1,693 research outputs found
Conductance through atomic point contacts between fcc(100) electrodes of gold
Electrical conductance through various nanocontacts between gold electrodes
is studied by using the density functional theory, scalar-relativistic
pseudopotentials, generalized gradient approximation for the
exchange-correlation energy and the recursion-transfer-matrix method along with
channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips
and 1 to 5 gold atoms between the tips. Upon elongation of the contact by
adding gold atoms between the tips, the conductance at Fermi energy E_F evolves
from G ~ 3 G_0 to G ~ 1 G_0 (G_0 = 2e/h^2). Formation of a true one-atom point
contact, with G ~ 1 G_0 and only one open channel, requires at least one atom
with coordination number 2 in the wire. Tips that share a common vertex atom or
tips with touching vertex atoms have three partially open conductance channels
at E_F, and the symmetries of the channels are governed by the wave functions
of the tips. The long 5-atom contact develops conductance oscillations and
conductance gaps in the studied energy range -3 < E-E_F < 5 eV, which reflects
oscillations in the local density of electron states in the 5-atom linear "gold
molecule" between the electrodes, and a weak coupling of this "molecule" to the
tips
The Potential Role of Aerobic Exercise-Induced Pentraxin 3 on Obesity-Related Inflammation and Metabolic Dysregulation
Obesity is defined as the excess accumulation of intra-abdominal body fat, resulting in a state of chronic, low-grade proinflammation that can directly contribute to the development of insulin resistance. Pentraxin 3 (PTX3) is an acute-phase protein that is expressed by a variety of tissue and cell sources and provides an anti-inflammatory property to downregulate the production of proinflammatory cytokines, in particular interleukin-1 beta and tumor necrosis factor alpha. Although PTX3 may therapeutically aid in altering the proinflammatory milieu in obese individuals, and despite elevated expression of PTX3 mRNA observed in adipose tissue, the circulating level of PTX3 is reduced with obesity. Interestingly, aerobic activity has been demonstrated to elevate PTX3 levels. Therefore, the purpose of this review is to discuss the therapeutic potential of PTX3 to positively regulate obesity-related inflammation and discuss the proposition for utilizing aerobic exercise as a nonpharmacological anti-inflammatory treatment strategy to enhance circulating PTX3 concentrations in obese individuals
Modulation of Host Immunity by Human Respiratory Syncytial Virus Virulence Factors: A Synergic Inhibition of Both Innate and Adaptive Immunity
Indexación: Web of Science; Scopus.The Human Respiratory Syncytial Virus (hRSV) is a major cause of acute lower respiratory tract infections (ARTIs) and high rates of hospitalizations in children and in the elderly worldwide. Symptoms of hRSV infection include bronchiolitis and pneumonia. The lung pathology observed during hRSV infection is due in part to an exacerbated host immune response, characterized by immune cell infiltration to the lungs. HRSV is an enveloped virus, a member of the Pneumoviridae family, with a non-segmented genome and negative polarity-single RNA that contains 10 genes encoding for 11 proteins. These include the Fusion protein (F), the Glycoprotein (G), and the Small Hydrophobic (SH) protein, which are located on the virus surface. In addition, the Nucleoprotein (N), Phosphoprotein (P) large polymerase protein (L) part of the RNA-dependent RNA polymerase complex, the M2-1 protein as a transcription elongation factor, the M2-2 protein as a regulator of viral transcription and (M) protein all of which locate inside the virion. Apart from the structural proteins, the hRSV genome encodes for the non-structural 1 and 2 proteins (NS1 and NS2). HRSV has developed different strategies to evade the host immunity by means of the function of some of these proteins that work as virulence factors to improve the infection in the lung tissue. Also, hRSV NS-1 and NS-2 proteins have been shown to inhibit the activation of the type I interferon response. Furthermore, the hRSV nucleoprotein has been shown to inhibit the immunological synapsis between the dendritic cells and T cells during infection, resulting in an inefficient T cell activation. Here, we discuss the hRSV virulence factors and the host immunological features raised during infection with this virus.https://www.frontiersin.org/articles/10.3389/fcimb.2017.00367/ful
New dynamical scaling universality for quantum networks across adiabatic quantum phase transitions
We reveal universal dynamical scaling behavior across adiabatic quantum phase
transitions (QPTs) in networks ranging from traditional spatial systems (Ising
model) to fully connected ones (Dicke and Lipkin-Meshkov-Glick models). Our
findings, which lie beyond traditional critical exponent analysis and adiabatic
perturbation approximations, are applicable even where excitations have not yet
stabilized and hence provide a time-resolved understanding of QPTs encompassing
a wide range of adiabatic regimes. We show explicitly that even though two
systems may traditionally belong to the same universality class, they can have
very different adiabatic evolutions. This implies more stringent conditions
need to be imposed than at present, both for quantum simulations where one
system is used to simulate the other, and for adiabatic quantum computing
schemes.Comment: 5 pages, 3 figures, plus supplementary material (6 pages, 1 figure
Robust quantum correlations in out-of-equilibrium matter-light systems
High precision macroscopic quantum control in interacting light-matter
systems remains a significant goal toward novel information processing and
ultra-precise metrology. We show that the out-of-equilibrium behavior of a
paradigmatic light-matter system (Dicke model) reveals two successive stages of
enhanced quantum correlations beyond the traditional schemes of near-adiabatic
and sudden quenches. The first stage features magnification of matter-only and
light-only entanglement and squeezing due to effective non-linear
self-interactions. The second stage results from a highly entangled
light-matter state, with enhanced superradiance and signatures of chaotic and
highly quantum states. We show that these new effects scale up consistently
with matter system size, and are reliable even in dissipative environments.Comment: 14 pages, 6 figure
Large dynamic light-matter entanglement from driving neither too fast nor too slow
A significant problem facing next-generation quantum technologies is how to
generate and manipulate macroscopic entanglement in light and matter systems.
Here we report a new regime of dynamical light-matter behavior in which a
giant, system-wide entanglement is generated by varying the light-matter
coupling at \emph{intermediate} velocities. This enhancement is far larger and
broader-ranged than that occurring near the quantum phase transition of the
same model under adiabatic conditions. By appropriate choices of the coupling
within this intermediate regime, the enhanced entanglement can be made to
spread system-wide or to reside in each subsystem separately.Comment: 7 pages, 7 figure
BDNF as a biomarker for neuropathic pain:Consideration of mechanisms of action and associated measurement challenges
IntroductionThe primary objective of this paper is to (1) provide a summary of human studies that have used brain derived neurotrophic factor (BDNF) as a biomarker, (2) review animal studies that help to elucidate the mechanistic involvement of BDNF in the development and maintenance of neuropathic pain (NP), and (3) provide a critique of the existing measurement techniques to highlight the limitations of the methods utilized to quantify BDNF in different biofluids in the blood (i.e., serum and plasma) with the intention of presenting a case for the most reliable and valid technique. Lastly, this review also explores potential moderators that can influence the measurement of BDNF and provides recommendations to standardize its quantification to reduce the inconsistencies across studies.MethodsIn this manuscript we examined the literature on BDNF, focusing on its role as a biomarker, its mechanism of action in NP, and critically analyzed its measurement in serum and plasma to identify factors that contribute to the discrepancy in results between plasma and serum BDNF values.ResultsA large heterogenous literature was reviewed that detailed BDNF's utility as a potential biomarker in healthy volunteers, patients with chronic pain, and patients with neuropsychiatric disorders but demonstrated inconsistent findings. The literature provides insight into the mechanism of action of BDNF at different levels of the central nervous system using animal studies. We identified multiple factors that influence the measurement of BDNF in serum and plasma and based on current evidence, we recommend assessing serum BDNF levels to quantify peripheral BDNF as they are more stable and sensitive to changes than plasma BDNF.ConclusionAlthough mechanistic studies clearly explain the role of BDNF, results from human studies are inconsistent. More studies are needed to evaluate the methodological challenges in using serum BDNF as a biomarker in NP
Quantum Hysteresis in Coupled Light-Matter Systems
We investigate the non-equilibrium quantum dynamics of a canonical
light-matter system, namely the Dicke model, when the light-matter interaction
is ramped up and down through a cycle across the quantum phase transition. Our
calculations reveal a rich set of dynamical behaviors determined by the cycle
times, ranging from the slow, near adiabatic regime through to the fast, sudden
quench regime. As the cycle time decreases, we uncover a crossover from an
oscillatory exchange of quantum information between light and matter that
approaches a reversible adiabatic process, to a dispersive regime that
generates large values of light-matter entanglement. The phenomena uncovered in
this work have implications in quantum control, quantum interferometry, as well
as in quantum information theory.Comment: 9 pages and 4 figure
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