbancy was in fact observed, no statistically significant difference of effect superior to cisplatin alone was observed. PMID:8908285

Koketsu, M; Suzuki, K; Yotsuyanagi, T; Baba, S

1996-01-01

235

Loss of p21Waf1/Cip1/Sdi1 enhances intestinal stem cell survival following radiation injury  

PubMed Central

The microcolony assay following gamma irradiation (IR) is a functional assay of intestinal stem cell fate. The cyclin-dependent kinase (CDK) inhibitor p21Waf1/Cip1/Sdi1 (p21) regulates cell cycle arrest following DNA damage. To explore the role of p21 on stem cell fate, we examined the effects of p21 deletion on intestinal crypt survival following IR and expression of the stem/progenitor cell marker Musashi-1 (Msi-1) and the antiapoptotic gene survivin. Intestinal stem cell survival in adult wild-type (WT) and p21?/? mice was measured using the microcolony assay. Msi-1, p21, and survivin mRNA were measured using real-time PCR and immunohistochemical analysis. Laser capture microdissection (LCM) was used to isolate mRNA from the crypt stem cell zone. No differences in radiation-induced apoptosis were observed between WT and p21?/? mice. However, increased crypt survival (3.0-fold) was observed in p21?/? compared with WT mice 3.5 days after 13 Gy. Msi-1 and survivin mRNA were elevated 12- and 7.5-fold, respectively, in LCM-dissected crypts of p21?/? compared with WT mice. In conclusion, deletion of p21 results in protection of crypt stem/progenitor cells from IR-induced cell death. Furthermore, the increase in crypt survival is associated with increased numbers of Msi-1- and survivin-expressing cells in regenerative crypts.

George, Robert J.; Sturmoski, Mark A.; May, Randal; Sureban, Sripathi M.; Dieckgraefe, Brian K.; Anant, Shrikant; Houchen, Courtney W.

2009-01-01

236

Statistical characteristics of the multiscale spallation of metal targets during dynamic loading and their relation to the mechanical properties of the materials  

Microsoft Academic Search

The damages that form in plane targets made of three steel grades during their shock loading at a rate of 100–650 m\\/s are\\u000a statistically processed, and the size distributions of defects are determined. In the general case, the damage accumulation\\u000a in this strain rate range is shown to be not self-similar. The dynamic fracture toughnesses of the steels are determined,

B. K. Barakhtin; Yu. I. Meshcheryakov; G. G. Savenkov

2010-01-01

237

Algebraic integrable dynamical systems, 2+1-dimensional models in wholly discrete space-time, and inhomogeneous models in 2-dimensional statistical physics  

Microsoft Academic Search

This paper is devoted to constructing and studying exactly solvable dynamical\\u000asystems in discrete time obtained from some algebraic operations on matrices,\\u000ato reductions of such systems leading to classical field theory models in\\u000a2+1-dimensional wholly discrete space-time, and to connection between those\\u000afield theories and inhomogoneous models in 2-dimensional statistical physics.

I. G. Korepanov

1995-01-01

238

Comparison of neural networks to statistical techniques for prediction of time series generated by nonlinear dynamic systems  

Microsoft Academic Search

The following paper is focused on comparison of neural networks to statistical techniques for time series prediction. Four statistical models, the ARIMA, the exponential smoothing, the exponential growth and the bilinear model are compared to two neural network architectures, the hierarchical multilayer perceptron and the ontogenic cascade correlation network. The intercomparison was done on two examples, a generic and a

R. Rape; D. Fefer; A. Jeglic

1995-01-01

239

Evaluation of the impact of quorum sensing transcriptional regulator SdiA on long-term persistence and fecal shedding of Escherichia coli O157:H7 in weaned calves.  

PubMed

Escherichia coli O157:H7 (O157) colonization of bovine intestine is mediated through the locus of enterocyte effacement (LEE)-encoded type III secretion system and secreted virulence proteins that promote colonization of the recto-anal junction (RAJ) of the large intestine of cattle. The quorum sensing transcriptional regulator SdiA, a homolog of LuxR, has been shown in vitro to repress LEE strongly when overexpressed from a multi-copy recombinant plasmid or when its activity is enhanced by the binding of N-acyl-L-homoserine lactones (AHLs), the quorum sensing signals that are detected by SdiA. Since LEE has been shown to be essential for colonization and persistence of O157 in bovine intestine, we examined whether a mutation in sdiA, which normally represses LEE in vitro, would also exert negative effect on colonization and long-term persistence of O157 in weaned calves. Ten-week old weaned calves (n = 4/group) were inoculated orally with 10(10) cfu of either the wild-type or sdiA mutant strain. Initial fecal shedding of the sdiA mutant and the wild-type strain were similar in magnitude and declined during the first 2 weeks post-inoculation. The sdiA mutant was detected in feces of only one of the four calves at low levels (?10(2) cfu/g feces) from days 19 - 27 post-inoculation, whereas, the fecal shedding of the wild-type strain persisted at approximately 4-logs in all four calves from days 19 - 27. We also confirmed that SdiA represses ler, which encodes a positive transcriptional regulator of LEE, in response to AHLs, and reduces adherence of O157 to HEp-2 cells. In conclusion, this study demonstrates that although in vitro the sdiA gene represses LEE and LEE-mediated adherence to cultured cells, the presence of sdiA is necessary for colonization of bovine large intestine that in turn promotes persistent fecal shedding of O157 by these animals. PMID:23415735

Sharma, V K; Bearson, S M D

2013-02-13

240

Statistical microeconomics  

NASA Astrophysics Data System (ADS)

A statistical generalization is made of microeconomics in the spirit of going from classical to statistical mechanics. The price and quantity of every commodity1The term commodities is used for goods and services. traded in the market, at each instant of time, is considered to be an independent random variable: all prices and quantities are considered to be stochastic processes, with the observed market prices being a random sample of the stochastic prices. The dynamics of market prices is determined by an action functional and, for concreteness, a specific model is proposed. The model can be calibrated from the unequal time correlation of the market commodity prices. A perturbation expansion for the correlation functions is defined in powers of the inverse of the total budget of the aggregate consumer and the propagator for the market prices is evaluated.

Baaquie, Belal E.

2013-10-01

241

Statistical analysis of polychaete population density: dynamics of dominant species and scaling properties in relative abundance fluctuations  

NASA Astrophysics Data System (ADS)

We consider here the dynamics of two polychaete populations based on a 20 yr temporal benthic survey of two muddy fine sand communities in the Bay of Morlaix, Western English Channel. These populations display high temporal variability, which is analyzed here using scaling approaches. We find that population densities have heavy tailed probability density functions. We analyze the dynamics of relative species abundance in two different communities of polychaetes by estimating in a novel way a "mean square drift" coefficient which characterizes their fluctuations in relative abundance over time. We show the usefulness of using new tools to approach and model such highly variable population dynamics in marine ecosystems.

Quiroz-Martinez, B.; Schmitt, F. G.; Dauvin, J.-C.

2012-01-01

242

Stochastics and Statistics Multi-objective time-cost trade-off in dynamic PERT networks using an interactive approach  

Microsoft Academic Search

We develop a multi-objective model for the time-cost trade-off problem in a dynamic PERT network using an interac- tive approach. The activity durations are exponentially distributed random variables and the new projects are generated according to a renewal process and share the same facilities. Thus, these projects cannot be analyzed independently. This dynamic PERT network is represented as a network

Amir Azaron; Reza Tavakkoli-Moghaddam

243

A new approach to resolving climate-cryosphere relations: Downscaling climate dynamics to glacier-scale mass and energy balance without statistical scale linking  

NASA Astrophysics Data System (ADS)

We present a novel combination of methods to quantify the local mass response of mountain glaciers to large-scale circulation. Previously, such multiscale approaches bypassed the mesoscale processes of the mountain-induced atmospheric flow, by statistical transfer functions or subgrid parameterizations, and included simplified glacier mass balance (MB) models. Here we show, on the basis of Kilimanjaro (East Africa) as a test case, that a limited area atmospheric model (LAM) and a process-resolving MB model can be linked without statistical corrections at their interface. This is evident from robust energy and MB patterns at the glacier surface, regardless of whether the MB model is forced by (1) in situ meteorological measurements or (2) uncorrected output from the high-resolution LAM grid over the glacier area. The latter is achieved by multiple grid nesting in the land-atmosphere-ocean domain of the LAM. Since this setup resolves the mesoscale process space, we also show the potential to increase knowledge of how dynamical, thermodynamic, and microphysical phenomena of the mountain-induced flow affect glacier MB. All these results are encouraging for future research because they demonstrate that a dynamical system, which operates on very different space-time scales, can be quantified in a fully physical way, if dynamic meteorology and glaciology are exploited in a complementary sense. This will enhance the process understanding of forward problems (glacier response to climate forcing) and backward problems (climate signal extraction from past extents of mountain glaciers).

MöLg, Thomas; Kaser, Georg

2011-08-01

244

Organization of the narrative components in autobiographical speech of anorexic adolescents: A statistical and non-linear dynamical analysis  

Microsoft Academic Search

Family theories of anorexia nervosa point out that patients’ autobiographic speech may reflect internalized family interactions. Our study characterizes the statistical distribution and temporal organization of the narrative components describing personal relationships in anorexic and control subjects. Semantic components related to personal interactions were encoded from life narratives of 14 adolescent girls with anorexia nervosa (restrictive type) and of 13

Karyn Doba; Jean-Louis Nandrino; Annick Lesne; Christine Humez; Laurent Pezard

2008-01-01

245

Generic features of the dynamics of complex open quantum systems: Statistical approach based on averages over the unitary group  

NASA Astrophysics Data System (ADS)

We obtain exact analytic expressions for a class of functions expressed as integrals over the Haar measure of the unitary group in d dimensions. Based on these general mathematical results, we investigate generic dynamical properties of complex open quantum systems, employing arguments from ensemble theory. We further generalize these results to arbitrary eigenvalue distributions, allowing a detailed comparison of typical regular and chaotic systems with the help of concepts from random matrix theory. To illustrate the physical relevance and the general applicability of our results we present a series of examples related to the fields of open quantum systems and nonequilibrium quantum thermodynamics. These include the effect of initial correlations, the average quantum dynamical maps, the generic dynamics of system-environment pure state entanglement and, finally, the equilibration of generic open and closed quantum systems.

Gessner, Manuel; Breuer, Heinz-Peter

2013-04-01

246

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

NASA Astrophysics Data System (ADS)

The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green Leaf Area Index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.

Kochendorfer, J. P.; Ramírez, J. A.

2008-03-01

247

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

NASA Astrophysics Data System (ADS)

The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green leaf area index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on complete or near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.

Kochendorfer, J. P.; Ramírez, J. A.

2010-10-01

248

Screening of SdiA inhibitors from Melia dubia seeds extracts towards the hold back of uropathogenic E.coli quorum sensing-regulated factors.  

PubMed

Plants have always been a supreme source of drugs and India is endowed with a wide variety of them with high medicinal values. The Quorum Sensing (QS) quenching efficiency of various solvent extracts of Melia dubia seeds was investigated against uropathogenic Escherichia coli (UPEC) to screen the competitive inhibitor of SdiA, a transcriptional activator of quorum sensing in E. coli. In this study, potentiality of five different extracts of Melia dubia seeds for quorum sensing inhibitory activity was investigated against uropathogenic Escherichia coli (UPEC). Assays such as cell density, swarming motility, protein, protease, hemolysis, hemagglutination, hydrophobicity and biofilm inhibition were performed. Biofilm, hemolysis and swarming motility were found to be inhibited by 92.1%, 20.9 % and 48.52% respectively, when the medium was supplemented with 30 mg/ml of the ethanolic extract. GC-MS spectrum of the ethanolic extract showed an array of 27 structurally unlinked compounds with natural ligand C8HSL. The docking against QS transcriptional regulator SdiA was predicted by in silico studies and the ligand C6 showed significant activity with -10.8 GScore. In vitro and in silico docking analysis showed fairly a good correlation, suggesting that the ethanolic extract showed potency to attenuate quorum sensing of uropathogenic E. coli. Further studies by in vitro and in vivo strategies are necessary to foresee the quorum quenching effect of the ligands. PMID:23210902

Ravichandiran, Vinothkannan; Shanmugam, Karthi; Solomon, Adline Princy

2013-09-01

249

Impact of global warming on the geobotanic zones: an experiment with a statistical–dynamical climate model  

Microsoft Academic Search

In this study, a zonally-averaged statistical climate model (SDM) is used to investigate the impact of global warming on the\\u000a distribution of the geobotanic zones over the globe. The model includes a parameterization of the biogeophysical feedback\\u000a mechanism that links the state of surface to the atmosphere (a bidirectional interaction between vegetation and climate).\\u000a In the control experiment (simulation of

Sergio H. Franchito; V. Brahmananda Rao; E. C. Moraes

250

Random walks along the streets and canals in compact cities: Spectral analysis, dynamical modularity, information, and statistical mechanics  

NASA Astrophysics Data System (ADS)

Different models of random walks on the dual graphs of compact urban structures are considered. Analysis of access times between streets helps to detect the city modularity. The statistical mechanics approach to the ensembles of lazy random walkers is developed. The complexity of city modularity can be measured by an informationlike parameter which plays the role of an individual fingerprint of Genius loci. Global structural properties of a city can be characterized by the thermodynamic parameters calculated in the random walk problem.

Volchenkov, D.; Blanchard, Ph.

2007-02-01

251

A statistical dynamics approach to the study of human health data: Resolving population scale diurnal variation in laboratory data  

NASA Astrophysics Data System (ADS)

Statistical physics and information theory is applied to the clinical chemistry measurements present in a patient database containing 2.5 million patients' data over a 20-year period. Despite the seemingly naive approach of aggregating all patients over all times (with respect to particular clinical chemistry measurements), both a diurnal signal in the decay of the time-delayed mutual information and the presence of two sub-populations with differing health are detected. This provides a proof in principle that the highly fragmented data in electronic health records has potential for being useful in defining disease and human phenotypes.

Albers, D. J.; Hripcsak, George

2010-02-01

252

A statistical dynamics approach to the study of human health data: resolving population scale diurnal variation in laboratory data  

PubMed Central

Statistical physics and information theory is applied to the clinical chemistry measurements present in a patient database containing 2.5 million patients’ data over a 20-year period. Despite the seemingly naive approach of aggregating all patients over all times (with respect to particular clinical chemistry measurements), both a diurnal signal in the decay of the time-delayed mutual information and the presence of two sub-populations with differing health are detected. This provides a proof in principle that the highly fragmented data in electronic health records has potential for being useful in defining disease and human phenotypes.

Albers, D. J.; Hripcsak, George

2010-01-01

253

SDI: Progress and Challengers.  

National Technical Information Service (NTIS)

Since March, 1983, when the President set forth his vision of a space-based defense, which, in his own words, would set us free from the prison of nuclear weapons' the United States has embarked on the most challenging, controversial and visionary defense...

D. Waller J. Bruce D. Cook

1986-01-01

254

The SDI approach  

Microsoft Academic Search

The US strategic defense initiative office (SDIO) recognizes that software will play a critical role in the development and deployment of the strategic defense system (SDS). Proper SDS software development will require attention in the following three areas: technology utilization, education, and policy. Several major efforts designed to reduce the risk associated with development and deployment of SDS software are

C. W. Lillie; B. R. Brykczynski

1989-01-01

255

SDI: Myth or reality  

SciTech Connect

This report reviews previous attempt to develop strategic defenses, the technologies currently under consideration, their main unknowns, and their likely performance relative to evolving threats. 28 refs.

Canavan, G.H.

1988-01-01

256

Evaluation of the impact of quorum sensing transcriptional regulator SdiA on long-term persistence and fecal shedding of Escherichia coli O157:H7 in weaned calves  

Technology Transfer Automated Retrieval System (TEKTRAN)

Quorum sensing transcriptional regulator SdiA has been shown to enhance the survival of Escherichia coli O157:H7 (O157) in the acidic compartment of bovine rumen in response to N-acyl-L-homoserine lactones (AHLs) produced by the rumen bacteria. Bacteria that survive the rumen environment subsequentl...

257

Statistical study of the effect of solar wind dynamic pressure fronts on the dayside and nightside ionospheric convection  

NASA Astrophysics Data System (ADS)

Over the past few years, the prominent role of solar wind dynamic pressure in enhancing dayside and nightside reconnection and driving-enhanced ionospheric convection has been documented by both ground and spaceborne instruments. For a previous case study of an abrupt increase in solar wind dynamic pressure, Super Dual Auroral Radar Network (SuperDARN) measurements of plasma convection within the dayside polar ionosphere revealed an immediate enhancement of plasma convection. The convection enhancement variation closely follows the variation in solar wind pressure. The dayside enhancement was followed by a nightside convection increase about 40 min later, which has similar variation characteristics as seen on the dayside. We now use SuperDARN flow measurements during a large number of solar wind pressure enhancements to conduct a superposed epoch analysis of the effects of solar wind pressure fronts on the dayside and nightside ionospheric convection. The results for the dayside show an increase of convection for nearly all interplanetary magnetic field (IMF) Bz values. The response is more pronounced and immediate (within minutes) for southward IMF, with a duration of 20-30 min. The response time scales increase to 5-10 min for northward IMF, and the enhanced flows last for 30-50 min. We also find a significant enhancement of nightside convection, particularly for small values of IMF By, that follows about 10-15 min after the dayside response and can last for 40-50 min.

Boudouridis, A.; Lyons, L. R.; Zesta, E.; Weygand, J. M.; Ribeiro, A. J.; Ruohoniemi, J. M.

2011-10-01

258

Statistical approach to dislocation dynamics: From dislocation correlations to a multiple-slip continuum theory of plasticity  

NASA Astrophysics Data System (ADS)

Due to recent successes of a statistical-based nonlocal continuum crystal plasticity theory for single-glide in explaining various aspects such as dislocation patterning and size-dependent plasticity, several attempts have been made to extend the theory to describe crystals with multiple-slip systems using ad hoc assumptions. We present here a mesoscale continuum theory of plasticity for multiple-slip systems of parallel edge dislocations. We begin by constructing the Bogolyubov Born Green Yvon Kirkwood integral equations relating different orders of dislocation correlation functions in a grand canonical ensemble. Approximate pair correlation functions are obtained for single-slip systems with two types of dislocations and, subsequently, for general multiple-slip systems of both charges. The effect of the correlations manifests itself in the form of an entropic force in addition to the external stress and the self-consistent internal stress. Comparisons with a previous multiple-slip theory based on phenomenological considerations shall be discussed.

Limkumnerd, Surachate; van der Giessen, Erik

2008-05-01

259

Equilibrium Statistical Mechanics, Non-Hamiltonian Molecular Dynamics, and Novel Applications from Resonance-Free Timesteps to Adiabatic Free Energy Dynamics  

NASA Astrophysics Data System (ADS)

Levinthal's paradox [1,2], first introduced in the 1960's (early in the childhood of simulations in Chemistry), serves as a good illustration of the limitations we still face in the application of molecular dynamics (MD). Levinthal reasoned that if we were to assume that every residue in a polypeptide has a least two stable conformations, then a small 100 residue polypeptide would have 2100 possible states. If we were to study such a protein using traditional, state of the art, MD techniques, the native state would only be deduced after a little more than a billion years.

Abrams, J. B.; Tuckerman, M. E.; Martyna, G. J.

260

Model-based statistical estimation of Sandia RF ohmic switch dynamic operation form stroboscopic, x-ray imaging.  

SciTech Connect

We define a new diagnostic method where computationally-intensive numerical solutions are used as an integral part of making difficult, non-contact, nanometer-scale measurements. The limited scope of this report comprises most of a due diligence investigation into implementing the new diagnostic for measuring dynamic operation of Sandia's RF Ohmic Switch. Our results are all positive, providing insight into how this switch deforms during normal operation. Future work should contribute important measurements on a variety of operating MEMS devices, with insights that are complimentary to those from measurements made using interferometry and laser Doppler methods. More generally, the work opens up a broad front of possibility where exploiting massive high-performance computers enable new measurements.

Diegert, Carl F.

2006-12-01

261

Cancer Statistics  

MedlinePLUS

... Rates Continue to Drop SEER Cancer Statistics Review, 1975-2010 Did You Know? Video Series Cancer Statistics ... and survival from the SEER Cancer Statistics Review, 1975-2010. Play Pause Volume Up Volume Down Mute ...

262

A generalized 3-D dynamic modeling for transverse flux homopolar linear machines based on statistical saliency-effect superposition method  

SciTech Connect

This paper will present a prototype of transverse flux homopolar linear machine system, along with a systematic and generalized 3-dimensional approach which is capable to analyze three kinds of linear machines, the transverse flux linear induction machine (TFLIM), the homopolar linear synchronous machine (HLSM), and the transverse flux linear reluctance machine (TFLRM), all in one compact mathematical model. Also, other than using the conventional steady-state geometric vector analysis or the concentrated magnetic circuit analysis in the modeling process, a novel methodology which combines the state-space technique with the statistical saliency-effect superposition method is proposed. With such detailed and generalized modeling approach, the capability of analyzing the saliency effects induced by the distributed windings in practical linear machine systems will be enhanced, and the representations of all the related linear machine system equations can be manipulated in compact matrix forms. From this comprehensive theoretical approach and the experimental verifications, it is shown that a convenient and reliable mathematical basis for the associated computer-aided analysis and design studies on linear machine systems will be provided.

Liu, C.T.; Kuo, J.L.; Wu, G.S. [National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China). Dept. of Electrical Engineering

1993-12-01

263

Mass action law versus local contagion dynamics. A mean-field statistical approach with application to the theory of epidemics  

NASA Astrophysics Data System (ADS)

A mean-field approach for epidemic processes with high migration is suggested by analogy with non-equilibrium statistical mechanics. For large systems a limit of the thermodynamic type is introduced for which both the total size of the system and the total number of individuals tend to infinity but the population density remains constant. In the thermodynamic limit the infection rate is proportional to the product of the proportion of individuals susceptible to infection and the average probability of infection. The limit form of the average probability of infection is insensitive to the detailed behaviour of the fluctuations of the number of infectious individuals and may belong to two universality classes: (1) if the fluctuation of the number of infectives is non-intermittent it increases with the increase of the partial density of infectives and approaches exponentially the asymptotic value one for large densities; (2) for intermittent fluctuations obeying a power-law scaling the average probability of infection also displays a saturation effect for large densities of infectives but the asymptotic value one is approached according to a power law rather than exponentially. For low densities of infectives both expressions for the average probability of infection are linear functions of the proportion of infectives and the infection rate is given by the mass-action law.

Ovidiu Vlad, Marcel; Schönfisch, Birgitt

1996-08-01

264

Statistical Neurodynamics.  

NASA Astrophysics Data System (ADS)

The primary objective of the thesis is to explore the dynamical properties of small nerve networks by means of the methods of statistical mechanics. To this end, a general formalism is developed and applied to elementary groupings of model neurons which are driven by either constant (steady state) or nonconstant (nonsteady state) forces. Neuronal models described by a system of coupled, nonlinear, first-order, ordinary differential equations are considered. A linearized form of the neuronal equations is studied in detail. A Lagrange function corresponding to the linear neural network is constructed which, through a Legendre transformation, provides a constant of motion. By invoking the Maximum-Entropy Principle with the single integral of motion as a constraint, a probability distribution function for the network in a steady state can be obtained. The formalism is implemented for some simple networks driven by a constant force; accordingly, the analysis focuses on a study of fluctuations about the steady state. In particular, a network composed of N noninteracting neurons, termed Free Thinkers, is considered in detail, with a view to interpretation and numerical estimation of the Lagrange multiplier corresponding to the constant of motion. As an archetypical example of a net of interacting neurons, the classical neural oscillator, consisting of two mutually inhibitory neurons, is investigated. It is further shown that in the case of a network driven by a nonconstant force, the Maximum-Entropy Principle can be applied to determine a probability distribution functional describing the network in a nonsteady state. The above examples are reconsidered with nonconstant driving forces which produce small deviations from the steady state. Numerical studies are performed on simplified models of two physical systems: the starfish central nervous system and the mammalian olfactory bulb. Discussions are given as to how statistical neurodynamics can be used to gain a better understanding of the behavior of these systems.

Paine, Gregory Harold

1982-03-01

265

Real-time dynamic range and signal to noise enhancement in beam-scanning microscopy by integration of sensor characteristics, data acquisition hardware, and statistical methods  

NASA Astrophysics Data System (ADS)

Despite the ubiquitous use of multi-photon and confocal microscopy measurements in biology, the core techniques typically suffer from fundamental compromises between signal to noise (S/N) and linear dynamic range (LDR). In this study, direct synchronous digitization of voltage transients coupled with statistical analysis is shown to allow S/N approaching the theoretical maximum throughout an LDR spanning more than 8 decades, limited only by the dark counts of the detector on the low end and by the intrinsic nonlinearities of the photomultiplier tube (PMT) detector on the high end. Synchronous digitization of each voltage transient represents a fundamental departure from established methods in confocal/multi-photon imaging, which are currently based on either photon counting or signal averaging. High information-density data acquisition (up to 3.2 GB/s of raw data) enables the smooth transition between the two modalities on a pixel-by-pixel basis and the ultimate writing of much smaller files (few kB/s). Modeling of the PMT response allows extraction of key sensor parameters from the histogram of voltage peak-heights. Applications in second harmonic generation (SHG) microscopy are described demonstrating S/N approaching the shot-noise limit of the detector over large dynamic ranges.

Kissick, David J.; Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

2013-02-01

266

Understanding shock dynamics in the inner heliosphere with modeling and type II radio data: A statistical study  

NASA Astrophysics Data System (ADS)

We study two methods of predicting interplanetary shock location and strength in the inner heliosphere: (1) the ENLIL simulation and (2) the kilometric type II (kmTII) prediction. To evaluate differences in the performance of the first method, we apply two sets of coronal mass ejections (CME) parameters from the cone-model fitting and flux-rope (FR) model fitting as input to the ENLIL model for 16 halo CMEs. The results show that the ENLIL model using the actual CME speeds from FR-fit provided an improved shock arrival time (SAT) prediction. The mean prediction errors for the FR and cone-model inputs are 4.90±5.92 h and 5.48±6.11 h, respectively. A deviation of 100 km s-1 from the actual CME speed has resulted in a SAT error of 3.46 h on average. The simulations show that the shock dynamics in the inner heliosphere agrees with the drag-based model. The shock acceleration can be divided as two phases: a faster deceleration phase within 50 Rs and a slower deceleration phase at distances beyond 50 Rs. The linear-fit deceleration in phase 1 is about 1 order of magnitude larger than that in phase 2. When applying the kmTII method to 14 DH-km CMEs, we found that combining the kmTII method with the ENLIL outputs improved the kmTII prediction. Due to a better modeling of plasma density upstream of shocks and the kmTII location, we are able to provide a more accurate shock time-distance and speed profiles. The mean kmTII prediction error using the ENLIL model density is 6.7±6.4 h; it is 8.4±10.4 h when the average solar wind plasma density is used. Applying the ENLIL density has reduced the mean kmTII prediction error by ˜2 h and the standard deviation by 4.0 h. Especially when we applied the combined approach to two interacting events, the kmTII prediction error was drastically reduced from 29.6 h to -4.9 h in one case and 10.6 h to 4.2 h in the other. Furthermore, the results derived from the kmTII method and the ENLIL simulation, together with white-light data, provide a valuable validation of shock formation location and strength. Such information has important implications for solar energetic particle acceleration.

Xie, H.; St. Cyr, O. C.; Gopalswamy, N.; Odstrcil, D.; Cremades, H.

2013-08-01

267

Statistical Inference  

Microsoft Academic Search

\\u000a An important application of probability theory is the use of statistics in science, in particular classical statistics as\\u000a devised by Fisher and Neyman and Pearson. Good introductions to this type of statistics are provided in (Barnett, 1999) and\\u000a in (Mood et al., 1974). We should emphasize that classical statistics is not an uncontroversial tool for reasoning statistically,\\u000a and that it

Rolf Haenni; Jan-Willem Romeijn; Gregory Wheeler; Jon Williamson

268

Experiments in statistical mechanics  

NASA Astrophysics Data System (ADS)

We present experiments designed to illustrate the basic concepts of statistical mechanics using a gas of ``motorized molecules.'' Two molecular motion machines are constructed. The pressure fluctuation machine (mechanical interaction simulator) is a working model of two gases separated by a movable piston. The Boltzmann machine (canonical simulator) is a working model of a two-level quantum system in a temperature bath. Dynamical probabilities (fraction of time) are measured using mechanical devices, such as stop watches and motion sensors. Statistical probabilities (fraction of states) are calculated using physical statistics, such as microcanonical and canonical statistics. The experiments enable one to quantitatively test the fundamental principles of statistical mechanics, including the fundamental postulate, the ergodic hypothesis, and the statistics of Boltzmann.

Prentis, Jeffrey J.

2000-12-01

269

Benefits from using combined dynamical-statistical downscaling approaches in building crop water demand scenarios in a semi-arid Mediterranean region.  

NASA Astrophysics Data System (ADS)

Various downscaling techniques have been developed to bridge the scale gap between global climate models (GCMs) and finer scales required to assess hydrological impacts of climate change. Although statistical downscaling (SD) has been traditionally seen as an alternative to dynamical downscaling (DD), recent works on statistical downscaling have aimed to combine the benefits of these two approaches. The overall objective of this study is to assess whether a DD processing performed before the SD permits to obtain more suitable scenarios of crop water demand. The case study presented here focuses on the north-western part of the Apulia region named Capitanata plain (South East of Italy, surface area about 4000 km2), dominated by agriculture (about 15% of the national production of cereals and olive trees) and mainly depending on surface water. The fifth-generation ECHAM model from the Max-Planck-Institute for Meteorology was adopted as GCM. The DD was carried out with the Protheus system (ENEA), while the SD was performed through a monthly quantile-quantile correction. Finally the crop water demand is estimated through the water mass-balance model G-MAP, considering monthly precipitation, monthly temperature and the major landscape features that determine the soil water balance. The latter introduces a strong non linearity with respect to the meteorological input, due to the non-linear solution of soil infiltration and moisture-dependent evapotranspiration and the threshold-based runoff mechanism, which prevents from forecasting the crop water demand as simple linear combination of the precipitation and temperature scenarios. The crop water demand scenarios resulting from the different downscaling and their combination are then compared in terms of bias, long term non stationarity and spatial variability.

Guyennon, Nicolas; Portoghese, Ivan; Romano, Emanuele; Calmanti, Sandro

2013-04-01

270

Mindless statistics  

Microsoft Academic Search

Statistical rituals largely eliminate statistical thinking in the social sciences. Rituals are indispensable for identification with social groups, but they should be the subject rather than the procedure of science. What I call the “null ritual” consists of three steps: (1) set up a statistical null hypothesis, but do not specify your own hypothesis nor any alternative hypothesis, (2) use

Gerd Gigerenzer; Max Planck

2004-01-01

271

Statistical Diversions  

ERIC Educational Resources Information Center

|As a branch of knowledge, Statistics is ubiquitous and its applications can be found in (almost) every field of human endeavour. In this article, the authors track down the possible source of the link between the "Siren song" and applications of Statistics. Answers to their previous five questions and five new questions on Statistics are…

Petocz, Peter; Sowey, Eric

2008-01-01

272

Health Statistics.  

ERIC Educational Resources Information Center

Overview of federal collection of health statistics highlights federal budgets; the National Center for Health Statistics (role, periodicity report); vital statistics (surveys of physicians, hospitals, nursing homes); household surveys (National Health Interview Survey); and proposed reorganization of the Office of the Assistant Secretary of…

Melnick, Daniel; Huckabee, David

1983-01-01

273

SIDS Statistics  

MedlinePLUS

... Alaska Natives (National Center for Health Statistics' (NCHS) linked birth/infant death data . See Chart 2 below. More information on these ... 2013. Infant mortality statistics from the 2009 period linked birth/infant death data set . National Vital Statistics Reports 61(8):1– ...

274

Dynamical localization in chaotic systems: spectral statistics and localization measure in the kicked rotator as a paradigm for time-dependent and time-independent systems.  

PubMed

We study the kicked rotator in the classically fully chaotic regime using Izrailev's N-dimensional model for various N?4000, which in the limit N?? tends to the quantized kicked rotator. We do treat not only the case K=5, as studied previously, but also many different values of the classical kick parameter 5?K?35 and many different values of the quantum parameter k?[5,60]. We describe the features of dynamical localization of chaotic eigenstates as a paradigm for other both time-periodic and time-independent (autonomous) fully chaotic or/and mixed-type Hamilton systems. We generalize the scaling variable ?=l(?)/N to the case of anomalous diffusion in the classical phase space by deriving the localization length l(?) for the case of generalized classical diffusion. We greatly improve the accuracy and statistical significance of the numerical calculations, giving rise to the following conclusions: (1) The level-spacing distribution of the eigenphases (or quasienergies) is very well described by the Brody distribution, systematically better than by other proposed models, for various Brody exponents ?(BR). (2) We study the eigenfunctions of the Floquet operator and characterize their localization properties using the information entropy measure, which after normalization is given by ?(loc) in the interval [0,1]. The level repulsion parameters ?(BR) and ?(loc) are almost linearly related, close to the identity line. (3) We show the existence of a scaling law between ?(loc) and the relative localization length ?, now including the regimes of anomalous diffusion. The above findings are important also for chaotic eigenstates in time-independent systems [Batisti? and Robnik, J. Phys. A: Math. Gen. 43, 215101 (2010); arXiv:1302.7174 (2013)], where the Brody distribution is confirmed to a very high degree of precision for dynamically localized chaotic eigenstates, even in the mixed-type systems (after separation of regular and chaotic eigenstates). PMID:23848746

Manos, Thanos; Robnik, Marko

2013-06-11

275

Dynamical localization in chaotic systems: Spectral statistics and localization measure in the kicked rotator as a paradigm for time-dependent and time-independent systems  

NASA Astrophysics Data System (ADS)

We study the kicked rotator in the classically fully chaotic regime using Izrailev's N-dimensional model for various N?4000, which in the limit N?? tends to the quantized kicked rotator. We do treat not only the case K=5, as studied previously, but also many different values of the classical kick parameter 5?K?35 and many different values of the quantum parameter k?[5,60]. We describe the features of dynamical localization of chaotic eigenstates as a paradigm for other both time-periodic and time-independent (autonomous) fully chaotic or/and mixed-type Hamilton systems. We generalize the scaling variable ?=l?/N to the case of anomalous diffusion in the classical phase space by deriving the localization length l? for the case of generalized classical diffusion. We greatly improve the accuracy and statistical significance of the numerical calculations, giving rise to the following conclusions: (1) The level-spacing distribution of the eigenphases (or quasienergies) is very well described by the Brody distribution, systematically better than by other proposed models, for various Brody exponents ?BR. (2) We study the eigenfunctions of the Floquet operator and characterize their localization properties using the information entropy measure, which after normalization is given by ?loc in the interval [0,1]. The level repulsion parameters ?BR and ?loc are almost linearly related, close to the identity line. (3) We show the existence of a scaling law between ?loc and the relative localization length ?, now including the regimes of anomalous diffusion. The above findings are important also for chaotic eigenstates in time-independent systems [Batisti? and Robnik, J. Phys. A: Math. Gen.1751-811310.1088/1751-8113/43/21/215101 43, 215101 (2010); arXiv:1302.7174 (2013)], where the Brody distribution is confirmed to a very high degree of precision for dynamically localized chaotic eigenstates, even in the mixed-type systems (after separation of regular and chaotic eigenstates).

Manos, Thanos; Robnik, Marko

2013-06-01

276

Role of p21Waf1\\/Cip1\\/Sdi1 in cell death and DNA repair as studied using a tetracycline-inducible system in p53-deficient cells  

Microsoft Academic Search

Postulated roles for p21Waf1\\/Cip1\\/Sdi1 (p21) in DNA repair and apoptosis remain controversial. Studies suggest both stimulatory and inhibitory effects of p21 in DNA repair. p21 has also been implicated in induction or protection from apoptosis. Using the tetracycline inducible expression system, we studied the role of p21 in DNA repair and apoptosis in wild-type p53 deficient DLD1 colorectal carcinoma cells.

M Saeed Sheikh; Yong Q Chen; Martin L Smith; Albert J Fornace Jr

1997-01-01

277

The Phosphatidylinositol 3Kinase\\/AKT Signal Transduction Pathway Plays a Critical Role in the Expression of p21WAF1\\/CIP1\\/SDI1 Induced by Cisplatin and Paclitaxel1  

Microsoft Academic Search

The cyclin-dependent kinase inhibitor p21WAF1\\/CIP1\\/SDI1 (p21) plays a crucial role in DNA repair, cell differentiation, and apoptosis through regulation of the cell cycle. A2780 human ovarian carcinoma cells, which are sensitive to cisplatin and paclitaxel, express wild-type p53 and exhibit a p53-mediated increase in p21 in response to the chemotherapeutic agents. Here, we demonstrate that phosphatidylinositol 3-kinase (PI3K) and its

Yasuhiro Mitsuuchi; Steven W. Johnson; Muthu Selvakumaran; Stephen J. Williams; Thomas C. Hamilton; Joseph R. Testa

278

p21Waf1\\/Cip1\\/Sdi1-induced growth arrest is associated with depletion of mitosis-control proteins and leads to abnormal mitosis and endoreduplication in recovering cells  

Microsoft Academic Search

Induction of a cyclin-dependent kinase inhibitor p21Waf1\\/Cip1\\/Sdi1 is an integral part of cell growth arrest associated with senescence and damage response. p21 overexpression from an inducible promoter resulted in senescence-like growth arrest in a human fibrosarcoma cell line. After release from p21-induced growth arrest, cells re-entered the cell cycle but displayed growth retardation, cell death and decreased clonogenicity. The failure

Bey-Dih Chang; Eugenia V Broude; Jing Fang; Tatiana V Kalinichenko; Ravil Abdryashitov; Jason C Poole; Igor B Roninson

2000-01-01

279

Examining the phase transition behavior of amphiphilic lipids in solution using statistical temperature molecular dynamics and replica-exchange Wang-Landau methods  

NASA Astrophysics Data System (ADS)

Two different techniques - replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) - were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (?) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results.

Gai, Lili; Vogel, Thomas; Maerzke, Katie A.; Iacovella, Christopher R.; Landau, David P.; Cummings, Peter T.; McCabe, Clare

2013-08-01

280

Statistical mechanics of solitons  

SciTech Connect

The status of statistical mechanics theory (classical and quantum, statics and dynamics) is reviewed for 1-D soliton or solitary-wave-bearing systems. Primary attention is given to (i) perspective for existing results with evaluation and representative literature guide; (ii) motivation and status report for remaining problems; (iii) discussion of connections with other 1-D topics.

Bishop, A.

1980-01-01

281

Filtered statistics  

Microsoft Academic Search

Column statistics are an important element of cardinality estimation frameworks. More accurate estimates allow the optimizer of a RDBMS to generate better plans and improve the overall system's efficiency. This paper introduces filtered statistics, which model value distribution over a set of rows restricted by a predicate. This feature, available in Microsoft SQL Server, can be used to handle column

Pawel Terlecki; Hardik Bati; César A. Galindo-legaria; Peter Zabback

2009-01-01

282

BAYESIAN STATISTICS  

Microsoft Academic Search

Mathematical statistics uses two major paradigms, conventional (or frequentist), and Bayesian. Bayesian methods provide a complete paradigm for both statistical inference and decision mak- ing under uncertainty. Bayesian methods may be derived from an axiomatic system, and hence provide a general, coherentmethodology. Bayesian methods contain as particular cases many of the more often used frequentist procedures, solve many of the

José M. Bernardo

283

Descriptive statistics  

Microsoft Academic Search

Statistics is a science that provides precise techniques for collecting and sorting information made easy by tools and methods for further analysis.The object of descriptive statistics, from sample data, is to describe the most important characteristics, by which we refer to those amounts that provide information on the topic of interest which we are studying.

S. Pérez-Vicente; M. Expósito Ruiz

2009-01-01

284

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: The dynamics on two different potential energy surfaces  

Microsoft Academic Search

The possible existence of a complex-forming pathway for the H+O2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time

Pedro Bargueño; Tomás González-Lezana; Pascal Larrégaray; Laurent Bonnet; Jean-Claude Rayez; Marlies Hankel; Sean C. Smith; Anthony J. H. M. Meijer

2008-01-01

285

MRSA Statistics  

MedlinePLUS

... better recognize and prevent MRSA skin infections MRSA Statistics Reducing methicillin-resistant Staphylococcus aureus (MRSA) in both ... to MRSA, visit: CDC MRSA website CDC Active Bacterial Core Surveillance CDC Vital Signs Report National Healthcare ...

286

Statistics Indonesia  

NSDL National Science Digital Library

Started in 1997, the Badan Pusat Statistik (BPS-Statistics Indonesia) is a non-departmental Indonesian government institution directly responsible to the Indonesian president. As the law that created this valuable institution stipulates, the BPS is intended to provide data to the government and the public, along cooperating with other international statistical institutions. Visitors looking for statistics on any number of topics will not be disappointed, as the areas covered include agriculture, consumer price indices, employment, energy, foreign trade, mining, population, public finance, tourism, and social welfare. Additionally, there are monthly macro-economic statistical reports for the years from 1998 to 2001 that can be downloaded and viewed as well. The site is rounded out by a collection of some 21 papers from the past four years that analyze various economic data from the country, such as earning data and manufacturing production.

287

Statistical optics  

NASA Astrophysics Data System (ADS)

This book is based on the thesis that some training in the area of statistical optics should be included as a standard part of any advanced optics curriculum. Random variables are discussed, taking into account definitions of probability and random variables, distribution functions and density functions, an extension to two or more random variables, statistical averages, transformations of random variables, sums of real random variables, Gaussian random variables, complex-valued random variables, and random phasor sums. Other subjects examined are related to random processes, some first-order properties of light waves, the coherence of optical waves, some problems involving high-order coherence, effects of partial coherence on imaging systems, imaging in the presence of randomly inhomogeneous media, and fundamental limits in photoelectric detection of light. Attention is given to deterministic versus statistical phenomena and models, the Fourier transform, and the fourth-order moment of the spectrum of a detected speckle image.

Goodman, J. W.

288

Statistical aspects of inhalation toxicokinetics  

Microsoft Academic Search

The statistical analysis of dynamic processes is a useful tool to learn how environmental and ecological systems work and how they respond to disturbances. In the context of human risk assessment of potentially harmful chemicals, many complex dynamic processes in terms of kinetics have to be taken into account. Thorough research of direct influence of chemicals to humans depends on

Michael Becka; Wolfgand Urfer

1996-01-01

289

Vital Statistics  

Microsoft Academic Search

This article questions the idea that quantitative methods, in particular the analysis of social statistics, is at odds with critical approaches to geography. It argues that numbers-based research is vital to highlight social injustice and oppression and that quantitative research can meet the requirements of critical geography to be reflexive, politically conscious, and activist. The article highlights two issues of

Mark Ellis

2009-01-01

290

``Applied Statistics''  

Microsoft Academic Search

IN his review of my book ``Statistical Methods in Electrical Engineering'' (Nature, March 19, p. 484), Mr. F. Downton criticizes my statement that Bayes' theorem is controversial. The heading of the paragraph in Sir Ronald Fisher's book which I cited is ``The Rejection of Inverse Probability''. Coupled with the lack of mention of Bayes beyond the introductory chapter, I can

D. A. Bell

1955-01-01

291

Statistical Issues  

Microsoft Academic Search

The present document sumarizes the methodology utilized by the UNESCO Division of Statistics in the 1994 assessment of estimates and projections of adult illiteracy by country in the world, Section I of this document provides an overview of the background and rationale behind the recent 1994 assessment, and the policy and monitoring relevance of literacy as a key indicator of

K. J. Holzinger

1924-01-01

292

Statistical Engineering  

NSDL National Science Digital Library

A good resource for problems in statistics in engineering. Contains some applets, and good textual examples related to engineering. Some topics include Monte Carlo method, Central Limit Theorem, Risk, Logistic Regression, Generalized Linear Models, and Confidence. Overall, this is a well presented and good site for anyone interested in engineering or mathematics.

Annis, Charles

2008-12-30

293

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: the dynamics on two different potential energy surfaces.  

PubMed

The possible existence of a complex-forming pathway for the H+O(2) reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O(2)(v=0,j=1)-->OH(v(')=1,j('))+O process reasonably well. PMID:18601333

Bargueño, Pedro; González-Lezana, Tomás; Larrégaray, Pascal; Bonnet, Laurent; Rayez, Jean-Claude; Hankel, Marlies; Smith, Sean C; Meijer, Anthony J H M

2008-06-28

294

Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: The dynamics on two different potential energy surfaces  

NASA Astrophysics Data System (ADS)

The possible existence of a complex-forming pathway for the H+O2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O2(v=0,j=1)-->OH(v'=1,j')+O process reasonably well.

Bargueño, Pedro; González-Lezana, Tomás; Larrégaray, Pascal; Bonnet, Laurent; Rayez, Jean-Claude; Hankel, Marlies; Smith, Sean C.; Meijer, Anthony J. H. M.

2008-06-01

295

Learning Statistics By Doing Statistics  

NSDL National Science Digital Library

This article, created by Gary Smith of Pomona College, discusses a project-based approach to teaching statistics. The article focuses on the team aspect of learning, it introduces concepts such as: working with data, learning by doing, learning by writing, learning by speaking, and authentic assessment of material. An appendix contains a list of twenty projects that have been successfully assigned.

Smith, Gary

2009-02-02

296

Statistics I  

NSDL National Science Digital Library

Students will encounter the concept of a distribution, along with parameters that describe a distribution's "typical" values (average) and a distribution's spread (variance). To understand simple distributions and uncertainty propagation in the coming sections, it is necessary to be familiar with the concept of statistical independence. When two variables fluctuate independently, their covariance vanishes, and the variance of their sum is the sum of their variances.

Liao, David

297

Statistical Shorts  

NSDL National Science Digital Library

In this statistics and probability activity students must determine whether each statement is always true, sometimes true, sometimes false, or always false. Students must have a basic understanding of probability statements and the foundation for understanding mean, median, and mode in order to complete this activity for all twelve statements. In addition to the task, tips for getting started, possible solutions, a teacher resource page, and a printable page are provided.

Nrich

2013-01-01

298

Dynamic structure of oxygen in liquid potassium studied by MD method and statistical geometry 1 Supported by the RFBR, Russia (Project #96-02-16315a). 1  

Microsoft Academic Search

Results of the molecular-dynamics simulation of dissolved oxygen in potassium at temperature of 550 K on the ternary model of (1?3x)K+2xK++xO2? where x=0.085 are presented. For neutral potassium\\/oxygen system as a whole, oxygen anions form clusters of ramified chains from K2+O2? units. The observed structure and atomic dynamics of threefold potassium\\/oxygen system shows the process of clustering oxygen in liquid

I. Yu. Shimkevich; V. V. Kuzin; A. L. Shimkevich

1999-01-01

299

Facilitating Disaster Management Using SDI  

Microsoft Academic Search

The role of spatial data and related technologies in disaster management has been well-known worldwide. One of the challenges concerned with such a role is access to and usage of reliable, accurate and up-to-date spatial data for disaster management. This is a very important aspect to disaster response as timely, up-to-date and accurate spatial data describing the current situation is

A. Mansourian; A. Rajabifard; M. J. Valadan Zoej; I. Williamson

300

Dynamics of the D+ + H2 --> HD + H+ reaction at the low energy regime by means of a statistical quantum method  

NASA Astrophysics Data System (ADS)

The D+ +H2(v = 0, j = 0, 1) --> HD+H+ reaction has been investigated at the low energy regime by means of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) between a collisional energy of 10-4 eV and 0.1 eV have been calculated and compared with previously reported results of a time independent quantum mechanical (TIQM) approach. The TIQM results exhibit a dense profile with numerous narrow resonances down to Ec ~ 10-2 eV and for the case of H2(v = 0, j = 0) a prominent peak is found at ~2.5 × 10-4 eV. The analysis at the state-to-state level reveals that this feature is originated in those processes which yield the formation of rotationally excited HD(v' = 0, j' > 0). The statistical predictions reproduce reasonably well the overall behaviour of the TIQM ICSs at the larger energy range (Ec >= 10-3 eV). Thermal rate constants are in qualitative agreement for the whole range of temperatures investigated in this work, 10-100 K, although the SQM values remain above the TIQM results for both initial H2 rotational states, j = 0 and 1. The enlargement of the asymptotic region for the statistical approach is crucial for a proper description at low energies. In particular, we find that the SQM method leads to rate coefficients in terms of the energy in perfect agreement with previously reported measurements if the maximum distance at which the calculation is performed increases noticeably with respect to the value employed to reproduce the TIQM results.

González-Lezana, Tomás; Honvault, Pascal; Scribano, Yohann

2013-08-01

301

Statistical physics of temporal intermittency  

Microsoft Academic Search

The thermodynamic formalism for dynamical systems is applied to a class of mappings of laminar-turbulent temporal intermittency. The corresponding statistical system is shown to be a lattice gas with many-body interactions of clustering type. This one-dimensional system bears a close analogy with the Fisher-Felderhof droplet model of condensation. The abnormal dynamic fluctuations give rise to a phase transition. The critical

Xiao-Jing Wang

1989-01-01

302

Three-dimensional electromagnetic strong turbulence: Dependence of the statistics and dynamics of strong turbulence on the electron to ion temperature ratio  

NASA Astrophysics Data System (ADS)

The temperature ratio Ti/Te of ions to electrons affects both the ion-damping rate and the ion-acoustic speed in plasmas. The effects of changing the ion-damping rate and ion-acoustic speed are investigated for electrostatic strong turbulence and electromagnetic strong turbulence in three dimensions. When ion damping is strong, density wells relax in place and act as nucleation sites for the formation of new wave packets. In this case, the density perturbations are primarily density wells supported by the ponderomotive force. For weak ion damping, corresponding to low Ti/Te, ion-acoustic waves are launched radially outwards when wave packets dissipate at burnout, thereby increasing the level of density perturbations in the system and thus raising the level of scattering of Langmuir waves off density perturbations. Density wells no longer relax in place so renucleation at recent collapse sites no longer occurs, instead wave packets form in background low density regions, such as superpositions of troughs of propagating ion-acoustic waves. This transition is found to occur at Ti/Te ~ 0.1. The change in behavior with Ti/Te is shown to change the bulk statistical properties, scaling behavior, spectra, and field statistics of strong turbulence. For Ti/Te>rsim0.1, the electrostatic results approach the predictions of the two-component model of Robinson and Newman, and good agreement is found for Ti/Te>rsim0.15.

Graham, D. B.; Cairns, Iver H.; Skjaeraasen, O.; Robinson, P. A.

2012-02-01

303

Stupid statistics!  

PubMed

The method of least squares is probably the most powerful data analysis tool available to scientists. Toward a fuller appreciation of that power, this work begins with an elementary review of statistics fundamentals, and then progressively increases in sophistication as the coverage is extended to the theory and practice of linear and nonlinear least squares. The results are illustrated in application to data analysis problems important in the life sciences. The review of fundamentals includes the role of sampling and its connection to probability distributions, the Central Limit Theorem, and the importance of finite variance. Linear least squares are presented using matrix notation, and the significance of the key probability distributions-Gaussian, chi-square, and t-is illustrated with Monte Carlo calculations. The meaning of correlation is discussed, including its role in the propagation of error. When the data themselves are correlated, special methods are needed for the fitting, as they are also when fitting with constraints. Nonlinear fitting gives rise to nonnormal parameter distributions, but the 10% Rule of Thumb suggests that such problems will be insignificant when the parameter is sufficiently well determined. Illustrations include calibration with linear and nonlinear response functions, the dangers inherent in fitting inverted data (e.g., Lineweaver-Burk equation), an analysis of the reliability of the van't Hoff analysis, the problem of correlated data in the Guggenheim method, and the optimization of isothermal titration calorimetry procedures using the variance-covariance matrix for experiment design. The work concludes with illustrations on assessing and presenting results. PMID:17964948

Tellinghuisen, Joel

2008-01-01

304

Generalized statistical mechanics for superstatistical systems.  

PubMed

Mesoscopic systems in a slowly fluctuating environment are often well described by superstatistical models. We develop a generalized statistical mechanics formalism for superstatistical systems, by mapping the superstatistical complex system onto a system of ordinary statistical mechanics with modified energy levels. We also briefly review recent examples of applications of the superstatistics concept for three very different subject areas, namely train delay statistics, turbulent tracer dynamics and cancer survival statistics. PMID:21149383

Beck, Christian

2011-01-28

305

On the efficiency of the equation-free closure of statistical moments: dynamical properties of a stochastic epidemic model on Erd?s-Rényi networks  

NASA Astrophysics Data System (ADS)

We show how different explicit statistical moment closures, including the mean field and the Kirkwood approximations as well as an Ursell-type expansion for the moments, compare with the equation-free approach in the case of a stochastic epidemic model evolving on Erd?s-Rényi networks. For illustration purposes we use a simple, discrete susceptible-infected-recovered stochastic model with a nonlinear recovering probability. For every closure scheme, we derive the corresponding macroscopic evolution equations and we construct the bifurcation diagrams with respect to the probability of infection. Finally, we construct the coarse-grained bifurcation diagram obtained with the equation-free method acting directly on the microscopic simulations, bypassing the derivation of explicit closures. We show that the equation-free approach captures the actual emergent nonlinear behavior and outperforms all the other explicit schemes.

Reppas, A. I.; De Decker, Y.; Siettos, C. I.

2012-08-01

306

Dynamics and Nonclassical Photon Statistics in the Interaction of Two-Level Spin Systems with a Two-Mode Cavity Field:. a Generalized Jaynes-Cummings Model  

NASA Astrophysics Data System (ADS)

The interaction of a two-level XY n-spin system with a two-mode cavity field is investigated through a generalized Jaynes-Cummings model in the rotating wave approximation. The spontaneous decay of a spin level was treated by considering the interaction of the two-level spin system with the modes of the universe in the vacuum state. The different cases of interest, characterized in terms of a detuning parameter for each mode, which emerge from the nonvanishing of certain commutation relations between interaction picture Hamiltonians associated with each mode, were analytically implemented and numerically discussed for various values of the initial mean photon number and spin-photon coupling constants. Photon distribution, time evolution of the spin population inversion, as well as the statistical properties of the field leading to the possible production of nonclassical states, such as antibunched light and violations of the Cauchy-Schwartz inequality are examined for an excited initial state. It was assumed that the two modes are initially in coherent states and have the same photon distribution. The case of zero detuning of both modes was treated in terms of a linearization of the expansion of the time evolution operator, while in other three cases, the computations were conducted via second- and third-order Dyson perturbation expansion of the time evolution operator matrix elements for the excited and ground states respectively.

Grinberg, Horacio

307

On the physical links between the dynamics of the Izu Islands 2000 dike intrusions and the statistics of the induced seismicity  

NASA Astrophysics Data System (ADS)

The frequency-magnitude distribution (FMD) of earthquakes has been widely studied in a variety of settings, from global to laboratory scale. The b-value of the FMD is in general close to one on a global scale; however, on a regional scale it is found to deviate significantly from this behavior. Spatial variations of the b-value have been evidenced around major fault systems, in subducting slabs as well as in volcanic and geothermal areas. Although in tectonics environments, such as fault systems, the b-value varies only spatially, generally in association with different stress levels, in volcanic areas b-value anomalies occur both spatially and temporally and are generally associated to the presence of fluids or large rock heterogeneities within the crust. The physical and mechanical interpretation of such anomalies is still a difficult task, in particular for areas where multiple seismic sources are in play, or for volcanic areas, where multiple physical processes influence earthquake occurrence. In this study we focus on the seismic swarm which accompanied the well-studied 2000 Izu islands (Japan) dike intrusion in order to link the intrusion dynamics to temporal and spatial variations of the b-value of the FMD. We first calculate the b-value anomalies relative to different areas in the different phases of the intrusion and then compare them with the stress levels we infer from the published inversions of time-dependent dike-induced deformation. Then, we study the evolution of the maximum expected magnitude in this area that experienced in a few weeks more than five earthquakes with magnitude greater than 6. Finally, we calculate the effect of the dike-induced stress on the observed seismicity in the region, highlighting the areas that experienced an enhancement in seismicity and the area where the seismicity is inhibited.

Passarelli, L.; Rivalta, E.; Maccaferri, F.; Aoki, Y.

2012-04-01

308

Use of remote sensing, geographic information systems, and spatial statistics to assess spatio-temporal population dynamics of Heterodera glycines and soybean yield quantity and quality  

NASA Astrophysics Data System (ADS)

Soybean, Glycine max (L.) Merr., is an important source of oil and protein worldwide, and soybean cyst nematode (SCN), Heterodera glycines, is among the most important yield-limiting factors in soybean production worldwide. Early detection of SCN is difficult because soybean plants infected by SCN often do not exhibit visible symptoms. It was hypothesized, however, that reflectance data obtained by remote sensing from soybean canopies may be used to detect plant stress caused by SCN infection. Moreover, reflectance measurements may be related to soybean growth and yield. Two field experiments were conducted from 2000 to 2002 to study the relationships among reflectance data, quantity and quality of soybean yield, and SCN population densities. The best relationships between reflectance and the quantity of soybean grain yield occurred when reflectance data were obtained late August to early September. Similarly, reflectance was best related to seed oil and seed protein content and seed size when measured during late August/early September. Grain quality-reflectance relationships varied spatially and temporally. Reflectance measured early or late in the season had the best relationships with SCN population densities measured at planting. Soil properties likely affected reflectance measurements obtained at the beginning of the season and somehow may have been related to SCN population densities at planting. Reflectance data obtained at the end of the growing season likely was affected by early senescence of SCN-infected soybeans. Spatio-temporal aspects of SCN population densities in both experiments were assessed using spatial statistics and regression analyses. In the 2000 and 2001 growing seasons, spring-to-fall changes in SCN population densities were best related to SCN population densities at planting for both experiments. However, within-season changes in SCN population densities were best related to SCN population densities at harvest for both experiments in 2002. Variograms were fitted to the data to describe the spatial characteristics of SCN population densities in both fields at planting and at harvest from 2000 to 2003 and these parameters varied within seasons and during overwinter periods in both experiments. Distinct relationships between temporal and spatial changes in SCN population densities were not detected.

Moreira, Antonio Jose De Araujo

309

Internet For Social Statistics  

NSDL National Science Digital Library

This site, created by the University of Bristol, is a tutorial that lets you practice your internet information skills in searching and researching statistics in the social sciences. This site has indexed other statistics resources into five main categories: official statistics, published statistics, timely statistics, datasets for secondary analysis and statistical help and teaching materials. This is a nice overview of this broad topic.

2009-01-29

310

Multivariable Statistical Modelling and Its Application.  

National Technical Information Service (NTIS)

The study of statistical identification of discrete, dynamic, multi-input and multi-output (MIMO) linear models for complex industrial processes is examined. Contributions that have been made in this area include: (1) The development of a MIMO estimation ...

L. K. Been

1984-01-01

311

Statistical nature of nuclear multifragmentation  

SciTech Connect

A recent analysis of multifragmentation data in terms of an elementary binary decay appears to imply that the decay is sequential and from a thermalized source. This last feature would imply a lack of sensitivity to dynamical effects, at least in this multifragmentation data. We discuss this analysis using a simultaneous statistical multifragmentation model (SMM), which assumes decay from a thermalized source, and also employing a molecular dynamics model (MDM). The elementary binary decay analysis of the SMM predictions yields results which are qualitatively similar to those of the data. The differences are shown to stem from superposition of processes associated with very different impact parameters. Thus the data are not inconsistent with simultaneous decay. The MDM calculations, on the other hand, disagree with the data. We suggest, however, that more reliable dynamical calculations are needed before accepting an absence of dynamical effects in these data. {copyright} {ital 1997} {ital The American Physical Society}

Donangelo, R.; Souza, S.R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, C.P. 68528, 21945-970 Rio de Janeiro (Brazil)

1997-09-01

312

Misconceptions About Statistics and Statistical Evidence  

Microsoft Academic Search

\\u000a Thanks in large part to advances in computing and information technology, statistics are everywhere. Whether the information\\u000a concerns business, health, politics, sports, or nearly anything else, it is likely to appear in statistical form. The front\\u000a page of the country’s highest circulation daily newspaper (USA Today) is littered with descriptive statistics and graphical depictions of those statistics. The star of

Jonathan J. Koehler

313

Statistics Poker: Reinforcing Basic Statistical Concepts  

ERIC Educational Resources Information Center

Learning basic statistical concepts does not need to be tedious or dry; it can be fun and interesting through cooperative learning in the small-group activity of Statistics Poker. This article describes a teaching approach for reinforcing basic statistical concepts that can help students who have high anxiety and makes learning and reinforcing…

Leech, Nancy L.

2008-01-01

314

Is there a statistical mechanics of turbulence  

SciTech Connect

The statistical-mechanical treatment of turbulence is made questionable by strong nonlinearity and strong disequilibrium that result in the creation of ordered structures imbedded in disorder. Model systems are described which may provide some hope that a compact, yet faithful, statistical description of turbulence nevertheless is possible. Some essential dynamic features of the models are captured by low-order statistical approximations despite strongly non-Gaussian behavior. 31 refs., 5 figs.

Kraichnan, R.H.; Chen, S.Y.

1988-09-01

315

Literate Statistical Practice  

Microsoft Academic Search

Literate Statistical Practice (LSP) is an method for statistical practice which suggests that documentation and specication occur at the same time as statistical coding. It applies literate programming Knuth (1992) to the practice of statistics. We discuss 2 dierent approaches for LSP, one currently implemented using Emacs with Noweb and Emacs Speaks Statistics (ESS), and the other developed based on

A. J. Rossini

316

Statistical trajectory models for phonetic recognition  

Microsoft Academic Search

The main goal of this work is to develop an alternative methodology for acoustic--phonetic modelling of speech sounds. The approach utilizes a segment--based frameworkto capture the dynamical behavior and statistical dependencies of the acousticattributes used to represent the speech waveform. Temporal behavior is modelledexplicitly by creating dynamic tracks of the acoustic attributes used to represent thewaveform, and by estimating the

William David Goldenthal; James R. Glass

1994-01-01

317

Statistical Trajectory Models for Phonetic Recognition  

Microsoft Academic Search

The main goal of this work is to develop an alternative methodology for acoustic-phonetic modelling of speech sounds. The approach utilizes a segment-based framework to capture the dynamical behavior and statistical dependencies of the acoustic attributes used to represent the speech waveform. Temporal behavior is modelled explicitly by creating dynamic tracks of the acoustic attributes used to represent the waveform,

William David Goldenthal

1994-01-01

318

Opportunities for Improved Statistical Process Control  

Microsoft Academic Search

Our Bayesian dynamic programming model builds on existing models to account for inspection delay, choice of keeping production going during inspection and\\/or restoration, and lot sizing. We focus on describing how dynamic statistical process control (DSPC) rules can improve on traditional, static ones. We explore numerical examples and identify nine opportunities for improvement. Some of these ideas are well known

Evan L. Porteus; Alexandar Angelus

1997-01-01

319

GIS, SPATIAL STATISTICAL GRAPHICS, AND FOREST HEALTH  

Microsoft Academic Search

This paper discusses the use of a geographic information systems (GIS), Arcview 2.1, linked with a dynamic graphics program, XGobi, in the statistical analysis of spatial data. The link allows multivariate data, collected at geographic locations and stored in Arcview, to be passed into XGobi and analyzed dynamically. The connection between the points in XGobi and the spatial locations from

James J. Majure; Noel Cressie; Dianne Cook; Jürgen Symanzik

320

Statistical Models in Sedimentology.  

National Technical Information Service (NTIS)

Three stages of statistical development can be recognized in sedimentology. The first is descriptive statistics, in which the sample is the object of interest, and the second is analytical statistics, in which the population assumes major importance. The ...

W. C. Krumbein

1967-01-01

321

STATLIB. Conversational Statistical Library  

Microsoft Academic Search

STATLIB is a conversational statistical program library developed in conjunction with a Sandia National Laboratories applied statistics course intended for practicing engineers and scientists. STATLIB is a group of 15 interactive, argument-free, statistical routines including analysis of sensitivity tests; sample statistics for the normal, exponential, hypergeometric, Weibull, and extreme value distributions; three models of multiple regression analysis; x-y data plots;

1992-01-01

322

Quality of Statistical Norms  

Microsoft Academic Search

This paper is acontribution to this work. Statistical Norms considered here encompasspopulations, statistical units, classifications, characteristics, reference periods and"statistical summaries". It is shown that specific quality components for norms canbe isolated, in a way consistent with the definition of quality in statistics. Thismakes possible to report on the quality of norms in a standard way.

Raoul Depoutot Eurostat; Batiment Jean Monnet

1998-01-01

323

International Statistical Institute - Glossary of Statistical Terms  

NSDL National Science Digital Library

This site shows the International Statistical Institutes alphabetical list of technical terms showing the translation in a number of languages. The page covers a myriad of different terms and our translated into many languages such as: English, French, German, Dutch, Italian, Spanish, Catalan, Portuguese, Romanian, Danish, Norwegian, Swedish, Greek and many more. This is a nice reference site for anyone interested in statistics.

2009-12-08

324

Applied Probability Statistical Methodology and Computational Statistics.  

National Technical Information Service (NTIS)

This final report form the Department of Statistics, University of Georgia, concerns the above referenced grant, an equipment grant that provided partial funding for the acquisition of specified computing equipment to support research in the department. T...

R. Bradley

1986-01-01

325

Statistical Science, Statistical Data Modeling, and Statistical Education.  

National Technical Information Service (NTIS)

This paper is intended to communicate to a general audience current directions in the discipline of statistics, and in my own research. It consists of three parts. Part I (Sections 1-3) explores perspectives on the future development of the science of sta...

E. Parzen

1979-01-01

326

Statistical Review & Evaluation - XYNTHA  

Center for Biologics Evaluation and Research (CBER)

... Descriptive statistics were used to summarize demographic and baseline data ... It was determined using an agreed upon Bayesian statistical model ... More results from www.fda.gov/biologicsbloodvaccines/bloodbloodproducts/approvedproducts

327

Tobacco Statistics Snapshot  

MedlinePLUS

... Trials Cancer Statistics Research & Funding News About NCI Tobacco Statistics Snapshot Updated: 11/09/2012 Page Options ... Professionals Cancer Trends Progress Report: 2011/2012 Update Tobacco Facts Tobacco is the leading cause of preventable ...

328

Metropolitan Statistical Areas, 1988.  

National Technical Information Service (NTIS)

The report is Office of Management and Budget Bulletin - 88-14 - Metropolitan Statistical Areas. It establishes a new Metropolitan Statistical Area (MSA) and changes the boundaries of an existing MSA.

1988-01-01

329

Metropolitan Statistical Areas, 1989.  

National Technical Information Service (NTIS)

The Bulletin establishes a new Metropolitan Statistical Area (MSA) and two new central cities of existing MSAs. The Bulletin also provides guidance on the use of the definitions of MSAs. Metropolitan Statistical Areas (MSAs) are defined in terms of entire...

1989-01-01

330

Artificial intelligence and statistics  

Microsoft Academic Search

This book explores the possible applications of artificial intelligence in statistics and conversely, statistics in artificial intelligence. It is a collection of seventeen papers written by leaders in the field. Most of the papers were prepared for the Workshop on Artificial Intelligence and Statistics held in April 1985 and sponsored by ATandT Bell Laboratories. The book is divided into six

Gale

1987-01-01

331

Editorial: Statistics and  

Microsoft Academic Search

What makes a problem suitable for statistical analysis? Are historical and religious questions addressable using statistical calculations? Such issues have long been debated in the statistical community and statisticians and others have used historical information and texts to analyze such questions as the economics of slavery, the authorship of the Federalist Papers and the question of the existence of God.

Stephen E. Fienberg

2008-01-01

332

Statistical quality management  

NASA Astrophysics Data System (ADS)

Some aspects of statistical quality management are discussed. Quality has to be defined as a concrete, measurable quantity. The concepts of Total Quality Management (TQM), Statistical Process Control (SPC), and inspection are explained. In most cases SPC is better than inspection. It can be concluded that statistics has great possibilities in the field of TQM.

Vanderlaan, Paul

1992-10-01

333

Library Statistics Cooperative Program.  

ERIC Educational Resources Information Center

The Library Statistics Cooperative Program collects statistics about all types of libraries--academic libraries, public libraries, school library media centers, state library agencies, federal libraries and information centers, and library cooperatives. The Library Statistics Cooperative Program depends on collaboration with all types of libraries…

National Commission on Libraries and Information Science, Washington, DC.

334

The Statistics of Style  

NSDL National Science Digital Library

Created by J. Swift of the Royal Statistical Society, this article describes an exercise, probability and statistics, which develops a statistic that measures the variety of noun usage in order to distinguish two authors. The exercise emphasizes the use of frequency.

Swift, J.

2009-03-10

335

Statistics for Chemists  

NSDL National Science Digital Library

This site is a comprehensive resource on statistics, including information on descriptive statistics, confidence intervals, hypothesis testing, regression, ANOVA, experimental design, and multivariate statistics. Web-based exercises are interspersed throughout the text, allowing students to practice what they are learning and to obtain immediate feedback.

Wehrens, R.

2011-02-14

336

Statistics Teacher Network  

NSDL National Science Digital Library

This website provides links to all current and past issues of "The Statistics Teacher Network". This newsletter for K-12 teachers is published three times a year, and presents up to date articles that describe statistical activities that have been successful in the classroom. It also informs educators of statistical workshops, programs, and reviews of books, software, and calculators.

2012-01-01

337

Nonlinear Statistical Modeling of Speech  

NASA Astrophysics Data System (ADS)

Contemporary approaches to speech and speaker recognition decompose the problem into four components: feature extraction, acoustic modeling, language modeling and search. Statistical signal processing is an integral part of each of these components, and Bayes Rule is used to merge these components into a single optimal choice. Acoustic models typically use hidden Markov models based on Gaussian mixture models for state output probabilities. This popular approach suffers from an inherent assumption of linearity in speech signal dynamics. Language models often employ a variety of maximum entropy techniques, but can employ many of the same statistical techniques used for acoustic models. In this paper, we focus on introducing nonlinear statistical models to the feature extraction and acoustic modeling problems as a first step towards speech and speaker recognition systems based on notions of chaos and strange attractors. Our goal in this work is to improve the generalization and robustness properties of a speech recognition system. Three nonlinear invariants are proposed for feature extraction: Lyapunov exponents, correlation fractal dimension, and correlation entropy. We demonstrate an 11% relative improvement on speech recorded under noise-free conditions, but show a comparable degradation occurs for mismatched training conditions on noisy speech. We conjecture that the degradation is due to difficulties in estimating invariants reliably from noisy data. To circumvent these problems, we introduce two dynamic models to the acoustic modeling problem: (1) a linear dynamic model (LDM) that uses a state space-like formulation to explicitly model the evolution of hidden states using an autoregressive process, and (2) a data-dependent mixture of autoregressive (MixAR) models. Results show that LDM and MixAR models can achieve comparable performance with HMM systems while using significantly fewer parameters. Currently we are developing Bayesian parameter estimation and discriminative training algorithms for these new models to improve noise robustness.

Srinivasan, S.; Ma, T.; May, D.; Lazarou, G.; Picone, J.

2009-12-01

338

Statistical Properties of Online Auctions  

NASA Astrophysics Data System (ADS)

We characterize the statistical properties of a large number of online auctions run on eBay. Both stationary and dynamic properties, like distributions of prices, number of bids etc., as well as relations between these quantities are studied. The analysis of the data reveals surprisingly simple distributions and relations, typically of power-law form. Based on these findings we introduce a simple method to identify suspicious auctions that could be influenced by a form of fraud known as shill bidding. Furthermore the influence of bidding strategies is discussed. The results indicate that the observed behavior is related to a mixture of agents using a variety of strategies.

Namazi, Alireza; Schadschneider, Andreas

339

Journal of Statistics Education  

NSDL National Science Digital Library

Provided by the American Statistical Association (ASA), the Journal of Statistics Education (JSE) "disseminates knowledge for the improvement of statistics education at all levels." Articles address such topics as curriculum reform, cooperative learning, and instruction methods, to name a few. Besides the regular articles, there are two extra features titled Teaching Bits and Data Sets and Stories. Teaching Bits give statistics teachers fun, original ideas to incorporate into their classes. Data Sets and Stories have downloadable material that can also be used in the classroom for statistical analysis. Past issues can be viewed from an archive that dates back to 1993.

2002-01-01

340

Meteor trail footprint statistics  

NASA Astrophysics Data System (ADS)

Footprint statistics derived from field-test data are presented. The statistics are the probability that two receivers will lie in the same footprint. The dependence of the footprint statistics on the transmitter range, link orientation, and antenna polarization are examined. Empirical expressions for the footprint statistics are presented. The need to distinguish the instantaneous footprint, which is the area illuminated at a particular instant, from the composite footprint, which is the total area illuminated during the lifetime of the meteor trail, is explained. The statistics for the instantaneous and composite footprints have been found to be similar. The only significant difference lies in the parameter that represents the probability of two colocated receivers being in the same footprint. The composite footprint statistics can be used to calculate the space diversity gain of a multiple-receiver system. The instantaneous footprint statistics are useful in the evaluation of the interference probability in a network of meteor burst communication nodes.

Mui, S. Y.; Ellicott, R. C.

341

Statistical mechanics of polymer systems. Final  

SciTech Connect

Work on computer simulation of polymer dynamics and the statistical mechanics of quenched systems carried out over seven years with the support of this grant is reviewed. The computer simulation work has focused on elucidation the roles of the excluded volume and the nearest-neighbor attractive interactions in the dynamics of polymers. To study quenched systems we have applied the formalism suggested long ago by Mazo to two model systems and found qualitative agreement with the properties of real glasses.

Kovac, J.

1993-06-01

342

Accelerated molecular dynamics methods  

SciTech Connect

The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.

Perez, Danny [Los Alamos National Laboratory

2011-01-04

343

Statistical Inference Using Extreme Order Statistics  

Microsoft Academic Search

A method is presented for making statistical inferences about the upper tail of a distribution function. It is useful for estimating the probabilities of future extremely large observations. The method is applicable if the underlying distribution function satisfies a condition which holds for all common continuous distribution functions.

James Pickands III

1975-01-01

344

Statistical mechanics recycled  

Microsoft Academic Search

spinsystem with long-range interactions can be converted into a chaotic dynamical system that is differentiable and low-dimensional. The thermodynamic limit quantities of the spin system are then equivalent to lo ng time averages of the dynamical system. In this way the spin system averages can be recast as the cycle expansions. If the resulting dynamical system is analytic, the convergence

R. Mainieri

345

Bayesian Statistical Inference  

Microsoft Academic Search

\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a \\u000a Bayesian statistics is much more easily connected to the inferential problem of Schema (1.1) than \\u000a \\u000a \\u000a \\u000a \\u000a classical statistics. The feature that distinguishes \\u000a \\u000a \\u000a \\u000a \\u000a Bayesian statistical inference from \\u000a \\u000a \\u000a \\u000a \\u000a classical statistics is that it also employs probability assignments over \\u000a \\u000a \\u000a \\u000a \\u000a statistical hypotheses. It is therefore possible to present a \\u000a \\u000a \\u000a \\u000a \\u000a Bayesian statistical procedure as an inference concerning probability assignments over hypotheses. Recall that we called\\u000a the

Rolf Haenni; Jan-Willem Romeijn; Gregory Wheeler; Jon Williamson

346

MEDICAL LIBRARY STATISTICS.  

PubMed

Four compilations of medical library statistics have been published to date, namely those by Louise Darling in 1956, by the Medical Library Association in its 1959 Directory, by Harold Bloomquist in 1962, and by the author in 1964. In addition to these sources and to the annual statistics compiled by the Library Services Branch of the U. S. Office of Education, surveys of pharmacy, hospital, and medical society libraries have been completed recently. Standards for medical and special libraries are being considered by the Medical Library Association through its Guidelines Survey and by the Special Libraries Association through its Statistics Coordinating Project and its Standards Survey. To coordinate the collection of medical library statistics and to make the information readily available to the profession, it is suggested that the Medical Library Association support the collection and publication of statistics of representative medical libraries until such time as the Library Services Branch is able to implement fully its program of library statistics. PMID:14271113

KEENAN, E L

1965-04-01

347

Statistics and Data Analysis  

NSDL National Science Digital Library

This online introductory statistics textbook covers basic descriptive, statistical, and graphical procedures for analyzing data sets and contains three data sets and a practice final exam. Chapter headings include: descriptive statistics, probability, resampling, discrete probability models, continuous probability models, central limit theorem, confidence intervals, tests of hypotheses, estimation of effect: two independent samples, design of experiments, and regression. The relation to this site includes exercises.

Abebe, Asheber; Daniels, John E.; Mckean, Joe W.; Kapenga, J. A.

2008-12-19

348

Media Awareness Network: Statistics  

NSDL National Science Digital Library

The Canadian media conglomerate Cochran Communications has provided this compilation of statistics to heighten public awareness of the media industry. Statistics on radio, television, film, video, and Internet ownership, production, and marketing are given in a concise, browsable format. Although Canadian statistics are emphasized, many American and international figures are included and students may benefit from clear bibliographic and web links to a variety of government, think-tank, and news sources.

349

Statistics on the Web  

NSDL National Science Digital Library

This site, by SPSS statistician Clay Helberg, is a broad resource containing statistical information, brief descriptions of professional organizations, lists of email discussion groups, and links to online textbooks and courses. The heart of the site is the Educational Resources section, which offers links to valuable Websites that describe and demonstrate statistical techniques. For graduate students and researchers alike, this statistics resource is sure to come in handy.

350

Statistical Process Control  

NSDL National Science Digital Library

Statistical Process Control is a lesson plan which provides an overview of Statistical Process Control, showing the value of collecting and analyzing data that enables people to systematically analyze and improve a process. After completing this module, students should be able to construct and interpret different statistical charts in order to evaluate a process. Note: This module is part of a modularized manufacturing technology curriculum created by the PSCME, found at www.pscme.org/educators.html.

King, John; Imre, John; Devine, Craig

2010-09-02

351

Statistics and Graphing  

NSDL National Science Digital Library

Statistics play a vital role in the scientific enterprise. This activity provides background information and tutorials on basic statistics (mean, median, standard deviation, etc.) used in science. Topics include descriptive statistics (measures of central tendency and dispersion) and presenting data (tables, figures, and graphs). Sample datasets from actual scientific experiments are used to illustrate points. Links to an online statisitical tool and an online graphing application are also provided.

Laposata, Matt

352

Federal Law Enforcement Statistics  

NSDL National Science Digital Library

Supplies census statistics about federal employees with law enforcement authority. Provides additional information about the functionality, budget, expenditures, and staffing of federal crime labs and police departments.

Justice, U. S.

353

Simple Interactive Statistical Analysis  

NSDL National Science Digital Library

Simple Interactive Statistical Analysis (SISA), designed by a research consultant in the Netherlands, "allows you to do statistical analysis directly on the Internet." The program will calculate a variety of statistical procedures, including T-Tests, Poisson Distributions, and other calculations. The ability to perform analysis online provides users an opportunity to assess the software, which is also for sale. The Guide to Procedures provides helpful explanations of the different statistical procedures and guidelines for deciding on the appropriate procedure and filling out the calculation form. Numerous spreadsheets are also available to download.

354

Black hole statistics  

SciTech Connect

The quantum statistics of charged, extremal black holes is investigated beginning with the hypothesis that the quantum state is a functional on the space of closed three-geometries, with each black hole connected to an oppositely charged black hole through a spatial wormhole. From this starting point a simple argument is given that a collection of extremal black holes obeys neither Bose nor Fermi statistics. Rather, they obey an exotic variety of particle statistics known as infinite statistics'' which resembles that of distinguishable particles and is realized by a [ital q] deformation of the quantum commutation relations.

Strominger, A. (Institute for Theoretical Physics and Department of Physics, University of California (enSanta Barbara, Santa Barbara, California 93106 (United States)))

1993-11-22

355

Statistical Review - Cervarix  

Center for Biologics Evaluation and Research (CBER)

... Executive Summary Statement and Conclusion. The applicant addressed all major concerns related to assay validation statistics. ... More results from www.fda.gov/biologicsbloodvaccines/vaccines/approvedproducts

356

Dynamic heterogeneity in amorphous materials  

NASA Astrophysics Data System (ADS)

Amorphous solids are mechanically rigid while possessing a disordered structure similar to that of dense liquids. Recent research indicates that dynamical heterogeneity, spatio-temporal fluctuations in local dynamical behavior, might help understanding the statistical mechanics of glassy states.

Berthier, Ludovic

2011-05-01

357

Algorithmic Statistical Process Control: An Elaboration  

Microsoft Academic Search

Statistical process control (SPC) has traditionally been applied to processes in which successive observations would ideally be independent and identically distributed as a basis for achieving fundamental process improvement. Stochastic control, on the other hand, addresses situations in which observations are dynamically related over time; its intent is to run the existing process well, as opposed to improving it as

William T. Tucker; Frederick W. Faltin; Scott A. Vander Wiel

1993-01-01

358

Explorations in Statistics: Regression  

ERIC Educational Resources Information Center

|Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of "Explorations in Statistics" explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive…

Curran-Everett, Douglas

2011-01-01

359

Confound Those Speculative Statistics  

Microsoft Academic Search

Speculative statistics are model-based statistics. These include deaths attributable to being in a group (deaths linked to a distant cause). Such deaths are those due to primary smoke, second-hand smoke, obesity and radon. This paper reviews the epidemiological model used and introduces a graphical technique to present three big ideas: that a confounder can influence (1) an association in an

Milo Schield

2009-01-01

360

Statistical Applets: Confidence Intervals  

NSDL National Science Digital Library

Created by Duckworth, McCabe, Moore and Sclove for W.H. Freeman and Co., this applet is a visual representation of confidence levels and accompanies "ÃÂÃÂPractice of Business Statistics;" however, it can be used without this text. Even though brief, this is a nice interactive resource for an introductory statistics course.

Sclove, Stanley; Moore, David; Mccabe, George; Duckworth, William

2009-03-04

361

Explorations in Statistics: Power  

ERIC Educational Resources Information Center

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fifth installment of "Explorations in Statistics" revisits power, a concept fundamental to the test of a null hypothesis. Power is the probability that we reject the null hypothesis when it is false. Four things affect…

Curran-Everett, Douglas

2010-01-01

362

Statistical Methods and Linguistics  

Microsoft Academic Search

In the space of the last ten years, statistical methods have gone from being virtually unknown in computational linguistics to being a fundamental given. In 1996, no one can profess to be a computational linguist without a passing knowl- edge of statistical methods. HMM's are as de rigeur as LR tables, and anyone who cannot at least use the terminology

Steven Abney

1996-01-01

363

Bayesian statistics for parasitologists  

Microsoft Academic Search

Bayesian statistical methods are increasingly being used in the analysis of parasitological data. Here, the basis of differences between the Bayesian method and the classical or frequentist approach to statistical inference is explained. This is illustrated with practical implications of Bayesian analyses using prevalence estimation of strongyloidiasis and onchocerciasis as two relevant examples. The strongyloidiasis example addresses the problem of

Mar??a-Gloria Basáñez; Clare Marshall; Hélène Carabin; Theresa Gyorkos; Lawrence Joseph

2004-01-01

364

Water Quality Statistics  

ERIC Educational Resources Information Center

Water quality experiments, especially the use of macroinvertebrates as indicators of water quality, offer an ideal context for connecting statistics and science. In the STAR program for secondary students and teachers, water quality experiments were also used as a context for teaching statistics. In this article, we trace one activity that uses…

Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain

2004-01-01

365

Visualizing natural image statistics.  

PubMed

Natural image statistics is an important area of research in cognitive sciences and computer vision. Visualization of statistical results can help identify clusters and anomalies as well as analyze deviation, distribution, and correlation. Furthermore, they can provide visual abstractions and symbolism for categorized data. In this paper, we begin our study of visualization of image statistics by considering visual representations of power spectra, which are commonly used to visualize different categories of images. We show that they convey a limited amount of statistical information about image categories and their support for analytical tasks is ineffective. We then introduce several new visual representations, which convey different or more information about image statistics. We apply ANOVA to the image statistics to help select statistically more meaningful measurements in our design process. A task-based user evaluation was carried out to compare the new visual representations with the conventional power spectra plots. Based on the results of the evaluation, we made further improvement of visualizations by introducing composite visual representations of image statistics. PMID:23661013

Fang, Hui; Tam, Gary Kwok-Leung; Borgo, Rita; Aubrey, Andrew J; Grant, Philip W; Rosin, Paul L; Wallraven, Christian; Cunningham, Douglas; Marshall, David; Chen, Min

2013-07-01

366

Applied Statistics with SPSS  

ERIC Educational Resources Information Center

Accessibly written and easy to use, "Applied Statistics Using SPSS" is an all-in-one self-study guide to SPSS and do-it-yourself guide to statistics. What is unique about Eelko Huizingh's approach is that this book is based around the needs of undergraduate students embarking on their own research project, and its self-help style is designed to…

Huizingh, Eelko K. R. E.

2007-01-01

367

Explorations in Statistics: Correlation  

ERIC Educational Resources Information Center

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This sixth installment of "Explorations in Statistics" explores correlation, a familiar technique that estimates the magnitude of a straight-line relationship between two variables. Correlation is meaningful only when the…

Curran-Everett, Douglas

2010-01-01

368

Issues in Labor Statistics  

NSDL National Science Digital Library

The US Department of Labor Bureau of Labor Statistics collects "succinct, up-to-the-minute background papers on current topics" at the Issues in Labor Statistics publication page. Each two-page edition addresses labor topics as diverse as auto dealer employment and highway fatalities with graphical summaries and BLS contacts for additional information.

369

Understanding descriptive statistics  

Microsoft Academic Search

There is an increasing expectation that critical care nurses use clinical research when making decisions about patient care. This article is the second in a series which addresses statistics for clinical nursing practice. In this article we provide an introduction to the use of descriptive statistics. Concepts such as levels of measurement, measures of central tendency and dispersion are described

Murray J. Fisher; Andrea P. Marshall

2009-01-01

370

The Statistical Drake Equation  

Microsoft Academic Search

We provide the statistical generalization of the Drake equation.From a simple product of seven positive numbers, the Drake equation is now turned into the product of seven positive random variables. We call this “the Statistical Drake Equation”. The mathematical consequences of this transformation are then derived. The proof of our results is based on the Central Limit Theorem (CLT) of

Claudio Maccone

2010-01-01

371

Water Quality Statistics  

ERIC Educational Resources Information Center

|Water quality experiments, especially the use of macroinvertebrates as indicators of water quality, offer an ideal context for connecting statistics and science. In the STAR program for secondary students and teachers, water quality experiments were also used as a context for teaching statistics. In this article, we trace one activity that uses…

Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain

2004-01-01

372

Frequentist Statistical Inference  

Microsoft Academic Search

The relative-frequency view of probability leads to statistical inferences using hypothesis tests and confidence intervals. Parametric tests target inference on distribution parameters, whereas nonparametric tests may relate to any sample statistic of interest. Special problems arise for correlated data, and for multiple simultaneous inferences (“field significance”).

D. S. Wilks

2011-01-01

373

Statistical Mapping by Computer.  

ERIC Educational Resources Information Center

The function of a statistical map is to provide readers with a visual impression of the data so that they may be able to identify any geographic characteristics of the displayed phenomena. The increasingly important role played by the computer in the production of statistical maps is manifested by the varied examples of computer maps in recent…

Utano, Jack J.

374

Statistical Tables Calculator  

NSDL National Science Digital Library

This page, created by Ino Dinov of the University of California, Berkeley, provides distribution calculators for the binomial, normal, Student's T, Chi-square, and Fisher's F distributions. Users set the parameters and enter either the probability or the test statistic and the calculators return the missing value. This is a simple, yet effective, statistical tool for instructors and students.

Dinov, Ivo

2009-01-20

375

Reform in Statistical Education  

ERIC Educational Resources Information Center

|Two questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed…

Huck, Schuyler W.

2007-01-01

376

Statistical Summaries: Public Institutions.  

ERIC Educational Resources Information Center

|This document, presents a statistical portrait of the Virginia's 17 public higher education institutions. Data provided include: enrollment figures (broken down in categories such as sex, residency, full- and part-time status, residence, ethnicity, age, and level of postsecondary education); FTE figures; admissions statistics (such as number…

Virginia State Council of Higher Education, Richmond.

377

Application Statistics, 1974.  

ERIC Educational Resources Information Center

|Statistics on application and registration patterns of applicants wishing to pursue full-time study in first-year places in the Ontario universities were obtained throughout the admission cycle from the processing of applicants by the Center and from the universities themselves. All application and registration statistics presented refer to…

Payton, L. C.

378

RECONCEPTUALISING 'STATISTICS' AND 'EDUCATION  

Microsoft Academic Search

Although most interesting problems are multivariate (MV) and students and citizens need to be able to reason using MV data, appropriate challenges are rarely encountered in class. In this paper we argue that the curriculum (and ideas about statistical literacy) should encompass reasoning with MV data. Statistics education can occur in a range of disciplines, and in informal settings -

Jim Ridgway; James Nicholson; Sean McCusker

379

Hate Crime Statistics, 1998.  

National Technical Information Service (NTIS)

Statistical publications like Hate Crime Statistics are designed to be factual presentations of data. Their purpose is not to evoke emotion, make pleas, or sway opinion. The neat columns and rows of numbers in this book cannot convey the suffering experie...

1998-01-01

380

Reform in Statistical Education  

ERIC Educational Resources Information Center

Two questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed…

Huck, Schuyler W.

2007-01-01

381

Elementary Concepts in Statistics  

NSDL National Science Digital Library

This introductory statistics introduction, by StatSoft, gives an overview of variables, classifications, measurements, relations, and other basic statistical concepts. There are also two animated graphs illustrating density and distribution functions, as well as how sample size influences sampling distribution.

2008-12-25

382

DISABILITY STATISTICS CENTER  

EPA Science Inventory

The purpose of the Disability Statistics Center is to produce and disseminate statistical information on disability and the status of people with disabilities in American society and to establish and monitor indicators of how conditions are changing over time to meet their health...

383

JSTOR: Statistical Science  

NSDL National Science Digital Library

This journals from The Institute of Mathematical Statistics is now available online. Statistical Science, Vols. 1-12 (1986-1997) is fully accessible to the hundreds of academic institutions participating in JSTOR. The journal may be searched by keyword, full-text, title, author, and abstract, or browsed by date of publication. A list of JSTOR participants is provided at the JSTOR site.

1999-01-01

384

Family Violence Statistics Including Statistics on Strangers and Acquaintances.  

National Technical Information Service (NTIS)

This compendium contains the most recent family violence statistics from these sources: surveys conducted by the Bureau of Justice Statistics (BJS), the BJS database of Federal statistics, and two statistical databases maintained by the FBI. The sources p...

2005-01-01

385

Australian Bureau of Statistics  

NSDL National Science Digital Library

For those looking for statistical information on a broad set of themes and geographical areas within Australia, they should visit the Australian Bureau of Statistics Web site. From the main page, visitors can view recent statistical reports, such as the Australian Consumer Price Index, information about the labor force (e.g., employment rates), and a series of occasional papers. Particularly helpful to the casual user will be the Themes section, which provides summary statistics about the environment, tourism, transportation, economic well-being, and education. Additionally, the Bureau publishes reports organized by administrative and regional divisions of the country, a feature that will be helpful to students doing research on a particular area of the country. If users are seeking to learn more about the organization, history, and mission of the Australian Bureau of Statistics, they will find this material located under the About the ABS section of the site.

2000-01-01

386

UCLA Statistics Series  

NSDL National Science Digital Library

The University of California Los Angeles Statistics Series presents a collection of more than 250 preprints covering a wide array of statistical topics, such as descriptive multivariate analysis, advanced linear models, survey construction and analysis, teaching statistics, and much more. The preprints are arranged by paper number only, hence users must browse the entire list to locate relevant items. Approximately half of the full-text preprints are accessible in HTML, .pdf, or postscript formats. To access preprints not available electronically, users must contact the authors of the papers; author addresses are provided.

387

Statistics and Probability Tutorial  

NSDL National Science Digital Library

This tutorial, created by Harvey Berman of Stat Trek, provides a basic introduction to many topics in statistics and probability. Topics include: sets and subsets, statistical experiments, counting, basic probability rules, Bayes' theorem, probability distributions, discrete versus continuous, binomial, negative binomial, hypergeometric, multinomial, Poisson, normal, sampling theory, central tendency, variability, sampling distributions, t-distribution, Chi-square distribution, F-distribution, estimation problems, hypothesis testing, power, survey sampling, simple random samples, stratified samples, cluster samples, sample size. This is a general overview of statistics and probability. It is geared towards a high school advanced placement level.

Berman, Harvey

2009-08-06

388

Learning Statistics Online: Tools for Teaching Science Methods and Statistics  

NSDL National Science Digital Library

The Utah online Virtual Lab is a JAVA program run dynamically off a database. Instructors author a statistical virtual reality simulating theories and data in a specific research focus area by defining independent, predictor, and dependent variables and the relations among them. Students work in an online virtual environment to discover the principles of this simulated reality: they go to a library, read theoretical overviews and scientific puzzles, and then go to a lab, design a study, collect and analyze data, and write a report. A student's design and data analysis decisions are computer-graded and recorded in a database; the written research report can be read by the instructor or by other students in peer groups simulating scientific conventions.

2008-10-27

389

Dynamical Systems in Neuropharmacology.  

National Technical Information Service (NTIS)

Quantitative techniques found to be useful in characterizing the complex attractors of dynamical systems and the non-convergent distribution functions of statistical hierarchies were applied to the problem of drug-induced phase-transitions in patterns of ...

M. A. Geyer A. J. Mandell

1992-01-01

390

Tools for Network Dynamics  

Microsoft Academic Search

Networks have been studied mainly by statistical methods which em- phasize their topological structure. Here one collects some mathematical tools and results which might be useful to study both the dynamics of

R. VILELA MENDES

2005-01-01

391

Labor Market Dynamics, Hawaii.  

National Technical Information Service (NTIS)

The Hawaii Labor Market Dynamics report focuses on significant labor market statistics and trends affecting Hawaiis economy in 2010. In addition to highlighting job trends over the past year and reporting anticipated short- and long-term job forecasts, st...

2011-01-01

392

STATISTICAL REVIEW AND EVALUATION  

Center for Biologics Evaluation and Research (CBER)

Text Version... of the Cochran-Mantel-Haenszel [CMH] test adjusted for the baseline NYHA class and using the mean score statistics with modified ridit scores. ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

393

Statistical Resampling Plans.  

National Technical Information Service (NTIS)

Statistical resampling plans can be thought of as procedures for 'recycling data.' They commonly involve computer-intensive methods for the interrogation of data through repeated inspection. The procedures detailed in this document free the data analyst f...

M. S. Taylor

1998-01-01

394

Statistics at Square One  

NSDL National Science Digital Library

Statistics at Square One "was one of the best selling statistical text books in the UK," and it has been revised for this online edition. It was written from a medical statistics perspective, and hence many of the examples involve health related topics. Despite this recurring focus, no prior medical knowledge is required and the book can be used by anyone to learn the fundamentals of statistics. Basic concepts such as confidence intervals, correlation, and standard deviation are clearly defined and illustrated in the text. Each chapter concludes with a number of sample exercises; solutions to these problems are provided, but unfortunately there is little explanation accompanying the solutions. In most cases, however, the chapter's contents provide all the information necessary to complete the problems.

Swinscow, T. D. V. (Thomas Douglas Victor)

395

Plague Maps and Statistics  

MedlinePLUS

... statement CDC Emergency Preparedness and Response Maps and Statistics Plague in the United States Plague was first ... Contact Us: Centers for Disease Control and Prevention Bacterial Diseases Branch Foothills Campus Fort Collins, CO 80521 ...

396

Data and Statistics  

MedlinePLUS

... 31% indicated they had received a doctor's recommendation. Economic Cost The annual medical care and surgical costs ... Cereals with Folic Acid Data and Statistics Research Global Initiative Articles & Key Findings Recommendations Free Materials Links ...

397

Embedded Statistical Profiling.  

National Technical Information Service (NTIS)

Embedded Statistical Profiling is an initiative to support both offensive and defensive computer network applications. The basis for the effort comprises the development of an environment framework known as Simplified Protocol Capture (SIMPCAP). The envir...

M. Corley

2007-01-01

398

Introduction to Weibull Statistics.  

National Technical Information Service (NTIS)

This report describes Weibull statistics with particular reference to the analysis of data obtained from mechanical tests on brittle materials. The basic equations are all derived from first principles and the construction and use of Weibull Probability G...

P. M. Braiden

1975-01-01

399

Introduction to Weibull Statistics.  

National Technical Information Service (NTIS)

Weibull statistics are described with particular reference to the analysis of data obtained from mechanical tests on brittle materials. The basic equations are all derived from principles and the construction and use of Weibull Probability Graphs are desc...

P. M. Braiden

1975-01-01

400

Understanding Solar Flare Statistics  

NASA Astrophysics Data System (ADS)

A review is presented of work aimed at understanding solar flare statistics, with emphasis on the well known flare power-law size distribution. Although avalanche models are perhaps the favoured model to describe flare statistics, their physical basis is unclear, and they are divorced from developing ideas in large-scale reconnection theory. An alternative model, aimed at reconciling large-scale reconnection models with solar flare statistics, is revisited. The solar flare waiting-time distribution has also attracted recent attention. Observed waiting-time distributions are described, together with what they might tell us about the flare phenomenon. Finally, a practical application of flare statistics to flare prediction is described in detail, including the results of a year of automated (web-based) predictions from the method.

Wheatland, M. S.

2005-12-01

401

International petroleum statistics report.  

National Technical Information Service (NTIS)

The International Petroleum Statistic Report, a monthly publication, presents data on international oil production, demand, imports, exports, and stocks. The four sections of this April 1995 report are as follows: time series data on world oil production ...

1995-01-01

402

Relativistic Statistical Thermodynamics.  

National Technical Information Service (NTIS)

The formalism of relativistic statistical mechanics, developed in previous papers, provides a very straightforward proof of the Lorentz invariance of the canonical equilibrium distribution function. This theorem automatically determines the Lorentz transf...

R. Balescu

1968-01-01

403

UNCTAD statistical pocketbook  

SciTech Connect

This book provides basic statistics on income, population, production and trade - including balance of payments, commodities and commodity markets - of the developing countries. Date is given up to 1982/83.

Not Available

1984-01-01

404

National Statistics Online  

NSDL National Science Digital Library

Perhaps you have a burning desire to find detailed statistical information about agriculture in Wales, or even about poverty in London's East End. All of this information can be found on the very thorough and usable National Statistics homepage, which provides information on Britain's economy, population, and society. Given the amount of information on the site, visitors would do well to look through the UK at a Glance area. Here they will find basic information on the gross domestic product, consumer spending, unemployment, and population estimates. Along with these aggregate figures for the entire nation, visitors can visit the neighborhood statistics section, where they can retrieve summary statistics for different locales around England and Wales. A number of fine reports based on the 2001 Census are also available for the general public's consideration, and they include considerations of the state of children's dental health to the provisioning of programs for the elderly.

405

Alaska Commercial Fisheries Statistics.  

National Technical Information Service (NTIS)

The following statistical reports and booklets were compiled, published, and distributed: (1) 1973 Alaska commercial fishing vessel register; (2) Weekly Alaska Salmon casepack reports; (3) Monthly Alaska shellfish reports; (4) Alaska tables for the INPFC ...

J. F. Jewell

1974-01-01

406

Probability and Statistical Inference  

Microsoft Academic Search

These lectures introduce key concepts in probability and statistical inference at a level suitable for graduate students in particle physics. Our goal is to paint as vivid a picture as possible of the concepts covered.

Harrison B. Prosper

2006-01-01

407

Agricultural Statistics 1994  

NSDL National Science Digital Library

The United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) has made full text of "Agricultural Statistics 1994" available via its Web site. Agricultural Statistics is an annual compendium of data (and selected charts) relating to all aspects of the U.S. agricultural economy. Subject coverage includes all major crop and livestock sectors, farm income and credit, stabilization and price support, agricultural conservation and forestry statistics, and fertilizers and pesticides, among others. Tables include both state and national breakdowns, and most national tables include between two and ten year time series. The book is available as one large Adobe Acrobat .PDF file (about 5 megabytes), so you'll need a fast connection to get it. You'll also need a free Acrobat Reader, which can be obtained at the same page. Acrobat allows selective searching for specific tables, as well as selective printing of those tables. (See Network Tools, below.)

1994-01-01

408

Statistics of Mass Production.  

National Technical Information Service (NTIS)

This paper summarizes the statistical quality control methods and procedures that can be employed in mass producing electronic parts (integrated circuits, buffers, capacitors, connectors) to reduce variability and ensure performance to specified radiation...

R. L. Williams W. Y. Gateley

1993-01-01

409

Statistical MIMO Radar.  

National Technical Information Service (NTIS)

Inspired by recent advances in multiple-input multiple-output (MIMO) communications, we introduce the statistical MIMO radar concept. Unlike beamforming, array radar, or STAP, which presuppose a high correlation between signals either transmitted or recei...

A. Haimovich E. Fishler R. Blum D. Chizhik R. Valenzuela

2004-01-01

410

Cooperative Learning in Statistics.  

ERIC Educational Resources Information Center

Formal use of cooperative learning techniques proved effective in improving student performance and retention in a freshman level statistics course. Lectures interspersed with group activities proved effective in increasing conceptual understanding and overall class performance. (11 references) (Author)

Keeler, Carolyn M.; And Others

1994-01-01

411

Titanic: A Statistical Exploration.  

ERIC Educational Resources Information Center

|Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)|

Takis, Sandra L.

1999-01-01

412

Epilepsy and Seizure Statistics  

MedlinePLUS

... Facebook MySpace Delicous Stumble Digg More... Epilepsy and Seizure Statistics Epilepsy and seizures affect nearly 3 million ... seizures and epilepsy in the United States: Incidence -- Seizures: 300,000 people have a first convulsion each ...

413

Probability Gate Statistics.  

National Technical Information Service (NTIS)

A probability gate presents a fixed but controllable transmission probability p to pulses arriving at its input. This report describes some statistical properties of the transformation imposed by a gate on the input distribution of interpulse intervals. T...

J. N. Cronholm

1970-01-01

414

Statistical mechanics of viscoelasticity  

SciTech Connect

A unified treatment of viscoelasticity is developed in the framework of nonequilibrium classical statistical mechanics. An exact correspondence between Mori's continued-fractions formalism and rheological circuits is shown.

Bavaud, F.

1987-02-01

415

Metropolitan Statistical Areas, 1983.  

National Technical Information Service (NTIS)

All metropolitan area definitions were reconsidered in the course of this revision process (which takes place every ten years), and certain terminology changes were also made. The previous term Standard Metropolitan Statistical Area is being shortened to ...

1983-01-01

416

203985 Everolimus Statistical BPCA  

Center for Drug Evaluation (CDER)

Text Version... from current submission showed that there is a statistically significant difference in the overall SEGA response rate as per central radiology review. ... More results from www.fda.gov/downloads/drugs/developmentapprovalprocess

417

Statistical Geneticist: Janet Sinsheimer  

NSDL National Science Digital Library

This is a PDF interview, PowerPoint slide set, and webpage biography of a statistical geneticist, detailing the importance of scientists fluent in the analysis of numbers to organize data and design studies.

2012-05-02

418

Statistics for anthropologists  

Microsoft Academic Search

David Hurst Thomas. Figuring Anthropology: First Principles of Probability and Statistics. New York: Holt, Rinehart and Winston, 1976. xi + 532 pp. Tables, figures, appendix, exercises, references, and index. $13.50.

Michael C. Robbins

1976-01-01

419

J-Adaptive Estimation with Estimated Noise Statistics.  

National Technical Information Service (NTIS)

The J-adaptive sequential estimator is extended to include simultaneous estimation of the noise statistics in a model for system dynamics. This extension completely automates the estimator, eliminating the requirement of an analyst in the loop. Simulation...

A. H. Jazwinski C. Hipkins

1973-01-01

420

United Nations Global Statistics  

NSDL National Science Digital Library

This UN directory site allows users to quickly access national statistics through the official outlets of UN-member states and international statistics through dozens of UN programs and agencies as well as autonomous organizations such as the World Trade Organization and Eurostat. Data covered include, but are not limited to, health care, economics, politics, environment, and social demographics. The site offers a simple search engine with Boolean capabilities and is updated on a biweekly basis.

Division., United N.

421

A Statistic on Involutions  

Microsoft Academic Search

We define a statistic, called weight, on involutions and consider two applications in which this statistic arises. Let I(n) denote the set of all involutions on [n](={1,2,..., n}) and let F(2n) denote the set of all fixed point free involutions on [2n]. For an involution ?, let |?| denote the number of 2-cycles in ?. Let[ n]q=1+q+?+qn-1 and let \\u000a

Rajendra S. Deodhar; Murali K. Srinivasan

2001-01-01

422

Environmental Quality Statistics  

NSDL National Science Digital Library

Hosted by the Council on Environmental Quality (CEQ), this site contains updated monthly tables with statistics about United States environmental quality. The major topics covered in these tables are population, economy and the environment, public lands, ecosystems, air quality, aquatic resources, terrestrial resources, pollution prevention, energy, transportation, and the global environment. The tables indicate data sources, and an archive of statistics for earlier years is provided.

423

Statistical Data Sets  

NSDL National Science Digital Library

This collection of datasets from the University of Massachusetts at Amherst is categorized by topic. Each dataset and its description are in text format. Topics include: analysis of variance, analysis of covariance, cluster analysis, contingency table analysis, correlation analysis, descriptive statistics, discriminant analysis, factor analysis, nonparametric analysis, multiple regression, nonlinear regression, logistic regression, survival analysis, and time series analysis. This is a large collection of data and software which can be implemented into different aspects of statistical study.

2009-01-23

424

Introduction to Descriptive Statistics  

NSDL National Science Digital Library

This tutorial, authored by Jay Hill of the University of Illinois at Urbana-Champaign, introduces mean, median, mode, variance, and standard deviation using sports statistics from the Internet and class-generated statistics. Students should understand stem-and-leaf plots before using this tutorial. This material is intended for class use. Excel spreadsheets with sample data are also available for download. The relation links to a letter for teachers.

Hill, Jay

2009-01-19

425

History of production statistics  

SciTech Connect

This work covers the history of production statistics for the states of Alabama, Alaska, Arizona, Arkansas, California, Colorado, Florida, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Viriginia, West Viriginia, and Wyoming. The following statistics are presented: annual oil production, percentage of US total production, producing oil wells at year-end, oil production, and annual gas production.

Not Available

1981-12-01

426

Statistical instability of barrier microdischarges operating in townsend regime  

SciTech Connect

The dynamics of barrier microdischarges operating in a Townsend regime is studied analytically and via kinetic particle-in-cell/Monte Carlo simulations. It is shown that statistical fluctuations of the number of charged particles in the discharge gap strongly influence the dynamics of natural oscillations of the discharge current and may even lead to a disruption of the discharge. Analysis of the statistical effects based on a simple model is suggested. The role of external sources in stabilizing microdischarges is clarified.

Nagorny, V. P. [Plasma Dynamics Corporation, Waterville, Ohio 43566-1062 (United States)

2007-01-15

427

Defending America: Why We Still Need SDI.  

National Technical Information Service (NTIS)

Since its creation by an Act of Congress in 1950, Civil Defense or CD has had what might be called a 'mission Impossible.' With fewer that 400 fulltime employees and a barebones budget - $138 million for fiscal year 1992, or about 1/20th of 1% of the Pent...

P. C. Clarke

1992-01-01

428

ABM treaty and the SDI program  

SciTech Connect

Included are statements by Ambassador Paul H. Nitze, Special Advisor to the President and Secretary of State on Arms Control Matters, and Abraham D. Sofaer, Legal Adviser, before the Subcommittee on Arms Control, International Security, and Science of the House Foreign Affairs Committee, Washington, DC, October 22, 1985

Not Available

1985-01-01

429

Statistical Mechanics of a Discrete Nonlinear System  

SciTech Connect

Statistical mechanics of the discrete nonlinear Schroedinger equation is studied by means of analytical and numerical techniques. The lower bound of the Hamiltonian permits the construction of standard Gibbsian equilibrium measures for positive temperatures. Beyond the line of T={infinity} , we identify a phase transition through a discontinuity in the partition function. The phase transition is demonstrated to manifest itself in the creation of breatherlike localized excitations. Interrelation between the statistical mechanics and the nonlinear dynamics of the system is explored numerically in both regimes. (c) 2000 The American Physical Society.

Rasmussen, K. Oe.; Cretegny, T.; Kevrekidis, P. G.; Groenbech-Jensen, Niels

2000-04-24

430

Statistical mechanics of a discrete nonlinear system  

SciTech Connect

Statistical mechanics of the discrete nonlinear Schroedinger equation is studied by means of analytical and numerical techniques. The lower bound of the Hamiltonian permits the construction of standard Gibbsian equilibrium measures for positive temperatures. Beyond the line of T=infinity, we identify a phase transition, through a discontinuity in the partition function. The phase transition is demonstrated to manifest itself in the creation of breather-like localized excitations. Interrelation between the statistical mechanics and the nonlinear dynamics of the system is explored numerically in both regimes.

Rasmussen, K.O.; Cretegny, T.; Kevrekidis, P.G.; Gronbech-Jensen, Niels

1999-09-01

431

Spectral Reduction: A Statistical Description of Turbulence  

SciTech Connect

A method is described for predicting statistical properties of turbulence. Collections of Fourier amplitudes are represented by nonuniformly spaced modes with enhanced coupling coefficients. The statistics of the full dynamics can be recovered from the time-averaged predictions of the reduced model. A Liouville theorem leads to inviscid equipartition solutions. Excellent agreement is obtained with two-dimensional forced-dissipative pseudospectral simulations. For the two-dimensional enstrophy cascade, logarithmic corrections to the high-order structure functions are observed. (c) 1999 The American Physical Society.

Bowman, John C. [Department of Mathematical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1 (Canada); Shadwick, B. A. [The Institute for Advanced Physics, Conifer, Colorado 80433-7727 (United States); Physics Department, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Morrison, P. J. [Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712-1081 (United States)

1999-12-27

432

Statistical Physics of Fracture  

SciTech Connect

Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.

Alava, Mikko [Helsinki University of Technology, Helsinki, Finland; Nukala, Phani K [ORNL; Zapperi, Stefano [University of La Sapienza, Rome

2006-05-01

433

Implications of quantum theory in the foundations of statistical mechanics  

Microsoft Academic Search

An investigation is made into how the foundations of statistical mechanics are aected once we treat classical mechanics as an approximation to quantum mechanics in certain domains rather than as a theory in its own right; this is necessary if we are to understand statistical-mechanical systems in our own world. Relevant structural and dynamical dierences are identified between classical and

David Wallace

434

Optimizing Statistical Information Extraction Programs over Evolving Text  

Microsoft Academic Search

Statistical information extraction (IE) programs are increasingly used to build real-world IE systems such as Alibaba, Cite Seer, Kylin, and YAGO. Current statistical IE approaches consider the text corpora underlying the extraction program to be static. However, many real-world text corpora are dynamic (documents are inserted, modified, and removed). As the corpus evolves, and IE programs must be applied repeatedly

Fei Chen; Xixuan Feng; Christopher Re; Min Wang

2012-01-01

435

A DP based Search Algorithm for Statistical Machine Translation  

Microsoft Academic Search

We introduce a novel search algorithm for statistical machine translation based on dynamic programming (DP). During the search process two statistical knowledge sources are combined: a translation model and a bigram language model. This search algorithm expands hypotheses along the positions of the target string while guaranteeing progressive coverage of the words in the source string. We present experimental results

Sonja Nießen; Stephan Vogel; Hermann Ney; Christoph Tillmann

1998-01-01

436

Statistical bandwidth sharing: a study of congestion at flow level  

Microsoft Academic Search

In this paper we study the statistics of the realized throughput of elastic document transfers, accounting for the way network bandwidth is shared dynamically between the randomly varying number of concurrent flows. We first discuss the way TCP realizes statistical bandwidth sharing, illustrating essential properties by means of packet level simulations. Mathematical flow level models based on the theory of

Slim Ben Fredj; Thomas Bonald; Alexandre Proutiére; G. Régnié; James W. Roberts

2001-01-01

437

Statistical Understanding Made Simple  

NSDL National Science Digital Library

Teaching statistics can be tough for even experienced instructors, so it is nice to learn about the Statistical Understanding Made Simple (SUMS) website. Created by researchers at the University of Glasgow, the site helps users build "interactive, fun and highly effective tutorials designed to help students understand basic statistics." Visitors who wish to have the resource generator create tutorials will need to register on the site and provide a small data set. Of course, visitors can also check out the "Ready Made Tutorials" area, where they will discover projects that examine the relationship between height and weight and the effect of cognitive behavioral therapy on depression. Additionally, the site also contains several games which students can use to explore the effects of standard deviation and histograms.

438

National Transportation Statistics 2001  

NSDL National Science Digital Library

Released in July 2002, this 431-page document prepared by the United States Bureau of Transportation Statistics contains almost every piece of aggregate data on transportation imaginable. While going through the entire document may be a challenge, the report is divided into more readily digestible sections such as Transportation System, Transportation Safety, and Transportation and the Economy. The majority of the report consists of tables and charts that summarize a variety of transportation statistics, such as Retail New Passenger Car Sales, Principal Means of Transportation to Work, and Railroad Passenger Safety Data. This exhaustive survey of the United States transportation system will be most helpful to those doing research in the field of transportation policy or those just looking for useful statistics.

2002-01-01

439

Statistical reconstruction of qutrits  

SciTech Connect

We discuss a procedure of measurement followed by the reproduction of the quantum state of a three-level optical system--a frequency--and spatially degenerate two-photon field. The method of statistical estimation of the quantum state based on solving the likelihood equation and analyzing the statistical properties of the obtained estimates is developed. Using the root approach of estimating quantum states, the initial two-photon state vector is reproduced from the measured fourth moments in the field. The developed approach applied to quantum-state reconstruction is based on the amplitudes of mutually complementary processes. The classical algorithm of statistical estimation based on the Fisher information matrix is generalized to the case of quantum systems obeying Bohr's complementarity principle. It has been experimentally proved that biphoton-qutrit states can be reconstructed with the fidelity of 0.995-0.999 and higher.

Bogdanov, Yu.I.; Chekhova, M.V.; Krivitsky, L.A.; Kulik, S.P.; Penin, A.N.; Zhukov, A.A.; Kwek, L.C.; Oh, C.H.; Tey, M.K. [Russian Control System Agency, Angstrem', Moscow 124460 (Russian Federation); Department of Physics, Moscow M.V. Lomonosov State University, 119992 Moscow (Russian Federation); National Institute of Education Nanyang Technological University, 637616 Singapore (Singapore); Department of Physics, Faculty of Science, National University of Singapore, 117542 Singapore (Singapore)

2004-10-01

440

Patients and Medical Statistics  

PubMed Central

BACKGROUND People are increasingly presented with medical statistics. There are no existing measures to assess their level of interest or confidence in using medical statistics. OBJECTIVE To develop 2 new measures, the STAT-interest and STAT-confidence scales, and assess their reliability and validity. DESIGN Survey with retest after approximately 2 weeks. SUBJECTS Two hundred and twenty-four people were recruited from advertisements in local newspapers, an outpatient clinic waiting area, and a hospital open house. MEASURES We developed and revised 5 items on interest in medical statistics and 3 on confidence understanding statistics. RESULTS Study participants were mostly college graduates (52%); 25% had a high school education or less. The mean age was 53 (range 20 to 84) years. Most paid attention to medical statistics (6% paid no attention). The mean (SD) STAT-interest score was 68 (17) and ranged from 15 to 100. Confidence in using statistics was also high: the mean (SD) STAT-confidence score was 65 (19) and ranged from 11 to 100. STAT-interest and STAT-confidence scores were moderately correlated (r=.36, P<.001). Both scales demonstrated good test–retest repeatability (r=.60, .62, respectively), internal consistency reliability (Cronbach's ?=0.70 and 0.78), and usability (individual item nonresponse ranged from 0% to 1.3%). Scale scores correlated only weakly with scores on a medical data interpretation test (r=.15 and .26, respectively). CONCLUSION The STAT-interest and STAT-confidence scales are usable and reliable. Interest and confidence were only weakly related to the ability to actually use data.

Woloshin, Steven; Schwartz, Lisa M; Welch, H Gilbert

2005-01-01

441

Pattern Analysis and Statistical Learning  

NASA Astrophysics Data System (ADS)

This chapter presents the fundamentals of statistical pattern recognition and statistical learning. First, we present the general framework of a statistical pattern recognition system and discuss pattern representation and classification, two important components of such a system. Second, we introduce the concept of statistical learning and examine the three main approaches to statistical learning: supervised learning, semi-supervised learning, and unsupervised learning.

Zheng, Nanning; Xue, Jianru

442

Query languages for statistical databases  

Microsoft Academic Search

Statistical database management systems keep raw, elementary and\\/or aggregated data and include query languages with facilities to calculate various statistics from this data. In this article we examine statistical database query languages with respect to the criteria identified and taxonomy developed in Ozsoyoglu and Ozsoyoglu (1985b). The criteria include statistical metadata and objects, aggregation features and interface to statistical packages.

Abdullah Uz Tansel

1995-01-01

443

Statistical Signal Processing  

NASA Astrophysics Data System (ADS)

The transfer of acoustic information can be represented as consisting of three parts: the source, the medium, and the receiver. The transmitted information (signal) arrives at the receiver distorted by the medium and corrupted by noise. Thus, even when the signal is deterministic in nature, a complete description of the received signal must be a statistical one. That is to say, any processing carried out on the received energy must contain the best characterization of the distortion by the medium and corruption by the noise that is available, and this can only be done in terms of statistics.

Sullivan, Edmund J.

444

Singular statistics revised  

NASA Astrophysics Data System (ADS)

In this paper, we analyze the 'singular statistics' of pseudointegrable Šeba billiards, i.e. billiards perturbed by zero-range perturbations. We have shown that the computation of a spectrum is reduced to the calculation of the uniquely defined renormalized Green's function. We relate a spectrum of the billiard to the scattering length, which is the only parameter describing the perturbation. We show that taking into account the growing number of resonances, one observes a transition from 'semi-Poissonian'-like statistics to Poissonian. This observation is in agreement with the argument that a classical particle does not feel a point perturbation.

Tudorovskiy, T.; Kuhl, U.; Stöckmann, H.-J.

2010-12-01

445

Interactive Business Statistics  

NSDL National Science Digital Library

This collection of applets, created by McGraw-Hill Higher Education, is designed illustrate key concepts described in "Statistical Techniques for Business and Economics," but does not require use of this textbook. Topics include: mean, median, mode, skewness, probability, probability distribution, comparing binomial distribution, normal distribution, central limit theorem, confidence intervals, ANOVA, simple linear regression, multiple linear regression, chi-square, Pareto charts, and time series forecasting. This is a nice collection of statistics modules. Although it was created in conjunction with a textbook, this resource is still free from the publisher.

2011-09-19

446

Noise, Statistics, and Signal Transduction in Non-Linear Systems  

Microsoft Academic Search

We show that Stochastic Resonance (SR), a phenomenon of improvement of signal transduction by addition of noise to the input signal, allows simple statistical explanation. The SR has been demonstrated in dynamical systems ranging from glaciers to models of neurons and also found in a number of non-dynamical systems with and without thresholds. In search for the interpretation of this

Sergey Bezrukov; Igor Vodyanoy

2000-01-01

447

Equations of motion in nonequilibrium statistical mechanics for nonextensive systems  

Microsoft Academic Search

Recent investigations of nanoscale quantum device systems and small clusters of atoms and molecules have shown new features of both nonequilibrium dynamics and nonextensivity. The challenge is to understand theoretically the fast dynamical processes on time scales of femtoseconds in these systems. An overview of the approaches to time-dependent nonequilibrium statistical mechanics, including a critical review of the entropic methods

A. K. Rajagopal

1998-01-01

448

Statistical modeling of cross-coupling effects in VLSI interconnects  

Microsoft Academic Search

In this paper, we develop an approach for statistical modeling of crosstalk noise and dynamic delay degradation in coupled RC interconnects under process variations. The proposed model enables closed-form computation of mean and variance of noise peak and worst case dynamic delay for given variabilities in physical dimensions. We compare the proposed model against HSPICE Monte Carlo simulations and report

Mridul Agarwal; Kanak Agarwal; Dennis Sylvester; David Blaauw

2005-01-01

449

Statistical Mechanics of Metallic Glasses and Liquids  

SciTech Connect

It is difficult to formulate the statistical mechanical theory of liquids and glasses, because phonons, which are the basis for the statistical mechanics of lattice dynamics in crystals, are strongly scattered and have a very short lifetime in liquids and glasses. Instead computer simulation and the free-volume theory are most frequently used in explaining experimental results on metallic glasses. However, both of them suffer from serious problems as discussed in this paper. We propose an alternative approach based upon the dynamics of the atomic level stresses. We review recent progress with this approach, and show that it is possible to calculate thermodynamic quantities, including the glass transition temperature and the kinetics of structural relaxation by this approach.

Egami, Takeshi [ORNL; Levashov, Valentin A [ORNL; Morris, James R [ORNL; Haruyama, O. [Tokyo University of Science, Japan

2010-01-01

450

Statistics and Nuclear Reactions  

Microsoft Academic Search

It is possible to apply statistical methods to the calculation of nuclear processes provided that the energies involved are large in comparison with the lowest excitation energies of nuclei. Expressions are obtained for the emission probability of neutrons or charged particles by highly excited heavy nuclei. These expressions are built up in a similar way to the formula for the

V. Weisskopf

1937-01-01

451

OECD Statistics Portal  

NSDL National Science Digital Library

As part of its mission, the Organisation for Economic Cooperation and Development (OECD) collects various statistics needed to create reports for both its member nations and the general public. Visitors can browse a variety of data sets as well as download data in Excel file format. A useful glossary is also provided.

452

Selected Manpower Statistics.  

ERIC Educational Resources Information Center

This document contains summaries of basic manpower statistical data for the Department of Defense, with the Army, Navy, Marine Corps, and Air Force totals shown separately and collectively. Included are figures for active duty military personnel, civilian personnel, reserve components, and retired military personnel. Some of the data show…

Office of the Assistant Secretary of Defense -- Comptroller (DOD), Washington, DC.

453

Statistics of Pi Mesons  

Microsoft Academic Search

By analyzing the decay of the tau+ meson, evidence for the boson character of pi+ mesons is obtained which is independent of the Pauli relation between spin and statistics. The usual Dalitz-Fabri expansion in angular momentum eigenfunctions is made, with the important difference that only antisymmetric states are allowed for the two like pions. The matrix elements and pi- distributions

Billy S. Thomas; Wendell G. Holladay

1958-01-01

454

Library Research and Statistics.  

ERIC Educational Resources Information Center

|These nine articles discuss research and statistics on libraries and librarianship, including libraries in the United States, Canada, and Mexico; acquisition expenditures in public, academic, special, and government libraries; price indexes; state rankings of public library data; library buildings; expenditures in school library media centers;…

Lynch, Mary Jo; St. Lifer, Evan; Halstead, Kent; Fox, Bette-Lee; Miller, Marilyn L.; Shontz, Marilyn L.

2001-01-01

455

Statistical origin of gravity  

SciTech Connect

Starting from the definition of entropy used in statistical mechanics we show that it is proportional to the gravity action. For a stationary black hole this entropy is expressed as S=E/2T, where T is the Hawking temperature and E is shown to be the Komar energy. This relation is also compatible with the generalized Smarr formula for mass.

Banerjee, Rabin; Majhi, Bibhas Ranjan [S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata-700098 (India)

2010-06-15

456

An Interactive Statistics Package.  

National Technical Information Service (NTIS)

An interactive statistics package of programs designed for use by research personnel. For data sets of up to 15 variables and 250 observations, data editing and standard data transformations plus the following analyses may be performed: t-tests, chi-squar...

1979-01-01

457

Statistical origin of gravity  

NASA Astrophysics Data System (ADS)

Starting from the definition of entropy used in statistical mechanics we show that it is proportional to the gravity action. For a stationary black hole this entropy is expressed as S=E/2T, where T is the Hawking temperature and E is shown to be the Komar energy. This relation is also compatible with the generalized Smarr formula for mass.

Banerjee, Rabin; Majhi, Bibhas Ranjan

2010-06-01

458

American Indian Population Statistics.  

ERIC Educational Resources Information Center

|This report summarizes American Indian and Alaska Native (AI/AN) population statistics from the 1990 Census. In 1990 there were about 2 million persons who identified themselves as American Indians in the United States, a 38 percent increase over the 1980 census. More than half of the Indian population lived in six states, with Oklahoma having…

Thomason, Timothy C., Ed.

459

Learning Statistical Concepts  

ERIC Educational Resources Information Center

|In order to learn the concept of statistical techniques one needs to run real experiments that generate reliable data. In practice, the data from some well-defined process or system is very costly and time consuming. It is difficult to run real experiments during the teaching period in the university. To overcome these difficulties, statisticians…

Akram, Muhammad; Siddiqui, Asim Jamal; Yasmeen, Farah

2004-01-01

460

Quartiles in Elementary Statistics  

ERIC Educational Resources Information Center

|The calculation of the upper and lower quartile values of a data set in an elementary statistics course is done in at least a dozen different ways, depending on the text or computer/calculator package being used (such as SAS, JMP, MINITAB, "Excel," and the TI-83 Plus). In this paper, we examine the various methods and offer a suggestion for a new…

Langford, Eric

2006-01-01

461

Statistical Reasoning over Lunch  

ERIC Educational Resources Information Center

|Students in the 21st century are exposed daily to a staggering amount of numerically infused media. In this era of abundant numeric data, students must be able to engage in sound statistical reasoning when making life decisions after exposure to varied information. The context of nutrition can be used to engage upper elementary and middle school…

Selmer, Sarah J.; Bolyard, Johnna J.; Rye, James A.

2011-01-01

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