2,384 research outputs found
Anharmonic phonon spectra of PbTe and SnTe in the self-consistent harmonic approximation
At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic
structure. At low temperature, SnTe undergoes a ferroelectric transition with a
critical temperature strongly dependent on the hole concentration, while PbTe
is an incipient ferroelectric. By using the stochastic self-consistent harmonic
approximation, we investigate the anharmonic phonon spectra and the occurrence
of a ferroelectric transition in both systems. We find that vibrational spectra
strongly depends on the approximation used for the exchange-correlation kernel
in density functional theory. If gradient corrections and the theoretical
volume are employed, then the calculation of the free energy Hessian leads to
phonon spectra in good agreement with experimental data for both systems. In
PbTe, we reproduce the transverse optical mode phonon satellite detected in
inelastic neutron scattering and the crossing between the transverse optical
and the longitudinal acoustic modes along the X direction. In the case
of SnTe, we describe the occurrence of a ferroelectric transition from the high
temperature Fmm structure to the low temperature R3m one.Comment: 12 pages, 15 Picture
Coalition Resilient Outcomes in Max k-Cut Games
We investigate strong Nash equilibria in the \emph{max -cut game}, where
we are given an undirected edge-weighted graph together with a set of colors. Nodes represent players and edges capture their mutual
interests. The strategy set of each player consists of the colors. When
players select a color they induce a -coloring or simply a coloring. Given a
coloring, the \emph{utility} (or \emph{payoff}) of a player is the sum of
the weights of the edges incident to , such that the color chosen
by is different from the one chosen by . Such games form some of the
basic payoff structures in game theory, model lots of real-world scenarios with
selfish agents and extend or are related to several fundamental classes of
games.
Very little is known about the existence of strong equilibria in max -cut
games. In this paper we make some steps forward in the comprehension of it. We
first show that improving deviations performed by minimal coalitions can cycle,
and thus answering negatively the open problem proposed in
\cite{DBLP:conf/tamc/GourvesM10}. Next, we turn our attention to unweighted
graphs. We first show that any optimal coloring is a 5-SE in this case. Then,
we introduce -local strong equilibria, namely colorings that are resilient
to deviations by coalitions such that the maximum distance between every pair
of nodes in the coalition is at most . We prove that -local strong
equilibria always exist. Finally, we show the existence of strong Nash
equilibria in several interesting specific scenarios.Comment: A preliminary version of this paper will appear in the proceedings of
the 45th International Conference on Current Trends in Theory and Practice of
Computer Science (SOFSEM'19
Signals and Power Distribution in the CMS Inner Tracker
\begin{abstract} This Note describes how the interconnection between the 3540 modules of the CMS Inner Tracker has been approached, focusing on the signal, high voltage and low voltage line distribution. The construction and tests of roughly a thousand interconnects called ``Mother Cables" is described. \end{abstract
Integration of biocontrol agents and food-grade additives for enhancing protection of stored apples from Penicillium expansum.
Forty-nine compounds currently used as additives in foods were tested in combination with three biocontrol agents, the yeasts Rhodotorula glutinis, Cryptococcus laurentii, and the yeastlike fungus Aureobasidium pullulans, to increase their antagonistic activity against Penicillium expansum, the causal agent of blue mold on apples. Twelve additives dramatically improved the antagonistic activity of one or more of the tested biocontrol agents. In a two-way factorial experiment with these selected additives the percentage of P. expansum rots on apples was significantly influenced by the antagonist and the additive as well as by their interaction. The combination of the biocontrol agents and some additives resulted in a significantly higher activity with respect to the single treatments applied separately, producing additive or synergistic effects. Some of the selected additives combined with a low yeast concentration (106 cells per ml) had comparable or higher efficacy than the biocontrol agents applied alone at a 100-fold higher concentration (10(8) cells per ml). Some organic and inorganic calcium salts, natural gums, and some antioxidants displayed the best results. In general, the effect of each additive was specific to the biocontrol isolate used in the experiments. Possible mechanisms involved in the activity of these beneficial additives and their potential application in effective formulations of postharvest biofungicides are discussed
MULTIPLE ORGAN HARVESTING: EVOLUTION OF SURGICAL TECHNIQUE. PERSONAL EXPERIENCE
SINCE 1950, kidney, liver, heart, and lung transplantations
have dramatically improved, emerging as the
elective treatment modality for organ failure. Nevertheless,
the indications to pancreas and bowel grafting are stili
controversial.
Several factors have contributed such results, namely the
introduction of cyclosporine (CyA) in 1981, the use of new
solutions for solid organ preservation (eg, the University of
Wisconsin solution), the improvement in donor selection
criteria, intensive care, as well as improvement management
of transplant operation and harvesting surgical technique
Phonon collapse and van der Waals melting of the 3D charge density wave of VSe
Among transition metal dichalcogenides (TMDs), VSe is considered to
develop a purely 3-dimensional (3D) charge-density wave (CDW) at T=110
K. Here, by means of high resolution inelastic x-ray scattering (IXS), we show
that the CDW transition is driven by the collapse of an acoustic mode at the
critical wavevector \textit{q}= (2.25 0 0.7) r.l.u. and critical
temperature T=110 K. The softening of this mode starts to be pronounced
for temperatures below 2 T and expands over a rather wide
region of the Brillouin zone, suggesting a large contribution of the
electron-phonon interaction to the CDW formation. This interpretation is
supported by our first principles calculations that determine a large
momentum-dependence of the electron-phonon interaction, peaking at the CDW
wavevector, in the presence of nesting. Fully anharmonic {\it ab initio}
calculations confirm the softening of one acoustic branch at \textit{q}
as responsible for the CDW formation and show that van der Waals interactions
are crucial to melt the CDW. Our work also highlights the important role of
out-of-plane interactions to describe 3D CDWs in TMDs
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