190 research outputs found
A general algorithm for manipulating non-linear and linear entanglement witnesses by using exact convex optimization
A generic algorithm is developed to reduce the problem of obtaining linear
and nonlinear entanglement witnesses of a given quantum system, to convex
optimization problem. This approach is completely general and can be applied
for the entanglement detection of any N-partite quantum system. For this
purpose, a map from convex space of separable density matrices to a convex
region called feasible region is defined, where by using exact convex
optimization method, the linear entanglement witnesses can be obtained from
polygonal shape feasible regions, while for curved shape feasible regions,
envelope of the family of linear entanglement witnesses can be considered as
nonlinear entanglement witnesses. This method proposes a new methodological
framework within which most of previous EWs can be studied. To conclude and in
order to demonstrate the capability of the proposed approach, besides providing
some nonlinear witnesses for entanglement detection of density matrices in
unextendible product bases, W-states, and GHZ with W-states, some further
examples of three qubits systems and their classification and entanglement
detection are included. Also it is explained how one can manipulate most of the
non-decomposable linear and nonlinear three qubits entanglement witnesses
appearing in some of the papers published by us and other authors, by the
method proposed in this paper. Keywords: non-linear and linear entanglement
witnesses, convex optimization. PACS number(s): 03.67.Mn, 03.65.UdComment: 37 page
Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis
The association between IGF-1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta-analysis investigates this complex relationship between IGF-1 and all-cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta-analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF-1 and were conducted among adults. A random-effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all-cause mortality. Nineteen studies involving 30,876 participants were included. Meta-analysis of the 19 eligible studies showed that with respect to the low IGF-1 category, higher IGF-1 was not associated with increased risk of all-cause mortality (HR = 0.84, 95% CI = 0.68–1.05). Dose–response analysis revealed a U-shaped relation between IGF-1 and mortality HR. Pooled results comparing low vs. middle IGF-1 showed a significant increase of all-cause mortality (HR = 1.33, 95% CI = 1.14–1.57), as well as comparing high vs. middle IGF-1 categories (HR = 1.23, 95% CI = 1.06–1.44). Finally, we provide data on the association between IGF-1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF-1 increase mortality risk, with a specific 120–160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF-1 levels and mortality
Thermal Transport in MoS from Molecular Dynamics using Different Empirical Potentials
Thermal properties of molybdenum disulfide (MoS) have recently attracted
attention related to fundamentals of heat propagation in strongly anisotropic
materials, and in the context of potential applications to optoelectronics and
thermoelectrics. Multiple empirical potentials have been developed for
classical molecular dynamics (MD) simulations of this material, but it has been
unclear which provides the most realistic results. Here, we calculate lattice
thermal conductivity of single- and multi-layer pristine MoS by employing
three different thermal transport MD methods: equilibrium, nonequilibrium, and
homogeneous nonequilibrium ones. These methods allow us to verify the
consistency of our results and also facilitate comparisons with previous works,
where different schemes have been adopted. Our results using variants of the
Stillinger-Weber potential are at odds with some previous ones and we analyze
the possible origins of the discrepancies in detail. We show that, among the
potentials considered here, the reactive empirical bond order (REBO) potential
gives the most reasonable predictions of thermal transport properties as
compared to experimental data. With the REBO potential, we further find that
isotope scattering has only a small effect on thermal conduction in MoS and
the in-plane thermal conductivity decreases with increasing layer number and
saturates beyond about three layers. We identify the REBO potential as a
transferable empirical potential for MD simulations of MoS which can be
used to study thermal transport properties in more complicated situations such
as in systems containing defects or engineered nanoscale features. This work
establishes a firm foundation for understanding heat transport properties of
MoS using MD simulations.Comment: 14 pages, 6 figure
Thermal Transport in MoS from Molecular Dynamics using Different Empirical Potentials
Thermal properties of molybdenum disulfide (MoS) have recently attracted
attention related to fundamentals of heat propagation in strongly anisotropic
materials, and in the context of potential applications to optoelectronics and
thermoelectrics. Multiple empirical potentials have been developed for
classical molecular dynamics (MD) simulations of this material, but it has been
unclear which provides the most realistic results. Here, we calculate lattice
thermal conductivity of single- and multi-layer pristine MoS by employing
three different thermal transport MD methods: equilibrium, nonequilibrium, and
homogeneous nonequilibrium ones. These methods allow us to verify the
consistency of our results and also facilitate comparisons with previous works,
where different schemes have been adopted. Our results using variants of the
Stillinger-Weber potential are at odds with some previous ones and we analyze
the possible origins of the discrepancies in detail. We show that, among the
potentials considered here, the reactive empirical bond order (REBO) potential
gives the most reasonable predictions of thermal transport properties as
compared to experimental data. With the REBO potential, we further find that
isotope scattering has only a small effect on thermal conduction in MoS and
the in-plane thermal conductivity decreases with increasing layer number and
saturates beyond about three layers. We identify the REBO potential as a
transferable empirical potential for MD simulations of MoS which can be
used to study thermal transport properties in more complicated situations such
as in systems containing defects or engineered nanoscale features. This work
establishes a firm foundation for understanding heat transport properties of
MoS using MD simulations.Comment: 14 pages, 6 figure
Opportunities and barriers to translating the hibernation phenotype for neurocritical care
Targeted temperature management (TTM) is standard of care for neonatal hypoxic ischemic encephalopathy (HIE). Prevention of fever, not excluding cooling core body temperature to 33°C, is standard of care for brain injury post cardiac arrest. Although TTM is beneficial, HIE and cardiac arrest still carry significant risk of death and severe disability. Mammalian hibernation is a gold standard of neuroprotective metabolic suppression, that if better understood might make TTM more accessible, improve efficacy of TTM and identify adjunctive therapies to protect and regenerate neurons after hypoxic ischemia brain injury. Hibernating species tolerate cerebral ischemia/reperfusion better than humans and better than other models of cerebral ischemia tolerance. Such tolerance limits risk of transitions into and out of hibernation torpor and suggests that a barrier to translate hibernation torpor may be human vulnerability to these transitions. At the same time, understanding how hibernating mammals protect their brains is an opportunity to identify adjunctive therapies for TTM. Here we summarize what is known about the hemodynamics of hibernation and how the hibernating brain resists injury to identify opportunities to translate these mechanisms for neurocritical care
Thermal transport in MoS2 from molecular dynamics using different empirical potentials
Thermal properties of molybdenum disulfide (MoS2) have recently attracted attention related to fundamentals
of heat propagation in strongly anisotropic materials, and in the context of potential applications to optoelectronics and thermoelectrics. Multiple empirical potentials have been developed for classical molecular dynamics
(MD) simulations of this material, but it has been unclear which provides the most realistic results. Here, we
calculate lattice thermal conductivity of single- and multilayer pristine MoS2 by employing three different
thermal transport MD methods: equilibrium, nonequilibrium, and homogeneous nonequilibrium ones. We mainly
use the Graphics Processing Units Molecular Dynamics code for numerical calculations, and the Large-scale
Atomic/Molecular Massively Parallel Simulator code for crosschecks. Using different methods and computer
codes allows us to verify the consistency of our results and facilitate comparisons with previous studies, where
different schemes have been adopted. Our results using variants of the Stillinger-Weber potential are at odds
with some previous ones and we analyze the possible origins of the discrepancies in detail. We show that, among
the potentials considered here, the reactive empirical bond order (REBO) potential gives the most reasonable
predictions of thermal transport properties as compared to experimental data. With the REBO potential, we
further find that isotope scattering has only a small effect on thermal conduction in MoS2 and the in-plane thermal
conductivity decreases with increasing layer number and saturates beyond about three layers. We identify the
REBO potential as a transferable empirical potential for MD simulations of MoS2 which can be used to study
thermal transport properties in more complicated situations such as in systems containing defects or engineered
nanoscale features. This work establishes a firm foundation for understanding heat transport properties of MoS2
using MD simulations
Perfect transference of a d-level quantum state over pseudo-distance-regular networks
Following the prescription of Ref. \cite{PST} in which perfect state
transference (PST) of a qubit over distance regular spin networks was
discussed, in this paper PST of an arbitrary -level quantum state (qudit)
over antipodes of more general networks called pseudo distance-regular
networks, is investigated. In fact, the spectral analysis techniques used in
the previous work \cite{PST}, and algebraic structures of pseudo
distance-regular graphs are employed to give an explicit formula for suitable
coupling constants in the Hamiltonians so that the state of a particular qudit
initially encoded on one site will evolve freely to the opposite site without
any dynamical control, i.e., we show that how to derive the parameters of the
system so that PST can be achieved.
Keywords:Perfect state transfer, -level quantum state, Stratification,
Pseudo-distance-regular network
PACs Index: 01.55.+b, 02.10.YnComment: 28 pages, 5 figure
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