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1

SDI: Statistical dynamic interactions  

SciTech Connect

We focus on the combined statistical and dynamical aspects of heavy ion induced reactions. The overall picture is illustrated by considering the reaction {sup 36}Ar + {sup 238}U at a projectile energy of 35 MeV/nucleon. We illustrate the time dependent bound excitation energy due to the fusion/relaxation dynamics as calculated with the Boltzmann master equation. An estimate of the mass, charge and excitation of an equilibrated nucleus surviving the fast (dynamic) fusion-relaxation process is used as input into an evaporation calculation which includes 20 heavy fragment exit channels. The distribution of excitations between residue and clusters is explicitly calculated, as is the further deexcitation of clusters to bound nuclei. These results are compared with the exclusive cluster multiplicity measurements of Kim et al., and are found to give excellent agreement. We consider also an equilibrated residue system at 25% lower initial excitation, which gives an unsatisfactory exclusive multiplicity distribution. This illustrates that exclusive fragment multiplicity may provide a thermometer for system excitation. This analysis of data involves successive binary decay with no compressional effects nor phase transitions. Several examples of primary versus final (stable) cluster decay probabilities for an A = 100 nucleus at excitations of 100 to 800 MeV are presented. From these results a large change in multifragmentation patterns may be understood as a simple phase space consequence, invoking neither phase transitions, nor equation of state information. These results are used to illustrate physical quantities which are ambiguous to deduce from experimental fragment measurements. 14 refs., 4 figs.

Blann, M.; Mustafa, M.G. (Lawrence Livermore National Lab., CA (USA)); Peilert, G.; Stoecker, H.; Greiner, W. (Frankfurt Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)

1991-04-01

2

Statistics on Depository Institutions (SDI)  

NSDL National Science Digital Library

New from the FDIC, the Statistics on Depository Institutions is an advanced feature of the FDIC's Institutional Directory system; SDI will help users create detailed financial reports, by either choosing between 24 predefined financial information reports or building their own custom reports. The criteria of the report may include "any combination of single FDIC-insured institutions or bank holding companies, custom peer groups of FDIC-insured institutions or bank holding companies, or standard peer groups of FDIC-insured institutions." A detailed FAQ offers help on creating reports and explains some of the terminology.

3

Statistics of football dynamics  

NASA Astrophysics Data System (ADS)

We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by q-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.

Mendes, R. S.; Malacarne, L. C.; Anteneodo, C.

2007-06-01

4

Statistics of football dynamics  

E-print Network

We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by $q$-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.

Mendes, R S; Anteneodo, C

2007-01-01

5

SDI a model for chaos  

SciTech Connect

The model discussed seems to indicate that if SDI evolves to the points where the defense can overwhelm the offense, the result is a crisis-unstable international system that cannot be mathematically distinguished from a system of war. SDI's acting as envisioned by its supporters does not provide the stable security desired by all. Previous independent qualitative discussions by both US and Soviet analysts have indicated the same instability for SDI. An effective SDI may be very desirable once it is completely in place and functioning, but the process of putting it into place, starting from the present world configuration, seems to be very dangerous. If the proposed defense looks as though it is going to become able to overcome the opponent's offense, then in a crisis, one side is likely to use its offense rather than chance losing it - the very definition of crisis stability. The similarity of the predictions made here and by the US and Soviet analysts concerning the results of SDI deployment lends credence to the forecasts and their underlying assumptions. It appears that SDI cannot be deployed to force major reductions in the offensive strategic nuclear weapons of the superpowers without jeopardizing stability.

Saperstein, A.M.

1988-10-01

6

SDI - pie in the sky  

SciTech Connect

Proponents of the controversial Strategic Defense Initiatives (SDI)reverse arrowfeel that the will to succeed will be as significant a factor as capability in their effort to make defense a popular concept. They reject the idea that a defensive system must be perfect, and want to loosen the hold of the Anti-Ballistic Missile (ABM) Treaty and Salt II. More than an improvement to deterrence, the goal of SDI is to make a technological leap over the Soviet Union to make its military investments obsolete. Scientists find research on defensive weapons more rewarding than work on offensive systems. Critics need to understand that the force of SDI is ideological in that it rejects the concept of mutually assured destruction (MAD) and concedes that nuclear war is possible.

Arkin, W.M.

1984-04-01

7

A User- Dependent SDI System  

ERIC Educational Resources Information Center

A large-scale selective dissemination of information (SDI) system which is in operation at the Agricultural Research Service is described. The unique characteristic of this system is that the users develop and modify their own profiles. The implications of this user-dependent approach for information system planners are discussed. (2 references)…

Burton, Hilary D.

1973-01-01

8

Statistics as a dynamical attractor  

E-print Network

It is demonstrated that any statistics can be represented by an attractor of the solution to a corresponding systen of ODE coupled with its Liouville equation. Such a non-Newtonian representation allows one to reduce foundations of statistics to better established foundations of ODE. In addition to that, evolution to the attractor reveals possible micro-mechanisms driving random events to the final distribution of the corresponding statistical law. Special attention is concentrated upon the power law and its dynamical interpretation: it is demonstrated that the underlying dynamics supports a " violent reputation" of the power law statistics.

Michail Zak

2012-08-30

9

SDI CFD MODELING ANALYSIS  

SciTech Connect

The Savannah River Remediation (SRR) Organization requested that Savannah River National Laboratory (SRNL) develop a Computational Fluid Dynamics (CFD) method to mix and blend the miscible contents of the blend tanks to ensure the contents are properly blended before they are transferred from the blend tank; such as, Tank 50H, to the Salt Waste Processing Facility (SWPF) feed tank. The work described here consists of two modeling areas. They are the mixing modeling analysis during miscible liquid blending operation, and the flow pattern analysis during transfer operation of the blended liquid. The transient CFD governing equations consisting of three momentum equations, one mass balance, two turbulence transport equations for kinetic energy and dissipation rate, and one species transport were solved by an iterative technique until the species concentrations of tank fluid were in equilibrium. The steady-state flow solutions for the entire tank fluid were used for flow pattern analysis, for velocity scaling analysis, and the initial conditions for transient blending calculations. A series of the modeling calculations were performed to estimate the blending times for various jet flow conditions, and to investigate the impact of the cooling coils on the blending time of the tank contents. The modeling results were benchmarked against the pilot scale test results. All of the flow and mixing models were performed with the nozzles installed at the mid-elevation, and parallel to the tank wall. From the CFD modeling calculations, the main results are summarized as follows: (1) The benchmark analyses for the CFD flow velocity and blending models demonstrate their consistency with Engineering Development Laboratory (EDL) and literature test results in terms of local velocity measurements and experimental observations. Thus, an application of the established criterion to SRS full scale tank will provide a better, physically-based estimate of the required mixing time, and elevation of transfer pump for minimum sludge disturbance. (2) An empirical equation for a tank with no cooling coils agrees reasonably with the current modeling results for the dual jet. (3) From the sensitivity study of the cooling coils, it was found that the tank mixing time for the coiled tank was about two times longer than that of the tank fluid with no coils under the 1/10th scale, while the coiled tank required only 50% longer than the one without coils under the full scale Tank 50H. In addition, the time difference is reduced when the pumping U{sub o}d{sub o} value is increased for a given tank. (4) The blending time for T-shape dual jet pump is about 20% longer than that of 15{sup o} upward V-shape pump under the 1/10th pilot-scale tank, while the time difference between the two pumps is about 12% for the full-scale Tank 50H. These results are consistent with the literature information. (5) A transfer pump with a solid-plate suction screen operating at 130 gpm can be located 9.5 inches above settled sludge for 2 in screen height in a 85 ft waste tank without disturbing any sludge. Detailed results are summarized in Table 13. Final pump performance calculations were made by using the established CW pump design, and operating conditions to satisfy the two requirements of minimum sludge disturbance, and adequate blending of tank contents. The final calculation results show that the blending times for the coiled and uncoiled tanks coupled with the CW pump design are 159 and 83 minutes, respectively. All the results are provided in Table 16.

Lee, S.

2011-05-05

10

The Evaluation of SISMAKOM (Computerized SDI Project).  

ERIC Educational Resources Information Center

A survey of 88 users of SISMAKOM, a computerized selective dissemination of information (SDI) and document delivery service provided by the Universiti Sains Malaysia and four other Malaysian universities, was conducted in August 1982 in order to collect data about SISMAKOM and to assess the value of a computerized SDI service in a developing…

University of Science, Penang (Malaysia).

11

Statistical Mechanics of Dynamical Systems  

NASA Astrophysics Data System (ADS)

A statistical-mechanical formalism of chaos based on the geometry of invariant sets in phase space is discussed to show that chaotic dynamical systems can be treated by a formalism analogous to that of thermodynamic systems if one takes a relevant coarse-grained quantity, but their statistical laws are quite different from those of thermodynamic systems. This is a generalization of statistical mechanics for dealing with dissipative and hamiltonian (i.e., conservative) dynamical systems of a few degrees of freedom. Thus the sum of the local expansion rate of nearby orbits along relevant orbit over a long but finite time has been introduced in order to describe and characterize (1) a drastic change of the structure of a chaotic attractor at a bifurcation and anomalous phenomena associated, (2) a critical scaling of chaos in the neighborhood of a critical point for the bifurcation to a nonexotic state, and a self-similar temporal structure of a critical orbit on the critical 2^? attractor an the critical golden tori without mixing, (3) the critical KAM torus, diffusion and repeated sticking of a chaotic orbit to a critical torus in hamiltonian systems. Here a q-phase transition, analogous to the ferromagnetic phase transition, plays an important role. They are illustrated numerically and theoretically by treating the driven damped pendulum, the driven Duffing equation, the Henon map, and the dissipative and conservative standard maps. This description of chaos breaks the time-reversal symmetry of hamiltonian dynamical laws analogously to statistical mechanics of irreversible processes. The broken time-reversal symmetry is brought about by orbital instability of chaos.

Mori, H.; Hata, H.; Horita, T.; Kobayashi, T.

12

Grumman and SDI-related technology  

Microsoft Academic Search

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

1985-01-01

13

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

14

Socratic Dialog-Inducing (SDI) Labs  

NSDL National Science Digital Library

SDI Labs are "guided construction" labs featuring hands-and-heads-on experiments in introductory mechanics. Their effectiveness in promoting student crossover to the the Newtonian World has been demonstrated by rigorous pre-post testing. Seven labs and references are included.

Hake, Richard

2003-10-10

15

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

16

Statistical dynamics of religion evolutions  

E-print Network

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, beside the well accepted "at birth" attachement 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, Marcel

2008-01-01

17

Multifragmentation at intermediate energy: Dynamics or statistics  

SciTech Connect

In this report the authors consider two contradictory claims that have been advanced recently: (1) the claim for a predominantly dynamical fragment production mechanism; and (2) the claim for a dominant statistical and thermal process. They present a new analysis in terms of Poissonian reducibility and thermal scaling, which addresses some of the criticisms of the binomial analysis.

Beaulieu, L.; Phair, L.; Moretto, L.G.; Wozniak, G.J.

1998-01-01

18

Geometrically Frustrated Antiferromagnets: Statistical Mechanics and Dynamics  

Microsoft Academic Search

\\u000a These lecture notes provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical\\u000a and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in\\u000a which the results provide an understanding of some of the main observed properties of these systems.

John T. Chalker

19

Geometrically frustrated antiferromagnets: statistical mechanics and dynamics  

Microsoft Academic Search

These lecture notes are intended to provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in which the results provide an understanding of some of the main observed properties of these systems.

J. T. Chalker

2009-01-01

20

Geometrically Frustrated Antiferromagnets: Statistical Mechanics and Dynamics  

NASA Astrophysics Data System (ADS)

These lecture notes provide a simple overview of the physics of geometrically frustrated magnets. The emphasis is on classical and semiclassical treatments of the statistical mechanics and dynamics of frustrated Heisenberg models, and on the ways in which the results provide an understanding of some of the main observed properties of these systems.

Chalker, John T.

21

Lost in space: SDI struggles through its sixth year  

SciTech Connect

After six years of debate, it is clear that Congress is willing to support a robust research program for SDI, but it is also clear that Congress will not support SDI annual outlays on the order of $10 billion. Thus the policy choice is between a good research program that meshes with fiscal reality, or an inadequate and wasteful development program that continues to focus on preparing for a Phase I deployment for which the funds simply will not be available. The Bush administration so far seems trapped by its own rhetoric from coming to grips with the implications of the new SDI reality. The responsibility for getting SDI on a steadier course toward more realistic research objectives thus seems to lie with Congress in the near term. Since Congress has been reluctant to earmark SDI research funds for specific objectives, it will take a change in administration perceptions before SDI program goals can be changed away from Phase I deployment. The only likely way this could happen in the near term would be as a result of a Congress-executive branch summit agreement on SDI objectives and funding levels. In the absence of such an agreement, SDI will be sailing under ever weaker fiscal and political winds and runs the risk of finding itself becalmed, working ceaselessly toward goals that will never be fulfilled.

MacDonald, B.W.

1989-09-01

22

Scaling SDI Systems via Query Clustering and Aggregation  

Microsoft Academic Search

XML-based Selective Dissemination of Information (SDI) systems aims to quickly deliver useful information to the users based on their profiles or user subscriptions. These subscriptions are specified in the form of XML queries. This paper investigates how clustering and aggregation of user queries can help scale SDI systems by reducing the number of document-subscription matchings required. We design a new

Xi Zhang; Liang Huai Yang; Mong-li Lee; Wynne Hsu

2004-01-01

23

Statistical Properties of the Cluster Dynamics of the Systems of Statistical Mechanics  

E-print Network

Statistical Properties of the Cluster Dynamics of the Systems of Statistical Mechanics A. Gabrielov dynamics was shown to exist in the one-dimensional sys- tems of statistical mechanics in [S1]. Consider "dynamical" explanation of irreversibility. The StoÃ?anzahlsatz can be applied to any system of statistical

Gabrielov, Andrei

24

Barotropic Vortex Dynamics and Statistical Mechanics-application to  

E-print Network

Barotropic Vortex Dynamics and Statistical Mechanics- application present a equilibrium statistical mechanics model for the BVE, known as the Spherical model, where will focus on the variational analysis of the BVE; the second part summarizes a recent statistical

Lim, Chjan C.

25

High statistics measurements of pedestrian dynamics  

E-print Network

Understanding the complex behavior of pedestrians walking in crowds is a challenge for both science and technology. In particular, obtaining reliable models for crowd dynamics, capable of exhibiting qualitatively and quantitatively the observed emergent features of pedestrian flows, may have a remarkable impact for matters as security, comfort and structural serviceability. Aiming at a quantitative understanding of basic aspects of pedestrian dynamics, extensive and high-accuracy measurements of pedestrian trajectories have been performed. More than 100.000 real-life, time-resolved trajectories of people walking along a trafficked corridor in a building of the Eindhoven University of Technology, The Netherlands, have been recorded. A measurement strategy based on Microsoft Kinect\\texttrademark has been used; the trajectories of pedestrians have been analyzed as ensemble data. The main result consists of a statistical descriptions of pedestrian characteristic kinematic quantities such as positions and fundamen...

Corbetta, Alessandro; Muntean, Adrian; Toschi, Federico

2014-01-01

26

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

27

Artificial intelligence applications in space and SDI: A survey  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to survey existing and planned Artificial Intelligence (AI) applications to show that they are sufficiently advanced for 32 percent of all space applications and SDI (Space Defense Initiative) software to be AI-based software. To best define the needs that AI can fill in space and SDI programs, this paper enumerates primary areas of research and lists generic application areas. Current and planned NASA and military space projects in AI will be reviewed. This review will be largely in the selected area of expert systems. Finally, direct applications of AI to SDI will be treated. The conclusion covers the importance of AI to space and SDI applications, and conversely, their importance to AI.

Fiala, Harvey E.

1988-01-01

28

UNL Researchers Studying SDI Technology Near Clay Center  

E-print Network

researchers have been burying plastic drip irrigation tubing in fields near Clay Center to get a better idea be assessed and best management practices can be developed for SDI-irrigated corn. "Burying the drip lines

Nebraska-Lincoln, University of

29

Air Force Satellite Control Network and SDI development  

NASA Astrophysics Data System (ADS)

The Air Force Satellite Control Network (AFSCN) represents a military, worldwide network of control centers and remote tracking sites (RTS). A relatively large and growing constellation of DOD satellites is supported. The near term and long term plans for the AFSCN are discussed, taking into account also the impact of the Space Defense Initiative (SDI) on the AFSCN. It is pointed out that the SDI adds a new dimension to the support provided by the AFSCN to the DOD satellites, because some SDI scenarios being considered include many more satellite platforms, each containing multiple kinetic energy weapons. Space-ground link sites are discussed along with AFSCN control sites, and communication between RTS and control centers. Attention is given to changing roles and responsibilities, the Satellite Test Center (STC) as an excellent site for the R and D phase of SDI development, and an operational concept for a highly proliferated weapons platforms architecture, and goals of developing more survivable satellite systems.

Bleier, T.

30

Teachers' Use of Transnumeration in Solving Statistical Tasks with Dynamic Statistical Software  

ERIC Educational Resources Information Center

This study examined a random stratified sample (n = 62) of teachers' work across eight institutions on three tasks that utilized dynamic statistical software. We considered how teachers may utilize and develop their statistical knowledge and technological statistical knowledge when investigating a statistical task. We examined how teachers…

Lee, Hollylynne S.; Kersaint, Gladis; Harper, Suzanne R.; Driskell, Shannon O.; Jones, Dusty L.; Leatham, Keith R.; Angotti, Robin L.; Adu-Gyamfi, Kwaku

2014-01-01

31

Statistical dynamics of continuous systems: perturbative and approximative approaches  

E-print Network

We discuss general concept of Markov statistical dynamics in the continuum. For a class of spatial birth-and-death models, we develop a perturbative technique for the construction of statistical dynamics. Particular examples of such systems are considered. For the case of Glauber type dynamics in the continuum we describe a Markov chain approximation approach that gives more detailed information about statistical evolution in this model.

Dmitri Finkelshtein; Yuri Kondratiev; Oleksandr Kutoviy

2014-02-07

32

Submitted to the Annals of Applied Statistics STATISTICAL ANALYSIS OF A DYNAMIC MODEL FOR  

E-print Network

of developing probabilistic methods for quantitative risk assessment, refer to [5; 14; 20; 41]. HenceSubmitted to the Annals of Applied Statistics STATISTICAL ANALYSIS OF A DYNAMIC MODEL FOR DIETARY ParisTech and INRA-M´et@risk This paper is devoted to the statistical analysis of a stochastic model

Del Moral , Pierre

33

SMOOTH DYNAMICS AND NEW THEORETICAL IDEAS IN NONEQUILIBRIUM STATISTICAL MECHANICS.  

E-print Network

SMOOTH DYNAMICS AND NEW THEORETICAL IDEAS IN NONEQUILIBRIUM STATISTICAL MECHANICS. by David Ruelle, and Gibbs, consists of two rather different parts: equilibrium and nonequilibrium statistical mechanics. The success of equilibrium statistical mechanics has been spectacular. It has been developed to a high degree

34

Statistical Mechanics of Recurrent Neural Networks II Dynamics  

E-print Network

CHAPTER 15 Statistical Mechanics of Recurrent Neural Networks II ± Dynamics A.C.C. COOLEN none- quilibrium statistical mechanical techniques, is the sequel of [1], which was devoted to solving networks and their properties. Equilibrium statistical mechanical techniques can provide much detailed quan

Coolen, ACC "Ton"

35

SMOOTH DYNAMICS AND NEW THEORETICAL IDEAS IN NONEQUILIBRIUM STATISTICAL MECHANICS.  

E-print Network

SMOOTH DYNAMICS AND NEW THEORETICAL IDEAS IN NONEQUILIBRIUM STATISTICAL MECHANICS. by David Ruelle, and Gibbs, consists of two rather di#11;erent parts: equilibrium and nonequilibrium statistical mechanics. The success of equilibrium statistical mechanics has been spectacular. It has been developed to a high degree

Ruelle, David

36

LDSG Workshop on Stochastic Dynamics and Nonequilibrium Statistical Mechanics  

E-print Network

LDSG Workshop on Stochastic Dynamics and Nonequilibrium Statistical Mechanics Organisers: Rosemary the same predictive power as that of equilibrium statistical mechanics? Though most researchers in statistical mechanics would hope and conjecture that the answer is yes, we do not have at present

Wright, Francis

37

Dynamic statistics of crayfish caudal photoreceptors.  

PubMed

Crayfish caudal photoreceptor units were monitored during transient and steady-state responses to light stimuli (step on, step off). A statistical analysis of interpulse interval distributions during quasi-stationary time periods was carried out. Firing statistics during transient conditions were superposable with statistics under whatever steady stimulation produced the same firing rate, indicating that mean firing rate is a sufficient statistic. Distributions encountered formed a continuum of possible shapes. Considerable variation in shape was found with temperature and also among species, with Orconectes clarkii tending to fire more regularly than Orconectes virilis. Some properties of O. virilis statistics are described, including a linear relation between mean and standard deviation, and a tendency for intervals to be nonindependent. The data are considered as constraints on closed form models of the photoreceptor nerve pulse generator. PMID:6035125

Hermann, H T; Olsen, R E

1967-05-01

38

Dynamic Statistics of Crayfish Caudal Photoreceptors  

PubMed Central

Crayfish caudal photoreceptor units were monitored during transient and steady-state responses to light stimuli (step on, step off). A statistical analysis of interpulse interval distributions during quasi-stationary time periods was carried out. Firing statistics during transient conditions were superposable with statistics under whatever steady stimulation produced the same firing rate, indicating that mean firing rate is a sufficient statistic. Distributions encountered formed a continuum of possible shapes. Considerable variation in shape was found with temperature and also among species, with Orconectes clarkii tending to fire more regularly than Orconectes virilis. Some properties of O. virilis statistics are described, including a linear relation between mean and standard deviation, and a tendency for intervals to be nonindependent. The data are considered as constraints on closed form models of the photoreceptor nerve pulse generator. PMID:6035125

Hermann, Howard T.; Olsen, Richard E.

1967-01-01

39

Different Fatigue Dynamics Under Statistically and Spectrally Similar Deterministic and  

E-print Network

Different Fatigue Dynamics Under Statistically and Spectrally Similar Deterministic and Stochastic dynamics is essential for fatigue failure prediction. A new experimental system-- coupling structural and crack growth dynamics--was used to show fatigue damage accumulation is different under chaotic (i

Chelidze, David

40

Summary of Twenty Years of Kansas SDI Research  

Microsoft Academic Search

This paper will summarize research efforts with subsurface drip irrigation in Kansas that have occurred during the period 1989 through 2009. Special emphasis will be made on brief summaries of the different types of research that have been conducted including water and nutrient management for the principal crops of the region, SDI design parameters and system longevity and economics. Annual

Danny H. Rogers; Extension Agricultural Engineer

41

Twenty Years of Progress with SDI in Kansas  

Microsoft Academic Search

This paper will summarize research efforts with subsurface drip irrigation in Kansas that have occurred during the period 1989 through 2009. Special emphasis will be made on brief summaries of the different types of research that have been conducted including water and nutrient management for the principal crops of the region, SDI design parameters and system longevity and economics. Annual

Danny H. Rogers; Extension Agricultural Engineer

42

Twenty-One Years of SDI Research in Kansas  

Microsoft Academic Search

This paper will summarize research efforts with subsurface drip irrigation in Kansas that has occurred during the period 1989 through 2009. Special emphasis will be made on brief summaries of the different types of research that have been conducted including water and nutrient management for the principal crops of the region, SDI design parameters and system longevity and economics. Annual

Freddie R. Lamm; Danny H. Rogers; Mahbub Alam; Daniel M. O'Brien; Todd P. Trooien

2010-01-01

43

Air Force Satellite Control Network and SDI development  

Microsoft Academic Search

The Air Force Satellite Control Network (AFSCN) represents a military, worldwide network of control centers and remote tracking sites (RTS). A relatively large and growing constellation of DOD satellites is supported. The near term and long term plans for the AFSCN are discussed, taking into account also the impact of the Space Defense Initiative (SDI) on the AFSCN. It is

T. Bleier

1985-01-01

44

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

45

Dynamical Ensembles in Nonequilibrium Statistical Mechanics  

Microsoft Academic Search

Ruelle's principle for turbulence leading to what is usually called the Sinai-Ruelle-Bowen (SRB) distribution is applied to the statistical mechanics of many particle systems in nonequilibrium stationary states. A specific prediction, obtained without the need to construct explicitly the SRB itself, is shown to be in agreement with a recent computer experiment on a strongly sheared fluid. This presents the

G. Gallavotti; E. G. D. Cohen

1995-01-01

46

Statistical visual-dynamic model for hand-eye coordination  

Microsoft Academic Search

This paper introduces a new statistical method for combining vision and robot dynamics to generate trajectories to intercept a moving object. Previous methods only use information from the kinematics without considering the forces needed to move along the trajectory. Using robot dynamics allows extra measures, such as energy efficiency, to be optimised alongside maximising the likelihood of intercepting the target.

Daniel Beale; Pejman Iravani; Peter Hall

2010-01-01

47

Photon Counts Statistics in Leukocyte Cell Dynamics  

NASA Astrophysics Data System (ADS)

In the present experiment ultra-weak photon emission/ chemiluminescence from isolated neutrophils was recorded. It is associated with the production of reactive oxygen species (ROS) in the "respiratory burst" process which can be activated by PMA (Phorbol 12-Myristate 13-Acetate). Commonly, the reaction is demonstrated utilizing the enhancer luminol. However, with the use of highly sensitive photomultiplier equipment it is also recorded without enhancer. In that case, it can be hypothesized that photon count statistics may assist in understanding the underlying metabolic activity and cooperation of these cells. To study this hypothesis leukocytes were stimulated with PMA and increased photon signals were recorded in the quasi stable period utilizing Fano factor analysis at different window sizes. The Fano factor is defined by the variance over the mean of the number of photon within the observation time. The analysis demonstrated that the Fano factor of true signal and not of the surrogate signals obtained by random shuffling increases when the window size increased. It is concluded that photon count statistics, in particular Fano factor analysis, provides information regarding leukocyte interactions. It opens the perspective to utilize this analytical procedure in (in vivo) inflammation research. However, this needs further validation.

van Wijk, Eduard; van der Greef, Jan; van Wijk, Roeland

2011-12-01

48

Nonequilibrium Statistical Mechanics and Thermodynamics from Darwinian Dynamics: a Primer  

E-print Network

We present here an exploration on on the physical implications of the Darwinian dynamics. We first show that how the nonequilibrium statistical mechanics emerges naturally. We then show that the first three laws of the thermodynamics, the Zeroth Law, the First Law and the Second Law can be followed from the Darwinian dynamics, except the Third Law. The inability to derive the Third Law indicates that the Darwinian dynamics belongs to the "classical" domain. Specifically, the Second Law is proved from the dynamical point of view. Two types of current dynamical equalities are explicitly discussed in the paper: one is based on Feynman-Kac formula and one is a generalization of the Einstein relation. Both are directly accessible to experimental tests. Our demonstration indicates that the Darwinian dynamics is logically a simple and straightforward starting point to get into thermodynamics and is complementary to the conservative dynamics dominated in physics.

Ao, P

2005-01-01

49

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

50

A Dynamical System Having Deterministic Behavior Governed by Statistics  

Microsoft Academic Search

We describe a holographic optoelectronic circuit whose dynamics to lowest order is described by a Lotka-Volterra system in which the parameters are determined by the second- and fourth- order statistical moments of a collection of input signals. The system is multistable, metastable, or monostable, depending on whether the input signal statistical fourth moments are sub-Gaussian, Gaussian, super-Gaussian, or a mixture

Martha-Elizabeth Baylor; Dana Anderson; Zoya Popovic

2007-01-01

51

Application of classical statistical mechanics to multifractals and dynamical systems  

E-print Network

Classical, self-consistent theory of statistical mechanics was developed for the thermodynamic and conservative Hamiltonian systems. Later there were many attempts (Sinai-Bowen-Ruelle's temperature, Tsallis' non-extensive theory) to apply similar formalism to non-Hamiltonian dynamical systems. Although these theories reveal aspects of complex behavior, they have limited applicability. This paper applies the classical Gibbs-Boltzmann statistical mechanics to complex systems such as i.i.d. processes, multifractals, and non-Hamiltonian dynamical systems with strange attractors. The effective thermolization of stochastic noise in the system is introduced and the formalism of a ruling (governing, free energy) potential is developed.

S. G. Abaimov

2008-05-03

52

A statistical–dynamical method for predicting estuary morphology  

Microsoft Academic Search

A statistical–dynamical model for estuary morphodynamics is presented and demonstrated with a case study on the Humber Estuary,\\u000a UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach.\\u000a The modelling methodology uses an inverse technique to construct an unknown source function in the model-governing equation,\\u000a using historic measurements of estuary bathymetry.

Dominic E. Reeve; Harshinie Karunarathna

2011-01-01

53

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 mechanics. 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

1998-01-01

54

PRELIMINARY RESULTS OF STATISTICAL DYNAMIC EXPERIMENTS ON A HEAT EXCHANGER  

Microsoft Academic Search

The inherent noise signals present in a heat exchanger were recorded and ; analyzed in order to determine some of the statistical dynamic characteristics of ; the heat exchanger. Preliminary results show that the primary-side temperature ; frequency response may be determined by analyzing the inherent noise. The ; secondary-side temperature frequency response and cross-coupled-temperature ; frequency responses between primary

E. R. Corran; J. D. Cummins

1962-01-01

55

Statistical analysis of a dynamic model for dietary contaminant exposure  

E-print Network

for quantitative risk assessment, refer to Boon et al. [2003], Edler et al. [2002], Gibney and van der Voet [2003Statistical analysis of a dynamic model for dietary contaminant exposure Patrice Bertail MODAL ParisTech - UMR541, 46 rue Barrault, 75634 Paris cedex 13, France Jessica Tressou Unit�e INRA Met@risk

Paris-Sud XI, Université de

56

Geometry and Dynamics in Zero Temperature Statistical Mechanics Models  

E-print Network

We consider several models whose motivation arises from statistical mechanics. We begin by investigating some families of distributions of translation invariant subgraphs of some Cayley graphs, and in particular subgraphs of the square lattice. We then discuss some properties of the Spin-Glass model in that lattice. We continue in describing some properties of the Spin-Glass models in some other graphs. The last two parts of this work are devoted to the understanding of two dynamical processes on graphs. The first one is the well known zero-temperature Glauber dynamics on some families of graphs. The second dynamics, which we call the Loop Dynamics, is a natural generalization of the zero-temperature Glauber dynamics, which appears to have some interesting properties. We analyzed some of its properties for planar lattices, though the exact same techniques are applied for larger families of graphs as well.

Ran J Tessler

2010-08-31

57

Suppressing speckle noise for simultaneous differential extrasolar planet imaging (SDI) at the VLT and MMT  

Microsoft Academic Search

We discuss data reduction techniques and results from the Simultaneous Differential Imager (SDI) implemented at the VLT (Lenzen et al. 2004a) and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 mum methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in

Beth A. Biller; Laird Close; Rainer Lenzen; Wolfgang Brandner; Donald W. McCarthy; Eric Nielsen; Markus Hartung

2004-01-01

58

Statistical Computations Underlying the Dynamics of Memory Updating  

PubMed Central

Psychophysical and neurophysiological studies have suggested that memory is not simply a carbon copy of our experience: Memories are modified or new memories are formed depending on the dynamic structure of our experience, and specifically, on how gradually or abruptly the world changes. We present a statistical theory of memory formation in a dynamic environment, based on a nonparametric generalization of the switching Kalman filter. We show that this theory can qualitatively account for several psychophysical and neural phenomena, and present results of a new visual memory experiment aimed at testing the theory directly. Our experimental findings suggest that humans can use temporal discontinuities in the structure of the environment to determine when to form new memory traces. The statistical perspective we offer provides a coherent account of the conditions under which new experience is integrated into an old memory versus forming a new memory, and shows that memory formation depends on inferences about the underlying structure of our experience. PMID:25375816

Gershman, Samuel J.; Radulescu, Angela; Norman, Kenneth A.; Niv, Yael

2014-01-01

59

Balanced excitation and inhibition lead to statistical and dynamical criticality  

NASA Astrophysics Data System (ADS)

We present a simple abstract model, an anti-Hebbian network which spontaneously poises itself, by balancing excitation and inhibition, at a dynamically critical state: an extensive number of degrees of freedom approach Hopf bifurcations, becoming arbitrarily sensitive to external perturbations (PRL 102, 258102 - 2009). As the dynamics controlling this state has itself a marginal fixed point, the eigenvalues fluctuate close to the imaginary axis; when they become slightly unstable, the corresponding mode ``breaks out'' and becomes more prominent, and as they become slightly stable the mode slowly damps out. This breakout dynamics displays avalanche-like activity bursts whose sizes may be power-law distributed, i.e. statistically critical. Within these epochs the neurons of our model are slightly correlated; yet, as the number of small but significant correlations is high, the model has strongly correlated network states. This system is, on the short time-scale, sensitive in bulk to any outside input, even if applied only to a small subset of the neurons. We also present preliminary results showing that human brain electro-physiological recordings display both statistical and dynamical criticality.

Cecchi, Guillermo

2010-03-01

60

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

2000-01-01

61

A new modelling framework for statistical cumulus dynamics.  

PubMed

We propose a new modelling framework suitable for the description of atmospheric convective systems as a collection of distinct plumes. The literature contains many examples of models for collections of plumes in which strong simplifying assumptions are made, a diagnostic dependence of convection on the large-scale environment and the limit of many plumes often being imposed from the outset. Some recent studies have sought to remove one or the other of those assumptions. The proposed framework removes both, and is explicitly time dependent and stochastic in its basic character. The statistical dynamics of the plume collection are defined through simple probabilistic rules applied at the level of individual plumes, and van Kampen's system size expansion is then used to construct the macroscopic limit of the microscopic model. Through suitable choices of the microscopic rules, the model is shown to encompass previous studies in the appropriate limits, and to allow their natural extensions beyond those limits. PMID:22291222

Plant, Robert S

2012-03-13

62

OPEN PROBLEM: Orbits' statistics in chaotic dynamical systems  

NASA Astrophysics Data System (ADS)

This paper shows how the measurement of the stochasticity degree of a finite sequence of real numbers, published by Kolmogorov in Italian in a journal of insurances' statistics, can be usefully applied to measure the objective stochasticity degree of sequences, originating from dynamical systems theory and from number theory. Namely, whenever the value of Kolmogorov's stochasticity parameter of a given sequence of numbers is too small (or too big), one may conclude that the conjecture describing this sequence as a sample of independent values of a random variables is highly improbable. Kolmogorov used this strategy fighting (in a paper in 'Doklady', 1940) against Lysenko, who had tried to disprove the classical genetics' law of Mendel experimentally. Calculating his stochasticity parameter value for the numbers from Lysenko's experiment reports, Kolmogorov deduced, that, while these numbers were different from the exact fulfilment of Mendel's 3 : 1 law, any smaller deviation would be a manifestation of the report's number falsification. The calculation of the values of the stochasticity parameter would be useful for many other generators of pseudorandom numbers and for many other chaotically looking statistics, including even the prime numbers distribution (discussed in this paper as an example).

Arnold, V.

2008-07-01

63

A statistical model for interpreting computerized dynamic posturography data  

NASA Technical Reports Server (NTRS)

Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.

Feiveson, Alan H.; Metter, E. Jeffrey; Paloski, William H.

2002-01-01

64

Stochastic Ontogenetic Allometry: The Statistical Dynamics of Relative Growth  

PubMed Central

Background In the absence of stochasticity, allometric growth throughout ontogeny is axiomatically described by the logarithm-transformed power-law model, , where and are the logarithmic sizes of two traits at any given time t. Realistically, however, stochasticity is an inherent property of ontogenetic allometry. Due to the inherent stochasticity in both and , the ontogenetic allometry coefficients, and k, can vary with t and have intricate temporal distributions that are governed by the central and mixed moments of the random ontogenetic growth functions, and . Unfortunately, there is no probabilistic model for analyzing these informative ontogenetic statistical moments. Methodology/Principal Findings This study treats and as correlated stochastic processes to formulate the exact probabilistic version of each of the ontogenetic allometry coefficients. In particular, the statistical dynamics of relative growth is addressed by analyzing the allometric growth factors that affect the temporal distribution of the probabilistic version of the relative growth rate, , where is the expected value of the ratio of stochastic to stochastic , and and are the numerator and the denominator of , respectively. These allometric growth factors, which provide important insight into ontogenetic allometry but appear only when stochasticity is introduced, describe the central and mixed moments of and as differentiable real-valued functions of t. Conclusions/Significance Failure to account for the inherent stochasticity in both and leads not only to the miscalculation of k, but also to the omission of all of the informative ontogenetic statistical moments that affect the size of traits and the timing and rate of development of traits. Furthermore, even though the stochastic process and the stochastic process are linearly related, k can vary with t. PMID:21966474

Papadopoulos, Anthony

2011-01-01

65

Statistical mechanics of helix bundles using a dynamic programming approach.  

PubMed

Despite much study, biomolecule folding cooperativity is not well understood. There are quantitative models for helix-coil transitions and for coil-to-globule transitions, but no accurate models yet treat both chain collapse and secondary structure formation together. We develop here a dynamic programming approach to statistical mechanical partition functions of foldamer chain molecules. We call it the ascending levels model. We apply it to helix-coil and helix-bundle folding and cooperativity. For 14- to 50-mer Baldwin peptides, the model gives good predictions for the heat capacity and helicity versus temperature and urea. The model also gives good fits for the denaturation of Oas's three-helix bundle B domain of protein A (F13W*) and synthetic protein alpha3C by temperature and guanidine. The model predicts the conformational distributions. It shows that these proteins fold with transitions that are two-state, although the transitions in the Baldwin helices are nearly higher order. The model shows that the recently developed three-helix bundle polypeptoids of Lee et al. fold anti-cooperatively, with a predicted value of DeltaHvH/DeltaHcal = 0.72. The model also predicts that two-helix bundles are unstable in proteins but stable in peptoids. Our dynamic programming approach provides a general way to explore cooperativity in complex foldable polymers. PMID:17362002

Lucas, Adam; Huang, Liang; Joshi, Aravind; Dill, Ken A

2007-04-11

66

Statistical prediction of dynamic distortion of inlet flow using minimum dynamic measurement. An application to the Melick statistical method and inlet flow dynamic distortion prediction without RMS measurements  

NASA Technical Reports Server (NTRS)

The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.

Schweikhard, W. G.; Chen, Y. S.

1986-01-01

67

Dynamical analogy between economical crisis and earthquake dynamics within the nonextensive statistical mechanics framework  

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 the dynamics of economic (financial) systems can be analyzed within similar mathematical frameworks. We apply concepts of the nonextensive statistical physics, on time-series data of observable manifestations of the underlying complex processes ending up with these different extreme events, in order to support the suggestion that a dynamical analogy exists between a financial crisis (in the form of share or index price collapse) and a single earthquake. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg-Richter distribution of event sizes). We show that the populations of: (i) fracto-electromagnetic events rooted in the activation of a single fault, emerging prior to a significant earthquake, (ii) the trade volume events of different shares/economic indices, prior to a collapse, and (iii) the price fluctuation (considered as the difference of maximum minus minimum price within a day) events of different shares/economic indices, prior to a collapse, follow both the traditional Gutenberg-Richter law as well as a nonextensive model for earthquake dynamics, with similar parameter values. The obtained results imply the existence of a dynamic analogy between earthquakes and economic crises, which moreover follow the dynamics of seizures, magnetic storms and solar flares.

Potirakis, Stelios M.; Zitis, Pavlos I.; Eftaxias, Konstantinos

2013-07-01

68

Statistical and dynamical properties of a dissipative kicked rotator  

NASA Astrophysics Data System (ADS)

Some dynamical and statistical properties for a conservative as well as the dissipative problem of relativistic particles in a waveguide are considered. For the first time, two different types of dissipation namely: (i) due to viscosity and; (ii) due to inelastic collision (upon the kick) are considered individually and acting together. For the first case, and contrary to what is expected for the original Zaslavsky’s relativistic model, we show there is a critical parameter where a transition from local to global chaos occurs. On the other hand, after considering the introduction of dissipation also on the kick, the structure of the phase space changes in the sense that chaotic and periodic attractors appear. We study also the chaotic sea by using scaling arguments and we proposed an analytical argument to reinforce the validity of the scaling exponents obtained numerically. In principle such an approach can be extended to any two-dimensional map. Finally, based on the Lyapunov exponent, we show that the parameter space exhibits infinite families of self-similar shrimp-shape structures, corresponding to periodic attractors, embedded in a large region corresponding to chaotic attractors.

Oliveira, Diego F. M.; Leonel, Edson D.

2014-11-01

69

Statistical Dynamics of the Royal Road Genetic Algorithm  

E-print Network

G . . . . . . . . . . . . . . . . . . . . 20 5.6 GA Dynamics as a Flow in Fitness Distribution Space an analytical model for the dynamics of a mutation- only genetic algorithm (GA) is introduced that identifies a new and general mechanism causing metastability in evolutionary dynamics. The GA's population dynamics

Mitchell, Melanie

70

Examining rainfall and cholera dynamics in Haiti using statistical and dynamic modeling approaches.  

PubMed

Haiti has been in the midst of a cholera epidemic since October 2010. Rainfall is thought to be associated with cholera here, but this relationship has only begun to be quantitatively examined. In this paper, we quantitatively examine the link between rainfall and cholera in Haiti for several different settings (including urban, rural, and displaced person camps) and spatial scales, using a combination of statistical and dynamic models. Statistical analysis of the lagged relationship between rainfall and cholera incidence was conducted using case crossover analysis and distributed lag nonlinear models. Dynamic models consisted of compartmental differential equation models including direct (fast) and indirect (delayed) disease transmission, where indirect transmission was forced by empirical rainfall data. Data sources include cholera case and hospitalization time series from the Haitian Ministry of Public Health, the United Nations Water, Sanitation and Health Cluster, International Organization for Migration, and Hôpital Albert Schweitzer. Rainfall data was obtained from rain gauges from the U.S. Geological Survey and Haiti Regeneration Initiative, and remote sensing rainfall data from the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission. A strong relationship between rainfall and cholera was found for all spatial scales and locations examined. Increased rainfall was significantly correlated with increased cholera incidence 4-7 days later. Forcing the dynamic models with rainfall data resulted in good fits to the cholera case data, and rainfall-based predictions from the dynamic models closely matched observed cholera cases. These models provide a tool for planning and managing the epidemic as it continues. PMID:24267876

Eisenberg, Marisa C; Kujbida, Gregory; Tuite, Ashleigh R; Fisman, David N; Tien, Joseph H

2013-12-01

71

Statistics of Dynamic Random Networks: A Depth Function Approach  

E-print Network

The study of random graphs and networks had an explosive development in the last couple of decades. Meanwhile, there are just a few references about statistical analysis on graphs. In this paper we focus on graphs with a fixed number of labeled nodes (such as those used to model brain networks) and study some statistical problems in a nonparametric framework. We introduce natural notions of center and a depth function for graphs that evolve in time. This allows us to develop several statistical techniques including testing, supervised and unsupervised classification, and a notion of principal component sets in the space of graphs. Some examples and asymptotic results are given.

Fraiman, Daniel; Fraiman, Ricardo

2014-01-01

72

Dynamical systems based non equilibrium statistical mechanics for Markov chains.  

E-print Network

??We introduce an abstract framework concerning non-equilibrium statistical mechanics in the specific context of Markov chains. This framework encompasses both the Evans-Searles and the Gallavotti-Cohen… (more)

Prévost, Mireille

2011-01-01

73

Modeling Dynamics in Online Auctions: A Modern Statistical Approach  

E-print Network

in speed, etc. An analogy is cars in a car race. Instead of focusing exclusively on the winner's score (or between these dynamics and the winner's score. However, the race dynamics are interesting in themselves performance of our driver can be an indication of a superior car. Thus, the dependent variable from our

Jank, Wolfgang

74

Memory Dynamics in Cross-Situational Statistical Learning  

E-print Network

learning conditions presented learners with varying numbers of items to hold in working memory.learning condition engendered retrieval dynamics that crossed the bounds of short-term/working memorylearning conditions. What is more likely is that working memory

Vlach, Haley Amelia Heublein

2012-01-01

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

Enriching Spatial Data Infrastructure (sdi) by User Generated Contents for Transportation  

NASA Astrophysics Data System (ADS)

Spatial data is one of the most critical elements underpinning decision making for many disciplines. Accessing and sharing spatial data have always been a great struggle for researchers. Spatial data infrastructure (SDI) plays a key role in spatial data sharing by building a suitable platform for collaboration and cooperation among the different data producer organizations. In recent years, SDI vision has been moved toward a user-centric platform which has led to development of a new and enriched generation of SDI (third generation). This vision is to provide an environment where users can cooperate to handle spatial data in an effective and satisfactory way. User-centric SDI concentrates on users, their requirements and preferences while in the past, SDI initiatives were mainly concentrated on technological issues such as the data harmonization, standardized metadata models, standardized web services for data discovery, visualization and download. On the other hand, new technologies such as the GPS-equipped smart phones, navigation devices and Web 2.0 technologies have enabled citizens to actively participate in production and sharing of the spatial information. This has led to emergence of the new phenomenon called the Volunteered Geographic Information (VGI). VGI describes any type of content that has a geographic element which has been voluntarily collected. However, its distinctive element is the geographic information that can be collected and produced by citizens with different formal expertise and knowledge of the spatial or geographical concepts. Therefore, ordinary citizens can cooperate in providing massive sources of information that cannot be ignored. These can be considered as the valuable spatial information sources in SDI. These sources can be used for completing, improving and updating of the existing databases. Spatial information and technologies are an important part of the transportation systems. Planning, design and operation of the transportation systems requires the exchange of large volumes of spatial data and often close cooperation among the various organizations. However, there is no technical and organizational process to get a suitable data infrastructure to address diverse needs of the transportation. Hence, development of a common standards and a simple data exchange mechanism is strongly needed in the field of transportation for decision support. Since one of the main purposes of transportation projects is to improve the quality of services provided to users, it is necessary to involve the users themselves in the decision making processes. This should be done through a public participation and involvement in all stages of the transportation projects. In other words, using public knowledge and information as another source of information is very important to make better and more efficient decisions. Public participation in transportation projects can also help organizations to enhance their public supports; because the lack of public support can lead to failure of technically valid projects. However, due to complexity of the transportation tasks, lack of appropriate environment and methods for facilitation of the public participation, collection and analysis of the public information and opinions, public participation in this field has not been well considered so far. This paper reviews the previous researches based on the enriched SDI development and its movement toward the VGI by focusing on the public participation in transportation projects. To this end, methods and models that have been used in previous researches are studied and classified initially. Then, methods of the previous researchers on VGI and transportation are conceptualized in SDI. Finally, the suggested method for transportation projects is presented. Results indicate success of the new generation of SDI in integration with public participation for transportation projects.

Shakeri, M.; Alimohammadi, A.; Sadeghi-Niaraki, A.; Alesheikh, A. A.

2013-09-01

77

In: Nonlinear Dynamics and Statistics, A. Mees (ed.), Birkhauser, 2000 Printer: Opaque this  

E-print Network

In: Nonlinear Dynamics and Statistics, A. Mees (ed.), Birkhauser, 2000 .... .. .... .. Printer in the initial condition can be evolved and then quanti#12;ed as a function of fore- cast time. If a speci#12;ed

Smith, Leonard A

78

A. Ford and H. Flynn: Statistical Screening of Models 273 Statistical screening of system dynamics  

E-print Network

and model expansion to arrive at tolerance intervals on model results. The appendices compare screening focuses on the photovoltaic supply chain and markets. She is responsible for the collection, analysis and dissemination of photovoltaic System Dynamics Review Vol. 21, No. 4, (Winter 2005): 273­303 Received March 2005

Ford, Andrew

79

Acta Cryst. (2001). A57, 231239 Chukhovskii et al. Statistical dynamical direct methods. II 231 research papers  

E-print Network

Acta Cryst. (2001). A57, 231±239 Chukhovskii et al. Statistical dynamical direct methods. II 231 Britain ± all rights reserved Statistical dynamical direct methods. II. The three- phase structure, conventional statistical direct methods will yield a reasonable approximation to the effective dynamical

Marks, Laurence D.

80

Statistical constraints on binary black hole inspiral dynamics  

E-print Network

We perform a statistical analysis of the binary black hole problem in the post-Newtonian approximation by systematically sampling and evolving the parameter space of initial configurations for quasi-circular inspirals. Through a principal component analysis of spin and orbital angular momentum variables we systematically look for uncorrelated quantities and find three of them which are highly conserved in a statistical sense, both as functions of time and with respect to variations in initial spin orientations. We also look for and find the variables that account for the largest variations in the problem. We present binary black hole simulations of the full Einstein equations analyzing to what extent these results might carry over to the full theory in the inspiral and merger regimes. Among other applications these results should be useful both in semi-analytical and numerical building of templates of gravitational waves for gravitational wave detectors.

Chad R. Galley; Frank Herrmann; John Silberholz; Manuel Tiglio; Gustavo Guerberoff

2010-05-30

81

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). PMID:17511876

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

2007-01-01

82

An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models  

ERIC Educational Resources Information Center

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…

Prindle, John J.; McArdle, John J.

2012-01-01

83

Statistical approaches for probing single-molecule dynamics photon-by-photon  

E-print Network

Statistical approaches for probing single-molecule dynamics photon-by-photon Haw Yang1 , X. Sunney 02138, USA Received 19 December 2001 Abstract The recently developed photon-by-photon approach [H. Yang, each photon represents a data point, thereby affording better statistics. Here, we utilize

Xie, Xiaoliang Sunney

84

Lars Onsager Prize Lecture: Statistical Dynamics of Disordered Systems  

NASA Astrophysics Data System (ADS)

The properties of many systems are strongly affected by quenched disorder that arose from their past history but is frozen on the time scales of interest. Although equilibrium phases and phase transitions in disordered materials can be very different from their counterparts in pure systems, the most striking phenomena involve non-equilibrium dynamics. The state of understanding of some of these will be reviewed including approach to equilibrium in spin glasses and the onset of motion in driven systems such as vortices in superconductors or earthquakes on geological faults. The potential for developing understanding of short-term evolutionary dynamics of microbial populations by taking advantage of the randomness of their past histories and the biological complexities will be discussed briefly.

Fisher, Daniel S.

2013-03-01

85

Viscoelastic Effects in Avalanche Dynamics: A Key to Earthquake Statistics  

NASA Astrophysics Data System (ADS)

In many complex systems a continuous input of energy over time can be suddenly relaxed in the form of avalanches. Conventional avalanche models disregard the possibility of internal dynamical effects in the interavalanche periods, and thus miss basic features observed in some real systems. We address this issue by studying a model with viscoelastic relaxation, showing how coherent oscillations of the stress field can emerge spontaneously. Remarkably, these oscillations generate avalanche patterns that are similar to those observed in seismic phenomena.

Jagla, E. A.; Landes, François P.; Rosso, Alberto

2014-05-01

86

SdiA of Salmonella enterica Is a LuxR Homolog That Detects Mixed Microbial Communities  

PubMed Central

Proteins of the LuxR family detect the presence of N-acylhomoserine lactones (AHLs) and regulate transcription accordingly. When AHLs are synthesized by the same species that detects them, the system allows a bacterium to measure the population density of its own species, a phenomenon known as quorum sensing. The sdiA genes of Escherichia coli and Salmonella enterica serovar Typhimurium are predicted to encode LuxR homologs. However, these species do not appear to synthesize AHLs or any other molecule detected by SdiA. It has previously been demonstrated that overexpression of sdiA results in the activation of the ftsQAZ locus in E. coli and four other loci in Salmonella serovar Typhimurium. Here we report that transcriptional fusions to these five loci fall into two classes. The first class requires overexpression of sdiA for activation. The second class responds to sdiA expressed from its natural position in the chromosome if the appropriate AHLs are added to the culture. The only member of the second class is a series of Prck-luxCDABE fusions in Salmonella serovar Typhimurium. SdiA responds with highest sensitivity to AHLs that have a keto modification at the third carbon and an acyl chain length of 6 or 8 (half-maximal response between 1 and 5 nM). Growth of Salmonella in proximity to species known to synthesize these AHLs results in sdiA-dependent activation of the Prck-luxCDABE fusions. SdiA appears to be the first AHL receptor discovered that detects signals emanating exclusively from other species. PMID:11544237

Michael, Bindhu; Smith, Jenee N.; Swift, Simon; Heffron, Fred; Ahmer, Brian M. M.

2001-01-01

87

Dynamic Modelling and Statistical Analysis of Event Times  

PubMed Central

This review article provides an overview of recent work in the modelling and analysis of recurrent events arising in engineering, reliability, public health, biomedical, and other areas. Recurrent event modelling possesses unique facets making it different and more difficult to handle than single event settings. For instance, the impact of an increasing number of event occurrences needs to be taken into account, the effects of covariates should be considered, potential association among the inter-event times within a unit cannot be ignored, and the effects of performed interventions after each event occurrence need to be factored in. A recent general class of models for recurrent events which simultaneously accommodates these aspects is described. Statistical inference methods for this class of models are presented and illustrated through applications to real data sets. Some existing open research problems are described. PMID:17906740

Pena, Edsel A.

2006-01-01

88

Statistical mechanics of neocortical interactions - Dynamics of synaptic modification  

NASA Technical Reports Server (NTRS)

A recent study has demonstrated that several scales of neocortical interactions can be consistently analyzed with the use of methods of modern nonlinear nonequilibrium statistical mechanics. The formation, stability, and interaction of spatial-temporal patterns of columnar firings are explicitly calculated, to test hypothesized mechanisms relating to information processing. In this context, most probable patterns of columnar firings are associated with chemical and electrical synaptic modifications. It is stressed that synaptic modifications and shifts in most-probable firing patterns are highly nonlinear and interactive sets of phenomena. A detailed scenario of information processing is calculated of columnar coding of external stimuli, short-term storage via hysteresis, and long-term storage via synaptic modification.

Ingber, L.

1983-01-01

89

Statistical methodologies for the control of dynamic remapping  

NASA Technical Reports Server (NTRS)

Following an initial mapping of a problem onto a multiprocessor machine or computer network, system performance often deteriorates with time. In order to maintain high performance, it may be necessary to remap the problem. The decision to remap must take into account measurements of performance deterioration, the cost of remapping, and the estimated benefits achieved by remapping. We examine the tradeoff between the costs and the benefits of remapping two qualitatively different kinds of problems. One problem assumes that performance deteriorates gradually, the other assumes that performance deteriorates suddenly. We consider a variety of policies for governing when to remap. In order to evaluate these policies, statistical models of problem behaviors are developed. Simulation results are presented which compare simple policies with computationally expensive optimal decision policies; these results demonstrate that for each problem type, the proposed simple policies are effective and robust.

Saltz, J. H.; Nicol, D. M.

1986-01-01

90

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

E-print Network

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, analysing 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 tw...

Eftaxias, Konstantinos; Potirakis, Stelios M; Balasis, George

2012-01-01

91

Suppressing speckle noise for simultaneous differential extrasolar planet imaging (SDI) at the VLT and MMT  

NASA Astrophysics Data System (ADS)

We discuss data reduction techniques and results from the Simultaneous Differential Imager (SDI) implemented at the VLT (Lenzen et al. 2004a) and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 ?m methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be attenuated by a factor of >102. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our commissioning runs at the VLT and MMT, we achieved contrasts up to a factor of 45000 (?H=11.7) at a separation of 0.6" from the primary star. With this degree of attenuation, we should be able to image a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We believe that our SDI images are the highest contrast astronomical images ever made from ground or space.

Biller, Beth A.; Close, Laird; Lenzen, Rainer; Brandner, Wolfgang; McCarthy, Donald W.; Nielsen, Eric; Hartung, Markus

2004-10-01

92

Suppressing Speckle Noise for Simultaneous Differential Extrasolar Planet Imaging (SDI) at the VLT and MMT  

E-print Network

We discuss the instrumental and data reduction techniques used to suppress speckle noise with the Simultaneous Differential Imager (SDI) implemented at the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data past 0.5''. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our survey of nearby young stars at the VLT and MMT (see Biller et al., this conference), we achieved H band contrasts >25000 (5 sigma Delta F1(1.575 um) > 10.0 mag, Delta H > 11.5 mag for a T6 spectral type object) at a separation of 0.5" from the primary star. We believe that our SDI images are among the highest contrast astronomical images ever made from ground or space for methane rich companions.

Beth A. Biller; Laird M. Close; Rainer Lenzen; Wolfgang Brandner; Donald McCarthy; Eric Nielsen; Stephan Kellner; Markus Hartung

2006-01-03

93

Human turnover dynamics during sleep: Statistical behavior and its modeling  

NASA Astrophysics Data System (ADS)

Turnover is a typical intermittent body movement while asleep. Exploring its behavior may provide insights into the mechanisms and management of sleep. However, little is understood about the dynamic nature of turnover in healthy humans and how it can be modified in disease. Here we present a detailed analysis of turnover signals that are collected by accelerometry from healthy elderly subjects and age-matched patients with neurodegenerative disorders such as Parkinson's disease. In healthy subjects, the time intervals between consecutive turnover events exhibit a well-separated bimodal distribution with one mode at ?10 s and the other at ?100 s, whereas such bimodality tends to disappear in neurodegenerative patients. The discovery of bimodality and fine temporal structures (?10 s) is a contribution that is not revealed by conventional sleep recordings with less time resolution (?30 s). Moreover, we estimate the scaling exponent of the interval fluctuations, which also shows a clear difference between healthy subjects and patients. We incorporate these experimental results into a computational model of human decision making. A decision is to be made at each simulation step between two choices: to keep on sleeping or to make a turnover, the selection of which is determined dynamically by comparing a pair of random numbers assigned to each choice. This decision is weighted by a single parameter that reflects the depth of sleep. The resulting simulated behavior accurately replicates many aspects of observed turnover patterns, including the appearance or disappearance of bimodality and leads to several predictions, suggesting that the depth parameter may be useful as a quantitative measure for differentiating between normal and pathological sleep. These findings have significant clinical implications and may pave the way for the development of practical sleep assessment technologies.

Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi

2014-03-01

94

Statistical mechanics of epidemics and population dynamics on networks  

NASA Astrophysics Data System (ADS)

After a short introduction to the modeling of epidemics and population dynamics, we investigate in chapter 2, the time-evolution and steady states of an epidemic model (susceptible-infected-recovered-susceptible) on a network having the topology of the hypercubic lattice. We compare the behavior of this system, obtained from computer simulations, with those obtained from the mean-field approximation and pair-approximation. We find that the latter is significantly better than the former. In chapter 3, we study the behavior of a simple epidemic process (susceptible-infected-susceptible) on realistic networks in which vertices represent individuals and edges the interactions between them. Of particular interest are scale free networks with power-law distribution of degree, the number of edges emanating from a vertex. Considering cases where the transmission of infection between vertices depends on their degree, we introduce a saturation function which reduces the infection transmission rate across an edge leading to a node with high connectivity. This leads to a finite epidemic threshold on scale free networks with infinite second moment degree distribution above which the endemic infected state will be sustained and below which the disease dies out. In chapter 4, we study the time evolution and stationary states of a stochastic population model (contact process) with spatial heterogeneity and imposed drift (wind) on one- and two-dimensional lattices. We consider in particular a situation in which space is divided into two regions: an oasis and a desert (low and high death rates). Depending on the values of the drift and other parameters the population in the stationary state will be zero, localized, or delocalized. Finally, in appendix A we discuss a very different delocalized to localized type phase transition: the Mott metal insulator transition occurring in a half-filled single-band Hubbard model on a Bethe lattice. In the limit of infinite lattice coordination this model is mapped onto a single impurity Anderson model supplemented by a self-consistency condition, called dynamical mean field theory (DMFT) which freezes spatial fluctuations but takes full account of temporal fluctuations between possible quantum states at a given lattice site. This DMFT is solved numerically by using Quantum Monte Carlo methods. We provide numerical evidence for the coexistence of delocalized(metallic) and localized (insulating) phases at finite temperature.

Joo, Jaewook

95

Statistical and dynamical properties of a vibrated granular polymer  

NASA Astrophysics Data System (ADS)

We investigate the structure and dynamics of granular polymers on a vibrated bed to test the applicability of models of self-avoiding random walks. The granular polymer is composed of a chain of hollow 3 mm steel beads connected by flexible links, and moves on a 30 cm diameter flat circular bed which is roughened by gluing a layer of 1 mm steel beads in order to give the chain random kicks in the vertical and horizontal directions. High speed digital imaging is used to track the position of the particles to a fraction of the bead diameter using a centroid technique. Using the identified bead positions, we analyze the motion of the center of mass over a time interval ?t, and its standard deviation as a function of chain length L. The standard deviation is consistent with a scaling of ??t / L. The chain end-to-end distance scales as L^?, with ? 3/4 as for self-avoiding walks. The evolution of the scattering functions and the effect of the size of the container on the observed scaling will be also discussed.

Kudrolli, Arshad; Veilleux, Micah; Kardar, Mehran

2006-03-01

96

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

97

Statistical and dynamical characteristics of the urban heat island intensity in Seoul  

Microsoft Academic Search

The statistical and dynamical characteristics of the urban heat island (UHI) intensity in Seoul are investigated for non-precipitation\\u000a days and precipitation days using 4-year surface meteorological data with 1-h time intervals. Furthermore, the quantitative\\u000a influence of synoptic pressure pattern on the UHI intensity is examined using a synoptic condition clustering method. The\\u000a statistical analysis shows that the daily maximum UHI

Sang-Hyun Lee; Jong-Jin Baik

2010-01-01

98

Quantum statistical mechanics of gases in terms of dynamical filling fractions and scattering amplitudes  

E-print Network

We develop a finite temperature field theory formalism in any dimension that has the filling fractions as the basic dynamical variables. The formalism efficiently decouples zero temperature dynamics from the quantum statistical sums. The zero temperature `data' is the scattering amplitudes. A saddle point condition leads to an integral equation which is similar in spirit to the thermodynamic Bethe ansatz for integrable models, and effectively resums infinite classes of diagrams. We present both relativistic and non-relativistic versions.

André LeClair

2006-11-17

99

Evaluation of the effects of sdiA, a luxR homologue, on adherence and motility of Escherichia coli O157 : H7.  

PubMed

Quorum-sensing (QS) signalling pathways are important regulatory networks for controlling the expression of genes promoting adherence of enterohaemorrhagic Escherichia coli (EHEC) O157 : H7 to epithelial cells. A recent study has shown that EHEC O157 : H7 encodes a luxR homologue, called sdiA, which upon overexpression reduces the expression of genes encoding flagellar and locus of enterocyte effacement (LEE) proteins, thus negatively impacting on the motility and intimate adherence phenotypes, respectively. Here, we show that the deletion of sdiA from EHEC O157 : H7 strain 86-24, and from a hha (a negative regulator of ler) mutant of this strain, enhanced bacterial adherence to HEp-2 epithelial cells of the sdiA mutant strains relative to the strains containing a wild-type copy of sdiA. Quantitative reverse transcription PCR showed that the expression of LEE-encoded genes ler, espA and eae in strains with the sdiA deletions was not significantly different from that of the strains wild-type for sdiA. Similarly, no additional increases in the expression of LEE genes were observed in a sdiA hha double mutant strain relative to that observed in the hha deletion mutant. While the expression of fliC, which encodes flagellin, was enhanced in the sdiA mutant strain, the expression of fliC was reduced by several fold in the hha mutant strain, irrespective of the presence or absence of sdiA, indicating that the genes sdiA and hha exert opposing effects on the expression of fliC. The strains with deletions in sdiA or hha showed enhanced expression of csgA, encoding curlin of the curli fimbriae, with the expression of csgA highest in the sdiA hha double mutant, suggesting an additive effect of these two gene deletions on the expression of csgA. No significant differences were observed in the expression of the genes lpfA and fimA of the operons encoding long polar and type 1 fimbriae in the sdiA mutant strain. These data indicate that SdiA has no significant effect on the expression of LEE genes, but that it appears to act as a strong repressor of genes encoding flagella and curli fimbriae, and the alleviation of the SdiA-mediated repression of these genes in an EHEC O157 : H7 sdiA mutant strain contributes to enhanced bacterial motility and increased adherence to HEp-2 epithelial cells. PMID:20110300

Sharma, Vijay K; Bearson, Shawn M D; Bearson, Bradley L

2010-05-01

100

A new statistical dynamic analysis of ecological niches for China’s financial centres  

NASA Astrophysics Data System (ADS)

This study, undertaken from the perspective of statistical dynamics, proposes the treatment of financial centres as an ecosystem, creates a multidimensional financial centre niche (FC-niche) under given generalised entropy and constraints, and interprets the evolutionary process of an FC-niche with dynamic equations obtained from the maximum generalised entropy principle (MGEP). To solve these dynamic equations, a self-organised feature map (SOM) is designed. Finally, the values and evolutionary rules of FC-niches in China’s 29 major cities are simulated as a case study.

Du, Huibin; Xia, Qiongqiong; Ma, Xuan; Chai, Lihe

2014-02-01

101

Classical statistical mechanics of the sine-Gordon and ?4 chain. II. Dynamic properties  

NASA Astrophysics Data System (ADS)

We present and discuss the classical statistical mechanics of the dynamic properties associated with a discretized sine-Gordon and ?4 system by using the molecular-dynamics technique. To calibrate the interpretation, various approximate expressions for the dynamic form factors of interest are derived on the basis of an interacting phonon gas and an ideal kink gas. On this basis, kink, phonon, and second-sound excitation branches are identified. The occurrence of the kink excitation branch turns out to be restricted to small wave numbers and frequencies and to low temperatures. Evidence for breather features, distinct from anharmonic contributions, is also given.

Schneider, T.; Stoll, E.

1981-05-01

102

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

103

Dynamic Graphics in Excel for Teaching Statistics: Understanding the Probability Density Function  

ERIC Educational Resources Information Center

In this article, we show a dynamic graphic in Excel that is used to introduce an important concept in our subject, Statistics I: the probability density function. This interactive graphic seeks to facilitate conceptual understanding of the main aspects analysed by the learners.

Coll-Serrano, Vicente; Blasco-Blasco, Olga; Alvarez-Jareno, Jose A.

2011-01-01

104

Collisional cross sections and momentum distributions in astrophysical plasmas: Dynamics and statistical mechanics link  

SciTech Connect

We show that in stellar core plasmas, the one-body momentum distribution function is strongly dependent, at least in the high velocity regime, on the microscopic dynamics of ion elastic collisions and therefore on the effective collisional cross sections if a random force field is present. We take into account two cross sections describing ion-dipole and ion-ion screened interactions. Furthermore, we introduce a third unusual cross section to link statistical distributions and a quantum effect originated by the energy-momentum uncertainty owing to many-body collisions. We also propose a possible physical interpretation in terms of a tidal-like force. We show that each collisional cross section gives rise to a slight peculiar correction on the Maxwellian momentum distribution function in a well defined velocity interval. We also find a possible link between microscopic dynamics of ions and statistical mechanics in interpreting our results in the framework of nonextensive statistical mechanics.

Ferro, F. [Dipartimento di Fisica, Politecnico di Torino, I-10129 Torino (Italy); INFN-Sezione di Torino, I-10125 Torino (Italy); Quarati, P. [Dipartimento di Fisica, Politecnico di Torino, I-10129 Torino (Italy); INFN-Sezione di Cagliari, I-09042 Monserrato (Italy)

2005-02-01

105

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

106

SERVIR's Contributions and Benefits to Belize thru Spatial Data Infrastructure (SDI) Development  

NASA Technical Reports Server (NTRS)

Dan Irwin, the SERVIR Project Manager is being honored with the privilege of delivering the opening remarks at Belize s second celebration of GIS Day, a weeklong event to be held at the University of Belize's campus in the nation s capital, Belmopan. The request has been extended by the GIS Day Planning Committee which operates under the auspices of Belize s Ministry of Natural Resources & the Environment, which is the focal ministry for SERVIR. In the 20-30 min. allotted for the opening remarks, the SERVIR Project Manager will expound on how SERVIR, operating under the auspices of NASA s Ecological Forecasting Program, contributes to spatial data infrastructure (SDI) development in Belize. NASA s contributions to the region - particularly work under the Mesoamerican Biological Corridor - will be highlighted. Continuing, the remarks will discuss SERVIR s role in Belize s steadily expanding SDI, particularly in the context of delivering integrated decision support products via web-based infrastructure. The remarks will close with a call to the parties assembled to work together in the application of Earth Observation Systems technologies for the benefit of Belizean society as a whole. NASA s strong presence in Belize s GIS Day celebrations will be highlighted as sustained goodwill of the American people - in partial fulfillment of goals set forth under the Global Earth Observation System of Systems (GEOSS).

Irwin, Daniel E.

2006-01-01

107

Suppressing Speckle Noise for Simultaneous Differential Extrasolar Planet Imaging (SDI) at the VLT and MMT  

E-print Network

We discuss the instrumental and data reduction techniques used to suppress speckle noise with the Simultaneous Differential Imager (SDI) implemented at the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data past 0.5''. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our survey of nearby young stars at the VLT and MMT (see Biller et al., this conference), we achieved H band contrasts >25000 (5 sigma D...

Biller, B A; Lenzen, R; Brandner, W; McCarthy, D; Nielsen, E; Kellner, S; Hartung, M; Biller, Beth A.; Close, Laird M.; Lenzen, Rainer; Brandner, Wolfgang; Carthy, Donald Mc; Nielsen, Eric; Kellner, Stephan; Hartung, Markus

2006-01-01

108

Unimolecular fragmentation induced by low-energy collision: statistically or dynamically driven?  

PubMed

By combining chemical dynamics simulations and RRKM statistical theory we have characterized collision induced dissociation (CID) mechanisms of [M(formamide)](2+) ions (M = Ca, Sr) at different timescales, from few femtoseconds to microseconds. Chemical dynamics simulations account for the short-time and dynamically driven reactivity, such as impulsive collision mechanism for formamide neutral loss. From the simulations, we also got the amounts of energy transferred during the collision and, especially important, the vibrational and rotational energy distributions of the ions that did not react during the simulation time length of 2.5 ps. These internal energy distributions were in turn used in combination with RRKM theory to estimate the rate constants of the possible reactive pathways. Hence, we performed a statistical analysis of the CID dynamics accounting for the long-time and statistical reactivity (i.e., through an IVR mechanism). This multiscale approach allowed us to account for all the products observed in the CID experimental spectra of [Ca(formamide)](2+) and [Sr(formamide)](2+) doubly charged cations, as well as the differences between them. PMID:25333680

Martín-Sómer, Ana; Yáñez, Manuel; Gaigeot, Marie-Pierre; Spezia, Riccardo

2014-11-20

109

Nutrient Management of Subsurface Drip Irrigated Cotton Installation of subsurface drip irrigated (SDI) in cotton fields in the Southern High Plains  

E-print Network

of the fertilizer salts such as 10-34-0 will occur if un-acidified irrigation water is used. Sulfuric acid) into SDI systems with sodium hypochlorite (NaOCl) (bleach) disinfects the water and prevents algae growth are available at SDI dealers. Nitrogen Fluid nitrogen (N) fertilizers based on urea-ammonium nitrate (32

Mukhtar, Saqib

110

research papers 458 Hu et al. Statistical dynamical direct methods. I Acta Cryst. (2000). A56, 458469  

E-print Network

research papers 458 Hu et al. Statistical dynamical direct methods. I Acta Cryst. (2000). A56, 458 reserved Statistical dynamical direct methods. I. The effective kinematical approximation J. J. Hu, F. N diffraction, substantial success has been achieved over the last few years in applying it via direct methods

Marks, Laurence D.

111

On Monte Carlo and molecular dynamics methods inspired by Tsallis statistics: Methodology, optimization, and application to atomic clusters  

E-print Network

On Monte Carlo and molecular dynamics methods inspired by Tsallis statistics: Methodology a generalized statistical distribution derived from a modification of the Gibbs­Shannon entropy proposed of the phase space may result in distinct time averages. Statistical theories of chemical sys- tems are often

Straub, John E.

112

a Statistical Dynamic Approach to Structural Evolution of Complex Capital Market Systems  

NASA Astrophysics Data System (ADS)

As an important part of modern financial systems, capital market has played a crucial role on diverse social resource allocations and economical exchanges. Beyond traditional models and/or theories based on neoclassical economics, considering capital markets as typical complex open systems, this paper attempts to develop a new approach to overcome some shortcomings of the available researches. By defining the generalized entropy of capital market systems, a theoretical model and nonlinear dynamic equation on the operations of capital market are proposed from statistical dynamic perspectives. The US security market from 1995 to 2001 is then simulated and analyzed as a typical case. Some instructive results are discussed and summarized.

Shao, Xiao; Chai, Li H.

113

J. Phys. A: Math. Gen. 14 (1981) 1701-1718. Printed in Great Britain H theorems in statistical fluid dynamics  

E-print Network

fluid dynamics George F Camevaleit, Uriel FrischO and Rick Salmon1 $National Center for Atmospheric in statistical macroscopic fluid dynamics. Naturally, since canonical equilibrium applies only to conservative fluid dynamics. This equation can be obtained by techniques directly analogous to those used

Salmon, Rick

114

Understanding the Multi-Scale and Multi-fractal Dynamics of Space Plasmas Through Tsallis Non-Extensive Statistical Theory  

E-print Network

In this study it is shown that the Tsallis q-extended statistical theory was found efficient to describe faithfully the space plasmas statistics in every case, from the planetic magnetospheres, to solar corona and solar dynamics, as well as cosmic rays and cosmic stars. Moreover, new theoretical concepts and experimental results are presented concerning the space plasma complex dynamics. The significant message of theoretical and experimental issues presented here is the necessity of generalized statistical and dynamical theory for understanding the non-equilibrium dynamics and the complex character of space plasmas. The q-extension of statistics coupled to the fractal extension of dynamics are the novel and appropriate theoretical framework for the description of space plasma complexity.

G. P. Pavlos

2012-03-18

115

Displaying R spatial statistics on Google dynamic maps with web applications created by Rwui  

PubMed Central

Background The R project includes a large variety of packages designed for spatial statistics. Google dynamic maps provide web based access to global maps and satellite imagery. We describe a method for displaying directly the spatial output from an R script on to a Google dynamic map. Methods This is achieved by creating a Java based web application which runs the R script and then displays the results on the dynamic map. In order to make this method easy to implement by those unfamiliar with programming Java based web applications, we have added the method to the options available in the R Web User Interface (Rwui) application. Rwui is an established web application for creating web applications for running R scripts. A feature of Rwui is that all the code for the web application being created is generated automatically so that someone with no knowledge of web programming can make a fully functional web application for running an R script in a matter of minutes. Results Rwui can now be used to create web applications that will display the results from an R script on a Google dynamic map. Results may be displayed as discrete markers and/or as continuous overlays. In addition, users of the web application may select regions of interest on the dynamic map with mouse clicks and the coordinates of the region of interest will automatically be made available for use by the R script. Conclusions This method of displaying R output on dynamic maps is designed to be of use in a number of areas. Firstly it allows statisticians, working in R and developing methods in spatial statistics, to easily visualise the results of applying their methods to real world data. Secondly, it allows researchers who are using R to study health geographics data, to display their results directly onto dynamic maps. Thirdly, by creating a web application for running an R script, a statistician can enable users entirely unfamiliar with R to run R coded statistical analyses of health geographics data. Fourthly, we envisage an educational role for such applications. PMID:22998945

2012-01-01

116

A Comparison of Statistical and Dynamical Downscaling of Winter Precipitation Over Complex Terrain  

NASA Astrophysics Data System (ADS)

Statistical downscaling is widely used to improve spatial and or temporal distributions of meteorological variables from regional and global climate models. This downscaling is important because climate models are spatially coarse (50-200km), and often misrepresent extremes in meteorological variables such as temperature and precipitation that are important to hydrologic models. However, these downscaling methods rely on current estimates of the spatial distributions of these variables, and largely assume that the small-scale spatial distribution will not change significantly in a modified climate. Here we compare data typically used to derive spatial distributions of precipitation (PRISM) to a high-resolution (2km) weather model (WRF) under current climate in the mountains of Colorado. We show that there are regions of significant difference in November-May precipitation totals (~100%) between the two, and discuss possible causes for these differences, including a new observation which shows WRF to be substantially more accurate in at least one location. We then present a simple statistical downscaling based on the 2km WRF data applied to a series of regional climate models from the North American Regional Climate Change Assessment Program (NARCCAP), and validate the downscaled precipitation data with observations at 65 SNOw TELemetry (SNOTEL) sites throughout Colorado for the winter seasons from 1988 to 2000. Finally, we use this statistical downscaling method to compare precipitation from a 36km model under an imposed warming scenario to dynamically downscaled data from a 2km model using the same boundary conditions. While the statistical downscaling improved the domain average precipitation and spatial distribution compared to the original 36km model, the changes in the spatial pattern of precipitation did not match the changes in the dynamically downscaled 2km model (r^2=0.05). This points to a serious deficiency in current statistical downscaling techniques. We suggest that it is possible to derive a better statistical downscaling from a dynamically downscaled model than it is from observations alone by leveraging additional model data such as the 500mb height, upper level wind direction, and vertical temperature gradients.

Gutmann, E. D.; Rasmussen, R.; Liu, C.; Ikeda, K.; Gochis, D. J.; Clark, M. P.; Dudhia, J.; Thompson, G.

2011-12-01

117

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. PMID:23086212

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

2013-01-01

118

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. PMID:18665275

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

119

Heterogeneous Structure of Stem Cells Dynamics: Statistical Models and Quantitative Predictions  

NASA Astrophysics Data System (ADS)

Understanding stem cell (SC) population dynamics is essential for developing models that can be used in basic science and medicine, to aid in predicting cells fate. These models can be used as tools e.g. in studying patho-physiological events at the cellular and tissue level, predicting (mal)functions along the developmental course, and personalized regenerative medicine. Using time-lapsed imaging and statistical tools, we show that the dynamics of SC populations involve a heterogeneous structure consisting of multiple sub-population behaviors. Using non-Gaussian statistical approaches, we identify the co-existence of fast and slow dividing subpopulations, and quiescent cells, in stem cells from three species. The mathematical analysis also shows that, instead of developing independently, SCs exhibit a time-dependent fractal behavior as they interact with each other through molecular and tactile signals. These findings suggest that more sophisticated models of SC dynamics should view SC populations as a collective and avoid the simplifying homogeneity assumption by accounting for the presence of more than one dividing sub-population, and their multi-fractal characteristics.

Bogdan, Paul; Deasy, Bridget M.; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu

2014-04-01

120

Molecular Dynamics and Statistical Mechanics of Water Near an Uncharged Silicate Surface  

NASA Astrophysics Data System (ADS)

Properties such as the swelling, mass transfer, and porosity in aqueous colloidal systems and natural soils are thought to vary in magnitude depending upon the extent of surface-induced perturbation in the water near silicate surfaces (vicinal water). Any satisfactory theoretical understanding of the interrelation between the perturbations in vicinal water and the properties of colloidal systems must involve the statistical mechanical analysis of an appropriate molecular model for the vicinal water. We have conducted a preliminary molecular dynamics simulation in order to elucidate the effects of an uncharged silicate surface on the structure and dynamics of vicinal water. Statistical mechanics were used to interpret position and velocity trajectories computed in the molecular dynamics simulation. The results of our simulation indicate that the vicinal water differs substantially from bulk water over appreciable distances for the static orientation of molecular dipole moments and the rate of relaxation of these moments and substantially over smaller distances for hydrogen bonding patterns and the rate of self-diffusion. No significant differences between the radial distribution functions of vicinal and bulk water are evident. Because vicinal water may be perturbed to large distances from a clay surface, one must take extreme care in deriving transport equations in saturated and unsaturated media which are high in clay. We may conclude that a satisfactory derivation of the solute transport equations in systems high in colloids and having low water content does not exist.

Mulla, David J.; Cushman, John H.; Low, Philip F.

1984-05-01

121

Heterogeneous structure of stem cells dynamics: statistical models and quantitative predictions.  

PubMed

Understanding stem cell (SC) population dynamics is essential for developing models that can be used in basic science and medicine, to aid in predicting cells fate. These models can be used as tools e.g. in studying patho-physiological events at the cellular and tissue level, predicting (mal)functions along the developmental course, and personalized regenerative medicine. Using time-lapsed imaging and statistical tools, we show that the dynamics of SC populations involve a heterogeneous structure consisting of multiple sub-population behaviors. Using non-Gaussian statistical approaches, we identify the co-existence of fast and slow dividing subpopulations, and quiescent cells, in stem cells from three species. The mathematical analysis also shows that, instead of developing independently, SCs exhibit a time-dependent fractal behavior as they interact with each other through molecular and tactile signals. These findings suggest that more sophisticated models of SC dynamics should view SC populations as a collective and avoid the simplifying homogeneity assumption by accounting for the presence of more than one dividing sub-population, and their multi-fractal characteristics. PMID:24769917

Bogdan, Paul; Deasy, Bridget M; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu

2014-01-01

122

Heterogeneous Structure of Stem Cells Dynamics: Statistical Models and Quantitative Predictions  

PubMed Central

Understanding stem cell (SC) population dynamics is essential for developing models that can be used in basic science and medicine, to aid in predicting cells fate. These models can be used as tools e.g. in studying patho-physiological events at the cellular and tissue level, predicting (mal)functions along the developmental course, and personalized regenerative medicine. Using time-lapsed imaging and statistical tools, we show that the dynamics of SC populations involve a heterogeneous structure consisting of multiple sub-population behaviors. Using non-Gaussian statistical approaches, we identify the co-existence of fast and slow dividing subpopulations, and quiescent cells, in stem cells from three species. The mathematical analysis also shows that, instead of developing independently, SCs exhibit a time-dependent fractal behavior as they interact with each other through molecular and tactile signals. These findings suggest that more sophisticated models of SC dynamics should view SC populations as a collective and avoid the simplifying homogeneity assumption by accounting for the presence of more than one dividing sub-population, and their multi-fractal characteristics. PMID:24769917

Bogdan, Paul; Deasy, Bridget M.; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu

2014-01-01

123

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

124

Cluster Statistics and Quasisoliton Dynamics in Microscopic Car-following Models  

E-print Network

Using the optimal velocity (OV) model as an example, we show that in the non-linear regime there is an emergent quantity that gives the extremum headways in the cluster formation, as well as the coexistence curve separating the absolute stable phase from the metastable phase. This emergent quantity is independent of the density of the traffic lane, and determines an intrinsic scale that characterizes the dynamics of localized quasisoliton structures given by the time derivative of the headways. The intrinsic scale is analogous to the "charge" of quasisolitons that controls the strength of interaction between multiple clusters, leading to non-trivial cluster statistics from random perturbations to initial uniform traffic. The cluster statistics depend both on the charge and the density of the traffic lane; the relationship is qualitatively universal for general car-following models.

Bo Yang; Xihua Xu; John Z. F. Pang; Christopher Monterola

2014-07-02

125

A unified n-body and statistical treatment of stellar dynamics  

NASA Technical Reports Server (NTRS)

The methods of a new 'hybrid' computed code for stellar dynamics are summarized. All particles in the inner spatial region are followed exactly via a direct N-body code and all particles in the outer spatial region are treated statistically via a distribution function and Fokker-Planck type methods. An intermediate region, with features of both, allows exchange of particles and energy between the outer and inner regions. The code is applied to the period just before core collapse and just after and the results are summarized.

Lightman, A. P.; Mcmillan, S. L. W.

1985-01-01

126

Have confidence in your coronagraph: statistical analysis of high-contrast coronagraph dynamics error budgets  

NASA Astrophysics Data System (ADS)

We have combined our Excel-based coronagraph dynamics error budget spreadsheets with DAKOTA scripts to perform statistical analyses of the predicted dark-hole contrast. Whereas in the past we have reported the expected contrast level for an input set of allocated parameters, we now generate confidence intervals for the predicted contrast. Further, we explore the sensitivity to individual or groups of parameters and model uncertainty factors through aleatory-epistemic simulations based on a surrogate model fitted to the error budget. We show example results for a generic high-contrast coronagraph.

Shaklan, Stuart B.; Marchen, Luis; Peterson, Lee; Levine, Marie B.

2014-08-01

127

Memory effects in avalanche dynamics: a key to the statistical properties of earthquakes  

E-print Network

Many complex systems respond to continuous input of energy by accumulation of stress over time and sudden energy releases in the form of avalanches. Avalanches are paradigmatic non-equilibrium phenomena displaying power law size distribution and involving all the length scales in the system. Conventional avalanche models disregard memory effects and thus miss basic features observed in real systems. Notable examples are aftershocks and the anomalous exponent of the Gutenberg-Richter law which characterize earthquake statistics. We propose a model which accounts for memory effects through the introduction of viscoelastic relaxation at an intermediate time scale. We demonstrate that in the resulting dynamics, coherent oscillations of the stress field emerge spontaneously without fine tuning of any parameter. Remarkably, in two dimensions, which is relevant in seismicity, these oscillations generate instability patterns that produce realistic earthquake dynamics with the correct Gutenberg-Richter exponent.

Jagla, E A; Rosso, Alberto

2013-01-01

128

A unified theory of chaos linking nonlinear dynamics and statistical physics  

E-print Network

A fundamental issue in nonlinear dynamics and statistical physics is how to distinguish chaotic from stochastic fluctuations in short experimental recordings. This dilemma underlies many complex systems models from stochastic gene expression or stock exchange to quantum chaos. Traditionally, deterministic chaos is characterized by "sensitive dependence on initial conditions" as indicated by a positive Lyapunov exponent. However, ambiguity arises when applying this criterion to real-world data that are corrupted by measurement noise or perturbed nonautonomously by exogenous deterministic or stochastic inputs. Here, we show that a positive Lyapunov exponent is surprisingly neither necessary nor sufficient proof of deterministic chaos, and that a nonlinear dynamical system under deterministic or stochastic forcing may exhibit multiple forms of nonautonomous chaos assessable by a noise titration assay. These findings lay the foundation for reliable analysis of low-dimensional chaos for complex systems modeling and prediction of a wide variety of physical, biological, and socioeconomic data.

Chi-Sang Poon; Cheng Li; Guo-Qiang Wu

2010-04-08

129

A combined statistical and dynamical approach for downscaling large-scale footprints of European windstorms  

NASA Astrophysics Data System (ADS)

The occurrence of mid-latitude windstorms is related to strong socio-economic effects. For detailed and reliable regional impact studies, large datasets of high-resolution wind fields are required. In this study, a statistical downscaling approach in combination with dynamical downscaling is introduced to derive storm related gust speeds on a high-resolution grid over Europe. Multiple linear regression models are trained using reanalysis data and wind gusts from regional climate model simulations for a sample of 100 top ranking windstorm events. The method is computationally inexpensive and reproduces individual windstorm footprints adequately. Compared to observations, the results for Germany are at least as good as pure dynamical downscaling. This new tool can be easily applied to large ensembles of general circulation model simulations and thus contribute to a better understanding of the regional impact of windstorms based on decadal and climate change projections.

Haas, Rabea; Pinto, Joaquim G.

2013-04-01

130

A combined statistical and dynamical approach for downscaling large-scale footprints of European windstorms  

NASA Astrophysics Data System (ADS)

The occurrence of mid-latitude windstorms is related to strong socio-economic effects. For detailed and reliable regional impact studies, large datasets of high-resolution wind fields are required. In this study, a statistical downscaling approach in combination with dynamical downscaling is introduced to derive storm related gust speeds on a high-resolution grid over Europe. Multiple linear regression models are trained using reanalysis data and wind gusts from regional climate model simulations for a sample of 100 top ranking windstorm events. The method is computationally inexpensive and reproduces individual windstorm footprints adequately. Compared to observations, the results for Germany are at least as good as pure dynamical downscaling. This new tool can be easily applied to large ensembles of general circulation model simulations and thus contribute to a better understanding of the regional impact of windstorms based on decadal and climate change projections.

Haas, R.; Pinto, J. G.

2012-12-01

131

Dynamic thermo-mechanical coupled response of random particulate composites: A statistical two-scale method  

NASA Astrophysics Data System (ADS)

This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of the problem by a statistical second-order two-scale (SSOTS) analysis method and the algorithm procedure based on the finite-element difference method are presented. Numerical results of coupled cases are compared with those of uncoupled cases. It shows that the coupling effects on temperature, thermal flux, displacement, and stresses are very distinct, and the micro-characteristics of particles affect the coupling effect of the random composites. Furthermore, the coupling effect causes a lag in the variations of temperature, thermal flux, displacement, and stresses.

Yang, Zi-Hao; Chen, Yun; Yang, Zhi-Qiang; Ma, Qiang

2014-07-01

132

Statistical complexity measures as telltale of relevant scales in emergent dynamics of spatial systems  

E-print Network

The definition of complexity through Statistical Complexity Measures (SCM) has recently seen major improvements. Mostly, effort is concentrated in measures on time series. We propose a SCM definition for spatial dynamical systems. Our definition is in line with the trend to combine entropy with measures of structure (such as disequilibrium). We study the behaviour of our definition against the vectorial noise model of Collective Motion. From a global perspective, we show how our SCM is minimal at both the microscale and macroscale, while it reaches a maximum at the ranges that define the mesoscale in this model. From a local perspective, the SCM is minimum both in highly ordered and chaotic areas, while it reaches a maximum at the edges between such areas. These characteristics suggest this is a good candidate for detecting the mesoscale of arbitrary dynamical systems as well as regions where the complexity is maximal in such systems.

A. Arbona; C. Bona; B. Miñano; A. Plastino

2013-11-06

133

Statistics of reversible bond dynamics observed in force-clamp spectroscopy  

E-print Network

We present a detailed analysis of two-state trajectories obtained from force-clamp spectroscopy (FCS) of reversibly bonded systems. FCS offers the unique possibility to vary the equilibrium constant in two-state kinetics, for instance the unfolding and refolding of biomolecules, over many orders of magnitude due to the force dependency of the respective rates. We discuss two different kinds of counting statistics, the event-counting usually employed in the statistical analysis of two-state kinetics and additionally the so-called cycle-counting. While in the former case all transitions are counted, cycle-counting means that we focus on one type of transitions. This might be advantageous in particular if the equilibrium constant is much larger or much smaller than unity because in these situations the temporal resolution of the experimental setup might not allow to capture all transitions of an event-counting analysis. We discuss how an analysis of FCS data for complex systems exhibiting dynamic disorder might be performed yielding information about the detailed force-dependence of the transition rates and about the time scale of the dynamic disorder. In addition, the question as to which extent the kinetic scheme can be viewed as a Markovian two-state model is discussed.

Gregor Diezemann; Thomas Schlesier; Burkhard Geil; Andreas Janshoff

2010-05-10

134

Statistical intercomparison of idealized rainfall measurements using a stochastic fractional dynamics model  

NASA Astrophysics Data System (ADS)

statistical method is developed for comparing precipitation data from measurements performed by (hypothetical) perfect instruments using a recently developed stochastic model of rainfall. The stochastic dynamical equation that describes the underlying random process naturally leads to a consistent spectrum and incorporates the subtle interdependence of the length and time scales governing the statistical fluctuations of the rain rate field. The main attraction of such a model is that the complete set of second-moment statistics embodied in the space-time covariance of both the area-averaged instantaneous rain rate (represented by radar or passive microwave data near the ground) and the time-averaged point rain rate (represented by rain gauge data) can be expressed as suitable integrals over the spectrum. With the help of this framework, the model allows one to carry out a faithful intercomparison of precipitation estimates derived from radar or passive microwave remote sensing over an area with direct observations by rain gauges or disdrometers, assuming all the measuring instruments to be ideal. A standard linear regression analysis approach to the intercomparison of radar and gauge rain rate estimates is formulated in terms of the appropriate observed and model-derived quantities. We also estimate the relative sampling error as well as separate absolute sampling errors for radar and gauge measurements of rainfall from the spectral model.

Kundu, Prasun K.; Marks, David A.; Travis, James E.

2014-09-01

135

Statistical downscaling based on dynamically downscaled predictors: Application to monthly precipitation in Sweden  

NASA Astrophysics Data System (ADS)

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.

Hellström, Cecilia; Chen, Deliang

2003-11-01

136

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. PMID:23226584

Calderhead, Ben; Girolami, Mark

2011-01-01

137

A Statistical Approach for the Concurrent Coupling of Molecular Dynamics and Finite Element Methods  

NASA Technical Reports Server (NTRS)

Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, increasing the size of the MD domain quickly presents intractable computational demands. A robust approach to surmount this computational limitation has been to unite continuum modeling procedures such as the finite element method (FEM) with MD analyses thereby reducing the region of atomic scale refinement. The challenging problem is to seamlessly connect the two inherently different simulation techniques at their interface. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the typical boundary value problem used to define a coupled domain. The method uses statistical averaging of the atomistic MD domain to provide displacement interface boundary conditions to the surrounding continuum FEM region, which, in return, generates interface reaction forces applied as piecewise constant traction boundary conditions to the MD domain. The two systems are computationally disconnected and communicate only through a continuous update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM) as opposed to a direct coupling method where interface atoms and FEM nodes are individually related. The methodology is inherently applicable to three-dimensional domains, avoids discretization of the continuum model down to atomic scales, and permits arbitrary temperatures to be applied.

Saether, E.; Yamakov, V.; Glaessgen, E.

2007-01-01

138

An Optimization Principle for Deriving Nonequilibrium Statistical Models of Hamiltonian Dynamics  

NASA Astrophysics Data System (ADS)

A general method for deriving closed reduced models of Hamiltonian dynamical systems is developed using techniques from optimization and statistical estimation. Given a vector of resolved variables, selected to describe the macroscopic state of the system, a family of quasi-equilibrium probability densities on phase space corresponding to the resolved variables is employed as a statistical model, and the evolution of the mean resolved vector is estimated by optimizing over paths of these densities. Specifically, a cost function is constructed to quantify the lack-of-fit to the microscopic dynamics of any feasible path of densities from the statistical model; it is an ensemble-averaged, weighted, squared-norm of the residual that results from submitting the path of densities to the Liouville equation. The path that minimizes the time integral of the cost function determines the best-fit evolution of the mean resolved vector. The closed reduced equations satisfied by the optimal path are derived by Hamilton-Jacobi theory. When expressed in terms of the macroscopic variables, these equations have the generic structure of governing equations for nonequilibrium thermodynamics. In particular, the value function for the optimization principle coincides with the dissipation potential that defines the relation between thermodynamic forces and fluxes. The adjustable closure parameters in the best-fit reduced equations depend explicitly on the arbitrary weights that enter into the lack-of-fit cost function. Two particular model reductions are outlined to illustrate the general method. In each example the set of weights in the optimization principle contracts into a single effective closure parameter.

Turkington, Bruce

2013-08-01

139

Extreme-values statistics and dynamics of water at protein interfaces.  

PubMed

Immobilized proteins present a unique interface with water. The water translational diffusive motions affect the high-frequency dynamics and the nuclear spin-lattice relaxation as with all surfaces; however, rare binding sites for water in protein systems add very low-frequency components to the dynamics spectrum. Water binding sites in protein systems are not identical, thus distributions of free energies and consequent dynamics are expected. (2)H(2)O spin-lattice relaxation rate measurements as a function of magnetic field strength characterize the local rotational fluctuations for protein-bound water molecules. The measurements are sensitive to dynamics down to the kilohertz range. To account for the data, we show that the extreme-values statistics of rare events, i.e., water dynamics in rare binding sites, implies an exponential distribution of activation energies for the strongest binding events. In turn, for an activated dynamical process, the exponential energy distribution leads to a Pareto distribution for the reorientational correlation times and a power law in the Larmor frequency for the (2)H(2)O spin-lattice relaxation rate constants at low field strengths. The most strongly held water molecules escape from rare binding sites in times on the order of microseconds, which interrupts the intramolecular correlations and causes a plateau in the spin-lattice relaxation rate at very low magnetic field strengths. We examine the magnetic relaxation dispersion (MRD) data using two simple but related models: a protein-bound environment for water characterized by a single potential well and a protein-bound environment characterized by a double potential well where the potential functions for the local motions of the bound-state water are of different depth. This analysis is applied to D(2)O deuterium spin-lattice relaxation on cross-linked albumin and lysozyme, which is dominated by the intramolecular relaxation driven by the dynamical modulation of the nuclear electric quadrupole coupling. We also separate the intramolecular from the intermolecular contribution to water proton spin-lattice relaxation by isotope dilution and show that the intramolecular proton data map onto the deuterium relaxation by a scale factor implied by the relative strength of the quadrupole and dipolar couplings. The temperature and pH dependence of the magnetic relaxation dispersion are complex and accounted for by changing only the weighting factors in a superposition of contributions from single-well and double-well contributions. These experiments show that the reorientational dynamics spectrum for water, in and on a protein, is characterized by a strongly asymmetric distribution with a long-time tail that extends at least to microseconds. PMID:21932852

Korb, Jean-Pierre; Goddard, Yanina; Pajski, Jason; Diakova, Galina; Bryant, Robert G

2011-11-10

140

Impaired long-term memory retention and working memory in sdy mutant mice with a deletion in Dtnbp1, a susceptibility gene for schizophrenia  

PubMed Central

Background Schizophrenia is a complex genetic disorder caused by multiple genetic and environmental factors. The dystrobrevin-binding protein 1 (DTNBP1: dysbindin-1) gene is a major susceptibility gene for schizophrenia. Genetic variations in DTNBP1 are associated with cognitive functions, general cognitive ability and memory function, and clinical features of patients with schizophrenia including negative symptoms and cognitive decline. Since reduced expression of dysbindin-1 has been observed in postmortem brains of patients with schizophrenia, the sandy (sdy) mouse, which has a deletion in the Dtnbp1 gene and expresses no dysbindin-1 protein, could be an animal model of schizophrenia. To address this issue, we have carried out a comprehensive behavioral analysis of the sdy mouse in this study. Results In a rotarod test, sdy mice did not exhibit motor learning whilst the wild type mice did. In a Barnes circular maze test both sdy mice and wild type mice learned to selectively locate the escape hole during the course of the training period and in the probe trial conducted 24 hours after last training. However, sdy mice did not locate the correct hole in the retention probe tests 7 days after the last training trial, whereas wild type mice did, indicating impaired long-term memory retention. A T-maze forced alternation task, a task of working memory, revealed no effect of training in sdy mice despite the obvious effect of training in wild type mice, suggesting a working memory deficit. Conclusion Sdy mouse showed impaired long-term memory retention and working memory. Since genetic variation in DTNBP1 is associated with both schizophrenia and memory function, and memory function is compromised in patients with schizophrenia, the sdy mouse may represent a useful animal model to investigate the mechanisms of memory dysfunction in the disorder. PMID:18945333

Takao, Keizo; Toyama, Keiko; Nakanishi, Kazuo; Hattori, Satoko; Takamura, Hironori; Takeda, Masatoshi; Miyakawa, Tsuyoshi; Hashimoto, Ryota

2008-01-01

141

4.1. INTRODUCTION TO EQUILIBRIUM STATISTICAL MECHANICS1 Monte Carlo Simulations of Molecular Dynamics  

E-print Network

4.1. INTRODUCTION TO EQUILIBRIUM STATISTICAL MECHANICS1 Monte Carlo Simulations Statistical Me- chanics Basic reference: C. Thompson, Classical Equilibrium Statistical Mechanics-canonical en- sembles of equilibrium statistical mechanics. We will therefore begin with a review

Lim, Chjan C.

142

BRG1 Controls the Activity of the Retinoblastoma Protein via Regulation of p21CIP1\\/WAF1\\/SDI  

Microsoft Academic Search

complexes regulate the expression of the cdk inhibitor p21CIP1\\/WAF1\\/SDI. Furthermore, we show that the physical interaction between BRG1 and pRB is not required for induction of cell growth arrest and transcrip- tional repression of E2F target genes by pRB. Instead, BRG1 activates pRB by inducing its hypophosphory- lation through up-regulation of the cdk inhibitor p21. The hypophosphorylation of pRB is

Hyeog Kang; Kairong Cui; Keji Zhao

2004-01-01

143

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

PubMed

Rural areas represent approximately 95% of the 14000 km(2) 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 was designed and installed as a field trial. The experimental system that integrates a seasonal cropping system was evaluated for two years on a 500-m(2) Houston clay site in west central Alabama from August 2006 to June 2008. The SDI system was designed to start hydraulic dosing only when field moisture was below field capacity. Hydraulic dosing rates fluctuated as expected with higher dosing rates during warm seasons with near zero or zero dosing rates during cold seasons. Lower hydraulic dosing in winter creates the need for at least a two-month waste storage structure which is an insurmountable challenge for rural homeowners. An estimated 30% of dosed water percolated below 45-cm depth during the first summer which included a 30-year historic drought. This massive volume of percolation was presumably the result of preferential flow stimulated by dry weather clay soil cracking. Although water percolation is necessary for OWTS, this massive water percolation loss indicated that this experimental system is not able to effective control soil moisture within its monitoring zone as designed. Overall findings of this study indicated that soil moisture controlled SDI wastewater dosing is not suitable as a standalone system in these Vertisols. However, the experimental soil moisture control system functioned as designed, demonstrating that soil moisture controlled SDI wastewater dosing may find application as a supplement to other wastewater disposal methods that can function during cold seasons. PMID:21621905

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

2011-10-01

144

Statistical decadal predictions for sea surface temperatures: a benchmark for dynamical GCM predictions  

NASA Astrophysics Data System (ADS)

Accurate decadal climate predictions could be used to inform adaptation actions to a changing climate. The skill of such predictions from initialised dynamical global climate models (GCMs) may be assessed by comparing with predictions from statistical models which are based solely on historical observations. This paper presents two benchmark statistical models for predicting both the radiatively forced trend and internal variability of annual mean sea surface temperatures (SSTs) on a decadal timescale based on the gridded observation data set HadISST. For both statistical models, the trend related to radiative forcing is modelled using a linear regression of SST time series at each grid box on the time series of equivalent global mean atmospheric CO2 concentration. The residual internal variability is then modelled by (1) a first-order autoregressive model (AR1) and (2) a constructed analogue model (CA). From the verification of 46 retrospective forecasts with start years from 1960 to 2005, the correlation coefficient for anomaly forecasts using trend with AR1 is greater than 0.7 over parts of extra-tropical North Atlantic, the Indian Ocean and western Pacific. This is primarily related to the prediction of the forced trend. More importantly, both CA and AR1 give skillful predictions of the internal variability of SSTs in the subpolar gyre region over the far North Atlantic for lead time of 2-5 years, with correlation coefficients greater than 0.5. For the subpolar gyre and parts of the South Atlantic, CA is superior to AR1 for lead time of 6-9 years. These statistical forecasts are also compared with ensemble mean retrospective forecasts by DePreSys, an initialised GCM. DePreSys is found to outperform the statistical models over large parts of North Atlantic for lead times of 2-5 years and 6-9 years, however trend with AR1 is generally superior to DePreSys in the North Atlantic Current region, while trend with CA is superior to DePreSys in parts of South Atlantic for lead time of 6-9 years. These findings encourage further development of benchmark statistical decadal prediction models, and methods to combine different predictions.

Ho, Chun Kit; Hawkins, Ed; Shaffrey, Len; Underwood, Fiona M.

2013-08-01

145

A statistical model for high-resolution mapping of quantitative trait loci determining HIV dynamics.  

PubMed

Are there specific genes that control the pathogenesis of HIV infection? This question, which is of fundamental importance in designing personalized strategies of gene therapy to control HIV infection, can be examined by genetic mapping approaches. In this article, we present a new statistical model for unravelling the genetic mechanisms for the dynamic change of HIV that causes AIDS by marker-based linkage disequilibrium (LD) analyses. This new model is the extension of our functional mapping theory to integrate viral load trajectories within a genetic mapping framework. Earlier studies of HIV dynamics have led to various mathematical functions for modelling the kinetic curves of plasma virions and CD4 lymphocytes in HIV patients. Through incorporating these functions into the LD-based mapping procedure, we can identify and map individual quantitative trait loci (or QTL) responsible for viral pathogenesis. We derive a closed-form solution for estimating QTL allele frequency and marker-QTL linkage disequilibrium in the context of EM algorithm and implement the simplex algorithm to estimate the mathematical parameters describing the curve shapes of HIV pathogenesis. We performed different simulation scenarios based on currently used clinical designs in AIDS/HIV research to illustrate the utility and power of our model for genetic mapping of HIV dynamics. The implications of our model for genetic and genomic research into AIDS pathogenesis are discussed. PMID:15351959

Wang, Zuoheng; Wu, Rongling

2004-10-15

146

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

147

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. PMID:23745140

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

2013-01-01

148

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

149

Development of a current collection loss management system for SDI homopolar power supplies  

SciTech Connect

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operated continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the first year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design and construction of a cryogenically-cooled brush test rig, design of a high speed brush test rig, loss analysis of the current collection system, and an application study which defines the air core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 15 figs.

Hannan, W.F. III.

1987-01-01

150

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

151

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

152

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

153

A copula approach on the dynamics of statistical dependencies in the US stock market  

NASA Astrophysics Data System (ADS)

We analyze the statistical dependence structure of the S&P 500 constituents in the 4-year period from 2007 to 2010 using intraday data from the New York Stock Exchange’s TAQ database. Instead of using a given parametric copula with a predetermined shape, we study the empirical pairwise copula directly. We find that the shape of this copula resembles the Gaussian copula to some degree, but exhibits a stronger tail dependence, for both correlated and anti-correlated extreme events. By comparing the tail dependence dynamically to the market’s average correlation level as a commonly used quantity we disclose the average level of error of the Gaussian copula, which is implied in the calculation of many correlation coefficients.

Münnix, Michael C.; Schäfer, Rudi

2011-11-01

154

The inclusion of dynamic factors in statistical power system cost models, Part I  

SciTech Connect

Power system production cost models which rely upon statistical analysis of load distributions, such as load duration models and most probabilistic methods, do not include the dynamic cost associated with thermal plant startup, banking and the need to maintain adequate levels of operating reserve. This limits their ability to model the real cost of operating power systems, and may lead to substantial inaccuracies if the models are used to assess the value of certain types of plant investment. This paper shows how the transition-frequency function may be used to estimate plant startup and banking costs under various conditions, and demonstrates how the calculations can be performed in terms of cumulants of the functions involved, thus enabling a very efficient formulation.

Grubb, M.

1989-05-01

155

Statistical moments for classical and quantum dynamics: Formalism and generalized uncertainty relations  

NASA Astrophysics Data System (ADS)

The classical and quantum evolution of a generic probability distribution is analyzed. To that end, a formalism based on the decomposition of the distribution in terms of its statistical moments is used, which makes explicit the differences between the classical and quantum dynamics. In particular, there are two different sources of quantum effects. Distributional effects, which are also present in the classical evolution of an extended distribution, are due to the fact that all moments cannot be vanishing because of the Heisenberg uncertainty principle. In addition, the noncommutativity of the basic quantum operators add some terms to the quantum equations of motion that explicitly depend on the Planck constant and are not present in the classical setting. These are thus purely quantum effects. Some particular Hamiltonians are analyzed that have very special properties regarding the evolution they generate in the classical and quantum sector. In addition, a large class of inequalities obeyed by high-order statistical moments, and in particular uncertainty relations that bound the information that is possible to obtain from a quantum system, are derived.

Brizuela, David

2014-10-01

156

Predicting and attributing recent East African Spring droughts with dynamical-statistical climate model ensembles  

NASA Astrophysics Data System (ADS)

During boreal spring, eastern portions of Kenya and Somalia have experienced more frequent droughts since 1999. Given the region's high levels of food insecurity, better predictions of these droughts could provide substantial humanitarian benefits. We show that dynamical-statistical seasonal climate forecasts, based on the latest generation of coupled atmosphere-ocean and uncoupled atmospheric models, effectively predict boreal spring rainfall in this area. Skill sources are assessed by comparing ensembles driven with full-ocean forcing with ensembles driven with ENSO-only sea surface temperatures (SSTs). Our analysis suggests that both ENSO and non-ENSO Indo-Pacific SST forcing have played an important role in the increase in drought frequencies. Over the past 30 years, La Niña drought teleconnections have strengthened, while non-ENSO Indo-Pacific convection patterns have also supported increased (decreased) Western Pacific (East African) rainfall. To further examine the relative contribution of ENSO, low frequency warming and the Pacific Decadal Oscillation, we present decompositions of ECHAM5, GFS, CAM4 and GMAO AMIP simulations. These decompositions suggest that rapid warming in the western Pacific and steeper western-to-central Pacific SST gradients have likely played an important role in the recent intensification of the Walker circulation, and the associated increase in East African aridity. A linear combination of time series describing the Pacific Decadal Oscillation and the strength of Indo-Pacific warming are shown to track East African rainfall reasonably well. The talk concludes with a few thoughts linking the potentially important interplay of attribution and prediction. At least for recent East African droughts, it appears that a characteristic Indo-Pacific SST and precipitation anomaly pattern can be linked statistically to support forecasts and attribution analyses. The combination of traditional AGCM attribution analyses with simple yet physically plausible statistical estimation procedures may help us better untangle some climate mysteries.

Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.

2013-12-01

157

The Master kinetic equation for the statistical treatment of the Boltzmann-Sinai classical dynamical system  

NASA Astrophysics Data System (ADS)

In this investigation, exact particular realizations are sought for the microscopic statistical description which is associated with the classical dynamical system (CDS) formed by N identical smooth hard spheres subject to elastic collisions ( S N -CDS). The problem is posed in the framework of the ab initio statistical description of S N -CDS recently developed. It is shown that the Liouville equation associated with SN-CDS admits an exact particular solution for the N-body probability density function (PDF). This is factorized in terms of the i-th particle 1-body PDF (for all i = 1, N) via suitable weighting factors, which are denoted here as particle occupation coefficients. The latter are found to depend functionally only on the 1-body PDFs which are associated with each of the remaining particles belonging to S N -CDS. Furthermore, the 1-body PDF is proved to obey a well-defined statistical equation, referred to here as Master kinetic equation. This is an exact kinetic equation which takes into account the occurrence of configuration-space correlations due to the finite size of the extended particles, while depending functionally on the same 1-body PDF only. The asymptotic approximation of the Master equation, which holds in validity of the Boltzmann-Grad limit, is shown to recover in a suitable asymptotic sense the customary Boltzmann equation. Finally, a critical analysis is presented of the original and modified versions of the Enskog kinetic equation, as well as of some of the non-linear kinetic approaches formulated in the past for dense granular gases. Their conditions of validity and main differences with respect to the present theory are pointed out.

Tessarotto, Massimo; Cremaschini, Claudio

2014-07-01

158

An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses  

NASA Technical Reports Server (NTRS)

The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.

Saether, E.; Glaessgen, E.H.; Yamakov, V.

2008-01-01

159

Equilibrium statistics and dynamics of point vortex flows on the sphere  

E-print Network

We present results for the equilibrium statistics and dynamic evolution of moderately large ($n = {\\mathcal{O}}(10^2 - 10^3)$) numbers of interacting point vortices on the unit sphere under the constraint of zero mean angular momentum. We consider a binary gas consisting of equal numbers of vortices with positive and negative circulations. When the circulations are chosen to be proportional to $1/\\sqrt{n}$, the energy probability distribution function, $p(E)$, converges rapidly with $n$ to a function that has a single maximum, corresponding to a maximum in entropy. Ensemble-averaged wavenumber spectra of the nonsingular velocity field induced by the vortices exhibit the expected $k^{-1}$ behavior at small scales for all energies. The spectra at the largest scales vary continuously with the inverse temperature $\\beta$ of the system and show a transition from positively sloped to negatively sloped as $\\beta$ becomes negative. The dynamics are ergodic and, regardless of the initial configuration of the vortices,...

Dritschel, David G; Poje, Andrew C

2014-01-01

160

Prequantum Classical Statistical Field Theory: Schrödinger Dynamics of Entangled Systems as a Classical Stochastic Process  

NASA Astrophysics Data System (ADS)

The idea that quantum randomness can be reduced to randomness of classical fields (fluctuating at time and space scales which are essentially finer than scales approachable in modern quantum experiments) is rather old. Various models have been proposed, e.g., stochastic electrodynamics or the semiclassical model. Recently a new model, so called prequantum classical statistical field theory (PCSFT), was developed. By this model a "quantum system" is just a label for (so to say "prequantum") classical random field. Quantum averages can be represented as classical field averages. Correlations between observables on subsystems of a composite system can be as well represented as classical correlations. In particular, it can be done for entangled systems. Creation of such classical field representation demystifies quantum entanglement. In this paper we show that quantum dynamics (given by Schrödinger's equation) of entangled systems can be represented as the stochastic dynamics of classical random fields. The "effect of entanglement" is produced by classical correlations which were present at the initial moment of time, cf. views of Albert Einstein.

Khrennikov, Andrei

2011-03-01

161

Dynamics of Infuence on Hierarchical Structures: Towards the Statistical Mechanics of Social Class Struggle  

E-print Network

The theory of class struggle is modeled within the framework of statistical physics. Dichotomous spin dynamics on a pyramid-shaped hierarchical structure are examined (akin to the Cayley tree). A "head node" is placed at the apex. The system embodies a number of "classes", corresponding to different levels of the hierarchy. A class is comprised of nodes that are equidistant from the head. Weighted links exist between nodes from the same and different classes. We study the effect of these weights on the dynamics. The spin (hereafter, "state") of the head node is fixed, and it imposes its state on the rest of the hierarchy. Necessary conditions so that the classes eventually repudiate or acquiesce in the state imposed by the head node are found. The results show that, to reach unanimity across the hierarchy, it suffices for the head node to make the bottom-most class adopt the same state. Then the rest of the hierarchy will inevitably comply, regardless of the inter/intra class link configurations. Hence the ro...

Fotouhi, Babak

2013-01-01

162

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

163

Fast computation of statistical uncertainty for spatiotemporal distributions estimated directly from dynamic cone beam SPECT projections  

SciTech Connect

The estimation of time-activity curves and kinetic model parameters directly from projection data is potentially useful for clinical dynamic single photon emission computed tomography (SPECT) studies, particularly in those clinics that have only single-detector systems and thus are not able to perform rapid tomographic acquisitions. Because the radiopharmaceutical distribution changes while the SPECT gantry rotates, projections at different angles come from different tracer distributions. A dynamic image sequence reconstructed from the inconsistent projections acquired by a slowly rotating gantry can contain artifacts that lead to biases in kinetic parameters estimated from time-activity curves generated by overlaying regions of interest on the images. If cone beam collimators are used and the focal point of the collimators always remains in a particular transaxial plane, additional artifacts can arise in other planes reconstructed using insufficient projection samples [1]. If the projection samples truncate the patient's body, this can result in additional image artifacts. To overcome these sources of bias in conventional image based dynamic data analysis, we and others 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 [2-8]. In our previous work we developed a computationally efficient method for fully four-dimensional (4-D) direct estimation of spatiotemporal distributions from dynamic SPECT projection data [5], which extended Formiconi's least squares algorithm for reconstructing temporally static distributions [9]. In addition, we studied the biases that result from modeling various orders temporal continuity and using various time samplings [5]. the present work, we address computational issues associated with evaluating the statistical uncertainty of spatiotemporal model parameter estimates, and use Monte Carlo simulations to a fast algorithm for computing the covariance matrix for the parameters. Given this covariance matrix, the covariance between the time-activity curve models for the blood input function and tissue volumes of interest can be calculated and used to estimate compartmental model kinetic parameters more precisely, using nonlinear weighted least squares [10,11].

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

2001-04-09

164

Argonne CW Linac (ACWL)—legacy from SDI and opportunities for the future  

NASA Astrophysics Data System (ADS)

The former Strategic Defense Initiative Organization (SDIO) invested significant resources over a 6-year period to develop and build an accelerator to demonstrate the launching of a cw beam with characteristics suitable for a space-based Neutral Particle Beam (NPB) system. This accelerator, the CWDD (Continuous Wave Deuterium Demonstrator) accelerator, was designed to accelerate 80 mA cw of D- to 7.5 MeV. A considerable amount of hardware was constructed and installed in the Argonne-based facility, and major performance milestones were achieved before program funding from the Department of Defense ended in October 1993. Existing assets have been turned over to Argonne. Assets include a fully functional 200 kV cw D- injector, a cw RFQ that has been tuned, leak checked and aligned, beam lines and a high-power beam stop, all installed in a shielded vault with appropriate safety and interlock systems. In addition, there are two high power (1 MW) cw rf amplifiers and all the ancillary power, cooling and control systems required for a high-power accelerator system. The SDI mission required that the CWDD accelerator structures operate at cryogenic temperatures (26K), a requirement that placed severe limitations on operating period (CWDD would have provided 20 seconds of cw beam every 90 minutes). However, the accelerator structures were designed for full-power rf operation with water cooling and ACWL (Argonne Continuous Wave Linac), the new name for CWDD in its water-cooled, positive-ion configuration, will be able to operate continuously. Project status and achievements will be reviewed. Preliminary design of a proton conversion for the RFQ, and other proposals for turning ACWL into a testbed for cw-linac engineering, will be discussed.

McMichael, G. E.; Yule, T. J.

1995-09-01

165

The SdiA-regulated gene srgE encodes a type III secreted effector.  

PubMed

Salmonella enterica serovar Typhimurium is a food-borne pathogen that causes severe gastroenteritis. The ability of Salmonella to cause disease depends on two type III secretion systems (T3SSs) encoded in two distinct Salmonella pathogenicity islands, 1 and 2 (SPI1 and SPI2, respectively). S. Typhimurium encodes a solo LuxR homolog, SdiA, which can detect the acyl-homoserine lactones (AHLs) produced by other bacteria and upregulate the rck operon and the srgE gene. SrgE is predicted to encode a protein of 488 residues with a coiled-coil domain between residues 345 and 382. In silico studies have provided conflicting predictions as to whether SrgE is a T3SS substrate. Therefore, in this work, we tested the hypothesis that SrgE is a T3SS effector by two methods, a ?-lactamase activity assay and a split green fluorescent protein (GFP) complementation assay. SrgE with ?-lactamase fused to residue 40, 100, 150, or 300 was indeed expressed and translocated into host cells, but SrgE with ?-lactamase fused to residue 400 or 488 was not expressed, suggesting interference by the coiled-coil domain. Similarly, SrgE with GFP S11 fused to residue 300, but not to residue 488, was expressed and translocated into host cells. With both systems, translocation into host cells was dependent upon SPI2. A phylogenetic analysis indicated that srgE is found only within Salmonella enterica subspecies. It is found sporadically within both typhoidal and nontyphoidal serovars, although the SrgE protein sequences found within typhoidal serovars tend to cluster separately from those found in nontyphoidal serovars, suggesting functional diversification. PMID:24727228

Habyarimana, Fabien; Sabag-Daigle, Anice; Ahmer, Brian M M

2014-06-01

166

Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment  

NASA Astrophysics Data System (ADS)

ERA-40 reanalyses, and simulations from three regional climate models (RCMs) (ALADIN, LMDZ, and WRF) and from one statistical downscaling model (CDF-t) are used to evaluate the uncertainty in downscaling of wind, temperature, and rainfall cumulative distribution functions (CDFs) for eight stations in the French Mediterranean basin over 1991-2000. The uncertainty is quantified using the Cramer-von Mises score (CvM) to measure the "distance" between the simulated and observed CDFs. The ability of the three RCMs and CDF-t to simulate the "climate" variability is quantified with the explained variance, variance ratio and extreme occurrence. The study shows that despite their differences, the three RCMs display very similar performance. In terms of global distributions (i.e. CvM), all models perform better than ERA-40 for both seasons and variables. However, looking at variance criteria, RCMs are not always much better than ERA-40 reanalyses, whereas CDF-t produces accurate results when applied to ERA-40. In a second step, a combined statistical/dynamical downscaling approach has been used, consisting in applying CDF-t to the RCM outputs. It shows that CDF-t applied to the RCM outputs does not necessarily produce better results than those from CDF-t directly applied to ERA-40. It also shows that CDF-t applied to RCMs generally improves the downscaled CDFs and that the "additional" added value of CDF-t applied to the RCMs is independent of the performance of the RCMs in terms of CvM, explained variance, variance ratio and extreme occurrence.

Vrac, M.; Drobinski, P.; Merlo, A.; Herrmann, M.; Lavaysse, C.; Li, L.; Somot, S.

2012-09-01

167

Comparison of statistical and dynamical downscaling of extreme precipitations over France in present-day and future climate  

Microsoft Academic Search

We present a comparison of two downscaling methods of extreme precipitations over France at a climatic time scale : a dynamical one performed with the Regional Climate Model ALADIN-Climate used at a resolution of 12 km, and a statistical one based on the weather regime approach and using the analog methodology to reconstruct daily fields of precipitations at a 8

Jeanne Colin; Michel Déqué; Emila Sanchez Gomez; Samuel Somot

2010-01-01

168

The Gcrc Two-Dimensional Zonally Averaged Statistical Dynamical Climate Model: Development, Model Performance, and Climate Sensitivity  

Microsoft Academic Search

The two-dimensional statistical dynamical climate model that has recently been developed at the Global Change Research Center and the Oregon Graduate Institute of Science & Technology (GCRC 2D climate model) is presented and several new results obtained using the model are discussed. The model solves the 2-D primitive equations in finite difference form (mass continuity, Newton's second law, and the

Robert Malcolm Mackay

1994-01-01

169

Bubble statistics and coarsening dynamics for quasi-two-dimensional foams with increasing liquid content  

NASA Astrophysics Data System (ADS)

We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling regime, all bubble distributions are independent not only of time, but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid; we achieve a factor of 4 reduction from the dry limit. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and decreasing bubble size. We successfully model this behavior by explicitly incorporating the border-blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry.

Roth, A. E.; Jones, C. D.; Durian, D. J.

2013-04-01

170

Passage Time Statistics in Exponential Distributed Time-Delay Models: Noisy Asymptotic Dynamics  

NASA Astrophysics Data System (ADS)

The stochastic dynamics toward the final attractor in exponential distributed time-delay non-linear models is presented, then the passage time statistic is studied analytically in the small noise approximation. The problem is worked out by going to the associated two-dimensional system. The mean first passage time from the unstable state for this non-Markovian type of system has been worked out using two different approaches: firstly, by a rigorous adiabatic Markovian approximation (in the small mean delay-time ); secondly, by introducing the stochastic path perturbation approach to get a non-adiabatic theory for any . This first passage time distribution can be written in terms of the important parameters of the models. We have compared both approaches and we have found excellent agreement between them in the adiabatic limit. In addition, using our non-adiabatic approach we predict a crossover and a novel behavior for the relaxation scaling-time as a function of the delay parameter which for goes as.

Cáceres, Manuel O.

2014-07-01

171

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

172

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

2013-04-01

173

Bubble statistics and coarsening dynamics for quasi-two-dimensional foams with increasing liquid content.  

PubMed

We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling regime, all bubble distributions are independent not only of time, but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid; we achieve a factor of 4 reduction from the dry limit. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and decreasing bubble size. We successfully model this behavior by explicitly incorporating the border-blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry. PMID:23679411

Roth, A E; Jones, C D; Durian, D J

2013-04-01

174

Bubble statistics and coarsening dynamics for quasi-two dimensional foams with increasing liquid content  

E-print Network

We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling state, all bubble distributions are independent not only of time but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and with decreasing bubble size. We successfully model this behavior by explicitly incorporating the border blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry.

A. E. Roth; C. D. Jones; D. J. Durian

2012-06-30

175

Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response  

NASA Astrophysics Data System (ADS)

An interesting opportunity to determine thermodynamic and transport properties in more detail is to identify generic statistical properties of initial density perturbations. Here we study event-by-event fluctuations in terms of correlation functions for two models that can be solved analytically. The first assumes Gaussian fluctuations around a distribution that is fixed by the collision geometry but leads to non-Gaussian features after averaging over the reaction plane orientation at non-zero impact parameter. In this context, we derive a three-parameter extension of the commonly used Bessel-Gaussian event-by-event distribution of harmonic flow coefficients. Secondly, we study a model of N independent point sources for which connected n-point correlation functions of initial perturbations scale like 1 /N n-1. This scaling is violated for non-central collisions in a way that can be characterized by its impact parameter dependence. We discuss to what extent these are generic properties that can be expected to hold for any model of initial conditions, and how this can improve the fluid dynamical analysis of heavy ion collisions.

Floerchinger, Stefan; Wiedemann, Urs Achim

2014-08-01

176

The formulation of quantum statistical mechanics based on the Feynman path centroid density. II. Dynamical properties  

E-print Network

The formulation of quantum statistical mechanics based on the Feynman path centroid density. II are particularly useful classical-like quantities in statistical mechanics. It seems ac- curate to characterize, these two developments present a systematic formulation of equilibrium quantum statistical mechanics from

Cao, Jianshu

177

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

2012-02-01

178

Statistical Analysis of the Geometric Properties of the Dynamic Polar Cusp Using a Global MHD Simulation  

NASA Astrophysics Data System (ADS)

The properties of particle precipitation and plasma waves in the low-altitude cusp are distinct from those in neighboring regions, so prediction of the cusp location and extent under dynamic conditions is important in understanding polar-region variability. The aim of this paper is to examine how the properties of the dayside cusp vary with solar wind conditions in the LFM global simulation. This variation is then compared to similar observations obtained from satellite data. The simulation is run for the August 31, 2005 to September 1, 2005 moderate storm where Bz peaked at -17 nT and Dst at -140 nT. The solar wind data from these two days exhibit a wide range of conditions that enable a statistical representation of the cusp to be obtained. The simulated cusp centre is identified by the position of maximum dayside dipole depression at 6 RE. This location is then mapped along field lines to the ionosphere. The latitude of the cusp is then co-correlated with the Bz component of the IMF to calculate the best time offset between solar wind data and cusp location. The correlation of the cusp latitude and various solar wind IMF coupling functions is explored. The linear correlation of the simulated cusp latitude with the southward component of the IMF is approximately 0.75. In agreement with Newell et al. 2006 a higher correlation is obtained using other solar wind coupling functions such as Kan-Lee electric field (0.89) and half wave rectifier (0.88). The MLT position of the simulated cusp is found to depend upon the strength of By. The linear correlation at 0.54 is not as strong as between Bz and cusp latitude. The width of the simulated cusp in both latitude and MLT is also examined. The area of the cusp is set to be the region at 6 RE where the dipole depression is more than 52 nT. The size of the cusp is found to depend on the solar wind dynamic pressure and electric field. Newell, P. T., T. Sotirelis, K. Liou, C.I. Meng, and F.J. Rich (2006), Cusp latitude and the optimal solar wind coupling function, J. Geophys. Res., 111, A09207, doi:10.1029/2006JA011731.

Dunlap-Shohl, W. A.; Brambles, O.; Lotko, W.; Zhang, B.

2010-12-01

179

Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part two: Solar flares dynamics  

NASA Astrophysics Data System (ADS)

In this study which is the continuation of the first part (Pavlos et al. 2012) [1], the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis (1988) [3]. The q-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the singular value decomposition (SVD) components of the solar flares timeseries. Also the multifractal scaling exponent spectrum f(a), the generalized Renyi dimension spectrum D(q) and the spectrum J(p) of the structure function exponents were estimated experimentally and theoretically by using theq-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2000) [25]. Our analysis showed clearly the following: (a) a phase transition process in the solar flare dynamics from a high dimensional non-Gaussian self-organized critical (SOC) state to a low dimensional also non-Gaussian chaotic state, (b) strong intermittent solar corona turbulence and an anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes a phase transition to low dimensional chaos, (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of the functions: (i) non-Gaussian probability distribution function P(x), (ii) f(a) and D(q), and (iii) J(p) for the solar flares timeseries and its underlying non-equilibrium solar dynamics, and (d) the solar flare dynamical profile is revealed similar to the dynamical profile of the solar corona zone as far as the phase transition process from self-organized criticality (SOC) to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.

Karakatsanis, L. P.; Pavlos, G. P.; Xenakis, M. N.

2013-09-01

180

Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part two: Solar Flares dynamics  

E-print Network

In the second part of this study and similarly with part one, the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis [1]. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the solar flares timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu [2]. Our analysis showed clearly the following: a) a phase transition process in the solar flare dynamics from high dimensional non Gaussian SOC state to a low dimensional also non Gaussian chaotic state, b) strong intermittent solar corona turbulence and anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes phase transition to low dimensional chaos: c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. e) The solar flare dynamical profile is revealed similar to the dynamical profile of the solar convection zone as far as the phase transition process from SOC to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.

L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis

2012-03-25

181

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

E-print Network

at the low energy regime by means of a statistical quantum method Tomás González-Lezana,1,a) Pascal Honvault of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) betweenDynamics of the D+ + H2 HD + H+ reaction at the low energy regime by means of a statistical

Honvault, Pascal

182

Doubled CO2 experiments with the Global change research center two-dimensional statistical dynamical climate model  

Microsoft Academic Search

The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics)

R. M. MacKay; M. A. K. Khalil

1995-01-01

183

The BA Previews Project: The Development and Evaluation of a Mechanised S.D.I. Service for Biologists. Final Report. OSTI Report No. 5140.  

ERIC Educational Resources Information Center

During a 2-year period (1970, 1971) SDI (Selective Dissemination of Information) search profiles were written for 353 biologists and other research workers with a need for biological information in academic, industrial, and government research institutions. At the beginning of the experiment a questionnaire and interview survey was made of the…

Leggate, P.; And Others

184

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

185

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 models for mean and extreme values of total column ozone on spatial scales to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes. The r-largest order statistics method is used for pointwise analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively). For the corresponding mean value analysis a pointwise autoregressive moving average model (ARMA) is used. The statistical models include important atmospheric covariates to describe the dynamical and chemical state of the atmosphere: 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 ozone distribution, respectively described by means 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.

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

2012-05-01

186

Journal of Statistical Physics, Vol. 82, Nos. 1/2, 1996 Molecular Dynamics Simulation of  

E-print Network

is known about the basic physical processes involved in the dynamics of granular media and many puzzles the preparation of food, drugs, detergents, cosmetics, cements, etc. (see, e.g., ref. 2). Granular dynamics in the granular media. As far as we know, our simulation is the first one able to reproduce this simple

Gallas, Jason

187

Complex networks for climate model evaluation with application to statistical versus dynamical modeling of South American climate  

NASA Astrophysics Data System (ADS)

In this study we introduce two new node-weighted difference measures on complex networks as a tool for climate model evaluation. The approach facilitates the quantification of a model's ability to reproduce the spatial covariability structure of climatological time series. We apply our methodology to compare the performance of a statistical and a dynamical regional climate model simulating the South American climate, as represented by the variables 2 m temperature, precipitation, sea level pressure, and geopotential height field at 500 hPa. For each variable, networks are constructed from the model outputs and evaluated against a reference network, derived from the ERA-Interim reanalysis, which also drives the models. We compare two network characteristics, the (linear) adjacency structure and the (nonlinear) clustering structure, and relate our findings to conventional methods of model evaluation. To set a benchmark, we construct different types of random networks and compare them alongside the climate model networks. Our main findings are: (1) The linear network structure is better reproduced by the statistical model statistical analogue resampling scheme (STARS) in summer and winter for all variables except the geopotential height field, where the dynamical model CCLM prevails. (2) For the nonlinear comparison, the seasonal differences are more pronounced and CCLM performs almost as well as STARS in summer (except for sea level pressure), while STARS performs better in winter for all variables.

Feldhoff, Jan H.; Lange, Stefan; Volkholz, Jan; Donges, Jonathan F.; Kurths, Jürgen; Gerstengarbe, Friedrich-Wilhelm

2014-05-01

188

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

189

Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma, Part one: Sunspot dynamics  

NASA Astrophysics Data System (ADS)

In this study, the non-linear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis (1988, 2004, 2009) [7,9,10]. The q-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum f(a), the generalized Renyi dimension spectrum D(q) and the spectrum J(p) of the structure function exponents were estimated experimentally and theoretically by using the q-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2001, 2000) [76,77]. Our analysis showed clearly the following: (a) a phase transition process in the solar dynamics from high dimensional non-Gaussian SOC state to a low dimensional non-Gaussian chaotic state, (b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes a phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov’s studies (Zelenyi and Milovanov (1991) [21]); Milovanov and Zelenyi (1993) [22]; Ruzmakin et al. (1996) [26]) (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of (i) non-Gaussian probability distribution function P(x), (ii) multifractal scaling exponent spectrum f(a) and generalized Renyi dimension spectrum Dq, (iii) exponent spectrum J(p) of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics.

Pavlos, G. P.; Karakatsanis, L. P.; Xenakis, M. N.

2012-12-01

190

Universal renormalization-group dynamics at the onset of chaos in logistic maps and nonextensive statistical mechanics  

NASA Astrophysics Data System (ADS)

We uncover the dynamics at the chaos threshold ?? of the logistic map and find that it consists of trajectories made of intertwined power laws that reproduce the entire period-doubling cascade that occurs for ?statistical mechanics to critical points of nonlinear maps.

Baldovin, F.; Robledo, A.

2002-10-01

191

A Statistical Study on the Morphology of Rays and Dynamics of Blobs in the Wake of Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

In this paper, with a survey through the Large Angle and Spectrometric Coronagraph data from 1996 to 2009, we present 11 events with plasma blobs flowing outwards sequentially along a bright coronal ray in the wake of coronal mass ejections. The rays are believed to be associated with the current sheet structure that formed as a result of the solar eruption, and the blobs are products of magnetic reconnections occurring along the current sheets. The ray morphology and blob dynamics are investigated statistically. It is found that the apparent angular widths of the rays at certain times vary in a range of 2.1° - 6.6° (2.0° - 4.4°) with an average of 3.5° (2.9°) at 3 Rs (4 Rs), and the observable time durations vary from 12 hours to a few days with an average of 27 hours. It is also found, based on the dynamical analysis on the blob motions, that 58% (26) of the blobs are accelerated, 20% (9) are decelerated, and 22% (10) move with a nearly-constant speed. Comparing the dynamics of our blobs and those that are observed above the tip of helmet streamers, we find that the speeds and accelerations of the blobs in these two cases differ significantly. It is suggested that these differences of the blob dynamics stem from the associated magnetic reconnections involving different magnetic field configurations and triggering processes.

Song, H.; Kong, X.; CHEN, Y.; Li, B.; Li, G.; Feng, S.; Xia, L.

2011-12-01

192

Statistical Analysis of the Geometric Properties of the Dynamic Polar Cusp Using a Global MHD Simulation  

Microsoft Academic Search

The properties of particle precipitation and plasma waves in the low-altitude cusp are distinct from those in neighboring regions, so prediction of the cusp location and extent under dynamic conditions is important in understanding polar-region variability. The aim of this paper is to examine how the properties of the dayside cusp vary with solar wind conditions in the LFM global

W. A. Dunlap-Shohl; O. Brambles; W. Lotko; B. Zhang

2010-01-01

193

An exemplar-based statistical model for the dynamics of neural synchrony  

E-print Network

to be. The proposed method is applied to predict mild cognitive impairment (MCI) from EEG for the dynamics of neural synchrony We will use our method to predict mild cognitive impairment (MCI) from EEG to diagnose MCI and leads to a more detailed understanding of the abnormalities in EEG synchrony in MCI

Cichocki, Andrzej

194

Dynamics of localized waves in one-dimensional random potentials: Statistical theory of the coherent forward scattering peak  

NASA Astrophysics Data System (ADS)

As recently discovered [T. Karpiuk et al., Phys. Rev. Lett. 109, 190601 (2012), 10.1103/PhysRevLett.109.190601], Anderson localization in a bulk disordered system triggers the emergence of a coherent forward scattering (CFS) peak in momentum space, which twins the well-known coherent backscattering (CBS) peak observed in weak localization experiments. Going beyond the perturbative regime, we address here the long-time dynamics of the CFS peak in a one-dimensional random system and we relate this novel interference effect to the statistical properties of the eigenfunctions and eigenspectrum of the corresponding random Hamiltonian. Our numerical results show that the dynamics of the CFS peak is governed by the logarithmic level repulsion between localized states, with a time scale that is, with good accuracy, twice the Heisenberg time. This is in perfect agreement with recent findings based on the nonlinear sigma model. In the stationary regime, the width of the CFS peak in momentum space is inversely proportional to the localization length, reflecting the exponential decay of the eigenfunctions in real space, while its height is exactly twice the background, reflecting the Poisson statistical properties of the eigenfunctions. It would be interesting to extend our results to higher dimensional systems and other symmetry classes.

Lee, Kean Loon; Grémaud, Benoît; Miniatura, Christian

2014-10-01

195

Dynamic changes in brewing yeast cells in culture revealed by statistical analyses of yeast morphological data.  

PubMed

The vitality of brewing yeasts has been used to monitor their physiological state during fermentation. To investigate the fermentation process, we used the image processing software, CalMorph, which generates morphological data on yeast mother cells and bud shape, nuclear shape and location, and actin distribution. We found that 248 parameters changed significantly during fermentation. Successive use of principal component analysis (PCA) revealed several important features of yeast, providing insight into the dynamic changes in the yeast population. First, PCA indicated that much of the observed variability in the experiment was summarized in just two components: a change with a peak and a change over time. Second, PCA indicated the independent and important morphological features responsible for dynamic changes: budding ratio, nucleus position, neck position, and actin organization. Thus, the large amount of data provided by imaging analysis can be used to monitor the fermentation processes involved in beer and bioethanol production. PMID:24012106

Ohnuki, Shinsuke; Enomoto, Kenichi; Yoshimoto, Hiroyuki; Ohya, Yoshikazu

2014-03-01

196

The inclusion of dynamic factors in statistical power system cost models, Part II  

SciTech Connect

This paper develops techniques for analysing the costs of maintaining adequate operating reserve on power systems, within probabilistic production costing models and others based upon load distribution functions. The aim is to show that such models can be developed to approximate the full range of dynamic penalties associated with practical power system operation. Algorithms for costing predetermined part loading are presented, including the need for bringing plant on-line out of strict merit order. The paper then describes how an prediction error function can be used to estimate the probability that the specified spinning reserve is insufficient, and hence approximate the cost of gas turbine or storage utilisation for dynamic control. This allows estimation of optimal reserve levels. The paper also discusses the analysis of longer term reserve from banked thermal units. Finally, some results of the model are compared with those reported from hourly simulation studies.

Grubb, M.

1989-05-01

197

The writer independent online handwriting recognition system frog on hand and cluster generative statistical dynamic time warping.  

PubMed

In this paper, we give a comprehensive description of our writer-independent online handwriting recognition system frog on hand. The focus of this work concerns the presentation of the classification/training approach, which we call cluster generative statistical dynamic time warping (CSDTW). CSDTW is a general, scalable, HMM-based method for variable-sized, sequential data that holistically combines cluster analysis and statistical sequence modeling. It can handle general classification problems that rely on this sequential type of data, e.g., speech recognition, genome processing, robotics, etc. Contrary to previous attempts, clustering and statistical sequence modeling are embedded in a single feature space and use a closely related distance measure. We show character recognition experiments of frog on hand using CSDTW on the UNIPEN online handwriting database. The recognition accuracy is significantly higher than reported results of other handwriting recognition systems. Finally, we describe the real-time implementation of frog on hand on a Linux Compaq iPAQ embedded device. PMID:15376878

Bahlmann, Claus; Burkhardt, Hans

2004-03-01

198

Dynamical and statistical modelling of many body collisions Part II: Energy exchange  

Microsoft Academic Search

While rarefied gas dynamics has traditionally assumed a dilute gas, whose densities are so low that only binary collisions and single-body gas surface interactions occur, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lower heights the dilute gas is not valid. In particular, in the pure rarefied regime, two-body GSIs

A. A. Agbormbai

2001-01-01

199

Dynamical and statistical modelling of many body collisions Part I: Scattering  

Microsoft Academic Search

Although rarefied gas dynamics has traditionally rested on the dilute gas assumption, which presupposes that only binary collisions and single-body gas surface interactions occur, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lesser heights the dilute gas assumption is not valid. In particular, in the pure rarefied regime, two-body GSIs

A. A. Agbormbai

2001-01-01

200

Regulation of signal duration and the statistical dynamics of kinase activation by scaffold proteins  

E-print Network

Scaffolding proteins that direct the assembly of multiple kinases into a spatially localized signaling complex are often essential for the maintenance of an appropriate biological response. Although scaffolds are widely believed to have dramatic effects on the dynamics of signal propagation, the mechanisms that underlie these consequences are not well understood. Here, Monte Carlo simulations of a model kinase cascade are used to investigate how the temporal characteristics of signaling cascades can be influenced by the presence of scaffold proteins. Specifically, we examine the effects of spatially localizing kinase components on a scaffold on signaling dynamics. The simulations indicate that a major effect that scaffolds exert on the dynamics of cell signaling is to control how the activation of protein kinases is distributed over time. Scaffolds can influence the timing of kinase activation by allowing for kinases to become activated over a broad range of times, thus allowing for signaling at both early and late times. Scaffold concentrations that result in optimal signal amplitude also result in the broadest distributions of times over which kinases are activated. These calculations provide insights into one mechanism that describes how the duration of a signal can potentially be regulated in a scaffold mediated protein kinase cascade. Our results illustrate another complexity in the broad array of control properties that emerge from the physical effects of spatially localizing components of kinase cascades on scaffold proteins.

Jason W. Locasale; Arup K. Chakraborty

2008-07-13

201

A new dynamic approach for statistical optimization of GNSS radio occultation bending angles for optimal climate monitoring utility  

NASA Astrophysics Data System (ADS)

Navigation Satellite System (GNSS)-based radio occultation (RO) is a satellite remote sensing technique providing accurate profiles of the Earth's atmosphere for weather and climate applications. Above about 30 km altitude, however, statistical optimization is a critical process for initializing the RO bending angles in order to optimize the climate monitoring utility of the retrieved atmospheric profiles. Here we introduce an advanced dynamic statistical optimization algorithm, which uses bending angles from multiple days of European Centre for Medium-range Weather Forecasts (ECMWF) short-range forecast and analysis fields, together with averaged-observed bending angles, to obtain background profiles and associated error covariance matrices with geographically varying background uncertainty estimates on a daily updated basis. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.4 (OPSv5.4) algorithm, using several days of simulated MetOp and observed CHAMP and COSMIC data, for January and July conditions. We find the following for the new method's performance compared to OPSv5.4: 1.) it significantly reduces random errors (standard deviations), down to about half their size, and leaves less or about equal residual systematic errors (biases) in the optimized bending angles; 2.) the dynamic (daily) estimate of the background error correlation matrix alone already improves the optimized bending angles; 3.) the subsequently retrieved refractivity profiles and atmospheric (temperature) profiles benefit by improved error characteristics, especially above about 30 km. Based on these encouraging results, we work to employ similar dynamic error covariance estimation also for the observed bending angles and to apply the method to full months and subsequently to entire climate data records.

Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Wu, S.; Schwaerz, M.; Fritzer, J.; Zhang, S.; Carter, B. A.; Zhang, K.

2013-12-01

202

Screening of promoter-specific transcription factors: multiple regulators for the sdiA gene involved in cell division control and quorum sensing.  

PubMed

Prokaryotic DNA-binding transcription factors (TFs) bind in close vicinity of the promoter and regulate transcription through interplay with the DNA-dependent RNA polymerase. Promoters associated with the genes involved in stress response have recently been found to be under the control of multiple regulators, each monitoring one specific environmental condition or factor. In order to identify TFs involved in regulation of one specific promoter, we have developed a PS-TF (promoter-specific TF) screening system, in which the binding of purified TFs to a test promoter was analysed by gel-shift assay. This PS-TF screening system was applied for detection of TFs involved in regulation of the promoter for the Escherichia coli sdiA gene encoding the master regulator of cell division and quorum sensing. After screening of a total of 191 purified TFs (two-thirds of the predicted E. coli TFs), at least 15 TFs have been identified to bind to the sdiA promoter, including five two-component system (TCS) regulators, ArcA, CpxR, OmpR, RcsB and TorR. In this study, we focus on these five TFs for detailed analysis of their regulatory roles in vivo. Under normal growth conditions in LB medium, all these TFs repressed the sdiA promoter and the repression levels correlated with their intracellular levels. Taken together, we propose that these TCS regulators repress transcription in vivo of the sdiA gene, ultimately leading to suppression of cell division. PMID:24025606

Shimada, Kaori; Ogasawara, Hiroshi; Yamada, Kayoko; Shimura, Miki; Kori, Ayako; Shimada, Tomohiro; Yamanaka, Yuki; Yamamoto, Kaneyoshi; Ishihama, Akira

2013-12-01

203

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. PMID:9707427

Coqueret, O; Berube, G; Nepveu, A

1998-01-01

204

q-deformed statistical-mechanical property in the dynamics of trajectories en route to the Feigenbaum attractor.  

PubMed

We demonstrate that the dynamics toward and within the Feigenbaum attractor combine to form a q -deformed statistical-mechanical construction. The rate at which ensemble trajectories converge to the attractor (and to the repellor) is described by a q entropy obtained from a partition function generated by summing distances between neighboring positions of the attractor. The values of the q indices involved are given by the unimodal map universal constants, while the thermodynamic structure is closely related to that formerly developed for multifractals. As an essential component in our demonstration we expose, in great detail, the features of the dynamics of trajectories that either evolve toward the Feigenbaum attractor or are captured by its matching repellor. The dynamical properties of the family of periodic superstable cycles in unimodal maps are seen to be key ingredients for the comprehension of the discrete scale invariance features present at the period-doubling transition to chaos. Elements in our analysis are the following. (i) The preimages of the attractor and repellor of each of the supercycles appear entrenched into a fractal hierarchical structure of increasing complexity as period doubling develops. (ii) The limiting form of this rank structure results in an infinite number of families of well-defined phase-space gaps in the positions of the Feigenbaum attractor or of its repellor. (iii) The gaps in each of these families can be ordered with decreasing width in accordance with power laws and are seen to appear sequentially in the dynamics generated by uniform distributions of initial conditions. (iv) The power law with log-periodic modulation associated with the rate of approach of trajectories toward the attractor (and to the repellor) is explained in terms of the progression of gap formation. (v) The relationship between the law of rate of convergence to the attractor and the inexhaustible hierarchy feature of the preimage structure is elucidated. (vi) A "mean field" evaluation of the atypical partition function, a thermodynamic interpretation of the time evolution process, and a crossover to ordinary exponential statistics are given. We make clear the dynamical origin of the anomalous thermodynamic framework existing at the Feigenbaum attractor. PMID:18517491

Robledo, A; Moyano, L G

2008-03-01

205

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. PMID:23300431

Zheng, Pengsheng; Dimitrakakis, Christos; Triesch, Jochen

2013-01-01

206

Network self-organization explains the statistics and dynamics of synaptic connection strengths in cortex.  

PubMed

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. PMID:23300431

Zheng, Pengsheng; Dimitrakakis, Christos; Triesch, Jochen

2013-01-01

207

Statistics of non-linear stochastic dynamical systems by a novel integral operator  

E-print Network

This paper introduces a novel integral operator of Wiener-Hopf type for the probabilistic characterization of non-linear dynamical systems excited by normal white noise. The differential equation ruling the evolution in time of the characteristic function is firstly expressed in integral form and then is resolved by the convolution quadrature method. This approach is especially suited for those problems in which the non-linear drift term is not of polynomial form. Both additive and multiplicative normal white excitations are dealt by the same formalism without any complications.

Cottone, Giulio

2010-01-01

208

Towards a theory of growing surfaces: Mapping two-dimensional Laplacian growth onto Hamiltonian dynamics and statistics  

SciTech Connect

I show that the evolution of a two dimensional surface in a Laplacian field can be described by Hamiltonian dynamics. First the growing region is mapped conformally to the interior of the unit circle, creating in the process a set of mathematical zeros and poles that evolve dynamically as the surface grows. Then the dynamics of these quasi-particles are transformed into a seperable action-angle Hamiltonian that describes an orbital motion on a torus. A specific case is discussed explicitly, which demonstrates the integrability of the surface-tension-free Laplacian growth process. This formulation holds as long as the singularities of the map are confined to within the unit circle. This approach further allows for surface tension to be introduced as an energetic term in the resulting Hamiltonian which effects repulsion between the quasi-particles and the surface. These results are used here to formulate a first-principles statistical theory of pattern formation in stochastic growth, where noise is a key player.

Blumenfeld, R.

1993-11-01

209

A Statistical Study on the Morphology of Rays and Dynamics of Blobs in the Wake of Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

In this paper, with a survey through the Large Angle and Spectrometric Coronagraph (LASCO) data from 1996 to 2009, we present 11 events with plasma blobs flowing outwards sequentially along a bright coronal ray in the wake of a coronal mass ejection. The ray is believed to be associated with the current-sheet structure that formed as a result of solar eruption, and the blobs are products of magnetic reconnection occurring along the current sheet. The ray morphology and blob dynamics are investigated statistically. It is found that the apparent angular widths of the rays at a fixed time vary in a range of 2.1 - 6.6? (2.0 - 4.4?) with an average of 3.5? (2.9?) at 3 R ? (4 R ?), respectively, and the observed durations of the events vary from 12 h to a few days with an average of 27 h. It is also found, based on the analysis of blob motions, that 58% (26) of the blobs were accelerated, 20% (9) were decelerated, and 22% (10) moved with a nearly constant speed. Comparing the dynamics of our blobs and those that are observed above the tip of a helmet streamer, we find that the speeds and accelerations of the blobs in these two cases differ significantly. It is suggested that these differences of the blob dynamics stem from the associated magnetic reconnection involving different magnetic field configurations and triggering processes.

Song, H. Q.; Kong, X. L.; Chen, Y.; Li, B.; Li, G.; Feng, S. W.; Xia, L. D.

2012-02-01

210

Double precision errors in the logistic map: statistical study and dynamical interpretation.  

PubMed

The nature of the round-off errors that occur in the usual double precision computation of the logistic map is studied in detail. Different iterative regimes from the whole panoply of behaviors exhibited in the bifurcation diagram are examined, histograms of errors in trajectories given, and for the case of fully developed chaos an explicit formula is found. It is shown that the statistics of the largest double precision error as a function of the map parameter is characterized by jumps whose location is determined by certain boundary crossings in the bifurcation diagram. Both jumps and locations seem to present geometric convergence characterized by the two first Feigenbaum constants. Eventually, a comparison with Benford's law for the distribution of the leading digit of compilation of numbers is discussed. PMID:17930330

Oteo, J A; Ros, J

2007-09-01

211

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

212

Refining calibration and predictions of a Bayesian statistical-dynamical model for long term avalanche forecasting using dendrochronological reconstructions  

NASA Astrophysics Data System (ADS)

A crucial step for proposing relevant long-term mitigation measures in long term avalanche forecasting is the accurate definition of high return period avalanches. Recently, "statistical-dynamical" approach combining a numerical model with stochastic operators describing the variability of its inputs-outputs have emerged. Their main interests is to take into account the topographic dependency of snow avalanche runout distances, and to constrain the correlation structure between model's variables by physical rules, so as to simulate the different marginal distributions of interest (pressure, flow depth, etc.) with a reasonable realism. Bayesian methods have been shown to be well adapted to achieve model inference, getting rid of identifiability problems thanks to prior information. An important problem which has virtually never been considered before is the validation of the predictions resulting from a statistical-dynamical approach (or from any other engineering method for computing extreme avalanches). In hydrology, independent "fossil" data such as flood deposits in caves are sometimes confronted to design discharges corresponding to high return periods. Hence, the aim of this work is to implement a similar comparison between high return period avalanches obtained with a statistical-dynamical approach and independent validation data resulting from careful dendrogeomorphological reconstructions. To do so, an up-to-date statistical model based on the depth-averaged equations and the classical Voellmy friction law is used on a well-documented case study. First, parameter values resulting from another path are applied, and the dendrological validation sample shows that this approach fails in providing realistic prediction for the case study. This may be due to the strongly bounded behaviour of runouts in this case (the extreme of their distribution is identified as belonging to the Weibull attraction domain). Second, local calibration on the available avalanche chronicle is performed with various prior distributions resulting from expert knowledge and/or other paths. For all calibrations, a very successful convergence is obtained, which confirms the robustness of the used Metropolis-Hastings estimation algorithm. This also demonstrates the interest of the Bayesian framework for aggregating information by sequential assimilation in the frequently encountered case of limited data quantity. Confrontation with the dendrological sample stresses the predominant role of the Coulombian friction coefficient distribution's variance on predicted high magnitude runouts. The optimal fit is obtained for a strong prior reflecting the local bounded behavior, and results in a 10-40 m difference for return periods ranging between 10 and 300 years. Implementing predictive simulations shows that this is largely within the range of magnitude of uncertainties to be taken into account. On the other hand, the different priors tested for the turbulent friction coefficient influence predictive performances only slightly, but have a large influence on predicted velocity and flow depth distributions. This all may be of high interest to refine calibration and predictive use of the statistical-dynamical model for any engineering application.

Eckert, Nicolas; Schläppy, Romain; Jomelli, Vincent; Naaim, Mohamed

2013-04-01

213

Molecular modeling and active site analysis of SdiA homolog, a putative quorum sensor for Salmonella typhimurium pathogenecity reveals specific binding patterns of AHL transcriptional regulators.  

PubMed

Salmonella typhimurium is a Gram-negative bacterium responsible for human diseases including gastroenteritis and typhoid fever and its quorum sensing system is currently being intensively researched. Molecular modeling and binding site analysis of SdiA homolog, a putative quorum sensor of the LuxR family and responsible for S. typhimurium pathogenecity revealed a high structural homology of their active site with three other LuxR family proteins LasR from Pseudomonas aeruginosa, TraR from Agrobacterium tumifaciens and CviR from Chromobacterium violaceum. The results show that all the LuxR family proteins harbor three conserved amino acids Tryptophan (W67) and Aspartic acid (D80) for formation of hydrogen bridges and Tyrosine (Y71) for the hydrophobic interactions (corresponding to their position in S. typhimurium SdiA) with acyl homoserine lactones (AHL)-dependent transcriptional regulators. However, in addition to the above conserved residues, Arginine (R60) also plays an important role in S. typhimurium SdiA binding with its AHL auto inducers and the complex is found to be stronger because of the interactions between nitrogen atoms of Arginine with the carbonyl oxygen in the lactone ring of AHL. The specific binding patterns would be helpful in guiding both enzymatic studies as well as design of specific inhibitors to overcome S. typhimurium pathogenecity. PMID:22660944

Gnanendra, Shanmugam; Anusuya, Shanmugam; Natarajan, Jeyakumar

2012-10-01

214

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

PubMed

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. PMID:23410385

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

2013-01-01

215

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

216

How Electronic Dynamics with Pauli Exclusion Produces Fermi-Dirac Statistics  

E-print Network

It is important that any dynamics method approaches the correct population distribution at long times. In this paper, we derive a one-body reduced density matrix dynamics for electrons in energetic contact with a bath. We obtain a remarkable equation of motion which shows that in order to reach equilibrium properly, rates of electron transitions depend on the density matrix. Even though the bath drives the electrons towards a Boltzmann distribution, hole blocking factors in our equation of motion cause the electronic populations to relax to a Fermi-Dirac distribution. These factors are an old concept, but we show how they can be derived with a combination of time-dependent perturbation theory, and the extended normal ordering of Mukherjee and Kutzelnigg. The resulting non-equilibrium kinetic equations generalize the usual Redfield theory to many-electron systems, while ensuring that the orbital occupations remain between zero and one. In numerical applications of our equations, we show that relaxation rates o...

Nguyen, Triet; Parkhill, John

2014-01-01

217

How Electronic Dynamics with Pauli Exclusion Produces Fermi-Dirac Statistics  

E-print Network

It is important that any dynamics method approaches the correct population distribution at long times. In this paper, we derive a one-body reduced density matrix dynamics for electrons in energetic contact with a bath. We obtain a remarkable equation of motion which shows that in order to reach equilibrium properly, rates of electron transitions depend on the density matrix. Even though the bath drives the electrons towards a Boltzmann distribution, hole blocking factors in our equation of motion cause the electronic populations to relax to a Fermi-Dirac distribution. These factors are an old concept, but we show how they can be derived with a combination of time-dependent perturbation theory, and the extended normal ordering of Mukherjee and Kutzelnigg. The resulting non-equilibrium kinetic equations generalize the usual Redfield theory to many-electron systems, while ensuring that the orbital occupations remain between zero and one. In numerical applications of our equations, we show that relaxation rates of molecules are not constant because of the blocking effect. Other applications to model atomic chains are also presented which highlight the importance of treating both dephasing and relaxation. Finally we show how the bath localizes the electron density matrix.

Triet Nguyen; Ravindra Nanguneri; John Parkhill

2014-11-19

218

Assessing spatial coupling in complex population dynamics using mutual prediction and continuity statistics  

USGS Publications Warehouse

A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.

Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.

2005-01-01

219

Dynamics of the instantaneous firing rate in response to changes in input statistics.  

PubMed

We review and extend recent results on the instantaneous firing rate dynamics of simplified models of spiking neurons in response to noisy current inputs. It has been shown recently that the response of the instantaneous firing rate to small amplitude oscillations in the mean inputs depends in the large frequency limit f on the spike initiation dynamics. A particular simplified model, the exponential integrate-and-fire (EIF) model, has a response that decays as 1/f in the large frequency limit and describes very well the response of conductance-based models with a Hodgkin-Huxley type fast sodium current. Here, we show that the response of the EIF instantaneous firing rate also decays as 1/f in the case of an oscillation in the variance of the inputs for both white and colored noise. We then compute the initial transient response of the firing rate of the EIF model to a step change in its mean inputs and/or in the variance of its inputs. We show that in both cases the response speed is proportional to the neuron stationary firing rate and inversely proportional to a 'spike slope factor' Delta(T) that controls the sharpness of spike initiation: as 1/Delta(T) for a step change in mean inputs, and as 1/Delta(T) (2) for a step change in the variance in the inputs. PMID:15830167

Fourcaud-Trocmé, Nicolas; Brunel, Nicolas

2005-06-01

220

A statistical study of plasma sheet dynamics using ISEE 1 and 2 energetic particle flux data  

NASA Technical Reports Server (NTRS)

Plasma sheet dynamics during substorms are studied by analyzing 461 cases of transient dropout events of the 1.5 and 6-keV particle fluxes detected by ISEE 1 and 2 satellites. The instruments for detecting low- and high-energy particles are described. The spatial distribution of flux dropout events, and the events' relationship to magnetospheric activity level are examined. Substorm events without observed flux dropout events are investigated. The data reveal that the flux dropout distribution is isotropic, between 12-23 earth radii, and is present in the entire nightside plasma sheet; and the substorms without flux dropout are more frequent near earth and magnetospheric flanks. It is observed that tailward of 12 earth radii the flux dropout events and substorms without flux dropout are similar. The Chao et al. (1977) MHD rarefaction wave propagation model and the Hones (1973, 1980) near-tail, X-type magnetic neutral line formation model are discussed and compared to the experimental data. It is noted that neither model explains the plasma sheet dynamics observed.

Dandouras, J.; Reme, H.; Saint-Marc, A.; Sauvaud, J. A.; Parks, G. K.

1986-01-01

221

STATISTICAL METHODS STATISTICAL METHODS  

E-print Network

STATISTICAL METHODS 1 STATISTICAL METHODS Arnaud Delorme, Swartz Center for Computational@salk.edu. Keywords: statistical methods, inference, models, clinical, software, bootstrap, resampling, PCA, ICA Abstract: Statistics represents that body of methods by which characteristics of a population are inferred

Delorme, Arnaud

222

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

223

Application of the statistical dynamical theory to gamma-ray diffraction experiments on low-dislocation quartz single crystals.  

PubMed

Highly monochromatic (Deltalambda/lambda = 10(-6)) short-wavelength (lambda = 0.03 Å) gamma radiation has been used in the study of the diffraction processes in real single crystals. Dislocation-free silicon crystals and quartz crystals with small concentrations of chaotically distributed dislocations were investigated. The experimental results were processed with use of statistical dynamical theories of diffraction, both fundamental and advanced. It is shown that the advanced version is more reliable in both cases. However, the values of the average lattice phase E, describing the long-range distortions of the lattice, can differ markedly from the value of 1 for quartz crystals, and parameter L = -ln(E) has a square dependence on the extinction length. PMID:10927257

Kurbakov; Sokolov

1999-03-01

224

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

225

Simulation of extreme precipitation indices in the Yangtze River basin by using statistical downscaling method (SDSM)  

Microsoft Academic Search

In this study, the applicability of the statistical downscaling model (SDSM) in modeling five extreme precipitation indices including R10 (no. of days with precipitation >=10 mm day-1), SDI (simple daily intensity), CDD (maximum number of consecutive dry days), R1d (maximum 1-day precipitation total) and R5d (maximum 5-day precipitation total) in the Yangtze River basin, China was investigated. The investigation mainly

Jin Huang; Jinchi Zhang; Zengxin Zhang; Shanlei Sun; Jian Yao

2011-01-01

226

Statistical and dynamical downscaling in CORDEX-Africa: differing views on the regional climate  

NASA Astrophysics Data System (ADS)

The need for credible regional climate change projections for use in adaptation actions and decision making is well recognised. The CORDEX activity has evolved in large part as a response to this need. For the most part, CORDEX has so far been dominated by regional climate modelling (RCM) activities. However, implicit in CORDEX is the use of statistical downscaling (SD) as a complement to RCMs, although the SD activities lag that of the RCMs. For Africa, the CORDEX RCM work is well advanced with the control climate simulations completed, and a number of RCM-based projections also available. The early results indicate the RCMs produce a credible representation of the regional climate when aggregated in time and/or space, and provide an initial multimodal suite of regional climate change projections for Africa. The SD activities are catching up with this process and the emerging challenge is how to integrate and compare the results from the two downscaling methods. The two approaches, SD and RCMs, have respective strengths and weaknesses, but are considered in the literature to be of comparable overall skill. Where climate change stationarity is not considered a major issue, such as on timescales out to perhaps 2050, it is arguable that SD (comprehensively undertaken) may possibly be more skillful. From the perspective of users of regional scale projections, decision makers and policy developers, it is critical to compare, and assess the relative strengths of the methods on a regional basis. To avoid confusion the contradictions and/or robust messages emerging from the two methods needs to be clearly understood and articulated. The inter-comparison between the RCMs is already the subject of a number of papers, and here we present an initial comparison of early results between the SD and the envelope of RCM downscaling for CORDEX-Africa. Using the available SD results, we consider where the overlap and/or marked differences lie between the two methods. The focus is primarily on the control climate, where the downscaling is forced by the ERA-reanalysis data set, to avoid complicating factors possibly arising from non-stationarity issues with both SD and the RCMs. Following this we consider some early results of future climate projections based on the boundary conditions from CMIP5 GCM data. The primary consideration is how the statistical downscaling results fall within the envelope of the regional climate models. In this we consider both the bias of the regional climate models, the seasonal cycle, and the shorter time scales of weather events and the histogram distribution of daily events including extremes. Of particular concern is how the downscaling methods handle both the high and low frequency variance of the regional climate systems. The SD method uses daily data to derive the deterministic response to the large-scale forcing and adds the high-frequency variants or stochastic component. From this time and space aggregates comparable to the RCM data may be compiled. The primary difference between SD and RCMs lies in the fact that the SD is inherently bias corrected by virtue of the method. Thus the first major difference is accountable for by the RCM bias. Following this the differences are regionally and seasonally dependent and examples of these are presented from which preliminary conclusions about the two methods are drawn

Hewitson, Bruce; Lennard, Christopher; Jack, Christopher; Coop, Lisa

2013-04-01

227

A New Sigmoid Catalog from Hinode and the Solar Dynamics Observatory: Statistical Properties and Evolutionary Histories  

NASA Astrophysics Data System (ADS)

We present a new sigmoid catalog covering the duration of the Hinode mission and the Solar Dynamics Observatory (SDO) until the end of 2012. The catalog consists of 72 mostly long-lasting sigmoids. We collect and make available all X-ray and EUV data from Hinode, SDO, and the Solar TErrestrial RElations Observatory (STEREO), and we determine the sigmoid lifetimes, sizes, and aspect ratios. We also collect the line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) for SDO or the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) to measure flux versus time for the lifetime of each region. We determine that the development of a sigmoidal shape and eruptive activity is more strongly correlated with flux cancelation than with emergence. We find that the eruptive properties of the regions correlate well with the maximum flux, largest change, and net change in flux in the regions. These results have implications for constraining future flux-rope models of ARs and gaining insight into their evolutionary properties.

Savcheva, A. S.; McKillop, S. C.; McCauley, P. I.; Hanson, E. M.; DeLuca, E. E.

2014-09-01

228

Numerical Simulations of Jupiter’s Moist Convection Layer: Structure and Dynamics in Statistically Steady States  

NASA Astrophysics Data System (ADS)

A series of long-term numerical simulations of moist convection in Jupiter's atmosphere are performed to investigate idealized characteristics of vertical structures of multi-composition clouds and convective motions associated with them, varying the deep abundances of condensible gases and the time constant of the auto-conversion process that is one of the most questionable parameters in the cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH. The results generally represent the following characteristics qualitatively similar to those found in Sugiyama et al (2011); stable layers associated with condensation and chemical reaction well behave as dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with the cumulonimbus clouds results in an establishment of the mean vertical profiles of condensates and condensible gases that are distinctly different from the hitherto accepted three-layered structure. Our results also demonstrate that the period of the intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL by latent cooling associated with re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. The active cloud development is terminated when the instability is completely exhausted. The period of the intermittency is roughly equal to the time obtained by dividing the mean temperature increase caused by active cumulonimbus development, by the rate of body cooling.

Nakajima, Kensuke; Sugiyama, Ko-ichiro; Odaka, Masatsugu; Kuramoto, Kiyoshi; Hayashi, Yoshi-Yuki

2014-11-01

229

A comparison of different initialization protocols to obtain statistically independent molecular dynamics simulations.  

PubMed

We study how the results of molecular dynamics (MD) simulations are affected by various choices during the setup, e.g., the starting velocities, the solvation, the location of protons, the conformation of His, Asn, and Gln residues, the protonation and titration of His residues, and the treatment of alternative conformations. We estimate the binding affinity of ligands to four proteins calculated with the MM/GBSA method (molecular mechanics combined with a generalized Born and surface area solvation energy). For avidin and T4 lysozyme, all variations gave similar results within 2 kJ/mol. For factor Xa, differences in the solvation or in the selection of alternative conformations gave results that are significantly different from those of the other approaches by 4-6 kJ/mol, whereas for galectin-3, changes in the conformations, rotations, and protonation gave results that differed by 10 kJ/mol, but only if residues close to the binding site were modified. This shows that the results of MM/GBSA calculations are reasonably reproducible even if the MD simulations are set up with different software. Moreover, we show that the sampling of phase space can be enhanced by solvating the systems with different equilibrated water boxes, in addition to the common use of different starting velocities. If different conformations are available in the crystal structure, they should also be employed to enhance the sampling. Protonation, ionization, and conformations of Asn, Gln, and His may also be used to enhance sampling, but great effort should be spent to obtain as reliable predictions as possible close to the active site. PMID:21132839

Genheden, Samuel; Ryde, Ulf

2011-01-30

230

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

231

Statistical Mechanics with focus on  

E-print Network

Statistical Mechanics with focus on Liquids, Solutions and Colloidal Systems Course contents A. Foundations of statistical mechanics Classical dynamics ­ Hamilton's and Liouville's equations The concept thermodynamics and statistical mechanics. B. Liquid state theory; Equilibrium statistical mechanics for liquids

Johannesson, Henrik

232

p21{sup WAF1/Cip1/Sdi1} knockout mice respond to doxorubicin with reduced cardiotoxicity  

SciTech Connect

Doxorubicin (Dox) is an antineoplastic agent that can cause cardiomyopathy in humans and experimental animals. As an inducer of reactive oxygen species and a DNA damaging agent, Dox causes elevated expression of p21{sup WAF1/Cip1/Sdi1} (p21) gene. Elevated levels of p21 mRNA and p21 protein have been detected in the myocardium of mice following Dox treatment. With chronic treatment of Dox, wild type (WT) animals develop cardiomyopathy evidenced by elongated nuclei, mitochondrial swelling, myofilamental disarray, reduced cardiac output, reduced ejection fraction, reduced left ventricular contractility, and elevated expression of ANF gene. In contrast, p21 knockout (p21KO) mice did not show significant changes in the same parameters in response to Dox treatment. In an effort to understand the mechanism of the resistance against Dox induced cardiomyopathy, we measured levels of antioxidant enzymes and found that p21KO mice did not contain elevated basal or inducible levels of glutathione peroxidase and catalase. Measurements of 6 circulating cytokines indicated elevation of IL-6, IL-12, IFN{gamma} and TNF{alpha} in Dox treated WT mice but not p21KO mice. Dox induced elevation of IL-6 mRNA was detected in the myocardium of WT mice but not p21KO mice. While the mechanism of the resistance against Dox induced cardiomyopathy remains unclear, lack of inflammatory response may contribute to the observed cardiac protection in p21KO mice. -- Highlights: Black-Right-Pointing-Pointer Doxorubicin induces p21 elevation in the myocardium. Black-Right-Pointing-Pointer Doxorubicin causes dilated cardiomyopathy in wild type mice. Black-Right-Pointing-Pointer p21 Knockout mice are resistant against doxorubicin induced cardiomyopathy. Black-Right-Pointing-Pointer Lack of inflammatory response correlates with the resistance in p21 knockout mice.

Terrand, Jerome; Xu, Beibei; Morrissy, Steve; Dinh, Thai Nho [Department of Pharmacology,College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 (United States)] [Department of Pharmacology,College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 (United States); Williams, Stuart [Biomedical Engineering Program, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 (United States)] [Biomedical Engineering Program, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 (United States); Chen, Qin M., E-mail: qchen@email.arizona.edu [Department of Pharmacology,College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 (United States)

2011-11-15

233

Developing a Web-based system by integrating VGI and SDI for real estate management and marketing  

NASA Astrophysics Data System (ADS)

Property importance of various aspects, especially the impact on various sectors of the economy and the country's macroeconomic is clear. Because of the real, multi-dimensional and heterogeneous nature of housing as a commodity, the lack of an integrated system includes comprehensive information of property, the lack of awareness of some actors in this field about comprehensive information about property and the lack of clear and comprehensive rules and regulations for the trading and pricing, several problems arise for the people involved in this field. In this research implementation of a crowd-sourced Web-based real estate support system is desired. Creating a Spatial Data Infrastructure (SDI) in this system for collecting, updating and integrating all official data about property is also desired in this study. In this system a Web2.0 broker and technologies such as Web services and service composition has been used. This work aims to provide comprehensive and diverse information about property from different sources. For this purpose five-level real estate support system architecture is used. PostgreSql DBMS is used to implement the desired system. Geoserver software is also used as map server and reference implementation of OGC (Open Geospatial Consortium) standards. And Apache server is used to run web pages and user interfaces. Integration introduced methods and technologies provide a proper environment for various users to use the system and share their information. This goal is only achieved by cooperation between all involved organizations in real estate with implementation their required infrastructures in interoperability Web services format.

Salajegheh, J.; Hakimpour, F.; Esmaeily, A.

2014-10-01

234

Numerical simulations of Jupiter’s moist convection layer: Structure and dynamics in statistically steady states  

NASA Astrophysics Data System (ADS)

A series of long-term numerical simulations of moist convection in Jupiter’s atmosphere is performed in order to investigate the idealized characteristics of the vertical structure of multi-composition clouds and the convective motions associated with them, varying the deep abundances of condensable gases and the autoconversion time scale, the latter being one of the most questionable parameters in cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents the convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH imposing a body cooling that substitutes the net radiative cooling. The results are qualitatively similar to those reported in Sugiyama et al. (Sugiyama, K. et al. [2011]. Intermittent cumulonimbus activity breaking the three-layer cloud structure of Jupiter. Geophys. Res. Lett. 38, L13201. doi:10.1029/2011GL047878): stable layers associated with condensation and chemical reaction act as effective dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with these clouds results in the establishment of mean vertical profiles of condensates and condensable gases that are distinctly different from the hitherto accepted three-layered structure (e.g., Atreya, S.K., Romani, P.N. [1985]. Photochemistry and clouds of Jupiter, Saturn and Uranus. In: Recent Advances in Planetary Meteorology. Cambridge Univ. Press, London, pp. 17-68). Our results also demonstrate that the period of intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The autoconversion time scale does not strongly affect the results, except for the vertical profiles of the condensates. Changing the autoconversion time scale by a factor of 100 changes the intermittency period by a factor of less than two, although it causes a dramatic increase in the amount of condensates in the upper troposphere. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL as a result of the latent cooling associated with the re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. Active cloud development is terminated when the instability is completely exhausted. The period of intermittency is roughly equal to the time obtained by dividing the mean temperature increase, which is caused by active cumulonimbus development, by the body cooling rate.

Sugiyama, K.; Nakajima, K.; Odaka, M.; Kuramoto, K.; Hayashi, Y.-Y.

2014-02-01

235

Control of cell division in Escherichia coli: regulation of transcription of ftsQA involves both rpoS and SdiA-mediated autoinduction.  

PubMed

The conditioning of culture medium by the production of growth-regulatory substances is a well-established phenomenon with eukaryotic cells. It has recently been shown that many prokaryotes are also capable of modulating growth, and in some cases sensing cell density, by production of extracellular signaling molecules, thereby allowing single celled prokaryotes to function in some respects as multicellular organisms. As Escherichia coli shifts from exponential growth to stationary growth, many changes occur, including cell division leading to formation of short minicells and expression of numerous genes not expressed in exponential phase. An understanding of the coordination between the morphological changes associated with cell division and the physiological and metabolic changes is of fundamental importance to understanding regulation of the prokaryotic cell cycle. The ftsQA genes, which encode functions required for cell division in E. coli, are regulated by promoters P1 and P2, located upstream of the ftsQ gene. The P1 promoter is rpoS-stimulated and the second, P2, is regulated by a member of the LuxR subfamily of transcriptional activators, SdiA, exhibiting features characteristic of an autoinduction (quorum sensing) mechanism. The activity of SdiA is potentiated by N-acyl-homoserine lactones, which are the autoinducers of luciferase synthesis in luminous marine bacteria as well as of pathogenesis functions in several pathogenic bacteria. A compound(s) produced by E. coli itself during growth in Luria Broth stimulates transcription from P2 in an SdiA-dependent process. Another substance(s) enhances transcription of rpoS and (perhaps indirectly) of ftsQA via promoter P1. It appears that this bimodal control mechanism may comprise a fail-safe system, such that transcription of the ftsQA genes may be properly regulated under a variety of different environmental and physiological conditions. PMID:8552633

Sitnikov, D M; Schineller, J B; Baldwin, T O

1996-01-01

236

A statistical analysis of the lateral displacement of Si atoms in molecular dynamics simulations of successive bombardment with 20keV C60 projectiles  

Microsoft Academic Search

An important factor that determines the possible lateral resolution in sputter depth profiling experiments is ion induced lateral displacement of substrate atoms. Molecular dynamics (MD) simulations are performed to model the successive bombardment of Si with 20 keV C60 at normal incidence. A statistical analysis of the lateral displacement of atoms that originate from the topmost layer is presented and

K. D. Krantzman; E. L. Cook; A. Wucher; B. J. Garrison

2011-01-01

237

A statistical analysis of the lateral displacement of Si atoms in molecular dynamics simulations of successive bombardment with 20keV C 60 projectiles  

Microsoft Academic Search

An important factor that determines the possible lateral resolution in sputter depth profiling experiments is ion induced lateral displacement of substrate atoms. Molecular dynamics (MD) simulations are performed to model the successive bombardment of Si with 20keV C60 at normal incidence. A statistical analysis of the lateral displacement of atoms that originate from the topmost layer is presented and discussed.

K. D. Krantzman; E. L. Cook; A. Wucher; B. J. Garrison

2011-01-01

238

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

239

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). PMID:7811955

Fattal, D R; Ben-Shaul, A

1994-01-01

240

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

241

Doubled CO2 experiments with the Global Change Research Center two-dimensional statistical dynamical climate model  

NASA Astrophysics Data System (ADS)

The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics) for the prognostic variables: zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p=?RT, and an assumed hydrostatic atmosphere, Delta;p=-?g?z, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The model includes seasonal variations in solar intensity, including the effects of eccentricity, and has observed land and ocean fractions set for each zone. Seasonally varying values of cloud amounts, relative humidity profiles, ozone, and sea ice are all prescribed in the model. Equator to pole ocean heat transport is simulated in the model by turbulent diffusion. The change in global mean annual surface air temperature due to a doubling of atmospheric CO2 in the 2-D model is 1.61 K, which is close to that simulated by the one-dimensional (1-D) radiative convective model (RCM) which is at the heart of the 2-D model radiation code (1.67 K for the moist adiabatic lapse rate assumption in 1-D RCM). We find that the change in temperature structure of the model atmosphere has many of the characteristics common to General Circulation Models, including amplified warming at the poles and the upper tropical troposphere, and stratospheric cooling. Because of the potential importance of atmospheric circulation feedbacks on climate change, we have also investigated the response of the zonal wind field to a doubling of CO2 and have found distinct patterns of change that are related to the change in temperature structure. In addition, we find that both the global mean kinetic energy and simulated Hadley circulation increase when CO2 is doubled. The increase in mean kinetic energy is a result of the increase in upper level meridional temperature gradients simulated by the model. It is stressed that changes in atmospheric dynamics associated with increased carbon dioxide may also be very important to the final steady state distribution of such greenhouse gases as ozone and water vapor. Hence further research in this regard is warranted.

Mackay, R. M.; Khalil, M. A. K.

1995-10-01

242

Molecular distributions in interphases: statistical mechanical theory combined with molecular dynamics simulation of a model lipid bilayer.  

PubMed Central

A mean-field statistical mechanical theory has been developed to describe molecular distributions in interphases. The excluded volume interaction has been modeled in terms of a reversible work that is required to create a cavity of the solute size against a pressure tensor exerted by the surrounding interphase molecules. The free energy change associated with this compression process includes the configuration entropy as well as the change in conformational energy of the surrounding chain molecules. The lateral pressure profile in a model lipid bilayer (30.5 A2/chain molecule) has been calculated as a function of depth in the bilayer interior by molecular dynamics simulation. The lateral pressure has a plateau value of 309 +/- 48 bar in the highly ordered region and decreases abruptly in the center of the bilayer. Model calculations have shown that for solute molecules with ellipsoidal symmetry, the orientational order increases with the ratio of the long to short molecular axes at a given solute volume and increases with solute volume at a given axial ratio, in accordance with recent experimental data. Increased lateral pressure (p perpendicular) results in higher local order and exclusion of solute from the interphase, in parallel with the effect of surface density on the partitioning and local order. The logarithm of the interphase/water partition coefficient for spherical solutes decreases linearly with solute volume. This is also an excellent approximation for elongated solutes because of the relatively weak dependence of solute partitioning on molecular shape. The slope is equal to (2p perpendicular - p parallel)/3KBT, where p parallel is the normal pressure component, and different from that predicted by the mean-field lattice theory. Finally, the lattice theory has been extended herein to incorporate an additional constraint on chain packing in the interphase and to account for the effect of solute size on partitioning. Images FIGURE 1 FIGURE 2 PMID:8011890

Xiang, T X; Anderson, B D

1994-01-01

243

The formulation of quantum statistical mechanics based on the Feynman path centroid density. IV. Algorithms for centroid molecular dynamics  

E-print Network

to calculate dynamical time correlation functions for general many-body quantum systems. Approaches based of the aforementioned research is an approximate method for computing quantum dynamical time correlation functions. Algorithms for centroid molecular dynamics Jianshu Cao and Gregory A. Voth Department of Chemistry

Cao, Jianshu

244

The Gcrc Two-Dimensional Zonally Averaged Statistical Dynamical Climate Model: Development, Model Performance, and Climate Sensitivity  

NASA Astrophysics Data System (ADS)

The two-dimensional statistical dynamical climate model that has recently been developed at the Global Change Research Center and the Oregon Graduate Institute of Science & Technology (GCRC 2D climate model) is presented and several new results obtained using the model are discussed. The model solves the 2-D primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics) for the prognostic variables zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p=rho RT and an assumed hydrostatic atmosphere, Delta p = -rho gDelta z, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The performance of the model at simulating the two-dimensional temperature, zonal winds, and mass stream function is explored. The strengths and weaknesses of the model are highlighted and suggestions for future model improvements are given. The parameterization of the transient eddy fluxes of heat and momentum developed by Stone and Yao (1987 and 1990) are used with small modifications. These modifications are shown to help the performance of the model at simulating the observed climate system as well as increase the model's computational stability. Following earlier work that analyzed the response of the zonal wind fields predicted by three GCM simulations for a doubling of atmospheric CO_2, the response of the GCRC 2D model's zonal wind fields is also explored for the same experiment. Unlike the GCM simulations, our 2D model results in distinct patterns of change. It is suggested that the observed changes in zonal winds for the 2xCO_2 experiment are related to the increase in the upper level temperature gradients predicted by our model and most climate models of adequate sophistication and resolution. We thus suggest that the same mechanism controlling the changes in zonal winds for the 2xCO_2 experiment in our model also contributes to the simulated changes in zonal winds of the more complex GCMs.

Mackay, Robert Malcolm

245

Columnar Aerosol Properties from Sun-and-star Photometry: Statistical Comparisons and Day-to-night Dynamic  

NASA Technical Reports Server (NTRS)

This work presents the first analysis of longterm correlative day-to-night columnar aerosol optical properties. The aim is to better understand columnar aerosol dynamic from ground-based observations, which are poorly studied until now. To this end we have used a combination of sun-and-star photometry measurements acquired in the city of Granada (37.16 N, 3.60 W, 680 ma.s.l.; South-East of Spain) from 2007 to 2010. For the whole study period, mean aerosol optical depth (AOD) around 440 nm (+/-standard deviation) is 0.18 +/- 0.10 and 0.19 +/- 0.11 for daytime and nighttime, respectively, while the mean Angstr¨om exponent (alpha ) is 1.0 +/- 0.4 and 0.9 +/- 0.4 for daytime and nighttime. The ANOVA statistical tests reveal that there are no significant differences between AOD and obtained at daytime and those at nighttime. Additionally, the mean daytime values of AOD and obtained during this study period are coherent with the values obtained in the surrounding AERONET stations. On the other hand, AOD around 440 nm present evident seasonal patterns characterised by large values in summer (mean value of 0.20 +/- 0.10 both at daytime and nighttime) and low values in winter (mean value of 0.15 +/- 0.09 at daytime and 0.17 +/- 0.10 at nighttime). The Angstr¨om exponents also present seasonal patterns, but with low values in summer (mean values of 0.8 +/- 0.4 and 0.9 +/- 0.4 at dayand night-time) and relatively large values in winter (mean values of 1.2 +/- 0.4 and 1.0 +/- 0.3 at daytime and nighttime). These seasonal patterns are explained by the differences in the meteorological conditions and by the differences in the strength of the aerosol sources. To take more insight about the changes in aerosol particles between day and night, the spectral differences of the Angstrom exponent as function of the Angstr¨om exponent are also studied. These analyses reveal increases of the fine mode radius and of the fine mode contribution to AOD during nighttime, being more remarkable in the summer seasons. These variations are explained by the changes of the local aerosol sources and by the meteorological conditions between daytime and nighttime, as well as aerosol aging processes. Case studies during summer and winter for different aerosol loads and types are also presented to clearly illustrate these findings.

Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Alados-Arboledas, L.

2012-01-01

246

Modified Statistical Dynamical Diffraction Theory: A Novel Metrological Analysis Method for Partially Relaxed and Defective Carbon-doped Silicon and Silicon Germanium Heterostructures  

NASA Astrophysics Data System (ADS)

The statistical dynamical diffraction theory, which has been initially developed by late Kato remained in obscurity for many years due to intense and difficult mathematical treatment that proved to be quite challenging to implement and apply. With assistance of many authors in past (including Bushuev, Pavlov, Pungeov, and among the others), it became possible to implement this unique x-ray diffraction theory that combines the kinematical (ideally imperfect) and dynamical (the characteristically perfect diffraction) into a single system of equations controlled by two factors determined by long range order and correlation function within the structure. The first stage is completed by the publication (Shreeman and Matyi, J. Appl. Cryst., 43, 550 (2010)) demonstrating the functionality of this theory with new modifications hence called modified statistical dynamical diffraction theory (mSDDT). The foundation of the theory is also incorporated into this dissertation, and the next stage of testing the model against several ion-implanted SiGe materials has been published: (Shreeman and Matyi, physica status solidi (a)208(11), 2533-2538, 2011). The dissertation with all the previous results summarized, dives into comprehensive analysis of HRXRD analyses complete with several different types of reflections (symmetrical, asymmetrical and skewed geometry). The dynamical results (with almost no defects) are compared with well-known commercial software. The defective materials, to which commercially available modeling software falls short, is then characterized and discussed in depth. The results will exemplify the power of the novel approach in the modified statistical dynamical diffraction theory: Ability to detect and measure defective structures qualitatively and quantitatively. The analysis will be compared alongside with TEM data analysis for verification and confirmation. The application of this theory will accelerate the ability to quickly characterize the relaxed/partially relaxed/fully strained semiconductors using non-destructive HRXRD metrology.

Shreeman, Paul K.

247

SDI: Solar Dome Instrument for Solar Irradiance Monitoring Tao Liu1, Ankur U. Kamthe1, Varick L. Erickson1, Carlos F. M. Coimbra2 and Alberto E. Cerpa1  

E-print Network

SDI: Solar Dome Instrument for Solar Irradiance Monitoring Tao Liu1, Ankur U. Kamthe1, Varick L data for ground solar irradiance (direct normal and global irradiance) is a major obstacle for the de- velopment of adequate policies to promote and take advan- tage of existing solar technologies. Although

Cerpa, Alberto E.

248

Velocity Dispersion of 335 Galaxy Clusters Selected from the Sloan Digital Sky Survey: Statistical Evidence for Dynamical Interaction, and Against Ram-Pressure Stripping  

E-print Network

There has been plenty of observational evidence of cluster galaxy evolution. However, it has been difficult to identify the origin of the cluster galaxy evolution. Here we show that gravitational interaction/friction between galaxies is the statistically dominant physical mechanism responsible for the cluster galaxy evolution, and that the well-favored ram-pressure stripping by the cluster gas is not statistically driving the cluster galaxy evolution. We have constructed the largest composite cluster with 14548 member galaxies out of 335 clusters with ~>300 km/s carefully selected from the SDSS. By measuring velocity dispersions of various subsamples of galaxies in this composite cluster, we found that bright cluster galaxies (Mzgalaxies (Mz>-23). We interpret this as direct evidence of the dynamical interaction/friction between cluster galaxies, where massive galaxies lose their velocity through the energy equipartition during the dynamical interaction/friction with less massive galaxies. We also found that star-forming late-type galaxies have a larger velocity dispersion than passive late-type galaxies. This is inconsistent with the ram-pressure stripping model; since the ram-pressure is proportional to sigma v^2 (i.e., stronger for galaxies with high velocity), the ram-pressure stripping cannot explain the observed trends of passive (evolved) galaxies having low velocity rather than high velocity. On the other hand, the result is again consistent with the dynamical galaxy-galaxy interaction/friction, where more evolved (passive) galaxies lose their velocity through dynamical interaction/friction.

Tomotsugu Goto

2005-03-03

249

A comparative study of the Si+O(2)-->SiO+O reaction dynamics from quasiclassical trajectory and statistical based methods.  

PubMed

The dynamics of the singlet channel of the Si+O(2)-->SiO+O reaction is investigated by means of quasiclassical trajectory (QCT) calculations and two statistical based methods, the statistical quantum method (SQM) and a semiclassical version of phase space theory (PST). The dynamics calculations have been performed on the ground (1)A(') potential energy surface of Dayou and Spielfiedel [J. Chem. Phys. 119, 4237 (2003)] for a wide range of collision energies (E(c)=5-400 meV) and initial O(2) rotational states (j=1-13). The overall dynamics is found to be highly sensitive to the selected initial conditions of the reaction, the increase in either the collisional energy or the O(2) rotational excitation giving rise to a continuous transition from a direct abstraction mechanism to an indirect insertion mechanism. The product state properties associated with a given collision energy of 135 meV and low rotational excitation of O(2) are found to be consistent with the inverted SiO vibrational state distribution observed in a recent experiment. The SQM and PST statistical approaches, especially designed to deal with complex-forming reactions, provide an accurate description of the QCT total integral cross sections and opacity functions for all cases studied. The ability of such statistical treatments in providing reliable product state properties for a reaction dominated by a competition between abstraction and insertion pathways is carefully examined, and it is shown that a valuable information can be extracted over a wide range of selected initial conditions. PMID:18465922

Dayou, Fabrice; Larrégaray, Pascal; Bonnet, Laurent; Rayez, Jean-Claude; Arenas, Pedro Nilo; González-Lezana, Tomás

2008-05-01

250

Slow dynamics in colloidal glasses and porous media as probed by NMR relaxometry: assessment of solvent levy statistics in the strong adsorption regime.  

PubMed

Mesoscopic media such as porous materials or colloidal pastes develop large specific surface area which strongly influence the dynamics of the embedded fluid. This fluid confinement can be used either to probe the interfacial geometry (frozen porous media) or the particle dynamics (paste and colloidal glass). In the strong adsorption regime, it was recently proposed that the effective surface diffusion on flat surface is anomalous and exhibits long time pathology (Lévy walks). This phenomena is directly related to the time and space properties of loop trajectories appearing in the bulk between a desorption and a readsorption step. The Lévy statistics extends the time domain of the embedded fluid dynamics toward the low frequency regime. An interesting way to probe such a slow interfacial process is to use field cycling NMR relaxometry. In the first part of this paper, we propose a simple theoretical model of NMR dispersion which only involves elementary time steps of the solvent dynamics near an interface (loops, trains, tails in relation with the confining geometry). In the second part, field cycling NMR relaxometry is used to probe the slow solvent dynamics in two type of interfacial systems: (i) a colloidal glass made of thin and flat particles (ii) two fully saturated porous media, the Vycor glass and MCM48 respectively. Experimental results are critically compared to closed-form analytical expressions and numerical simulations. PMID:12850705

Levitz, P E

2003-01-01

251

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

E-print Network

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.

Manuel Gessner; Heinz-Peter Breuer

2013-01-06

252

Introduction Statistical  

E-print Network

Advanced Natural Language Processing Introduction Statistical NLP MIA - Master on Artificial Statistical NLP 1 Introduction Course goals Practical information 2 Statistical NLP #12;Advanced Natural Language Processing Introduction Course goals Statistical NLP 1 Introduction Course goals Practical

Ageno, Alicia

253

Retrieval the statistical-dynamical model of western Pacific subtropical high ridge line index and key members of Asian summer monsoon system  

NASA Astrophysics Data System (ADS)

The western Pacific subtropical high (WPSH) is closely correlated with the East Asian climate. To date, the underlying mechanisms and sustaining factors have not been positively elucidated. Based on the concept of dynamical system model reconstruction, this paper presents a nonlinear statistical-dynamical model of the subtropical high ridge line (SHRL) in concurrence with four summer monsoon factors. SHRL variations from 1990 to 2011 are subdivided into three categories, while parameter differences relating to three differing models are examined. Dynamical characteristics of SHRL are analyzed and an aberrance mechanism subsequently developed. Modeling suggests that different parameters may lead to significant variance pertaining to monsoon variables corresponding with numerous WPSH activities. Dynamical system bifurcation and mutation indicates that the South China Sea monsoon trough is a significant factor with respect to the occurrence and maintenance of the 'double-ridge' phenomenon. Moreover, the occurrence of the Mascarene cold high is predicted to cause an abnormal northward location of WPSH, resulting in the “empty plum” phenomenon.

Hong, Mei; Zhang, Ren; Wang, Dong; Chen, Xi; Shi, Jian; Singh, Vijay

2014-12-01

254

Extended-range seasonal hurricane forecasts for the North Atlantic2 with a hybrid dynamical-statistical model3  

E-print Network

Oscillation: ENSO, the Atlantic Multidecadal52 Oscillation: AMO, the Atlantic Meridional Mode: AMM, and the North Atlantic53 Oscillation: NAO) affecting changes in large-scale circulations on decadal and541 Extended-range seasonal hurricane forecasts for the North Atlantic2 with a hybrid dynamical

Webster, Peter J.

255

Indicators of Structural Change in the Dynamics of Science: Entropy Statistics of the SCI Journal Citation Reports  

E-print Network

Can change in citation patterns among journals be used as an indicator of structural change in the organization of the sciences? Aggregated journal-journal citations for 1999 are compared with similar data in the Journal Citation Reports 1998 of the Science Citation Index. In addition to indicating local change, probabilistic entropy measures enable us to analyze changes in distributions at different levels of aggregation. The results of various statistics are discussed and compared by elaborating the journal-journal mappings. The relevance of this indicator for science and technology policies is further specified.

Leydesdorff, Loet

2009-01-01

256

A Comparison of a Statistical and Computational Fluid Dynamics Approach to Estimate Heat Release Rate in Road Tunnel Fires  

Microsoft Academic Search

Computational tools such as one-dimensional models or Computational Fluid Dynamics (CFD) have been used for the fire safety\\u000a design of road tunnels. However, most of these analyses are performed using a specified fire source where the heat release\\u000a rate (HRR) in the tunnel is fixed by the user and the influences of ventilation conditions and tunnel geometry are not considered.

M. K. Cheong; M. J. Spearpoint; C. M. Fleischmann

2010-01-01

257

Dynamically biased statistical model for the ortho/para conversion in the H2+H3+ --> H3++ H2 reaction  

NASA Astrophysics Data System (ADS)

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007), 10.1063/1.2430711]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H_5^+ complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H_5^+ complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, ?(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011), 10.1063/1.3587246] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-01

258

Dynamically biased statistical model for the ortho/para conversion in the H2 + H3+ ? H3+ + H2 reaction.  

PubMed

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H(5)(+) complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H(5)(+) complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, ?(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest. PMID:22957565

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-01

259

Horizontal flow fields observed in Hinode G-band images IV. Statistical properties of the dynamical environment around pores  

E-print Network

The extensive database of high-resolution G-band images observed with the Hinode/SOT is a unique resource to derive statistical properties of pores using advanced digital image processing techniques. The study is based on two data sets: (1) Photometric and morphological properties inferred from single G-band images cover almost seven years from 2006 October 25 to 2013 August 31. (2) Horizontal flow fields have been derived from 356 one-hour sequences of G-band images using LCT for a shorter period of time from 2006 November 3 to 2008 January 6 comprising 13 active regions. A total of 7643/2863 (single/time-averaged) pores builds the foundation of the statistical analysis. Pores are preferentially observed at low latitudes in the southern hemisphere during the deep minimum of solar cycle No. 23. This imbalance reverses during the rise of cycle No. 24, when the pores migrate from high to low latitudes. Pores are rarely encountered in quiet-Sun G-band images, and only about 10% of pores exists in isolation. In g...

Verma, Meetu

2014-01-01

260

Dynamics Simulations and Statistical Modeling of Thermal Decomposition of 1-Ethyl-3-methylimidazolium Dicyanamide and 1-Ethyl-2,3-dimethylimidazolium Dicyanamide.  

PubMed

Quasi-classical, direct dynamics trajectories were calculated at the B3LYP/6-31G* level of theory, in an attempt to understand decomposition mechanisms of 1-ethyl-3-methylimidazolium dicyanamide (EMIM(+)DCA(-)) and 1-ethyl-2,3-dimethylimidazolium dicyanamide (EMMIM(+)DCA(-)). The trajectories showed many dissociation paths for these two ionic liquids. Using trajectory results as a guide, structures of transition states and products that might be important for decomposition of these two compounds were determined using density functional theory calculations. Rice-Ramsperger-Kassel-Marcus (RRKM) theory was then utilized to examine properties of energized ionic liquids and to determine unimolecular rates for crossing various transition states. On the basis of RRKM modeling, initial decomposition paths for energized EMIM(+)DCA(-) correspond to formation of an N-heterocyclic carbene and acid pair via transfer of the C2 proton of EMIM(+) to DCA(-), and evolution of methylimidazole and ethylimidazole via SN2 alkyl abstraction by DCA(-). Similar decomposition paths were identified for energized EMMIM(+)DCA(-), except that the reactivity of C2 of the imidazolium cation is significantly reduced upon substitution of a methyl group for a hydrogen atom at this position. The present work demonstrates that dynamics simulations, in conjunction with statistical modeling, are able to provide insight into decomposition mechanisms, kinetics, and dynamics for alkylimidazolium-based ionic liquids and to predict product branching ratios and how they vary with decomposition temperatures. PMID:25275818

Liu, Jianbo; Chambreau, Steven D; Vaghjiani, Ghanshyam L

2014-11-26

261

Statistical moment equations for stochastic spin dynamics in phase space: A uniaxial paramagnet subjected to a dc bias field of arbitrary orientation  

NASA Astrophysics Data System (ADS)

Spin dynamics in a dissipative environment are treated via the evolution (master) equation for the quasiprobability density function of spin orientations in the phase space of the polar and azimuthal angles in the weak spin-bath coupling and high-temperature limits. The explicit solution is written for an arbitrary spin Hamiltonian as a finite series of spherical harmonics analogous to the (infinite) Fourier series representation of the classical case governed by the Fokker-Planck equation. Therefore, the expansion coefficients, i.e., the statistical averages of the spherical harmonics, may be determined as before from a differential-recurrence relation, yielding the stochastic spin dynamics for arbitrary spin number S. For large S the differential-recurrence relations reduce to those generated by the Fokker-Planck equation. Thus, the spin dynamics may be treated in a manner transparently linking to the classical representations, thereby providing quantum corrections to classical averages. The method is illustrated via the magnetization relaxation of a uniaxial paramagnet with a dc field H0 applied at an arbitrary angle to the easy axis, which is the quantum version of the most basic model in classical superparamagnetism.

Kalmykov, Yuri P.; Titov, Serguey V.; Coffey, William T.

2012-09-01

262

Horizontal flow fields observed in Hinode G-band images. IV. Statistical properties of the dynamical environment around pores  

NASA Astrophysics Data System (ADS)

Context. Solar pores are penumbra-lacking magnetic features, that mark two important transitions in the spectrum of magnetohydrodynamic processes: (1) the magnetic field becomes sufficiently strong to suppress the convective energy transport and (2) at some critical point some pores develop a penumbra and become sunspots. Aims: The purpose of this statistical study is to comprehensively describe solar pores in terms of their size, perimeter, shape, photometric properties, and horizontal proper motions. The seeing-free and uniform data of the Japanese Hinode mission provide an opportunity to compare flow fields in the vicinity of pores in different environments and at various stages of their evolution. Methods: The extensive database of high-resolution G-band images observed with the Hinode Solar Optical Telescope (SOT) is a unique resource to derive statistical properties of pores using advanced digital image processing techniques. The study is based on two data sets: (1) photometric and morphological properties inferred from single G-band images cover almost seven years from 2006 October 25 to 2013 August 31; and (2) horizontal flow fields derived from 356 one-hour sequences of G-band images using local correlation tracking (LCT) for a shorter period of time from 2006 November 3 to 2008 January 6 comprising 13 active regions. Results: A total of 7643/2863 (single/time-averaged) pores builds the foundation of the statistical analysis. Pores are preferentially observed at low latitudes in the southern hemisphere during the deep minimum of solar cycle No. 23. This imbalance reverses during the rise of cycle No. 24, when the pores migrate from high to low latitudes. Pores are rarely encountered in quiet-Sun G-band images, and only about 10% of pores exist in isolation. In general, pores do not exhibit a circular shape. Typical aspect ratios of the semi-major and -minor axes are 3:2 when ellipses are fitted to pores. Smaller pores (more than two-thirds are smaller than 5 Mm2) tend to be more circular, and their boundaries are less corrugated. Both the area and perimeter length of pores obey log-normal frequency distributions. The frequency distribution of the intensity can be reproduced by two Gaussians representing dark and bright components. Bright features resembling umbral dots and even light bridges cover about 20% of the pores' area. Averaged radial profiles show a peak in the intensity at normalized radius RN = r/Rpore = 2.1, followed by maxima of the divergence at RN = 2.3 and the radial component of the horizontal velocity at RN = 4.6. The divergence is negative within pores strongly suggesting converging flows towards the center of pores, whereas exterior flows are directed towards neighboring supergranular boundaries. The photometric radius of pores, where the intensity reaches quiet-Sun levels at RN = 1.4, corresponds to the position where the divergence is zero at RN = 1.6. Conclusions: Morphological and photometric properties as well as horizontal flow fields have been obtained for a statistically meaningful sample of pores. This provides critical boundary conditions for MHD simulations of magnetic flux concentrations, which eventually evolve into sunspots or just simply erode and fade away. Numerical models of pores (and sunspots) have to fit within these confines, and more importantly ensembles of pores have to agree with the frequency distributions of observed parameters.

Verma, M.; Denker, C.

2014-03-01

263

The Dynamic Behavior of Quantum Statistical Entropy in 5D Ricci-flat Black String with Thin-layer Approach  

E-print Network

In this paper, the statistical-mechanical entropies of 5D Ricci-flat black string is calculated through the wave modes of the quantum field with improved thin-layer brick-wall method. The modes along the fifth dimension are semi-classically quantized by Randall-Sundrum mass relationship. We use the two-dimensional area to describe this black string's entropy which, in the small-mass approximation, is a linear sum of the area of the black hole horizon and the cosmological horizon. The proportionality coefficients of entropy are discretized with quantized extra dimensional modes. It should be noted that the small-mass approximation used in our calculation is naturally justified by the assumption that the two branes are located far apart.

Molin Liu; Hongya Liu

2008-11-05

264

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

265

32. Statistics 1 32. STATISTICS  

E-print Network

32. Statistics 1 32. STATISTICS Revised September 2007 by G. Cowan (RHUL). This chapter gives an overview of statistical methods used in High Energy Physics. In statistics, we are interested in using's validity or to determine the values of its parameters. There are two main approaches to statistical

Masci, Frank

266

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] [National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China). Dept. of Electrical Engineering

1993-12-01

267

Statistical and dynamical analysis of internal waves on the continental shelf of the Middle Atlantic Bight from Space Shuttle photographs  

NASA Technical Reports Server (NTRS)

The internal waves on the continental shelf on the Middle Atlantic Bight seen on Space Shuttle photographs taken during the STS-40 mission in June 1991 are measured and analyzed. The internal wave field in the sample area has a three-level structure which consists of packet groups, packets, and solitons. An average packet group wavelength of 17.5 km and an average soliton wavelength of 0.6 km are measured. Finite-depth theory is used to derive the dynamic parameters of the internal solitons: the maximum amplitude of 5.6 m, the characteristic phase speed of 0.42 m/s, the characteristic period of 23.8 min, the velocity amplitude of the water particles in the upper and lower layers of 0.13 m/s and 0.030 m/s respectively, and the theoretical energy per unit crest line of 6.8 x 10 exp 4 J/m. The frequency distribution of solitons is triple-peaked rather than continuous. The major generation source is at 160 m water depth, and a second is at 1800 m depth, corresponding to the upper and lower edges of the shelf break.

Zheng, Quanan; Yan, Xiao-Hai; Klemas, Vic

1993-01-01

268

Statistical analysis of the dynamics of secondary electrons in the flare of a high-voltage beam-type discharge  

NASA Astrophysics Data System (ADS)

In the present work, results of investigations into the dynamics of secondary electrons with helium atoms in the presence of the reverse electric field arising in the flare of a high-voltage pulsed beam-type discharge and leading to degradation of the primary electron beam are presented. The electric field in the discharge of this type at moderate pressures can reach several hundred V/cm and leads to considerable changes in the kinetics of secondary electrons created in the process of propagation of the electron beam generated in the accelerating gap with a grid anode. Moving in the accelerating electric field toward the anode, secondary electrons create the so-called compensating current to the anode. The character of electron motion and the compensating current itself are determined by the ratio of the field strength to the concentration of atoms (?/n). The energy and angular spectra of secondary electrons are calculated by the Monte Carlo method for different ratios E/n of the electric field strength to the helium atom concentration. The motion of secondary electrons with threshold energy is studied for inelastic collisions of helium atoms and differential analysis is carried out of the collisional processes causing energy losses of electrons in helium for different E/n values. The mechanism of creation and accumulation of slow electrons as a result of inelastic collisions of secondary electrons with helium atoms and selective population of metastable states of helium atoms is considered. It is demonstrated that in a wide range of E/n values the motion of secondary electrons in the beam-type discharge flare has the character of drift. At E/n values characteristic for the discharge of the given type, the drift velocity of these electrons is calculated and compared with the available experimental data.

Demkin, V. P.; Mel'nichuk, S. V.

2014-09-01

269

Combining mathematical models and statistical methods to understand and predict the dynamics of antibiotic-sensitive mutants in a population of resistant bacteria during experimental evolution.  

PubMed

Temporarily discontinuing the use of antibiotics has been proposed as a means to eliminate resistant bacteria by allowing sensitive clones to sweep through the population. In this study, we monitored a tetracycline-sensitive subpopulation that emerged during experimental evolution of E. coli K12 MG1655 carrying the multiresistance plasmid pB10 in the absence of antibiotics. The fraction of tetracycline-sensitive mutants increased slowly over 500 generations from 0.1 to 7%, and loss of resistance could be attributed to a recombination event that caused deletion of the tet operon. To help understand the population dynamics of these mutants, three mathematical models were developed that took into consideration recurrent mutations, increased host fitness (selection), or a combination of both mechanisms (full model). The data were best explained by the full model, which estimated a high mutation frequency (lambda = 3.11 x 10(-5)) and a significant but small selection coefficient (sigma = 0.007). This study emphasized the combined use of experimental data, mathematical models, and statistical methods to better understand and predict the dynamics of evolving bacterial populations, more specifically the possible consequences of discontinuing the use of antibiotics. PMID:15579675

De Gelder, Leen; Ponciano, José M; Abdo, Zaid; Joyce, Paul; Forney, Larry J; Top, Eva M

2004-11-01

270

Descriptive statistics.  

PubMed

In this article, we introduced basic concepts of statistics, type of distributions, and descriptive statistics. A few examples were also provided. The basic concepts presented herein are only a fraction of the concepts related to descriptive statistics. Also, there are many commonly used distributions not presented herein, such as Poisson distributions for rare events and exponential distributions, F distributions, and logistic distributions. More information can be found in many statistics books and publications. PMID:19891281

Shi, Runhua; McLarty, Jerry W

2009-10-01

271

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

272

Statistical Diversions  

ERIC Educational Resources Information Center

The term "data snooping" refers to the practice of choosing which statistical analyses to apply to a set of data after having first looked at those data. Data snooping contradicts a fundamental precept of applied statistics, that the scheme of analysis is to be planned in advance. In this column, the authors shall elucidate the statistical

Petocz, Peter; Sowey, Eric

2012-01-01

273

Projecting Mid- and End-of-Century Climate Change in the Los Angeles Mountainous Region by a Combination of Dynamical and Statistical Downscaling Techniques  

NASA Astrophysics Data System (ADS)

Using a combination of dynamical and statistical downscaling techniques, we produced 2-km-resolution regional climate reconstructions and future projections of surface warming and snowfall changes in the Los Angeles region at the middle and end of the 21st century. Projections for both time periods were compared to a validated simulation of a baseline period (1981-2000). We examined outcomes associated with two IPCC-AR5 greenhouse gas emissions scenarios: a "business-as-usual" scenario (RCP8.5) and a "mitigation" scenario (RCP2.6). Output from all available global climate models in the CMIP5 archive was downscaled. We first statistically downscaled surface warming and then applied a statistical model between the surface temperature and snowfall to project the snowfall change. By mid-century, the mountainous areas in the Los Angeles region are likely to receive substantially less snowfall than in the baseline period. In RCP8.5, about 60% of the snowfall is most likely to persist, while in RCP2.6, the likely amount remaining is somewhat higher (about 70%). By end-of-century, however, the two scenarios diverge significantly. In RCP8.5, snowfall sees a dramatic further reduction, with only about a third of baseline snowfall persisting. For RCP2.6, snowfall sees only a negligible further reduction from mid-century. Due to significant differences in climate change outcomes across the global models, we estimated these numbers associated with uncertainty, in the range of 15-30 percentage points. For both scenarios and both time slices, the snowfall loss is consistently greatest at low elevations, and the lower-lying mountain ranges are somewhat more vulnerable to snowfall loss. The similarity in the two scenarios' most likely snowfall outcomes at mid-century illustrates the inevitability of climate change in the coming decades, no matter what mitigation measures are taken. Their stark contrast at century's end reveals that reduction of greenhouse gas emissions will help avoid a dramatic loss of snowfall by the end of the century. In addition to snowfall projections, the warming-accelerated snow melting of the already reduced snowfall will be discussed as well.

Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Reich, K.

2013-12-01

274

A statistical analysis of the lateral displacement of Si atoms in molecular dynamics simulations of successive bombardment with 20-keV C 60 projectiles  

NASA Astrophysics Data System (ADS)

An important factor that determines the possible lateral resolution in sputter depth profiling experiments is ion induced lateral displacement of substrate atoms. Molecular dynamics (MD) simulations are performed to model the successive bombardment of Si with 20 keV C60 at normal incidence. A statistical analysis of the lateral displacement of atoms that originate from the topmost layer is presented and discussed. From these results, it is determined that the motion is isotropic and can be described mathematically by a simple diffusion equation. A “diffusion coefficient” for lateral displacement is determined to be 3.5 Å2/impact. This value can be used to calculate the average lateral distance moved as a function of the number of impacts. The maximum distance an atom may move is limited by the time that it remains on the surface before it is sputtered. After 800 impacts, 99% of atoms from the topmost layer have been removed, and the average distance moved by these atoms is predicted to be 100 Å. Although the behavior can be described mathematically by the diffusion equation, the behavior of the atoms is different than what is thought of as normal diffusion. Atoms are displaced a large distance due to infrequent large hops.

Krantzman, K. D.; Cook, E. L.; Wucher, A.; Garrison, B. J.

2011-07-01

275

Statistics Tools  

NSDL National Science Digital Library

This collection of calculators, created by Thomas Kirkman of the College of Saint Bendict/Saint Joseph, allows users to perform a number of statistical applications. Each provides background on the procedure and an example. Users can compute descriptive statistics and perform t-tests, Chi-square tests, Kolmogorov-Smirnov tests, Fisher's Exact Test, contingency tables, ANOVA, and regression. This is a nice collection of useful applications for a statistics classroom.

Kirkman, Thomas

2009-02-04

276

Morbidity statistics  

PubMed Central

This paper is based on an analysis of questionnaires sent to the health ministries of Member States of WHO asking for information about the extent, nature, and scope of morbidity statistical information. It is clear that most countries collect some statistics of morbidity and many countries collect extensive data. However, few countries relate their collection to the needs of health administrators for information, and many countries collect statistics principally for publication in annual volumes which may appear anything up to 3 years after the year to which they refer. The desiderata of morbidity statistics may be summarized as reliability, representativeness, and relevance to current health problems. PMID:5306722

Smith, Alwyn

1969-01-01

277

Statistical Diversions  

ERIC Educational Resources Information Center

In this article, the authors focus on hypothesis testing--that peculiarly statistical way of deciding things. Statistical methods for testing hypotheses were developed in the 1920s and 1930s by some of the most famous statisticians, in particular Ronald Fisher, Jerzy Neyman and Egon Pearson, who laid the foundations of almost all modern methods of…

Petocz, Peter; Sowey, Eric

2008-01-01

278

Development of a two-dimensional zonally averaged statistical-dynamical model. I - The parameterization of moist convection and its role in the general circulation  

NASA Technical Reports Server (NTRS)

The moist convection parameterization used in the GISS 3-D GCM is adapted for use in a two-dimensional (2-D) zonally averaged statistical-dynamical model. Experiments with different versions of the parameterization show that its impact on the general circulation in the 2-D model does not parallel its impact in the 3-D model unless the effect of zonal variations is parameterized in the moist convection calculations. A parameterization of the variations in moist static energy is introduced in which the temperature variations are calculated from baroclinic stability theory, and the relative humidity is assumed to be constant. Inclusion of the zonal variations of moist static energy in the 2-D moist convection parameterization allows just a fraction of a latitude circle to be unstable and enhances the amount of deep convection. This leads to a 2-D simulation of the general circulation very similar to that in the 3-D model. The experiments show that the general circulation is sensitive to the parameterized amount of deep convection in the subsident branch of the Hadley cell. The more there is, the weaker are the Hadley cell circulations and the westerly jets. The experiments also confirm the effects of momentum mixing associated with moist convection found by earlier investigators and, in addition, show that the momentum mixing weakens the Ferrel cell. An experiment in which the moist convection was removed while the hydrological cycle was retained and the eddy forcing was held fixed shows that moist convection by itself stabilizes the tropics, reduces the Hadley circulation, and reduces the maximum speeds in the westerly jets.

Yao, Mao-Sung; Stone, Peter H.

1987-01-01

279

Statistical Laboratory & Department of Statistics  

E-print Network

will coordinate the teaching of the first two courses in business statistics. The undergraduate program continues and statistical methodology in the nutritional sciences. We were also very pleased to secure a permanent lecturer reviewing achievements of the past seven years and planning for the future. A written report was submitted

280

Statistics Clinic  

NASA Technical Reports Server (NTRS)

Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.

Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James

2014-01-01

281

Rainbow statistics  

E-print Network

Non-commutative quantum field theories and their global quantum group symmetries provide an intriguing attempt to go beyond the realm of standard local quantum field theory. A common feature of these models is that the quantum group symmetry of their Hilbert spaces induces additional structure in the multiparticle states which reflects a non-trivial momentum-dependent statistics. We investigate the properties of this "rainbow statistics" in the particular context of $\\kappa$-quantum fields and discuss the analogies/differences with models with twisted statistics.

Michele Arzano; Dario Benedetti

2008-09-04

282

Injury Statistics  

MedlinePLUS

... 2012 1998 Electrocutions Associated With Consumer Products July 17, 2012 2000 Electrocutions Associated with Consumer Products (9999) ... Furniture and Decor Injury Statistics Other Sports July 17, 2012 Unpowered Scooters July 10, 2012 Trampolines May ...

283

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.

284

Statistical Mechanics  

Microsoft Academic Search

We review and further develop a mathematical framework for non-equilibrium quantum statistical mechanics recently proposed in (JP4, JP5, JP6, Ru3, Ru4, Ru5, Ru6). In the alge- braic formalism of quantum statistical mechanics we introduce notions of non-equilibrium steady states, entropy production and heat fluxes, and study their properties. Our basic paradigm is a model of a small (finite) quantum system

V. Jaksi ´; C.-A. Pillet

1937-01-01

285

Engineering Statistics From "Engineering Statistics" , Top &  

E-print Network

Engineering Statistics From "Engineering Statistics" , Top & Wiley, Prapaisri & Pongchanun 2 From "Engineering Statistics" , Top & Wiley, Prapaisri & Pongchanun 3 " "(Sample) (Sampling) ""(Population) " "(Statistics) ""(Parameter) From "Engineering Statistics" , Top & Wiley, Prapaisri

Kovintavewat, Piya

286

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

287

Statistical Fun  

ERIC Educational Resources Information Center

Following the announcement last year that there will be no more math coursework assessment at General Certificate of Secondary Education (GCSE), teachers will in the future be able to devote more time to preparing learners for formal examinations. One of the key things that the author has learned when teaching statistics is that it makes for far…

Catley, Alan

2007-01-01

288

Delayed expression of hpS2 and prolonged expression of CIP1/WAF1/SDI1 in human tumour cells irradiated with X-rays, fission neutrons or 1 GeV/nucleon Fe ions  

NASA Technical Reports Server (NTRS)

PURPOSE: Differences in gene expression underlie the phenotypic differences between irradiated and unirradiated cells. The goal was to identify late-transcribed genes following irradiations differing in quality, and to determine the RBE of 1 GeV/n Fe ions. MATERIALS AND METHODS: Clonogenic assay was used to determine the RBE of Fe ions. Differential hybridization to cDNA target clones was used to detect differences in expression of corresponding genes in mRNA samples isolated from MCF7 cells irradiated with iso-survival doses of Fe ions (0 or 2.5 Gy) or fission neutrons (0 or 1.2 Gy) 7 days earlier. Northern analysis was used to confirm differential expression of cDNA-specific mRNA and to examine expression kinetics up to 2 weeks after irradiation. RESULTS: Fe ion RBE values were between 2.2 and 2.6 in the lines examined. Two of 17 differentially expressed cDNA clones were characterized. hpS2 mRNA was elevated from 1 to 14 days after irradiation, whereas CIP1/WAF1/SDI1 remained elevated from 3 h to 14 days after irradiation. Induction of hpS2 mRNA by irradiation was independent of p53, whereas induction of CIP1/WAF1/SDI1 was observed only in wild-type p53 lines. CONCLUSIONS: A set of coordinately regulated genes, some of which are independent of p53, is associated with change in gene expression during the first 2 weeks post-irradiation.

Balcer-Kubiczek, E. K.; Zhang, X. F.; Harrison, G. H.; Zhou, X. J.; Vigneulle, R. M.; Ove, R.; McCready, W. A.; Xu, J. F.

1999-01-01

289

1. Van Kampen, N.G., Elimination of fast variables, Physics Reports, 124 (1985), 2. Bogolyubov, N.N., Dynamic theory problems in statistical physics, Gostekhiz-  

E-print Network

of dynamical systems applied to some dissipative fluid mechanics, in: Nonlinear dynamics from lasers to butter. Gorban, A.N., Karlin, I.V., Method of invariant manifolds and regularization of acoustic spectra-Afanasyeva, T., in: Mechanics Enziklop�adie der Math- ematischen Wissenschaften, Vol.4., Leipzig, 1911

Gorban, Alexander N.

290

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

291

Stats 10 -Introduction to Statistical Reasoning Stats 13 -Statistical Methods for the  

E-print Network

of dynamic computer games demonstrating a variety of situations where chance and variation and unavoidable and Life Sciences Stats 100A - Probability Theory Stats 100B - Mathematical Statistics Stats 100C Probability & Statistics for Engineers Stats 130D - Statistical Computing Stat 251 - Statistical Methods

California at Los Angeles, University of

292

CRITIQUING AND IMPROVING DATA USE FROM HIGH STAKES TESTS: UNDERSTANDING VARIATION AND DISTRIBUTION IN RELATION TO EQUITY USING DYNAMIC STATISTICS SOFTWARE  

Microsoft Academic Search

Executive Summary: This paper reveals how current approaches to data use by schools, even with disaggregation by subgroup, can fail to recognize the importance of the statistical concepts of variation and distribution in monitoring systemic progress of all students. A case study in which a high poverty, majority Hispanic urban school dismantled its Standards-based reform program after the school was

Jere Confrey; Katie Makar

293

Spike statistics  

E-print Network

In this paper we explore stochastical and statistical properties of so-called recurring spike induced Kasner sequences. Such sequences arise in recurring spike formation, which is needed together with the more familiar BKL scenario to yield a complete description of generic spacelike singularities. In particular we derive a probability distribution for recurring spike induced Kasner sequences, complementing similar available BKL results, which makes comparisons possible. As examples of applications, we derive results for so-called large and small curvature phases and the Hubble-normalized Weyl scalar.

J. Mark Heinzle; Claes Uggla

2012-12-21

294

Four Faculty Positions Applied Statistics & Computational Statistics  

E-print Network

Four Faculty Positions Applied Statistics & Computational Statistics The Department of Statistics at the Assistant Professor rank. Two positions are open in the area of Applied Statistics, with a focus on the development of statistical methodology and statistical consulting. The other two positions are open

Shepp, Larry

295

Monitoring the sandstorm during spring season 2002 and desertification in northern China using the SSM/I data and Getis statistics  

NASA Astrophysics Data System (ADS)

A massive sandstorm has enveloped most northern China during the spring season 2002. Monitoring the evolution of sandstorm and desertification has become one of most serious problems for China's environment. Since 1989, one of the most advanced and operational passive microwave sensors is the DMSP SSM/I (special sensor microwave imager) operated at seven channels (19, 37, 85GHz with vertical and horizontal polarization and 22GHz with vertical polarization only). In the paper, the sandstorm and desertification indexes, SDI and DI, are derived from the radiative transfer equation, and are employed with multi-channel measurements of the DMSP SSM/I for monitoring the sandstorm and desertification in Northern China. Some SSM/I data in 1997 and 2001 are employed. The algorithm of the Getis statistics is developed to categorize the spatial correlation and its evolution during these days. It is demonstrated that the SSM/I indexes, SDI and DI, and its Getis statistics are well applicable for monitoring the sandstorm and desertification.

Jin, Yaqiu; Yan, Fenghua

2003-04-01

296

Entropy and free energy of a polymer chain from dynamic Monte Carlo simulations on the lattice. An extension of the statistical counting method  

NASA Astrophysics Data System (ADS)

The main assumptions of the statistical counting (SC) method [D. Zhao et al., J. Chem. Phys. 104, 1672 (1996)] for the calculation of the conformational entropy of a chain modeled on the lattice are presented. The method is discussed in terms of its applicability to different physical systems and the integrity of results. Also, an extension of the SC method for the analysis of the statistics of some Verdier-Stockmayer algorithms in the Metropolis Monte Carlo simulation is proposed. The results of the application of this new method, named here as the micomodification probabilities (MMP) method, for the study of the effect of different solvent conditions, different types of geometrical constraints and deforming external forces on the free energy of a polymer chain, are presented. The use of the MMP method for the investigation of a charged polymer in the presence of other charged objects (ions, nanoparticles) is also reported.

Nowicki, W.; Nowicka, G.; Ma?ka, A.

2014-10-01

297

Statistical Digest No. 70 Fishery Statistics of  

E-print Network

Statistical Digest No. 70 Statistics of the United States 1976 Washington National Marine Fisheries Service #12;#12;Statistical Digest No. 70 Fishery Statistics of the United States 1976 Prepared by: Resource Statistics Division Joseph Pileggi, Chief B.G. Thompson, Assistant Chief

298

Covariant Equilibrium Statistical Mechanics  

E-print Network

A manifest covariant equilibrium statistical mechanics is constructed starting with a 8N dimensional extended phase space which is reduced to the 6N physical degrees of freedom using the Poincare-invariant constrained Hamiltonian dynamics describing the micro-dynamics of the system. The reduction of the extended phase space is initiated forcing the particles on energy shell and fixing their individual time coordinates with help of invariant time constraints. The Liouville equation and the equilibrium condition are formulated in respect to the scalar global evolution parameter which is introduced by the time fixation conditions. The applicability of the developed approach is shown for both, the perfect gas as well as the real gas. As a simple application the canonical partition integral of the monatomic perfect gas is calculated and compared with other approaches. Furthermore, thermodynamical quantities are derived. All considerations are shrinked on the classical Boltzmann gas composed of massive particles and hence quantum effects are discarded.

E. Lehmann

2006-02-25

299

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

300

Statistics (Program Description)  

NSF Publications Database

... of Mathematical Sciences Statistics Description The Statistics Program supports research for ... robust methods, experimental design, spatial statistics, resampling methods, and the analysis of ...

301

Methodology, Measurement, and Statistics  

NSF Publications Database

... federal statistical agencies for competitive survey and statistical methodology proposals.) Proposal ... models that cross traditional disciplinary boundaries, including research on statistical methodology ...

302

Statistical mechanics of the vacuum  

E-print Network

The vacuum is full of virtual particles which exist for short moments of time. In this paper we construct a chaotic model of vacuum fluctuations associated with a fundamental entropic field that generates an arrow of time. The dynamics can be physically interpreted in terms of fluctuating virtual momenta. This model leads to a generalized statistical mechanics that distinguishes fundamental constants of nature.

Christian Beck

2011-12-07

303

A new'' approach to the quantitative statistical dynamics of plasma turbulence: The optimum theory of rigorous bounds on steady-state transport  

SciTech Connect

The fundamental problem in the theory of turbulent transport is to find the flux {Gamma} of a quantity such as heat. Methods based on statistical closures are mired in conceptual controversies and practical difficulties. However, it is possible to bound {Gamma} by employing constraints derived rigorously from the equations of motion. Brief reviews of the general theory and its application to passive advection are given. Then, a detailed application is made to anomalous resistivity generated by self-consistent turbulence in a reversed-field pinch. A nonlinear variational principle for an upper bound on the turbulence electromotive force for fixed current is formulated from the magnetohydrodynamic equations in cylindrical geometry. Numerical solution of a case constrained solely by energy balance leads to a reasonable bound and nonlinear eigenfunctions that share intriguing features with experimental data: the dominant mode numbers appear to be correct, and field reversal is predicted at reasonable values of the pinch parameter. Although open questions remain upon considering all bounding calculations to date one can conclude, remarkably, that global energy balance constrains transport sufficiently so that bounds derived therefrom are not unreasonable and that bounding calculations are feasible even for involved practical problems. The potential of the method has hardly been tapped; it provides a fertile area for future research. 29 refs.

Krommes, J.A. (Princeton Univ., NJ (USA). Plasma Physics Lab.); Kim, Chang-Bae (Texas Univ., Austin, TX (USA). Inst. for Fusion Studies)

1990-06-01

304

Statistical questions in experimental evolution  

NASA Astrophysics Data System (ADS)

Recent advances in the mathematical analysis of models describing evolutionary dynamics are rapidly increasing our ability to make precise quantitative predictions. These advances have created a growing need for corresponding improvements in our ability to observe evolutionary dynamics in laboratory evolution experiments. High-throughput experimental methods are particularly crucial, in order to maintain many replicate populations and measure statistical differences in evolutionary outcomes at both phenotypic and genomic levels. In this paper, I describe recent technical developments which have greatly increased the throughput of laboratory evolution experiments, and outline a few promising directions for further improvements. I then highlight a few ways in which these new experimental methods can help to answer simple statistical questions about evolutionary dynamics, and potentially guide future theoretical work.

Desai, Michael M.

2013-01-01

305

FISHERY STATISTICS UNITED STATES  

E-print Network

FISHERY STATISTICS OF THE UNITED STATES 1973 STATISTICAL DIGEST NO. 67 Prepared by STATISTICS a review of the fishery statistics for the year 1973 . These statistics include data on the volume in assembling data on the fisheries. In certain areas, information complete enough to be used by the statistical

306

The application of statistical mechanics on the study of glassy behaviors in transportation networks and dynamics in models of financial markets  

NASA Astrophysics Data System (ADS)

In this thesis, we study two interdisciplinary problems in the framework of statistical physics, which show the broad applicability of physics on problems with various origins. The first problem corresponds to an optimization problem in allocating resources on random regular networks. Frustrations arise from competition for resources. When the initial resources are uniform, different regimes with discrete fractions of satisfied nodes are observed, resembling the Devil's staircase. We apply the spin glass theory in analyses and demonstrate how functional recursions are converted to simple recursions of probabilities. Equilibrium properties such as the average energy and the fraction of free nodes are derived. When the initial resources are bimodally distributed, increases in the fraction of rich nodes induce a glassy transition, entering a glassy phase described by the existence of multiple metastable states, in which we employ the replica symmetry breaking ansatz for analysis. The second problem corresponds to the study of multi-agent systems modeling financial markets. Agents in the system trade among themselves, and self-organize to produce macroscopic trading behaviors resembling the real financial markets. These behaviors include the arbitraging activities, the setting up and the following of price trends. A phase diagram of these behaviors is obtained, as a function of the sensitivity of price and the market impact factor. We finally test the applicability of the models with real financial data including the Hang Seng Index, the Nasdaq Composite and the Dow Jones Industrial Average. A substantial fraction of agents gains faster than the inflation rate of the indices, suggesting the possibility of using multi-agent systems as a tool for real trading.

Yeung, Chi Ho

307

Quantum particles from classical statistics  

E-print Network

Quantum particles and classical particles are described in a common setting of classical statistical physics. The property of a particle being "classical" or "quantum" ceases to be a basic conceptual difference. The dynamics differs, however, between quantum and classical particles. We describe position, motion and correlations of a quantum particle in terms of observables in a classical statistical ensemble. On the other side, we also construct explicitly the quantum formalism with wave function and Hamiltonian for classical particles. For a suitable time evolution of the classical probabilities and a suitable choice of observables all features of a quantum particle in a potential can be derived from classical statistics, including interference and tunneling. Besides conceptual advances, the treatment of classical and quantum particles in a common formalism could lead to interesting cross-fertilization between classical statistics and quantum physics.

C. Wetterich

2009-04-20

308

Modeling interacting dynamic networks: II. Systematic study of the statistical properties of cross-links between two networks with preferred degrees  

NASA Astrophysics Data System (ADS)

In a recent work (Liu et al, 2013 J. Stat. Mech. P08001), we introduced dynamic networks with preferred degrees and presented simulation and analytic studies of a single, homogeneous system as well as two interacting networks. Here, we extend these studies to a wider range of parameter space, in a more systematic fashion. Though the interaction we introduced seems simple and intuitive, it produced dramatically different behavior in the single- and two-network systems. Specifically, partitioning the single network into two identical sectors, we find the cross-link distribution to be a sharply peaked Gaussian. In stark contrast, we find a very broad and flat plateau in the case of two interacting identical networks. A sound understanding of this phenomenon remains elusive. Exploring more asymmetric interacting networks, we discover a kind of ‘universal behavior’ for systems in which the ‘introverts’ (nodes with smaller preferred degree) are far outnumbered. Remarkably, an approximation scheme for their degree distribution can be formulated, leading to very successful predictions.

Liu, Wenjia; Schmittmann, B.; Zia, R. K. P.

2014-05-01

309

[Consolidate statistics work, reform the statistics system].  

PubMed

China learned about statistics from the Soviet Union in the 1950s. The statistics work of the entire country was under centralized and unified leadership. The state's statistics system and methods were implemented and practiced uniformly throughout China. Any false report was considered dishonest and an act detrimental to the interests of the country. In the first 5 years, the statistical information was usually reliable, with the exception of that concerning agriculture. Some problems with false figures led to the Central Committee of the Chinese Communist Party and the State Council deciding to consolidate statistics work in 1962. The decision was made to establish a powerful, centralized, and unified statistics system as quickly as possible. At present the strength of statistics departments at or above the county level throughout China is only about 76% of that of 1965, and the strength of the State Statistics Bureau is less than that of 1976. The statistics bureaus of many cities and counties have not yet been reestablished. Viewed from examples of inaccurate statistical figures and incomplete statistical content, the tendency of party and government leaders meddling in statistical figures and making false reports has not yet been eliminated. It appears that many people in the party and in the country have not really learned a lesson from the serious mistakes caused by putting forth strong demands without first having a clear understanding of the situation. Many localities, departments, and units still fail to understand the importance of statistics. The following action needs to be taken to consolidate statistics work: 1) raise the social status of statistics work; 2) reform the system of administration in statistics work; 3) establish a powerful statistics system; and 4) improve the laws and regulations governing statistics. PMID:12311439

Sun, Y

1981-03-26

310

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

311

Chemistry 427f/1480f: Statistical Mechanics Prof. Jeremy Schofield  

E-print Network

Chemistry 427f/1480f: Statistical Mechanics Prof. Jeremy Schofield · Office: Lash Miller 420E/biological systems Reference Books: · Statistical Mechanics, by Donald A. McQuarrie (M) · Statistical Physics: Statics, Dynamics and Renormalization, L.P. Kadanoff (K) · Statistical Mechanics, T.L. Hill · A Modern

Schofield, Jeremy

312

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 emplacement of magma-filled dikes often induce abundant seismicity in the surrounding host rocks. Most of the earthquakes are thought to occur close to the propagating tip (or edges, in 3D) of the dike, where stresses are concentrated. The resulting seismicity often appears as a swarm, controlled mainly by dike-induced stresses and stressing rate and by other factors, such as the background stressing rate, tectonic setting, regional stresses and tectonic history. The spatial distribution and focal mechanisms of the seismicity bear information on the interaction of the dike stress field and the tectonic setting of the area. The seismicity accompanying the intrusion of a dike is usually characterized by weak events, for which it is difficult to calculate the focal mechanisms. Therefore, only for a few well-recorded dike intrusions a catalog of focal mechanisms, allowing to perform a robust statistical analysis, is available. The 2000 dike intrusion at Miyakejima is in this sense an outstanding case, as about 18000 seismic events were recorded in a time span of three months. This seismic swarm was one of the most energetic ever recorded with five M>6 earthquakes. For this swarm a catalog of 1500 focal mechanisms is avalable (NIED, Japan). We perform a clustering analysis of the focal mechanism solutions, in order to infer the most frequent focal mechanism features prior to the intrusion (pre-diking period) and during the co-diking period. As previously suggested, we find that the dike stress field modified substantially the pre-existing seismicity pattern, by shadowing some non-optimally oriented strike-slip structures and increasing seismic rate on optimally oriented strike-slip tectonic structures. Alongside, during the co-diking period a large number of normal and oblique-normal faulting were observed. These events cannot be explained within the tectonics of the intrusion area. We suggest they are directly generated by the intense stress field induced at the dike edges. We further investigate the distribution of the two main clusters we identify, i.e. strike-slip and oblique-normal mechanisms. We find that the strike-slip family obeys a Gutenberg-Richter law with a b-value close to one. The oblique-normal family of events deviates from the Gutenberg-Richter distribution and is slightly bimodal, with a marked roll-off on its right-hand tail suggesting a lack of large magnitude events (M>5.5). This set of events seems to collect earthquakes rupturing above the dike, similar to graben faulting events widely observed in volcanic areas during diking. A possible explanation of the anomalous frequency-magnitude distribution is that these earthquakes may be limited in size by the thickness of the layer where they nucleate, being spatially constrained between the dike upper edge and the Earth's surface.

Passarelli, Luigi; Rivalta, Eleonora; Simone, Cesca; Aoki, Yosuke

2014-05-01

313

Renyi statistics in equilibrium statistical mechanics  

E-print Network

The Renyi statistics in the canonical and microcanonical ensembles is examined in the general case and in particular for the ideal gas. In the microcanonical ensemble the Renyi statistics is equivalent with the Boltzmann-Gibbs statistics. By the exact analytical results for the ideal gas, it is shown that in the canonical ensemble in the thermodynamic limit the Renyi statistics is also equivalent with the Boltzmann-Gibbs statistics. Furthermore it satisfies the requirements of the equilibrium thermodynamics, i.e. the thermodynamical potential of the statistical ensemble is a homogeneous function of degree 1 of its extensive variables of state. We conclude that the Renyi statistics duplicates the thermodynamical relations stemming from the Boltzmann-Gibbs statistics in the thermodynamical limit.

A. S. Parvan; T. S. Biro

2009-10-16

314

Statistical physics ""Beyond equilibrium  

SciTech Connect

The scientific challenges of the 21st century will increasingly involve competing interactions, geometric frustration, spatial and temporal intrinsic inhomogeneity, nanoscale structures, and interactions spanning many scales. We will focus on a broad class of emerging problems that will require new tools in non-equilibrium statistical physics and that will find application in new material functionality, in predicting complex spatial dynamics, and in understanding novel states of matter. Our work will encompass materials under extreme conditions involving elastic/plastic deformation, competing interactions, intrinsic inhomogeneity, frustration in condensed matter systems, scaling phenomena in disordered materials from glasses to granular matter, quantum chemistry applied to nano-scale materials, soft-matter materials, and spatio-temporal properties of both ordinary and complex fluids.

Ecke, Robert E [Los Alamos National Laboratory

2009-01-01

315

Royal Statistical Society Center for Statistical Education  

NSDL National Science Digital Library

Created by the Royal Statistical Society, this website's purpose it to promote the improvement of statistical education, training and understanding. You will find activities, resources and current news to help in teaching statistics. The site breaks down its resources in this manner: for school, higher education, for all levels, problem solving and MSOR@RSSCSE. The page is quite broad in scope. For this reason, it is a great resource for those interested in almost any aspect of statistics education.

2009-05-04

316

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

317

FISHERY STATISTICS UNITED STATES  

E-print Network

FISHERY STATISTICS OF THE UNITED STATES 1972 STATISTICAL DIGEST NO. 66 Prepared by STATISTICS;ACKNOWLEDGMENTS The data in this edition of "Fishery Statistics of the United States" were collected in co- operation with the various States and tabulated by the staff of the Statistics and Market News Division

318

Molecular Dynamics study of transport properties (self-diffusion, shear viscosity, thermal conductivity) in CMAS liquids at elevated temperature and pressure: Relations between coordination statistics, activation energy and activation volume. (Invited)  

NASA Astrophysics Data System (ADS)

Empirical Potential Molecular Dynamics (EPMD) simulations have been carried out for molten MgSiO3, Mg2SiO4, CaMgSi2O6, CaAl2Si2O8 and 1-bar eutectic liquid in the binary system CaMgSi2O6-CaAl2Si2O8 using a Coulomb-Born-Mayer-van der Waals pair potential form and the potential parameters from Matsui (1996, GRL 23:395) for the system CaO-MgO-Al2O3-SiO2. Simulations were performed in the microcanonical ensemble (NEV) with 8000 atoms, a 1 fs time step, and simulation durations up to 2 ns. Computations were carried out every 500 K over a temperature range of 2500 - 5000 K along 10-20 isochores for each composition to insure good coverage in P-T space. During run T and P fluctuations, giving the uncertainty of state point coordinates was typically ± 30 K and ± 0.5 GPa, respectively. Coordination statistics are determined by counting nearest neighbor configurations up to a cutoff defined by the first minima of the pair correlation function. A complete set of coordination statistics was collected at each state point for each composition. At each state point self-diffusivity of each atom was determined from the Einstein relation between Mean Square Displacement and time. Shear viscosity was computed for a subset of state points using Green-Kubo linear response theory, by studying the autocorrelated regressions of spontaneous fluctuations of appropriate components of the stress tensor. Thermodynamic models (and EOS) for each liquid previously developed from these simulations based on combining the Rosenfeld-Tarazona (1998, Mol Phys 95:141) potential energy-temperature scaling law with the Universal EOS (1986, J Phys C, 19:L467) enable self-consistent computation of liquid sound speeds and isochoric heat capacity used to develop phonon thermal conductivity values at high T and P. Self-diffusivity, shear viscosity and phonon thermal conductivity values from the MD simulations vary systematically with composition, temperature and pressure. These systematic relations correlate with and can be modeled from average first nearest neighbor mean coordination numbers especially for Si and Al around oxygen, oxygen around oxygen, and Ca and Mg around oxygen. Generalized versions of the Stokes-Einstein and Eyring relationships connecting self-diffusivity of oxygen to liquid shear viscosity, T and a characteristic length scale based on coordination statistics can be constructed from MD generated transport properties to capture laboratory data reasonably well in many instances.

Spera, F. J.; Martin, B.; Creamer, J. B.; Nevins, D.; Cutler, I.; Ghiorso, M. S.; Tikunoff, D.

2010-12-01

319

Statistical validation of stochastic models  

SciTech Connect

It is common practice in structural dynamics to develop mathematical models for system behavior, and the authors are now capable of developing stochastic models, i.e., models whose parameters are random variables. Such models have random characteristics that are meant to simulate the randomness in characteristics of experimentally observed systems. This paper suggests a formal statistical procedure for the validation of mathematical models of stochastic systems when data taken during operation of the stochastic system are available. The statistical characteristics of the experimental system are obtained using the bootstrap, a technique for the statistical analysis of non-Gaussian data. The authors propose a procedure to determine whether or not a mathematical model is an acceptable model of a stochastic system with regard to user-specified measures of system behavior. A numerical example is presented to demonstrate the application of the technique.

Hunter, N.F. [Los Alamos National Lab., NM (United States). Engineering Science and Analysis Div.; Barney, P.; Paez, T.L. [Sandia National Labs., Albuquerque, NM (United States). Experimental Structural Dynamics Dept.; Ferregut, C.; Perez, L. [Univ. of Texas, El Paso, TX (United States). Dept. of Civil Engineering

1996-12-31

320

9/6/10 9:41 PMAPS -51st Annual Meeting of the APS Division of Plasma Physics -Event -...onal Heating: Unsteady Dynamics and Scaling in Statistical Steady State Page 1 of 2http://meetings.aps.org/Meeting/DPP09/Event/109258  

E-print Network

this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.DPP.GM9.2 APS Home | APS9/6/10 9:41 PMAPS -51st Annual Meeting of the APS Division of Plasma Physics - Event -...onal Heating: Unsteady Dynamics and Scaling in Statistical Steady State Page 1 of 2http://meetings.aps.org/Meeting

Ng, Chung-Sang

321

FMRI data analysis: statistics, information and dynamics  

Microsoft Academic Search

Abstract: In this thesis, we discuss and propose several methods for functional MRI-magnetic resonanceimagingdata analysis. Functional MRI is a recent modality for the study of brainfunction: it produces image sequences that reect local brain metabolic activity, which inturn reects neural activity. Werst deal with the modeling of each voxel-based temporalpattern, using linear prediction techniques and estimating the information containedin the

Bertrand Thirion

2003-01-01

322

Teaching Introductory Statistics: From dull to Dynamic!  

E-print Network

attacks, and other diseases Growing better plants (pest resistant, high yield, etc) Determining what, meditation, taking an aspirin a day, night-lights for children) As intelligent, curious beings, we want

Utts, Jessica

323

Statistical Reference Datasets  

NSDL National Science Digital Library

A project designed to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software. Dataset archives (Analysis of Variance, Linear Regression, Nonlinear Regression, and Univariate Summary Statistics); background information; related resources and links; FAQs. A project component of of NIST's Tools for Evaluating Mathematical and Statistical Software.

2008-01-31

324

Statistical Reference Datasets  

National Institute of Standards and Technology Data Gateway

Statistical Reference Datasets (Web, free access)   The Statistical Reference Datasets is also supported by the Standard Reference Data Program. The purpose of this project is to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software.

325

Sampling in Statistical Inference  

NSDL National Science Digital Library

This site, presented by the Department of Statistics at Yale University, gives an explanation, a definition and an example of sampling in statistical inference. Topics include parameters, statistics, sampling distributions, bias, and variability. Overall, this is a great resource for any mathematics classroom studying statistics.

Lacey, Michelle

2008-12-23

326

FISHERY STATISTICS UNITED STATES  

E-print Network

FISHERY STATISTICS OF THE UNITED STATES 1974 STATISTICAL DIGEST NO. 68 Prepared by Data Management;PREFACE This report contains a review of U . S. commercial fishery statistics for the calendar year 1974 statistical surveys covering the fisheries of the United States were made by the National Marine Fisheries

327

FISHERY STATISTICS UNITED STATES  

E-print Network

FISHERY STATISTICS OF THE UNITED STATES 1971 STATISTICAL DIGEST NO. 65 Prepared by STATISTICS Service for the years 1931 , 1950 , 1954 - 60, and 1962 - 69 . ii i #12;FISHERY STATISTICS OF THE UNITED DEPARTMENT Of COMMERCE ATMO SPHE RIC ADMINI STRATION Fisheries Service frederick B. Dent, Secretary Robert M

328

STATISTICAL METHODS INFECTIOUS METHODS  

E-print Network

Appendix G STATISTICAL METHODS INFECTIOUS METHODS STATISTICAL ROADMAP Prepared in Support of: CDC for Environmental Health 1 #12;Statistical Methods for Analyzing Data Collected During the Churchill County Study 1 with the complex statistical analysis, investigators from the CDC contracted with Battelle for their assistance

329

Statistical properties of cosmological billiards  

SciTech Connect

Belinski, Khalatnikov, and Lifshitz pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a spacelike singularity. We show how the use of a 'cosmological billiard' description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the 'Kasner circle' which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics of the Bianchi-IX (a, b, c or mixmaster) model; (ii) its quotienting by the group of permutations of (a, b, c); and (iii) the billiard dynamics that arose in recent studies suggesting the hidden presence of Kac-Moody symmetries in cosmological billiards.

Damour, Thibault [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France); ICRANet, Pescara (Italy); Lecian, Orchidea Maria [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France); ICRANet, Pescara (Italy); APC, UMR 7164 du CNRS, Universite Paris 7, 10, rue A. Domon et L. Duquet, 75205 Paris Cedex 13 (France)

2011-02-15

330

Equilibrium statistical mechanics for incomplete nonextensive statistics  

E-print Network

The incomplete nonextensive statistics in the canonical and microcanonical ensembles is explored in the general case and in a particular case for the ideal gas. By exact analytical results for the ideal gas it is shown that taking the thermodynamic limit, with $z=q/(1-q)$ being an extensive variable of state, the incomplete nonextensive statistics satisfies the requirements of equilibrium thermodynamics. The thermodynamical potential of the statistical ensemble is a homogeneous function of the first degree of the extensive variables of state. In this case, the incomplete nonextensive statistics is equivalent to the usual Tsallis statistics. If $z$ is an intensive variable of state, i.e. the entropic index $q$ is a universal constant, the requirements of the equilibrium thermodynamics are violated.

A. S. Parvan; T. S. Biro

2010-03-29

331

Atomic Line Filter for SDI Applications.  

National Technical Information Service (NTIS)

When optical signals are embedded in background noise, narrowband optical filters are needed for receivers to achieve quantum limited performance. Such is typically the case with daytime optical communications and lidar. Narrowband filtered detectors. wit...

J. Menders, S. H. Bloom, E. Korevaar, M. Rivers, C. S. Liu

1994-01-01

332

Statistical Convergence and Convergence in Statistics  

E-print Network

Statistical convergence was introduced in connection with problems of series summation. The main idea of the statistical convergence of a sequence l is that the majority of elements from l converge and we do not care what is going on with other elements. We show (Section 2) that being mathematically formalized the concept of statistical convergence is directly connected to convergence of such statistical characteristics as the mean and standard deviation. At the same time, it known that sequences that come from real life sources, such as measurement and computation, do not allow, in a general case, to test whether they converge or statistically converge in the strict mathematical sense. To overcome limitations induced by vagueness and uncertainty of real life data, neoclassical analysis has been developed. It extends the scope and results of the classical mathematical analysis by applying fuzzy logic to conventional mathematical objects, such as functions, sequences, and series. The goal of this work is the further development of neoclassical analysis. This allows us to reflect and model vagueness and uncertainty of our knowledge, which results from imprecision of measurement and inaccuracy of computation. In the context on the theory of fuzzy limits, we develop the structure of statistical fuzzy convergence and study its properties.

Mark Burgin; Oktay Duman

2006-12-07

333

Statistics for Chemists: Exercises  

NSDL National Science Digital Library

This website contains a group of exercises that allow students to practice basic statistical calculations for descriptive statistics, confidence intervals, hypothesis tests, regression and experimental design. The exercises are interactive and provide feedback for students who submit wrong answers.

Wehrens, Ron

2011-03-25

334

Blood Facts and Statistics  

MedlinePLUS

... About Blood > Blood Facts and Statistics Printable Version Blood Facts and Statistics Facts about blood needs Facts ... about American Red Cross Blood Services Facts about blood needs Every two seconds someone in the U.S. ...

335

Data and Statistics  

MedlinePLUS

... Cell Disease (SCD) National Center Homepage Share Compartir Data & Statistics Sickle cell disease (SCD) affects millions of ... Healthy Living Living Well Preventing Infections Emergency Guide Data & Statistics Research National Resource Directory Text Version Articles & ...

336

Interpreting Accident Statistics  

E-print Network

Accident statistics have often been used to support the argument that an abnormally small proportion of drivers account for a large proportion of the accidents. This paper compares statistics developed from six-year data ...

Ferreira, Joseph Jr.

337

Immigration and Naturalization Statistics  

NSDL National Science Digital Library

The Immigration and Naturalizations Service Statistics site provides "comprehensive annual immigration statistics from 1994-1996, as well as state estimates of the United States' illegal alien resident and foreign-born populations."

Service., United S.

1997-01-01

338

Mathematical and statistical analysis  

NASA Technical Reports Server (NTRS)

The goal of the mathematical and statistical analysis component of RICIS is to research, develop, and evaluate mathematical and statistical techniques for aerospace technology applications. Specific research areas of interest include modeling, simulation, experiment design, reliability assessment, and numerical analysis.

Houston, A. Glen

1988-01-01

339

Environment for statistical computing  

Microsoft Academic Search

This paper is a short exposition on the current state of art as far as statistical software is concerned. The main aims are to take a look at current tendencies in information technologies for statistics and data analysis, especially for describing selected programs and systems.We start with statistical packages, i.e. a suite of computer programs that are specialized in statistical analysis,

Jaromír Antoch

2008-01-01

340

Statistical Database Security  

Microsoft Academic Search

Statistical database security focuses on the protection of confidential individual values stored in so-called statistical databases and used for statistical purposes. Examples include patient records used by medical researchers, and detailed phone call\\u000a records, statistically analyzed by phone companies in order to improve their services. This problem became apparent in the\\u000a 1970s and has escalated in recent years due to

Ljiljana Brankovic; Helen Giggins

341

Statistics: Power from Data!  

NSDL National Science Digital Library

Statistics Canada's website designed to teach secondary mathematics and information studies students statistical information. Each chapter is intended to be complete in itself, with exercises and lesson plans. The site covers a broad spectrum of topics involving statistics. Overall, it is a comprehensive view of this vast field.

2008-12-29

342

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

343

Common statistical tests  

Microsoft Academic Search

A recent survey by BeGole of four major orthodontic journals revealed that76% of the original and scientific articles published in 1997 incorporated statistical procedures in their methodologies. To evaluate the information presented in these scientific articles, the clinician needs to have an understanding of the statistical techniques used in them. Although a number of the statistical methodologies were complex, requiring

Rose D. Sheats; V. Shane Pankratz

2002-01-01

344

Statistical Mechanics its applications  

E-print Network

Statistical Mechanics and its applications Dr A. Alavi Part II Chemistry 2007-2008 1 #12;I. INTRODUCTION Statistical Mechanics is concerned with how to describe the behaviour of systems containing large, and how this is done, as well as its theoretical justification, is the subject of Statistical Mechanics. A

Alavi, Ali

345

Giovanni Gallavotti STATISTICAL MECHANICS  

E-print Network

Giovanni Gallavotti STATISTICAL MECHANICS Short Treatise Roma 1999 #12;. #12;Short treatise of Statistical Mechanics Giovanni Gallavotti Dipartimento di Fisica Universit`a di Roma La Sapienza 00185 Roma that started with my involvement as Coordinator of the Statistical Mechanics section of the Italian Encyclo

Roma "La Sapienza", Università di

346

Giovanni Gallavotti STATISTICAL MECHANICS  

E-print Network

Giovanni Gallavotti STATISTICAL MECHANICS Short Treatise Roma 1999 #12; . #12; Short treatise of Statistical Mechanics Giovanni Gallavotti Dipartimento di Fisica Universitâ??a di Roma La Sapienza 00185 Roma that started with my involvement as Coordinator of the Statistical Mechanics section of the Italian Encyclo

Roma "La Sapienza", Università di

347

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

348

Glossary of Statistical Terms  

Cancer.gov

Defines common statistical terms, NCI terminology, and the five key statistical measures of cancer: incidence, mortality, survival, prevalence, and lifetime risk. NCI monitors these cancer statistics to assess progress and to identify population subgroups and geographic areas in which cancer control efforts need to be concentrated.

349

Dynamic Optimization  

NASA Technical Reports Server (NTRS)

We distinguish static and dynamic optimization of programs: whereas static optimization modifies a program before runtime and is based only on its syntactical structure, dynamic optimization is based on the statistical properties of the input source and examples of program execution. Explanation-based generalization is a commonly used dynamic optimization method, but its effectiveness as a speedup-learning method is limited, in part because it fails to separate the learning process from the program transformation process. This paper describes a dynamic optimization technique called a learn-optimize cycle that first uses a learning element to uncover predictable patterns in the program execution and then uses an optimization algorithm to map these patterns into beneficial transformations. The technique has been used successfully for dynamic optimization of pure Prolog.

Laird, Philip

1992-01-01

350

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

351

Statistical theory of cubic Langmuir turbulence  

NASA Technical Reports Server (NTRS)

The cubic direct interaction approximation is applied to a truncated (in Fourier space) version of the cubically nonlinear Schroedinger equation model of Langmuir physics. The results are compared (in the three-mode case) to those for an ensemble of numerical solutions of the dynamical equations with 10,000 different sets of Gaussianly distributed initial conditions. In the undriven, undamped case, the statistical theory (but not the ensemble) evolves to a state of thermal equilibrium. In the driven, damped case, the statistical theory appears to evolve to a state close to that corresponding to one of the limit cycles of the dynamical equations.

Sun, G.-Z.; Nicholson, D. R.; Rose, H. A.

1985-01-01

352

Nonstationary statistical theory for multipactor  

SciTech Connect

This work presents a new and general approach to the real dynamics of the multipactor process: the nonstationary statistical multipactor theory. The nonstationary theory removes the stationarity assumption of the classical theory and, as a consequence, it is able to adequately model electron exponential growth as well as absorption processes, above and below the multipactor breakdown level. In addition, it considers both double-surface and single-surface interactions constituting a full framework for nonresonant polyphase multipactor analysis. This work formulates the new theory and validates it with numerical and experimental results with excellent agreement.

Anza, S.; Vicente, C.; Gil, J. [Aurora Software and Testing S.L., Edificio de Desarrollo Empresarial 9B, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Boria, V. E. [Departamento de Comunicaciones-iTEAM, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Gimeno, B. [Departamento de Fisica Aplicada y Electromagnetismo-ICMUV, Universitat de Valencia, c/Dr. Moliner, 50, 46100 Valencia (Spain); Raboso, D. [Payloads Systems Division, European Space Agency, 2200-AG Noordwijk (Netherlands)

2010-06-15

353

Statistical mechanics of violent relaxation  

NASA Technical Reports Server (NTRS)

We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.

Spergel, David N.; Hernquist, Lars

1992-01-01

354

Statistics for Ecologists  

NSDL National Science Digital Library

This Website, maintained by Carlos Herrera of the Donana Biological Station in Seville, Spain, is "a collection of links to sites with mathematical and statistical material (software, documents) which may be useful to ecologists and evolutionary ecologists." Organized into eight sections, the site points users to resources from Ecologically-oriented software to General Statistical Libraries. For graduate students and researchers alike, this statistics resource is sure to come in handy.

355

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

356

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.

357

Statistical distribution sampling  

NASA Technical Reports Server (NTRS)

Determining the distribution of statistics by sampling was investigated. Characteristic functions, the quadratic regression problem, and the differential equations for the characteristic functions are analyzed.

Johnson, E. S.

1975-01-01

358

Springer Series in Statistics Springer Series in Statistics  

E-print Network

Springer Series in Statistics Springer Series in Statistics Inference in Hidden Markov Models class of statistical models with applications in diverse areas such as communications engineering models, including both algo- rithms and statistical theory. Topics range from filtering and smoothing

Cappé, Olivier

359

Statistical models of flares  

NASA Astrophysics Data System (ADS)

By 'statistical' models of flares we denote the global stochastic models of the dynamics of the energy-release process and its associated phenomena which consider flares to consist in a large number of constituent small-scale processes. The observations strongly support such a kind of models: a) Radio-and HXR-emission of flares are highly fragmented in space and time, suggesting that the flare process itself is spatially and temporarily fragmented (De Jager and De Jonge 1978, Benz 1985, Aschwanden et al. 1990). b) The temporal dynamics of flares has been shown to be 'complex' (relatively high-dimensional chaotic or stochastic) through time-series analysis of radio-emission (dimension-estimate and power-spectra: Isliker and Benz (1994), Isliker (1996), Ryabov et al. (1997); wavelet transform: Aschwanden et al. 1998, Schwarz et al. 1998). c) Spatially, there are only weak and local correlations between neighbouring burst-sites, reminiscent of a chain-reaction (analysis of nb-spikes spectrograms with symbolic dynamics: Schwarz et al. 1993). The most prominent global dynamical models of the energy-release process which comprise entire flares are Cellular Automata (CA) models (Lu and Hamilton 1991, Lu et al. 1993; extended to model nano-flares: Vlahos et al. 1995, Georgoulis and Vlahos 1996; including non-local communications: MacKinnon et al. 1996; an analytic approach: MacKinnon and MacPherson 1997). In these models, the local processes (reconnection) are modeled in a strongly simplified way, by simple evolution rules, so that inhomogeneous active regions can be modeled entirely. Alternatively, Isliker (1996) proposed a shot noise model for flares. This model is able to explain the temporal characteristics of the flare-process, however, it is formal, so-far, it has not been tied to physics, yet. A different class of stochastic models has been proposed to explain the dynamics of the corona as a whole, with randomly occurring flares (Rosner and Vaiana 1978, criticized in Lu 1995b; Litvinenko 1996; a new approach (a master equation for the flare occurrence probability): Wheatland and Glukhov 1998). In this approach, structures within a flare are not resolved, the aim is to explain the occurrence rate and total sizes of flares. The CA models are successful in explaining the distributions of the peak-fluxes, total fluxes, and durations of HXR-emission, which are all power-laws (see references in Aschwanden et al. 1998). In the radio range, peak-flux distributions of generalized power-law and exponential shape are observed, which generally are steeper than in the HXR (type I: Mercier and Trottet (1997); type III, decim. pulsations, nb-spikes: Aschwanden et al. 1998; type III: Isliker and Vlahos 1998; nb-spikes: Isliker and Benz 1998). Since radio-waves can be emitted in low energy events, the steep distributions might be a hint that small flares (micro-flares) have a steep distribution, too, and might therewith substantially contribute to coronal heating. It must be noted, however, that poor time- or frequency-resolution can lead to a steepening of the peak-flux distributions (Isliker and Benz 1998), an effect whose influence on the published events has to be discussed, still. Originally, the evolution rules of the CAs were only loosely motivated through physical considerations and basically taken from the 'sand-pile' paradigm, above all the connection between CA and MHD (the local theory of magnetic reconnection) was missing. Recently, Isliker et al. (1998) have shown that the evolution rules of the CAs correspond to localized, threshold dependent diffusion, implementing directly the solution of a diffusion equation, with unknown diffusivity and scales. Thus, CAs can be interpreted as an implementation of the (simplified) induction equation in a large, inhomogeneous medium. A complete flare model needs to incorporate not just the energy release process, but also the acceleration and transport of particles, as well as the generation of EM-emission. First steps towards this direction are done: Anastasiadis et al. 1997 studied acce

Isliker, H.

360

Statistical Characteristics of Earthquake Ground Motion;  

E-print Network

Statistical Characteristics of Earthquake Ground Motion; Has PBEE Broken the Power Law? Tom Heaton · Currently the Director of the Earthquake Engineering Research Laboratory (EERL) · BS in physics from Indiana Dynamics and most of my students are EE · Not your typical Earthquake Engineer #12;Caltech asked me

Greer, Julia R.

361

Statistical power analysis for nanoscale CMOS  

Microsoft Academic Search

With the scaling down of CMOS technology, process variations are becoming significant. Power consumption is a major constraint on IC yield. However, there has been little research on statistical power analysis compared with that on timing analysis. Here, both the static and dynamic power are considered. We characterize a cell library containing mean power. A standard deviation power library is

Yangang Wang; Michael Merrett; Mark Zwolinski

2010-01-01

362

Statistical analysis of slow crack growth experiments  

Microsoft Academic Search

A common approach for the determination of slow crack growth (SCG) parameters are the static and dynamic loading method. Since materials with small Weibull module show a large variability in strength, a correct statistical analysis of the data is indispensable. In this work we propose the use of the Maximum Likelihood Method and a Baysian Analysis, which, in contrast to

Tobias Pfingsten; Karsten Glien

2006-01-01

363

BS in STATISTICS: Statistical Science Emphasis (695220) MAP Sheet Department of Statistics  

E-print Network

BS in STATISTICS: Statistical Science Emphasis (695220) MAP Sheet Department of Statistics the following: Stat 121 Principles of Statistics Stat 151 Introduction to Bayesian Statistics Stat 201 Statistics for Engineers & Scientists Stat 301 Statistics & Probability for Sec Ed Note: Students who have

Olsen Jr., Dan R.

364

Some More Statistical Exercises  

NSDL National Science Digital Library

A continuation of a previous unit, expanding to talk about standard deviation, tell some stories about statistics, show what statistics is, and provide three computer programs to demonstrate activities one may do in class, or students may use independently. In passing, it answers the question: How can you tell if the coin flips or the dice are random?

Langan, James F.

2007-03-24

365

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

366

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.

367

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 connection.…

Curran-Everett, Douglas

2011-01-01

368

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

369

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

370

The Stock Statistics Parser  

Microsoft Academic Search

This paper describes how use the HTMLEditorKit to perform web data mining on stock statistics for listed firms. Our focus is on making use of the web to get information about companies, using their stock symbols and YAHOO finance. We show how to map a stock ticker symbol into a company name gather statistics and derive new information. Our example

Douglas Lyon

2008-01-01

371

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.

372

ROOT Statistical Software  

E-print Network

Advanced mathematical and statistical computational methods are required by the LHC experiments for analyzing their data. Some of these methods are provided by the ROOT project, a C++ Object Oriented framework for large scale data handling applications. We review the current mathematical and statistical classes present in ROOT, emphasizing the recent developments.

Moneta, Lorenzo; Brun, R; Kreshuk, Anna

2008-01-01

373

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.

374

Weakly sufficient quantum statistics  

E-print Network

Some aspects of weak sufficiency of quantum statistics are investigated. In particular, we give necessary and sufficient conditions for the existence of a weakly sufficient statistic for a given family of vector states, investigate the problem of its minimality, and find the relation between weak sufficiency and other notions of sufficiency employed so far.

Katarzyna Lubnauer; Andrzej ?uczak; Hanna Pods?dkowska

2009-11-23

375

Scalable statistical bug isolation  

Microsoft Academic Search

We present a statistical debugging algorithm that isolates bugs in programs containing multiple undiagnosed bugs. Earlier statistical algorithms that focus solely on identifying predictors that correlate with program failure perform poorly when there are multiple bugs. Our new technique separates the effects of different bugs and identifies predictors that are associated with individual bugs. These predictors reveal both the circumstances

Ben Liblit; Mayur Naik; Alice X. Zheng; Alexander Aiken; Michael I. Jordan

2005-01-01

376

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

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

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.

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

2009-03-04

379

Defence Statistics 1998  

NSDL National Science Digital Library

This new UK government report are from the House of Commons Library contains statistics on defense spending and manpower and addresses "the problems involved in using such statistics, particularly when making international comparisons." The report also contains numerous graphs and tables.

Library., Great B.; Morgan, Bryn.

1998-01-01

380

Statistical Science Web  

NSDL National Science Digital Library

This site contains links in several statistical categories, including other meta-sites (catalogs), universities, statistics departments, software, journals, data sets, methodology, conferences, and teaching, among others. It has an Australian flavor, but is international in scope. Gordon K. Smyth, Research scientist and mathematician, maintains this site.

1998-01-01

381

Statistical Parsing Inside Algorithm  

E-print Network

Parsing · Review · Statistical Parsing · SCFG · Inside Algorithm · Outside Algorithm NLP statistical parsing 1 · Outside Algorithm · Viterbi Algorithm · Learning models · SCFG extensions · Other approaches · Grammar acquisition: · Grammatical induction · Dependency Parsing #12;Parsing · Parsing

Ageno, Alicia

382

Statistical Reference Datasets: Archives  

NSDL National Science Digital Library

The datasets on this page are classified by analysis techniqueand by level of difficulty (lower, average, higher). They were originally intended to test statistical software. The sets cover these topics: ANOVA, linear regression, Markov Chain Monte Carlo, nonlinear regression, and univariate summary statistics. This is a nice collection as it not only contains raw data but also helps explain the different methods and tests.

2009-08-18

383

Multidimensional Visual Statistical Learning  

ERIC Educational Resources Information Center

Recent studies of visual statistical learning (VSL) have demonstrated that statistical regularities in sequences of visual stimuli can be automatically extracted, even without intent or awareness. Despite much work on this topic, however, several fundamental questions remain about the nature of VSL. In particular, previous experiments have not…

Turk-Browne, Nicholas B.; Isola, Phillip J.; Scholl, Brian J.; Treat, Teresa A.

2008-01-01

384

Practical Statistical Thinking Probability: The Language of Statistics  

E-print Network

Practical Statistical Thinking Probability: The Language of Statistics Essentials of Statistics and Probability Dhruv Sharma May 22, 2007 Department of Statistics, NC State University dbsharma@ncsu.edu SAMSI Undergrad Workshop Dhruv Sharma Essentials of Statistics and Probability #12;Practical Statistical Thinking

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

Statistics at a glance.  

PubMed

I still remember my first book on statistics: "Elementary statistics with applications in medicine and the biological sciences" by Frederick E. Croxton. For me, it has been the start of pursuing understanding statistics in daily life and in medical practice. It was the first volume in a long row of books. In his introduction, Croxton pretends that"nearly everyone involved in any aspect of medicine needs to have some knowledge of statistics". The reality is that for many clinicians, statistics are limited to a "P < 0.05 = ok". I do not blame my colleagues who omit the paragraph on statistical methods. They have never had the opportunity to learn concise and clear descriptions of the key features. I have experienced how some authors can describe difficult methods in a well understandable language. Others fail completely. As a teacher, I tell my students that life is impossible without a basic knowledge of statistics. This feeling has resulted in an annual seminar of 90 minutes. This tutorial is the summary of this seminar. It is a summary and a transcription of the best pages I have detected. PMID:21302664

Ector, Hugo

2010-12-01

387

R for Statistics Rafal Kulik  

E-print Network

R for Statistics Rafal Kulik Department of Mathematics and Statistics University of Ottawa Statistical Society of Ottawa 23 September 2011 Rafal Kulik #12;R for Statistics SSO meeting Plan Rafal Kulik 1 #12;R for Statistics SSO meeting Plan What is R? Rafal Kulik 1 #12;R for Statistics SSO meeting

Kulik, Rafal

388

Quantum-Statistical Computation  

E-print Network

Systems of spin 1, such as triplet pairs of spin-1/2 fermions (like orthohydrogen nuclei) make useful three-terminal elements for quantum computation, and when interconnected by qubit equality relations are universal for quantum computation. This is an instance of quantum-statistical computation: some of the logical relations of the problem are satisfied identically in virtue of quantum statistics, which takes no time. We show heuristically that quantum-statistical ground-mode computation is substantially faster than pure ground-mode computation when the ground mode is reached by annealing.

Giuseppe Castagnoli; David Ritz Finkelstein

2001-11-22

389

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

390

Cancer Statistics, 2003  

NSDL National Science Digital Library

This Web site contains a recent report on cancer statistics prepared by the American Cancer Society (ACS) that uses incidence data from the National Cancer Institute and mortality data from the National Center for Health Statistics. The report offers "an up-to-date perspective on the occurrence of cancer" in the United States, including cancer frequency, incidence, mortality, and survival statistics for 2003. The Web site provides links to similar articles, the PubMed citation for the report and other bibliographic resources, and a course based on the article from ACS Online Continuing Medical Education for credit toward the Physician's Recognition Award of the American Medical Association (free registration required).

Ghafoor, Asma.; Jemal, Ahmedin.; Murray, Taylor.; Samuels, Alicia.; Thun, Michael J.; Ward, Elizabeth.

2003-01-01

391

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.

392

Statistics at Square One  

NSDL National Science Digital Library

Created by T.D.V. Swinscow for the BMJ Publishing group, this textbook for medical statistics covers many topics such as: data display and summary, mean, standard deviation, populations , samples, statements of probability, confidence intervals, differences between means: type I and type II errors and power, differences between percentages, paired alternatives, t-tests, chi-squared tests, exact probability test, rank score tests, correlation, regression, survival analysis, study design and choosing a statistical test. This is a great resource for those interested in a broad overview of many different statistical methods.

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

2009-05-05

393

More Intelligent Statistical Software and Statistical Expert Systems: Future Directions  

Microsoft Academic Search

Statistical computer programs are becoming increasingly accessible to people with limited statistical training. More intelligent statistical software is clearly needed. In this article, new or improved offerings—ranging from computer-based indexes of the literature to expert statistical systems—are discussed and illustrated. Three general levels of statistical software are differentiated: computerized statistical answering and referral services, expert guidance embedded in statistical programs,

Gerald J. Hahn

1985-01-01

394

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

395

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

396

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

397

How Statistics "Excel" Online.  

ERIC Educational Resources Information Center

Discusses the use of Microsoft Excel software and provides examples of its use in an online statistics course at Golden Gate University in the areas of randomness and probability, sampling distributions, confidence intervals, and regression analysis. (LRW)

Chao, Faith; Davis, James

2000-01-01

398

Introduction Statistical Models  

E-print Network

model represents air pollution from line sources based on Gaussian diffusion. One might simply make of Statistics; University of California, Berkeley and Department of Biostatistics; Harvard School of Public

Paciorek, Chris

399

Quantum statistics on graphs  

E-print Network

Quantum graphs are commonly used as models of complex quantum systems, for example molecules, networks of wires, and states of condensed matter. We consider quantum statistics for indistinguishable spinless particles on a graph, concentrating on the simplest case of abelian statistics for two particles. In spite of the fact that graphs are locally one-dimensional, anyon statistics emerge in a generalized form. A given graph may support a family of independent anyon phases associated with topologically inequivalent exchange processes. In addition, for sufficiently complex graphs, there appear new discrete-valued phases. Our analysis is simplified by considering combinatorial rather than metric graphs -- equivalently, a many-particle tight-binding model. The results demonstrate that graphs provide an arena in which to study new manifestations of quantum statistics. Possible applications include topological quantum computing, topological insulators, the fractional quantum Hall effect, superconductivity and molecular physics.

JM Harrison; JP Keating; JM Robbins

2011-01-07

400

Playing at Statistical Mechanics  

ERIC Educational Resources Information Center

Discussed are the applications of counting techniques of a sorting game to distributions and concepts in statistical mechanics. Included are the following distributions: Fermi-Dirac, Bose-Einstein, and most probable. (RH)

Clark, Paul M.; And Others

1974-01-01

401

Country Statistical Profiles  

NSDL National Science Digital Library

Database of a series of statistical indicators, primarily economic, but also social and educational, on each OECD countries. Can be viewed either online or downloaded as excel files. The excel downloads also allow for graphical comparisons with other OECD countries.

Development, Organisation F.

402

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

403

Statistics on Banking  

NSDL National Science Digital Library

The FDIC Statistics on Banking is a "quarterly publication that provides aggregate financial and structure information on FDIC-insured institutions, with summary totals by state and charter type." The latest figures for third quarter 1997 are now available.

404

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

405

Statistical Analysis of Data  

NSDL National Science Digital Library

Treatise on statistical analysis of data geared toward students in the advanced physics lab. Includes instructions on using Excel for linear and nonlinear regression and the "delta chi-square equals 1 rule" for finding uncertainties for nonlinear regression.

Deserio, Robert

2009-01-30

406

Fisheries Statistics Office Publications  

E-print Network

Fisheries Statistics Office Publications How is the Potential Sector Contribution Calculated? Science, Service, Stewardship NOAA FISHERIES SERVICE U.S. Department of Commerce | National Oceanic and Atmospheric Administration | National Marine Fisheries Service #12;How is the Potential Sector Contribution

407

Mathematics and Statistics Models  

NSDL National Science Digital Library

Developed by Bob MacKay, Clark College. What are Mathematical and Statistical Models These types of models are obviously related, but there are also real differences between them. Mathematical Models: grow out of ...

408

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.

409

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

410

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.

411

Statistical pattern analysis of ultrasonic signals for fatigue damage detection in mechanical structures  

Microsoft Academic Search

This paper addresses online monitoring of fatigue damage in polycrystalline alloy structures based on statistical pattern analysis of ultrasonic sensor signals. The real-time data-driven method for fatigue damage monitoring is based on the concepts derived from statistical mechanics, symbolic dynamics and statistical pattern identification. The underlying concept is detection and identification of small changes in statistical patterns of ultrasonic data

Shalabh Gupta; Dheeraj S. Singh; Asok Ray

2008-01-01

412

Statistical Mechanics of Turbulent Dynamos  

NASA Technical Reports Server (NTRS)

Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much investigation, by greatly extending the statistical theory of ideal MHD turbulence. The mathematical details of broken ergodicity, in fact, give a quantitative explanation of how coherent structure, dynamic alignment and force-free states appear in turbulent magnetofluids. The relevance of these ideal results to real MHD turbulence occurs because broken ergodicity is most manifest in the ideal case at the largest length scales and it is in these largest scales that a real magnetofluid has the least dissipation, i.e., most closely approaches the behavior of an ideal magnetofluid. Furthermore, the effects grow stronger when cross and magnetic helicities grow large with respect to energy, and this is exactly what occurs with time in a real magnetofluid, where it is called selective decay. The relevance of these results found in ideal MHD turbulence theory to the real world is that they provide at least a qualitative explanation of why confined turbulent magnetofluids, such as the liquid iron that fills the Earth's outer core, produce stationary, large-scale magnetic fields, i.e., the geomagnetic field. These results should also apply to other planets as well as to plasma confinement devices on Earth and in space, and the effects should be manifest if Reynolds numbers are high enough and there is enough time for stationarity to occur, at least approximately. In the presentation, details will be given for both theoretical and numerical results, and references will be provided.

Shebalin, John V.

2014-01-01

413

Statistics: Part 1 1. Why bother with statistics?  

E-print Network

Statistics: Part 1 1. Why bother with statistics? Why is statistics so necessary for observational. But your data just don't seem to back up their claim. Statistics allows you to determine how confidently) practical introduction to those bits of statistics most vital to observational astronomy. 2. What

Francis, Paul

414

Statistics 36-756: Advanced Statistics II Syllabus: Fall, 2006  

E-print Network

Statistics 36-756: Advanced Statistics II Syllabus: Fall, 2006 Instructor: Stephen E. Fienberg 132G: · To consider major topics from statistical theory and the foundations of inference not covered in Statistics 36-756: Advanced Statistics I, such as exchangeability, the axiomatic foundation of subjective probability

Fienberg, Stephen E.

415

Applied Math & Statistics: Statistics Minor Curriculum Chart: 2013-2014  

E-print Network

Applied Math & Statistics: Statistics Minor Curriculum Chart: 2013-2014 http PSYC 181 CMPE 108 SOCY 103A CMPS 142 TIM 230 Information on the Statistics Minor The statistics minor as preparation for a graduate degree in statistics or biostatistics. Course Information With permission from

Stuart, Josh

416

Social and economic sustainability of urban systems: comparative analysis of metropolitan statistical areas in Ohio, USA  

EPA Science Inventory

This article presents a general and versatile methodology for assessing sustainability with Fisher Information as a function of dynamic changes in urban systems. Using robust statistical methods, six Metropolitan Statistical Areas (MSAs) in Ohio were evaluated to comparatively as...

417

Statistical Framework for Video Decoding Complexity Modeling and Prediction  

Microsoft Academic Search

Video decoding complexity modeling and prediction is an increasingly important issue for efficient resource utilization in a variety of applications, including task scheduling, receiver-driven complexity shaping, and adaptive dynamic voltage scaling. In this paper we present a novel view of this problem based on a statistical framework perspective. We explore the statistical structure (clustering) of the execution time required by

Nikolaos Kontorinis; Yiannis Andreopoulos; Mihaela van der Schaar

2009-01-01

418

Statistical identification and optimal control of thermal power plants  

Microsoft Academic Search

Statistical system identification and its use for the optimal control of thermal power plants are discussed. The analysis of the plant dynamics and derivation of the state-space representation are performed by fitting a multivariate AR model to the plant data obtained by an experiment. The basic concept of the power plant control and the motivation that necessitated the statistical approach

H. Nakamura; Y. Toyota

1988-01-01

419

Statistics in the Physical Sciences and Engineering Diane Lambert 1  

E-print Network

Statistics in the Physical Sciences and Engineering Diane Lambert 1 Bell Lab s, Lucent Technologies scientists and engineers feel. The vignettes are loosely grouped by field of application. The first two to statistics. As Jerry Lawless points out, product degradation in dynamic environments leads to models like

Lambert, Diane

420

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

421

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

422

Environmental Statistics and Optimal Regulation  

PubMed Central

Any organism is embedded in an environment that changes over time. The timescale for and statistics of environmental change, the precision with which the organism can detect its environment, and the costs and benefits of particular protein expression levels all will affect the suitability of different strategies–such as constitutive expression or graded response–for regulating protein levels in response to environmental inputs. We propose a general framework–here specifically applied to the enzymatic regulation of metabolism in response to changing concentrations of a basic nutrient–to predict the optimal regulatory strategy given the statistics of fluctuations in the environment and measurement apparatus, respectively, and the costs associated with enzyme production. We use this framework to address three fundamental questions: (i) when a cell should prefer thresholding to a graded response; (ii) when there is a fitness advantage to implementing a Bayesian decision rule; and (iii) when retaining memory of the past provides a selective advantage. We specifically find that: (i) relative convexity of enzyme expression cost and benefit influences the fitness of thresholding or graded responses; (ii) intermediate levels of measurement uncertainty call for a sophisticated Bayesian decision rule; and (iii) in dynamic contexts, intermediate levels of uncertainty call for retaining memory of the past. Statistical properties of the environment, such as variability and correlation times, set optimal biochemical parameters, such as thresholds and decay rates in signaling pathways. Our framework provides a theoretical basis for interpreting molecular signal processing algorithms and a classification scheme that organizes known regulatory strategies and may help conceptualize heretofore unknown ones. PMID:25254493

2014-01-01

423

Environmental statistics and optimal regulation.  

PubMed

Any organism is embedded in an environment that changes over time. The timescale for and statistics of environmental change, the precision with which the organism can detect its environment, and the costs and benefits of particular protein expression levels all will affect the suitability of different strategies--such as constitutive expression or graded response--for regulating protein levels in response to environmental inputs. We propose a general framework-here specifically applied to the enzymatic regulation of metabolism in response to changing concentrations of a basic nutrient-to predict the optimal regulatory strategy given the statistics of fluctuations in the environment and measurement apparatus, respectively, and the costs associated with enzyme production. We use this framework to address three fundamental questions: (i) when a cell should prefer thresholding to a graded response; (ii) when there is a fitness advantage to implementing a Bayesian decision rule; and (iii) when retaining memory of the past provides a selective advantage. We specifically find that: (i) relative convexity of enzyme expression cost and benefit influences the fitness of thresholding or graded responses; (ii) intermediate levels of measurement uncertainty call for a sophisticated Bayesian decision rule; and (iii) in dynamic contexts, intermediate levels of uncertainty call for retaining memory of the past. Statistical properties of the environment, such as variability and correlation times, set optimal biochemical parameters, such as thresholds and decay rates in signaling pathways. Our framework provides a theoretical basis for interpreting molecular signal processing algorithms and a classification scheme that organizes known regulatory strategies and may help conceptualize heretofore unknown ones. PMID:25254493

Sivak, David A; Thomson, Matt

2014-09-01

424

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

425

FISHERY STATISTICS E UNITED STATES  

E-print Network

SH 11 .A443X FISH FISHERY STATISTICS E UNITED STATES ^ 1951 &ch 3. \\§^ ^/'· m:^ STATISTICAL DIGEST. Farley, Director Statistical Digest 30 FISHERY STATISTICS OF THE UNITED STATES 1951 BY A. W. ANDERSON;Fishery Statistics of the United States and Alaska are compiled and published annually to make available

426

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.

427

Statistical Mechanics of Wormholes  

E-print Network

The statistical mechanics of a gas of Einstein-Kalb-Ramond wormholes is studied in this paper. The wormholes studied are the result of sewing together two Reissner-Nordstrom-type black hole metrics at their horizons. By requiring the stress-energy tensor associated with this geometry to be that of a Kalb-Ramond field, we obtain the mass and Kalb-Ramond `charge` of the wormholes in terms of the parameters describing the mass density, tension and pressure. We investigate the statistical mechanics of this system of wormholes within the context of the statistical bootstrap model. A gas of such wormholes is found to obey the bootstrap condition only for an extreme, non-thermodynamic, energy and `charge` distribution among the particles. We comment briefly on the scattering of quantum wormholes.

Paul H. Cox; Benjamin C. Harms; Shaoqi Hou

2011-09-29

428

GSE statistics without spin  

NASA Astrophysics Data System (ADS)

Energy level statistics following the Gaussian Symplectic Ensemble (GSE) of Random Matrix Theory have been predicted theoretically and observed numerically in numerous quantum chaotic systems. However, in all these systems there has been one unifying feature: the combination of half-integer spin and time-reversal invariance. Here we provide an alternative mechanism for obtaining GSE statistics that is derived from geometric symmetries of a quantum system which alleviates the need for spin. As an example, we construct a quantum graph with a discrete symmetry given by the quaternion group Q8 and observe GSE statistics within one of its subspectra. We then show how to isolate this subspectrum and construct a quantum graph with a scalar valued wave function and a pure GSE spectrum.

Joyner, Christopher H.; Müller, Sebastian; Sieber, Martin

2014-09-01

429

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

430

Footprints of Statistical Anisotropies  

E-print Network

We propose and develop a formalism to describe and constrain statistically anisotropic primordial perturbations. Starting from a decomposition of the primordial power spectrum in spherical harmonics, we find how the temperature fluctuations observed in the CMB sky are directly related to the coefficients in this harmonic expansion. Although the angular power spectrum does not discriminate between statistically isotropic and anisotropic perturbations, it is possible to define analogous quadratic estimators that are direct measures of statistical anisotropy. As a simple illustration of our formalism we test for the existence of a preferred direction in the primordial perturbations using full-sky CMB maps. We do not find significant evidence supporting the existence of a dipole component in the primordial spectrum.

C. Armendariz-Picon

2005-09-29

431

UNESCO Institute for Statistics  

NSDL National Science Digital Library

Established in 1999, the UNESCO Institute for Statistics (UIS) was designed to meet both the needs of UNESCO Member States and to provide the international community with a wide range of statistical information in order to "analyze the efficiency and effectiveness of their programmes and to inform their policy decisions." The UIC is hosted by the University of Montreal, and performs work around four primary themes, including education, literacy, culture & communication, and science & technology. Overall, the site is a remarkable source of information, including databases, working papers, country profiles, statistical tables, and methodological material about the conduct of their research. Several of these works are featured prominently on their homepage including a working paper on financing the expansion of educational opportunity in Latin America and the Caribbean and an electronic questionnaire on science and technology.

432

Perspectives in Statistical Mechanics  

E-print Network

Without attempting to summarize the vast field of statistical mechanics, we briefly mention some of the progress that was made in areas which have enjoyed Barry Simon's interests. In particular, we focus on rigorous non-perturbative results which provide insight on the spread of correlations in Gibbs equilibrium states and yield information on phase transitions and critical phenomena. Briefly mentioned also are certain spinoffs, where ideas which have been fruitful within the context of statistical mechanics proved to be of use in other areas, and some recent results which relate to previously open questions and conjectures.

Michael Aizenman

2006-07-12

433

Statistical Data Mining Tutorials  

NSDL National Science Digital Library

These tutorial, created by Professor Andrew Moore at Carnegie-Mellon University, cover a range of topics in statistical data mining "including the foundations of probability, the foundations of statistical data analysis, and most of the classic machine learning and data mining algorithms." Decision Trees, Information Gain, and Cross-Validation are just a few of the items presented here. Each topic contains a set of tutorial slides in PDF, excellent for converting into a classroom presentation or left as they are for a classroom handout or online learning resource.

Moore, Andrew W., Ph.D.

2011-04-18

434

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

435

Uniiversity o Traffic Statist  

E-print Network

. The department's focus is to reduce the Community's fear of crime by the prevention of crime, the protection in this report were compiled through use of the Computer Aided Dispatch System and the Report Management System not allow for exact numbers to be captured. A new and improved system of computer entries and statistical

Van Stryland, Eric

436

Uniiversity o Traffic Statist  

E-print Network

the Community's fear of crime by the prevention of crime, the protection of life and property; the preservation of the Computer Aided Dispatch System and the Report Management System. While we strive to provide the most to be captured. A new and improved system of computer entries and statistical capture was brought online

Kik, Pieter

437

Statistical Abstract, 1986.  

ERIC Educational Resources Information Center

The first annual Statistical Abstract for the University of Alaska System provides factual information for use by the Board of Regents, college administrators, and public officials in the development of university plans and programs. Topics cover: enrollments, programs and awards, faculty and staff, facilities and space, fiscal analysis,…

Alaska Univ., Fairbanks.

438

MATHEMATICS AND STATISTICS  

E-print Network

MATHEMATICS AND STATISTICS Canterbury The UK's European university Undergraduate study #12;2 ACADEMIC EXCELLENCE AND INSPIRATIONAL TEACHING Much of science is based upon the application of mathematics as for computer science. New discoveries within mathematics affect not only science, but also our general

Banaji,. Murad

439

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; and…

Lynch, Mary Jo; St. Lifer, Evan; Halstead, Kent; Fox, Bette-Lee; Miller, Marilyn L.; Shontz, Marilyn L.

2001-01-01

440

Statistical Identification of Language  

Microsoft Academic Search

A statistically based program has been written which learns to distinguishbetween languages. The amount of training text that such a program needsis surprisingly small, and the amount of text needed to make an identificationis also quite small. The program incorporates no linguistic presuppositionsother than the assumption that text can be encoded as a string of bytes. Sucha program can be

Ted Dunning

1994-01-01