433 research outputs found
Real-Time Data Processing in the Muon System of the D0 Detector
This paper presents a real-time application of the 16-bit fixed point Digital
Signal Processors (DSPs), in the Muon System of the D0 detector located at the
Fermilab Tevatron, presently the world's highest-energy hadron collider. As
part of the Upgrade for a run beginning in the year 2000, the system is
required to process data at an input event rate of 10 KHz without incurring
significant deadtime in readout. The ADSP21csp01 processor has high I/O
bandwidth, single cycle instruction execution and fast task switching support
to provide efficient multisignal processing. The processor's internal memory
consists of 4K words of Program Memory and 4K words of Data Memory. In addition
there is an external memory of 32K words for general event buffering and 16K
words of Dual Port Memory for input data queuing. This DSP fulfills the
requirement of the Muon subdetector systems for data readout. All error
handling, buffering, formatting and transferring of the data to the various
trigger levels of the data acquisition system is done in software. The
algorithms developed for the system complete these tasks in about 20
microseconds per event.Comment: 4 pages, Presented and published at the 11th IEEE NPSS Real Time
Conference, held at Santa Fe, New Mexico, USA, from June 14-18, 199
Корекція якості систем стабілізації
Considered the methods of determining the desired frequency characteristics of the stabilizationsystems of the inertial control objects while the synthesis of their corrective devicesРассмотрены способы определения желаемых частотных характеристик систем стабилизации инерционныхобъектов управления при синтезе их корректирующих устройствРозглянуто способи визначення бажаних частотних характеристик систем стабілізації інерційних об’єктів керування під час синтезу їх коригувальних пристрої
Transverse Demagnetization Dynamics of a Unitary Fermi Gas
Understanding the quantum dynamics of strongly interacting fermions is a
problem relevant to diverse forms of matter, including high-temperature
superconductors, neutron stars, and quark-gluon plasma. An appealing benchmark
is offered by cold atomic gases in the unitary limit of strong interactions.
Here we study the dynamics of a transversely magnetized unitary Fermi gas in an
inhomogeneous magnetic field. We observe the demagnetization of the gas, caused
by diffusive spin transport. At low temperatures, the diffusion constant
saturates to the conjectured quantum-mechanical lower bound ,
where is the particle mass. The development of pair correlations,
indicating the transformation of the initially non-interacting gas towards a
unitary spin mixture, is observed by measuring Tan's contact parameter.Comment: 8 pages, 6 figures. Accepted versio
Liquid Crystal-Solid Interface Structure at the Antiferroelectric-Ferroelectric Phase Transition
Total Internal Reflection (TIR) is used to probe the molecular organization
at the surface of a tilted chiral smectic liquid crystal at temperatures in the
vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are
interpreted using an exact analytical solution of a real model for
ferroelectric order at the surface. In the mixture T3, ferroelectric surface
order is expelled with the bulk ferroelectric-antiferroelectric transition. The
conditions for ferroelectric order at the surface of an antiferroelectric bulk
are presented
Insecticidal activities of diketopiperazines of Nomuraea rileyi entomopathogenic fungus
Entomopathogenic fungi are fungal organisms extensively used in various parts of the world as biopesticides against insect pests that cause important economic damage. Various secondary metabolites produced by these fungi have many potential biological activities. The present study was undertaken to evaluate the insecticidal activity of extracts and pure compounds from Nomuraea rileyi (Farlow) Samson entomopathogenic fungi against Spodoptera frugiperda Smith (Lepidoptera), Ceratitis capitata Wiedemann (Diptera) and Tribolium castaneum Herbst (Coleoptera), three insect pests that generate serious economic losses in the northwest of Argentina. Diketopiperazines were extracted from the culture free supernatant of the media with ethyl acetate. Antifeedant properties were detected in all extracts under dietary choice conditions (300 ug/ g of diet). The maximum antifeedant activity was noted in cycles (Pro-Val) (86.02) and cycle (Pro-Phe) (73.47), while the rest of the extracts and metabolites exhibited varying degrees of moderate or less toxic effects. The maximum oviposition deterrence against C. capitata (55.86%) was recorded with cycle (Pro-Phe) at a 50 µm/cm2 dose. Culture medium extracts supplemented with insect remains and all pure compounds showed repellent action against T. castaneum. The main repellency was observed in phenylacetic acid and cycle (Pro-Val) with RI values of 42 and 41% respectively. The present study would suggest the possible utilization of entomopathogenic fungal metabolites as an effective agent for controlling insect pests that cause important economic losses
Levosimendan increases brain tissue oxygen levels after cardiopulmonary resuscitation independent of cardiac function and cerebral perfusion
Prompt reperfusion is important to rescue ischemic tissue; however, the process itself presents a key pathomechanism that contributes to a poor outcome following cardiac arrest. Experimental data have suggested the use of levosimendan to limit ischemia–reperfusion injury by improving cerebral microcirculation. However, recent studies have questioned this effect. The present study aimed to investigate the influence on hemodynamic parameters, cerebral perfusion and oxygenation following cardiac arrest by ventricular fibrillation in juvenile male pigs. Following the return of spontaneous circulation (ROSC), animals were randomly assigned to levosimendan (12 µg/kg, followed by 0.3 µg/kg/min) or vehicle treatment for 6 h. Levosimendan-treated animals showed significantly higher brain PbtO(2) levels. This effect was not accompanied by changes in cardiac output, preload and afterload, arterial blood pressure, or cerebral microcirculation indicating a local effect. Cerebral oxygenation is key to minimizing damage, and thus, current concepts are aimed at improving impaired cardiac output or cerebral perfusion. In the present study, we showed that NIRS does not reliably detect low PbtO(2) levels and that levosimendan increases brain oxygen content. Thus, levosimendan may present a promising therapeutic approach to rescue brain tissue at risk following cardiac arrest or ischemic events such as stroke or traumatic brain injury
Distributed and dynamic modelling of hydrology, phosphorus and ecology in the Hampshire Avon and Blashford Lakes: evaluating alternative strategies to meet WFD standards.
The issues of diffuse and point source phosphorus (P) pollution in the Hampshire Avon and Blashford Lakes are explored using a catchment model of the river system. A multibranch, process based, dynamic water quality model (INCA-P) has been applied to the whole river system to simulate water fluxes, total phosphorus (TP) and soluble reactive phosphorus (SRP) concentrations and ecology. The model has been used to assess impacts of both agricultural runoff and point sources from waste water treatment plants (WWTPs) on water quality. The results show that agriculture contributes approximately 40% of the phosphorus load and point sources the other 60% of the load in this catchment. A set of scenarios have been investigated to assess the impacts of alternative phosphorus reduction strategies and it is shown that a combined strategy of agricultural phosphorus reduction through either fertiliser reductions or better phosphorus management together with improved treatment at WWTPs would reduce the SRP concentrations in the river to acceptable levels to meet the EU Water Framework Directive (WFD) requirements. A seasonal strategy for WWTP phosphorus reductions would achieve significant benefits at reduced cost
Quantum transport in ultracold atoms
Ultracold atoms confined by engineered magnetic or optical potentials are
ideal systems for studying phenomena otherwise difficult to realize or probe in
the solid state because their atomic interaction strength, number of species,
density, and geometry can be independently controlled. This review focuses on
quantum transport phenomena in atomic gases that mirror and oftentimes either
better elucidate or show fundamental differences with those observed in
mesoscopic and nanoscopic systems. We discuss significant progress in
performing transport experiments in atomic gases, contrast similarities and
differences between transport in cold atoms and in condensed matter systems,
and survey inspiring theoretical predictions that are difficult to verify in
conventional setups. These results further demonstrate the versatility offered
by atomic systems in the study of nonequilibrium phenomena and their promise
for novel applications.Comment: 24 pages, 7 figures. A revie
Theory and applications of atomic and ionic polarizabilities
Atomic polarization phenomena impinge upon a number of areas and processes in
physics. The dielectric constant and refractive index of any gas are examples
of macroscopic properties that are largely determined by the dipole
polarizability. When it comes to microscopic phenomena, the existence of
alkaline-earth anions and the recently discovered ability of positrons to bind
to many atoms are predominantly due to the polarization interaction. An
imperfect knowledge of atomic polarizabilities is presently looming as the
largest source of uncertainty in the new generation of optical frequency
standards. Accurate polarizabilities for the group I and II atoms and ions of
the periodic table have recently become available by a variety of techniques.
These include refined many-body perturbation theory and coupled-cluster
calculations sometimes combined with precise experimental data for selected
transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index
measurements in microwave cavities, ab initio calculations of atomic structures
using explicitly correlated wave functions, interferometry with atom beams, and
velocity changes of laser cooled atoms induced by an electric field. This
review examines existing theoretical methods of determining atomic and ionic
polarizabilities, and discusses their relevance to various applications with
particular emphasis on cold-atom physics and the metrology of atomic frequency
standards.Comment: Review paper, 44 page
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