1,190 research outputs found
Retrospective evaluation of the association between admission blood glucose and l-lactate concentrations in ponies and horses with gastrointestinal disease (2008-2016): 545 cases
A recent study described increased l‐lactate concentrations in ponies with gastrointestinal disease compared to horses, but blood glucose (BG) concentrations were not considered. The study tested the hypothesis that BG and l‐lactate concentrations are correlated in horses and ponies with gastrointestinal disease and that BG concentrations, not equid type (pony vs horse), are an independent predictor of L‐lactate concentrations. It was further hypothesized that equid type was an independent predictor of BG concentrations
Stationarity, soft ergodicity, and entropy in relativistic systems
Recent molecular dynamics simulations show that a dilute relativistic gas
equilibrates to a Juettner velocity distribution if ensemble velocities are
measured simultaneously in the observer frame. The analysis of relativistic
Brownian motion processes, on the other hand, implies that stationary
one-particle distributions can differ depending on the underlying
time-parameterizations. Using molecular dynamics simulations, we demonstrate
how this relativistic phenomenon can be understood within a deterministic model
system. We show that, depending on the time-parameterization, one can
distinguish different types of soft ergodicity on the level of the one-particle
distributions. Our analysis further reveals a close connection between time
parameters and entropy in special relativity. A combination of different
time-parameterizations can potentially be useful in simulations that combine
molecular dynamics algorithms with randomized particle creation, annihilation,
or decay processes.Comment: 4 page
Design, Manufacture and Measurement of three Permanent Magnet Dipoles for FASER Experiment
FASER, the ForwArd Search ExpeRiment, is designed to search for new, yet undiscovered, light and weakly-interacting particles and study the interactions of high-energy neutrinos. Three dipoles, one 1.5 m-long and the other two 1.0 m-long each, installed upstream of the ATLAS experiment at CERN, are required to achieve sufficient separation of pairs of oppositely charged, high-energy Standard Model particles originating from decays of new physics particles. The dipoles have an aperture of 200 mm in diameter and a required magnetic field at the centre ≥ 0.55 T. Due to tight space constraints, a design based on permanent magnet technology was proposed. This paper describes the design, manufacturing, assembly and magnetic measurement of these large Halbach array dipoles
Thermal equilibrium and statistical thermometers in special relativity
There is an intense debate in the recent literature about the correct
generalization of Maxwell's velocity distribution in special relativity. The
most frequently discussed candidate distributions include the Juettner function
as well as modifications thereof. Here, we report results from fully
relativistic one-dimensional (1D) molecular dynamics (MD) simulations that
resolve the ambiguity. The numerical evidence unequivocally favors the Juettner
distribution. Moreover, our simulations illustrate that the concept of 'thermal
equilibrium' extends naturally to special relativity only if a many-particle
system is spatially confined. They make evident that 'temperature' can be
statistically defined and measured in an observer frame independent way.Comment: version accepted for publication (5 pages), part of the introduction
modified, new figures, additional reference
Relative entropy, Haar measures and relativistic canonical velocity distributions
The thermodynamic maximum principle for the Boltzmann-Gibbs-Shannon (BGS)
entropy is reconsidered by combining elements from group and measure theory.
Our analysis starts by noting that the BGS entropy is a special case of
relative entropy. The latter characterizes probability distributions with
respect to a pre-specified reference measure. To identify the canonical BGS
entropy with a relative entropy is appealing for two reasons: (i) the maximum
entropy principle assumes a coordinate invariant form; (ii) thermodynamic
equilibrium distributions, which are obtained as solutions of the maximum
entropy problem, may be characterized in terms of the transformation properties
of the underlying reference measure (e.g., invariance under group
transformations). As examples, we analyze two frequently considered candidates
for the one-particle equilibrium velocity distribution of an ideal gas of
relativistic particles. It becomes evident that the standard J\"uttner
distribution is related to the (additive) translation group on momentum space.
Alternatively, imposing Lorentz invariance of the reference measure leads to a
so-called modified J\"uttner function, which differs from the standard
J\"uttner distribution by a prefactor, proportional to the inverse particle
energy.Comment: 15 pages: extended version, references adde
Nonlocal observables and lightcone-averaging in relativistic thermodynamics
The unification of relativity and thermodynamics has been a subject of
considerable debate over the last 100 years. The reasons for this are twofold:
(i) Thermodynamic variables are nonlocal quantities and, thus, single out a
preferred class of hyperplanes in spacetime. (ii) There exist different,
seemingly equally plausible ways of defining heat and work in relativistic
systems. These ambiguities led, for example, to various proposals for the
Lorentz transformation law of temperature. Traditional 'isochronous'
formulations of relativistic thermodynamics are neither theoretically
satisfactory nor experimentally feasible. Here, we demonstrate how these
deficiencies can be resolved by defining thermodynamic quantities with respect
to the backward-lightcone of an observation event. This approach yields novel,
testable predictions and allows for a straightforward-extension of
thermodynamics to General Relativity. Our theoretical considerations are
illustrated through three-dimensional relativistic many-body simulations.Comment: typos in Eqs. (12) and (14) corrected, minor additions in the tex
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A conceptual framework for studying collective reactions to events in location-based social media
Events are a core concept of spatial information, but location-based social media (LBSM) provide information on reactions to events. Individuals have varied degrees of agency in initiating, reacting to or modifying the course of events, and reactions include observations of occurrence, expressions containing sentiment or emotions, or a call to action. Key characteristics of reactions include referent events and information about who reacted, when, where and how. Collective reactions are composed of multiple individual reactions sharing common referents. They can be characterized according to the following dimensions: spatial, temporal, social, thematic and interlinkage. We present a conceptual framework, which allows characterization and comparison of collective reactions. For a thematically well-defined class of event such as storms, we can explore differences and similarities in collective attribution of meaning across space and time. Other events may have very complex spatio-temporal signatures (e.g. political processes such as Brexit or elections), which can be decomposed into series of individual events (e.g. a temporal window around the result of a vote). The purpose of our framework is to explore ways in which collective reactions to events in LBSM can be described and underpin the development of methods for analysing and understanding collective reactions to events
A meta-analysis of effectiveness studies on computer technology-supported language learning
With the aim of summarizing years of research comparing pedagogies for second/foreign language teaching supported with computer technology and pedagogy not-supported by computer technology, a meta-analysis was conducted of empirical research investigating language outcomes. Thirty-seven studies yielding 52 effect sizes were included, following a search of literature from 1970 to 2006 and screening of studies based on stated criteria. The differences in research designs required subdivision of studies, but overall results favored the technology-supported pedagogy, with a small, but positive and statistically significant effect size. Second/foreign language instruction supported by computer technology was found to be at least as effective as instruction without technology, and in studies using rigorous research designs the CALL groups outperformed the non-CALL groups. The analyses of instructional conditions, characteristics of participants, and conditions of the research design did not provide reliable results because of the small number of effect sizes representing each group. The meta-analysis results provide an empirically-based response to the questions of whether or not technology-supported pedagogies enhance language learning, and the process of conducting the meta-analysis pointed to areas in research methodology that would benefit from attention in future research
Dark matter in the framework of shell-universe
We show that the shell-universe model, used to explain the observed expansion
rate of the universe without a dark energy component, provides also a natural
mechanism for local increasing of the shell's tension leading to the modified
Newton's law alternative to galactic dark matter.Comment: 8 pages, minor corrections, version to appear in GR
Relativistic diffusion processes and random walk models
The nonrelativistic standard model for a continuous, one-parameter diffusion
process in position space is the Wiener process. As well-known, the Gaussian
transition probability density function (PDF) of this process is in conflict
with special relativity, as it permits particles to propagate faster than the
speed of light. A frequently considered alternative is provided by the
telegraph equation, whose solutions avoid superluminal propagation speeds but
suffer from singular (non-continuous) diffusion fronts on the light cone, which
are unlikely to exist for massive particles. It is therefore advisable to
explore other alternatives as well. In this paper, a generalized Wiener process
is proposed that is continuous, avoids superluminal propagation, and reduces to
the standard Wiener process in the non-relativistic limit. The corresponding
relativistic diffusion propagator is obtained directly from the nonrelativistic
Wiener propagator, by rewriting the latter in terms of an integral over
actions. The resulting relativistic process is non-Markovian, in accordance
with the known fact that nontrivial continuous, relativistic Markov processes
in position space cannot exist. Hence, the proposed process defines a
consistent relativistic diffusion model for massive particles and provides a
viable alternative to the solutions of the telegraph equation.Comment: v3: final, shortened version to appear in Phys. Rev.
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