116 research outputs found
Binding Energy of Charged Excitons in ZnSe-based Quantum Wells
Excitons and charged excitons (trions) are investigated in ZnSe-based quantum
well structures with (Zn,Be,Mg)Se and (Zn,Mg)(S,Se) barriers by means of
magneto-optical spectroscopy. Binding energies of negatively () and positively
(X+) charged excitons are measured as functions of quantum well width, free
carrier density and in external magnetic fields up to 47 T. The binding energy
of shows a strong increase from 1.4 to 8.9 meV with decreasing quantum well
width from 190 to 29 A. The binding energies of X+ are about 25% smaller than
the binding energy in the same structures. The magnetic field behavior of and
X+ binding energies differ qualitatively. With growing magnetic field strength,
increases its binding energy by 35-150%, while for X+ it decreases by 25%.
Zeeman spin splittings and oscillator strengths of excitons and trions are
measured and discussed
Health-training, individual correction of the physical development and physical fitness,development of the needs and motivation to the regular physical culture and sports activities classes
The emergence of physical culture and sports activities and physical recreation is due to various reasons: on a current basis of the accumulation of knowledge and practical experience the general idea has been formed, implying that the physical recreation has arisen within the system of physical education, originally performing the pedagogical role, then it has been widely used for the religious rituals, national games, holidays, entertainment, buying the mass character, having eventually become an integral part of the life of people. They act as system of integration of sciences about the nature and human being while representing to the full the trends of the process of “domestication” of the body, so necessary for the sur-vival of the modern civilization. The transformations in the system of multilevel education, taking place at present in the Russian Federation and the Republic of Belarus, resulted in motion of the mechanisms with high demands for the individual student, the quality of knowledge and skills, its adaptation to the conditions of the dynamic and unpredictable changing life, health significance, high efficiency and constant motor rehabilitation.Возникновение физкультурно-спортивной деятельности и физической рекреации обусловлено многообразными причинами: по мере накопления знаний и практического опыта сформировалось общее представление, что физическая рекреация возникла в системе физического воспитания, первоначально выполняла педагогическую функцию, затем она широко использовалась в религиозных обрядах, национальных играх, праздниках, развлечениях, приобретая массовый характер, со временем становилась неотъемлемой частью жизнедеятельности людей. Они выступают как система интеграции наук о природе и человеке, наиболее полно представляют тенденции процесса «окультуривания» тела, так необходимого для выживания современной цивилизации. Происходя-щие в настоящее время в Российской Федерации и Республике Беларусь преобразования в системе многоуровневого образования привели в движение механизмы, предъявляющие повышенные требования к личности обучаемого, качеству знаний, умений и навыков, его адаптации к условиям динамично и непредсказуемо меняющейся жизни, значимости здоровья, высокой работоспособности и постоянной двигательной реабилитации
Cooling of Neutron Stars with Strong Toroidal Magnetic Fields
We present models of temperature distribution in the crust of a neutron star in the presence of a strong toroidal component superposed to the poloidal component of the magnetic field. The presence of such a toroidal field hinders heat flow toward the surface in a large part of the crust. As a result, the neutron star surface presents two warm regions surrounded by extended cold regions and has a thermal luminosity much lower than in the case the magnetic field is purely poloidal. We apply these models to calculate the thermal evolution of such neutron stars and show that the lowered photon luminosity naturally extends their life-time as detectable thermal X-ray sources
Two-loop Anomalous Dimensions of Heavy Baryon Currents in Heavy Quark Effective Theory
We present results on the two-loop anomalous dimensions of the heavy baryon
HQET currents with arbitrary Dirac matrices
and . From our general result we obtain the two-loop
anomalous dimensions for currents with quantum numbers of the ground state
heavy baryons , and . As a by-product of our
calculation and as an additional check we rederive the known two-loop anomalous
dimensions of mesonic scalar, pseudoscalar, vector, axial vector and tensor
currents in massless QCD as well as in HQET.Comment: 21 pages, LaTeX, 2 figures are included in PostScript forma
СОВРЕМЕННЫЕ ТЕХНОЛОГИИ В ХИРУРГИЧЕСКОМ ЛЕЧЕНИИ ПОСЛЕДСТВИЙ ТРАВМЫ ЧЕРЕПА И ГОЛОВНОГО МОЗГА
The paper presents main types of surgically relevant posttraumatic lesions in 4136 patients with skull vault as well as skull base defects, craniofacial deformities, recurrent CSF leaks, arterio-venous fistulas, aneurysms and pseudoaneurysms etc. Classification of TBI sequelae and complications as well as its clinical course grading is presented. The use of modern neuroimaging techniques for studying pathophysiologic mechanisms and complications of TBI has been demonstrated. Special emphasis was given to minimally invasive and reconstructive surgery; computer modeling with subsequent full-copy stereolitographic laser implant setup was shown which is of great importance in cases of large and complex skull base and craniofacial deformities. Patient selection for transcranial and endonasal CSF leak closure techniques was justified. Treatment of post-traumatic vascular injuries using Serbinenko balloon-catheters as well as modern techniques such as stents, coils and embolization has been demonstrated. В сообщении (созданном по материалам доклада, представленного на Сессии общего собрания РАМН, Санкт-Петербург, 14−15 июня 2012 г.) представлены основные хирургически значимые формы посттравматической патологии у 4136 пациентов с дефектами и деформациями костей свода, основания черепа и лицевого скелета, рецидивирующей ликвореей, артериосинусными соустьями, истинными и ложными аневризмами и др. Разработана классификация последствий и осложнений черепно-мозговой травмы, а также периодизация ее клинического течения. Раскрыты возможности современных нейровизуализационных технологий распознавания и исследования патогенеза последствий и осложнений черепно-мозговой травмы. Особое внимание уделено реконструктивной и минимально инвазивной хирургии, детально описан метод компьютерного моделирования и последующего стереолитографического лазерного воспроизведения полномасштабных копий черепа, его дефектов и имплантатов, что особенно значимо при обширных и сложных краниобазальных и краниофациальных повреждениях. Обосновано дифференцированное применение интракраниальных и эндоназальных доступов для закрытия хронических ликворных фистул. Вместе с впервые созданной в НИИ нейрохирургии им. Н.Н. Бурденко методикой эндоваскулярной реконструкции магистральных сосудов с помощью баллонов-катетеров Ф.А. Сербиненко представлены новые подходы, опирающиеся на современные технологии с использованием стентов, микроспиралей и эмболизирующих композиций.
In Situ Spectral Magnetoellipsometry for Structural, Magnetic and Optical Properties of Me/Si (Me Mn, Fe) Nanolayers
In our work we present in-situ spectral magnetoellipsometer is equipped with sapphire manipulator. which allows us to carry out in-situ and in-time optical and magnetooptical measurements in the range from 10 K to 1500 K in spectral range 1.5 eV-4.0 eV (830 nm-300 nm), the range of magnetic fields is +/-0.4 T.
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Calculations of binding energies and masses of heavy quarkonia using renormalon cancellation
We use various methods of Borel integration to calculate the binding ground
energies and masses of b-bbar and t-tbar quarkonia. The methods take into
account the leading infrared renormalon structure of the hard+soft part of the
binding energies E(s), and of the corresponding quark pole masses m_q, where
the contributions of these singularities in M(s) = 2 m_q + E(s) cancel.
Beforehand, we carry out the separation of the binding energy into its
hard+soft and ultrasoft parts. The resummation formalisms are applied to
expansions of m_q and E(s) in terms of quantities which do not involve
renormalon ambiguity, such as MSbar quark mass, and alpha_s. The
renormalization scales are different in calculations of m_q, E(s) and E(us).
The MSbar mass of b quark is extracted, and the binding energies of t-tbar and
the peak (resonance) energies for (t+tbar) production are obtained.Comment: 23 pages, 8 double figures, revtex4; the version to appear in
Phys.Rev.D; extended discussion between Eqs.(25) and (26); the paragraph
between Eqs.(32) and (33) is new and explains the numerical dependence of the
residue parameter on the factorization scale; several new references were
added; acknowledgments were modified; the numerical results are unchange
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
Neutrino Cooling of Neutron Stars. Medium effects
This review demonstrates that neutrino emission from dense hadronic component
in neutron stars is subject of strong modifications due to collective effects
in the nuclear matter. With the most important in-medium processes incorporated
in the cooling code an overall agreement with available soft X ray data can be
easily achieved. With these findings so called "standard" and "non-standard"
cooling scenarios are replaced by one general "nuclear medium cooling scenario"
which relates slow and rapid neutron star coolings to the star masses (interior
densities). In-medium effects take important part also at early hot stage of
neutron star evolution decreasing the neutrino opacity for less massive and
increasing for more massive neutron stars. A formalism for calculation of
neutrino radiation from nuclear matter is presented that treats on equal
footing one-nucleon and multiple-nucleon processes as well as reactions with
resonance bosons and condensates. Cooling history of neutron stars with quark
cores is also discussed.Comment: To be published in "Physics of Neutron Star Interiors", Eds. D.
Blaschke, N.K. Glendenning, A. Sedrakian, Springer, Heidelberg (2001
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