1,552 research outputs found
TMbarrier: speculative barriers using hardware transactional memory
Barrier is a very common synchronization method used in parallel programming. Barriers are used typically to enforce a partial thread execution order, since there may be dependences between code sections before and after the barrier. This work proposes TMbarrier, a new design of a barrier intended to be used in transactional applications. TMbarrier allows threads to continue executing speculatively after the barrier assuming that there are not dependences with safe threads that have not yet reached the barrier. Our design leverages transactional memory (TM) (specifically, the implementation offered by the IBM POWER8 processor) to hold the speculative updates and to detect possible conflicts between speculative and safe threads. Despite the limitations of the best-effort hardware TM implementation present in current processors, experiments show a reduction in wasted time due to synchronization compared to standard barriers.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
In: Fischer W.B. (eds) Viral Membrane Proteins: Structure, Function, and Drug Design.
This chapter is devoted to reviewing some characteristics of membrane permeabilization by viral proteins. In addition, the methodology used to assay enhanced permeability in animal cells is described. Finally, the design of selective viral inhibitors based on the modification of cellular membranes during virus entry or at late times of infection is also discussed.This work was supported by grants from the Fundación para la Investigación y Prevención del SIDA en España (24291), Instituto de Salud Carlos III (01/0042) and the DGICYT PM99-0002. The authors also acknowledge the Fundación Ramón Areces for an institutional grant awarded to the Centro de Biología Molecular "Severo Ochoa"1. Introduction 2. Measuring alterations in membrane permeability 2.1. The hygromycin B test 2.2. Entry of macromolecules into virus-infected cells 2.3. Other assays to test the entry or exit of macromolecules from virus-infected cells 3. Viral proteins that modify permeability 3.1. Viroporins 3.2. Viral glycoproteins that modify membrane permeability 4. Membrane permeabilization and drug design 4.1. Antibiotics and toxins that selectively enter virus-infected cells 4.2. Viroporin inhibitors 4.3. Antiviral agents that interfere with viral glycoproteins 5. Acknowledgments References FiguresS
Critical behavior of su(1|1) supersymmetric spin chains with long-range interactions
We introduce a general class of su supersymmetric spin chains with
long-range interactions which includes as particular cases the su
Inozemtsev (elliptic) and Haldane-Shastry chains, as well as the XX model. We
show that this class of models can be fermionized with the help of the
algebraic properties of the su permutation operator, and take advantage
of this fact to analyze their quantum criticality when a chemical potential
term is present in the Hamiltonian. We first study the low energy excitations
and the low temperature behavior of the free energy, which coincides with that
of a -dimensional conformal field theory (CFT) with central charge
when the chemical potential lies in the critical interval , being the dispersion relation. We also analyze the
von Neumann and R\'enyi ground state entanglement entropies, showing that they
exhibit the logarithmic scaling with the size of the block of spins
characteristic of a one-boson -dimensional CFT. Our results thus show
that the models under study are quantum critical when the chemical potential
belongs to the critical interval, with central charge . From the analysis
of the fermion density at zero temperature, we also conclude that there is a
quantum phase transition at both ends of the critical interval. This is further
confirmed by the behavior of the fermion density at finite temperature, which
is studied analytically (at low temperature), as well as numerically for the
su elliptic chain.Comment: 13 pages, 6 figures, typeset in REVTe
The Radio Jet Associated with the Multiple V380 Ori System
The giant Herbig-Haro object 222 extends over 6 in the plane of the
sky, with a bow shock morphology. The identification of its exciting source has
remained uncertain over the years. A non-thermal radio source located at the
core of the shock structure was proposed to be the exciting source. However,
Very Large Array studies showed that the radio source has a clear morphology of
radio galaxy and a lack of flux variations or proper motions, favoring an
extragalactic origin. Recently, an optical-IR study proposed that this giant HH
object is driven by the multiple stellar system V380 Ori, located about 23
to the SE of HH 222. The exciting sources of HH systems are usually detected as
weak free-free emitters at centimeter wavelengths. Here we report the detection
of an elongated radio source associated with the Herbig Be star or with its
close infrared companion in the multiple V380 Ori system. This radio source has
the characteristics of a thermal radio jet and is aligned with the direction of
the giant outflow defined by HH~222 and its suggested counterpart to the SE,
HH~1041. We propose that this radio jet traces the origin of the large scale HH
outflow. Assuming that the jet arises from the Herbig Be star, the radio
luminosity is a few times smaller than the value expected from the
radio-bolometric correlation for radio jets, confirming that this is a more
evolved object than those used to establish the correlation.Comment: 13 pages, 3 figure
Generalized isotropic Lipkin-Meshkov-Glick models: ground state entanglement and quantum entropies
We introduce a new class of generalized isotropic Lipkin-Meshkov-Glick models
with su spin and long-range non-constant interactions, whose
non-degenerate ground state is a Dicke state of su type. We evaluate in
closed form the reduced density matrix of a block of spins when the whole
system is in its ground state, and study the corresponding von Neumann and
R\'enyi entanglement entropies in the thermodynamic limit. We show that both of
these entropies scale as when tends to infinity, where the
coefficient is equal to in the ground state phase with
vanishing su magnon densities. In particular, our results show that none
of these generalized Lipkin-Meshkov-Glick models are critical, since when
their R\'enyi entropy becomes independent of the parameter
. We have also computed the Tsallis entanglement entropy of the ground state
of these generalized su Lipkin-Meshkov-Glick models, finding that it can
be made extensive by an appropriate choice of its parameter only when
. Finally, in the su case we construct in detail the phase
diagram of the ground state in parameter space, showing that it is determined
in a simple way by the weights of the fundamental representation of su.
This is also true in the su case; for instance, we prove that the region
for which all the magnon densities are non-vanishing is an -simplex in
whose vertices are the weights of the fundamental representation
of su.Comment: Typeset with LaTeX, 32 pages, 3 figures. Final version with
corrections and additional reference
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