87,922 research outputs found
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GRIDCC - Providing a real-time grid for distributed instrumentation
The GRIDCC project is extending the use of Grid computing to include access to and control of distributed instrumentation.
Access to the instruments will be via an interface to a Virtual Instrument Grid Service (VIGS). VIGS is a new concept and its design and implementation, together
with middleware that can provide the appropriate Quality of Service (QoS), is a key part of the GRIDCC development plan. An overall architecture for GRIDCC has been
defined and some of the application areas, which include distributed power systems, remote control of an accelerator and the remote monitoring of a large particle physics
experiment, are briefly discussed.E
In situ growth regime characterization of cubic GaN using reflection high energy electron diffraction
Cubic GaN layers were grown by plasma-assisted molecular beam epitaxy on
3C-SiC (001)substrates. In situ reflection high energy electron diffraction was
used to quantitatively determine the Ga coverage of the GaN surface during
growth. Using the intensity of the electron beam as a probe,optimum growth
conditions of c-GaN were found when a 1 ML Ga coverage is formed at the
surface. 1 micrometer thick c-GaN layers had a minimum surface roughness of 2.5
nm when a Ga coverage of 1 ML was established during growth. These samples
revealed also a minimum full width at half maximum of the (002)rocking curve.Comment: 3pages with 4 figure
Fineâscale measurement of diffusivity in a microbial mat with nuclear magnetic resonance imaging
Noninvasive 1Hânuclear magnetic resonance (NMR) imaging was used to investigate the diffusive properties of microbial mats in two dimensions. Pulsed field gradient NMR was used to acquire images of the H2O diffusion coefficient, Ds, and multiecho imaging NMR was used to obtain images of the water density in two structurally different microbial mats sampled from Solar Lake (Egypt). We found a pronounced lateral and vertical variability of both water density and water diffusion coefficient, correlated with the laminated and heterogeneous distribution of microbial cells and exopolymers within the mats. The average water density varied from 0.5 to 0.9, whereas the average water diffusion coefficient ranged from 0.4 to 0.9 relative to the values obtained in the stagnant water above the mat samples. The apparent water diffusivities estimated from NMR imaging compared well to apparent O2 diffusivities measured with a diffusivity microsensor. Analysis of measured O2 concentration profiles with a diffusionâreaction model showed that both the magnitude of calculated rates and the depth distribution of calculated O2 consumption/production zones changed when the observed variations of diffusivity were taken into account. With NMR imaging, diffusivity can be determined at high spatial resolution, which can resolve inherent lateral and vertical heterogeneities found in most natural benthic systems
Continuous variable entanglement measurement without phase locking
A new simple entanglement measurement method is proposed for the bright EPR
beams generated from a non-degenerate optical parametric amplifier operating at
deamplification. Due to the output signal and idler modes are frequency
degenerate and in phase, the needed phase shift of interference for the
measurement of the correlated phase quadratures and anti-correlated amplitude
quadratures can be accomplished by a quarter-wave plate and a half wave plate
without separating the signal and idler beam. Therefore, phase locking and
local oscillators are avoided.Comment: 8 pages,3 figure
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Apical endosomes isolated from kidney collecting duct principal cells lack subunits of the proton pumping ATPase.
Endocytic vesicles that are involved in the vasopressin-stimulated recycling of water channels to and from the apical membrane of kidney collecting duct principal cells were isolated from rat renal papilla by differential and Percoll density gradient centrifugation. Fluorescence quenching measurements showed that the isolated vesicles maintained a high, HgCl2-sensitive water permeability, consistent with the presence of vasopressin-sensitive water channels. They did not, however, exhibit ATP-dependent luminal acidification, nor any N-ethylmaleimide-sensitive ATPase activity, properties that are characteristic of most acidic endosomal compartments. Western blotting with specific antibodies showed that the 31- and 70-kD cytoplasmically oriented subunits of the vacuolar proton pump were not detectable in these apical endosomes from the papilla, whereas they were present in endosomes prepared in parallel from the cortex. In contrast, the 56-kD subunit of the proton pump was abundant in papillary endosomes, and was localized at the apical pole of principal cells by immunocytochemistry. Finally, an antibody that recognizes the 16-kD transmembrane subunit of oat tonoplast ATPase cross-reacted with a distinct 16-kD band in cortical endosomes, but no 16-kD band was detectable in endosomes from the papilla. This antibody also recognized a 16-kD band in affinity-purified H+ ATPase preparations from bovine kidney medulla. Therefore, early endosomes derived from the apical plasma membrane of collecting duct principal cells fail to acidify because they lack functionally important subunits of a vacuolar-type proton pumping ATPase, including the 16-kD transmembrane domain that serves as the proton-conducting channel, and the 70-kD cytoplasmic subunit that contains the ATPase catalytic site. This specialized, non-acidic early endosomal compartment appears to be involved primarily in the hormonally induced recycling of water channels to and from the apical plasma membrane of vasopressin-sensitive cells in the kidney collecting duct
All-Optical Ultrafast Control and Read-Out of a Single Negatively Charged Self-Assembled InAs Quantum Dot
We demonstrate the all-optical ultrafast manipulation and read-out of optical
transitions in a single negatively charged self-assembled InAs quantum dot, an
important step towards ultrafast control of the resident spin. Experiments
performed at zero magnetic field show the excitation and decay of the trion
(negatively charged exciton) as well as Rabi oscillations between the electron
and trion states. Application of a DC magnetic field perpendicular to the
growth axis of the dot enables observation of a complex quantum beat structure
produced by independent precession of the ground state electron and the excited
state heavy hole spins
Optimal control of predictive mean-field equations and applications to finance
We study a coupled system of controlled stochastic differential equations
(SDEs) driven by a Brownian motion and a compensated Poisson random measure,
consisting of a forward SDE in the unknown process and a
\emph{predictive mean-field} backward SDE (BSDE) in the unknowns . The driver of the BSDE at time may depend not just upon the
unknown processes , but also on the predicted future
value , defined by the conditional expectation . \\ We give a sufficient and a necessary
maximum principle for the optimal control of such systems, and then we apply
these results to the following two problems:\\ (i) Optimal portfolio in a
financial market with an \emph{insider influenced asset price process.} \\ (ii)
Optimal consumption rate from a cash flow modeled as a geometric It\^ o-L\'
evy SDE, with respect to \emph{predictive recursive utility}
Status of Zero Degree Calorimeter for CMS Experiment
The Zero Degree Calorimeter (ZDC) is integral part of the CMS experiment,
especially, for heavy ion studies. The design of the ZDC includes two
independent calorimeter sections: an electromagnetic section and a hadronic
section. Sampling calorimeters using tungsten and quartz fibers have been
chosen for the energy measurements. An overview of the ZDC is presented along
with a current status of calorimeter's preparation for Day 1 of LHC.Comment: 8 pages, 5 figures, 1 table, to appear in the proceedings of CALOR06,
June 5-9, 2006 Chicago, US
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