2,442 research outputs found
Quantum Mechanics and the Third Law of Thermodynamics
Rodebush has recently discussed certain points concerning the third law of thermodynamics in terms of quantum mechanics. His recognition of the significance of quantum mechanics in considering the behavior of solutions and glasses at low temperatures we believe to be of interest, and we agree with the more important of his conclusions. However, there have arisen some questions of interpretation in which we differ from the statements of his paper. We have thought it of value to present here, as explicitly as possible and at the risk of some duplication of ideas, an outline of these points and a discussion of their bearing on the expected behavior of the systems under treatment. It is our opinion that the views presented below have been in the main accepted by investigators interested in the theory of the third law; however, so far we are aware no equivalent discussion has been published
Periodic substorm activity in the geomagnetic tail
On 19 May 1978 an anusual series of events is observed with the Quadrispherical LEPEDEA on board the ISEE-1 satellite in the Earth's geomagnetic tail. For 13 hours periodic bursts of both ions and electrons are seen in all the particle detectors on the spacecraft. On this day periodic activity is also seen on the ground, where multiple intensifications of the electrojets are observed. At the same time the latitudinal component of the interplanetary magnetic field shows a number of strong southward deflections. It is concluded that an extended period of substorm activity is occurring, which causes repeated thinnings and recoveries of the plasma sheet. These are detected by ISEE, which is situated in the plasma sheet boundary layer, as periodic dropouts and reappearances of the plasma. Comparisons of the observations at ISEE with those at IMP-8, which for a time is engulfed by the plasma sheet, indicate that the activity is relatively localized in spatial extent. For this series of events it is clear that a global approach to magnetospheric dynamics, e.g., reconnection, is inappropriate
Effectively Serving the Needs of the Millennial Marketing Student: The Product Life Cycle Approach to Class Organization
We illustrate a class organization process utilizing the concept of the Product Life Cycle to meet the needs of today’s millennial student. In the Introduction stage of a business course, professors need to build structure to encourage commitment. In the Growth stage, professors need to promote the structure through multiple, brief activities that can keep the attention of business students. In the Mature stage, professors need to use the structure to stabilize engagement levels and learning rates but be willing to make adjustments to prevent apathy in the course. Finally, in the Decline stage, professors need to dismantle the structure while allowing opportunities for utilizing materials for future business courses and addressing today’s millennial students’ need for achievement and sense of entitlement with the course grades. The value is that this paper illustrates an approach to aid professors in organizing business courses that can be utilized in a variety of courses to better serve millennial students
An Exploration of Systematic Errors in Transiting Planets and Their Host Stars
Transiting planet systems offer the best opportunity to measure the masses
and radii of a large sample of planets and their host stars. However, relative
photometry and radial velocity measurements alone only constrain the density of
the host star. Thus, there is a one-parameter degeneracy in the mass and radius
of the host star, and by extension the planet. Several theoretical,
semi-empirical, and nearly empirical methods have been used to break this
degeneracy and independently measure the mass and radius of the host star and
planets(s). As we approach an era of few percent precisions on some of these
properties, it is critical to assess whether these different methods are
providing accuracies that are of the same order, or better than, the stated
statistical precisions. We investigate the differences in the planet parameter
estimates inferred when using the Torres empirical relations, YY isochrones,
MIST isochrones, and a nearly-direct empirical measurement of the radius of the
host star using its spectral energy distribution, effective temperature, and
\textit{Gaia} parallax. We focus our analysis on modelling KELT-15b, a fairly
typical hot Jupiter, using each of these methods. We globally model TESS
photometry, optical-to-NIR flux densities of the host star, and \textit{Gaia}
parallaxes, in conjunction with extant KELT ground-based follow-up photometric
and radial velocity measurements. We find systematic differences in several of
the inferred parameters of the KELT-15 system when using different methods,
including a () difference in the inferred stellar and
planetary radii between the MIST isochrones and SED fitting.Comment: 12 Figures, 20 Tables, Submitted to Ap
Nonequilibrium candidate Monte Carlo: A new tool for efficient equilibrium simulation
Metropolis Monte Carlo simulation is a powerful tool for studying the
equilibrium properties of matter. In complex condensed-phase systems, however,
it is difficult to design Monte Carlo moves with high acceptance probabilities
that also rapidly sample uncorrelated configurations. Here, we introduce a new
class of moves based on nonequilibrium dynamics: candidate configurations are
generated through a finite-time process in which a system is actively driven
out of equilibrium, and accepted with criteria that preserve the equilibrium
distribution. The acceptance rule is similar to the Metropolis acceptance
probability, but related to the nonequilibrium work rather than the
instantaneous energy difference. Our method is applicable to sampling from both
a single thermodynamic state or a mixture of thermodynamic states, and allows
both coordinates and thermodynamic parameters to be driven in nonequilibrium
proposals. While generating finite-time switching trajectories incurs an
additional cost, driving some degrees of freedom while allowing others to
evolve naturally can lead to large enhancements in acceptance probabilities,
greatly reducing structural correlation times. Using nonequilibrium driven
processes vastly expands the repertoire of useful Monte Carlo proposals in
simulations of dense solvated systems
Time-dependent radiative transfer with PHOENIX
Aims. We present first results and tests of a time-dependent extension to the
general purpose model atmosphere code PHOENIX. We aim to produce light curves
and spectra of hydro models for all types of supernovae. Methods. We extend our
model atmosphere code PHOENIX to solve time-dependent non-grey, NLTE, radiative
transfer in a special relativistic framework. A simple hydrodynamics solver was
implemented to keep track of the energy conservation of the atmosphere during
free expansion. Results. The correct operation of the new additions to PHOENIX
were verified in test calculations. Conclusions. We have shown the correct
operation of our extension to time-dependent radiative transfer and will be
able to calculate supernova light curves and spectra in future work.Comment: 7 pages, 12 figure
Genome-wide profiling of chromosome interactions in Plasmodium falciparum characterizes nuclear architecture and reconfigurations associated with antigenic variation.
Spatial relationships within the eukaryotic nucleus are essential for proper nuclear function. In Plasmodium falciparum, the repositioning of chromosomes has been implicated in the regulation of the expression of genes responsible for antigenic variation, and the formation of a single, peri-nuclear nucleolus results in the clustering of rDNA. Nevertheless, the precise spatial relationships between chromosomes remain poorly understood, because, until recently, techniques with sufficient resolution have been lacking. Here we have used chromosome conformation capture and second-generation sequencing to study changes in chromosome folding and spatial positioning that occur during switches in var gene expression. We have generated maps of chromosomal spatial affinities within the P. falciparum nucleus at 25 Kb resolution, revealing a structured nucleolus, an absence of chromosome territories, and confirming previously identified clustering of heterochromatin foci. We show that switches in var gene expression do not appear to involve interaction with a distant enhancer, but do result in local changes at the active locus. These maps reveal the folding properties of malaria chromosomes, validate known physical associations, and characterize the global landscape of spatial interactions. Collectively, our data provide critical information for a better understanding of gene expression regulation and antigenic variation in malaria parasites
Why is the bandwidth of sodium observed to be narrower in photoemission experiments?
The experimentally predicted narrowing in the bandwidth of sodium is
interpreted in terms of the non-local self-energy effect on quasi-particle
energies of the electron liquid. The calculated self-energy correction is a
monotonically increasing function of the wavenumber variable. The usual
analysis of photo-emission experiments assumes the final state energies on the
nearly-free-electron-like model and hence it incorrectly ascribes the non-local
self-energy correction to the final state energies to the occupied state
energies, thus leading to a seeming narrowing in the bandwidth.Comment: 9 page
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