31,261 research outputs found
Hadronic Correlators from All-point Quark Propagators
A method for computing all-point quark propagators is applied to a variety of
processes of physical interest in lattice QCD. The method allows, for example,
efficient calculation of disconnected parts and full momentum-space 2 and 3
point functions. Examples discussed include: extraction of chiral Lagrangian
parameters from current correlators, the pion form factor, and the unquenched
eta-prime.Comment: LATTICE01(Algorithms and Machines
INDIVISIBILITY AND DIVISIBILITY IN LAND DEVELOPMENT DECISIONS OVER TIME AND UNDER UNCERTAINTY
The quasi-option value (QOV) literature originated by Arrow and Fisher (1974) and by Henry (1974) is largely concerned with the analysis of two-period models of land development. Our paper extends this literature by analyzing two scenarios in which the decision to develop land is made in a multi-period and stochastic framework. In the first scenario, the development decision is indivisible. In contrast, in the second scenario, the development decision is divisible. Specifically, we study the properties of the indivisible development decision when there is a time constraint on when land is to be developed. We then analyze the ways in which the divisible land development decision depends on the extent of a landowner's landholding and on the number of development opportunities awaiting this landowner.Land Economics/Use,
Cool-associated Tyrosine-phosphorylated Protein 1 Is Required for the Anchorage-independent Growth of Cervical Carcinoma Cells by Binding Paxillin and Promoting AKT Activation.
Cool-associated tyrosine-phosphorylated protein 1 (Cat-1) is a signaling scaffold as well as an ADP-ribosylation factor-GTPase-activating protein. Although best known for its role in cell migration, we recently showed that the ability of Cat-1 to bind paxillin, a major constituent of focal complexes, is also essential for the anchorage-independent growth of HeLa cervical carcinoma cells. Here we set out to learn more about the underlying mechanism by which Cat-paxillin interactions mediate this effect. We show that knocking down paxillin expression in HeLa cells promotes their ability to form colonies in soft agar, whereas ectopically expressing paxillin in these cells inhibits this transformed growth phenotype. Although knocking down Cat-1 prevents HeLa cells from forming colonies in soft agar, when paxillin is knocked down together with Cat-1, the cells are again able to undergo anchorage-independent growth. These results suggest that the requirement of Cat-1 for this hallmark of cellular transformation is coupled to its ability to bind paxillin and abrogate its actions as a negative regulator of anchorage-independent growth. We further show that knocking down Cat-1 expression in HeLa cells leads to a reduction in Akt activation, which can be reversed by knocking down paxillin. Moreover, expression of constitutively active forms of Akt1 and Akt2 restores the anchorage-independent growth capability of HeLa cells depleted of Cat-1 expression. Together, these findings highlight a novel mechanism whereby interactions between Cat-1 and its binding partner paxillin are necessary to ensure sufficient Akt activation so that cancer cells are able to grow under anchorage-independent conditions
Oxygen surface exchange kinetics of erbia-stabilized bismuth oxide
The surface oxygen exchange kinetics of bismuth\ud
oxide stabilized with 25 mol% erbia (BE25) has been studied\ud
in the temperature and pO2 ranges 773–1,023 K and 0.1–\ud
0.95 atm, respectively, using pulse-response 18O–16O isotope\ud
exchange measurements. The results indicate that BE25\ud
exhibits a comparatively high exchange rate, which is rate\ud
determined by the dissociative adsorption of oxygen. Defect\ud
chemical considerations and the observed pO2\ud
1=2 dependence\ud
of the rate of dissociative oxygen adsorption suggest\ud
electron transfer to intermediate superoxide ions as the rate\ud
determining step in surface oxygen exchange on BE2
Engineering Heteromaterials to Control Lithium Ion Transport Pathways.
Safe and efficient operation of lithium ion batteries requires precisely directed flow of lithium ions and electrons to control the first directional volume changes in anode and cathode materials. Understanding and controlling the lithium ion transport in battery electrodes becomes crucial to the design of high performance and durable batteries. Recent work revealed that the chemical potential barriers encountered at the surfaces of heteromaterials play an important role in directing lithium ion transport at nanoscale. Here, we utilize in situ transmission electron microscopy to demonstrate that we can switch lithiation pathways from radial to axial to grain-by-grain lithiation through the systematic creation of heteromaterial combinations in the Si-Ge nanowire system. Our systematic studies show that engineered materials at nanoscale can overcome the intrinsic orientation-dependent lithiation, and open new pathways to aid in the development of compact, safe, and efficient batteries
The Second Virial Coefficient of Spin-1/2 Interacting Anyon System
Evaluating the propagator by the usual time-sliced manner, we use it to
compute the second virial coefficient of an anyon gas interacting through the
repulsive potential of the form . All the cusps for the
unpolarized spin-1/2 as well as spinless cases disappear in the
limit, where is a frequency of harmonic oscillator which is introduced
as a regularization method. As approaches to zero, the result reduces to
the noninteracting hard-core limit.Comment: 9 pages, 2 figs include
Recent results using all-point quark propagators
Pseudofermion methods for extracting all-point quark propagators are
reviewed, with special emphasis on techniques for reducing or eliminating
autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent
applications, including high statistics evaluations of hadronic current
correlators and the pion form factor, are also described.Comment: LateX, 3 pages, 6 eps figures, Lattice2002(algor), corrected some
typo
Lensing reconstruction of cluster-mass cross-correlation with cosmic microwave background polarization
We extend our maximum likelihood method for reconstructing the cluster-mass
cross-correlation from cosmic microwave background (CMB) temperature
anisotropies and develop new estimators that utilize six different quadratic
combinations of CMB temperature and polarization fields. Our maximum likelihood
estimators are constructed with delensed CMB temperature and polarization
fields by using an assumed model of the convergence field and they can be
iteratively applied to a set of clusters, approaching to the optimal condition
for the lensing reconstruction as the assumed initial model is refined. Using
smoothed particle hydrodynamics simulations, we create a catalog of realistic
clusters obtainable from the current Sunyaev-Zel'dovich (SZ) surveys, and we
demonstrate the ability of the maximum likelihood estimators to reconstruct the
cluster-mass cross-correlation from the massive clusters. The iTT temperature
estimator provides a signal-to-noise ratio of a factor 3 larger than the iEB
polarization estimator, unless the detector noise for measuring polarization
anisotropies is controlled under 3 microK.Comment: 10 pages, 6 figures, accepted for publication in Physical Review
Chaos at the border of criticality
The present paper points out to a novel scenario for formation of chaotic
attractors in a class of models of excitable cell membranes near an
Andronov-Hopf bifurcation (AHB). The mechanism underlying chaotic dynamics
admits a simple and visual description in terms of the families of
one-dimensional first-return maps, which are constructed using the combination
of asymptotic and numerical techniques. The bifurcation structure of the
continuous system (specifically, the proximity to a degenerate AHB) endows the
Poincare map with distinct qualitative features such as unimodality and the
presence of the boundary layer, where the map is strongly expanding. This
structure of the map in turn explains the bifurcation scenarios in the
continuous system including chaotic mixed-mode oscillations near the border
between the regions of sub- and supercritical AHB. The proposed mechanism
yields the statistical properties of the mixed-mode oscillations in this
regime. The statistics predicted by the analysis of the Poincare map and those
observed in the numerical experiments of the continuous system show a very good
agreement.Comment: Chaos: An Interdisciplinary Journal of Nonlinear Science
(tentatively, Sept 2008
Drosophila Cappuccino alleles provide insight into formin mechanism and role in oogenesis.
During Drosophila development, the formin actin nucleator Cappuccino (Capu) helps build a cytoplasmic actin mesh throughout the oocyte. Loss of Capu leads to female sterility, presumably because polarity determinants fail to localize properly in the absence of the mesh. To gain deeper insight into how Capu builds this actin mesh, we systematically characterized seven capu alleles, which have missense mutations in Capu's formin homology 2 (FH2) domain. We report that all seven alleles have deleterious effects on fly fertility and the actin mesh in vivo but have strikingly different effects on Capu's biochemical activity in vitro. Using a combination of bulk and single- filament actin-assembly assays, we find that the alleles differentially affect Capu's ability to nucleate and processively elongate actin filaments. We also identify a unique "loop" in the lasso region of Capu's FH2 domain. Removing this loop enhances Capu's nucleation, elongation, and F-actin-bundling activities in vitro. Together our results on the loop and the seven missense mutations provides mechanistic insight into formin function in general and Capu's role in the Drosophila oocyte in particular
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