1,305 research outputs found
Regulation of the neuronal proteasome by Zif268 (Egr1)
Most forms of neuronal plasticity are associated with induction of the transcription factor Zif268 (Egr1/Krox24/NGF-IA). In a genomewide
scan, we obtained evidence for potential modulation of proteasome subunit and regulatory genes by Zif268 in neurons, a finding of
significance considering emerging evidence that the proteasome modulates synaptic function. Bioinformatic analysis indicated that the
candidate proteasome Zif268 target genes had a rich concentration of putative Zif268 binding sites immediately upstream of the transcriptional
start sites. Regulation of the mRNAs encoding the psmb9 (Lmp2) and psme2 (PA28�) proteasome subunits, along with the
proteasome-regulatory kinase serum/glucocorticoid-regulated kinase (SGK) and the proteasome-associated antigen peptide transporter
subunit 1 (Tap1), was confirmed after transfection of a neuronal cell line with Zif268. Conversely, these mRNAs were upregulated in
cerebral cortex tissue from Zif268 knock-out mice relative to controls, confirming that Zif268 suppresses their expression in the CNS.
Transfected Zif268 reduced the activity of psmb9, SGK, and Tap1 promoter–reporter constructs. Altered psmb9, SGK, and Tap1 mRNA
levels were also observed in an in vivo model of neuronal plasticity involving Zif268 induction: the effect of haloperidol administration on
striatal gene expression. Consistent with these effects on proteasome gene expression, increased Zif268 expression suppressed proteasome
activity, whereas Zif268 knock-out mice exhibited elevated cortical proteasome activity. Our findings reveal that Zif268 regulates
the expression of proteasome and related genes in neuronal cells and provide new evidence that altered expression of proteasome activity
after Zif268 induction may be a key component of long-lasting CNS plasticity
First principles simulations of direct coexistence of solid and liquid aluminium
First principles calculations based on density functional theory, with
generalised gradient corrections and ultrasoft pseudopotentials, have been used
to simulate solid and liquid aluminium in direct coexistence at zero pressure.
Simulations have been carried out on systems containing up to 1000 atoms for 15
ps. The points on the melting curve extracted from these simulations are in
very good agreement with previous calculations, which employed the same
electronic structure method but used an approach based on the explicit
calculation of free energies [L. Vo\v{c}adlo and D. Alf\`e, Phys. Rev. B, {\bf
65}, 214105 (2002).]Comment: To appear in Phys. Rev.
Tachyon Condensation, Open-Closed Duality, Resolvents, and Minimal Bosonic and Type 0 Strings
Type 0A string theory in the (2,4k) superconformal minimal model backgrounds
and the bosonic string in the (2,2k-1) conformal minimal models, while
perturbatively identical in some regimes, may be distinguished
non-perturbatively using double scaled matrix models. The resolvent of an
associated Schrodinger operator plays three very important interconnected
roles, which we explore perturbatively and non-perturbatively. On one hand, it
acts as a source for placing D-branes and fluxes into the background, while on
the other, it acts as a probe of the background, its first integral yielding
the effective force on a scaled eigenvalue. We study this probe at disc, torus
and annulus order in perturbation theory, in order to characterize the effects
of D-branes and fluxes on the matrix eigenvalues. On a third hand, the
integrated resolvent forms a representation of a twisted boson in an associated
conformal field theory. The entire content of the closed string theory can be
expressed in terms of Virasoro constraints on the partition function, which is
realized as wavefunction in a coherent state of the boson. Remarkably, the
D-brane or flux background is simply prepared by acting with a vertex operator
of the twisted boson. This generates a number of sharp examples of open-closed
duality, both old and new. We discuss whether the twisted boson conformal field
theory can usefully be thought of as another holographic dual of the
non-critical string theory.Comment: 37 pages, some figures, LaTe
Nonperturbative renormalization group approach to frustrated magnets
This article is devoted to the study of the critical properties of classical
XY and Heisenberg frustrated magnets in three dimensions. We first analyze the
experimental and numerical situations. We show that the unusual behaviors
encountered in these systems, typically nonuniversal scaling, are hardly
compatible with the hypothesis of a second order phase transition. We then
review the various perturbative and early nonperturbative approaches used to
investigate these systems. We argue that none of them provides a completely
satisfactory description of the three-dimensional critical behavior. We then
recall the principles of the nonperturbative approach - the effective average
action method - that we have used to investigate the physics of frustrated
magnets. First, we recall the treatment of the unfrustrated - O(N) - case with
this method. This allows to introduce its technical aspects. Then, we show how
this method unables to clarify most of the problems encountered in the previous
theoretical descriptions of frustrated magnets. Firstly, we get an explanation
of the long-standing mismatch between different perturbative approaches which
consists in a nonperturbative mechanism of annihilation of fixed points between
two and three dimensions. Secondly, we get a coherent picture of the physics of
frustrated magnets in qualitative and (semi-) quantitative agreement with the
numerical and experimental results. The central feature that emerges from our
approach is the existence of scaling behaviors without fixed or pseudo-fixed
point and that relies on a slowing-down of the renormalization group flow in a
whole region in the coupling constants space. This phenomenon allows to explain
the occurence of generic weak first order behaviors and to understand the
absence of universality in the critical behavior of frustrated magnets.Comment: 58 pages, 15 PS figure
Predominantly Non-Solar Origin of Nitrogen in Lunar Soils
Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon, extracted from the same aliquot of sample by high-resolution stepped combustion, have been made for a suite of five lunar soils.
Noble gas isotope ratios show that the majority of noble gases are derived from a solar wind source; for example, at peak release temperatures of 500–600 °C,21Ne/22Ne = 0.0313 ± 0.0007 to 0.0333 ± 0.0007, and 20Ne/22Ne = 11.48 ± 0.05 to 12.43 ± 0.07, with values at the lowest temperature steps less fractionated during implantation from, and therefore even closer to, solar values (21Ne/22NeSW = 0.03361 ± 0.00018 and 20Ne/22NeSW = 14.001 ± 0.042 (Pepin et al., 2012)). Despite the co-release of nitrogen and solar wind argon, measured nitrogen isotopic signatures at each temperature step, whilst variable, are significantly more enriched in 15N compared to the measured solar wind nitrogen value from the Genesis mission. Therefore, mixing between a 15N-enriched non-solar planetary nitrogen source with solar wind nitrogen is required to explain the measured isotopic values from the stepped combustion analysis of lunar soils. Binary mixing calculations, made under different assumptions about the degree of loss of solar wind 36Ar, reveal that the majority (up to 98%) of the nitrogen released is derived from a non-solar source. The range of modelled non-solar end-member nitrogen compositions required to satisfy the measuredδ15N values varies between samples and temperature steps from +5‰ up to +300‰, or between +87‰ and +160‰ for bulk samples. This range of modelled isotopic compositions for the non-solar source of nitrogen encompasses measured values for several different groups of carbonaceous chondrite, as well as IDPs
Domain wall generation by fermion self-interaction and light particles
A possible explanation for the appearance of light fermions and Higgs bosons
on the four-dimensional domain wall is proposed. The mechanism of light
particle trapping is accounted for by a strong self-interaction of
five-dimensional pre-quarks. We obtain the low-energy effective action which
exhibits the invariance under the so called \tau-symmetry. Then we find a set
of vacuum solutions which break that symmetry and the five-dimensional
translational invariance. One type of those vacuum solutions gives rise to the
domain wall formation with consequent trapping of light massive fermions and
Higgs-like bosons as well as massless sterile scalars, the so-called branons.
The induced relations between low-energy couplings for Yukawa and scalar field
interactions allow to make certain predictions for light particle masses and
couplings themselves, which might provide a signature of the higher dimensional
origin of particle physics at future experiments. The manifest translational
symmetry breaking, eventually due to some gravitational and/or matter fields in
five dimensions, is effectively realized with the help of background scalar
defects. As a result the branons acquire masses, whereas the ratio of Higgs and
fermion (presumably top-quark) masses can be reduced towards the values
compatible with the present-day phenomenology. Since the branons do not couple
to fermions and the Higgs bosons do not decay into branons, the latter ones are
essentially sterile and stable, what makes them the natural candidates for the
dark matter in the Universe.Comment: 34 pages, 2 figures, JHEP style,few important refs. adde
Differential Effects of Environmental and Genetic Factors on T and B Cell Immune Traits
Effective immunity requires a complex network of cellular and humoral components that interact with each other and are influenced by different environmental and host factors. We used a systems biology approach to comprehensively assess the impact of environmental and genetic factors on immune cell populations in peripheral blood, including associations with immunoglobulin concentrations, from ∼500 healthy volunteers from the Human Functional Genomics Project. Genetic heritability estimation showed that variations in T cell numbers are more strongly driven by genetic factors, while B cell counts are more environmentally influenced. Quantitative trait loci (QTL) mapping identified eight independent genomic loci associated with leukocyte count variation, including four associations with T and B cell subtypes. The QTLs identified were enriched among genome-wide association study (GWAS) SNPs reported to increase susceptibility to immune-mediated diseases. Our systems approach provides insights into cellular and humoral immune trait variability in humans
Factorization of integrals, defining the beta-function, into integrals of total derivatives in N=1 SQED, regularized by higher derivatives
Some calculations in supersymmetric theories, made with the higher derivative
regularization, show that the beta-function is given by integrals of total
derivatives. This is qualitatively explained for the N=1 supersymmetric
electrodynamics in all orders.Comment: 14 page
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
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