8,000 research outputs found
Flash of photons from the early stage of heavy-ion collisions
The dynamics of partonic cascades may be an important aspect for particle
production in relativistic collisions of nuclei at CERN SPS and BNL RHIC
energies. Within the Parton-Cascade Model, we estimate the production of single
photons from such cascades due to scattering of quarks and gluons q g -> q
gamma, quark-antiquark annihilation q qbar -> g gamma, or gamma gamma, and from
electromagnetic brems-strahlung of quarks q -> q gamma. We find that the latter
QED branching process plays the dominant role for photon production, similarly
as the QCD branchings q -> q g and g -> g g play a crucial role for parton
multiplication. We conclude therefore that photons accompanying the parton
cascade evolution during the early stage of heavy-ion collisions shed light on
the formation of a partonic plasma.Comment: 4 pages including 3 postscript figure
Quantum Field Kinetics
Using the general framework of quantum field theory, we derive basic
equations of quantum field kinetics. The main goal of this approach is to
compute the observables associated with a quark-gluon plasma at different
stages of its evolution. We start by rewriting the integral equations for the
field correlators in different forms, depending on the relevant dynamical
features at each different stage. Next, two versions of perturbation expansion
are considered. The first is best suited for the calculation of electromagnetic
emission from chaotic, but not equilibrated, strongly interacting matter. The
second version allows one to derive evolution equations, which are
generalizations of the familiar QCD evolution equations, and provide a basis
for the calculation of the initial quark and gluon distributions after the
first hard interaction of the heavy ions.Comment: 13 pages, REVTeX, 2 postscript figures appende
Reflection and interference of electromagnetic waves in inhomogeneous media
Solutions were obtained of the wave equation for a plane horizontally polarized electro-magnetic wave incident on a semi infinite two dimensional inhomogeneous medium. Two problems were considered: An inhomogeneous half space, and an inhomogeneous layer of arbitrary thickness. Solutions of the wave equation were obtained in terms of Hankel functions with complex arguments. Numerical calculations were made of the reflection coefficient R at the interface of the homogeneous medium. The startling results show that the reflection coefficient for a complex dielectric constant with gradient, can be less than that of the same medium with zero gradient
Space station integrated wall design and penetration damage control. Task 3: Theoretical analysis of penetration mechanics
The efforts to provide a penetration code called PEN4 version 10 is documented for calculation of projectile and target states for the impact of 2024-T3 aluminum, R sub B 90 1018 steel projectiles and icy meteoroids onto 2024-T3 aluminum plates at impact velocities from 0 to 16 km/s. PEN4 determines whether a plate is perforated by calculating the state of fragmentation of projectile and first plate. Depth of penetration into the second to n sup th plate by fragments resulting from first plate perforation is determined by multiple cratering. The results from applications are given
Help Our Young Folks Help Themselves
What kind of recreation and entertainment do rural young people between the ages of 16 and 25 enjoy most? And do the activities now available to rural young people satisfy their needs
Analysis of reaction dynamics at RHIC in a combined parton/hadron transport approach
We introduce a transport approach which combines partonic and hadronic
degrees of freedom on an equal footing and discuss the resulting reaction
dynamics. The initial parton dynamics is modeled in the framework of the parton
cascade model, hadronization is performed via a cluster hadronization model and
configuration space coalescence, and the hadronic phase is described by a
microscopic hadronic transport approach. The resulting reaction dynamics
indicates a strong influence of hadronic rescattering on the space-time pattern
of hadronic freeze-out and on the shape of transverse mass spectra. Freeze-out
times and transverse radii increase by factors of 2 - 3 depending on the hadron
species.Comment: 10 pages, 4 eps figures include
Shaping Intellectual Property Rights through Human Rights Adjudication: The Example of the European Court of Human Rights
Shaping Intellectual Property Rights through Human Rights Adjudication: The Example of the European Court of Human Rights
Biochemistry and functional aspects of human glandular kallikreins
Human urinary kallikrein was purified by gel filtration on Sephacryl S-200 and affinity chromatography on aprotinin-Sepharose, followed by ion exchange chromatography on DEAE-Sepharose. In dodecylsulfate gel electrophoresis two protein bands with molecular weights of 41,000 and 34,000 were separated. The amino acid composition and the carbohydrate content of the kallikrein preparation were determined; isoleucine was identified as the only aminoterminal amino acid. The bimolecular velocity constant for the inhibition by diisopropyl fluorophosphate was determined as 9±2 l mol–1 min–1. The hydrolysis of a number of substrates was investigated and AcPheArgOEt was found to be the most sensitive substrate for human urinary kallikrein. Using this substrate an assay method for kallikrein in human urine was developed.
It was shown by radioimmunoassay that pig pancreatic kallikrein can be absorbed in the rat intestinal tract. Furthermore, in dogs the renal excretion of glandular kallikrein from blood was demonstrated by radioimmunological methods
Inelastic Multiple Scattering of Interacting Bosons in Weak Random Potentials
We develop a diagrammatic scattering theory for interacting bosons in a
three-dimensional, weakly disordered potential. We show how collisional energy
transfer between the bosons induces the thermalization of the inelastic
single-particle current which, after only few collision events, dominates over
the elastic contribution described by the Gross-Pitaevskii ansatz.Comment: 5 pages, 3 figures, very close to published versio
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