3,729 research outputs found
Vector modulation instability induced by vacuum fluctuations in highly birefringent fibers in the anomalous dispersion regime
We report a detailed experimental study of vector modulation instability in
highly birefringent optical fibers in the anomalous dispersion regime. We prove
that the observed instability is mainly induced by vacuum fluctuations. The
detuning of the spectral peaks agrees with linear perturbation analysis. The
exact shape of the spectrum is well reproduced by numerical integration of
stochastic nonlinear Schrodinger equations describing quantum propagation.Comment: 11 pages, 4 figures, to be published in Optics Letter
Boundary String Field Theory of the DDbar System
We develop the boundary string field theory approach to tachyon condensation
on the DDbar system. Particular attention is paid to the gauge fields, which
combine with the tachyons in a natural way. We derive the RR-couplings of the
system and express the result in terms of Quillen's superconnection. The result
is related to an index theorem, and is thus shown to be exact.Comment: 38 pages, harvmac. v2: added reference
Dual Descriptions of SO(10) SUSY Gauge Theories with Arbitrary Numbers of Spinors and Vectors
We examine the low energy structure of N=1 supersymmetric SO(10) gauge theory
with matter chiral superfields in N_Q spinor and N_f vector representations. We
construct a dual to this model based upon an SU(N_f+2N_Q-7) x Sp(2N_Q-2) gauge
group without utilizing deconfinement methods. This product theory generalizes
all previously known Pouliot-type duals to SO(N_c) models with spinor and
vector matter. It also yields large numbers of new dual pairs along various
flat directions. The dual description of the SO(10) theory satisfies multiple
consistency checks including an intricate renormalization group flow analysis
which links it with Seiberg's duality transformations. We discuss its
implications for building grand unified theories that contain all Standard
Model fields as composite degrees of freedom.Comment: 36 pages, harvmac and tables macros, 1 figur
NADPH Oxidase 5 Is a ProâContractile Nox Isoform and a Point of CrossâTalk for Calcium and Redox SignalingâImplications in Vascular Function
Background
NADPH Oxidase 5 (Nox5) is a calciumâsensitive superoxideâgenerating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in proâcontractile signaling and vascular function.
Methods and Results
Transgenic mice expressing human Nox5 in a vascular smooth muscle cellâspecific manner (Nox5 mice) and Rhodnius prolixus, an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5âexpressing mice, agonistâinduced vasoconstriction was exaggerated and endotheliumâdependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by Nâacetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca2+]i, increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of proâcontractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wildâtype and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus, gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor).
Conclusions
Nox5 is a proâcontractile Nox isoform important in redoxâsensitive contraction. This involves calciumâcalmodulin and endoplasmic reticulumâregulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the proâcontractile molecular machinery in vascular smooth muscle cells
Digital technology and governance in transition: The case of the British Library
Comment on the organizational consequences of the new information and communications technologies (ICTs) is pervaded by a powerful imagery of disaggregation and a tendency for ?virtual? forms of production to be seen as synonymous with the ?end? of bureaucracy. This paper questions the underlying assumptions of the ?virtual organization?, highlighting the historically enduring, diversified character of the bureaucratic form. The paper then presents case study findings on the web-based access to information resources now being provided by the British Library (BL). The case study evidence produces two main findings. First, radically decentralised virtual forms of service delivery are heavily dependent on new forms of capacity-building and information aggregation. Second, digital technology is embedded in an inherently contested and contradictory context of institutional change. Current developments in the management and control of digital rights are consistent with the commodification of the public sphere. However, the evidence also suggests that scholarly access to information resources is being significantly influenced by the ?information society? objectives of the BL and other institutional players within the network of UK research libraries
NADPH oxidase 5 is a proâcontractile Nox isoform and a point of crossâtalk for calcium and redox signalingâimplications in vascular function
Background:
NADPH Oxidase 5 (Nox5) is a calciumâsensitive superoxideâgenerating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in proâcontractile signaling and vascular function.
Methods and Results:
Transgenic mice expressing human Nox5 in a vascular smooth muscle cellâspecific manner (Nox5 mice) and Rhodnius prolixus, an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5âexpressing mice, agonistâinduced vasoconstriction was exaggerated and endotheliumâdependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by Nâacetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca2+]i, increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of proâcontractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wildâtype and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus, gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor).
Conclusions:
Nox5 is a proâcontractile Nox isoform important in redoxâsensitive contraction. This involves calciumâcalmodulin and endoplasmic reticulumâregulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the proâcontractile molecular machinery in vascular smooth muscle cells
Space-based research in fundamental physics and quantum technologies
Space-based experiments today can uniquely address important questions
related to the fundamental laws of Nature. In particular, high-accuracy physics
experiments in space can test relativistic gravity and probe the physics beyond
the Standard Model; they can perform direct detection of gravitational waves
and are naturally suited for precision investigations in cosmology and
astroparticle physics. In addition, atomic physics has recently shown
substantial progress in the development of optical clocks and atom
interferometers. If placed in space, these instruments could turn into powerful
high-resolution quantum sensors greatly benefiting fundamental physics.
We discuss the current status of space-based research in fundamental physics,
its discovery potential, and its importance for modern science. We offer a set
of recommendations to be considered by the upcoming National Academy of
Sciences' Decadal Survey in Astronomy and Astrophysics. In our opinion, the
Decadal Survey should include space-based research in fundamental physics as
one of its focus areas. We recommend establishing an Astronomy and Astrophysics
Advisory Committee's interagency ``Fundamental Physics Task Force'' to assess
the status of both ground- and space-based efforts in the field, to identify
the most important objectives, and to suggest the best ways to organize the
work of several federal agencies involved. We also recommend establishing a new
NASA-led interagency program in fundamental physics that will consolidate new
technologies, prepare key instruments for future space missions, and build a
strong scientific and engineering community. Our goal is to expand NASA's
science objectives in space by including ``laboratory research in fundamental
physics'' as an element in agency's ongoing space research efforts.Comment: a white paper, revtex, 27 pages, updated bibliograph
The Internet for weight control in an obese sample: results of a randomised controlled trial
Rising levels of obesity coupled with the limited success of currently available weight control methods highlight the need for investigation of novel approaches to obesity treatment. This study aims to determine the effectiveness and cost-effectiveness of an Internet-based resource for obesity management
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