24 research outputs found
ОСОБЕННОСТИ ДЕТСКОГО РАССЕЯННОГО СКЛЕРОЗА
Введение. Демиелинизующие заболевания – одна из самых актуальных и дискутабельных проблем в неврологии. Несмотря на появление улучшенных диагностических критериев и новых направлений в терапии, рассеянный склероз занимает лидирующее место в инвалидизации молодых пациентов. По данным эпидемиологических исследований, во всем мире рассеянным склерозом страдают около 3 млн человек. При этом от 2,7 до 10,5% всех случаев рассеянного склероза во всем мире наблюдается у детей в возрасте до 18 лет с тенденцией к росту заболеваемости.
Цель. Провести анализ результатов научных исследований случаев детского рассеянного склероза.
Материал и методы. Проведен качественный анализ русскоязычных и англоязычных источников, содержащих в себе данные о случаях детского рассеянного склероза.
Результаты. Установлено, что заболеваемость рассеянным склерозом среди педиатрических пациентов существенно меньше в сравнении со взрослым населением. Клиническая картина полиморфна и в некоторых случаях атипична.
Выводы. Cовременное понимание термина «педиатрический рассеянный склероз» указывает на узкое окно начала с отличным от взрослых когнитивным снижением, сочетанное с более высоким числом рецидивов и количеством очагов воспаления по сравнению с взрослым рассеянным склерозом.
Полиморфная клиническая картина и атипичные проявления в детском возрасте, а также дебют в виде клинически изолированного синдрома могут затруднять раннюю дифференциальную диагностику и увеличивать промежуток от манифестации заболевания до назначения необходимой фармакотерапии, которая способна снизить тяжесть течения заболевания, частоту рецидивов и увеличить промежуток «дебют – инвалидизация»
Quark and pion condensation in a chromomagnetic background field
The general features of quark and pion condensation in dense quark matter
with flavor asymmetry have been considered at finite temperature in the
presence of a chromomagnetic background field modelling the gluon condensate.
In particular, pion condensation in the case of a constant abelian
chromomagnetic field and zero temperature has been studied both analytically
and numerically. Under the influence of the chromomagnetic background field the
effective potential of the system is found to have a global minimum for a
finite pion condensate even for small values of the effective quark coupling
constant. In the strong field limit, an effective dimensional reduction has
been found to take place.Comment: 17 pages, 6 figure
Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model
The influence of a constant uniform external chromomagnetic field on the
formation of color superconductivity has been investigated. The consideration
was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model
with two different four-fermionic structures responsible for condensates. In particular, it was shown that there exists a
critical value of the external chromomagnetic field such that at
a nonvanishing diquark condensate is dynamically created (the so-called
chromomagnetic catalysis effect of color superconductivity). Moreover, external
chromomagnetic fields may in some cases enhance the diquark condensate of color
superconductivity.Comment: 32 pages, 2 figures, revte
Statistical Mechanical Calculation of Anisotropic Step Stiffness of a Two-Dimensional Hexagonal Lattice Gas Model with Next-Nearest-Neighbor Interactions: Application to Si(111) Surface
We study a two-dimensional honeycomb lattice gas model with both nearest- and
next-nearest-neighbor interactions in a staggered field, which describes the
surface of stoichiometrically binary crystal.
We calculate anisotropic step tension, step stiffness, and equilibrium island
shape, by an extended random walk method. We apply the results to Si(111)
77 reconstructed surface and high-temperature Si(111) 11
surface. We also calculate inter-step interaction coefficient.Comment: revised on May 29 1999: RevTeX v3.1, 10 pages with 9 figures (one
figure added
The Influence of an External Chromomagnetic Field on Color Superconductivity
We study the competition of quark-antiquark and diquark condensates under the
influence of an external chromomagnetic field modelling the gluon condensate
and in dependence on the chemical potential and temperature. As our results
indicate, an external chromomagnetic field might produce remarkable qualitative
changes in the picture of the color superconducting (CSC) phase formation. This
concerns, in particular, the possibility of a transition to the CSC phase and
diquark condensation at finite temperature.Comment: 27 pages, RevTex, 8 figures; the version accepted for the publication
in PRD (few references added; new numerical results added; main conclusions
are not changed
Magnetic Oscillations in Dense Cold Quark Matter with Four-Fermion Interactions
The phase structures of Nambu-Jona-Lasinio models with one or two flavours
have been investigated at non-zero values of and , where is an
external magnetic field and is the chemical potential. In the phase
portraits of both models there arise infinitely many massless chirally
symmetric phases, as well as massive ones with spontaneously broken chiral
invariance, reflecting the existence of infinitely many Landau levels. Phase
transitions of first and second orders and a lot of tricritical points have
been shown to exist in phase diagrams. In the massless case, such a phase
structure leads unavoidably to the standard van Alphen-de Haas magnetic
oscillations of some thermodynamical quantities, including magnetization,
pressure and particle density. In the massive case we have found an oscillating
behaviour not only for thermodynamical quantities, but also for a dynamical
quantity as the quark mass. Besides, in this case we have non-standard, i.e.
non-periodic, magnetic oscillations, since the frequency of oscillations is an
-dependent quantity.Comment: latex, 29 pages, 8 figure
Magnetic Catalysis: A Review
We give an overview of the magnetic catalysis phenomenon. In the framework of
quantum field theory, magnetic catalysis is broadly defined as an enhancement
of dynamical symmetry breaking by an external magnetic field. We start from a
brief discussion of spontaneous symmetry breaking and the role of a magnetic
field in its a dynamics. This is followed by a detailed presentation of the
essential features of the phenomenon. In particular, we emphasize that the
dimensional reduction plays a profound role in the pairing dynamics in a
magnetic field. Using the general nature of underlying physics and its
robustness with respect to interaction types and model content, we argue that
magnetic catalysis is a universal and model-independent phenomenon. In support
of this claim, we show how magnetic catalysis is realized in various models
with short-range and long-range interactions. We argue that the general nature
of the phenomenon implies a wide range of potential applications: from certain
types of solid state systems to models in cosmology, particle and nuclear
physics. We finish the review with general remarks about magnetic catalysis and
an outlook for future research.Comment: 37 pages, to appear in Lect. Notes Phys. "Strongly interacting matter
in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Yee. Version 2: references adde
Pion condensation of quark matter in the static Einstein universe
In the framework of an extended Nambu--Jona-Lasinio model we are studying
pion condensation in quark matter with an asymmetric isospin composition in a
gravitational field of the static Einstein universe at finite temperature and
chemical potential. This particular choice of the gravitational field
configuration enables us to investigate phase transitions of the system with
exact consideration of the role of this field in the formation of quark and
pion condensates and to point out its influence on the phase portraits. We
demonstrate the effect of oscillations of the thermodynamic quantities as
functions of the curvature and also refer to a certain similarity between the
behavior of these quantities as functions of curvature and finite temperature.
Finally, the role of quantum fluctuations for spontaneous symmetry breaking in
the case of a finite volume of the universe is shortly discussed.Comment: RevTex4; 15 pages, 10 figure