1,499 research outputs found
The Standard Quantum Limit of Coherent Beam Combining
Coherent beam combining refers to the process of generating a bright output
beam by merging independent input beams with locked relative phases. We report
the first quantum mechanical noise limit calculations for coherent beam
combining and compare our results to quantum-limited amplification. Our
coherent beam combining scheme is based on an optical Fourier transformation
which renders the scheme compatible with integrated optics. The scheme can be
layed out for an arbitrary number of input beams and approaches the shot noise
limit for a large number of inputs
Neuroprotective effects of the novel ethylthiadiazole derivatives (LHT 4-15) in male rats
The study was performed on male rats of the Wistar line. The animals were simulated with total cerebral ischemia with preliminary administration of LHT 4-15 compounds in doses of 25 and 50 mg/kg for 60 min. The data obtained from the neurological deficit and in the behavioral tests of the experimental groups confirm the theory of the presence of ethylthiadiazole derivatives under the LHT code 4–15 neuroprotective properti
Premartensitic Transition in Ni2+xMn1-xGa Heusler Alloys
The temperature dependencies of the resistivity and magnetization of a series
of Ni2+XMn1-XGa (X = 0 - 0.09) alloys were investigated. Along with the
anomalies associated with ferromagnetic and martensitic transitions,
well-defined anomalies were observed at the temperature of premartensitic
transformation. The premartensitic phase existing in a temperature range 200 -
260 K in the stoichiometric Ni2MnGa is suppressed by the martensitic phase with
increasing Ni content and vanishes in Ni2.09Mn0.91Ga composition
Influence of intermartensitic transitions on transport properties of Ni2.16Mn0.84Ga alloy
Magnetic, transport, and x-ray diffraction measurements of ferromagnetic
shape memory alloy NiMnGa revealed that this alloy undergoes
an intermartensitic transition upon cooling, whereas no such a transition is
observed upon subsequent heating. The difference in the modulation of the
martensite forming upon cooling from the high-temperature austenitic state
[5-layered (5M) martensite], and the martensite forming upon the
intermartensitic transition [7-layered (7M) martensite] strongly affects the
magnetic and transport properties of the alloy and results in a large thermal
hysteresis of the resistivity and magnetization . The
intermartensitic transition has an especially marked influence on the transport
properties, as is evident from a large difference in the resistivity of the 5M
and 7M martensite, , which is larger than the jump of resistivity at
the martensitic transition from the cubic austenitic phase to the monoclinic 5M
martensitic phase. We assume that this significant difference in between
the martensitic phases is accounted for by nesting features of the Fermi
surface. It is also suggested that the nesting hypothesis can explain the
uncommon behavior of the resistivity at the martensitic transition, observed in
stoichiometric and near-stoichiometric Ni-Mn-Ga alloys.Comment: 7 pages, 6 figures, REVTEX
The soft and the hard pomerons in hadron elastic scattering at small t
We consider simple-pole descriptions of soft elastic scattering for pp, pbar
p, pi+ p, pi- p, K+ p and K- p. We work at t and s small enough for
rescatterings to be neglected, and allow for the presence of a hard pomeron.
After building and discussing an exhaustive dataset, we show that simple poles
provide an excellent description of the data in the region - 0.5 GeV^2 < t <
-0.1 GeV^2, 6 GeV<sqrt(s)< 63 GeV. We show that new form factors have to be
used, and get information on the trajectories of the soft and hard pomerons.Comment: 27 pages, 9 figures, LaTeX. A few typos fixed, and references
correcte
Forward Physics at the LHC (Elba 2010)
The papers review the main theoretical and experimental aspects of the
Forward Physics at the Large Hadron Collider
On the rise of proton-proton cross-sections at high energies
The rise of the total, elastic and inelastic hadronic cross sections at high
energies is investigated by means of an analytical parametrization, with the
exponent of the leading logarithm contribution as a free fit parameter. Using
derivative dispersion relations with one subtraction, two different fits to
proton-proton and antiproton-proton total cross section and rho parameter data
are developed, reproducing well the experimental information in the energy
region 5 GeV - 7 TeV. The parametrization for the total cross sections is then
extended to fit the elastic (integrated) cross section data in the same energy
region, with satisfactory results. From these empirical results we extract the
energy dependence of several physical quantities: inelastic cross section,
ratios elastic/total, inelastic/total cross sections, ratio
total-cross-section/elastic-slope, elastic slope and optical point. All data,
fitted and predicted, are quite well described. We find a statistically
consistent solution indicating: (1) an increase of the hadronic cross sections
with the energy faster than the log-squared bound by Froissart and Martin; (2)
asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total
cross sections, respectively, a result in agreement with unitarity. These
indications corroborate recent theoretical arguments by Ya. I. Azimov on the
rise of the total cross section.Comment: 35 pages, 12 figures, discussions improved with further
clarifications, references added and updated, one note added, results and
conclusions unchanged. Version to be published in J. Phys. G: Nucl. Part.
Phy
P-P Total Cross Sections at VHE from Accelerator Data
Comparison of P-P total cross-sections estimations at very high energies -
from accelerators and cosmic rays - shows a disagreement amounting to more than
10 %, a discrepancy which is beyond statistical errors. Here we use a
phenomenological model based on the Multiple-Diffraction approach to
successfully describe data at accelerator energies. The predictions of the
model are compared with data On the basis of regression analysis we determine
confident error bands, analyzing the sensitivity of our predictions to the
employed data for extrapolation. : using data at 546 and 1.8 TeV, our
extrapolations for p-p total cross-sections are only compatible with the Akeno
cosmic ray data, predicting a slower rise with energy than other cosmic ray
results and other extrapolation methods. We discuss our results within the
context of constraints in the light of future accelerator and cosmic ray
experimental results.Comment: 26 pages aqnd 11 figure
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