376 research outputs found
Note on the single-shock solutions of the Korteweg-de Vries-Burgers equation
The well-known shock solutions of the Korteweg-de Vries-Burgers equation are
revisited, together with their limitations in the context of plasma
(astro)physical applications. Although available in the literature for a long
time, it seems to have been forgotten in recent papers that such shocks are
monotonic and unique, for a given plasma configuration, and cannot show
oscillatory or bell-shaped features. This uniqueness is contrasted to solitary
wave solutions of the two parent equations (Korteweg-de Vries and Burgers),
which form a family of curves parameterized by the excess velocity over the
linear phase speed.Comment: Accepted for publication in Astrophysics & Space Scienc
Distance and the pattern of intra-European trade
Given an undirected graph G = (V, E) and subset of terminals T â V, the element-connectivity Îș âČ G (u, v) of two terminals u, v â T is the maximum number of u-v paths that are pairwise disjoint in both edges and non-terminals V \ T (the paths need not be disjoint in terminals). Element-connectivity is more general than edge-connectivity and less general than vertex-connectivity. Hind and Oellermann [21] gave a graph reduction step that preserves the global element-connectivity of the graph. We show that this step also preserves local connectivity, that is, all the pairwise element-connectivities of the terminals. We give two applications of this reduction step to connectivity and network design problems. âą Given a graph G and disjoint terminal sets T1, T2,..., Tm, we seek a maximum number of elementdisjoint Steiner forests where each forest connects each Ti. We prove that if each Ti is k element k connected then there exist âŠ( log hlog m) element-disjoint Steiner forests, where h = | i Ti|. If G is planar (or more generally, has fixed genus), we show that there exist âŠ(k) Steiner forests. Our proofs are constructive, giving poly-time algorithms to find these forests; these are the first non-trivial algorithms for packing element-disjoint Steiner Forests. âą We give a very short and intuitive proof of a spider-decomposition theorem of Chuzhoy and Khanna [12] in the context of the single-sink k-vertex-connectivity problem; this yields a simple and alternative analysis of an O(k log n) approximation. Our results highlight the effectiveness of the element-connectivity reduction step; we believe it will find more applications in the future
TI-games I: An Exploration of Type Indeterminacy In Strategic Decision-Making
The Type Indeterminacy model is a theoretical framework that formalizes the
constructive preference perspective suggested by Kahneman and Tversky. In this
paper we explore an extention of the TI-model from simple to strategic
decision-making. A 2X2 game is investigated. We first show that in a one-shot
simultaneaous move setting the TI-model is equivalent to a standard incomplete
information model. We then let the game be preceded by a cheap-talk promise
exchange game. We show in an example that in the TI-model the promise stage can
have impact on next following behavior when the standard classical model
predicts no impact whatsoever. The TI approach differs from other behavioral
approaches in identifying the source of the effect of cheap-talk promises in
the intrinsic indeterminacy of the players' type.Comment: 18
Cholic acid induces a Cftr dependent biliary secretion and liver growth response in mice
The cause of Cystic fibrosis liver disease (CFLD), is unknown. It is well recognized that hepatic exposure to hydrophobic bile salts is associated with the development of liver disease. For this reason, we hypothesize that, CFTR dependent variations, in the hepatic handling of hydrophobic bile salts, are related to the development CFLD. To test our hypothesis we studied, in Cftr-/- and control mice, bile production, bile composition and liver pathology, in normal feeding condition and during cholate exposure, either acute (intravenous) or chronic (three weeks via the diet). In Cftr-/- and control mice the basal bile production was comparable. Intravenous taurocholate increased bile production to the same extent in Cftr-/- and control mice. However, chronic cholate exposure incre
Isospin splitting in heavy baryons and mesons
A recent general analysis of light-baryon isospin splittings is updated and
extended to charmed baryons.
The measured and splittings stand out as being difficult
to understand in terms of two-body forces alone.
We also discuss heavy-light mesons; though the framework here is necessarily
less general, we nevertheless obtain some predictions that are not strongly
model-dependent.Comment: 12 pages REVTEX 3, plus 4 uuencoded ps figures, CMU-HEP93-
Aharonov-Bohm spectral features and coherence lengths in carbon nanotubes
The electronic properties of carbon nanotubes are investigated in the
presence of disorder and a magnetic field parallel or perpendicular to the
nanotube axis. In the parallel field geometry, the -periodic
metal-insulator transition (MIT) induced in metallic or semiconducting
nanotubes is shown to be related to a chirality-dependent shifting of the
energy of the van Hove singularities (VHSs). The effect of disorder on this
magnetic field-related mechanism is considered with a discussion of mean free
paths, localization lengths and magnetic dephasing rate in the context of
recent experiments.Comment: 22 pages, 6 Postscript figures. submitted to Phys. Rev.
Positions, Regions, and Clusters: Strata of Granularity in Location Modelling
Abstract. Location models are data structures or knowledge bases used in Ubiquitous Computing for representing and reasoning about spatial relationships between so-called smart objects, i.e. everyday objects, such as cups or buildings, containing computational devices with sensors and wireless communication. The location of an object is in a location model either represented by a region, by a coordinate position, or by a cluster of regions or positions. Qualitative reasoning in location models could advance intelligence of devices, but is impeded by incompatibilities between the representation formats: topological reasoning applies to regions; directional reasoning, to positions; and reasoning about set-membership, to clusters. We present a mathematical structure based on scale spaces giving an integrated semantics to all three types of relations and representations. The structure reflects concepts of granularity and uncertainty relevant for location modelling, and gives semantics to applications of RCC-reasoning and projection-based directional reasoning in location models
Continuously improving the practice of cardiology
Guidelines for the management of patients with
cardiovascular disease are designed to assist
cardiologists and other physicans in their practice.
Surveys are conducted to assess whether guidelines
are followed in practice. The results of surveys on
acute coronary syndromes, coronary revascularisation,
secondary prevention, valvular heart disease
and heart failure are presented. Comparing surveys
conducted between 1995 and 2002, a gradual improvement
in use ofsecondary preventive therapy
is observed. Nevertheless, important deviations
from established guidelines are noted, with a
significant variation among different hospitals in
the Netherlands and in other European countries.
Measures for fiuther improvement of clinical
practice indude more rapid treatment of patients
with evolving myocardial infarction, more frequent
use of clopidogrel and glycoprotein IIb/IIIa
receptor blockers in patients with acute coronary
syndromes, more frequent use of 5-blockers in
patients with heart failure and more intense
measures to encourage patients to stop smoking.
Targets for the proportion ofpatients who might
receive specific therapies are presented
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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