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1

The Stability of Dynamic Feedback in an SDI System.

ERIC Educational Resources Information Center

The SDI system now operational at the Institute for Atomic Research, Iowa State University, is implemented with the concept of feedback. The profile user is notified of a document which may be of interest to him and indicates his response to this document on the response card accompanying the notification. The profile words carry individual…

Anderson, R. R.; And Others

2

The Atlantic Alliance was disturbed when the Strategic Defense Initiative (SDI) was conceived and presented primarily as an American unilateral initiative, with no political or strategic consultation with the allies. It was also disturbed by the confused and contradictory objectives of SDI; i.e., its rejection of the logic of deterrence as a dangerous and unethical proposition at the same time

Lellouche

2009-01-01

3

ERIC Educational Resources Information Center

Library staff at Louisiana State University Medical Center in Shreveport have written two computer programs automating much of its selective dissemination of information (SDI) postprocessing. The software sorts SDI results, gathers and reports statistical data without requiring manual data entry, allows delivery of search results as hard copy or…

Watson, Michael; And Others

1997-01-01

4

SDI supply chain builder: SDI supply chain builder: simulation from atoms to the enterprise

The SDI Supply Chain Builder Product Suite is a high-level simulation toolset that provides solutions to enterprise problems. The product suite contains four specific elements for enterprise modeling: SDI Supply Chain Builder for supply\\/distribution chains, SDI Plant Builder for multi-stage plants driven by schedules, Extend+Industry for high-speed, high-volume production line modeling, and the SDI Data-Framework for high-speed data import and

Richard A. Phelps; David J. Parsons; Andrew J. Siprelle

2001-01-01

5

The role, if any, of ballistic missile defense is not an issue that can be decided by any individual nation. Even a dedicated US or Soviet unilateral military-technological drive toward a defense of the nation against ballistic missiles could not succeed. The very dynamics of the arms competition, manifesting itself in reciprocal measures and counter-measures, would preclude attaining an effective defense of either country. And in the extreme case, a perceived impending mortal threat could provoke direct military interference in any attempt to deploy such a system. The security and the fate of the two superpowers - and of the world - are ineluctably bound together. The problems of deterrence, defense, and survival are shared, and any solution must also be shared. The author attempts here to recast the problem and suggest a possible solution to both American and Soviet readers. The analytical approach is new, and so is the policy course recommended on the basis of the analysis. It does not correspond to the present positions of either the US or the Soviet Union, and debate and further consideration in both countries are, of course, required. It is, in short, an interim prescription for a common course of action that could be accepted by both the US and the Soviet Union while the leadership of both countries in the years ahead decide on further resolution of this mutual security dilemma.

Garthoff, R.L.

1987-09-01

6

The economic common sense of SDI

The present development history and current status evaluation of the economic viability of SDI technologies suggests that much of the exaggeration of SDI costs has been due to an effort of the part of the program's opponents to consider only the most exotic, and commensurately expensive, options for orbital missile defense. It is noted that, by contrast, extraordinary advancements in

1990-01-01

7

A Framework for Comparing SDI Systems.

ERIC Educational Resources Information Center

The process of comparing the many Selective Dissemination of Information (SDI) systems is a complicated task, requiring proper test procedures and the control of critical variables. The necessity for controlling the interest level as well as the number of documents disseminated when evaluating systems is demonstrated. The process of SDI is…

Jordan, John R.

8

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).

9

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

Statistical properties of fermionic molecular dynamics.

National Technical Information Service (NTIS)

Statistical properties of Fermionic Molecular Dynamics are studied. It is shown that, although the centroids of the single-particle wave-packets follow classical trajectories in the case of a harmonic oscillator potential, the equilibrium properties of th...

J. Schnack H. Feldmeier

1995-01-01

11

SDI (Strategic Defense Initiative): Myth or reality

This report reviews previous attempts to develop strategic defenses, the technologies currently under consideration by the Strategic Defense Initiative (SDI), their main unknowns, and the likely performance of strategic defense concepts against evolving threats. 47 refs.

Canavan, G.H.

1988-06-01

12

Statistical-dynamical downscaling of wind climatologies

A statistical-dynamical downscaling procedure is applied for an investigation into the availability of wind power over a region of 80 × 87 km which covers flat and hilly terrain. The approach is based on the statistical coupling of a regionally representative wind climate with a numerical atmospheric mesoscale model. The large-scale wind climatology is calculated by a cluster-analysis of a

Heinz-Theo Mengelkamp; Hartmut Kapitza; Ulrich Pflüger

1997-01-01

13

The economic common sense of SDI

The present development history and current status evaluation of the economic viability of SDI technologies suggests that much of the exaggeration of SDI costs has been due to an effort of the part of the program's opponents to consider only the most exotic, and commensurately expensive, options for orbital missile defense. It is noted that, by contrast, extraordinary advancements in microelectronics have made possible the creation of 20-100 lb devices which detect hostile missile launches, calculate the paths of enemy missiles and warheads through space, and fly to pinpoint accuracy to intercept targets and destroy them by means of high-speed collision. This 'Brilliant Pebbles' scheme has reduced the cost of an effective SDI system to below 25 billion.

Graham, D.O. (High Frontier, Inc., Arlington, VA (USA))

1990-01-01

14

SDI spinoffs: research now, standards later

A major benefit of the Strategic Defense Initiative (SDI) its is potential for technological spinoffs. The lack of a consistent answer on the feasibility of developing an effective ballistic missile defense system may force Congress to look at the possible spinoffs in order to make a funding decision on SDI. Spinoffs have historically played an important role in providing industry with commercial applications, but there are also a number of unattractive aspects: unpredictability and possible suppression for national security reasons. Edward Teller is among those who promote X-ray lasers, while others support gamma-ray laser research. The possibility of SDI technology and spinoffs gives scientists and engineers a chance to participate in the development of new standards. 7 references.

Smith, T.K. Jr.

1986-04-01

15

SDI Supply Chain Builder: simulation from atoms to the enterprise

The SDI Supply Chain Builder Product Suite is a high-level simulation toolset that provides solutions to enterprise problems. The product suite contains four specific elements for enterprise modeling: SDI Supply Chain Builder for supply\\/distribution chains, SDI Plant Builder for multi-stage plants driven by schedules, Extend+Industry for high-speed, high-volume production line modeling, and the SDI Data-Framework for high-speed data import and

R. A. Phelps; D. J. Parsons; A. J. Siprelle

2001-01-01

16

The SDI Industry®Product Suite is a versatile, high-level simulation toolset for solving problems of whole enterprises. It adds important capabilities to an existing simulation package, Extend#8482;, which provides a robust simulation architecture and a wealth of existing building blocks. The SDI Industry Product Suite contains 5 specific elements for modeling the enterprise: SDI Database for high-speed data import\\/export; SDI Industry

Richard A. Phelps; David J. Parsons; Andrew J. Siprelle

2000-01-01

17

SDI (Strategic Defense Initiative): a policy analysis

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

Fought, S.O.

1987-01-01

18

SDI and deterrence: A Western European perspective

Many Western European critics of the Strategic Defense Initiative (SDI) argue that ballistic missile defenses (BMD) will upset deterrence stability, promote crisis instability, increase the likelihood of conventional and\\/or limited nuclear war confined to Europe, and degrade the credibility of French and British nuclear deterrents. Underlying these criticisms is an approach to nuclear strategy that views mutual vulnerability as the

1988-01-01

19

Grumman and SDI-related technology

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

20

Small SDI battle stations - More is better

It is presently suggested that large numbers of lower capability SDI systems, in contrast to small numbers of large battle stations, offer better overall defense performance at lower total cost, with lower technical risk, lower sensitivity to threat scenario variability, and improved survivability. This follows from such factors as the positioning of more platforms within effective range of targets during all phases of an attack, less exacting optics requirements, mass production economies-of-scale, and improved survivability.

Cornet, E.

1986-09-01

21

International Information Transfer and SDI.

ERIC Educational Resources Information Center

A summary is presented of data gathered for a survey of information center services in the form of statistics for a hypothetical typical information center. The extent of information transfer on national and international levels among the responding centers is discussed. (Author)

Stewart, Alan K.; Williams, Martha E.

22

SDI (Strategic Defense Initiative): Shield or sword. Study Project

The paper attempts to answer the fundamental question, is SDI an adjunct to a first strike strategy. As its criteria, it discusses Soviet and U.S. opposing views on SDI, an historical application of Mutual Assured Destruction strategy, and a discussion of Soviet and U.S. thinking on first-strike capability. President Reagan's March 1983 address on SDI is used as the backdrop

C. S. Butler; G. R. Spiczak

1989-01-01

23

Statistical Coarse-Graining of Molecular Dynamics into Peridynamics.

National Technical Information Service (NTIS)

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 scale...

R. B. Lehoucq S. A. Silling

2007-01-01

24

Statistics and Dynamics of Persistent Anomalies.

NASA Astrophysics Data System (ADS)

Persistent anomalies with recurrent spatial patterns play an important role in the atmosphere's low-frequency variability. We establish a connection between statistical and dynamical methods of description and prediction of persistent anomalies. This is done by computing and analyzing the empirical orthogonal functions (EOFs) in a simple deterministic model, on the one hand, and in Southern Hemisphere geopotential heights, on the other.The dynamical model is governed by the fully nonlinear, equivalent-barotropic vorticity equation on the sphere, with simplified forcing, dissipation and topography. Model solutions exhibit persistent anomalies identifiable with blocked, zonal and wave-train anomalies in Northern Hemisphere atmospheric data. Flow structures similar to the patterns above occur as high-variance EOFs of this nonlinear model.The Southern Hemisphere data we analyze consist in gridded daily maps of 500 mb heights from June 1972 to July 1983. Two types of persistent anomalies appear in this time series, both having a strong wavenumber-three component; they differ by the value of the constant phase of this wave and by the strength of the wavenumber-one component. The first two EOFs bear a striking resemblance to these two patterns.We conclude that the dynamical interpretation of EOFs is their pointing from the time mean to the most populated regions of the system's phase space. Pursuing this interpretation, we introduce a Markov-chain formulation of transitions from one persistent anomaly regime to another, and discuss the implications for long-range forecasting.

Mo, Kingtse C.; Ghil, Michael

1987-03-01

25

SDI (Strategic Defense Initiative): Shield or sword. Study Project

The paper attempts to answer the fundamental question, is SDI an adjunct to a first strike strategy. As its criteria, it discusses Soviet and U.S. opposing views on SDI, an historical application of Mutual Assured Destruction strategy, and a discussion of Soviet and U.S. thinking on first-strike capability. President Reagan's March 1983 address on SDI is used as the backdrop to set the stage for the discussion. It is the objective of the authors to evaluate and analyze the potential impact of SDI on first strike.

Butler, C.S.; Spiczak, G.R.

1989-05-15

26

Statistical Physics Applied to Human Heartbeat Dynamics

NASA Astrophysics Data System (ADS)

A major problem in biology is the quantitative analysis of nonstationary time series. A central question is whether such noisy fluctuating signals contain information useful for understanding underlying physiological mechanisms. This review talk summarizes recent work that analyzes physiological signals--principally lengthy time series of interbeat heart intervals--using a range of approaches adapted from modern statistical mechanics. These approaches include (i) detrended fluctuation analysis of long-range anticorrelations, (ii) wavelet analysis, and (iii) multifractal analysis. The work reported here was carried out primarily by L. A. Nunes Amaral, A. L. Goldberger, S. Havlin, P. Ch. Ivanov, C.-K. Peng, M. G. Rosenblum, and Z. Struzik; see [1-5] and references therein for details. [1] For an overview, see H. E. Stanley, L. A. N. Amaral, A. L. Goldberger, S. Havlin, P. Ch. Ivanov, and C.-K. Peng, ``Statistical Physics and Physiology: Monofractal and Multifractal Approaches,'' Physica A 270 (1999) 309. [2] C.-K. Peng, S. Havlin, H. E. Stanley, and A. L. Goldberger, ``Quantification of Scaling Exponents and Crossover Phenomena in Nonstationary Heartbeat Time Series,'' Chaos 5 (1995) 82. [3] L. A. N. Amaral, A. L. Goldberger, P. Ch. Ivanov, and H. E. Stanley, ``Scale-Independent Measures and Pathologic Cardiac Dynamics,'' Phys. Rev. Lett. 81 (1998) 2388. [4] P. Ch. Ivanov, A. L. Goldberger, S. Havlin, C.-K. Peng, and H. E. Stanley, ``Wavelets in Medicine and Physiology,'' in Wavelets, edited by H. C. van den Berg (Cambridge University Press, Cambridge, 1999). [5] P. Ch. Ivanov, L. A. N. Amaral, A. L. Goldberger, S. Havlin, M. G. Rosenblum, Z. Struzik, and H. E. Stanley, ``Multifractality in Human Heartbeat Dynamics,'' Nature 399 (1999) 461.

Stanley, H. Eugene

2000-03-01

27

Applications of submillimeter wave technology for SDI

NASA Technical Reports Server (NTRS)

This paper examines the potential use of using submillimeter wave technology (actually 3 mm to 100 microns, or frequencies between 100 GHz and 3 THz) for SDI applications, especially for endo-KEW systems. The requirements and functions for a multipurpose weapon sensor are considered. The emphasis is on active sensors, but certain elements of passive sensors are mentioned that could play an important role. The rest of the paper provides information on the state-of-the-art in submillimeter wave technology, especially current component activity, and future plans.

Kile, J. N.; Mcgrath, W. R.; Leduc, H. G.; Siegel, P. H.; Smith, R. P.; Hayes, D. T.

1992-01-01

28

Grumman and SDI-related technology

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

Lewis, B.

1985-01-01

29

Soviet military on SDI (Strategic Defense Initiative). Professional paper

Numerous Western analysts have suggested that all American assessments of SDI should proceed not only from a consideration of American intentions, but also from the outlook of Soviet perceptions. Since 23 March 1983, the prevailing tone of Soviet military writings on SDI has been overwhelmingly negative. Myron Hedlin has concluded that this harsh reaction to a U.S. initiative still years

1987-01-01

30

The Implementation, Evaluation, and Refinement of a Manual SDI Service

The Missouri Institute of Psychiatry Library has implemented an inexpensive, manual SDI (Selective Dissemination of Information) service based upon the monthly issues of Index Medicus. The implementation and refinement of the system are documented, and the very favorable response to the system is examined. The SDI service is compared to Current Contents, with the finding that 60 percent of the SDI participants prefer it to Current Contents. For this select portion of researchers the Index Medicus SDI is the more suitable mode of current awareness. For a significant portion of the MIP staff, however, the scope of Index Medicus is too restricted to suitably replace Current Contents. All SDI users find it a highly acceptable current awareness service for use in addition to Current Contents and have indicated the desire to continue participation in the service.

Yunis, Susan S.

1973-01-01

31

Statistical coarse-graining of molecular dynamics into peridynamics

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

Stewart Andrew Silling; Richard B. Lehoucq

2007-01-01

32

Role of pumping statistics in laser dynamics: Quantum Langevin approach

We study in detail the influence of pumping statistics on the laser dynamics. We apply the technique of quantum Langevin operators and generalize the corresponding noise operators to incorporate the statistical properties of the pump mechanism. These equations are then used to derive expressions for the phase and intensity fluctuations of lasers with various pump statistics. We find that a

Claus Benkert; M. O. Scully; J. Bergou; L. Davidovich; M. Hillery; M. Orszag

1990-01-01

33

Analysis of the Soviet response to the Strategic Defense Initiative (SDI). Student report

Since President Reagan announced the Strategic Defense Initiative (SDI) in March 1983, the Soviet Union has consistently condemned it. This study examines the Soviet response to SDI and provides an explanation for their response. The study identifies military, political, and economic factors that influence the Soviet response to SDI. The author concludes that the Soviets have a genuine concern about SDI, and they will continue their attempts to stop the SDI program at the arms-control negotiations.

Morgan, D.E.

1987-04-01

34

Dynamic multivariate statistical process control using subspace identification

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

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

2004-01-01

35

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

36

Dynamic Visualizations for Soccer Statistical Analysis

The analysis of large sums of soccer statistics can be extremely difficult if the data is not presented graphically. As a result, we developed an application, titled Soccer Scoop, which provides two separate visualizations that can aid a soccer team manager. With our application, a team manager can compare two players on different teams, analyze a particular player before signing

Adrian Rusu; Doru Stoica; Edward Burns; Benjamin Hample; Kevin McGarry; Robert Russell

2010-01-01

37

Dynamical Ensembles in Nonequilibrium Statistical Mechanics

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

38

Statistical-dynamical downscaling procedure for global climate simulations.

National Technical Information Service (NTIS)

A statistical-dynamical downscaling procedure for global climate simulations is described. The procedure is based on the assumption that any regional climate is associated with a specific frequency distribution of classified large-scale weather situations...

A. Frey-Buness D. Heimann R. Sausen U. Schumann

1994-01-01

39

Improving Dynamic Calibration through Statistical Process Control

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

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

2005-01-01

40

Segmenting Dynamic Human Action via Statistical Structure

ERIC Educational Resources Information Center

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

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

2008-01-01

41

Extreme Events: Dynamics, Statistics and Prediction

NASA Astrophysics Data System (ADS)

In this talk, I will review some recent work on extreme events, their causes and consequences. The review covers theoretical aspects of time series analysis and of extreme value theory, as well as of the deterministic modeling of extreme events, via continuous and discrete dynamic models. The applications include climatic, seismic and socio-economic events, along with their prediction. Two important results refer to (i) the complementarity of spectral analysis of a time series in terms of the continuous and the discrete part of its power spectrum; and (ii) the need for coupled modeling of natural and socio-economic systems. Both these results have implications for the study and prediction of natural hazards and their human impacts. US GDP data used in validating the vulnerability paradox found in a Non-Equilibrium Dynamical Model (NEDyM) for studying the impact of extreme events on a dynamic economy. The paradoxical result is that natural hazards affect more strongly an economy in expansion than when it is in a recession. The connection to the macroeconomic data is given by fluctuation-dissipation theory.

Ghil, M.

2013-05-01

42

Protein electron transfer: Dynamics and statistics.

Electron transfer between redox proteins participating in energy chains of biology is required to proceed with high energetic efficiency, minimizing losses of redox energy to heat. Within the standard models of electron transfer, this requirement, combined with the need for unidirectional (preferably activationless) transitions, is translated into the need to minimize the reorganization energy of electron transfer. This design program is, however, unrealistic for proteins whose active sites are typically positioned close to the polar and flexible protein-water interface to allow inter-protein electron tunneling. The high flexibility of the interfacial region makes both the hydration water and the surface protein layer act as highly polar solvents. The reorganization energy, as measured by fluctuations, is not minimized, but rather maximized in this region. Natural systems in fact utilize the broad breadth of interfacial electrostatic fluctuations, but in the ways not anticipated by the standard models based on equilibrium thermodynamics. The combination of the broad spectrum of static fluctuations with their dispersive dynamics offers the mechanism of dynamical freezing (ergodicity breaking) of subsets of nuclear modes on the time of reaction/residence of the electron at a redox cofactor. The separation of time-scales of nuclear modes coupled to electron transfer allows dynamical freezing. In particular, the separation between the relaxation time of electro-elastic fluctuations of the interface and the time of conformational transitions of the protein caused by changing redox state results in dynamical freezing of the latter for sufficiently fast electron transfer. The observable consequence of this dynamical freezing is significantly different reorganization energies describing the curvature at the bottom of electron-transfer free energy surfaces (large) and the distance between their minima (Stokes shift, small). The ratio of the two reorganization energies establishes the parameter by which the energetic efficiency of protein electron transfer is increased relative to the standard expectations, thus minimizing losses of energy to heat. Energetically efficient electron transfer occurs in a chain of conformationally quenched cofactors and is characterized by flattened free energy surfaces, reminiscent of the flat and rugged landscape at the stability basin of a folded protein. PMID:23862967

Matyushov, Dmitry V

2013-07-14

43

Protein electron transfer: Dynamics and statistics

NASA Astrophysics Data System (ADS)

Electron transfer between redox proteins participating in energy chains of biology is required to proceed with high energetic efficiency, minimizing losses of redox energy to heat. Within the standard models of electron transfer, this requirement, combined with the need for unidirectional (preferably activationless) transitions, is translated into the need to minimize the reorganization energy of electron transfer. This design program is, however, unrealistic for proteins whose active sites are typically positioned close to the polar and flexible protein-water interface to allow inter-protein electron tunneling. The high flexibility of the interfacial region makes both the hydration water and the surface protein layer act as highly polar solvents. The reorganization energy, as measured by fluctuations, is not minimized, but rather maximized in this region. Natural systems in fact utilize the broad breadth of interfacial electrostatic fluctuations, but in the ways not anticipated by the standard models based on equilibrium thermodynamics. The combination of the broad spectrum of static fluctuations with their dispersive dynamics offers the mechanism of dynamical freezing (ergodicity breaking) of subsets of nuclear modes on the time of reaction/residence of the electron at a redox cofactor. The separation of time-scales of nuclear modes coupled to electron transfer allows dynamical freezing. In particular, the separation between the relaxation time of electro-elastic fluctuations of the interface and the time of conformational transitions of the protein caused by changing redox state results in dynamical freezing of the latter for sufficiently fast electron transfer. The observable consequence of this dynamical freezing is significantly different reorganization energies describing the curvature at the bottom of electron-transfer free energy surfaces (large) and the distance between their minima (Stokes shift, small). The ratio of the two reorganization energies establishes the parameter by which the energetic efficiency of protein electron transfer is increased relative to the standard expectations, thus minimizing losses of energy to heat. Energetically efficient electron transfer occurs in a chain of conformationally quenched cofactors and is characterized by flattened free energy surfaces, reminiscent of the flat and rugged landscape at the stability basin of a folded protein.

Matyushov, Dmitry V.

2013-07-01

44

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

Ochmanek, D.A.

1987-08-01

45

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

46

MEANINGS' CONSTRUCTION ABOUT SAMPLING DISTRIBUTIONS IN A DYNAMIC STATISTICS ENVIRONMENT

This paper presents an analysis of the meanings of sampling distribution as supplied by some undergraduate students in a dynamic statistics environment (Fathom). The paper identifies stages in the simulation process where multiple and dynamic representations were crucial to students' understanding of the relationships among sample size, the behavior of sampling distributions and the probabilities of some sample results. One

Ernesto Sánchez

2006-01-01

47

Statistical Dynamics of Pressure-Coupled Burgerlence

NASA Astrophysics Data System (ADS)

The probability distributions of shock structures in pressure-coupled burgerlence are discussed. A Fokker-Planck calculation of these distributions is compared and contrasted with a path integral approach. It is shown that the velocity structures lead to an asymmetric velocity PDF, as in ordinary Burgerlence. Pressure fluctuations, however, are symmetrically distributed. These symmetries are manifested in the generating function (action) of the dynamical system. The extremization of this action (instanton solution) suggests that the system maintains its characteristic directions in steady-state turbulence. Physically, this result implies equi-dissipation, not equipartition, of energy, supporting the earlier results from perturbation theory^1. ^1 J. Fleischer and P.H. Diamond, Phys. Rev. E 58, R2709 (1998).

Fleischer, J.; Diamond, P. H.

1999-11-01

48

Visual statistical analysis of three-dimensional structural dynamics data

NASA Astrophysics Data System (ADS)

A scanning laser Doppler vibrometer provides high-spatial-density vibration measurements of a structure under test. These in-the-field laser-based measurements are the basis for deriving spatial dynamics models. Statistical analysis of the experimental structural dynamics data is essential to determine the quality of the time signal data measurements. Statistically qualifying the time signal data at each point on the structure is particularly important to the process of deriving spatial dynamics models from the data. Analysis of numeric statistics of these large vibration data sets is tedious and time consuming. A new technique for visual statistical analysis using graphical computer modeling is introduced to aid the interpretation of the signal processing statistics measured at numerous spatial locations over a structure. Estimates of the error variance, maximum sample cross-correlation coefficients, and Ftest p-values for regression are computed for time signal data acquired at each measurement location on a structure. Colour and graphical glyphs added to the computer model quickly draw attention to areas on a structure where the time signal data measurements have poor statistical values. The visual statistical model can be a guide during data acquisition to indicate the quality of the acquired data as well as regions where additional measurements may be necessary.

Montgomery, David E.; West, Robert L.

1995-05-01

49

The SDI Industry Product Suite: simulation from the production line to the supply chain

The SDI Industry(R)Product Suite is a versatile, high-level simulation toolset for solving problems of whole enterprises. It adds important capabilities to an existing simulation package, ExtendTM , which provides a robust simulation architecture and a wealth of existing building blocks. The SDI Industry Product Suite contains 5 specific elements for modeling the enterprise: SDI Database for high-speed data import\\/export; SDI

Richard A. Phelps; David J. Parsons; A. J. Siprelle

2000-01-01

50

Analysis of the Soviet response to the Strategic Defense Initiative (SDI). Student report

Since President Reagan announced the Strategic Defense Initiative (SDI) in March 1983, the Soviet Union has consistently condemned it. This study examines the Soviet response to SDI and provides an explanation for their response. The study identifies military, political, and economic factors that influence the Soviet response to SDI. The author concludes that the Soviets have a genuine concern about

1987-01-01

51

Dynamaps: dynamic queries on a health statistics atlas

Dynamic queries are user-controlled animated displays of visual or textual data. On an application developed for the National Center for Health Statistics and running on their ordinary staff equipment, a thematic map of the United States is animated by moving a time slider to illustrate trends of mortality rates. Other sliders filter parts of the maps interactively according to parameters

Catherine Plaisant; Vinit Jain

1994-01-01

52

Hydrological responses to dynamically and statistically downscaled climate model output

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 simulations of basin scale

Robert L. Wilby; Lauren E. Hay; William J. Gutowski Jr.; Raymond W. Arritt; Eugene S. Takle; Zaitao Pan; George H. Leavesley; Martyn P. Clark

2000-01-01

53

Smooth dynamics and new theoretical ideas in nonequilibrium statistical mechanics

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

SDI (Strategic Defense Initiative): technology, survivability, and software

This report reviews the status of the various SDI technologies and system components. It analyzes the feasibility of producing dependable software of the complexity that advanced BMD systems would require. Finally, it summarizes what is now known, and unknown, about the probable survivability of such systems against concerted enemy attacks of various kinds.

Not Available

1988-05-01

55

SDI Investigation, 1967-1969. Volumes 1-5.

ERIC Educational Resources Information Center

The investigation of the performance, economics, and acceptability to users of the selective dissemination of information (SDI) computer system that supported the International Information Service in Physics, Electrotechnology, Computers, and Control (INSPEC) during its initial testing phase is described. The initial design of the study, involving…

Clague, P.

56

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

ERIC Educational Resources Information Center

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

Kelley, Colleen E.

57

Computerized Information Service--SDI. Annual Report 1974-75.

ERIC Educational Resources Information Center

The Information and Documentation Centre of the Royal Institute of Technology Library performs research and development in information science. The two main areas of this continuing research and development programme are (1) development of a comprehensive SDI service and (2) investigations in interactive retrieval services. This annual report…

Hjerppe, Roland

58

Air Force Satellite Control Network and SDI development

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

59

SDI: O, what a tangled web we weave

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

Keeny, S.M. Jr.

1993-11-01

60

Dynamic computation of network statistics via updating schema.

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

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

2009-03-01

61

Dynamical origin of enhanced conformational searches of Tsallis statistics sampling

NASA Astrophysics Data System (ADS)

The characteristic sampling dynamics of importance samplings driven by the Tsallis weight [C. Tsallis, J. Stat. Phys. 52, 479 (1988)] has been analyzed in terms of recently developed Langevin stochastic model by considering the effects of the density of states and the potential smoothing of the Tsallis transformation. Our study reveals that the fixed points, which are determined by the crossing points of the statistical temperature and the Tsallis effective temperature, play a critical role in overall dynamics of the Tsallis statistics sampling. The dynamical origin of enhanced conformational searches of the Tsallis weight has been investigated by unveiling the intimate relationship between the sampling dynamics and the stability change of corresponding fixed points. Based on this stochastic analysis, we propose one effective method to realize a broad energy distribution in the Tsallis statistics sampling by determining optimal Tsallis parameters systematically based on preliminary canonical samplings. The effectiveness of our method has been validated in the folding simulation of Met-Enkephalin and liquid-solid transition simulation of Lennard-Jones cluster systems.

Kim, Jae Gil; Fukunishi, Yoshifumi; Nakamura, Haruki

2004-07-01

62

A statistical-dynamical downscaling procedure for global climate simulations

A statistical-dynamical downscaling procedure for global climate simulations is described. The procedure is based on the assumption that any regional climate is associated with a specific frequency distribution of classified large-scale weather situations. The frequency distributions are derived from multi-year episodes of low resolution global climate simulations. Highly resolved regional distributions of wind and temperature are calculated with a regional

F. Frey-Buness; D. Heimann; R. Sausen

1995-01-01

63

Assessing North American influenza dynamics with a statistical SIRS model

We present a general statistical modeling framework to characterize continental-level influenza dynamics in the United States for the purposes of examining state-level epidemiological sources and sinks. The methods we describe depend directly on state-level influenza data that are prepared on a weekly basis by Google Flu Trends. The Google Flu Trends team has provided a powerful new approach to collecting

Mevin B. Hooten; Jessica Anderson; Lance A. Waller

2010-01-01

64

Statistical method of evaluation of flip-flop dynamical parameters

NASA Astrophysics Data System (ADS)

This paper presents statistical algorithm and measurement system for precise evaluation of flip-flop dynamical parameters in asynchronous operation. The analyzed flip-flop parameters are failure probability, MTBF and propagation delay. It is shown how these parameters depend on metastable operation of flip-flops. The numerical and hardware solutions shown in article allow for precise and reliable comparison of flip-flops. Also the analysis of influence of flip-flop electrical parameters of flip-flop electrical parameters on their metastable operation is possible with use of presented statistical method. Statistical estimation of parameters of flip-flops in which metastability occurs, seems to be more reliable than standard empirical methods of flip-flop analysis. Presented method allows for showing inaccuracies in theoretical model of metastability.

Wieczorek, P. Z.; Opalski, L. J.

2008-01-01

65

A study on modeling the dynamics of statistically dependent returns

NASA Astrophysics Data System (ADS)

This paper develops a method to characterize the dynamic behavior of statistically dependent returns of assets via a scenario set. The proposed method uses heteroskedastic time series to model serial correlations of returns, as well as Cholesky decomposition to generate the set of scenarios such that the statistical dependence of different asset returns is preserved. In addition, this scenario generation method preserves marginal distributions of returns. To demonstrate the performance of the proposed method, a multi-period portfolio optimization model is presented. Then, the method is implemented through a number of stocks selected from New York Stock Exchange (NYSE). Computational results show a high performance of the proposed method from the statistical point of view. Also, results confirm sufficiency and in-sample stability of the generated scenario set. Besides, out-of-sample simulations, for both risk and return, illustrate a good performance of the proposed method.

Davari-Ardakani, Hamed; Aminnayeri, Majid; Seifi, Abbas

2014-07-01

66

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

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

Blankenship, G.L.; Bennett, W.

1989-06-01

67

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

68

Accelerated Dynamics for Monte Carlo Simulations in Statistical Mechanics.

NASA Astrophysics Data System (ADS)

I discuss a new family of accelerated Monte Carlo simulation algorithms based on cluster percolation concepts. Critical slowing down hinders standard Monte Carlo simulations of statistical systems at criticality. New algorithms, featuring collective-update steps such as large cluster flips, result in increased efficiency and reduced critical slowing down. The algorithms of Swendsen-Wang and single-cluster for the Ising Model are analyzed and compared with standard algorithms. A scaling ansatz based on length rescaling arguments is introduced and shown to be in good agreement with numerical results. The dynamic critical exponents are obtained by the study of finite size scaling of autocorrelation times. Numerical results which illustrate different interesting aspects of these new dynamics are presented for the Ising Model in d = 2, 3, 4 and mean-field. An extension of the Swendsen -Wang dynamics to continuous spin models such as the Landau -Ginzburg (phi^4 scalar field theory) is introduced. This model based on an "embedding" scheme is shown to reduce critical slowing down and conjectured to lie in the same dynamic universality class as the Swendsen -Wang Ising model. Finally the effect of global vs local conservation laws in critical dynamics is studied by two techniques: global exchange and magnetization-demon exchange. Global conservation seems to be enough to characterize Hohenberg and Halperin's Model B dynamical universality class.

Tamayo, Pablo

69

Software maturity model applied to SDI. Final report

The Strategic Defense Initiative Organization (SDIO) is undertaking initiatives to mitigate software risks and to stimulate the DoD contractor community to improve its software practices. To that end, IDA assessed the Software Engineering Institute's (SEI) software process maturity model and developed an implementation plan for its use within the SDI program. Under this plan, SDI element programs will use the SEI method to select software contractors with mature practices and to monitor contracts after they have been awarded. This document describes the SEI maturity model and the experience of contractors and government agencies. It also explains SDIO's plans to implement the model program-wide and the benefits and lessons learned from using the model on two contracts.

Springsteen, B.

1991-09-01

70

Slum\\/Shack Dwellers International (SDI) - foundations to treetops

This paper describes the formation and development of Slum\\/Shack Dwellers International (SDI), an international people’s organization which represents member federations of urban poor and homeless groups from 11 countries in Africa, Asia and Latin America. It also describes the evolution of these national federations and how they grew to challenge conventional development thinking and to develop new, community-directed precedents for

Sheela Patel; Sundar Burra; Celine D’Cruz

2001-01-01

71

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

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

Cunningham, C.

1991-03-20

72

E. coli K-12 and EHEC Genes Regulated by SdiA

Background Escherichia and Salmonella encode SdiA, a transcription factor of the LuxR family that regulates genes in response to N-acyl homoserine lactones (AHLs) produced by other species of bacteria. E. coli genes that change expression in the presence of plasmid-encoded sdiA have been identified by several labs. However, many of these genes were identified by overexpressing sdiA on a plasmid and have not been tested for a response to sdiA produced from its natural position in the chromosome or for a response to AHL. Methodology/Principal Findings We determined that two important loci reported to respond to plasmid-based sdiA, ftsQAZ and acrAB, do not respond to sdiA expressed from its natural position in the chromosome or to AHLs. To identify genes that are regulated by chromosomal sdiA and/or AHLs, we screened 10,000 random transposon-based luciferase fusions in E. coli K-12 and a further 10,000 in E. coli O157:H7 for a response to AHL and then tested these genes for sdiA-dependence. We found that genes encoding the glutamate-dependent acid resistance system are up-regulated, and fliE is down-regulated, by sdiA. Gene regulation by sdiA of E. coli is only partially dependent upon AHL. Conclusions/Significance The genes of E. coli that respond to plasmid-based expression of sdiA are largely different than those that respond to chromosomal sdiA and/or AHL. This has significant implications for determining the true function of AHL detection by E. coli.

Swearingen, Matthew C.; Lindsay, Amber; Smith, Jenee N.; Ahmer, Brian M. M.

2010-01-01

73

Dynamical and statistical properties of a rotating oval billiard

NASA Astrophysics Data System (ADS)

Some dynamical and statistical properties of a time-dependent rotating oval billiard are studied. We considered cases with (i) positive and (ii) negative curvature for the boundary. For (i) we show the system does not present unlimited energy growth. For case (ii) however the average velocity for an ensemble of noninteracting particles grows as a power law with acceleration exponent well defined. Finally, we show for both cases that after introducing time-dependent perturbation, the mixed structure of the phase space observed for static case is recovered by making a suitable transformation in the angular position of the particle.

da Costa, Diogo Ricardo; Oliveira, Diego F. M.; Leonel, Edson D.

2014-06-01

74

Solar wind dynamic pressure variations: Quantifying the statistical magnetospheric response

NASA Technical Reports Server (NTRS)

Solar wind dynamic pressure variations are common and have large amplitudes. Existing models for the transient magnetospheric and ionospheric response to the solar wind dynamic pressure variation are quantified. The variations drive large amplitude (approx 1 R sub E) magnetopause motion with velocities of approx. 60 km/s and transient dayside ionospheric flows of 2 km/s which are organized into double convection vortices. Ground magnetometer signatures are more pronounced under the auroral ionosphere, where they reach 60 to 300 nT, and under the equatorial electrojet. A statistical comparison of transient ground magnetometer events seen at a South Pole station and geosynchronous orbit indicates that all but the weakest ground events are associated with clear compressional signatures at the dayside geosynchronous orbit.

Sibeck, D. G.

1990-01-01

75

Dynamically strained ferroelastics: Statistical behavior in elastic and plastic regimes

NASA Astrophysics Data System (ADS)

The dynamic evolution in ferroelastic crystals under external shear is explored by computer simulation of a two-dimensional model. The characteristic geometrical patterns obtained during shear deformation include dynamic tweed in the elastic regime as well as interpenetrating needle domains in the plastic regime. As a result, the statistics of jerk energy differ in the elastic and plastic regimes. In the elastic regime the distributions of jerk energy are sensitive to temperature and initial configurations. However, in the plastic regime the jerk distributions are rather robust and do not depend much on the details of the configurations, although the geometrical pattern formed after yield is strongly influenced by the elastic constants of the materials and the configurations we used. Specifically, for all geometrical configurations we studied, the energy distribution of jerks shows a power-law noise pattern P(E)˜E-(?-1)(?-1=1.3-2) at low temperatures and a Vogel-Fulcher distribution P(E) ˜ exp-(E/E0) at high temperatures. More complex behavior occurs at the crossover between these two regimes where our simulated jerk distributions are very well described by a generalized Poisson distributions P(E)˜E-(?-1) exp-(E/E0)n with n = 0.4-0.5 and ?-1 ? 0 (Kohlrausch law). The geometrical mechanisms for the evolution of the ferroelastic microstructure under strain deformation remain similar in all thermal regimes, whereas their thermodynamic behavior differs dramatically: on heating, from power-law statistics via the Kohlrausch law to a Vogel-Fulcher law. There is hence no simple way to predict the local evolution of the twin microstructure from just the observed statistical behavior of a ferroelastic crystal. It is shown that the Poisson distribution is a convenient way to describe the crossover behavior contained in all the experimental data without recourse to specific scaling functions or temperature-dependent cutoff lengths.

Ding, X.; Lookman, T.; Zhao, Z.; Saxena, A.; Sun, J.; Salje, E. K. H.

2013-03-01

76

Static, statistical, and dynamical properties of small sodium clusters

NASA Astrophysics Data System (ADS)

This paper reports results obtained in the study of small alkali metal clusters (2? n?34). Properties of interest include static descriptions of the Potential Energy Surfaces (PES) using a Distance-Dependent Tight Binding hamiltonian (DDTB) and new results obtained with the same hamiltonian through a Monte-Carlo Growth Method (MCGM) which is shown to give an efficient way to sample the PES, but may also be helpful to estimate the statistical occurrences of the various isomers (catching areas). The probability for generating a given configuration is proportional to a Boltzmann distribution factor and hence a temperature dependence is introduced in the study of the PES. In section 2, the temperature dependence of the optical response for small clusters (on the example of Na4) is simulated through ab initio calculations of the electronic structure coupled with Monte-Carlo dynamics on the absorbing system in the ground state.

Poteau, R.; Maynau, D.; Daudey, J.-P.; Spiegelmann, F.

1993-03-01

77

The intermediate level statistics in dynamically localized chaotic eigenstates

NASA Astrophysics Data System (ADS)

We demonstrate that the energy or quasienergy level spacing distribution in dynamically localized chaotic eigenstates is excellently described by the Brody distribution, displaying the fractional power law level repulsion. This we show in two paradigmatic systems, namely for the fully chaotic eigenstates of the kicked rotator at K = 7, and for the chaotic eigenstates in the mixed-type billiard system (Robnik 1983), after separating the regular and chaotic eigenstates by means of the Poincaré Husimi function, at very high energies with great statistical significance (587654 eigenstates, starting at about 1000000 above the ground state). This separation confirms the Berry-Robnik picture, and is performed for the first time at such high energies.

Batisti?, B.; Manos, T.; Robnik, M.

2013-06-01

78

A high contrast survey for extrasolar giant planets with the Simultaneous Differential Imager (SDI)

We present the results of a survey of 45 young (< 250 Myr), close (< 50 pc) stars with the Simultaneous Differential Imager (SDI) implemented at the VLT and the MMT for the direct detection of extrasolar planets. Our SDI devices use a double Wollaston prism and a quad filter to take images simultaneously at three wavelengths surrounding the 1.62

Beth Alison Biller

2007-01-01

79

SDI (Strategic Defense Initiative) and the Soviet defense burden. Interim report

The Soviets' response to the Strategic Defense Initiative (SDI) must be understood within the context of their deteriorating economic situation and need to modernize their economy. This Note evaluates the defense burden to the Soviets of both an offsetting and an emulation response to the U.S. SDI effort. The analysis is conducted within the context of General Secretary Gorbachev's modernization

1988-01-01

80

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

81

Statistical dynamical subgrid-scale parameterizations for geophysical flows

NASA Astrophysics Data System (ADS)

Simulations of both atmospheric and oceanic circulations at given finite resolutions are strongly dependent on the form and strengths of the dynamical subgrid-scale parameterizations (SSPs) and in particular are sensitive to subgrid-scale transient eddies interacting with the retained scale topography and the mean flow. In this paper, we present numerical results for SSPs of the eddy-topographic force, stochastic backscatter, eddy viscosity and eddy-mean field interaction using an inhomogeneous statistical turbulence model based on a quasi-diagonal direct interaction approximation (QDIA). Although the theoretical description on which our model is based is for general barotropic flows, we specifically focus on global atmospheric flows where large-scale Rossby waves are present. We compare and contrast the closure-based results with an important earlier heuristic SSP of the eddy-topographic force, based on maximum entropy or statistical canonical equilibrium arguments, developed specifically for general ocean circulation models (Holloway 1992 J. Phys. Oceanogr. 22 1033-46). Our results demonstrate that where strong zonal flows and Rossby waves are present, such as in the atmosphere, maximum entropy arguments are insufficient to accurately parameterize the subgrid contributions due to eddy-eddy, eddy-topographic and eddy-mean field interactions. We contrast our atmospheric results with findings for the oceans. Our study identifies subgrid-scale interactions that are currently not parameterized in numerical atmospheric climate models, which may lead to systematic defects in the simulated circulations.

O'Kane, T. J.; Frederiksen, J. S.

2008-12-01

82

Modeling Insurgent Dynamics Including Heterogeneity. A Statistical Physics Approach

NASA Astrophysics Data System (ADS)

Despite the myriad complexities inherent in human conflict, a common pattern has been identified across a wide range of modern insurgencies and terrorist campaigns involving the severity of individual events—namely an approximate power-law x - ? with exponent ??2.5. We recently proposed a simple toy model to explain this finding, built around the reported loose and transient nature of operational cells of insurgents or terrorists. Although it reproduces the 2.5 power-law, this toy model assumes every actor is identical. Here we generalize this toy model to incorporate individual heterogeneity while retaining the model's analytic solvability. In the case of kinship or team rules guiding the cell dynamics, we find that this 2.5 analytic result persists—however an interesting new phase transition emerges whereby this cell distribution undergoes a transition to a phase in which the individuals become isolated and hence all the cells have spontaneously disintegrated. Apart from extending our understanding of the empirical 2.5 result for insurgencies and terrorism, this work illustrates how other statistical physics models of human grouping might usefully be generalized in order to explore the effect of diverse human social, cultural or behavioral traits.

Johnson, Neil F.; Manrique, Pedro; Hui, Pak Ming

2013-05-01

83

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

84

A sample of 35 independent molecular dynamics (MD) simulations of calmodulin (CaM) equilibrium dynamics was prepared from different but equally plausible initial conditions (20 simulations of the wild-type protein and 15 simulations of the D129N mutant). CaM's radius of gyration and backbone mean-square fluctuations were analyzed for the effect of the D129N mutation, and simulations were compared with experiments. Statistical tests were employed for quantitative comparisons at the desired error level. The computational model predicted statistically significant compaction of CaM relative to the crystal structure, consistent with the results of small-angle X-ray scattering (SAXS) experiments. This effect was not observed in several previously reported studies of (Ca2+)(4)-CaM, which relied on a single MD run. In contrast to radius of gyration, backbone mean-square fluctuations showed a distinctly non-normal and positively skewed distribution for nearly all residues. Furthermore, the D129N mutation affected the backbone dynamics in a complex manner and reduced the mobility of Glu123, Met124, Ile125, Arg126, and Glu127 located in the adjacent alpha-helix G. The implications of these observations for the comparisons of MD simulations with experiments are discussed. The proposed approach may be useful in studies of protein equilibrium dynamics where MD simulations fall short of properly sampling the conformational space, and when the comparison with experiments is affected by the reproducibility of the computational model. PMID:16322577

Likic, Vladimir A; Gooley, Paul R; Speed, Terence P; Strehler, Emanuel E

2005-12-01

85

A sample of 35 independent molecular dynamics (MD) simulations of calmodulin (CaM) equilibrium dynamics was prepared from different but equally plausible initial conditions (20 simulations of the wild-type protein and 15 simulations of the D129N mutant). CaM’s radius of gyration and backbone mean-square fluctuations were analyzed for the effect of the D129N mutation, and simulations were compared with experiments. Statistical tests were employed for quantitative comparisons at the desired error level. The computational model predicted statistically significant compaction of CaM relative to the crystal structure, consistent with the results of small-angle X-ray scattering (SAXS) experiments. This effect was not observed in several previously reported studies of (Ca2+)4-CaM, which relied on a single MD run. In contrast to radius of gyration, backbone mean-square fluctuations showed a distinctly non-normal and positively skewed distribution for nearly all residues. Furthermore, the D129N mutation affected the backbone dynamics in a complex manner and reduced the mobility of Glu123, Met124, Ile125, Arg126, and Glu127 located in the adjacent ?-helix G. The implications of these observations for the comparisons of MD simulations with experiments are discussed. The proposed approach may be useful in studies of protein equilibrium dynamics where MD simulations fall short of properly sampling the conformational space, and when the comparison with experiments is affected by the reproducibility of the computational model.

Likic, Vladimir A.; Gooley, Paul R.; Speed, Terence P.; Strehler, Emanuel E.

2005-01-01

86

We consider temporal approximation of stationary statistical properties of dissipa- tive complex dynamical systems. We demonstrate that stationary statistical properties of the time discrete approximations (numerical scheme) converge to those of the un- derlying continuous dissipative complex dynamical system under three very natural assumptions as the time step approaches zero. The three conditions that are sufficient for the convergence of

Xiaoming Wang

2010-01-01

87

Statistical and dynamical downscaling of precipitation over Spain from DEMETER seasonal forecasts

Statistical and dynamical downscaling methods are tested and compared for downscaling seasonal precipitation forecasts over Spain from two DEMETER models: the European Centre for Medium-Range Weather Forecasts (ECMWF) and the UK Meteorological Office (UKMO). The statistical method considered is a particular implementation of the standard analogue technique, based on close neighbours of the predicted atmospheric geopotential and humidity fields. Dynamical

E. Díez; C. Primo; J. A. García-Moya; J. M. Gutiérrez; B. Orfila

2005-01-01

88

Solar Wind Dynamic Pressure Variations: Quantifying the Statistical Magnetospheric Response.

National Technical Information Service (NTIS)

Solar wind dynamic pressure variations are common and have large amplitudes. Existing models for the transient magnetospheric and ionospheric response to the solar wind dynamic pressure variation are quantified. The variations drive large amplitude (appro...

D. G. Sibeck

1990-01-01

89

ERIC Educational Resources Information Center

This study examined a random stratified sample (n = 62) of prospective teachers' work across eight institutions on three tasks that utilized dynamic statistical software. The authors considered how teachers utilized their statistical knowledge and technological statistical knowledge to engage in cycles of investigation. This paper characterizes…

Lee, Hollylynne Stohl; Kersaint, Gladis; Harper, Suzanne; Driskell, Shannon O.; Leatham, Keith R.

2012-01-01

90

Dynamical instability and statistical behaviour of N-body systems

NASA Astrophysics Data System (ADS)

In this paper, we argue about a synthetic characterization of the qualitative properties of generic many-degrees-of-freedom (mdf) dynamical systems (DS's) by means of a geometric description of the dynamics [Geometro-Dynamical Approach (GDA)]. We exhaustively describe the mathematical framework needed to link geometry and dynamical (in)stability, discussing in particular which geometrical quantity is actually related to instability and why some others cannot give, in general, any indication of the occurrence of chaos. The relevance of the Schur theorem to select such Geometrodynamic Indicators (GDI) of instability is then emphasized, as its implications seem to have been underestimated in some of the previous works. We then compare the analytical and numerical results obtained by us and by Pettini and coworkers concerning the FPU chain, verifying a complete agreement between the outcomes of averaging the relevant GDI's over phase space (Casetti and Pettini, 1995) and our findings (Cipriani, 1993), obtained in a more conservative way, time-averaging along geodesics. Along with the check of the ergodic properties of GDI's, these results confirm that the mechanism responsible for chaos in realistic DS's largely depends on the fluctuations of curvatures rather than on their negative values, whose occurrence is very unlikely. On these grounds we emphasize the importance of the virialization process, which separates two different regimes of instability. This evolutionary path, predicted on the basis of analytical estimates, receives clear support from numerical simulations, which, at the same time, confirm also the features of the evolution of the GDI's along with their dependence on the number of degrees of freedom, N, and on the other relevant parameters of the system, pointing out the scarce relevance of negative curvature (for N ? 1) as a source of instability. The general arguments outlined above, are then concretely applied to two specific N-body problems, obtaining some new insights into known outcomes and also some new results The comparative analysis of the FPU chain and the gravitational N-body system allows us to suggest a new definition of strong stochasticity, for any DS. The generalization of the concept of dynamical time-scale, tD, is at the basis of this new criterion. We derive for both the mdf systems considered the ( N, ?)-dependence of tD (? being the specific energy) of the system. In light of this, the results obtained (Cerruti-Sola and Pettini, 1995), indeed turn out to be reliable, the perplexity there raised originating from the neglected N-dependence of tD, and not to an excessive degree of approximation in the averaged equations used. This points out also the peculiarities of gravitationally bound systems, which are always in a regime of strong instability; the dimensionless quantity L1 = ?1 · tD [? 1 is the maximal Lyapunov Characteristic Number (LCN)] being always positive and independent of ?, as it happens for the FPU chain only above the strong stochasticity threshold (SST). The numerical checks on the analytical estimates about the ( N, ?)-dependence of GDI's, allow us to single out their scaling laws, which support our claim that, for N ? 1, the probability of finding a negative value of Ricci curvature is practically negligible, always for the FPU chain, whereas in the case of the Gravitational N-body system, this is certainly true when the virial equilibrium has been attained. The strong stochasticity of the latter DS is clearly due to the large amplitude of curvature fluctuations. To prove the positivity of Ricci curvature, we need to discuss the pathologies of mathematical Newtonian interaction, which have some implications also on the ergodicity of the GDI's for this DS. We discuss the Statistical Mechanical properties of gravity, arguing how they are related to its long range nature rather than to its short scale divergencies. The N-scaling behaviour of the single terms entering the Ricci curvature show that the dominant contribution comes from the Laplacian of the potential e

Cipriani, Piero; Di Bari, Maria

1998-12-01

91

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

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

92

FACILITATING DATA EXPLORATION: DYNAMIC QUERIES ON A HEALTH STATISTICS MAP

Users with no specialized computer training are often discouraged by the complex syntax of query languages and the output of long tables of alphanumerica l values. The Human-Computer Interaction Laboratory has recently developed the concept of dynamic queries which allows user control of animated visual displays of information. Experiments with our first applications have shown that dynamic queries can help

Catherine Plaisant; A. V. Williams

1993-01-01

93

Solar wind dynamic pressure variations: Quantifying the statistical magnetospheric response

Solar wind dynamic pressure variations are common and have large amplitudes. Existing models for the transient magnetospheric and ionospheric response to the solar wind dynamic pressure variation are quantified. The variations drive large amplitude (approx 1 RE) magnetopause motion with velocities of approx. 60 km\\/s and transient dayside ionospheric flows of 2 km\\/s which are organized into double convection vortices.

D. G. Sibeck

1990-01-01

94

Dynamic analysis of framed structures with statistical uncertainties

SUMMARY The forced harmonic vibration analysis of portal frames consisting of viscously damped beams with spatial stochastic variation of mass and stiness properties is considered. The analysis is based on the assembly of element stochastic dynamic stiness matrices. The solution involves inversion of the global dynamic stiness matrix, which, in this case, turns out to be a complex-valued symmetric random

Sondipon Adhikari; C. S. Manohar

1999-01-01

95

Dynamical and Statistical Modeling of the Multiscale Magnetosphere

NASA Astrophysics Data System (ADS)

Earth's magnetosphere exhibits both global and multiscale behavior and the extensive database from spacecraft and ground-based measurements has been used to develop dynamical models. The dominant feature of the magnetosphere is its large scale or global behavior, as is evident during substorms. The dynamical features can be modeled using the techniques of phase space reconstruction and this has led to near real-time forecasts of space weather. The multiscale nature limits the predictability of such dynamical models and this is quantified in terms of conditional probabilities. The combination of the dynamical and probabilistic descriptions provides a comprehensive approach to the modeling of Earth's magnetosphere. The spatial structure of the magnetosphere is modeled using distributed data from ground magnetometer stations and can be used to make local forecasts.

Sharma, A. Surjalal; Veeramani, Thangamani; Chen, Jian; Shao, Xi

2011-01-01

96

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics

NASA Astrophysics Data System (ADS)

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 Rényi divergence.

Crooks, Gavin E.; Sivak, David A.

2011-06-01

97

Statistics of transverse mode turn-on dynamics in VCSELs

The turn-on process of a multimode VCSEL is investigated from a statistical point of view. Special attention Is paid to quantities such as time jitter and bit error rate. The single-mode performance of VCSELs during current modulation is compared to that of edge-emitting lasers

J. Dellunde; M. C. Torrent; J. M. Sancho; K. A. Shore

1997-01-01

98

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics

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

99

SdiA aids enterohemorrhagic Escherichia coli carriage by cattle fed a forage or grain diet.

Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis and life-threatening complications. The main reservoirs for EHEC are healthy ruminants. We reported that SdiA senses acyl homoserine lactones (AHLs) in the bovine rumen to activate expression of the glutamate acid resistance (gad) genes priming EHEC's acid resistance before they pass into the acidic abomasum. Conversely, SdiA represses expression of the locus of enterocyte effacement (LEE) genes, whose expression is not required for bacterial survival in the rumen but is necessary for efficient colonization at the rectoanal junction (RAJ) mucosa. Our previous studies show that SdiA-dependent regulation was necessary for efficient EHEC colonization of cattle fed a grain diet. Here, we compared the SdiA role in EHEC colonization of cattle fed a forage hay diet. We detected AHLs in the rumen of cattle fed a hay diet, and these AHLs activated gad gene expression in an SdiA-dependent manner. The rumen fluid and fecal samples from hay-fed cattle were near neutrality, while the same digesta samples from grain-fed animals were acidic. Cattle fed either grain or hay and challenged with EHEC orally carried the bacteria similarly. EHEC was cleared from the rumen within days and from the RAJ mucosa after approximately one month. In competition trials, where animals were challenged with both wild-type and SdiA deletion mutant bacteria, diet did not affect the outcome that the wild-type strain was better able to persist and colonize. However, the wild-type strain had a greater advantage over the SdiA deletion mutant at the RAJ mucosa among cattle fed the grain diet. PMID:23836826

Sheng, Haiqing; Nguyen, Y N; Hovde, Carolyn J; Sperandio, Vanessa

2013-09-01

100

Nonlinear Dynamics of Wrinkled Premixed Flames and Related Statistical Problems

The flames propagating through premixed gaseous reactants are surface-like interfaces, that consume the former at a local\\u000a curvature-dependent burning speed, and heat them. The Michelson-Sivashinsky (MS) equation and its variants well describe how\\u000a the fluid-mechanical (Landau-Darrieus) instability competes with curvature and geometrical (Huygens) non-linearity in the\\u000a overall flame shape dynamics. For nearly-straight or nearly-circular fronts, the dynamics translates into N-body

Guy Joulin; Gael Boury; Pierre Cambray; Yves D’Angelo; Karl Joulain

2001-01-01

101

Bubble statistics and dynamics in double-stranded DNA

NASA Astrophysics Data System (ADS)

The dynamical properties of double-stranded DNA are studied in the framework of the Peyrard-Bishop-Dauxois model using Langevin dynamics. Our simulations are analyzed in terms of two distribution functions describing localized separations (“bubbles”) of the double strand. The result that the bubble distributions are more sharply peaked at the active sites than thermodynamically obtained distributions is ascribed to the fact that the bubble lifetimes affect the distributions. Certain base-pair sequences are found to promote long-lived bubbles, and we argue that this is a result of length scale competition between the nonlinearity and disorder present in the system.

Alexandrov, B. S.; Wille, L. T.; Rasmussen, K. Ø.; Bishop, A. R.; Blagoev, K. B.

2006-11-01

102

Bubble statistics and dynamics in double-stranded DNA.

The dynamical properties of double-stranded DNA are studied in the framework of the Peyrard-Bishop-Dauxois model using Langevin dynamics. Our simulations are analyzed in terms of two distribution functions describing localized separations ("bubbles") of the double strand. The result that the bubble distributions are more sharply peaked at the active sites than thermodynamically obtained distributions is ascribed to the fact that the bubble lifetimes affect the distributions. Certain base-pair sequences are found to promote long-lived bubbles, and we argue that this is a result of length scale competition between the nonlinearity and disorder present in the system. PMID:17279870

Alexandrov, B S; Wille, L T; Rasmussen, K Ø; Bishop, A R; Blagoev, K B

2006-11-01

103

Remarkable statistical behavior for truncated Burgers-Hopf dynamics

A simplified one-dimensional model system is introduced and studied here that exhibits intrinsic chaos with many degrees of freedom as well as increased predictability and slower decay of correlations for the large-scale features of the system. These are important features in common with vastly more complex problems involving climate modeling or molecular biological systems. This model is a suitable approximation of the Burgers–Hopf equation involving Galerkin projection on Fourier modes. The model has a detailed mathematical structure that leads to a well-defined equilibrium statistical theory as well as a simple scaling theory for correlations. The numerical evidence presented here strongly supports the behavior predicted from these statistical theories. Unlike the celebrated dissipative and dispersive approximations of the Burgers–Hopf equation, which exhibit exactly solvable and/or completely integrable behavior, these model approximations have strong intrinsic chaos with ergodic behavior.

Majda, Andrew J.; Timofeyev, Ilya

2000-01-01

104

Dynamical and statistical modeling of seasonal precipitation over Mexico

NASA Astrophysics Data System (ADS)

Simulated patterns of seasonal precipitation over Mexico (Pmex) by a statistical model and by the recently-released version of the Regional Climate Model (RegCM4) are compared. The European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis ERA-Interim is used to provide initial and lateral boundary conditions for the RegCM4 simulation over the CORDEX Central America region; while regions of high correlation between Pmex and global sea surface temperatures (SST) over the Atlantic and Pacific Oceans are used as predictors in the statistical model. Compared with observations, the RegCM4 simulation shows a wet bias in topographically complex regions and a dry bias over Yucatan and northwestern Mexico. The wet bias is probably caused by the model's convection scheme, but the dry bias may be due to a lack of topographical features (in Yucatan) and a weakened representation of the North American Monsoon (in northwestern Mexico). RegCM4 simulates quite well the seasonal precipitation patterns and also the inter-seasonal variability, reproducing well the observed wetter or drier than normal seasons. RegCM4 is also able to reproduce adequately well the mid-summer drought in the south of Mexico. The statistical model also reproduces well the inter-seasonal precipitation variability, simulating Pmex better over southern and central Mexico than over northern Mexico. This may suggest that Pmex over northern Mexico is less dependent on SST than over other regions of the country.

Fuentes-Franco, R.; Coppola, E.; Giorgi, F.; Pavia, E. G.; Graef Ziehl, F.

2012-12-01

105

Dynamic Model Extraction and Statistical Analysis of Web Applications

Abstract The World Wide Web, initially intended as a way to pub- lish static hypertexts on the Internet, is moving toward com- plex applications. Static Web sites are being gradually re- placed by dynamic sites, where information is stored in databases and non trivial computation is performed. Reverse engineering of a model from an existing Web application is useful for

Paolo Tonella; Filippo Ricca

2002-01-01

106

Non-standard Neutral Kaon Dynamics from Infinite Statistics

The neutral kaon system can be effectively described by non-unitary, dissipative, completely positive dynamics that extend the usual treatment. In the framework of open quantum systems, we show how the origin of these non-standard time evolutions can be traced to the interaction of the kaon system with a large environment. We find that a heat bath of quanta obeying infnite

F. Benatti; R. Floreanini

1999-01-01

107

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

108

Flow Equation Approach to the Statistics of Nonlinear Dynamical Systems

The probability distribution function of non-linear dynamical systems is governed by a linear framework that resembles quantum many-body theory, in which stochastic forcing and\\/or averaging over initial conditions play the role of non-zero . Besides the well-known Fokker-Planck approach, there is a related Hopf functional method ootnotetextUriel Frisch, Turbulence: The Legacy of A. N. Kolmogorov (Cambridge University Press, 1995) chapter

J. B. Marston; M. B. Hastings

2005-01-01

109

Viscoelastic effects in avalanche dynamics: a key to earthquake statistics.

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. PMID:24836251

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

2014-05-01

110

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

111

BACKGROUND: The structure of molecular networks derives from dynamical processes on evolutionary time scales. For protein interaction networks, global statistical features of their structure can now be inferred consistently from several large-throughput datasets. Understanding the underlying evolutionary dynamics is crucial for discerning random parts of the network from biologically important properties shaped by natural selection. RESULTS: We present a detailed

Johannes Berg; Michael Lässig; Andreas Wagner

2004-01-01

112

Dynamic Cartographic Methods for Visualisation of Health Statistics

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

Radim Stampach; Milan Konecny; Petr Kubicek; Edvard Geryk

113

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

114

Noisy inverted pendulums with time-delayed feedback: Statistical Dynamics

NASA Astrophysics Data System (ADS)

The question of how an inverted pendulum can be stabilized has puzzled scientists for over 300 years. Studies of postural sway and stick balancing at the fingertip provide insights into how the human nervous system solves this problem. Time delays and noise are intrinsic features of the neural control and thus models are in the form of stochastic delay-differential equations. Examples are presented to show that the statistical properties of the fluctuations in posture and stick balancing are dominated by noise-dependent, nonlinear phenomena: noise-induced switching between limit cycle attractors (postural sway) and "on-off intermittency" arising from the stochastic forcing of a control parameter across a stability boundary (stick balancing). The existence of these phenomena is difficult to reconcile with classical concepts of neural feedback control.

Milton, John G.

2001-03-01

115

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

116

Human turnover dynamics during sleep: statistical behavior and its modeling.

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. PMID:24730888

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

2014-03-01

117

Superconducting Magnetic Energy Storage and other large-scale SDI cryogenic applications programs

NASA Astrophysics Data System (ADS)

The paper describes the Superconducting Magnetic Energy Storage (SMES) program for terrestrial storage of energy for use in powering ground-based directed energy weapons. Special attention is given to SMES technology for SDI applications, the components of a SMES system, the SMES Engineering Test Model Development Program, and the SMES critical technologies. It is pointed out that SMES has applications other than SDI, such as the commercial electric utility industry and space power systems, including hydrogen-cooled cryoconductors, superconducting turboalternators, and high-temperature superconductor power leads.

Verga, Richard L.

118

We show that electrostatic fluctuations of the protein-water interface are globally non-Gaussian. The electrostatic component of the optical transition energy (energy gap) in a hydrated green fluorescent protein is studied here by classical molecular dynamics simulations. The distribution of the energy gap displays a high excess in the breadth of electrostatic fluctuations over the prediction of the Gaussian statistics. The energy gap dynamics include a nanosecond component. When simulations are repeated with frozen protein motions, the statistics shifts to the expectations of linear response and the slow dynamics disappear. We therefore suggest that both the non-Gaussian statistics and the nanosecond dynamics originate largely from global, low-frequency motions of the protein coupled to the interfacial water. The non-Gaussian statistics can be experimentally verified from the temperature dependence of the first two spectral moments measured at constant-volume conditions. Simulations at different temperatures are consistent with other indicators of the non-Gaussian statistics. In particular, the high-temperature part of the energy gap variance (second spectral moment) scales linearly with temperature and extrapolates to zero at a temperature characteristic of the protein glass transition. This result, violating the classical limit of the fluctuation-dissipation theorem, leads to a non-Boltzmann statistics of the energy gap and corresponding non-Arrhenius kinetics of radiationless electronic transitions, empirically described by the Vogel-Fulcher-Tammann law. PMID:22861814

Martin, Daniel R; Matyushov, Dmitry V

2012-08-30

119

Dynamic cortical involvement in implicit anticipation during statistical learning.

The prediction of future events is fundamental in a large number of critical neurobehavioral contexts including implicit motor learning. This learning process relies on the probabilities with which events occur, and is a dynamic phenomenon. The aim of present study was to investigate the development of anticipatory processes during implicit learning. A decision making task was employed in which the frequency of trial types was manipulated such that one trial type was disproportionately prevalent as compared to the remaining three trial types. A 275 channel whole-head magnetoencephalography (MEG) system was used to investigate the spatiotemporal distribution of event-related desynchronization (ERD) and synchronization (ERS). The results revealed that oscillations within the alpha (10-12 Hz) and beta (14-30 Hz) frequencies were associated with anticipatory processes in distinct networks in the course of learning. During early phases of learning the contralateral motor cortex, the anterior cingulate, the caudate and the inferior frontal gyrus showed ERDs within beta and alpha frequencies, putatively reflecting preparation of next motor response. As the task progressed, alpha ERSs in occipitotemporal regions and putamen likely reflect perceptual anticipation of the forthcoming stimuli. PMID:24080375

Altamura, Mario; Carver, Frederick W; Elvevåg, Brita; Weinberger, Daniel R; Coppola, Richard

2014-01-13

120

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

121

Statistical Physics Approaches to Respiratory Dynamics and Lung Structure

NASA Astrophysics Data System (ADS)

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

Suki, Bela

2004-03-01

122

An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models

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

John J. Prindle; John J. McArdle

2012-01-01

123

Scarcity of fresh high-quality water has heightened the importance of wastewater reuse primarily in dry regions together with improving its efficient use by implementing the Subsurface Drip Irrigation (SDI) method. Sustainable effluent reuse combines soil and plant aspects, along with the maintainability of the application system. In this study, field experiments were conducted for two years on the commercial farm of Revivim and Mashabay-Sade farm (RMF) southeast of the City of Beer-Sheva, Israel. The purpose was to examine the response of alfalfa (Medicago sativa) as a perennial model crop to secondary domestic effluent application by means of a SDI system as compared with conventional overhead sprinkler irrigation. Emitters were installed at different depths and spacing. Similar amounts of effluent were applied to all plots during the experimental period. The results indicated that in all SDI treatments, the alfalfa yields were 11% to 25% higher than the ones obtained under sprinkler irrigated plots, besides the one in which the drip laterals were 200 cm apart. The average Water Use Efficiency (WUE) was better in all SDI treatments in comparison with the sprinkler irrigated plots. An economic assessment reveals the dependence of the net profit on the emitters' installation geometry, combined with the return for alfalfa in the market. PMID:20150698

Kazumba, Shija; Gillerman, Leonid; DeMalach, Yoel; Oron, Gideon

2010-01-01

124

Selective Dissemination of Information (Sdi). Volume I. Pilot Test at U.S. Army Natick Laboratories.

National Technical Information Service (NTIS)

The report presents the results of a nine-month test of a prototype SDI system developed for Army Technical Libraries. During the pilot test, one thousand documents were cataloged and indexed and disseminated to twenty-five scientific and technical person...

W. A. Bivona

1967-01-01

125

Superconducting Magnetic Energy Storage and other large-scale SDI cryogenic applications programs

The paper describes the Superconducting Magnetic Energy Storage (SMES) program for terrestrial storage of energy for use in powering ground-based directed energy weapons. Special attention is given to SMES technology for SDI applications, the components of a SMES system, the SMES Engineering Test Model Development Program, and the SMES critical technologies. It is pointed out that SMES has applications other

Richard L. Verga

1990-01-01

126

The Importance of SDI for Current Awareness in Fields with Severe Scatter of Information.

ERIC Educational Resources Information Center

Exploring the use and effectiveness of current awareness (CA) methods, especially selective dissemination of information (SDI) among chemists at Canadian universities, this study focuses on the perceived dispersal of information, use of various CA methods, time spent on CA, perceived success in CA, and CA efficiency. (FM)

Packer, Katherine H.; Soergel, Dagobert

1979-01-01

127

Ion Channel Biosensors—Part II: Dynamic Modeling, Analysis, and Statistical Signal Processing

This paper deals with the dynamic modeling, analysis, and statistical signal processing of the ion channel switch biosensor. The electrical dynamics are described by a second-order linear system. The chemical kinetics of the biosensor response to analyte concentration in the reaction-rate-limited regime are modeled by a two-timescale nonlinear system of differential equations. Also, the analyte concentration in the mass-transport-influenced regime

Vikram Krishnamurthy; Sahar Moradi Monfared; Bruce Cornell

2010-01-01

128

Predictions of climate change over Europe using statistical and dynamical downscaling techniques

Statistical and dynamical downscaling predictions of changes in surface temperature and precipitation for 2080-2100, relative to pre-industrial conditions, are compared at 976 European observing sites, for January and July. Two dynamical downscaling methods are considered, involving the use of surface temperature or precipitation simulated at the nearest grid point in a coupled ocean-atmosphere general circulation model (GCM) of resolution 300

James Murphy

2000-01-01

129

Escherichia coli SdiA is a quorum-sensing (QS) receptor that responds to autoinducers produced by other bacterial species to control cell division and virulence. Crystal structures reveal that E. coli SdiA, which is composed of an N-terminal ligand-binding domain and a C-terminal DNA-binding domain (DBD), forms a symmetrical dimer. Although each domain shows structural similarity to other QS receptors, SdiA differs from them in the relative orientation of the two domains, suggesting that its ligand-binding and DNA-binding functions are independent. Consistently, in DNA gel-shift assays the binding affinity of SdiA for the ftsQP2 promoter appeared to be insensitive to the presence of autoinducers. These results suggest that autoinducers increase the functionality of SdiA by enhancing the protein stability rather than by directly affecting the DNA-binding affinity. Structural analyses of the ligand-binding pocket showed that SdiA cannot accommodate ligands with long acyl chains, which was corroborated by isothermal titration calorimetry and thermal stability analyses. The formation of an intersubunit disulfide bond that might be relevant to modulation of the DNA-binding activity was predicted from the proximal position of two Cys residues in the DBDs of dimeric SdiA. It was confirmed that the binding affinity of SdiA for the uvrY promoter was reduced under oxidizing conditions, which suggested the possibility of regulation of SdiA by multiple independent signals such as quorum-sensing inducers and the oxidation state of the cell. PMID:24598739

Kim, Truc; Duong, Thao; Wu, Chun-ai; Choi, Jongkeun; Lan, Nguyen; Kang, Sung Wook; Lokanath, Neratur K; Shin, DongWoo; Hwang, Hye-Yeon; Kim, Kyeong Kyu

2014-03-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

131

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

132

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

133

Effect of injected field statistics on transient dynamics of an injection seeded laser

A recent experiment demonstrated a means of detecting very weak optical signals by measuring the initiation times of an injection seeded, Q-switched laser. Digital simulations and analytic expressions for transient dynamics of an injection seeded laser were subsequently reported and were in excellent agreement with experimental results. This paper reports on the effect of statistical fluctuations on the injected signal

Gautam Vemuri; Rajarshi Roy

1990-01-01

134

An Evaluation of Statistical and Dynamical Techniques for Downscaling Local Climate

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

James Murphy

1999-01-01

135

SdiA is a homolog of quorum-sensing regulators that detects N-acylhomoserine lactone (AHL) signals from other bacteria. Escherichia coli uses SdiA to reduce its biofilm formation in the presence of both AHLs and its own signal indole. Here we reconfigured SdiA (240 amino acids) to control biofilm formation using protein engineering. Four SdiA variants were obtained with altered biofilm formation, including truncation variants SdiA1E11 (F7L, F59L, Y70C, M94K, and K153X) and SdiA14C3 (W9R, P49T, N87T, frameshift at N96, and L123X), which reduced biofilm formation by 5- to 20-fold compared to wild-type SdiA in the presence of endogenous indole. Whole-transcriptome profiling revealed that wild-type SdiA reduced biofilm formation by repressing genes related to indole synthesis and curli synthesis compared to when no SdiA was expressed, while variant SdiA1E11 induced genes related to indole synthesis in comparison to wild-type SdiA. These results suggested altered indole metabolism, and corroborating the DNA microarray results in regard to indole synthesis, variant SdiA1E11 produced ninefold more indole, which led to reduced swimming motility and cell density. Also, wild-type SdiA decreased curli production and tnaA transcription, while SdiA1E11 increased tnaA transcription (tnaA encodes tryptophanase, which forms indole) compared to wild-type SdiA. Hence, wild-type SdiA decreased biofilm formation by reducing curli production and motility, and SdiA1E11 reduced biofilm formation via indole. Furthermore, an AHL-sensitive variant (SdiA2D10, having four mutations at E31G, Y42F, R116H, and L165Q) increased biofilm formation sevenfold in the presence of N-octanoyl-dl-homoserine lactone and N-(3-oxododecatanoyl)-l-homoserine lactone. Therefore, SdiA can be evolved to increase or decrease biofilm formation, and biofilm formation may be controlled by altering sensors rather than signals.

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

2009-01-01

136

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

137

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

138

The RNA binding protein CsrA is the central component of a conserved global regulatory system that activates or represses gene expression posttranscriptionally. In every known example of CsrA-mediated translational control, CsrA binds to the 5? untranslated region of target transcripts, thereby repressing translation initiation and/or altering the stability of the RNA. Furthermore, with few exceptions, repression by CsrA involves binding directly to the Shine-Dalgarno sequence and blocking ribosome binding. sdiA encodes the quorum-sensing receptor for N-acyl-l-homoserine lactone in Escherichia coli. Because sdiA indirectly stimulates transcription of csrB, which encodes a small RNA (sRNA) antagonist of CsrA, we further explored the relationship between sdiA and the Csr system. Primer extension analysis revealed four putative transcription start sites within 85 nucleotides of the sdiA initiation codon. Potential ?70-dependent promoters were identified for each of these primer extension products. In addition, two CsrA binding sites were predicted in the initially translated region of sdiA. Expression of chromosomally integrated sdiA?-?lacZ translational fusions containing the entire promoter and CsrA binding site regions indicates that CsrA represses sdiA expression. The results from gel shift and footprint studies demonstrate that tight binding of CsrA requires both of these sites. Furthermore, the results from toeprint and in vitro translation experiments indicate that CsrA represses translation of sdiA by directly competing with 30S ribosomal subunit binding. Thus, this represents the first example of CsrA preventing translation by interacting solely within the coding region of an mRNA target.

Yakhnin, Helen; Baker, Carol S.; Berezin, Igor; Evangelista, Michael A.; Rassin, Alisa; Romeo, Tony; Babitzke, Paul

2011-01-01

139

The RNA binding protein CsrA is the central component of a conserved global regulatory system that activates or represses gene expression posttranscriptionally. In every known example of CsrA-mediated translational control, CsrA binds to the 5' untranslated region of target transcripts, thereby repressing translation initiation and/or altering the stability of the RNA. Furthermore, with few exceptions, repression by CsrA involves binding directly to the Shine-Dalgarno sequence and blocking ribosome binding. sdiA encodes the quorum-sensing receptor for N-acyl-l-homoserine lactone in Escherichia coli. Because sdiA indirectly stimulates transcription of csrB, which encodes a small RNA (sRNA) antagonist of CsrA, we further explored the relationship between sdiA and the Csr system. Primer extension analysis revealed four putative transcription start sites within 85 nucleotides of the sdiA initiation codon. Potential ?(70)-dependent promoters were identified for each of these primer extension products. In addition, two CsrA binding sites were predicted in the initially translated region of sdiA. Expression of chromosomally integrated sdiA'-'lacZ translational fusions containing the entire promoter and CsrA binding site regions indicates that CsrA represses sdiA expression. The results from gel shift and footprint studies demonstrate that tight binding of CsrA requires both of these sites. Furthermore, the results from toeprint and in vitro translation experiments indicate that CsrA represses translation of sdiA by directly competing with 30S ribosomal subunit binding. Thus, this represents the first example of CsrA preventing translation by interacting solely within the coding region of an mRNA target. PMID:21908661

Yakhnin, Helen; Baker, Carol S; Berezin, Igor; Evangelista, Michael A; Rassin, Alisa; Romeo, Tony; Babitzke, Paul

2011-11-01

140

HDX-Analyzer: a novel package for statistical analysis of protein structure dynamics

Background HDX mass spectrometry is a powerful platform to probe protein structure dynamics during ligand binding, protein folding, enzyme catalysis, and such. HDX mass spectrometry analysis derives the protein structure dynamics based on the mass increase of a protein of which the backbone protons exchanged with solvent deuterium. Coupled with enzyme digestion and MS/MS analysis, HDX mass spectrometry can be used to study the regional dynamics of protein based on the m/z value or percentage of deuterium incorporation for the digested peptides in the HDX experiments. Various software packages have been developed to analyze HDX mass spectrometry data. Despite the progresses, proper and explicit statistical treatment is still lacking in most of the current HDX mass spectrometry software. In order to address this issue, we have developed the HDXanalyzer for the statistical analysis of HDX mass spectrometry data using R, Python, and RPY2. Implementation and results HDXanalyzer package contains three major modules, the data processing module, the statistical analysis module, and the user interface. RPY2 is employed to enable the connection of these three components, where the data processing module is implemented using Python and the statistical analysis module is implemented with R. RPY2 creates a low-level interface for R and allows the effective integration of statistical module for data processing. The data processing module generates the centroid for the peptides in form of m/z value, and the differences of centroids between the peptides derived from apo and ligand-bound protein allow us to evaluate whether the regions have significant changes in structure dynamics or not. Another option of the software is to calculate the deuterium incorporation rate for the comparison. The two types of statistical analyses are Paired Student’s t-test and the linear combination of the intercept for multiple regression and ANCOVA model. The user interface is implemented with wxpython to facilitate the data visualization in graphs and the statistical analysis output presentation. In order to evaluate the software, a previously published xylanase HDX mass spectrometry analysis dataset is processed and presented. The results from the different statistical analysis methods are compared and shown to be similar. The statistical analysis results are overlaid with the three dimensional structure of the protein to highlight the regional structure dynamics changes in the xylanase enzyme. Conclusion Statistical analysis provides crucial evaluation of whether a protein region is significantly protected or unprotected during the HDX mass spectrometry studies. Although there are several other available software programs to process HDX experimental data, HDXanalyzer is the first software program to offer multiple statistical methods to evaluate the changes in protein structure dynamics based on HDX mass spectrometry analysis. Moreover, the statistical analysis can be carried out for both m/z value and deuterium incorporation rate. In addition, the software package can be used for the data generated from a wide range of mass spectrometry instruments.

2011-01-01

141

On the inverse problem of statistical physics: from irreversible semigroups to chaotic dynamics

NASA Astrophysics Data System (ADS)

We show that all measure preserving stationary Markov processes arise as projections of Kolmogorov dynamical systems which have positive entropy production and are prototypes of chaos. This result not only contributes to the clarification of the relation of dynamics with stochastic processes but also shows the physical significance of the Misra-Prigogine-Courbage theory of irreversibility in the more general context of the inverse problem of statistical physics. Because we want positivity preserving transformations, our procedure although analogous to the Sz-Nagy-Foias Dilation theory has a different viewpoint, that of positive dilations.

Antoniou, I.; Gustafson, K.; Suchanecki, Z.

142

Sensitivity Properties of a Biosphere Model Based on BATS and a Statistical-Dynamical Climate Model

A biosphere model based on the Biosphere-Atmosphere Transfer Scheme (BATS) and the Saltzman-Vernekar (SV) statistical-dynamical climate model is developed. Some equations of BATS are adopted either intact or with modifications, some are conceptually modified, and still others are replaced with equations of the SV model.The model is designed so that it can be run independently as long as the parameters

Taiping Zhang

1994-01-01

143

Activities in HPM effects phenomenology at LLNL under the DNA/SDI Lth-6 effort

During the fiscal years 1984-1986, DNA funded an effort at the Lawrence Livermore National Laboratory under the SDI/Lth-6 program to develop models and to study the phenomenology of HPM interaction with systems. The effort concentrated on the following areas: linear coupling/modeling; linear coupling/experiments; nonlinear coupling/modeling; component failure/modeling; component characterization; and electronic subsystem characterization. This report sumarizes these subject areas.

Cabayan, H.S.; King, R.J.

1988-01-01

144

Path integral molecular dynamics for Bose-Einstein and Fermi-Dirac statistics

NASA Astrophysics Data System (ADS)

In this paper, we propose a promising extension of the path integral molecular dynamics method to Bose-Einstein and Fermi-Dirac statistics. The partition function for the quantum statistics was rewritten in a form amenable to the molecular dynamics method with the aid of an idea of pseudopotential for the permutation of particles. Our pseudopotential, here, is a rigorous one describing the whole effect of Bose-Einstein and Fermi-Dirac statistics. For a model calculation, we chose a system consisting of three independent particles in a one-dimensional harmonic well. The calculation has been performed for the particles obeying Bose-Einstein and Fermi-Dirac statistics. The calculated kinetic and potential energies were in excellent agreement with the analytical results even near the ground state. It was found that the pseudopotential shows attractive and repulsive characters for the static properties of Bose-Einstein and Fermi-Dirac particles, respectively. For interacting model particle systems, we studied a bosonic triatomic cluster. The calculated thermodynamic quantities were in qualitative agreement with those obtained by Fourier path integral Monte Carlo calculation.

Miura, Shinichi; Okazaki, Susumu

2000-06-01

145

The non-equilibrium statistical mechanics of a simple geophysical fluid dynamics model

NASA Astrophysics Data System (ADS)

Lorenz [1] has devised a dynamical system that has proved to be very useful as a benchmark system in geophysical fluid dynamics. The system in its simplest form consists of a periodic array of variables that can be associated with an atmospheric field on a latitude circle. The system is driven by a constant forcing, is damped by linear friction and has a simple advection term that causes the model to behave chaotically if the forcing is large enough. Our aim is to predict the statistics of Lorenz' model on the basis of a given average value of its total energy - obtained from a numerical integration - and the assumption of statistical stationarity. Our method is the principle of maximum entropy [2] which in this case reads: the information entropy of the system's probability density function shall be maximal under the constraints of normalization, a given value of the average total energy and statistical stationarity. Statistical stationarity is incorporated approximately by using `stationarity constraints', i.e., by requiring that the average first and possibly higher-order time-derivatives of the energy are zero in the maximization of entropy. The analysis [3] reveals that, if the first stationarity constraint is used, the resulting probability density function rather accurately reproduces the statistics of the individual variables. If the second stationarity constraint is used as well, the correlations between the variables are also reproduced quite adequately. The method can be generalized straightforwardly and holds the promise of a viable non-equilibrium statistical mechanics of the forced-dissipative systems of geophysical fluid dynamics. [1] E.N. Lorenz, 1996: Predictability - A problem partly solved, in Proc. Seminar on Predictability (ECMWF, Reading, Berkshire, UK), Vol. 1, pp. 1-18. [2] E.T. Jaynes, 2003: Probability Theory - The Logic of Science (Cambridge University Press, Cambridge). [3] W.T.M. Verkley and C.A. Severijns, 2014: The maximum entropy principle applied to a dynamical system proposed by Lorenz, Eur. Phys. J. B, 87:7, http://dx.doi.org/10.1140/epjb/e2013-40681-2 (open access).

Verkley, Wim; Severijns, Camiel

2014-05-01

146

Statistical dynamics and predictability in a climate model of intermediate complexity

NASA Astrophysics Data System (ADS)

The notion of climate predictability is introduced in terms of the relative importance of initial and boundary conditions to the evolution of climate-like dynamical systems. The dominance of the latter is identified by a newly introduced time scale called the climate predictability time. Because climate data sets defined with averages shorter than the predictability time are especially susceptible to internal variability, special attention was given to investigating the sensitivity that the climate predictability time exhibits to various physical processes. To accomplish this, the statistical dynamical model (SDM) framework is combined with turbulence closure theory to create simplified climate models whose predictability properties can easily be deduced. A quasigeostrophic model of intermediate complexity (MIC) is formulated using statistical closure theory and closed using the direct interaction approximation (DIA). A preliminary set of experiments indicate that that the predictability time is extended considerably by the presence of a more slowly evolving medium, such as an ocean. These experiments also indicate that climate statistics in ocean-atmosphere coupled systems can be just as sensitive to initial conditions in the atmosphere as they are to initial conditions in the ocean. These results suggest that the ocean may play an important role in amplifying errors in the atmosphere and that special care may be necessary when initializing the atmospheric component of general circulation models (GCMs) to avoid contaminating climate projections with chaotic error growth. More generally, this work details a robust application of statistical closure theory to the climate problem. It demonstrates how the SDM framework can be flexibly applied to studies of climate and, most importantly, provides a highly flexible implementation of an SDM, which can continue to serve as a tool to help fill the gap in our current understanding of climate dynamics.

Andrade, David B.

147

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

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.

2012-01-01

148

NASA Astrophysics Data System (ADS)

To bridge the resolution gap between the outputs of global climate models (GCMs) and finer-scale data needed for studies of the climate change impacts, two approaches are widely used: dynamical downscaling, based on application of regional climate models (RCMs) embedded into the domain of the GCM simulation, and statistical downscaling (SDS), using empirical transfer functions between the large-scale data generated by the GCM and local measurements. In our contribution, we compare the performance of different variants of both techniques for the region of Central Europe. The dynamical downscaling is represented by the outputs of two regional models run in the 10 km horizontal grid, ALADIN-CLIMATE/CZ (co-developed by the Czech Hydrometeorological Institute and Meteo-France) and RegCM3 (developed by the Abdus Salam Centre for Theoretical Physics). The applied statistical methods were based on multiple linear regression, as well as on several of its nonlinear alternatives, including techniques employing artificial neural networks. Validation of the downscaling outputs was carried out using measured data, gathered from weather stations in the Czech Republic, Slovakia, Austria and Hungary for the end of the 20th century; series of daily values of maximum and minimum temperature, precipitation and relative humidity were analyzed. None of the regional models or statistical downscaling techniques could be identified as the universally best one. For instance, while most statistical methods misrepresented the shape of the statistical distribution of the target variables (especially in the more challenging cases such as estimation of daily precipitation), RCM-generated data often suffered from severe biases. It is also shown that further enhancement of the simulated fields of climate variables can be achieved through a combination of dynamical downscaling and statistical postprocessing. This can not only be used to reduce biases and other systematic flaws in the generated time series, but also to further localize the RCM outputs beyond the resolution of their original grid. The resulting data then provide a suitable input for subsequent studies of the local climate and its change in the target region.

Miksovsky, J.; Huth, R.; Halenka, T.; Belda, M.; Farda, A.; Skalak, P.; Stepanek, P.

2009-12-01

149

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

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

2014-01-01

150

Specificity of mathematical description of statistical and dynamical properties of CELSS

NASA Astrophysics Data System (ADS)

CELSS for long-term space missions has to be possessed high level of matter turnover closure. Designing, studying, and maintaining such kind of systems seems to be not possible without accounting their specificity -high closure. For measuring this specific property potentially universal coefficient of closure is suggested and disscussed. It can be shown standard statistical formulas are incorrect for estimating mean values of biomass of CELSS components. Account-ing closure as specific constraint of closed ecological systems allows obtaining correct formulas for calculating mean values of biomass and composition of chemical compounds of CELSS. Errors due to using standard statistical evaluations are discussed. Organisms composing bi-ological LSS consume and produce spectrum of different substances. Providing high level of closure -the absence of deadlocks -depends on accuracy of adjusting all organisms input and output to each other. This is practical objective of high importance. Adequate mathematical models ought to describe possibility of organisms to vary their consumption and production spectrum (stoichiometric ratio). Traditional ecological models describing dynamics of limiting element can not be adequately applied for describing CELSS dynamics over all possible oper-ating regimes. Possible use of adaptive metabolism models for providing correct description of CELSS dynamics is considered.

Bartsev, Sergey

151

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

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

152

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

153

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

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

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

2013-10-21

154

Novel dynamic measures of emetic behavior in musk shrews.

The emetic reflex occurs as a pattern of motor responses produced by a network of neurons in the hindbrain. Despite an understanding of the sequence of motor outputs that form an emetic episode (EE), the variability in the dynamics of multiple EEs across time remains a mystery. Many clinical investigations rely on once a day patient recall of total amount of vomiting, and preclinical studies frequently report only the total number of EE per unit time. The aim of the current study was to develop novel temporal measures of emetic activation in a preclinical model. Male and female musk shrews were tested with prototypical emetic stimuli: motion exposure (1 Hz), nicotine (5 mg/kg, sc), and copper sulfate (120 mg/kg, ig). New emetic measures included duration (time from first to last episode), rate, standard deviation of the inter-episode interval (SD-I), and a survival analysis of emetic latency (analyzed with Cox regression). Behavioral patterns associated with emesis were also assessed using statistical temporal pattern (T-pattern) analysis to measure nausea-like behaviors (e.g., immobility). The emetic stimuli produced different levels of total EE number, duration, rate, and SD-I. A typical antiemetic, the neurokinin 1 receptor antagonist CP-99,994, suppressed the number of EEs but was less effective for reducing the duration or prolonging the emetic latency. Overall, the current study shows the use of novel dynamic behavioral measures to more comprehensively assess emesis and the impact of therapies. PMID:23953843

Horn, Charles C; Wang, Hong; Estival, Laureline; Meyers, Kelly; Magnusson, Magnus S

2013-12-01

155

Summary An improved statistical-dynamical downscaling method for the regionalization of large-scale climate analyses or simulations\\u000a is introduced. The method is based on the disaggregation of a multi-year time-series of large-scale meteorological data into\\u000a multi-day episodes of quasi-stationary circulation. The episodes are subsequently grouped into a defined number of classes.\\u000a A regional model is used to simulate the evolution of weather

U. Fuentes; D. Heimann

2000-01-01

156

q-deformed statistical-mechanical structure in the dynamics of the Feigenbaum attractor

NASA Astrophysics Data System (ADS)

We show that the two complementary parts of the dynamics associated to the Feigenbaum attractor, inside and towards the attractor, form together a q-deformed statistical-mechanical structure. A time-dependent partition function produced by summing distances between neighboring positions of the attractor leads to a q-entropy that measures the ratio of ensemble trajectories still away at a given time from the attractor (and the repellor). The values of the q-indexes are given by the attractor's universal constants, while the thermodynamic framework is closely related to that first developed for multifractals.

Robledo, A.

2010-09-01

157

NASA Astrophysics Data System (ADS)

Conventional studies of electron dynamics are usually based on summed measurements of the electron counts so as to produce average velocity phase space densities. The auto-correlation technique implemented on Cluster allows short time scale dynamics to also be inferred from the analysis of the auto-correlation functions (ACFs) of the DWP Particle Correlator experiment , which is based on rapidly sampled time series of electron counts of approximately millisecond duration. This allows meaningful energy dependent categorization of the underlying non - Poisson statistical electron state via such parameters as the Index of Dispersion (variance/mean ratio of time series of electron counts). Examples are presented of this analysis in the plasma regions encountered by Cluster e.g. near reconnection sites at the magnetopause and in the magnetotail, together with a discussion of what this may reveal about the kinetic , non-linear processes that are occurring in such plasma regions.

Buckley, A. M.; Carozzi, T.; Gough, M. P.; Chambers, E. C.

2003-04-01

158

NASA Astrophysics Data System (ADS)

The definition of complexity through Statistical Complexity Measures (SCM) has recently seen major improvements. Mostly, the 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 disordered 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.

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

2014-09-01

159

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

160

NASA Astrophysics Data System (ADS)

We examine the implications for the distribution of extrasolar planets based on the null results from two of the largest direct imaging surveys published to date. Combining the measured contrast curves from 22 of the stars observed with the VLT NACO adaptive optics system by Masciadri and coworkers and 48 of the stars observed with the VLT NACO SDI and MMT SDI devices by Biller and coworkers (for a total of 60 unique stars), we consider what distributions of planet masses and semimajor axes can be ruled out by these data, based on Monte Carlo simulations of planet populations. We can set the following upper limit with 95% confidence: the fraction of stars with planets with semimajor axis between 20 and 100 AU, and mass above 4 MJup, is 20% or less. Also, with a distribution of planet mass of dN/dM~M-1.16 in the range of 0.5-13 MJup, we can rule out a power-law distribution for semimajor axis (dN/da~a?) with index 0 and upper cutoff of 18 AU, and index -0.5 with an upper cutoff of 48 AU. For the distribution suggested by Cumming et al., a power-law of index -0.61, we can place an upper limit of 75 AU on the semimajor axis distribution. In general, we find that even null results from direct imaging surveys are very powerful in constraining the distributions of giant planets (0.5-13 MJup) at large separations, but more work needs to be done to close the gap between planets that can be detected by direct imaging, and those to which the radial velocity method is sensitive.

Nielsen, Eric L.; Close, Laird M.; Biller, Beth A.; Masciadri, Elena; Lenzen, Rainer

2008-02-01

161

An open-source wireless sensor stack: from Arduino to SDI-12 to Water One Flow

NASA Astrophysics Data System (ADS)

Implementing a large-scale streaming environmental sensor network has previously been limited by the high cost of the datalogging and data communication infrastructure. The Christina River Basin Critical Zone Observatory (CRB-CZO) is overcoming the obstacles to large near-real-time data collection networks by using Arduino, an open source electronics platform, in combination with XBee ZigBee wireless radio modules. These extremely low-cost and easy-to-use open source electronics are at the heart of the new DIY movement and have provided solutions to countless projects by over half a million users worldwide. However, their use in environmental sensing is in its infancy. At present a primary limitation to widespread deployment of open-source electronics for environmental sensing is the lack of a simple, open-source software stack to manage streaming data from heterogeneous sensor networks. Here we present a functioning prototype software stack that receives sensor data over a self-meshing ZigBee wireless network from over a hundred sensors, stores the data locally and serves it on demand as a CUAHSI Water One Flow (WOF) web service. We highlight a few new, innovative components, including: (1) a versatile open data logger design based the Arduino electronics platform and ZigBee radios; (2) a software library implementing SDI-12 communication protocol between any Arduino platform and SDI12-enabled sensors without the need for additional hardware (https://github.com/StroudCenter/Arduino-SDI-12); and (3) 'midStream', a light-weight set of Python code that receives streaming sensor data, appends it with metadata on the fly by querying a relational database structured on an early version of the Observations Data Model version 2.0 (ODM2), and uses the WOFpy library to serve the data as WaterML via SOAP and REST web services.

Hicks, S.; Damiano, S. G.; Smith, K. M.; Olexy, J.; Horsburgh, J. S.; Mayorga, E.; Aufdenkampe, A. K.

2013-12-01

162

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

163

Using statistical mean state dynamics to understand jet and zonon formation in beta-plane turbulence

NASA Astrophysics Data System (ADS)

Zonal jets and associated non-zonal structures, such as nonlinearly modified Rossby waves (zonons) and vortices, are prominent features of beta-plane turbulence and also play a central role in determining the statistical mean turbulent state. Understanding the emergence and equilibration of these large scale coherent structures and their coexistence with turbulence in planetary atmospheres constitutes a fundamental theoretical problem. Stochastic Structural Stability Theory (S3T) provides a framework for understanding turbulence based on the statistical mean state dynamics closed at second order. In order to elucidate coherent structure dynamics, predictions for formation and equilibration of zonal and non-zonal structures made using S3T will be compared with results of simulations made using the associated quasi-linear and nonlinear models. S3T will be shown to accurately predict the bifurcation structure associated with coherent structure formation as well as their finite amplitude equilibrium and their ultimate breakdown as a function of parameters. The physical mechanism by which jets and zonons form as linear S3T instabilities and the finite amplitude regime of jet and non-zonal structure coexistence in S3T and nonlinear simulations will be described.

Farrell, B.; Ioannou, P.; Constantinou, N.

2013-12-01

164

NASA Astrophysics Data System (ADS)

Winter storms cause very high insurance losses in Europe. In order to allow for a valuable risk assessment, both storm frequency on a large scale and storm and gust intensity on a small scale are precondition for construction of loss estimation tools. The presented common effort between research and insurance consists of a large scale identification of intense storms for both historical (reanalysis) data and present day climate simulations in order to extend the statistical basis of extreme events to a number of 10000 storms. For historical storms, dynamical downscaling is performed with the regional climate model COSMO-CLM. Since dynamical downscaling is not feasible for 10000 events, a statistical downscaling tool is derived from large scale storm tracks, historical storms in the period 1960-2010, defined from potential loss estimation based on NCEP reanalyses, re-simulated in a two-step nesting approach using COSMO-CLM 4.8 in 0.165° and 0.0625° resolution with ERA-forcing and from observations. A method of a combined probabilistic downscaling and MOS technique is proposed for the enhancement of gust speed estimations. The methodical procedure is presented along with results and a quality check for both spatial and temporal correctness, considering errors in terms of RMSE and the form of gust distributions in order to provide gust estimations which are unbiased in comparison to the observations.

Born, K.; Drinka, R.; Georgiadis, A.; Haas, R.; Ludwig, P.; Karremann, M. K.; Podlaha, A.; Ulbrich, S.; Pinto, J. G.

2012-04-01

165

NASA Astrophysics Data System (ADS)

The various core technologies developed from the SDI programs are described and the cost and weight reductions that have resulted from the systematic exploitation of today's aerospace expertise are characterized. Avionics, sensors, and on-orbit propulsion systems can be utilized in developing small, low-cost devices for space exploration with significant performance capabilities. It is shown how the resulting core technologies can be employed in constructing three specific types of miniaturized spacecraft: a 16 kg planetary rover, a 200 kg lunar lander, and a 45 kg space vehicle repair and rescue craft.

Farmer, Dean A.

1992-08-01

166

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

167

National Technical Information Service (NTIS)

The DoD / SDI-DEW Program has asked LLNL to study the feasibility of designing and constructing large ultra-precision machine tools for directly machining and inspecting precision components for the SDI sponsored Alpha Laser Program. Recently, they have a...

I. F. Stowers

1992-01-01

168

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

169

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

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

170

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

171

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

172

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

173

Defect-phase-dynamics approach to statistical domain-growth problem of clock models

NASA Technical Reports Server (NTRS)

The growth of statistical domains in quenched Ising-like p-state clock models with p = 3 or more is investigated theoretically, reformulating the analysis of Ohta et al. (1982) in terms of a phase variable and studying the dynamics of defects introduced into the phase field when the phase variable becomes multivalued. The resulting defect/phase domain-growth equation is applied to the interpretation of Monte Carlo simulations in two dimensions (Kaski and Gunton, 1983; Grest and Srolovitz, 1984), and problems encountered in the analysis of related Potts models are discussed. In the two-dimensional case, the problem is essentially that of a purely dissipative Coulomb gas, with a sq rt t growth law complicated by vertex-pinning effects at small t.

Kawasaki, K.

1985-01-01

174

Graphical models for probabilistic reasoning are now in widespread use. Many approaches have been developed such as Bayesian network. A newly developed approach named as dynamic uncertain causality graph (DUCG) is initially presented in a previous paper, in which only the inference algorithm in terms of individual events and probabilities is addressed. In this paper, we first explain the statistic basis of DUCG. Then, we extend the algorithm to the form of matrices of events and probabilities. It is revealed that the representation of DUCG can be incomplete and the exact probabilistic inference may still be made. A real application of DUCG for fault diagnoses of a generator system of a nuclear power plant is demonstrated, which involves variables. Most inferences take with a laptop computer. The causal logic between inference result and observations is graphically displayed to users so that they know not only the result, but also why the result obtained. PMID:24807944

Qin Zhang; Chunling Dong; Yan Cui; Zhihui Yang

2014-04-01

175

Purpose: To investigate the statistical reproducibility of craniocaudal probability distribution function (PDF) of interfraction lung motion using dynamic magnetic resonance imaging. Methods and Materials: A total of 17 subjects, 9 healthy volunteers and 8 lung tumor patients, underwent two to three continuous 300-s magnetic resonance imaging scans in the sagittal plane, repeated 2 weeks apart. Three pulmonary vessels from different lung regions (upper, middle, and lower) in the healthy subjects and lung tumor patients were selected for tracking, and the displacement PDF reproducibility was evaluated as a function of scan time and frame rate. Results: For both healthy subjects and patients, the PDF reproducibility improved with increased scan time and converged to an equilibrium state during the 300-s scan. The PDF reproducibility at 300 s (mean, 0.86; range, 0.70-0.96) were significantly (p < 0.001) increased compared with those at 5 s (mean, 0.65; range, 0.25-0.79). PDF reproducibility showed less sensitivity to imaging frame rates that were >2 frames/s. Conclusion: A statistically significant improvement in PDF reproducibility was observed with a prolonged scan time among the 17 participants. The confirmation of PDF reproducibility over times much shorter than stereotactic body radiotherapy delivery duration is a vital part of the initial validation process of probability-based treatment planning for stereotactic body radiotherapy for lung cancer.

Cai Jing; Read, Paul W.; Larner, James M. [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States); Jones, David R. [Department of Surgery, University of Virginia, Charlottesville, VA (United States); Benedict, Stanley H. [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States); Sheng Ke [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States)], E-mail: ks2mc@virginia.edu

2008-11-15

176

NASA Astrophysics Data System (ADS)

This paper concerns the response of uncertain vibro-acoustic and structural dynamic systems. Here, exact expressions are presented for the statistics of systems with a random rank-one component. The expressions are derived using the Sherman-Morrison update formula that gives the exact expression of the disturbed response for any magnitude of the disturbance. It is shown that the probability density function (pdf) of any transfer function is a simple function of the pdf of the disturbance magnitude of the random component. The expressions for the mean, variance, and covariance of any transfer function, and at any frequency, of a random system necessitate non-trivial integrals. Exact, including closed-form, expressions of these integrals are derived in the particular cases of a real or complex normal disturbance magnitude, and qualitative differences between these two cases are highlighted. The theoretical and practical advantages of the theory are discussed and applied to a model of a bladed disk subjected to random damage. The comparison with Monte-Carlo simulations demonstrates that the statistics can be evaluated efficiently and precisely. The theory, derived formally in the context of discretised systems, is directly applicable to continuous systems.

Lecomte, Christophe

2013-05-01

177

NASA Astrophysics Data System (ADS)

Global circulation models (GCM) are increasingly capable of making relevant predictions of seasonal and long-term climate variability, thus improving prospects of predicting impact on crop yields. This is particularly important for semi-arid West Africa where climate variability and drought threaten food security. Translating GCM outputs into attainable crop yields is difficult because GCM grid boxes are of larger scale than the processes governing yield, involving partitioning of rain among runoff, evaporation, transpiration, drainage and storage at plot scale. It therefore requires the use of downscaling methods. This study analyzes the performance of both dynamical and statistical downscaling techniques in simulating crop yield at local scale. A detailed case study is conducted using historical weather data for Senegal, applied to the crop model SARRAH for simulating several tropical cereals (sorghum, millet, maize) at local scale. This control simulation is used as a benchmark to evaluate a set of Regional Climate Models (RCM) simulations, forced by ERA-Interim, from the ENSEMBLES project and a statistical downscaling method, the CDF-Transform, used to correct biases in RCM outputs. We first evaluate each climate variable that drives the simulated yield in the control simulation (radiation, rainfall, temperatures). We then simulate crop yields with RCM outputs (with or without applying the CDG-Transform) and evaluate the performance of each RCM in regards to crop yield simulations.

Sultan, B.; Oettli, P.; Vrac, M.; Baron, C.

2010-12-01

178

The recently developed statistical temperature molecular dynamics (STMD) method [Kim et al., Phys. Rev. Lett. 97, 050601 (2006)] is applied to the simulation of liquid crystalline soft matter systems. Results are presented demonstrating how, in combination with anisotropic soft core potentials, STMD simulation is able to sample efficiently across a large temperature window; and thus bridge across isotropic-liquid crystal phase transitions. Data is presented for two separate systems, namely, a single-site interaction model and an AB rod-coil block copolymer. The results are in excellent agreement with phase diagrams calculated by a series of traditional canonical molecular dynamics simulations bridging similar temperature/energy windows. In addition to the usual energetic and structural information, the STMD technique provides the temperature dependence of the entropy, free energy and heat capacity of the system as by-products of the single simulation. The combined soft-core/STMD strategy is presented as an effective means of scanning the phase diagram of a simple molecular interaction model to understand the relationship between molecular structure and phase behavior. PMID:20550414

Lintuvuori, Juho S; Wilson, Mark R

2010-06-14

179

NASA Astrophysics Data System (ADS)

Future loss estimation is an important planning tool for insurance companies. In particular, good estimates of ranges of uncertainty are necessary for the assessment of climate change impacts and its implications. In this study, the probabilistic aspect of loss estimation is considered by prediction of loss distributions instead of best estimates for average values. For this purpose, downscaling of global climate model data is combined with regional modelling and a probabilistic loss function, which describes the relation between wind speeds and losses. The statistical-dynamical downscaling (SDD) approach is applied to reanalysis data and ECHAM5 climate scenarios for 1960-2100. The SDD consists of a cluster classification of storm relevant weather episodes, referred to as weather types (WT), dynamical downscaling for WT episodes and a recombination of wind speed distributions on the regional scale using frequencies of WT occurrences. Changes in wind distributions for different time periods are divided into external changes due to variability of WT frequencies and internal changes due to wind speed distributions within WT classes. The losses are estimated using generalized loss functions, which fit wind speeds locally to observed loss frequencies via quantile regression. The results corroborate earlier findings, which describe an enhancement of loss potentials for Germany associated with winter storms under future climate conditions. In addition, uncertainty ranges in terms of quantile functions allow for a discussion of loss potential changes with respect to the relative sizes of events.

Born, K.; Karremann, M. K.; Ludwig, P.; Pinto, J.

2010-09-01

180

NASA Astrophysics Data System (ADS)

We present a detailed experimental study of high-temperature self-propagating fronts using image processing techniques. The intrinsic features of the wave propagation are investigated as a function of the combustion temperature TC for a model system made of titanium and silicon powders. Different front behavior is realized by changing the molar ratio x of the mixture Ti+xSi . Outside the range x=[0.3,1.5] , no thermal front is propagating while inside, three regimes are observed: steady-state combustion which is characterized by a flat front propagating at constant velocity and two unsteady regimes. The combustion temperature (or the corresponding ratio x ) is thus playing the role of bifurcation parameter leading from stationary state to complex behavior. In the titanium-rich mixture, the position of the front oscillates and hot spots propagate along the external border of the sample. At lower amounts of Ti, localized bright regions appear randomly and deform the front profile. The associated dynamical behavior is a relay-race mechanism which becomes more pronounced close to the combustion limit. Methods are developed to characterize the structural and dynamical properties of thermal waves near instabilities, with a special emphasis on the statistical aspects. It is clearly demonstrated that the mesoscopic scale phenomena interfere significantly with the macroscopic behavior. The experiments reveal front behaviors that cannot be described using the usual macroscopic theories.

Rogachev, A. S.; Baras, F.

2009-02-01

181

Dynamical and Statistical Wind Downscaling in the Northeast of the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Estimations of possible changes of wind variability at the regional scale as a response to the evolution of large scale climate entail relevant economic and ecological implications for society, as for instance, the assessment of the variations and sustainability in wind energy resources. Not only in this context but also from a meteorological point of view, the evaluation of surface wind variability involves many interesting aspects that are worth to be analyzed. The limited reliability of the general circulation models at the regional/local scale requires the use of downscaling techniques to derive regional climate variability from the large scale circulation. Dynamical, statistical or a combination or both approaches can be applied to the downscaling problem to explore the wind field behavior in the region of interest. In this work, the potential predictability of the wind speed is evaluated by means of its relationship with the atmospheric circulation over the North Atlantic area using different methodologies. For this aim, wind speed observations from the region of Navarra, Northeast of the Iberian Peninsula, are employed; the data span a 14 years period, from 1992 to 2005. A dynamical downscaling using the Weather Research and Forecast (WRF) model is used to analyze the wind variability at daily time scales. The spatial wind variability is analyzed by dividing the region into various subregions by means of cluster analysis. The temporal variability is addressed by classifying the wind fields into weather types (wind circulation types) with similar spatial structure. The model is skillful in identifying the observed subregions and in reproducing the temporal wind variability at most of them. In addition, the spatial structure of the wind circulation types is generally reproduced by the simulation, with a tendency to underestimate the spatial wind speed variability. The statistical methodology explores the variability of wind speed and also wind power production at monthly timescales and consists in a linear technique which isolates optimal correlated modes of variability between the synoptic fields over the North Atlantic and the observed wind velocity (Canonical Correlation Analysis). Results evidence the existence of wind predictability in the region of study at monthly timescales. An assessment of the sensitivity of the methodology is performed as a first step in the evaluation of the potential sources of uncertainty affecting the regional estimations of the wind field. The statistical relationship found during the period of available observations is used to perform a climatological reconstruction of the surface wind field within the last five centuries using reanalysis, observational and reconstruction data sources. This evaluation of past wind variability could have relevant applications for the study of regional wind predictability over the 21th century.

Gonzalez-Rouco, J.; Jimenez, P. A.; Bustamante, E. G.; Navarro, J.; Montavez, J.

2008-12-01

182

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

183

ERIC Educational Resources Information Center

The report describes a large-scale computerized system for Selective Dissemination of Information (SDI) developed over the past five years at the U.S. Army Electronics Command to serve its technical personnel. The system, which uses as its document base the current accessions of the Defense Documentation Center, was developed in three phases: (1)…

Wixon, D. W.; Housman, E. M.

184

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

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

2011-01-01

185

A statistical-dynamical approach to represent Greenland ocean-ice sheet interactions

NASA Astrophysics Data System (ADS)

An understanding of the dynamics of the Greenland ice sheet is fundamental, because of its potential to contribute strongly to future sea level rise. In recent years there has been a discussion about the role of the ocean in the Greenland ice sheet's present and future mass balance. The ocean interacts with the ice sheet's outlet glaciers via the water circulation in the fjords and considerably affects melting at the termini of the outlet glaciers. Processes related to this interaction are difficult to represent in Greenland-wide ice-sheet models because grid resolution of such models is typically 10 km, whereas large fjords are more commonly only 1 to 5 km wide. Local refinement techniques (e.g. finite elements with adaptive mesh) can be a way of addressing that problem but are still computationally expensive to run. Here we propose a simpler, statistical-dynamical approach suited for large ensemble simulations over 100- to 1000-year integration times, in the EMIC spirit: the fjord-outlet glacier system is restricted to its most fundamental dynamics, controlled by a handful of parameters describing the major characteristics of the system. The model has a generic structure, i.e., it is designed such that it applies to every Greenland outlet glacier. Some of its parameters are fixed by using the (little) available observational data - e.g. for Helheim, Kangerdlugssuaq and Jakobshavn Isbrae - other parameters may vary depending on location. It is not our aim to simulate every single small outlet glacier in its full accuracy; but we aim to represent, on average, important characteristics like ice discharge and general advance/retreat rate on a regional scale over major catchment areas. Aspects of the coupling strategy with the 3D ice-sheet model (SICOPOLIS) are discussed, e.g., critical issues such as the treatment of mass balance. Preliminary design and results will be presented.

Perrette, Mahé; Calov, Reinhard; Ganopolski, Andrey; Robinson, Alex

2013-04-01

186

NASA Astrophysics Data System (ADS)

Dynamical complexity detection for output time series of complex systems is one of the foremost problems in physics, biology, engineering, and economic sciences. Especially in geomagnetism and magnetospheric physics, accurate detection of the dissimilarity between normal and abnormal states (e.g. pre-storm activity and magnetic storms) can vastly improve geomagnetic field modelling as well as space weather forecasting, respectively. Nonextensive statistical mechanics through Tsallis entropy provides a solid theoretical basis for describing and analyzing complex systems out of equilibrium, particularly systems exhibiting long-range correlations or fractal properties. Entropy measures (e.g., Tsallis entropy, Shannon entropy, block entropy, Kolmogorov entropy, T-complexity, and approximate entropy) have been proven effectively applicable for the investigation of dynamical complexity in Dst time series. It has been demonstrated that as a magnetic storm approaches, there is clear evidence of significantly lower complexity in the magnetosphere. The observed higher degree of organization of the system agrees with results previously inferred from fractal analysis via estimates of the Hurst exponent based on wavelet transform. This convergence between entropies and linear analyses provides a more reliable detection of the transition from the quiet time to the storm time magnetosphere, thus showing evidence that the occurrence of an intense magnetic storm is imminent. Moreover, based on the general behavior of complex system dynamics it has been recently found that Dst time series exhibit discrete scale invariance which in turn leads to log-periodic corrections to scaling that decorate the pure power law. The latter can be used for the determination of the time of occurrence of an approaching magnetic storm.

Balasis, G.

2012-04-01

187

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; Gunasekaran, Paramasamy

2013-01-01

188

Statistical Relation of Dynamic Sar Arc Characteristics To Substorms and Storms

NASA Astrophysics Data System (ADS)

It is known that mid-latitude red arcs (SAR arcs) are related to magnetic storms de- fined by variations of the Dst index. By using data of spectrophotometric observations at the Yakutsk meridian (Maimaga st. CGMC: 57 N; 200 E) we have shown that the occurence and/or brightness of SAR arc take place during the substorm expan- sion phase (Geomagnetism and Aeronomy, V.39, N.6,P.697, 1999). Here we use of SAR arc 700 hours registration data in 1989-2000 and carry out the correlation cou- pling analysis of 630 nm emission intensity in an arc (Im) and the velocity of the arc equatorward movement (Vm) with magnetic indices AL, Dst and ASYH. The follow- ing peculiarities of influence of the substorm and storm to the SAR arc dynamics are revealed: 1) The SAR arc intensity during the weak magnetic storm of Dst-50 nT is defined by the auroral index AL with a correlation coefficient R=-0.45-0.55. The significant rela- tion of arc intensity to Dst is not but it is essential with ASYH-index. It is assumed that the AL-dependence of Im is most likely caused by the considerable contribution of the asymmetric ring currrent arising during a substorm to the SAR arc generation. 2) In the samplings of data for the moderate storms of -50Dst-120 nT the statistically significant dependence (R=-0.5-0.7) of arc luminosity on the ring currrent intensity appears, that is in agreement with early results. In this case, the significant relation of Im to AL remains constant. 3) The velocity of SAR arc equatorward movement is of the significant dependence only on AL-index with R-0.5, that can be indicative of a conditionallity of this phenomenon by penetration of the non- stationary convection electric field to plasmasphere latitudes during a substorm. 4) The latitudinal distribu- tion of SAR arc intensity maximum location by the number of observation hours at the Yakutsk meridian is close to the normal one with a median at c=55 N (L=3) and it is of a half-width 6. It is supported that this latitude interval of SAR arc ob- servation is the statistical mapping of a more dynamic region of outer plasmasphere L-shells into which the ring currrent penetrates during substorms at Kp=3-5. 5) Most probable values of hourly average parameters of SAR arc and geomagnetic activity in used rows of data are: Im=140 R, Vm=20 m/s, AL=-230 nT, Dst=-40 nT.

Ievenko, I. B.; Alexeyev, V. N.

189

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

NASA Astrophysics Data System (ADS)

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

Campa, Alessandro; Dauxois, Thierry; Ruffo, Stefano

2009-09-01

190

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

Wereszczynski, Jeff; McCammon, J Andrew

2012-02-01

191

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 < terangle 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 ? =? ^{-1} ); 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 ? ? 1 goes as < terangle ˜ 1/sqrt{? }.

Cáceres, Manuel O.

2014-04-01

192

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

193

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

NASA Technical Reports Server (NTRS)

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

Zhang, Taiping

1994-01-01

194

Statistical-dynamical downscaling of wind roses over the Czech Republic

NASA Astrophysics Data System (ADS)

The present study describes a new method for statistical-dynamical downscaling that combines two different approaches, namely, a set of patterns simulated with a numerical flow model and a transformation function used to process both calculated data and measurements at a reference station. The combined method produces wind roses and wind speed histograms at an arbitrary location in the model domain. The inflow wind direction represented the key parameter to define a set of wind field simulations. The other two inflow parameters, namely, thermal stratification and geostrophic wind speed, were derived from corresponding averaged soundings. The results showed that in the Czech Republic, there are areas where wind roses are deformed by the surrounding terrain. The deformations occur in relatively shallow and wide valleys, and they are more sensitive to the inflow wind direction. Calculated wind roses are compared to corresponding observations at 22 synoptic stations. The most frequent wind direction sector in simulations agreed with measurements at 17 stations. The resulting error in frequency in that sector was under 5 % at 10 stations. In general, the main features of the wind roses are modelled well, even at a relatively large distance from the reference station. However, better performance was achieved for smaller distances between reference station and the site. In further studies, a more extensive set of flow patterns with reduced intervals of thermal stratification and wind speed will likely improve calculated wind roses.

Svoboda, Jaroslav; Chladova, Zuzana; Pop, Lukas; Hosek, Jiri

2013-05-01

195

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

196

Complexity of the magnetosphere: Dynamical and statistical features from extensive correlated data.

NASA Astrophysics Data System (ADS)

The magnetosphere of Earth is a large scale open system driven by the turbulent solar wind, with the plasma processes ranging from the electron to the magnetohydrodynamic scales. The dynamical features exhibit spatio-temporal variations over four orders of magnitude, with the additional feature of overlapping scales in the solar wind and the magnetosphere. This makes the prediction of space weather (the variable conditions of geospace) from first principles a challenge. The extensive time series data of ground-based magnetic field measurements of the magnetospheric response and the spacecraft measurements of the solar wind plasma and field variables have been used to study the geospace using many techniques of complexity science. A database of geospace substorms consisting of more than million events is used in a study of the inherent statistical characteristics, with the main objective of characterizing the extreme events. The long-term correlations are studied using auto-correlation and mutual-information functions, yielding features represented by two exponents. The break in the exponents reflects the existence of two kinds of behavior, viz. the directly driven and internal magnetospheric features. The auto-correlation functions show stronger long-term correlation than the mutual information functions, which represent correlations of all orders. The return intervals for varying thresholds show long-range correlations with decreasing strength for higher thresholds, similar to multifractal systems. The detrended fluctuation analysis is used to compare the features of the magnetosphere to those of multiplicative random cascade processes.

Sharma, S.; Veeramani, T.

2009-05-01

197

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

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

198

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

199

This paper describes the use of multiple on-line sensors including electrical resistance tomography (ERT), dynamic light scattering (DLS) and ultrasound spectroscopy (USS) for real-time characterization of process operations processing emulsions and nanoparticle slurries. The focus is on making novel use of the spectroscopic data to develop multivariate statistical process control (MSPC) strategies. The ERT data at different normal operating conditions

Rui F. Li; Lande Liu; Xue Z. Wang; Richard Tweedie; Ken Primrose; Jason Corbett; Fraser McNeil-Watson

2009-01-01

200

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

201

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

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

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

2004-01-01

202

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

203

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

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

2013-01-01

204

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

205

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

206

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

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

207

OneGeology Web Services and Portal as a global geological SDI - latest standards and technology

NASA Astrophysics Data System (ADS)

The global coverage of OneGeology Web Services (www.onegeology.org and portal.onegeology.org) achieved since 2007 from the 120 participating geological surveys will be reviewed and issues arising discussed. Recent enhancements to the OneGeology Web Services capabilities will be covered including new up to 5 star service accreditation scheme utilising the ISO/OGC Web Mapping Service standard version 1.3, core ISO 19115 metadata additions and Version 2.0 Web Feature Services (WFS) serving the new IUGS-CGI GeoSciML V3.2 geological web data exchange language standard (http://www.geosciml.org/) with its associated 30+ IUGS-CGI available vocabularies (http://resource.geosciml.org/ and http://srvgeosciml.brgm.fr/eXist2010/brgm/client.html). Use of the CGI simpelithology and timescale dictionaries now allow those who wish to do so to offer data harmonisation to query their GeoSciML 3.2 based Web Feature Services and their GeoSciML_Portrayal V2.0.1 (http://www.geosciml.org/) Web Map Services in the OneGeology portal (http://portal.onegeology.org). Contributing to OneGeology involves offering to serve ideally 1:1000,000 scale geological data (in practice any scale now is warmly welcomed) as an OGC (Open Geospatial Consortium) standard based WMS (Web Mapping Service) service from an available WWW server. This may either be hosted within the Geological Survey or a neighbouring, regional or elsewhere institution that offers to serve that data for them i.e. offers to help technically by providing the web serving IT infrastructure as a 'buddy'. OneGeology is a standards focussed Spatial Data Infrastructure (SDI) and works to ensure that these standards work together and it is now possible for European Geological Surveys to register their INSPIRE web services within the OneGeology SDI (e.g. see http://www.geosciml.org/geosciml/3.2/documentation/cookbook/INSPIRE_GeoSciML_Cookbook%20_1.0.pdf). The Onegeology portal (http://portal.onegeology.org) is the first port of call for anyone wishing to discover the availability of global geological web services and has new functionality to view and use such services including multiple projection support. KEYWORDS : OneGeology; GeoSciML V 3.2; Data exchange; Portal; INSPIRE; Standards; OGC; Interoperability; GeoScience information; WMS; WFS; Cookbook.

Duffy, Tim; Tellez-Arenas, Agnes

2014-05-01

208

NASA Astrophysics Data System (ADS)

First, we analyze trajectories inside the Feigenbaum attractor and obtain the atypical weak sensitivity to initial conditions and loss of information associated to their dynamics. We identify the Mori singularities in its Lyapunov spectrum with the appearance of a special value for the entropic index q of the Tsallis statistics. Secondly, the dynamics of iterates at the noise-perturbed transition to chaos is shown to exhibit the characteristic elements of the glass transition, e.g. two-step relaxation, aging, subdiffusion and arrest. The properties of the bifurcation gap induced by the noise are seen to be comparable to those of a supercooled liquid above a glass transition temperature.

Robledo, A.; Baldovin, F.; Mayoral, E.

2005-09-01

209

This paper compares six statistical downscaling models (SDMs) and three regional climate models (RCMs) in their ability to downscale daily precipitation statistics in a region of complex topography. The six SDMs include regression methods, weather typing methods, a conditional weather generator, and a bias correction and spatial disaggregation approach. The comparison is carried out over the European Alps for current

J. Schmidli; C. M. Goodess; C. Frei; M. R. Haylock; Y. Hundecha; J. Ribalaygua; T. Schmith

2007-01-01

210

The authors have systematically examined the statistical properties of the unfolded states of series of polypeptides and the kinetics of their end-to-end contact (ring closure) formation by molecular dynamics simulations. The formation of an end-to-end contact follows a single-exponential decay as measured by the first-passage time. It is shown that the shifted Gaussian chain model can be applied to describe

Guanghui Ping; Shubhra Ghosh Dastidar; Yong Duan

2007-01-01

211

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

212

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

213

Artefacts can result when reconstructing a dynamic image sequence from inconsistent single photon emission computed tomography (SPECT) projection data acquired by a slowly rotating gantry. The artefacts can lead to biases in kinetic parameters estimated from time-activity curves generated by overlaying volumes of interest on the images. Insufficient sampling and truncation of projections by cone-beam collimators can cause additional artefacts. To overcome these sources of bias 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 modelling the spatial and temporal distribution of the radiopharmaceutical throughout the projected field of view. In the present work, we perform Monte Carlo simulations to study the effects of the temporal modelling on the statistical variability of the reconstructed spatiotemporal distributions. The simulations utilize fast methods for fully four-dimensional (4D) direct estimation of spatiotemporal distributions and their statistical uncertainties, using a spatial segmentation and temporal B-splines. The simulation results suggest that there is benefit in modelling higher orders of temporal spline continuity. In addition, the accuracy of the time modelling can be increased substantially without unduly increasing the statistical uncertainty, by using relatively fine initial time sampling to capture rapidly changing activity distributions. PMID:12200931

Reutter, B W; Gullberg, G T; Huesman, R H

2002-08-01

214

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

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

215

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

216

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation\\u000a Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining\\u000a the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical\\u000a downscaling. The method uses predictors that

Cecilia Hellström; Deliang Chen

2003-01-01

217

Dynamic Range Adaptation to Sound Level Statistics in the Auditory Nerve

The auditory system operates over a vast range of sound pressure levels (100–120 dB) with nearly constant discrimination ability across most of the range, well exceeding the dynamic range of most auditory neurons (20–40 dB). Dean et al. (Nat. Neurosci. 8:1684, 2005) have reported that the dynamic range of midbrain auditory neurons adapts to the distribution of sound levels in a continuous, dynamic stimulus by shifting towards the most frequently occurring level. Here we show that dynamic range adaptation, distinct from classic firing rate adaptation, also occurs in primary auditory neurons in anesthetized cats for tone and noise stimuli. Specifically, the range of sound levels over which firing rates of auditory-nerve (AN) fibers grows rapidly with level shifts nearly linearly with the most probable levels in a dynamic sound stimulus. This dynamic range adaptation was observed for fibers with all characteristic frequencies and spontaneous discharge rates. As in the midbrain, dynamic range adaptation improved the precision of level coding by the AN fiber population for the prevailing sound levels in the stimulus. However, dynamic range adaptation in the AN was weaker than in the midbrain, and not sufficient (0.25 dB/dB on average for broadband noise) to prevent a significant degradation of the precision of level coding by the AN population above 60 dB SPL. These findings suggest that adaptive processing of sound levels first occurs in the auditory periphery and is enhanced along the auditory pathway.

Wen, Bo; Wang, Grace I.; Dean, Isabel; Delgutte, Bertrand

2009-01-01

218

Statistical dynamics of classical systems: A self-consistent field approach.

We develop a self-consistent field theory for particle dynamics by extremizing the functional integral representation of a microscopic Langevin equation with respect to the collective fields. Although our approach is general, here we formulate it in the context of polymer dynamics to highlight satisfying formal analogies with equilibrium self-consistent field theory. An exact treatment of the dynamics of a single chain in a mean force field emerges naturally via a functional Smoluchowski equation, while the time-dependent monomer density and mean force field are determined self-consistently. As a simple initial demonstration of the theory, leaving an application to polymer dynamics for future work, we examine the dynamics of trapped interacting Brownian particles. For binary particle mixtures, we observe the kinetics of phase separation. PMID:24985678

Grzetic, Douglas J; Wickham, Robert A; Shi, An-Chang

2014-06-28

219

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

220

NASA Astrophysics Data System (ADS)

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

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

1996-02-01

221

Investigation of statistical properties of lymph-flow dynamics using speckle microscopy

NASA Astrophysics Data System (ADS)

At different pathological stages, the changes both of blood and lymph microcirculation parameters are observed. These parameters are of great importance in diagnostics. The type of these changes may indicate both the kind and the degree of disease. Investigation of the behavior of dynamic characteristics of these flows at different stages is of special interest. In this paper the peculiarities both of blood and lymph motion have been considered. The further development of speckle-interferometrical method has been carried out for the investigation of the dynamic characteristics of blood and lymph flows in microvessels. Analysis of two dynamic parameters which had been introduced in previous papers concerning this problem, is made in this paper. The influence of lymphotropic agent both on lymph flow and its dynamic characteristics is also discussed.

Bednov, Andrey A.; Zakharova, Ekateryna I.; Tuchin, Valery V.; Ul'Yanov, Sergey S.; Brill, Grigory E.

1997-05-01

222

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

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

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

2012-03-28

223

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

224

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

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{sup -} 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{sup -} 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. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1995-09-15

225

Static Numbers to Dynamic Statistics: Designing a Policy-Friendly Social Policy Indicator Framework

ERIC Educational Resources Information Center

In line with the economic crisis and rapid socio-demographic changes, the interest in "social" and "well-being" indicators has been revived. Social indicator movements of the 1960s resulted in the establishment of social indicator statistical frameworks; that legacy has remained intact in many national governments and international organisations.…

Ahn, Sang-Hoon; Choi, Young Jun; Kim, Young-Mi

2012-01-01

226

1. NTRODUCTION Analyses performed for the US National Assessment require accurate projections of climate at scales below those resolved by global General Circulation Models (GCMs). Two techniques have been developed that counter this deficiency: semi- empirical (statistical) downscaling (SDS) of GCM outputs, and regional climate models (RCMs) nested within a GCM. To date, few studies have compared SDS and RCM

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

227

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

A multivariate statistical downscaling methodology is implemented to generate local precipitation and temperature series at different sites based on the results from a variable resolution general circulation model. It starts from regional climate properties to establish discriminating weather types for the chosen local variable, precipitation in this case. Intratype variations of the relevant forcing parameters are then taken into account

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

2006-01-01

228

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

229

Data from photomultiplier tubes are typically analyzed using either counting or averaging techniques, which are most accurate in the dim and bright signal limits, respectively. A statistical means of adjoining these two techniques is presented by recovering the Poisson parameter from averaged data and relating it to the statistics of binomial counting from Kissick et al. [Anal. Chem. 82, 10129 (2010)]. The point at which binomial photon counting and averaging have equal signal to noise ratios is derived. Adjoining these two techniques generates signal to noise ratios at 87% to approaching 100% of theoretical maximum across the full dynamic range of the photomultiplier tube used. The technique is demonstrated in a second harmonic generation microscope. PMID:22535131

Muir, Ryan D; Kissick, David J; Simpson, Garth J

2012-04-23

230

NASA Astrophysics Data System (ADS)

For a simple model of chaotic dynamical systems with a large number of degrees of freedom, we find that there is an ensemble of unstable periodic orbits (UPOs) with the special property that the expectation values of macroscopic quantities can be calculated using only one UPO sampled from the ensemble. Evidence to support this conclusion is obtained by generating the ensemble by Monte Carlo calculation for a statistical mechanical model described by a space-time Hamiltonian that is expressed in terms of Floquet exponents of UPOs. This result allows us to interpret the recent interesting discovery that statistical properties of turbulence can be obtained from only one UPO [G. Kawahara and S. Kida, J. Fluid Mech. 449, 291 (2001); S. Kato and M. Yamada, Phys. Rev. E 68, 025302(R) (2003)].

Kawasaki, Mitsuhiro; Sasa, Shin-Ichi

2005-09-01

231

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

232

National Technical Information Service (NTIS)

The formulation of quantum statistical mechanics based on the path centroid variable in Feynman path integration is generalized to a phase space perspective, thereby including the momentum as an independent dynamical variable. By virtue of this approach, ...

J. Cao G. A. Voth

1994-01-01

233

The relationship between strategic offensive capabilities (reflected in the SIOP) and emerging strategic defensive capabilities (reflected by SDI) is not being adequately addressed. A summary of the existing nuclear war planning process is provided, and an analagous defensive process is postulated. Parallels and differences between the two processes are discussed. Potential areas for information exchange and cooperation are identified to enhance deterrence and improve war fighting potential. Operational, technical and political issues requiring resolution are raised and recommendations to resolve these issues are made.

Zank, G.D.

1989-05-01

234

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

NASA Astrophysics Data System (ADS)

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

Weatherley, D.; Abe, S.

2004-11-01

235

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

236

NASA Astrophysics Data System (ADS)

The statistical properties of over 300 different proxy records of the last two thousand years derived from the PAGES 2k database years are stochastically analysed. Analyses include estimation of their first four moments and their autocorrelation functions (ACF), as well as the determination of the presence of Hurst-Kolmogorov behaviour (known also as long term persistence). The data are investigated in groups according to their proxy type and location, while their statistical properties are also compared to those of the final temperature reconstructions. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

Koukas, Ioannis; Koukoravas, Vasilis; Mantesi, Konstantina; Sakellari, Katerina; Xanthopoulou, Themis-Demetra; Zarkadoulas, Akis; Markonis, Yannis; Papalexiou, Simon Michael; Koutsoyiannis, Demetris

2014-05-01

237

Static Numbers to Dynamic Statistics: Designing a Policy-Friendly Social Policy Indicator Framework

In line with the economic crisis and rapid socio-demographic changes, the interest in ‘social’ and ‘well-being’ indicators\\u000a has been revived. Social indicator movements of the 1960s resulted in the establishment of social indicator statistical frameworks;\\u000a that legacy has remained intact in many national governments and international organisations. With this background, this research\\u000a examines whether existing social indicator frameworks are valid

Sang-Hoon Ahn; Young Jun Choi; Young-Mi Kim

238

A comparison of statistical and dynamical downscaling for surface temperature in North America

Projections from general circulation model (GCM) simulations must be downscaled to the high spatial resolution needed for assessing local and regional impacts of climate change, but uncertainties in the downscaling process are difficult to quantify. We employed a multiple linear regression model and the MM5 dynamical model to downscale June, July, and August monthly mean surface temperature over eastern North

Scott Spak; Tracey Holloway; Barry Lynn; Richard Goldberg

2007-01-01

239

N-Acyl homoserine lactones (AHLs) are molecules that are synthesized and detected by many gram-negative bacteria to monitor the population density, a phenomenon known as quorum sensing. Salmonella enterica serovar Typhimurium is an exceptional species since it does not synthesize its own AHLs, while it does encode a LuxR homologue, SdiA, which enables this bacterium to detect AHLs that are produced by other species. To obtain more information about the specificity of the ligand binding by SdiA, we synthesized and screened a limited library of AHL analogues. We identified two classes of analogues that are strong activators of SdiA: the N-(3-oxo-acyl)-homocysteine thiolactones (3O-AHTLs) and the N-(3-oxo-acyl)-trans-2-aminocyclohexanols. To our knowledge, this is the first report of compounds (the 3O-AHTLs) that are able to activate a LuxR homologue at concentrations that are lower than the concentrations of the most active AHLs. SdiA responds with greatest sensitivity to AHTLs that have a keto modification at the third carbon atom and an acyl chain that is seven or eight carbon atoms long. The N-(3-oxo-acyl)-trans-2-aminocyclohexanols were found to be less sensitive to deactivation by lactonase and alkaline pH than the 3O-AHTLs and the AHLs are. We also examined the activity of our library with LuxR of Vibrio fischeri and identified three new inhibitors of LuxR. Finally, we performed preliminary binding experiments which suggested that SdiA binds its activators reversibly. These results increase our understanding of the specificity of the SdiA-ligand interaction, which could have uses in the development of anti-quorum-sensing-based antimicrobials. PMID:17085703

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

2007-01-01

240

N-Acyl homoserine lactones (AHLs) are molecules that are synthesized and detected by many gram-negative bacteria to monitor the population density, a phenomenon known as quorum sensing. Salmonella enterica serovar Typhimurium is an exceptional species since it does not synthesize its own AHLs, while it does encode a LuxR homologue, SdiA, which enables this bacterium to detect AHLs that are produced by other species. To obtain more information about the specificity of the ligand binding by SdiA, we synthesized and screened a limited library of AHL analogues. We identified two classes of analogues that are strong activators of SdiA: the N-(3-oxo-acyl)-homocysteine thiolactones (3O-AHTLs) and the N-(3-oxo-acyl)-trans-2-aminocyclohexanols. To our knowledge, this is the first report of compounds (the 3O-AHTLs) that are able to activate a LuxR homologue at concentrations that are lower than the concentrations of the most active AHLs. SdiA responds with greatest sensitivity to AHTLs that have a keto modification at the third carbon atom and an acyl chain that is seven or eight carbon atoms long. The N-(3-oxo-acyl)-trans-2-aminocyclohexanols were found to be less sensitive to deactivation by lactonase and alkaline pH than the 3O-AHTLs and the AHLs are. We also examined the activity of our library with LuxR of Vibrio fischeri and identified three new inhibitors of LuxR. Finally, we performed preliminary binding experiments which suggested that SdiA binds its activators reversibly. These results increase our understanding of the specificity of the SdiA-ligand interaction, which could have uses in the development of anti-quorum-sensing-based antimicrobials.

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

2007-01-01

241

Chemical communication mediates signaling between cells. Bacteria also engage in chemical signaling, termed quorum sensing (QS), to coordinate population-wide behavior. The bacterial pathogen enterohemorrhagic E. coli (EHEC), responsible for outbreaks of bloody diarrhea worldwide, exploits QS to promote expression of virulence factors in humans. Although EHEC is a human pathogen, it is a member of the gastrointestinal (GI) flora in cattle, the main reservoir for this bacterium. EHEC cattle colonization requires SdiA, a QS transcription factor that uses acyl-homoserine lactones (AHLs), for proper folding and function. EHEC harbors SdiA, but does not produce AHLs, consequently having to sense AHLs produced by other bacterial species. We recently showed that SdiA is necessary for efficient EHEC passage through the bovine GI tract, and show that AHLs are prominent within cattle rumen, but absent from the other sections of the GI tract. EHEC utilizes the locus of enterocyte effacement (LEE) to colonize the recto-anal junction of cattle, and the glutamate decarboxylase (gad) system to colonize cows. Transcription of the LEE genes is decreased by rumen AHLs through SdiA, while transcription of the gad acid resistant system is increased. It would be expensive for EHEC to express the LEE genes in the rumen where they are not necessary. However, in preparation for the acidic distal stomachs the EHEC gad is activated in the rumen. Hence AHL signaling through SdiA aids EHEC in gauging these environments, and modulates gene expression towards adaptation to a commensal life-style in cattle.1 Inasmuch as EHEC is largely prevalent in cattle herds, interference with SdiA-mediated QS inhibition of cattle colonization could be an attractive approach to diminish contamination of food products due to cattle shedding of this pathogen.

2010-01-01

242

Highlights: {yields} Reduced p21 expression in senescent cells treated with DNA damaging agents. {yields} Increase of [{sup 3}H]thymidine and BrdU incorporations in DNA damaged-senescent cells. {yields} Upregulation of miR-93 expression in senescent cells in response to DSB. {yields} Failure of p53 binding to p21 promoter in senescent cells in response to DSB. {yields} Molecular mechanism of increased cancer development in aged than young individuals. -- Abstract: To answer what is a critical event for higher incidence of tumor development in old than young individuals, primary culture of human diploid fibroblasts were employed and DNA damage was induced by doxorubicin or X-ray irradiation. Response to the damage was different between young and old cells; loss of p21{sup sdi1} expression in spite of p53{sup S15} activation in old cells along with [{sup 3}H]thymidine and BrdU incorporation, but not in young cells. The phenomenon was confirmed by other tissue fibroblasts obtained from different donor ages. Induction of miR-93 expression and reduced p53 binding to p21 gene promoter account for loss of p21{sup sdi1} expression in senescent cells after DNA damage, suggesting a mechanism of in vivo carcinogenesis in aged tissue without repair arrest.

Choi, Ok Ran [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of)] [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of); Lim, In Kyoung, E-mail: iklim@ajou.ac.kr [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of)

2011-04-08

243

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

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

2002-05-20

244

With continuing improvements in spatial resolution of PET scanners, small subject movements become a significant source of resolution degradation. This work assesses the impact of an accurate motion correction (MC) method, modeling the 'motion-induced' interaction of lines-of-response (LORs) inside and outside the field-of-view, on the task of kinetic parametric estimation in high resolution dynamic PET. Following extensive prior phantom and

A. Rahmim; K. Dinelle; J. C. Cheng; G. Topping; H. A. Vajihollahi; D. F. Wong; V. Sossi

2007-01-01

245

Non-Standard neutral kaons dynamics from D-brane statistics

The neutral kaon system can be effectively described by non-unitary,\\u000adissipative, completely positive dynamics that extend the usual treatment. In\\u000athe framework of open quantum systems, we show how the origin of these\\u000anon-standard time evolutions can be traced to the interaction of the kaon\\u000asystem with a large environment. We find that D-branes, effectively described\\u000aby a heat-bath of

F. Benatti; R. Floreanini

1998-01-01

246

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. PMID:18584022

Locasale, Jason W; Chakraborty, Arup K

2008-06-01

247

Universal Behaviour of Extreme Value Statistics for Selected Observables of Dynamical Systems

NASA Astrophysics Data System (ADS)

The main results of the extreme value theory developed for the investigation of the observables of dynamical systems rely, up to now, on the block maxima approach. In this framework, extremes are identified with the block maxima of the time series of the chosen observable, in the limit of infinitely long blocks. It has been proved that, assuming suitable mixing conditions for the underlying dynamical systems, the extremes of a specific class of observables are distributed according to the so called Generalised Extreme Value (GEV) distribution. Direct calculations show that in the case of quasi-periodic dynamics the block maxima are not distributed according to the GEV distribution. In this paper we show that considering the exceedances over a given threshold instead of the block-maxima approach it is possible to obtain a Generalised Pareto Distribution also for extremes computed in systems which do not satisfy mixing conditions. Requiring that the invariant measure locally scales with a well defined exponent—the local dimension—, we show that the limiting distribution for the exceedances of the observables previously studied with the block maxima approach is a Generalised Pareto distribution where the parameters depend only on the local dimensions and the values of the threshold but not on the number of observations considered. We also provide connections with the results obtained with the block maxima approach. In order to provide further support to our findings, we present the results of numerical experiments carried out considering the well-known Chirikov standard map.

Lucarini, Valerio; Faranda, Davide; Wouters, Jeroen

2012-04-01

248

NASA Astrophysics Data System (ADS)

The problems of using Global Climate Models (GCMs) in local impact studies are well known, especially concerning events on tails of the distribution. The development of GCMs in terms of resolution and physical processes is progressing, but there is still a need today to downscale the output from the large scale to the local scale. The two main tools for this are classically dynamical downscaling through Regional Climate Models (RCMs), and statistical downscaling (SD) through a transfer function. However, also RCMs have biases in there output variables, originating both from the driving GCM and from limitations in the model itself, and the output often has to be modified before it can be used in impact studies, so called model output statistics (MOS). SD methods are usually good at capturing the statistical properties, but it is not straight-forward to model spatial and temporal correlations between variables. In this study, RCM and SD methods were applied to precipitation from the HadCM3 ensemble runs from the UKCP09 under the future scenario A1B from 1950-2099. A simple MOS was also applied to the RCM. The precipitation together with modeled temperature was then used to drive two hydrological models, LISFLOOD-RR and HBV to analyse future flood producing patterns in discharge. The results show the benefit of using two methods, and thereby assessing more of the uncertainty in climate impact studies.

Wetterhall, F.; Pappenberger, F.; He, Y.; Freer, J.; Cloke, H.; Wilson, M.; McGregor, G.

2010-05-01

249

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

250

Statistical analysis of global wind dynamics in vigorous Rayleigh-Bénard convection.

Experimental and numerical studies of thermal convection have shown that sufficiently vigorous convective flows exhibit a large-scale thermal wind component sweeping along small-scale thermal boundary layer instabilities. A characteristic feature of these flows is an intermittent behavior in the form of irregular reversals in the orientation of the large-scale circulation. There have been several attempts toward a better understanding and description of the phenomenon of flow reversals, but so far most of these models are based on a statistical analysis of few-point measurements or on simplified theoretical assumptions. The analysis of long-term data sets (>5×10(5) turnover times ?(t)=d/u(rms)) obtained by numerical simulations of turbulent two-dimensional Rayleigh-Bénard convection allows us to get a more comprehensive view of the spatio-temporal flow behavior. By means of a global statistical analysis of the characteristic spatial modes of the flow we extract information about the stability of dominant large-scale modes as well as the reversal paths in state subspace. We examine probability density functions and drift vector fields of two-dimensional state subspaces spanned by different large-scale spatial modes. This also provides information about the coexistence of dominant modes. PMID:21929092

Petschel, K; Wilczek, M; Breuer, M; Friedrich, R; Hansen, U

2011-08-01

251

Statistical analysis of global wind dynamics in vigorous Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Experimental and numerical studies of thermal convection have shown that sufficiently vigorous convective flows exhibit a large-scale thermal wind component sweeping along small-scale thermal boundary layer instabilities. A characteristic feature of these flows is an intermittent behavior in the form of irregular reversals in the orientation of the large-scale circulation. There have been several attempts toward a better understanding and description of the phenomenon of flow reversals, but so far most of these models are based on a statistical analysis of few-point measurements or on simplified theoretical assumptions. The analysis of long-term data sets (>5×105 turnover times ?t=d/urms) obtained by numerical simulations of turbulent two-dimensional Rayleigh-Bénard convection allows us to get a more comprehensive view of the spatio-temporal flow behavior. By means of a global statistical analysis of the characteristic spatial modes of the flow we extract information about the stability of dominant large-scale modes as well as the reversal paths in state subspace. We examine probability density functions and drift vector fields of two-dimensional state subspaces spanned by different large-scale spatial modes. This also provides information about the coexistence of dominant modes.

Petschel, K.; Wilczek, M.; Breuer, M.; Friedrich, R.; Hansen, U.

2011-08-01

252

Dynamics and Statistical Mechanics of Rotating and non-Rotating Vortical Flows

Three projects were analyzed with the overall aim of developing a computational/analytical model for estimating values of the energy, angular momentum, enstrophy and total variation of fluid height at phase transitions between disordered and self-organized flow states in planetary atmospheres. It is believed that these transitions in equilibrium statistical mechanics models play a role in the construction of large-scale, stable structures including super-rotation in the Venusian atmosphere and the formation of the Great Red Spot on Jupiter. Exact solutions of the spherical energy-enstrophy models for rotating planetary atmospheres by Kac's method of steepest descent predicted phase transitions to super-rotating solid-body flows at high energy to enstrophy ratio for all planetary spins and to sub-rotating modes if the planetary spin is large enough. These canonical statistical ensembles are well-defined for the long-range energy interactions that arise from 2D fluid flows on compact oriented manifolds such as the surface of the sphere and torus. This is because in Fourier space available through Hodge theory, the energy terms are exactly diagonalizable and hence has zero range, leading to well-defined heat baths.

Lim, Chjan [RPI] [RPI

2013-12-18

253

NASA Astrophysics Data System (ADS)

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

Avissar, Roni

1991-03-01

254

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

Zheng, Pengsheng; Dimitrakakis, Christos; Triesch, Jochen

2013-01-01

255

Statistics of small-scale structures and a dynamical mechanism of cascade

A dynamical view of the cascade process in turbulence is presented consistently with the worm structure and the rate-of-strain\\u000a field observed in the computer simulations, the negative skewness of the longitudinal velocity difference ?v\\u000a \\u000a s\\u000a (s) across a distance s in the experimental observations, and Kolmogorov's law for the third-order structure function (?v\\u000a \\u000a s\\u000a )3. First, a model of a

T. Kambe; I. Hosokawa

1995-01-01

256

Escape beam statistics and dynamical properties for a periodically corrugated waveguide

NASA Astrophysics Data System (ADS)

Some escape and dynamical properties for a beam of light inside a corrugated waveguide are discussed by using Fresnel reflectance. The system is described by a mapping and is controlled by a parameter ? defining a transition from integrability (?=0) to non integrability (??0). The phase space is mixed containing periodic islands, chaotic seas and invariant tori. The histogram of escaping orbits is shown to be scaling invariant with respect to ?. The waveguide is immersed in a region with different refractive index. Different optical materials are used to overcame the results.

da Costa, Diogo Ricardo; Silva, Mário R.; Leonel, Edson D.

2014-04-01

257

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

258

NASA Astrophysics Data System (ADS)

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.

Robledo, A.; Moyano, L. G.

2008-03-01

259

NASA Astrophysics Data System (ADS)

Orthoexcitonic gas in cuprous oxide is generated by one and two photon resonant excitations at different excitation intensities and at different temperatures between 1.8 and 4.2 K. The experimental results are analyzed by simulation with a Boltzmann equation. When the exciton density is low, the observed luminescence is found to originate from a nonequilibrium excitonic gas where the exciton-LA phonon scattering dominates. When the exciton density is very high, not only the exciton-LA phonon scattering but also the exciton-exciton scattering is important. The observed luminescence consists of two systems: one is from an exciton system that is distributed according to the usual Bose-Einstein statistics with chemical potential ?=0, while the other is from excitons with zero kinetic energy. The two systems were found to be in thermal equilibrium. The latter system might be a form of Bose-Einstein condensation.

Shen, M. Y.; Yokouchi, T.; Koyama, S.; Goto, T.

1997-11-01

260

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

NASA Astrophysics Data System (ADS)

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.

Oteo, J. A.; Ros, J.

2007-09-01

261

Improved dynamic programming-based handwritten word recognition using optimal order statistics

NASA Astrophysics Data System (ADS)

Handwritten word recognition is a difficult problem. In the standard segmentation-based approach to handwritten word recognition, individual character class confidence scores are combined to estimate confidences concerning the various hypothesized identities for a word. The standard combination method is the mean. Previously, we demonstrated that the Choquet integral provided higher recognition rates than the mean. Our previous work with the Choquet integral relied on a restricted class of measures. For this class of measures, operators based on the Choquet integral are equivalent to a subset of a class of operators known as linear combinations of order statistics. In this paper, we extend our previous work to find the optimal LOS operator for combining character class confidence scores. Experimental results are provided on about 1300 word images.

Chen, Wen-Tsong; Gader, Paul D.; Shi, Hongchi

1997-10-01

262

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

263

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

264

Research on rail surface non-touch statistic and dynamic measuring technique

NASA Astrophysics Data System (ADS)

On the basis of laser displacement sense principle, one non-contact rail surface sense measuring program is designed. Surface measuring instrument is made. Inspection and measuring for the single-section of rail surface are carried on and data-based image formation is given. The precise measuring is realized for rail surface, especial trail parts; By using the stepper motor diving technique and program operating imagine formation technique, combining the MTLAB programming, the single-surface measurement data is transformed into image and the dynamic measuring for rail vertical smoothing is achieved. By comparing to the standard data, the rail wear state and surface parameters are concluded .This technique met with the needs of non-touch automatic measuring for rail surface.

Bi, Zong-qi; Wang, Lian-fen; Wang, Ai-fang

2014-02-01

265

The Tectonics Model of Coronal Heating: Unsteady Dynamics and Scaling in Statistical Steady State

NASA Astrophysics Data System (ADS)

The tectonics model of coronal heating, proposed by Priest et al. [Astrophys. J., 576, 533 (2002)] envisions coronal heating caused by a hierarchy of current sheets produced by the movement of a myriad of flux elements in the magnetic carpet covering the Sun. We have recently obtained new scaling results in two dimensions (2D) suggesting that the heating rate becomes independent of resistivity in a statistical steady state [C. S. Ng and A. Bhattacharjee, Astrophys. J., 675, 899 (2008)]. Our numerical work has now been extended to 3D. Random photospheric footpoint motion is applied to obtain converged average coronal heating rates. In the large Lundquist number limit, we find that the heating rate is independent of the Lundquist number, with average magnetic energy saturating at a constant level due to the formation of strong current layers and subsequent disruptions. In this talk, we will present our latest numerical results from large-scale 3D simulations, and discuss differences with previous scaling laws.

Ng, C. S.; Lin, L.; Bhattacharjee, A.

2009-11-01

266

Dynamical model and nonextensive statistical mechanics of a market index on large time windows

NASA Astrophysics Data System (ADS)

The shape and tails of partial distribution functions (PDF) for a financial signal, i.e., the S&P500 and the turbulent nature of the markets are linked through a model encompassing Tsallis nonextensive statistics and leading to evolution equations of the Langevin and Fokker-Planck type. A model originally proposed to describe the intermittent behavior of turbulent flows describes the behavior of normalized log returns for such a financial market index, for small and large time windows, and both for small and large log returns. These turbulent market volatility (of normalized log returns) distributions can be sufficiently well fitted with a ?2 distribution. The transition between the small time scale model of nonextensive, intermittent process, and the large scale Gaussian extensive homogeneous fluctuation picture is found to be at ca. a 200 day time lag. The intermittency exponent ? in the framework of the Kolmogorov log-normal model is found to be related to the scaling exponent of the PDF moments, thereby giving weight to the model. The large value of ? points to a large number of cascades in the turbulent process. The first Kramers-Moyal coefficient in the Fokker-Planck equation is almost equal to zero, indicating “no restoring force.” A comparison is made between normalized log returns and mere price increments.

Ausloos, M.; Ivanova, K.

2003-10-01

267

Downscaling from GCM precipitation: a benchmark for dynamical and statistical downscaling methods

NASA Astrophysics Data System (ADS)

A precipitation downscaling method is presented using precipitation from a general circulation model (GCM) as predictor. The method extends a previous method from monthly to daily temporal resolution. The simplest form of the method corrects for biases in wet-day frequency and intensity. A more sophisticated variant also takes account of flow-dependent biases in the GCM. The method is flexible and simple to implement. It is proposed here as a correction of GCM output for applications where sophisticated methods are not available, or as a benchmark for the evaluation of other downscaling methods.Applied to output from reanalyses (ECMWF, NCEP) in the region of the European Alps, the method is capable of reducing large biases in the precipitation frequency distribution, even for high quantiles. The two variants exhibit similar performances, but the ideal choice of method can depend on the GCM/reanalysis and it is recommended to test the methods in each case. Limitations of the method are found in small areas with unresolved topographic detail that influence higher-order statistics (e.g. high quantiles). When used as benchmark for three regional climate models (RCMs), the corrected reanalysis and the RCMs perform similarly in many regions, but the added value of the latter is evident for high quantiles in some small regions.

Schmidli, Jürg; Frei, Christoph; Vidale, Pier Luigi

2006-04-01

268

Statistical techniques for modeling extreme price dynamics in the energy market

NASA Astrophysics Data System (ADS)

Extreme events have large impact throughout the span of engineering, science and economics. This is because extreme events often lead to failure and losses due to the nature unobservable of extra ordinary occurrences. In this context this paper focuses on appropriate statistical methods relating to a combination of quantile regression approach and extreme value theory to model the excesses. This plays a vital role in risk management. Locally, nonparametric quantile regression is used, a method that is flexible and best suited when one knows little about the functional forms of the object being estimated. The conditions are derived in order to estimate the extreme value distribution function. The threshold model of extreme values is used to circumvent the lack of adequate observation problem at the tail of the distribution function. The application of a selection of these techniques is demonstrated on the volatile fuel market. The results indicate that the method used can extract maximum possible reliable information from the data. The key attraction of this method is that it offers a set of ready made approaches to the most difficult problem of risk modeling.

Mbugua, L. N.; Mwita, P. N.

2013-02-01

269

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

270

Personal exposure meters (PEM) are routinely used for the exposure assessment to radio frequency electric or magnetic fields. However, their readings are subject to errors associated with perturbations of the fields caused by the presence of the human body. This paper presents a novel analysis method for the characterization of this effect. Using ray-tracing techniques, PEM measurements have been emulated, with and without an approximation of this shadowing effect. In particular, the Global System for Mobile Communication mobile phone frequency band was chosen for its ubiquity and, specifically, we considered the case where the subject is walking outdoors in a relatively open area. These simulations have been contrasted with real PEM measurements in a 35-min walk. Results show a good agreement in terms of root mean square error and E-field cumulative distribution function (CDF), with a significant improvement when the shadowing effect is taken into account. In particular, the Kolmogorov-Smirnov (KS) test provides a P-value of 0.05 when considering the shadowing effect, versus a P-value of 10?¹? when this effect is ignored. In addition, although the E-field levels in the absence of a human body have been found to follow a Nakagami distribution, a lognormal distribution fits the statistics of the PEM values better than the Nakagami distribution. As a conclusion, although the mean could be adjusted by using correction factors, there are also other changes in the CDF that require particular attention due to the shadowing effect because they might lead to a systematic error. PMID:21365665

Rodríguez, Begoña; Blas, Juan; Lorenzo, Rubén M; Fernández, Patricia; Abril, Evaristo J

2011-04-01

271

Global nannoplankton dynamics across the Paleocene-Eocene Thermal Maximum: A statistical approach

NASA Astrophysics Data System (ADS)

Global warming during the Paleocene-Eocene Thermal Maximum (PETM; 55.8 Ma) had a profound effect on life on land and in the ocean. With global temperatures rising 5°C over ~20 kyr, the PETM is considered to be the most analogous interval to modern day climate change. Calcareous nannoplankton, a group of calcifying marine phytoplankton, have been extensively studied across this event. Results from these studies indicate nannoplankton assemblages responded to changing surface water temperatures and nutrient availability. Together, these records can provide a global picture of nannofossil assemblage dynamics during this critical interval. Issues such as the timing and nature of assemblage change on a global scale, the rate of assemblage change, and how assemblage shifts differ regionally can be further resolved. Here we use an ordination technique (detrended correspondence analysis; DCA), which condenses complex assemblage data and displays it in a simple, interpretable way. We applied the DCA to previously published nannofossil abundance data from 7 globally distributed sites and compared these results to published benthic and bulk ?13C records across the PETM. Our initial results show that changes in the nannofossil assemblage, as displayed through DCA 1, closely follow the trends of the ?13C curves at each site. This suggests that the organisms are closely linked to the carbon cycle in some way during this time period. From this study we will have a better understanding of how global nannoplankton populations responded to rapid climate change and when environmental alterations began to take place.

Schneider, L. J.; Bralower, T. J.; Patzkowsky, M.; Kump, L.

2012-12-01

272

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.

2014-01-01

273

Bose-Einstein S=1 Spinor Condensates, Dynamics, Noise Statistics and Scaling

NASA Astrophysics Data System (ADS)

We examine Bose-Einstein spinor condensates in the short-time non-linear regime for S=1 atoms in the context of ^87Rb studied experimentally by the Stamper-Kurn group [L. Sadler et al, Nature 443, p193, 2006]. We will describe the quantum dynamics of a sample that starts as a condensate of N atoms in a pure S=1, mf=0 state. Our approach seeks to improve the mean-field description of such systems by including the contributions of quantum fluctuations that seed the eventual formation of ferromagnetic domains. We will give a simple quantum description of the system for the short-time regime in analogy with ``two-mode squeezing" of quantum optics, treating the initial mf=0 condensate as a source for the conversion to pairs of mf=1,-1 states. Even though the system as a whole is described by a pure state with zero entropy, the reduced density matrix for the mf=+1 degree of freedom, obtained by tracing out the mf=-1,0 degrees of freedom, is a thermal state. We propose to observe the large fluctuations associated with this thermal state using Hanbury-Brown-Twiss noise correlation measurements in the density and momentum distributions of the individual mf species. Finally, we will discuss the effect of excitations in connection to the seeding and ultimate formation of domains of ferromagnetically aligned spins. (Supported by NSF DMR-0603369).

Mias, George I.; Girvin, Steven M.

2007-03-01

274

Dynamics of CMEs in the LASCO Field of View - Statistical Analysis

NASA Astrophysics Data System (ADS)

A large set of CMEs (2207) has been selected to study their dynamics in the SOHO/LASCO field of view (LFOV). These selected events have at least seven height-time measurements and their acceleration can be determined separately in the C2 and C3 LFOVs. It was demonstrated that the balance between the aerodynamic drag and driving Lorentz forces may change during CME propagation in the LFOV. The drag force dominates the CME propagation close to the Sun (in the C2 LFOV), but farther from the Sun (in the C3 LFOV) the Lorentz force takes over the drag force. We also demonstrated that the acceleration of CMEs depends not only on their velocities but also on their masses and widths. Less massive CMEs (mass <3×1014 kg) are generally decelerated and more massive CMEs (mass >3×1014 kg) are accelerated in the LFOV. Based on the acceleration behavior we are able to classify the observed events into four different types.

Michalek, G.

2012-02-01

275

In dynamic mode, positron emission tomography (PET) can be used to track the evolution of injected radio-labelled molecules in living tissue. This is a powerful diagnostic imaging technique that provides a unique opportunity to probe the status of healthy and pathological tissue by examining how it processes substrates. The spatial aspect of PET is well established in the computational statistics literature. This article focuses on its temporal aspect. The interpretation of PET time-course data is complicated because the measured signal is a combination of vascular delivery and tissue retention effects. If the arterial time-course is known, the tissue time-course can typically be expressed in terms of a linear convolution between the arterial time-course and the tissue residue. In statistical terms, the residue function is essentially a survival function - a familiar life-time data construct. Kinetic analysis of PET data is concerned with estimation of the residue and associated functionals such as flow, flux, volume of distribution and transit time summaries. This review emphasises a nonparametric approach to the estimation of the residue based on a piecewise linear form. Rapid implementation of this by quadratic programming is described. The approach provides a reference for statistical assessment of widely used one- and two-compartmental model forms. We illustrate the method with data from two of the most well-established PET radiotracers, 15O-H2O and 18F-fluorodeoxyglucose, used for assessment of blood perfusion and glucose metabolism respectively. The presentation illustrates the use of two open-source tools, AMIDE and R, for PET scan manipulation and model inference.

Hawe, David; Hernandez Fernandez, Francisco R.; O'Suilleabhain, Liam; Huang, Jian; Wolsztynski, Eric; O'Sullivan, Finbarr

2012-01-01

276

NASA Astrophysics Data System (ADS)

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

Habasaki, J.; Ngai, K. L.

2013-08-01

277

ERIC Educational Resources Information Center

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

Chicot, Katie; Holmes, Hilary

2012-01-01

278

Coupled flow-polymer dynamics via statistical field theory: Modeling and computation

NASA Astrophysics Data System (ADS)

Field-theoretic models, which replace interactions between polymers with interactions between polymers and one or more conjugate fields, offer a systematic framework for coarse-graining of complex fluids systems. While this approach has been used successfully to investigate a wide range of polymer formulations at equilibrium, field-theoretic models often fail to accurately capture the non-equilibrium behavior of polymers, especially in the early stages of phase separation. Here the "two-fluid" approach serves as a useful alternative, treating the motions of fluid components separately in order to incorporate asymmetries between polymer molecules. In this work we focus on the connection of these two theories, drawing upon the strengths of each of the approaches in order to couple polymer microstructure with the dynamics of the flow in a systematic way. For illustrative purposes we work with an inhomogeneous melt of elastic dumbbell polymers, though our methodology will apply more generally to a wide variety of inhomogeneous systems. First we derive the model, incorporating thermodynamic forces into a two-fluid model for the flow through the introduction of conjugate chemical potential and elastic strain fields for the polymer density and stress. The resulting equations are composed of a system of fourth order PDEs coupled with a non-linear, non-local optimization problem to determine the conjugate fields. The coupled system is severely stiff and with a high degree of computational complexity. Next, we overcome the formidable numerical challenges posed by the model by designing a robust semi-implicit method based on linear asymptotic behavior of the leading order terms at small scales, by exploiting the exponential structure of global (integral) operators, and by parallelizing the non-linear optimization problem. The semi-implicit method effectively removes the fourth order stability constraint associated with explicit methods and we observe only a first order time-step restriction. The algorithm for solving the non-linear optimization problem, which takes advantage of the form of the operators being optimized, reduces the overall simulation time by several orders of magnitude. We illustrate the methodology with several examples of phase separation in an initially quiescent flow.

Ceniceros, Hector D.; Fredrickson, Glenn H.; Mohler, George O.

2009-03-01

279

Lactide-co-?-valerolactone copolymers (PLVL) have not attracted as much research interest as the more popular poly(lactide-co-?-caprolactone) (PLCL) elastomeric materials. In this work the study of the mechanical performance is focused on the former with the aim of identifying the potential advantages of these thermoplastic elastomers for their application in the biomedical field. Mechanical testing (at 21°C and at 37°C) of at least 5 specimens and dynamic mechanical analysis (DMA) in duplicate were carried out on various PLVL, which include a moderately blocky l-lactide/?-valerolactone copolymer (~70% of l-LA and R=0.68) and several that showed a random distribution of sequences (R~1): some terpolymers based on l-lactide, d-lactide and ?-valerolactone (with a lactone content of ~25 and ~14%) and a series of copolymers of l-LA and ?-VL having l-LA molar contents ranging from 69 to 74%. In view of the results, it can be concluded that noteworthy improvements in stiffness and strength were achieved by adding ?-VL to the reaction mix instead of ?-CL, although both monomers have analogous chemical properties. For example, a PLVL with a 75:25M composition of l-LA/?-VL at 21°C presented a secant modulus of 213.7±36.5MPa and ?u=14.7±1.4MPa whereas a previously studied PLCL of equal composition had a secant modulus and an ultimate stress value of 19.4±1.3MPa and 3.2±0.6MPa, respectively. At 37°C, the differences in the mechanical properties between the different PLVLs of this work were far less relevant, with most of them showing a fully elastomeric behavior. Referring to the DMA measurements, the reduction in the peak of tan ? (from ~2.5 to 0.5) through the glass transition was a clear indicator that crystalline domains formed during hydrolytic degradation in some of the polymers. However, the more amorphous PLVLs with short l-LA average sequence lengths (ll-LA<2.91) did not undergo changes in the storage modulus and tan ? curves after two weeks submerged in PBS at 37°C. PMID:24732304

Fernández, J; Larrañaga, A; Etxeberria, A; Sarasua, J R

2014-07-01

280

NASA Astrophysics Data System (ADS)

A statistical-dynamical downscaling (SDD) approach for the regionalisation of wind energy output (Eout) over Europe with special focus on Germany is proposed. SDD uses an extended circulation weather type (CWT) analysis on global daily MSLP fields with the central point being located over Germany. 77 weather classes based on the associated circulation weather type and the intensity of the geostrophic flow are identified. Representatives of these classes are dynamical downscaled with the regional climate model COSMO-CLM. By using weather class frequencies of different datasets the simulated representatives are recombined to probability density functions (PDFs) of near-surface wind speed and finally to Eout of a sample wind turbine for present and future climate. This is performed for reanalysis, decadal hindcasts and long-term future projections. For evaluation purposes results of SDD are compared to wind observations and to simulated Eout of purely dynamical downscaling (DD) methods. For the present climate SDD is able to simulate realistic PDFs of 10m-wind speed for most stations in Germany. The resulting spatial Eout patterns are similar to DD simulated Eout. In terms of decadal hindcasts results of SDD are similar to DD simulated Eout over Germany, Poland, Czech Republic, and Benelux, for which high correlations between annual Eout timeseries of SDD and DD are detected for selected hindcasts. Lower correlation is found for other European countries. It is demonstrated that SDD can be used to downscale the full ensemble of the MPI-ESM decadal prediction system. Long-term climate change projections in SRES scenarios of ECHAM5/MPI-OM as obtained by SDD agree well to results of other studies using DD methods, with increasing Eout over Northern Europe and a negative trend over Southern Europe. Despite some biases it is concluded that SDD is an adequate tool to assess regional wind energy changes in large model ensembles.

Pinto, Joaquim G.; Reyers, Mark; Mömken, Julia

2014-05-01

281

Dynamic Statistical Parametric Mapping

Functional magnetic resonance imaging (fMRI) can provide maps of brain activation with millimeter spatial resolution but is limited in its temporal resolution to the order of seconds. Here, we describe a technique that combines structural and functional MRI with magnetoencephalography (MEG) to obtain spatiotemporal maps of human brain activity with millisecond temporal resolution. This new technique was used to obtain

Anders M. Dale; Arthur K. Liu; Bruce R. Fischl; Randy L. Buckner; John W. Belliveau; Jeffrey D. Lewine; Eric Halgren

2000-01-01

282

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

283

This paper examines the hydrologic model performance in three snowmelt-dominated basins in the western United States to dynamically- and statistically downscaled output from the National Centers for Environmental Prediction\\/National Center for Atmospheric Research Reanalysis (NCEP). Runoff produced using a distributed hydrologic model is compared using daily precipitation and maximum and minimum temperature timeseries derived from the following sources: (1) NCEP

L. E. Hay; M. P. Clark

2003-01-01

284

National Technical Information Service (NTIS)

Numerical algorithms are developed for the centroid molecular dynamics (centroid MD) method to calculate dynamical time correlation functions for general many-body quantum systems. Approaches based on the normal mode path integral molecular dynamics and s...

J. Cao G. A. Voth

1994-01-01

285

Statistical Applets: Statistical Significance

NSDL National Science Digital Library

Created by authors Duckworth, McCabe, Moore and Sclove for W.H. Freeman of Co., this applet is designed to help students visualize the rejection region of a statistical test by allowing them to set null and alternate hypotheses, population parameters, sample statistics, and significance level. It accompanies "ÃÂÃÂPractice of Business Statistics," but 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

2009-03-05

286

NASA Astrophysics Data System (ADS)

We report on early science results from the newly-commissioned Magellan AO (MagAO) system's VisAO camera in Simultaneous Differential Imaging (SDI) mode. The MagAO Adaptive Secondary Mirror's high actuator pitch allow us to achieve AO correction into the visible wavelength regime, and VisAO is the first visible light science camera behind a large (d>6m) telescope AO system. This opens up an interesting new region of parameter space to high contrast, high spatial resolution science. As a natural guide star system, MagAO is optimized for circumstellar science, including both point source detection and high resolution imaging of circumstellar disks. Early SDI science results include the first circumstellar disk imaged in silhouette from the ground, high-resolution images of a binary propylid in Orion and high contrast images of an accreting point source at small separation.

Follette, Kate; Close, Laird; Wu, Ya-Lin; Males, Jared; Morzinski, Katie; Kopon, Derek

2013-07-01

287

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

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

2007-01-01

288

NASA Astrophysics Data System (ADS)

A substructure for the wheel sets is developed. The problem of relating the substructures to the general body system by the calculation of statistical linearized, generalized force vectors for various linear and nonlinear joining elements is solved. Nonlinear spring and damper connections, Coulomb translation friction dampers, and Coulomb rotation friction dampers are covered. Statistically linearized dynamic connecting elements are modelized. It is shown how the general differential equation system is to be constructed. The iteration process for the determination of the free linearization parameter is presented.

Renger, A.

289

Software Built-In Test (BIT) is a design technique for collecting information from operational software that will assist in identifying differences between the real Operating Environment and either the Design or Test Environments. The BIT senses and indicates where the software is operating in new or overload environmental conditions and may, therefore, be more likely to fail. (This anomalous situation may be the result of either hardware failure or software design error.) The technical challenge is to incorporate the large number of relatively simple BIT tests into the fault-tolerant and continuously operating environment likely to characterize a solution to the battle management portion of the SDI mission. The management challenge is to provide these technical assists in such a way that they can be implemented in operational software with a minimal increase in software development time; it is then reasonable to expect that BIT will not shift from a hard requirement to a nice-to-have feature as schedule pressures potentially impact development. This approach overcomes the management problem by providing a standard set of tools for use within the software development environment which will implement BIT with a minimum amount of programmer action.

Healey, R.D.

1987-08-15

290

NASA Astrophysics Data System (ADS)

The behavior of a family of dissipative dynamical systems representing transformations a of a two-dimensional torus is studied on a discrete lattice and compared with that of conservative hyperbolic automorphisms of the torus. Applying dissipative dynamical systems to generation of pseudorandom numbers is shown to be advantageous and equidistribution of probabilities for the sequences of bits can be achieved. A new algorithm for generating uniform pseudorandom numbers is proposed. The theory of the generator, which includes proofs of periodic properties and of statistical independence of bits at distances up to logarithm of mesh size, is presented. Extensive statistical testing using available test packages demonstrates excellent results, while the speed of the generator is comparable to other modern generators.

Barash, L. Yu.

2011-07-01

291

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

292

NASA Astrophysics Data System (ADS)

We study the quantum mechanics of a billiard (Robnik 1983 J. Phys. A: Math. Gen. 16 3971) in the regime of mixed-type classical phase space (the shape parameter ? = 0.15) at very high-lying eigenstates, starting at about 1.000.000th eigenstate and including the consecutive 587654 eigenstates. By calculating the normalized Poincaré-Husimi functions of the eigenstates and comparing them with the classical phase space structure, we introduce the overlap criterion which enables us to separate with great accuracy and reliability the regular and chaotic eigenstates, and the corresponding energies. The chaotic eigenstates appear all to be dynamically localized, meaning that they do not uniformly occupy the entire available chaotic classical phase space component, but are localized on a proper subset. We find with unprecedented precision and statistical significance that the level spacing distributions of the regular levels obey the Poisson statistics, and the chaotic ones obey the Brody statistics, as anticipated in a recent paper by Batisti? and Robnik (2010 J. Phys. A: Math. Theor. 43 215101), where the entire spectrum was found to obey the Berry-Robnik-Brody statistics. There are no effects of dynamical tunneling in this regime, due to the high energies, as they decay exponentially with the inverse effective Planck constant which is proportional to the square root of the energy.

Batisti?, Benjamin; Robnik, Marko

2013-08-01

293

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.

294

... Data Consumer Opinion Surveys Home / Research & Statistics Injury Statistics This is the statistic reports page for scientific ... Home Appliances, Maintenance and Construction Injury Statistics Injury Statistics September 30, 2012 Submersions Related to Non-Pool ...

295

National Technical Information Service (NTIS)

The feasibility of estimating temperature profiles (synthetic temperature profiles) from Geodetic Earth Orbiting Satellite (GEOSAT) altimeter-derived sea-surface heights in the Gulf Stream region has been explored. The scheme was based on a statistical re...

D. S. Ko

1992-01-01

296

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

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

297

... a medical procedure. These are all types of health statistics. Health statistics are numbers about some aspect of health. Statistics about births, deaths, marriages, and divorces are sometimes ...

298

National Technical Information Service (NTIS)

The purpose of this project was to better understand brain-like network dynamics by incorporated biological parameters into large-scale computer simulations using parallel distributed 'Beowulf' clustering. Milestones included improved single- processor ef...

P. H. Goodman S. J. Louis H. Markram

2000-01-01

299

NASA Astrophysics Data System (ADS)

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

MöLg, Thomas; Kaser, Georg

2011-08-01

300

... Role Our Leadership Newsroom Publications Statistics Contact Us Statistics All statistics correspond with the U.S. Government fiscal year, which ... and ends on September 30. For example, adoption statistics for FY2013 show the period from October 1, ...

301

... 1975-2010 Did You Know? Video Series Cancer Statistics Understanding Cancer Statistics Learn definitions of statistical terms, ... and software tools. Did You Know? Colorectal Cancer Statistics You will need Adobe Flash Player 8 or ...

302

Statistical mechanics of pluripotency.

Recent reports using single-cell profiling have indicated a remarkably dynamic view of pluripotent stem cell identity. Here, we argue that the pluripotent state is not well defined at the single-cell level but rather is a statistical property of stem cell populations, amenable to analysis using the tools of statistical mechanics and information theory. PMID:23911316

MacArthur, Ben D; Lemischka, Ihor R

2013-08-01

303

... Topics Drugs & Supplements Videos & Cool Tools ESPAÑOL MedlinePlus Statistics To use the sharing features on this page, please enable JavaScript. Quarterly User Statistics Graph | Quarterly User Statistics Table | Number of Health ...

304

Discrete hidden Markov models (HMMs) were applied to classify pregnancy disorders. The observation sequence was generated by transforming RR and systolic blood pressure time series using symbolic dynamics. Time series were recorded from 15 women with pregnancy-induced hypertension, 34 with preeclampsia and 41 controls beyond 30th gestational week. HMMs with five to ten hidden states were found to be sufficient to characterize different blood pressure variability, whereas significant classification in RR-based HMMs was found using fifteen hidden states. Pregnancy disorders preeclampsia and pregnancy induced hypertension revealed different patho-physiological autonomous regulation supposing different etiology of both disorders. PMID:16402614

Baier, V; Baumert, M; Caminal, P; Vallverdú, M; Faber, R; Voss, A

2006-01-01

305

SDIs from global to local levels rely on standardization and interoperable GI services. In the GI field, factual standards are those from the Open Geospatial Consortium (OGC). Therefore, the use and further development of OGC standards are crucial for the success of SDIs. Despite a lack of qualified personnel in OGC issues, OGC topics are rarely included in current GI

Ingo Simonis; Christoph Brox

2006-01-01

306

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

307

NASA Astrophysics Data System (ADS)

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

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

308

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

309

NASA Technical Reports Server (NTRS)

The role of eddy momentum fluxes in the general circulation was investigated using a two-dimensional zonally averaged statistical-dynamical model described by Yao and Stone (1987), which is almost two orders of magnitude faster than the three-dimensional climate model of Hansen et al. (1983). Results show that the vertical structure of the meridional eddy flux has relatively little impact on the general circulation, presumably because the vertical structure is strongly constrained by the thermal wind relation and surface friction. On the other hand, it was found that, in order to simulate accurately the general circulation and its response to climate changes, parameterization of the vertically integrated meridional eddy flux of angular momentum is necessary. A new parameterization of this eddy momentum transport was carried out, which is intended to represent the transport due to large-scale transient eddies arising from baroclinic instability.

Stone, Peter H.; Yao, Mao-Sung

1987-01-01

310

NSDL National Science Digital Library

This site contains 100 modules designed to introduce concepts in statistics. The modules are divided into categories such as descriptive statistics, inferential statistics, related measures, enumeration statistics and ANOVA. Click the green button on the side to start the modules, then click "Main Menu" at the top to see a list of topics. Topics include: describing numbers, normal curve, sampling distributions, hypothesis testing, regression and Chi-Square. The site also includes a glossary, statistical tables and simulations, and a personalized progress report.

Hoffman, Howard

2009-07-14

311

During in vitro selection process, it is very valuable to monitor the binding properties of the ligand population in real time, particularly the population average of the association constant in the population. If this monitoring can be realized, the selection process can be controlled in a rational way. In this paper, we present a simple method to estimate the binding properties of the ligand population during in vitro selection. The framework of the method is as follows. First, the number of all the collected ligand molecules, which are eluted after incubation and washing, is measured. Ideally, this number corresponds to the number of all the ligand molecules bound with the target-receptor or other materials in a test tube. This measurement is performed through several successive rounds of selection. Second, the measured numbers of molecules are subjected to a theoretical analysis, based on the mathematical theory of population dynamics in the selection process. Then, we can estimate the probability density of the binding free energy in the ligand population. The validity of our method was confirmed by several computer simulations based on a physicochemical model. PMID:24239675

Aita, Takuyo; Nishigaki, Koichi; Husimi, Yuzuru

2014-01-01

312

An experimentally simple photon counting method is demonstrated providing 7 orders of magnitude in linear dynamic range (LDR) for a single photomultiplier tube (PMT) detector. In conventional photon/electron counting methods, the linear range is dictated by the agreement between the binomially distributed measurement of counted events and the underlying Poisson distribution of photons/electrons. By explicitly considering the log-normal probability distribution in voltage transients as a function of the number of photons present and the Poisson distribution of photons, observed counts for a given threshold can be related to the mean number of photons well beyond the conventional limit. Analytical expressions are derived relating counts and photons that extend the linear range to an average of ?11 photons arriving simultaneously with a single threshold. These expressions can be evaluated numerically for multiple thresholds extending the linear range to the saturation point of the PMT. The peak voltage distributions are experimentally shown to follow a Poisson weighted sum of log-normal distributions that can all be derived from the single photoelectron voltage peak-height distribution. The LDR that results from this method is compared to conventional single photon counting (SPC) and to signal averaging by analog to digital conversion (ADC). PMID:21114249

Kissick, David J; Muir, Ryan D; Simpson, Garth J

2010-12-15

313

Background In the cardiovascular system, laminar shear stress (SS) is one of the most important source of endothelial protecting signals. Physical and chemical agents, however, including ionising radiations and anticancer drugs, may injure endothelial cells determining an increase in oxidative stress and genotoxic damage. Whether the SS protective function remains intact in the presence of strong oxidants or DNA damage is currently unclear. Methods and Results To investigate this aspect a series of experiments were performed in which HUVEC were exposed to sub-lethal doses of the radio-mimetic compound Bleomycin (Bleo; 10 µg/ml) which generated free radicals (ROS) without significantly compromising cell survival. Remarkably, the application of a SS of 12 dyne/cm2 did not protect endothelial cells but markedly accelerated apoptosis compared to controls kept in static culture and in the presence of Bleo. Experiments with the inducible nitric oxide synthase (iNOS) inhibitor GW274150 significantly reduced the SS-dependent apoptosis indicating that the production of NO was relevant for this effect. At molecular level, the ataxia-telangectasia-mutated (ATM) kinase, the homeodomain-interacting protein kinase-2 (HIPK2) and p53 were found activated along a pro-apoptotic signalling pathway while p21waf1,cip1,sdi1 was prevented from its protective action. RNA interference experiments revealed that HIPK2 and p53 were both important for this process, however, only the forced expression p21waf1,cip1,sdi1 fully restored the SS-dependent pro-survival function. Conclusions This study provides the first evidence that, in the presence of genotoxic damage, laminar flow contributes to endothelial toxicity and death and identifies molecular targets potentially relevant in endothelial dysfunction and cardiovascular disease pathogenesis.

Mattiussi, Stefania; Lazzari, Chiara; Truffa, Silvia; Antonini, Annalisa; Soddu, Silvia; Capogrossi, Maurizio C.; Gaetano, Carlo

2009-01-01

314

NASA Astrophysics Data System (ADS)

This study analyzes the effects of thermocline shoaling on the ocean internal wave (IW) generation in the north South China Sea (NSCS). Seven years of satellite synthetic aperture radar (SAR) images from 1995 to 2001 are used for the statistical analysis of IW occurrence, and field measurements of sea surface wind, sea state, and vertical temperature profiles are used for analyzing IW generation and SAR imaging conditions. Latitudinal distribution of IW packets shows that 22% of IW packets distributed in the east of 118°E obviously originate from the Luzon Strait, and 78% of IW packets west of 118°E may propagate from the east or evolve into the solitons originating from the east boundary owing to the fission effect of shoaling thermocline. The yearly distribution of IW occurrence frequencies reveals an interannual variability, implying that there are long-term and large-scale processes modifying the SAR-observed IW occurrence. The monthly SAR-observed IW occurrence frequencies show that the high frequencies are distributed from April to July and reach a peak in June with a maximum frequency of 20%. The low occurrence frequencies are distributed in winter from December to February of next year with a minimum frequency of 1.5% in February. This study proposes that the IW generation needs the necessary and sufficient conditions: initial disturbance formation and wave amplitude growth. Owing to the dissipation effect on the initial disturbance, only fully grown waves have a chance to radiate out of the source region. A physical model and PKdV equation are adopted for analyzing the sufficient conditions for solitary IW amplitude growth. The results indicate that the thermocline shoaling provides the forcing to soliton amplitude growth, so that the soliton amplitude growth ratio (SAGR) serves as a decisive factor for the IW occurrence frequency. Theoretical analysis predicts a linear relation between the two. Application of theoretical models to field measurements in the Luzon Strait gives a correlation coefficient as high as 0.845 with a confidence level of 99% for months from March to November. The linear regression gives a correlation coefficient (R2) of 0.6519 and a SAGR threshold (minimum) value of 0.90 for IW occurrence. According to the theoretical solutions, the eastward propagating disturbances have no chance to grow up, so that they hardly appear on the east side of the submarine ridges in the eastern Luzon Strait.

Zheng, Quanan; Susanto, R. Dwi; Ho, Chung-Ru; Song, Y. Tony; Xu, Qing

2007-03-01

315

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

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

2014-01-01

316

... Añadir en... Favorites Delicious Digg Google Bookmarks Histoplasmosis Statistics Between 50% and 80% of people who live ... Prevention Sources Diagnosis & Testing Treatment & Outcomes Health Professionals Statistics Additional Information Blastomycosis Definition Symptoms People at Risk & ...

317

Statistics on Family Caregivers and Family Caregiving Caregiving Population Economics of Caregiving Impact on Family Caregiver's Health ... Identified Family Caregivers, 2001. Top State by State Statistics The economic value of family caregiving is detailed ...

318

National Technical Information Service (NTIS)

The areas of research included were graph theory, error-correcting codes, information retrieval, large-sample statistical tests, design of experiments, asymptotic behavior of linear rank statistics, approximation theory, nonparametric tests, fitting frequ...

N. L. Johnson

1973-01-01

319

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

320

ERIC Educational Resources Information Center

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

Petocz, Peter; Sowey, Eric

2008-01-01

321

ERIC Educational Resources Information Center

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

Melnick, Daniel; Huckabee, David

1983-01-01

322

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

323

NASA Technical Reports Server (NTRS)

A dynamic rain attenuation prediction model is developed for use in obtaining the temporal characteristics, on time scales of minutes or hours, of satellite communication link availability. Analagous to the associated static rain attenuation model, which yields yearly attenuation predictions, this dynamic model is applicable at any location in the world that is characterized by the static rain attenuation statistics peculiar to the geometry of the satellite link and the rain statistics of the location. Such statistics are calculated by employing the formalism of Part I of this report. In fact, the dynamic model presented here is an extension of the static model and reduces to the static model in the appropriate limit. By assuming that rain attenuation is dynamically described by a first-order stochastic differential equation in time and that this random attenuation process is a Markov process, an expression for the associated transition probability is obtained by solving the related forward Kolmogorov equation. This transition probability is then used to obtain such temporal rain attenuation statistics as attenuation durations and allowable attenuation margins versus control system delay.

Manning, Robert M.

1987-01-01

324

NSDL National Science Digital Library

This article may help the user understand the concept of statistical significance and the meaning of the numbers produced by The Survey System. This article is presented in two parts. The first part simplifies the concept of statistical significance as much as possible; so that non-technical readers can use the concept to help make decisions based on their data. The second part provides more technical readers with a fuller discussion of the exact meaning of statistical significance numbers.

2008-06-30

325

ERIC Educational Resources Information Center

This guide outlines an Option Y course, which has seven learner objectives geared to providing students with an introduction to the concerns and methods of statistics and equipping pupils to deal with the many statistical matters of importance in society. Topics included in the course are graphs and charts, collection and organization of data,…

Singer, Arlene; And Others

326

Statistical mechanics of solitons

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

Bishop, A.

1980-01-01

327

NASA Astrophysics Data System (ADS)

Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state.

Li, Zheng; Borner, Arnaud; Levin, Deborah A.

2014-06-01

328

Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state. PMID:24929401

Li, Zheng; Borner, Arnaud; Levin, Deborah A

2014-06-14

329

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

330

NSDL National Science Digital Library

Collaborative Statistics was written by Barbara Illowsky and Susan Dean, faculty members at De Anza College in Cupertino, California. The textbook was developed over several years and has been used in regular and honors-level classroom settings and in distance learning classes. This textbook is intended for introductory statistics courses being taken by students at twoÃ¢ÂÂ and fourÃ¢ÂÂyear colleges who are majoring in fields other than math or engineering. Intermediate algebra is the only prerequisite. The book focuses on applications of statistical knowledge rather than the theory behind it.

Dean, Susan; Illowsky, Barbara

2009-11-17

331

The mechanisms responsible for the increase in ceftazidime MIC in two Escherichia coli in vitro selected mutants, Caz/20-1 and Caz/20-2, were studied. OmpF loss and overexpression of acrB, acrD and acrF that were associated with acrR and marR mutations and sdiA overexpression, together with mutations A233T and I332V in FtSI (PBP3) resulted in ceftazidime resistance in Caz/20-2, multiplying by 128-fold the ceftazidime MIC in the parental clinical isolate PS/20. Absence of detectable ?-lactamase hydrolytic activity in the crude extract of Caz/20-2 was observed, and coincided with Q191K and P209S mutations in AmpC and a nucleotide substitution at -28 in the ampC promoter, whereas ?-lactamase hydrolytic activity in crude extracts of PS/20 and Caz/20-1 strains was detected. Nevertheless, a fourfold increase in ceftazidime MIC in Caz/20-1 compared with that in PS/20 was due to the increased transcript level of acrB derived from acrR mutation. The two Caz mutants and PS/20 showed the same mutations in AmpG and ParE. PMID:24089577

Tavío, María M; Aquili, Virginia D; Vila, Jordi; Poveda, José B

2014-01-01

332

National Technical Information Service (NTIS)

This article is a detailed discussion of several classes of statistical software including subroutine libraries, software systems, languages and software/hardware combinations. A comparison of a large number of packages is made across 16 classes of statis...

A. R. Hayes E. J. Wegman

1988-01-01

333

NSDL National Science Digital Library

Created by Richard Dudley of the Massachusetts Institute of Technology, this lesson, Mathematical Statistics, is a graduate-level course featuring book chapters and sections presented as lecture notes, problem sets, exams, and a description for an optional term-paper. The course covers: decision theory, estimation, confidence intervals, hypothesis testing, asymptotic efficiency of estimates, exponential families, sequential analysis, and large sample theory. This is a comprehensive overview of this upper level statistics course.

Dudley, Richard

2009-01-29

334

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

335

Entropy in Nonequilibrium Statistical Mechanics.

National Technical Information Service (NTIS)

Nonequilibrium statistical mechanics aims at deriving from the first principles of microscopic dynamics an entropy theorem which guarantees the approach to thermodynamic equilibrium. Recent developments are reviewed with focus on the position currently he...

A. H. Kritz G. Sandri

1966-01-01

336

Heterogeneity in statistical mechanics

NASA Astrophysics Data System (ADS)

An overview of four studies is presented, each relating to a distinct statistical mechanical model that is at least partially characterized by some form of heterogeneity. The first concerns discreteness effects in interhelical interactions. The second relates to more general discreteness effects relevant to chemical and molecular interactions. The third is a dynamic renormalization group calculation of the fluctuations within a certain model of sedimenting elastic media - one in which the drag depends sensitively on any heterogeneities that develop in the system. Finally, the fourth is a study of the spherical model of a spin glass, which is a statistical mechanical model that is dominated by disorder effects.

Landy, Jonathan Steven

337

NASA Technical Reports Server (NTRS)

Core (0-50 eV) ion pitch angle measurements from the retarding ion mass spectrometer on Dynamics Explorer 1 are examined with respect to magnetic disturbance, invariant latitude, magnetic local time, and altitude for ions H(+), He(+), O(+), M/Z = 2 (D(+) or He(++)), and O(++). Included are outflow events in the auroral zone, polar cap, and cusp, separated into altitude regions below and above 3 R(sub E). In addition to the customary division into beam, conic, and upwelling distributions, the high-latitude observations fall into three categories corresponding to ion bulk speeds that are (1) less than, (2) comparable to, or (3) faster than that of the spacecraft. This separation, along with the altitude partition, serves to identify conditions under which ionospheric source ions are gravita- tionally bound and when they are more energetic and able to escape to the outer magnetosphere. Features of the cleft ion fountain inferred from single event studies are clearly identifiable in the statistical results. In addition, it is found that the dayside pre-noon cleft is a dayside afternoon cleft, or auroral zone, becomes an additional source for increased activity. The auroral oval as a whole appears to be a steady source of escape velocity H(+), a steady source of escape velocity He(+) ions for the dusk sector, and a source of escape velocity heavy ions for dusk local times primarily during increased activity. The polar cap above the auroral zone is a consistent source of low-energy ions, although only the lighter mass particles appear to have sufficient velocity, on average, to escape to higher altitudes. The observations support two concepts for outflow: (1) The cleft ion fountain consists of ionospheric plasma of 1-20 eV energy streaming upward into the magnetosphere where high-latitude convection electric fields cause poleward dispersion. (2) The auroral ion fountain involves field-aligned beams which flow out along auroral latitude field lines; and, in addition, for late afternoon local times, they experience additional acceleration such that the ion energy distribution tends to exceed the detection range of the instrument (greater than 50-60 eV).

Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.

1994-01-01

338

NASA Astrophysics Data System (ADS)

While many scientists are familiar with fractals, fewer are familiar with the concepts of scale-invariance and universality which underly the ubiquity of their shapes. These properties may emerge from the collective behaviour of simple fundamental constituents, and are studied using statistical field theories. Based on lectures for a course in statistical mechanics taught by Professor Kardar at Massachusetts Institute of Technology, this textbook demonstrates how such theories are formulated and studied. Perturbation theory, exact solutions, renormalization groups, and other tools are employed to demonstrate the emergence of scale invariance and universality, and the non-equilibrium dynamics of interfaces and directed paths in random media are discussed. Ideal for advanced graduate courses in statistical physics, it contains an integrated set of problems, with solutions to selected problems at the end of the book. A complete set of solutions is available to lecturers on a password protected website at www.cambridge.org/9780521873413. Based on lecture notes from a course on Statistical Mechanics taught by the author at MIT Contains 65 exercises, with solutions to selected problems Features a thorough introduction to the methods of Statistical Field theory Ideal for graduate courses in Statistical Physics

Kardar, Mehran

2006-06-01

339

Statistical malpractice is an insidious, and indeed prestige-laden and grant-rewarded, activity. Brilliantly clever, but fundamentally wrong-headed, number-crunchers are encouraged to devise inappropriate applications of mathematical methods to health problems. This species of misdirected zealot has so far been immune from criticism. PMID:8709054

Charlton, B G

1996-01-01

340

Background Performance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load. Methods and Results Thirty-two thalassaemia patients (16 males), aged 26.8±6.9 years, without heart failure and 17 healthy controls were studied. Their left ventricular (LV) volumes, ejection fraction, systolic dyssynchrony index (SDI), and myocardial acceleration during isovolumic LV contraction (IVA) were determined at rest and during submaximal bicycle exercise testing using 3-dimensional and tissue Doppler echocardiography. Myocardial iron load as assessed by T2* cardiac magnetic resonance in patients were further related to indices of LV dyssynchrony and contractile reserve. At rest, patients had significantly greater LV SDI (p<0.001) but similar IVA (p?=?0.22) compared with controls. With exercise stress, the prevalence of mechanical dyssynchrony (SDI>4.6%, control+2SD) increased from baseline 25% to 84% in patients. ? SDIexercise-baseline correlated with exercise-baseline differences in LV ejection fraction (p<0.001) and stroke volume (p?=?0.006). Compared with controls, patients had significantly less exercise-induced increase in LV ejection fraction, cardiac index, and IVA (interaction, all p<0.05) and had impaired contractile reserve as reflected by the gentler IVA-heart rate slope (p?=?0.018). Cardiac T2* in patients correlated with baseline LV SDI (r?=??0.44, p?=?0.011) and IVA-heart rate slope (r?=?0.36, p?=?0.044). Conclusions Resting LV dyssynchrony is associated with myocardial iron load. Exercise stress further unveils LV dynamic dyssynchrony and impaired contractile reserve in patients with beta-thalassaemia major.

Cheung, Yiu-fai; Yu, Wei; Li, Shu-na; Lam, Wendy W. M.; Ho, Yuen-chi; Wong, Sophia J.; Chan, Godfrey C. F.; Ha, Shau-yin

2012-01-01

341

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

342

NSDL National Science Digital Library

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

Nrich

2013-01-01

343

NSDL National Science Digital Library

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

Liao, David

344

Assessment of yield stability in sorghum using univariate and multivariate statistical approaches.

The experiment was carried out to estimate GEI in sorghum for grain yield using univariate and multivariate statistical approaches based on two sets of performance trials (T1 and T2). While T1 consisted of 15 genotypes and tested in 8 environments, T2 that consisted of 13 genotypes was carried out in 13 environments. Because the combined ANOVA of each trial revealed significant differences among the genotypes, among the environments and GEI, the five univariate stability estimates: CV(i), S(i)(2), W(i)(2), sigma(i)(2), b(i) and Sd(i)(2) were evaluated for ranking the genotypes. There was positive rank-correlation between CVi and S(i)(2) and among W(i)(2), sigma(i)(2), b(i). Sd(i)(2) had significant positive rank-correlation with sigma(i)(2) and bi in T1 but weak rank-correlation with the remaining parameters in both trials. The three types of univariate stability estimates and the only multivariate stability estimate, the AMMI analysis declared genotypes 2 and 5 to be the most stable in T1, but they gave quite unrelated ranking in T2. Because of the lack of correspondence among the tested stability estimates in the two trials, it was difficult to reach a conclusion on producing genotype recommendation based on the univariate statistical approach. However, as GEI has multivariate nature, the multivariate approach is believed to give more robust inference. Hence, some stable genotypes were suggested using the AMMI model for sorghum growing dry lowlands of the country. PMID:18439231

Adugna, Asfaw

2008-02-01

345

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

346

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

347

Statistical characterization of dislocation ensembles

We outline a method to study the spatial and orientation statistics of dynamical dislocation systems by modeling the dislocations as a stochastic fiber process. Statistical measures have been introduced for the density, velocity, and flux of dislocations, and the connection between these measures and the dislocation state and plastic distortion rate in the crystal is explained. A dislocation dynamics simulation model has been used to extract numerical data to study the evolution of these statistical measures numerically in a body-centered cubic crystal under deformation. The orientation distribution of the dislocation density, velocity and dislocation flux, as well as the dislocation correlations have been computed. The importance of the statistical measures introduced here in building continuum models of dislocation systems is highlighted.

El-Azab, A; Deng, J; Tang, M

2006-05-17

348

Statistical Thermodynamics of Biomembranes

An overview of the major issues involved in the statistical thermodynamic treatment of phospholipid membranes at the atomistic level is summarized: thermodynamic ensembles, initial configuration (or the physical system being modeled), force field representation as well as the representation of long-range interactions. This is followed by a description of the various ways that the simulated ensembles can be analyzed: area of the lipid, mass density profiles, radial distribution functions (RDFs), water orientation profile, Deuteurium order parameter, free energy profiles and void (pore) formation; with particular focus on the results obtained from our recent molecular dynamic (MD) simulations of phospholipids interacting with dimethylsulfoxide (Me2SO), a commonly used cryoprotective agent (CPA).

Devireddy, Ram V.

2010-01-01

349

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

350

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

González-Lezana, Tomás [Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid (Spain)] [Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid (Spain); Honvault, Pascal [Lab. Interdisciplinaire Carnot de Bourgogne, UMR CNRS 6303, Univ. Bourgogne, 21078 Dijon Cedex, France and UFR Sciences et Techniques, Univ. de Franche-Comté, 25030 Besançon cedex (France)] [Lab. Interdisciplinaire Carnot de Bourgogne, UMR CNRS 6303, Univ. Bourgogne, 21078 Dijon Cedex, France and UFR Sciences et Techniques, Univ. de Franche-Comté, 25030 Besançon cedex (France); Scribano, Yohann [Lab. Univers et Particules de Montpellier, Univ. de Montpellier II, LUPM - UMR CNRS 5299, 34095 Montpellier Cedex (France)] [Lab. Univers et Particules de Montpellier, Univ. de Montpellier II, LUPM - UMR CNRS 5299, 34095 Montpellier Cedex (France)

2013-08-07

351

NASA Astrophysics Data System (ADS)

The rotational effects of the S 1 ( 1B 3u) excited state of pyrazine were studied at higher-energy vibrational states. Emission quantum yields were measured and compared using both an incoherent pulsed lamp and a dye laser with a larger coherence width. At E? = 586 cm -1 the rotational dependence of the emission quantum yield ( Y) showed a clear saturation to a value close to that found in the saturation of the dependence of Y on the vibrational energy E?. The asymptotic saturation value of Y = 6 × 10 -4 is shown to be dominated by the contribution of the short time emission ( A+) in the bi-exponential time-resolved emission to Y. This contribution of A+ to Y enhances the "grass" excitation background between transitions, which is now observed in both excitation and absorption spectra. At E? = 586 cm -1, the time-resolved emission decay curves were similar in their rotational dependence to those obtained in the electronic origin, except for an order of magnitude increase in the time-resolved short to long component amplitude ratio ( A+/ A-). Near resonance Raman light scattering is shown again to be irrelevant to the decay of pyrazine. The statistical limit is defined and analysed. Both the time-resolved emission and emission quantum yield clearly demonstrate the transition to a genuine statistical limit, with the implication of the existence of spectrally unresolved absorption. The experimental observations and the observed transition from small molecule to statistical limit behavior (as both E? or J are increased) are discussed in terms of the vibrational crossing model.

Amirav, Aviv

1988-11-01

352

Core (0-50 eV) ion pitch angle measurements from the retarding ion mass spectrometer on Dynamics Explorer 1 are examined with respect to magnetic disturbance, invariant latitude, magnetic local time, and altitude for ions H{sup +}, He{sup +}, O{sup +}, M\\/Z=2 (D{sup +} or He{sup ++}), and O{sup ++}. Included are outflow events in the auroral zone, polar cap, and cusp,

B. L. Giles; T. E. Moore; C. R. Chappell; R. H. Comfort; J. H. Waite

1994-01-01

353

Statistics (Program Description)

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

354

NASA Technical Reports Server (NTRS)

Non-Bayesian statistics were used in simulation studies centered around laser range observations to LAGEOS. The capabilities of satellite laser ranging especially in connection with relative station positioning are evaluated. The satellite measurement system under investigation may fall short in precise determinations of the earth's orientation (precession and nutation) and earth's rotation as opposed to systems as very long baseline interferometry (VLBI) and lunar laser ranging (LLR). Relative station positioning, determination of (differential) polar motion, positioning of stations with respect to the earth's center of mass and determination of the earth's gravity field should be easily realized by satellite laser ranging (SLR). The last two features should be considered as best (or solely) determinable by SLR in contrast to VLBI and LLR.

Vangelder, B. H. W.

1978-01-01

355

Generating Statistical Tables with Canned Statistical Software.

ERIC Educational Resources Information Center

A method of generating common statistical tables using canned statistical computer software is presented. This method allows instructors to provide statistical tables for their students, tailored to their needs. The four most common tables used in elementary college statistics courses are z (standard normal), t, F, and chi square. Specific "p"…

McLean, James E.; Hebbler, Stephen W.

356

Statistical Learning for Humanoid Robots

Abstract: The unknown complexity of the kinematic and dynamic structure ofhumanoid robots make conventional analytical approaches to control increasinglyunsuitable for such systems. Learning techniques oer a possible way to aid controllerdesign if insucient analytical knowledge is available, and learning approachesseem mandatory when humanoid systems are supposed to become completely autonomous.While recent research in neural networks and statistical learning hasfocused mostly

Sethu Vijayakumar; Aaron D'souza; Tomohiro Shibata; Jörg Conradt; Stefan Schaal

2002-01-01

357

NASA Astrophysics Data System (ADS)

The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500 hPa geopotential height and 1,000 hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50 years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our findings are encouraging for the prospects of basin-scale ocean dynamical downscaling using a weather-typing approach to reconstruct forcing fields for high resolution ocean models (Part II) from coarse resolution climate models.

Cassou, Christophe; Minvielle, Marie; Terray, Laurent; Périgaud, Claire

2011-01-01

358

... MQSA) Scorecard Articles MQSA National Statistics MQSA National Statistics In this section of the MQSA Scorecard, we present the most commonly requested national statistics regarding the MQSA program. These statistics are updated ...

359

NASA Astrophysics Data System (ADS)

Documenting past avalanche activity represents an indispensable step in avalanche hazard assessment. Nevertheless, (i) archival records of past avalanche events do not normally yield data with satisfying spatial and temporal resolution and (ii) precision concerning runout distance is generally poorly defined. In addition, historic documentation is most often (iii) biased toward events that caused damage to structure or loss of life on the one hand and (iv) undersampled in unpopulated areas on the other hand. On forested paths dendrogeomorphology has been demonstrated to represent a powerful tool to reconstruct past activity of avalanches with annual resolution and for periods covering the past decades to centuries. This method is based on the fact that living trees may be affected by snow avalanches during their flow and deposition phases. Affected trees will react upon these disturbances with a certain growth response. An analysis of the responses recorded in tree rings coupled with an evaluation of the position of reacting trees within the path allows the dendrogeomorphic expert to identify past snow avalanche events and deduced their minimum runout distance. The objective of the work presented here is firstly to dendrochronogically -reconstruct snow avalanche activity in the Château Jouan path located near Montgenèvre in the French Alps. Minimal runout distances are then determined for each reconstructed event by considering the point of further reach along the topographic profile. Related empirical return intervals are evaluated, combining the extent of each event with the average local frequency of the dendrological record. In a second step, the runout distance distribution derived from dendrochronological reconstruction is compared to the one derived from historical archives and to high return period avalanches predicted by an up-to-date locally calibrated statistical-numerical model. It appears that dendrochronological reconstructions correspond mostly to rare events, i.e. to the tail of the local runout distance distribution. Furthermore, a good agreement exists with the statistical-numerical model's prediction, i.e. a 10-40 m difference for return periods ranging between 10 and 300 years, which is rather small with regards to the uncertainty levels to be considered in avalanche probabilistic modeling and dendrochronological reconstructions. It is important to note that such a cross validation on independent extreme predictions has never been undertaken before. It suggest that i) dendrochronological reconstruction can provide valuable information for anticipating future extreme avalanche events in the context of risk management, and, in turn, that ii) the statistical-numerical model, while properly calibrated, can be used with reasonable confidence to refine these predictions, with for instance evaluation of pressure and flow depth distributions at each position of the runout zone. A strong sensitivity to the determination of local avalanche and dendrological record frequencies is however highlighted, indicating that this step is an essential step for an accurate probabilistic characterization of large-extent events.

Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed

2013-04-01

360

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

361

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

362

Internet For Social Statistics

NSDL National Science Digital Library

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

2009-01-29

363

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

364

Asymptotic Modal Analysis and Statistical Energy Analysis.

National Technical Information Service (NTIS)

Asymptotic Modal Analysis (AMA) is a method which is used to model linear dynamical systems with many participating modes. The AMA method was originally developed to show the relationship between statistical energy analysis (SEA) and classical modal analy...

E. H. Dowell

1992-01-01

365

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

366

Statistical physics ""Beyond equilibrium

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

367

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

368

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

369

Automated regression-based statistical downscaling tool

Many impact studies require climate change information at a finer resolution than that provided by Global Climate Models (GCMs). In the last 10 years, downscaling techniques, both dynamical (i.e. Regional Climate Model) and statistical methods, have been developed to obtain fine resolution climate change scenarios. In this study, an automated statistical downscaling (ASD) regression-based approach inspired by the SDSM method

Masoud Hessami; Philippe Gachon; Taha B. M. J. Ouarda; André St-hilaire

2008-01-01

370

BOOK REVIEW: Statistical Mechanics of Turbulent Flows

This is a handbook for a computational approach to reacting flows, including background material on statistical mechanics. In this sense, the title is somewhat misleading with respect to other books dedicated to the statistical theory of turbulence (e.g. Monin and Yaglom). In the present book, emphasis is placed on modelling (engineering closures) for computational fluid dynamics. The probabilistic (pdf) approach

S. Heinz

2004-01-01

371

... Resources by Topic / Limb Loss Statistics Limb Loss Statistics There are nearly 2 million people living with ... Disease Control and Prevention, National Center for Health Statistics; 1998. HCUP Nationwide Inpatient Sample (NIS). Healthcare Cost ...

372

Obesity Data/Statistics Obesity is a growing epidemic in the United States. From 1980 to 2008, the prevalence of obesity among ... likely to be obese than Non-Hispanic whites. Statistics on African Americans and Obesity . Statistics on American ...

373

Arthritis: Data and Statistics

... en... Favorites Delicious Digg Google Bookmarks Data and Statistics National Statistics Based on 2010-2012 data from the National ... survey conducted by the National Center for Health Statistics. Each year, the NHIS samples U.S. households and ...

374

Hirotugu Akaike, Statistical Scientist.

National Technical Information Service (NTIS)

(1) Change jokes; (2) Toasts; (3) History of statistics in real time: hammers and nails; (4) Akaike's career in statistical science; (5) The phases of Akaike's research; (6) Information statistical literacy.

E. Parzen

1992-01-01

375

Statistical Models in Sedimentology.

National Technical Information Service (NTIS)

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

W. C. Krumbein

1967-01-01

376

... Releases Press Room Assistance Society Overview Hormone Therapy Statistics Home > Publications > Clinical Practice Materials > Hormone Therapy Statistics (Updated June 2011) HT Prescriptions: A Continued Slow ...

377

Methodology, Measurement, and Statistics

... economic, and statistical sciences. The primary goal of the fellowships are to facilitate the ... statistical sciences. In fulfillment of the primary goal, proposals must concretely demonstrate how ...

378

ERIC Educational Resources Information Center

Presents arguments for offering introductory statistics courses to undergraduate sociology majors taught within departments of sociology rather than using statistics courses taught by other departments. (Author)

Caine, Robert; And Others

1978-01-01

379

Opportunities for Improved Statistical Process Control

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

Evan L. Porteus; Alexandar Angelus

1997-01-01

380

American Statistical Association: Statistics in Sports

NSDL National Science Digital Library

This section of the American Statistical Association website covers Statistics in Sports. Available here are a few older articles dealing with sports statistics and links to websites containing data for several professional and amateur sports, as well as websites with general news and information about sports, and a listing of official team websites for pro teams. A section called Statistics on the Web provides links to academic departments, conferences, and employers, while another section answers some frequently asked questions about sports statistics as a career. The website also provides an explanation of the Player Game Percentage (PGP) technique and uses the 2004 World Series as an example to demonstrate the technique. Educators will find a link to a website that offers suggestions of ways to incorporate sports statistics in the classroom.

381

Statistical validation of stochastic models

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

382

Statistical Ensemble of Large Eddy Simulations

NASA Technical Reports Server (NTRS)

A statistical ensemble of large eddy simulations (LES) is run simultaneously for the same flow. The information provided by the different large scale velocity fields is used to propose an ensemble averaged version of the dynamic model. This produces local model parameters that only depend on the statistical properties of the flow. An important property of the ensemble averaged dynamic procedure is that it does not require any spatial averaging and can thus be used in fully inhomogeneous flows. Also, the ensemble of LES's provides statistics of the large scale velocity that can be used for building new models for the subgrid-scale stress tensor. The ensemble averaged dynamic procedure has been implemented with various models for three flows: decaying isotropic turbulence, forced isotropic turbulence, and the time developing plane wake. It is found that the results are almost independent of the number of LES's in the statistical ensemble provided that the ensemble contains at least 16 realizations.

Carati, Daniele; Rogers, Michael M.; Wray, Alan A.; Mansour, Nagi N. (Technical Monitor)

2001-01-01

383

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

384

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

385

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

386

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.

387

The security problem of a statistical database is to limit the use of the database so that no sequence of statistical queries is sufficient to deduce confidential or private information. In this paper it is suggested that the problem be investigated at the conceptual data model level. The design of a statistical database should utilize a statistical security management facility

Francis Y. L. Chin; Gultekin Ozsoyoglu

1981-01-01

388

Generalized quantum statistics

In the paper, a non-anyonic generalization of quantum statistics is presented, in which Fermi-Dirac statistics (FDS) and Bose-Einstein statistics (BES) appear as two special cases. The new quantum statistics, which is characterized by the dimension of its single particle Fock space, contains three consistent parts, namely the generalized bilinear quantization, the generalized quantum mechanical description and the corresponding statistical mechanics.

Chou, C. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Physics)

1992-09-21

389

Strong coupling expansion for classical statistical dynamics

We discuss the simple, randomly driven system dx/dt =-..mu..x-yx/sup 3/+f(t), where f(t) is a Gaussian random function or stirring force with

Bender, C.M.; Cooper, F.; Guralnik, G.; Rose, H.A.; Sharp, D.H.

1980-06-01

390

Statistical Downscaling Method for Climate Data to preserve Statistical Properties

NASA Astrophysics Data System (ADS)

Climate projections produced from the general circulation models (GCMs) need to be spatially and temporally downscaled before applied to the land surface models. Dynamic and statistical downscaling methods have been widely used. The U.S. Bureau of Reclamation and the Lawrence Livermore National Laboratory (LLNL) have developed a Bias Corrected Spatially Downscaled (BCSD) precipitation and temperature data in a monthly scale from the 112 World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) datasets using a statistical downscaling method described by Maurer et al. (2007). However, we need to downscale the monthly CMIP3 BCSD data to daily scale for the hydrologic model simulations. We applied the constant bias (anomaly) correction for the temperature, while we used the four downscaling schemes for precipitation. Four methods are constant bias correction method, ratio method, Gamma-Gamma transformation, and Gamma-Gamma transformation with ratio adjustment method. We evaluates if statistical downscaling methods can preserve the statistical properties such as mean, variance, frequency, and minimum and maximum. Gamma-Gamma distribution is derived for each month using the monthly values of historical data (1950-1999) at each cell and the monthly value of climate projection is found from the Gamma-Gamma distribution function. We further use the nearest neighbor search technique to assign temporal precipitation pattern when there is no event in the daily historical data during the month while the monthly climate data shows any precipitation. We simulate the streamflow using the Variable Infiltration Capacity (VIC) model and assess the performance of the downscaling methods. The Gamma-Gamma transformation with ratio adjustment method preserves the statistical properties, while other methods partially preserve statistical properties.

Park, G.; Song, T.

2010-12-01

391

Osteoporosis Facts and Statistics

... You are here Home - Data & Publications - Facts and Statistics Printer friendly Email Share Tweet Like Osteoporosis - General ... rate of age-related bone loss ( 123 ). Key statistics for Europe Bone mineral density measurement is underutilized ...

392

Ehrlichiosis: Statistics and Epidemiology

... Persons at risk Other Ehrlichiosis, Undetermined Further Reading Statistics and Epidemiology Annual Cases of Ehrlichiosis in the ... PDF - 21 pages] Ehrlichiosis Symptoms, Diagnosis, and Treatment Statistics and Epidemiology In-Depth Information Related Tick Topics ...

393

Overweight and Obesity Statistics

... refers to non-Hispanic whites. top ? Physical Activity Statistics Adults Research Findings Research suggests that staying active ... Centers for Disease Control and Prevention. Summary health statistics for U.S. adults: National Health Interview Survey, 2010. ...

394

Background & Statistics FAQ About Homeless Veterans Homeless Veterans Facts Demographics of Homeless Veterans Incarcerated Veterans Research Briefs Sources FAQ ... VETERANS In May 2007, the Bureau of Justice Statistics released a special report on incarcerated veterans. The ...

395

Listeria (Listeriosis) Statistics

... to... Añadir en... Favorites Delicious Digg Google Bookmarks Statistics Estimates CDC estimates that approximately 1600 illnesses and ... 12, 2011 Case Count Map Epi Curve Surveillance Statistics People at Risk Prevention Sources of Infection Diagnosis & ...

396

... Use Social Media Poster Presentation Buttons and Badges Statistics for Other Types of Cancer Breast Cervical Colorectal ( ... Lung Ovarian Prostate Skin Cancer Home Uterine Cancer Statistics Uterine cancer is the fourth most common cancer ...

397

... en... Favorites Delicious Digg Google Bookmarks Data and Statistics Behavioral Risk Factor Surveillance System ( BRFSS ) Population : Adults ... Podcasts and Sleep e-Cards Fact Sheets Data & Statistics Resources Events File Formats Help: How do I ...

398

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

399

Pneumocystis Pneumonia Statistics

... Añadir en... Favorites Delicious Digg Google Bookmarks Pneumocystis pneumonia Statistics Before the beginning of the HIV/AIDS ... Diagnosis & Testing Treatment & Outcomes Statistics Additional Information Pneumocystis pneumonia Definition Symptoms People at Risk & Prevention Sources Diagnosis & ...

400

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

401

Statistical Quality Management.

National Technical Information Service (NTIS)

Some aspects of statistical quality management are discussed. Quality has to be defined as a concrete, measurable quantity. The concepts of Total Quality Management (TQM), Statistical Process Control (SPC), and inspection are explained. In most cases SPC ...

P. Vanderlaan

1992-01-01

402

Statistical Software Engineering.

National Technical Information Service (NTIS)

This book identifies challenges and opportunities in the development and implementation of software that contain significant statistical content. While emphasizing the relevance of using rigorous statistical and probabilistic techniques in software engine...

1996-01-01

403

Environment for statistical computing

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

404

ERIC Educational Resources Information Center

Presents a search strategy for locating time-series or cross-sectional statistical data in published sources which was designed for undergraduate students who require 30 units of data for five separate variables in a statistical model. Instructional context and the broader applicability of the search strategy for general statistical research is…

Bopp, Richard E.; Van Der Laan, Sharon J.

1985-01-01

405

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.

406

NSDL National Science Digital Library

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

2012-01-01

407

When IFLA needed reliable data about libraries and their services worldwide, it became apparent that there are no such data. Therefore, the IFLA Section on Statistics and Evaluation, the UNESCO Institute for Statistics and the International Organisation for Standardisation (ISO) committee TC 46 SC 8 `Quality — statistics and performance evaluation' have joined forces in order to develop and test

Simon Ellis; Michael Heaney; Pierre Meunier; Roswitha Poll

2009-01-01

408

ERIC Educational Resources Information Center

Avoiding statistical mistakes is important for educators at all levels. Basic concepts will help you to avoid making mistakes using statistics and to look at data with a critical eye. Statistical data is used at educational institutions for many purposes. It can be used to support budget requests, changes in educational philosophy, changes to…

Strasser, Nora

2007-01-01

409

Statistical quality management

NASA Astrophysics Data System (ADS)

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

Vanderlaan, Paul

1992-10-01

410

NSDL National Science Digital Library

This site, created by Robert Jernigan of American University, presents several photographs from real life situations that demonstrate natural statistical concepts. Each picture shows a statistical distribution made by some pattern occurring in everyday life. An explanation of each picture tells what distribution is being represented and how. This is a fun, and different, website devoted to statistics.

Jernigan, Robert

2009-01-28

411

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

412

Artificial intelligence and statistics

This book explores the possible applications of artificial intelligence in statistics and conversely, statistics in artificial intelligence. It is a collection of seventeen papers written by leaders in the field. Most of the papers were prepared for the Workshop on Artificial Intelligence and Statistics held in April 1985 and sponsored by ATandT Bell Laboratories. The book is divided into six parts: uncertainly propagation, clustering and learning, expert systems, environments for supporting statistical strategy, knowledge acquisition, and strategy. The editor ties the collection together in the first chapter by providing an overview of AI and statistics, discussing the Workshop, and exploring future research in the field.

Gale, W.A.

1987-01-01

413

Measuring statistical literacy.

This study considers the measurement of Statistical Literacy understanding that goes beyond the basic chance and data skills and knowledge in the mathematics curriculum. This understanding requires application of mathematical skills in a range of contextual situations and draws on aspects of statistics, such as variation and inference, which may not be explicit in the school curriculum. The study reports the outcomes from tests of Statistical Literacy given to 673 students from Grades 5 to 10. It confirms the nature and structure of a previously identified construct of Statistical Literacy and proposes three subgroups of items that address aspects of Statistical Literacy that might usefully be measured by classroom teachers. PMID:15701942

Callingham, Rosemary; Watson, Jane M

2005-01-01

414

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

415

Statistical Properties of Online Auctions

NASA Astrophysics Data System (ADS)

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

Namazi, Alireza; Schadschneider, Andreas

416

Nonstationary statistical theory for multipactor

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

417

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

418

Statistical regimes of random laser fluctuations

Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on external control parameters. In the Levy regime, the output pulse is highly irregular leading to huge deviations from a mean-field description. Monte Carlo simulations of a simplified model which includes the population of the medium demonstrate the two statistical regimes and provide a comparison with dynamical rate equations. Different statistics of the fluctuations helps to explain recent experimental observations reported in the literature.

Lepri, Stefano [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Cavalieri, Stefano [Dipartimento di Fisica, Universita di Firenze, via G. Sansone 1, I-50019 Sesto Fiorentino (Italy); European Laboratory for Non-linear Spectroscopy, via N. Carrara 1, I-50019 Sesto Fiorentino (Italy); Oppo, Gian-Luca [SUPA and Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow, G4 0NG, Scotland (United Kingdom); Wiersma, Diederik S. [European Laboratory for Non-linear Spectroscopy, via N. Carrara 1, I-50019 Sesto Fiorentino (Italy); BEC-INFM Center, I-38050 Povo, Trento (Italy)

2007-06-15

419

Statistical mechanics of polymer systems. Final

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

Kovac, J.

1993-06-01

420

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

421

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

422

NSDL National Science Digital Library

The 1998 issue of this annual United States Department of Agriculture National Agricultural Statistics Service compendium is available (Adobe Acrobat [.pdf] format only) from the Agricultural Statistics site. Its fifteen chapters consist of time series tables covering all aspects of the US agricultural economy, including crops, livestock, farm income and expenses, price-support, and fertilizer and pesticides. Time series and geographic coverage vary. The site also contains national and state tables and an archive of Agricultural Statistics back to 1994.

423

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.

424

NSDL National Science Digital Library

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

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

2008-12-19

425

Simple Interactive Statistical Analysis

NSDL National Science Digital Library

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

426

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

427

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

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

1993-11-22

428

Statistics Canada = Statistique Canada

NSDL National Science Digital Library

Statistics Canada, a national statistical agency, offers this excellent collection on the economic and social conditions in Canada. Statistical information is divided into four broad topics: The Land, The People, The Economy, and the State. Within each are a number of sub-topics which offer lists of statistical tables. Newly released data, research papers, downloadable publications (Adobe Acrobat [.pdf] format only), and notices of seminars and conferences are featured in addition to The Daily, a collection of the latest news releases and publications from the agency. This site can be viewed in English or French. Note that there is a combination of free and fee based material available.