Statistics on Depository Institutions (SDI)
NSDL National Science Digital Library
New from the FDIC, the Statistics on Depository Institutions is an advanced feature of the FDIC's Institutional Directory system; SDI will help users create detailed financial reports, by either choosing between 24 predefined financial information reports or building their own custom reports. The criteria of the report may include "any combination of single FDIC-insured institutions or bank holding companies, custom peer groups of FDIC-insured institutions or bank holding companies, or standard peer groups of FDIC-insured institutions." A detailed FAQ offers help on creating reports and explains some of the terminology.
SDI: setting the record straight
Adelman, K.L.
1985-01-01
After a few introductory remarks, Mr. Adelman first discusses Soviet propaganda against SDI. He then poses and answers questions regarding the following: SDI and the ABM Treaty; SDI and US arms control objectives; and the ethics of SDI. The final portion of the address reviews US nonproliferation efforts.
Marsh, G.E.
1987-03-01
Recent efforts to redefine the Strategic Defense Initiative (SDI) are mostly aimed at building support for a system to defend US land-based missiles. This is thought to be a more feasible goal than President Reagan's dream of an impregnable shield to defend the US population against ballistic missiles. But a feasible idea is not necessarily a good one. While chasing the population-defense fantasy would destroy the existing arms control regime and waste the national treasure of money and talent, defending land-based missiles would be dangerous and destabilizing. Defense Secretary Caspar Weinberger held fast to the idea of population defense in January, when he told the Senate Armed Services Committee that even early deployments of SDI systems that could be developed in the near future should be the first phase of a system that would protect the continent. But such statements may reflect the administration's determination to do away with the 1972 Anti-Ballistic Missile Treaty more than its belief that population defense is a reasonable goal. The author notes that, to those longstanding problems of defense decision making, they must now add the pressures of SDI. Furthermore, whatever the motives of those who advocate redirecting SDI, it is clear that concerns about the vulnerability of land-based missiles could be addressed in more sensible ways. 5 references.
SDI QUALIFICATION USING TQM CONCEPT
A. Daneshpour Moghaddam; M. R Delavar
By analysis of performed spatial data infrastructures (SDIs) in developed countries, it is believed that one of the most important problems which obstacles the implementation of SDI's objectives, is the lack of enough harmony in different parts. The solution given in management systems for more adaptability is using total quality management (TQM). In this paper, we compare SDI and TQM
Statistics of football dynamics
NASA Astrophysics Data System (ADS)
Mendes, R. S.; Malacarne, L. C.; Anteneodo, C.
2007-06-01
We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by q-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.
Statistics of football dynamics
Mendes, R S; Anteneodo, C
2007-01-01
We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by $q$-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.
Saperstein, A.M.
1988-10-01
The model discussed seems to indicate that if SDI evolves to the points where the defense can overwhelm the offense, the result is a crisis-unstable international system that cannot be mathematically distinguished from a system of war. SDI's acting as envisioned by its supporters does not provide the stable security desired by all. Previous independent qualitative discussions by both US and Soviet analysts have indicated the same instability for SDI. An effective SDI may be very desirable once it is completely in place and functioning, but the process of putting it into place, starting from the present world configuration, seems to be very dangerous. If the proposed defense looks as though it is going to become able to overcome the opponent's offense, then in a crisis, one side is likely to use its offense rather than chance losing it - the very definition of crisis stability. The similarity of the predictions made here and by the US and Soviet analysts concerning the results of SDI deployment lends credence to the forecasts and their underlying assumptions. It appears that SDI cannot be deployed to force major reductions in the offensive strategic nuclear weapons of the superpowers without jeopardizing stability.
Arkin, W.M.
1984-04-01
Proponents of the controversial Strategic Defense Initiatives (SDI)reverse arrowfeel that the will to succeed will be as significant a factor as capability in their effort to make defense a popular concept. They reject the idea that a defensive system must be perfect, and want to loosen the hold of the Anti-Ballistic Missile (ABM) Treaty and Salt II. More than an improvement to deterrence, the goal of SDI is to make a technological leap over the Soviet Union to make its military investments obsolete. Scientists find research on defensive weapons more rewarding than work on offensive systems. Critics need to understand that the force of SDI is ideological in that it rejects the concept of mutually assured destruction (MAD) and concedes that nuclear war is possible.
SDI ladar technology program update
NASA Astrophysics Data System (ADS)
Dezenberg, George
1992-06-01
SDI's Global Protection Against Limited Strikes program has undertaken the development of both solid-state laser and CO2 laser-based ladars. CO2 ladar development is intensively concerned with the reduction of system volumes and weights for orbital deployment, as can be seen in the development milestones of the LOWKATER space-traceable ladar system, Laser Imager Component Development, and a compact, multiple-CO2-laser ladar configuration for interceptor applications.
Lee, S.
2011-05-05
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.
A Framework for Comparing SDI Systems.
ERIC Educational Resources Information Center
Jordan, John R.
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…
The Evaluation of SISMAKOM (Computerized SDI Project).
ERIC Educational Resources Information Center
University of Science, Penang (Malaysia).
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…
Statistics as a dynamical attractor
Michail Zak
2012-08-30
It is demonstrated that any statistics can be represented by an attractor of the solution to a corresponding systen of ODE coupled with its Liouville equation. Such a non-Newtonian representation allows one to reduce foundations of statistics to better established foundations of ODE. In addition to that, evolution to the attractor reveals possible micro-mechanisms driving random events to the final distribution of the corresponding statistical law. Special attention is concentrated upon the power law and its dynamical interpretation: it is demonstrated that the underlying dynamics supports a " violent reputation" of the power law statistics.
SDI evaluation and budgeting processes: linkages and lessons
Kate Lance
Despite the number of SDI initiatives underway worldwide, routine SDI evaluation by public managers is limited. To explore the puzzling gap in SDI evaluation, this chapter examines the institutional arrangements governing the demand for evaluation (internal, external) and the content (inputs, outputs, outcomes). Examples of SDI evaluation practice were identified and analysed and among the examples found, budgeting processes appear
Statistical physics of social dynamics
Claudio Castellano; Santo Fortunato; Vittorio Loreto
2009-01-01
Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide list of topics are reviewed ranging from opinion and cultural and language dynamics to crowd behavior,
The SDI and European security interests
Deschamps, L.
1987-01-01
This paper examines Europe's reactions to President Reagan's Strategic Defense Initiative (SDI). On the one hand, the American proposals have inspired forceful European opposition of a kind potentially damaging to Alliance solidarity. On the other, paradoxically, the debate occurred in a period of rare Alliance harmony, when the deployment of cruise and Pershing II missiles was satisfactorily completed despite Soviet hostility. Yet the nature of the discussion and the compromises reached between Europe and the United States on the SDI have meant that a true strategic debate has not yet begun. Although the SDI is largely an American response to an American strategic problem, Europeans are intimately affected by many of its implications. The author argues that if the SDI program is not to cause great difficulties in the future a more sophisticated discussion of the purposes of strategic defense must now be undertaken. Contents. Introduction; defense in the nuclear age; defense or deterrence: The limits of western consensus; the Euro-American debate on the SDI; European concerns and American responses; and conclusion.
SDI (Strategic Defense Initiative): a policy analysis
Fought, S.O.
1987-01-01
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.
Linear dynamical models, Kalman filtering and statistics.
Gerhardy, Philipp
Linear dynamical models, Kalman filtering and statistics. Lecture notes to IN-ST 259 Erik Bølviken addresses students in both computer science (mathematical modeling) and statistics at the advanced have been motivated by our need for addressing students in both mathematical modeling and statistics
A Modelling Framework for Statistical Cumulus Dynamics
Plant, Robert
A Modelling Framework for Statistical Cumulus Dynamics Bob Plant Department of Meteorology, University of Reading COST ES0905 meeting on Hamiltonian approaches and statistical mechanics in convection results Generalizations? Summary Framework for statistical cumulus dyanmics p.1/4 #12;The cumulus
Statistical physics of social dynamics Claudio Castellano
TAGora project
Statistical physics of social dynamics Claudio Castellano SMC, INFM-CNR and Dipartimento di Fisica-ITALY Statistical physics has proven to be a very fruitful framework to describe phenomena outside the realm the connections between these problems and other, more traditional, topics of statistical physics. We also
Grumman and SDI-related technology
Lewis, B.
1985-01-01
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.
Surface drip irrigation (SDI): Status of the technology in 2010
Technology Transfer Automated Retrieval System (TEKTRAN)
Subsurface drip irrigation (SDI), although a much smaller fraction of the microirrigated land area than surface drip irrigation, is growing at a much faster rate and is the subject of considerable research and educational efforts in the United States. This paper will discuss the growth in SDI, highl...
SDI: Fallacy of last move in arms race
2009-01-01
The Strategic Defense Initiative (SDI), sold to the American people by a persuasive president as the weapons system to end all weapons systems, turned out to be only another step in the continuing arms race, contends the author. It might already have been terminated if President Bush did not fear the conservatives who see SDI as the strategic centerpiece of
Statistics from dynamics in curved spacetime
Parker, L.; Wang, Y.
1989-06-15
We consider quantum fields of spin 0, 1/2, 1,3/2, and 2 with a nonzero mass in curved spacetime. We show thatthe dynamical Bogolubov transformations associated with gravitationally inducedparticle creation imply the connection between spin and statistics: Byembedding two flat regions in a curved spacetime, we find that only when oneimposes Bose-Einstein statistics for an integer-spin field and Fermi-Diracstatistics for a half-integer-spin field in the first flat region is the sametype of statistics propagated from the first to the second flat region. Thisderivation of the flat-spacetime spin-statistics theorem makes use ofcurved-spacetime dynamics and does not reduce to any proof given in flatspacetime. We also show in the same manner that parastatistics, up to thefourth order, are consistent with the dynamical evolution of curved spacetime.
Artificial intelligence applications in space and SDI: A survey
NASA Technical Reports Server (NTRS)
Fiala, Harvey E.
1988-01-01
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.
Replica Exchange Statistical Temperature Molecular Dynamics Jaegil Kim,*,
Straub, John E.
simulations of complex fluids and biomolecules, molecular dynamics (MD) is preferable to MC, dueReplica Exchange Statistical Temperature Molecular Dynamics Algorithm Jaegil Kim,*, John E. Straub ABSTRACT: The replica exchange statistical temperature molecular dynamics (RESTMD) algorithm is presented
Statistical kinetics of macromolecular dynamics.
Shaevitz, Joshua W; Block, Steven M; Schnitzer, Mark J
2005-10-01
Fluctuations in biochemical processes can provide insights into the underlying kinetics beyond what can be gleaned from studies of average rates alone. Historically, analysis of fluctuating transmembrane currents supplied information about ion channel conductance states and lifetimes before single-channel recording techniques emerged. More recently, fluctuation analysis has helped to define mechanochemical pathways and coupling ratios for the motor protein kinesin as well as to probe the contributions of static and dynamic disorder to the kinetics of single enzymes. As growing numbers of assays are developed for enzymatic or folding behaviors of single macromolecules, the range of applications for fluctuation analysis increases. To evaluate specific biochemical models against experimental data, one needs to predict analytically the distribution of times required for completion of each reaction pathway. Unfortunately, using traditional methods, such calculations can be challenging for pathways of even modest complexity. Here, we derive an exact expression for the distribution of completion times for an arbitrary pathway with a finite number of states, using a recursive method to solve algebraically for the appropriate moment-generating function. To facilitate comparisons with experiments on processive motor proteins, we develop a theoretical formalism for the randomness parameter, a dimensionless measure of the variance in motor output. We derive the randomness for motors that take steps of variable sizes or that move on heterogeneous substrates, and then discuss possible applications to enzymes such as RNA polymerase, which transcribes varying DNA sequences, and to myosin V and cytoplasmic dynein, which may advance by variable increments. PMID:16040752
Ochmanek, D.A.
1987-08-01
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.
Teaching the principles of statistical dynamics
Ghosh, Kingshuk; Dill, Ken A.; Inamdar, Mandar M.; Seitaridou, Effrosyni; Phillips, Rob
2012-01-01
We describe a simple framework for teaching the principles that underlie the dynamical laws of transport: Fick’s law of diffusion, Fourier’s law of heat flow, the Newtonian viscosity law, and the mass-action laws of chemical kinetics. In analogy with the way that the maximization of entropy over microstates leads to the Boltzmann distribution and predictions about equilibria, maximizing a quantity that E. T. Jaynes called “caliber” over all the possible microtrajectories leads to these dynamical laws. The principle of maximum caliber also leads to dynamical distribution functions that characterize the relative probabilities of different microtrajectories. A great source of recent interest in statistical dynamics has resulted from a new generation of single-particle and single-molecule experiments that make it possible to observe dynamics one trajectory at a time. PMID:23585693
SDI: O, what a tangled web we weave
Keeny, S.M. Jr.
1993-11-01
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.
Survey of Current Systems for Selective Dissemination of Information. (SDI).
ERIC Educational Resources Information Center
Houseman, Edward M., Ed.
Reproductions of 100 fact sheets received in response to a comprehensive survey of known and suspected Selective Dissemination of Information (SDI) systems are organized into operational, pilot and planned systems. The survey form was designed to give a detailed picture of system design features, organized so that the reader can rapidly locate…
Spectral statistics and dynamics of Lévy matrices
NASA Astrophysics Data System (ADS)
Araujo, Mariela; Medina, Ernesto; Aponte, Eduardo
1999-10-01
We study the spectral statistics and dynamics of a random matrix model where matrix elements are taken from power-law tailed distributions. Such distributions, labeled by a parameter ?, converge on the Lévy basin, giving the matrix model the label ``Lévy matrix'' [P. Cizeau and J. P. Bouchaud, Phys. Rev. E 50, 1810 (1994)]. Such matrices are interesting because their properties go beyond the Gaussian universality class and they model many physically relevant systems such as spin glasses with dipolar or Ruderman-Kittel-Kasuya-Yosida interactions, electronic systems with power-law decaying interactions, and the spectral behavior at the metal insulator transition. Regarding the density of states we extend previous work to reveal the sparse matrix limit as ?-->0. Furthermore, we find for 2×2 Lévy matrices that geometrical level repulsion is not affected by the distribution's broadness. Nevertheless, essential singularities particular to Lévy distributions for small arguments break geometrical repulsion and make it ? dependent. Level dynamics as a function of a symmetry breaking parameter gives new insight into the phases found by Cizeau and Bouchaud (CB). We map the phase diagram drawn qualitatively by CB by using the ?3 statistic. Finally we compute the conductance of each phase by using the Thouless formula, and find that the mixed phase separating conducting and insulating phases has a unique character.
Dynamic stochastic blockmodels: Statistical models for time-evolving networks
Hero, Alfred O.
Dynamic stochastic blockmodels: Statistical models for time-evolving networks Kevin S. Xu or an aggregate view over time. There has been recent interest in statistical modeling of dynamic networks, which to the development of many formal statistical models for networks. Most research has focused on static networks
Teachers' Use of Transnumeration in Solving Statistical Tasks with Dynamic Statistical Software
ERIC Educational Resources Information Center
Lee, Hollylynne S.; Kersaint, Gladis; Harper, Suzanne R.; Driskell, Shannon O.; Jones, Dusty L.; Leatham, Keith R.; Angotti, Robin L.; Adu-Gyamfi, Kwaku
2014-01-01
This study examined a random stratified sample (n = 62) of teachers' work across eight institutions on three tasks that utilized dynamic statistical software. We considered how teachers may utilize and develop their statistical knowledge and technological statistical knowledge when investigating a statistical task. We examined how teachers…
Soviet military on SDI (Strategic Defense Initiative). Professional paper
Fitzgerald, M.C.
1987-08-01
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 from realization suggests both a strong concern about the ultimate impact of these plans on the strategic balance, and a perceived opportunity for scoring propaganda points. Indeed, the present review of Soviet writings since President Reagan's so-called Star Wars speech has yielded both objective Soviet concerns and regressions to psychological warfare. This, in turn, has necessitated a careful effort to separate rhetoric from more official assessments of SDI. While there has long been dispute in the West over the validity of Soviet statements, they have time and again been subsequently confirmed in Soviet hardware, exercises, and operational behavior. Some Western analysts will nonetheless contend that the Soviet statements under examination in this study are merely a commodity for export.
A. Ford and H. Flynn: Statistical Screening of Models 273 Statistical screening of system dynamics
Ford, Andrew
A. Ford and H. Flynn: Statistical Screening of Models 273 Statistical screening of system dynamics models Andrew Forda * and Hilary Flynnb Abstract This paper describes a pragmatic method of searching for the key inputs to a system dynamics model. This analysis is known as screening. The goal is to learn which
Statistical mechanical analysis of the dynamics of learning in perceptrons
Coolen, ACC "Ton"
Statistical mechanical analysis of the dynamics of learning in perceptrons C. W. H. MACE and A. C, statistical mechanics 0960-3174 Ó 1998 Chapman & Hall Contents 1. Introduction 1.1. Supervised learning in neural networks 1.2. Statistical mechanics and its applicability 1.3. A preview 2. On-line learning
For more information, please contact: Professor Sandra Petersen, SDI Executive Director
Massachusetts at Amherst, University of
.umass.edu/sdi diversity science·technology·engineering·mathematics STEM DIVERSITY INSTITUTE University of Massachusetts 524 Goodell Bldg 140 Hicks Way Amherst, MA 01003-9272 www.umass.edu/sdi diversity science·technology·engineering·mathematics development workshops for Ph.D.students diversity science·technology·engineering·mathematics diversity science·technology·engineering·mathematics
Microform Informing: Use of DIALOG SDI to Produce a Microfiche Announcement Bulletin.
ERIC Educational Resources Information Center
Rowe, Gladys E.
1984-01-01
Describes use of selective dissemination of information (SDI) feature on DIALOG at Sandia Technical Library to produce bulletin announcing library acquisitions of technical reports in microfiche. Microfiche acquisition, developing profile, assembling profile output, costs, and suggestions for improvement are highlighted. Examples of SDI profiles…
Subsurface drip irrigation (SDI) research at USDA-ARS in Bushland, TX
Technology Transfer Automated Retrieval System (TEKTRAN)
Producers in the Texas High Plains have recently adopted subsurface drip irrigation (SDI) at unprecedented rates in response to drought, declining water resources from the Ogallala Aquifer, and increasing energy costs to pump groundwater. However, SDI has much greater capital and maintenance require...
Statistical methods for HIV dynamic studies in AIDS clinical trials.
Wu, Hulin
2005-04-01
Studies of HIV dynamics in AIDS research are very important for understanding pathogenesis of HIV infection and for assessing the potency of antiviral therapies. Since the viral dynamic results from clinical data were first published by Ho et al. and Wei et al., the study of HIV-1 dynamics in vivo has drawn a great attention from AIDS clinicians and researchers. Although the important findings from HIV dynamic studies have been published in many prestigious scientific journals, statistical methods for estimating viral dynamic parameters have not been paid enough attention by HIV dynamic investigators. The estimation methods in many viral dynamic studies are very crude and inefficient. In this paper, we review the statistical methods and mathematical models for HIV dynamic data analysis developed in recent years. We also address some practical issues and share our experiences in the design and analysis of viral dynamic studies. Some principles and guidelines for the design and analysis of viral dynamic studies are provided. The methodologies reviewed in this paper are also applicable to studies of other viruses such as hepatitis B virus or hepatitis C virus. We also pose some challenging statistical problems in this area in order to stimulate further study by the statistical research community. PMID:15807150
Multifragmentation: New dynamics or old statistics?
Moretto, L.G.; Delis, D.N.; Wozniak, G.J.
1993-10-01
The understanding of the fission process as it has developed over the last fifty years has been applied to multifragmentation. Two salient aspects have been discovered: 1) a strong decoupling of the entrance and exit channels with the formation of well-characterized sources: 2) a statistical competition between two-, three-, four-, five-, ... n-body decays.
Statistical dynamics of a non-Abelian anyonic quantum walk
Lauri Lehman; Vaclav Zatloukal; Gavin K. Brennen; Jiannis K. Pachos; Zhenghan Wang
2010-09-04
We study the single particle dynamics of a mobile non-Abelian anyon hopping around many pinned anyons on a surface. The dynamics is modelled by a discrete time quantum walk and the spatial degree of freedom of the mobile anyon becomes entangled with the fusion degrees of freedom of the collective system. Each quantum trajectory makes a closed braid on the world lines of the particles establishing a direct connection between statistical dynamics and quantum link invariants. We find that asymptotically a mobile Ising anyon becomes so entangled with its environment that its statistical dynamics reduces to a classical random walk with linear dispersion in contrast to particles with Abelian statistics which have quadratic dispersion.
Segmenting Dynamic Human Action via Statistical Structure
ERIC Educational Resources Information Center
Baldwin, Dare; Andersson, Annika; Saffran, Jenny; Meyer, Meredith
2008-01-01
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…
Photon Counts Statistics in Leukocyte Cell Dynamics
NASA Astrophysics Data System (ADS)
van Wijk, Eduard; van der Greef, Jan; van Wijk, Roeland
2011-12-01
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.
Extreme Events: Dynamics, Statistics and Prediction
NASA Astrophysics Data System (ADS)
Ghil, M.
2013-05-01
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.
Protein electron transfer: Dynamics and statistics.
Matyushov, Dmitry V
2013-07-14
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
Application of braid statistics to particle dynamics
NASA Astrophysics Data System (ADS)
Skjeltorp, Arne T.; Clausen, Sigmund; Helgesen, Geir
1999-12-01
How, in a simple and forceful way, do we characterize the dynamics of systems with several moving components? The methods based on the theory of braids may provide the answer. Knot and braid theory is a subfield of mathematics known as topology. It involves classifying different ways of tracing curves in space. Knot theory originated more than a century ago and is today a very active area of mathematics. Recently, we have been able to use notions from braid theory to map the complicated trajectories of tiny magnetic beads confined between two plates and subjected to complex magnetic fields. The essentially two-dimensional motion of a bead can be represented as a curve in a three-dimensional space-time diagram, and so several beads in motion produce a set of braided curves. The topological description of these braids thus provides a simple and concise language for describing the dynamics of the system, as if the beads perform a complicated dance as they move about one another, and the braid encodes the choreography of this dance.
Statistical dynamics of religions and adherents
NASA Astrophysics Data System (ADS)
Ausloos, M.; Petroni, F.
2007-02-01
Religiosity is one of the most important sociological aspects of populations. All religions may evolve in their beliefs and adapt to the society developments. A religion is a social variable, like a language or wealth, to be studied like any other organizational parameter. Several questions can be raised, as considered in this study; e.g.: i) From a "macroscopic" point of view: How many religions exist at a given time? ii) From a "microscopic" viewpoint: How many adherents belong to one religion? Does the number of adherents increase or not, and how? No need to say that if quantitative answers and mathematical laws are found, agent-based models can be imagined to describe such non-equilibrium processes. It is found that empirical laws can be deduced and related to preferential attachment processes, like on an evolving network; we propose two different algorithmic models reproducing as well the data. Moreover, a population growth-death equation is shown to be a plausible modeling of evolution dynamics in a continuous-time framework. Differences with language dynamic competition are emphasized.
SDI (Strategic Defense Initiative) and the Soviet defense burden. Interim report
Hildebrandt, G.G.
1988-12-01
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 program, which is designed to increase the productivity of economic resources. The analysis suggests that the Soviets can partially offset a U.S. SDI effort with a ruble expenditure that is a small percentage of current defense spending. Although the Soviets may regard such a response as unsatisfactory, it is important to consider the striking contrast compared with the burden of an emulation response. The author hypothesizes, therefore, that the Soviets will choose not to directly emulate the U.S. SDI activities, at least until they have modernized their technical-economic base.
Application of Tube Dynamics to Non-Statistical Reaction Processes
NASA Astrophysics Data System (ADS)
Gabern, F.; Koon, W. S.; Marsden, J. E.; Ross, S. D.; Yanao, T.
2006-06-01
A technique based on dynamical systems theory is introduced for the computation of lifetime distributions and rates of chemical reactions and scattering phenomena, even in systems that exhibit non-statistical behavior. In particular, we merge invariant manifold tube dynamics with Monte Carlo volume determination for accurate rate calculations. This methodology is applied to a three-degree-of-freedom model problem and some ideas on how it might be extended to higher-degree-of-freedom systems are presented.
INVITED ARTICLE: Nonlinear dynamics and statistical physics of DNA
Michel Peyrard
2004-01-01
DNA is not only an essential object of study for biologists---it also raises very interesting questions for physicists. This paper discuss its nonlinear dynamics, its statistical mechanics, and one of the experiments that one can now perform at the level of a single molecule and which leads to a non-equilibrium transition at the molecular scale. After a review of experimental
Exploring Foundation Concepts in Introductory Statistics Using Dynamic Data Points
ERIC Educational Resources Information Center
Ekol, George
2015-01-01
This paper analyses introductory statistics students' verbal and gestural expressions as they interacted with a dynamic sketch (DS) designed using "Sketchpad" software. The DS involved numeric data points built on the number line whose values changed as the points were dragged along the number line. The study is framed on aggregate…
Stochastics and Statistics Exploiting structure in adaptive dynamic programming
Powell, Warren B.
Stochastics and Statistics Exploiting structure in adaptive dynamic programming algorithms and Financial Engineering, School of Engineering/Applied Science, Princeton University, Princeton, NJ 08544, USA and establish some theoretical results including monotonicity of the value functions. Then, we use our adaptive
Smooth Dynamics and New Theoretical Ideas in Nonequilibrium Statistical Mechanics
David Ruelle
1999-01-01
This paper reviews various applications of the theory of smooth dynamical systems to conceptual problems of nonequilibrium statistical mecanics. We adopt a new point of view which has emerged progressively in recent years, and which takes seriously into account the chaotic character of the microscopic time evolution. The emphasis is on nonequilibrium steady states rather than the traditional approach to
Dynamic Statistical Graphics in the CAVE Virtual Reality Environment
Symanzik, Jürgen
nition of the term Virtual Reality, but almost every person has a di erent understanding. In CruzDynamic Statistical Graphics in the CAVE Virtual Reality Environment Jurgen Symanzik, Dianne Cook: symanzik@iastate.edu Abstract The CAVE is a high end immersive virtual reality environment that allows 3
Statistical Analysis of Molecular Dynamics Simulations
NASA Astrophysics Data System (ADS)
Atkinson, R. A.
Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the specification and analysis of stochastic models of molecular motion and interaction in simple liquids. Basic chemical terminology is introduced and a brief description is given of the technique of molecular dynamics simulation. Stochastic process theory, in so far as it is relevant to the modelling of molecular trajectories and chemical reaction, is reviewed. First passage densities are shown to be important in the analysis of diffusion controlled chemical reaction. The relationship between first passage densities and flux or flow across the absorbing boundary is given. A formula proposed by Durbin is discussed and shown to be valid for diffusion processes under certain regularity conditions. The simplest integrated diffusion, integrated Brownian motion, is considered and a detailed derivation of McKean's half-winding formula is given. An explicit expression for the return-time density is derived, from which the large time asymptotics can be deduced. Goldman's formula for the density of the hitting-time of positive levels is extended to all real values and a simple intuitive derivation is given. Similar arguments enable the results of Gor'kov to be extended to a wider class of integrated diffusions. First passage time densities are computed numerically using the extension of Goldman's formula and compared with approximations which have been suggested by Hesse. Small drift asymptotics are derived for the escape probability of integrated Brownian motion with drift. A number of results are obtained for the integrated Ornstein -Uhlenbeck process, by using martingale methods. Finally, the empirical observations of Lynden-Bell, Hutchinson and Doyle are analysed. A stochastic model of single-particle motion based on the velocity autocorrelation function is proposed and shown to be in excellent agreement with the computer generated data.
Spatial statistics and attentional dynamics in scene viewing.
Engbert, Ralf; Trukenbrod, Hans A; Barthelmé, Simon; Wichmann, Felix A
2015-01-01
In humans and in foveated animals visual acuity is highly concentrated at the center of gaze, so that choosing where to look next is an important example of online, rapid decision-making. Computational neuroscientists have developed biologically-inspired models of visual attention, termed saliency maps, which successfully predict where people fixate on average. Using point process theory for spatial statistics, we show that scanpaths contain, however, important statistical structure, such as spatial clustering on top of distributions of gaze positions. Here, we develop a dynamical model of saccadic selection that accurately predicts the distribution of gaze positions as well as spatial clustering along individual scanpaths. Our model relies on activation dynamics via spatially-limited (foveated) access to saliency information, and, second, a leaky memory process controlling the re-inspection of target regions. This theoretical framework models a form of context-dependent decision-making, linking neural dynamics of attention to behavioral gaze data. PMID:25589298
Dynamical versus statistical mesoscopic models for DNA denaturation
Joyeux, Marc
2008-01-01
We recently proposed a dynamical mesoscopic model for DNA, which is based, like statistical ones, on site-dependent finite stacking and pairing enthalpies. In the present article, we first describe how the parameters of this model are varied to get predictions in better agreement with experimental results that were not addressed up to now, like mechanical unzipping, the evolution of the critical temperature with sequence length, and temperature resolution. We show that the model with the new parameters provides results that are in quantitative agreement with those obtained from statistical models. Investigation of the critical properties of the dynamical model suggests that DNA denaturation looks like a first-order phase transition in a broad temperature interval, but that there necessarily exists, very close to the critical temperature, a crossover to another regime. The exact nature of the melting dynamics in this second regime still has to be elucidated. We finally point out that the descriptions of the ph...
Seasonal statistical-dynamical forecasts of droughts over Western Iberia
NASA Astrophysics Data System (ADS)
Ribeiro, Andreia; Pires, Carlos
2015-04-01
The Standard Precipitation Index (SPI) has been used here as a drought predictand in order to assess seasonal drought predictability over the western Iberia. Hybrid (statistical-dynamical) long-range forecasts of the drought index SPI are estimated with lead-times up to 6 months, over the period of 1987-2008. Operational forecasts of geopotential height and total precipitation from the UK Met Office operational forecasting system are considered. Past ERA-Interim reanalysis data, prior to the forecast launching, are used for the purpose of build a set of SPI predictors, integrating recent past observations. Then, a two-step hybridization procedure is adopted: in the first-step both forecasted and observational large-scale fields are subjected to a Principal Component Analysis (PCA) and forecasted PCs and persistent PCs are used as predictors. The second hybridization step consists on a statistical/hybrid downscaling to the regional scale based on regression techniques, after the selection of the statistically significant predictors. The large-scale filter predictors from past observations and operational forecasts are used to downscale SPI and the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. The SPI estimations and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode. Results show that winter is the most predictable season, and most of the predictive power is on the large-scale fields and at the shorter lead-times. The hybridization improves forecasting drought skill in comparison to purely dynamical forecasts, since the persistence of large-scale patterns displays the main role in the long-range predictability of precipitation. These findings provide clues about the predictability of the SPI, particularly in Portugal, and may contribute to the predictability of crops yields and to some guidance on users (such as farmers) decision making process.
Fractional-power-law level statistics due to dynamical tunneling.
Bäcker, Arnd; Ketzmerick, Roland; Löck, Steffen; Mertig, Normann
2011-01-14
For systems with a mixed phase space we demonstrate that dynamical tunneling universally leads to a fractional power law of the level-spacing distribution P(s) over a wide range of small spacings s. Going beyond Berry-Robnik statistics, we take into account that dynamical tunneling rates between the regular and the chaotic region vary over many orders of magnitude. This results in a prediction of P(s) which excellently describes the spectral data of the standard map. Moreover, we show that the power-law exponent is proportional to the effective Planck constant h(eff). PMID:21405229
A study on modeling the dynamics of statistically dependent returns
NASA Astrophysics Data System (ADS)
Davari-Ardakani, Hamed; Aminnayeri, Majid; Seifi, Abbas
2014-07-01
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.
Statistical energy conservation principle for inhomogeneous turbulent dynamical systems
Majda, Andrew J.
2015-01-01
Understanding the complexity of anisotropic turbulent processes over a wide range of spatiotemporal scales in engineering shear turbulence as well as climate atmosphere ocean science is a grand challenge of contemporary science with important societal impact. In such inhomogeneous turbulent dynamical systems there is a large dimensional phase space with a large dimension of unstable directions where a large-scale ensemble mean and the turbulent fluctuations exchange energy and strongly influence each other. These complex features strongly impact practical prediction and uncertainty quantification. A systematic energy conservation principle is developed here in a Theorem that precisely accounts for the statistical energy exchange between the mean flow and the related turbulent fluctuations. This statistical energy is a sum of the energy in the mean and the trace of the covariance of the fluctuating turbulence. This result applies to general inhomogeneous turbulent dynamical systems including the above applications. The Theorem involves an assessment of statistical symmetries for the nonlinear interactions and a self-contained treatment is presented below. Corollary 1 and Corollary 2 illustrate the power of the method with general closed differential equalities for the statistical energy in time either exactly or with upper and lower bounds, provided that the negative symmetric dissipation matrix is diagonal in a suitable basis. Implications of the energy principle for low-order closure modeling and automatic estimates for the single point variance are discussed below. PMID:26150510
Statistical energy conservation principle for inhomogeneous turbulent dynamical systems.
Majda, Andrew J
2015-07-21
Understanding the complexity of anisotropic turbulent processes over a wide range of spatiotemporal scales in engineering shear turbulence as well as climate atmosphere ocean science is a grand challenge of contemporary science with important societal impact. In such inhomogeneous turbulent dynamical systems there is a large dimensional phase space with a large dimension of unstable directions where a large-scale ensemble mean and the turbulent fluctuations exchange energy and strongly influence each other. These complex features strongly impact practical prediction and uncertainty quantification. A systematic energy conservation principle is developed here in a Theorem that precisely accounts for the statistical energy exchange between the mean flow and the related turbulent fluctuations. This statistical energy is a sum of the energy in the mean and the trace of the covariance of the fluctuating turbulence. This result applies to general inhomogeneous turbulent dynamical systems including the above applications. The Theorem involves an assessment of statistical symmetries for the nonlinear interactions and a self-contained treatment is presented below. Corollary 1 and Corollary 2 illustrate the power of the method with general closed differential equalities for the statistical energy in time either exactly or with upper and lower bounds, provided that the negative symmetric dissipation matrix is diagonal in a suitable basis. Implications of the energy principle for low-order closure modeling and automatic estimates for the single point variance are discussed below. PMID:26150510
Dynamics, stability, and statistics on lattices and networks
NASA Astrophysics Data System (ADS)
Livi, Roberto
2014-07-01
These lectures aim at surveying some dynamical models that have been widely explored in the recent scientific literature as case studies of complex dynamical evolution, emerging from the spatio-temporal organization of several coupled dynamical variables. The first message is that a suitable mathematical description of such models needs tools and concepts borrowed from the general theory of dynamical systems and from out-of-equilibrium statistical mechanics. The second message is that the overall scenario is definitely reacher than the standard problems in these fields. For instance, systems exhibiting complex unpredictable evolution do not necessarily exhibit deterministic chaotic behavior (i.e., Lyapunov chaos) as it happens for dynamical models made of a few degrees of freedom. In fact, a very large number of spatially organized dynamical variables may yield unpredictable evolution even in the absence of Lyapunov instability. Such a mechanism may emerge from the combination of spatial extension and nonlinearity. Moreover, spatial extension allows one to introduce naturally disorder, or heterogeneity of the interactions as important ingredients for complex evolution. It is worth to point out that the models discussed in these lectures share such features, despite they have been inspired by quite different physical and biological problems. Along these lectures we describe also some of the technical tools employed for the study of such models, e.g., Lyapunov stability analysis, unpredictability indicators for "stable chaos," hydrodynamic description of transport in low spatial dimension, spectral decomposition of stochastic dynamics on directed networks, etc.
SDI (Strategic Defense Initiative): where do we go from here. Study project
Dierker, R.R.
1988-03-30
President Reagan's announcement five years ago of his vision for a Strategic Defense Initiative (SDI) has had strong implications for the United States nuclear strategy. Implementation of any or all parts of a strategic defense system would constitute a shift away from the offense-dominant strategy that the U.S. has espoused for over forty years. Effecting a shift in U.S. nuclear strategy while maintaining stability between the superpowers is an extremely difficult task. Opponents of SDI have raised the question of whether we should pursue SDI and the ensuing shift in strategy at all. The only real question to be answered is how to effect a stable shift in U.S. strategy. The key to that shift is understanding and then considering the Soviets' views of SDI. The author discusses Soviet views of the U.S.'s Strategic Defense Initiative and then examines four possible U.S. options for SDI, ranging from unilateral deployment to use as a bargaining chip.
Straub, John E.
Structure optimization and folding mechanisms of off-lattice protein models using statistical. The distinct folding features of the models are analyzed in terms of the statistical temperature and other temperature molecular dynamics simulation: Statistical temperature annealing Jaegil Kim,* John E. Straub
A Stochastic Fractional Dynamics Model of Rainfall Statistics
NASA Astrophysics Data System (ADS)
Kundu, Prasun; Travis, James
2013-04-01
Rainfall varies in space and time in a highly irregular manner and is described naturally in terms of a stochastic process. A characteristic feature of rainfall statistics is that they depend strongly on the space-time scales over which rain data are averaged. A spectral model of precipitation has been developed based on a stochastic differential equation of fractional order for the point rain rate, that allows a concise description of the second moment statistics of rain at any prescribed space-time averaging scale. The model is designed to faithfully reflect the scale dependence and is thus capable of providing a unified description of the statistics of both radar and rain gauge data. The underlying dynamical equation can be expressed in terms of space-time derivatives of fractional orders that are adjusted together with other model parameters to fit the data. The form of the resulting spectrum gives the model adequate flexibility to capture the subtle interplay between the spatial and temporal scales of variability of rain but strongly constrains the predicted statistical behavior as a function of the averaging length and times scales. The main restriction is the assumption that the statistics of the precipitation field is spatially homogeneous and isotropic and stationary in time. We test the model with radar and gauge data collected contemporaneously at the NASA TRMM ground validation sites located near Melbourne, Florida and in Kwajalein Atoll, Marshall Islands in the tropical Pacific. We estimate the parameters by tuning them to the second moment statistics of the radar data. The model predictions are then found to fit the second moment statistics of the gauge data reasonably well without any further adjustment. Some data sets containing periods of non-stationary behavior that involves occasional anomalously correlated rain events, present a challenge for the model.
Nonlinear Dynamics and Statistical Theories for Basic Geophysical Flows
NASA Astrophysics Data System (ADS)
Majda, Andrew; Wang, Xiaoming
2006-05-01
The general area of geophysical fluid mechanics is truly interdisciplinary. Now ideas from statistical physics are being applied in novel ways to inhomogeneous complex systems such as atmospheres and oceans. In this book, the basic ideas of geophysics, probability theory, information theory, nonlinear dynamics and equilibrium statistical mechanics are introduced and applied to large time-selective decay, the effect of large scale forcing, nonlinear stability, fluid flow on a sphere and Jupiter's Great Red Spot. The book is the first to adopt this approach and it contains many recent ideas and results. Its audience ranges from graduate students and researchers in both applied mathematics and the geophysical sciences. It illustrates the richness of the interplay of mathematical analysis, qualitative models and numerical simulations which combine in the emerging area of computational science. First book combining nonlinear dynamical and statistical approaches at elementary level Only basic prerequisites; many topics introduced through examples as and when required Many applications to geophysics including Great Red Spot of Jupiter
Hydrological responses to dynamically and statistically downscaled climate model output
Wilby, R.L.; Hay, L.E.; Gutowski, W.J., Jr.; Arritt, R.W.; Takle, E.S.; Pan, Z.; Leavesley, G.H.; Clark, M.P.
2000-01-01
Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis. A distributed hydrological model was then applied to the downscaled data. Relative to raw NCEP output, downscaled climate variables provided more realistic stimulations of basin scale hydrology. However, the results highlight the sensitivity of modeled processes to the choice of downscaling technique, and point to the need for caution when interpreting future hydrological scenarios.
Dynamical and statistical properties of a rotating oval billiard
NASA Astrophysics Data System (ADS)
da Costa, Diogo Ricardo; Oliveira, Diego F. M.; Leonel, Edson D.
2014-06-01
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.
Statistical Molecular Dynamics study of displacement energies in diamond
NASA Astrophysics Data System (ADS)
Delgado, Diego; Vila, Rafael
2011-12-01
Molecular Dynamics simulations in bulk diamond using AIREBO potential have been used to calculate minimum displacement energy. A statistical approach has been applied calculating displacement probability curves along the main crystallographic directions. With these curves a minimum displacement energy of around 30 eV can be obtained, and a weighted average energy of around 70 eV. This value has been estimated as more accurate for its use in BCA displacement equations to obtain Frenkel pairs at moderate temperatures. This work also includes a study of defect states whose analysis reveals interesting results concerning the evolution of primary damage at higher PKA energies.
Solar wind dynamic pressure variations: Quantifying the statistical magnetospheric response
NASA Technical Reports Server (NTRS)
Sibeck, D. G.
1990-01-01
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.
A whirlwind tour of statistical methods in structural dynamics.
Booker, J. M.
2004-01-01
Several statistical methods and their corresponding principles of application to structural dynamics problems will be presented. This set was chosen based upon the projects and their corresponding challenges in the Engineering Sciences & Applications (ESA) Division at Los Alamos National Laboratory and focuses on variance-based uncertainty quantification. Our structural dynamics applications are heavily involved in modeling and simulation, often with sparse data availability. In addition to models, heavy reliance is placed upon the use of expertise and experience. Beginning with principles of inference and prediction, some statistical tools for verification and validation are introduced. Among these are the principles of good experimental design for test and model computation planning, and the combination of data, models and knowledge through the use of Bayes Theorem. A brief introduction to multivariate methods and exploratory data analysis will be presented as part of understanding relationships and variation among important parameters, physical quantities of interest, measurements, inputs and outputs. Finally, the use of these methods and principles will be discussed in drawing conclusions from the validation assessment process under uncertainty.
Extreme event statistics of daily rainfall: Dynamical systems approach
G. Cigdem Yalcin; Pau Rabassa; Christian Beck
2015-08-15
We analyse the probability densities of daily rainfall amounts at a variety of locations on the Earth. The observed distributions of the amount of rainfall fit well to a q-exponential distribution with exponent q close to q=1.3. We discuss possible reasons for the emergence of this power law. On the contrary, the waiting time distribution between rainy days is observed to follow a near-exponential distribution. A careful investigation shows that a q-exponential with q=1.05 yields actually the best fit of the data. A Poisson process where the rate fluctuates slightly in a superstatistical way is discussed as a possible model for this. We discuss the extreme value statistics for extreme daily rainfall, which can potentially lead to flooding. This is described by Frechet distributions as the corresponding distributions of the amount of daily rainfall decay with a power law. On the other hand, looking at extreme event statistics of waiting times between rainy days (leading to droughts for very long dry periods) we obtain from the observed near-exponential decay of waiting times an extreme event statistics close to Gumbel distributions. We discuss superstatistical dynamical systems as simple models in this context.
Universality of Tsallis Non-Extensive Statistics and Fractal Dynamics for Complex Systems
G. P. Pavlos; M. N. Xenakis; L. P. Karakatsanis; A. C. Iliopoulos; A. E. G. Pavlos; D. V. Sarafopoulos
2012-03-25
Tsallis q-extension of statistics and fractal generalization of dynamics are two faces of the same physical reality, as well as the Kernel modern complexity theory. The fractal generalization dynamics is based at the multiscale - multifractal characters of complex dynamics in the physical space-time and the complex system's dynamical phase space. Tsallis q-triplet of non-extensive statistics can be used for the experiment test of q-statistic as well as of the fractal dynamics. In this study we present indicative experimental verifications of Tsallis theory in various complex systems such as solar plasmas, (planetic magnetospheres, cosmic stars and cosmic rays), atmospheric dynamics, seismogenesis and brain dynamics.
Near-surface soil water and temperature for SDI, LEPA, and spray irrigation
Technology Transfer Automated Retrieval System (TEKTRAN)
Near-surface soil temperatures and volumetric soil water contents were compared for SDI, LEPA, and spray irrigation in a Pullman clay loam soil planted in cotton. Soil temperatures were measured by type-T thermocouples and volumetric water contents were measured by time domain reflectometry (TDR) in...
Social Development in Hong Kong: Development Issues Identified by Social Development Index (SDI)
ERIC Educational Resources Information Center
Chua, Hoi-wai; Wong, Anthony K. W.; Shek, Daniel T. L.
2010-01-01
Surviving the aftermaths of the Asian Financial Crisis and SARS in 2003, Hong Kong's economy has re-gained its momentum and its economic growth has been quite remarkable too in recent few years. Nevertheless, as reflected by the Social Development Index (SDI), economic growth in Hong Kong does not seem to have benefited the people of the city at…
Statistical work-energy theorems in deterministic dynamics
NASA Astrophysics Data System (ADS)
Kim, Chang Sub
2015-07-01
We theoretically explore the Bochkov-Kuzovlev-Jarzynski-Crooks work theorems in a finite system subject to external control, which is coupled to a heat reservoir. We first elaborate the mechanical energy balance between the system and the surrounding reservoir and then proceed to formulate its statistical counterpart under the general nonequilibrium conditions. Consequently, a consistency condition is derived, underpinning the nonequilibrium equalities, both in the framework of the system-centric and nonautonomous Hamiltonian pictures, and its utility is examined in a few examples. Also, we elucidate that the symmetric fluctuation associated with forward and backward manipulation of the nonequilibrium work is contingent on time-reversal invariance of the underlying mesoscopic dynamics.
Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange
M. Sebawe Abdalla; Faisal A. A. El-Orany; J. Perina
2011-07-29
In this paper we derive the quantum statistical and dynamical properties of nonlinear optical couplers composed of two nonlinear waveguides operating by the second subharmonic generation, which are coupled linearly through evanescent waves and nonlinearly through nondegenerate optical parametric interaction. Main attention is paid to generation and transmission of nonclassical light, based on a discussion of squeezing phenomenon, normalized second-order correlation function, and quasiprobability distribution functions. Initially coherent, number and thermal states of optical beams are considered. In particular, results are discussed in dependence on the strength of the nonlinear coupling relatively to the linear coupling. We show that if the Fock state $|1>$ enters the first waveguide and the vacuum state $|0>$ enters the second waveguide, the coupler can serve as a generator of squeezed vacuum state governed by the coupler parameters. Further, if thermal fields enter initially the waveguides the coupler plays similar role as a microwave Josephson-junction parametric amplifier to generate squeezed thermal light.
The intermediate level statistics in dynamically localized chaotic eigenstates
NASA Astrophysics Data System (ADS)
Batisti?, B.; Manos, T.; Robnik, M.
2013-06-01
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.
Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange
Abdalla, M Sebawe; Perina, J
2011-01-01
In this paper we derive the quantum statistical and dynamical properties of nonlinear optical couplers composed of two nonlinear waveguides operating by the second subharmonic generation, which are coupled linearly through evanescent waves and nonlinearly through nondegenerate optical parametric interaction. Main attention is paid to generation and transmission of nonclassical light, based on a discussion of squeezing phenomenon, normalized second-order correlation function, and quasiprobability distribution functions. Initially coherent, number and thermal states of optical beams are considered. In particular, results are discussed in dependence on the strength of the nonlinear coupling relatively to the linear coupling. We show that if the Fock state $|1>$ enters the first waveguide and the vacuum state $|0>$ enters the second waveguide, the coupler can serve as a generator of squeezed vacuum state governed by the coupler parameters. Further, if thermal fields enter initially the waveguides the coupler play...
A statistical model for interpreting computerized dynamic posturography data
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Metter, E. Jeffrey; Paloski, William H.
2002-01-01
Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.
OPEN PROBLEM: Orbits' statistics in chaotic dynamical systems
NASA Astrophysics Data System (ADS)
Arnold, V.
2008-07-01
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).
Vegetation patchiness: Pareto statistics, cluster dynamics and desertification.
NASA Astrophysics Data System (ADS)
Shnerb, N. M.
2009-04-01
Recent studies [1-4] of cluster distribution of vegetation in the dryland revealed Pareto statistics for the size of spatial colonies. These results were supported by cellular automata simulations that yield robust criticality for endogenous pattern formation based on positive feedback. We show that this self-organized criticality is a manifestation of the law of proportion effec: mapping the stochastic model to a Markov birth-death process, the transition rates are shown to scale linearly with cluster size. This mapping provides a connection between patch statistics and the dynamics of the ecosystem; the "first passage time" for different colonies emerges as a powerful tool that discriminates between endogenous and exogenous clustering mechanisms. Imminent catastrophic shifts (like desertification) manifest themselves in a drastic change of the stability properties of spatial colonies, as the chance of a cluster to disappear depends logarithmically, rather than linearly, on its size. [1] Scanlon et. al., Nature 449, 209212 [2007]. [2] Kefi et. al., Nature 449, 213217 [2007]. [3] Sole R., Nature 449, p. 151 [2007]. [4] Vandermeer et. al., Nature 451, p. 457 [2008].
Enriching Spatial Data Infrastructure (sdi) by User Generated Contents for Transportation
NASA Astrophysics Data System (ADS)
Shakeri, M.; Alimohammadi, A.; Sadeghi-Niaraki, A.; Alesheikh, A. A.
2013-09-01
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.
NASA Technical Reports Server (NTRS)
Schweikhard, W. G.; Chen, Y. S.
1986-01-01
The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.
NASA Astrophysics Data System (ADS)
Schweikhard, W. G.; Chen, Y. S.
1986-04-01
The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.
NASA Astrophysics Data System (ADS)
Potirakis, Stelios M.; Zitis, Pavlos I.; Eftaxias, Konstantinos
2013-07-01
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.
SDI-based business processes: A territorial analysis web information system in Spain
NASA Astrophysics Data System (ADS)
Béjar, Rubén; Latre, Miguel Á.; Lopez-Pellicer, Francisco J.; Nogueras-Iso, Javier; Zarazaga-Soria, F. J.; Muro-Medrano, Pedro R.
2012-09-01
Spatial Data Infrastructures (SDIs) provide access to geospatial data and operations through interoperable Web services. These data and operations can be chained to set up specialized geospatial business processes, and these processes can give support to different applications. End users can benefit from these applications, while experts can integrate the Web services in their own business processes and developments. This paper presents an SDI-based territorial analysis Web information system for Spain, which gives access to land cover, topography and elevation data, as well as to a number of interoperable geospatial operations by means of a Web Processing Service (WPS). Several examples illustrate how different territorial analysis business processes are supported. The system has been established by the Spanish National SDI (Infraestructura de Datos Espaciales de España, IDEE) both as an experimental platform for geoscientists and geoinformation system developers, and as a mechanism to contribute to the Spanish citizens knowledge about their territory.
Not Available
1993-06-08
The recent profound shift in the global balance of power in favor of the United States of America has had major repercussions on Strategic Defense Initiative (SDI) planning. In particular, the focus has shifted from the provision of protection for the United States against a massive raid, involving possibly thousands of reentry vehicles, to defense against a much more limited attack which could now, however, be launched from any part of the world. Additionally, the United States is seeking to protect its forces and allies overseas, and in the task of missile detection and tracking, allowance must now be made for trajectories which can begin and end in almost any inhabited area of the globe. Thus SDI demands on surveillance technology have been significantly expanded. Space-based imaging systems will play a vital role in the surveillance task. In this report a description is first given of a typical scenario. The potential imaging problems are then examined, the mathematical background is discussed, and the innovative algorithms which have been developed for correcting and enhancing the performance of the imaging sensor are described.
Whither SDI (Strategic Defensive Initiative): Strategic defenses in the next administration
Kanter, A.
1988-09-01
This document examines the legacy of strategic defenses the next president will inherit from the Reagan administration. Concentrating on SDI, it describes the programmatic, budgetary, arms control, and political contours of the strategic defense agenda that the new president is likely to confront. It then considers the options he will face and plots a course he should take. This essay is intended to stimulate and structure debate about the future of strategic defenses. An earlier version of this paper was prepared for a Council on Foreign Relations study group on the Arms Control Agenda of the Next Administration. Since it was initially drafted in spring 1988, the politics of SDI have changed with a speed that few could have predicted. Abruptly and unexpectedly, SDI all but disappeared from the political debate at precisely the time when a multitude of candidates were vying for their parties' nominations, and then the two nominees were seeking to define and distinguish their positions. Despite these changed circumstances, this document should be of interest to those who are concerned with how developments in strategic defense bear on nuclear policy, programs, and arms control.
Straub, John E.
Statistical temperature molecular dynamics: Application to coarse-grained -barrel-forming protein models Jaegil Kim,a John E. Straub, and Thomas Keyes Department of Chemistry, Boston University, Boston the authors proposed a novel sampling algorithm, "statistical temperature molecular dynamics" STMD J. Kim et
Mechanical-statistical modelling in ecology: from outbreak detections to pest dynamics
Jyväskylä, University of
Mechanical-statistical modelling in ecology: from outbreak detections to pest dynamics S by irregular abundance explosions, i.e. outbreaks, it is common to report detected outbreaks rather than-statistical model for analysing such outbreak occurrence data and making inference about population dynamics
Johannes Berg; Michael Lässig; Andreas Wagner
2002-01-01
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. We present a detailed statistical analysis
Dynamic causal modelling: A critical review of the biophysical and statistical foundations
Daunizeau, Jean
Review Dynamic causal modelling: A critical review of the biophysical and statistical foundations J and (ii) efficient statistical methods for parameter estimation and model comparison. These two key then discuss both the plausibility of the underlying biophysical models and the robustness of the statistical
Assessment of MJO Predictability for Boreal Winter with Various Statistical and Dynamical Models
Kang, In-Sik
Assessment of MJO Predictability for Boreal Winter with Various Statistical and Dynamical Models IN for all models. The statistical models include the models based on a multilinear regression, a wavelet.5) of statistical models for RMM1 (RMM2) index are at days 1617 (1415) for the multiregression model, whereas
ERIC Educational Resources Information Center
Lee, Hollylynne Stohl; Kersaint, Gladis; Harper, Suzanne; Driskell, Shannon O.; Leatham, Keith R.
2012-01-01
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…
Nguyen, Y; Nguyen, Nam X.; Rogers, Jamie L.; Liao, Jun; MacMillan, John B.
2015-01-01
ABSTRACT Bacteria engage in chemical signaling, termed quorum sensing (QS), to mediate intercellular communication, mimicking multicellular organisms. The LuxR family of QS transcription factors regulates gene expression, coordinating population behavior by sensing endogenous acyl homoserine lactones (AHLs). However, some bacteria (such as Escherichia coli) do not produce AHLs. These LuxR orphans sense exogenous AHLs but also regulate transcription in the absence of AHLs. Importantly, this AHL-independent regulatory mechanism is still largely unknown. Here we present several structures of one such orphan LuxR-type protein, SdiA, from enterohemorrhagic E. coli (EHEC), in the presence and absence of AHL. SdiA is actually not in an apo state without AHL but is regulated by a previously unknown endogenous ligand, 1-octanoyl-rac-glycerol (OCL), which is ubiquitously found throughout the tree of life and serves as an energy source, signaling molecule, and substrate for membrane biogenesis. While exogenous AHL renders to SdiA higher stability and DNA binding affinity, OCL may function as a chemical chaperone placeholder that stabilizes SdiA, allowing for basal activity. Structural comparison between SdiA-AHL and SdiA-OCL complexes provides crucial mechanistic insights into the ligand regulation of AHL-dependent and -independent function of LuxR-type proteins. Importantly, in addition to its contribution to basic science, this work has implications for public health, inasmuch as the SdiA signaling system aids the deadly human pathogen EHEC to adapt to a commensal lifestyle in the gastrointestinal (GI) tract of cattle, its main reservoir. These studies open exciting and novel avenues to control shedding of this human pathogen in the environment. PMID:25827420
Salmon, Rick
V-1 5 Statistical Fluid Dynamics In the previous chapter, we considered fluid turbulence from quantitative and deductive fashion, beginning with the governing dynamical equations for the fluid. None of fluid dynamics can always be written in the abstract form dyi dt = Aijkyj yk j ,k -i yi , (1.1) where
Material Phase Causality or a Dynamics-Statistical Interpretation of Quantum Mechanics
Koprinkov, I. G. [Department of Applied Physics, Technical University of Sofia, 1756 Sofia (Bulgaria)
2010-11-25
The internal phase dynamics of a quantum system interacting with an electromagnetic field is revealed in details. Theoretical and experimental evidences of a causal relation of the phase of the wave function to the dynamics of the quantum system are presented sistematically for the first time. A dynamics-statistical interpretation of the quantum mechanics is introduced.
SDI Statistical Analysis for Data type Identification Sarah J. Moody and Robert F. Erbacher
Erbacher, Robert F.
.j.m@aggiemail.usu.edu and Robert.Erbacher@usu.edu Abstract A key task in digital forensic analysis is the location of relevant the identification of the type of data being examined. Typical file type identification is based upon file extension or magic keys. These typical techniques fail in many typical forensic analysis scenarios such as needing
Dynamical instability and statistical behaviour of N-body systems
NASA Astrophysics Data System (ADS)
Cipriani, Piero; Di Bari, Maria
1998-12-01
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
An open-source wireless sensor stack: from Arduino to SDI-12 to Water One Flow
NASA Astrophysics Data System (ADS)
Hicks, S.; Damiano, S. G.; Smith, K. M.; Olexy, J.; Horsburgh, J. S.; Mayorga, E.; Aufdenkampe, A. K.
2013-12-01
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.
Statistics of Dynamic Random Networks: A Depth Function Approach
Fraiman, Daniel; Fraiman, Ricardo
2014-01-01
The study of random graphs and networks had an explosive development in the last couple of decades. Meanwhile, there are just a few references about statistical analysis on graphs. In this paper we focus on graphs with a fixed number of labeled nodes (such as those used to model brain networks) and study some statistical problems in a nonparametric framework. We introduce natural notions of center and a depth function for graphs that evolve in time. This allows us to develop several statistical techniques including testing, supervised and unsupervised classification, and a notion of principal component sets in the space of graphs. Some examples and asymptotic results are given.
A CATLINE SDI for the reference department: collection development and current awareness tool.
McKinin, E J
1987-01-01
A method for using a CATLINE SDI (selected dissemination of information) as a current awareness and collection development tool for the health sciences reference department is described. This paper reports three years of experience with this service in an academic health sciences library. It emphasizes the exploitation of four data elements in the CATLINE file: the Abstracting and Indexing Tag (AI) Data Element; the Shelving Location (SL) Data Element; the MeSH Heading (MH) Data Element; the Subheading Qualifier (SH) Data Element. PMID:3329923
Sapsis, Themistoklis
A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to ...
Statistical Kinetics of Macromolecular Dynamics Joshua W. Shaevitz,* Steven M. Block,yz
Schnitzer, Mark
Statistical Kinetics of Macromolecular Dynamics Joshua W. Shaevitz,* Steven M. Block,yz and Mark J to define mechanochemical pathways and coupling ratios for the motor protein kinesin as well as to probe
NMR detection of adventitious xylose binding to the quorum-sensing protein SdiA of Escherichia coli.
Yao, Yong; Dickerson, Tobin J; Hixon, Mark S; Dyson, H Jane
2007-11-15
During the solution structure determination of the Escherichia coli quorum-sensing protein SdiA in the presence of N-octanoyl-l-homoserine lactone (HSL), NMR signals were detected in (13)C-filter-(13)C-filter spectra for the bound HSL molecule. An additional set of coupled signals, independent of those of HSL, were also detected, indicating the presence of another unlabeled molecule, also bound to the labeled SdiA. Analysis of the NMR spectrum of this ligand and of the mass spectrum of the dissociated components indicates that the ligand is most likely xylose. Further analysis of xylose-bound SdiA defines a site close to the C terminus, remote from the HSL binding site. These observations provide an example of the sensitivity of high-resolution NMR experiments and their ability to detect, identify, and map the adventitious binding of a small organic molecule to a protein. PMID:17889538
Statistical approaches for probing single-molecule dynamics photon-by-photon
Xie, Xiaoliang Sunney
Statistical approaches for probing single-molecule dynamics photon-by-photon Haw Yang1 , X. Sunney 02138, USA Received 19 December 2001 Abstract The recently developed photon-by-photon approach [H. Yang, each photon represents a data point, thereby affording better statistics. Here, we utilize
Kang, In-Sik
A statistical approach to Indian Ocean sea surface temperature prediction using a dynamical ENSO (SST) in the Indian Ocean. It is a linear regression model based on a lagged relationship between the Indian Ocean SST and the NINO3 SST. A new approach to the statistical modeling has been tried out
Nonlinear Dynamics and Statistical Physics of Excitable Systems.
NASA Astrophysics Data System (ADS)
Kurrer, Christian Martin
In the search for the mechanisms of neuronal information coding, attention has recently shifted towards the possible role of neuronal firing correlation. The present thesis addresses the question of how coupled neuronal systems synchronize. Neurons can be described as dynamical systems through the Bonhoeffer-Van der Pol equations. The Bonhoeffer-Van der Pol equations yield either excitable system behavior or oscillator dynamics, depending on a control parameter. Since the neurons are microscopic objects in a fluctuating environment, it is important to add noise to the Bonhoeffer-Van der Pol dynamics in order to achieve a realistic description of neuronal behavior. Our aim is to understand how the dynamical properties of an ensemble of coupled noisy dynamical systems depend on the properties of its constituents and on the coupling between these constituents. Our calculations and simulations describe two different transitions between phases with uncorrelated neuronal firing and with synchronous neuronal firing. The dynamical system which we investigate is of a very general nature and its study therefore allows us to draw some general conclusions. First, as far as dynamical systems are concerned, the study leads to a reappraisal of the role of Hopf bifurcations in the emergence of limit cycles in stochastic dynamical systems. Second, as far as neuronal systems are concerned, our investigations indicate that firing synchronicity is fairly common in a large variety of neuronal systems, and draw the attention to the change of firing frequency that accompanies the synchronization transition.
SERVIR's Contributions and Benefits to Belize thru Spatial Data Infrastructure (SDI) Development
NASA Technical Reports Server (NTRS)
Irwin, Daniel E.
2006-01-01
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).
Markov Chain Markov Field Dynamics: Models and Statistics X. GUYON and C. HARDOUIN
Paris-Sud XI, Université de
Markov Chain Markov Field Dynamics: Models and Statistics X. GUYON and C. HARDOUIN SAMOS - Université Paris 11 Abstract This study deals with time dynamics of Markov fields defined on a finite set of sites with state space E, focussing on Markov Chain Markov Field (MCMF) evolution. Such a model
Teaching the principles of statistical dynamics Kingshuk Ghosh and Ken A. Dill
Phillips, Rob
and simplest models in statistical mechanics, the dog-flea or two urn model.1517 Courses in dynamics often far from equilibrium to function. Thus, many problems of current interest involve small systems about the dynamical fluctuations away from those average values for systems with small numbers
Detection of Cardiac Alternans via Statistical Analysis of Eigenvalues of a Dynamical System
Zhao, Xiaopeng
Detection of Cardiac Alternans via Statistical Analysis of Eigenvalues of a Dynamical System Adam Petrie Xiaopeng Zhao Abstract Predicting cardiac alternans is a crucial step toward detection in the US each year. According to the theory of dynamical systems, cardiac alternans is mediated by a period
J.-Ch. Anglès d'Auriac; S. Boukraa; J.-M. Maillard
1999-01-01
We recall some non-trivial, non-linear functional relations appearing in various domains of mathematics and physics, such as lattice statistical mechanics, quantum mechanics, or enumerative combinatorics. We focus, more particularly, on the analyticity properties of the solutions of these functional relations. We then consider discrete dynamical systems corresponding to birational transformations. The rational expressions for dynamical zeta functions obtained for a
Introduction to Focus Issue: statistical mechanics and billiard-type dynamical systems.
Leonel, Edson D; Beims, Marcus W; Bunimovich, Leonid A
2012-06-01
Dynamical systems of the billiard type are of fundamental importance for the description of numerous phenomena observed in many different fields of research, including statistical mechanics, Hamiltonian dynamics, nonlinear physics, and many others. This Focus Issue presents the recent progress in this area with contributions from the mathematical as well as physical stand point. PMID:22757560
Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics
Crooks, Gavin; Sivak, David
2011-06-03
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.
Statistics of transverse mode turn-on dynamics in VCSELs
J. Dellunde; M. C. Torrent; J. M. Sancho; K. A. Shore
1997-01-01
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
Statistical Computations Underlying the Dynamics of Memory Updating
Gershman, Samuel J.
Psychophysical and neurophysiological studies have suggested that memory is not simply a carbon copy of our experience: Memories are modified or new memories are formed depending on the dynamic structure of our experience, ...
Unified model for network dynamics exhibiting nonextensive statistics.
Thurner, Stefan; Kyriakopoulos, Fragiskos; Tsallis, Constantino
2007-09-01
We introduce a dynamical network model which unifies a number of network families which are individually known to exhibit q-exponential degree distributions. The present model dynamics incorporates static (nongrowing) self-organizing networks, preferentially growing networks, and (preferentially) rewiring networks. Further, it exhibits a natural random graph limit. The proposed model generalizes network dynamics to rewiring and growth modes which depend on internal topology as well as on a metric imposed by the space they are embedded in. In all of the networks emerging from the presented model we find q-exponential degree distributions over a large parameter space. We comment on the parameter dependence of the corresponding entropic index q for the degree distributions, and on the behavior of the clustering coefficients and neighboring connectivity distributions. PMID:17930310
Unified model for network dynamics exhibiting nonextensive statistics
NASA Astrophysics Data System (ADS)
Thurner, Stefan; Kyriakopoulos, Fragiskos; Tsallis, Constantino
2007-09-01
We introduce a dynamical network model which unifies a number of network families which are individually known to exhibit q -exponential degree distributions. The present model dynamics incorporates static (nongrowing) self-organizing networks, preferentially growing networks, and (preferentially) rewiring networks. Further, it exhibits a natural random graph limit. The proposed model generalizes network dynamics to rewiring and growth modes which depend on internal topology as well as on a metric imposed by the space they are embedded in. In all of the networks emerging from the presented model we find q -exponential degree distributions over a large parameter space. We comment on the parameter dependence of the corresponding entropic index q for the degree distributions, and on the behavior of the clustering coefficients and neighboring connectivity distributions.
Martin, Daniel R; Matyushov, Dmitry V
2012-08-30
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
Novel dynamic measures of emetic behavior in musk shrews
Horn, Charles C.; Wang, Hong; Estival, Laureline; Meyers, Kelly; Magnusson, Magnus
2013-01-01
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. Nearly all clinical studies 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
Technology Transfer Automated Retrieval System (TEKTRAN)
Subsurface drip irrigation (SDI) as with all microirrigation systems is typically only used on crops with greater value. In the U.S. Great Plains region, the typical irrigated crops are the cereal and oil seed crops and cotton. These crops have less economic revenue than typical microirrigated cro...
ERIC Educational Resources Information Center
Tell, B.
The information service performed by the Royal Institute of Technology handles requests from both university users and from industry. Fourteen data bases are currently used for SDI purposes. The system is of a general nature which permits inclusion of various data bases of completely different tape formats. Any combination of elements of a…
Technology Transfer Automated Retrieval System (TEKTRAN)
An experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial in a Vertisol in the Alabama Black Belt region for two years. The system was designed to start hydraulic dosing only when field moisture was below field capacity. Results sho...
Statistical Mechanics of Recurrent Neural Networks II Dynamics
Coolen, ACC "Ton"
. . . . . . . . . . . . . . . . . . . . . . . 637 5.3. Parallel dynamics HopÂ®eld model near saturation . . . . . . . . . . . . . . . . . . . . . . . 645 5.4. Extremely diluted attractor networks near saturation alignment of neuronal Â®ring rates to postsynaptic potentials which, in turn, depend linearly on the Â®ring
Extreme event statistics of daily rainfall: Dynamical systems approach
Yalcin, G Cigdem; Beck, Christian
2015-01-01
We analyse the probability densities of daily rainfall amounts at a variety of locations on the Earth. The observed distributions of the amount of rainfall fit well to a q-exponential distribution with exponent q close to q=1.3. We discuss possible reasons for the emergence of this power law. On the contrary, the waiting time distribution between rainy days is observed to follow a near-exponential distribution. A careful investigation shows that a q-exponential with q=1.05 yields actually the best fit of the data. A Poisson process where the rate fluctuates slightly in a superstatistical way is discussed as a possible model for this. We discuss the extreme value statistics for extreme daily rainfall, which can potentially lead to flooding. This is described by Frechet distributions as the corresponding distributions of the amount of daily rainfall decay with a power law. On the other hand, looking at extreme event statistics of waiting times between rainy days (leading to droughts for very long dry periods) w...
Process-oriented statistical-dynamical evaluation of LM precipitation forecasts
NASA Astrophysics Data System (ADS)
Claußnitzer, A.; Langer, I.; Névir, P.; Reimer, E.; Cubasch, U.
2008-04-01
The objective of this study is the scale dependent evaluation of precipitation forecasts of the Lokal-Modell (LM) from the German Weather Service in relation to dynamical and cloud parameters. For this purpose the newly designed Dynamic State Index (DSI) is correlated with clouds and precipitation. The DSI quantitatively describes the deviation and relative distance from a stationary and adiabatic solution of the primitive equations. A case study and statistical analysis of clouds and precipitation demonstrates the availability of the DSI as a dynamical threshold parameter. This confirms the importance of imbalances of the atmospheric flow field, which dynamically induce the generation of rainfall.
Statistical methodologies for the control of dynamic remapping
NASA Technical Reports Server (NTRS)
Saltz, J. H.; Nicol, D. M.
1986-01-01
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.
Dynamic Modelling and Statistical Analysis of Event Times
Peña, Edsel A.
2006-01-01
This review article provides an overview of recent work in the modelling and analysis of recurrent events arising in engineering, reliability, public health, biomedical, and other areas. Recurrent event modelling possesses unique facets making it different and more difficult to handle than single event settings. For instance, the impact of an increasing number of event occurrences needs to be taken into account, the effects of covariates should be considered, potential association among the inter-event times within a unit cannot be ignored, and the effects of performed interventions after each event occurrence need to be factored in. A recent general class of models for recurrent events which simultaneously accommodates these aspects is described. Statistical inference methods for this class of models are presented and illustrated through applications to real data sets. Some existing open research problems are described. PMID:17906740
Statistical mechanics of neocortical interactions - Dynamics of synaptic modification
NASA Technical Reports Server (NTRS)
Ingber, L.
1983-01-01
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.
Measuring dynamical randomness of quantum chaos by statistics of Schmidt eigenvalues.
Kubotani, Hiroto; Adachi, Satoshi; Toda, Mikito
2013-06-01
We study statistics of entanglement generated by quantum chaotic dynamics. Using an ensemble of the very large number (>/~10(7)) of quantum states obtained from the temporally evolving coupled kicked tops, we verify that the estimated one-body distribution of the squared Schmidt eigenvalues for the quantum chaotic dynamics can agree surprisingly well with the analytical one for the universality class of the random matrices described by the fixed trace ensemble (FTE). In order to quantify this agreement, we introduce the L(1) norm of the difference between the one-body distributions for the quantum chaos and FTE and use it as an indicator of the dynamical randomness. As we increase the scaled coupling constant, the L(1) difference decreases. When the effective Planck constant is not small enough, the decrease saturates, which implies quantum suppression of dynamical randomness. On the other hand, when the effective Planck constant is small enough, the decrease of the L(1) difference continues until it is masked by statistical fluctuation due to finiteness of the ensemble. Furthermore, we carry out two statistical analyses, the ?(2) goodness of fit test and an autocorrelation analysis, on the difference between the distributions to seek for dynamical remnants buried under the statistical fluctuation. We observe that almost all fluctuating deviations are statistical. However, even for well-developed quantum chaos, unexpectedly, we find a slight nonstatistical deviation near the largest Schmidt eigenvalue. In this way, the statistics of Schmidt eigenvalues enables us to measure dynamical randomness of quantum chaos with reference to the random matrix theory of FTE. PMID:23848762
The scientists' opposition to SDI: How political views affect technical analysis
Tait, G.E.
1989-01-01
This study examines the scientists' opposition to President Reagan's Strategic Defense Initiative (1983-1989) with a focus on the relationship between the scientists' political and strategic opposition to ballistic missile defenses (BMD) and their technical doubts about BMD technologies. The study begins with a review of the scientists' increased influence in United State's national security decision making because of the development of atomic weapons. The study then examines the scientists' role in developing and promoting a theory of arms control based upon mutual societal vulnerability. Because of this theory, a large segment of the American scientific community came to believe that the development of ballistic missile defenses would destabilize the strategic balance and therefore took the lead in arguing against BMD deployments. These background chapters conclude with an analysis of the scientists' involvement in the political campaign to stop the proposed Sentinel and Safeguard Anti-Ballistic Missile defense. The study then turns to the contemporary scientific opposition to BMD deployments and the SDI research program. After examining the polls and petitions that identify the scientists opposed to SDI, the study analyzes the tactics that three scientists use in their political effort to prevent BMD deployments. Next, an examination of the political and strategic assumptions behind the scientists' opposition to BMD reveals that a belief in the arms control process and deterrence by punishment, especially Assured Destruction deterrence, with a fear of an action-reaction arms race inspires much of the contemporary opposition to BMD. Finally, the scientists' technical doubts about BMD technologies are analyzed through the prism of peer critique. These critiques show that the scientists opposed to BMD deployments us pessimistic and unrealistic assumptions to skew their technical analysis of BMD technologies.
The statistical mechanics of dynamic pathways to self-assembly.
Whitelam, Stephen; Jack, Robert L
2015-04-01
This review describes some important physical characteristics of the pathways (i.e., dynamical processes) by which molecular, nanoscale, and micrometer-scale self-assembly occurs. We highlight the existence of features of self-assembly pathways that are common to a wide range of physical systems, even though those systems may differ with respect to their microscopic details. We summarize some existing theoretical descriptions of self-assembly pathways and highlight areas-notably, the description of self-assembly pathways that occur far from equilibrium-that are likely to become increasingly important. PMID:25493714
Statistical test for dynamical nonstationarity in observed time-series data
Kennel, M.B.
1997-07-01
Information in the time distribution of points in a state space reconstructed from observed data yields a test for {open_quotes}nonstationarity.{close_quotes} Framed in terms of a statistical hypothesis test, this numerical algorithm can discern whether some underlying slow changes in parameters have taken place. The method examines a fundamental object in nonlinear dynamics, the geometry of orbits in state space, with corrections to overcome difficulties in real dynamical data which cause naive statistics to fail. {copyright} {ital 1997} {ital The American Physical Society}
Sapsis, Themistoklis P.; Majda, Andrew J.
2013-01-01
A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398
Sapsis, Themistoklis P; Majda, Andrew J
2013-08-20
A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398
Statistical and dynamical properties of a vibrated granular polymer
NASA Astrophysics Data System (ADS)
Kudrolli, Arshad; Veilleux, Micah; Kardar, Mehran
2006-03-01
We investigate the structure and dynamics of granular polymers on a vibrated bed to test the applicability of models of self-avoiding random walks. The granular polymer is composed of a chain of hollow 3 mm steel beads connected by flexible links, and moves on a 30 cm diameter flat circular bed which is roughened by gluing a layer of 1 mm steel beads in order to give the chain random kicks in the vertical and horizontal directions. High speed digital imaging is used to track the position of the particles to a fraction of the bead diameter using a centroid technique. Using the identified bead positions, we analyze the motion of the center of mass over a time interval ?t, and its standard deviation as a function of chain length L. The standard deviation is consistent with a scaling of ??t / L. The chain end-to-end distance scales as L^?, with ? 3/4 as for self-avoiding walks. The evolution of the scattering functions and the effect of the size of the container on the observed scaling will be also discussed.
Dynamic Graphics in Excel for Teaching Statistics: Understanding the Probability Density Function
ERIC Educational Resources Information Center
Coll-Serrano, Vicente; Blasco-Blasco, Olga; Alvarez-Jareno, Jose A.
2011-01-01
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.
NetVisia: Heat Map & Matrix Visualization of Dynamic Social Network Statistics & Content
Golbeck, Jennifer
NetVisia: Heat Map & Matrix Visualization of Dynamic Social Network Statistics & Content Robert, esefer, awalin, cdunne, ben}@cs.umd.edu, meiravta@bgu.ac.il Abstract--Visualizations of static networks visualization system designed to support users in exploring temporal evolution in networks by using heat maps
Coupled flow-polymer dynamics via statistical field theory: modeling and computation
Bigelow, Stephen
Coupled flow-polymer dynamics via statistical field theory: modeling and computation Hector D interactions between polymers with interac- tions between polymers and one or more conjugate fields, offer successfully to investigate a wide range of polymer formulations at equilibrium, field-theoretic models often
NASA Astrophysics Data System (ADS)
Schepen, Andrew; Wang, Q. J.
2015-03-01
The Australian Bureau of Meteorology produces statistical and dynamic seasonal streamflow forecasts. The statistical and dynamic forecasts are similarly reliable in ensemble spread; however, skill varies by catchment and season. Therefore, it may be possible to optimize forecasting skill by weighting and merging statistical and dynamic forecasts. Two model averaging methods are evaluated for merging forecasts for 12 locations. The first method, Bayesian model averaging (BMA), applies averaging to forecast probability densities (and thus cumulative probabilities) for a given forecast variable value. The second method, quantile model averaging (QMA), applies averaging to forecast variable values (quantiles) for a given cumulative probability (quantile fraction). BMA and QMA are found to perform similarly in terms of overall skill scores and reliability in ensemble spread. Both methods improve forecast skill across catchments and seasons. However, when both the statistical and dynamical forecasting approaches are skillful but produce, on special occasions, very different event forecasts, the BMA merged forecasts for these events can have unusually wide and bimodal distributions. In contrast, the distributions of the QMA merged forecasts for these events are narrower, unimodal and generally more smoothly shaped, and are potentially more easily communicated to and interpreted by the forecast users. Such special occasions are found to be rare. However, every forecast counts in an operational service, and therefore the occasional contrast in merged forecasts between the two methods may be more significant than the indifference shown by the overall skill and reliability performance.
Symanzik, Jürgen
Virtual reality and dynamic statistical graphics: A bidirectional link in a heterogeneous and real-time navigation are provided by typical virtual reality systems. Database function- ality must interact properly with the virtual reality/database system. This is easier said than done
Dynamic Statistical Graphics in the C2 Virtual Reality Environment J. Symanzik D. Cook
Symanzik, Jürgen
a unique de nition of the term Virtual Reality, but almost ev- ery person has a di erent understandingDynamic Statistical Graphics in the C2 Virtual Reality Environment J. Symanzik D. Cook Department immersive virtual reality environ- ment that allows 3 dimensional projections of higher di- mensional
Bargueño, P; Jambrina, P G; Alvariño, J M; Menéndez, M; Verdasco, E; Hankel, M; Smith, S C; Aoiz, F J; González-Lezana, T
2011-05-14
The dynamics of the reaction O((1)D) + HCl ? ClO + H, OH + Cl has been investigated in detail by means of a time-dependent wave packet (TDWP) method in comparison with quasiclassical trajectory (QCT) and statistical approaches on the ground potential energy surface by Martínez et al. [Phys. Chem. Chem. Phys., 2000, 2, 589]. Fully coupled quantum mechanical (QM) reaction probabilities for high values of the total angular momentum (J? 50) are reported for the first time. At the low collision energy regime (E(c)? 0.4 eV) the TDWP probabilities are well reproduced by the QCT and statistical results for the ClO forming product channel, but for the OH + Cl arrangement, only QCT probabilities are found to agree with the QM values. The good accordance found between the rigorous statistical models and the dynamical QM and QCT calculations for the O + HCl ? ClO + H process underpins the assumption that the reaction pathway leading to ClO is predominantly governed by a complex-forming mechanism. In addition, to further test the statistical character of this reaction channel, the laboratory angular distribution and time-of-flight spectra obtained in a crossed molecular beam study by Balucani et al. [Chem. Phys. Lett. 1991, 180, 34] at a collision energy as high as 0.53 eV have been simulated using the state resolved differential cross section obtained with the statistical approaches yielding a satisfactory agreement with the experimental results. For the other channel, O + HCl ? OH + Cl, noticeable differences between the statistical results and those found with the QCT calculation suggest that the dynamics of the reaction are controlled by a direct mechanism. The comparison between the QCT and QM-TDWP results in the whole range of collision energies lends credence to the QCT description of the dynamics of this reaction. PMID:21431209
Pseudo-dynamic source modelling with 1-point and 2-point statistics of earthquake source parameters
NASA Astrophysics Data System (ADS)
Song, Seok Goo; Dalguer, Luis A.; Mai, P. Martin
2014-03-01
Ground motion prediction is an essential element in seismic hazard and risk analysis. Empirical ground motion prediction approaches have been widely used in the community, but efficient simulation-based ground motion prediction methods are needed to complement empirical approaches, especially in the regions with limited data constraints. Recently, dynamic rupture modelling has been successfully adopted in physics-based source and ground motion modelling, but it is still computationally demanding and many input parameters are not well constrained by observational data. Pseudo-dynamic source modelling keeps the form of kinematic modelling with its computational efficiency, but also tries to emulate the physics of source process. In this paper, we develop a statistical framework that governs the finite-fault rupture process with 1-point and 2-point statistics of source parameters in order to quantify the variability of finite source models for future scenario events. We test this method by extracting 1-point and 2-point statistics from dynamically derived source models and simulating a number of rupture scenarios, given target 1-point and 2-point statistics. We propose a new rupture model generator for stochastic source modelling with the covariance matrix constructed from target 2-point statistics, that is, auto- and cross-correlations. Our sensitivity analysis of near-source ground motions to 1-point and 2-point statistics of source parameters provides insights into relations between statistical rupture properties and ground motions. We observe that larger standard deviation and stronger correlation produce stronger peak ground motions in general. The proposed new source modelling approach will contribute to understanding the effect of earthquake source on near-source ground motion characteristics in a more quantitative and systematic way.
Pseudo-dynamic source modeling with 1-point and 2-point statistics of earthquake source parameters
NASA Astrophysics Data System (ADS)
Song, S.; Dalguer, L. A.; Mai, P. M.
2013-12-01
Ground motion prediction is an essential element in seismic hazard and risk analysis. Empirical ground motion prediction approaches have been widely used in the community, but efficient simulation based ground motion prediction methods are needed to complement empirical approaches, especially in the regions with limited data constraints. Recently, dynamic rupture modeling has been successfully adopted in physics-based source and ground motion modeling, but it is still computationally demanding and many input parameters are not well constrained by observational data. Pseudo-dynamic source modeling keeps the form of kinematic modeling with its computational efficiency, but also tries to emulate the physics of source process. In this paper we develop a statistical framework that governs the finite-fault rupture process with 1-point and 2-point statistics of source parameters in order to quantify the variability of finite source models for future scenario events. We test this method by extracting 1-point and 2-point statistics from dynamically derived source models and simulating a number of rupture scenarios, given target 1-point and 2-point statistics. We propose a new rupture model generator for stochastic source modeling with the covariance matrix constructed from target 2-point statistics, i.e., auto- and cross-correlations. Our sensitivity analysis of near-source ground motions to 1-point and 2-point statistics of source parameters provides insights into relations between statistical rupture properties and ground motions. We observe that larger standard deviation and stronger correlation produce stronger ground motions in general. The proposed new source modeling approach will contribute to understanding the effect of earthquake source on near-source ground motion characteristics in a more quantitative and systematic way.
Takao, Keizo; Toyama, Keiko; Nakanishi, Kazuo; Hattori, Satoko; Takamura, Hironori; Takeda, Masatoshi; Miyakawa, Tsuyoshi; Hashimoto, Ryota
2008-01-01
Background Schizophrenia is a complex genetic disorder caused by multiple genetic and environmental factors. The dystrobrevin-binding protein 1 (DTNBP1: dysbindin-1) gene is a major susceptibility gene for schizophrenia. Genetic variations in DTNBP1 are associated with cognitive functions, general cognitive ability and memory function, and clinical features of patients with schizophrenia including negative symptoms and cognitive decline. Since reduced expression of dysbindin-1 has been observed in postmortem brains of patients with schizophrenia, the sandy (sdy) mouse, which has a deletion in the Dtnbp1 gene and expresses no dysbindin-1 protein, could be an animal model of schizophrenia. To address this issue, we have carried out a comprehensive behavioral analysis of the sdy mouse in this study. Results In a rotarod test, sdy mice did not exhibit motor learning whilst the wild type mice did. In a Barnes circular maze test both sdy mice and wild type mice learned to selectively locate the escape hole during the course of the training period and in the probe trial conducted 24 hours after last training. However, sdy mice did not locate the correct hole in the retention probe tests 7 days after the last training trial, whereas wild type mice did, indicating impaired long-term memory retention. A T-maze forced alternation task, a task of working memory, revealed no effect of training in sdy mice despite the obvious effect of training in wild type mice, suggesting a working memory deficit. Conclusion Sdy mouse showed impaired long-term memory retention and working memory. Since genetic variation in DTNBP1 is associated with both schizophrenia and memory function, and memory function is compromised in patients with schizophrenia, the sdy mouse may represent a useful animal model to investigate the mechanisms of memory dysfunction in the disorder. PMID:18945333
Influence of vortex dynamics and structure on turbulence statistics at large scales
NASA Astrophysics Data System (ADS)
Yoshimatsu, Katsunori; Anayama, Koujiro; Kaneda, Yukio
2015-05-01
The question whether the vortex dynamics and structure at small scales have significant influence on the statistics at large scales is addressed on the basis of quantitative comparison of two turbulent fields. One is a reference field generated by direct numerical simulation of turbulence of an incompressible fluid obeying the Navier-Stokes (NS) equation in a periodic box. The other is an artificial field in which the coherent vortical structures at small scales (˜?) that could be formed by the NS dynamics in the reference field are destroyed by an artificial computational operation, where ? is the Kolmogorov micro-length scale. The comparison of the two fields suggests that the statistics at larger scale (??) are not sensitive to the exact vortex dynamics and structure, at least in the case studied here.
Gaffney, Inez M.
1973-01-01
CAN/SDI is Canada's national Selective Dissemination of Information Service offering a choice of nine data bases to its scientific and technical community. The system is based on central processing at the National Science Library combined with the utilization of decentralized expertise and resources for profile formulation and user education. Its greatest strength lies in its wide interdisciplinary quality. The major advantage of centralized processing of many data bases is that Canadians need learn only one method of profile formulation to access many files. A breakdown of services used confirms that a single tape service does not cover all the information requirements of most users. On the average each profile accesses approximately 1.5 data bases. Constant subscriber growth and a low cancellation rate indicate that CAN/SDI is and will continue to be an important element in Canada's information system. PMID:4740714
OneGeology Web Services and Portal as a global geological SDI - latest standards and technology
NASA Astrophysics Data System (ADS)
Duffy, Tim; Tellez-Arenas, Agnes
2014-05-01
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.
p21WAF1/Cip1/Sdi1 Knockout Mice Respond to Doxorubicin with Reduced Cardiotoxicity
Terrand, Jerome; Xu, Beibei; Morrissy, Steve; Dinh, Thai Nho; Williams, Stuart; Chen, Qin M.
2014-01-01
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 p21WAF1/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? and TNF?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. PMID:21920376
Development of a current collection loss management system for SDI homopolar power supplies
Hannan, W.F. III.
1987-01-01
High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operated continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the first year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design and construction of a cryogenically-cooled brush test rig, design of a high speed brush test rig, loss analysis of the current collection system, and an application study which defines the air core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 15 figs.
Development of a current collection loss management system for SDI homopolar power supplies
NASA Astrophysics Data System (ADS)
Brown, D. W.
1991-04-01
High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/sq cm, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To date, no system has achieved these conditions simultaneously. This is the final report covering the three year period of performance on DOE contract AC03-86SF-16518. Major areas covered include design, construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80 kW/kg generator power density.
NACO-SDI direct imaging search for the exoplanet Eps Eri b
Janson, M; Henning, T; Lenzen, R; McArthur, B; Benedict, G F; Reffert, S; Nielsen, E; Close, L; Biller, B; Kellner, S; Günther, E; Hatzes, A; Masciadri, E; Geissler, Kryno K; Hartung, M; Janson, Markus; Brandner, Wolfgang; Henning, Thomas; Lenzen, Rainer; Arthur, Barbara Mc; Reffert, Sabine; Nielsen, Eric; Close, Laird; Biller, Beth; Kellner, Stephan; Guenther, Eike; Hatzes, Artie; Masciadri, Elena; Geissler, Kerstin; Hartung, Markus
2007-01-01
The active K2V star $\\epsilon$ Eri hosts the most nearby known extrasolar planet. With an angular separation of about 1" on average, and an age of a few to several hundred Myrs, $\\epsilon$ Eri b is one of the prime candidates for becoming the first definitive extrasolar planet imaged directly. We present a multi-epoch deep differential imaging survey performed with NACO-SDI at the VLT with the aim of finding the planet. The results are combined with recent astrometry in an attempt to further constrain the detection limits. No convincing candidate is found among the many coherent structures that constitute the residual speckle noise, which is the dominant noise at small angular scales. We present our detection limits, compare them with the estimated brightness of $\\epsilon$ Eri b, and analyze how the limits can be improved further. It is found that integration time remains a very important parameter for achieving good results, even in the speckle-dominated regimes. The results yield new, improved upper 3$\\sigm...
Development of a current collection loss management system for SDI homopolar power supplies
Brown, D.W.
1989-01-01
High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the second year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design, construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 17 figs., 2 tabs.
A dynamic scanning method based on signal-statistics for scanning electron microscopy.
Timischl, F
2014-01-01
A novel dynamic scanning method for noise reduction in scanning electron microscopy and related applications is presented. The scanning method dynamically adjusts the scanning speed of the electron beam depending on the statistical behavior of the detector signal and gives SEM images with uniform and predefined standard deviation, independent of the signal value itself. In the case of partially saturated images, the proposed method decreases image acquisition time without sacrificing image quality. The effectiveness of the proposed method is shown and compared to the conventional scanning method and median filtering using numerical simulations. PMID:23813342
a Statistical Dynamic Approach to Structural Evolution of Complex Capital Market Systems
NASA Astrophysics Data System (ADS)
Shao, Xiao; Chai, Li H.
As an important part of modern financial systems, capital market has played a crucial role on diverse social resource allocations and economical exchanges. Beyond traditional models and/or theories based on neoclassical economics, considering capital markets as typical complex open systems, this paper attempts to develop a new approach to overcome some shortcomings of the available researches. By defining the generalized entropy of capital market systems, a theoretical model and nonlinear dynamic equation on the operations of capital market are proposed from statistical dynamic perspectives. The US security market from 1995 to 2001 is then simulated and analyzed as a typical case. Some instructive results are discussed and summarized.
The applications of Complexity Theory and Tsallis Non-extensive Statistics at Solar Plasma Dynamics
NASA Astrophysics Data System (ADS)
Pavlos, George
2015-04-01
As the solar plasma lives far from equilibrium it is an excellent laboratory for testing complexity theory and non-equilibrium statistical mechanics. In this study, we present the highlights of complexity theory and Tsallis non extensive statistical mechanics as concerns their applications at solar plasma dynamics, especially at sunspot, solar flare and solar wind phenomena. Generally, when a physical system is driven far from equilibrium states some novel characteristics can be observed related to the nonlinear character of dynamics. Generally, the nonlinearity in space plasma dynamics can generate intermittent turbulence with the typical characteristics of the anomalous diffusion process and strange topologies of stochastic space plasma fields (velocity and magnetic fields) caused by the strange dynamics and strange kinetics (Zaslavsky, 2002). In addition, according to Zelenyi and Milovanov (2004) the complex character of the space plasma system includes the existence of non-equilibrium (quasi)-stationary states (NESS) having the topology of a percolating fractal set. The stabilization of a system near the NESS is perceived as a transition into a turbulent state determined by self-organization processes. The long-range correlation effects manifest themselves as a strange non-Gaussian behavior of kinetic processes near the NESS plasma state. The complex character of space plasma can also be described by the non-extensive statistical thermodynamics pioneered by Tsallis, which offers a consistent and effective theoretical framework, based on a generalization of Boltzmann - Gibbs (BG) entropy, to describe far from equilibrium nonlinear complex dynamics (Tsallis, 2009). In a series of recent papers, the hypothesis of Tsallis non-extensive statistics in magnetosphere, sunspot dynamics, solar flares, solar wind and space plasma in general, was tested and verified (Karakatsanis et al., 2013; Pavlos et al., 2014; 2015). Our study includes the analysis of solar plasma time series at three cases: sunspot index, solar flare and solar wind data. The non-linear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis (1988; 2004; 2009). 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 (2000, 2001). 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, Zelenyi and Milovanov's studies (Zelenyi and Milovanov, 1991; Milovanov and Zelenyi, 1993; Ruzmakin et al., 1996), (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. Also, 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 the q-entropy principle included in Tsallis non-ext
NASA Astrophysics Data System (ADS)
Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Méndez, Fernando
2014-12-01
The estimation of possible impacts related to climate change on the wave climate is subject to several levels of uncertainty. In this work, we focus on the uncertainties inherent in the method applied to project the wave climate using atmospheric simulations. Two approaches are commonly used to obtain the regional wave climate: dynamical and statistical downscaling from atmospheric data. We apply both approaches based on the outputs of a global climate model (GCM), ARPEGE-CLIMAT, under three possible future scenarios (B1, A1B and A2) of the Fourth Assessment Report, AR4 (IPCC, 2007), along the French coast and evaluate their results for the wave climate with a high level of precision. The performance of the dynamical and the statistical methods is determined through a comparative analysis of the estimated means, standard deviations and monthly quantile distributions of significant wave heights, the joint probability distributions of wave parameters and seasonal and interannual variability. Analysis of the results shows that the statistical projections are able to reproduce the wave climatology as well as the dynamical projections, with some deficiencies being observed in the summer and for the upper tail of the significant wave height. In addition, with its low computational time requirements, the statistical downscaling method allows an ensemble of simulations to be calculated faster than the dynamical method. It then becomes possible to quantify the uncertainties associated with the choice of the GCM or the socio-economic scenarios, which will improve estimates of the impact of wave climate change along the French coast.
An efficient climate model with a 3D ocean and statistical-dynamical atmosphere
I. V. Kamenkovich; A. P. Sokolov; P. H. Stone
2002-01-01
We describe a coupled climate model of intermediate complexity designed for use in global warming experiments. The atmospheric component is a two-dimensional (zonally averaged) statistical-dynamical model based on the Goddard Institute for Space Study's atmospheric general circulation model (GCM). In contrast with energy-balance models used in some climate models of intermediate complexity, this model includes full representation of the hydrological
NASA Astrophysics Data System (ADS)
Moradkhani, Hamid
2015-04-01
Drought forecasting is vital for resource management and planning. Both societal and agricultural requirements for water weigh heavily on the natural environment, which may become scarce in the event of drought. Although drought forecasts are an important tool for managing water in hydrologic systems, these forecasts are plagued by uncertainties, owing to the complexities of water dynamics and the spatial heterogeneities of pertinent variables. Due to these uncertainties, it is necessary to frame forecasts in a probabilistic manner. Here we present a statistical-dynamical probabilistic drought forecast framework within Bayesian networks. The statistical forecast model applies a family of multivariate distribution functions to forecast future drought conditions given the drought status in the past. The advantage of the statistical forecast model is that it develops conditional probabilities of a given forecast variable, and returns the highest probable forecast along with an assessment of the uncertainty around that value. The dynamical model relies on data assimilation to characterize the initial land surface condition uncertainty which correspondingly reflect on drought forecast. In addition, the recovery of drought will be examined. From these forecasts, it is found that drought recovery is a longer process than suggested in recent literature. Drought in land surface variables (snow, soil moisture) is shown to be persistent up to a year in certain locations, depending on the intensity of the drought. Location within the basin appears to be a driving factor in the ability of the land surface to recover from drought, allowing for differentiation between drought prone and drought resistant regions.
G. P. Pavlos
2012-03-18
In this study it is shown that the Tsallis q-extended statistical theory was found efficient to describe faithfully the space plasmas statistics in every case, from the planetic magnetospheres, to solar corona and solar dynamics, as well as cosmic rays and cosmic stars. Moreover, new theoretical concepts and experimental results are presented concerning the space plasma complex dynamics. The significant message of theoretical and experimental issues presented here is the necessity of generalized statistical and dynamical theory for understanding the non-equilibrium dynamics and the complex character of space plasmas. The q-extension of statistics coupled to the fractal extension of dynamics are the novel and appropriate theoretical framework for the description of space plasma complexity.
The non-equilibrium statistical mechanics of a simple geophysical fluid dynamics model
NASA Astrophysics Data System (ADS)
Verkley, Wim; Severijns, Camiel
2014-05-01
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).
Alternative to the Well-known Statistical Dynamics of Linear Systems
V. N. Tibabishev
2013-01-22
The problem of determining the mathematical model of the dynamics of multi-dimensional control systems in the presence of noise under the condition that the correlation functions cannot be found. Known statistical dynamics of linear systems is a more effective alternative. Background information is presented in the form of individual implementations nonergodic stochastic processes. Such a realization is deterministic functions. We introduce the concept of systems of sets of signals for the components on the semiring. For the system of sets of linearly dependent and linearly independent of the measured signals of a certain frequency properties. Frequency method is designed to deal with the noise on the set of deterministic functions. Example is the determination of the dynamic characteristics of the aircraft in accordance with the data obtained in one automatic landing.
The SdiA-regulated gene srgE encodes a type III secreted effector.
Habyarimana, Fabien; Sabag-Daigle, Anice; Ahmer, Brian M M
2014-06-01
Salmonella enterica serovar Typhimurium is a food-borne pathogen that causes severe gastroenteritis. The ability of Salmonella to cause disease depends on two type III secretion systems (T3SSs) encoded in two distinct Salmonella pathogenicity islands, 1 and 2 (SPI1 and SPI2, respectively). S. Typhimurium encodes a solo LuxR homolog, SdiA, which can detect the acyl-homoserine lactones (AHLs) produced by other bacteria and upregulate the rck operon and the srgE gene. SrgE is predicted to encode a protein of 488 residues with a coiled-coil domain between residues 345 and 382. In silico studies have provided conflicting predictions as to whether SrgE is a T3SS substrate. Therefore, in this work, we tested the hypothesis that SrgE is a T3SS effector by two methods, a ?-lactamase activity assay and a split green fluorescent protein (GFP) complementation assay. SrgE with ?-lactamase fused to residue 40, 100, 150, or 300 was indeed expressed and translocated into host cells, but SrgE with ?-lactamase fused to residue 400 or 488 was not expressed, suggesting interference by the coiled-coil domain. Similarly, SrgE with GFP S11 fused to residue 300, but not to residue 488, was expressed and translocated into host cells. With both systems, translocation into host cells was dependent upon SPI2. A phylogenetic analysis indicated that srgE is found only within Salmonella enterica subspecies. It is found sporadically within both typhoidal and nontyphoidal serovars, although the SrgE protein sequences found within typhoidal serovars tend to cluster separately from those found in nontyphoidal serovars, suggesting functional diversification. PMID:24727228
An Evaluation of Statistical and Dynamical Techniques for Downscaling Local Climate.
NASA Astrophysics Data System (ADS)
Murphy, James
1999-08-01
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 two climate models. In one integration a global general circulation model (GCM) is constrained to reproduce the observed atmospheric circulation over the period of interest, while the second involves a high-resolution regional climate model (RCM) nested inside the GCM.The dynamical and statistical methods are compared in terms of the correlation between the estimated and observed time series of monthly anomalies. For estimates of temperature a high degree of skill is found, especially over western, central, and northern Europe; for precipitation skill is lower (average correlations ranging from 0.4 in summer to 0.7 in winter). Overall, the dynamical and statistical methods show similar levels of skill, although the statistical method is better for summertime estimates of temperature while the dynamical methods give slightly better estimates of wintertime precipitation. In general, therefore, the skill with which present-day surface climate anomalies can be derived from atmospheric observations is not improved by using the sophisticated calculations of subgrid-scale processes made in climate models rather than simple empirical relationships. It does not necessarily follow that statistical and dynamical downscaling estimates of changes in surface climate will also possess equal skill.By the above measure the two dynamical techniques possess approximately equal skill; however, they are also compared by assessing errors in the mean and variance of monthly values and errors in the simulated distributions of daily values. Such errors arise from systematic biases in the models plus the effect of unresolved local forcings. For precipitation the results show that the RCM offers clear benefits relative to the GCM: the simulated variability of both daily and monthly values, although lower than observed, is much more realistic than in the GCM because the finer grid reduces the amount of spatial smoothing implicit in the use of grid-box variables. The climatological means are also simulated better in the winter half of the year because the RCM captures some of the mesoscale detail present in observed distributions. The temperature fields contain a mesoscale orographic signal that is skillfully reproduced by the RCM; however, this is not a source of increased skill relative to the GCM since elevation biases can be largely removed using simple empirical corrections based on spatially averaged lapse rates. Nevertheless, the average skill of downscaled climatological mean temperature values is higher in the RCM in nearly all months. The additional skill arises from better resolution of local physiographical features, especially coastlines, and also from the dynamical effects of higher resolution, which generally act to reduce the large-scale systematic biases in the simulated values. Both models tend to overestimate the variability of both daily and monthly mean temperature. On average the RCM is more skillful in winter but less skillful in summer, due to excessive drying of the soil over central and southern Europe.The downscaling scores for monthly means are compared against scores obtained by using a predictor variable consisting of observations from the nearest station to the predictand station. In general the downscaling scores are significantly worse than those obtained from adjacent stations, indicating that there remains considerable scope for refining the techniques in future. In the case of dynamical downscaling progress can be made by reducing systematic errors through improvements in the representation of physical processes and increased resolution; the prospects for improving statistical downscaling will
NASA Astrophysics Data System (ADS)
Miksovsky, J.; Huth, R.; Halenka, T.; Belda, M.; Farda, A.; Skalak, P.; Stepanek, P.
2009-12-01
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.
Predicting near-term climate change using a hierarchy of dynamical and statistical models
NASA Astrophysics Data System (ADS)
Saravanan, R.; Chang, P.; Ji, L.
2010-12-01
Near-term climate prediction poses more of a challenge to climate models than long-term climate projection, because the anthropogenic climate change signal, which increases with time, is still not very strong compared to natural climate variability, which can be assumed to be stationary. When a dynamical global climate model is used to make climate predictions, the near-term anthropogenic signal, and the limited predictability gained from knowledge of the initial conditions, can easily be swamped by the climate drift associated with model biases. The use of statistical models can circumvent the model bias issue, but the statistical approach suffers from the lack of sufficient training data to characterize an unprecedented event like anthropogenic climate change. In this study, we evaluate the use of models simpler than coupled global climate models (CGCMs) to predict near-term climate change. We have carried out ensembles of century-long climate predictions with a global atmospheric coupled model coupled to a slab ocean model, using simple extrapolative projections of future greenhouse gas forcing etc. The use of the slab ocean model mitigates the problem of climate drift and reduces the effect of initial condition errors in the ocean, but we also lose any predictability gained from knowledge of the deep oceanic initial condition. We compare these dynamical predictions, on global and regional scales, to those obtained from CGCMs as well as simple statistical models.
Heterogeneous Structure of Stem Cells Dynamics: Statistical Models and Quantitative Predictions
NASA Astrophysics Data System (ADS)
Bogdan, Paul; Deasy, Bridget M.; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu
2014-04-01
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.
Statistics of voltage drop in distribution circuits: a dynamic programming approach
Turitsyn, Konstantin S [Los Alamos National Laboratory
2010-01-01
We analyze a power distribution line with high penetration of distributed generation and strong variations of power consumption and generation levels. In the presence of uncertainty the statistical description of the system is required to assess the risks of power outages. In order to find the probability of exceeding the constraints for voltage levels we introduce the probability distribution of maximal voltage drop and propose an algorithm for finding this distribution. The algorithm is based on the assumption of random but statistically independent distribution of loads on buses. Linear complexity in the number of buses is achieved through the dynamic programming technique. We illustrate the performance of the algorithm by analyzing a simple 4-bus system with high variations of load levels.
A unified N-body and statistical treatment of stellar dynamics. I - The hybrid code.
NASA Astrophysics Data System (ADS)
McMillan, S. L. W.; Lightman, A. P.
1984-08-01
A unified N-body and statistical treatment of stellar dynamics is developed and applied to the late stages of core collapse and early stages of post collapse evolution in globular clusters. A 'hybrid' computer code is joined to a direct N-body code which is used to calculate exactly the behavior of particles in the inner spatial region, and the combination is used to follow particles statistically in the outer spatial region. A transition zone allows the exchange of particles and energy between the two regions. The main application results include: formation of a hard central binary system, reversal of core collapse and expansion due to the heat input from this binary, ejection of the binary from the core, and recollapse of the core; density profiles that form a one-parameter sequence during the core oscillations; and indications that these oscillations will eventually cease.
Cluster Statistics and Quasisoliton Dynamics in Microscopic Car-following Models
Bo Yang; Xihua Xu; John Z. F. Pang; Christopher Monterola
2014-08-20
Using the optimal velocity (OV) model as an example, we show that in the non-linear regime there is an emergent quantity that gives the extremum headways in the cluster formation, as well as the coexistence curve separating the absolute stable phase from the metastable phase. This emergent quantity is independent of the density of the traffic lane, and determines an intrinsic scale that characterizes the dynamics of localized quasisoliton structures given by the time derivative of the headways. The intrinsic scale is analogous to the "charge" of quasisolitons that controls the strength of interaction between multiple clusters, leading to non-trivial cluster statistics from random perturbations to initial uniform traffic. The cluster statistics depend both on the charge and the density of the traffic lane; the relationship is qualitatively universal for general car-following models.
Schweikhard, W.G.; Chen, Y.S.
1986-04-01
The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.
Dynamic whole-body PET parametric imaging: II. Task-oriented statistical estimation
NASA Astrophysics Data System (ADS)
Karakatsanis, Nicolas A.; Lodge, Martin A.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman
2013-10-01
In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (˜15-20 cm) of a single-bed position and have not been translated to the whole-body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of whole-body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical 18F-deoxyglucose patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of whole-body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ˜30 min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, whole-body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection.
Dynamic whole-body PET parametric imaging: II. Task-oriented statistical estimation.
Karakatsanis, Nicolas A; Lodge, Martin A; Zhou, Y; Wahl, Richard L; Rahmim, Arman
2013-10-21
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
Choi, Ok Ran; Lim, In Kyoung
2011-04-08
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.
Dynamics and statistics of wave-particle interactions in a confined geometry.
Gilet, Tristan
2014-11-01
A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors. PMID:25493868
q-deformed statistical-mechanical structure in the dynamics of the Feigenbaum attractor
A. Robledo
2007-10-04
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 fraction 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.
NASA Astrophysics Data System (ADS)
Shaklan, Stuart B.; Marchen, Luis; Peterson, Lee; Levine, Marie B.
2014-08-01
We have combined our Excel-based coronagraph dynamics error budget spreadsheets with DAKOTA scripts to perform statistical analyses of the predicted dark-hole contrast. Whereas in the past we have reported the expected contrast level for an input set of allocated parameters, we now generate confidence intervals for the predicted contrast. Further, we explore the sensitivity to individual or groups of parameters and model uncertainty factors through aleatory-epistemic simulations based on a surrogate model fitted to the error budget. We show example results for a generic high-contrast coronagraph.
NASA Astrophysics Data System (ADS)
Haas, R.; Pinto, J. G.
2012-12-01
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.
NASA Astrophysics Data System (ADS)
Haas, Rabea; Pinto, Joaquim G.
2013-04-01
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.
NASA Astrophysics Data System (ADS)
Arbona, A.; Bona, C.; Miñano, B.; Plastino, A.
2014-09-01
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.
Statistical Stability Analysis for Particle Swarm Optimization Dynamics with Random Coefficients
NASA Astrophysics Data System (ADS)
Koguma, Yuji; Aiyhosi, Eitaro
Particle Swarm Optimization (PSO), a meta-heuristic global optimization method, has attracted special interest for its simple algorithm and high searching ability. The updating formula of PSO involves coefficients with random numbers as parameters to enhance diversification ability in searching for the global optimum. However, the randomness makes stability of the searching points difficult to be analyzed mathematically, and the users need to adjust the parameter values by trial and error. In this paper, stability of the stochastic dynamics of PSO is analyzed mathematically and exact stability condition taking the randomness into consideration is presented with an index “statistical eigenvalue”, which is a new concept to evaluate the degree of the stability of PSO dynamics. Accuracy and effectiveness of the proposed stability discrimination using the presented index are certified in numerical simulation for simple examples.
NASA Astrophysics Data System (ADS)
Mittal, A. K.; Singh, U. P.; Tiwari, A.; Dwivedi, S.; Joshi, M. K.; Tripathi, K. C.
2015-08-01
In a nonlinear, chaotic dynamical system, there are typically regions in which an infinitesimal error grows and regions in which it decays. If the observer does not know the evolution law, recourse is taken to non-dynamical methods, which use the past values of the observables to fit an approximate evolution law. This fitting can be local, based on past values in the neighborhood of the present value as in the case of Farmer-Sidorowich (FS) technique, or it can be global, based on all past values, as in the case of Artificial Neural Networks (ANN). Short-term predictions are then made using the approximate local or global mapping so obtained. In this study, the dependence of statistical prediction errors on dynamical error growth rates is explored using the Lorenz-63 model. The regions of dynamical error growth and error decay are identified by the bred vector growth rates or by the eigenvalues of the symmetric Jacobian matrix. The prediction errors by the FS and ANN techniques in these two regions are compared. It is found that the prediction errors by statistical methods do not depend on the dynamical error growth rate. This suggests that errors using statistical methods are independent of the dynamical situation and the statistical methods may be potentially advantageous over dynamical methods in regions of low dynamical predictability.
Enhancing dynamic graphical analysis with the Lisp-Stat language and the ViSta statistical program.
Ledesma, Rubén; Molina, J Gabriel; Young, Forrest W
2005-11-01
Presented is a sample of computerized methods aimed at multidimensional scaling and psychometric item analysis that offer a dynamic graphical interface to execute analyses and help visualize the results. These methods show how the Lisp-Stat programming language and the ViSta statistical program can be jointly applied to develop powerful computer applications that enhance dynamic graphical analysis methods. The feasibility of this combined strategy relies on two main features: (1) The programming architecture of ViSta enables users to add new statistical methods as plug-ins, which are integrated into the program environment and can make use of all the functions already available in ViSta (e.g., data manipulation, editing, printing); and (2) the set of powerful statistical and graphical functions integrated into the Lisp-Stat programming language provides the means for developing statistical methods with dynamic graphical visualizations, which can be implemented as ViSta plug-ins. PMID:16629303
Neutral dynamics with environmental noise: Age-size statistics and species lifetimes
NASA Astrophysics Data System (ADS)
Kessler, David; Suweis, Samir; Formentin, Marco; Shnerb, Nadav M.
2015-08-01
Neutral dynamics, where taxa are assumed to be demographically equivalent and their abundance is governed solely by the stochasticity of the underlying birth-death process, has proved itself as an important minimal model that accounts for many empirical datasets in genetics and ecology. However, the restriction of the model to demographic [O (?{N }) ] noise yields relatively slow dynamics that appears to be in conflict with both short-term and long-term characteristics of the observed systems. Here we analyze two of these problems—age-size relationships and species extinction time—in the framework of a neutral theory with both demographic and environmental stochasticity. It turns out that environmentally induced variations of the demographic rates control the long-term dynamics and modify dramatically the predictions of the neutral theory with demographic noise only, yielding much better agreement with empirical data. We consider two prototypes of "zero mean" environmental noise, one which is balanced with regard to the arithmetic abundance, another balanced in the logarithmic (fitness) space, study their species lifetime statistics, and discuss their relevance to realistic models of community dynamics.
Statistics of reversible bond dynamics observed in force-clamp spectroscopy
Gregor Diezemann; Thomas Schlesier; Burkhard Geil; Andreas Janshoff
2010-10-30
We present a detailed analysis of two-state trajectories obtained from force-clamp spectroscopy (FCS) of reversibly bonded systems. FCS offers the unique possibility to vary the equilibrium constant in two-state kinetics, for instance the unfolding and refolding of biomolecules, over many orders of magnitude due to the force dependency of the respective rates. We discuss two different kinds of counting statistics, the event-counting usually employed in the statistical analysis of two-state kinetics and additionally the so-called cycle-counting. While in the former case all transitions are counted, cycle-counting means that we focus on one type of transitions. This might be advantageous in particular if the equilibrium constant is much larger or much smaller than unity because in these situations the temporal resolution of the experimental setup might not allow to capture all transitions of an event-counting analysis. We discuss how an analysis of FCS data for complex systems exhibiting dynamic disorder might be performed yielding information about the detailed force-dependence of the transition rates and about the time scale of the dynamic disorder. In addition, the question as to which extent the kinetic scheme can be viewed as a Markovian two-state model is discussed.
A Statistical Approach for the Concurrent Coupling of Molecular Dynamics and Finite Element Methods
NASA Technical Reports Server (NTRS)
Saether, E.; Yamakov, V.; Glaessgen, E.
2007-01-01
Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, increasing the size of the MD domain quickly presents intractable computational demands. A robust approach to surmount this computational limitation has been to unite continuum modeling procedures such as the finite element method (FEM) with MD analyses thereby reducing the region of atomic scale refinement. The challenging problem is to seamlessly connect the two inherently different simulation techniques at their interface. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the typical boundary value problem used to define a coupled domain. The method uses statistical averaging of the atomistic MD domain to provide displacement interface boundary conditions to the surrounding continuum FEM region, which, in return, generates interface reaction forces applied as piecewise constant traction boundary conditions to the MD domain. The two systems are computationally disconnected and communicate only through a continuous update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM) as opposed to a direct coupling method where interface atoms and FEM nodes are individually related. The methodology is inherently applicable to three-dimensional domains, avoids discretization of the continuum model down to atomic scales, and permits arbitrary temperatures to be applied.
NASA Astrophysics Data System (ADS)
Hellström, Cecilia; Chen, Deliang
2003-11-01
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.
Avalappampatty Sivasamy, Aneetha; Sundan, Bose
2015-01-01
The ever expanding communication requirements in today's world demand extensive and efficient network systems with equally efficient and reliable security features integrated for safe, confident, and secured communication and data transfer. Providing effective security protocols for any network environment, therefore, assumes paramount importance. Attempts are made continuously for designing more efficient and dynamic network intrusion detection models. In this work, an approach based on Hotelling's T2 method, a multivariate statistical analysis technique, has been employed for intrusion detection, especially in network environments. Components such as preprocessing, multivariate statistical analysis, and attack detection have been incorporated in developing the multivariate Hotelling's T2 statistical model and necessary profiles have been generated based on the T-square distance metrics. With a threshold range obtained using the central limit theorem, observed traffic profiles have been classified either as normal or attack types. Performance of the model, as evaluated through validation and testing using KDD Cup'99 dataset, has shown very high detection rates for all classes with low false alarm rates. Accuracy of the model presented in this work, in comparison with the existing models, has been found to be much better.
NASA Astrophysics Data System (ADS)
Huth, Radan; Mikšovský, Ji?í; Št?pánek, Petr; Belda, Michal; Farda, Aleš; Chládová, Zuzana; Pišoft, Petr
2015-05-01
Minimum and maximum temperature in two regional climate models and five statistical downscaling models are validated according to a unified set of criteria that have a potential relevance for impact assessments: persistence (temporal autocorrelations), spatial autocorrelations, extreme quantiles, skewness, kurtosis, and the degree of fit to observed data on both short and long times scales. The validation is conducted on two dense grids in central Europe as follows: (1) a station network and (2) a grid with a resolution of 10 km. The gridded dataset is not contaminated by artifacts of the interpolation procedure; therefore, we claim that using a gridded dataset as a validation base is a valid approach. The fit to observations in short time scales is equally good for the statistical downscaling (SDS) models and regional climate models (RCMs) in winter, while it is much better for the SDS models in summer. The reproduction of variability on long time scales, expressed as linear trends, is similarly successful by both SDS models and RCMs. Results for other criteria suggest that there is no justification for preferring dynamical models at the expense of statistical models—and vice versa. The non-linear SDS models do not outperform the linear ones.
on statistical physics, nonlinear dynamics, and complex systems, some over-sea and mainland China physicists initiated the First Cross Taiwan-strait Conference on Statistical Physics. The organization parallel sessions on the topics: Basic theory in statistical physics, nonlinear dynamics, physics
Statistical Testing of Dynamically Downscaled Rainfall Data for the East Coast of Australia
NASA Astrophysics Data System (ADS)
Parana Manage, Nadeeka; Lockart, Natalie; Willgoose, Garry; Kuczera, George
2015-04-01
This study performs a validation of statistical properties of downscaled climate data, concentrating on the rainfall which is required for hydrology predictions used in reservoir simulations. The data sets used in this study have been produced by the NARCliM (NSW/ACT Regional Climate Modelling) project which provides a dynamically downscaled climate dataset for South-East Australia at 10km resolution. NARCliM has used three configurations of the Weather Research Forecasting Regional Climate Model and four different GCMs (MIROC-medres 3.2, ECHAM5, CCCMA 3.1 and CSIRO mk3.0) from CMIP3 to perform twelve ensembles of simulations for current and future climates. Additionally to the GCM-driven simulations, three control run simulations driven by the NCEP/NCAR reanalysis for the entire period of 1950-2009 has also been performed by the project. The validation has been performed in the Upper Hunter region of Australia which is a semi-arid to arid region 200 kilometres North-West of Sydney. The analysis used the time series of downscaled rainfall data and ground based measurements for selected Bureau of Meteorology rainfall stations within the study area. The initial testing of the gridded rainfall was focused on the autoregressive characteristics of time series because the reservoir performance depends on long-term average runoffs. A correlation analysis was performed for fortnightly, monthly and annual averaged time resolutions showing a good statistical match between reanalysis and ground truth. The spatial variation of the statistics of gridded rainfall series were calculated and plotted at the catchment scale. The spatial correlation analysis shows a poor agreement between NARCliM data and ground truth at each time resolution. However, the spatial variability plots show a strong link between the statistics and orography at the catchment scale.
NASA Astrophysics Data System (ADS)
Ho, Chun Kit; Hawkins, Ed; Shaffrey, Len; Underwood, Fiona M.
2013-08-01
Accurate decadal climate predictions could be used to inform adaptation actions to a changing climate. The skill of such predictions from initialised dynamical global climate models (GCMs) may be assessed by comparing with predictions from statistical models which are based solely on historical observations. This paper presents two benchmark statistical models for predicting both the radiatively forced trend and internal variability of annual mean sea surface temperatures (SSTs) on a decadal timescale based on the gridded observation data set HadISST. For both statistical models, the trend related to radiative forcing is modelled using a linear regression of SST time series at each grid box on the time series of equivalent global mean atmospheric CO2 concentration. The residual internal variability is then modelled by (1) a first-order autoregressive model (AR1) and (2) a constructed analogue model (CA). From the verification of 46 retrospective forecasts with start years from 1960 to 2005, the correlation coefficient for anomaly forecasts using trend with AR1 is greater than 0.7 over parts of extra-tropical North Atlantic, the Indian Ocean and western Pacific. This is primarily related to the prediction of the forced trend. More importantly, both CA and AR1 give skillful predictions of the internal variability of SSTs in the subpolar gyre region over the far North Atlantic for lead time of 2-5 years, with correlation coefficients greater than 0.5. For the subpolar gyre and parts of the South Atlantic, CA is superior to AR1 for lead time of 6-9 years. These statistical forecasts are also compared with ensemble mean retrospective forecasts by DePreSys, an initialised GCM. DePreSys is found to outperform the statistical models over large parts of North Atlantic for lead times of 2-5 years and 6-9 years, however trend with AR1 is generally superior to DePreSys in the North Atlantic Current region, while trend with CA is superior to DePreSys in parts of South Atlantic for lead time of 6-9 years. These findings encourage further development of benchmark statistical decadal prediction models, and methods to combine different predictions.
NASA Astrophysics Data System (ADS)
Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Mendez, Fernando
2013-04-01
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).
The Stark effect and different photon statistics in two-photon atomic dynamics
NASA Astrophysics Data System (ADS)
Cardimona, D. A.; Kovanis, V.; Sharma, M. P.
Our main thrust in this paper is to investigate the effect of the Stark shifts on the atomic inversion dynamics when a multilevel atom interacts with a two-mode quantized radiation field. We utilize Hamiltonians that describe a Raman-type process as well as equal- and unequal-frequency two-photon absorption, and include the power-dependent Stark effect terms. We find that the Stark effect can fundamentally alter the atomic dynamics, by introducing exact periodicity depending on the tuning of the two modes of the applied field. Periodic collapses and revivals occur when the pump field is tuned on resonance for Raman scattering, tuned one coupling constant below resonance for unequal-frequency two-photon absorption, or tuned one or three coupling constants below resonance for equal-frequency two-photon absorption. After finding this major result, we briefly describe the effects of changing the width and mean in the photon statistical distributions, and find that as the photon mean increases, the early dynamics persist for longer times, and as the photon width increases, the widths of the revivals broaden.
Statistical analysis of a new European Cloud Dynamics and Radiation Database
NASA Astrophysics Data System (ADS)
Casella, D.; Formenton, M.; Leung, W.-Y.; Mugnai, A.; Sanò, P.; Smith, E. A.; Tripoli, G. J.
2009-04-01
Physically-based algorithms for the retrieval of precipitation from satellite-borne microwave (MW) radiometers, make use of Cloud Radiation Databases (CRD's) that are composed of thousands of detailed microphysical cloud profiles, obtained from Cloud Resolving Model (CRM) simulations, coupled with the corresponding brightness temperatures (TB's), calculated by applying Radiative Transfer (RT) schemes to the CRM outputs. Usually, CRD's are generated on the basis of CRM simulations of past precipitation events and then utilized for the analysis of satellite observations of new events. Notably, retrieval precision and accuracy is strictly related to the appropriate generation of the cloud profile datasets associated to the typologies of the observed precipitation events more than to an a-posteriori statistical treatment of uncertainties. In essence, the retrieval performance can be improved by generating a statistically significant CRD by means of a large number of different CRM simulations representing all precipitation regimes that are of interest for the zone(s) and season(s) under investigation. In addition, it should be noted that despite some reasonable successes with the CRD and the Bayesian approach, there is a considerable reservoir of potential information available that has not been yet tapped. This ancillary information exists in the knowledge of the "synoptic situation" of the considered event and the geographical and temporal location of the event. This knowledge renders some entries into the CRD more relevant than others by virtue of how similar the circumstances of the simulated events are to those of the event for which the database is applied. We can capture this information in the form of "dynamical tags" which can be used to link a satellite-observed event to a subset of the entire CRD using an independent estimate of these tags. To accomplish this, we have expanded the CRD approach so as to include these "dynamical tags" and have developed a new passive MW precipitation retrieval algorithm which employs these tags in addition to the upwelling TB's. We call these the Cloud Dynamics and Radiation Database (CDRD) approach and the CDRD Algorithm, respectively. Recently, we have generated a CDRD database for Europe using a large amount of CRM simulations of precipitating systems over this area by means of the "University of Wisconsin - Non-hydrostatic Modeling System" (UW-NMS). In our presentation, we will briefly review the main design features of the CDRD approach and will show an analysis of the statistical properties of this highly-populated European CDRD database. Finally, we will compare its radiative characteristics with an equivalent set of MW radiometric measurements from polar satellites.
The non-statistical dynamics of the ¹?O + ³²O? isotope exchange reaction at two energies.
Van Wyngarden, Annalise L; Mar, Kathleen A; Quach, Jim; Nguyen, Anh P Q; Wiegel, Aaron A; Lin, Shi-Ying; Lendvay, Gyorgy; Guo, Hua; Lin, Jim J; Lee, Yuan T; Boering, Kristie A
2014-08-14
The dynamics of the (18)O((3)P) + (32)O2 isotope exchange reaction were studied using crossed atomic and molecular beams at collision energies (E(coll)) of 5.7 and 7.3 kcal/mol, and experimental results were compared with quantum statistical (QS) and quasi-classical trajectory (QCT) calculations on the O3(X(1)A') potential energy surface (PES) of Babikov et al. [D. Babikov, B. K. Kendrick, R. B. Walker, R. T. Pack, P. Fleurat-Lesard, and R. Schinke, J. Chem. Phys. 118, 6298 (2003)]. In both QS and QCT calculations, agreement with experiment was markedly improved by performing calculations with the experimental distribution of collision energies instead of fixed at the average collision energy. At both collision energies, the scattering displayed a forward bias, with a smaller bias at the lower E(coll). Comparisons with the QS calculations suggest that (34)O2 is produced with a non-statistical rovibrational distribution that is hotter than predicted, and the discrepancy is larger at the lower E(coll). If this underprediction of rovibrational excitation by the QS method is not due to PES errors and/or to non-adiabatic effects not included in the calculations, then this collision energy dependence is opposite to what might be expected based on collision complex lifetime arguments and opposite to that measured for the forward bias. While the QCT calculations captured the experimental product vibrational energy distribution better than the QS method, the QCT results underpredicted rotationally excited products, overpredicted forward-bias and predicted a trend in the strength of forward-bias with collision energy opposite to that measured, indicating that it does not completely capture the dynamic behavior measured in the experiment. Thus, these results further underscore the need for improvement in theoretical treatments of dynamics on the O3(X(1)A') PES and perhaps of the PES itself in order to better understand and predict non-statistical effects in this reaction and in the formation of ozone (in which the intermediate O3* complex is collisionally stabilized by a third body). The scattering data presented here at two different collision energies provide important benchmarks to guide these improvements. PMID:25134575
Technology Transfer Automated Retrieval System (TEKTRAN)
QseA and SdiA are two of several transcriptional regulators that regulate virulence gene expression of enterohemorrhagic Escherichia coli (EHEC) O157:H7 via quorum sensing (QS). QseA regulates the expression of the locus of enterocyte effacement (LEE). LEE encodes for a type III secretion (T3S) sys...
ERIC Educational Resources Information Center
Olive, G.; And Others
A selective dissemination of information service based on computer scanning of Nuclear Science Abstracts tapes has operated at the Atomic Energy Research Establishment, Harwell, England since October, 1968. The performance of the mechanized SDI service has been compared with that of the pre-existing current awareness service which is based on…
Kinematic and dynamic collision statistics of cloud droplets from high-resolution simulations
NASA Astrophysics Data System (ADS)
Rosa, Bogdan; Parishani, Hossein; Ayala, Orlando; Grabowski, Wojciech W.; Wang, Lian-Ping
2013-04-01
We study the dynamic and kinematic collision statistics of cloud droplets for a range of flow Taylor microscale Reynolds numbers (up to 500), using a highly scalable hybrid direct numerical simulation approach. Accurate results of radial relative velocity (RRV) and radial distribution function (RDF) at contact have been obtained by taking advantage of their power-law scaling at short separation distances. Three specific but inter-related questions have been addressed in a systematic manner for geometric collisions of same-size droplets (of radius from 10 to 60 ?m) in a typical cloud turbulence (dissipation rate at 400 cm2 s-3). Firstly, both deterministic and stochastic forcing schemes were employed to test the sensitivity of the simulation results on the large-scale driving mechanism. We found that, in general, the results are quantitatively similar, with the deterministic forcing giving a slightly larger RDF and collision kernel. This difference, however, is negligible for droplets of radius less than 30 ?m. Secondly, we have shown that the dependence of pair statistics on the flow Reynolds number R? or larger scale fluid motion is of secondary importance, with a tendency for this effect to saturate at high enough R? leading to R?-independent results. Both DNS results and theoretical arguments show that the saturation happens at a smaller R? for smaller droplets. Finally, since most previous studies of turbulent collision of inertial particles concerned non-sedimenting particles, we have specifically addressed the role of gravity on collision statistics, by simultaneously simulating collision statistics with and without gravity. It is shown that the collision statistics is not affected by gravity when a < ac, where the critical droplet radius ac is found to be around 30 ?m for the RRV, and around 20 ?m for the RDF. For larger droplets, gravity alters the particle-eddy interaction time and significantly reduces the RRV. The effect of gravity on the RDF is rather complex: gravity reduces the RDF for intermediate-sized droplets but enhances the RDF for larger droplets. In addition, we have studied the scaling exponents of both RDF and RRV, and found that gravity modifies the RDF scaling exponents for both intermediate and large particles, in a manner very similar to the effect of gravity on the RDF at contact. Gravity is shown to cause the scaling exponents for RDF and RRV to level off for large droplets, in contrast to diminishing exponents for non-sedimenting particles.
Defect-phase-dynamics approach to statistical domain-growth problem of clock models
NASA Technical Reports Server (NTRS)
Kawasaki, K.
1985-01-01
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.
Statistical analysis of vesicle morphology dynamics based on a free energy landscape.
Tsuda, Soichiro; Suzuki, Hiroaki; Yomo, Tetsuya
2014-08-28
We here present a method to reconstruct effective free energy landscapes (FELs) of lipid vesicles from the statistical analysis of a large number of microscope images. This method, not only allows us to define possible energy landscapes, but also highlights minority vesicle shapes that were otherwise hidden in the majority. When compared with temporal evolution of deforming lipid vesicles, it was found that the trajectory of deforming vesicles was in accordance with the reconstructed landscape, in which the minority shapes play a key role. When compared with theoretical models, it revealed that the vesicle shapes characterised in the reconstructed FELs were consistent with the theoretically predicted shapes. These results suggest that the FEL analysis can be a useful tool to investigate the morphological dynamics of lipid vesicles, in conjunction with other analytical methods. PMID:24998870
Extended Dynamic Subgraph Statistics Using h-Index Parameterized Data Structures
NASA Astrophysics Data System (ADS)
Eppstein, David; Goodrich, Michael T.; Strash, Darren; Trott, Lowell
We present techniques for maintaining subgraph frequencies in a dynamic graph, using data structures that are parameterized in terms of h, the h-index of the graph. Our methods extend previous results of Eppstein and Spiro for maintaining statistics for undirected subgraphs of size three to directed subgraphs and to subgraphs of size four. For the directed case, we provide a data structure to maintain counts for all 3-vertex induced subgraphs in O(h) amortized time per update. For the undirected case, we maintain the counts of size-four subgraphs in O(h 2) amortized time per update. These extensions enable a number of new applications in Bioinformatics and Social Networking research.
Collisional statistics and dynamics of two-dimensional hard-disk systems: From fluid to solid
NASA Astrophysics Data System (ADS)
Taloni, Alessandro; Meroz, Yasmine; Huerta, Adrián
2015-08-01
We perform extensive MD simulations of two-dimensional systems of hard disks, focusing on the collisional statistical properties. We analyze the distribution functions of velocity, free flight time, and free path length for packing fractions ranging from the fluid to the solid phase. The behaviors of the mean free flight time and path length between subsequent collisions are found to drastically change in the coexistence phase. We show that single-particle dynamical properties behave analogously in collisional and continuous-time representations, exhibiting apparent crossovers between the fluid and the solid phases. We find that, both in collisional and continuous-time representation, the mean-squared displacement, velocity autocorrelation functions, intermediate scattering functions, and self-part of the van Hove function (propagator) closely reproduce the same behavior exhibited by the corresponding quantities in granular media, colloids, and supercooled liquids close to the glass or jamming transition.
Statistical and dynamical study of disease propagation in a small world network
NASA Astrophysics Data System (ADS)
Zekri, Nouredine; Clerc, Jean Pierre
2001-11-01
Statistical properties and dynamical disease propagation have been studied numerically using a percolation model in a one dimensional small world network. The parameters chosen correspond to a realistic network of school age children. It has been found that percolation threshold decreases as a power law as the shortcut fluctuations increase. It has also been found that the number of infected sites grows exponentially with time and its rate depends logarithmically on the density of susceptibles. This behavior provides an interesting way to estimate the serology for a given population from the measurement of the disease growing rate during an epidemic phase. The case in which the infection probability of nearest neighbors is different from that of short cuts has also been examined. A double diffusion behavior with a slower diffusion between the characteristic times has been found.
Dislocation dynamics, plasticity and avalanche statistics using the phase-field crystal model
NASA Astrophysics Data System (ADS)
Angheluta, Luiza
2013-03-01
The plastic deformation of stressed crystalline materials is characterized by intermittency and scaling behavior. The sudden strain bursts arise from collective interactions between depinned crystal defects such as dislocations. Recent experiments on sheared nanocrystals provide insights into the connection between the crystal plasticity and the mean field theory of the depinning transition, based on the similar power-law statistics of avalanche events. However, a complete theoretical formulation of this connection is still lacking, as are high quality numerical data. Phase field crystal modelling provides an efficient numerical approach to simulating the dynamics of dislocations in plastic flows at finite temperature. Dislocations are naturally created as defects in a periodic ground state that is being sheared, without any ad hoc creation and annihilation rules. These crystal defects interact and annihilate with one another, generating a collective effect of avalanches in the global plastic strain rate. We examine the statistics of plastic avalanches both at finite and zero temperatures, and find good agreement with the predictions of the mean field interface depinning theory. Moreover, we predict universal scaling forms for the extreme statistics of avalanches and universal relations between the power-law exponents of avalanche duration, size and extreme value. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity, but are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. The work reported here was performed in collaboration with: Georgios Tsekenis, Michael LeBlanc, Patrick Y Chan, Jon Dantzig, Karin Dahmen, and Nigel Goldenfeld. The plastic deformation of stressed crystalline materials is characterized by intermittency and scaling behavior. The sudden strain bursts arise from collective interactions between depinned crystal defects such as dislocations. Recent experiments on sheared nanocrystals provide insights into the connection between the crystal plasticity and the mean field theory of the depinning transition, based on the similar power-law statistics of avalanche events. However, a complete theoretical formulation of this connection is still lacking, as are high quality numerical data. Phase field crystal modelling provides an efficient numerical approach to simulating the dynamics of dislocations in plastic flows at finite temperature. Dislocations are naturally created as defects in a periodic ground state that is being sheared, without any ad hoc creation and annihilation rules. These crystal defects interact and annihilate with one another, generating a collective effect of avalanches in the global plastic strain rate. We examine the statistics of plastic avalanches both at finite and zero temperatures, and find good agreement with the predictions of the mean field interface depinning theory. Moreover, we predict universal scaling forms for the extreme statistics of avalanches and universal relations between the power-law exponents of avalanche duration, size and extreme value. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity, but are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. The work reported here was performed in collaboration with: Georgios Tsekenis, Michael LeBlanc, Patrick Y Chan, Jon Dantzig, Karin Dahmen, and Nigel Goldenfeld. The work was supported by the Center for Physics of Geological Processes (Norway) through a post-doctoral grant, the National Science Foundation through grant NSF-DMR-03-25939, NSF_DMR-1005209 and NSF-DMS-1069224 and DOE Subcontract No. 4000076535 (J.D.)
NASA Astrophysics Data System (ADS)
Liu, Y.; Rostkier-Edelstein, D.; Givati, A.; Wu, W.; Descombes, G.; Ge, M.; Warner, T.; Swerdlin, S.
2010-09-01
Major weather centers, such as National Center for Environment Prediction (NCEP) and ECMWF, produce inter-seasonal weather predictions 6 - 9 months ahead. However, the products from these centers have ~200 km grid sizes, which are too coarse for regional applications. For hydrological applications, such as flood forecasting, watershed control, and water resource planning, detailed spatial and temporal distributions of precipitations are very critical. Existing precipitation downscaling approaches include statistical downscaling algorithms (SDA) and dynamical downscaling algorithms (DDA). SDAs are mostly based on regression using reanalysis and/or hindcasts and may apply for future forecast downscaling. SDAs impose three assumptions: a) the past regression relation is (static) valid for the future, b) there is no feedback of local physical forcing (terrain, coastlines and land-use/soil properties) in response to weather/climate changes and c) downscaling valid at the stations where long historical observations are available. DDAs, by which a regional climate model is embedded (nested) in a global seasonal model, overcome many of the shortcomings of a SDA. However, DDAs are computationally costly and data handling is complicated. In this paper, we present a dynamic-enforced statistical downscaling algorithm (DESDA) for effectively downscaling global-model seasonal forecasts. Four steps are involved with DESDA: 1) using the NCAR Four-Dimensional Data Assimilation (FDDA) modeling system, built upon the Weather Research and Forecasting (WRF) model, to produce 1 - 4 km gridded climatological precipitation-distribution analyses over the eastern Mediterranean region, driven by global analyses; 2) calibrating the gridded model precipitation with available precipitation measurements; 3) Applying an advanced KNN based regression downscaling approach based on the calibrated high-resolution gridded precipitation analysis, NCEP global analysis, and NCEP climate forecasting system (CFS) model 29 years of reforecasts for downscaling the CFS seasonal forecasts of precipitation anomalies; and 4) reconstructing precipitation amounts of the seasonal forecasts on the high-resolution WRF analysis grids. The algorithm and preliminary results will be presented.
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-08-01
We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS)-based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAllenging Minisatellite Payload (CHAMP) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction of random errors (standard deviations) of optimized bending angles down to about half of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; and (4) realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well-characterized and high-quality atmospheric profiles over the entire stratosphere.
An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses
NASA Technical Reports Server (NTRS)
Saether, E.; Glaessgen, E.H.; Yamakov, V.
2008-01-01
The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.
Statistical Testing of Dynamically Downscaled Rainfall Data for the East Coast of Australia
NASA Astrophysics Data System (ADS)
Nadeeka, P. M.; Lockart, N.; Willgoose, G. R.; Kuczera, G. A.; Chowdhury, A. F. M. K.
2014-12-01
This study performs a validation of statistical properties of downscaled climate data, concentrating on the rainfall which is required for hydrology predictions used in reservoir simulations. The data sets used in this study have been produced by the NARCliM (NSW/ACT Regional Climate Modelling) project which provides a dynamically downscaled climate dataset for South-East Australia at 10km resolution. NARCliM has used three configurations of the Weather Research Forecasting regional climate model and four different GCMs (MIROC-medres 3.2, ECHAM5, CGCM 3.1 and CSIRO mk3.0) from CMIP3 to perform twelve ensembles of simulations for current and future climates. The validation has been performed in the Upper Hunter region of Australia which is a semi-arid to arid region 200 kilometres North-West of Sydney. The analysis used the time series of downscaled rainfall data and ground based measurements for selected climate stations within the study area. The initial testing of the gridded rainfall was focused on the Auto Regressive characteristics of time series. The focus on correlations was because the reservoir performance depends on long-term average runoffs. In order to compare the datasets, a correlation analysis was performed at daily, fortnightly, monthly, three monthly and annual time scales. Moreover, the spatial variability of statistics of gridded rainfall series were calculated and plotted at the catchment scale. The NARCLiM data were able to successfully reproduce the autocorrelations of observed rainfall at each time scale. The correlation analysis shows a good agreement between NARCliM data and ground truth at three months and annual time scales. The spatial variability plots show a possible link between the statistics and orography at the catchment scale. Preliminary results for an orographic analysis will be shown.
David Brizuela
2014-11-03
The classical and quantum evolution of a generic probability distribution is analyzed. To that end, a formalism based on the decomposition of the distribution in terms of its statistical moments is used, which makes explicit the differences between the classical and quantum dynamics. In particular, there are two different sources of quantum effects. Distributional effects, which are also present in the classical evolution of an extended distribution, are due to the fact that all moments can not be vanishing because of the Heisenberg uncertainty principle. In addition, the non-commutativity of the basic quantum operators add some terms to the quantum equations of motion that explicitly depend on the Planck constant and are not present in the classical setting. These are thus purely-quantum effects. Some particular Hamiltonians are analyzed that have very special properties regarding the evolution they generate in the classical and quantum sector. In addition, a large class of inequalities obeyed by high-order statistical moments, and in particular uncertainty relations that bound the information that is possible to obtain from a quantum system, are derived.
Cai Jing; Read, Paul W.; Larner, James M.; Jones, David R.; Benedict, Stanley H.; Sheng Ke
2008-11-15
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.
Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin
2014-01-01
The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al. 2012 Proc. R. Soc. A 468, 1799–1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi–Dirac or Bose–Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas. PMID:24399919
A Statistical Survey of Dynamic Pressure Pulses in the Solar Wind Based on WIND Observations
NASA Astrophysics Data System (ADS)
Zuo, Pingbing; Feng, Xueshang; Xie, Yanqiong; Wang, Yi; Xu, Xiaojun
2015-07-01
Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure changes abruptly over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. The space weather effects of DPPs on the magnetosphere–ionosphere coupling system have been widely investigated in the last two decades. In this study, we perform a statistical survey on the properties of DPPs near 1 AU based on nearly 20 years of observations from the WIND spacecraft. It is found that only a tiny fraction of DPPs (around 4.2%) can be regarded as interplanetary shocks. For most DPPs, the total pressure (the sum of the thermal pressure and magnetic pressure) remains in equilibrium, but there also exists a small fraction of DPPs that are not pressure-balanced. The overwhelming majority of DPPs are associated with solar wind disturbances, including coronal mass ejection-related flows, corotating interaction regions, as well as complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activity during solar cycle 23, and during the rising phase of solar cycle 24.
NASA Astrophysics Data System (ADS)
Khrennikov, Andrei
2011-03-01
The idea that quantum randomness can be reduced to randomness of classical fields (fluctuating at time and space scales which are essentially finer than scales approachable in modern quantum experiments) is rather old. Various models have been proposed, e.g., stochastic electrodynamics or the semiclassical model. Recently a new model, so called prequantum classical statistical field theory (PCSFT), was developed. By this model a "quantum system" is just a label for (so to say "prequantum") classical random field. Quantum averages can be represented as classical field averages. Correlations between observables on subsystems of a composite system can be as well represented as classical correlations. In particular, it can be done for entangled systems. Creation of such classical field representation demystifies quantum entanglement. In this paper we show that quantum dynamics (given by Schrödinger's equation) of entangled systems can be represented as the stochastic dynamics of classical random fields. The "effect of entanglement" is produced by classical correlations which were present at the initial moment of time, cf. views of Albert Einstein.
NASA Astrophysics Data System (ADS)
Rogachev, A. S.; Baras, F.
2009-02-01
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
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. PMID:19391827
NASA Astrophysics Data System (ADS)
Ahn, J.; Lee, J.; Shim, K.; Kim, Y.
2013-12-01
In spite of dense meteorological observation conducting over South Korea (The average distance between stations: ~ 12.7km), the detailed topographical effect is not reflected properly due to its mountainous terrains and observation sites mostly situated on low altitudes. A model represents such a topographical effect well, but due to systematic biases in the model, the general temperature distribution is sometimes far different from actual observation. This study attempts to produce a detailed mean temperature distribution for South Korea through a method combining dynamical downscaling and statistical correction. For the dynamical downscaling, a multi-nesting technique is applied to obtain 3-km resolution data with a focus on the domain for the period of 10 years (1999-2008). For the correction of systematic biases, a perturbation method divided into the mean and the perturbation part was used with a different correction method being applied to each part. The mean was corrected by a weighting function while the perturbation was corrected by the self-organizing maps method. The results with correction agree well with the observed pattern compared to those without correction, improving the spatial and temporal correlations as well as the RMSE. In addition, they represented detailed spatial features of temperature including topographic signals, which cannot be expressed properly by gridded observation. Through comparison with in-situ observation with gridded values after objective analysis, it was found that the detailed structure correctly reflected topographically diverse signals that could not be derived from limited observation data. We expect that the correction method developed in this study can be effectively used for the analyses and projections of climate downscaled by using region climate models. Acknowledgements This work was carried out with the support of Korea Meteorological Administration Research and Development Program under Grant CATER 2012-3083 and Rural Development Administration Cooperative Research Program for Agriculture Science and Technology Development under Grant Project No. PJ009353, Republic of Korea. Reference Ahn, J.-B., Lee, J.-L., and Im, E.-S., 2012: The reproducibility of surface air temperature over South Korea using dynamical downscaling and statistical correction, J. Meteor. Soc. Japan, 90, 493-507, doi: 10.2151/jmsj.2012-404
Reutter, Bryan W.; Gullberg, Grant T.; Huesman, Ronald H.
2001-04-09
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].
Planar distribution of the galaxies in the Local Group: a statistical and dynamical analysis
Stefano Pasetto; Cesare Chiosi
2006-11-23
Adopting known data on positions and distances, we make use of the analytical geometry and look for the plane that minimizes the distances of all galaxies to it. A planar distribution is indeed found that, however, does not coincide with the plane found by Sawa & Fujimoto 2005. Why? The second part of this study is devoted to answer this question and to find a dynamical justification for the planar distribution. To this aim, we apply the Hamilton Method (Minimum Action) to investigate the dynamics of the two major system of the Local Group, Milky Way and Andromeda, under the action of external forces exerted by nearby galaxies or groups external to the Local Group. We find that the planar istribution is fully compatible with the minimum action and that the external force field is likely parallel to the plane. It pulls the galaxies of the Local Group without altering their planar distribution. Special care is paid to evaluate the robustness of this result. Conclusion: in this paper we have examined the spatial distribution of galaxies in the Local Group. They are confined to a plane that can be statistically and dynamically understood as the result of the Minimum Action. The planar distribution seems to be stable for a large fraction of the Hubble time. The external force field, that has likely been constant over the same time interval, does not alter the planar distribution as it is nearly parallel to it. Effects due to undetected halos of sole Dark Matter are briefly discussed. They could be a point of uncertainty of the present study.
NASA Astrophysics Data System (ADS)
Molini, A.
2012-12-01
Precipitation is one of the major drivers of ecosystem dynamics. Such control is the result of complex dynamical interactions, seldom non linear, and exerted over a wide range of space and time scales. For this reason, if for example precipitation variability and intermittency are known to be among the main drivers of plants production, with a consequent influence on Carbon and Nitrogen cycles, the complete pathway of such a forcing remains often unclear. Traditional time series analysis bases the study of these inter-connections on linear correlation statistics. However, the possible presence of causal dynamical connections, as well as non-linear couplings and non-stationarity can affect the performance of these tools. Additionally, dynamical drivers can act simultaneously over different space and time scales. Given this premise, this talk explores linear and non-linear correlation patterns, information flows and directional couplings characterizing the control of precipitation on ecosystem dynamics by using an ensemble of statistics borrowed from information theory, non-linear dynamical systems analysis and multi-resolution spectral decomposition. In particular, we focus on the development of an extension to the frequency domain of delayed correlation and conditional mutual information functions, and on the implementation of directional coupling measures as conditional spectral causality, phase-slope index, and transfer entropy in the wavelet domain. Several examples, from different climatic regimes, are discussed with the goal of highlighting strengths and weaknesses of these statistics.
Journal of Statistical Physics, Vol. 83, Nos. 1/2, 1996 Asymptotic Dynamics of the Dual Billiard
Tabachnikov, Sergei
Journal of Statistical Physics, Vol. 83, Nos. 1/2, 1996 Asymptotic Dynamics of the Dual Billiard curve, the dual billiard transformation is the trans- formation of its exterior defined as follows point. We show that the dual billiard transformation far from the curve is well approximated by the time
Cofré, Rodrigo
2012-01-01
We investigate the effect of electric synapses (gap junctions) on collective neuronal dynamics and spike statistics in a conductance-based Integrate-and-Fire neural network, driven by a Brownian noise, where conductances depend upon spike history. We compute explicitly the time evolution operator and show that, given the spike-history of the network and the membrane potentials at a given time, the further dynamical evolution can be written in a closed form. We show that spike train statistics is described by a Gibbs distribution whose potential can be approximated with an explicit formula, when the noise is weak. This potential form encompasses existing models for spike trains statistics analysis such as maximum entropy models or Generalized Linear Models (GLM). We also discuss the different types of correlations: those induced by a shared stimulus and those induced by neurons interactions.
Physical insight into superdiffusive dynamics of Sinai billiard through collision statistics
NASA Astrophysics Data System (ADS)
Kokshenev, Valery B.; Vicentini, Eduardo
2006-02-01
We report on distinct steady-motion dynamic regimes in chaotic Sinai billiard (SB). A numerical study on elastic reflections from the SB boundary (square wall of length L and circle obstacle of radius R) is carried out for different R/L. The research is based on the exploration of the generalized diffusion equation and on the analysis of wall-collision and the circle-collision distributions observed at late times. The asymptotes for the diffusion coefficientDR and the corresponding diffusion exponentzR are established for all geometries. The universal ( R-independent) diffusion with D1?t and z1=1.5 replaces the ballistic motion regime ( z0=1) attributed to square billiard ( R=0). Geometrically, this superdiffusive regime is bounded by small radii 0
Refining Homology Models by Combining Replica-Exchange Molecular Dynamics and Statistical Potentials
Zhu, Jiang; Fan, Hao; Periole, Xavier; Honig, Barry; Mark, Alan E.
2009-01-01
A protocol is presented for the global refinement of homology models of proteins. It combines the advantages of temperature-based replica-exchange molecular dynamics (REMD) for conformational sampling and the use of statistical potentials for model selection. The protocol was tested using 21 models. Of these 14 were models of 10 small proteins for which high-resolution crystal structures were available, the remainder were targets of the recent CASPR exercise. It was found that REMD in combination with currently available force fields could sample near-native conformational states starting from high-quality homology models. Conformations in which the backbone RMSD of secondary structure elements (SSE-RMSD) was lower than the starting value by 0.5 to 1.0 Å were found for 15 out of the 21 cases (average 0.82 Å). Furthermore, when a simple scoring function consisting of two statistical potentials was used to rank the structures, one or more structures with SSE-RMSD of at least 0.2 Å lower than the starting value was found among the 5 best ranked structures in 11 out of the 21 cases. The average improvement in SSE-RMSD for the best models was 0.42 Å. However, none of the scoring functions tested identified the structures with the lowest SSE-RMSD as the best models although all identified the native conformation as the one with lowest energy. This suggests that while the proposed protocol proved effective for the refinement of high-quality models of small proteins scoring functions remain one of the major limiting factors in structure refinement. This and other aspects by which the methodology could be further improved are discussed. PMID:18338384
people would buy the drug. Assume X = Binom(n; #18; 2 ). Then f(#18; 2 j x) / #18; n x #19; #18; x 2 (1 of statistical knowledge. Example (Berger): A drug company is deciding whether or not to market a new pain reliever. Two important factors: 1. Proportion of people #18; 1 for whom the drug will be effective 2
[Statistical and dynamic analysis of crime in relation to primary dimensions in various countries].
Krohn, M; Wellford, C
1976-01-01
The examination of the effects of social change on crime has experienced a revival of interest in the past decade. With the increasing availability of cross-national data such analyses are being done in a comparative perspective. The current effort is designed to examine the relationship between three variables which have been shown to be empirically and theoretically pertinent to the study of social change and crime indices. Specifically, the variables of population, gross national product per capita and political orientation are regressed on the homicide rates, property crime rates and total crime rates for a number of countries. This analysis is done statically for 1965 and dynamically, for the change in the variables from 1960 to 1965. The data for the independent variables were acquired from the World Handbook of Political and Social Indicators, Second Edition. The source of the dependent variables was the International Crime Statistics published by the International Criminal Police Organization (Interpol). The problems with such data are recongized and discussed. The results indicate that in the static analysis the three variables explain a substantial amount of the variance in property crime rates and total crime rates whereas they do not explain much of the variance in the homicide rate. Gross national product per capita contributes the most to the explained variance in all the analyses. A theoretical perspective combining the ideas incorporated in control theory and in environmental opportunity theory was employed to account for the results. The results of the dynamic analyses parallel those of the static analyses, with the exception of the equation employing the total crime rate at the dependent variable. The total variance explained in this equation was significantly lower than in the static analysis for the total crime rate. Durkheim's notions of the functions of crime and the expected stability in crime rates were offered as an explanation for this finding. PMID:1023275
Forecasts of the 500 mb height using a dynamically oriented statistical model
NASA Technical Reports Server (NTRS)
Roads, J. O.; Barnett, T. P.
1984-01-01
The forecast skill of a simple dynamically inspired statistical model of the Northern Hemisphere 500 mb height field is evaluated in spectral and physical space for a variety of forecast lead times (1-32 days) and predictand averaging times (1-32 days). The model includes viscous damping, wave propagation, climatology and implicit stochastic forcing. The largest model skill was found for forecasts of the zonal flow and the largest waves. In general, the largest forecast skills were also associated with the largest forecast error, there being a slight geographic phase shift of the skill with respect to the error. Model skills for climate (time-averaged) forecasts are greater when using instantaneous rather than time averages to forecast time averages. Analysis of model errors suggests areas for improvement in representing forcing terms and model physics. However, the model error fields are largely 'white noise' which suggests that global forecast skills substantially larger than those obtained here are unlikely to be achieved by more sophisticated models.
A. E. Roth; C. D. Jones; D. J. Durian
2013-03-26
We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling state, all bubble distributions are independent not only of time but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and with decreasing bubble size. We successfully model this behavior by explicitly incorporating the border blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry.
Exploring the String Landscape: The Dynamics, Statistics, and Cosmology of Parallel Worlds
NASA Astrophysics Data System (ADS)
Ahlqvist, Stein Pontus
This dissertation explores various facets of the low-energy solutions in string theory known as the string landscape. Three separate questions are addressed - the tunneling dynamics between these vacua, the statistics of their location in moduli space, and the potential realization of slow-roll inflation in the flux potentials generated in string theory. We find that the tunneling transitions that occur between a certain class of supersymmetric vacua related to each other via monodromies around the conifold point are sensitive to the details of warping in the near-conifold regime. We also study the impact of warping on the distribution of vacua near the conifold and determine that while previous work has concluded that the conifold point acts as an accumulation point for vacua, warping highly dilutes the distribution in precisely this regime. Finally we investigate a novel form of inflation dubbed spiral inflation to see if it can be realized near the conifold point. We conclude that for our particular models, spiral inflation seems to rely on a de Sitter-like vacuum energy. As a result, whenever spiral inflation is realized, the inflation is actually driven by a vacuum energy.
Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response
Stefan Floerchinger; Urs Achim Wiedemann
2014-08-28
An interesting opportunity to determine thermodynamic and transport properties in more detail is to identify generic statistical properties of initial density perturbations. Here we study event-by-event fluctuations in terms of correlation functions for two models that can be solved analytically. The first assumes Gaussian fluctuations around a distribution that is fixed by the collision geometry but leads to non-Gaussian features after averaging over the reaction plane orientation at non-zero impact parameter. In this context, we derive a three-parameter extension of the commonly used Bessel-Gaussian event-by-event distribution of harmonic flow coefficients. Secondly, we study a model of N independent point sources for which connected n-point correlation functions of initial perturbations scale like 1/N^(n-1). This scaling is violated for non-central collisions in a way that can be characterized by its impact parameter dependence. We discuss to what extent these are generic properties that can be expected to hold for any model of initial conditions, and how this can improve the fluid dynamical analysis of heavy ion collisions.
Sensitivity properties of a biosphere model based on BATS and a statistical-dynamical climate model
NASA Technical Reports Server (NTRS)
Zhang, Taiping
1994-01-01
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.
Temporal Evolution of Soil Moisture Statistical Fractal: Seasonal and Rainfall Dynamics
NASA Astrophysics Data System (ADS)
Ji, X.; Shen, C.; Riley, W. J.
2014-12-01
Soil moisture statistical multi-fractal can potentially be an important tool for multi-scale hydrologic modeling. The fractal scaling exponents (?), the slopes of the log-log relation between soil moisture moments and scales, have the potential to predict the parameters for soil moisture distribution at higher grid-resolution. We demonstrate here that the magnitude and temporal development of ? is related to basin water storage, seasonal mode of wetting and drying, and topography. We used PAWS + CLM, a physically-based surface-subsurface process model, to explore soil moisture spatial and temporal fractal patterns by running several scenarios in two Midwest basins of the United States. We applied homogenous meteorological forcing to focus on the control from heterogeneity of watershed static properties and examined the temporal evolution of ? in different soil depths and in non-freezing days. We found that ? in the top 10cm layer is approximately linearly related to basin-average water storage. In non-freezing seasons, ? shows strong hysteretic patterns. Wetting and drying dominated processes weakens previous organization, and reorganization process is linked to the hydrologic characteristics of the basin. We explained the difference between the seasonal and event dynamic of the fractal exponents.
McCauley, Patrick I; Schanche, Nicole; Evans, Kaitlin E; Su, Chuan; McKillop, Sean; Reeves, Katharine K
2015-01-01
We present a statistical study of prominence and filament eruptions observed by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). Several properties are recorded for 904 events that were culled from the Heliophysics Event Knowledgebase (HEK) and incorporated into an online catalog for general use. These characteristics include the filament and eruption type, eruption symmetry and direction, apparent twisting and writhing motions, and the presence of vertical threads and coronal cavities. Associated flares and white-light coronal mass ejections (CME) are also recorded. Total rates are given for each property along with how they differ among filament types. We also examine the kinematics of 106 limb events to characterize the distinct slow- and fast-rise phases often exhibited by filament eruptions. The average fast-rise onset height, slow-rise duration, slow-rise velocity, maximum field-of-view (FOV) velocity, and maximum FOV acceleration are 83 Mm, 4.4 hours, 2.1 km/s, 106 km...
Wereszczynski, Jeff; McCammon, J. Andrew
2012-01-01
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
Statistical-dynamical downscaling of wind roses over the Czech Republic
NASA Astrophysics Data System (ADS)
Svoboda, Jaroslav; Chladova, Zuzana; Pop, Lukas; Hosek, Jiri
2013-05-01
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.
Background Tropospheric Aerosols: Incorporation within a statistical-dynamical climate model
Potter, G.L.; Cess, R.D.
1984-10-20
To evaluate the possible influence of natural background tropospheric aerosols upon the earth's present climate, we have incorporated aerosol radiation models for continental and maritime aerosols into the Lawrence Livermore National Laboratory statistical-dynamical climate model. The model results suggest that background tropospheric aerosols produce 3/sup 0/-4/sup 0/C global surface cooling, with maximum cooling occurring at high latitudes, results which are essentially consistent with an energy balance climate model study by Coakley et al. (1983). To specifically delineate effects caused directly by the aerosols, as opposed to indirect effects resulting from aerosol-induced climate change, a second climate perturbation was considered that consisted of reducing the solar constant so as to give exactly the same initial reduction in surface-atmosphere solar absorption as for the inclusion of tropospheric aerosols. These separate climate perturbations produced nearly identical climate feedback effects, together with similar changes in atmospheric stability and hydrological cycle, despite the fact that the two perturbations have quite different latitudinal and vertical distributions. This finding is consistent with a general circulation model study by Manabe and Wetherald (1980) concerning perturbations of both atmospheric CO/sub 2/ and the solar constant. A related conclusion is that the model's climate response to tropospheric aerosols is insensitive to the manner in which the aerosols are vertically distributed.
Observation and Nature of Non-statistical Dynamic Effects in Ordinary Organic Reactions
Quijano, Larisa Mae Mangaliman 1984-
2012-10-17
Statistical models like Transition State Theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) Theory have generally been successful in predicting the rates and selectivities of chemical reactions. However, these statistical models can fail...
L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis
2012-04-03
In the second part of this study and similarly with part one, the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis [1]. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the solar flares timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu [2]. Our analysis showed clearly the following: a) a phase transition process in the solar flare dynamics from high dimensional non Gaussian SOC state to a low dimensional also non Gaussian chaotic state, b) strong intermittent solar corona turbulence and anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes phase transition to low dimensional chaos: c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. e) The solar flare dynamical profile is revealed similar to the dynamical profile of the solar convection zone as far as the phase transition process from SOC to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.
Mignotte, Max
Unsupervised Detection and Semi-Automatic Extraction of Contours Using a Statistical Model : destremp@iro.umontreal.ca ABSTRACT In this paper, we describe a statistical model for the gradient vector for contours in images that uses this statistical mo- del for the likelihood. Our model is suitable for an ICE
Evans, Jason
Evaluation of downscaled daily rainfall hindcasts over Sydney, Australia using statistical. The two approaches are evaluated for their ability to reproduce important at-site rainfall statistics at a network of 45 raingauge stations and regional statistics over the catchment area of the Warragamba Dam (9
NASA Astrophysics Data System (ADS)
Yoon, Jin-Ho; Ruby Leung, L.; Correia, James, Jr.
2012-11-01
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.
Coqueret, O; Bérubé, G; Nepveu, A
1998-01-01
Cut is a homeodomain transcription factor which has the unusual property of containing several DNA-binding domains: three regions called Cut repeats and the Cut homeodomain. Genetic studies in Drosophila melanogaster indicate that cut plays important roles in the determination and maintenance of cell-type specificity. In the present study, we show that mammalian Cut proteins may yet play another biological role, specifically in proliferating cells. We found that the binding of Cut to a consensus binding site varies during the cell cycle. Binding was virtually undetectable in G0 and early G1, but became very strong as cells reached S phase. This was shown to result both from an increase in Cut expression and dephosphorylation of the Cut homeodomain by the Cdc25A phosphatase. We also show that the increase in Cut activity coincides with a decrease in p21WAF1/CIP1/SDI1 mRNAs. In co-transfection experiments, Cut proteins repressed p21WAF1/CIP1/SDI1 gene expression through binding to a sequence that overlaps the TATA box. Moreover, p21WAF1/CIP1/SDI1 expression was repressed equally well by either Cdc25A or Cut. Altogether, these results suggest a model by which Cdc25A activates the Cut repressor which then downregulates transcription of p21WAF1/CIP1/SDI1 in S phase. Thus, in addition to their role during cellular differentiation, Cut proteins also serve as cell-cycle-dependent transcriptional factors in proliferating cells. PMID:9707427
NASA Astrophysics Data System (ADS)
Gai, Lili; Iacovella, Christopher R.; Wan, Li; McCabe, Clare; Cummings, Peter T.
2015-08-01
The fluid-solid phase transition behavior of nano-confined Lennard-Jones fluids as a function of temperature and degree of nanoconfinement has been studied via statistical temperature molecular dynamics (STMD). The STMD method allows the direct calculation of the density of states and thus the heat capacity with high efficiency. The fluids are simulated between parallel solid surfaces with varying pore sizes, wall-fluid interaction energies, and registry of the walls. The fluid-solid phase transition behavior has been characterized through determination of the heat capacity. The results show that for pores of ideal-spacing, the order-disorder transition temperature (TODT) is reduced as the pore size increases until values consistent with that seen in a bulk system. Also, as the interaction between the wall and fluid is reduced, TODT is reduced due to weak constraints from the wall. However, for non-ideal spacing pores, quite different behavior is obtained, e.g., generally TODT are largely reduced, and TODT is decreased as the wall constraint becomes larger. For unaligned walls (i.e., whose lattices are not in registry), the fluid-solid transition is also detected as T is reduced, indicating non-ideality in orientation of the walls does not impact the formation of a solid, but results in a slight change in TODT compared to the perfectly aligned systems. The STMD method is demonstrated to be a robust way for probing the phase transitions of nanoconfined fluids systematically, enabling the future examination of the phase transition behavior of more complex fluids.
Gai, Lili; Iacovella, Christopher R; Wan, Li; McCabe, Clare; Cummings, Peter T
2015-08-01
The fluid-solid phase transition behavior of nano-confined Lennard-Jones fluids as a function of temperature and degree of nanoconfinement has been studied via statistical temperature molecular dynamics (STMD). The STMD method allows the direct calculation of the density of states and thus the heat capacity with high efficiency. The fluids are simulated between parallel solid surfaces with varying pore sizes, wall-fluid interaction energies, and registry of the walls. The fluid-solid phase transition behavior has been characterized through determination of the heat capacity. The results show that for pores of ideal-spacing, the order-disorder transition temperature (TODT) is reduced as the pore size increases until values consistent with that seen in a bulk system. Also, as the interaction between the wall and fluid is reduced, TODT is reduced due to weak constraints from the wall. However, for non-ideal spacing pores, quite different behavior is obtained, e.g., generally TODT are largely reduced, and TODT is decreased as the wall constraint becomes larger. For unaligned walls (i.e., whose lattices are not in registry), the fluid-solid transition is also detected as T is reduced, indicating non-ideality in orientation of the walls does not impact the formation of a solid, but results in a slight change in TODT compared to the perfectly aligned systems. The STMD method is demonstrated to be a robust way for probing the phase transitions of nanoconfined fluids systematically, enabling the future examination of the phase transition behavior of more complex fluids. PMID:26254658
NASA Astrophysics Data System (ADS)
McCauley, P. I.; Su, Y. N.; Schanche, N.; Evans, K. E.; Su, C.; McKillop, S.; Reeves, K. K.
2015-06-01
We present a statistical study of prominence and filament eruptions observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Several properties are recorded for 904 events that were culled from the Heliophysics Event Knowledgebase (HEK) and incorporated into an online catalog for general use. These characteristics include the filament and eruption type, eruption symmetry and direction, apparent twisting and writhing motions, and the presence of vertical threads and coronal cavities. Associated flares and white-light coronal mass ejections (CME) are also recorded. Total rates are given for each property along with how they differ among filament types. We also examine the kinematics of 106 limb events to characterize the distinct slow- and fast-rise phases often exhibited by filament eruptions. The average fast-rise onset height, slow-rise duration, slow-rise velocity, maximum field-of-view (FOV) velocity, and maximum FOV acceleration are 83 Mm, 4.4 hours, 2.1 km s-1, 106 km s-1, and 111 m s-2, respectively. All parameters exhibit lognormal probability distributions similar to that of CME speeds. A positive correlation between latitude and fast-rise onset height is found, which we attribute to a corresponding negative correlation in the average vertical magnetic field gradient, or decay index, estimated from potential field source surface (PFSS) extrapolations. We also find the decay index at the fast-rise onset point to be 1.1 on average, consistent with the critical instability threshold theorized for straight current channels. Finally, we explore relationships between the derived kinematics properties and apparent twisting motions. We find that events with evident twist have significantly faster CME speeds and significantly lower fast-rise onset heights, suggesting relationships between these values and flux rope helicity.
Statistical properties and pre-hit dynamics of price limit hits in the Chinese stock markets.
Wan, Yu-Lei; Xie, Wen-Jie; Gu, Gao-Feng; Jiang, Zhi-Qiang; Chen, Wei; Xiong, Xiong; Zhang, Wei; Zhou, Wei-Xing
2015-01-01
Price limit trading rules are adopted in some stock markets (especially emerging markets) trying to cool off traders' short-term trading mania on individual stocks and increase market efficiency. Under such a microstructure, stocks may hit their up-limits and down-limits from time to time. However, the behaviors of price limit hits are not well studied partially due to the fact that main stock markets such as the US markets and most European markets do not set price limits. Here, we perform detailed analyses of the high-frequency data of all A-share common stocks traded on the Shanghai Stock Exchange and the Shenzhen Stock Exchange from 2000 to 2011 to investigate the statistical properties of price limit hits and the dynamical evolution of several important financial variables before stock price hits its limits. We compare the properties of up-limit hits and down-limit hits. We also divide the whole period into three bullish periods and three bearish periods to unveil possible differences during bullish and bearish market states. To uncover the impacts of stock capitalization on price limit hits, we partition all stocks into six portfolios according to their capitalizations on different trading days. We find that the price limit trading rule has a cooling-off effect (object to the magnet effect), indicating that the rule takes effect in the Chinese stock markets. We find that price continuation is much more likely to occur than price reversal on the next trading day after a limit-hitting day, especially for down-limit hits, which has potential practical values for market practitioners. PMID:25874716
Statistical Properties and Pre-Hit Dynamics of Price Limit Hits in the Chinese Stock Markets
Wan, Yu-Lei; Xie, Wen-Jie; Gu, Gao-Feng; Jiang, Zhi-Qiang; Chen, Wei; Xiong, Xiong; Zhang, Wei; Zhou, Wei-Xing
2015-01-01
Price limit trading rules are adopted in some stock markets (especially emerging markets) trying to cool off traders’ short-term trading mania on individual stocks and increase market efficiency. Under such a microstructure, stocks may hit their up-limits and down-limits from time to time. However, the behaviors of price limit hits are not well studied partially due to the fact that main stock markets such as the US markets and most European markets do not set price limits. Here, we perform detailed analyses of the high-frequency data of all A-share common stocks traded on the Shanghai Stock Exchange and the Shenzhen Stock Exchange from 2000 to 2011 to investigate the statistical properties of price limit hits and the dynamical evolution of several important financial variables before stock price hits its limits. We compare the properties of up-limit hits and down-limit hits. We also divide the whole period into three bullish periods and three bearish periods to unveil possible differences during bullish and bearish market states. To uncover the impacts of stock capitalization on price limit hits, we partition all stocks into six portfolios according to their capitalizations on different trading days. We find that the price limit trading rule has a cooling-off effect (object to the magnet effect), indicating that the rule takes effect in the Chinese stock markets. We find that price continuation is much more likely to occur than price reversal on the next trading day after a limit-hitting day, especially for down-limit hits, which has potential practical values for market practitioners. PMID:25874716
NASA Astrophysics Data System (ADS)
Paulus, Martin P.; Geyer, Mark A.; Mandell, Arnold J.
1991-06-01
The singularity spectrum of local entropies ( S(?)) computed from the microcanonical dynamical partition function is used to describe the sequential dynamical structure of rat locomotor paths under the influence of cocaine. The approach used was analogous to the microcanonical ensemble of statistical mechanics and permitted the sensitive detection of “phase-transition”-like behavior. The results suggest that the behavioral sequences exhibited by the rats are determined by two processes, each with its own entropy (? i, ? h). The processes are changed simultaneously by cocaine, suggesting that they coexist as local repellers with overlapping insets and undergo a change to first order phase transition.
Satoshi Chiba; Osamu Iwamoto; Tokio Fukahori; Koji Niita; Toshiki Maruyama; Tomoyuki Maruyama; Akira Iwamoto
1996-02-13
The production cross sections of various fragments from proton-induced reactions on $^{56}$Fe and $^{27}$Al have been analyzed by the Quantum Molecular Dynamics (QMD) plus Statistical Decay Model (SDM). It was found that the mass and charge distributions calculated with and without the statistical decay have very different shapes. These results also depend strongly on the impact parameter, showing an importance of the dynamical treatment as realized by the QMD approach. The calculated results were compared with experimental data in the energy region from 50 MeV to 5 GeV. The QMD+SDM calculation could reproduce the production cross sections of the light clusters and intermediate-mass to heavy fragments in a good accuracy. The production cross section of $^{7}$Be was, however, underpredicted by approximately 2 orders of magnitude, showing the necessity of another reaction mechanism not taken into account in the present model.
BRG1 Controls the Activity of the Retinoblastoma Protein via Regulation of p21CIP1/WAF1/SDI
Kang, Hyeog; Cui, Kairong; Zhao, Keji
2004-01-01
The ubiquitous mammalian chromatin-remodeling SWI/SNF-like BAF complexes play critical roles in tumorigenesis. It was suggested that the direct interaction of BRG1 with the retinoblastoma protein pRB is required for regulation of cell cycle progression by pRB. We present evidence that the BRG1-containing 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 transcriptional repression of E2F target genes by pRB. Instead, BRG1 activates pRB by inducing its hypophosphorylation through up-regulation of the cdk inhibitor p21. The hypophosphorylation of pRB is reinforced by down-regulation of critical components, including cdk2, cyclin E, and cyclin D, in the pRB regulatory network. We demonstrate that up-regulation of p21 by BRG1 is necessary to induce formation of flat cells, growth arrest, and finally, cell senescence. Our results suggest that the BRG1-containing complexes control cellular proliferation and senescence by modulating the pRB pathway via multiple mechanisms. PMID:14729964
Elisabete C. Moraes; Sergio H. Franchito; V. Brahmananda Rao
2005-01-01
A statistical-dynamical climate model is used for investigating the relative contribution of the changes in the radiation budget and surface air temperature due to the increase of the anthropogenic greenhouse gases predicted for 2100 on the basis of IPCC SRES A1FI (the highest greenhouse level scenario). Five experiments are performed considering the changes in concentrations of (1) CO2, (2) CH4,
G. P. Pavlos; L. P. Karakatsanis; M. N. Xenakis
2012-01-31
In this study, the nonlinear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis. The 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, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu. 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 phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov studies c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics.
de Groot, Bert
Kinetics, Statistics, and Energetics of Lipid Membrane Electroporation Studied by Molecular-Planck-Institute for Biophysical Chemistry, Go¨ttingen, Germany; z Physical Chemistry III (Bio-PC), Department for Chemistry strengths between 0.04 and 0.7 V/nm. A statistical theory is developed to facilitate direct comparison
Reutter, Bryan W.; Gullberg, Grant T.; Huesman, Ronald H.
2001-04-30
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.
Bruce Turkington; Petr Plechac
2010-10-21
A new method of deriving reduced models of Hamiltonian dynamical systems is developed using techniques from optimization and statistical estimation. Given a set of resolved variables that define a model reduction, the quasi-equilibrium ensembles associated with the resolved variables are employed as a family of trial probability densities on phase space. The residual that results from submitting these trial densities to the Liouville equation is quantified by an ensemble-averaged cost function related to the information loss rate of the reduction. From an initial nonequilibrium state, the statistical state of the system at any later time is estimated by minimizing the time integral of the cost function over paths of trial densities. Statistical closure of the underresolved dynamics is obtained at the level of the value function, which equals the optimal cost of reduction with respect to the resolved variables, and the evolution of the estimated statistical state is deduced from the Hamilton-Jacobi equation satisfied by the value function. In the near-equilibrium regime, or under a local quadratic approximation in the far-from-equilibrium regime, this best-fit closure is governed by a differential equation for the estimated state vector coupled to a Riccati differential equation for the Hessian matrix of the value function. Since memory effects are not explicitly included in the trial densities, a single adjustable parameter is introduced into the cost function to capture a time-scale ratio between resolved and unresolved motions. Apart from this parameter, the closed equations for the resolved variables are completely determined by the underlying deterministic dynamics.
NASA Astrophysics Data System (ADS)
Grotjahn, Richard; Black, Robert; Leung, Ruby; Wehner, Michael F.; Barlow, Mathew; Bosilovich, Mike; Gershunov, Alexander; Gutowski, William J.; Gyakum, John R.; Katz, Richard W.; Lee, Yun-Young; Lim, Young-Kwon; Prabhat
2015-05-01
The objective of this paper is to review statistical methods, dynamics, modeling efforts, and trends related to temperature extremes, with a focus upon extreme events of short duration that affect parts of North America. These events are associated with large scale meteorological patterns (LSMPs). The statistics, dynamics, and modeling sections of this paper are written to be autonomous and so can be read separately. Methods to define extreme events statistics and to identify and connect LSMPs to extreme temperature events are presented. Recent advances in statistical techniques connect LSMPs to extreme temperatures through appropriately defined covariates that supplement more straightforward analyses. Various LSMPs, ranging from synoptic to planetary scale structures, are associated with extreme temperature events. Current knowledge about the synoptics and the dynamical mechanisms leading to the associated LSMPs is incomplete. Systematic studies of: the physics of LSMP life cycles, comprehensive model assessment of LSMP-extreme temperature event linkages, and LSMP properties are needed. Generally, climate models capture observed properties of heat waves and cold air outbreaks with some fidelity. However they overestimate warm wave frequency and underestimate cold air outbreak frequency, and underestimate the collective influence of low-frequency modes on temperature extremes. Modeling studies have identified the impact of large-scale circulation anomalies and land-atmosphere interactions on changes in extreme temperatures. However, few studies have examined changes in LSMPs to more specifically understand the role of LSMPs on past and future extreme temperature changes. Even though LSMPs are resolvable by global and regional climate models, they are not necessarily well simulated. The paper concludes with unresolved issues and research questions.
Dynamic topic adaptation for improved contextual modelling in statistical machine translation
Hasler, Eva Cornelia
2015-06-29
In recent years there has been an increased interest in domain adaptation techniques for statistical machine translation (SMT) to deal with the growing amount of data from different sources. Topic modelling techniques ...
Statistical and dynamical assessment of vegetation feedbacks on climate over the boreal forest
Wisconsin at Madison, University of
ensemble experiments in which the forest cover fraction is initially reduced over Asiatic Russia, replaced by grass cover, and then the climatic response is determined. The statistical feedback approach, adopted
Planning and Moving in Dynamic Environments: A statistical machine learning approach
Vijayakumar, Sethu; Toussaint, Marc; Petkos, Georgios; Howard, Matthew
2009-01-01
processing problem, i.e., a problem of computing a posterior distribution over unknown variables conditioned on the available information (targets, goals, constraints). Further, problems of adaptation and learning are formulated as statistical learning...
Paula, Luciana C. [Departamento de Fisica, Instituto de Biociencias Letras e Ciencias Exatas, Universidade Estadual Paulista, Sao Jose do Rio Preto, Sao Paulo 15054-000 (Brazil); Departamento de Estudos Basicos e Instrumentais, Universidade Estadual do Sudoeste da Bahia, Itapetinga, Bahia 45700-000 (Brazil); Wang Jin [Department of Chemistry, Physics and Applied Mathematics, State University of New York at Stony Brook, Stony Brook, New York 11794-3800 (United States); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry of Chinese Academy of Sciences, Changchun 130022 (China); Leite, Vitor B. P. [Departamento de Fisica, Instituto de Biociencias Letras e Ciencias Exatas, Universidade Estadual Paulista, Sao Jose do Rio Preto, Sao Paulo 15054-000 (Brazil)
2008-12-14
Dynamics of the environments of complex systems such as biomolecules, polar solvents, and glass plays an important role in controlling electron transfer reactions. The kinetics is determined by the nature of a complex multidimensional landscape. By quantifying the mean and high-order statistics of the first-passage time and the associated ratios, the dynamics in electron transfer reactions controlled by the environments can be revealed. We consider real experimental conditions with finite observation time windows. At high temperatures, exponential kinetics is observed and there are multiple kinetic paths leading to the product state. At and below an intermediate temperature, nonexponential kinetics starts to appear, revealing the nature of the distribution of local traps on the landscape. Discrete kinetic paths emerge. At very low temperatures, nonexponential kinetics continues to be observed. We point out that the size of the observational time window is crucial in revealing the intrinsic nature of the real kinetics. The mean first-passage time is defined as a characteristic time. Only when the observational time window is significantly larger than this characteristic time does one have the opportunity to collect enough statistics to capture rare statistical fluctuations and characterize the kinetics accurately.
Paula, Luciana C; Wang, Jin; Leite, Vitor B P
2008-12-14
Dynamics of the environments of complex systems such as biomolecules, polar solvents, and glass plays an important role in controlling electron transfer reactions. The kinetics is determined by the nature of a complex multidimensional landscape. By quantifying the mean and high-order statistics of the first-passage time and the associated ratios, the dynamics in electron transfer reactions controlled by the environments can be revealed. We consider real experimental conditions with finite observation time windows. At high temperatures, exponential kinetics is observed and there are multiple kinetic paths leading to the product state. At and below an intermediate temperature, nonexponential kinetics starts to appear, revealing the nature of the distribution of local traps on the landscape. Discrete kinetic paths emerge. At very low temperatures, nonexponential kinetics continues to be observed. We point out that the size of the observational time window is crucial in revealing the intrinsic nature of the real kinetics. The mean first-passage time is defined as a characteristic time. Only when the observational time window is significantly larger than this characteristic time does one have the opportunity to collect enough statistics to capture rare statistical fluctuations and characterize the kinetics accurately. PMID:19071925
Quantum dynamics and statistics of two-coupled down-conversion processes
Ladislav Mista; Jiri Herec; Viktor Jelinek; Jaroslav Rehacek; Jan Perina
2001-01-01
In the framework of the Heisenberg-Langevin theory the statistical effects arising from a mutual interaction of two non-degenerate down-conversion processes are investigated. Primarily, we focus on the possibility to control the intensity and statistical properties of the light generate din one nonlinear medium by the light entering the other one. We also show that the model discussed is an interesting
Developing a Web-based system by integrating VGI and SDI for real estate management and marketing
NASA Astrophysics Data System (ADS)
Salajegheh, J.; Hakimpour, F.; Esmaeily, A.
2014-10-01
Property importance of various aspects, especially the impact on various sectors of the economy and the country's macroeconomic is clear. Because of the real, multi-dimensional and heterogeneous nature of housing as a commodity, the lack of an integrated system includes comprehensive information of property, the lack of awareness of some actors in this field about comprehensive information about property and the lack of clear and comprehensive rules and regulations for the trading and pricing, several problems arise for the people involved in this field. In this research implementation of a crowd-sourced Web-based real estate support system is desired. Creating a Spatial Data Infrastructure (SDI) in this system for collecting, updating and integrating all official data about property is also desired in this study. In this system a Web2.0 broker and technologies such as Web services and service composition has been used. This work aims to provide comprehensive and diverse information about property from different sources. For this purpose five-level real estate support system architecture is used. PostgreSql DBMS is used to implement the desired system. Geoserver software is also used as map server and reference implementation of OGC (Open Geospatial Consortium) standards. And Apache server is used to run web pages and user interfaces. Integration introduced methods and technologies provide a proper environment for various users to use the system and share their information. This goal is only achieved by cooperation between all involved organizations in real estate with implementation their required infrastructures in interoperability Web services format.
p21{sup WAF1/Cip1/Sdi1} knockout mice respond to doxorubicin with reduced cardiotoxicity
Terrand, Jerome; Xu, Beibei; Morrissy, Steve; Dinh, Thai Nho; Williams, Stuart; Chen, Qin M.
2011-11-15
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.
NASA Astrophysics Data System (ADS)
Perdigão, Rui A. P.; Blöschl, Günter
2015-04-01
Emerging Processes in Flood Regime Dynamics are evaluated on the basis of symmetry breaks in the spatiotemporal sensitivity of flood regimes to changes in annual precipitation and a new dynamical model of flood regime change under nonlinearly interacting landscape-climate dynamics. The spatiotemporal sensitivity analysis is performed at regional scale using data from 804 catchments in Austria from 1976 to 2008. Results show that flood peaks change in a more responsive manner with spatial (regional) than with temporal (decadal) variability. Space-wise a 10% increase in precipitation leads to a 23% increase in flood peaks in Austria, whereas timewise a 10% increase in precipitation leads to an increase of just 6% in flood peaks. Looking at hydroclimatic regions in particular, catchments from stable dry lowlands and high wetlands exhibit similarity between the spatial and temporal flood responses to changes in precipitation (spatiotemporal symmetry) and low landscape-climate codependence. This suggests that these regions are not coevolving significantly. However, intermediate regions show differences between those responses (symmetry breaks) and higher landscape-climate codependence, suggesting undergoing coevolution. The break of symmetry is an emergent behaviour of the coupled system, stemming from the nonlinear interactions in the coevolving hydroclimate system. A dynamic coevolution index is then proposed relating spatiotemporal symmetry with relative characteristic celerities, which need to be taken into account in hydrological space-time trading. Coevolution is expressed here by the scale interaction between slow and fast dynamics, represented respectively by spatial and temporal characteristics. The diagnostic assessment of coevolution is complemented by a stylised nonlinear dynamical model of landscape-climate coevolution, in which landform evolution processes take place at the millennial scale (slow dynamics), and climate adjusts in years to decades (fast dynamics). Coevolution is expressed by the interplay between slow and fast dynamics, represented, respectively, by spatial and temporal characteristics of the hydroclimate system. The model captures key features of the joint landscape-climate distribution and associated flood regime changes, supporting the diagnostic assessment. This paper ultimately brings to light signatures of emergence in flood regime dynamics that arise from the nonlinear coupling of the landscape-climate system at slow and fast time scales. The present work builds on Perdigão and Blöschl (2014). Perdigão, R. A. P., and G. Blöschl (2014), Spatiotemporal flood sensitivity to annual precipitation: Evidence for landscape-climate coevolution, Water Resour. Res., 50, doi:10.1002/2014WR015365.
NASA Astrophysics Data System (ADS)
Chiang, Thomas C.; Yu, Hai-Chin; Wu, Ming-Chya
2009-04-01
This paper investigates statistical properties of high-frequency intraday stock returns across various frequencies. Both time series and panel data are utilized to explore the properties of probability distribution, dynamic conditional correlations, and scaling analysis in Dow Jones Industrial Average (DJIA) and Nasdaq intraday returns across 10-min, 30-min, 60-min, 120-min, and 390-min frequencies. The evidence shows that both returns and volatility (standard deviation) increase with the increasing scaling from 10-min to 390-min intervals. By fitting an AR(1)-GARCH(1,1) model to intraday data, we find that AR(1) coefficients are negative for DJIA returns and positive for Nasdaq, exhibiting a positive and negative feedback strategy in DJIA and Nasdaq, respectively. The evidence also shows that these coefficients are statistically significant for either including or excluding opening returns for the 10-min and 30-min frequencies. By examining the dynamic conditional correlation between the DJIA and the Nasdaq across different frequencies, a positive correlation ranging from 0.6 to 0.8 was found. In addition, the variance of the dynamic correlation coefficients is decreasing and appears to be stable for the 2001-2003 period. Finally, both returns on DJIA and Nasdaq satisfy the stable Lévy distributions, implying that both markets can converge to equilibrium by self-governing mechanism after shocks. Results of this work provide relevant implications for investors and policy makers.
Notaro, Michael; Wang, Yi; Liu, Zhengyu; Gallimore, Robert; Levis, Samuel
2008-01-05
A negative feedback of vegetation cover on subsequent annual precipitation is simulated for the mid-Holocene over North Africa using a fully coupled general circulation model with dynamic vegetation, FOAM-LPJ (Fast Ocean Atmosphere Model-Lund Potsdam Jena Model). By computing a vegetation feedback parameter based on lagged autocovariances, the simulated impact of North African vegetation on precipitation is statistically quantified. The feedback is also dynamically assessed through initial value ensemble experiments, in which North African grass cover is initially reduced and the climatic response analyzed. The statistical and dynamical assessments of the negative vegetation feedback agree in sign and relative magnitude for FOAM-LPJ. The negative feedback on annual precipitation largely results from a competition between bare soil evaporation and plant transpiration, with increases in the former outweighing reductions in the latter given reduced grass cover. This negative feedback weakens and eventually reverses sign over time during a transient simulation from the mid-Holocene to present. A similar, but weaker, negative feedback is identified in Community Climate System Model Version 2 (CCSM2) over North Africa for the mid-Holocene.
Muir, Ryan D.; Kissick, David J.; Simpson, Garth J.
2012-01-01
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
Valery B. Kokshenev; Eduardo Vicentini
2004-01-01
We report on the stationary dynamics in classical Sinai billiard (SB) corresponding to the unit cell of the periodic Lorentz gas (LG) formed by square lattice of length $L$ and dispersing circles of radius $R$ placed in the center of unit cell. Dynamic correlation effects for classical particles, initially distributed by random way, are considered within the scope of deterministic
Statistical dynamics of classical systems: A self-consistent field approach
NASA Astrophysics Data System (ADS)
Grzetic, Douglas J.; Wickham, Robert A.; Shi, An-Chang
2014-06-01
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.
Statistical dynamics of classical systems: A self-consistent field approach
Grzetic, Douglas J. Wickham, Robert A.; Shi, An-Chang
2014-06-28
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.
Sitnikov, D M; Schineller, J B; Baldwin, T O
1996-01-01
The conditioning of culture medium by the production of growth-regulatory substances is a well-established phenomenon with eukaryotic cells. It has recently been shown that many prokaryotes are also capable of modulating growth, and in some cases sensing cell density, by production of extracellular signaling molecules, thereby allowing single celled prokaryotes to function in some respects as multicellular organisms. As Escherichia coli shifts from exponential growth to stationary growth, many changes occur, including cell division leading to formation of short minicells and expression of numerous genes not expressed in exponential phase. An understanding of the coordination between the morphological changes associated with cell division and the physiological and metabolic changes is of fundamental importance to understanding regulation of the prokaryotic cell cycle. The ftsQA genes, which encode functions required for cell division in E. coli, are regulated by promoters P1 and P2, located upstream of the ftsQ gene. The P1 promoter is rpoS-stimulated and the second, P2, is regulated by a member of the LuxR subfamily of transcriptional activators, SdiA, exhibiting features characteristic of an autoinduction (quorum sensing) mechanism. The activity of SdiA is potentiated by N-acyl-homoserine lactones, which are the autoinducers of luciferase synthesis in luminous marine bacteria as well as of pathogenesis functions in several pathogenic bacteria. A compound(s) produced by E. coli itself during growth in Luria Broth stimulates transcription from P2 in an SdiA-dependent process. Another substance(s) enhances transcription of rpoS and (perhaps indirectly) of ftsQA via promoter P1. It appears that this bimodal control mechanism may comprise a fail-safe system, such that transcription of the ftsQA genes may be properly regulated under a variety of different environmental and physiological conditions. PMID:8552633
NASA Astrophysics Data System (ADS)
Pavlos, G. P.; Karakatsanis, L. P.; Xenakis, M. N.
2012-12-01
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.
Static Numbers to Dynamic Statistics: Designing a Policy-Friendly Social Policy Indicator Framework
ERIC Educational Resources Information Center
Ahn, Sang-Hoon; Choi, Young Jun; Kim, Young-Mi
2012-01-01
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.…
Dynamic Range Adaptation to Sound Level Statistics in the Auditory Nerve
Dean, Isabel
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 ...
Valery B. Kokshenev; Eduardo Vicentini
2004-05-10
We report on the stationary dynamics in classical Sinai billiard (SB) corresponding to the unit cell of the periodic Lorentz gas (LG) formed by square lattice of length $L$ and dispersing circles of radius $R$ placed in the center of unit cell. Dynamic correlation effects for classical particles, initially distributed by random way, are considered within the scope of deterministic and stochastic descriptions. A temporal analysis of elastic reflections from the SB square walls and circle obstacles is given for distinct geometries in terms of the wall-collision and the circle-collision distributions. Late-time steady dynamic regimes are explicit in the diffusion exponent $z(R)$, which plays a role of the order-disorder crossover dynamical parameter. The ballistic ($z_{0}=1$) ordered motion in the square lattice (R=0) switches to the superdiffusion regime with $z_{1}=1.5$, which is geometry-independent when $Rmotion corridors are closed in LG with finite horizon ($R\\geq L/2$) and the interplay between square and circle geometries results in the chaotic dynamics ensured by the normal Brownian diffusion ($z_{2}=2$) and by the normal Gaussian distribution of collisions.
NASA Astrophysics Data System (ADS)
Sanchezgomez, E.; Page, C.; Deque, M.; Terray, L.
2010-12-01
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.
Nonequilibrium statistical mechanics of a two-temperature Ising ring with conserved dynamics.
Borchers, Nicholas; Pleimling, Michel; Zia, R K P
2014-12-01
The statistical mechanics of a one-dimensional Ising model in thermal equilibrium is well-established, textbook material. Yet, when driven far from equilibrium by coupling two sectors to two baths at different temperatures, it exhibits remarkable phenomena, including an unexpected "freezing by heating." These phenomena are explored through systematic numerical simulations. Our study reveals complicated relaxation processes as well as a crossover between two very different steady-state regimes. PMID:25615050
M. Bleicher; F. M. Liu; A. Keränen; J. Aichelin; S. A. Bass; F. Becattini; K. Redlich; K. Werner
2002-01-01
The Omegabar\\/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies ( Elab = 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
Statistical state dynamics of jet/wave coexistence in beta-plane turbulence
Constantinou, Navid C; Ioannou, Petros J
2015-01-01
Jets are commonly observed to coexist in the turbulence of planetary atmospheres with planetary scale waves and embedded vortices. These large-scale coherent structures arise and are maintained in the turbulence on time scales long compared to dissipation or advective time scales. The emergence, equilibration at finite amplitude, maintenance and stability of these structures pose fundamental theoretical problems. The emergence of jets and vortices from turbulence is not associated with an instability of the mean flow and their equilibration and stability at finite amplitude does not arise solely from the linear or nonlinear dynamics of these structures in isolation from the turbulence surrounding them. Rather the dynamics of these large-scale structures arises essentially from their cooperative interaction with the small-scale turbulence in which they are embedded. It follows that fundamental theoretical understanding of the dynamics of jets and vortices in turbulence requires adopting the perspective of the ...
NASA Astrophysics Data System (ADS)
Flaounas, Emmanouil; Drobinski, Philippe; Vrac, Mathieu; Bastin, Sophie; Lebeaupin-Brossier, Cindy; Stéfanon, Marc; Borga, Marco; Calvet, Jean-Christophe
2013-06-01
This study evaluates how statistical and dynamical downscaling models as well as combined approach perform in retrieving the space-time variability of near-surface temperature and rainfall, as well as their extremes, over the whole Mediterranean region. The dynamical downscaling model used in this study is the Weather Research and Forecasting (WRF) model with varying land-surface models and resolutions (20 and 50 km) and the statistical tool is the Cumulative Distribution Function-transform (CDF-t). To achieve a spatially resolved downscaling over the Mediterranean basin, the European Climate Assessment and Dataset (ECA&D) gridded dataset is used for calibration and evaluation of the downscaling models. In the frame of HyMeX and MED-CORDEX international programs, the downscaling is performed on ERA-I reanalysis over the 1989-2008 period. The results show that despite local calibration, CDF-t produces more accurate spatial variability of near-surface temperature and rainfall with respect to ECA&D than WRF which solves the three-dimensional equation of conservation. This first suggests that at 20-50 km resolutions, these three-dimensional processes only weakly contribute to the local value of temperature and precipitation with respect to local one-dimensional processes. Calibration of CDF-t at each individual grid point is thus sufficient to reproduce accurately the spatial pattern. A second explanation is the use of gridded data such as ECA&D which smoothes in part the horizontal variability after data interpolation and damps the added value of dynamical downscaling. This explains partly the absence of added-value of the 2-stage downscaling approach which combines statistical and dynamical downscaling models. The temporal variability of statistically downscaled temperature and rainfall is finally strongly driven by the temporal variability of its forcing (here ERA-Interim or WRF simulations). CDF-t is thus efficient as a bias correction tool but does not show any added-value regarding the time variability of the downscaled field. Finally, the quality of the reference observation dataset is a key issue. Comparison of CDF-t calibrated with ECA&D dataset and WRF simulations to local measurements from weather stations not assimilated in ECA&D, shows that the temporal variability of the downscaled data with respect to the local observations is closer to the local measurements than to ECA&D data. This highlights the strong added-value of dynamical downscaling which improves the temporal variability of the atmospheric dynamics with regard to the driving model. This article highlights the benefits and inconveniences emerging from the use of both downscaling techniques for climate research. Our goal is to contribute to the discussion on the use of downscaling tools to assess the impact of climate change on regional scales.
SU-E-J-261: Statistical Analysis and Chaotic Dynamics of Respiratory Signal of Patients in BodyFix
Michalski, D; Huq, M; Bednarz, G; Lalonde, R; Yang, Y; Heron, D
2014-06-01
Purpose: To quantify respiratory signal of patients in BodyFix undergoing 4DCT scan with and without immobilization cover. Methods: 20 pairs of respiratory tracks recorded with RPM system during 4DCT scan were analyzed. Descriptive statistic was applied to selected parameters of exhale-inhale decomposition. Standardized signals were used with the delay method to build orbits in embedded space. Nonlinear behavior was tested with surrogate data. Sample entropy SE, Lempel-Ziv complexity LZC and the largest Lyapunov exponents LLE were compared. Results: Statistical tests show difference between scans for inspiration time and its variability, which is bigger for scans without cover. The same is for variability of the end of exhalation and inhalation. Other parameters fail to show the difference. For both scans respiratory signals show determinism and nonlinear stationarity. Statistical test on surrogate data reveals their nonlinearity. LLEs show signals chaotic nature and its correlation with breathing period and its embedding delay time. SE, LZC and LLE measure respiratory signal complexity. Nonlinear characteristics do not differ between scans. Conclusion: Contrary to expectation cover applied to patients in BodyFix appears to have limited effect on signal parameters. Analysis based on trajectories of delay vectors shows respiratory system nonlinear character and its sensitive dependence on initial conditions. Reproducibility of respiratory signal can be evaluated with measures of signal complexity and its predictability window. Longer respiratory period is conducive for signal reproducibility as shown by these gauges. Statistical independence of the exhale and inhale times is also supported by the magnitude of LLE. The nonlinear parameters seem more appropriate to gauge respiratory signal complexity since its deterministic chaotic nature. It contrasts with measures based on harmonic analysis that are blind for nonlinear features. Dynamics of breathing, so crucial for 4D-based clinical technologies, can be better controlled if nonlinear-based methodology, which reflects respiration characteristic, is applied. Funding provided by Varian Medical Systems via Investigator Initiated Research Project.
Statistical mechanical theory for non-equilibrium systems. IX. Stochastic molecular dynamics
Attard, Phil
density and for the transition probability of a nonequilibrium system is given. Maximization of the latter systems, which is tested for steady heat flow and for a time-varying, driven Brownian particle. © 2009 and Attard13 combined molecular dynamics with a stochastic transition probability. These stochastic
Functional ANOVA and Regional Climate Experiments: A Statistical Analysis of Dynamic Downscaling
Sain, Steve
changes. Moreover, the scientific consensus that human activities has led to warming of the atmosphere has affecting model output and projections of climate change. Recently, such experiments have been used to also for dynamic downscaling of global models. In this paper, we discuss an initial analysis of a subset
NASA Astrophysics Data System (ADS)
Eckert, Nicolas; Schläppy, Romain; Jomelli, Vincent; Naaim, Mohamed
2013-04-01
A crucial step for proposing relevant long-term mitigation measures in long term avalanche forecasting is the accurate definition of high return period avalanches. Recently, "statistical-dynamical" approach combining a numerical model with stochastic operators describing the variability of its inputs-outputs have emerged. Their main interests is to take into account the topographic dependency of snow avalanche runout distances, and to constrain the correlation structure between model's variables by physical rules, so as to simulate the different marginal distributions of interest (pressure, flow depth, etc.) with a reasonable realism. Bayesian methods have been shown to be well adapted to achieve model inference, getting rid of identifiability problems thanks to prior information. An important problem which has virtually never been considered before is the validation of the predictions resulting from a statistical-dynamical approach (or from any other engineering method for computing extreme avalanches). In hydrology, independent "fossil" data such as flood deposits in caves are sometimes confronted to design discharges corresponding to high return periods. Hence, the aim of this work is to implement a similar comparison between high return period avalanches obtained with a statistical-dynamical approach and independent validation data resulting from careful dendrogeomorphological reconstructions. To do so, an up-to-date statistical model based on the depth-averaged equations and the classical Voellmy friction law is used on a well-documented case study. First, parameter values resulting from another path are applied, and the dendrological validation sample shows that this approach fails in providing realistic prediction for the case study. This may be due to the strongly bounded behaviour of runouts in this case (the extreme of their distribution is identified as belonging to the Weibull attraction domain). Second, local calibration on the available avalanche chronicle is performed with various prior distributions resulting from expert knowledge and/or other paths. For all calibrations, a very successful convergence is obtained, which confirms the robustness of the used Metropolis-Hastings estimation algorithm. This also demonstrates the interest of the Bayesian framework for aggregating information by sequential assimilation in the frequently encountered case of limited data quantity. Confrontation with the dendrological sample stresses the predominant role of the Coulombian friction coefficient distribution's variance on predicted high magnitude runouts. The optimal fit is obtained for a strong prior reflecting the local bounded behavior, and results in a 10-40 m difference for return periods ranging between 10 and 300 years. Implementing predictive simulations shows that this is largely within the range of magnitude of uncertainties to be taken into account. On the other hand, the different priors tested for the turbulent friction coefficient influence predictive performances only slightly, but have a large influence on predicted velocity and flow depth distributions. This all may be of high interest to refine calibration and predictive use of the statistical-dynamical model for any engineering application.
Technology Transfer Automated Retrieval System (TEKTRAN)
It is known that irrigation application method can impact crop water use and water use efficiency, but the mechanisms involved are incompletely understood, particularly in terms of the water and energy balances during the growing season from pre-irrigation through planting, early growth and yield de...
Bleicher, M; Keränen, A; Aichelin, Jörg; Bass, S A; Becattini, F; Redlich, Krzysztof; Werner, K
2002-01-01
The $\\bar{\\Omega}/\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\rm lab}$=160 GeV). The anti-omega 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.
M. Bleicher; F. M. Liu; A. Keränen; J. Aichelin; S. A. Bass; F. Becattini; K. Redlich; K. Werner
2001-11-15
The $\\bar{\\Omega}/\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\rm lab}$=160 GeV). The anti-omega 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.
The non-statistical dynamics of the 18O + 32O2 isotope exchange reaction at two energies
NASA Astrophysics Data System (ADS)
Van Wyngarden, Annalise L.; Mar, Kathleen A.; Quach, Jim; Nguyen, Anh P. Q.; Wiegel, Aaron A.; Lin, Shi-Ying; Lendvay, Gyorgy; Guo, Hua; Lin, Jim J.; Lee, Yuan T.; Boering, Kristie A.
2014-08-01
The dynamics of the 18O(3P) + 32O2 isotope exchange reaction were studied using crossed atomic and molecular beams at collision energies (Ecoll) of 5.7 and 7.3 kcal/mol, and experimental results were compared with quantum statistical (QS) and quasi-classical trajectory (QCT) calculations on the O3(X1A') potential energy surface (PES) of Babikov et al. [D. Babikov, B. K. Kendrick, R. B. Walker, R. T. Pack, P. Fleurat-Lesard, and R. Schinke, J. Chem. Phys. 118, 6298 (2003)]. In both QS and QCT calculations, agreement with experiment was markedly improved by performing calculations with the experimental distribution of collision energies instead of fixed at the average collision energy. At both collision energies, the scattering displayed a forward bias, with a smaller bias at the lower Ecoll. Comparisons with the QS calculations suggest that 34O2 is produced with a non-statistical rovibrational distribution that is hotter than predicted, and the discrepancy is larger at the lower Ecoll. If this underprediction of rovibrational excitation by the QS method is not due to PES errors and/or to non-adiabatic effects not included in the calculations, then this collision energy dependence is opposite to what might be expected based on collision complex lifetime arguments and opposite to that measured for the forward bias. While the QCT calculations captured the experimental product vibrational energy distribution better than the QS method, the QCT results underpredicted rotationally excited products, overpredicted forward-bias and predicted a trend in the strength of forward-bias with collision energy opposite to that measured, indicating that it does not completely capture the dynamic behavior measured in the experiment. Thus, these results further underscore the need for improvement in theoretical treatments of dynamics on the O3(X1A') PES and perhaps of the PES itself in order to better understand and predict non-statistical effects in this reaction and in the formation of ozone (in which the intermediate O3* complex is collisionally stabilized by a third body). The scattering data presented here at two different collision energies provide important benchmarks to guide these improvements.
Ohnuki, Shinsuke; Enomoto, Kenichi; Yoshimoto, Hiroyuki; Ohya, Yoshikazu
2014-03-01
The vitality of brewing yeasts has been used to monitor their physiological state during fermentation. To investigate the fermentation process, we used the image processing software, CalMorph, which generates morphological data on yeast mother cells and bud shape, nuclear shape and location, and actin distribution. We found that 248 parameters changed significantly during fermentation. Successive use of principal component analysis (PCA) revealed several important features of yeast, providing insight into the dynamic changes in the yeast population. First, PCA indicated that much of the observed variability in the experiment was summarized in just two components: a change with a peak and a change over time. Second, PCA indicated the independent and important morphological features responsible for dynamic changes: budding ratio, nucleus position, neck position, and actin organization. Thus, the large amount of data provided by imaging analysis can be used to monitor the fermentation processes involved in beer and bioethanol production. PMID:24012106
NASA Astrophysics Data System (ADS)
Rodriguez, Roger; Tuckwell, Henry C.
1996-11-01
Dynamical stochastic models of single neurons and neural networks often take the form of a system of n>=2 coupled stochastic differential equations. We consider such systems under the assumption that third and higher order central moments are relatively small. In the general case, a system of 1/2n(n+3) (generally) nonlinear coupled ordinary differential equations holds for the approximate means, variances, and covariances. For the general linear system the solutions of these equations give exact results-this is illustrated in a simple case. Generally, the moment equations can be solved numerically. Results are given for a spiking Fitzhugh-Nagumo model neuron driven by a current with additive white noise. Differential equations are obtained for the means, variances, and covariances of the dynamical variables in a network of n connected spiking neurons in the presence of noise.
Physical insight into superdiffusive dynamics of Sinai billiard through collision statistics
Valery B. Kokshenev; Eduardo Vicentini
2006-01-01
We report on distinct steady-motion dynamic regimes in chaotic Sinai billiard (SB). A numerical study on elastic reflections from the SB boundary (square wall of length L and circle obstacle of radius R) is carried out for different R\\/L. The research is based on the exploration of the generalized diffusion equation and on the analysis of wall-collision and the circle-collision
Regulation of signal duration and the statistical dynamics of kinase activation by scaffold proteins
Jason W. Locasale; Arup K. Chakraborty
2008-10-29
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.
Dynamical and statistical effects of the intrinsic curvature of internal space of molecules
NASA Astrophysics Data System (ADS)
Teramoto, Hiroshi; Takatsuka, Kazuo
2005-02-01
The Hamilton dynamics of a molecule in a translationally and/or rotationally symmetric field is kept rigorously constrained in its phase space. The relevant dynamical laws should therefore be extracted from these constrained motions. An internal space that is induced by a projection of such a limited phase space onto configuration space is an intrinsically curved space even for a system of zero total angular momentum. In this paper we discuss the general effects of this curvedness on dynamics and structures of molecules in such a manner that is invariant with respect to the selection of coordinates. It is shown that the regular coordinate originally defined by Riemann is particularly useful to expose the curvature correction to the dynamics and statisitcal properties of molecules. These effects are significant both qualitatively and quantitatively and are studied in two aspects. One is the direct effect on dynamics: A trajectory receives a Lorentz-like force from the curved space as though it was placed in a magnetic field. The well-known problem of the trapping phenomenon at the transition state is analyzed from this point of view. By showing that the trapping force is explicitly described in terms of the curvature of the internal space, we clarify that the physical origin of the trapped motion is indeed originated from the curvature of the internal space and hence is not dependent of the selection of coordinate system. The other aspect is the effect of phase space volume arising from the curvedness: We formulate a general expression of the curvature correction of the classical density of states and extract its physical significance in the molecular geometry along with reaction rate in terms of the scalar curvature and volume loss (gain) due to the curvature. The transition state theory is reformulated from this point of view and it is applied to the structural transition of linear chain molecules in the so-called dihedral angle model. It is shown that the curvature effect becomes large roughly linearly with the size of molecule.
Dynamics and statistics of noise-like pulses in modelocked lasers
NASA Astrophysics Data System (ADS)
Donovan, Graham M.
2015-08-01
Noise-like pulses and optical rogue waves are connected nonlinear phenomena which can occur in passively modelocked laser systems. Here we consider a range of model systems to explore the conditions under which noise-like pulses can be expected to occur, and further when the resulting statistics meet the optical rogue wave criteria. We show, via a series of careful simulations, that noise-like pulses and optical rogue waves can arise either separately or together, and that they may emerge from standard soliton-like solutions via different mechanisms. We also propose a quantitative definition of noise-like pulses, and explore the issues carefully in convergence testing numerical methods for such systems.
A dynamical and statistical investigation of the shape of splashform tektites
NASA Astrophysics Data System (ADS)
Butler, S. L.; Stauffer, M.
2008-12-01
Splash-form tektites are believed to represent molten rock that was ejected by a large impactor that solidified while in flight. These glassy rocks are found in a number of strewn fields around the Earth and are found in a number of intriguing shapes including near spheres, axisymmetric biconcave shapes as well as rods and "dumb-bells". In this contribution, we will present the results of a statistical study of the shapes of over 1000 tektites from South-East Asia and the results of a numerical study of the evolution of fluid droplets under the influence of a centrifugal force and surface tension. As we will show, the numerical simulations first evolve to an oblate, axisymmetric form before becoming subject to a non-axisymmetric instability which results in a prolate shape. The numerical model results are consistent with the measurements of real tektites that show that there is a dearth of weakly deformed, highly prolate tektites.
DYNAMIC STABILITY OF THE SOLAR SYSTEM: STATISTICALLY INCONCLUSIVE RESULTS FROM ENSEMBLE INTEGRATIONS
Zeebe, Richard E.
2015-01-01
Due to the chaotic nature of the solar system, the question of its long-term stability can only be answered in a statistical sense, for instance, based on numerical ensemble integrations of nearby orbits. Destabilization of the inner planets, leading to close encounters and/or collisions can be initiated through a large increase in Mercury's eccentricity, with a currently assumed likelihood of ?1%. However, little is known at present about the robustness of this number. Here I report ensemble integrations of the full equations of motion of the eight planets and Pluto over 5 Gyr, including contributions from general relativity. The results show that different numerical algorithms lead to statistically different results for the evolution of Mercury's eccentricity (e{sub M}). For instance, starting at present initial conditions (e{sub M}?0.21), Mercury's maximum eccentricity achieved over 5 Gyr is, on average, significantly higher in symplectic ensemble integrations using heliocentric rather than Jacobi coordinates and stricter error control. In contrast, starting at a possible future configuration (e{sub M}?0.53), Mercury's maximum eccentricity achieved over the subsequent 500 Myr is, on average, significantly lower using heliocentric rather than Jacobi coordinates. For example, the probability for e{sub M} to increase beyond 0.53 over 500 Myr is >90% (Jacobi) versus only 40%-55% (heliocentric). This poses a dilemma because the physical evolution of the real system—and its probabilistic behavior—cannot depend on the coordinate system or the numerical algorithm chosen to describe it. Some tests of the numerical algorithms suggest that symplectic integrators using heliocentric coordinates underestimate the odds for destabilization of Mercury's orbit at high initial e{sub M}.
Dynamic Stability of the Solar System: Statistically Inconclusive Results from Ensemble Integrations
NASA Astrophysics Data System (ADS)
Zeebe, Richard E.
2015-01-01
Due to the chaotic nature of the solar system, the question of its long-term stability can only be answered in a statistical sense, for instance, based on numerical ensemble integrations of nearby orbits. Destabilization of the inner planets, leading to close encounters and/or collisions can be initiated through a large increase in Mercury's eccentricity, with a currently assumed likelihood of ~1%. However, little is known at present about the robustness of this number. Here I report ensemble integrations of the full equations of motion of the eight planets and Pluto over 5 Gyr, including contributions from general relativity. The results show that different numerical algorithms lead to statistically different results for the evolution of Mercury's eccentricity (e_M}). For instance, starting at present initial conditions (e_M}? 0.21), Mercury's maximum eccentricity achieved over 5 Gyr is, on average, significantly higher in symplectic ensemble integrations using heliocentric rather than Jacobi coordinates and stricter error control. In contrast, starting at a possible future configuration (e_M}? 0.53), Mercury's maximum eccentricity achieved over the subsequent 500 Myr is, on average, significantly lower using heliocentric rather than Jacobi coordinates. For example, the probability for e_M} to increase beyond 0.53 over 500 Myr is >90% (Jacobi) versus only 40%-55% (heliocentric). This poses a dilemma because the physical evolution of the real system—and its probabilistic behavior—cannot depend on the coordinate system or the numerical algorithm chosen to describe it. Some tests of the numerical algorithms suggest that symplectic integrators using heliocentric coordinates underestimate the odds for destabilization of Mercury's orbit at high initial e_M}.
Cerpa, Alberto E.
SDI: Solar Dome Instrument for Solar Irradiance Monitoring Tao Liu1, Ankur U. Kamthe1, Varick L data for ground solar irradiance (direct normal and global irradiance) is a major obstacle for the de- velopment of adequate policies to promote and take advan- tage of existing solar technologies. Although
Technology Transfer Automated Retrieval System (TEKTRAN)
Quorum sensing transcriptional regulator SdiA has been shown to enhance the survival of Escherichia coli O157:H7 (O157) in the acidic compartment of bovine rumen in response to N-acyl-L-homoserine lactones (AHLs) produced by the rumen bacteria. Bacteria that survive the rumen environment subsequentl...
NASA Astrophysics Data System (ADS)
Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.
2013-03-01
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.
Temporal Dynamics and Nonclassical Photon Statistics of Quadratically Coupled Optomechanical Systems
Shailendra Kumar Singh; S. V. Muniandy
2015-06-24
Quantum optomechanical system serves as an interface for coupling between photons and phonons due to mechanical oscillations. We used the Heisenberg-Langevin approach under Markovian white noise approximation to study a quadratically coupled optomechanical system which contains a thin dielectric membrane quadratically coupled to the cavity field. A decorrelation method is employed to solve for a larger number of coupled equations. Transient mean numbers of cavity photons and phonons that provide dynamical behaviour are computed for different coupling regime. We have also obtained the two-boson second-order correlation functions for the cavity field, membrane oscillator and their cross correlations that provide nonclassical properties governed by quadratic optomechanical system.
Temporal Dynamics and Nonclassical Photon Statistics of Quadratically Coupled Optomechanical Systems
NASA Astrophysics Data System (ADS)
Singh, Shailendra Kumar; Muniandy, S. V.
2015-05-01
Quantum optomechanical system serves as an interface for coupling between photons and phonons due to mechanical oscillations. We used the Heisenberg-Langevin approach under Markovian white noise approximation to study a quadratically coupled optomechanical system which contains a thin dielectric membrane quadratically coupled to the cavity field. A decorrelation method is employed to solve for a larger number of coupled equations. Transient mean numbers of cavity photons and phonons that provide dynamical behaviour are computed for different coupling regime. We have also obtained the two-boson second-order correlation functions for the cavity field, membrane oscillator and their cross correlations that provide nonclassical properties governed by quadratic optomechanical system.
Financial price dynamics and pedestrian counterflows: A comparison of statistical stylized facts
NASA Astrophysics Data System (ADS)
Parisi, Daniel R.; Sornette, Didier; Helbing, Dirk
2013-01-01
We propose and document the evidence for an analogy between the dynamics of granular counterflows in the presence of bottlenecks or restrictions and financial price formation processes. Using extensive simulations, we find that the counterflows of simulated pedestrians through a door display eight stylized facts observed in financial markets when the density around the door is compared with the logarithm of the price. Finding so many stylized facts is very rare indeed among all agent-based models of financial markets. The stylized properties are present when the agents in the pedestrian model are assumed to display a zero-intelligent behavior. If agents are given decision-making capacity and adapt to partially follow the majority, periods of herding behavior may additionally occur. This generates the very slow decay of the autocorrelation of absolute return due to an intermittent dynamics. Our findings suggest that the stylized facts in the fluctuations of the financial prices result from a competition of two groups with opposite interests in the presence of a constraint funneling the flow of transactions to a narrow band of prices with limited liquidity.
Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.
2005-01-01
A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.
Planar distribution of the galaxies in the Local Group: a statistical and dynamical analysis
Chiosi, S P C
2006-01-01
Adopting known data on positions and distances, we make use of the analytical geometry and look for the plane that minimizes the distances of all galaxies to it. A planar distribution is indeed found that, however, does not coincide with the plane found by Sawa & Fujimoto 2005. Why? The second part of this study is devoted to answer this question and to find a dynamical justification for the planar distribution. To this aim, we apply the Hamilton Method (Minimum Action) to investigate the dynamics of the two major system of the Local Group, Milky Way and Andromeda, under the action of external forces exerted by nearby galaxies or groups external to the Local Group. We find that the planar istribution is fully compatible with the minimum action and that the external force field is likely parallel to the plane. It pulls the galaxies of the Local Group without altering their planar distribution. Special care is paid to evaluate the robustness of this result. Conclusion: in this paper we have examined the spa...
How Electronic Dynamics with Pauli Exclusion Produces Fermi-Dirac Statistics
Triet Nguyen; Ravindra Nanguneri; John Parkhill
2015-01-15
It is important that any dynamics method approaches the correct population distribution at long times. In this paper, we derive a one-body reduced density matrix dynamics for electrons in energetic contact with a bath. We obtain a remarkable equation of motion which shows that in order to reach equilibrium properly, rates of electron transitions depend on the density matrix. Even though the bath drives the electrons towards a Boltzmann distribution, hole blocking factors in our equation of motion cause the electronic populations to relax to a Fermi-Dirac distribution. These factors are an old concept, but we show how they can be derived with a combination of time-dependent perturbation theory, and the extended normal ordering of Mukherjee and Kutzelnigg. The resulting non-equilibrium kinetic equations generalize the usual Redfield theory to many-electron systems, while ensuring that the orbital occupations remain between zero and one. In numerical applications of our equations, we show that relaxation rates of molecules are not constant because of the blocking effect. Other applications to model atomic chains are also presented which highlight the importance of treating both dephasing and relaxation. Finally we show how the bath localizes the electron density matrix.
Financial price dynamics and pedestrian counterflows: a comparison of statistical stylized facts.
Parisi, Daniel R; Sornette, Didier; Helbing, Dirk
2013-01-01
We propose and document the evidence for an analogy between the dynamics of granular counterflows in the presence of bottlenecks or restrictions and financial price formation processes. Using extensive simulations, we find that the counterflows of simulated pedestrians through a door display eight stylized facts observed in financial markets when the density around the door is compared with the logarithm of the price. Finding so many stylized facts is very rare indeed among all agent-based models of financial markets. The stylized properties are present when the agents in the pedestrian model are assumed to display a zero-intelligent behavior. If agents are given decision-making capacity and adapt to partially follow the majority, periods of herding behavior may additionally occur. This generates the very slow decay of the autocorrelation of absolute return due to an intermittent dynamics. Our findings suggest that the stylized facts in the fluctuations of the financial prices result from a competition of two groups with opposite interests in the presence of a constraint funneling the flow of transactions to a narrow band of prices with limited liquidity. PMID:23410385
A statistical and dynamical analysis of some Winter and Summer temperature extremes in Europe
NASA Astrophysics Data System (ADS)
Andrade, Cristina; Santos, João
2013-04-01
Over the last decades Europe has been facing strong extreme events, particularly temperature extremes, with foremost influence on economy, agriculture, water management and society in general. The study of the large-scale atmospheric mechanisms linked to their occurrence is thus significant and is going to be discussed for the winter and summer seasons in this region for 50 years (1961-2010). Additionally, a canonical correlation analysis, coupled with a principal component analysis (BPCCA), is applied between the monthly mean sea level pressure fields and the monthly occurrences of four temperature extreme indices (TN10p - cold nights, TN90p - warm nights, and TX90p - warm days, TX10p - cold days) within a large Euro-Atlantic sector. Each co-variability mode represents a large-scale forcing on the occurrence of those extremes. North Atlantic Oscillation-like patterns and strong anomalies in the atmospheric flow westwards of the British Isles are leading couplings between large-scale atmospheric circulation and wintertime occurrences of both cold (warm) nights and warm (cold) days in Europe. Although summer couplings show lower coherence between warm and cold events, their key driving mechanisms are significant to explain their atmospheric anomalies. In order to get a better insight for both seasons of these extremes, the main features of the statistical distributions of the minima (TNn and TXn) and maxima (TXx and TNx) are also analyzed. Moreover, statistically significant downward (upward) trends are detected in the cold nights and days (warm nights and days) occurrences over the period 1961-2010 throughout Europe for the winters. These tendencies can also be found in summer for the cold nights and warm days, which is in clear agreement with the overall warming. For the summer warm nights and cold days these tendencies are weaker and its signal is geographically dependent. This work is supported by European Union Funds (FEDER/COMPETE - Operational Competitiveness Programme) and by national funds (FCT - Portuguese Foundation for Science and Technology) under the project FCOMP-01-0124-FEDER-022692.
Statistical techniques for modeling extreme price dynamics in the energy market
NASA Astrophysics Data System (ADS)
Mbugua, L. N.; Mwita, P. N.
2013-02-01
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.
A stochastic-dynamic model for global atmospheric mass field statistics
NASA Technical Reports Server (NTRS)
Ghil, M.; Balgovind, R.; Kalnay-Rivas, E.
1981-01-01
A model that yields the spatial correlation structure of atmospheric mass field forecast errors was developed. The model is governed by the potential vorticity equation forced by random noise. Expansion in spherical harmonics and correlation function was computed analytically using the expansion coefficients. The finite difference equivalent was solved using a fast Poisson solver and the correlation function was computed using stratified sampling of the individual realization of F(omega) and hence of phi(omega). A higher order equation for gamma was derived and solved directly in finite differences by two successive applications of the fast Poisson solver. The methods were compared for accuracy and efficiency and the third method was chosen as clearly superior. The results agree well with the latitude dependence of observed atmospheric correlation data. The value of the parameter c sub o which gives the best fit to the data is close to the value expected from dynamical considerations.
The influence of lexical statistics on temporal lobe cortical dynamics during spoken word listening.
Cibelli, Emily S; Leonard, Matthew K; Johnson, Keith; Chang, Edward F
2015-08-01
Neural representations of words are thought to have a complex spatio-temporal cortical basis. It has been suggested that spoken word recognition is not a process of feed-forward computations from phonetic to lexical forms, but rather involves the online integration of bottom-up input with stored lexical knowledge. Using direct neural recordings from the temporal lobe, we examined cortical responses to words and pseudowords. We found that neural populations were not only sensitive to lexical status (real vs. pseudo), but also to cohort size (number of words matching the phonetic input at each time point) and cohort frequency (lexical frequency of those words). These lexical variables modulated neural activity from the posterior to anterior temporal lobe, and also dynamically as the stimuli unfolded on a millisecond time scale. Our findings indicate that word recognition is not purely modular, but relies on rapid and online integration of multiple sources of lexical knowledge. PMID:26072003
NASA Astrophysics Data System (ADS)
Vaittinada Ayar, Pradeebane; Vrac, Mathieu; Bastin, Sophie; Carreau, Julie; Déqué, Michel; Gallardo, Clemente
2015-05-01
Given the coarse spatial resolution of General Circulation Models, finer scale projections of variables affected by local-scale processes such as precipitation are often needed to drive impacts models, for example in hydrology or ecology among other fields. This need for high-resolution data leads to apply projection techniques called downscaling. Downscaling can be performed according to two approaches: dynamical and statistical models. The latter approach is constituted by various statistical families conceptually different. If several studies have made some intercomparisons of existing downscaling models, none of them included all those families and approaches in a manner that all the models are equally considered. To this end, the present study conducts an intercomparison exercise under the EURO- and MED-CORDEX initiative hindcast framework. Six Statistical Downscaling Models (SDMs) and five Regional Climate Models (RCMs) are compared in terms of precipitation outputs. The downscaled simulations are driven by the ERAinterim reanalyses over the 1989-2008 period over a common area at 0.44° of resolution. The 11 models are evaluated according to four aspects of the precipitation: occurrence, intensity, as well as spatial and temporal properties. For each aspect, one or several indicators are computed to discriminate the models. The results indicate that marginal properties of rain occurrence and intensity are better modelled by stochastic and resampling-based SDMs, while spatial and temporal variability are better modelled by RCMs and resampling-based SDM. These general conclusions have to be considered with caution because they rely on the chosen indicators and could change when considering other specific criteria. The indicators suit specific purpose and therefore the model evaluation results depend on the end-users point of view and how they intend to use with model outputs. Nevertheless, building on previous intercomparison exercises, this study provides a consistent intercomparison framework, including both SDMs and RCMs, which is designed to be flexible, i.e., other models and indicators can easily be added. More generally, this framework provides a tool to select the downscaling model to be used according to the statistical properties of the local-scale climate data to drive properly specific impact models.
Globus, Tatiana; Sizov, Igor; Gelmont, Boris
2014-01-01
Hydrogen bonds (H-bonds) in biological macromolecules are important for the molecular structure and functions. Since interactions via hydrogen bonds are weaker than covalent bonds, it can be expected that atomic movements involving H-bonds have low frequency vibrational modes. Sub-Terahertz (sub-THz) vibrational spectroscopy that combines measurements with molecular dynamics (MD) computational prediction has been demonstrated as a promising approach for biological molecule characterization. Multiple resonance absorption lines have been reported. The knowledge of relaxation times of atomic oscillations is critical for the successful application of THz spectroscopy for hydrogen bond characterization. The purpose of this work is to use atomic oscillations in the 0.35-0.7 THz range, found from molecular dynamic (MD) simulations of E.coli thioredoxin (2TRX), to study relaxation dynamics of two intra-molecular H-bonds, OH-N and OH-C. Two different complimentary techniques are used in this study, one is the analysis of the statistical distribution of relaxation time and dissipation factor values relevant to low frequency oscillations, and the second is the analysis of the autocorrelation function of low frequency quasi-periodic movements. By studying hydrogen bond atomic displacements, it was found that the atoms are involved in a number of collective oscillations, which are characterized by different relaxation time scales ranging from 2-3 ps to more than 150 ps. The existence of long lasting relaxation processes opens the possibility to directly observe and study H-bond vibrational modes in sub-THz absorption spectra of bio-molecules if measured with an appropriate spectral resolution. The results of measurements using a recently developed frequency domain spectroscopic sensor with a spectral resolution of 1 GHz confirm the MD analysis. PMID:25415676
Statistical and dynamical downscaling in CORDEX-Africa: differing views on the regional climate
NASA Astrophysics Data System (ADS)
Hewitson, Bruce; Lennard, Christopher; Jack, Christopher; Coop, Lisa
2013-04-01
The need for credible regional climate change projections for use in adaptation actions and decision making is well recognised. The CORDEX activity has evolved in large part as a response to this need. For the most part, CORDEX has so far been dominated by regional climate modelling (RCM) activities. However, implicit in CORDEX is the use of statistical downscaling (SD) as a complement to RCMs, although the SD activities lag that of the RCMs. For Africa, the CORDEX RCM work is well advanced with the control climate simulations completed, and a number of RCM-based projections also available. The early results indicate the RCMs produce a credible representation of the regional climate when aggregated in time and/or space, and provide an initial multimodal suite of regional climate change projections for Africa. The SD activities are catching up with this process and the emerging challenge is how to integrate and compare the results from the two downscaling methods. The two approaches, SD and RCMs, have respective strengths and weaknesses, but are considered in the literature to be of comparable overall skill. Where climate change stationarity is not considered a major issue, such as on timescales out to perhaps 2050, it is arguable that SD (comprehensively undertaken) may possibly be more skillful. From the perspective of users of regional scale projections, decision makers and policy developers, it is critical to compare, and assess the relative strengths of the methods on a regional basis. To avoid confusion the contradictions and/or robust messages emerging from the two methods needs to be clearly understood and articulated. The inter-comparison between the RCMs is already the subject of a number of papers, and here we present an initial comparison of early results between the SD and the envelope of RCM downscaling for CORDEX-Africa. Using the available SD results, we consider where the overlap and/or marked differences lie between the two methods. The focus is primarily on the control climate, where the downscaling is forced by the ERA-reanalysis data set, to avoid complicating factors possibly arising from non-stationarity issues with both SD and the RCMs. Following this we consider some early results of future climate projections based on the boundary conditions from CMIP5 GCM data. The primary consideration is how the statistical downscaling results fall within the envelope of the regional climate models. In this we consider both the bias of the regional climate models, the seasonal cycle, and the shorter time scales of weather events and the histogram distribution of daily events including extremes. Of particular concern is how the downscaling methods handle both the high and low frequency variance of the regional climate systems. The SD method uses daily data to derive the deterministic response to the large-scale forcing and adds the high-frequency variants or stochastic component. From this time and space aggregates comparable to the RCM data may be compiled. The primary difference between SD and RCMs lies in the fact that the SD is inherently bias corrected by virtue of the method. Thus the first major difference is accountable for by the RCM bias. Following this the differences are regionally and seasonally dependent and examples of these are presented from which preliminary conclusions about the two methods are drawn
Statistical properties of the dense hydrogen plasma: An ab initio molecular dynamics investigation
NASA Astrophysics Data System (ADS)
Kohanoff, Jorge; Hansen, Jean-Pierre
1996-07-01
The hydrogen plasma is studied in the very high density (atomic and metallic) regime by extensive ab initio molecular dynamics simulations. Protons are treated classically, and electrons in the Born-Oppenheimer framework, within the local density approximation to density functional theory. Densities and temperatures studied fall within the strong coupling regime of the protons. We address the question of the validity of linear screening, and we find it yields a reasonably good description up to rs~=0.5, but already too crude for rs=1 (with rs=(3/4??)1/3 the ion sphere radius). These values are typical of Jovian planets interiors. Finite-size and Brillouin zone sampling effects in metallic systems are studied and shown to be very delicate also in the fluid (liquid metal) phase. We analyze the low-temperature phase diagram and the melting transition. A remarkably fast decrease of the melting temperature with decreasing density is found, up to a point when it becomes comparable to the Fermi temperature of the protons. The possible vicinity of a triple point bcc-hcp(fcc)-liquid is discussed in the region of rs~=1.1 and T~=100-200 K. The fluid phase is studied in detail for several temperatures. The structure of the fluid is found to be reminiscent of the underlying bcc (solid) phase. Proton-electron correlations show a weak temperature dependence, and proton-proton correlations exhibit a well-defined first coordination shell, thus characterizing fluid H in this regime as an atomic liquid. Diffusion coefficients are computed and compared to the values for the one-component plasma. Vibrational densities of states (VDOS) show a plasmon renormalization due to electron screening, and the presence of a plasmon-coupled single-particle mode up to very high temperatures. Collective modes are studied through dynamical structure factors. In close relationship with the VDOS, the simulations reveal the remarkable persistence of a weakly damped high-frequency ion-acoustic mode, even under conditions of strong electron screening. The possibility of using this observation as a diagnostic for the plasma phase transition to the fluid molecular phase at lower densities is discussed.
Statistical effects on the dynamics of a multilevel system studied in S 1-butynal
NASA Astrophysics Data System (ADS)
Derler, S.; Bitto, H.; Huber, J. R.
1993-01-01
We have investigated the dynamics of butynal (CH 3C?CCHO) in the S 1 state after excitation of single rovibronic states in the 4 10 band with FTL nanosecond laser pulses in a supersonic jet. The time-resolved fluorescence exhibits the characteristics for an intermediate coupling case, i.e. a biexponential decay with quantum beats or recurrences superimposed on the slow decay component which arises from a coherently excited multilevel structure of singlet triplet eigenstates. Correlation holes were observed in some fluorescence decays implying the presence of correlations in the excited eigenstates. For this clear example of the intermediate coupling case numerical simulation of the fluorescence decays were carried out to study the effects of triplet state density and coupling strength and in particular of spectral correlations and intensity fluctuations on the characteristics of the fluorescence decay. Neglect of correlations and fluctuations are shown to result in an underestimation of the state density, if determined from the fluorescence decays. Furthermore, it is predicted that correlations, already present in the zero-order triplet states, influence the decay parameters such as the amplitude ratio of the fast to the slow decay component and the correlation recovery time which, in turn, influence the inferred state density.
van Milligen, Boudewijn
Quiet-time statistics: A tool to probe the dynamics of self-organized-criticality systems from of a self- organized-criticality system even when the strong-overlapping or hydrodynamic regime in which.1103/PhysRevE.66.036124 PACS number s : 05.65. b, 45.70. n, 52.25.Fi I. INTRODUCTION Self-organized
NASA Astrophysics Data System (ADS)
Nakajima, Kensuke; Sugiyama, Ko-ichiro; Odaka, Masatsugu; Kuramoto, Kiyoshi; Hayashi, Yoshi-Yuki
2014-11-01
A series of long-term numerical simulations of moist convection in Jupiter's atmosphere are performed to investigate idealized characteristics of vertical structures of multi-composition clouds and convective motions associated with them, varying the deep abundances of condensible gases and the time constant of the auto-conversion process that is one of the most questionable parameters in the cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH. The results generally represent the following characteristics qualitatively similar to those found in Sugiyama et al (2011); stable layers associated with condensation and chemical reaction well behave as dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with the cumulonimbus clouds results in an establishment of the mean vertical profiles of condensates and condensible gases that are distinctly different from the hitherto accepted three-layered structure. Our results also demonstrate that the period of the intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL by latent cooling associated with re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. The active cloud development is terminated when the instability is completely exhausted. The period of the intermittency is roughly equal to the time obtained by dividing the mean temperature increase caused by active cumulonimbus development, by the rate of body cooling.
Fernández, J; Larrañaga, A; Etxeberria, A; Sarasua, J R
2014-07-01
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
Coupled flow-polymer dynamics via statistical field theory: Modeling and computation
Ceniceros, Hector D. [Department of Mathematics, University of California, Santa Barbara, CA 93106-5080 (United States)], E-mail: hdc@math.ucsb.edu; Fredrickson, Glenn H. [Department of Chemical Engineering and Materials Research Laboratory, University of California, Santa Barbara, CA 93106-5080 (United States)], E-mail: ghf@mrl.ucsb.edu; Mohler, George O. [Department of Mathematics, University of California, Santa Barbara, CA 93106-5080 (United States)], E-mail: georgemohler@gmail.com
2009-03-20
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.
NASA Astrophysics Data System (ADS)
Chatzopoulos, S.; Fritz, T. K.; Gerhard, O.; Gillessen, S.; Wegg, C.; Genzel, R.; Pfuhl, O.
2015-02-01
We derive new constraints on the mass, rotation, orbit structure, and statistical parallax of the Galactic old nuclear star cluster and the mass of the supermassive black hole. We combine star counts and kinematic data from Fritz et al., including 2500 line-of-sight velocities and 10 000 proper motions obtained with VLT instruments. We show that the difference between the proper motion dispersions ?l and ?b cannot be explained by rotation, but is a consequence of the flattening of the nuclear cluster. We fit the surface density distribution of stars in the central 1000 arcsec by a superposition of a spheroidal cluster with scale ˜100 arcsec and a much larger nuclear disc component. We compute the self-consistent two-integral distribution function f(E, Lz) for this density model, and add rotation self-consistently. We find that (i) the orbit structure of the f(E, Lz) gives an excellent match to the observed velocity dispersion profiles as well as the proper motion and line-of-sight velocity histograms, including the double-peak in the vl-histograms. (ii) This requires an axial ratio near q1 = 0.7 consistent with our determination from star counts, q1 = 0.73 ± 0.04 for r < 70 arcsec. (iii) The nuclear star cluster is approximately described by an isotropic rotator model. (iv) Using the corresponding Jeans equations to fit the proper motion and line-of-sight velocity dispersions, we obtain best estimates for the nuclear star cluster mass, black hole mass, and distance M*(r < 100 arcsec) = (8.94 ± 0.31|stat ± 0.9|syst) × 106 M?, M• = (3.86 ± 0.14|stat ± 0.4|syst) × 106 M?, and R0 = 8.27 ± 0.09|stat ± 0.1|syst kpc, where the estimated systematic errors account for additional uncertainties in the dynamical modelling. (v) The combination of the cluster dynamics with the S-star orbits around Sgr A* strongly reduces the degeneracy between black hole mass and Galactic Centre distance present in previous S-star studies. A joint statistical analysis with the results of Gillessen et al., gives M• = (4.23 ± 0.14) × 106 M? and R0 = 8.33 ± 0.11 kpc.
NASA Astrophysics Data System (ADS)
Sugiyama, K.; Nakajima, K.; Odaka, M.; Kuramoto, K.; Hayashi, Y.-Y.
2014-02-01
A series of long-term numerical simulations of moist convection in Jupiter’s atmosphere is performed in order to investigate the idealized characteristics of the vertical structure of multi-composition clouds and the convective motions associated with them, varying the deep abundances of condensable gases and the autoconversion time scale, the latter being one of the most questionable parameters in cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents the convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH imposing a body cooling that substitutes the net radiative cooling. The results are qualitatively similar to those reported in Sugiyama et al. (Sugiyama, K. et al. [2011]. Intermittent cumulonimbus activity breaking the three-layer cloud structure of Jupiter. Geophys. Res. Lett. 38, L13201. doi:10.1029/2011GL047878): stable layers associated with condensation and chemical reaction act as effective dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with these clouds results in the establishment of mean vertical profiles of condensates and condensable gases that are distinctly different from the hitherto accepted three-layered structure (e.g., Atreya, S.K., Romani, P.N. [1985]. Photochemistry and clouds of Jupiter, Saturn and Uranus. In: Recent Advances in Planetary Meteorology. Cambridge Univ. Press, London, pp. 17-68). Our results also demonstrate that the period of intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The autoconversion time scale does not strongly affect the results, except for the vertical profiles of the condensates. Changing the autoconversion time scale by a factor of 100 changes the intermittency period by a factor of less than two, although it causes a dramatic increase in the amount of condensates in the upper troposphere. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL as a result of the latent cooling associated with the re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. Active cloud development is terminated when the instability is completely exhausted. The period of intermittency is roughly equal to the time obtained by dividing the mean temperature increase, which is caused by active cumulonimbus development, by the body cooling rate.
NASA Astrophysics Data System (ADS)
Chae, Kyu-Hyun; Gong, In-Taek
2015-08-01
Modified Newtonian dynamics (MOND) proposed by Milgrom provides a paradigm alternative to dark matter (DM) that has been successful in fitting and predicting the rich phenomenology of rotating disc galaxies. There have also been attempts to test MOND in dispersion-supported spheroidal early-type galaxies, but it remains unclear whether MOND can fit the various empirical properties of early-type galaxies for the whole ranges of mass and radius. As a way of rigorously testing MOND in elliptical galaxies we calculate the MOND-predicted velocity dispersion profiles (VDPs) in the inner regions of ˜2000 nearly round Sloan Digital Sky Survey elliptical galaxies under a variety of assumptions on velocity dispersion (VD) anisotropy, and then compare the predicted distribution of VDP slopes with the observed distribution in 11 ATLAS3D galaxies selected with essentially the same criteria. We find that the MOND model parametrized with an interpolating function that works well for rotating galaxies can also reproduce the observed distribution of VDP slopes based only on the observed stellar mass distribution without DM or any other galaxy-to-galaxy varying factor. This is remarkable in view that Newtonian dynamics with DM requires a specific amount and/or profile of DM for each galaxy in order to reproduce the observed distribution of VDP slopes. When we analyse non-round galaxy samples using the MOND-based spherical Jeans equation, we do not find any systematic difference in the mean property of the VDP slope distribution compared with the nearly round sample. However, in line with previous studies of MOND through individual analyses of elliptical galaxies, varying MOND interpolating function or VD anisotropy can lead to systematic change in the VDP slope distribution, indicating that a statistical analysis of VDPs can be used to constrain specific MOND models with an accurate measurement of VDP slopes or a prior constraint on VD anisotropy.
NASA Astrophysics Data System (ADS)
Florez, Carlos; Pachón, Leonardo
2015-03-01
The study of quantum dissipation and non-local dynamics in phase space demands an extension of the Ullersma-Caldeira-Leggett framework to include non-linearities either in the system or the bath or even in the couplings between them. In this work, the special case of a linear open system interacting with a harmonic thermal bath by means of non-linear couplings is considered. This framework is constructed by extending the path integral formulation into phase space and applying the Feynam-Vernon influence functional theory to study the perturbative regime at different orders in the couplings. In doing so, the formal correspondence between the perturbative contributions and the Feynman diagrams that arise from the n-point correlation functions in the canonical variables are used. The effect of the non-local behavior induced by the non-linear contributions on the dissipative and decohering mechanisms are analyzed. The main features are the presence of non-Gaussian statistics and multiplicative, instead of additive, noises.
NASA Astrophysics Data System (ADS)
Mezghani, Abdelkader; Benestad, Rasmus E.
2014-05-01
The global climate community has produced a wide range of results from atmospheric-ocean general circulation models, which are considered as the primary source of information on the future climate change. However, there are still gaps between the spatial resolution of climate model outputs and the point-scale requirement of most of climate change impact studies. Thus, empirical-statistical downscaling (ESD) and dynamical downscaling (DD) techniques continue to be used as alternatives and various models have been made available by the scientific community. Several comparative studies have been done during the last decade,dealing with downscaling local weather variables such as temperature and precipitation over a region of interest. Accordingly, in this work, new methods and strategies based on merging ESD and DD results will be proposed in order to increase the quality of the local climate projections with a special focus on seasonal and decadal precipitation and temperature based on CMIP3/5 experiments. A new freely available ESD R-package developed by MET Norway is used and will be also presented.
NASA Astrophysics Data System (ADS)
Krantz, Richard; Douthett, Jack; Cartwright, Julyan; Gonzalez, Diego; Piro, Oreste
2010-10-01
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.
NASA Astrophysics Data System (ADS)
Eslamizadeh, H.
2015-09-01
The fission probability, pre-scission neutron, proton and alpha multiplicities, anisotropy of fission fragment angular distribution and the fission time have been calculated for the compound nuclei 200Pb and 197Tl based on the modified statistical model and four-dimensional dynamical model. In dynamical calculations, dissipation was generated through the chaos weighted wall and window friction formula. The projection of the total spin of the compound nucleus to the symmetry axis, K, was considered as the fourth-dimension in Langevin dynamical calculations. In our dynamical calculations, we have used a constant dissipation coefficient of K, {? }K=0.077{({{MeV}} {{zs}})}-{1/2}, and a non-constant dissipation coefficient to reproduce the above-mentioned experimental data. Comparison of the theoretical results of the fission probability and pre-scission particle multiplicities with the experimental data showed that the difference between the results of both dynamical models is small whereas, for the anisotropy of fission fragment angular distribution, it is slightly large. Furthermore, comparison of the results of the modified statistical model with the above-mentioned experimental data showed that with choosing appropriate values of the temperature coefficient of the effective potential, ? , and the scaling factor of the fission-barrier height, {r}s, the experimental data were satisfactorily reproduced.
Bendersky, Marina; Santore, Maria M; Davis, Jeffrey M
2015-07-01
Electrostatic surface heterogeneity on the order of a few nanometers is common in colloidal and bacterial systems, dominating adhesion and aggregation and inducing deviations from classical DLVO theory based on a uniform distribution of surface charge. Topographical heterogeneity and roughness also strongly influence adhesion. In this work, a model is introduced to quantify the spatial fluctuations in the interaction of microparticles in a flowing suspension with a wall aligned parallel to the flow. The wall contains nanoscale chemical and topographical heterogeneities ("patches") that are randomly distributed and produce localized attraction and repulsion. These attractive and repulsive regions induce fluctuations in the trajectories of the flowing particles that are critical to particle capture by the wall. The statistical distribution of patches is combined with mean-field DLVO calculations between a particle and two homogeneous surfaces: one with the surface potential of the patches and one with the potential of the underlying wall. These surface potentials could be obtained in experiments from zeta potential measurements for the bare wall and for one saturated with patches. This simple model reproduces the mean DLVO interaction force or energy vs. particle-wall separation distance, its variance, and particle adhesion thresholds from direct simulations of particle trajectories over patchy surfaces. The predictions of the model are consistent with experimental findings of significant microparticle deposition onto patchy, net-repulsive surfaces whose apparent zeta potential has the same sign as that of the particles. Deposition is significantly enhanced if the patches protrude even slightly from the surface. The model predictions are also in agreement with the observed variation of the adhesion threshold with the shear rate in published studies of dynamic microparticle adhesion on patchy surfaces. PMID:25804202
I. G. Korepanov
1995-01-01
This paper is devoted to constructing and studying exactly solvable dynamical\\u000asystems in discrete time obtained from some algebraic operations on matrices,\\u000ato reductions of such systems leading to classical field theory models in\\u000a2+1-dimensional wholly discrete space-time, and to connection between those\\u000afield theories and inhomogoneous models in 2-dimensional statistical physics.
NASA Astrophysics Data System (ADS)
Batisti?, Benjamin; Robnik, Marko
2013-08-01
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.
Benjamin Batisti?; Marko Robnik
2013-07-04
We study the quantum mechanics of a billiard (Robnik 1983) in the regime of mixed-type classical phase space (the shape parameter \\lambda=0.15) at very high-lying eigenstates, starting at about 1.000.000th eigenstate and including the consecutive 587654 eigenstates. By calculating the normalized Poincar\\'e 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 occupy unformly 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 distribution of the regular levels obeys the Poisson statistics, and the chaotic ones obey the Brody statistics, as anticipated in a recent paper by Batisti\\'c and Robnik (2010), where the entire spectrum was found to obey the BRB 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.
Statistical Applets: Statistical Significance
NSDL National Science Digital Library
Duckworth, William
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 "Â?Â?Practice of Business Statistics," but can be used without this text. Even though brief, this is a nice interactive resource for an introductory statistics course.
NASA Astrophysics Data System (ADS)
Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Qu, X.; Huang, H. J.; Berg, N.; Jousse, A.; Schwartz, M.; Nakamura, M.; Cerezo-Mota, R.
2012-12-01
Using a combination of dynamical and statistical downscaling techniques, we projected mid-21st century warming in the Los Angeles region at 2-km resolution. To account for uncertainty associated with the trajectory of future greenhouse gas emissions, we examined projections for both "business-as-usual" (RCP8.5) and "mitigation" (RCP2.6) emissions scenarios from the Fifth Coupled Model Intercomparison Project (CMIP5). To account for the considerable uncertainty associated with choice of global climate model, we downscaled results for all available global climate models in CMIP5. For the business-as-usual scenario, we find that by the mid-21st century, the most likely warming is roughly 2.6°C averaged over the region's land areas, with a 95% confidence that the warming lies between 0.9 and 4.2°C. The high resolution of the projections reveals a pronounced spatial pattern in the warming: High elevations and inland areas separated from the coast by at least one mountain complex warm 20 to 50% more than the areas near the coast or within the Los Angeles basin. This warming pattern is especially apparent in summertime. The summertime warming contrast between the inland and coastal zones has a large effect on the most likely expected number of extremely hot days per year. Coastal locations and areas within the Los Angeles basin see roughly two to three times the number of extremely hot days, while high elevations and inland areas typically experience approximately three to five times the number of extremely hot days. Under the mitigation emissions scenario, the most likely warming and increase in heat extremes are somewhat smaller. However, the majority of the warming seen in the business-as-usual scenario still occurs at all locations in the most likely case under the mitigation scenario, and heat extremes still increase significantly. This warming study is the first part of a series studies of our project. More climate change impacts on the Santa Ana wind, rainfall, snowfall and snowmelt, cloud and surface hydrology are forthcoming and could be found in www.atmos.ucla.edu/csrl.he ensemble-mean, annual-mean surface air temperature change and its uncertainty from the available CMIP5 GCMs under the RCP8.5 (left) and RCP2.6 (right) emissions scenarios, unit: °C.
NASA Technical Reports Server (NTRS)
Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Alados-Arboledas, L.
2012-01-01
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.
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM JEROME FRIEDMAN Department of Statistics Stanford Ensemble methods have emerged as being among the most powerful statistical learning techniques. It is shown
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM GOURAB MUKHERJEE Department of Statistics Stanford directions in statistical probability forecasting. Building on these parallels we present a frequentist
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM ADRIAN RAFTERY Department of Statistics University will describe a Bayesian statistical method for probabilistic population projections for all countries
NASA Astrophysics Data System (ADS)
MöLg, Thomas; Kaser, Georg
2011-08-01
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).
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM DAVID BLEI Department of Statistics and Computer posterior inference algorithms have revolutionized Bayesian statistics, revealing its potential as a usable and general-purpose language for data analysis. Bayesian statistics, however, has not yet reached
NASA Astrophysics Data System (ADS)
Russotto, P.; De Filippo, E.; Pagano, A.; Acosta, L.; Auditore, L.; Baran, V.; Berceanu, I.; Borderie, B.; Bougault, R.; Bruno, M.; Cap, T.; Cardella, G.; Cavallaro, S.; Chatterjee, M. B.; Chbihi, A.; Colonna, M.; D'Agostino, M.; Di Toro, M.; Francalanza, L.; Frankland, J.; Galichet, E.; Gawlikowicz, W.; Geraci, E.; Gnoffo, B.; Grzeszczuk, A.; Guazzoni, P.; Kowalski, S.; Lanzalone, G.; Lanzanò, G.; Le Neindre, N.; Lombardo, I.; Maiolino, C.; Minniti, T.; Pagano, E. V.; Papa, M.; Piasecki, E.; Pirrone, S.; P?aneta, R.; Politi, G.; Porto, F.; Quattrocchi, L.; Rivet, M. F.; Rosato, E.; Rizzo, F.; Schmidt, K.; Siwek-Wilczy?ska, K.; Skwira-Chalot, I.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.; Wieleczko, J. P.; Wilczy?ski, J.; Zetta, L.; Zipper, W.
2015-01-01
Background: In heavy-ion collisions at intermediate energies the production of light charged particles and intermediate mass fragments (IMFs) is due to different reaction mechanisms and different time scales, ranging from fast dynamical processes to statistical emission from the equilibrated system. Purpose: We compare the IMF statistical and dynamical emission probabilities in collisions of a neutron-rich 124Sn+64Ni system and a neutron-poor 112Sn+58Ni system at the laboratory energy of 35 A MeV. Method: The IMFs production mechanism in semiperipheral reactions has been investigated in our previous works. In this paper, the analysis is expanded for the same set of data and production cross sections have been evaluated for dynamical and statistical emission in a coherent way for light and heavy fragments. Results: The data analysis has evidenced a strong competition between dynamical and statistical emission mechanisms. Probability of the dynamical emission of IMFs is strongly influenced by the (N /Z ) ratio of the colliding system. Conclusions: It is demonstrated that the statistical emission is equally probable for the two systems, while the dynamical emission is enhanced for the neutron-rich system, especially for heavy fragments (Z ?6 ). The observed effect points at a high sensitivity of the prompt-dynamical emission to the (N /Z ) ratio of a given system.
NASA Astrophysics Data System (ADS)
Kochendorfer, J. P.; Ramírez, J. A.
2008-03-01
The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green Leaf Area Index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.
NASA Astrophysics Data System (ADS)
Kochendorfer, J. P.; Ramírez, J. A.
2010-10-01
The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green leaf area index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on complete or near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.
Majda, Andrew J.
A statistically accurate modi...ed quasilinear Gaussian closure for uncertainty quanti...cation second-order closure methodology for uncertainty quanti...cation in damped forced nonlinear systems and quantify uncertainty rather than trying to `avoid' it. Here we will mainly focus on uncertainty quanti...cation
LaBry, Zachary Alexander
2015-01-01
One of the most difficult challenges facing the development of modern gas turbines-for power generation, and propulsion-is the mitigation of dynamic instabilities in the presence of efficiency and emissions constraints. ...
NASA Astrophysics Data System (ADS)
Gupta, V. K.
2009-05-01
The Hydro-Kansas (HK) is a multi-institutional, multi-investigator, multi-disciplinary research project. It represents the first illustrative example of a Natural Laboratory (NL), as described in the Water, Earth, Biota (WEB) report to the National Science Foundation (http://cires.colorado.edu/hydrology). HK combines theoretical analyses, numerical modeling, and an observational field program to understand and predict floods during periods of stationary and non-stationary changes in global hydro-climate. The framework is being generalized to include riparian evapotranspiration (RET). The central observational facility of HK is the 1,100 km2 Whitewater basin 50 km east of Wichita, Kansas. HK is addressing the long-standing problem of predicting spatial statistical scale invariance, or scaling, in floods and RET from bio-physical processes on multiple time scales that range from those of individual rainfall-runoff events to annual and longer. Physical predictions of statistical scaling involve non-linear interactions among hydrologic, geomorphologic, atmospheric, climatic, and ecologic processes in mesoscale basins. They require, (i) multi-scale dynamical formulations, (ii) a new ensemble approach to solve multi-scale dynamical equations on random self-similar (RSN) river networks, (iii) diagnostic analyses of theoretical predictions using observations, and (iv) a framework to generalize the results across global hydroclimates. Progress on these four sets of research challenges will be illustrated through examples.
M. Matilla-GarcÍa; R. Queralt; P. Sanz; F. J. VÁzquez
2004-01-01
The BDS statistic, rooted on the correlation integral, has been proven to be useful for different problems. But although the correlation integral is defined for any choice of delay time, the BDS statistic assumes delay time is one. As different studies have shown, an adequate choice of delay time is important in order to determine the dynamical properties of a
NASA Astrophysics Data System (ADS)
Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio
2012-09-01
In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007), 10.1063/1.2430711]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H_5^+ complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H_5^+ complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, ?(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011), 10.1063/1.3587246] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.
M Bleicher; Liu Fu Ming; A Keränen; Jörg Aichelin; S A Bass; F Becattini; Krzysztof Redlich; K Werner
2001-01-01
The $\\\\bar{\\\\Omega}\\/\\\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\\\rm lab}$=160 GeV). The anti-omega 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
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM Joint seminar with Stevanovich Center PHILIPPE RIGOLLET Operations Research and Financial Engineering, Princeton University The Statistical Price to Pay ABSTRACT Computational limitations of statistical problems have largely been ignored or simply over- come
Fractional exclusion statistics and anyons
Chen, W.; Ng, Y.J.
1995-05-15
Do anyons, dynamically realized by the field theoretic Chern-Simons construction, obey fractional exclusion statistics? We find that they do if the statistical interaction between anyons and antianyons is taken into account. For this anyon model, we show perturbatively that the exchange statistical parameter of anyons is equal to the exclusion statistical parameter. We obtain the same result by applying the relation between the exclusion statistical parameter and the second virial coefficient in the nonrelativistic limit.
of the surface is r2 = az, where a is a positive constant. First, find the kinetic energy of the particle. Secondly, given that the potential energy is mgz, where g is a positive constant, write down the Lagrange) describes the dynamics of a system of N particles, with i = 1...N. It is a function of the generalised co
L. Rossi; G. Turchetti; S. Vaienti
2005-01-01
Poincaré recurrences seem able to capture some of the fundamental properties of dynamical systems. In fact, the asymptotic distribution of Poincaré recurrences is exponential for a wide class of mixing systems, even if they are not uniformly hyperbolic. On the other hand, we found strong numerical evidences that for integrable systems such distribution follows an algebraic decay law, showing this
H. Hernández-Saldaña; A. Robledo
2006-03-15
We analyze the fluctuating dynamics at the golden-mean transition to chaos in the critical circle map and find that trajectories within the critical attractor consist of infinite sets of power laws mixed together. We elucidate this structure assisted by known renormalization group (RG) results. Next we proceed to weigh the new findings against Tsallis' entropic and Mori's thermodynamic theoretical schemes and observe behavior to a large extent richer than previously reported. We find that the sensitivity to initial conditions has the form of families of intertwined q-exponentials, of which we determine the q-indexes and the generalized Lyapunov coefficient spectra. Further, the dynamics within the critical attractor is found to consist of not one but a collection of Mori's q-phase transitions with a hierarchical structure. The value of Mori's `thermodynamic field' variable q at each transition corresponds to the same special value for the entropic index q. We discuss the relationship between the two formalisms and indicate the usefulness of the methods involved to determine the universal trajectory scaling function and/or the ocurrence and characterization of dynamical phase transitions.
NASA Astrophysics Data System (ADS)
Zekri, Nouredine; Clerc, Jean Pierre
We study numerically in this work the statistical and dynamical properties of the clusters in a one dimensional small world model. The parameters chosen correspond to a realistic network of children of school age where a disease like measles can propagate. Extensive results on the statistical behavior of the clusters around the percolation threshold, as well as the evoltion with time, are discussed. To cite this article: N. Zekri, J.P. Clerc, C. R. Physique 3 (2002) 741-747.
NASA Technical Reports Server (NTRS)
Stone, Peter H.; Yao, Mao-Sung
1987-01-01
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.
Cancer Statistics Cancer has a major impact on society in the United States and across the world. Cancer statistics ... prognosis, see the Understanding Cancer Prognosis page. Cancer Statistics | Did You Know? View this video on YouTube. ...
Shakhanina, I L; Kucherovskaia, T V; Chernova, T P
1990-04-01
To solve various problems connected with epidemiological analysis concerning evaluation of the level, direction and intensity of the time course of the epidemic process and character of the cyclic component, the indications and limitations to the use of the following statistical methods have been worked out: equalizing by the method of the least squares on a straight line, a parabola, an exponential or power curve; calculation of the average annual rate of increase; leveling of dynamic series by the methods of internal prolongation, sliding and suspended sliding mean values; calculation of deviations from the theoretical tendency line; autocorrection. 11 computer programs have been compiled on the basis of the algorithms of the above methods, complete with the service menu, for the program complex "Epidanalysis" which permits an epidemiologist to proceed from the problem via indications and limitations to the adequate statistical method and the corresponding software. The programs are intended for different types of computers (EC-1840, Robotron 1715, IBM PC XT). PMID:2385989
Stephane Vannitsem; Valerio Lucarini
2015-10-01
We study a simplified coupled atmosphere-ocean model using the formalism of covariant Lyapunov vectors (CLVs), which link physically-based directions of perturbations to growth/decay rates. The model is obtained via a severe truncation of quasi-geostrophic equations for the two fluids, and includes a simple yet physically meaningful representation of their dynamical/thermodynamical coupling. The model has 36 degrees of freedom, and the parameters are chosen so that a chaotic behaviour is observed. One finds two positive Lyapunov exponents (LEs), sixteen negative LEs, and eighteen near-zero LEs. The presence of many near-zero LEs results from the vast time-scale separation between the characteristic time scales of the two fluids, and leads to nontrivial error growth properties in the tangent space spanned by the corresponding CLVs, which are geometrically very degenerate. Such CLVs correspond to two different classes of ocean/atmosphere coupled modes. The tangent space spanned by the CLVs corresponding to the positive and negative LEs has, instead, a non-pathological behaviour, and one can construct robust large deviations laws for the finite time LEs, thus providing a universal model for assessing predictability on long to ultra-long scales along such directions. It is somewhat surprising to find that the tangent space of the unstable manifold has strong projection on both atmospheric and oceanic components. Our results underline the difficulties in using hyperbolicity as a conceptual framework for multiscale chaotic dynamical systems, whereas the framework of partial hyperbolicity seems better suited, possibly indicating an alternative definition for the chaotic hypothesis. Our results suggest the need for accurate analysis of error dynamics on different time scales and domains and for a careful set-up of assimilation schemes when looking at coupled atmosphere-ocean models.
Stephane Vannitsem; Valerio Lucarini
2015-10-11
We study a simplified coupled atmosphere-ocean model using the formalism of covariant Lyapunov vectors (CLVs), which link physically-based directions of perturbations to growth/decay rates. The model is obtained via a severe truncation of quasi-geostrophic equations for the two fluids, and includes a simple yet physically meaningful representation of their dynamical/thermodynamical coupling. The model has 36 degrees of freedom, and the parameters are chosen so that a chaotic behaviour is observed. One finds two positive Lyapunov exponents (LEs), sixteen negative LEs, and eighteen near-zero LEs. The presence of many near-zero LEs results from the vast time-scale separation between the characteristic time scales of the two fluids, and leads to nontrivial error growth properties in the tangent space spanned by the corresponding CLVs, which are geometrically very degenerate. Such CLVs correspond to two different classes of ocean/atmosphere coupled modes. The tangent space spanned by the CLVs corresponding to the positive and negative LEs has, instead, a non-pathological behaviour, and one can construct robust large deviations laws for the finite time LEs, thus providing a universal model for assessing predictability on long to ultra-long scales along such directions. It is somewhat surprising to find that the tangent space of the unstable manifold has strong projection on both atmospheric and oceanic components. Our results underline the difficulties in using hyperbolicity as a conceptual framework for multiscale chaotic dynamical systems, whereas the framework of partial hyperbolicity seems better suited, possibly indicating an alternative definition for the chaotic hypothesis. Our results suggest the need for accurate analysis of error dynamics on different time scales and domains and for a careful set-up of assimilation schemes when looking at coupled atmosphere-ocean models.
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM PO-LING LOH Department of Statistics University the seminar in Eckhart 110 ABSTRACT Noisy and missing data are prevalent in many real-world statistical, and provide theoretical guarantees for the statistical consistency of our methods. Although our estimators
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM ERIC KOLACZYK Department of Statistics Boston University Statistical Analysis of Network Data: (Re)visiting the Foundations MONDAY, October 13, 2014, at 4, statistical methods and modeling have been central to these efforts. But how well do we truly understand
32. Statistics 1 32. STATISTICS
Masci, Frank
32. Statistics 1 32. STATISTICS Revised September 2007 by G. Cowan (RHUL). This chapter gives an overview of statistical methods used in High Energy Physics. In statistics, we are interested in using's validity or to determine the values of its parameters. There are two main approaches to statistical
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM SAYAN MUKHERJEE Department of Statistical Science vignettes where topological ideas are explored in statistical models of complex traits, machine learning such as sufficient statistics and dictionary learning will be touched on. I will describe an application
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM NOUREDDINE EL KAROUI Department of Statistics will discuss the behavior of widely used statistical methods in the high-dimensional setting where the number surprising statistical phenomena occur: for instance, maximum likelihood methods are shown to be (grossly
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM ERNST WIT Statistics and Probability University devices collect a lot of information, typically about few independent statistical subjects or units statistics. In certain special cases the method can be tweaked to obtain L1-penalized GLM solution paths
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM GONGJUN XU Department of Statistics Columbia University Statistical Inference for Diagnostic Classification Models MONDAY, February 18, 2013 at 4:00 PM-driven construction (estimation) of the Q-matrix and related statistical issues of DCMs. I will first give
Experiments in statistical mechanics
NASA Astrophysics Data System (ADS)
Prentis, Jeffrey J.
2000-12-01
We present experiments designed to illustrate the basic concepts of statistical mechanics using a gas of "motorized molecules." Two molecular motion machines are constructed. The pressure fluctuation machine (mechanical interaction simulator) is a working model of two gases separated by a movable piston. The Boltzmann machine (canonical simulator) is a working model of a two-level quantum system in a temperature bath. Dynamical probabilities (fraction of time) are measured using mechanical devices, such as stop watches and motion sensors. Statistical probabilities (fraction of states) are calculated using physical statistics, such as microcanonical and canonical statistics. The experiments enable one to quantitatively test the fundamental principles of statistical mechanics, including the fundamental postulate, the ergodic hypothesis, and the statistics of Boltzmann.
NASA Astrophysics Data System (ADS)
Mutz, Sebastian; Paeth, Heiko; Winkler, Stefan
2015-05-01
The long-term behaviour of Norwegian glaciers is reflected by the long mass-balance records provided by the Norwegian Water Resources and Energy Directorate. These show positive annual mass balances in the 1980s and 1990s at maritime glaciers followed by rapid mass loss since 2000. This study assesses the influence of various atmospheric variables on mass changes of selected Norwegian glaciers by correlation- and cross-validated stepwise multiple regression analyses. The atmospheric variables are constructed from reanalyses by the National Centers for Environmental Prediction and the European Centre for Medium-Range Weather Forecasts. Transfer functions determined by the multiple regression are applied to predictors derived from a multi-model ensemble of climate projections to estimate future mass-balance changes until 2100. The statistical relationship to the North Atlantic Oscillation (NAO), the strongest predictor, is highest for maritime glaciers and less for more continental ones. The mass surplus in the 1980s and 1990s can be attributed to a strong NAO phase and lower air temperatures during the ablation season. The mass loss since 2000 can be explained by an increase of summer air temperatures and a slight weakening of the NAO. From 2000 to 2100 the statistical model predicts predicts changes for glaciers in more continental settings of c. -20 m w.e. (water equivalent) or 0.2 m w.e./a. The corresponding range for their more maritime counterparts is -0.5 to +0.2 m w.e./a. Results from Bayesian classification of observed atmospheric states associated with high melt or high accumulation in the past into different simulated climates in the future suggest that climatic conditions towards the end of the twenty-first century favour less winterly accumulation and more ablation in summer. The posterior probabilities for high accumulation at the end of the twenty-first century are typically 1.5-3 times lower than in the twentieth century while the posterior probabilities for high melt are often 1.5-3 times higher at the end of the twenty-first century than in the twentieth and early twenty-first century.
Fukunishi, Yoshifumi; Nakamura, Haruki
2012-01-01
We have developed a method for estimating protein-ligand binding free energy (?G) based on the direct protein-ligand interaction obtained by a molecular dynamics simulation. Using this method, we estimated the ?G value statistically by the average values of the van der Waals and electrostatic interactions between each amino acid of the target protein and the ligand molecule. In addition, we introduced fluctuations in the accessible surface area (ASA) and dihedral angles of the protein-ligand complex system as the entropy terms of the ?G estimation. The present method included the fluctuation term of structural change of the protein and the effective dielectric constant. We applied this method to 34 protein-ligand complex structures. As a result, the correlation coefficient between the experimental and calculated ?G values was 0.81, and the average error of ?G was 1.2 kcal/mol with the use of the fixed parameters. These results were obtained from a 2 nsec molecular dynamics simulation. PMID:24281257
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM YUVAL BENJAMINI Department of Statistics University) and imaging (e.g. functional MRI) data from the visual cortex. These encoding models are trained to describe
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM PETER GUTTORP University of Washington and Norwegian Computing Center The Heat Is On! A Statistical Look at the State of the Climate MONDAY, May 6, 2013 at 4
Liu, C.T.; Kuo, J.L.; Wu, G.S. [National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China). Dept. of Electrical Engineering] [National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China). Dept. of Electrical Engineering
1993-12-01
This paper will present a prototype of transverse flux homopolar linear machine system, along with a systematic and generalized 3-dimensional approach which is capable to analyze three kinds of linear machines, the transverse flux linear induction machine (TFLIM), the homopolar linear synchronous machine (HLSM), and the transverse flux linear reluctance machine (TFLRM), all in one compact mathematical model. Also, other than using the conventional steady-state geometric vector analysis or the concentrated magnetic circuit analysis in the modeling process, a novel methodology which combines the state-space technique with the statistical saliency-effect superposition method is proposed. With such detailed and generalized modeling approach, the capability of analyzing the saliency effects induced by the distributed windings in practical linear machine systems will be enhanced, and the representations of all the related linear machine system equations can be manipulated in compact matrix forms. From this comprehensive theoretical approach and the experimental verifications, it is shown that a convenient and reliable mathematical basis for the associated computer-aided analysis and design studies on linear machine systems will be provided.
Diegert, Carl F.
2006-12-01
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.
NASA Technical Reports Server (NTRS)
Zheng, Quanan; Yan, Xiao-Hai; Klemas, Vic
1993-01-01
The internal waves on the continental shelf on the Middle Atlantic Bight seen on Space Shuttle photographs taken during the STS-40 mission in June 1991 are measured and analyzed. The internal wave field in the sample area has a three-level structure which consists of packet groups, packets, and solitons. An average packet group wavelength of 17.5 km and an average soliton wavelength of 0.6 km are measured. Finite-depth theory is used to derive the dynamic parameters of the internal solitons: the maximum amplitude of 5.6 m, the characteristic phase speed of 0.42 m/s, the characteristic period of 23.8 min, the velocity amplitude of the water particles in the upper and lower layers of 0.13 m/s and 0.030 m/s respectively, and the theoretical energy per unit crest line of 6.8 x 10 exp 4 J/m. The frequency distribution of solitons is triple-peaked rather than continuous. The major generation source is at 160 m water depth, and a second is at 1800 m depth, corresponding to the upper and lower edges of the shelf break.
NSDL National Science Digital Library
Hoffman, Howard
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.
Vannitsem, Stephane
2015-01-01
We study a simplified coupled atmosphere-ocean model using the formalism of covariant Lyapunov vectors (CLVs), which link physically-based directions of perturbations to growth/decay rates. The model is obtained via a severe truncation of quasi-geostrophic equations for the two fluids, and includes a simple yet physically meaningful representation of their dynamical/thermodynamical coupling. The model has 36 degrees of freedom, and the parameters are chosen so that a chaotic behaviour is observed. One finds two positive Lyapunov exponents (LEs), sixteen negative LEs, and eighteen near-zero LEs. The presence of many near-zero LEs results from the vast time-scale separation between the characteristic time scales of the two fluids, and leads to nontrivial error growth properties in the tangent space spanned by the corresponding CLVs, which are geometrically very degenerate. Such CLVs correspond to two different classes of ocean/atmosphere coupled modes. The tangent space spanned by the CLVs corresponding to the ...
NASA Astrophysics Data System (ADS)
Paine, Gregory Harold
1982-03-01
The primary objective of the thesis is to explore the dynamical properties of small nerve networks by means of the methods of statistical mechanics. To this end, a general formalism is developed and applied to elementary groupings of model neurons which are driven by either constant (steady state) or nonconstant (nonsteady state) forces. Neuronal models described by a system of coupled, nonlinear, first-order, ordinary differential equations are considered. A linearized form of the neuronal equations is studied in detail. A Lagrange function corresponding to the linear neural network is constructed which, through a Legendre transformation, provides a constant of motion. By invoking the Maximum-Entropy Principle with the single integral of motion as a constraint, a probability distribution function for the network in a steady state can be obtained. The formalism is implemented for some simple networks driven by a constant force; accordingly, the analysis focuses on a study of fluctuations about the steady state. In particular, a network composed of N noninteracting neurons, termed Free Thinkers, is considered in detail, with a view to interpretation and numerical estimation of the Lagrange multiplier corresponding to the constant of motion. As an archetypical example of a net of interacting neurons, the classical neural oscillator, consisting of two mutually inhibitory neurons, is investigated. It is further shown that in the case of a network driven by a nonconstant force, the Maximum-Entropy Principle can be applied to determine a probability distribution functional describing the network in a nonsteady state. The above examples are reconsidered with nonconstant driving forces which produce small deviations from the steady state. Numerical studies are performed on simplified models of two physical systems: the starfish central nervous system and the mammalian olfactory bulb. Discussions are given as to how statistical neurodynamics can be used to gain a better understanding of the behavior of these systems.
NASA Technical Reports Server (NTRS)
Manning, Robert M.
1987-01-01
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.
NASA Astrophysics Data System (ADS)
Demkin, V. P.; Mel'nichuk, S. V.
2014-09-01
In the present work, results of investigations into the dynamics of secondary electrons with helium atoms in the presence of the reverse electric field arising in the flare of a high-voltage pulsed beam-type discharge and leading to degradation of the primary electron beam are presented. The electric field in the discharge of this type at moderate pressures can reach several hundred V/cm and leads to considerable changes in the kinetics of secondary electrons created in the process of propagation of the electron beam generated in the accelerating gap with a grid anode. Moving in the accelerating electric field toward the anode, secondary electrons create the so-called compensating current to the anode. The character of electron motion and the compensating current itself are determined by the ratio of the field strength to the concentration of atoms (?/n). The energy and angular spectra of secondary electrons are calculated by the Monte Carlo method for different ratios E/n of the electric field strength to the helium atom concentration. The motion of secondary electrons with threshold energy is studied for inelastic collisions of helium atoms and differential analysis is carried out of the collisional processes causing energy losses of electrons in helium for different E/n values. The mechanism of creation and accumulation of slow electrons as a result of inelastic collisions of secondary electrons with helium atoms and selective population of metastable states of helium atoms is considered. It is demonstrated that in a wide range of E/n values the motion of secondary electrons in the beam-type discharge flare has the character of drift. At E/n values characteristic for the discharge of the given type, the drift velocity of these electrons is calculated and compared with the available experimental data.
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM SRIRAM SANKARARAMAN Department of Genetics Harvard Medical School Statistical Models for Analyzing Ancient Human Admixture WEDNESDAY, January 21, 2015, at 4 become available, as well as appropriate statistical models. In the first part of my talk, I will focus
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM PIOTR ZWIERNIK Department of Mathematics University of Genoa Understanding Statistical Models Through Their Geometry MONDAY, January 26, 2015, at 4:00 PM and Gaussian statistical models have a rich geometric structure and can be often viewed as algebraic sets
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM ROBERT NOWAK Department of Electrical and Computer-dimensional statistical models to capture the complexity of such problems. Most of the work in this direction has focused of statistical inference. These procedures automatically adapt the measurements in order to focus and optimize
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM INGRAM OLKIN Department of Statistics Stanford the concept of majorization is called mixing and in physics it is referred to as chaotic (one vector is more probability, statistics, combinatorics and graphs, numerical analysis and matrix theory. Special emphasis
NASA Technical Reports Server (NTRS)
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
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.
NASA Astrophysics Data System (ADS)
Guyennon, Nicolas; Portoghese, Ivan; Romano, Emanuele; Calmanti, Sandro
2013-04-01
Various downscaling techniques have been developed to bridge the scale gap between global climate models (GCMs) and finer scales required to assess hydrological impacts of climate change. Although statistical downscaling (SD) has been traditionally seen as an alternative to dynamical downscaling (DD), recent works on statistical downscaling have aimed to combine the benefits of these two approaches. The overall objective of this study is to assess whether a DD processing performed before the SD permits to obtain more suitable scenarios of crop water demand. The case study presented here focuses on the north-western part of the Apulia region named Capitanata plain (South East of Italy, surface area about 4000 km2), dominated by agriculture (about 15% of the national production of cereals and olive trees) and mainly depending on surface water. The fifth-generation ECHAM model from the Max-Planck-Institute for Meteorology was adopted as GCM. The DD was carried out with the Protheus system (ENEA), while the SD was performed through a monthly quantile-quantile correction. Finally the crop water demand is estimated through the water mass-balance model G-MAP, considering monthly precipitation, monthly temperature and the major landscape features that determine the soil water balance. The latter introduces a strong non linearity with respect to the meteorological input, due to the non-linear solution of soil infiltration and moisture-dependent evapotranspiration and the threshold-based runoff mechanism, which prevents from forecasting the crop water demand as simple linear combination of the precipitation and temperature scenarios. The crop water demand scenarios resulting from the different downscaling and their combination are then compared in terms of bias, long term non stationarity and spatial variability.
Hay, L.E.; Clark, M.P.
2003-01-01
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 output (horizontal grid spacing of approximately 210 km); (2) dynamically downscaled (DDS) NCEP output using a Regional Climate Model (RegCM2, horizontal grid spacing of approximately 52 km); (3) statistically downscaled (SDS) NCEP output; (4) spatially averaged measured data used to calibrate the hydrologic model (Best-Sta) and (5) spatially averaged measured data derived from stations located within the area of the RegCM2 model output used for each basin, but excluding Best-Sta set (All-Sta). In all three basins the SDS-based simulations of daily runoff were as good as runoff produced using the Best-Sta timeseries. The NCEP, DDS, and All-Sta timeseries were able to capture the gross aspects of the seasonal cycles of precipitation and temperature. However, in all three basins, the NCEP-, DDS-, and All-Sta-based simulations of runoff showed little skill on a daily basis. When the precipitation and temperature biases were corrected in the NCEP, DDS, and All-Sta timeseries, the accuracy of the daily runoff simulations improved dramatically, but, with the exception of the bias-corrected All-Sta data set, these simulations were never as accurate as the SDS-based simulations. This need for a bias correction may be somewhat troubling, but in the case of the large station-timeseries (All-Sta), the bias correction did indeed 'correct' for the change in scale. It is unknown if bias corrections to model output will be valid in a future climate. Future work is warranted to identify the causes for (and removal of) systematic biases in DDS simulations, and improve DDS simulations of daily variability in local climate. Until then, SDS based simulations of runoff appear to be the safer downscaling choice.
Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy
2015-10-15
The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii) assessment of modelling the onset of transient and compression settling. Furthermore, the optimal level of model discretization both in 2-D and 1-D was undertaken. Results suggest that the iCFD model developed for the SST through the proposed methodology is able to predict solid distribution with high accuracy - taking a reasonable computational effort - when compared to multi-dimensional numerical experiments, under a wide range of flow and design conditions. iCFD tools could play a crucial role in reliably predicting systems' performance under normal and shock events. PMID:26248321
NASA Astrophysics Data System (ADS)
Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Reich, K.
2013-12-01
Using a combination of dynamical and statistical downscaling techniques, we produced 2-km-resolution regional climate reconstructions and future projections of surface warming and snowfall changes in the Los Angeles region at the middle and end of the 21st century. Projections for both time periods were compared to a validated simulation of a baseline period (1981-2000). We examined outcomes associated with two IPCC-AR5 greenhouse gas emissions scenarios: a "business-as-usual" scenario (RCP8.5) and a "mitigation" scenario (RCP2.6). Output from all available global climate models in the CMIP5 archive was downscaled. We first statistically downscaled surface warming and then applied a statistical model between the surface temperature and snowfall to project the snowfall change. By mid-century, the mountainous areas in the Los Angeles region are likely to receive substantially less snowfall than in the baseline period. In RCP8.5, about 60% of the snowfall is most likely to persist, while in RCP2.6, the likely amount remaining is somewhat higher (about 70%). By end-of-century, however, the two scenarios diverge significantly. In RCP8.5, snowfall sees a dramatic further reduction, with only about a third of baseline snowfall persisting. For RCP2.6, snowfall sees only a negligible further reduction from mid-century. Due to significant differences in climate change outcomes across the global models, we estimated these numbers associated with uncertainty, in the range of 15-30 percentage points. For both scenarios and both time slices, the snowfall loss is consistently greatest at low elevations, and the lower-lying mountain ranges are somewhat more vulnerable to snowfall loss. The similarity in the two scenarios' most likely snowfall outcomes at mid-century illustrates the inevitability of climate change in the coming decades, no matter what mitigation measures are taken. Their stark contrast at century's end reveals that reduction of greenhouse gas emissions will help avoid a dramatic loss of snowfall by the end of the century. In addition to snowfall projections, the warming-accelerated snow melting of the already reduced snowfall will be discussed as well.
Cosmic statistics of statistics
NASA Astrophysics Data System (ADS)
Szapudi, István; Colombi, Stéphane; Bernardeau, Francis
1999-12-01
The errors on statistics measured in finite galaxy catalogues are exhaustively investigated. The theory of errors on factorial moments by Szapudi & Colombi is applied to cumulants via a series expansion method. All results are subsequently extended to the weakly non-linear regime. Together with previous investigations this yields an analytic theory of the errors for moments and connected moments of counts in cells from highly non-linear to weakly non-linear scales. For non-linear functions of unbiased estimators, such as the cumulants, the phenomenon of cosmic bias is identified and computed. Since it is subdued by the cosmic errors in the range of applicability of the theory, correction for it is inconsequential. In addition, the method of Colombi, Szapudi & Szalay concerning sampling effects is generalized, adapting the theory for inhomogeneous galaxy catalogues. While previous work focused on the variance only, the present article calculates the cross-correlations between moments and connected moments as well for a statistically complete description. The final analytic formulae representing the full theory are explicit but somewhat complicated. Therefore we have made available a fortran program capable of calculating the described quantities numerically (for further details e-mail SC at colombi@iap.fr). An important special case is the evaluation of the errors on the two-point correlation function, for which this should be more accurate than any method put forward previously. This tool will be immensely useful in the future for assessing the precision of measurements from existing catalogues, as well as aiding the design of new galaxy surveys. To illustrate the applicability of the results and to explore the numerical aspects of the theory qualitatively and quantitatively, the errors and cross-correlations are predicted under a wide range of assumptions for the future Sloan Digital Sky Survey. The principal results concerning the cumulants ?, Q3 and Q4 is that the relative error is expected to be smaller than 3, 5 and 15per cent, respectively, in the scale range of 1-10h-1Mpc the cosmic bias will be negligible.
NASA Astrophysics Data System (ADS)
Manos, Thanos; Robnik, Marko
2013-06-01
We study the kicked rotator in the classically fully chaotic regime using Izrailev's N-dimensional model for various N?4000, which in the limit N?? tends to the quantized kicked rotator. We do treat not only the case K=5, as studied previously, but also many different values of the classical kick parameter 5?K?35 and many different values of the quantum parameter k?[5,60]. We describe the features of dynamical localization of chaotic eigenstates as a paradigm for other both time-periodic and time-independent (autonomous) fully chaotic or/and mixed-type Hamilton systems. We generalize the scaling variable ?=l?/N to the case of anomalous diffusion in the classical phase space by deriving the localization length l? for the case of generalized classical diffusion. We greatly improve the accuracy and statistical significance of the numerical calculations, giving rise to the following conclusions: (1) The level-spacing distribution of the eigenphases (or quasienergies) is very well described by the Brody distribution, systematically better than by other proposed models, for various Brody exponents ?BR. (2) We study the eigenfunctions of the Floquet operator and characterize their localization properties using the information entropy measure, which after normalization is given by ?loc in the interval [0,1]. The level repulsion parameters ?BR and ?loc are almost linearly related, close to the identity line. (3) We show the existence of a scaling law between ?loc and the relative localization length ?, now including the regimes of anomalous diffusion. The above findings are important also for chaotic eigenstates in time-independent systems [Batisti? and Robnik, J. Phys. A: Math. Gen.1751-811310.1088/1751-8113/43/21/215101 43, 215101 (2010); arXiv:1302.7174 (2013)], where the Brody distribution is confirmed to a very high degree of precision for dynamically localized chaotic eigenstates, even in the mixed-type systems (after separation of regular and chaotic eigenstates).
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Gai, Lili; Vogel, Thomas; Maerzke, Katie A.; Iacovella, Christopher R.; Landau, David P.; Cummings, Peter T.; McCabe, Clare
2013-01-01
Two different techniques – replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) – were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (?) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results. PMID:23927268
NASA Astrophysics Data System (ADS)
Li, R.; Wang, S.-Y.; Gillies, R. R.
2015-03-01
Large biases associated with climate projections are problematic when it comes to their regional application in the assessment of water resources and ecosystems. Here, we demonstrate a method that can reduce systematic biases in regional climate projections. The global and regional climate models employed to demonstrate the technique are the Community Climate System Model (CCSM) and the Weather Research and Forecasting (WRF) model. The method first utilized a statistical regression technique and a global reanalysis dataset to correct biases in the CCSM-simulated variables (e.g., temperature, geopotential height, specific humidity, and winds) that are subsequently used to drive the WRF model. The WRF simulations were conducted for the western United States and were driven with (a) global reanalysis, (b) original CCSM, and (c) bias-corrected CCSM data. The bias-corrected CCSM data led to a more realistic regional climate simulation of precipitation and associated atmospheric dynamics, as well as snow water equivalent (SWE), in comparison to the original CCSM-driven WRF simulation. Since most climate applications rely on existing global model output as the forcing data (i.e., they cannot re-run or change the global model), which often contain large biases, this method provides an effective and economical tool to reduce biases in regional climate downscaling simulations of water resource variables.
Term statistics Zipf's law text statistics
Lu, Jianguo
Term statistics Zipf's law text statistics October 20, 2014 text statistics 1 / 19 #12;Term statistics Zipf's law Overview 1 Term statistics 2 Zipf's law text statistics 2 / 19 #12;Term statistics Zipf's law Outline 1 Term statistics 2 Zipf's law text statistics 3 / 19 #12;Term statistics Zipf's law Model
Statistically accurate sensor networking
C. M. Okino; M. G. Corr
2002-01-01
We propose an alternate approach to ad-hoc networking called best effort multi-hop geographical routing (BEHGR). BEHGR does not fit under the current classifications of on-demand or table-based approaches to ad-hoc routing, but instead statistically attempts to dynamically route packets to a central location in a \\
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM CRISTOPHER MOORE Santa Fe Institute Message an accessible explanation of this algorithm, including its connections with the cavity method of statistical physics. I will also discuss a phase transition in the detectability of communities, that we conjectured
Pseudochaos in Statistical Physics
Boris Chirikov
1997-04-30
A new generic dynamical phenomenon of pseudochaos and its relevance to the statistical physics both modern as well as traditional one are considered and explained in some detail. The pseudochaos is defined as a statistical behavior of the dynamical system with discrete energy and/or frequency spectrum. In turn, the statistical behavior is understood as time-reversible but nonrecurrent relaxation to some steady state, at average, superimposed with irregular fluctuations. The main attention is payed to the most important and universal example of pseudochaos, the so-called quantum chaos that is dynamical chaos in bounded mesoscopic quantum systems. The quantum chaos as a mechanism for implementation of the fundamental correspondence principle is also discussed. The quantum relaxation localization, a peculiar characteristic implication of pseudochaos, is reviewed in both time-dependent and conservative systems with special emphasis on the dynamical decoherence of quantum chaotic states. Recent results on the peculiar global structure of the energy shell, the Green function spectra and the eigenfunctions, both localized and ergodic, in a generic conservative quantum system are presented. Examples of pseudochaos in classical systems are given including linear oscillator and waves, digital computer and completely integrable systems. A far-reaching similarity between the dynamics of a few-freedom quantum system at high energy levels (n >> 1) and that of many--freedom one (N >> 1) is also discussed.
NASA Technical Reports Server (NTRS)
Yao, Mao-Sung; Stone, Peter H.
1987-01-01
The moist convection parameterization used in the GISS 3-D GCM is adapted for use in a two-dimensional (2-D) zonally averaged statistical-dynamical model. Experiments with different versions of the parameterization show that its impact on the general circulation in the 2-D model does not parallel its impact in the 3-D model unless the effect of zonal variations is parameterized in the moist convection calculations. A parameterization of the variations in moist static energy is introduced in which the temperature variations are calculated from baroclinic stability theory, and the relative humidity is assumed to be constant. Inclusion of the zonal variations of moist static energy in the 2-D moist convection parameterization allows just a fraction of a latitude circle to be unstable and enhances the amount of deep convection. This leads to a 2-D simulation of the general circulation very similar to that in the 3-D model. The experiments show that the general circulation is sensitive to the parameterized amount of deep convection in the subsident branch of the Hadley cell. The more there is, the weaker are the Hadley cell circulations and the westerly jets. The experiments also confirm the effects of momentum mixing associated with moist convection found by earlier investigators and, in addition, show that the momentum mixing weakens the Ferrel cell. An experiment in which the moist convection was removed while the hydrological cycle was retained and the eddy forcing was held fixed shows that moist convection by itself stabilizes the tropics, reduces the Hadley circulation, and reduces the maximum speeds in the westerly jets.
NASA Astrophysics Data System (ADS)
Murphy, K. R.; Bender, S.; Kepko, L.; Watt, C.; Rae, J.; Sibeck, D. G.; Mann, I. R.; Donovan, E.; Spanswick, E.; Jackel, B. J.; Frey, H. U.
2014-12-01
Careful analysis of auroral morphology can be used to indirectly probe the magnetospheric counterparts to energetic particle precipitation and magnetic perturbations in the ionosphere, providing insight into the processes generating these perturbations and the location in the magnetotail where these processes occur. During the substorm growth phase and early expansion phase, observations of the electron and proton aurora provide the necessary measurements to map magnetospheric boundaries to the ionosphere, in particular the open-closed field line boundary and the nightside transition region, which separates the nearly dipolar inner field line topology from the highly stretched field line region that corresponds to the thin current sheet. In this study we present a statistical analysis of the auroral substorm through the growth and early expansion phase using the open-closed field line and transition region boundaries to provide spatial context to ionospheric observations. Using the THEMIS all-sky imagers we provide a detailed analysis of the location and brightness of the onset and poleward arcs through the substorm growth phase. We also characterize the motion of the aurora, detailing its velocity and direction of motion through the substorm growth phase and early expansion phase. The purpose of this study is to develop a clear and consistent picture of auroral dynamics and morphology during the growth phase, through substorm onset, and during the early expansion phase. Preliminary results demonstrate that substorm auroral onset occurs on closed field lines, that the growth phase is characterized by the equatorward motion of the onset arc and that the motion of aurora features in the onset and poleward arcs during the growth phase is predominantly azimuthal.
NSDL National Science Digital Library
Kirkman, Thomas
This collection of calculators, created by Thomas Kirkman of the College of Saint Bendict/Saint Joseph, allows users to perform a number of statistical applications. Each provides background on the procedure and an example. Users can compute descriptive statistics and perform t-tests, Chi-square tests, Kolmogorov-Smirnov tests, Fisher's Exact Test, contingency tables, ANOVA, and regression. This is a nice collection of useful applications for a statistics classroom.
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James
2014-01-01
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.
NASA Technical Reports Server (NTRS)
Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.
1994-01-01
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).
NSDL National Science Digital Library
Started in 1997, the Badan Pusat Statistik (BPS-Statistics Indonesia) is a non-departmental Indonesian government institution directly responsible to the Indonesian president. As the law that created this valuable institution stipulates, the BPS is intended to provide data to the government and the public, along cooperating with other international statistical institutions. Visitors looking for statistics on any number of topics will not be disappointed, as the areas covered include agriculture, consumer price indices, employment, energy, foreign trade, mining, population, public finance, tourism, and social welfare. Additionally, there are monthly macro-economic statistical reports for the years from 1998 to 2001 that can be downloaded and viewed as well. The site is rounded out by a collection of some 21 papers from the past four years that analyze various economic data from the country, such as earning data and manufacturing production.
NSDL National Science Digital Library
Dudley, Richard
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.
Stationary Statistics of Turbulence as an Attractor
Ammons, Edsel A
2010-01-01
A calculational approach in fluid turbulence is presented. Use is made of the attracting nature of the fluid-dynamic dynamical system. An approach is offered that effectively propagates the statistics in time. Loss of sensitivity to an initial probability density functional and generation of stationary statistical effects is speculated.
Learning Informative Statistics: A Nonparametric Approach
Ihler, Alexander
Learning Informative Statistics: A Nonparametric Approach John W. Fisher III, Alexander T. Ihler and mod- eling dynamic processes. The approach can learn a compact and informa- tive statistic which is characterized nonpara- metrically by a joint density over the learned statistic and present obser- vation. We
ERIC Educational Resources Information Center
Catley, Alan
2007-01-01
Following the announcement last year that there will be no more math coursework assessment at General Certificate of Secondary Education (GCSE), teachers will in the future be able to devote more time to preparing learners for formal examinations. One of the key things that the author has learned when teaching statistics is that it makes for far…
NSDL National Science Digital Library
Anderson-Cook, C.
This is a collection of applets regarding various topics in statistics. Topics include central limit theorem, probability distributions, hypothesis testing, power, confidence intervals, correlation, control charts, experimental design, data analysis, and regression. Each topic has a description page and links to one or more applets.
NSDL National Science Digital Library
Annis, Charles
A good resource for problems in statistics in engineering. Contains some applets, and good textual examples related to engineering. Some topics include Monte Carlo method, Central Limit Theorem, Risk, Logistic Regression, Generalized Linear Models, and Confidence. Overall, this is a well presented and good site for anyone interested in engineering or mathematics.
Statistical characterization of dislocation ensembles
El-Azab, A; Deng, J; Tang, M
2006-05-17
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.
Hauert, Christoph
Journal of Statistical Physics, Vol. 116, Nos. 5/6, September 2004 (© 2004) Of Dogs and Fleas the jumps of N fleas between two dogs. In each time step a single randomly selected flea jumps on the other dog. The more fleas there are on a dog, the more will jump off it. In the long time limit
Akira Ishikawa; Tetsuo Ogawa
2002-01-01
We study theoretically dynamics of the spinodal decomposition in finite-lifetime systems to clarify effects of the interparticle interactions beyond the Ginzburg-Landau-Wilson phenomenology. Our theory is based on the coarse-grained Hamiltonian derived from the interacting lattice-gas model with a finite lifetime. The information of a system is reduced to closed-form coupled integrodifferential equations for the single-point distribution function and the dynamical
Learning Statistics By Doing Statistics
NSDL National Science Digital Library
Smith, Gary
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.
NSDL National Science Digital Library
NRICH
2013-01-01
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.
E. Bogomolny; U. Gerland; C. Schmit
2000-12-04
We consider the statistical distribution of zeros of random meromorphic functions whose poles are independent random variables. It is demonstrated that correlation functions of these zeros can be computed analytically and explicit calculations are performed for the 2-point correlation function. This problem naturally appears in e.g. rank-one perturbation of an integrable Hamiltonian and, in particular, when a $\\delta$-function potential is added to an integrable billiard.
NSDL National Science Digital Library
2013-06-21
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.
This section of the BCSC web site details the information collected and used in research by the BCSC. Statistics includes charts and tables that provide an overview of the data collected. These data are used in a wide range of studies that evaluate the performance of mammography in community settings. Some studies analyze data collected from individual sites; others examine data pooled from two or more sites.
NASA Astrophysics Data System (ADS)
Goodman, Joseph W.
2000-07-01
The Wiley Classics Library consists of selected books that have become recognized classics in their respective fields. With these new unabridged and inexpensive editions, Wiley hopes to extend the life of these important works by making them available to future generations of mathematicians and scientists. Currently available in the Series: T. W. Anderson The Statistical Analysis of Time Series T. S. Arthanari & Yadolah Dodge Mathematical Programming in Statistics Emil Artin Geometric Algebra Norman T. J. Bailey The Elements of Stochastic Processes with Applications to the Natural Sciences Robert G. Bartle The Elements of Integration and Lebesgue Measure George E. P. Box & Norman R. Draper Evolutionary Operation: A Statistical Method for Process Improvement George E. P. Box & George C. Tiao Bayesian Inference in Statistical Analysis R. W. Carter Finite Groups of Lie Type: Conjugacy Classes and Complex Characters R. W. Carter Simple Groups of Lie Type William G. Cochran & Gertrude M. Cox Experimental Designs, Second Edition Richard Courant Differential and Integral Calculus, Volume I RIchard Courant Differential and Integral Calculus, Volume II Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume I Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume II D. R. Cox Planning of Experiments Harold S. M. Coxeter Introduction to Geometry, Second Edition Charles W. Curtis & Irving Reiner Representation Theory of Finite Groups and Associative Algebras Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume I Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume II Cuthbert Daniel Fitting Equations to Data: Computer Analysis of Multifactor Data, Second Edition Bruno de Finetti Theory of Probability, Volume I Bruno de Finetti Theory of Probability, Volume 2 W. Edwards Deming Sample Design in Business Research
Book Reviews Chaos and Coarse Graining in Statistical Mechanics.
Boehning, Dankmar
dynamics and statistical mechanics, but with a sharp and ever-present eye to the practicalities of applying of statistical mechanics. The discussion assumes a graduate-level understanding of statistical mechanics looking to expand their understanding of statisti- cal mechanics and dynamics from the basic
Statistical physics of temporal intermittency
Xiao-Jing Wang
1989-01-01
The thermodynamic formalism for dynamical systems is applied to a class of mappings of laminar-turbulent temporal intermittency. The corresponding statistical system is shown to be a lattice gas with many-body interactions of clustering type. This one-dimensional system bears a close analogy with the Fisher-Felderhof droplet model of condensation. The abnormal dynamic fluctuations give rise to a phase transition. The critical
J. Mark Heinzle; Claes Uggla
2012-12-21
In this paper we explore stochastical and statistical properties of so-called recurring spike induced Kasner sequences. Such sequences arise in recurring spike formation, which is needed together with the more familiar BKL scenario to yield a complete description of generic spacelike singularities. In particular we derive a probability distribution for recurring spike induced Kasner sequences, complementing similar available BKL results, which makes comparisons possible. As examples of applications, we derive results for so-called large and small curvature phases and the Hubble-normalized Weyl scalar.
Mitrikas, V G
2014-01-01
The on-going 24th solar cycle (SC) is distinguished from the previous ones by low activity. On the contrary, levels of proton fluxes from galactic cosmic rays (GCR) are high, which increases the proton flow striking the Earth's radiation belts (ERB). Therefore, at present the absorbed dose from ERB protons should be calculated with consideration of the tangible increase of protons intensity built into the model descriptions based on experimental measurements during the minimum between cycles 19 and 20, and the cycle 21 maximum. The absorbed dose from GCR and ERB protons copies galactic protons dynamics, while the ERB electrons dose copies SC dynamics. The major factors that determine the absorbed dose value are SC phase, ISS orbital altitude and shielding of the dosimeter readings of which are used in analysis. The paper presents the results of dynamic analysis of absorbed doses measured by a variety of dosimeters, namely, R-16 (2 ionization chambers), DB8-1, DB8-2, DB8-3, DB8-4 as a function of ISS orbit altitude and SC phase. The existence of annual variation in the absorbed dose dynamics has been confirmed; several additional variations with the periods of 17 and 52 months have been detected. Modulation of absorbed dose variations by the SC and GCR amplitudes has been demonstrated. PMID:25035897
Verification, Testing and Statistics
NASA Astrophysics Data System (ADS)
Rajamani, Sriram K.
Programming tools have expanded both in scope of the problems they solve, and in the kinds of techniques they use. Traditionally, programming tools have focused on detecting errors in programs. Recently, this scope has broadened to help with other programming tasks, including inferring specifications, helping diagnose root cause of errors during debugging, and managing knowledge in large projects. Also, traditionally programming tools have been based on either static or dynamic program analysis. Modern programming tools combine static and dynamic program analysis together with techniques from other disciplines such as statistical and probabilistic inference, and information retrieval. This paper reports on some such tools built by the Rigorous Software Engineering group at Microsoft Research India.
Covariant Equilibrium Statistical Mechanics
E. Lehmann
2006-02-25
A manifest covariant equilibrium statistical mechanics is constructed starting with a 8N dimensional extended phase space which is reduced to the 6N physical degrees of freedom using the Poincare-invariant constrained Hamiltonian dynamics describing the micro-dynamics of the system. The reduction of the extended phase space is initiated forcing the particles on energy shell and fixing their individual time coordinates with help of invariant time constraints. The Liouville equation and the equilibrium condition are formulated in respect to the scalar global evolution parameter which is introduced by the time fixation conditions. The applicability of the developed approach is shown for both, the perfect gas as well as the real gas. As a simple application the canonical partition integral of the monatomic perfect gas is calculated and compared with other approaches. Furthermore, thermodynamical quantities are derived. All considerations are shrinked on the classical Boltzmann gas composed of massive particles and hence quantum effects are discarded.
Chemistry 427f/1480f: Statistical Mechanics Prof. Jeremy Schofield
Schofield, Jeremy
Chemistry 427f/1480f: Statistical Mechanics Prof. Jeremy Schofield · Office: Lash Miller 420E/biological systems Reference Books: · Statistical Mechanics, by Donald A. McQuarrie (M) · Statistical Physics: Statics, Dynamics and Renormalization, L.P. Kadanoff (K) · Statistical Mechanics, T.L. Hill · A Modern
Department of Statistics STATISTICS COLLOQUIUM
of Texas at Austin Evidence that the Brain Codes a Scalar Variable with Diverse Populations of Continuous of representation and communication in the brain -- are forgetful and noisy. How does the brain overcome-dimensional continuous attractor dynamics in the brain. Simultaneously, I will describe how the same system clearly
Department of Statistics STATISTICS COLLOQUIUM
Stephens, Matthew
of a synapse from a single scalar to an entire dynamical system with many internal molecular functional states such theorems, we uncover a framework, based on first passage time theory, to impose an order on the internal email list, please visit the following website: https://lists.uchicago.edu/web/arc/statseminars. #12;
Zweimüller, Roland
Return-time statistics, Hitting-time statistics and Inducing Nicolai Haydn, Nicole Winterberg- formations, we prove that the limiting return-time statistics and hitting-time statistics persist if we pass of return-time and hitting-time distributions of small sets H in an ergodic probability-preserving dynamical
NASA Astrophysics Data System (ADS)
Graham, D. B.; Cairns, Iver H.; Skjaeraasen, O.; Robinson, P. A.
2012-02-01
The temperature ratio Ti/Te of ions to electrons affects both the ion-damping rate and the ion-acoustic speed in plasmas. The effects of changing the ion-damping rate and ion-acoustic speed are investigated for electrostatic strong turbulence and electromagnetic strong turbulence in three dimensions. When ion damping is strong, density wells relax in place and act as nucleation sites for the formation of new wave packets. In this case, the density perturbations are primarily density wells supported by the ponderomotive force. For weak ion damping, corresponding to low Ti/Te, ion-acoustic waves are launched radially outwards when wave packets dissipate at burnout, thereby increasing the level of density perturbations in the system and thus raising the level of scattering of Langmuir waves off density perturbations. Density wells no longer relax in place so renucleation at recent collapse sites no longer occurs, instead wave packets form in background low density regions, such as superpositions of troughs of propagating ion-acoustic waves. This transition is found to occur at Ti/Te ? 0.1. The change in behavior with Ti/Te is shown to change the bulk statistical properties, scaling behavior, spectra, and field statistics of strong turbulence. For Ti/Te>rsim0.1, the electrostatic results approach the predictions of the two-component model of Robinson and Newman, and good agreement is found for Ti/Te>rsim0.15.
Statistical Mechanics of Motorized Molecules
NASA Astrophysics Data System (ADS)
Prentis, Jeffrey
2002-03-01
We have designed a set of experiments that illustrate the basic principles of statistical mechanics, including the fundamental postulate, the ergodic hypothesis, and the canonical statistics. The experimental system is a granular fluid of "motorized molecules" (self-propelled balls). Mechanical properties are measured using motion sensors, force probes, and digital video. Statistical properties are determined by a dynamical probability - the fraction of time that the system spends in each state. Thermal properties are represented by time averages. The process by which statistical patterns appear in the mechanical data vividly illustrates how thermal order emerges from molecular chaos. The pV diagram of a gas of motorized molecules is obtained by monitoring the random force exerted by the molecules beating against a piston. Brownian motion is studied by monitoring the random walk of a Brownian cube in a fluid of self-propelled spheres. Canonical statistics is illustrated using a "Boltzmann machine" - a working dynamical model of a two-level quantum system in a temperature bath. Polymer statistics is illustrated using a granular polymer solution - a chain of ping-pong balls immersed in a solvent of motorized molecules.
NASA Technical Reports Server (NTRS)
Vangelder, B. H. W.
1978-01-01
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.
NASA Astrophysics Data System (ADS)
Reppas, A. I.; De Decker, Y.; Siettos, C. I.
2012-08-01
We show how different explicit statistical moment closures, including the mean field and the Kirkwood approximations as well as an Ursell-type expansion for the moments, compare with the equation-free approach in the case of a stochastic epidemic model evolving on Erd?s-Rényi networks. For illustration purposes we use a simple, discrete susceptible-infected-recovered stochastic model with a nonlinear recovering probability. For every closure scheme, we derive the corresponding macroscopic evolution equations and we construct the bifurcation diagrams with respect to the probability of infection. Finally, we construct the coarse-grained bifurcation diagram obtained with the equation-free method acting directly on the microscopic simulations, bypassing the derivation of explicit closures. We show that the equation-free approach captures the actual emergent nonlinear behavior and outperforms all the other explicit schemes.
Statistical ecology comes of age
Gimenez, Olivier; Buckland, Stephen T.; Morgan, Byron J. T.; Bez, Nicolas; Bertrand, Sophie; Choquet, Rémi; Dray, Stéphane; Etienne, Marie-Pierre; Fewster, Rachel; Gosselin, Frédéric; Mérigot, Bastien; Monestiez, Pascal; Morales, Juan M.; Mortier, Frédéric; Munoz, François; Ovaskainen, Otso; Pavoine, Sandrine; Pradel, Roger; Schurr, Frank M.; Thomas, Len; Thuiller, Wilfried; Trenkel, Verena; de Valpine, Perry; Rexstad, Eric
2014-01-01
The desire to predict the consequences of global environmental change has been the driver towards more realistic models embracing the variability and uncertainties inherent in ecology. Statistical ecology has gelled over the past decade as a discipline that moves away from describing patterns towards modelling the ecological processes that generate these patterns. Following the fourth International Statistical Ecology Conference (1–4 July 2014) in Montpellier, France, we analyse current trends in statistical ecology. Important advances in the analysis of individual movement, and in the modelling of population dynamics and species distributions, are made possible by the increasing use of hierarchical and hidden process models. Exciting research perspectives include the development of methods to interpret citizen science data and of efficient, flexible computational algorithms for model fitting. Statistical ecology has come of age: it now provides a general and mathematically rigorous framework linking ecological theory and empirical data. PMID:25540151
Quantum particles from classical statistics
C. Wetterich
2010-02-11
Quantum particles and classical particles are described in a common setting of classical statistical physics. The property of a particle being "classical" or "quantum" ceases to be a basic conceptual difference. The dynamics differs, however, between quantum and classical particles. We describe position, motion and correlations of a quantum particle in terms of observables in a classical statistical ensemble. On the other side, we also construct explicitly the quantum formalism with wave function and Hamiltonian for classical particles. For a suitable time evolution of the classical probabilities and a suitable choice of observables all features of a quantum particle in a potential can be derived from classical statistics, including interference and tunneling. Besides conceptual advances, the treatment of classical and quantum particles in a common formalism could lead to interesting cross-fertilization between classical statistics and quantum physics.
Statistical Properties of Cosmological Billiards
Damour, Thibault
2010-01-01
Belinski, Khalatnikov and Lifshitz (BKL) pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a space-like singularity. We show how the use of a ``cosmological billiard'' description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the ``Kasner circle'' which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics o...
... Act and Program National Statistics (MQSA) MQSA National Statistics Share Tweet Linkedin Pin it More sharing options ... Scorecard, we present the most commonly requested national statistics regarding the MQSA program. These statistics are updated ...
Statistics 5126 Introduction to Applied Statistics
Barbu, Adrian
-0218 Office: 308 BIO UNIT 1 Office Hours: T/R 3:00-4:00pm Textbook: Probability and Statistics With R, Ugarte to confidently carry out statistical analyses using the R system. Prerequisite: One of STA 2122, 2171, 3032, 4322Statistics 5126 Introduction to Applied Statistics Fall 2012 Course Information Class Meeting Time
Atomic line filter for SDI applications
NASA Astrophysics Data System (ADS)
Menders, Jim; Bloom, S. H.; Korevaar, Eric; Rivers, M.; Liu, C. S.
1994-04-01
When optical signals are embedded in background noise, narrowband optical filters are needed for receivers to achieve quantum limited performance. Such is typically the case with daytime optical communications and lidar. Narrowband filtered detectors. with acceptance bands of just a few picometers (pm) and high out of band rejection are well suited for these applications. The main thrust of this program has been the development of two means for narrowband detection: the Fast Atomic Line Filter/Field Ion Detector (FALF/FID) and the Faraday magneto-optic filter. The FALF/FIDs transduce optical radiation within a narrow band directly into electrical signals. They are laser pumped filters based on the spectroscopy of atomic vapors. We designed, built and tested an infrared FALF/FID with an rise time of under 10 ns and a quantum efficiency of greater than 25%. Faraday filters are imaging magneto-optic filters with passbands of a few pm. Faraday filters with passbands in the visable and the near infra-red were constructed and tested. Transmission spectra were measured, and found to agree closely with theoretical predictions. Both of these narrowband detection schemes must be used in conjunction with a tuned narrowband laser source. We developed a frequency locked alexandrite laser designed to match the acceptance band of a rubidium based filter. Finally, a preliminary demonstration of a laser interrogator using a tuned infrared diode laser in conjunction with a filtered receiver was demonstrated.
Atomic line filter for SDI applications
Jim Menders; S. H. Bloom; Eric Korevaar; M. Rivers; C. S. Liu
1994-01-01
When optical signals are embedded in background noise, narrowband optical filters are needed for receivers to achieve quantum limited performance. Such is typically the case with daytime optical communications and lidar. Narrowband filtered detectors. with acceptance bands of just a few picometers (pm) and high out of band rejection are well suited for these applications. The main thrust of this
NASA Astrophysics Data System (ADS)
Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed
2013-04-01
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.
Statistical dependency in visual scanning
NASA Technical Reports Server (NTRS)
Ellis, Stephen R.; Stark, Lawrence
1986-01-01
A method to identify statistical dependencies in the positions of eye fixations is developed and applied to eye movement data from subjects who viewed dynamic displays of air traffic and judged future relative position of aircraft. Analysis of approximately 23,000 fixations on points of interest on the display identified statistical dependencies in scanning that were independent of the physical placement of the points of interest. Identification of these dependencies is inconsistent with random-sampling-based theories used to model visual search and information seeking.
The University of Chicago Department of Statistics
Stephens, Matthew
Department of Statistics The University of Chicago Capacity Analysis of Attractor Neural Networks with Binary) experiments, the attractor states of neural network dynamics are considered to be the un- derlying mechanism of inhibition, the dynamics can be stabilized, especially when the coding levels of patterns varies
NASA Astrophysics Data System (ADS)
Moreira, Antonio Jose De Araujo
Soybean, Glycine max (L.) Merr., is an important source of oil and protein worldwide, and soybean cyst nematode (SCN), Heterodera glycines, is among the most important yield-limiting factors in soybean production worldwide. Early detection of SCN is difficult because soybean plants infected by SCN often do not exhibit visible symptoms. It was hypothesized, however, that reflectance data obtained by remote sensing from soybean canopies may be used to detect plant stress caused by SCN infection. Moreover, reflectance measurements may be related to soybean growth and yield. Two field experiments were conducted from 2000 to 2002 to study the relationships among reflectance data, quantity and quality of soybean yield, and SCN population densities. The best relationships between reflectance and the quantity of soybean grain yield occurred when reflectance data were obtained late August to early September. Similarly, reflectance was best related to seed oil and seed protein content and seed size when measured during late August/early September. Grain quality-reflectance relationships varied spatially and temporally. Reflectance measured early or late in the season had the best relationships with SCN population densities measured at planting. Soil properties likely affected reflectance measurements obtained at the beginning of the season and somehow may have been related to SCN population densities at planting. Reflectance data obtained at the end of the growing season likely was affected by early senescence of SCN-infected soybeans. Spatio-temporal aspects of SCN population densities in both experiments were assessed using spatial statistics and regression analyses. In the 2000 and 2001 growing seasons, spring-to-fall changes in SCN population densities were best related to SCN population densities at planting for both experiments. However, within-season changes in SCN population densities were best related to SCN population densities at harvest for both experiments in 2002. Variograms were fitted to the data to describe the spatial characteristics of SCN population densities in both fields at planting and at harvest from 2000 to 2003 and these parameters varied within seasons and during overwinter periods in both experiments. Distinct relationships between temporal and spatial changes in SCN population densities were not detected.
Statistical Ensemble of Large Eddy Simulations
NASA Technical Reports Server (NTRS)
Carati, Daniele; Rogers, Michael M.; Wray, Alan A.; Mansour, Nagi N. (Technical Monitor)
2001-01-01
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.
Ng, Chung-Sang
9/6/10 9:41 PMAPS -51st Annual Meeting of the APS Division of Plasma Physics - Event -...onal Heating: Unsteady Dynamics and Scaling in Statistical Steady State Page 1 of 2http://meetings.aps.org/Meeting/DPP09/Event/109258 Bulletin of the American Physical Society 51st Annual Meeting of the APS Division
NASA Astrophysics Data System (ADS)
Passarelli, L.; Rivalta, E.; Maccaferri, F.; Aoki, Y.
2012-04-01
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.
Statistical physics ""Beyond equilibrium
Ecke, Robert E
2009-01-01
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.
The Importance Statistics Education
Utts, Jessica
strategies, and so on GAISE Report #12;Common Core for grades K to 5 Use data displays to ask and answerThe Importance of Statistics Education Professor Jessica Utts Department of Statistics University examples of statistical decisions in daily life why statistics education matters Introducing Statistics
FISHERY STATISTICS UNITED STATES
FISHERY STATISTICS OF THE UNITED STATES 1972 STATISTICAL DIGEST NO. 66 Prepared by STATISTICS;ACKNOWLEDGMENTS The data in this edition of "Fishery Statistics of the United States" were collected in co- operation with the various States and tabulated by the staff of the Statistics and Market News Division
Statistics Poker: Reinforcing Basic Statistical Concepts
ERIC Educational Resources Information Center
Leech, Nancy L.
2008-01-01
Learning basic statistical concepts does not need to be tedious or dry; it can be fun and interesting through cooperative learning in the small-group activity of Statistics Poker. This article describes a teaching approach for reinforcing basic statistical concepts that can help students who have high anxiety and makes learning and reinforcing…
Mark Levene; Alexandra Poulovassilis
2002-01-01
The global usage and continuing exponential growth of the World-Wide-Web poses a host of challenges to the research community. In particular, there is an urgent need to understand and manage the dynamics of the Web, in order to develop new techniques which will make the Web tractable. We provide an overview of recent statistics relating to the size of the
NASA Astrophysics Data System (ADS)
Spera, F. J.; Martin, B.; Creamer, J. B.; Nevins, D.; Cutler, I.; Ghiorso, M. S.; Tikunoff, D.
2010-12-01
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.
... at NIMH News About Us Home > Health & Education Statistics Prevalence Disability Suicide Cost Global More Prevalence Disability ... those affected receive treatment. The information on these statistics pages includes the best statistics currently available on ...
Neuroendocrine Tumor: Statistics
... Statistics Request Permissions Print to PDF Neuroendocrine Tumor: Statistics Approved by the Cancer.Net Editorial Board , 04/ ... nodes or distant parts of the body. Survival statistics should be interpreted with caution. These estimates are ...
Department of Statistical Science
Keinan, Alon
Corporate Strategy Manager Senior Data Analyst Statistician Risk Analyst Statistical Modeler Consulting Joslin Diabetes Center LG Electronics Monsanto Risk Management Solutions Samsung Insurance (3) Statistics
Statistical properties of cosmological billiards
Damour, Thibault; Lecian, Orchidea Maria
2011-02-15
Belinski, Khalatnikov, and Lifshitz pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a spacelike singularity. We show how the use of a 'cosmological billiard' description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the 'Kasner circle' which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics of the Bianchi-IX (a, b, c or mixmaster) model; (ii) its quotienting by the group of permutations of (a, b, c); and (iii) the billiard dynamics that arose in recent studies suggesting the hidden presence of Kac-Moody symmetries in cosmological billiards.
Statistical Properties of Cosmological Billiards
Thibault Damour; Orchidea Maria Lecian
2011-02-28
Belinski, Khalatnikov and Lifshitz (BKL) pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a space-like singularity. We show how the use of a "cosmological billiard" description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the "Kasner circle" which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics of the Bianchi IX (a, b, c or mixmaster) model; (ii) its quotienting by the group of permutations of (a, b, c); and (iii) the billiard dynamics that arose in recent studies suggesting the hidden presence of Kac-Moody symmetries in cosmological billiards.
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.
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.
Physics 630 Statistical Physics
Kioussis, Nicholas
Physics 630 Statistical Physics Spring 2005 Logistics Lecture Room: 1100 (Science I, 1st floor strongly the issue of problem solving and understanding of the main concepts in Statistical Physics and Statistical Mechanics at 430 level Textbook Statistical Mechanics, by Kerson Huang, Wiley, 2nd Edition
Accelerated molecular dynamics methods
Perez, Danny [Los Alamos National Laboratory
2011-01-04
The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.
Statistical Applets: Animated Exercise
NSDL National Science Digital Library
Duckworth, William
This collection of statistical applets is designed to accompany the textbook, "Practice of Business Statistics." The applets can be used without the textbook and cover many introductory statistics concepts including mean, normal curve, correlation and regression, probability, the law of large numbers, the central limit theorem, confidence intervals, statistical significance, power, and ANOVA. This is a great collection of interactive materials for either instructors or students studying statistics.
Principles of statistical mechanics of random networks
S. N. Dorogovtsev; J. F. F. Mendes; A. N. Samukhin
2002-12-29
We develop a statistical mechanics approach for random networks with uncorrelated vertices. We construct equilibrium statistical ensembles of such networks and obtain their partition functions and main characteristics. We find simple dynamical construction procedures that produce equilibrium uncorrelated random graphs with an arbitrary degree distribution. In particular, we show that in equilibrium uncorrelated networks, fat-tailed degree distributions may exist only starting from some critical average number of connections of a vertex, in a phase with a condensate of edges.
Statistical dynamics of early river networks
NASA Astrophysics Data System (ADS)
Wang, Xu-Ming; Wang, Peng; Zhang, Ping; Hao, Rui; Huo, Jie
2012-10-01
Based on local erosion rule and fluctuations in rainfall, geology and parameters of a river channel, a generalized Langevin equation is proposed to describe the random prolongation of a river channel. This equation is transformed into the Fokker-Plank equation to follow the early evolution of a river network and the variation of probability distribution of channel lengths. The general solution of the equation is in the product form of two terms. One term is in power form and the other is in exponent form. This distribution shows a complete history of a river network evolving from its infancy to “adulthood”). The infancy is characterized by the Gaussian distribution of the channel lengths, while the adulthood is marked by a power law distribution of the channel lengths. The variation of the distribution from the Gaussian to the power law displays a gradual developing progress of the river network. The distribution of basin areas is obtained by means of Hack's law. These provide us with new understandings towards river networks.
Teaching Introductory Statistics: From dull to Dynamic!
Utts, Jessica
public service announcements help change behavior (smoking, safe-sex, etc) Deciding whether building personal decisions, like: What to eat to remain healthy Cost versus benefit for lifestyle changes (exercise, meditation, taking an aspirin a day, night-lights for children) As intelligent, curious beings, we want
Statistical Learning Theory of Protein Dynamics
Haas, Kevin
2013-01-01
diffusion constant D[153] because CHAPTER 5. INFORMATION THERMODYNAMICSthermodynamics formulation which works in the space of ? and the logarithm of diffusiondiffusion constant from single- molecule FRET. The framework of information thermodynamics
STATISTICAL THINKING IN NEUROSCIENCE Department of Statistics
Spirtes, Peter
for Statistics in Neuroscience #12;Report of ASA Working Group on Statistics and Brain of the properties of vision hat are familliar to us from behavioral xperiments on animnals, from psycho- hysical, from the laterial eye of Limtlol/is, stimulated by illumination of the facet aissociated with its
Statistical theory of cubic Langmuir turbulence
NASA Technical Reports Server (NTRS)
Sun, G.-Z.; Nicholson, D. R.; Rose, H. A.
1985-01-01
The cubic direct interaction approximation is applied to a truncated (in Fourier space) version of the cubically nonlinear Schroedinger equation model of Langmuir physics. The results are compared (in the three-mode case) to those for an ensemble of numerical solutions of the dynamical equations with 10,000 different sets of Gaussianly distributed initial conditions. In the undriven, undamped case, the statistical theory (but not the ensemble) evolves to a state of thermal equilibrium. In the driven, damped case, the statistical theory appears to evolve to a state close to that corresponding to one of the limit cycles of the dynamical equations.
Quantum Statistical Processes in the Early Universe
B. L. Hu
1993-02-22
We show how the concept of quantum open system and the methods in non-equilibrium statistical mechanics can be usefully applied to studies of quantum statistical processes in the early universe. We first sketch how noise, fluctuation, dissipation and decoherence processes arise in a wide range of cosmological problems. We then focus on the origin and nature of noise in quantum fields and spacetime dynamics. We introduce the concept of geometrodynamic noise and suggest a statistical mechanical definition of gravitational entropy. We end with a brief discussion of the theoretical appropriateness to view the physical universe as an open system.
A statistical mechanical problem?
Costa, Tommaso; Ferraro, Mario
2014-01-01
The problem of deriving the processes of perception and cognition or the modes of behavior from states of the brain appears to be unsolvable in view of the huge numbers of elements involved. However, neural activities are not random, nor independent, but constrained to form spatio-temporal patterns, and thanks to these restrictions, which in turn are due to connections among neurons, the problem can at least be approached. The situation is similar to what happens in large physical ensembles, where global behaviors are derived by microscopic properties. Despite the obvious differences between neural and physical systems a statistical mechanics approach is almost inescapable, since dynamics of the brain as a whole are clearly determined by the outputs of single neurons. In this paper it will be shown how, starting from very simple systems, connectivity engenders levels of increasing complexity in the functions of the brain depending on specific constraints. Correspondingly levels of explanations must take into account the fundamental role of constraints and assign at each level proper model structures and variables, that, on one hand, emerge from outputs of the lower levels, and yet are specific, in that they ignore irrelevant details. PMID:25228891
Nonuniversality in level dynamics
Kunstman, P.; Zyczkowski, K.; Zakrzewski, J.
1997-03-01
Statistical properties of parametric motion in ensembles of Hermitian banded random matrices are studied. We analyze the distribution of level velocities and level curvatures as well as their correlation functions in the crossover regime between three universality classes. It is shown that the statistical properties of level dynamics are in general {ital nonuniversal} and strongly depend on the way in which the parametric dynamics is introduced. {copyright} {ital 1997} {ital The American Physical Society}
Statistics for Chemists: Exercises
NSDL National Science Digital Library
Wehrens, Ron
This website contains a group of exercises that allow students to practice basic statistical calculations for descriptive statistics, confidence intervals, hypothesis tests, regression and experimental design. The exercises are interactive and provide feedback for students who submit wrong answers.
Interpreting Accident Statistics
Ferreira, Joseph Jr.
Accident statistics have often been used to support the argument that an abnormally small proportion of drivers account for a large proportion of the accidents. This paper compares statistics developed from six-year data ...
... Blood > Blood Facts and Statistics Printable Version Blood Facts and Statistics Facts about blood needs Facts about ... donors Facts about American Red Cross Blood Services Facts about blood needs Every two seconds someone in ...
Immigration and Naturalization Statistics
NSDL National Science Digital Library
United States. Immigration and Naturalization Service.
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."
Pneumocystis Pneumonia Statistics
... CDC.gov . Fungal Diseases Share Compartir Pneumocystis pneumonia Statistics Before the beginning of the HIV/AIDS epidemic ... Risk & Prevention Sources Diagnosis & Testing Treatment Health Professionals Statistics More Resources Blastomycosis Definition Symptoms People at Risk & ...
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 ...
... Research AMIGAS Fighting Cervical Cancer Worldwide Stay Informed Statistics for Other Kinds of Cancer Breast Cervical Colorectal ( ... Skin Vaginal and Vulvar Cancer Home Uterine Cancer Statistics Language: English Español (Spanish) Recommend on Facebook Tweet ...
Statistical Parametric Speech Synthesis
Cortes, Corinna
Statistical Parametric Speech Synthesis Heiga Zen Google June 9th, 2014 #12;Outline Background HMM-based statistical parametric speech synthesis (SPSS) Flexibility Improvements Statistical parametric speech synthesis with neural networks Deep neural network (DNN)-based SPSS Deep mixture density network (DMDN
NSDL National Science Digital Library
Wehrens, R.
This site is a comprehensive resource on statistics, including information on descriptive statistics, confidence intervals, hypothesis testing, regression, ANOVA, experimental design, and multivariate statistics. Web-based exercises are interspersed throughout the text, allowing students to practice what they are learning and to obtain immediate feedback.
Minnesota Health Statistics 1988.
ERIC Educational Resources Information Center
Minnesota State Dept. of Health, St. Paul.
This document comprises the 1988 annual statistical report of the Minnesota Center for Health Statistics. After introductory technical notes on changes in format, sources of data, and geographic allocation of vital events, an overview is provided of vital health statistics in all areas. Thereafter, separate sections of the report provide tables…
NSDL National Science Digital Library
Panchenko, Dmitry
Dmitry Panchenko of the Massachusetts Institute of Technology is an undergraduate course in Statistics for Applications. The site features lecture notes, a syllabus and assignments. Course topics include hypothesis testing and estimation, confidence intervals, chi-square tests, nonparametric statistics, analysis of variance, regression and correlation. This is a nice example of a course structure for an applied statistics course.
Department of Mathematics & Statistics
Sorin, Eric J.
in mathematics and statistics for graduate students who will use that training professionally as mathematiciansDepartment of Mathematics & Statistics Program Review Self-Study Report June 2006 #12;Table..........................................72 Appendix 6..........................................82 #12;Department of Mathematics & Statistics Self
MATHMATICS & APPLIED STATISTICS
Frey, Jesse C.
MATHMATICS & APPLIED STATISTICS Graduate Studies in Build Your Future with Graduate Study in Mathematics or Applied Statistics Our graduate programs can help you advance your career in education will deepen your knowledge and prepare you for further study. The Master of Science in Applied Statistics
NSDL National Science Digital Library
Swift, J.
Created by J. Swift of the Royal Statistical Society, this article describes an exercise, probability and statistics, which develops a statistic that measures the variety of noun usage in order to distinguish two authors. The exercise emphasizes the use of frequency.
J. M. Harrison; J. P. Keating; J. M. Robbins
2011-01-01
Quantum graphs are commonly used as models of complex quantum systems, for example molecules, networks of wires, and states of condensed matter. We consider quantum statistics for indistinguishable spinless particles on a graph, concentrating on the simplest case of abelian statistics for two particles. In spite of the fact that graphs are locally one-dimensional, anyon statistics emerge in a generalized
Oldford, R.W.
STATISTICS, SCIENCE AND PUBLIC POLICY RECOMMENDATIONS FOR GOVERNMENT AND THE SCIENTIFIC COMMUNITY Review of Conferences on Statistics, Science and Public Policy Held at Herstmonceux Castle, Hailsham, U;#12;Executive Summary Science, including statistics, is fundamental to the society in which we live. It forms
Statistical mechanics of violent relaxation
NASA Technical Reports Server (NTRS)
Spergel, David N.; Hernquist, Lars
1992-01-01
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.
Statistical Properties of Online Auctions
NASA Astrophysics Data System (ADS)
Namazi, Alireza; Schadschneider, Andreas
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.
The Statistical Mechanics of Zombies
NASA Astrophysics Data System (ADS)
Alemi, Alexander A.; Bierbaum, Matthew; Myers, Christopher R.; Sethna, James P.
2015-03-01
We present results and analysis from a large scale exact stochastic dynamical simulation of a zombie outbreak. Zombies have attracted some attention lately as a novel and interesting twist on classic disease models. While most of the initial investigations have focused on the continuous, fully mixed dynamics of a differential equation model, we have explored stochastic, discrete simulations on lattices. We explore some of the basic statistical mechanical properties of the zombie model, including its phase diagram and critical exponents. We report on several variant models, including both homogeneous and inhomogeneous lattices, as well as allowing diffusive motion of infected hosts. We build up to a full scale simulation of an outbreak in the United States, and discover that for `realistic' parameters, we are largely doomed.
Shalabh Gupta; Dheeraj S. Singh; Asok Ray
2008-01-01
This paper addresses online monitoring of fatigue damage in polycrystalline alloy structures based on statistical pattern analysis of ultrasonic sensor signals. The real-time data-driven method for fatigue damage monitoring is based on the concepts derived from statistical mechanics, symbolic dynamics and statistical pattern identification. The underlying concept is detection and identification of small changes in statistical patterns of ultrasonic data
Statistical physics, seismogenesis, and seismic hazard
Ian Main
1996-01-01
The scaling properties of earthquake populations show remarkable similarities to those observed at or near the critical point of other composite systems in statistical physics. This has led to the development of a variety of different physical models of seismogenesis as a critical phenomenon, involving locally nonlinear dynamics, with simplified rheologies exhibiting instability or avalanche-type behavior, in a material composed