20,343 research outputs found
Effect of physical parameters on the reaction of graphite with silica in vacuum
Effect of physical parameters on reduction of silica graphite mixtures under vacuum condition
Photoemission Spectra in t-J Ladders with Two Legs
Photoemission spectra for the isotropic two-leg t-J ladder are calculated at
various hole-doping levels using exact diagonalization techniques. Low-energy
sharp features caused by short-range antiferromagnetic correlations are
observed at finite doping levels close to half-filling, above the naive Fermi
momentum. These features should be observable in angle-resolved photoemission
experiments. In addition, the formation of a d-wave pairing condensate as the
ratio J/t is increased leads to dynamically generated spectral weight for
momenta close to where the -order parameter is large.Comment: 9 pages, RevTex, to be published in Phys. Rev. B (RC
Iron economy in Chlamydomonas reinhardtii.
While research on iron nutrition in plants has largely focused on iron-uptake pathways, photosynthetic microbes such as the unicellular green alga Chlamydomonas reinhardtii provide excellent experimental systems for understanding iron metabolism at the subcellular level. Several paradigms in iron homeostasis have been established in this alga, including photosystem remodeling in the chloroplast and preferential retention of some pathways and key iron-dependent proteins in response to suboptimal iron supply. This review presents our current understanding of iron homeostasis in Chlamydomonas, with specific attention on characterized responses to changes in iron supply, like iron-deficiency. An overview of frequently used methods for the investigation of iron-responsive gene expression, physiology and metabolism is also provided, including preparation of media, the effect of cell size, cell density and strain choice on quantitative measurements and methods for the determination of metal content and assessing the effect of iron supply on photosynthetic performance
The uniting of Europe and the foundation of EU studies: revisiting the neofunctionalism of Ernst B. Haas
This article suggests that the neofunctionalist theoretical legacy left by Ernst B. Haas is somewhat richer and more prescient than many contemporary discussants allow. The article develops an argument for routine and detailed re-reading of the corpus of neofunctionalist work (and that of Haas in particular), not only to disabuse contemporary students and scholars of the normally static and stylized reading that discussion of the theory provokes, but also to suggest that the conceptual repertoire of neofunctionalism is able to speak directly to current EU studies and comparative regionalism. Neofunctionalism is situated in its social scientific context before the theory's supposed erroneous reliance on the concept of 'spillover' is discussed critically. A case is then made for viewing Haas's neofunctionalism as a dynamic theory that not only corresponded to established social scientific norms, but did so in ways that were consistent with disciplinary openness and pluralism
State-Dependent Modulation of Gap Junction Signaling by the Persistent Sodium Current
Thalamic neurons fluctuate between two states: a hyperpolarized state associated with burst firing and sleep spindles, and a depolarized state associated with tonic firing and rapid, reliable information transmission between the sensory periphery and cortex. The thalamic reticular nucleus (TRN) plays a central role in thalamocortical processing by providing feed-forward and feedback inhibition to thalamic relay cells; TRN cells participate in the generation of sleep spindles, and have been suggested to focus the neural âsearchlightâ of attention. The mechanisms underlying synchrony in the TRN during different behavioral states are largely unknown. TRN cells are densely interconnected by electrical synapses. Here we show that activation of the persistent sodium current (INaP) by depolarization causes up to fourfold changes in electrical synaptic efficacy between TRN neurons. We further show that amplification of electrical synaptic responses strongly enhances tonic spike synchrony but, surprisingly, does not affect burst coordination. We use a HodgkinâHuxley model to gain insight into the differences between the effects of burstlets, spikelets, and amplification on burst and spike times
A Whole Genome Association Study to Detect Loci Associated with Somatic Cell Score in Dairy Cattle
Quantum disorder and Griffiths singularities in bond-diluted two-dimensional Heisenberg antiferromagnets
We investigate quantum phase transitions in the spin-1/2 Heisenberg
antiferromagnet on square lattices with inhomogeneous bond dilution. It is
shown that quantum fluctuations can be continuously tuned by inhomogeneous bond
dilution, eventually leading to the destruction of long-range magnetic order on
the percolating cluster. Two multicritical points are identified at which the
magnetic transition separates from the percolation transition, introducing a
novel quantum phase transition. Beyond these multicritical points a
quantum-disordered phase appears, characterized by an infinite percolating
cluster with short ranged antiferromagnetic order. In this phase, the
low-temperature uniform susceptibility diverges algebraically with
non-universal exponents. This is a signature that the novel quantum-disordered
phase is a quantum Griffiths phase, as also directly confirmed by the
statistical distribution of local gaps. This study thus presents evidence of a
genuine quantum Griffiths phenomenon in a two-dimensional Heisenberg
antiferromagnet.Comment: 14 pages, 17 figures; published versio
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