Future directions for SDI development
NASA Astrophysics Data System (ADS)
Rajabifard, Abbas; Feeney, Mary-Ellen F.; Williamson, Ian P.
2002-08-01
Understanding the role of spatial data infrastructure (SDI) in the society is important to acceptance of the concept and its alignment with spatial industry objectives. Much has been done to describe and understand the components and operation of different aspects of SDIs and their integration into the spatial data community. However, what is often miss-understood is that the role SDI plays is by necessity greater than the sum of individual components of SDI and stakeholder groups. SDI is fundamentally about facilitation and coordination of the exchange and sharing of spatial data between stakeholders in the spatial data community. To this end, the authors propose that the roles of SDI have been pursued through two different approaches: product- and process-based. Both approaches have value, but contribute to the evolution, uptake and utilization of the SDI concept in different ways. They provide different frameworks for dealing with SDI mandates for the objectives of spatial data access and sharing. This paper reviews the nature and concept of SDI, including the components, which have helped to build the current understanding about the importance of an infrastructure to support the interactions of the spatial data community. Several examples of how SDIs have been described are offered to aid understanding of their complexity. The need for descriptions to represent the discrepancies between the role and deliverables of an SDI, and thus, contribute to a simpler, but dynamic, understanding of the complexity of the SDI concept, are postulated. The transition between the understanding of SDIs from product-based to process-based approaches is investigated, with a review of the positions taken by current SDI initiatives throughout the world. A model of how these approaches provide a framework to meet the mandates of the relevant jurisdictions is proposed, and factors contributing to the success of such positions in the future are discussed.
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.
Graybeal, S.N.
1988-01-01
This article analyses compatibility and conflict between the SDI research program and the ABM Treaty; includes a scenario for managing conflicts that may arise from SDI technological advances and research.
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.
DeWolf, H.G.
1989-11-01
President Reagan's Strategic Defense Initiative, or SDI, and the pursuit of defenses to protect against ballistic missile attack are issues of significant debate. Some praise the proposal, first made in a presidential address to the nation on 23 March 1983, as a grand vision that will abolish nuclear blackmail by adopting a totally defensive posture. Others condemn it as being destabilizing, a Pandora's box of strategic transition that could precipitate armed conflict.
Nitze, P.H.
1985-01-01
Because of fixed preconceptions or erroneous assumptions, this is an attempt by Mr. Nitze, mostly, to clarify the background and rationale for SDI. After discussing briefly the three factors that led to the President's decision in early 1983 to launch SDI, he emphasizes that SDI is a research program that is investigating the feasibility of new defense technologies, both earth- and space-based. Further, he emphasizes what SDI is not: (1) a deployment program, but research only; (2) an attempt of the US to obtain superiority; and (3) designed to produce a regime that would replace deterrence, but rather to shift its means.
Statistical Mechanics of Dynamical Systems
NASA Astrophysics Data System (ADS)
Mori, H.; Hata, H.; Horita, T.; Kobayashi, T.
A statistical-mechanical formalism of chaos based on the geometry of invariant sets in phase space is discussed to show that chaotic dynamical systems can be treated by a formalism analogous to that of thermodynamic systems if one takes a relevant coarse-grained quantity, but their statistical laws are quite different from those of thermodynamic systems. This is a generalization of statistical mechanics for dealing with dissipative and hamiltonian (i.e., conservative) dynamical systems of a few degrees of freedom. Thus the sum of the local expansion rate of nearby orbits along relevant orbit over a long but finite time has been introduced in order to describe and characterize (1) a drastic change of the structure of a chaotic attractor at a bifurcation and anomalous phenomena associated, (2) a critical scaling of chaos in the neighborhood of a critical point for the bifurcation to a nonexotic state, and a self-similar temporal structure of a critical orbit on the critical 2^∞ attractor an the critical golden tori without mixing, (3) the critical KAM torus, diffusion and repeated sticking of a chaotic orbit to a critical torus in hamiltonian systems. Here a q-phase transition, analogous to the ferromagnetic phase transition, plays an important role. They are illustrated numerically and theoretically by treating the driven damped pendulum, the driven Duffing equation, the Henon map, and the dissipative and conservative standard maps. This description of chaos breaks the time-reversal symmetry of hamiltonian dynamical laws analogously to statistical mechanics of irreversible processes. The broken time-reversal symmetry is brought about by orbital instability of chaos.
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.
ERIC Educational Resources Information Center
Burton, Hilary D.
1973-01-01
A large-scale selective dissemination of information (SDI) system which is in operation at the Agricultural Research Service is described. The unique characteristic of this system is that the users develop and modify their own profiles. The implications of this user-dependent approach for information system planners are discussed. (2 references)…
Application of SDI technology in space propulsion
Klein, A.J.
1992-01-01
Numerous technologies developed by the DOD within the SDI program are now available for adaptation to the requirements of commercial spacecraft; SDI has accordingly organized the Technology Applications Information System data base, which contains nearly 2000 nonproprietary abstracts on SDI technology. Attention is here given to such illustrative systems as hydrogen arcjets, ammonia arcjets, ion engines, SSTO launch vehicles, gel propellants, lateral thrusters, pulsed electrothermal thrusters, laser-powered rockets, and nuclear propulsion.
ERIC Educational Resources Information Center
Watson, Michael; And Others
1997-01-01
Library staff at Louisiana State University Medical Center in Shreveport have written two computer programs automating much of its selective dissemination of information (SDI) postprocessing. The software sorts SDI results, gathers and reports statistical data without requiring manual data entry, allows delivery of search results as hard copy or…
NASP and SDI Spearhead CFD Developments
NASA Technical Reports Server (NTRS)
Mehta, Unmeel B.
1992-01-01
The National Aerospace Plane (NASP) program's purpose, as stated by the National Space Council, is to "develop and demonstrate hypersonic technologies with the ultimate goal of single stage to orbit." The council has also directed that "performance of the experimental flight vehicle will be constrained to the minimum necessary to meet the highest priority research, as opposed to operational objectives .... The program will be conducted in such a way as to minimize technical and cost uncertainty associated with the experimental vehicle." The purpose of the Strategic Defense Initiative (SDI), as defined by President Bush, is "...protection from limited ballistic missile strikes, whatever their source." Computational fluid dynamics (CFD) plays a vital role in both endeavors.
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.
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
Perspective: chemical dynamics simulations of non-statistical reaction dynamics.
Ma, Xinyou; Hase, William L
2017-04-28
Non-statistical chemical dynamics are exemplified by disagreements with the transition state (TS), RRKM and phase space theories of chemical kinetics and dynamics. The intrinsic reaction coordinate (IRC) is often used for the former two theories, and non-statistical dynamics arising from non-IRC dynamics are often important. In this perspective, non-statistical dynamics are discussed for chemical reactions, with results primarily obtained from chemical dynamics simulations and to a lesser extent from experiment. The non-statistical dynamical properties discussed are: post-TS dynamics, including potential energy surface bifurcations, product energy partitioning in unimolecular dissociation and avoiding exit-channel potential energy minima; non-RRKM unimolecular decomposition; non-IRC dynamics; direct mechanisms for bimolecular reactions with pre- and/or post-reaction potential energy minima; non-TS theory barrier recrossings; and roaming dynamics.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.
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…
Automated SDI Service Using CDROM Databases.
ERIC Educational Resources Information Center
Herala, M. Krishnananda; And Others
1995-01-01
Discusses the benefits of using bibliographic databases on CD-ROM for SDI (selective dissemination of information) in developing countries like India, and describes a method of running an SDI service automatically using two Terminate and Stay Resident (TSR) software programs called Stackey and Batutil. (Author/LRW)
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…
Nonequilibrium transient dynamics of photon statistics
NASA Astrophysics Data System (ADS)
Ali, Md. Manirul; Zhang, Wei-Min
2017-03-01
We investigate the transient dynamics of photon statistics through two-time correlation functions for optical field coupled to a non-Markovian environment, described by the Fano-type Hamiltonian. We exactly solve the time-evolution of an initially nonclassical state which exhibits photon antibunching. We find that the transient correlations at different times t yield a smooth transition from antibunching to bunching photon statistics in the weak system-environment coupling regime. In the strong-coupling regime, the two-time correlations exhibit oscillations that persists both in the transient process and in the steady-state limit. The oscillatory behavior of photon statistics is a manifestation of strong non-Markovian memory dynamics where the system remains in nonequilibrium from its environment. We also find that the antibunching-to-bunching transition in the weak-coupling regime and the photon statistical oscillations in the strong-coupling regime are strongly influenced by the environment temperature.
INSPEC SDI Investigation, 1967-1969. Volume III.
ERIC Educational Resources Information Center
Clague, P.
The third volume of this five volume study of the INSPEC SDI system contains: Recall performance of SDI profiles; Assessment of the Recall performance of the SDI system in relation to particularly valuable articles; Subjective assessment of the SDI system Recall performance; Relation between Precision performance of the system and document…
Particle size statistics in dynamic fragmentation
Grady, D.E. )
1990-12-15
Condensed matter, when subjected to intense disrupting forces through impact or radiation deposition, will break up into a randomly distributed array of fragments. An earlier analysis of random fragmentation is extended to account for fragmentation in bodies which are finite in extent and for bodies within which the minimum fragment size is bounded. The statistical fragment size relations are compared with molecular dynamic simulations of dynamic fragmentation, with fragmentation caused by the high-energy collision of nuclear particles, and with the distribution of galaxies in the universe which are assumed to be fragment debris from the primordial Big Bang.
SDI (Strategic Defense Initiative): Myth or reality
Canavan, G.H.
1988-06-01
This report reviews previous attempts to develop strategic defenses, the technologies currently under consideration by the Strategic Defense Initiative (SDI), their main unknowns, and the likely performance of strategic defense concepts against evolving threats. 47 refs.
Technology Applications Program, SDI, Strategic Defense Initiative
2007-11-02
6. Developments in High-Energy Physics Used for Cancer Therapy 15 C. SDI SPINOFFS IN COMPUTER TECHNOLOGY j5 1. Introduction 2. A New Generation...materi- als for thermal and photochemical reactions and by biophysicists to study the physiological responses of biological materials. 3...research; eye surgery; materials that produce lighter, stronger leg braces; and cancer therapy . 2. Lasers in Medicine SDI laser work is yielding
ERIC Educational Resources Information Center
Hoshovsky, Alexander G.
The impetus for the nation-wide study of SDI (Selective Dissemination of Information) came from the desire to learn more about the options available for the application of the SDI concept prior to decisions about its possible use in Air Force research and development activities. For this purpose, data on user populations, literature coverage,…
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 spinoffs: research now, standards later
Smith, T.K. Jr.
1986-04-01
A major benefit of the Strategic Defense Initiative (SDI) its is potential for technological spinoffs. The lack of a consistent answer on the feasibility of developing an effective ballistic missile defense system may force Congress to look at the possible spinoffs in order to make a funding decision on SDI. Spinoffs have historically played an important role in providing industry with commercial applications, but there are also a number of unattractive aspects: unpredictability and possible suppression for national security reasons. Edward Teller is among those who promote X-ray lasers, while others support gamma-ray laser research. The possibility of SDI technology and spinoffs gives scientists and engineers a chance to participate in the development of new standards. 7 references.
The economic common sense of SDI
Graham, D.O. )
1990-01-01
The present development history and current status evaluation of the economic viability of SDI technologies suggests that much of the exaggeration of SDI costs has been due to an effort of the part of the program's opponents to consider only the most exotic, and commensurately expensive, options for orbital missile defense. It is noted that, by contrast, extraordinary advancements in microelectronics have made possible the creation of 20-100 lb devices which detect hostile missile launches, calculate the paths of enemy missiles and warheads through space, and fly to pinpoint accuracy to intercept targets and destroy them by means of high-speed collision. This 'Brilliant Pebbles' scheme has reduced the cost of an effective SDI system to below 25 billion.
Operational Results of an Adaptive SDI System.
ERIC Educational Resources Information Center
Sage, C. R.; Fitzwater, D. R.
The Ames Laboratory SDI system requires a minimum of human intervention. The adaptability of the system provides two major contributions to information dissemination. (1) The user benefits proportionately from the amount of effort he expends in setting up his profile and the diligence in sending back responses. (2) The document input has only to…
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.
Automated SDI Services. (Selective Dissemination of Information).
ERIC Educational Resources Information Center
Altmann, Berthold
An automated SDI service based on tapes supplied by DDC, Science Abstracts, and Engineering Index is evaluated as a component element of the entire HDL information system. Current studies for improving the efficiency are briefly described,--in particular, the establishment of a parameter reference service that should shorten the lead-time for the…
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 engaged…
The origins of SDI, 1944--1983
Baucom, D.R.
1992-01-01
The most distinctive and important contribution of this new book on the Strategic Defense Initiative is that it ends where most other studies begin, with President Ronald Reagan's famous (or infamous, depending on one's perspective) March 1983 speech that introduced the Star Wars concept. In taking this approach, Donald R. Baucom - a former Air Force historian who has been the official historian who has been the official historian of the Strategic Defense Initiative Organization since May 1987 - helps to correct the common misperception that US efforts in strategic defense began and ended with the SDI. Although Baucom tells us that The Origins of SDI is a significantly revised version of an SDIO study he completed in 1989, representing his own views and not those of the SDIO, the reader should be warned that the book reads like an official history. It is often dry or too episodic and offers little that is new in the way of analysis or interpretation.
Small SDI battle stations - More is better
Cornet, E.
1986-09-01
It is presently suggested that large numbers of lower capability SDI systems, in contrast to small numbers of large battle stations, offer better overall defense performance at lower total cost, with lower technical risk, lower sensitivity to threat scenario variability, and improved survivability. This follows from such factors as the positioning of more platforms within effective range of targets during all phases of an attack, less exacting optics requirements, mass production economies-of-scale, and improved survivability.
SDI Large-Scale System Technology Study.
2007-11-02
Boost Phase Architecture Language Sensor Midcourse Producibility Algorithm Weapon Research Target BM C3 Technology Model Simulation AI Network SDI...problem is illustrated in Figures 7-3 through 7-7. The problem chosen for this example is the post-interceptor-launch midcourse - guidance problem, which...optimal interconnection of the blocks. The possible relevance to the post-interceptor-launch midcourse - guidance problem of the candidate architecture
Dynamic Statistics of Crayfish Caudal Photoreceptors
Hermann, Howard T.; Olsen, Richard E.
1967-01-01
Crayfish caudal photoreceptor units were monitored during transient and steady-state responses to light stimuli (step on, step off). A statistical analysis of interpulse interval distributions during quasi-stationary time periods was carried out. Firing statistics during transient conditions were superposable with statistics under whatever steady stimulation produced the same firing rate, indicating that mean firing rate is a sufficient statistic. Distributions encountered formed a continuum of possible shapes. Considerable variation in shape was found with temperature and also among species, with Orconectes clarkii tending to fire more regularly than Orconectes virilis. Some properties of O. virilis statistics are described, including a linear relation between mean and standard deviation, and a tendency for intervals to be nonindependent. The data are considered as constraints on closed form models of the photoreceptor nerve pulse generator. PMID:6035125
SDI (Strategic Defense Initiative): Shield or sword. Study Project
Butler, C.S.; Spiczak, G.R.
1989-05-15
The paper attempts to answer the fundamental question, is SDI an adjunct to a first strike strategy. As its criteria, it discusses Soviet and U.S. opposing views on SDI, an historical application of Mutual Assured Destruction strategy, and a discussion of Soviet and U.S. thinking on first-strike capability. President Reagan's March 1983 address on SDI is used as the backdrop to set the stage for the discussion. It is the objective of the authors to evaluate and analyze the potential impact of SDI on first strike.
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…
Using SDI-12 with ST microelectronics MCU's
Saari, Alexandra; Hinzey, Shawn Adrian; Frigo, Janette Rose; Proicou, Michael Chris; Borges, Louis
2015-09-03
ST Microelectronics microcontrollers and processors are readily available, capable and economical processors. Unfortunately they lack a broad user base like similar offerings from Texas Instrument, Atmel, or Microchip. All of these devices could be useful in economical devices for remote sensing applications used with environmental sensing. With the increased need for environmental studies, and limited budgets, flexibility in hardware is very important. To that end, and in an effort to increase open support of ST devices, I am sharing my teams' experience in interfacing a common environmental sensor communication protocol (SDI-12) with ST devices.
Applications of submillimeter wave technology for SDI
NASA Technical Reports Server (NTRS)
Kile, J. N.; Mcgrath, W. R.; Leduc, H. G.; Siegel, P. H.; Smith, R. P.; Hayes, D. T.
1992-01-01
This paper examines the potential use of using submillimeter wave technology (actually 3 mm to 100 microns, or frequencies between 100 GHz and 3 THz) for SDI applications, especially for endo-KEW systems. The requirements and functions for a multipurpose weapon sensor are considered. The emphasis is on active sensors, but certain elements of passive sensors are mentioned that could play an important role. The rest of the paper provides information on the state-of-the-art in submillimeter wave technology, especially current component activity, and future plans.
Applications of submillimeter wave technology for SDI
Kile, J.N.; Mcgrath, W.R.; Leduc, H.G.; Siegel, P.H.; Smith, R.P.; Hayes, D.T. JPL, Pasadena, Ca USAF, Rome Laboratory, Hanscom AFB, MA )
1992-05-01
This paper examines the potential use of using submillimeter wave technology (actually 3 mm to 100 microns, or frequencies between 100 GHz and 3 THz) for SDI applications, especially for endo-KEW systems. The requirements and functions for a multipurpose weapon sensor are considered. The emphasis is on active sensors, but certain elements of passive sensors are mentioned that could play an important role. The rest of the paper provides information on the state-of-the-art in submillimeter wave technology, especially current component activity, and future plans. 27 refs.
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.
Hardening SDI links against nuclear explosions
Pierre, J.MA; Wittwer, L.A.
1987-11-01
An evaluation is made of the threat posed to the communications network binding the sensor, weapon, and battle management elements of SDI into a cohesive system by nuclear detonations that may be encountered during operation. The interaction among hundreds or thousands of nuclear bursts is not well understood, and calls for a major research effort; the nuclear effects anticipated encompass absorption, increased levels of RF noise, and above all, multipath scintillations. All these effects are caused by the high levels of ionization generated by high altitude nuclear explosions. The mitigation of these various effects by system design measures is discussed.
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.
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.
Investigating strategies to improve crop germination when using SDI
Technology Transfer Automated Retrieval System (TEKTRAN)
As the nation's population increases and available irrigation water decreases, new technologies are being developed to maintain or increase production on fewer acres. One of these advancements has been the use of subsurface drip irrigation (SDI) on field crops. Research has shown that SDI is the m...
Lost in space: SDI struggles through its sixth year
MacDonald, B.W.
1989-09-01
After six years of debate, it is clear that Congress is willing to support a robust research program for SDI, but it is also clear that Congress will not support SDI annual outlays on the order of $10 billion. Thus the policy choice is between a good research program that meshes with fiscal reality, or an inadequate and wasteful development program that continues to focus on preparing for a Phase I deployment for which the funds simply will not be available. The Bush administration so far seems trapped by its own rhetoric from coming to grips with the implications of the new SDI reality. The responsibility for getting SDI on a steadier course toward more realistic research objectives thus seems to lie with Congress in the near term. Since Congress has been reluctant to earmark SDI research funds for specific objectives, it will take a change in administration perceptions before SDI program goals can be changed away from Phase I deployment. The only likely way this could happen in the near term would be as a result of a Congress-executive branch summit agreement on SDI objectives and funding levels. In the absence of such an agreement, SDI will be sailing under ever weaker fiscal and political winds and runs the risk of finding itself becalmed, working ceaselessly toward goals that will never be fulfilled.
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...
INSPEC SDI Investigation, 1967-1969. Volume I.
ERIC Educational Resources Information Center
Clague, P.
The performance, economics and acceptability to users of the INSPEC SDI system were investigated in this study. The effect that provision of an SDI service might have on the information-use habits of users was also studied. The sample group of users consisted of 600 individuals of whom 540 were drawn equally from: universities and colleges,…
SDI Use and Productivity in the Corporate Research Environment.
ERIC Educational Resources Information Center
Mondschein, Lawrence G.
1990-01-01
Use of selective dissemination of information (SDI) by 156 research scientists at 6 corporate research and development facilities was surveyed to assess its relationship to research productivity as measured by the number of papers authored. Findings showed that 70 percent of the scientists use SDI, and regular users are more productive than either…
Developing and Implementing a Computerized SDI Service for Educational Administrators.
ERIC Educational Resources Information Center
Sanders, Jean E.
This practicum report describes the development and implementation of an SDI (Selective Dissemination of Information) system for administrators. The purpose of the SDI system was to provide current and economical retrieval and dissemination of the published educational literature in order to encourage educational improvements. Practicum procedures…
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.
Modeling Statistical and Dynamic Features of Earthquakes
NASA Astrophysics Data System (ADS)
Rydelek, P. A.; Suyehiro, K.; Sacks, S. I.; Smith, D. E.; Takanami, T.; Hatano, T.
2015-12-01
The cellular automaton earthquake model by Sacks and Rydelek (1995) is extended to explain spatio-temporal change in seismicity with the regional tectonic stress buildup. Our approach is to apply a simple Coulomb failure law to our model space of discrete cells, which successfully reproduces empirical laws (e.g. Gutenberg-Richter law) and dynamic failure characteristics (e.g. stress drop vs. magnitude and asperities) of earthquakes. Once the stress condition supersedes the Coulomb threshold on a discrete cell, its accumulated stress is transferred to only neighboring cells, which cascades to more neighboring cells to create various size ruptures. A fundamental point here is the cellular view of the continuous earth. We suggest the cell size varies regionally with the maturity of the faults of the region. Seismic gaps (e.g. Mogi, 1979) and changes in seismicity such as indicated by b-values have been known but poorly understood. There have been reports of magnitude dependent seismic quiescence before large event at plate boundaries and intraplate (Smith et al., 2013). Recently, decreases in b-value for large earthquakes have been reported (Nanjo et al., 2012) as anticipated from lab experiments (Mogi, 1963). Our model reproduces the b-value decrease towards eventual large earthquake (increasing tectonic stress and its heterogeneous distribution). We succeeded in reproducing the cut-off of larger events above some threshold magnitude (M3-4) by slightly increasing the Coulomb failure level for only 2 % or more of the highly stressed cells. This is equivalent to reducing the pore pressure in these distributed cells. We are working on the model to introduce the recovery of pore pressure incorporating the observed orders of magnitude higher permeability fault zones than the surrounding rock (Lockner, 2009) allowing for a large earthquake to be generated. Our interpretation requires interactions of pores and fluids. We suggest heterogeneously distributed patches hardened
Statistical inference for noisy nonlinear ecological dynamic systems.
Wood, Simon N
2010-08-26
Chaotic ecological dynamic systems defy conventional statistical analysis. Systems with near-chaotic dynamics are little better. Such systems are almost invariably driven by endogenous dynamic processes plus demographic and environmental process noise, and are only observable with error. Their sensitivity to history means that minute changes in the driving noise realization, or the system parameters, will cause drastic changes in the system trajectory. This sensitivity is inherited and amplified by the joint probability density of the observable data and the process noise, rendering it useless as the basis for obtaining measures of statistical fit. Because the joint density is the basis for the fit measures used by all conventional statistical methods, this is a major theoretical shortcoming. The inability to make well-founded statistical inferences about biological dynamic models in the chaotic and near-chaotic regimes, other than on an ad hoc basis, leaves dynamic theory without the methods of quantitative validation that are essential tools in the rest of biological science. Here I show that this impasse can be resolved in a simple and general manner, using a method that requires only the ability to simulate the observed data on a system from the dynamic model about which inferences are required. The raw data series are reduced to phase-insensitive summary statistics, quantifying local dynamic structure and the distribution of observations. Simulation is used to obtain the mean and the covariance matrix of the statistics, given model parameters, allowing the construction of a 'synthetic likelihood' that assesses model fit. This likelihood can be explored using a straightforward Markov chain Monte Carlo sampler, but one further post-processing step returns pure likelihood-based inference. I apply the method to establish the dynamic nature of the fluctuations in Nicholson's classic blowfly experiments.
Statistical coarse-graining of molecular dynamics into peridynamics.
Silling, Stewart Andrew; Lehoucq, Richard B.
2007-10-01
This paper describes an elegant statistical coarse-graining of molecular dynamics at finite temperature into peridynamics, a continuum theory. Peridynamics is an efficient alternative to molecular dynamics enabling dynamics at larger length and time scales. In direct analogy with molecular dynamics, peridynamics uses a nonlocal model of force and does not employ stress/strain relationships germane to classical continuum mechanics. In contrast with classical continuum mechanics, the peridynamic representation of a system of linear springs and masses is shown to have the same dispersion relation as the original spring-mass system.
Statistical properties of chaotic dynamical systems which exhibit strange attractors
Jensen, R.V.; Oberman, C.R.
1981-07-01
A path integral method is developed for the calculation of the statistical properties of turbulent dynamical systems. The method is applicable to conservative systems which exhibit a transition to stochasticity as well as dissipative systems which exhibit strange attractors. A specific dissipative mapping is considered in detail which models the dynamics of a Brownian particle in a wave field with a broad frequency spectrum. Results are presented for the low order statistical moments for three turbulent regimes which exhibit strange attractors corresponding to strong, intermediate, and weak collisional damping.
Analysis of the Soviet response to the Strategic Defense Initiative (SDI). Student report
Morgan, D.E.
1987-04-01
Since President Reagan announced the Strategic Defense Initiative (SDI) in March 1983, the Soviet Union has consistently condemned it. This study examines the Soviet response to SDI and provides an explanation for their response. The study identifies military, political, and economic factors that influence the Soviet response to SDI. The author concludes that the Soviets have a genuine concern about SDI, and they will continue their attempts to stop the SDI program at the arms-control negotiations.
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.
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…
Entropic fluctuations in statistical mechanics: I. Classical dynamical systems
NASA Astrophysics Data System (ADS)
Jakšić, V.; Pillet, C.-A.; Rey-Bellet, L.
2011-03-01
Within the abstract framework of dynamical system theory we describe a general approach to the transient (or Evans-Searles) and steady state (or Gallavotti-Cohen) fluctuation theorems of non-equilibrium statistical mechanics. Our main objective is to display the minimal, model independent mathematical structure at work behind fluctuation theorems. In addition to its conceptual simplicity, another advantage of our approach is its natural extension to quantum statistical mechanics which will be presented in a companion paper. We shall discuss several examples including thermostated systems, open Hamiltonian systems, chaotic homeomorphisms of compact metric spaces and Anosov diffeomorphisms.
Dynamics, stability, and statistics on lattices and networks
Livi, Roberto
2014-07-15
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.
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.
Seasonal drought predictability in Portugal using statistical-dynamical techniques
NASA Astrophysics Data System (ADS)
Ribeiro, A. F. S.; Pires, C. A. L.
2016-08-01
Atmospheric forecasting and predictability are important to promote adaption and mitigation measures in order to minimize drought impacts. This study estimates hybrid (statistical-dynamical) long-range forecasts of the regional drought index SPI (3-months) over homogeneous regions from mainland Portugal, based on forecasts from the UKMO operational forecasting system, with lead-times up to 6 months. ERA-Interim reanalysis data is used for the purpose of building a set of SPI predictors integrating recent past information prior to the forecast launching. Then, the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. A two-step hybridization procedure is performed, in which both forecasted and observed 500 hPa geopotential height fields are subjected to a PCA in order to use forecasted PCs and persistent PCs as predictors. A second hybridization step consists on a statistical/hybrid downscaling to the regional SPI, based on regression techniques, after the pre-selection of the statistically significant predictors. The SPI forecasts and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode, using the R2 and binary event scores. Results are obtained for the four seasons and it was found that winter is the most predictable season, and that most of the predictive power is on the large-scale fields from past observations. The hybridization improves the downscaling based on the forecasted PCs, since they provide complementary information (though modest) beyond that of persistent PCs. 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.
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.
Balanced excitation and inhibition lead to statistical and dynamical criticality
NASA Astrophysics Data System (ADS)
Cecchi, Guillermo
2010-03-01
We present a simple abstract model, an anti-Hebbian network which spontaneously poises itself, by balancing excitation and inhibition, at a dynamically critical state: an extensive number of degrees of freedom approach Hopf bifurcations, becoming arbitrarily sensitive to external perturbations (PRL 102, 258102 - 2009). As the dynamics controlling this state has itself a marginal fixed point, the eigenvalues fluctuate close to the imaginary axis; when they become slightly unstable, the corresponding mode ``breaks out'' and becomes more prominent, and as they become slightly stable the mode slowly damps out. This breakout dynamics displays avalanche-like activity bursts whose sizes may be power-law distributed, i.e. statistically critical. Within these epochs the neurons of our model are slightly correlated; yet, as the number of small but significant correlations is high, the model has strongly correlated network states. This system is, on the short time-scale, sensitive in bulk to any outside input, even if applied only to a small subset of the neurons. We also present preliminary results showing that human brain electro-physiological recordings display both statistical and dynamical criticality.
SDI (Strategic Defense Initiative) and national security policy. Research report
Davis, R.W.
1988-04-01
The paper attempts to answer the fundamental question of Can SDI make a significant contribution to US national security. It uses as its evaluation criteria historical arms-control measurements of stability, reduction in the probability of war, reduction in the consequences of war, economic benefits, and political benefits. A historical discussion of US nuclear strategy development along with Soviet thinking is provided as a backdrop to set the stage for an analysis of the reasons for President Reagan's March 1983 speech. The objectives of SDI are discussed along with the major concerns expressed by the program critics. Using the evaluation criteria defined above, the author analyzes SDI potential position in a long-term integrated national strategy that includes arms control and competitive strategies.
Future SDI (Strategic Defense Initiative) decision making. Study project
Holman, B.W.
1988-03-29
Nearly five years have lapsed since President Reagan made his now famous speech launching his Strategic Defense Initiative. Yet, polarized debate continues over the program's feasibility, desirability, affordability, goals, and direction. Some claim the program's goals have changed over time, and that today the primary goal is for an enhanced deterrence rather than providing a population defense as originally envisioned. Although the Congress has provided continuing and expanded funding for SDI, a consensus does not exist between the Congress and the Administration over the program's direction and goals. Some concerns exist within the Congress that the Administration is rushing too quickly to reach a decision on initial system development. Others would like to see initial development of a more limited defensive capability than that envisioned by the SDI program. This paper examines the evolution of SDI from a policy standpoint and addresses a series of questions that taken together may suggest parameters for future decision making.
General Properties of Landscapes: Vacuum Structure, Dynamics and Statistics
NASA Astrophysics Data System (ADS)
Zukowski, Claire Elizabeth
Even the simplest extra-dimensional theory, when compactified, can lead to a vast and complex landscape. To make progress, it is useful to focus on generic features of landscapes and compactifications. In this work we will explore universal features and consequences of (i) vacuum structure, (ii) dynamics resulting from symmetry breaking, and (iii) statistical predictions for low-energy parameters and observations. First, we focus on deriving general properties of the vacuum structure of a theory independent of the details of the geometry. We refine the procedure for performing compactifications by proposing a general gauge-invariant method to obtain the full set of Kaluza-Klein towers of fields for any internal geometry. Next, we study dynamics in a toy model for flux compactifications. We show that the model exhibits symmetry-breaking instabilities for the geometry to develop lumps, and suggest that similar dynamical effects may occur generically in other landscapes. The questions of the observed arrow of time as well as the observed value of the neutrino mass lead us to consider statistics within a landscape, and we verify that our observations are in fact typical given the correct vacuum structure and (in the case of the arrow of time) initial conditions. Finally, we address the question of subregion duality in AdS/CFT, arguing for a criterion for a bulk region to be reconstructable from a given boundary subregion by local operators. While of less direct relevance to cosmological space-times, this work provides an improved understanding of the UV/IR correspondence, a principle that underlies the construction of many holographically-inspired measures used to make statistical predictions in landscapes.
Hydrological responses to dynamically and statistically downscaled climate model output
Wilby, R.L.; Hay, L.E.; Gutowski, W.J.; 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.
Classifying cardiac biosignals using ordinal pattern statistics and symbolic dynamics.
Parlitz, U; Berg, S; Luther, S; Schirdewan, A; Kurths, J; Wessel, N
2012-03-01
The performance of (bio-)signal classification strongly depends on the choice of suitable features (also called parameters or biomarkers). In this article we evaluate the discriminative power of ordinal pattern statistics and symbolic dynamics in comparison with established heart rate variability parameters applied to beat-to-beat intervals. As an illustrative example we distinguish patients suffering from congestive heart failure from a (healthy) control group using beat-to-beat time series. We assess the discriminative power of individual features as well as pairs of features. These comparisons show that ordinal patterns sampled with an additional time lag are promising features for efficient classification.
Role of quantum statistics in multi-particle decay dynamics
Marchewka, Avi; Granot, Er’el
2015-04-15
The role of quantum statistics in the decay dynamics of a multi-particle state, which is suddenly released from a confining potential, is investigated. For an initially confined double particle state, the exact dynamics is presented for both bosons and fermions. The time-evolution of the probability to measure two-particle is evaluated and some counterintuitive features are discussed. For instance, it is shown that although there is a higher chance of finding the two bosons (as oppose to fermions, and even distinguishable particles) at the initial trap region, there is a higher chance (higher than fermions) of finding them on two opposite sides of the trap as if the repulsion between bosons is higher than the repulsion between fermions. The results are demonstrated by numerical simulations and are calculated analytically in the short-time approximation. Furthermore, experimental validation is suggested.
ERIC Educational Resources Information Center
Cole, Elliot
1981-01-01
Examines the assumptions which underlie the design of SDI systems with respect to context of use, activities supported by SDI, and characteristics which make documents useful. Relates these assumptions to the failure of SDI to gain widespread acceptance among scientific information users. A 43-item reference list is included. (JL)
Spectral statistics and dynamics of Lévy matrices.
Araujo, M; Medina, E; Aponte, E
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 mu, 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 mu-->0. Furthermore, we find for 2 x 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 mu 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 delta3 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.
A statistical state dynamics approach to wall turbulence
NASA Astrophysics Data System (ADS)
Farrell, B. F.; Gayme, D. F.; Ioannou, P. J.
2017-03-01
This paper reviews results obtained using statistical state dynamics (SSD) that demonstrate the benefits of adopting this perspective for understanding turbulence in wall-bounded shear flows. The SSD approach used in this work employs a second-order closure that retains only the interaction between the streamwise mean flow and the streamwise mean perturbation covariance. This closure restricts nonlinearity in the SSD to that explicitly retained in the streamwise constant mean flow together with nonlinear interactions between the mean flow and the perturbation covariance. This dynamical restriction, in which explicit perturbation-perturbation nonlinearity is removed from the perturbation equation, results in a simplified dynamics referred to as the restricted nonlinear (RNL) dynamics. RNL systems, in which a finite ensemble of realizations of the perturbation equation share the same mean flow, provide tractable approximations to the SSD, which is equivalent to an infinite ensemble RNL system. This infinite ensemble system, referred to as the stochastic structural stability theory system, introduces new analysis tools for studying turbulence. RNL systems provide computationally efficient means to approximate the SSD and produce self-sustaining turbulence exhibiting qualitative features similar to those observed in direct numerical simulations despite greatly simplified dynamics. The results presented show that RNL turbulence can be supported by as few as a single streamwise varying component interacting with the streamwise constant mean flow and that judicious selection of this truncated support or `band-limiting' can be used to improve quantitative accuracy of RNL turbulence. These results suggest that the SSD approach provides new analytical and computational tools that allow new insights into wall turbulence.
A statistical state dynamics approach to wall turbulence.
Farrell, B F; Gayme, D F; Ioannou, P J
2017-03-13
This paper reviews results obtained using statistical state dynamics (SSD) that demonstrate the benefits of adopting this perspective for understanding turbulence in wall-bounded shear flows. The SSD approach used in this work employs a second-order closure that retains only the interaction between the streamwise mean flow and the streamwise mean perturbation covariance. This closure restricts nonlinearity in the SSD to that explicitly retained in the streamwise constant mean flow together with nonlinear interactions between the mean flow and the perturbation covariance. This dynamical restriction, in which explicit perturbation-perturbation nonlinearity is removed from the perturbation equation, results in a simplified dynamics referred to as the restricted nonlinear (RNL) dynamics. RNL systems, in which a finite ensemble of realizations of the perturbation equation share the same mean flow, provide tractable approximations to the SSD, which is equivalent to an infinite ensemble RNL system. This infinite ensemble system, referred to as the stochastic structural stability theory system, introduces new analysis tools for studying turbulence. RNL systems provide computationally efficient means to approximate the SSD and produce self-sustaining turbulence exhibiting qualitative features similar to those observed in direct numerical simulations despite greatly simplified dynamics. The results presented show that RNL turbulence can be supported by as few as a single streamwise varying component interacting with the streamwise constant mean flow and that judicious selection of this truncated support or 'band-limiting' can be used to improve quantitative accuracy of RNL turbulence. These results suggest that the SSD approach provides new analytical and computational tools that allow new insights into wall turbulence.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'.
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.
Deterrence enhanced by SDI (Strategic Defense Initiative). Student essay
Sowa, P.T.
1987-03-23
The Strategic Defense Initiative (SDI) is an investigation by scientists, military leaders, and technologists of the feasibility of strategic defenses against ballistic missiles. Whether strategic defense is the way to go in the future remains to be seen. Although the capability of the envisioned layered, ground, and space-based defensive systems is not specifically addressed, the SDI research program's affect on national-security strategy and its formulation is examined. If found to be feasible and cost-effective, SDI will require a drastic change in our military strategy. This essay reviews how that strategy was formulated in the past in terms of a model and how strategic-defense strategy would be used in the future. More importantly, a discussion of how the SDI impacts on present US national strategy and enhances deterrence is presented. Its influence on technology, conventional defense, and arms controls are offered on this evolving strategic concept and the renewed vigor and interest it has provided in strategy formulation.
SDI (Strategic Defense Initiative): technology, survivability, and software
Not Available
1988-05-01
This report reviews the status of the various SDI technologies and system components. It analyzes the feasibility of producing dependable software of the complexity that advanced BMD systems would require. Finally, it summarizes what is now known, and unknown, about the probable survivability of such systems against concerted enemy attacks of various kinds.
Computerized Information Service--SDI. Annual Report 1974-75.
ERIC Educational Resources Information Center
Hjerppe, Roland
The Information and Documentation Centre of the Royal Institute of Technology Library performs research and development in information science. The two main areas of this continuing research and development programme are (1) development of a comprehensive SDI service and (2) investigations in interactive retrieval services. This annual report…
Design and Installation of SDI Systems in North Carolina
Technology Transfer Automated Retrieval System (TEKTRAN)
As a part of the humid Southeast, North Carolina’s climate, topography, soils, cropping systems, and water sources require special consideration when considering and implementing a subsurface drip irrigation (SDI) system. This publication is not a step-by-step design manual, but it will help you in ...
Soviet SDI Rhetoric: The "Evil Empire" Vision of Mikhail Gorbachev.
ERIC Educational Resources Information Center
Kelley, Colleen E.
The symbolic presence of Ronald Reagan's Strategic Defense Initiative (SDI) has been and continues to be the pivot point in all summitry rhetoric between the American President and Soviet General Secretary Mikhail Gorbachev. To examine some of the rhetorical choices made by Gorbachev to dramatize his vision of why Ronald Reagan refuses to…
SDI Investigation, 1967-1969. Volumes 1-5.
ERIC Educational Resources Information Center
Clague, P.
The investigation of the performance, economics, and acceptability to users of the selective dissemination of information (SDI) computer system that supported the International Information Service in Physics, Electrotechnology, Computers, and Control (INSPEC) during its initial testing phase is described. The initial design of the study, involving…
SDI and University Research: An Exchange of Views.
ERIC Educational Resources Information Center
Abrahamson, James A.; Ballantyne, Joseph M.
1986-01-01
Lt. General Abrahamson suggested that SDI policy is developing increased respect for university policies that oppose classified research, with such research conducted in nonuniversity settings, autonomous institutes, or institutions that do not have such policies. Ballantyne describes Cornell University's policy on open research. (Author/MLW)
INSPEC SDI Investigation, 1967-1969. Volume IV.
ERIC Educational Resources Information Center
Clague, P.
Volume IV of this five volume study of the INSPEC SDI system consists of the following appendices to the study: A proposal to investigate the selective dissemination of information; Covering letter to questionnaire; Questionnaire: survey of information use; Chasing letter; Letter of invitation to participate; Chasing letter; Statement of…
Selective Dissemination of Information (SDI) in a Technological University Library
ERIC Educational Resources Information Center
Tell, Bjorn V.
1972-01-01
The Royal Institute of Technology Library in Stockholm operates a computerized SDI service to industry which has encouraged greater use of the library's collections through loans and photocopies. A useful by-product is a union catalog of serials in machine-readable form, from which a photo-composed list was published. (4 references) (Author/SJ)
Use of Automatic Text Analyzer in Preparation of SDI Profiles
ERIC Educational Resources Information Center
Carroll, John M.; Tague, Jean M.
1973-01-01
This research shows that by submitting samples of the client's recent professional reading material to automatic text analysis, Selective Dissemination of Information (SDI) profiles can be prepared that result in significantly higher initial recall scores than do those prepared by conventional techniques; relevance scores are not significantly…
Ames Selective Dissemination of Information (SDI) System Operating Manual.
ERIC Educational Resources Information Center
Anderson, Lloyd E.; Wegner, Waldo W.
The Ames Selective Dissemination of Information (SDI) System is an attempt to efficiently place rapidly increasing amounts of information into the hands of scientists and engineers who can exploit it. It is a computerized current awareness system designed to increase researchers' literature searching capabilities by bringing to their attention…
INSPEC SDI Investigation, 1967-1969. Volume II.
ERIC Educational Resources Information Center
Clague, P.
Volume II of this five volume investigation of the INSPEC SDI system contains discussions of the following topics: (1) Composition of user and control groups and the information use habits of users and controls, (2) thesaurus development and document indexing, (3) problems of printing notification cards and assessing numbers required for each…
INSPEC SDI Investigation, 1967-1969. Volume V.
ERIC Educational Resources Information Center
Clague, P.
The appendices included in Volume V of this five volume study of the INSPEC SDI system are a continuation of those in Volume IV and consist of: Communications with users etc.; Specimen sheets from descriptor file; Time on profile modification and analysis, and user assessment; Profiles compiled by compilers 1, 2, and 3; Proposed comparison of…
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…
Extreme value statistics for dynamical systems with noise
NASA Astrophysics Data System (ADS)
Faranda, Davide; Milhazes Freitas, Jorge; Lucarini, Valerio; Turchetti, Giorgio; Vaienti, Sandro
2013-09-01
We study the distribution of maxima (extreme value statistics) for sequences of observables computed along orbits generated by random transformations. The underlying, deterministic, dynamical system can be regular or chaotic. In the former case, we show that, by perturbing rational or irrational rotations with additive noise, an extreme value law appears, regardless of the intensity of the noise, while unperturbed rotations do not admit such limiting distributions. In the case of deterministic chaotic dynamics, we will consider observables specially designed to study the recurrence properties in the neighbourhood of periodic points. Hence, the exponential limiting law for the distribution of maxima is modified by the presence of the extremal index, a positive parameter not larger than one, whose inverse gives the average size of the clusters of extreme events. The theory predicts that such a parameter is unitary when the system is perturbed randomly. We perform sophisticated numerical tests to assess how strong the impact of noise level is when finite time series are considered. We find agreement with the asymptotic theoretical results but also non-trivial behaviour in the finite range. In particular, our results suggest that, in many applications where finite datasets can be produced or analysed, one must be careful in assuming that the smoothing nature of noise prevails over the underlying deterministic dynamics.
Forecasting: it is not about statistics, it is about dynamics.
Judd, Kevin; Stemler, Thomas
2010-01-13
In 1963, the mathematician and meteorologist Edward Lorenz published a paper (Lorenz 1963 J. Atmos. Sci. 20, 130-141) that changed the way scientists think about the prediction of geophysical systems, by introducing the ideas of chaos, attractors, sensitivity to initial conditions and the limitations to forecasting nonlinear systems. Three years earlier, the mathematician and engineer Rudolf Kalman had published a paper (Kalman 1960 Trans. ASME Ser. D, J. Basic Eng. 82, 35-45) that changed the way engineers thought about prediction of electronic and mechanical systems. Ironically, in recent years, geophysicists have become increasingly interested in Kalman filters, whereas engineers have become increasingly interested in chaos. It is argued that more often than not the tracking and forecasting of nonlinear systems has more to do with the nonlinear dynamics that Lorenz considered than it has to do with statistics that Kalman considered. A position with which both Lorenz and Kalman would appear to agree.
Managing Performance Analysis with Dynamic Statistical Projection Pursuit
Vetter, J.S.; Reed, D.A.
2000-05-22
Computer systems and applications are growing more complex. Consequently, performance analysis has become more difficult due to the complex, transient interrelationships among runtime components. To diagnose these types of performance issues, developers must use detailed instrumentation to capture a large number of performance metrics. Unfortunately, this instrumentation may actually influence the performance analysis, leading the developer to an ambiguous conclusion. In this paper, we introduce a technique for focusing a performance analysis on interesting performance metrics. This technique, called dynamic statistical projection pursuit, identifies interesting performance metrics that the monitoring system should capture across some number of processors. By reducing the number of performance metrics, projection pursuit can limit the impact of instrumentation on the performance of the target system and can reduce the volume of performance data.
Statistical characteristics of topographic surfaces and dynamic smoothing of landscapes
NASA Astrophysics Data System (ADS)
Bartlett, M. S.; Laio, F.; Ridolfi, L.; Vico, G.; Porporato, A. M.
2011-12-01
We analyze the local statistics of topographic surfaces, including slope and aspect, as a function of scale, and explore their relations with landscape features, such as age, vegetation, and geology. These results build upon the previous work of Vico and Porporato (JGR 114, F01011, 2009), which characterized slope using generalized t-Student distributions. We find that the number of degrees of freedom of such distributions, which determines the heaviness of their tails, is linked to the age of the topographic relief of the considered regions, tending to normal distributions for very old mountain ranges. Based on these findings, and inspired by models of critical phenomena, we develop physically-based, space-time stochastic differential equations that reproduce this dynamic smoothing of rough landscapes.
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.
Statistical analysis of a dynamic model for dietary contaminant exposure.
Bertail, P; Clémençon, S; Tressou, J
2010-03-01
This paper is devoted to the statistical analysis of a stochastic model introduced in [P. Bertail, S. Clémençon, and J. Tressou, A storage model with random release rate for modelling exposure to food contaminants, Math. Biosci. Eng. 35 (1) (2008), pp. 35-60] for describing the phenomenon of exposure to a certain food contaminant. In this modelling, the temporal evolution of the contamination exposure is entirely determined by the accumulation phenomenon due to successive dietary intakes and the pharmacokinetics governing the elimination process inbetween intakes, in such a way that the exposure dynamic through time is described as a piecewise deterministic Markov process. Paths of the contamination exposure process are scarcely observable in practice, therefore intensive computer simulation methods are crucial for estimating the time-dependent or steady-state features of the process. Here we consider simulation estimators based on consumption and contamination data and investigate how to construct accurate bootstrap confidence intervals (CI) for certain quantities of considerable importance from the epidemiology viewpoint. Special attention is also paid to the problem of computing the probability of certain rare events related to the exposure process path arising in dietary risk analysis using multilevel splitting or importance sampling (IS) techniques. Applications of these statistical methods to a collection of data sets related to dietary methyl mercury contamination are discussed thoroughly.
Algorithm development for SDI weapons system allocation. Final report, December 1987-May 1989
Blankenship, G.L.; Bennett, W.
1989-06-01
While several SDI weapons systems can provide adequate defense in a one-on-one basis, a coordinated attack by several enemy missiles launched over a substantial volume will be difficult to resist without an efficient command and control system for warfare coordination. This study of weapons allocation - coordination algorithms, is based on dynamical models for the missile/decoy systems including noise effects and uncertainties in the model parameters. Performance of the weapons targeting system may be measured in terms of the expected number of targets eliminated in a given interval (phase of operations) or the expected time to eliminate all the targets in a given region. Scheduling weapons deployment is a problem of constrained optimal (weapons) and state variables. The selection of weapons deployment tactics is based on solution of a complex optimization problem. We have conducted an investigation of advanced modeling, stochastic control, and scheduling methodologies for aspects of the SDI weapons allocation problem - several platforms with assets of different character defending against a diverse collection of targets. The models for such scenarios lead to stochastic scheduling problems that can not be handled by conventional analytical methods. The authors describe several different analytical approaches that have the potential for synthesis of effective engagement algorithms.
SDI (Strategic Defense Initiative) software technology program plan. Final report
Linn, C.J.; Redwine, S.T.; Bloom, M.I.; Brykczynski, B.; Chludzinski, J.
1987-06-01
This paper was prepared in response to a request from the Battle Management C3 office within the Strategic Defense Initiative Organization (SDIO) of the Department of Defense (DoD). The request was for a software-technology program plan to define software research and development (RandD) efforts required by the SDI, and to provide the basis for integrating the SDIO software technology program with ongoing non-SDIO programs. The paper emphasizes reviewing the ongoing software programs and plans within the DoD and academia. The reviews identify critical software technology areas required to meet the unique SDI requirements, and indicate priorities among the software technologies to meet attainability, productivity, and reliability goals, as well as functional performance objectives.
Software maturity model applied to SDI. Final report
Springsteen, B.
1991-09-01
The Strategic Defense Initiative Organization (SDIO) is undertaking initiatives to mitigate software risks and to stimulate the DoD contractor community to improve its software practices. To that end, IDA assessed the Software Engineering Institute's (SEI) software process maturity model and developed an implementation plan for its use within the SDI program. Under this plan, SDI element programs will use the SEI method to select software contractors with mature practices and to monitor contracts after they have been awarded. This document describes the SEI maturity model and the experience of contractors and government agencies. It also explains SDIO's plans to implement the model program-wide and the benefits and lessons learned from using the model on two contracts.
Statistical and dynamical remastering of classic exoplanet systems
NASA Astrophysics Data System (ADS)
Nelson, Benjamin Earl
The most powerful constraints on planet formation will come from characterizing the dynamical state of complex multi-planet systems. Unfortunately, with that complexity comes a number of factors that make analyzing these systems a computationally challenging endeavor: the sheer number of model parameters, a wonky shaped posterior distribution, and hundreds to thousands of time series measurements. In this dissertation, I will review our efforts to improve the statistical analyses of radial velocity (RV) data and their applications to some renown, dynamically complex exoplanet system. In the first project (Chapters 2 and 4), we develop a differential evolution Markov chain Monte Carlo (RUN DMC) algorithm to tackle the aforementioned difficult aspects of data analysis. We test the robustness of the algorithm in regards to the number of modeled planets (model dimensionality) and increasing dynamical strength. We apply RUN DMC to a couple classic multi-planet systems and one highly debated system from radial velocity surveys. In the second project (Chapter 5), we analyze RV data of 55 Cancri, a wide binary system known to harbor five planetary orbiting the primary. We find the inner-most planet "e" must be coplanar to within 40 degrees of the outer planets, otherwise Kozai-like perturbations will cause the planet to enter the stellar photosphere through its periastron passage. We find the orbits of planets "b" and "c" are apsidally aligned and librating with low to median amplitude (50+/-6 10 degrees), but they are not orbiting in a mean-motion resonance. In the third project (Chapters 3, 4, 6), we analyze RV data of Gliese 876, a four planet system with three participating in a multi-body resonance, i.e. a Laplace resonance. From a combined observational and statistical analysis computing Bayes factors, we find a four-planet model is favored over one with three-planets. Conditioned on this preferred model, we meaningfully constrain the three-dimensional orbital
Characterizing Uncertainties in Hydrologic Extremes: Statistical vs. Dynamical Downscaling
NASA Astrophysics Data System (ADS)
Mauger, G. S.; Salathe, E. P., Jr.
2013-12-01
Numerous agencies are now charged with considering the impacts of climate change in management decisions, both from the standpoint of adapting to changing conditions and minimizing emissions of greenhouse gases. These decisions require robust projections of change and defensible estimates of their uncertainty. We present work that is specifically focused on characterizing the uncertainty in projections of hydrologic extremes. Much recent work has been devoted to characterizing the uncertainty in hydrologic projections due to differences in downscaling methodology (e.g., Abatzoglou and Brown, 2012; Bürger et al., 2012; Rasmussen et al., 2011; Wetterhall et al., 2012) and among hydrologic models (e.g., Bennett et al., 2012; Clark et al., 2008; Fenicia et al., 2008; Smith and Marshall, 2010; Vano et al., 2012). These have established a basis for such analyses, but have generally focused on the implications for monthly and annual flows rather than flow extremes. In addition, few among these have been focused within the Pacific Northwest. In this work we assess the uncertainty in projected changes to hydrologic extremes associated with dynamical vs. statistical downscaling. The analysis is focused on 3 distinct watersheds within the Pacific Northwest - the Skagit, Green, and Willamette river basins. Results highlight the sensitivity of flood projections to downscaling approach and hydrologic model assumptions. Sensitivities are characterized as a function of geographic location, hydrologic regime, and climate - identifying circumstances under which projections are reliable and others in which answers differ markedly based on methodology. For example, one notable result is that dynamically downscaled projections appear to refute the assumed relationship between watershed type (snow-dominant vs. rain-dominant) and projected changes to flood risk - currently considered a key indicator of future flood risk. Results presented here provide key information for decision
SDI performance and START constraints: Modeling Phase-1 defense engagements
Cunningham, C.
1991-03-20
My interest has been the performance of near-term Strategic Defense Initiative (SDI) systems rather than the kinds of questions discussed at this Workshop (e.g., implications of US force structure). It is clear, though, that the two issues are closely related. Arms control along with treaties that impact the force structure of the Soviet Union will greatly affect the performance of SDI systems. Similarly, the US intention to pursue SDI will be a driver in arms control negotiations, as well it should be. Indeed, the implications of SDI for Strategic Arms Reduction Treaty (START)-constrained Soviet forces are the focus of my discussion. To put this in some context, I will begin with the premises underlying my results: the United States and the Soviet Union reach an arms control agreement limiting strategic forces below current levels. The United States decides to pursue defense deployments to limit damage to the US and, eventually, to provide robust protection against ballistic missile attack. The Soviet Union responds by improving its forces within the numerical bounds of the treaty. My basic calculations are: Under START and in the absence of defenses, the offenses has sufficient weapons to attack 10,000 targets with strong value contrast. START constraints are severely limiting against an adaptive preferential defense, even with adaptive targeting. The adaptive preferential defense may contain a random-subtractive SBI tier. PBV redesign alone is insufficient to stress the SBI. Offload penalties to defeat endoatmospheric interceptors appear significant. Despite increased flexibility to modernize, a small attacking force is vulnerable to a small defense. 6 figs., 2 tabs.
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.
New Statistical Learning Methods for Estimating Optimal Dynamic Treatment Regimes
Zhao, Ying-Qi; Zeng, Donglin; Laber, Eric B.; Kosorok, Michael R.
2014-01-01
Dynamic treatment regimes (DTRs) are sequential decision rules for individual patients that can adapt over time to an evolving illness. The goal is to accommodate heterogeneity among patients and find the DTR which will produce the best long term outcome if implemented. We introduce two new statistical learning methods for estimating the optimal DTR, termed backward outcome weighted learning (BOWL), and simultaneous outcome weighted learning (SOWL). These approaches convert individualized treatment selection into an either sequential or simultaneous classification problem, and can thus be applied by modifying existing machine learning techniques. The proposed methods are based on directly maximizing over all DTRs a nonparametric estimator of the expected long-term outcome; this is fundamentally different than regression-based methods, for example Q-learning, which indirectly attempt such maximization and rely heavily on the correctness of postulated regression models. We prove that the resulting rules are consistent, and provide finite sample bounds for the errors using the estimated rules. Simulation results suggest the proposed methods produce superior DTRs compared with Q-learning especially in small samples. We illustrate the methods using data from a clinical trial for smoking cessation. PMID:26236062
A Statistical Model for In Vivo Neuronal Dynamics
Surace, Simone Carlo; Pfister, Jean-Pascal
2015-01-01
Single neuron models have a long tradition in computational neuroscience. Detailed biophysical models such as the Hodgkin-Huxley model as well as simplified neuron models such as the class of integrate-and-fire models relate the input current to the membrane potential of the neuron. Those types of models have been extensively fitted to in vitro data where the input current is controlled. Those models are however of little use when it comes to characterize intracellular in vivo recordings since the input to the neuron is not known. Here we propose a novel single neuron model that characterizes the statistical properties of in vivo recordings. More specifically, we propose a stochastic process where the subthreshold membrane potential follows a Gaussian process and the spike emission intensity depends nonlinearly on the membrane potential as well as the spiking history. We first show that the model has a rich dynamical repertoire since it can capture arbitrary subthreshold autocovariance functions, firing-rate adaptations as well as arbitrary shapes of the action potential. We then show that this model can be efficiently fitted to data without overfitting. We finally show that this model can be used to characterize and therefore precisely compare various intracellular in vivo recordings from different animals and experimental conditions. PMID:26571371
Modeling Insurgent Dynamics Including Heterogeneity. A Statistical Physics Approach
NASA Astrophysics Data System (ADS)
Johnson, Neil F.; Manrique, Pedro; Hui, Pak Ming
2013-05-01
Despite the myriad complexities inherent in human conflict, a common pattern has been identified across a wide range of modern insurgencies and terrorist campaigns involving the severity of individual events—namely an approximate power-law x - α with exponent α≈2.5. We recently proposed a simple toy model to explain this finding, built around the reported loose and transient nature of operational cells of insurgents or terrorists. Although it reproduces the 2.5 power-law, this toy model assumes every actor is identical. Here we generalize this toy model to incorporate individual heterogeneity while retaining the model's analytic solvability. In the case of kinship or team rules guiding the cell dynamics, we find that this 2.5 analytic result persists—however an interesting new phase transition emerges whereby this cell distribution undergoes a transition to a phase in which the individuals become isolated and hence all the cells have spontaneously disintegrated. Apart from extending our understanding of the empirical 2.5 result for insurgencies and terrorism, this work illustrates how other statistical physics models of human grouping might usefully be generalized in order to explore the effect of diverse human social, cultural or behavioral traits.
Statistical analysis of dynamic sequences for functional imaging
NASA Astrophysics Data System (ADS)
Kao, Chien-Min; Chen, Chin-Tu; Wernick, Miles N.
2000-04-01
Factor analysis of medical image sequences (FAMIS), in which one concerns the problem of simultaneous identification of homogeneous regions (factor images) and the characteristic temporal variations (factors) inside these regions from a temporal sequence of images by statistical analysis, is one of the major challenges in medical imaging. In this research, we contribute to this important area of research by proposing a two-step approach. First, we study the use of the noise- adjusted principal component (NAPC) analysis developed by Lee et. al. for identifying the characteristic temporal variations in dynamic scans acquired by PET and MRI. NAPC allows us to effectively reject data noise and substantially reduce data dimension based on signal-to-noise ratio consideration. Subsequently, a simple spatial analysis based on the criteria of minimum spatial overlapping and non-negativity of the factor images is applied for extraction of the factors and factor images. In our simulation study, our preliminary results indicate that the proposed approach can accurately identify the factor images. However, the factors are not completely separated.
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.
Dynamical instability and statistical behaviour of N-body systems
NASA Astrophysics Data System (ADS)
Cipriani, Piero; Di Bari, Maria
1998-12-01
, 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, ɛ)-dependence of tD (ɛ 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 = γ1 · tD [γ 1 is the maximal Lyapunov Characteristic Number (LCN)] being always positive and independent of ɛ, as it happens for the FPU chain only above the strong stochasticity threshold (SST). The numerical checks on the analytical estimates about the ( N, ɛ)-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
Examining rainfall and cholera dynamics in Haiti using statistical and dynamic modeling approaches.
Eisenberg, Marisa C; Kujbida, Gregory; Tuite, Ashleigh R; Fisman, David N; Tien, Joseph H
2013-12-01
Haiti has been in the midst of a cholera epidemic since October 2010. Rainfall is thought to be associated with cholera here, but this relationship has only begun to be quantitatively examined. In this paper, we quantitatively examine the link between rainfall and cholera in Haiti for several different settings (including urban, rural, and displaced person camps) and spatial scales, using a combination of statistical and dynamic models. Statistical analysis of the lagged relationship between rainfall and cholera incidence was conducted using case crossover analysis and distributed lag nonlinear models. Dynamic models consisted of compartmental differential equation models including direct (fast) and indirect (delayed) disease transmission, where indirect transmission was forced by empirical rainfall data. Data sources include cholera case and hospitalization time series from the Haitian Ministry of Public Health, the United Nations Water, Sanitation and Health Cluster, International Organization for Migration, and Hôpital Albert Schweitzer. Rainfall data was obtained from rain gauges from the U.S. Geological Survey and Haiti Regeneration Initiative, and remote sensing rainfall data from the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission. A strong relationship between rainfall and cholera was found for all spatial scales and locations examined. Increased rainfall was significantly correlated with increased cholera incidence 4-7 days later. Forcing the dynamic models with rainfall data resulted in good fits to the cholera case data, and rainfall-based predictions from the dynamic models closely matched observed cholera cases. These models provide a tool for planning and managing the epidemic as it continues.
Quantum statistical effects on fusion dynamics of heavy ions
Ayik, S.; Yilmaz, B.; Gokalp, A.; Yilmaz, O.; Takigawa, N.
2005-05-01
To describe the fusion of two very heavy nuclei at near barrier energies, a generalized Langevin approach is proposed. The approach incorporates the quantum statistical fluctuations in accordance with the fluctuation and dissipation theorem. It is illustrated that the quantum statistical effects introduce an enhancement of the formation of a compound nucleus, though the quantum enhancement is somewhat less pronounced as indicated in the previous calculations.
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…
Links to sources of cancer-related statistics, including the Surveillance, Epidemiology and End Results (SEER) Program, SEER-Medicare datasets, cancer survivor prevalence data, and the Cancer Trends Progress Report.
ERIC Educational Resources Information Center
Scheffler, F. L.; March, J. F.
The Aerospace Materials Information Center (AMIC) Selective Dissemination of Information (SDI) program was evaluated by an interview technique after one year of operation. The data base for the SDI consists of the periodic document index records input to the AMIC system. The users are 63 engineers, scientists, and technical administrators at the…
SDI Citation Checking as a Measure of the Performance of Library Document Delivery Systems.
ERIC Educational Resources Information Center
Bourne, Charles P.; Robinson, Jo.
Document delivery support for selective dissemination of information (SDI) services provided by the Center for Information Services, University of California at Los Angeles, was measured by the following: (1) Obtaining copies of all steady-state SDI searches from Biological Abstracts'"BA Previews" data base delivered to the University of…
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…
ERIC Educational Resources Information Center
Mondschein, Lawrence G.
1990-01-01
Discussion of the use of selective dissemination of information (SDI) focuses on a study that proposed a model for evaluating the relationship between SDI and the number of publications authored by basic research scientists working in a corporate research and development (R&D) environment. Hypotheses and their findings are presented. (Seven…
Revealing physical interaction networks from statistics of collective dynamics.
Nitzan, Mor; Casadiego, Jose; Timme, Marc
2017-02-01
Revealing physical interactions in complex systems from observed collective dynamics constitutes a fundamental inverse problem in science. Current reconstruction methods require access to a system's model or dynamical data at a level of detail often not available. We exploit changes in invariant measures, in particular distributions of sampled states of the system in response to driving signals, and use compressed sensing to reveal physical interaction networks. Dynamical observations following driving suffice to infer physical connectivity even if they are temporally disordered, are acquired at large sampling intervals, and stem from different experiments. Testing various nonlinear dynamic processes emerging on artificial and real network topologies indicates high reconstruction quality for existence as well as type of interactions. These results advance our ability to reveal physical interaction networks in complex synthetic and natural systems.
Revealing physical interaction networks from statistics of collective dynamics
Nitzan, Mor; Casadiego, Jose; Timme, Marc
2017-01-01
Revealing physical interactions in complex systems from observed collective dynamics constitutes a fundamental inverse problem in science. Current reconstruction methods require access to a system’s model or dynamical data at a level of detail often not available. We exploit changes in invariant measures, in particular distributions of sampled states of the system in response to driving signals, and use compressed sensing to reveal physical interaction networks. Dynamical observations following driving suffice to infer physical connectivity even if they are temporally disordered, are acquired at large sampling intervals, and stem from different experiments. Testing various nonlinear dynamic processes emerging on artificial and real network topologies indicates high reconstruction quality for existence as well as type of interactions. These results advance our ability to reveal physical interaction networks in complex synthetic and natural systems. PMID:28246630
Statistical Anomaly Detection for Monitoring of Human Dynamics
NASA Astrophysics Data System (ADS)
Kamiya, K.; Fuse, T.
2015-05-01
Understanding of human dynamics has drawn attention to various areas. Due to the wide spread of positioning technologies that use GPS or public Wi-Fi, location information can be obtained with high spatial-temporal resolution as well as at low cost. By collecting set of individual location information in real time, monitoring of human dynamics is recently considered possible and is expected to lead to dynamic traffic control in the future. Although this monitoring focuses on detecting anomalous states of human dynamics, anomaly detection methods are developed ad hoc and not fully systematized. This research aims to define an anomaly detection problem of the human dynamics monitoring with gridded population data and develop an anomaly detection method based on the definition. According to the result of a review we have comprehensively conducted, we discussed the characteristics of the anomaly detection of human dynamics monitoring and categorized our problem to a semi-supervised anomaly detection problem that detects contextual anomalies behind time-series data. We developed an anomaly detection method based on a sticky HDP-HMM, which is able to estimate the number of hidden states according to input data. Results of the experiment with synthetic data showed that our proposed method has good fundamental performance with respect to the detection rate. Through the experiment with real gridded population data, an anomaly was detected when and where an actual social event had occurred.
Effect of aging on regulation of sdi-1 in rat hepatocytes.
Kitano, S; Venable, S; Smith, J R; Reed, T D; Roth, G S
1996-08-05
We examined basal and EGF stimulated DNA synthesis as well as sdi-1 mRNA and protein in primary hepatocyte cultures, and basal levels of sdi-1 mRNA and protein in whole liver homogenates from 6 and 24 month old rats. Since EGF stimulated DNA synthesis decreases with age, it was hypothesized that basal and EGF stimulated levels of sdi-1 mRNA and protein, an inhibitor of DNA synthesis, might increase. Surprisingly, however both sdi-1 mRNA and protein actually decreased both in cells and homogenates of old rats. These results indicate that the age-related impairment in EGF stimulated DNA synthesis in hepatocytes appears to occur prior to or parallel with sdi-1 expression and cannot be explained on the basis of increased inhibition due to elevated levels of this protein.
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.
Dynamical trapping of particles as a challenge to statistical thermodynamics
NASA Astrophysics Data System (ADS)
Čápek, V.; Frege, O.
2000-03-01
A model of a dynamical trap is considered. This type of trapping appears as a result of reorganization of the trap surroundings (relaxation to a new local configuration) upon particle arrival. This can dynamically break existing overlaps of localized particle orbitals, i.e. to interrupt the return path for the particle. Thus, e.g., trapping at even a local potential maximum appears. The effect has nothing to do with, e.g., renormalization of particle energies owing to the bath. Scaling arguments are also presented to make the used kinetic treatment unquestionable.
Statistical analysis of modeling error in structural dynamic systems
NASA Technical Reports Server (NTRS)
Hasselman, T. K.; Chrostowski, J. D.
1990-01-01
The paper presents a generic statistical model of the (total) modeling error for conventional space structures in their launch configuration. Modeling error is defined as the difference between analytical prediction and experimental measurement. It is represented by the differences between predicted and measured real eigenvalues and eigenvectors. Comparisons are made between pre-test and post-test models. Total modeling error is then subdivided into measurement error, experimental error and 'pure' modeling error, and comparisons made between measurement error and total modeling error. The generic statistical model presented in this paper is based on the first four global (primary structure) modes of four different structures belonging to the generic category of Conventional Space Structures (specifically excluding large truss-type space structures). As such, it may be used to evaluate the uncertainty of predicted mode shapes and frequencies, sinusoidal response, or the transient response of other structures belonging to the same generic category.
Dynamical Systems Based Non Equilibrium Statistical Mechanics for Markov Chains
NASA Astrophysics Data System (ADS)
Prevost, Mireille
We introduce an abstract framework concerning non-equilibrium statistical mechanics in the specific context of Markov chains. This framework encompasses both the Evans-Searles and the Gallavotti-Cohen fluctuation theorems. To support and expand on these concepts, several results are proven, among which a central limit theorem and a large deviation principle. The interest for Markov chains is twofold. First, they model a great variety of physical systems. Secondly, their simplicity allows for an easy introduction to an otherwise complicated field encompassing the statistical mechanics of Anosov and Axiom A diffeomorphisms. We give two examples relating the present framework to physical cases modelled by Markov chains. One of these concerns chemical reactions and links key concepts from the framework to their well known physical counterpart.
Dynamical and statistical modeling of seasonal precipitation over Mexico
NASA Astrophysics Data System (ADS)
Fuentes-Franco, R.; Coppola, E.; Giorgi, F.; Pavia, E. G.; Graef Ziehl, F.
2012-12-01
Simulated patterns of seasonal precipitation over Mexico (Pmex) by a statistical model and by the recently-released version of the Regional Climate Model (RegCM4) are compared. The European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis ERA-Interim is used to provide initial and lateral boundary conditions for the RegCM4 simulation over the CORDEX Central America region; while regions of high correlation between Pmex and global sea surface temperatures (SST) over the Atlantic and Pacific Oceans are used as predictors in the statistical model. Compared with observations, the RegCM4 simulation shows a wet bias in topographically complex regions and a dry bias over Yucatan and northwestern Mexico. The wet bias is probably caused by the model's convection scheme, but the dry bias may be due to a lack of topographical features (in Yucatan) and a weakened representation of the North American Monsoon (in northwestern Mexico). RegCM4 simulates quite well the seasonal precipitation patterns and also the inter-seasonal variability, reproducing well the observed wetter or drier than normal seasons. RegCM4 is also able to reproduce adequately well the mid-summer drought in the south of Mexico. The statistical model also reproduces well the inter-seasonal precipitation variability, simulating Pmex better over southern and central Mexico than over northern Mexico. This may suggest that Pmex over northern Mexico is less dependent on SST than over other regions of the country.
Lars Onsager Prize Lecture: Statistical Dynamics of Disordered Systems
NASA Astrophysics Data System (ADS)
Fisher, Daniel S.
2013-03-01
The properties of many systems are strongly affected by quenched disorder that arose from their past history but is frozen on the time scales of interest. Although equilibrium phases and phase transitions in disordered materials can be very different from their counterparts in pure systems, the most striking phenomena involve non-equilibrium dynamics. The state of understanding of some of these will be reviewed including approach to equilibrium in spin glasses and the onset of motion in driven systems such as vortices in superconductors or earthquakes on geological faults. The potential for developing understanding of short-term evolutionary dynamics of microbial populations by taking advantage of the randomness of their past histories and the biological complexities will be discussed briefly.
Development and Evaluation of a Hybrid Dynamical-Statistical Downscaling Method
NASA Astrophysics Data System (ADS)
Walton, Daniel Burton
Regional climate change studies usually rely on downscaling of global climate model (GCM) output in order to resolve important fine-scale features and processes that govern local climate. Previous efforts have used one of two techniques: (1) dynamical downscaling, in which a regional climate model is forced at the boundaries by GCM output, or (2) statistical downscaling, which employs historical empirical relationships to go from coarse to fine resolution. Studies using these methods have been criticized because they either dynamical downscaled only a few GCMs, or used statistical downscaling on an ensemble of GCMs, but missed important dynamical effects in the climate change signal. This study describes the development and evaluation of a hybrid dynamical-statstical downscaling method that utilizes aspects of both dynamical and statistical downscaling to address these concerns. The first step of the hybrid method is to use dynamical downscaling to understand the most important physical processes that contribute to the climate change signal in the region of interest. Then a statistical model is built based on the patterns and relationships identified from dynamical downscaling. This statistical model can be used to downscale an entire ensemble of GCMs quickly and efficiently. The hybrid method is first applied to a domain covering Los Angeles Region to generate projections of temperature change between the 2041-2060 and 1981-2000 periods for 32 CMIP5 GCMs. The hybrid method is also applied to a larger region covering all of California and the adjacent ocean. The hybrid method works well in both areas, primarily because a single feature, the land-sea contrast in the warming, controls the overwhelming majority of the spatial detail. Finally, the dynamically downscaled temperature change patterns are compared to those produced by two commonly-used statistical methods, BCSD and BCCA. Results show that dynamical downscaling recovers important spatial features that the
Statistical characterization of spatiotemporal sediment dynamics in the Venice lagoon
NASA Astrophysics Data System (ADS)
Carniello, Luca; D'Alpaos, Andrea; Botter, Gianluca; Rinaldo, Andrea
2016-05-01
Characterizing the dynamics of suspended sediment is crucial when investigating the long-term evolution of tidal landscapes. Here we apply a widely tested mathematical model which describes the dynamics of cohesive and noncohesive sediments, driven by the combined effect of tidal currents and wind waves, using 1 year long time series of observed water levels and wind data from the Venice lagoon. The spatiotemporal evolution of the computed suspended sediment concentration (SSC) is analyzed on the basis of the "peak over threshold" theory. Our analysis suggests that events characterized by high SSC can be modeled as a marked Poisson process over most of the lagoon. The interarrival time between two consecutive over threshold events, the intensity of peak excesses, and the duration are found to be exponentially distributed random variables over most of tidal flats. Our study suggests that intensity and duration of over threshold events are temporally correlated, while almost no correlation exists between interarrival times and both durations and intensities. The benthic vegetation colonizing the central southern part of the Venice lagoon is found to exert a crucial role on sediment dynamics: vegetation locally decreases the frequency of significant resuspension events by affecting spatiotemporal patterns of SSCs also in adjacent areas. Spatial patterns of the mean interarrival of over threshold SSC events are found to be less heterogeneous than the corresponding patterns of mean interarrivals of over threshold bottom shear stress events because of the role of advection/dispersion processes in mixing suspended sediments within the lagoon. Implications for long-term morphodynamic modeling of tidal environments are discussed.
Intensity dynamics and statistical properties of random distributed feedback fiber laser.
Gorbunov, Oleg A; Sugavanam, Srikanth; Churkin, Dmitry V
2015-04-15
We present first experimental investigation of fast-intensity dynamics of random distributed feedback (DFB) fiber lasers. We found that the laser dynamics are stochastic on a short time scale and exhibit pronounced fluctuations including generation of extreme events. We also experimentally characterize statistical properties of radiation of random DFB fiber lasers. We found that statistical properties deviate from Gaussian and depend on the pump power.
Noisy inverted pendulums with time-delayed feedback: Statistical Dynamics
NASA Astrophysics Data System (ADS)
Milton, John G.
2001-03-01
The question of how an inverted pendulum can be stabilized has puzzled scientists for over 300 years. Studies of postural sway and stick balancing at the fingertip provide insights into how the human nervous system solves this problem. Time delays and noise are intrinsic features of the neural control and thus models are in the form of stochastic delay-differential equations. Examples are presented to show that the statistical properties of the fluctuations in posture and stick balancing are dominated by noise-dependent, nonlinear phenomena: noise-induced switching between limit cycle attractors (postural sway) and "on-off intermittency" arising from the stochastic forcing of a control parameter across a stability boundary (stick balancing). The existence of these phenomena is difficult to reconcile with classical concepts of neural feedback control.
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.
Do You Need to See It to Believe It? Let's See Statistics and Geometry Dynamically Together!
ERIC Educational Resources Information Center
Martins, José Alexandre; Roca, Assumpta Estrada; Nascimento, Maria Manuel
2014-01-01
Statistical graphs, measures of central tendency and measures of spread are key concepts in the statistics curriculum, so we present here a dynamic method (software) that may be used in the classroom. In this work we begin with an introductory approach. This is done to emphasize the importance of stimulating the visualization of statistical…
An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models
ERIC Educational Resources Information Center
Prindle, John J.; McArdle, John J.
2012-01-01
This study used statistical simulation to calculate differential statistical power in dynamic structural equation models with groups (as in McArdle & Prindle, 2008). Patterns of between-group differences were simulated to provide insight into how model parameters influence power approximations. Chi-square and root mean square error of…
SDI and the lawyers: Evolving interpretations of international arms control accords
Kaman, E.J.; Loprest, F.J. Jr.; Pisano, N.A.; Steiner, R.W.
1989-01-01
This note surveys international agreements that SDI may violate and discusses the policies underlying these potential legal and diplomatic conflicts. Part I provides an overview of the ABM Treaty, with emphasis on the provisions involved in the present interpretation controversy. Part II considers five other international covenants containing provisions upon which SDI may ultimately encroach. Part III evaluates several policy proposals that would permit SDI to proceed consistently with American international diplomatic commitments. This part also examines how an outright abrogation of the ABM Treaty or other agreements might affect American credibility and the arms-control process.
Human turnover dynamics during sleep: statistical behavior and its modeling.
Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi
2014-03-01
Turnover is a typical intermittent body movement while asleep. Exploring its behavior may provide insights into the mechanisms and management of sleep. However, little is understood about the dynamic nature of turnover in healthy humans and how it can be modified in disease. Here we present a detailed analysis of turnover signals that are collected by accelerometry from healthy elderly subjects and age-matched patients with neurodegenerative disorders such as Parkinson's disease. In healthy subjects, the time intervals between consecutive turnover events exhibit a well-separated bimodal distribution with one mode at ⩽10 s and the other at ⩾100 s, whereas such bimodality tends to disappear in neurodegenerative patients. The discovery of bimodality and fine temporal structures (⩽10 s) is a contribution that is not revealed by conventional sleep recordings with less time resolution (≈30 s). Moreover, we estimate the scaling exponent of the interval fluctuations, which also shows a clear difference between healthy subjects and patients. We incorporate these experimental results into a computational model of human decision making. A decision is to be made at each simulation step between two choices: to keep on sleeping or to make a turnover, the selection of which is determined dynamically by comparing a pair of random numbers assigned to each choice. This decision is weighted by a single parameter that reflects the depth of sleep. The resulting simulated behavior accurately replicates many aspects of observed turnover patterns, including the appearance or disappearance of bimodality and leads to several predictions, suggesting that the depth parameter may be useful as a quantitative measure for differentiating between normal and pathological sleep. These findings have significant clinical implications and may pave the way for the development of practical sleep assessment technologies.
Human turnover dynamics during sleep: Statistical behavior and its modeling
NASA Astrophysics Data System (ADS)
Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi
2014-03-01
Turnover is a typical intermittent body movement while asleep. Exploring its behavior may provide insights into the mechanisms and management of sleep. However, little is understood about the dynamic nature of turnover in healthy humans and how it can be modified in disease. Here we present a detailed analysis of turnover signals that are collected by accelerometry from healthy elderly subjects and age-matched patients with neurodegenerative disorders such as Parkinson's disease. In healthy subjects, the time intervals between consecutive turnover events exhibit a well-separated bimodal distribution with one mode at ⩽10 s and the other at ⩾100 s, whereas such bimodality tends to disappear in neurodegenerative patients. The discovery of bimodality and fine temporal structures (⩽10 s) is a contribution that is not revealed by conventional sleep recordings with less time resolution (≈30 s). Moreover, we estimate the scaling exponent of the interval fluctuations, which also shows a clear difference between healthy subjects and patients. We incorporate these experimental results into a computational model of human decision making. A decision is to be made at each simulation step between two choices: to keep on sleeping or to make a turnover, the selection of which is determined dynamically by comparing a pair of random numbers assigned to each choice. This decision is weighted by a single parameter that reflects the depth of sleep. The resulting simulated behavior accurately replicates many aspects of observed turnover patterns, including the appearance or disappearance of bimodality and leads to several predictions, suggesting that the depth parameter may be useful as a quantitative measure for differentiating between normal and pathological sleep. These findings have significant clinical implications and may pave the way for the development of practical sleep assessment technologies.
Algebraic Statistical Model for Biochemical Network Dynamics Inference.
Linder, Daniel F; Rempala, Grzegorz A
2013-12-01
With modern molecular quantification methods, like, for instance, high throughput sequencing, biologists may perform multiple complex experiments and collect longitudinal data on RNA and DNA concentrations. Such data may be then used to infer cellular level interactions between the molecular entities of interest. One method which formalizes such inference is the stoichiometric algebraic statistical model (SASM) of [2] which allows to analyze the so-called conic (or single source) networks. Despite its intuitive appeal, up until now the SASM has been only heuristically studied on few simple examples. The current paper provides a more formal mathematical treatment of the SASM, expanding the original model to a wider class of reaction systems decomposable into multiple conic subnetworks. In particular, it is proved here that on such networks the SASM enjoys the so-called sparsistency property, that is, it asymptotically (with the number of observed network trajectories) discards the false interactions by setting their reaction rates to zero. For illustration, we apply the extended SASM to in silico data from a generic decomposable network as well as to biological data from an experimental search for a possible transcription factor for the heat shock protein 70 (Hsp70) in the zebrafish retina.
Statistical mechanics of epidemics and population dynamics on networks
NASA Astrophysics Data System (ADS)
Joo, Jaewook
After a short introduction to the modeling of epidemics and population dynamics, we investigate in chapter 2, the time-evolution and steady states of an epidemic model (susceptible-infected-recovered-susceptible) on a network having the topology of the hypercubic lattice. We compare the behavior of this system, obtained from computer simulations, with those obtained from the mean-field approximation and pair-approximation. We find that the latter is significantly better than the former. In chapter 3, we study the behavior of a simple epidemic process (susceptible-infected-susceptible) on realistic networks in which vertices represent individuals and edges the interactions between them. Of particular interest are scale free networks with power-law distribution of degree, the number of edges emanating from a vertex. Considering cases where the transmission of infection between vertices depends on their degree, we introduce a saturation function which reduces the infection transmission rate across an edge leading to a node with high connectivity. This leads to a finite epidemic threshold on scale free networks with infinite second moment degree distribution above which the endemic infected state will be sustained and below which the disease dies out. In chapter 4, we study the time evolution and stationary states of a stochastic population model (contact process) with spatial heterogeneity and imposed drift (wind) on one- and two-dimensional lattices. We consider in particular a situation in which space is divided into two regions: an oasis and a desert (low and high death rates). Depending on the values of the drift and other parameters the population in the stationary state will be zero, localized, or delocalized. Finally, in appendix A we discuss a very different delocalized to localized type phase transition: the Mott metal insulator transition occurring in a half-filled single-band Hubbard model on a Bethe lattice. In the limit of infinite lattice coordination
Dynamic cortical involvement in implicit anticipation during statistical learning.
Altamura, Mario; Carver, Frederick W; Elvevåg, Brita; Weinberger, Daniel R; Coppola, Richard
2014-01-13
The prediction of future events is fundamental in a large number of critical neurobehavioral contexts including implicit motor learning. This learning process relies on the probabilities with which events occur, and is a dynamic phenomenon. The aim of present study was to investigate the development of anticipatory processes during implicit learning. A decision making task was employed in which the frequency of trial types was manipulated such that one trial type was disproportionately prevalent as compared to the remaining three trial types. A 275 channel whole-head magnetoencephalography (MEG) system was used to investigate the spatiotemporal distribution of event-related desynchronization (ERD) and synchronization (ERS). The results revealed that oscillations within the alpha (10-12 Hz) and beta (14-30 Hz) frequencies were associated with anticipatory processes in distinct networks in the course of learning. During early phases of learning the contralateral motor cortex, the anterior cingulate, the caudate and the inferior frontal gyrus showed ERDs within beta and alpha frequencies, putatively reflecting preparation of next motor response. As the task progressed, alpha ERSs in occipitotemporal regions and putamen likely reflect perceptual anticipation of the forthcoming stimuli.
NASA Astrophysics Data System (ADS)
Abramov, Rafail V.
2017-03-01
The classical fluctuation-dissipation theorem predicts the average response of a dynamical system to an external deterministic perturbation via time-lagged statistical correlation functions of the corresponding unperturbed system. In this work we develop a fluctuation-response theory and test a computational framework for the leading order response of statistical averages of a deterministic or stochastic dynamical system to an external stochastic perturbation. In the case of a stochastic unperturbed dynamical system, we compute the leading order fluctuation-response formulas for two different cases: when the existing stochastic term is perturbed, and when a new, statistically independent, stochastic perturbation is introduced. We numerically investigate the effectiveness of the new response formulas for an appropriately rescaled Lorenz 96 system, in both the deterministic and stochastic unperturbed dynamical regimes.
Statistical Physics Approaches to Respiratory Dynamics and Lung Structure
NASA Astrophysics Data System (ADS)
Suki, Bela
2004-03-01
The lung consists of a branching airway tree embedded in viscoelastic tissue and provides life-sustaining gas exchange to the body. In diseases, its structure is damaged and its function is compromised. We review two recent works about lung structure and dynamics and how they change in disease. 1) We introduced a new acoustic imaging approach to study airway structure. When airways in a collapsed lung are inflated, they pop open in avalanches. A single opening emits a sound package called crackle consisting of an initial spike (s) followed by ringing. The distribution n(s) of s follows a power law and the exponent of n(s) can be used to calculate the diameter ratio d defined as the ratio of the diameters of an airway to that of its parent averaged over all bifurcations. To test this method, we measured crackles in dogs, rabbits, rats and mice by inflating collapsed isolated lungs with air or helium while recording crackles with a microphone. In each species, n(s) follows a power law with an exponent that depends on species, but not on gas in agreement with theory. Values of d from crackles compare well with those calculated from morphometric data suggesting that this approach is suitable to study airway structure in disease. 2) Using novel experiments and computer models, we studied pulmonary emphysema which is caused by cigarette smoking. In emphysema, the elastic protein fibers of the tissue are actively remodeled by lung cells due to the chemicals present in smoke. We measured the mechanical properties of tissue sheets from normal and emphysematous lungs and imaged its structure which appears as a heterogeneous hexagonal network of fibers. We found evidence that during uniaxial stretching, the collagen and elastin fibers in emphysematous tissue can fail at a critical stress generating holes of various sizes (h). We developed network models of the failure process. When the failure is governed by mechanical forces, the distribution n(h) of h is a power law which
Monthly to seasonal low flow prediction: statistical versus dynamical models
NASA Astrophysics Data System (ADS)
Ionita-Scholz, Monica; Klein, Bastian; Meissner, Dennis; Rademacher, Silke
2016-04-01
the Alfred Wegener Institute a purely statistical scheme to generate streamflow forecasts for several months ahead. Instead of directly using teleconnection indices (e.g. NAO, AO) the idea is to identify regions with stable teleconnections between different global climate information (e.g. sea surface temperature, geopotential height etc.) and streamflow at different gauges relevant for inland waterway transport. So-called stability (correlation) maps are generated showing regions where streamflow and climate variable from previous months are significantly correlated in a 21 (31) years moving window. Finally, the optimal forecast model is established based on a multiple regression analysis of the stable predictors. We will present current results of the aforementioned approaches with focus on the River Rhine (being one of the world's most frequented waterways and the backbone of the European inland waterway network) and the Elbe River. Overall, our analysis reveals the existence of a valuable predictability of the low flows at monthly and seasonal time scales, a result that may be useful to water resources management. Given that all predictors used in the models are available at the end of each month, the forecast scheme can be used operationally to predict extreme events and to provide early warnings for upcoming low flows.
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.
Comparison of grain sorghum, soybean, and cotton production under spray, LEPA, and SDI
Technology Transfer Automated Retrieval System (TEKTRAN)
Crop production was compared under subsurface drip irrigation (SDI), low energy precision applicators (LEPA), low elevation spray applicators (LESA), and mid elevation spray applicators (MESA) at the USDA-Agricultural Research Service Conservation and Production Research Laboratory, Bushland, Tex., ...
Building Better SDI Profiles for Users of Large, Multidisciplinary Data Bases.
ERIC Educational Resources Information Center
Sprague, Robert J.; Frendenreich, L. Ben
1978-01-01
Reports an investigation conducted to improve the performance of SDI profiles in a large, complex data base that contains over a million references to scientific and technical literature, and uses full text indexing for retrieval. (Author/MBR)
NASA Astrophysics Data System (ADS)
Madadgar, Shahrbanou; AghaKouchak, Amir; Shukla, Shraddhanand; Wood, Andrew W.; Cheng, Linyin; Hsu, Kou-Lin; Svoboda, Mark
2016-07-01
Improving water management in water stressed-regions requires reliable seasonal precipitation predication, which remains a grand challenge. Numerous statistical and dynamical model simulations have been developed for predicting precipitation. However, both types of models offer limited seasonal predictability. This study outlines a hybrid statistical-dynamical modeling framework for predicting seasonal precipitation. The dynamical component relies on the physically based North American Multi-Model Ensemble (NMME) model simulations (99 ensemble members). The statistical component relies on a multivariate Bayesian-based model that relates precipitation to atmosphere-ocean teleconnections (also known as an analog-year statistical model). Here the Pacific Decadal Oscillation (PDO), Multivariate ENSO Index (MEI), and Atlantic Multidecadal Oscillation (AMO) are used in the statistical component. The dynamical and statistical predictions are linked using the so-called Expert Advice algorithm, which offers an ensemble response (as an alternative to the ensemble mean). The latter part leads to the best precipitation prediction based on contributing statistical and dynamical ensembles. It combines the strength of physically based dynamical simulations and the capability of an analog-year model. An application of the framework in the southwestern United States, which has suffered from major droughts over the past decade, improves seasonal precipitation predictions (3-5 month lead time) by 5-60% relative to the NMME simulations. Overall, the hybrid framework performs better in predicting negative precipitation anomalies (10-60% improvement over NMME) than positive precipitation anomalies (5-25% improvement over NMME). The results indicate that the framework would likely improve our ability to predict droughts such as the 2012-2014 event in the western United States that resulted in significant socioeconomic impacts.
Crystallization and preliminary X-ray studies of SdiA from Escherichia coli
Wu, Chunai; Lokanath, Neratur K.; Kim, Dong Young; Nguyen, Lan Dao Ngoc; Kim, Kyeong Kyu
2008-01-01
E. coli SdiA was overexpressed, purified and crystallized. The crystals belonged to the hexagonal space group P6{sub 1}22 or P6{sub 5}22 and diffracted to 2.7 Å resolution. SdiA enhances cell division by regulating the ftsQAZ operon in Escherichia coli as a transcription activator. In addition, SdiA is suggested to play a role in detecting quorum signals that emanate from other species. It is therefore a homologue of LuxR, a cognate quorum-sensing receptor that recognizes a quorum signal and activates the quorum responses. To elucidate the role of SdiA and its functional and structural relationship to LuxR, structural studies were performed on E. coli SdiA. Recombinant SdiA was overexpressed, purified and crystallized at 287 K using the hanging-drop vapour-diffusion method. X-ray diffraction data from a native crystal were collected with 99.7% completeness to 2.7 Å resolution with an R{sub merge} of 6.0%. The crystals belong to the hexagonal space group P6{sub 1}22 or P6{sub 5}22, with unit-cell parameters a = b = 130.47, c = 125.23 Å.
NASA Astrophysics Data System (ADS)
Eftaxias, Konstantinos; Minadakis, George; Potirakis, Stelios. M.; Balasis, Georgios
2013-02-01
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 neurodynamics can be analyzed within similar mathematical frameworks. Recently, authors have shown that a dynamical analogy supported by scale-free statistics exists between seizures and earthquakes, analyzing populations of different seizures and earthquakes, respectively. The purpose of this paper is to suggest a shift in emphasis from the large to the small scale: our analyses focus on a single epileptic seizure generation and the activation of a single fault (earthquake) and not on the statistics of sequences of different seizures and earthquakes. We apply the concepts of the nonextensive statistical physics to support the suggestion that a dynamical analogy exists between the two different extreme events, seizures and earthquakes. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg-Richter distribution of event sizes and the distribution of the waiting time until the next event). The performed analysis confirms the existence of a dynamic analogy between earthquakes and seizures, which moreover follow the dynamics of magnetic storms and solar flares.
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 χ(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.
Dynamics of statistical distance: Quantum limits for two-level clocks
Braunstein, S.L. ); Milburn, G.J. )
1995-03-01
We study the evolution of statistical distance on the Bloch sphere under unitary and nonunitary dynamics. This corresponds to studying the limits to clock precision for a clock constructed from a two-state system. We find that the initial motion away from pure states under nonunitary dynamics yields the greatest accuracy for a one-tick'' clock; in this case the clock's precision is not limited by the largest frequency of the system.
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.
Shiraishi, Hideaki; Stufflebeam, Steven M; Knake, Susanne; Ahlfors, Seppo P; Sudo, Akira; Asahina, Naoko; Egawa, Kiyoshi; Hatanaka, Keisaku; Kohsaka, Shinobu; Saitoh, Shinji; Grant, P Ellen; Dale, Anders M; Halgren, Eric
2005-04-01
Our current purpose is to evaluate the applicability of dynamic statistical parametric mapping, a novel method for localizing epileptiform activity recorded with magnetoencephalography in patients with epilepsy. We report four pediatric patients with focal epilepsies. Magnetoencephalographic data were collected with a 306-channel whole-head helmet-shaped sensor array. We calculated equivalent current dipoles and dynamic statistical parametric mapping movies of the interictal epileptiform discharges that were based in the minimum-L2 norm estimate, minimizing the square sum of the dipole element amplitudes. The dynamic statistical parametric mapping analysis of interictal epileptiform discharges can demonstrate the rapid change and propagation of interical epileptiform discharges. According to these findings, specific epileptogenic lesion-focal cortical dysplasia could be found and patients could be operated on successfully. The presurgical analysis of interictal epileptiform discharges using dynamic statistical parametric mapping seems to be promising in patients with a possible underlying focal cortical dysplasia and might help to guide the placement of invasive electrodes.
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.
Statistical-dynamical modeling of the cloud-to-ground lightning activity in Portugal
NASA Astrophysics Data System (ADS)
Sousa, J. F.; Fragoso, M.; Mendes, S.; Corte-Real, J.; Santos, J. A.
2013-10-01
The present study employs a dataset of cloud-to-ground discharges over Portugal, collected by the Portuguese lightning detection network in the period of 2003-2009, to identify dynamically coherent lightning regimes in Portugal and to implement a statistical-dynamical modeling of the daily discharges over the country. For this purpose, the high-resolution MERRA reanalysis is used. Three lightning regimes are then identified for Portugal: WREG, WREM and SREG. WREG is a typical cold-core cut-off low. WREM is connected to strong frontal systems driven by remote low pressure systems at higher latitudes over the North Atlantic. SREG is a combination of an inverted trough and a mid-tropospheric cold-core nearby Portugal. The statistical-dynamical modeling is based on logistic regressions (statistical component) developed for each regime separately (dynamical component). It is shown that the strength of the lightning activity (either strong or weak) for each regime is consistently modeled by a set of suitable dynamical predictors (65-70% of efficiency). The difference of the equivalent potential temperature in the 700-500 hPa layer is the best predictor for the three regimes, while the best 4-layer lifted index is still important for all regimes, but with much weaker significance. Six other predictors are more suitable for a specific regime. For the purpose of validating the modeling approach, a regional-scale climate model simulation is carried out under a very intense lightning episode.
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.
Identification of sdiA-regulated genes in a mouse commensal strain of Enterobacter cloacae
Sabag-Daigle, Anice; Dyszel, Jessica L.; Gonzalez, Juan F.; Ali, Mohamed M.; Ahmer, Brian M. M.
2015-01-01
Many bacteria determine their population density using quorum sensing. The most intensively studied mechanism of quorum sensing utilizes proteins of the LuxI family to synthesize a signaling molecule of the acylhomoserine lactone (AHL) type, and a protein of the LuxR family to bind AHL and regulate transcription. Genes regulated by quorum sensing often encode functions that are most effective when a group of bacteria are working cooperatively (e.g., luminescence, biofilm formation, host interactions). Bacteria in the Escherichia, Salmonella, Klebsiella, and Enterobacter genera do not encode an AHL synthase but they do encode an AHL receptor of the LuxR family, SdiA. Instead of detecting their own AHL synthesis, these organisms use SdiA to detect the AHLs synthesized by other bacterial species. In this study, we used a genetic screen to identify AHL-responsive genes in a commensal Enterobacter cloacae strain that was isolated from a laboratory mouse. The genes include a putative type VI secretion system, copA (a copper transporter), and fepE (extends O-antigen chain length). A new transposon mutagenesis strategy and suicide vectors were used to construct an sdiA mutant of E. cloacae. The AHL-responsiveness of all fusions was entirely sdiA-dependent, although some genes were regulated by sdiA in the absence of AHL. PMID:26075189
Identification of sdiA-regulated genes in a mouse commensal strain of Enterobacter cloacae.
Sabag-Daigle, Anice; Dyszel, Jessica L; Gonzalez, Juan F; Ali, Mohamed M; Ahmer, Brian M M
2015-01-01
Many bacteria determine their population density using quorum sensing. The most intensively studied mechanism of quorum sensing utilizes proteins of the LuxI family to synthesize a signaling molecule of the acylhomoserine lactone (AHL) type, and a protein of the LuxR family to bind AHL and regulate transcription. Genes regulated by quorum sensing often encode functions that are most effective when a group of bacteria are working cooperatively (e.g., luminescence, biofilm formation, host interactions). Bacteria in the Escherichia, Salmonella, Klebsiella, and Enterobacter genera do not encode an AHL synthase but they do encode an AHL receptor of the LuxR family, SdiA. Instead of detecting their own AHL synthesis, these organisms use SdiA to detect the AHLs synthesized by other bacterial species. In this study, we used a genetic screen to identify AHL-responsive genes in a commensal Enterobacter cloacae strain that was isolated from a laboratory mouse. The genes include a putative type VI secretion system, copA (a copper transporter), and fepE (extends O-antigen chain length). A new transposon mutagenesis strategy and suicide vectors were used to construct an sdiA mutant of E. cloacae. The AHL-responsiveness of all fusions was entirely sdiA-dependent, although some genes were regulated by sdiA in the absence of AHL.
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.
Determination of Slake Durability Index (Sdi) Values on Different Shape of Laminated Marl Samples
NASA Astrophysics Data System (ADS)
Ankara, Hüseyin; Çiçek, Fatma; Talha Deniz, İsmail; Uçak, Emre; Yerel Kandemir, Süheyla
2016-10-01
The slake durability index (SDI) test is widely used to determine the disintegration characteristic of the weak and clay-bearing rocks in geo-engineering problems. However, due to the different shapes of sample pieces, such as, irregular shapes displayed mechanical breakages in the slaking process, the SDI test has some limitations that affect the index values. In addition, shape and surface roughness of laminated marl samples have a severe influence on the SDI. In this study, a new sample preparation method called Pasha Method was used to prepare spherical specimens from the laminated marl collected from Seyitomer collar (SLI). Moreover the SDI tests were performed on equal size and weight specimens: three sets with different shapes were used. The three different sets were prepared as the test samples which had sphere shape, parallel to the layers in irregular shape, and vertical to the layers in irregular shape. Index values were determined for the three different sets subjected to the SDI test for 4 cycles. The index values at the end of fourth cycle were found to be 98.43, 98.39 and 97.20 %, respectively. As seen, the index values of the sphere sample set were found to be higher than irregular sample sets.
NASA Astrophysics Data System (ADS)
Chaikov, Leonid L.; Kirichenko, Marina N.; Krivokhizha, Svetlana V.; Zaritskiy, Alexander R.
2015-05-01
The work is devoted to the study of sizes and concentrations of proteins, and their aggregates in blood plasma samples, using static and dynamic light scattering methods. A new approach is proposed based on multiple repetition of measurements of intensity size distribution and on counting the number of registrations of different sizes, which made it possible to obtain statistically confident particle sizes and concentrations in the blood plasma. It was revealed that statistically confident particle sizes in the blood plasma were stable during 30 h of observations, whereas the concentrations of particles of different sizes varied as a result of redistribution of material between them owing to the protein degradation processes.
Chaikov, Leonid L; Kirichenko, Marina N; Krivokhizha, Svetlana V; Zaritskiy, Alexander R
2015-05-01
The work is devoted to the study of sizes and concentrations of proteins, and their aggregates in blood plasma samples, using static and dynamic light scattering methods. A new approach is proposed based on multiple repetition of measurements of intensity size distribution and on counting the number of registrations of different sizes, which made it possible to obtain statistically confident particle sizes and concentrations in the blood plasma. It was revealed that statistically confident particle sizes in the blood plasma were stable during 30 h of observations, whereas the concentrations of particles of different sizes varied as a result of redistribution of material between them owing to the protein degradation processes.
NASA Astrophysics Data System (ADS)
Koparan, Timur
2016-02-01
In this study, the effect on the achievement and attitudes of prospective teachers is examined. With this aim ahead, achievement test, attitude scale for statistics and interviews were used as data collection tools. The achievement test comprises 8 problems based on statistical data, and the attitude scale comprises 13 Likert-type items. The study was carried out in 2014-2015 academic year fall semester at a university in Turkey. The study, which employed the pre-test-post-test control group design of quasi-experimental research method, was carried out on a group of 80 prospective teachers, 40 in the control group and 40 in the experimental group. Both groups had four-hour classes about descriptive statistics. The classes with the control group were carried out through traditional methods while dynamic statistics software was used in the experimental group. Five prospective teachers from the experimental group were interviewed clinically after the application for a deeper examination of their views about application. Qualitative data gained are presented under various themes. At the end of the study, it was found that there is a significant difference in favour of the experimental group in terms of achievement and attitudes, the prospective teachers have affirmative approach to the use of dynamic software and see it as an effective tool to enrich maths classes. In accordance with the findings of the study, it is suggested that dynamic software, which offers unique opportunities, be used in classes by teachers and students.
Security implications of SDI. Will we be more secure in 2010
Simon, J.
1990-01-01
the current debate as to whether the Strategic Defense Initiative will make this nation more secure by the year 2010 rests on the question of whether such weapons might be developed and deployed by that time. The question is a complex one, involving political commitment, economic strength, and technological accomplishment, as well as international conditions. But if SDI is assumed to play even a minor role in US national strategy, then the needs of that strategy for the next century must be anticipated now. this is an anthology of the views of specialists on the issue. What they see varies according to assumptions and forecasts in such areas as technological feasibility and the progress of arms control. They agree that SDI would have inescapable consequences for our force structure and relations with our allies and adversaries. They offer insights from their particular areas of expertise. Different conclusions about SDI and the long-range security of the United States are presented.
Signal analysis applications of nonlinear dynamics and higher-order statistics
NASA Astrophysics Data System (ADS)
Solinsky, James C.; Feeney, John J.
1994-03-01
The use of higher-order statistics (HOS) in acoustic, and financial signal analysis applications is outlined in theory and followed with specific data examples. HOS analysis is used to identify data regions of interest, and nonlinear dynamics (ND) analysis is used in a 4D embedded space to show structural density changes resulting from the HOS regions. A second-order statistical comparison is made with the same data processed to have random Fourier phase, since the HOS information is contained in this nonrandom phase. These empirical results indicate that HOS data regions are structural distortions to a second-order planar disk in the 4D ND analysis space.
Aziz, Nabil; Sharma, Rakesh K; Mahfouz, Reda; Jha, Rajesh; Agarwal, Ashok
2011-06-30
Apoptosis was induced in immature and mature sperm in the presence or absence of poly (ADP-ribose) polymerase (PARP) inhibitor. The association of cleaved (cPARP) with sperm morphology was examined using sperm deformity index (SDI) score. The SDI scores are associated with PARP cleavage as an early marker of apoptosis.
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.
Energy-level statistics in the fine conformational resolution of RNA folding dynamics
NASA Astrophysics Data System (ADS)
Fernández, Ariel; Burastero, Teresita; Salthú, Rodolfo; Tablar, Ana
1999-11-01
This work is aimed at determining the energy-level statistics of the fine resolution of soft-mode dynamics warranting an adiabatically simplified structural relaxation of a folding biopolymer chain. The parameters defining the intrabasin structure relaxation are specified for RNA, so that each Watson-Crick base-pairing pattern may be treated as a quasiequilibrium ensemble of substates or torsional isomers within relevant folding time scales. The temperature-dependent threshold for energy dispersion associated with the fine structure of each superbasin is determined so as to warrant the adiabatic entrainment of the torsional dynamics.
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
Inducible expression of p21WAF-1/CIP-1/SDI-1 from a promoter conversion retroviral vector.
Mrochen, S; Klein, D; Nikol, S; Smith, J R; Salmons, B; Günzburg, W H
1997-01-01
Constitutive, high-level expression of the potentially therapeutic WAF-1/CIP-1/SDI-1 gene is incompatible with cell growth. A promoter conversion retroviral vector carrying the WAF-1/CIP-1/SDI-1 gene under the transcriptional control of the glucocorticoid inducible promoter of mouse mammary tumor virus was used to infect human bladder carcinoma or feline kidney cells. Reduced cell growth due to a greater proportion of cells being in the G0/G1 phase of the cell cycle was observed when WAF-1/CIP-1/SDI-1 expression was activated by addition of glucocorticoid hormone. This system demonstrates the potential long-term therapeutic use of WAF-1/CIP-1/SDI-1 delivered by retroviral vectors for inhibiting the growth of rapidly proliferating cells. Moreover, the conditional expression of genes such as WAF-1/CIP-1/SDI-1 from such retroviral vectors may facilitate analysis of their function.
NASA Astrophysics Data System (ADS)
Kaplya, E. V.
2016-11-01
The statistical regularity in the chaotic dynamics of wind direction is established. The distribution density of the increment in a wind-direction angle is approximated by generalizing the logistic law of distribution. Parameters of the approximation function are calculated by the least square method using the experimental data. The conformity between the function proposed and the meteorological data is verified by the Pearson's chi-squared test and the Kolmogorov test.
2015-06-23
AFRL-OSR-VA-TR-2015-0143 DYNAMIC INFORMATION NETWORKS: GEOMETRY, TOPOLOGY, AND STATISTICAL LEARNING FOR THE ARTICULATION OF STRUCTURE Daniel Rockmore...and machine learning . 15. SUBJECT TERMS Information networks, machine learning , link prediction, hyperbolic geometry, multiscale networks, complex...ideas from linear algebra, markov processes, diffusion networks, differential geometry, and machine learning
Dynamic heterogeneity and non-Gaussian statistics for acetylcholine receptors on live cell membrane
NASA Astrophysics Data System (ADS)
He, W.; Song, H.; Su, Y.; Geng, L.; Ackerson, B. J.; Peng, H. B.; Tong, P.
2016-05-01
The Brownian motion of molecules at thermal equilibrium usually has a finite correlation time and will eventually be randomized after a long delay time, so that their displacement follows the Gaussian statistics. This is true even when the molecules have experienced a complex environment with a finite correlation time. Here, we report that the lateral motion of the acetylcholine receptors on live muscle cell membranes does not follow the Gaussian statistics for normal Brownian diffusion. From a careful analysis of a large volume of the protein trajectories obtained over a wide range of sampling rates and long durations, we find that the normalized histogram of the protein displacements shows an exponential tail, which is robust and universal for cells under different conditions. The experiment indicates that the observed non-Gaussian statistics and dynamic heterogeneity are inherently linked to the slow-active remodelling of the underlying cortical actin network.
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…
Kazumba, Shija; Gillerman, Leonid; DeMalach, Yoel; Oron, Gideon
2010-01-01
Scarcity of fresh high-quality water has heightened the importance of wastewater reuse primarily in dry regions together with improving its efficient use by implementing the Subsurface Drip Irrigation (SDI) method. Sustainable effluent reuse combines soil and plant aspects, along with the maintainability of the application system. In this study, field experiments were conducted for two years on the commercial farm of Revivim and Mashabay-Sade farm (RMF) southeast of the City of Beer-Sheva, Israel. The purpose was to examine the response of alfalfa (Medicago sativa) as a perennial model crop to secondary domestic effluent application by means of a SDI system as compared with conventional overhead sprinkler irrigation. Emitters were installed at different depths and spacing. Similar amounts of effluent were applied to all plots during the experimental period. The results indicated that in all SDI treatments, the alfalfa yields were 11% to 25% higher than the ones obtained under sprinkler irrigated plots, besides the one in which the drip laterals were 200 cm apart. The average Water Use Efficiency (WUE) was better in all SDI treatments in comparison with the sprinkler irrigated plots. An economic assessment reveals the dependence of the net profit on the emitters' installation geometry, combined with the return for alfalfa in the market.
ERIC Educational Resources Information Center
DOWNIE, CURRIE S.; HOSHOVSKY, ALEXANDER G.
AN OVERVIEW OF THE OPERATIONAL AND EXPERIMENTAL SYSTEMS ESTABLISHED FOR THE SELECTIVE DISSEMINATION OF SCIENTIFIC AND TECHNICAL INFORMATION (SDI) IS PRESENTED. AN ATTEMPT HAS ALSO BEEN MADE TO IDENTIFY THE TRENDS WHICH MAY SHAPE THE FUTURE DEVELOPMENT OF THE SELECTIVE DISSEMINATION PROCEDURES. THE REPORT IS BASED IN PART ON THE EXISTING SDI…
Using SDI's to Get Primary Journals--A New Online Way
ERIC Educational Resources Information Center
Seba, Douglas B.; Forrest, Beth
1978-01-01
A study evaluated the relevance of the journal collection at the National Enforcement Investigation Center based on journals retrieved from online SDI searches. Use of the method to select the most relevant journals for a given user group are discussed. (KP)
The Importance of SDI for Current Awareness in Fields with Severe Scatter of Information.
ERIC Educational Resources Information Center
Packer, Katherine H.; Soergel, Dagobert
1979-01-01
Exploring the use and effectiveness of current awareness (CA) methods, especially selective dissemination of information (SDI) among chemists at Canadian universities, this study focuses on the perceived dispersal of information, use of various CA methods, time spent on CA, perceived success in CA, and CA efficiency. (FM)
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
Sojoudi, Alireza; Goodyear, Bradley G
2016-12-01
Spontaneous fluctuations of blood-oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) signals are highly synchronous between brain regions that serve similar functions. This provides a means to investigate functional networks; however, most analysis techniques assume functional connections are constant over time. This may be problematic in the case of neurological disease, where functional connections may be highly variable. Recently, several methods have been proposed to determine moment-to-moment changes in the strength of functional connections over an imaging session (so called dynamic connectivity). Here a novel analysis framework based on a hierarchical observation modeling approach was proposed, to permit statistical inference of the presence of dynamic connectivity. A two-level linear model composed of overlapping sliding windows of fMRI signals, incorporating the fact that overlapping windows are not independent was described. To test this approach, datasets were synthesized whereby functional connectivity was either constant (significant or insignificant) or modulated by an external input. The method successfully determines the statistical significance of a functional connection in phase with the modulation, and it exhibits greater sensitivity and specificity in detecting regions with variable connectivity, when compared with sliding-window correlation analysis. For real data, this technique possesses greater reproducibility and provides a more discriminative estimate of dynamic connectivity than sliding-window correlation analysis. Hum Brain Mapp 37:4566-4580, 2016. © 2016 Wiley Periodicals, Inc.
Statistical Techniques Complement UML When Developing Domain Models of Complex Dynamical Biosystems
Timmis, Jon; Qwarnstrom, Eva E.
2016-01-01
Computational modelling and simulation is increasingly being used to complement traditional wet-lab techniques when investigating the mechanistic behaviours of complex biological systems. In order to ensure computational models are fit for purpose, it is essential that the abstracted view of biology captured in the computational model, is clearly and unambiguously defined within a conceptual model of the biological domain (a domain model), that acts to accurately represent the biological system and to document the functional requirements for the resultant computational model. We present a domain model of the IL-1 stimulated NF-κB signalling pathway, which unambiguously defines the spatial, temporal and stochastic requirements for our future computational model. Through the development of this model, we observe that, in isolation, UML is not sufficient for the purpose of creating a domain model, and that a number of descriptive and multivariate statistical techniques provide complementary perspectives, in particular when modelling the heterogeneity of dynamics at the single-cell level. We believe this approach of using UML to define the structure and interactions within a complex system, along with statistics to define the stochastic and dynamic nature of complex systems, is crucial for ensuring that conceptual models of complex dynamical biosystems, which are developed using UML, are fit for purpose, and unambiguously define the functional requirements for the resultant computational model. PMID:27571414
Statistical Techniques Complement UML When Developing Domain Models of Complex Dynamical Biosystems.
Williams, Richard A; Timmis, Jon; Qwarnstrom, Eva E
2016-01-01
Computational modelling and simulation is increasingly being used to complement traditional wet-lab techniques when investigating the mechanistic behaviours of complex biological systems. In order to ensure computational models are fit for purpose, it is essential that the abstracted view of biology captured in the computational model, is clearly and unambiguously defined within a conceptual model of the biological domain (a domain model), that acts to accurately represent the biological system and to document the functional requirements for the resultant computational model. We present a domain model of the IL-1 stimulated NF-κB signalling pathway, which unambiguously defines the spatial, temporal and stochastic requirements for our future computational model. Through the development of this model, we observe that, in isolation, UML is not sufficient for the purpose of creating a domain model, and that a number of descriptive and multivariate statistical techniques provide complementary perspectives, in particular when modelling the heterogeneity of dynamics at the single-cell level. We believe this approach of using UML to define the structure and interactions within a complex system, along with statistics to define the stochastic and dynamic nature of complex systems, is crucial for ensuring that conceptual models of complex dynamical biosystems, which are developed using UML, are fit for purpose, and unambiguously define the functional requirements for the resultant computational model.
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.
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
Statistical characterization of the dynamic human body communication channel at 45 MHz.
Nie, Zedong; Ma, Jingjing; Chen, Hong; Wang, Lei
2013-01-01
The dynamic human body communication (HBC) propagation channel at 45 MHz was statistical characterized in this paper. A large amount of measurement data has been gathered in practical environment with real activities -treadmill running at different speeds in a lab room. The received power between two lower legs was acquired from three volunteers, with more than 60,000 snap shot of data in total. The statistical analyses confirmed that the HBC propagation channel at 45 MHz followed the Gamma and Lognormal distributions at the slower (2 km/h and 4 km/h) and faster (6 km/h and 8 km/h) running activities, respectively. The channel is insensitive to body motion with the maximum average fade duration is 0.0413 s and the most averaging bad channel duration time being less than 60 ms with the percentage of the bad channel duration time being less than 4.35%.
A Statistical Approach to Touchdown Dynamics for ExoMars 2016
NASA Astrophysics Data System (ADS)
Jauregui, Y. E.; Prieto, M.; del Campo, F.; Biondetti, G.; Walloschek, T.
2014-06-01
One of the major challenges of any space mission involving planetary Landers is to predict realistic impact conditions, in terms of load and stability. The strong uncertainty inherent to the touchdown event entails the development of accurate predictive methods.The main novelty introduced in this paper is the way this problem is faced for ExoMars 2016. The adopted solution is based on a Statistical Approach in which the relevant outputs are derived statistically from a set of random landing cases.This paper presents both the dynamic analyses and the qualification impact tests that are performed to demonstrate the reliability at touchdown of the ExoMars 2016 Entry, Descent and Landing Demonstrator Module.
Reaction Event Counting Statistics of Biopolymer Reaction Systems with Dynamic Heterogeneity.
Lim, Yu Rim; Park, Seong Jun; Park, Bo Jung; Cao, Jianshu; Silbey, Robert J; Sung, Jaeyoung
2012-04-10
We investigate the reaction event counting statistics (RECS) of an elementary biopolymer reaction in which the rate coefficient is dependent on states of the biopolymer and the surrounding environment and discover a universal kinetic phase transition in the RECS of the reaction system with dynamic heterogeneity. From an exact analysis for a general model of elementary biopolymer reactions, we find that the variance in the number of reaction events is dependent on the square of the mean number of the reaction events when the size of measurement time is small on the relaxation time scale of rate coefficient fluctuations, which does not conform to renewal statistics. On the other hand, when the size of the measurement time interval is much greater than the relaxation time of rate coefficient fluctuations, the variance becomes linearly proportional to the mean reaction number in accordance with renewal statistics. Gillespie's stochastic simulation method is generalized for the reaction system with a rate coefficient fluctuation. The simulation results confirm the correctness of the analytic results for the time dependent mean and variance of the reaction event number distribution. On the basis of the obtained results, we propose a method of quantitative analysis for the reaction event counting statistics of reaction systems with rate coefficient fluctuations, which enables one to extract information about the magnitude and the relaxation times of the fluctuating reaction rate coefficient, without a bias that can be introduced by assuming a particular kinetic model of conformational dynamics and the conformation dependent reactivity. An exact relationship is established between a higher moment of the reaction event number distribution and the multitime correlation of the reaction rate for the reaction system with a nonequilibrium initial state distribution as well as for the system with the equilibrium initial state distribution.
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.
Hotspots of boundary accumulation: dynamics and statistics of micro-swimmers in flowing films
Mathijssen, Arnold J. T. M.; Doostmohammadi, Amin; Yeomans, Julia M.; Shendruk, Tyler N.
2016-01-01
Biological flows over surfaces and interfaces can result in accumulation hotspots or depleted voids of microorganisms in natural environments. Apprehending the mechanisms that lead to such distributions is essential for understanding biofilm initiation. Using a systematic framework, we resolve the dynamics and statistics of swimming microbes within flowing films, considering the impact of confinement through steric and hydrodynamic interactions, flow and motility, along with Brownian and run–tumble fluctuations. Micro-swimmers can be peeled off the solid wall above a critical flow strength. However, the interplay of flow and fluctuations causes organisms to migrate back towards the wall above a secondary critical value. Hence, faster flows may not always be the most efficacious strategy to discourage biofilm initiation. Moreover, we find run–tumble dynamics commonly used by flagellated microbes to be an intrinsically more successful strategy to escape from boundaries than equivalent levels of enhanced Brownian noise in ciliated organisms. PMID:26841796
Nguyen, Y.; Nguyen, Nam X.; Rogers, Jamie L.; Liao, Jun; MacMillan, John B.; Jiang, Youxing; Sperandio, Vanessa
2015-05-19
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. IMPORTANCE Quorum sensing refers to bacterial chemical signaling. The QS acyl homoserine lactone (AHL) signals are recognized by LuxR-type receptors that regulate gene transcription. However, some bacteria have orphan LuxR-type receptors and
Nguyen, Y.; Nguyen, Nam X.; Rogers, Jamie L.; ...
2015-05-19
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 inmore » 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. IMPORTANCE Quorum sensing refers to bacterial chemical signaling. The QS acyl homoserine lactone (AHL) signals are recognized by LuxR-type receptors that regulate gene transcription. However, some bacteria have orphan Lux
Conn, Paul B.; Johnson, Devin S.; Ver Hoef, Jay M.; Hooten, Mevin B.; London, Joshua M.; Boveng, Peter L.
2015-01-01
Ecologists often fit models to survey data to estimate and explain variation in animal abundance. Such models typically require that animal density remains constant across the landscape where sampling is being conducted, a potentially problematic assumption for animals inhabiting dynamic landscapes or otherwise exhibiting considerable spatiotemporal variation in density. We review several concepts from the burgeoning literature on spatiotemporal statistical models, including the nature of the temporal structure (i.e., descriptive or dynamical) and strategies for dimension reduction to promote computational tractability. We also review several features as they specifically relate to abundance estimation, including boundary conditions, population closure, choice of link function, and extrapolation of predicted relationships to unsampled areas. We then compare a suite of novel and existing spatiotemporal hierarchical models for animal count data that permit animal density to vary over space and time, including formulations motivated by resource selection and allowing for closed populations. We gauge the relative performance (bias, precision, computational demands) of alternative spatiotemporal models when confronted with simulated and real data sets from dynamic animal populations. For the latter, we analyze spotted seal (Phoca largha) counts from an aerial survey of the Bering Sea where the quantity and quality of suitable habitat (sea ice) changed dramatically while surveys were being conducted. Simulation analyses suggested that multiple types of spatiotemporal models provide reasonable inference (low positive bias, high precision) about animal abundance, but have potential for overestimating precision. Analysis of spotted seal data indicated that several model formulations, including those based on a log-Gaussian Cox process, had a tendency to overestimate abundance. By contrast, a model that included a population closure assumption and a scale prior on total
Dynamic Statistical Characterization of Variation in Source Processes of Microseismic Events
NASA Astrophysics Data System (ADS)
Smith-Boughner, L.; Viegas, G. F.; Urbancic, T.; Baig, A. M.
2015-12-01
During a hydraulic fracture, water is pumped at high pressure into a formation. A proppant, typically sand is later injected in the hope that it will make its way into a fracture, keep it open and provide a path for the hydrocarbon to enter the well. This injection can create micro-earthquakes, generated by deformation within the reservoir during treatment. When these injections are monitored, thousands of microseismic events are recorded within several hundred cubic meters. For each well-located event, many source parameters are estimated e.g. stress drop, Savage-Wood efficiency and apparent stress. However, because we are evaluating outputs from a power-law process, the extent to which the failure is impacted by fluid injection or stress triggering is not immediately clear. To better detect differences in source processes, we use a set of dynamic statistical parameters which characterize various force balance assumptions using the average distance to the nearest event, event rate, volume enclosed by the events, cumulative moment and energy from a group of events. One parameter, the Fracability index, approximates the ratio of viscous to elastic forcing and highlights differences in the response time of a rock to changes in stress. These dynamic parameters are applied to a database of more than 90 000 events in a shale-gas play in the Horn River Basin to characterize spatial-temporal variations in the source processes. In order to resolve these differences, a moving window, nearest neighbour approach was used. First, the center of mass of the local distribution was estimated for several source parameters. Then, a set of dynamic parameters, which characterize the response of the rock were estimated. These techniques reveal changes in seismic efficiency and apparent stress and often coincide with marked changes in the Fracability index and other dynamic statistical parameters. Utilizing these approaches allowed for the characterization of fluid injection related
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.
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
NASA Astrophysics Data System (ADS)
Pierce, David W.; Das, Tapash; Cayan, Daniel R.; Maurer, Edwin P.; Miller, Norman L.; Bao, Yan; Kanamitsu, M.; Yoshimura, Kei; Snyder, Mark A.; Sloan, Lisa C.; Franco, Guido; Tyree, Mary
2013-02-01
Sixteen global general circulation models were used to develop probabilistic projections of temperature (T) and precipitation (P) changes over California by the 2060s. The global models were downscaled with two statistical techniques and three nested dynamical regional climate models, although not all global models were downscaled with all techniques. Both monthly and daily timescale changes in T and P are addressed, the latter being important for a range of applications in energy use, water management, and agriculture. The T changes tend to agree more across downscaling techniques than the P changes. Year-to-year natural internal climate variability is roughly of similar magnitude to the projected T changes. In the monthly average, July temperatures shift enough that that the hottest July found in any simulation over the historical period becomes a modestly cool July in the future period. Januarys as cold as any found in the historical period are still found in the 2060s, but the median and maximum monthly average temperatures increase notably. Annual and seasonal P changes are small compared to interannual or intermodel variability. However, the annual change is composed of seasonally varying changes that are themselves much larger, but tend to cancel in the annual mean. Winters show modestly wetter conditions in the North of the state, while spring and autumn show less precipitation. The dynamical downscaling techniques project increasing precipitation in the Southeastern part of the state, which is influenced by the North American monsoon, a feature that is not captured by the statistical downscaling.
Indole is an inter-species biofilm signal mediated by SdiA
Lee, Jintae; Jayaraman, Arul; Wood, Thomas K
2007-01-01
Background As a stationary phase signal, indole is secreted in large quantities into rich medium by Escherichia coli and has been shown to control several genes (e.g., astD, tnaB, gabT), multi-drug exporters, and the pathogenicity island of E. coli; however, its impact on biofilm formation has not been well-studied. Results Through a series of global transcriptome analyses, confocal microscopy, isogenic mutants, and dual-species biofilms, we show here that indole is a non-toxic signal that controls E. coli biofilms by repressing motility, inducing the sensor of the quorum sensing signal autoinducer-1 (SdiA), and influencing acid resistance (e.g., hdeABD, gadABCEX). Isogenic mutants showed these associated proteins are directly related to biofilm formation (e.g., the sdiA mutation increased biofilm formation 50-fold), and SdiA-mediated transcription was shown to be influenced by indole. The reduction in motility due to indole addition results in the biofilm architecture changing from scattered towers to flat colonies. Additionally, there are 12-fold more E. coli cells in dual-species biofilms grown in the presence of Pseudomonas cells engineered to express toluene o-monooxygenase (TOM, which converts indole to an insoluble indigoid) than in biofilms with pseudomonads that do not express TOM due to a 22-fold reduction in extracellular indole. Also, indole stimulates biofilm formation in pseudomonads. Further evidence that the indole effects are mediated by SdiA and homoserine lactone quorum sensing is that the addition of N-butyryl-, N-hexanoyl-, and N-octanoyl-L-homoserine lactones repress E. coli biofilm formation in the wild-type strain but not with the sdiA mutant. Conclusion Indole is an interspecies signal that decreases E. coli biofilms through SdiA and increases those of pseudomonads. Indole may be manipulated to control biofilm formation by oxygenases of bacteria that do not synthesize it in a dual-species biofilm. Furthermore, E. coli changes its biofilm in
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.
Statistical analysis of nonlinear dynamical systems using differential geometric sampling methods.
Calderhead, Ben; Girolami, Mark
2011-12-06
Mechanistic models based on systems of nonlinear differential equations can help provide a quantitative understanding of complex physical or biological phenomena. The use of such models to describe nonlinear interactions in molecular biology has a long history; however, it is only recently that advances in computing have allowed these models to be set within a statistical framework, further increasing their usefulness and binding modelling and experimental approaches more tightly together. A probabilistic approach to modelling allows us to quantify uncertainty in both the model parameters and the model predictions, as well as in the model hypotheses themselves. In this paper, the Bayesian approach to statistical inference is adopted and we examine the significant challenges that arise when performing inference over nonlinear ordinary differential equation models describing cell signalling pathways and enzymatic circadian control; in particular, we address the difficulties arising owing to strong nonlinear correlation structures, high dimensionality and non-identifiability of parameters. We demonstrate how recently introduced differential geometric Markov chain Monte Carlo methodology alleviates many of these issues by making proposals based on local sensitivity information, which ultimately allows us to perform effective statistical analysis. Along the way, we highlight the deep link between the sensitivity analysis of such dynamic system models and the underlying Riemannian geometry of the induced posterior probability distributions.
Martin, David; Boyle, Fergal
2015-09-01
Several clinical studies have identified a strong correlation between neointimal hyperplasia following coronary stent deployment and both stent-induced arterial injury and altered vessel hemodynamics. As such, the sequential structural and fluid dynamics analysis of balloon-expandable stent deployment should provide a comprehensive indication of stent performance. Despite this observation, very few numerical studies of balloon-expandable coronary stents have considered both the mechanical and hemodynamic impact of stent deployment. Furthermore, in the few studies that have considered both phenomena, only a small number of stents have been considered. In this study, a sequential structural and fluid dynamics analysis methodology was employed to compare both the mechanical and hemodynamic impact of six balloon-expandable coronary stents. To investigate the relationship between stent design and performance, several common stent design properties were then identified and the dependence between these properties and both the mechanical and hemodynamic variables of interest was evaluated using statistical measures of correlation. Following the completion of the numerical analyses, stent strut thickness was identified as the only common design property that demonstrated a strong dependence with either the mean equivalent stress predicted in the artery wall or the mean relative residence time predicted on the luminal surface of the artery. These results corroborate the findings of the large-scale ISAR-STEREO clinical studies and highlight the crucial role of strut thickness in coronary stent design. The sequential structural and fluid dynamics analysis methodology and the multivariable statistical treatment of the results described in this study should prove useful in the design of future balloon-expandable coronary stents.
McKie, F.
1987-03-23
The Strategic Defense Initiative (SDI) is an intensive research program aimed at determining whether there are cost-effective defensive technologies that could enhance deterrence, strengthen stability, and increase the security of the United States and its allies against ballistic missile nuclear attack. Since its inception in March 1983, opposition to the SDI program has been widely publicized by the media. The most prominent sources of such opposition have been members of the scientific, political, and Allied communities. The sources and rationale for this opposition, along with effects on calibre of support for SDI research efforts, congressional funding, and program changes in the SDI research schedule were examined. Information was gathered through a review of the literature.
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)
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
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.
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.
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.
Equilibrium Statistical Mechanics as a Novel Closure for Atmosphere-Ocean Dynamics
NASA Astrophysics Data System (ADS)
Turkington, B. E.; Majda, A. J.
2001-05-01
rim current that governs the lateral spread of the temperature anomaly; the effects of preconditioning from wind-driven gyres and topography are also realistically represented. In these and other related models, the statistical theory captures the nonlinear behavior of the large scales without detailed resolution of the small scales. Moreover, a corresponding quasi-equilibrium theory can be applied to systems with forcing and dissipation, reducing the full dynamics to the evolution of a few quasi-invariants and thereby providing a novel, dynamically-consistent closure.
Activities in HPM effects phenomenology at LLNL under the DNA/SDI Lth-6 effort
Cabayan, H.S.; King, R.J.
1988-01-01
During the fiscal years 1984-1986, DNA funded an effort at the Lawrence Livermore National Laboratory under the SDI/Lth-6 program to develop models and to study the phenomenology of HPM interaction with systems. The effort concentrated on the following areas: linear coupling/modeling; linear coupling/experiments; nonlinear coupling/modeling; component failure/modeling; component characterization; and electronic subsystem characterization. This report sumarizes these subject areas.
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.
NASA Astrophysics Data System (ADS)
Turchaninova, A.
2012-04-01
The estimation of extreme avalanche runout distances, flow velocities, impact pressures and volumes is an essential part of snow engineering in mountain regions of Russia. It implies the avalanche hazard assessment and mapping. Russian guidelines accept the application of different avalanche models as well as approaches for the estimation of model input parameters. Consequently different teams of engineers in Russia apply various dynamics and statistical models for engineering practice. However it gives more freedom to avalanche practitioners and experts but causes lots of uncertainties in case of serious limitations of avalanche models. We discuss these problems by presenting the application results of different well known and widely used statistical (developed in Russia) and avalanche dynamics models for several avalanche test sites in the Khibini Mountains (The Kola Peninsula) and the Caucasus. The most accurate and well-documented data from different powder and wet, big rare and small frequent snow avalanche events is collected from 1960th till today in the Khibini Mountains by the Avalanche Safety Center of "Apatit". This data was digitized and is available for use and analysis. Then the detailed digital avalanche database (GIS) was created for the first time. It contains contours of observed avalanches (ESRI shapes, more than 50 years of observations), DEMs, remote sensing data, description of snow pits, photos etc. Thus, the Russian avalanche data is a unique source of information for understanding of an avalanche flow rheology and the future development and calibration of the avalanche dynamics models. GIS database was used to analyze model input parameters and to calibrate and verify avalanche models. Regarding extreme dynamic parameters the outputs using different models can differ significantly. This is unacceptable for the engineering purposes in case of the absence of the well-defined guidelines in Russia. The frequency curves for the runout distance
Tanaka, Naoaki; Cole, Andrew J.; von Pechmann, Deidre; Wakeman, Daniel G.; Hämäläinen, Matti S.; Liu, Hesheng; Madsen, Joseph R.; Bourgeois, Blaise F.; Stufflebeam, Steven M.
2009-01-01
The purpose of this study is to assess the clinical value of spatiotemporal source analysis for analyzing ictal magnetoencephalography (MEG). Ictal MEG and simultaneous scalp EEG was recorded in five patients with medically intractable frontal lobe epilepsy. Dynamic statistical parametric maps (dSPMs) were calculated at the peak of early ictal spikes for the purpose of estimating the spatiotemporal cortical source distribution. DSPM solutions were mapped onto a cortical surface, which was derived from each patient's MRI. Equivalent current dipoles (ECDs) were calculated using a single-dipole model for comparison with dSPMs. In all patients, dSPMs tended to have a localized activation, consistent with the clinically-determined ictal onset zone, whereas most ECDs were considered to be inappropriate sources according to their goodness-of-fit values. Analyzing ictal MEG spikes by using dSPMs may provide useful information in presurgical evaluation of epilepsy. PMID:19394198
Tanaka, Naoaki; Cole, Andrew J; von Pechmann, Deidre; Wakeman, Daniel G; Hämäläinen, Matti S; Liu, Hesheng; Madsen, Joseph R; Bourgeois, Blaise F; Stufflebeam, Steven M
2009-08-01
The purpose of this study is to assess the clinical value of spatiotemporal source analysis for analyzing ictal magnetoencephalography (MEG). Ictal MEG and simultaneous scalp EEG was recorded in five patients with medically intractable frontal lobe epilepsy. Dynamic statistical parametric maps (dSPMs) were calculated at the peak of early ictal spikes for the purpose of estimating the spatiotemporal cortical source distribution. DSPM solutions were mapped onto a cortical surface, which was derived from each patient's MRI. Equivalent current dipoles (ECDs) were calculated using a single-dipole model for comparison with dSPMs. In all patients, dSPMs tended to have a localized activation, consistent with the clinically determined ictal onset zone, whereas most ECDs were considered to be inappropriate sources according to their goodness-of-fit values. Analyzing ictal MEG spikes by using dSPMs may provide useful information in presurgical evaluation of epilepsy.
Zhang, Qin; Dong, Chunling; Cui, Yan; Yang, Zhihui
2014-04-01
Graphical models for probabilistic reasoning are now in widespread use. Many approaches have been developed such as Bayesian network. A newly developed approach named as dynamic uncertain causality graph (DUCG) is initially presented in a previous paper, in which only the inference algorithm in terms of individual events and probabilities is addressed. In this paper, we first explain the statistic basis of DUCG. Then, we extend the algorithm to the form of matrices of events and probabilities. It is revealed that the representation of DUCG can be incomplete and the exact probabilistic inference may still be made. A real application of DUCG for fault diagnoses of a generator system of a nuclear power plant is demonstrated, which involves > 600 variables. Most inferences take < 1 s with a laptop computer. The causal logic between inference result and observations is graphically displayed to users so that they know not only the result, but also why the result obtained.
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.
Collisional statistics and dynamics of two-dimensional hard-disk systems: From fluid to solid.
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 mechanical model of gas adsorption in porous crystals with dynamic moieties.
Simon, Cory M; Braun, Efrem; Carraro, Carlo; Smit, Berend
2017-01-17
Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.
A copula approach on the dynamics of statistical dependencies in the US stock market
NASA Astrophysics Data System (ADS)
Münnix, Michael C.; Schäfer, Rudi
2011-11-01
We analyze the statistical dependence structure of the S&P 500 constituents in the 4-year period from 2007 to 2010 using intraday data from the New York Stock Exchange’s TAQ database. Instead of using a given parametric copula with a predetermined shape, we study the empirical pairwise copula directly. We find that the shape of this copula resembles the Gaussian copula to some degree, but exhibits a stronger tail dependence, for both correlated and anti-correlated extreme events. By comparing the tail dependence dynamically to the market’s average correlation level as a commonly used quantity we disclose the average level of error of the Gaussian copula, which is implied in the calculation of many correlation coefficients.
Development of a Dynamics-Based Statistical Prediction Model for the Changma Onset
NASA Astrophysics Data System (ADS)
Park, H. L.; Seo, K. H.; Son, J. H.
2015-12-01
The timing of the changma onset has high impacts on the Korean Peninsula, yet its seasonal prediction remains a great challenge because the changma undergoes various influences from the tropics, subtropics, and midlatitudes. In this study, a dynamics-based statistical prediction model for the changma onset is proposed. This model utilizes three predictors of slowly varying sea surface temperature anomalies (SSTAs) over the northern tropical central Pacific, the North Atlantic, and the North Pacific occurring in the preceding spring season. SSTAs associated with each predictor persist until June and have an effect on the changma onset by inducing an anticyclonic anomaly to the southeast of the Korean Peninsula earlier than the climatological changma onset date. The persisting negative SSTAs over the northern tropical central Pacific and accompanying anomalous trade winds induce enhanced convection over the far-western tropical Pacific; in turn, these induce a cyclonic anomaly over the South China Sea and an anticyclonic anomaly southeast of the Korean Peninsula. Diabatic heating and cooling tendency related to the North Atlantic dipolar SSTAs induces downstream Rossby wave propagation in the upper troposphere, developing a barotropic anticyclonic anomaly to the south of the Korean Peninsula. A westerly wind anomaly at around 45°N resulting from the developing positive SSTAs over the North Pacific directly reduces the strength of the Okhotsk high and gives rise to an anticyclonic anomaly southeast of the Korean Peninsula. With the dynamics-based statistical prediction model, it is demonstrated that the changma onset has considerable predictability of r = 0.73 for the period from 1982 to 2014.
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.
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-01-01
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 CHAMP and 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 in random errors (standard deviations) of optimized bending angles down to about two-thirds 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; (4) produces 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.
Drought episodes over Greece as simulated by dynamical and statistical downscaling approaches
NASA Astrophysics Data System (ADS)
Anagnostopoulou, Christina
2016-04-01
Drought over the Greek region is characterized by a strong seasonal cycle and large spatial variability. Dry spells longer than 10 consecutive days mainly characterize the duration and the intensity of Greek drought. Moreover, an increasing trend of the frequency of drought episodes has been observed, especially during the last 20 years of the 20th century. Moreover, the most recent regional circulation models (RCMs) present discrepancies compared to observed precipitation, while they are able to reproduce the main patterns of atmospheric circulation. In this study, both a statistical and a dynamical downscaling approach are used to quantify drought episodes over Greece by simulating the Standardized Precipitation Index (SPI) for different time steps (3, 6, and 12 months). A statistical downscaling technique based on artificial neural network is employed for the estimation of SPI over Greece, while this drought index is also estimated using the RCM precipitation for the time period of 1961-1990. Overall, it was found that the drought characteristics (intensity, duration, and spatial extent) were well reproduced by the regional climate models for long term drought indices (SPI12) while ANN simulations are better for the short-term drought indices (SPI3).
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
NASA Astrophysics Data System (ADS)
Sultan, B.; Oettli, P.; Vrac, M.; Baron, C.
2010-12-01
Global circulation models (GCM) are increasingly capable of making relevant predictions of seasonal and long-term climate variability, thus improving prospects of predicting impact on crop yields. This is particularly important for semi-arid West Africa where climate variability and drought threaten food security. Translating GCM outputs into attainable crop yields is difficult because GCM grid boxes are of larger scale than the processes governing yield, involving partitioning of rain among runoff, evaporation, transpiration, drainage and storage at plot scale. It therefore requires the use of downscaling methods. This study analyzes the performance of both dynamical and statistical downscaling techniques in simulating crop yield at local scale. A detailed case study is conducted using historical weather data for Senegal, applied to the crop model SARRAH for simulating several tropical cereals (sorghum, millet, maize) at local scale. This control simulation is used as a benchmark to evaluate a set of Regional Climate Models (RCM) simulations, forced by ERA-Interim, from the ENSEMBLES project and a statistical downscaling method, the CDF-Transform, used to correct biases in RCM outputs. We first evaluate each climate variable that drives the simulated yield in the control simulation (radiation, rainfall, temperatures). We then simulate crop yields with RCM outputs (with or without applying the CDG-Transform) and evaluate the performance of each RCM in regards to crop yield simulations.
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.
NASA Astrophysics Data System (ADS)
Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.
2013-12-01
During boreal spring, eastern portions of Kenya and Somalia have experienced more frequent droughts since 1999. Given the region's high levels of food insecurity, better predictions of these droughts could provide substantial humanitarian benefits. We show that dynamical-statistical seasonal climate forecasts, based on the latest generation of coupled atmosphere-ocean and uncoupled atmospheric models, effectively predict boreal spring rainfall in this area. Skill sources are assessed by comparing ensembles driven with full-ocean forcing with ensembles driven with ENSO-only sea surface temperatures (SSTs). Our analysis suggests that both ENSO and non-ENSO Indo-Pacific SST forcing have played an important role in the increase in drought frequencies. Over the past 30 years, La Niña drought teleconnections have strengthened, while non-ENSO Indo-Pacific convection patterns have also supported increased (decreased) Western Pacific (East African) rainfall. To further examine the relative contribution of ENSO, low frequency warming and the Pacific Decadal Oscillation, we present decompositions of ECHAM5, GFS, CAM4 and GMAO AMIP simulations. These decompositions suggest that rapid warming in the western Pacific and steeper western-to-central Pacific SST gradients have likely played an important role in the recent intensification of the Walker circulation, and the associated increase in East African aridity. A linear combination of time series describing the Pacific Decadal Oscillation and the strength of Indo-Pacific warming are shown to track East African rainfall reasonably well. The talk concludes with a few thoughts linking the potentially important interplay of attribution and prediction. At least for recent East African droughts, it appears that a characteristic Indo-Pacific SST and precipitation anomaly pattern can be linked statistically to support forecasts and attribution analyses. The combination of traditional AGCM attribution analyses with simple yet
Four-level atom dynamics and emission statistics using a quantum jump approach
NASA Astrophysics Data System (ADS)
Sandhya, S. N.
2007-01-01
Four-level atom dynamics is studied in a ladder system in the nine parameter space consisting of driving field strengths, detunings and decay constants, {Ω1,Ω2,Ω3,Δ1,Δ2,Δ3,Γ2,Γ3,Γ4} . One can selectively excite or induce two-level behavior between particular levels of ones choice by appropriately tuning the driving field strengths at three-photon resonance. The dynamics may be classified into two main regions of interest (i) small Ω2 coupling the ∣2⟩-∣3⟩ transition and (ii) large Ω2 . In case (i) one sees two-level behavior consisting of adjacent levels and in a particular region in the parameter space, there is an intermittent shelving of the electrons in one of the two subsystems. In case (ii) the levels consist of the ground state and the upper most level. Emission statistics is studied using the delay function approach in both the cases. In case (i), the behavior of the second order correlation function g2(t) , is similar to that of two-level emission for low Ω1 coupling the ∣1⟩-∣2⟩ transition, and the correlation increases with Ω1 for smaller time delays. While, in case (ii) when, in addition, Ω3 coupling the ∣3⟩-∣4⟩ transitionis kept low, g2(t) shows superpoissonian distribution, which may be attributed to three-photon processes.
Ingber, Lester; Nunez, Paul L
2011-02-01
The dynamic behavior of scalp potentials (EEG) is apparently due to some combination of global and local processes with important top-down and bottom-up interactions across spatial scales. In treating global mechanisms, we stress the importance of myelinated axon propagation delays and periodic boundary conditions in the cortical-white matter system, which is topologically close to a spherical shell. By contrast, the proposed local mechanisms are multiscale interactions between cortical columns via short-ranged non-myelinated fibers. A mechanical model consisting of a stretched string with attached nonlinear springs demonstrates the general idea. The string produces standing waves analogous to large-scale coherent EEG observed in some brain states. The attached springs are analogous to the smaller (mesoscopic) scale columnar dynamics. Generally, we expect string displacement and EEG at all scales to result from both global and local phenomena. A statistical mechanics of neocortical interactions (SMNI) calculates oscillatory behavior consistent with typical EEG, within columns, between neighboring columns via short-ranged non-myelinated fibers, across cortical regions via myelinated fibers, and also derives a string equation consistent with the global EEG model.
A STATISTICAL SURVEY OF DYNAMIC PRESSURE PULSES IN THE SOLAR WIND BASED ON WIND OBSERVATIONS
Zuo, Pingbing; Feng, Xueshang; Wang, Yi; Xie, Yanqiong; Xu, Xiaojun E-mail: fengx@spaceweather.ac.cn
2015-07-20
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.
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
Dynamical and statistical effects of the intrinsic curvature of internal space of molecules.
Teramoto, Hiroshi; Takatsuka, Kazuo
2005-02-15
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 statistical 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
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
A statistical-dynamical approach to represent Greenland ocean-ice sheet interactions
NASA Astrophysics Data System (ADS)
Perrette, Mahé; Calov, Reinhard; Ganopolski, Andrey; Robinson, Alex
2013-04-01
An understanding of the dynamics of the Greenland ice sheet is fundamental, because of its potential to contribute strongly to future sea level rise. In recent years there has been a discussion about the role of the ocean in the Greenland ice sheet's present and future mass balance. The ocean interacts with the ice sheet's outlet glaciers via the water circulation in the fjords and considerably affects melting at the termini of the outlet glaciers. Processes related to this interaction are difficult to represent in Greenland-wide ice-sheet models because grid resolution of such models is typically 10 km, whereas large fjords are more commonly only 1 to 5 km wide. Local refinement techniques (e.g. finite elements with adaptive mesh) can be a way of addressing that problem but are still computationally expensive to run. Here we propose a simpler, statistical-dynamical approach suited for large ensemble simulations over 100- to 1000-year integration times, in the EMIC spirit: the fjord-outlet glacier system is restricted to its most fundamental dynamics, controlled by a handful of parameters describing the major characteristics of the system. The model has a generic structure, i.e., it is designed such that it applies to every Greenland outlet glacier. Some of its parameters are fixed by using the (little) available observational data - e.g. for Helheim, Kangerdlugssuaq and Jakobshavn Isbrae - other parameters may vary depending on location. It is not our aim to simulate every single small outlet glacier in its full accuracy; but we aim to represent, on average, important characteristics like ice discharge and general advance/retreat rate on a regional scale over major catchment areas. Aspects of the coupling strategy with the 3D ice-sheet model (SICOPOLIS) are discussed, e.g., critical issues such as the treatment of mass balance. Preliminary design and results will be presented.
Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method
Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.
2014-07-15
Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937
Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method
Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.
2014-01-01
Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937
Glauber Dynamics in a Zero Magnetic Field and Eigenvalue Spacing Statistics
NASA Astrophysics Data System (ADS)
Mélin, R.
1996-04-01
We discuss the eigenvalue spacing statistics of the Glauber matrix for various models of statistical mechanics (a one dimensional Ising model, a two dimensional Ising model, a one dimensional model with a disordered ground state, and a SK model with and without a ferromagnetic bias). The dynamics of the one dimensional Ising model are integrable and the eigenvalue spacing statistics are non-universal. In the other cases, the eigenvalue statistics in the high temperature regime are intermediate between Poisson and G.O.E. (with P(0) of the order of 0.5). In the intermediate temperature regime, the statistics are G.O.E.. In the low temperature regime, the statistics have a peak at s=0. In the low temperature regime, and for disordered systems, the eigenvalues condense around integers, due to the fact that the local field on any spin never vanishes. This property is still valid for the Ising model on the Cayley tree, even if it is not disordered. We also study the spacing between the two largest eigenvalues as a function of temperature. This quantity seems to be sensitive to the existence of a broken symmetry phase. Nous discutons les statistiques d'écart entre valeurs propres de la matrice de Glauber pour différents modèles de mécanique statistique (modèle d'Ising unidimensionnel, modèle d'Ising bidimensionnel, modèle unidimensionnel avec un état fondamental désordonné, modèle SK avec ou sans biais ferromagnétique). La dynamique du modèle d'Ising unidimensionnel est intégrable, et la statistique d'écart entre valeurs propres est non universelle. Dans les autres cas, la statistique de valeurs propres dans le régime haute température est intermédiaire entre la loi de Poisson et la loi G.O.E. (avec P(0) de l'ordre de 0.5). Dans le régime intermédiaire, les statistiques sont G.O.E.. Dans le régime de basses températures, les statistiques présentent un pic pour s=0. A basse température et pour des systèmes désordonnés, les valeurs propres
NASA Astrophysics Data System (ADS)
Kim, Ok-Yeon; Kim, Hye-Mi; Lee, Myong-In; Min, Young-Mi
2017-01-01
This study aims at predicting the seasonal number of typhoons (TY) over the western North Pacific with an Asia-Pacific Climate Center (APCC) multi-model ensemble (MME)-based dynamical-statistical hybrid model. The hybrid model uses the statistical relationship between the number of TY during the typhoon season (July-October) and the large-scale key predictors forecasted by APCC MME for the same season. The cross validation result from the MME hybrid model demonstrates high prediction skill, with a correlation of 0.67 between the hindcasts and observation for 1982-2008. The cross validation from the hybrid model with individual models participating in MME indicates that there is no single model which consistently outperforms the other models in predicting typhoon number. Although the forecast skill of MME is not always the highest compared to that of each individual model, the skill of MME presents rather higher averaged correlations and small variance of correlations. Given large set of ensemble members from multi-models, a relative operating characteristic score reveals an 82 % (above-) and 78 % (below-normal) improvement for the probabilistic prediction of the number of TY. It implies that there is 82 % (78 %) probability that the forecasts can successfully discriminate between above normal (below-normal) from other years. The forecast skill of the hybrid model for the past 7 years (2002-2008) is more skillful than the forecast from the Tropical Storm Risk consortium. Using large set of ensemble members from multi-models, the APCC MME could provide useful deterministic and probabilistic seasonal typhoon forecasts to the end-users in particular, the residents of tropical cyclone-prone areas in the Asia-Pacific region.
Providing Geographic Datasets as Linked Data in Sdi
NASA Astrophysics Data System (ADS)
Hietanen, E.; Lehto, L.; Latvala, P.
2016-06-01
In this study, a prototype service to provide data from Web Feature Service (WFS) as linked data is implemented. At first, persistent and unique Uniform Resource Identifiers (URI) are created to all spatial objects in the dataset. The objects are available from those URIs in Resource Description Framework (RDF) data format. Next, a Web Ontology Language (OWL) ontology is created to describe the dataset information content using the Open Geospatial Consortium's (OGC) GeoSPARQL vocabulary. The existing data model is modified in order to take into account the linked data principles. The implemented service produces an HTTP response dynamically. The data for the response is first fetched from existing WFS. Then the Geographic Markup Language (GML) format output of the WFS is transformed on-the-fly to the RDF format. Content Negotiation is used to serve the data in different RDF serialization formats. This solution facilitates the use of a dataset in different applications without replicating the whole dataset. In addition, individual spatial objects in the dataset can be referred with URIs. Furthermore, the needed information content of the objects can be easily extracted from the RDF serializations available from those URIs. A solution for linking data objects to the dataset URI is also introduced by using the Vocabulary of Interlinked Datasets (VoID). The dataset is divided to the subsets and each subset is given its persistent and unique URI. This enables the whole dataset to be explored with a web browser and all individual objects to be indexed by search engines.
Murphy, Kyle R; Mann, Ian R; Rae, I Jonathan; Sibeck, David G; Watt, Clare E J
2016-08-01
Wave-particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However, statistical averages poorly characterize extreme events such as geomagnetic storms in that storm-time ultralow frequency wave power is typically larger than that derived over a solar cycle and Kp is a poor proxy for storm-time wave power.
Mann, Ian R.; Rae, I. Jonathan; Sibeck, David G.; Watt, Clare E. J.
2016-01-01
Abstract Wave‐particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However, statistical averages poorly characterize extreme events such as geomagnetic storms in that storm‐time ultralow frequency wave power is typically larger than that derived over a solar cycle and Kp is a poor proxy for storm‐time wave power. PMID:27867798
NASA Astrophysics Data System (ADS)
Murphy, Kyle R.; Mann, Ian R.; Rae, I. Jonathan; Sibeck, David G.; Watt, Clare E. J.
2016-08-01
Wave-particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However, statistical averages poorly characterize extreme events such as geomagnetic storms in that storm-time ultralow frequency wave power is typically larger than that derived over a solar cycle and Kp is a poor proxy for storm-time wave power.
Statistical characteristics of dynamics for population migration driven by the economic interests
NASA Astrophysics Data System (ADS)
Huo, Jie; Wang, Xu-Ming; Zhao, Ning; Hao, Rui
2016-06-01
Population migration typically occurs under some constraints, which can deeply affect the structure of a society and some other related aspects. Therefore, it is critical to investigate the characteristics of population migration. Data from the China Statistical Yearbook indicate that the regional gross domestic product per capita relates to the population size via a linear or power-law relation. In addition, the distribution of population migration sizes or relative migration strength introduced here is dominated by a shifted power-law relation. To reveal the mechanism that creates the aforementioned distributions, a dynamic model is proposed based on the population migration rule that migration is facilitated by higher financial gains and abated by fewer employment opportunities at the destination, considering the migration cost as a function of the migration distance. The calculated results indicate that the distribution of the relative migration strength is governed by a shifted power-law relation, and that the distribution of migration distances is dominated by a truncated power-law relation. These results suggest the use of a power-law to fit a distribution may be not always suitable. Additionally, from the modeling framework, one can infer that it is the randomness and determinacy that jointly create the scaling characteristics of the distributions. The calculation also demonstrates that the network formed by active nodes, representing the immigration and emigration regions, usually evolves from an ordered state with a non-uniform structure to a disordered state with a uniform structure, which is evidenced by the increasing structural entropy.
Dynamical and statistical behavior of discrete combustion waves: a theoretical and numerical study.
Bharath, Naine Tarun; Rashkovskiy, Sergey A; Tewari, Surya P; Gundawar, Manoj Kumar
2013-04-01
We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius' macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius' microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.
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 mechanical model of gas adsorption in porous crystals with dynamic moieties
Braun, Efrem; Carraro, Carlo; Smit, Berend
2017-01-01
Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes. PMID:28049851
Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response
NASA Astrophysics Data System (ADS)
Floerchinger, Stefan; Wiedemann, Urs Achim
2014-08-01
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.
Dynamical and statistical behavior of discrete combustion waves: A theoretical and numerical study
NASA Astrophysics Data System (ADS)
Bharath, Naine Tarun; Rashkovskiy, Sergey A.; Tewari, Surya P.; Gundawar, Manoj Kumar
2013-04-01
We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius’ macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius’ microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.
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.
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.
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.
A stereoscopic diagonal inverter (SDI) for wide-angle vitreous surgery.
Spitznas, M; Reiner, J
1987-01-01
All known methods of wide-angle observation of the fundus deliver an inverted image. To overcome these difficulties a stereoscopic diagonal inverter (SDI) was developed, which serves as an accessory to the operating microscope. This device permits the microscopic image to be vertically inverted and laterally reversed, while retaining full stereopsis, and thus makes wide-angle observation devices such as the Rodenstock Panfundoscope contact lens (150 degrees) and a modified version of the binocular indirect ophthalmoscope (70 degrees-90 degrees) usable in vitreous microsurgery.
Timchenko, N A; Wilde, M; Nakanishi, M; Smith, J R; Darlington, G J
1996-04-01
C/EBPalpha has a role in growth arrest and differentiation of mouse preadipocytes. To study the mechanism of C/EBPalpha-induced growth arrest, we developed a cell line, HT1, that contained the human C/EBPalpha gene under Lac repressor control. IPTG-induced C/EBPalpha caused inhibition of cell proliferation and DNA synthesis as measured by colony growth assays, cell counting, and BrdU uptake. A number of proteins that are known to be involved in the regulation of the cell cycle, such as cyclin-dependent kinase (CDK)2 and CDK4, proliferating cell nuclear antigen (PCNA), p53, c-fos, and the CDK inhibitor p16 and p27 were investigated by Western analysis. No change in their expression was observed. However, the p21 (WAF-1/CIP-1/SDI-1) protein was significantly elevated in growth-arrested HT1 cells. Elevation of p21/SDI-1 mRNA (threefold) and activation of the p21/SDI-1 promoter by C/EBPalpha did not account for the 12- to 20-fold increase in p21/SDI-1 protein. Protein synthesis inhibition by cycloheximide (CHX) treatment indicated that the half-life of p21/SDI-1 in dividing HT1 cells was approximately 30 min. However, in C/EBPalpha growth-arrested cells, the level of the p21/SDI-1 did not change for > 80 min after CHX addition. Our studies demonstrate that C/EBPalpha activates p21/SDI-1 by increasing p21/SDI-1 gene expression and by post-translational stabilization of p21/SDI-1 protein. Furthermore, induction of p21/SDI-1 is responsible for the ability of C/EBPalpha to inhibit proliferation because transcription of antisense p21/SDI-1 mRNA eliminated growth inhibition by C/EBPalpha.
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
ERIC Educational Resources Information Center
Callamaras, Peter
1983-01-01
This buyer's guide to seven major types of statistics software packages for microcomputers reviews Edu-Ware Statistics 3.0; Financial Planning; Speed Stat; Statistics with DAISY; Human Systems Dynamics package of Stats Plus, ANOVA II, and REGRESS II; Maxistat; and Moore-Barnes' MBC Test Construction and MBC Correlation. (MBR)
NASA Astrophysics Data System (ADS)
Schubert, David; Reyers, Mark; Pinto, Joaquim; Fink, Andreas; Massmeyer, Klaus
2016-04-01
Southeast Asia has been identified as one of the hot-spots of climate change. While the projected changes in annual precipitation are comparatively small, there is a clear tendency towards more rainfall in the dry season and an increase in extreme precipitation events. In this study, a statistical dynamical downscaling (SDD) approach is applied to obtain higher resolution and more robust regional climate change projections for tropical Southeast Asia with focus on Vietnam. First, a recent climate (RC) simulation with the regional climate model COSMO-CLM with a spatial resolution of ~50 km driven by ERA-Interim (1979-2008) is performed for the tropical region of Southeast Asia. For the SDD, six weather types (WTs) are selected for Vietnam during the wet season (April - October) using a k-means cluster analysis of daily zonal wind component in 850 hPa and 200 hPa from the RC run. For each calculated weather type, simulated representatives are selected from the RC run and are then further dynamically downscaled to a resolution of 0.0625° (7 km). By using historical WT frequencies, the simulated representatives are recombined to a high resolution rainfall climatology for the recent climate. It is shown that the SDD is generally able to capture the present day climatology and that the employment of the higher resolved simulated representatives enhances the performance of the SDD. However, an overestimation of rainfall at higher altitudes is found. To obtain future climate projections, an ensemble of eight CMIP5 model members are selected to study precipitation changes. For these projections, WT frequencies of future scenarios under two representative Concentration Pathways (RCP4.5 and RCP8.5) are taken into account for the mid-term scenario (2046-2065) and the long-term scenario (2081-2100). The strongest precipitation changes are found for the RCP8.5 scenario. Most of the models indicate a generally increase in precipitation amount in the wet period over Southeast
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.
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
Sensitivity properties of a biosphere model based on BATS and a statistical-dynamical climate model
Zhang, T. )
1994-06-01
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. 46 refs., 10 figs., 6 tabs.
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).
ERIC Educational Resources Information Center
Koparan, Timur
2016-01-01
In this study, the effect on the achievement and attitudes of prospective teachers is examined. With this aim ahead, achievement test, attitude scale for statistics and interviews were used as data collection tools. The achievement test comprises 8 problems based on statistical data, and the attitude scale comprises 13 Likert-type items. The study…
Ginestet, Cedric E; Simmons, Andrew
2011-03-15
Network analysis has become a tool of choice for the study of functional and structural Magnetic Resonance Imaging (MRI) data. Little research, however, has investigated connectivity dynamics in relation to varying cognitive load. In fMRI, correlations among slow (<0.1 Hz) fluctuations of blood oxygen level dependent (BOLD) signal can be used to construct functional connectivity networks. Using an anatomical parcellation scheme, we produced undirected weighted graphs linking 90 regions of the brain representing major cortical gyri and subcortical nuclei, in a population of healthy adults (n=43). Topological changes in these networks were investigated under different conditions of a classical working memory task - the N-back paradigm. A mass-univariate approach was adopted to construct statistical parametric networks (SPNs) that reflect significant modifications in functional connectivity between N-back conditions. Our proposed method allowed the extraction of 'lost' and 'gained' functional networks, providing concise graphical summaries of whole-brain network topological changes. Robust estimates of functional networks are obtained by pooling information about edges and vertices over subjects. Graph thresholding is therefore here supplanted by inference. The analysis proceeds by firstly considering changes in weighted cost (i.e. mean between-region correlation) over the different N-back conditions and secondly comparing small-world topological measures integrated over network cost, thereby controlling for differences in mean correlation between conditions. The results are threefold: (i) functional networks in the four conditions were all found to satisfy the small-world property and cost-integrated global and local efficiency levels were approximately preserved across the different experimental conditions; (ii) weighted cost considerably decreased as working memory load increased; and (iii) subject-specific weighted costs significantly predicted behavioral
Chládek, J; Brázdil, M; Halámek, J; Plešinger, F; Jurák, P
2013-01-01
We present an off-line analysis procedure for exploring brain activity recorded from intra-cerebral electroencephalographic data (SEEG). The objective is to determine the statistical differences between different types of stimulations in the time-frequency domain. The procedure is based on computing relative signal power change and subsequent statistical analysis. An example of characteristic statistically significant event-related de/synchronization (ERD/ERS) detected across different frequency bands following different oddball stimuli is presented. The method is used for off-line functional classification of different brain areas.
NASA Astrophysics Data System (ADS)
Shibkov, A. A.; Kazakov, A. A.
2009-03-01
Statistical analysis of the plastic deformation steps and fracture of polycrystalline ice has been performed. It is established that an increase in deformation leads to gradual evolution of the statistics of amplitudes of mesoscopic deformation jumps from random (with a Poisson distribution of dislocation avalanche amplitudes) to “critical” (with a power-law distribution), which indicates occurrence of long-range correlations of the dislocation mesodynamics of deformed polycrystalline ice. The state of self-organized criticality at subcritical ice fracture has been revealed from the power-law statistics of the amplitudes of electric pulses and pauses between them, flicker-noise structure, and almost monofractal character of signals.
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...
ERIC Educational Resources Information Center
BIVONA, WILLIAM A.
A SET OF GUIDELINES FOR IMPLEMENTING AND OPERATING A REPLICA OF A PROTOTYPE SELECTIVE DISSEMINATION OF INFORMATION (SDI) SYSTEM TESTED AT U.S. ARMY NATICK LABORATORIES, AND REPORTED IN LI 000 273, IS GIVEN IN THIS MANUAL. INFORMATION IS SUPPLIED WHICH IS USEFUL IN THE INITIAL STAGES OF IMPLEMENTATION. THE APPLICATION OF SPECIFIC CRITERIA FOR…
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...
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.
Shankar, Manoharan; Ponraj, Paramasivan; Illakkiam, Devaraj; Rajendhran, Jeyaprakash
2013-01-01
Enterobacter cloacae GS1 is a plant growth-promoting bacterium which colonizes rice roots. In the rhizosphere environment, N-acyl homoserine lactone (NAHL)-like quorum-sensing signals are known to be produced by host plants and other microbial inhabitants. E. cloacae GS1 was unable to synthesize NAHL quorum-sensing signals but had the NAHL-dependent transcriptional regulator-encoding gene sdiA. This study was aimed at understanding the effects of SdiA and NAHL-dependent cross talk in rice root colonization by E. cloacae GS1. Pleiotropic effects of sdiA inactivation included substantial increases in root colonization and biofilm formation, suggesting a negative role for SdiA in bacterial adhesion. We provide evidence that sdiA inactivation leads to elevated levels of biosynthesis of curli, which is involved in cellular adhesion. Extraneous addition of NAHLs had a negative effect on root colonization and biofilm formation. However, the sdiA mutant of E. cloacae GS1 was insensitive to NAHLs, suggesting that this NAHL-induced inhibition of root colonization and biofilm formation is SdiA dependent. Therefore, it is proposed that NAHLs produced by both plant and microbes in the rice rhizosphere act as cross-kingdom and interspecies signals to negatively impact cellular adhesion and, thereby, root colonization in E. cloacae GS1. PMID:23086212
Soares, Jitesh A.; Ellermeier, Craig D.; Altier, Craig; Lawhon, Sara D.; Adams, L. Garry; Konjufca, Vjollca; Curtiss, Roy; Slauch, James M.; Ahmer, Brian M. M.
2008-01-01
Background LuxR-type transcription factors are typically used by bacteria to determine the population density of their own species by detecting N-acylhomoserine lactones (AHLs). However, while Escherichia and Salmonella encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species. Methodology/Principal Findings In this report, we tested the hypothesis that SdiA detects the AHL-production of other bacterial species within the animal host. SdiA did not detect AHLs during the transit of Salmonella through the gastrointestinal tract of a guinea pig, a rabbit, a cow, 5 mice, 6 pigs, or 12 chickens. However, SdiA was activated during the transit of Salmonella through turtles. All turtles examined were colonized by the AHL-producing species Aeromonas hydrophila. Conclusions/Significance We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals. PMID:18665275
Onisko, Agnieszka; Druzdzel, Marek J.; Austin, R. Marshall
2016-01-01
Background: Classical statistics is a well-established approach in the analysis of medical data. While the medical community seems to be familiar with the concept of a statistical analysis and its interpretation, the Bayesian approach, argued by many of its proponents to be superior to the classical frequentist approach, is still not well-recognized in the analysis of medical data. Aim: The goal of this study is to encourage data analysts to use the Bayesian approach, such as modeling with graphical probabilistic networks, as an insightful alternative to classical statistical analysis of medical data. Materials and Methods: This paper offers a comparison of two approaches to analysis of medical time series data: (1) classical statistical approach, such as the Kaplan–Meier estimator and the Cox proportional hazards regression model, and (2) dynamic Bayesian network modeling. Our comparison is based on time series cervical cancer screening data collected at Magee-Womens Hospital, University of Pittsburgh Medical Center over 10 years. Results: The main outcomes of our comparison are cervical cancer risk assessments produced by the three approaches. However, our analysis discusses also several aspects of the comparison, such as modeling assumptions, model building, dealing with incomplete data, individualized risk assessment, results interpretation, and model validation. Conclusion: Our study shows that the Bayesian approach is (1) much more flexible in terms of modeling effort, and (2) it offers an individualized risk assessment, which is more cumbersome for classical statistical approaches. PMID:28163973
[Tissue mechanical behavior of tendinous fibers under statistical and dynamic requirements].
Arnold, G; Gross, F; Moll, C
1977-01-01
With a device for dynamical processes tension tests were performed on bundles of collagen fibres of human and bovin origin. Part of the studies were performed under statical condition with an universal materials testing machine, equipped with a closed loop feed back control system. If the force is to be kept constant subsequently to a strain process on a collagen fiber bundle (isotonic condition), the fiber length must increase (creep phenomenon, retardation). The force decreases under constant length after a preceding strain process (relaxation). In analogy to the statical relaxation, statical isorheological line, and statical force recovery curve the dynamical (cyclic) relaxation, dynamical (cyclic) isorheological curve, and dynamical (cyclic) force recovery curve are described. The mechanical-rheological properties collagen fiber bundles are discussed in relation to functional anatomy.
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
2016-02-01
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.
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…
NASA Astrophysics Data System (ADS)
De Bacco, Caterina; Guggiola, Alberto; Kühn, Reimer; Paga, Pierre
2016-05-01
Rare event statistics for random walks on complex networks are investigated using the large deviation formalism. Within this formalism, rare events are realised as typical events in a suitably deformed path-ensemble, and their statistics can be studied in terms of spectral properties of a deformed Markov transition matrix. We observe two different types of phase transition in such systems: (i) rare events which are singled out for sufficiently large values of the deformation parameter may correspond to localised modes of the deformed transition matrix; (ii) ‘mode-switching transitions’ may occur as the deformation parameter is varied. Details depend on the nature of the observable for which the rare event statistics is studied, as well as on the underlying graph ensemble. In the present paper we report results on rare events statistics for path averages of random walks in Erdős-Rényi and scale free networks. Large deviation rate functions and localisation properties are studied numerically. For observables of the type considered here, we also derive an analytical approximation for the Legendre transform of the large deviation rate function, which is valid in the large connectivity limit. It is found to agree well with simulations.
NASA Astrophysics Data System (ADS)
Burkholder, Michael B.; Litster, Shawn
2016-05-01
In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.
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.
NASA Astrophysics Data System (ADS)
Koukas, Ioannis; Koukoravas, Vasilis; Mantesi, Konstantina; Sakellari, Katerina; Xanthopoulou, Themis-Demetra; Zarkadoulas, Akis; Markonis, Yannis; Papalexiou, Simon Michael; Koutsoyiannis, Demetris
2014-05-01
The statistical properties of over 300 different proxy records of the last two thousand years derived from the PAGES 2k database years are stochastically analysed. Analyses include estimation of their first four moments and their autocorrelation functions (ACF), as well as the determination of the presence of Hurst-Kolmogorov behaviour (known also as long term persistence). The data are investigated in groups according to their proxy type and location, while their statistical properties are also compared to those of the final temperature reconstructions. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.
Inferring earthquake statistics from soft-glass dynamics below yield stress
NASA Astrophysics Data System (ADS)
Kumar, Pinaki; Toschi, Federico; Benzi, Roberto; Trampert, Jeannot
2016-11-01
The current practice to generate synthetic earthquake catalogs employs purely statistical models, mechanical methods based on ad-hoc constitutive friction laws or a combination of the above. We adopt a new numerical approach based on the multi-component Lattice Boltzmann method to simulate yield stress materials. Below yield stress, under shear forcing, we find that the highly intermittent in time, irreversible T1 topological changes in the soft-glass (termed plastic events) bear a statistical resemblance to seismic events, radiating elastic perturbations through the system. Statistical analysis reveals scaling laws for magnitude similar to the Gutenberg-Richter law for quakes, a recurrence time scale with similar slope, a well-defined clustering of events into causal-aftershock sequences and Poisson events leading to the Omori law. Additionally space intermittency reveals a complex multi-fractal structure, like real quakes, and a characterization of the stick-slip behavior in terms of avalanche size and time distribution agrees with the de-pinning transition. The model system once properly tuned using real earthquake data, may help highlighting the origin of scaling in phenomenological seismic power laws. This research was partly funded by the Shell-NWO/FOM programme "Computational sciences for energy research" under Project Number 14CSER022.
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
Wirz, D; Becker, R; Li, S Feng; Friederich, N F; Müller, W
2002-01-01
In vitro dynamic pressure measurements in the healthy and pathologically altered knee joint help to improve our understanding of the loading pattern on femorotibial surfaces. The aim of the study was to evaluate a piezoresistive pressure measuring system. A human cadaveric knee was mounted in a material-testing machine (Bionix 858) using a specially designed knee-holding device. Axial loading of the knee, flexed at 20o, at 500 N, 1000N and 1500 N was then carried out. For the static investigations, the piezoresistive measuring system (Tekscan), was compared with the FUJI measuring system. In addition, dynamic measurements were also performed with the Tekscan System. With the exception of the lateral compartment at a load of 1500 N, no differences in maximum pressures were observed between the two systems. Nor were there any differences with regard to contact surfaces, either in the medial or lateral compartment (p > 0.05). However, the reproducibility of the data was significantly higher with the Tekscan System (p < 0.01). Dynamic pressure measurements obtained with the knee flexed 20 to 90o showed that the lateral contact area shifted from anterior to posterior, while the medial contact area remained virtually unchanged. The Tekscan System proved to be more reliable than the FUJI System, and permits simultaneous measurements in both compartments. The Tekscan System is suitable for dynamic measurement of the femorotibial joint, and permits measurements to be made under more physiological conditions.
NASA Astrophysics Data System (ADS)
Souto, R. Seoane; Martín-Rodero, A.; Yeyati, A. Levy
2016-12-01
We analyze the quantum quench dynamics in the formation of a phase-biased superconducting nanojunction. We find that in the absence of an external relaxation mechanism and for very general conditions the system gets trapped in a metastable state, corresponding to a nonequilibrium population of the Andreev bound states. The use of the time-dependent full counting statistics analysis allows us to extract information on the asymptotic population of even and odd many-body states, demonstrating that a universal behavior, dependent only on the Andreev state energy, is reached in the quantum point contact limit. These results shed light on recent experimental observations on quasiparticle trapping in superconducting atomic contacts.
NASA Astrophysics Data System (ADS)
Baldovin, F.; Robledo, A.
2002-10-01
We uncover the dynamics at the chaos threshold μ∞ of the logistic map and find that it consists of trajectories made of intertwined power laws that reproduce the entire period-doubling cascade that occurs for μ<μ∞. We corroborate this structure analytically via the Feigenbaum renormalization-group (RG) transformation and find that the sensitivity to initial conditions has precisely the form of a q exponential, of which we determine the q index and the q-generalized Lyapunov coefficient λq. Our results are an unequivocal validation of the applicability of the nonextensive generalization of Boltzmann-Gibbs statistical mechanics to critical points of nonlinear maps.
Retrieval dynamics and retention in cross-situational statistical word learning.
Vlach, Haley A; Sandhofer, Catherine M
2014-01-01
Previous research on cross-situational word learning has demonstrated that learners are able to reduce ambiguity in mapping words to referents by tracking co-occurrence probabilities across learning events. In the current experiments, we examined whether learners are able to retain mappings over time. The results revealed that learners are able to retain mappings for up to 1 week later. However, there were interactions between the amount of retention and the different learning conditions. Interestingly, the strongest retention was associated with a learning condition that engendered retrieval dynamics that initially challenged the learner but eventually led to more successful retrieval toward the end of learning. The ease/difficulty of retrieval is a critical process underlying cross-situational word learning and is a powerful example of how learning dynamics affect long-term learning outcomes.
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.
Craig, Ian R; Manolopoulos, David E
2004-08-22
We propose an approximate method for calculating Kubo-transformed real-time correlation functions involving position-dependent operators, based on path integral (Parrinello-Rahman) molecular dynamics. The method gives the exact quantum mechanical correlation function at time zero, exactly satisfies the quantum mechanical detailed balance condition, and for correlation functions of the form C(Ax)(t) and C(xB)(t) it gives the exact result for a harmonic potential. It also works reasonably well at short times for more general potentials and correlation functions, as we illustrate with some example calculations. The method provides a consistent improvement over purely classical molecular dynamics that is most apparent in the low-temperature regime.
NASA Astrophysics Data System (ADS)
Hong, Mei; Zhang, Ren; Wang, Dong; Feng, Mang; Wang, Zhengxin; Singh, Vijay P.
2015-07-01
To address the inaccuracy of long-term El Niño-Southern Oscillation (ENSO) forecasts, a new dynamical-statistical forecasting model of the ENSO index was developed based on dynamical model reconstruction and improved self-memorization. To overcome the problem of single initial prediction values, the largest Lyapunov exponent was introduced to improve the traditional self-memorization function, thereby making it more effective for describing chaotic systems, such as ENSO. Equation reconstruction, based on actual data, was used as a dynamical core to overcome the problem of using a simple core. The developed dynamical-statistical forecasting model of the ENSO index is used to predict the sea surface temperature anomaly in the equatorial eastern Pacific and El Niño/La Niña events. The real-time predictive skills of the improved model were tested. The results show that our model predicted well within lead times of 12 months. Compared with six mature models, both temporal correlation and root mean square error of the improved model are slightly worse than those of the European Centre for Medium-Range Weather Forecasts model, but better than those of the other five models. Additionally, the margin between the forecast results in summer and those in winter is not great, which means that the improved model can overcome the "spring predictability barrier", to some extent. Finally, a real-time prediction experiment is carried out beginning in September 2014. Our model is a new exploration of the ENSO forecasting method.
Statistical structuring theory in parametrically excitable dynamical systems with a Gaussian pump
NASA Astrophysics Data System (ADS)
Klyatskin, V. I.; Koshel, K. V.
2016-03-01
Based on the idea of the statistical topography, we analyze the problem of emergence of stochastic structure formation in linear and quasilinear problems described by first-order partial differential equations. The appearance of a parametric excitation on the background of a Gaussian pump is a specific feature of these problems. We obtain equations for the probability density of the solutions of these equations, whence it follows that the stochastic structure formation emerges with probability one, i.e., for almost every realization of the random parameters of the medium.
Dynamics and Statistical Mechanics of Rotating and non-Rotating Vortical Flows
Lim, Chjan
2013-12-18
Three projects were analyzed with the overall aim of developing a computational/analytical model for estimating values of the energy, angular momentum, enstrophy and total variation of fluid height at phase transitions between disordered and self-organized flow states in planetary atmospheres. It is believed that these transitions in equilibrium statistical mechanics models play a role in the construction of large-scale, stable structures including super-rotation in the Venusian atmosphere and the formation of the Great Red Spot on Jupiter. Exact solutions of the spherical energy-enstrophy models for rotating planetary atmospheres by Kac's method of steepest descent predicted phase transitions to super-rotating solid-body flows at high energy to enstrophy ratio for all planetary spins and to sub-rotating modes if the planetary spin is large enough. These canonical statistical ensembles are well-defined for the long-range energy interactions that arise from 2D fluid flows on compact oriented manifolds such as the surface of the sphere and torus. This is because in Fourier space available through Hodge theory, the energy terms are exactly diagonalizable and hence has zero range, leading to well-defined heat baths.
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
1988-12-01
Copy 20 o5o 00 IDA MEMORANDUM REPORT M-305 CDNN N 3 SDI BATTLE MANAGEMENT/C NETWORKING ! TECHNOLOGY PROGRAM PLAN Robert Botta Sharon Noll December...Battle Management/C3 Networking Technology Program Plan 12. PERSONAL AUTHOR(S). Robert Botta, Sharon Noll 12. TYPE OF REPORT 3b. TIME COVERED 14. DATE OF...The Institute for Defense Analyses (IDA) has collected and analyzed information on network technology that is relevant to Battle Management Command
He, Jiajie; Dougherty, Mark; Shaw, Joey; Fulton, John; Arriaga, Francisco
2011-10-01
Rural areas represent approximately 95% of the 14000 km(2) Alabama Black Belt, an area of widespread Vertisols dominated by clayey, smectitic, shrink-swell soils. These soils are unsuitable for conventional onsite wastewater treatment systems (OWTS) which are nevertheless widely used in this region. In order to provide an alternative wastewater dosing system, an experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial. The experimental system that integrates a seasonal cropping system was evaluated for two years on a 500-m(2) Houston clay site in west central Alabama from August 2006 to June 2008. The SDI system was designed to start hydraulic dosing only when field moisture was below field capacity. Hydraulic dosing rates fluctuated as expected with higher dosing rates during warm seasons with near zero or zero dosing rates during cold seasons. Lower hydraulic dosing in winter creates the need for at least a two-month waste storage structure which is an insurmountable challenge for rural homeowners. An estimated 30% of dosed water percolated below 45-cm depth during the first summer which included a 30-year historic drought. This massive volume of percolation was presumably the result of preferential flow stimulated by dry weather clay soil cracking. Although water percolation is necessary for OWTS, this massive water percolation loss indicated that this experimental system is not able to effective control soil moisture within its monitoring zone as designed. Overall findings of this study indicated that soil moisture controlled SDI wastewater dosing is not suitable as a standalone system in these Vertisols. However, the experimental soil moisture control system functioned as designed, demonstrating that soil moisture controlled SDI wastewater dosing may find application as a supplement to other wastewater disposal methods that can function during cold seasons.
NASA Astrophysics Data System (ADS)
Lee, Kean Loon; Grémaud, Benoît; Miniatura, Christian
2014-10-01
As recently discovered [T. Karpiuk et al., Phys. Rev. Lett. 109, 190601 (2012), 10.1103/PhysRevLett.109.190601], Anderson localization in a bulk disordered system triggers the emergence of a coherent forward scattering (CFS) peak in momentum space, which twins the well-known coherent backscattering (CBS) peak observed in weak localization experiments. Going beyond the perturbative regime, we address here the long-time dynamics of the CFS peak in a one-dimensional random system and we relate this novel interference effect to the statistical properties of the eigenfunctions and eigenspectrum of the corresponding random Hamiltonian. Our numerical results show that the dynamics of the CFS peak is governed by the logarithmic level repulsion between localized states, with a time scale that is, with good accuracy, twice the Heisenberg time. This is in perfect agreement with recent findings based on the nonlinear sigma model. In the stationary regime, the width of the CFS peak in momentum space is inversely proportional to the localization length, reflecting the exponential decay of the eigenfunctions in real space, while its height is exactly twice the background, reflecting the Poisson statistical properties of the eigenfunctions. It would be interesting to extend our results to higher dimensional systems and other symmetry classes.
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.
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.
Statistical Mechanics and Dynamics of a Three-Dimensional Glass-Forming System
NASA Astrophysics Data System (ADS)
Lerner, Edan; Procaccia, Itamar; Zylberg, Jacques
2009-03-01
In the context of a classical example of glass formation in three dimensions, we exemplify how to construct a statistical-mechanical theory of the glass transition. At the heart of the approach is a simple criterion for verifying a proper choice of upscaled quasispecies that allow the construction of a theory with a finite number of “states.” Once constructed, the theory identifies a typical scale ξ that increases rapidly with lowering the temperature and which determines the α-relaxation time τα as τα˜exp(μξ/T), with μ a typical chemical potential. The theory can predict relaxation times at temperatures that are inaccessible to numerical simulations.
Statistical Properties and Multifractal Behaviors of Market Returns by Ising Dynamic Systems
NASA Astrophysics Data System (ADS)
Fang, Wen; Wang, Jun
An interacting-agent model of speculative activity explaining price formation in financial markets is considered in the present paper, which based on the stochastic Ising model and the mean field theory. The model describes the interaction strength among the agents as well as an external field, and the corresponding random logarithmic price return process is investigated. According to the empirical research of the model, the time series formed by this Ising model exhibits the bursting typical of volatility clustering, the fat-tail phenomenon, the power-law distribution tails and the long-time memory. The statistical properties of the returns of Hushen 300 Index, Shanghai Stock Exchange (SSE) Composite Index and Shenzhen Stock Exchange (SZSE) Component Index are also studied for comparison between the real time series and the simulated ones. Further, the multifractal detrended fluctuation analysis is applied to investigate the time series returns simulated by Ising model have the distribution multifractality as well as the correlation multifractality.
Chen, Nan; Majda, Andrew J
2017-02-14
The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model.
Chen, Nan; Majda, Andrew J.
2017-01-01
The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean–atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model. PMID:28137886
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}.
Gadomski, Adam; Ausloos, Marcel; Casey, Tahlia
2017-04-01
This article addresses a set of observations framed in both deterministic as well as statistical formal guidelines. It operates within the framework of nonlinear dynamical systems theory (NDS). It is argued that statistical approaches can manifest themselves ambiguously, creating practical discrepancies in psychological and cognitive data analyses both quantitatively and qualitatively. This is sometimes termed in literature as 'questionable research practices.' This communication points to the demand for a deeper awareness of the data 'initial conditions, allowing to focus on pertinent evolution constraints in such systems.' It also considers whether the exponential (Malthus-type) or the algebraic (Pareto-type) statistical distribution ought to be effectively considered in practical interpretations. The role of repetitive specific behaviors by patients seeking treatment is examined within the NDS frame. The significance of these behaviors, involving a certain memory effect seems crucial in determining a patient's progression or regression. With this perspective, it is discussed how a sensitively applied hazardous or triggering factor can be helpful for well-controlled psychological strategic treatments; those attributable to obsessive-compulsive disorders or self-injurious behaviors are recalled in particular. There are both inherent criticality- and complexity-exploiting (reduced-variance based) relations between a therapist and a patient that can be intrinsically included in NDS theory.
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.
How electronic dynamics with Pauli exclusion produces Fermi-Dirac statistics
Nguyen, Triet S.; Nanguneri, Ravindra; Parkhill, John
2015-04-07
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 for a general electronic state. 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.
Bonnot, Caroline A; Gélabert, Alexandre; Louvat, Pascale; Morin, Guillaume; Proux, Olivier; Benedetti, Marc F
2016-05-24
Three sub-basins of the Seine River (France) under contrasted land uses (i.e., forested, agricultural, and urban) have been investigated in order to assess the origin and seasonal variation of trace metals, and evaluate their geochemical background and dynamics. Our results highlight a high anthropogenic impact on all elements for both the dissolved and particulate fractions. The main source for each element in the dissolved phase was determined and shows that transition and post-transition metals mainly originate from forested areas, while alkali and alkaline earth elements, metalloids, and halogens rather originate from agricultural land use. Conversely, for the particulate phase, most of the elements cannot be associated with a specific land use. Seasonal variation of elements was assessed according to the forested and agricultural land uses, and geochemical backgrounds were determined using average export rates, highlighting that the geochemical background for the forested land use is higher than the agricultural one for most of the elements. Finally, to confirm those results, Zn dynamics in the three characteristic sub-basins and between the different land uses was investigated using a combination of Zn speciation, Zn isotopic ratio, and Zn export rates.
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.
NASA Astrophysics Data System (ADS)
Jacquelin, E.; Adhikari, S.; Sinou, J.-J.; Friswell, M. I.
2015-11-01
Polynomial chaos solution for the frequency response of linear non-proportionally damped dynamic systems has been considered. It has been observed that for lightly damped systems the convergence of the solution can be very poor in the vicinity of the deterministic resonance frequencies. To address this, Aitken's transformation and its generalizations are suggested. The proposed approach is successfully applied to the sequences defined by the first two moments of the responses, and this process significantly accelerates the polynomial chaos convergence. In particular, a 2-dof system with respectively 1 and 2 parameter uncertainties has been studied. The first two moments of the frequency response were calculated by Monte Carlo simulation, polynomial chaos expansion and Aitken's transformation of the polynomial chaos expansion. Whereas 200 polynomials are required to have a good agreement with Monte Carlo results around the deterministic eigenfrequencies, less than 50 polynomials transformed by the Aitken's method are enough. This latter result is improved if a generalization of Aitken's method (recursive Aitken's transformation, Shank's transformation) is applied. With the proposed convergence acceleration, polynomial chaos may be reconsidered as an efficient method to estimate the first two moments of a random dynamic response.
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.
Grotjahn, Richard; Black, Robert; Leung, Ruby; ...
2015-05-22
This paper reviews research approaches and open questions regarding data, statistical analyses, dynamics, modeling efforts, and trends in relation to temperature extremes. Our specific focus is upon extreme events of short duration (roughly less than 5 days) that affect parts of North America. These events are associated with large scale meteorological patterns (LSMPs). Methods used to define extreme events statistics and to identify and connect LSMPs to extreme temperatures are presented. Recent advances in statistical techniques can connect LSMPs to extreme temperatures through appropriately defined covariates that supplements more straightforward analyses. A wide array of LSMPs, ranging from synoptic tomore » planetary scale phenomena, have been implicated as contributors to extreme temperature events. Current knowledge about the physical nature of these contributions and the dynamical mechanisms leading to the implicated LSMPs is incomplete. There is a pressing need for (a) systematic study of the physics of LSMPs life cycles and (b) comprehensive model assessment of LSMP-extreme temperature event linkages and LSMP behavior. Generally, climate models capture the observed heat waves and cold air outbreaks with some fidelity. However they overestimate warm wave frequency and underestimate cold air outbreaks frequency, and underestimate the collective influence of low-frequency modes on temperature extremes. Climate models have been used to investigate past changes and project future trends in extreme temperatures. Overall, modeling studies have identified important mechanisms such as the effects of large-scale circulation anomalies and land-atmosphere interactions on changes in extreme temperatures. However, few studies have examined changes in LSMPs more specifically to 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 so
Grotjahn, Richard; Black, Robert; Leung, Ruby; Wehner, Michael F.; Barlow, Mathew; Bosilovich, Michael; Gershunov, Alexander; Gutowski, Jr., William J.; Gyakum, John R.; Katz, Richard W.; Lee, Yun -Young; Lim, Young -Kwon; Prabhat, -
2015-05-22
This paper reviews research approaches and open questions regarding data, statistical analyses, dynamics, modeling efforts, and trends in relation to temperature extremes. Our specific focus is upon extreme events of short duration (roughly less than 5 days) that affect parts of North America. These events are associated with large scale meteorological patterns (LSMPs). Methods used to define extreme events statistics and to identify and connect LSMPs to extreme temperatures are presented. Recent advances in statistical techniques can connect LSMPs to extreme temperatures through appropriately defined covariates that supplements more straightforward analyses. A wide array of LSMPs, ranging from synoptic to planetary scale phenomena, have been implicated as contributors to extreme temperature events. Current knowledge about the physical nature of these contributions and the dynamical mechanisms leading to the implicated LSMPs is incomplete. There is a pressing need for (a) systematic study of the physics of LSMPs life cycles and (b) comprehensive model assessment of LSMP-extreme temperature event linkages and LSMP behavior. Generally, climate models capture the observed heat waves and cold air outbreaks with some fidelity. However they overestimate warm wave frequency and underestimate cold air outbreaks frequency, and underestimate the collective influence of low-frequency modes on temperature extremes. Climate models have been used to investigate past changes and project future trends in extreme temperatures. Overall, modeling studies have identified important mechanisms such as the effects of large-scale circulation anomalies and land-atmosphere interactions on changes in extreme temperatures. However, few studies have examined changes in LSMPs more specifically to 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 so more
Po river plume patterns variability and dynamics: a numerical modeling and statistical approach.
NASA Astrophysics Data System (ADS)
Falcieri, Francesco M.; Benetazzo, Alvise; Bergamasco, Andrea; Bonaldo, Davide; Carniel, Sandro; Sclavo, Mauro; Russo, Aniello
2013-04-01
Processes and dynamics of estuarine-shelf environments are defined by many drivers, some of the most important being riverine inputs, winds (and wind driven currents) and tides. Two of them are directly involved in the formation and spatial evolution of a coastal river plume: on the one hand the amount of fresh water entering into the sea through river' discharge, on the other hand the direction and intensity of winds blowing over the domain. The Adriatic Sea is generally considered a dilution basin due to the large amount of freshwater inputs received. These inputs have a significant influence on the basin, both from a physical point of view (by affecting buoyancy) and on the biogeochemical characteristics (by introducing large quantities of nutrients, which sustain primary production in the areas interested by the rivers' plumes). The Po River (mean daily discharge between 275 and 11600 m3/s, yearly mean of 1500 m3/s) is the single largest freshwater source of the Adriatic; its discharges result in a plume that directly influences the characteristics of the coastal areas of the whole Northern sub-basin and as far South as Ancona. The development of strong lateral gradients in salinity is an all year around driver (particularly in Spring and Autumn) of the general and coastal circulation, and influences the water column vertical structure and an important process such as the formation of the Northern Adriatic Dense Water. The Po plume generally follows two major patterns of evolution: southward along the Italian coasts in a ribbon that can fill the whole water column, or across the northern part of the basin toward the Istrian coasts in a generally more stratified condition. A model-based assessment, albeit semi-quantitative, of the dynamics and variability of the Po plume has not been yet reported in literature. In this work we investigated its dynamics by means of an 8 years (2003-2010) numerical simulation with the Regional Ocean Modelling System (ROMS). The
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Wu, S.; Schwaerz, M.; Fritzer, J.; Zhang, S.; Carter, B. A.; Zhang, K.
2013-12-01
Navigation Satellite System (GNSS)-based radio occultation (RO) is a satellite remote sensing technique providing accurate profiles of the Earth's atmosphere for weather and climate applications. Above about 30 km altitude, however, statistical optimization is a critical process for initializing the RO bending angles in order to optimize the climate monitoring utility of the retrieved atmospheric profiles. Here we introduce an advanced dynamic statistical optimization algorithm, which uses bending angles from multiple days of European Centre for Medium-range Weather Forecasts (ECMWF) short-range forecast and analysis fields, together with averaged-observed bending angles, to obtain background profiles and associated error covariance matrices with geographically varying background uncertainty estimates on a daily updated basis. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.4 (OPSv5.4) algorithm, using several days of simulated MetOp and observed CHAMP and COSMIC data, for January and July conditions. We find the following for the new method's performance compared to OPSv5.4: 1.) it significantly reduces random errors (standard deviations), down to about half their size, and leaves less or about equal residual systematic errors (biases) in the optimized bending angles; 2.) the dynamic (daily) estimate of the background error correlation matrix alone already improves the optimized bending angles; 3.) the subsequently retrieved refractivity profiles and atmospheric (temperature) profiles benefit by improved error characteristics, especially above about 30 km. Based on these encouraging results, we work to employ similar dynamic error covariance estimation also for the observed bending angles and to apply the method to full months and subsequently to entire climate data records.
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.
An in-house alternative to traditional SDI services at Argonne National Laboratory
Noel, R.E.; Dominiak, R.R.
1997-02-20
Selective Dissemination of Information (SDIs) are based on automated, well-defined programs that regularly produce precise, relevant bibliographic information. Librarians have typically turned to information vendors such as Dialog or STN international to design and implement these searches for their users in business, academia, and the science community. Because Argonne National Laboratory (ANL) purchases the Institute for Scientific Information (ISI) Current Contents tapes (all subject areas excluding Humanities). ANL scientists enjoy the benefit of in-house developments with BASISplus software programming and no longer need to turn to outside companies for reliable SDI service. The database and its customized services are known as ACCESS (Argonne Current Contents Electronic Search Service). Through collaboration with librarians on Boolean logic and selection of terms, users can now design their own personal profiles to comb the new data, thereby avoiding service fees from outside providers. Based on the feedback from scientists, it seems that this new service can help transform the ANL distributed libraries into more efficient central functioning entities that better serve the users. One goal is to eliminate the routing of paper copies of many new journal issues to different library locations for users to browse; instead users may be expected to rely more on electronic dissemination of both table of contents and customized SDIs for new scientific and technical information.
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.
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.
A review of gas-cooled reactor concepts for SDI (Strategic Defense Initiative) applications
Marshall, A.C.
1989-08-01
We have completed a review of multimegawatt gas-cooled reactor concepts proposed for SDI applications. Our study concluded that the principal reason for considering gas-cooled reactors for burst-mode operation was the potential for significant system mass savings over closed-cycle systems if open-cycle gas-cooled operation (effluent exhausted to space) is acceptable. The principal reason for considering gas-cooled reactors for steady-state operation is that they may represent a lower technology risk than other approaches. In the review, nine gas-cooled reactor concepts were compared to identify the most promising. For burst-mode operation, the NERVA (Nuclear Engine for Rocket Vehicle Application) derivative reactor concept emerged as a strong first choice since its performance exceeds the anticipated operational requirements and the technology has been demonstrated and is retrievable. Although the NERVA derivative concepts were determined to be the lead candidates for the Multimegawatt Steady-State (MMWSS) mode as well, their lead over the other candidates is not as great as for the burst mode. 90 refs., 2 figs., 10 tabs.
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.
NASA Astrophysics Data System (ADS)
Liu, Zhichao; Zhao, Yunjie; Zeng, Chen; Computational Biophysics Lab Team
As the main protein of the bacterial flagella, flagellin plays an important role in perception and defense response. The newly discovered locus, FLS2, is ubiquitously expressed. FLS2 encodes a putative receptor kinase and shares many homologies with some plant resistance genes and even with some components of immune system of mammals and insects. In Arabidopsis, FLS2 perception is achieved by the recognition of epitope flg22, which induces FLS2 heteromerization with BAK1 and finally the plant immunity. Here we use both analytical methods such as Direct Coupling Analysis (DCA) and Molecular Dynamics (MD) Simulations to get a better understanding of the defense mechanism of FLS2. This may facilitate a redesign of flg22 or de-novo design for desired specificity and potency to extend the immune properties of FLS2 to other important crops and vegetables.
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
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.
Dynamical model and nonextensive statistical mechanics of a market index on large time windows
NASA Astrophysics Data System (ADS)
Ausloos, M.; Ivanova, K.
2003-10-01
The shape and tails of partial distribution functions (PDF) for a financial signal, i.e., the S&P500 and the turbulent nature of the markets are linked through a model encompassing Tsallis nonextensive statistics and leading to evolution equations of the Langevin and Fokker-Planck type. A model originally proposed to describe the intermittent behavior of turbulent flows describes the behavior of normalized log returns for such a financial market index, for small and large time windows, and both for small and large log returns. These turbulent market volatility (of normalized log returns) distributions can be sufficiently well fitted with a χ2 distribution. The transition between the small time scale model of nonextensive, intermittent process, and the large scale Gaussian extensive homogeneous fluctuation picture is found to be at ca. a 200 day time lag. The intermittency exponent κ in the framework of the Kolmogorov log-normal model is found to be related to the scaling exponent of the PDF moments, thereby giving weight to the model. The large value of κ points to a large number of cascades in the turbulent process. The first Kramers-Moyal coefficient in the Fokker-Planck equation is almost equal to zero, indicating “no restoring force.” A comparison is made between normalized log returns and mere price increments.
Rodríguez, Begoña; Blas, Juan; Lorenzo, Rubén M; Fernández, Patricia; Abril, Evaristo J
2011-04-01
Personal exposure meters (PEM) are routinely used for the exposure assessment to radio frequency electric or magnetic fields. However, their readings are subject to errors associated with perturbations of the fields caused by the presence of the human body. This paper presents a novel analysis method for the characterization of this effect. Using ray-tracing techniques, PEM measurements have been emulated, with and without an approximation of this shadowing effect. In particular, the Global System for Mobile Communication mobile phone frequency band was chosen for its ubiquity and, specifically, we considered the case where the subject is walking outdoors in a relatively open area. These simulations have been contrasted with real PEM measurements in a 35-min walk. Results show a good agreement in terms of root mean square error and E-field cumulative distribution function (CDF), with a significant improvement when the shadowing effect is taken into account. In particular, the Kolmogorov-Smirnov (KS) test provides a P-value of 0.05 when considering the shadowing effect, versus a P-value of 10⁻¹⁴ when this effect is ignored. In addition, although the E-field levels in the absence of a human body have been found to follow a Nakagami distribution, a lognormal distribution fits the statistics of the PEM values better than the Nakagami distribution. As a conclusion, although the mean could be adjusted by using correction factors, there are also other changes in the CDF that require particular attention due to the shadowing effect because they might lead to a systematic error.
Global nannoplankton dynamics across the Paleocene-Eocene Thermal Maximum: A statistical approach
NASA Astrophysics Data System (ADS)
Schneider, L. J.; Bralower, T. J.; Patzkowsky, M.; Kump, L.
2012-12-01
Global warming during the Paleocene-Eocene Thermal Maximum (PETM; 55.8 Ma) had a profound effect on life on land and in the ocean. With global temperatures rising 5°C over ~20 kyr, the PETM is considered to be the most analogous interval to modern day climate change. Calcareous nannoplankton, a group of calcifying marine phytoplankton, have been extensively studied across this event. Results from these studies indicate nannoplankton assemblages responded to changing surface water temperatures and nutrient availability. Together, these records can provide a global picture of nannofossil assemblage dynamics during this critical interval. Issues such as the timing and nature of assemblage change on a global scale, the rate of assemblage change, and how assemblage shifts differ regionally can be further resolved. Here we use an ordination technique (detrended correspondence analysis; DCA), which condenses complex assemblage data and displays it in a simple, interpretable way. We applied the DCA to previously published nannofossil abundance data from 7 globally distributed sites and compared these results to published benthic and bulk δ13C records across the PETM. Our initial results show that changes in the nannofossil assemblage, as displayed through DCA 1, closely follow the trends of the δ13C curves at each site. This suggests that the organisms are closely linked to the carbon cycle in some way during this time period. From this study we will have a better understanding of how global nannoplankton populations responded to rapid climate change and when environmental alterations began to take place.
2016-01-01
We propose and develop a general approach based on reaction-diffusion equations for modelling a species dynamics in a realistic two-dimensional (2D) landscape crossed by linear one-dimensional (1D) corridors, such as roads, hedgerows or rivers. Our approach is based on a hybrid “2D/1D model”, i.e, a system of 2D and 1D reaction-diffusion equations with homogeneous coefficients, in which each equation describes the population dynamics in a given 2D or 1D element of the landscape. Using the example of the range expansion of the tiger mosquito Aedes albopictus in France and its main highways as 1D corridors, we show that the model can be fitted to realistic observation data. We develop a mechanistic-statistical approach, based on the coupling between a model of population dynamics and a probabilistic model of the observation process. This allows us to bridge the gap between the data (3 levels of infestation, at the scale of a French department) and the output of the model (population densities at each point of the landscape), and to estimate the model parameter values using a maximum-likelihood approach. Using classical model comparison criteria, we obtain a better fit and a better predictive power with the 2D/1D model than with a standard homogeneous reaction-diffusion model. This shows the potential importance of taking into account the effect of the corridors (highways in the present case) on species dynamics. With regard to the particular case of A. albopictus, the conclusion that highways played an important role in species range expansion in mainland France is consistent with recent findings from the literature. PMID:26986201
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
NASA Astrophysics Data System (ADS)
Andricioaei, Ioan; Straub, John E.
1997-12-01
Generalized Monte Carlo and molecular dynamics algorithms which provide enhanced sampling of the phase space in the calculation of equilibrium thermodynamic properties is presented. The algorithm samples trial moves from a generalized statistical distribution derived from a modification of the Gibbs-Shannon entropy proposed by Tsallis. Results for a one-dimensional model potential demonstrate that the algorithm leads to a greatly enhanced rate of barrier crossing and convergence in the calculation of equilibrium averages. Comparison is made with standard Metropolis Monte Carlo and the J-walking algorithm of Franz, Freeman and Doll. Application to a 13-atom Lennard-Jones cluster demonstrates the ease with which the algorithm may be applied to complex molecular systems.
Lu, Yang; Zeng, Jianming; Wu, Binning; E, Shunmei; Wang, Lina; Cai, Renxin; Zhang, Ni; Li, Youqiang; Huang, Xianzhang; Huang, Bin; Chen, Cha
2017-01-01
Conjugation is a key mechanism for horizontal gene transfer and plays an important role in bacterial evolution, especially with respect to antibiotic resistance. However, little is known about the role of donor and recipient cells in regulation of conjugation. Here, using an Escherichia coli (SM10λπ)-Pseudomonas aeruginosa (PAO1) conjugation model, we demonstrated that deficiency of lasI/rhlI, genes associated with generation of the quorum sensing signals N-acyl homoserine lactones (AHLs) in PAO1, or deletion of the AHLs receptor SdiA in the donor SM10λπ both facilitated conjugation. When using another AHLs-non-producing E. coli strain EC600 as recipient cells, deficiency of sdiA in donor SM10λπ hardly affect the conjugation. More importantly, in the presence of exogenous AHLs, the conjugation efficiency between SM10λπ and EC600 was dramatically decreased, while deficiency of sdiA in SM10λπ attenuated AHLs-inhibited conjugation. These data suggest the conjugation suppression function of AHLs-SdiA chemical signaling. Further bioinformatics analysis, β-galactosidase reporter system and electrophoretic mobility shift assays characterized the binding site of SdiA on the promoter region of traI gene. Furthermore, deletion of lasI/rhlI or sdiA promoted traI mRNA expression in SM10λπ and PAO1 co-culture system, which was abrogated by AHLs. Collectively, our results provide new insight into an important contribution of quorum sensing system AHLs-SdiA to the networks that regulate conjugation. PMID:28164039
Almeida, Felipe Alves de; Pinto, Uelinton Manoel; Vanetti, Maria Cristina Dantas
2016-10-01
Quorum sensing is a cell-to-cell communication mechanism leading to differential gene expression in response to high population density. The autoinducer-1 (AI-1) type quorum sensing system is incomplete in Escherichia coli and Salmonella due to the lack of the AI-1 synthase (LuxI homolog) responsible for acyl homoserine lactone (AHL) synthesis. However, these bacteria encode the AHL receptor SdiA (a LuxR homolog) leading to gene regulation in response to AI-1 produced by other bacteria. This study aimed to model the SdiA protein of Salmonella enterica serovar Enteritidis PT4 578 based on three crystallized SdiA structures from Enterohemorrhagic E. coli (EHEC) with different ligands. Molecular docking of these predicted structures with AHLs, furanones and 1-octanoyl-rac-glycerol were also performed. The available EHEC SdiA structures provided good prototypes for modeling SdiA from Salmonella. The molecular docking of these proteins showed that residues Y63, W67, Y71, D80 and S134 are common binding sites for different quorum modulating signals, besides being conserved among other LuxR type proteins. We also show that AHLs with twelve carbons presented better binding affinity to SdiA than AHLs with smaller side chains in our docking analysis, regardless of the protein structures used. Interestingly, the conformational changes provided by AHL binding resulted in structural models with increased affinities to brominated furanones. These results suggest that the use of brominated furanones to inhibit phenotypes controlled by quorum sensing in Salmonella and EHEC may present a good strategy since these inhibitors seem to specifically compete with AHLs for binding to SdiA in both pathogens.
NASA Astrophysics Data System (ADS)
van Tassel, Paul Robert
1993-01-01
This thesis describes a fully detailed molecular simulation and modeling effort aimed at understanding the fundamentals of adsorption and diffusion of small molecules in zeolite micropores. The primary emphasis is on determining the relationship between the structure and chemistry of the zeolite adsorbent and the structure, dynamics, and thermodynamics of the adsorbed phase. Further emphasis is on developing simple, predictive models of zeolite adsorption and diffusion. We begin by presenting a Monte Carlo simulation of single component adsorption of xenon, methane, and argon in zeolite NaA. The form of the adsorbate density distribution indicates the presence of discrete adsorption sites which arrange in polyhedra whose geometry depends on the number and position of zeolite framework ions. Isotherm plateaus are attributed to either (i) a low energy adsorbate configuration or (ii) the saturation of polyhedral sites. Viewing the adsorbed phase as an ordered arrangement differs from the conventional delocalized model, yet it helps explain certain experimental observations. Next, a study of binary mixtures of small molecules in zeolite NaA using the Monte Carlo method is presented. The mixing in the pore is determined to be highly nonideal by comparison to a simple pore volume filling model. Strong selectivity for a more polarizable molecule (xenon) is observed only at low pore loading. At higher pore loading, a smaller, less polarizable molecule (argon) adsorbs selectively at a significantly lower pressure than predicted by the model. This enhanced selectivity is due to the ability of the smaller molecule to pack more efficiently inside of the pore. Finally, we present two simple lattice models whose forms are arrived at following careful consideration of simulation results. The first describes the adsorption of small molecules in a zeolite. A polyhedral lattice is postulated whose neighboring sites interact energetically and entropically. The second model describes
Coupled flow-polymer dynamics via statistical field theory: Modeling and computation
Ceniceros, Hector D. Fredrickson, Glenn H. Mohler, George O.
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
Ilk Capar, M; Nar, A; Ferrarini, A; Frezza, E; Greco, C; Zakharov, A V; Vakulenko, A A
2013-03-21
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.
Argonne CW Linac (ACWL) -- Legacy from SDI and opportunities for the future
McMichael, G.E.; Yule, T.J.
1994-08-01
The former Strategic Defense Initiative Organization (SDIO) invested significant resources over a 6-year period to develop and build an accelerator to demonstrate the launching of a cw beam with characteristics suitable for a space-based Neutral Particle Beam (NPD) system. This accelerator, the CWDD (Continuous Wave Deuterium Demonstrator) accelerator, was designed to accelerate 80 mA cw of D{sup {minus}} to 7.5 MeV. A considerable amount of hardware was constructed and installed in the Argonne-based facility, and major performance milestones were achieved before program funding from the Department of Defense ended in October 1993. Existing assets have been turned over to Argonne. Assets include a fully functional 200 kV cw D{sup {minus}} injector, a cw RFQ that has been tuned, leak checked and aligned, beam lines and a high-power beam stop, all installed in a shielded vault with appropriate safety and interlock systems. In addition, there are two high power (1 MW) cw rf amplifiers and all the ancillary power, cooling and control systems required for a high-power accelerator system. The SDI mission required that the CWDD accelerator structures operate at cryogenic temperatures (26 K), a requirement that placed severe limitations on operating period (CWDD would have provided 20 seconds of cw beam every 90 minutes). However, the accelerator structures were designed for full-power rf operation with water cooling and ACWL (Argonne Continuous Wave Linac), the new name for CWDD in its water-cooled, positive-ion configuration, will be able to operate continuously. Project status and achievements will be reviewed. Preliminary design of a proton conversion for the RFQ, and other proposals for turning ACWL into a testbed for cw-linac engineering, will be discussed.
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.
Bouchard, Kristofer E.; Brainard, Michael S.
2016-01-01
Predicting future events is a critical computation for both perception and behavior. Despite the essential nature of this computation, there are few studies demonstrating neural activity that predicts specific events in learned, probabilistic sequences. Here, we test the hypotheses that the dynamics of internally generated neural activity are predictive of future events and are structured by the learned temporal–sequential statistics of those events. We recorded neural activity in Bengalese finch sensory-motor area HVC in response to playback of sequences from individuals’ songs, and examined the neural activity that continued after stimulus offset. We found that the strength of response to a syllable in the sequence depended on the delay at which that syllable was played, with a maximal response when the delay matched the intersyllable gap normally present for that specific syllable during song production. Furthermore, poststimulus neural activity induced by sequence playback resembled the neural response to the next syllable in the sequence when that syllable was predictable, but not when the next syllable was uncertain. Our results demonstrate that the dynamics of internally generated HVC neural activity are predictive of the learned temporal–sequential structure of produced song and that the strength of this prediction is modulated by uncertainty. PMID:27506786
ERIC Educational Resources Information Center
Chicot, Katie; Holmes, Hilary
2012-01-01
The use, and misuse, of statistics is commonplace, yet in the printed format data representations can be either over simplified, supposedly for impact, or so complex as to lead to boredom, supposedly for completeness and accuracy. In this article the link to the video clip shows how dynamic visual representations can enliven and enhance the…
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.
NASA Astrophysics Data System (ADS)
Vaittinada Ayar, Pradeebane; Vrac, Mathieu; Bastin, Sophie; Carreau, Julie; Déqué, Michel; Gallardo, Clemente
2016-02-01
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
NASA Astrophysics Data System (ADS)
Bocaniov, Serghei A.; Scavia, Donald
2016-06-01
Hypoxia or low bottom water dissolved oxygen (DO) is a world-wide problem of management concern requiring an understanding and ability to monitor and predict its spatial and temporal dynamics. However, this is often made difficult in large lakes and coastal oceans because of limited spatial and temporal coverage of field observations. We used a calibrated and validated three-dimensional ecological model of Lake Erie to extend a statistical relationship between hypoxic extent and bottom water DO concentrations to explore implications of the broader temporal and spatial development and dissipation of hypoxia. We provide the first numerical demonstration that hypoxia initiates in the nearshore, not the deep portion of the basin, and that the threshold used to define hypoxia matters in both spatial and temporal dynamics and in its sensitivity to climate. We show that existing monitoring programs likely underestimate both maximum hypoxic extent and the importance of low oxygen in the nearshore, discuss implications for ecosystem and drinking water protection, and recommend how these results could be used to efficiently and economically extend monitoring programs.
Zank, G.D.
1989-05-01
The relationship between strategic offensive capabilities (reflected in the SIOP) and emerging strategic defensive capabilities (reflected by SDI) is not being adequately addressed. A summary of the existing nuclear war planning process is provided, and an analagous defensive process is postulated. Parallels and differences between the two processes are discussed. Potential areas for information exchange and cooperation are identified to enhance deterrence and improve war fighting potential. Operational, technical and political issues requiring resolution are raised and recommendations to resolve these issues are made.
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 σl and σb 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
NASA Astrophysics Data System (ADS)
Zuo, Pingbing; Feng, Xueshang
2016-07-01
Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure abruptly changes over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. Recently we have developed a novel procedure that is able to rapidly identify the DPPs from the plasma data stream, and simultaneously define the transition region and smartly select the upstream and downstream region for analysis. The plasma data with high time-resolution from 3DP instrument on board the WIND spacecraft are inspected with this automatic DPP-searching code, and a complete list of solar wind DPPs of historic WIND observations are built up. We perform a statistical survey on the properties of DPPs near 1 AU based on this event list. It is found that overwhelming majority of DPPs are associated with the solar wind disturbances including the CME-related flows, the corotating interaction regions, as well as the complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activities. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears no systematic investigations on the response of GMFs to negative DPPs. Here we also study the decompression/compression effects of very strong negative/positive DPPs on GMFs under northward IMFs. In response to the decompression of strong negative DPPs, GMFs on dayside, near the dawn and dusk on nightside are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of events when GOES is located at the midnight sector, GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that on certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Statistically, both the decompression effect of
NASA Astrophysics Data System (ADS)
Colin, Jeanne; Déqué, Michel; Sanchez Gomez, Emila; Somot, Samuel
2010-05-01
We present a comparison of two downscaling methods of extreme precipitations over France at a climatic time scale : a dynamical one performed with the Regional Climate Model ALADIN-Climate used at a resolution of 12 km, and a statistical one based on the weather regime approach and using the analog methodology to reconstruct daily fields of precipitations at a 8 km resolution. We focus on the most heavy precipitations of the area of interest, which occur in southeastern France in Autumn. Those involve small-scale processes than can be explicitly resolved only with 2-1 km resolution non-hydrostatic models. However, such models can not be used for climate simulations because of their computational cost is still too high. Yet these extreme events cause rather heavy damages, so that their possible evolution in the context of climate change is of great concern. Thus, there is strong need in assessing downscaling methods' ability to represent them. First, we downscale the low-resolution ERA40 re-analysis over the 1958-2000 time period with ALADIN-Climate, and from the year 1980 to the year 2000 with the statistical method. Then, we apply a quantile-quantile correction to the daily precipitations of the last twenty years of the ALADIN-Climate simulation. The correction rates are computed over the first part of the simulation (1958-1979) using a high-resolution gridded database : the SAFRAN analysis, which provides series of hourly fields for the 1958-2008 period over the french territory at a 8 km resolution. We assess the performances of each downscaling method in present-day climate by comparing the simulated precipitations to the SAFRAN database. The use of the ERA40 re-analysis allows to reproduce the real chronology in both downscalings, which enables to analyze the results not only from a statistical point of view but also through day-to-day diagnosis such as time correlations or spatial patterns of rain for given extreme events. Secondly, we apply these downscaling
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.
NASA Astrophysics Data System (ADS)
Unnikrishnan, C. S.
The fact that the fundamental theories of physics were completed well before any significant knowledge about the real universe and its enormous gravity was available necessitates a re-examination of these theories, especially that of dynamics and relativity. The results of this analysis, along with several experimental facts, reveal that the matter frame of the universe provides a preferred absolute frame and that its gravity determines the laws of motion. Newton's law of motion arises as a relativistic gravito-magnetic effect, the equivalence principle as a natural consequence of the gravitational reaction to motion in the massive universe, and the familiar dilation of the rates of clocks as a cosmic gravitational time dilation with absolute cosmic frame velocity as a key factor. In the quantum regime, partial contribution to the fine structure splitting of spectral lines, and the phases that determine the vastly different collective behavior of fermions and bosons are also linked to cosmic gravity; phenomena like Bose-Einstein condensation and Fermi pressure seem to have a cosmic connection. For the first time we seem to be able to grasp the physical basis of the spin-statistics connection as linked to a fundamental universal interaction. These ideas of cosmic relativity unify kinematics and dynamics, answering outstanding fundamental questions. A new experiment to compare the true one-way speed of light in different directions relative to an inertially moving observer, as well as a reanalysis of several earlier experiments on the propagation of light confirm the importance of the cosmic absolute frame. These results, with firm empirical support, imply important revisions in the theoretical physics of motion and relativity.
Mylari, B L; Oates, P J; Beebe, D A; Brackett, N S; Coutcher, J B; Dina, M S; Zembrowski, W J
2001-08-16
We report here on our medicinal chemistry and pharmacology efforts to provide a potent sorbitol dehydrogenase inhibitor (SDI) as a tool to probe a recently disclosed hypothesis centered on the role of sorbitol dehydrogenase (SDH) in the second step of the polyol pathway, under conditions of high glucose flux. Starting from a weak literature lead, 2, and through newly developed structure-activity relationships, we have designed and executed an unambiguous synthesis of enantiomeric SDI, 6, which is at least 10x more potent than 2. Also, 6 potently inhibits SDH in streptozotocin-diabetic rat sciatic nerve. We have described an expedient synthesis of a key building template, 33, for future research in the SDI area that may facilitate the discovery of even more potent SDIs with longer duration of action in vivo.
Dodds, Peter Sheridan; Mitchell, Lewis; Reagan, Andrew J.; Danforth, Christopher M.
2016-01-01
Instabilities and long term shifts in seasons, whether induced by natural drivers or human activities, pose great disruptive threats to ecological, agricultural, and social systems. Here, we propose, measure, and explore two fundamental markers of location-sensitive seasonal variations: the Summer and Winter Teletherms—the on-average annual dates of the hottest and coldest days of the year. We analyse daily temperature extremes recorded at 1218 stations across the contiguous United States from 1853–2012, and observe large regional variation with the Summer Teletherm falling up to 90 days after the Summer Solstice, and 50 days for the Winter Teletherm after the Winter Solstice. We show that Teletherm temporal dynamics are substantive with clear and in some cases dramatic shifts reflective of system bifurcations. We also compare recorded daily temperature extremes with output from two regional climate models finding considerable though relatively unbiased error. Our work demonstrates that Teletherms are an intuitive, powerful, and statistically sound measure of local climate change, and that they pose detailed, stringent challenges for future theoretical and computational models. PMID:27167740
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.
Kooijman, S A L M; Sousa, T; Pecquerie, L; van der Meer, J; Jager, T
2008-11-01
The standard model of the dynamic energy budget theory for metabolic organisation has variables and parameters that can be quantified using indirect methods only. We present new methods (and software) to extract food-independent parameter values of the energy budget from food-dependent quantities that are easy to observe, and so facilitate the practical application of the theory to enhance predictability and extrapolation. A natural sequence of 10 steps is discussed to obtain some compound parameters first, then the primary parameters, then the composition parameters and finally the thermodynamic parameters; this sequence matches a sequence of required data of increasing complexity which is discussed in detail. Many applications do not require knowledge of all parameters, and we discuss methods to extrapolate parameters from one species to another. The conversion of mass, volume and energy measures of biomass is discussed; these conversions are not trivial because biomass can change in chemical composition in particular ways thanks to different forms of homeostasis. We solve problems like "What would be the ultimate reproduction rate and the von Bertalanffy growth rate at a specific food level, given that we have measured these statistics at abundant food?" and "What would be the maximum incubation time, given the parameters of the von Bertalanffy growth curve?". We propose a new non-destructive method for quantifying the chemical potential and entropy of living reserve and structure, that can potentially change our ideas on the thermodynamic properties of life. We illustrate the methods using data on daphnids and molluscs.
Fattal, D R; Ben-Shaul, A
1994-01-01
A molecular, mean-field theory of chain packing statistics in aggregates of amphiphilic molecules is applied to calculate the conformational properties of the lipid chains comprising the hydrophobic cores of dipalmitoyl-phosphatidylcholine (DPPC), dioleoyl-phosphatidylcholine (DOPC), and palmitoyl-oleoyl-phosphatidylcholine (POPC) bilayers in their fluid state. The central quantity in this theory, the probability distribution of chain conformations, is evaluated by minimizing the free energy of the bilayer assuming only that the segment density within the hydrophobic region is uniform (liquidlike). Using this distribution we calculate chain conformational properties such as bond orientational order parameters and spatial distributions of the various chain segments. The lipid chains, both the saturated palmitoyl (-(CH2)14-CH3) and the unsaturated oleoyl (-(CH2)7-CH = CH-(CH2)7-CH3) chains are modeled using rotational isomeric state schemes. All possible chain conformations are enumerated and their statistical weights are determined by the self-consistency equations expressing the condition of uniform density. The hydrophobic core of the DPPC bilayer is treated as composed of single (palmitoyl) chain amphiphiles, i.e., the interactions between chains originating from the same lipid headgroup are assumed to be the same as those between chains belonging to different molecules. Similarly, the DOPC system is treated as a bilayer of oleoyl chains. The POPC bilayer is modeled as an equimolar mixture of palmitoyl and oleoyl chains. Bond orientational order parameter profiles, and segment spatial distributions are calculated for the three systems above, for several values of the bilayer thickness (or, equivalently, average area/headgroup) chosen, where possible, so as to allow for comparisons with available experimental data and/or molecular dynamics simulations. In most cases the agreement between the mean-field calculations, which are relatively easy to perform, and the
NASA Astrophysics Data System (ADS)
Eslamizadeh, H.
2017-02-01
Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei {}168{{Y}}{{b}}, {}172{{Y}}{{b}}, {}178{{W}} and {}227{{P}}{{a}} produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, K, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of K, {γ }k, was applied in the four-dimensional dynamical calculations. A comparison of the results of the three- and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s.
NASA Astrophysics Data System (ADS)
Sherman, James P.; She, Chiao-Yao
2006-06-01
One thousand three hundred and eleven 15-min profiles of nocturnal mesopause region (80 105 km) temperature and horizontal wind, observed by Colorado State University sodium lidar over Fort Collins, CO (41°N, 105°W), between May 2002 and April 2003, were analyzed. From these profiles, taken over 390 h and each possessing vertical resolution of 2 km, a statistical analysis of seasonal variations in wind shears, convective and dynamical instabilities was performed. Large wind shears were most often observed near 100 km and during winter months. Thirty-five percent of the winter profiles contained wind shears exceeding 40 m/s per km at some altitude. In spite of large winds and shears, the mesopause region (at a resolution of 2 km and 15 min) is a very stable region. At a given altitude, the probability for convective instability is less than 1.4% for all seasons and the probability for dynamic instability (in the sense of Richardson number) ranges from 2.7% to 6.0%. Wind shear measurements are compared with four decades of chemical release measurements, compiled in a study by Larson [2002. Winds and shears in the mesosphere and lower thermosphere: results from four decades of chemical release wind measurements. Journal of Geophysical Research 107(A8), 1215]. Instability results are compared with those deduced from an annual lidar study conducted with higher spatial and temporal resolution at the Starfire Optical Range (SOR) in Albuquerque, NM, by Zhao et al. [2003. Measurements of atmospheric stability in the mesopause region at Starfire Optical Range, NM. Journal of Atmospheric and Solar-Terrestrial Physics 65, 219 232], and from a study by Li et al. [2005b. Characteristics of instabilities in the mesopause region over Maui, Hawaii. Journal of Geophysical Research 110, D09S12] with 19 days of data acquired from Maui Mesosphere and Lower Thermosphere (Maui MALT) Campaign . The Fort Collins lidar profiles were also analyzed using 1-h temporal resolution to compare
NASA Astrophysics Data System (ADS)
Farrell, Brian F.; Ioannou, Petros J.; Jiménez, Javier; Constantinou, Navid C.; Lozano-Durán, Adrián; Nikolaidis, Marios-Andreas
2016-12-01
The perspective of statistical state dynamics (SSD) has recently been applied to the study of mechanisms underlying turbulence in various physical systems. An example implementation of SSD is the second order closure referred to as stochastic structural stability theory (S3T), which has provided insight into the dynamics of wall turbulence and specifically the emergence and maintenance of the roll/streak structure. This closure eliminates nonlinear interactions among the perturbations has been removed, restricting nonlinearity in the dynamics to that of the mean equation and the interaction between the mean and perturbation covariance. Here, this quasi-linear restriction of the dynamics is used to study the structure and dynamics of turbulence in plane Poiseuille flow at moderately high Reynolds numbers in a closely related dynamical system, referred to as the restricted nonlinear (RNL) system. RNL simulations reveal that the essential features of wall-turbulence dynamics are retained. Remarkably, the RNL system spontaneously limits the support of its turbulence to a small set of streamwise Fourier components giving rise to a naturally minimal representation of its turbulence dynamics. Although greatly simplified, this RNL turbulence exhibits natural-looking structures and statistics. Surprisingly, even when further truncation of the perturbation support to a single streamwise component is imposed the RNL system continues to produce self-sustaining turbulent structure and dynamics. RNL turbulence at the Reynolds numbers studied is dominated by the roll/streak structure in the buffer layer and similar very-large-scale structure (VLSM) in the outer layer. Diagnostics of the structure, spectrum and energetics of RNL and DNS turbulence are used to demonstrate that the roll/streak dynamics supporting the turbulence in the buffer and logarithmic layer is essentially similar in RNL and DNS.
NASA Astrophysics Data System (ADS)
Larsen, L.; Watts, D.; Khurana, A.; Anderson, J. L.; Xu, C.; Merritts, D. J.
2015-12-01
The classic signal of self-organization in nature is pattern formation. However, the interactions and feedbacks that organize depositional landscapes do not always result in regular or fractal patterns. How might we detect their existence and effects in these "irregular" landscapes? Emergent landscapes such as newly forming deltaic marshes or some restoration sites provide opportunities to study the autogenic processes that organize landscapes and their physical signatures. Here we describe a quest to understand autogenic vs. allogenic controls on landscape evolution in Big Spring Run, PA, a landscape undergoing restoration from bare-soil conditions to a target wet meadow landscape. The contemporary motivation for asking questions about autogenic vs. allogenic controls is to evaluate how important initial conditions or environmental controls may be for the attainment of management objectives. However, these questions can also inform interpretation of the sedimentary record by enabling researchers to separate signals that may have arisen through self-organization processes from those resulting from environmental perturbations. Over three years at Big Spring Run, we mapped the dynamic evolution of floodplain vegetation communities and distributions of abiotic variables and topography. We used principal component analysis and transition probability analysis to detect associative interactions between vegetation and geomorphic variables and convergent cross-mapping on lidar data to detect causal interactions between biomass and topography. Exploratory statistics revealed that plant communities with distinct morphologies exerted control on landscape evolution through stress divergence (i.e., channel initiation) and promoting the accumulation of fine sediment in channels. Together, these communities participated in a negative feedback that maintains low energy and multiple channels. Because of the spatially explicit nature of this feedback, causal interactions could not
Technology Transfer Automated Retrieval System (TEKTRAN)
Subsurface drip irrigation (SDI) wets the soil at the depth of the drip line and in a volume around each emitter, but the soil wetted often does not include the soil surface. Because of this, the soil surface remains completely or at least partially dry and evaporative losses of irrigation water are...
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…
Balucani, Nadia; Capozza, Giovanni; Segoloni, Enrico; Russo, Andrea; Bobbenkamp, Rolf; Casavecchia, Piergiorgio; Gonzalez-Lezana, Tomas; Rackham, Edward J; Bañares, Luis; Aoiz, F Javier
2005-06-15
In this paper we report a combined experimental and theoretical study on the dynamics of the insertion reaction C((1)D)+D(2) at 15.5 kJ mol(-1) collision energy. Product angular and velocity distributions have been obtained in crossed beam experiments and quasiclassical trajectory (QCT) and rigorous statistical calculations have been performed on the recent and accurate ab initio potential energy surface of Bussery-Honvault, Honvault, and Launay at the energy of the experiment. The molecular-beam results have been simulated using the theoretical calculations. Good agreement between experiment and both QCT and statistical predictions is found.
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
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
NASA Astrophysics Data System (ADS)
Shreeman, Paul K.
The statistical dynamical diffraction theory, which has been initially developed by late Kato remained in obscurity for many years due to intense and difficult mathematical treatment that proved to be quite challenging to implement and apply. With assistance of many authors in past (including Bushuev, Pavlov, Pungeov, and among the others), it became possible to implement this unique x-ray diffraction theory that combines the kinematical (ideally imperfect) and dynamical (the characteristically perfect diffraction) into a single system of equations controlled by two factors determined by long range order and correlation function within the structure. The first stage is completed by the publication (Shreeman and Matyi, J. Appl. Cryst., 43, 550 (2010)) demonstrating the functionality of this theory with new modifications hence called modified statistical dynamical diffraction theory (mSDDT). The foundation of the theory is also incorporated into this dissertation, and the next stage of testing the model against several ion-implanted SiGe materials has been published: (Shreeman and Matyi, physica status solidi (a)208(11), 2533-2538, 2011). The dissertation with all the previous results summarized, dives into comprehensive analysis of HRXRD analyses complete with several different types of reflections (symmetrical, asymmetrical and skewed geometry). The dynamical results (with almost no defects) are compared with well-known commercial software. The defective materials, to which commercially available modeling software falls short, is then characterized and discussed in depth. The results will exemplify the power of the novel approach in the modified statistical dynamical diffraction theory: Ability to detect and measure defective structures qualitatively and quantitatively. The analysis will be compared alongside with TEM data analysis for verification and confirmation. The application of this theory will accelerate the ability to quickly characterize the relaxed
Rundle, John B.; Klein, William
2015-09-29
We have carried out research to determine the dynamics of failure in complex geomaterials, specifically focusing on the role of defects, damage and asperities in the catastrophic failure processes (now popularly termed “Black Swan events”). We have examined fracture branching and flow processes using models for invasion percolation, focusing particularly on the dynamics of bursts in the branching process. We have achieved a fundamental understanding of the dynamics of nucleation in complex geomaterials, specifically in the presence of inhomogeneous structures.
Erguler, Kamil; Stumpf, Michael P H
2011-05-01
The size and complexity of cellular systems make building predictive models an extremely difficult task. In principle dynamical time-course data can be used to elucidate the structure of the underlying molecular mechanisms, but a central and recurring problem is that many and very different models can be fitted to experimental data, especially when the latter are limited and subject to noise. Even given a model, estimating its parameters remains challenging in real-world systems. Here we present a comprehensive analysis of 180 systems biology models, which allows us to classify the parameters with respect to their contribution to the overall dynamical behaviour of the different systems. Our results reveal candidate elements of control in biochemical pathways that differentially contribute to dynamics. We introduce sensitivity profiles that concisely characterize parameter sensitivity and demonstrate how this can be connected to variability in data. Systematically linking data and model sloppiness allows us to extract features of dynamical systems that determine how well parameters can be estimated from time-course measurements, and associates the extent of data required for parameter inference with the model structure, and also with the global dynamical state of the system. The comprehensive analysis of so many systems biology models reaffirms the inability to estimate precisely most model or kinetic parameters as a generic feature of dynamical systems, and provides safe guidelines for performing better inferences and model predictions in the context of reverse engineering of mathematical models for biological systems.
Sawada, N; Kojima, T; Obata, H; Saitoh, M; Isomura, H; Kokai, Y; Satoh, M; Mori, M
1996-11-21
To elucidate whether p21waf-1/cip-1/sdi-1 expression is associated with loss of growth potential of hepatocytes of old rats, we determined p21waf-1/cip-1/sdi-1 expression of hepatocytes from old (30 months) rats during the cell cycle in primary culture. A high level of expression of p21waf-1/cip-1/sdi-1 was detected at the G1 phase in old-rat hepatocytes, but after the S phase in young-rat hepatocytes. Consistently, the incidence of the cells positive for p21waf-1/cip-1/sdi-1 in nuclei before entering the S phase was significantly higher in old-rat hepatocytes than in young-rat hepatocytes. These results account for the loss of growth potential of old-rat hepatocytes in vitro and the marked retardation of regeneration of liver in old rats in vivo.
Heo, Jee-In; Oh, Soo-Jin; Kho, Yoon-Jung; Kim, Jeong-Hyeon; Kang, Hong-Joon; Park, Seong-Hoon; Kim, Hyun-Seok; Shin, Jong-Yeon; Kim, Min-Ju; Kim, Sung Chan; Park, Jae-Bong; Kim, Jaebong; Lee, Jae-Yong
2011-04-01
Since anti-apoptotic effect of ERK has not been elucidated clearly in DNA-damage-induced cell death, the role of ERK was examined in normal HEF cells treated with mild DNA damage using etoposide or camptothecin. ERK was activated by DNA damage in HEF cells. PD98059 increased apoptosis and reduced DNA-damage-induced p21Waf1/Cip1/Sdi level. Depletion of p21Waf1/Cip1/Sdi induced cell death and PD98059 induced additional cell death. DNA-damage-induced increase in cytoplasmic localization and phosphorylation of threonine residues of p21Waf1/Cip1/Sdi was reversed by PD98059. Thus, the results suggest that ERK pathway mediates anti-apoptotic effects through phosphorylation and cytoplasmic localization of p21Waf1/Cip1/Sdi in response to mild DNA damage.
1985-11-01
Memorandum Report has been reviewed by the committee members listed on page ix. v.- pJ. ?. S- • iii ABSTRACT Issues and procedures that the SDI/IST...programs and activities. v 4. • m - *.***-"* -,,. ’. "*. -~--<~ " : : - CONTENTS Preface iii 5,. Abstract v List of Participants ix I. Introduction 1...II. Identification of Likely Technological Fallout from the Program of the SDI/IST Directorate 3 III . Issues and Procedures 9 Appendices--Edited
Fife, D.W.; Campbell, K.; Chludzinski, J.; Corcoran, N.; Gonzalez, C.
1987-10-01
This IDA paper was prepared at the request of the Strategic Defense Initiative Organization. The paper documents findings of an evaluation on the capabilities of certain computer software/computer-aided software engineering (CASE) tools to provide computer-aided graphic design of Battle Management/C3 for the SDIO. Each tool (of the five selected on the basis of the best available at this time), was installed at IDA. After training by vendor tool staff, an IDA team, using a hands-on design experience determined the merits of the tools for SDI application. A comparative summary of the tools is given relative to envisaged SDI requirements and an extensive questionnaire is answered for each.
Madkour, Tarek M; Salem, Sarah A; Miller, Stephen A
2013-04-28
To fully understand the thermodynamic nature of polymer blends and accurately predict their miscibility on a microscopic level, a hybrid model employing both statistical mechanics and molecular dynamics techniques was developed to effectively predict the total free energy of mixing. The statistical mechanics principles were used to derive an expression for the deformational entropy of the chains in the polymeric blends that could be evaluated from molecular dynamics trajectories. Evaluation of the entropy loss due to the deformation of the polymer chains in the case of coiling as a result of the repulsive interactions between the blend components or in the case of swelling due to the attractive interactions between the polymeric segments predicted a negative value for the deformational entropy resulting in a decrease in the overall entropy change upon mixing. Molecular dynamics methods were then used to evaluate the enthalpy of mixing, entropy of mixing, the loss in entropy due to the deformation of the polymeric chains upon mixing and the total free energy change for a series of polar and non-polar, poly(glycolic acid), PGA, polymer blends.
NASA Astrophysics Data System (ADS)
Massei, N.; Duran, L. P.; Fournier, M.; Jardani, A.; Lecoq, N.
2015-12-01
In this research we study the capability of time series analysis approaches to extract meaningful components of karst spring hydrographs. In this aim we compare these statistical components to the internal components of a conceptual precipitation/discharge model based on the physical knowledge of the site studied. We used the conceptual modeling software KARSTMOD developed by the INSU/CNRS National Karst Observatory to model discharge at a small karst spring in Normandy (France). The model comprised four reservoirs E, L, M and C (interpreted as epikarst, high- inertia/highly capacitive matrix, fissure network and conduits), consistent with previous works showing the existence of a triple porosity in chalk of Normandy. KARSTMOD internal flow components were analyzed with correlation and Fourier spectral analysis, and compared to statistical components extracted from spring discharge by wavelet multiresolution analysis and Ensemble Empirical Mode Decomposition (EEMD). We could also analyze how the hydrological signal acquired its red noise statistical characteristics while water flow propagates into the conceptual model. The trend of the discharge signal, given by the residue of EEMD, appeared quite similar to the variation in reservoir L and well correlated to the variation of the water level within the aquifer. Exchanges between fissured matrix and conduits (reservoirs M and C) could be also investigated: a high frequency pressure pulse-controlled flow from C to M (intermittent recharge from the conduits) was identified, as well as fissured matrix flow likely to take place in the surroundings of the conduit network. Flow from reservoir M to reservoir C could be recovered by recombining wavelet components of spring discharge. This study demonstrated that statistical components extracted from a discharge signal of a karst spring can provide meaningful hydrological information. Comparison with a physics-based model would however be required in order to complement this
Analysis and Tradeoffs Supporting the SDI System Architecture (Phase 2C Program)
2007-11-02
narrow beam links by employing electronically -agile, multi- beam antennas. When parallel links and the relay of information among the satellites are... wire and cable -based alterna- tives. Ultra-wideband signaling (2-20 gigabits per second [GBPS]) is today being demonstrated in the laboratory with...antenna/ beam slewing over large solid angles in response to spacecraft dynamics and line-of-sight constraints. The achievement of electronically
BRG1 controls the activity of the retinoblastoma protein via regulation of p21CIP1/WAF1/SDI.
Kang, Hyeog; Cui, Kairong; Zhao, Keji
2004-02-01
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 p21(CIP1/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.
Cigarette smoke triggers code red: p21CIP1/WAF1/SDI1 switches on danger responses in the lung.
Tuder, Rubin M; Yun, Jeong H; Graham, Brian B
2008-07-01
The article by Yao and coworkers in this issue (Am. J. Respir. Cell Mol. Biol. 2008;39:7-18) reveals that the cyclin-dependent kinase inhibitor p21CIP1/WAF1/SDI1 (designated hereafter as p21), which has been linked to cell cycle growth arrest due to stress or danger cell responses, may modulate alveolar inflammation and alveolar destruction, and thus enlightens our present understanding of how the lung senses injury due to cigarette smoke and integrates these responses with those that activate inflammatory pathways potentially harmful to the lung. Furthermore, the interplay of p21 and cellular processes involving cell senescence and the imbalance of cell proliferation/apoptosis may provide us with a more logical explanation of how p21, acting as a sensor of cellular stress, might have such potent and wide roles in lung responses triggered by cigarette smoke. Molecular switches, ontologically designed for the protection of the host, are now hijacked by injurious stresses (such as cigarette smoke), leading to organ damage.
Nogueira, F; Couto, E G; Bernardi, C J
2002-11-01
The Pantanal of Mato Grosso presents distinct landscape units: permanently, occasionally and periodically flooded areas. In the last ones, sampling is especially difficult due to the high heterogeneity occurring inter and intrastratas. This paper presents a comparison of different methodological approaches showing that they can influence decisively the knowledge of distribution organic matter dynamics. In such an area in order to understand the role of the flood pulse in the distribution dynamics of organic matter in a wetland at the Pantanal, we considered that there is spatial dependence between points. This consideration contradicts the classical statistic principle that focuses on the aleatority, and allowed the obtainment of a larger volume of information from a minor sampling effort, which means better performance, with time and money economy.
NASA Astrophysics Data System (ADS)
Albers, D. J.; Hripcsak, George
2010-02-01
Statistical physics and information theory is applied to the clinical chemistry measurements present in a patient database containing 2.5 million patients' data over a 20-year period. Despite the seemingly naive approach of aggregating all patients over all times (with respect to particular clinical chemistry measurements), both a diurnal signal in the decay of the time-delayed mutual information and the presence of two sub-populations with differing health are detected. This provides a proof in principle that the highly fragmented data in electronic health records has potential for being useful in defining disease and human phenotypes.
Albers, D. J.; Hripcsak, George
2010-01-01
Statistical physics and information theory is applied to the clinical chemistry measurements present in a patient database containing 2.5 million patients’ data over a 20-year period. Despite the seemingly naive approach of aggregating all patients over all times (with respect to particular clinical chemistry measurements), both a diurnal signal in the decay of the time-delayed mutual information and the presence of two sub-populations with differing health are detected. This provides a proof in principle that the highly fragmented data in electronic health records has potential for being useful in defining disease and human phenotypes. PMID:20544004
NASA Astrophysics Data System (ADS)
Hong, Mei; Zhang, Ren; Wang, Dong; Chen, Xi; Shi, Jian; Singh, Vijay
2014-12-01
The western Pacific subtropical high (WPSH) is closely correlated with the East Asian climate. To date, the underlying mechanisms and sustaining factors have not been positively elucidated. Based on the concept of dynamical system model reconstruction, this paper presents a nonlinear statistical-dynamical model of the subtropical high ridge line (SHRL) in concurrence with four summer monsoon factors. SHRL variations from 1990 to 2011 are subdivided into three categories, while parameter differences relating to three differing models are examined. Dynamical characteristics of SHRL are analyzed and an aberrance mechanism subsequently developed. Modeling suggests that different parameters may lead to significant variance pertaining to monsoon variables corresponding with numerous WPSH activities. Dynamical system bifurcation and mutation indicates that the South China Sea monsoon trough is a significant factor with respect to the occurrence and maintenance of the 'double-ridge' phenomenon. Moreover, the occurrence of the Mascarene cold high is predicted to cause an abnormal northward location of WPSH, resulting in the “empty plum” phenomenon.
NASA Astrophysics Data System (ADS)
Zhao, Jun-Hu; Yang, Liu; Hou, Wei; Liu, Gang; Zeng, Yu-Xing
2015-05-01
The cold vortex is a major high impact weather system in northeast China during the warm season, its frequent activities also affect the short-term climate throughout eastern China. How to objectively and quantitatively predict the intensity trend of the cold vortex is an urgent and difficult problem for current short-term climate prediction. Based on the dynamical-statistical combining principle, the predicted results of the Beijing Climate Center’s global atmosphere-ocean coupled model and rich historical data are used for dynamic-statistical extra-seasonal prediction testing and actual prediction of the summer 500-hPa geopotential height over the cold vortex activity area. The results show that this method can significantly reduce the model’s prediction error over the cold vortex activity area, and improve the prediction skills. Furthermore, the results of the sensitivity test reveal that the predicted results are highly dependent on the quantity of similar factors and the number of similar years. Project supported by the National Natural Science Foundation of China (Grant No. 41375078), the National Basic Research Program of China (Grant Nos. 2012CB955902 and 2013CB430204), and the Special Scientific Research Fund of Public Welfare Profession of China (Grant No. GYHY201306021).
NASA Astrophysics Data System (ADS)
Verma, M.; Denker, C.
2014-03-01
Context. Solar pores are penumbra-lacking magnetic features, that mark two important transitions in the spectrum of magnetohydrodynamic processes: (1) the magnetic field becomes sufficiently strong to suppress the convective energy transport and (2) at some critical point some pores develop a penumbra and become sunspots. Aims: The purpose of this statistical study is to comprehensively describe solar pores in terms of their size, perimeter, shape, photometric properties, and horizontal proper motions. The seeing-free and uniform data of the Japanese Hinode mission provide an opportunity to compare flow fields in the vicinity of pores in different environments and at various stages of their evolution. Methods: The extensive database of high-resolution G-band images observed with the Hinode Solar Optical Telescope (SOT) is a unique resource to derive statistical properties of pores using advanced digital image processing techniques. The study is based on two data sets: (1) photometric and morphological properties inferred from single G-band images cover almost seven years from 2006 October 25 to 2013 August 31; and (2) horizontal flow fields derived from 356 one-hour sequences of G-band images using local correlation tracking (LCT) for a shorter period of time from 2006 November 3 to 2008 January 6 comprising 13 active regions. Results: A total of 7643/2863 (single/time-averaged) pores builds the foundation of the statistical analysis. Pores are preferentially observed at low latitudes in the southern hemisphere during the deep minimum of solar cycle No. 23. This imbalance reverses during the rise of cycle No. 24, when the pores migrate from high to low latitudes. Pores are rarely encountered in quiet-Sun G-band images, and only about 10% of pores exist in isolation. In general, pores do not exhibit a circular shape. Typical aspect ratios of the semi-major and -minor axes are 3:2 when ellipses are fitted to pores. Smaller pores (more than two-thirds are smaller than
NASA Astrophysics Data System (ADS)
Limkumnerd, Surachate; van der Giessen, Erik
2008-05-01
Due to recent successes of a statistical-based nonlocal continuum crystal plasticity theory for single-glide in explaining various aspects such as dislocation patterning and size-dependent plasticity, several attempts have been made to extend the theory to describe crystals with multiple-slip systems using ad hoc assumptions. We present here a mesoscale continuum theory of plasticity for multiple-slip systems of parallel edge dislocations. We begin by constructing the Bogolyubov Born Green Yvon Kirkwood integral equations relating different orders of dislocation correlation functions in a grand canonical ensemble. Approximate pair correlation functions are obtained for single-slip systems with two types of dislocations and, subsequently, for general multiple-slip systems of both charges. The effect of the correlations manifests itself in the form of an entropic force in addition to the external stress and the self-consistent internal stress. Comparisons with a previous multiple-slip theory based on phenomenological considerations shall be discussed.
Spezia, Riccardo; Martínez-Nuñez, Emilio; Vazquez, Saulo; Hase, William L
2017-04-28
In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces 'on the fly' has paved the way to directly study chemical reactions. This has provided a valuable tool to explore molecular mechanisms at given temperatures and energies and to see whether these reactive trajectories follow statistical laws and/or minimum energy pathways. This themed issue collects different aspects of the problem and gives an overview of recent works and developments in different contexts, from the gas phase to the condensed phase to excited states.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.
Spezia, Riccardo; Martínez-Nuñez, Emilio; Vazquez, Saulo; Hase, William L.
2017-01-01
In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces ‘on the fly’ has paved the way to directly study chemical reactions. This has provided a valuable tool to explore molecular mechanisms at given temperatures and energies and to see whether these reactive trajectories follow statistical laws and/or minimum energy pathways. This themed issue collects different aspects of the problem and gives an overview of recent works and developments in different contexts, from the gas phase to the condensed phase to excited states. This article is part of the themed issue ‘Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces’. PMID:28320909
NASA Astrophysics Data System (ADS)
Sterl, Sebastian; Li, Hui-Min; Zhong, Jin-Qiang
2016-12-01
In this paper, we present results from an experimental study into turbulent Rayleigh-Bénard convection forced externally by periodically modulated unidirectional rotation rates. We find that the azimuthal rotation velocity θ ˙(t ) and thermal amplitude δ (t ) of the large-scale circulation (LSC) are modulated by the forcing, exhibiting a variety of dynamics including increasing phase delays and a resonant peak in the amplitude of θ ˙(t ) . We also focus on the influence of modulated rotation rates on the frequency of occurrence η of stochastic cessation or reorientation events, and on the interplay between such events and the periodically modulated response of θ ˙(t ) . Here we identify a mechanism by which η can be amplified by the modulated response, and these normally stochastic events can occur with high regularity. We provide a modeling framework that explains the observed amplitude and phase responses, and we extend this approach to make predictions for the occurrence of cessation events and the probability distributions of θ ˙(t ) and δ (t ) during different phases of a modulation cycle, based on an adiabatic approach that treats each phase separately. Last, we show that such periodic forcing has consequences beyond influencing LSC dynamics, by investigating how it can modify the heat transport even under conditions where the Ekman pumping effect is predominant and strong enhancement of heat transport occurs. We identify phase and amplitude responses of the heat transport, and we show how increased modulations influence the average Nusselt number.
NASA Astrophysics Data System (ADS)
Stosic, Tatijana; Telesca, Luciano; de Souza Ferreira, Diego Vicente; Stosic, Borko
2016-09-01
In this paper we investigated the influence of the construction of Sobradinho dam on daily streamflow of São Francisco river, Brazil, using permutation entropy method. We analyzed a long daily streamflow time series recorded during the period 1929-2010 encompassing the construction of Sobradinho dam between 1973 and 1979. We found that the original and deseasonalized streamflow time series are characterized by clear different complexity and entropy patterns before the construction of the dam; while, after it, their degree of randomness and complexity are nearly identical. Furthermore, investigating the oscillatory behavior of the entropy and complexity time variation, the periodicity of 3.67 years was identified, identical to one of the main periodicities revealed in the Multivariate ENSO Index (MEI). Such finding confirms the close relationship between streamflow dynamics and ENSO phenomenon. After the construction of the dam, the time variation of entropy and complexity changes almost abruptly toward stochastic regime characterized by higher entropy and lower complexity. Although the dam operations could be considered responsible for such abrupt dynamical change in the streamflow, we cannot exclude the presence of a co-induced ENSO effect; in fact, the analysis of MEI shows a strikingly similar and concomitant change in the long-term trend, identified by using the singular spectrum analysis.
Jambrina, P G; Aoiz, F J; Bulut, N; Smith, Sean C; Balint-Kurti, G G; Hankel, M
2010-02-07
A detailed study of the proton exchange reaction H(+) + D(2)(v = 0, j = 0) --> HD + D(+) on its ground 1(1)A' potential energy surface has been carried out using 'exact' close-coupled quantum mechanical wavepacket (WP-EQM), quasi-classical trajectory (QCT), and statistical quasi-classical trajectory (SQCT) calculations for a range of collision energies starting from the reaction threshold to 1.3 eV. The WP-EQM calculations include all total angular momenta up to J(max) = 50, and therefore the various dynamical observables are converged up to 0.6 eV. It has been found that it is necessary to include all Coriolis couplings to obtain reliable converged results. Reaction probabilities obtained using the different methods are thoroughly compared as a function of the total energy for a series of J values. Comparisons are also made of total reaction cross sections as function of the collision energy, and rate constants. In addition, opacity functions, integral cross sections (ICS) and differential cross sections (DCS) are presented at 102 meV, 201.3 meV and 524.6 meV collision energy. The agreement between the three sets of results is only qualitative. The QCT calculations fail to describe the overall reactivity and most of the dynamical observables correctly. At low collision energies, the QCT method is plagued by the lack of conservation of zero point energy, whilst at higher collision energies and/or total angular momenta, the appearance of an effective repulsive potential associated with the centrifugal motion "over" the well causes a substantial decrease of the reactivity. In turn, the statistical models overestimate the reactivity over the whole range of collision energies as compared with the WP-EQM method. Specifically, at sufficiently high collision energies the reaction cannot be deemed to be statistical and important dynamical effects seem to be present. In general the WP-EQM results lie in between those obtained using the QCT and SQCT methods. One of the main
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, α(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.
NASA Astrophysics Data System (ADS)
Galiazzo, M. A.; Bazsó, Á.; Huber, M. S.; Losiak, A.; Dvorak, R.; Koeberl, C.
2013-11-01
The study of meteorite craters on Earth provides information about the dynamic evolution of bodies within the Solar System. the Bosumtwi crater is a well studied, 10.5 km in diameter, ca. 1.07 Myr old impact structure located in Ghana. (Koeberl et al., 1997a). The impactor was ˜ 1 km in diameter, an ordinary chondrite and struck the Earth with an angle between 30o and 45o (Artemieva et al., 2004) from the horizontal. We have used a two phase backward integration to constrain the most probable parent region of the impactor. We find that the most likely source region is a high inclination object from the Middle Main Belt.
NASA Technical Reports Server (NTRS)
Mcmillan, S. L. W.
1986-01-01
The period immediately following the core collapse phase in the evolution of a globular cluster is studied using a hybrid N-body/Fokker-Planck stellar dynamical code. Several core oscillations of the type predicted in earlier work are seen. The oscillations are driven by the formation, hardening, and ejection of binaries by three-body processes, and appear to decay on a timescale of about 10 to the 7th yr, for the choice of 'typical' cluster parameters made here. There is no evidence that they are gravothermal in nature. The mechanisms responsible for the decay are discussed in some detail. The distribution of hard binaries produced by the oscillations is compared with theoretical expectations and the longer term evolution of the system is considered.
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)
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
Wang, Xiaodong; Ratnaweera, Harsha; Holm, Johan Abdullah; Olsbu, Vibeke
2017-02-07
The on-line monitoring of Chemical oxygen demand (COD) and total phosphorus (TP) restrains wastewater treatment plants to achieve better control of aeration and chemical dosing. In this study, we applied principal components analysis (PCA) to find out significant variables for COD and TP prediction. Multiple regression method applied the variables suggested by PCA to predict influent COD and TP. Moreover, a model of full-scale wastewater treatment plant with moving bed bioreactor (MBBR) and ballasted separation process was developed to simulate the performance of wastewater treatment. The predicted COD and TP data by multiple regression served as model input for dynamic simulation. Besides, the wastewater characteristic of the wastewater treatment plant and MBBR model parameters were given for model calibration. As a result, R(2) of predicted COD and TP versus measured data are 81.6% and 77.2%, respectively. The model output in terms of sludge production and effluent COD based on predicted input data fitted measured data well, which provides possibility to enabled model predictive control of aeration and coagulant dosing in practice. This study provide a feasible and economical approach to overcome monitoring and modelling restrictions that limits model predictive control of wastewater treatment plant.
Kissick, David J; Muir, Ryan D; Simpson, Garth J
2010-12-15
An experimentally simple photon counting method is demonstrated providing 7 orders of magnitude in linear dynamic range (LDR) for a single photomultiplier tube (PMT) detector. In conventional photon/electron counting methods, the linear range is dictated by the agreement between the binomially distributed measurement of counted events and the underlying Poisson distribution of photons/electrons. By explicitly considering the log-normal probability distribution in voltage transients as a function of the number of photons present and the Poisson distribution of photons, observed counts for a given threshold can be related to the mean number of photons well beyond the conventional limit. Analytical expressions are derived relating counts and photons that extend the linear range to an average of ∼11 photons arriving simultaneously with a single threshold. These expressions can be evaluated numerically for multiple thresholds extending the linear range to the saturation point of the PMT. The peak voltage distributions are experimentally shown to follow a Poisson weighted sum of log-normal distributions that can all be derived from the single photoelectron voltage peak-height distribution. The LDR that results from this method is compared to conventional single photon counting (SPC) and to signal averaging by analog to digital conversion (ADC).
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.
Demkin, V. P.; Mel'nichuk, S. V.
2014-09-15
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 (E/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.
Pasquaretta, Cristian; Klenschi, Elizabeth; Pansanel, Jérôme; Battesti, Marine; Mery, Frederic; Sueur, Cédric
2016-01-01
Social learning – the transmission of behaviors through observation or interaction with conspecifics – can be viewed as a decision-making process driven by interactions among individuals. Animal group structures change over time and interactions among individuals occur in particular orders that may be repeated following specific patterns, change in their nature, or disappear completely. Here we used a stochastic actor-oriented model built using the RSiena package in R to estimate individual behaviors and their changes through time, by analyzing the dynamic of the interaction network of the fruit fly Drosophila melanogaster during social learning experiments. In particular, we re-analyzed an experimental dataset where uninformed flies, left free to interact with informed ones, acquired and later used information about oviposition site choice obtained by social interactions. We estimated the degree to which the uninformed flies had successfully acquired the information carried by informed individuals using the proportion of eggs laid by uninformed flies on the medium their conspecifics had been trained to favor. Regardless of the degree of information acquisition measured in uninformed individuals, they always received and started interactions more frequently than informed ones did. However, information was efficiently transmitted (i.e., uninformed flies predominantly laid eggs on the same medium informed ones had learn to prefer) only when the difference in contacts sent between the two fly types was small. Interestingly, we found that the degree of reciprocation, the tendency of individuals to form mutual connections between each other, strongly affected oviposition site choice in uninformed flies. This work highlights the great potential of RSiena and its utility in the studies of interaction networks among non-human animals. PMID:27148146
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.
Sitnikov, D M; Schineller, J B; Baldwin, T O
1996-01-09
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.
Shi, Runhua; McLarty, Jerry W
2009-10-01
In this article, we introduced basic concepts of statistics, type of distributions, and descriptive statistics. A few examples were also provided. The basic concepts presented herein are only a fraction of the concepts related to descriptive statistics. Also, there are many commonly used distributions not presented herein, such as Poisson distributions for rare events and exponential distributions, F distributions, and logistic distributions. More information can be found in many statistics books and publications.
Fukunishi, Yoshifumi; Nakamura, Haruki
2012-01-01
We have developed a method for estimating protein-ligand binding free energy (ΔG) based on the direct protein-ligand interaction obtained by a molecular dynamics simulation. Using this method, we estimated the ΔG 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 ΔG 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 ΔG values was 0.81, and the average error of ΔG 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
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
As a branch of knowledge, Statistics is ubiquitous and its applications can be found in (almost) every field of human endeavour. In this article, the authors track down the possible source of the link between the "Siren song" and applications of Statistics. Answers to their previous five questions and five new questions on Statistics are presented.
Howarth, Jonathan R; Parmar, Saroj; Barraclough, Peter B; Hawkesford, Malcolm J
2009-02-01
A sulphate deficiency-induced gene, sdi1, has been identified by cDNA-amplified fragment length polymorphism (AFLP) analysis utilizing field-grown, nutrient-deficient wheat (Triticum aestivum var. Hereward). The expression of sdi1 was specifically induced in leaf and root tissues in response to sulphate deficiency, but was not induced by nitrogen, phosphorus, potassium or magnesium deficiency. Expression was also shown to increase in plant tissues as the external sulphate concentration in hydroponically grown plants was reduced from 1.0 to 0.0 mm. On this basis, sdi1 gene expression has potential as a sensitive indicator of sulphur nutritional status in wheat. Genome-walking techniques were used to clone the 2.7-kb region upstream of sdi1 from genomic DNA, revealing several cis-element motifs previously identified as being associated with sulphur responses in plants. The Arabidopsis thaliana gene most highly homologous to sdi1 is At5g48850, which was also demonstrated to be induced by sulphur deficiency, an observation confirmed by the analysis of microarray data available in the public domain. The expression of Atsdi1 was induced more rapidly than previously characterized sulphur-responsive genes in the period immediately following the transfer of plants to sulphur-deficient medium. Atsdi1 T-DNA 'knockout' mutants were shown to maintain higher tissue sulphate concentrations than wild-type plants under sulphur-limiting conditions, indicating a role in the utilization of stored sulphate under sulphur-deficient conditions. The structural features of the sdi1 gene and its application in the genetic determination of the sulphur nutritional status of wheat crops are discussed.
Balko, B.; Albini, F.A.; Cohen, L.; Penner, S.S.; Sworder, D.D.
1988-08-01
Battle Management and Command, Control and Communications (BM/C3) issues in the Strategic Defense Initiative (SDI) context were discussed at a two-day workshop at the Institute for Defense Analyses (IDA). Another workshop-probed civilian systems that require handling of large amounts of data and that have fault-tolerant features that may be useful in resolving the SDI BM/C3 problems. The findings are summarized in this report, with special emphasis on possible research to be supported by the Innovative Science and Technology Office of SDIO.
NASA Astrophysics Data System (ADS)
Pahlavani, M. R.; Firoozi, B.
2015-11-01
Within a developed particle-hole approach, a systematic study of the β- transition from the ground state of the 16N nucleus to the ground and some exited states of the 16O nucleus has been carried out. The energy spectrum and the wave functions of pure configuration of the 16N and 16O nuclei are numerically obtained using the mean-field shell model with respect to the Woods-Saxon nuclear potential accompanying spin-orbit and Coulomb interaction. Considering SDI residual interaction, mixed configuration of ground and excited pnTDA and TDA states are extracted for the aforementioned nucleus. These energy spectra and corresponding eigenstates are highly correspondent to the experimental energy spectrum and eigenstates after adjusting the residual potential parameters using the Nelder-Mead (NM) algorithm. In this approach, the endpoint energy, log ft and the partial half-lives of some possible transitions are calculated. The obtained results using the optimized SDI approach are reasonably close to the available experimental data.
Canavan, G.H.
1988-01-01
This report reviews previous attempt to develop strategic defenses, the technologies currently under consideration, their main unknowns, and their likely performance relative to evolving threats. 28 refs.
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...
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.
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
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
NASA Astrophysics Data System (ADS)
Zhang, Wei; Villarini, Gabriele; Vecchi, Gabriel A.; Murakami, Hiroyuki; Gudgel, Richard
2016-06-01
This study examines the seasonal prediction of western North Pacific [WNP) and East Asia landfalling tropical cyclones (TCs) using the Geophysical Fluid Dynamics Laboratory(GFDL) Forecast-oriented Low Ocean Resolution version of CM2.5 with Flux Adjustment (FLOR-FA) and finite-mixture-model (FMM)-based statistical cluster analysis. Using the FMM-based cluster analysis, seven clusters are identified from the historical and FLOR-FA-predicted TC tracks for the period 1980-2013. FLOR-FA has significant skill in predicting year-to-year variations in the frequency of TCs within clusters 1 (recurving TCs) and 5 (straight-moving TCs). By building Poisson regression models for each cluster using key predictors (i.e., sea surface temperature, 500 hPa geopotential height, and zonal vertical wind shear), the predictive skill for almost all the clusters at all initialization months improves with respect to the dynamic prediction. The prediction of total WNP TC frequency made by combining hybrid predictions for each of the seven clusters in the hybrid model shows skill higher than what achieved using the TC frequency directly from FLOR-FA initialized from March to July. However, the hybrid predictions for total WNP TC frequency initialized from January to February exhibit lower skill than FLOR-FA. The prediction of TC landfall over East Asia made by combining the hybrid models of TC frequency in each cluster and its landfall rate over East Asia also outperforms FLOR-FA for all initialization months January through July.
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
In this article, the authors focus on hypothesis testing--that peculiarly statistical way of deciding things. Statistical methods for testing hypotheses were developed in the 1920s and 1930s by some of the most famous statisticians, in particular Ronald Fisher, Jerzy Neyman and Egon Pearson, who laid the foundations of almost all modern methods of…
Gai, Lili; Vogel, Thomas; Maerzke, Katie A; Iacovella, Christopher R; Landau, David P; Cummings, Peter T; McCabe, Clare
2013-08-07
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 (ε) 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.
NASA Astrophysics Data System (ADS)
Gai, Lili; Vogel, Thomas; Maerzke, Katie A.; Iacovella, Christopher R.; Landau, David P.; Cummings, Peter T.; McCabe, Clare
2013-08-01
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 (ɛ) 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.
NASA Astrophysics Data System (ADS)
Li, R.; Wang, S.-Y.; Gillies, R. R.
2016-04-01
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.
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.
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 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.
... population, or about 25 million Americans, has experienced tinnitus lasting at least five minutes in the past ... by NIDCD Epidemiology and Statistics Program staff: (1) tinnitus prevalence was obtained from the 2008 National Health ...
Li, Zheng; Borner, Arnaud; Levin, Deborah A
2014-06-14
Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and
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 Λ=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 βBR. (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 βloc in the interval [0,1]. The level repulsion parameters βBR and βloc are almost linearly related, close to the identity line. (3) We show the existence of a scaling law between βloc and the relative localization length Λ, now including the regimes of anomalous diffusion. The above findings are important also for chaotic eigenstates in time-independent systems [Batistić 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
South, Paul F; Fingerman, Ian M; Mersman, Douglas P; Du, Hai-Ning; Briggs, Scott D
2010-01-01
In Saccharomyces cerevisiae, lysine 4 on histone H3 (H3K4) is methylated by the Set1 complex (Set1C or COMPASS). Besides the catalytic Set1 subunit, several proteins that form the Set1C (Swd1, Swd2, Swd3, Spp1, Bre2, and Sdc1) are also needed to mediate proper H3K4 methylation. Until this study, it has been unclear how individual Set1C members interact and how this interaction may impact histone methylation and gene expression. In this study, Bre2 and Sdc1 are shown to directly interact, and it is shown that the association of this heteromeric complex is needed for proper H3K4 methylation and gene expression to occur. Interestingly, mutational and biochemical analysis identified the C terminus of Bre2 as a critical protein-protein interaction domain that binds to the Dpy-30 domain of Sdc1. Using the human homologs of Bre2 and Sdc1, ASH2L and DPY-30, respectively, we demonstrate that the C terminus of ASH2L also interacts with the Dpy-30 domain of DPY-30, suggesting that this protein-protein interaction is maintained from yeast to humans. Because of the functionally conserved nature of the C terminus of Bre2 and ASH2L, this region was named the SDI (Sdc1 Dpy-30 interaction) domain. Finally, we show that the SDI-Dpy-30 domain interaction is physiologically important for the function of Set1 in vivo, because specific disruption of this interaction prevents Bre2 and Sdc1 association with Set1, resulting in H3K4 methylation defects and decreases in gene expression. Overall, these and other mechanistic studies on how H3K4 methyltransferase complexes function will likely provide insights into how human MLL and SET1-like complexes or overexpression of ASH2L leads to oncogenesis.
NASA Astrophysics Data System (ADS)
Khan, Shahjahan
Often scientific information on various data generating processes are presented in the from of numerical and categorical data. Except for some very rare occasions, generally such data represent a small part of the population, or selected outcomes of any data generating process. Although, valuable and useful information is lurking in the array of scientific data, generally, they are unavailable to the users. Appropriate statistical methods are essential to reveal the hidden "jewels" in the mess of the row data. Exploratory data analysis methods are used to uncover such valuable characteristics of the observed data. Statistical inference provides techniques to make valid conclusions about the unknown characteristics or parameters of the population from which scientifically drawn sample data are selected. Usually, statistical inference includes estimation of population parameters as well as performing test of hypotheses on the parameters. However, prediction of future responses and determining the prediction distributions are also part of statistical inference. Both Classical or Frequentists and Bayesian approaches are used in statistical inference. The commonly used Classical approach is based on the sample data alone. In contrast, increasingly popular Beyesian approach uses prior distribution on the parameters along with the sample data to make inferences. The non-parametric and robust methods are also being used in situations where commonly used model assumptions are unsupported. In this chapter,we cover the philosophical andmethodological aspects of both the Classical and Bayesian approaches.Moreover, some aspects of predictive inference are also included. In the absence of any evidence to support assumptions regarding the distribution of the underlying population, or if the variable is measured only in ordinal scale, non-parametric methods are used. Robust methods are employed to avoid any significant changes in the results due to deviations from the model
NASA Astrophysics Data System (ADS)
Khan, Shahjahan
Often scientific information on various data generating processes are presented in the from of numerical and categorical data. Except for some very rare occasions, generally such data represent a small part of the population, or selected outcomes of any data generating process. Although, valuable and useful information is lurking in the array of scientific data, generally, they are unavailable to the users. Appropriate statistical methods are essential to reveal the hidden “jewels” in the mess of the row data. Exploratory data analysis methods are used to uncover such valuable characteristics of the observed data. Statistical inference provides techniques to make valid conclusions about the unknown characteristics or parameters of the population from which scientifically drawn sample data are selected. Usually, statistical inference includes estimation of population parameters as well as performing test of hypotheses on the parameters. However, prediction of future responses and determining the prediction distributions are also part of statistical inference. Both Classical or Frequentists and Bayesian approaches are used in statistical inference. The commonly used Classical approach is based on the sample data alone. In contrast, increasingly popular Beyesian approach uses prior distribution on the parameters along with the sample data to make inferences. The non-parametric and robust methods are also being used in situations where commonly used model assumptions are unsupported. In this chapter,we cover the philosophical andmethodological aspects of both the Classical and Bayesian approaches.Moreover, some aspects of predictive inference are also included. In the absence of any evidence to support assumptions regarding the distribution of the underlying population, or if the variable is measured only in ordinal scale, non-parametric methods are used. Robust methods are employed to avoid any significant changes in the results due to deviations from the model
Rendón-Macías, Mario Enrique; Villasís-Keever, Miguel Ángel; Miranda-Novales, María Guadalupe
2016-01-01
Descriptive statistics is the branch of statistics that gives recommendations on how to summarize clearly and simply research data in tables, figures, charts, or graphs. Before performing a descriptive analysis it is paramount to summarize its goal or goals, and to identify the measurement scales of the different variables recorded in the study. Tables or charts aim to provide timely information on the results of an investigation. The graphs show trends and can be histograms, pie charts, "box and whiskers" plots, line graphs, or scatter plots. Images serve as examples to reinforce concepts or facts. The choice of a chart, graph, or image must be based on the study objectives. Usually it is not recommended to use more than seven in an article, also depending on its length.
Order Statistics and Nonparametric Statistics.
2014-09-26
Topics investigated include the following: Probability that a fuze will fire; moving order statistics; distribution theory and properties of the...problem posed by an Army Scientist: A fuze will fire when at least n-i (or n-2) of n detonators function within time span t. What is the probability of
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
Wang, Hai-long; Zhang, Zhou-long
2014-09-01
Ultrasonic light scattering tomography system is a new imaging technique for breast function, which associates with diffused optical tomography (DOT) with ultrasonic examination. It locates breast neoplasm with ultrasonic examination and measures the total hemoglobin concentration inside the tumor with DOT photon emission to reflect the metabolic state of tumors and then comes to synthesis diagnostic index to judge benign and malignant tumors. This diagnosis method has significant affection on diagnosis of benign and malignant tumors at home and abroad. In the development of breast cancer, local tissue hypoxia leads to a large number of new blood vessels when the tumor grows faster than the rate of angiogenesis. A recent study found microvessel density (MVD), vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 alpha (HIF-1α) play a major role in angiogenesis of breast cancer. This study analyses the relationship between breast cancer ultrasound synthesis diagnostic index (SDI) and the expression of MVD, VEGF and HIF-1α by testing the expression level of the breast cancer gene MVD, VEGF and HIF-1α.
Tellinghuisen, Joel
2008-01-01
The method of least squares is probably the most powerful data analysis tool available to scientists. Toward a fuller appreciation of that power, this work begins with an elementary review of statistics fundamentals, and then progressively increases in sophistication as the coverage is extended to the theory and practice of linear and nonlinear least squares. The results are illustrated in application to data analysis problems important in the life sciences. The review of fundamentals includes the role of sampling and its connection to probability distributions, the Central Limit Theorem, and the importance of finite variance. Linear least squares are presented using matrix notation, and the significance of the key probability distributions-Gaussian, chi-square, and t-is illustrated with Monte Carlo calculations. The meaning of correlation is discussed, including its role in the propagation of error. When the data themselves are correlated, special methods are needed for the fitting, as they are also when fitting with constraints. Nonlinear fitting gives rise to nonnormal parameter distributions, but the 10% Rule of Thumb suggests that such problems will be insignificant when the parameter is sufficiently well determined. Illustrations include calibration with linear and nonlinear response functions, the dangers inherent in fitting inverted data (e.g., Lineweaver-Burk equation), an analysis of the reliability of the van't Hoff analysis, the problem of correlated data in the Guggenheim method, and the optimization of isothermal titration calorimetry procedures using the variance-covariance matrix for experiment design. The work concludes with illustrations on assessing and presenting results.
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.
... PRS GO PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the ... Plastic Surgery Statistics 2005 Plastic Surgery Statistics 2016 Plastic Surgery Statistics Stats Report 2016 National Clearinghouse of ...
NASA Astrophysics Data System (ADS)
Cerrillo, Javier; Buser, Maximilian; Brandes, Tobias
2016-12-01
Nonequilibrium transport properties of quantum systems have recently become experimentally accessible in a number of platforms in so-called full-counting experiments that measure transient and steady-state nonequilibrium transport dynamics. We show that the effect of the measurement back-action can be exploited to establish general relationships between transport coefficients in the transient regime which take the form of fluctuation-dissipation theorems in the steady state. This result becomes most conspicuous in the transient dynamics of open quantum systems under strong-coupling to non-Markovian environments in nonequilibrium settings. In order to explore this regime, a new simulation method based in a hierarchy of equations of motion has been developed. We instantiate our proposal with the study of energetic conductance between two baths connected via a few level system.
Carnley, Mark V.
2016-09-30
The Design Analysis Associates (DAA) DAA H-3613i radar water-level sensor (DAA H-3613i), manufactured by Xylem Incorporated, was evaluated by the U.S. Geological Survey (USGS) Hydrologic Instrumentation Facility (HIF) for conformance to manufacturer’s accuracy specifications for measuring a distance throughout the sensor’s operating temperature range, for measuring distances from 3 to 15 feet at ambient temperatures, and for compliance with the SDI-12 serial-to-digital interface at 1200-baud communication standard. The DAA H-3613i is a noncontact water-level sensor that uses pulsed radar to measure the distance between the radar and the water surface from 0.75 to 131 feet over a temperature range of −40 to 60 degrees Celsius (°C). Manufacturer accuracy specifications that were evaluated, the test procedures that followed, and the results obtained are described in this report. The sensor’s accuracy specification of ± 0.01 feet (± 3 millimeters) meets USGS requirements for a primary water-stage sensor used in the operation of a streamgage. The sensor met the manufacturer’s stated accuracy specifications for water-level measurements during temperature testing at a distance of 8 feet from the target over its temperature-compensated operating range of −40 to 60 °C, except at 60 °C. At 60 °C, about half the measurements exceeded the manufacturer’s accuracy specification by not more than 0.005 feet.The sensor met the manufacturer’s stated accuracy specifications for water-level measurements during distance-accuracy testing at the tested distances from 3 to 15 feet above the water surface at the HIF.
Didenko, V V; Wang, X; Yang, L; Hornsby, P J
1996-01-01
p21(WAF1/CIP1/SDI1), an inhibitor of cyclin-dependent kinases, is expressed at varying levels in human adrenal glands removed during surgery or organ recovery. In glands with p21 mRNA, nuclear p21 immunoreactivity, which was occasionally extensive, colocalized with p53 immunoreactivity and DNA damage, as evidenced by in situ end-labeling. Many cells showed morphological features of apoptosis when observed by fluorescent DNA dye staining and electron microscopy. This pattern was also associated with high levels of cytoplasmic heat shock protein 70. To address the question of the origin of p21 expression in some human adrenal glands, rat adrenal glands were subjected to 30 min of ischemia followed by 8 h of reperfusion. Cells with nuclear p21 and p53 appeared in the adrenal cortex together with DNA damage detected by in situ end-labeling. Nuclear p21 immunoreactivity was also produced in adrenal tissue fragments incubated at 37 degrees C in vitro. However, in this case, p21 expression was confined to the cut edge of the tissue. In contrast, p21 in human adrenal glands, as in ischemic rat glands, was within the inner regions of the cortex, supporting an origin of the protein in vivo rather than postmortem. The p53/p21 pathway of reaction to cellular injury, potentially leading to apoptosis, may play a role in tissue damage such as that resulting from ischemia/reperfusion. In the human adrenal cortex this process may be a precursor of adrenal failure. PMID:8601638
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.
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)
Cassou, Christophe; Minvielle, Marie; Terray, Laurent; Périgaud, Claire
2011-01-01
The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500 hPa geopotential height and 1,000 hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50 years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our
... Standards Act and Program MQSA Insights MQSA National Statistics Share Tweet Linkedin Pin it More sharing options ... but should level off with time. Archived Scorecard Statistics 2017 Scorecard Statistics 2016 Scorecard Statistics (Archived) 2015 ...
NASA Astrophysics Data System (ADS)
Liu, Wenjia; Schmittmann, B.; Zia, R. K. P.
2014-05-01
In a recent work (Liu et al, 2013 J. Stat. Mech. P08001), we introduced dynamic networks with preferred degrees and presented simulation and analytic studies of a single, homogeneous system as well as two interacting networks. Here, we extend these studies to a wider range of parameter space, in a more systematic fashion. Though the interaction we introduced seems simple and intuitive, it produced dramatically different behavior in the single- and two-network systems. Specifically, partitioning the single network into two identical sectors, we find the cross-link distribution to be a sharply peaked Gaussian. In stark contrast, we find a very broad and flat plateau in the case of two interacting identical networks. A sound understanding of this phenomenon remains elusive. Exploring more asymmetric interacting networks, we discover a kind of ‘universal behavior’ for systems in which the ‘introverts’ (nodes with smaller preferred degree) are far outnumbered. Remarkably, an approximation scheme for their degree distribution can be formulated, leading to very successful predictions.
NASA Astrophysics Data System (ADS)
Rabbel, Hauke; Frey, Holger; Schmid, Friederike
2015-12-01
The reaction of ABm monomers (m = 2, 3) with a multifunctional Bf-type polymer chain ("hypergrafting") is studied by coarse-grained molecular dynamics simulations. The ABm monomers are hypergrafted using the slow monomer addition strategy. Fully dendronized, i.e., perfectly branched polymers are also simulated for comparison. The degree of branching of the molecules obtained with the "hypergrafting" process critically depends on the rate with which monomers attach to inner monomers compared to terminal monomers. This ratio is more favorable if the ABm monomers have lower reactivity, since the free monomers then have time to diffuse inside the chain. Configurational chain properties are also determined, showing that the stretching of the polymer backbone as a consequence of the "hypergrafting" procedure is much less pronounced than for perfectly dendronized chains. Furthermore, we analyze the scaling of various quantities with molecular weight M for large M (M > 100). The Wiener index scales as M2.3, which is intermediate between linear chains (M3) and perfectly branched polymers (M2ln(M)). The polymer size, characterized by the radius of gyration Rg or the hydrodynamic radius Rh, is found to scale as Rg,h ∝ Mν with ν ≈ 0.38, which lies between the exponent of diffusion limited aggregation (ν = 0.4) and the mean-field exponent predicted by Konkolewicz and co-workers [Phys. Rev. Lett. 98, 238301 (2007)] (ν = 0.33).
Nakajima, Masahiro; Negishi, Yoichi; Tanaka, Hiroyasu; Kawashima, Kohtaro
2004-08-06
The embryonal carcinoma-derived cell line, ATDC5, differentiates into chondrocytes in response to insulin or insulin-like growth factor-I stimulation. In this study, we investigated the roles of mitogen-activated protein (MAP) kinases in insulin-induced chondrogenic differentiation of ATDC5 cells. Insulin-induced accumulation of glycosaminoglycan and expression of chondrogenic differentiation markers, type II collagen, type X collagen, and aggrecan mRNA were inhibited by the MEK1/2 inhibitor (U0126) and the p38 MAP kinase inhibitor (SB203580). Conversely, the JNK inhibitor (SP600125) enhanced the synthesis of glycosaminoglycan and expression of chondrogenic differentiation markers. Insulin-induced phosphorylation of ERK1/2 and JNK but not that of p38 MAP kinase. We have previously clarified that the induction of the cyclin-dependent kinase inhibitor, p21(Cip-1/SDI-1/WAF-1), is essential for chondrogenic differentiation of ATDC5 cells. To assess the relationship between the induction of p21 and MAP kinase activity, we investigated the effect of these inhibitors on insulin-induced p21 expression in ATDC5 cells. Insulin-induced accumulation of p21 mRNA and protein was inhibited by the addition of U0126 and SB203580. In contrast, SP600125 enhanced it. Inhibitory effects of U0126 or stimulatory effects of SP600125 on insulin-induced chondrogenic differentiation were observed when these inhibitors exist in the early phase of differentiation, suggesting that MEK/ERK and JNK act on early phase differentiation. SB202580, however, is necessary not only for early phase but also for late phase differentiation, indicating that p38 MAP kinase stimulates differentiation by acting during the entire period of cultivation. These results for the first time demonstrate that up-regulation of p21 expression by ERK1/2 and p38 MAP kinase is required for chondrogenesis, and that JNK acts as a suppressor of chondrogenesis by down-regulating p21 expression.
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
2014-12-01
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.
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…
Predict! Teaching Statistics Using Informational Statistical Inference
ERIC Educational Resources Information Center
Makar, Katie
2013-01-01
Statistics is one of the most widely used topics for everyday life in the school mathematics curriculum. Unfortunately, the statistics taught in schools focuses on calculations and procedures before students have a chance to see it as a useful and powerful tool. Researchers have found that a dominant view of statistics is as an assortment of tools…
Rossell, David
2016-01-01
Big Data brings unprecedented power to address scientific, economic and societal issues, but also amplifies the possibility of certain pitfalls. These include using purely data-driven approaches that disregard understanding the phenomenon under study, aiming at a dynamically moving target, ignoring critical data collection issues, summarizing or preprocessing the data inadequately and mistaking noise for signal. We review some success stories and illustrate how statistical principles can help obtain more reliable information from data. We also touch upon current challenges that require active methodological research, such as strategies for efficient computation, integration of heterogeneous data, extending the underlying theory to increasingly complex questions and, perhaps most importantly, training a new generation of scientists to develop and deploy these strategies. PMID:27722040
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.
Statistical Thermodynamics of Biomembranes
Devireddy, Ram V.
2010-01-01
An overview of the major issues involved in the statistical thermodynamic treatment of phospholipid membranes at the atomistic level is summarized: thermodynamic ensembles, initial configuration (or the physical system being modeled), force field representation as well as the representation of long-range interactions. This is followed by a description of the various ways that the simulated ensembles can be analyzed: area of the lipid, mass density profiles, radial distribution functions (RDFs), water orientation profile, Deuteurium order parameter, free energy profiles and void (pore) formation; with particular focus on the results obtained from our recent molecular dynamic (MD) simulations of phospholipids interacting with dimethylsulfoxide (Me2SO), a commonly used cryoprotective agent (CPA). PMID:19460363
Statistical physics of vaccination
NASA Astrophysics Data System (ADS)
Wang, Zhen; Bauch, Chris T.; Bhattacharyya, Samit; d'Onofrio, Alberto; Manfredi, Piero; Perc, Matjaž; Perra, Nicola; Salathé, Marcel; Zhao, Dawei
2016-12-01
Historically, infectious diseases caused considerable damage to human societies, and they continue to do so today. To help reduce their impact, mathematical models of disease transmission have been studied to help understand disease dynamics and inform prevention strategies. Vaccination-one of the most important preventive measures of modern times-is of great interest both theoretically and empirically. And in contrast to traditional approaches, recent research increasingly explores the pivotal implications of individual behavior and heterogeneous contact patterns in populations. Our report reviews the developmental arc of theoretical epidemiology with emphasis on vaccination, as it led from classical models assuming homogeneously mixing (mean-field) populations and ignoring human behavior, to recent models that account for behavioral feedback and/or population spatial/social structure. Many of the methods used originated in statistical physics, such as lattice and network models, and their associated analytical frameworks. Similarly, the feedback loop between vaccinating behavior and disease propagation forms a coupled nonlinear system with analogs in physics. We also review the new paradigm of digital epidemiology, wherein sources of digital data such as online social media are mined for high-resolution information on epidemiologically relevant individual behavior. Armed with the tools and concepts of statistical physics, and further assisted by new sources of digital data, models that capture nonlinear interactions between behavior and disease dynamics offer a novel way of modeling real-world phenomena, and can help improve health outcomes. We conclude the review by discussing open problems in the field and promising directions for future research.
Elements of Statistical Mechanics
NASA Astrophysics Data System (ADS)
Sachs, Ivo; Sen, Siddhartha; Sexton, James
2006-05-01
This textbook provides a concise introduction to the key concepts and tools of modern statistical mechanics. It also covers advanced topics such as non-relativistic quantum field theory and numerical methods. After introducing classical analytical techniques, such as cluster expansion and Landau theory, the authors present important numerical methods with applications to magnetic systems, Lennard-Jones fluids and biophysics. Quantum statistical mechanics is discussed in detail and applied to Bose-Einstein condensation and topics in astrophysics and cosmology. In order to describe emergent phenomena in interacting quantum systems, canonical non-relativistic quantum field theory is introduced and then reformulated in terms of Feynman integrals. Combining the authors' many years' experience of teaching courses in this area, this textbook is ideal for advanced undergraduate and graduate students in physics, chemistry and mathematics. Analytical and numerical techniques in one text, including sample codes and solved problems on the web at www.cambridge.org/0521841984 Covers a wide range of applications including magnetic systems, turbulence astrophysics, and biology Contains a concise introduction to Markov processes and molecular dynamics
Tsallis statistics and neurodegenerative disorders
NASA Astrophysics Data System (ADS)
Iliopoulos, Aggelos C.; Tsolaki, Magdalini; Aifantis, Elias C.
2016-08-01
In this paper, we perform statistical analysis of time series deriving from four neurodegenerative disorders, namely epilepsy, amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Huntington's disease (HD). The time series are concerned with electroencephalograms (EEGs) of healthy and epileptic states, as well as gait dynamics (in particular stride intervals) of the ALS, PD and HDs. We study data concerning one subject for each neurodegenerative disorder and one healthy control. The analysis is based on Tsallis non-extensive statistical mechanics and in particular on the estimation of Tsallis q-triplet, namely {qstat, qsen, qrel}. The deviation of Tsallis q-triplet from unity indicates non-Gaussian statistics and long-range dependencies for all time series considered. In addition, the results reveal the efficiency of Tsallis statistics in capturing differences in brain dynamics between healthy and epileptic states, as well as differences between ALS, PD, HDs from healthy control subjects. The results indicate that estimations of Tsallis q-indices could be used as possible biomarkers, along with others, for improving classification and prediction of epileptic seizures, as well as for studying the gait complex dynamics of various diseases providing new insights into severity, medications and fall risk, improving therapeutic interventions.
Neuroendocrine Tumor: Statistics
... Tumor > Neuroendocrine Tumor: Statistics Request Permissions Neuroendocrine Tumor: Statistics Approved by the Cancer.Net Editorial Board , 11/ ... the body. It is important to remember that statistics on how many people survive this type of ...
Adrenal Gland Tumors: Statistics
... Gland Tumor: Statistics Request Permissions Adrenal Gland Tumor: Statistics Approved by the Cancer.Net Editorial Board , 03/ ... primary adrenal gland tumor is very uncommon. Exact statistics are not available for this type of tumor ...
STATISTICAL ANALYSIS, REPORTS), (*PROBABILITY, REPORTS), INFORMATION THEORY, DIFFERENTIAL EQUATIONS, STATISTICAL PROCESSES, STOCHASTIC PROCESSES, MULTIVARIATE ANALYSIS, DISTRIBUTION THEORY , DECISION THEORY, MEASURE THEORY, OPTIMIZATION
Statistical Methods for Turbine Blade Dynamics
2008-09-30
Charles Vining, Tom Tibbals The successful completion of the project relied on the availability of test data on which the proposed methodology can be...Bayes networks," Reliability Engineering and System Safety, vol. 87, pp. 223- 232, February 2005. [62] MANSON , G., "Calculating frequency response...449, October 1988. 175 107] WORDEN, K., MANSON , T. M., LORD, T. M., and FRISWELL, M. I., "Some obser- vations on uncertainty propagation through a
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.
Statistical validation of stochastic models
Hunter, N.F.; Barney, P.; Paez, T.L.; Ferregut, C.; Perez, L.
1996-12-31
It is common practice in structural dynamics to develop mathematical models for system behavior, and the authors are now capable of developing stochastic models, i.e., models whose parameters are random variables. Such models have random characteristics that are meant to simulate the randomness in characteristics of experimentally observed systems. This paper suggests a formal statistical procedure for the validation of mathematical models of stochastic systems when data taken during operation of the stochastic system are available. The statistical characteristics of the experimental system are obtained using the bootstrap, a technique for the statistical analysis of non-Gaussian data. The authors propose a procedure to determine whether or not a mathematical model is an acceptable model of a stochastic system with regard to user-specified measures of system behavior. A numerical example is presented to demonstrate the application of the technique.
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.
Explorations in statistics: statistical facets of reproducibility.
Curran-Everett, Douglas
2016-06-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This eleventh installment of Explorations in Statistics explores statistical facets of reproducibility. If we obtain an experimental result that is scientifically meaningful and statistically unusual, we would like to know that our result reflects a general biological phenomenon that another researcher could reproduce if (s)he repeated our experiment. But more often than not, we may learn this researcher cannot replicate our result. The National Institutes of Health and the Federation of American Societies for Experimental Biology have created training modules and outlined strategies to help improve the reproducibility of research. These particular approaches are necessary, but they are not sufficient. The principles of hypothesis testing and estimation are inherent to the notion of reproducibility in science. If we want to improve the reproducibility of our research, then we need to rethink how we apply fundamental concepts of statistics to our science.
Statistical properties of cosmological billiards
NASA Astrophysics Data System (ADS)
Damour, Thibault; Lecian, Orchidea Maria
2011-02-01
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 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.
NASA Astrophysics Data System (ADS)
Kryza, Maciej; Wałaszek, Kinga; Ojrzyńska, Hanna; Szymanowski, Mariusz; Werner, Małgorzata; Dore, Anthony J.
2017-02-01
In this work, we present the results of high-resolution dynamical downscaling of air temperature, relative humidity, wind speed and direction, for the area of Poland, with the Weather Research and Forecasting (WRF) model. The model is configured using three nested domains, with spatial resolution of 45 km × 45 km, 15 km × 15 km and 5 km × 5 km. The ERA-Interim database is used for boundary conditions. The results are evaluated by comparison with station measurements for the period 1981-2010. The model is capable of reproducing the main climatological features of the study area. The results are in very close agreement with the measurements, especially for the air temperature. For all four meteorological variables, the model performance captures seasonal and daily cycles. For the air temperature and winter season, the model underestimates the measurements. For summer, the model shows higher values, compared with the measurements. The opposite is the case for relative humidity. There is a strong diurnal pattern in mean error, which changes seasonally. The agreement with the measurements is worse for the seashore and mountain areas, which suggests that the 5 km × 5 km grid might still have an insufficient spatial resolution. There is no statistically significant temporal trend in the model performance. The larger year-to-year changes in the model performance, e.g. for the years 1982 and 2010 for the air temperature should therefore be linked with the natural variability of meteorological conditions.
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.
Mathematical and statistical analysis
NASA Technical Reports Server (NTRS)
Houston, A. Glen
1988-01-01
The goal of the mathematical and statistical analysis component of RICIS is to research, develop, and evaluate mathematical and statistical techniques for aerospace technology applications. Specific research areas of interest include modeling, simulation, experiment design, reliability assessment, and numerical analysis.
... 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 ...
Experiment in Elementary Statistics
ERIC Educational Resources Information Center
Fernando, P. C. B.
1976-01-01
Presents an undergraduate laboratory exercise in elementary statistics in which students verify empirically the various aspects of the Gaussian distribution. Sampling techniques and other commonly used statistical procedures are introduced. (CP)
The standard map: From Boltzmann-Gibbs statistics to Tsallis statistics
NASA Astrophysics Data System (ADS)
Tirnakli, Ugur; Borges, Ernesto P.
2016-03-01
As well known, Boltzmann-Gibbs statistics is the correct way of thermostatistically approaching ergodic systems. On the other hand, nontrivial ergodicity breakdown and strong correlations typically drag the system into out-of-equilibrium states where Boltzmann-Gibbs statistics fails. For a wide class of such systems, it has been shown in recent years that the correct approach is to use Tsallis statistics instead. Here we show how the dynamics of the paradigmatic conservative (area-preserving) stan-dard map exhibits, in an exceptionally clear manner, the crossing from one statistics to the other. Our results unambiguously illustrate the domains of validity of both Boltzmann-Gibbs and Tsallis statistical distributions. Since various important physical systems from particle confinement in magnetic traps to autoionization of molecular Rydberg states, through particle dynamics in accelerators and comet dynamics, can be reduced to the standard map, our results are expected to enlighten and enable an improved interpretation of diverse experimental and observational results.
The standard map: From Boltzmann-Gibbs statistics to Tsallis statistics.
Tirnakli, Ugur; Borges, Ernesto P
2016-03-23
As well known, Boltzmann-Gibbs statistics is the correct way of thermostatistically approaching ergodic systems. On the other hand, nontrivial ergodicity breakdown and strong correlations typically drag the system into out-of-equilibrium states where Boltzmann-Gibbs statistics fails. For a wide class of such systems, it has been shown in recent years that the correct approach is to use Tsallis statistics instead. Here we show how the dynamics of the paradigmatic conservative (area-preserving) stan-dard map exhibits, in an exceptionally clear manner, the crossing from one statistics to the other. Our results unambiguously illustrate the domains of validity of both Boltzmann-Gibbs and Tsallis statistical distributions. Since various important physical systems from particle confinement in magnetic traps to autoionization of molecular Rydberg states, through particle dynamics in accelerators and comet dynamics, can be reduced to the standard map, our results are expected to enlighten and enable an improved interpretation of diverse experimental and observational results.
ERIC Educational Resources Information Center
Lenard, Christopher; McCarthy, Sally; Mills, Terence
2014-01-01
There are many different aspects of statistics. Statistics involves mathematics, computing, and applications to almost every field of endeavour. Each aspect provides an opportunity to spark someone's interest in the subject. In this paper we discuss some ethical aspects of statistics, and describe how an introduction to ethics has been…
Teaching Statistics Using SAS.
ERIC Educational Resources Information Center
Mandeville, Garrett K.
The Statistical Analysis System (SAS) is presented as the single most appropriate statistical package to use as an aid in teaching statistics. A brief review of literature in which SAS is compared to SPSS, BMDP, and other packages is followed by six examples which demonstrate features unique to SAS which have pedagogical utility. Of particular…
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…
Statistical Methods for Astronomy
NASA Astrophysics Data System (ADS)
Feigelson, Eric D.; Babu, G. Jogesh
Statistical methodology, with deep roots in probability theory, providesquantitative procedures for extracting scientific knowledge from astronomical dataand for testing astrophysical theory. In recent decades, statistics has enormouslyincreased in scope and sophistication. After a historical perspective, this reviewoutlines concepts of mathematical statistics, elements of probability theory,hypothesis tests, and point estimation. Least squares, maximum likelihood, andBayesian approaches to statistical inference are outlined. Resampling methods,particularly the bootstrap, provide valuable procedures when distributionsfunctions of statistics are not known. Several approaches to model selection andgoodness of fit are considered.
Nonlinear Statistical Modeling of Speech
NASA Astrophysics Data System (ADS)
Srinivasan, S.; Ma, T.; May, D.; Lazarou, G.; Picone, J.
2009-12-01
Contemporary approaches to speech and speaker recognition decompose the problem into four components: feature extraction, acoustic modeling, language modeling and search. Statistical signal processing is an integral part of each of these components, and Bayes Rule is used to merge these components into a single optimal choice. Acoustic models typically use hidden Markov models based on Gaussian mixture models for state output probabilities. This popular approach suffers from an inherent assumption of linearity in speech signal dynamics. Language models often employ a variety of maximum entropy techniques, but can employ many of the same statistical techniques used for acoustic models. In this paper, we focus on introducing nonlinear statistical models to the feature extraction and acoustic modeling problems as a first step towards speech and speaker recognition systems based on notions of chaos and strange attractors. Our goal in this work is to improve the generalization and robustness properties of a speech recognition system. Three nonlinear invariants are proposed for feature extraction: Lyapunov exponents, correlation fractal dimension, and correlation entropy. We demonstrate an 11% relative improvement on speech recorded under noise-free conditions, but show a comparable degradation occurs for mismatched training conditions on noisy speech. We conjecture that the degradation is due to difficulties in estimating invariants reliably from noisy data. To circumvent these problems, we introduce two dynamic models to the acoustic modeling problem: (1) a linear dynamic model (LDM) that uses a state space-like formulation to explicitly model the evolution of hidden states using an autoregressive process, and (2) a data-dependent mixture of autoregressive (MixAR) models. Results show that LDM and MixAR models can achieve comparable performance with HMM systems while using significantly fewer parameters. Currently we are developing Bayesian parameter estimation and
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.
Nonstationary statistical theory for multipactor
Anza, S.; Vicente, C.; Gil, J.
2010-06-15
This work presents a new and general approach to the real dynamics of the multipactor process: the nonstationary statistical multipactor theory. The nonstationary theory removes the stationarity assumption of the classical theory and, as a consequence, it is able to adequately model electron exponential growth as well as absorption processes, above and below the multipactor breakdown level. In addition, it considers both double-surface and single-surface interactions constituting a full framework for nonresonant polyphase multipactor analysis. This work formulates the new theory and validates it with numerical and experimental results with excellent agreement.
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.
... Naloxone Pain Prevention Treatment Trends & Statistics Women and Drugs Publications Funding Funding Opportunities Clinical Research Post-Award Concerns General Information Grant & Contract Application ...
Statistical distribution sampling
NASA Technical Reports Server (NTRS)
Johnson, E. S.
1975-01-01
Determining the distribution of statistics by sampling was investigated. Characteristic functions, the quadratic regression problem, and the differential equations for the characteristic functions are analyzed.
Introductory statistical mechanics for electron storage rings
Jowett, J.M.
1986-07-01
These lectures introduce the beam dynamics of electron-positron storage rings with particular emphasis on the effects due to synchrotron radiation. They differ from most other introductions in their systematic use of the physical principles and mathematical techniques of the non-equilibrium statistical mechanics of fluctuating dynamical systems. A self-contained exposition of the necessary topics from this field is included. Throughout the development, a Hamiltonian description of the effects of the externally applied fields is maintained in order to preserve the links with other lectures on beam dynamics and to show clearly the extent to which electron dynamics in non-Hamiltonian. The statistical mechanical framework is extended to a discussion of the conceptual foundations of the treatment of collective effects through the Vlasov equation.
Explorations in Statistics: Power
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2010-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fifth installment of "Explorations in Statistics" revisits power, a concept fundamental to the test of a null hypothesis. Power is the probability that we reject the null hypothesis when it is false. Four…
Teaching Statistics without Sadistics.
ERIC Educational Resources Information Center
Forte, James A.
1995-01-01
Five steps designed to take anxiety out of statistics for social work students are outlined. First, statistics anxiety is identified as an educational problem. Second, instructional objectives and procedures to achieve them are presented and methods and tools for evaluating the course are explored. Strategies for, and obstacles to, making…
STATSIM: Exercises in Statistics.
ERIC Educational Resources Information Center
Thomas, David B.; And Others
A computer-based learning simulation was developed at Florida State University which allows for high interactive responding via a time-sharing terminal for the purpose of demonstrating descriptive and inferential statistics. The statistical simulation (STATSIM) is comprised of four modules--chi square, t, z, and F distribution--and elucidates the…
Understanding Undergraduate Statistical Anxiety
ERIC Educational Resources Information Center
McKim, Courtney
2014-01-01
The purpose of this study was to understand undergraduate students' views of statistics. Results reveal that students with less anxiety have a higher interest in statistics and also believe in their ability to perform well in the course. Also students who have a more positive attitude about the class tend to have a higher belief in their…
ERIC Educational Resources Information Center
Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain
2004-01-01
Water quality experiments, especially the use of macroinvertebrates as indicators of water quality, offer an ideal context for connecting statistics and science. In the STAR program for secondary students and teachers, water quality experiments were also used as a context for teaching statistics. In this article, we trace one activity that uses…
Towards Statistically Undetectable Steganography
2011-06-30
Statistically Undciectable Steganography 5a. CONTRACT NUMBER FA9550-08-1-0084 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Prof. Jessica...approved for public release: distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Fundamental asymptotic laws for imperfect steganography ...formats. 15. SUBJECT TERMS Steganography . covert communication, statistical detectability. asymptotic performance, secure pay load, minimum
Explorations in Statistics: Regression
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2011-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of "Explorations in Statistics" explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive…
ERIC Educational Resources Information Center
Singer, Arlene
This guide outlines a one semester Option Y course, which has seven learner objectives. The course is designed to provide students with an introduction to the concerns and methods of statistics, and to equip them to deal with the many statistical matters of importance to society. Topics covered include graphs and charts, collection and…
ERIC Educational Resources Information Center
Huberty, Carl J.
An approach to statistical testing, which combines Neyman-Pearson hypothesis testing and Fisher significance testing, is recommended. The use of P-values in this approach is discussed in some detail. The author also discusses some problems which are often found in introductory statistics textbooks. The problems involve the definitions of…
Croarkin, M. Carroll
2001-01-01
For more than 50 years, the Statistical Engineering Division (SED) has been instrumental in the success of a broad spectrum of metrology projects at NBS/NIST. This paper highlights fundamental contributions of NBS/NIST statisticians to statistics and to measurement science and technology. Published methods developed by SED staff, especially during the early years, endure as cornerstones of statistics not only in metrology and standards applications, but as data-analytic resources used across all disciplines. The history of statistics at NBS/NIST began with the formation of what is now the SED. Examples from the first five decades of the SED illustrate the critical role of the division in the successful resolution of a few of the highly visible, and sometimes controversial, statistical studies of national importance. A review of the history of major early publications of the division on statistical methods, design of experiments, and error analysis and uncertainty is followed by a survey of several thematic areas. The accompanying examples illustrate the importance of SED in the history of statistics, measurements and standards: calibration and measurement assurance, interlaboratory tests, development of measurement methods, Standard Reference Materials, statistical computing, and dissemination of measurement technology. A brief look forward sketches the expanding opportunity and demand for SED statisticians created by current trends in research and development at NIST. PMID:27500023
Pestana, Dinis
2013-01-01
Statistics is a privileged tool in building knowledge from information, since the purpose is to extract from a sample limited information conclusions to the whole population. The pervasive use of statistical software (that always provides an answer, the question being adequate or not), and the absence of statistics to confer a scientific flavour to so much bad science, has had a pernicious effect on some disbelief on statistical research. Would Lord Rutherford be alive today, it is almost certain that he would not condemn the use of statistics in research, as he did in the dawn of the 20th century. But he would indeed urge everyone to use statistics quantum satis, since to use bad data, too many data, and statistics to enquire on irrelevant questions, is a source of bad science, namely because with too many data we can establish statistical significance of irrelevant results. This is an important point that addicts of evidence based medicine should be aware of, since the meta analysis of two many data will inevitably establish senseless results.
Reform in Statistical Education
ERIC Educational Resources Information Center
Huck, Schuyler W.
2007-01-01
Two questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed…
Deconstructing Statistical Analysis
ERIC Educational Resources Information Center
Snell, Joel
2014-01-01
Using a very complex statistical analysis and research method for the sake of enhancing the prestige of an article or making a new product or service legitimate needs to be monitored and questioned for accuracy. 1) The more complicated the statistical analysis, and research the fewer the number of learned readers can understand it. This adds a…
Statistics 101 for Radiologists.
Anvari, Arash; Halpern, Elkan F; Samir, Anthony E
2015-10-01
Diagnostic tests have wide clinical applications, including screening, diagnosis, measuring treatment effect, and determining prognosis. Interpreting diagnostic test results requires an understanding of key statistical concepts used to evaluate test efficacy. This review explains descriptive statistics and discusses probability, including mutually exclusive and independent events and conditional probability. In the inferential statistics section, a statistical perspective on study design is provided, together with an explanation of how to select appropriate statistical tests. Key concepts in recruiting study samples are discussed, including representativeness and random sampling. Variable types are defined, including predictor, outcome, and covariate variables, and the relationship of these variables to one another. In the hypothesis testing section, we explain how to determine if observed differences between groups are likely to be due to chance. We explain type I and II errors, statistical significance, and study power, followed by an explanation of effect sizes and how confidence intervals can be used to generalize observed effect sizes to the larger population. Statistical tests are explained in four categories: t tests and analysis of variance, proportion analysis tests, nonparametric tests, and regression techniques. We discuss sensitivity, specificity, accuracy, receiver operating characteristic analysis, and likelihood ratios. Measures of reliability and agreement, including κ statistics, intraclass correlation coefficients, and Bland-Altman graphs and analysis, are introduced.
ERIC Educational Resources Information Center
Huizingh, Eelko K. R. E.
2007-01-01
Accessibly written and easy to use, "Applied Statistics Using SPSS" is an all-in-one self-study guide to SPSS and do-it-yourself guide to statistics. What is unique about Eelko Huizingh's approach is that this book is based around the needs of undergraduate students embarking on their own research project, and its self-help style is designed to…
Vijayaraj, Veeraraghavan; Cheriyadat, Anil M; Bhaduri, Budhendra L; Vatsavai, Raju; Bright, Eddie A
2008-01-01
Statistical properties of high-resolution overhead images representing different land use categories are analyzed using various local and global statistical image properties based on the shape of the power spectrum, image gradient distributions, edge co-occurrence, and inter-scale wavelet coefficient distributions. The analysis was performed on a database of high-resolution (1 meter) overhead images representing a multitude of different downtown, suburban, commercial, agricultural and wooded exemplars. Various statistical properties relating to these image categories and their relationship are discussed. The categorical variations in power spectrum contour shapes, the unique gradient distribution characteristics of wooded categories, the similarity in edge co-occurrence statistics for overhead and natural images, and the unique edge co-occurrence statistics of downtown categories are presented in this work. Though previous work on natural image statistics has showed some of the unique characteristics for different categories, the relationships for overhead images are not well understood. The statistical properties of natural images were used in previous studies to develop prior image models, to predict and index objects in a scene and to improve computer vision models. The results from our research findings can be used to augment and adapt computer vision algorithms that rely on prior image statistics to process overhead images, calibrate the performance of overhead image analysis algorithms, and derive features for better discrimination of overhead image categories.
Statistical regimes of random laser fluctuations
Lepri, Stefano; Cavalieri, Stefano; Oppo, Gian-Luca; Wiersma, Diederik S.
2007-06-15
Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on external control parameters. In the Levy regime, the output pulse is highly irregular leading to huge deviations from a mean-field description. Monte Carlo simulations of a simplified model which includes the population of the medium demonstrate the two statistical regimes and provide a comparison with dynamical rate equations. Different statistics of the fluctuations helps to explain recent experimental observations reported in the literature.
Introductory statistical mechanics for electron storage rings
NASA Astrophysics Data System (ADS)
Jowett, John M.
1987-02-01
These lectures concentrate on statistical phenomena in electron storage rings. A stored electron beam is a dissipative, fluctuating system far from equilibrium whose mathematical description can be based upon non-equilibrium statistical mechanics. Stochastic differential equations are used to describe the quantum fluctuations of synchrotron radiation which is the main cause of randomness in electron dynamics. Fluctuating radiation reaction forces can be described via stochastic terms in Hamilton's equations of motion. Normal modes of particle motion, radiation damping effects, quantum diffusion in single-particle phase space are all discussed in this statistical formalism. (AIP)
Ector, Hugo
2010-12-01
I still remember my first book on statistics: "Elementary statistics with applications in medicine and the biological sciences" by Frederick E. Croxton. For me, it has been the start of pursuing understanding statistics in daily life and in medical practice. It was the first volume in a long row of books. In his introduction, Croxton pretends that"nearly everyone involved in any aspect of medicine needs to have some knowledge of statistics". The reality is that for many clinicians, statistics are limited to a "P < 0.05 = ok". I do not blame my colleagues who omit the paragraph on statistical methods. They have never had the opportunity to learn concise and clear descriptions of the key features. I have experienced how some authors can describe difficult methods in a well understandable language. Others fail completely. As a teacher, I tell my students that life is impossible without a basic knowledge of statistics. This feeling has resulted in an annual seminar of 90 minutes. This tutorial is the summary of this seminar. It is a summary and a transcription of the best pages I have detected.
NASA Technical Reports Server (NTRS)
Young, M.; Koslovsky, M.; Schaefer, Caroline M.; Feiveson, A. H.
2017-01-01
Back by popular demand, the JSC Biostatistics Laboratory and LSAH statisticians are offering an opportunity to discuss your statistical challenges and needs. Take the opportunity to meet the individuals offering expert statistical support to the JSC community. Join us for an informal conversation about any questions you may have encountered with issues of experimental design, analysis, or data visualization. Get answers to common questions about sample size, repeated measures, statistical assumptions, missing data, multiple testing, time-to-event data, and when to trust the results of your analyses.
Commentary: statistics for biomarkers.
Lovell, David P
2012-05-01
This short commentary discusses Biomarkers' requirements for the reporting of statistical analyses in submitted papers. It is expected that submitters will follow the general instructions of the journal, the more detailed guidance given by the International Committee of Medical Journal Editors, the specific guidelines developed by the EQUATOR network, and those of various specialist groups. Biomarkers expects that the study design and subsequent statistical analyses are clearly reported and that the data reported can be made available for independent assessment. The journal recognizes that there is continuing debate about different approaches to statistical science. Biomarkers appreciates that the field continues to develop rapidly and encourages the use of new methodologies.
LED champing: statistically blessed?
Wang, Zhuo
2015-06-10
LED champing (smart mixing of individual LEDs to match the desired color and lumens) and color mixing strategies have been widely used to maintain the color consistency of light engines. Light engines with champed LEDs can easily achieve the color consistency of a couple MacAdam steps with widely distributed LEDs to begin with. From a statistical point of view, the distributions for the color coordinates and the flux after champing are studied. The related statistical parameters are derived, which facilitate process improvements such as Six Sigma and are instrumental to statistical quality control for mass productions.
Playing at Statistical Mechanics
ERIC Educational Resources Information Center
Clark, Paul M.; And Others
1974-01-01
Discussed are the applications of counting techniques of a sorting game to distributions and concepts in statistical mechanics. Included are the following distributions: Fermi-Dirac, Bose-Einstein, and most probable. (RH)
Hemophilia Data and Statistics
... Hemophilia Women Healthcare Providers Partners Media Policy Makers Data & Statistics Language: English Español (Spanish) Recommend on Facebook ... at a very young age. Based on CDC data, the median age at diagnosis is 36 months ...
Cooperative Learning in Statistics.
ERIC Educational Resources Information Center
Keeler, Carolyn M.; And Others
1994-01-01
Formal use of cooperative learning techniques proved effective in improving student performance and retention in a freshman level statistics course. Lectures interspersed with group activities proved effective in increasing conceptual understanding and overall class performance. (11 references) (Author)