9,413 research outputs found
Sum rule for a difference of proton and neutron total photoproduction cross-sections
Starting from very high energy inelastic electron-nucleon scattering with a
production of a hadronic state to be moved closely to the direction of the
initial nucleon, then utilizing analytic properties of parts of forward virtual
Compton scattering amplitudes on proton and neutron, one obtains the relation
between nucleon form factors and a difference of proton and neutron
differential electroproduction cross-sections. In particular, for the case of
small transferred momenta, one finally derives sum rule, relating Dirac proton
mean square radius and anomalous magnetic moments of proton and neutron to the
integral over a difference of the total proton and neutron photoproduction
cross-sections.Comment: LaTeX2e, 7 pages, 1 eps figure (revised version
Two Detector Reactor Neutrino Oscillation Experiment Kr2Det at Krasnoyarsk. Status Report
We consider status of the Kr2Det project aimed at sensitive searches for
neutrino oscillations in the atmospheric neutrino mass parameter region around
Dm2 ~ 3x10-3 eV2and at obtaining new information on the electron neutrino mass
structure (Ue3).Comment: 4 pages in pdf file. Talk presented at NANP-2001 International
Conference in Dubna, Russia, June 200
Microphysical Retrievals from Dual-Polarization Radar Measurements at X Band
Abstract
The recent advances in attenuation correction methodology are based on the use of a constraint represented by the total amount of the attenuation encountered along the path shared over each range bin in the path. This technique is improved by using the inner self-consistency of radar measurements. The full self-consistency methodology provides an optimization procedure for obtaining the best estimate of specific and cumulative attenuation and specific and cumulative differential attenuation.
The main goal of the study is to examine drop size distribution (DSD) retrieval from X-band radar measurements after attenuation correction. A new technique for estimating the slope of a linear axis ratio model from polarimetric radar measurements at attenuated frequencies is envisioned. A new set of improved algorithms immune to variability in the raindrop shape–size relation are presented for the estimation of the governing parameters characterizing a gamma raindrop size distribution.
Simulations based on the use of profiles of gamma drop size distribution parameters obtained from S-band observations are used for quantitative analysis. Radar data collected by the NOAA/Earth System Research Laboratory (ESRL) X-band polarimetric radar are used to provide examples of the DSD parameter retrievals using attenuation-corrected radar measurements. Retrievals agree fairly well with disdrometer data. The radar data are also used to observe the prevailing shape of raindrops directly from the radar measurements. A significant result is that oblateness of drops is bounded between the two shape models of Pruppacher and Beard, and Beard and Chuang, the former representing the upper boundary and the latter the lower boundary
Dilepton production in nucleus-nucleus collisions at top SPS energy within the Parton-Hadron-String Dynamics (PHSD) transport approach
Dilepton production in In+In collisions at 158 AGeV is studied within the
microscopic parton-hadron-string dynamics (PHSD) transport approach that
incorporates explicit partonic degrees-of-freedom, dynamical hadronization as
well as the more familiar hadronic dynamics in the final reaction stages. A
comparison to the data of the NA60 Collaboration shows that the measured
dilepton yield is well described by including the collisional broadening of
vector mesons, while simultaneously accounting for the electromagnetic
radiation of the strongly coupled quark-gluon plasma (sQGP) via off-shell
quark-antiquark annihilation, quark annihilation with additional gluon
Bremsstrahlung and the gluon-Compton scattering mechanisms. In particular, the
spectra in the intermediate mass range (1 GeV < M < 2.5 GeV) are dominated by
quark-antiquark annihilation in the nonperturbative QGP. Also, the observed
softening of the transverse mass spectra at intermediate masses (1 GeV < M <
2.5 GeV) is approximately reproduced. Furthermore, for dileptons of low masses
(M < 0.6 GeV), we find a sizable contribution from the quark annihilation with
additional gluon bremsstrahlung, thus providing another possible window for
probing the properties of the sQGP.Comment: 16 pages, 14 figure
The Kr2Det project: Search for mass-3 state contribution |U_{e3}|^2 to the electron neutrino using a one reactor - two detector oscillation experiment at Krasnoyarsk underground site
The main physical goal of the project is to search with reactor antineutrinos
for small mixing angle oscillations in the atmospheric mass parameter region
around {\Delta}m^{2}_{atm} ~ 2.5 10^{-3} eV^2 in order to find the element
U_{e3} of the neutrino mixing matrix or to set a new more stringent constraint
(U_{e3} is the contribution of mass-3 state to the electron neutrino flavor
state). To achieve this we propose a "one reactor - two detector" experiment:
two identical antineutrino spectrometers with 50 ton liquid scintillator
targets located at ~100 m and ~1000 m from the Krasnoyarsk underground reactor
(~600 mwe). In no-oscillation case ratio of measured positron spectra of the
\bar{{\nu}_e} + p \to e^{+} + n reaction is energy independent. Deviation from
a constant value of this ratio is the oscillation signature. In this scheme
results do not depend on the exact knowledge of the reactor power, nu_e
spectra, burn up effects, target volumes and, which is important, the
backgrounds can periodically be measured during reactor OFF periods. In this
letter we present the Krasnoyarsk reactor site, give a schematic description of
the detectors, calculate the neutrino detection rates and estimate the
backgrounds. We also outline the detector monitoring and calibration
procedures, which are of a key importance. We hope that systematic
uncertainties will not accede 0.5% and the sensitivity U^{2}_{e3} ~4 10^{-3}
(at {\Delta}m^{2} = 2.5 10^{-3} eV^2) can be achieved.Comment: Latex 2e, 9 pages and 5 ps figure
Perfused Platforms to Mimic Bone Microenvironment at the Macro/Milli/Microscale: Pros and Cons
As life expectancy increases, the population experiences progressive ageing. Ageing, in turn, is connected to an increase in bone-related diseases (i.e., osteoporosis and increased risk of fractures). Hence, the search for new approaches to study the occurrence of bone-related diseases and to develop new drugs for their prevention and treatment becomes more pressing. However, to date, a reliable in vitro model that can fully recapitulate the characteristics of bone tissue, either in physiological or altered conditions, is not available. Indeed, current methods for modelling normal and pathological bone are poor predictors of treatment outcomes in humans, as they fail to mimic the in vivo cellular microenvironment and tissue complexity. Bone, in fact, is a dynamic network including differently specialized cells and the extracellular matrix, constantly subjected to external and internal stimuli. To this regard, perfused vascularized models are a novel field of investigation that can offer a new technological approach to overcome the limitations of traditional cell culture methods. It allows the combination of perfusion, mechanical and biochemical stimuli, biological cues, biomaterials (mimicking the extracellular matrix of bone), and multiple cell types. This review will discuss macro, milli, and microscale perfused devices designed to model bone structure and microenvironment, focusing on the role of perfusion and encompassing different degrees of complexity. These devices are a very first, though promising, step for the development of 3D in vitro platforms for preclinical screening of novel anabolic or anti-catabolic therapeutic approaches to improve bone health
Intersession reliability of a posturo-stabilometric test, using a force platform
To evaluate the intersession reliability of a posturo-stabilometric examination.
METHODS:
Single blind clinical trial conducted in two sessions over two weeks. 44 healthy volunteers free from postural and temporomandibular disorders. All the subjects complied with the criteria for completing the study. All the subjects underwent two sessions of posturo-stabilometric examinations in different visual and mandibular conditions. Sway area, sway length and the coordinates of the center of pressure were evaluated and statistically analyzed using the Intraclass correlation coefficient (ICC).
RESULTS:
All the posturo-stabilometric parameters seemed to have an excellent reproducibility with overall ICCs higher than 70% and good confidence intervals except for the sway area (ICC 0.422 with CI 0.283-0.560 with open eyes and ICC 0.554 with CI 0.424-0.683 with closed eyes).
CONCLUSIONS:
The posturo-stabilometric examination carried out using a force platform has a good intrasession and intersession reliability, especially considering sway velocity, COP X and COP Y parameters. The force platform usefulness in analyzing static posture is confirmed in any medical field
Plasduino: an inexpensive, general purpose data acquisition framework for educational experiments
Based on the Arduino development platform, Plasduino is an open-source data
acquisition framework specifically designed for educational physics
experiments. The source code, schematics and documentation are in the public
domain under a GPL license and the system, streamlined for low cost and ease of
use, can be replicated on the scale of a typical didactic lab with minimal
effort. We describe the basic architecture of the system and illustrate its
potential with some real-life examples.Comment: 11 pages, 10 figures, presented at the XCIX conference of the
Societ\`a Italiana di Fisic
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