4,830 research outputs found
Semiclassical Theory of Chaotic Quantum Transport
We present a refined semiclassical approach to the Landauer conductance and
Kubo conductivity of clean chaotic mesoscopic systems. We demonstrate for
systems with uniformly hyperbolic dynamics that including off-diagonal
contributions to double sums over classical paths gives a weak-localization
correction in quantitative agreement with results from random matrix theory. We
further discuss the magnetic field dependence. This semiclassical treatment
accounts for current conservation.Comment: 4 pages, 1 figur
Radio observations of four anticenter 2CG gamma-ray sources
The 2CG sources 218-00, 135+01, 121+04 and 95+04 have been observed at two radio frequencies and the flux values and spectra of the radio sources observed within the gamma-ray fields are catalogued down to a sensitivity of approx 30 mJy at lambda 11 cm. Possible gamma-ray counterpart candidate objects are briefly discussed
Characteristic matrices for linear periodic delay differential equations
Copyright © 2011 Society for Industrial and Applied MathematicsSzalai, Stépán, and Hogan [SIAM J. Sci. Comput., 28 (2006), pp. 1301–1317] gave a general construction for characteristic matrices for systems of linear delay differential equations with periodic coefficients. First, we show that matrices constructed in this way can have a discrete set of poles in the complex plane, which may possibly obstruct their use when determining the stability of the linear system. Then we modify and generalize the original construction such that the poles get pushed into a small neighborhood of the origin of the complex plane
Aspects of plant behaviour under anoxia and post-anoxia
All plants are able to survive anoxic periods, but the degree of tolerance shows large variation. The main injuries related to anoxia are eventually due to changes in energy metabolism. Low energy charge values indicate a cessation of many ATP consuming processes. Sugar starvation, lactic acid fermentation and proton release from leaky vacuoles are responsible for cell death. Long-term anoxia tolerance is dependent on storage products in the vicinity of sinks, on an adequate control of glycolysis, synthesis of essential proteins, and stability of membranes and organelles. However, no fundamental differences between the metabolic pathways of tolerant and non-tolerant tissues are known. It is rather a question of minor changes and the regulation of anaerobic metabolism. Re-exposure of anoxic tissues to air may even be more detrimental than anoxia itself. These injuries are mainly due to enhanced radical generation. Lipid peroxidation processes lead to membrane damage, disintegration, and leakage of solutes. Under natural conditions plants are equipped with radical-detoxifying systems (SOD, peroxidases and antioxidants). Natural detoxifying systems can be reduced in non-adapted plants under anoxia and they become more sensitive to post-anoxic damage. In addition, the rapid conversion of ethanol to extremely toxic acetaldehyde seems to be a cause of tissue injury and deat
Critical review of Ames Life Science participation in Spacelab Mission Development Test 3: The SMD 3 management study
A management study was conducted to specify activities and problems encountered during the development of procedures for documentation and crew training on experiments, as well as during the design, integration, and delivery of a life sciences experiment payload to Johnson Space Center for a 7 day simulation of a Spacelab mission. Conclusions and recommendations to project management for current and future Ames' life sciences projects are included. Broader issues relevant to the conduct of future scientific missions under the constraints imposed by the environment of space are also addressed
Periodic orbit bifurcations and scattering time delay fluctuations
We study fluctuations of the Wigner time delay for open (scattering) systems
which exhibit mixed dynamics in the classical limit. It is shown that in the
semiclassical limit the time delay fluctuations have a distribution that
differs markedly from those which describe fully chaotic (or strongly
disordered) systems: their moments have a power law dependence on a
semiclassical parameter, with exponents that are rational fractions. These
exponents are obtained from bifurcating periodic orbits trapped in the system.
They are universal in situations where sufficiently long orbits contribute. We
illustrate the influence of bifurcations on the time delay numerically using an
open quantum map.Comment: 9 pages, 3 figures, contribution to QMC200
Operating Experience and Economic Assessment of Commercial and Industrial Cool Storage Systems - TVA Case Study
Thermal storage systems offer utilities a
means to change the energy use patterns of both
residential and commercial and industrial (C&I)
customers by moving water-heating and space-conditioning
loads from peak to offpeak periods.
Benefits from investments in these systems
include reduced capital investment in new generating capacity, reduced operating costs, and
reduced risk associated with load growth projections and future environmental legislation.
This paper presents the results of a study
undertaken to evaluate the performance of and
quantify the potential economic benefits of C&I
cool storage systems. The paper is organized
into three major sections. Section one discusses
the empirical data gathered from TVA's C&I Cool
Storage Demonstration conducted during the summer
of 1984. Section two discusses TVA's methodology
For quantifying the potential economic benefits
of these systems. Finally, the results are
summarized with regard to future program
activities
Intensity distribution in rotational line spectra
Completely resolved Doppler-free rotational line spectra of six vibronic two-photon bands in benzene C6 H6 and C6 D6 are presented. The excited final states possess different excess energies in S1 (1567 to 2727 cm−1 ) and are embedded in dense manifolds of background states with differing densities of states (1<rho<60 1/cm−1 ). The bands are analyzed by a statistical procedure. The intensity distribution of several hundreds of lines of each band is investigated. It is found that all weakly perturbed bands display a similar, peaked intensity distribution while in strongly perturbed bands the number of lines decreases monotonically with increasing intensity. The origin of this difference is discussed in terms of coupling to the many background states. The Journal of Chemical Physics is copyrighted by The American Institute of Physics
On the Form Factor for the Unitary Group
We study the combinatorics of the contributions to the form factor of the
group U(N) in the large limit. This relates to questions about
semiclassical contributions to the form factor of quantum systems described by
the unitary ensemble.Comment: 35 page
- …