1,427 research outputs found
Evidence for a role for the group I metabotropic glutamate receptor in the inhibitory effect of tumor necrosis factor-α on long-term potentiation
Pro-inflammatory cytokines are known to be elevated in several neuropathological states
that are associated with learning and memory. We have previously demonstrated in our
laboratory that the inhibition of long-term potentiation (LTP) in the dentate gyrus region of
the rat hippocampus, by tumor necrosis factor (TNF)-α, represents a biphasic response, an
early phase dependent on p38 mitogen activated protein kinase (MAPK) activation and a
later phase, possible dependent on protein synthesis. Many of the factors involved in the
early modulation of LTP by TNF-α have yet to be elucidated. This study investigated if
metabotropic glutamate receptors (mGluRs) are functionally linked to the inhibitory effect of
TNF-α on LTP in the rat dentate gyrus in vitro. We report that the impairment of early-LTP by
TNF-α is significantly attenuated by prior application of the group I/II mGluR antagonist
MCPG and more specifically the mGluR5 antagonist MPEP. Since TNF-α is now known to
cause transient increases in intracellular Ca2+ levels from ryanodine-sensitive stores, we
explored the possibility that disruption of intracellular Ca2+ homeostasis could be involved.
Ryanodine was found to significantly reverse the inhibition of LTP by TNF-α. From these
studies we propose that the TNF-α inhibition of LTP is dependent upon the activation of
TNFR1 and mGlu5-receptors. Importantly this study provides the first proof of the
involvement of ryanodine-sensitive intracellular Ca2+ stores in TNF-α mediated inhibition
of LTP
Innovate with Complex Information Technologies: A Theoretical Model and Empirical Examination
Complex information technologies (CITs), such as ERP packages, have become the core component of modern organizations. Corporate investments in CITs have soared to a record high. Firms need to creatively apply the technologies in order to adapt to the ever-changing environments and realize the full potential of the technologies. We approach this issue from the perspective of ‘Innovate with IT’, a post-acceptance usage behavior that describes innovative use of information technologies to support individual task performances. Drawing upon the IS Continuance (ISC) model, as well as the managerial and individual factors that facilitate higher level IT use, a model is theoretically developed to understand employees’ novel use of CITs. A field study was conducted in a large manufacturing firm using ERP packages to empirically validate the model. The results suggest that the ISC model, personal propensity toward IT innovations, and management support jointly nurture employees’ creative use of complex technologies
Sources of Differences in On-Orbit Total Solar Irradiance Measurements and Description of Proposed Laboratory Intercomparison
There is a 5 W/sq m (about 0.35 %) difference between current on-orbit Total Solar Irradiance (TSI) measurements. On 18-20 July 2005, a workshop was held at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland that focused on understanding possible reasons for this difference, through an examination of the instrument designs, calibration approaches, and appropriate measurement equations. The instruments studied in that workshop included the Active Cavity Radiometer Irradiance Monitor III (ACRIM III) on the Active Cavity Radiometer Irradiance Monitor SATellite (ACRIMSAT), the Total Irradiance Monitor (TIM) on the Solar Radiation and Climate Experiment (SORCE), the Variability of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and Heliospheric Observatory (SOHO), and the Earth Radiation Budget Experiment (ERBE) on the Earth Radiation Budget Satellite (ERBS). Presentations for each instrument included descriptions of its design, its measurement equation and uncertainty budget, and the methods used to assess on-orbit degradation. The workshop also included a session on satellite- and ground-based instrument comparisons and a session on laboratory-based comparisons and the application of new laboratory comparison techniques. The workshop has led to investigations of the effects of diffraction and of aperture area measurements on the differences between instruments. In addition, a laboratory-based instrument comparison is proposed that uses optical power measurements (with lasers that underEll the apertures of the TSI instruments), irradiance measurements (with lasers that overfill the apertures of the TSI instrument), and a cryogenic electrical substitution radiometer as a standard for comparing the instruments. A summary of the workshop and an overview of the proposed research efforts are presented here
Weak Liouville-Arnold Theorems & Their Implications
This paper studies the existence of invariant smooth Lagrangian graphs for
Tonelli Hamiltonian systems with symmetries. In particular, we consider Tonelli
Hamiltonians with n independent but not necessarily involutive constants of
motion and obtain two theorems reminiscent of the Liouville-Arnold theorem.
Moreover, we also obtain results on the structure of the configuration spaces
of such systems that are reminiscent of results on the configuration space of
completely integrable Tonelli Hamiltonians.Comment: 24 pages, 1 figure; v2 corrects typo in online abstract; v3 includes
new title (was: A Weak Liouville-Arnold Theorem), re-arrangement of
introduction, re-numbering of main theorems; v4 updates the authors' email
and physical addresses, clarifies notation in section 4. Final versio
Structural and magnetic properties of Fe/ZnSe(001) interfaces
We have performed first principles electronic structure calculations to
investigate the structural and magnetic properties of Fe/ZnSe(001) interfaces.
Calculations involving full geometry optimizations have been carried out for a
broad range of thickness of Fe layers(0.5 monolayer to 10 monolayers) on top of
a ZnSe(001) substrate. Both Zn and Se terminated interfaces have been explored.
Total energy calculations show that Se segregates at the surface which is in
agreement with recent experiments.
For both Zn and Se terminations, the interface Fe magnetic moments are higher
than the bulk bcc Fe moment.
We have also investigated the effect of adding Fe atoms on top of a
reconstructed ZnSe surface to explore the role of reconstruction of
semiconductor surfaces in determining properties of metal-semiconductor
interfaces. Fe breaks the Se dimer bond formed for a Se-rich (2x1)
reconstructed surface. Finally, we looked at the reverse growth i.e. growth of
Zn and Se atoms on a bcc Fe(001) substrate to investigate the properties of the
second interface of a magnetotunnel junction. The results are in good agreement
with the theoretical and experimental results, wherever available.Comment: 7 pages, 8 figures, accepted for publication in PR
Formation of the Xigaze Metamorphic Sole under Tibetan continental lithosphere reveals generic characteristics of subduction initiation
Metamorphic soles found under allochthonous oceanic lithosphere, or ophiolites, are interpreted as derived from lower plate oceanic crust material accreted to upper plate mantle during intraoceanic subduction initiation. Their metamorphic evolution is inferred to reflect the thermal structure at the site of subduction nucleation, with granulite-bearing soles linked to initiation at hot spreading centers. Here we present garnet Lu-Hf geochronology for the granulite-bearing sole of the Xigaze ophiolite in South Tibet, whose oceanic crust formed ∼130 Ma through continental forearc extension. Our study shows that sole metamorphism was ongoing by 144 Ma, implying that north-directed subduction began at least 14 million years before oceanic forearc spreading. The upper plate at the time of subduction initiation was thus continental, not oceanic. Our results demonstrate that metamorphic characteristics of soles are independent of the specific tectonic setting at the subduction nucleation site and rather provide generic constraints on the subduction initiation process
The Centurion 18 telescope of the Wise Observatory
We describe the second telescope of the Wise Observatory, a 0.46-m Centurion
18 (C18) installed in 2005, which enhances significantly the observing
possibilities. The telescope operates from a small dome and is equipped with a
large-format CCD camera. In the last two years this telescope was intensively
used in a variety of monitoring projects.
The operation of the C18 is now automatic, requiring only start-up at the
beginning of a night and close-down at dawn. The observations are mostly
performed remotely from the Tel Aviv campus or even from the observer's home.
The entire facility was erected for a component cost of about 70k$ and a labor
investment of a total of one man-year.
We describe three types of projects undertaken with this new facility: the
measurement of asteroid light variability with the purpose of determining
physical parameters and binarity, the following-up of transiting extrasolar
planets, and the study of AGN variability. The successful implementation of the
C18 demonstrates the viability of small telescopes in an age of huge
light-collectors, provided the operation of such facilities is very efficient.Comment: 16 pages, 13 figures, some figures quality was degraded, accepted for
publication in Astrophysics and Space Scienc
Nonmonotonic inelastic tunneling spectra due to surface spin excitations in ferromagnetic junctions
The paper addresses inelastic spin-flip tunneling accompanied by surface spin
excitations (magnons) in ferromagnetic junctions. The inelastic tunneling
current is proportional to the magnon density of states which is
energy-independent for the surface waves and, for this reason, cannot account
for the bias-voltage dependence of the observed inelastic tunneling spectra.
This paper shows that the bias-voltage dependence of the tunneling spectra can
arise from the tunneling matrix elements of the electron-magnon interaction.
These matrix elements are derived from the Coulomb exchange interaction using
the itinerant-electron model of magnon-assisted tunneling. The results for the
inelastic tunneling spectra, based on the nonequilibrium Green's function
calculations, are presented for both parallel and antiparallel magnetizations
in the ferromagnetic leads.Comment: 9 pages, 4 figures, version as publishe
Seabird sensitivity mapping tool: project report [issue number 3]
This project builds upon the existing evidence base for seabird habitat use at sea to develop a fast, user-friendly tool to estimate the sensitivities of key seabird species to ORDs in all British Isles shelf seas. The tool produces estimates for the sensitivity and exposure of all at sea locations in UK waters for 13 seabird species (Atlantic puffin, Common guillemot, Razorbill, Black-legged kittiwake, European shag, European storm petrel, Great skua, Herring gull, Lesser black-backed gull, Northern gannet, Northern fulmar, Great black-backed gull and Red-throated diver) in both the breeding and non-breeding seasons, based on GPS tracking and at sea survey data
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