4,323 research outputs found
Selective Over-Expression of Endothelin-1 in Endothelial Cells Exacerbates Inner Retinal Edema and Neuronal Death in Ischemic Retina
The level of endothelin-1 (ET-1), a potent vasoconstrictor, was associated with retinopathy under ischemia. The effects of endothelial endothelin-1 (ET-1) over-expression in a transgenic mouse model using Tie-1 promoter (TET-1 mice) on pathophysiological changes of retinal ischemia were investigated by intraluminal insertion of a microfilament up to middle cerebral artery (MCA) to transiently block the ophthalmic artery. Two-hour occlusion and twenty-two-hour reperfusion were performed in homozygous (Hm) TET-1 mice and their non-transgenic (NTg) littermates. Presence of pyknotic nuclei in ganglion cell layer (GCL) was investigated in paraffin sections of ipsilateral (ischemic) and contralateral (non-ischemic) retinae, followed by measurement of the thickness of inner retinal layer. Moreover, immunocytochemistry of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS) and aquaporin-4 (AQP4) peptides on retinal sections were performed to study glial cell reactivity, glutamate metabolism and water accumulation, respectively after retinal ischemia. Similar morphology was observed in the contralateral retinae of NTg and Hm TET-1 mice, whereas ipsilateral retina of NTg mice showed slight structural and cellular changes compared with the corresponding contralateral retina. Ipsilateral retinae of Hm TET-1 mice showed more significant changes when compared with ipsilateral retina of NTg mice, including more prominent cell death in GCL characterized by the presence of pyknotic nuclei, elevated GS immunoreactivity in Müller cell bodies and processes, increased AQP-4 immunoreactivity in Müller cell processes, and increased inner retinal thickness. Thus, over-expression of endothelial ET-1 in TET-1 mice may contribute to increased glutamate-induced neurotoxicity on neuronal cells and water accumulation in inner retina leading to edema
Neurological Soft Signs Are Not "Soft" in Brain Structure and Functional Networks: Evidence From ALE Meta-Analysis
Background: Neurological soft signs (NSS) are associated with schizophrenia and related psychotic disorders. NSS have been conventionally considered as clinical neurological signs without localized brain regions. However, recent brain imaging studies suggest that NSS are partly localizable and may be associated with deficits in specific brain areas. Method: We conducted an activation likelihood estimation meta-analysis to quantitatively review structural and functional imaging studies that evaluated the brain correlates of NSS in patients with schizophrenia and other psychotic disorders. Six structural magnetic resonance imaging (sMRI) and 15 functional magnetic -resonance imaging (fMRI) studies were included. Results: The results from meta-analysis of the sMRI studies-indicated that NSS were associated with atrophy of the precentral gyrus, the cerebellum, the inferior frontal gyrus, and the thalamus. The results from meta-analysis of the fMRI studies demonstrated that the NSS-related task was significantly associated with altered brain activation in the inferior frontal gyrus, bilateral putamen, the cerebellum, and the superior temporal gyrus. Conclusions: Ourfindings from both sMRI and fMRI meta-analyses further support the conceptualization of NSS as a manifestation of the "cerebello-thalamo-prefrontal" brain network model of schizophrenia and related psychotic disorders
Spinor Helicity and Dual Conformal Symmetry in Ten Dimensions
The spinor helicity formalism in four dimensions has become a very useful
tool both for understanding the structure of amplitudes and also for practical
numerical computation of amplitudes. Recently, there has been some discussion
of an extension of this formalism to higher dimensions. We describe a
particular implementation of the spinor-helicity method in ten dimensions.
Using this tool, we study the tree-level S-matrix of ten dimensional super
Yang-Mills theory, and prove that the theory enjoys a dual conformal symmetry.
Implications for four-dimensional computations are discussed.Comment: 24 pages, 1 figure
Commissioning of the CMS High Level Trigger
The CMS experiment will collect data from the proton-proton collisions
delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to
14 TeV. The CMS trigger system is designed to cope with unprecedented
luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger
architecture only employs two trigger levels. The Level-1 trigger is
implemented using custom electronics, while the High Level Trigger (HLT) is
based on software algorithms running on a large cluster of commercial
processors, the Event Filter Farm. We present the major functionalities of the
CMS High Level Trigger system as of the starting of LHC beams operations in
September 2008. The validation of the HLT system in the online environment with
Monte Carlo simulated data and its commissioning during cosmic rays data taking
campaigns are discussed in detail. We conclude with the description of the HLT
operations with the first circulating LHC beams before the incident occurred
the 19th September 2008
The Single-Particle density of States, Bound States, Phase-Shift Flip, and a Resonance in the Presence of an Aharonov-Bohm Potential
Both the nonrelativistic scattering and the spectrum in the presence of the
Aharonov-Bohm potential are analyzed. The single-particle density of states
(DOS) for different self-adjoint extensions is calculated. The DOS provides a
link between different physical quantities and is a natural starting point for
their calculation. The consequences of an asymmetry of the S matrix for the
generic self-adjoint extension are examined.
I. Introduction
II. Impenetrable flux tube and the density of states
III. Penetrable flux tube and self-adjoint extensions
IV. The S matrix and scattering cross sections
V. The Krein-Friedel formula and the resonance
VI. Regularization
VII. The R --> 0 limit and the interpretation of self-adjoint extensions
VIII. Energy calculations
IX. The Hall effect in the dilute vortex limit
X. Persistent current of free electrons in the plane pierced by a flux tube
XI. The 2nd virial coefficient of nonrelativistic interacting anyons
XII. Discussion of the results and open questionsComment: 68 pages, plain latex, 7 figures, 3 references and one figure added
plus a few minor text correction
A Complete Model of Low-Scale Gauge Mediation
Recent signs of a Standard Model-like Higgs at 125 GeV point towards large
A-terms in the MSSM. This presents special challenges for gauge mediation,
which by itself predicts vanishing A-terms at the messenger scale. In this
paper, we review the general problems that arise when extending gauge mediation
to achieve large A-terms, and the mechanisms that exist to overcome them. Using
these mechanisms, we construct weakly-coupled models of low-scale gauge
mediation with extended Higgs-messenger couplings that generate large A-terms
at the messenger scale and viable mu/B_mu-terms. Our models are simple,
economical, and complete realizations of supersymmetry at the weak scale.Comment: 33 pages; v2: refs added, minor change
Why Social Enterprises Are Asking to Be Multi-stakeholder and Deliberative: An Explanation around the Costs of Exclusion.
The study of multi-stakeholdership (and multi-stakeholder social enterprises in particular) is only at the start. Entrepreneurial choices which have emerged spontaneously, as well as the first legal frameworks approved in this direction, lack an adequate theoretical support. The debate itself is underdeveloped, as the existing understanding of organisations and their aims resist an inclusive, public interest view of enterprise. Our contribution aims at enriching the thin theoretical reflections on multi-stakeholdership, in a context where they are already established, i.e. that of social and personal services.
The aim is to provide an economic justification on why the governance structure and decision-making praxis of the firm needs to account for multiple stakeholders. In particular with our analysis we want: a) to consider production and the role of firms in the context of the “public interest” which may or may not coincide with the non-profit objective; b) to ground the explanation of firm governance and processes upon the nature of production and the interconnections between demand and supply side; c) to explain that the costs associated with multi-stakeholder governance and deliberation in decision-making can increase internal efficiency and be “productive” since they lower internal costs and utilise resources that otherwise would go astray.
The key insight of this work is that, differently from major interpretations, property costs should be compared with a more comprehensive range of costs, such as the social costs that emerge when the supply of social and personal services is insufficient or when the identification of aims and means is not shared amongst stakeholders. Our model highlights that when social costs derived from exclusion are high, even an enterprise with costly decisional processes, such as the multistakeholder, can be the most efficient solution amongst other possible alternatives
Observations of Milky Way Dwarf Spheroidal galaxies with the Fermi-LAT detector and constraints on Dark Matter models
We report on the observations of 14 dwarf spheroidal galaxies with the Fermi
Gamma-Ray Space Telescope taken during the first 11 months of survey mode
operations. The Fermi telescope provides a new opportunity to test particle
dark matter models through the expected gamma-ray emission produced by pair
annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf
spheroidal galaxies, the largest galactic substructures predicted by the cold
dark matter scenario, are attractive targets for such indirect searches for
dark matter because they are nearby and among the most extreme dark matter
dominated environments. No significant gamma-ray emission was detected above
100 MeV from the candidate dwarf galaxies. We determine upper limits to the
gamma-ray flux assuming both power-law spectra and representative spectra from
WIMP annihilation. The resulting integral flux above 100 MeV is constrained to
be at a level below around 10^-9 photons cm^-2 s^-1. Using recent stellar
kinematic data, the gamma-ray flux limits are combined with improved
determinations of the dark matter density profile in 8 of the 14 candidate
dwarfs to place limits on the pair annihilation cross-section of WIMPs in
several widely studied extensions of the standard model. With the present data,
we are able to rule out large parts of the parameter space where the thermal
relic density is below the observed cosmological dark matter density and WIMPs
(neutralinos here) are dominantly produced non-thermally, e.g. in models where
supersymmetry breaking occurs via anomaly mediation. The gamma-ray limits
presented here also constrain some WIMP models proposed to explain the Fermi
and PAMELA e^+e^- data, including low-mass wino-like neutralinos and models
with TeV masses pair-annihilating into muon-antimuon pairs. (Abridged)Comment: 25 pages, 4 figures, accepted to ApJ, Corresponding authors: J.
Cohen-Tanugi, C. Farnier, T.E. Jeltema, E. Nuss, and S. Profum
Detection of GD2-positive cells in bone marrow samples and survival of patients with localised neuroblastoma
The impact of bone marrow (BM) GD2-positive cells on survival has been evaluated in 145 Italian children with localised neuroblastoma (NB) evaluated at diagnosis by anti-GD2 immunocytochemistry. Nineteen of these (13.1%) were found to be BM GD2-positive, with the number of positive cells ranging between 1 and 155 out of 1 × 106 total cells analysed. Seven/19 (38.8%) GD2-positive vs 12/126 (9.5%) GD2-negative patients relapsed. The 5-year event-free survival (EFS) and overall survival of the GD2-positive patients was significantly worse than that of the GD2-negative ones (62.2 vs 89.9%, P<0.001; and 74.9 vs 95.9%, P=0.005, respectively). GD2 positivity was not associated to other known risk factors, and in particular to Myc-N amplification and 1p deletion. Among Myc-N-negative patients, the EFS of those negative for both GD2 and 1p deletion was significantly better than in children positive for either one of these two markers (EFS=96.9 vs 66.0%, P<0.001). In conclusion, GD2 positivity may represent a prognostic marker for patients with non-metastatic NB without Myc-N amplification, and its combination with genetic alterations might help identifying patients that require a more careful follow-up
A Solvable Regime of Disorder and Interactions in Ballistic Nanostructures, Part I: Consequences for Coulomb Blockade
We provide a framework for analyzing the problem of interacting electrons in
a ballistic quantum dot with chaotic boundary conditions within an energy
(the Thouless energy) of the Fermi energy. Within this window we show that the
interactions can be characterized by Landau Fermi liquid parameters. When ,
the dimensionless conductance of the dot, is large, we find that the disordered
interacting problem can be solved in a saddle-point approximation which becomes
exact as (as in a large-N theory). The infinite theory shows a
transition to a strong-coupling phase characterized by the same order parameter
as in the Pomeranchuk transition in clean systems (a spontaneous
interaction-induced Fermi surface distortion), but smeared and pinned by
disorder. At finite , the two phases and critical point evolve into three
regimes in the plane -- weak- and strong-coupling regimes separated
by crossover lines from a quantum-critical regime controlled by the quantum
critical point. In the strong-coupling and quantum-critical regions, the
quasiparticle acquires a width of the same order as the level spacing
within a few 's of the Fermi energy due to coupling to collective
excitations. In the strong coupling regime if is odd, the dot will (if
isolated) cross over from the orthogonal to unitary ensemble for an
exponentially small external flux, or will (if strongly coupled to leads) break
time-reversal symmetry spontaneously.Comment: 33 pages, 14 figures. Very minor changes. We have clarified that we
are treating charge-channel instabilities in spinful systems, leaving
spin-channel instabilities for future work. No substantive results are
change
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