3,117 research outputs found
Interpretation of High Energy String Scattering in terms of String Configurations
High energy string scattering at fixed momentum transfer, known to be
dominated by Regge trajectory exchange, is interpreted by identifying families
of string states which induce each type of trajectory exchange. These include
the usual leading trajectory and its daughters as
well as the ``sister'' trajectories and their
daughters. The contribution of the sister to high energy scattering
is dominated by string excitations in the mode. Thus, at large ,
string scattering is dominated by wee partons, consistently with a picture of
string as an infinitely composite system of ``constituents'' which carry zero
energy and momentum.Comment: 14 pages, phyzzx, psfig required, Florida Preprint UFIFT-94-
Radiolytic corrosion and related problems in the cooling water circuits of high-energy particle accelerators
Photoluminescence and Terahertz Emission from Femtosecond Laser-Induced Plasma Channels
Luminescence as a mechanism for terahertz emission from femtosecond
laser-induced plasmas is studied. By using a fully microscopic theory, Coulomb
scattering between electrons and ions is shown to lead to luminescence even for
a spatially homogeneous plasma. The spectral features introduced by the rod
geometry of laser-induced plasma channels in air are discussed on the basis of
a generalized mode-function analysis.Comment: 4 pages with 2 figures
An infrared study of the double nucleus in NGC3256
We present new resolved near and mid-IR imaging and N-band spectroscopy of
the two nuclei in the merger system NGCA3256, the most IR luminous galaxy in
the nearby universe. The results from the SED fit to the data are consistent
with previous estimates of the amount of obscuration towards the nuclei and the
nuclear star formation rates. However, we also find substantial differences in
the infrared emission from the two nuclei which cannot be explained by
obscuration alone. We conclude that the northern nucleus requires an additional
component of warm dust in order to explain its properties. This suggests that
local starforming conditions can vary significantly within the environment of a
single system.Comment: Accepted for publication (MNRAS
Influence of Coulomb and Phonon Interaction on the Exciton Formation Dynamics in Semiconductor Heterostructures
A microscopic theory is developed to analyze the dynamics of exciton
formation out of incoherent carriers in semiconductor heterostructures. The
carrier Coulomb and phonon interaction is included consistently. A cluster
expansion method is used to systematically truncate the hierarchy problem. By
including all correlations up to the four-point (i.e. two-particle) level, the
fundamental fermionic substructure of excitons is fully included. The analysis
shows that the exciton formation is an intricate process where Coulomb
correlations rapidly build up on a picosecond time scale while phonon dynamics
leads to true exciton formation on a slow nanosecond time scale.Comment: 18 pages, 7 figure
Renal disease in nail-patella syndrome: Clinical and morphologic studies
Renal disease in nail-patella syndrome: Clinical and morphological studies. Clinical and morphological features of seven patients with the nail-patella syndrome are described. Progression to renal failure after a prolonged period of asymptomatic proteinuria is reported. Kidney tissue from these seven patients studied by light, immunofluorescent and electron microscopy demonstrated abnormalities characteristic of this disease. Focal glomerular basement membrane thickening was observed by light microscopy. Immunofluorescent microscopy showed focal glomerular basement membrane and arteriolar staining with serum proteins, predominantly IgM and β1C. Electron microscopy revealed markedly abnormal glomerular basement membranes containing bundles of cross-striated fibrils. These fibrils were more readily demonstrated in phosphotungstic acid-stained sections. The data presented suggest that the inborn error of connective tissue metabolism of the nail-patella syndrome is associated with renal disease as the result of deposition of collagen moieties in glomerular basement membranes with subsequent alterations of glomerular structure and function
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