343 research outputs found
High energy inelastic electron hadron scattering, in peripheral kinematics. Sum rules for hadron form factors
Relations between differential cross section for inelastic scattering of
electrons on hadrons and hadron form factors (sum rules) are derived on the
basis of analytical properties of heavy photon forward Compton scattering on
hadrons. Sum rules relating the slope of form-factors at zero momentum transfer
and anomalous magnetic moments of hadrons with some integrals on
photo-production on a hadrons is obtained as well. To provide the convergence
of these integrals we construct differences of individual sum rules for
different hadrons. Universal interaction of Pomeron with nucleons is assumed.
We derive the explicit formulae for processes of electro-production on proton
and light isobar nuclei. Sudakov's parametrization of momenta, for peripheral
kinematics relevant here, is used. The light-cone form of differential cross
sections is also discussed. The accuracy of sum rules estimated in frames of
point-like hadrons and it is shown to be at the level of precision achievable
by experiments. Suggestions and predictions for future experiments are also
given.Comment: 18 pages, 5 figure
Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+
Frequency and dc magnetic field dependences of dynamic susceptibility in
diluted paramagnets LiYF:Ho have been measured at liquid helium
temperatures in the ac and dc magnetic fields parallel to the symmetry axis of
a tetragonal crystal lattice. Experimental data are analyzed in the framework
of microscopic theory of relaxation rates in the manifold of 24
electron-nuclear sublevels of the lowest non-Kramers doublet and the first
excited singlet in the Ho ground multiplet split by the crystal
field of S symmetry. The one-phonon transition probabilities were computed
using electron-phonon coupling constants calculated in the framework of
exchange charge model and were checked by optical piezospectroscopic
measurements. The specific features observed in field dependences of the in-
and out-of-phase susceptibilities (humps and dips, respectively) at the
crossings (anti-crossings) of the electron-nuclear sublevels are well
reproduced by simulations when the phonon bottleneck effect and the cross-spin
relaxation are taken into account
Triplet Production by Linearly Polarized Photons
The process of electron-positron pair production by linearly polarized
photons is used as a polarimeter to perform mobile measurement of linear photon
polarization. In the limit of high photon energies, omega, the distributions of
the recoil-electron momentum and azimuthal angle do not depend on the photon
energy in the laboratory frame. We calculate the power corrections of order
m/omega to the above distributions and estimate the deviation from the
asymptotic result for various values of omega.Comment: LaTeX2e, 13 pages, 5 figure files (eps), submitted to Phys. Rev.
CEREBRAL REVASCULIZATION IN PATIENTS OF 70 YEARS AND OLDER
The aim of the work was to evaluate the perioperative management of aged patients after elective surgical cerebral revascularization. We analyzed the outcomes of 813 patients of 70 years and older who had surgery for stenosis of the internal carotid artery [ІСА]. There were two groups: 392 patients who had carotid endarterectomy [CEA] and 421 patients who had the stenting. Age of the patients, severity of disease and comorbidity were similar in both groups In aged patients, the incidence of acute disorders of cerebral circulation (stroke] after CEA was significantly lower than the one after stenting (p = 0,04]. Frequency of perioperative myocardial infarction [MI] was 3 times higher in cases with CEA (p = 0,03]. in patients of 70 years and older, CEA shown lower incidence of stroke, however, there is increase of perioperative MI while using this method. Endovascular treatment could be chosen in patients with severe cardiac disease according to atherosclerotic plaques with no risk of embolism. In addition, the individual approach and assessment of social aspect are necessary
Non-invasive control of influence of polyethylene glycol on transport function of fluorescent colored liposomal nanoparticles
The studies were carried out on groups of clinically healthy mice line of outbred CD-1 stock. The model animals were divided into 2 groups and received experimental liposomal formulations. Using the method of fluorescence spectroscopy, we investigated the effectiveness of penetration into the circulatory system of fluorescently stained liposomes with polyethylene glycol (PEG) and without PEG when administered orally. Fluorescence channel with a fiber probe series of multifunctional laser non-invasive diagnostic system "LAKK-M" (SPE "LAZMA" Ltd, Russia) was used as the measuring equipment
FEATURES OF POSTOPERATIVE PERIOD IN PATIENTS AFTER BRAIN REVASCULARIZATION
The aim of the research was to compare incidence of small complications after carotid endarterectomy (CEA) versus carotid artery stenting, as well as to evaluate its application in specific clinical situations. The outcomes of1826 patients who underwent surgery for stenosis of the internal carotid artery (ICA) were analyzed. There were two groups: 1018 patients who underwent CEA and 808 patients who carried the stenting. Age of patients was greater and coronary heart disease, diabetes, chronic obstructive pulmonary disease occurs more often in group with endovascular treatment, and they had rife stroke anamnesis. The mortality rate, uncontrolled hypertension and transient ischemic attacks were similar in early postoperative period. Stroke frequency was higher in patients with carotid artery stenting (35 (4,3 %) versus 27 patients (2,6 %) with CEA (p = 0,02)), and myocardial infarction took place more often after CEA (38 (3,7 %) versus 13 (1,6 %) patients with endovascular treatment (p = 0,008)). There was no statistically significant difference in security between CEA and stenting. However, treatment of carotid stenosis should be chosen according to individual characteristics, including individual anatomy
Possible Method for Measuring the Proton Form Factors in Processes with and without Proton Spin Flip
The ratio of the squares of the electric and magnetic proton form factors is
shown to be proportional to the ratio of the cross sections for the elastic
scattering of an unpolarized electron on a partially polarized proton with and
without proton spin flip. The initial proton at rest should be polarized along
the direction of the motion of the final proton. Similar results are valid for
both radiative scattering and the photoproduction of pairs on a proton in
the Bethe--Heitler kinematics. When the initial proton is fully polarized in
the direction of the motion of the final proton, the cross section for the process, as well as for the and processes, without (with) proton spin flip is expressed only in terms of
the square of the electric (magnetic) proton form factor. Such an experiment on
the measurement of the cross sections without and with proton spin flip would
make it possible to acquire new independent data on the behavior of
and , which are necessary for resolving the
contradictions appearing after the experiment of the JLab collaboration on the
measurement of the proton form factors with the method of polarization transfer
from the initial electron to the final proton.Comment: 7 pages, revtex
Polarized triplet production by circularly polarized photons
A process of the pair production by a circularly polarized photon in the
field of unpolarized atomic electron has been considered in the
Weizaecker-Williams approximation. The degree of longitudinal polarization of
positron and electron has been calculated. An exclusive cross-section as well
as a spectral distribution are obtained. We estimate the accuracy of our
calculations at the level of a few percent. We show the identity of the
positron polarization for considered process and for process of pair production
in the screened Coulomb field of nucleus.Comment: 9 pages, 3 picture
SCIENTIFIC AND METHODICAL APPROACHES TO INCREASE PROSPECTING EFFICIENCY OF THE RUSSIAN ARCTIC SHELF STATE GEOLOGICAL MAPPING
A rationale for the set of theoretical and methodological techniques of mapping and deep modeling in the Russian Arctic shelf and adjacent sedimentary basins in continental Russia is based on the materials for the Barents and Kara Seas region. This article provides the factual basis of the research and shows how to apply zonal-block model of the crust and generalized models of geodynamic settings in terms of the different geophysical data inconsistency. The necessity and approach for global and regional paleo-reconstructions are also discussed.
It is shown that localization of the principal structural and compositional units of the lithosphere being a consequence of geodynamic processes at the boundaries of lithospheric plates, form at the basis of sedimentary cover and crystalline basement layered maps as well as cross-sections of the continental crust. The identified parameters of the deep structure and milestones of the regional tectonic history open new opportunities to explore the regularities of ore deposits distribution. The shown example of the forecast and metallogeny problems solution within Western Siberia and Khatanga-Vilyui petroleum provinces is made using the parameters of known industrial oil and gas fields for training the pattern recognition system
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