228 research outputs found
Биология воспроизведения и жизненный цикл диатомовой водоросли Nitzschia cf. thermaloides, населяющей грязевые вулканы Крыма
В биологии актуально изучение способности организмов к существованию в экстремальных условиях, к которым особенно чувствительна фаза жизненного цикла, связанная с половым размножением и возможностью оставить следующее поколение. В пробах, которые были взяты из луж и озёр, образующихся в местах действия грязевых вулканов Булганакского сопочного поля (Керченский полуостров, Крым), обнаружена в большом количестве Nitzschia cf. thermaloides Hustedt. Из проб микропипеточным способом выделены и введены в культуру отдельные клоны, скрещивание которых позволило инициировать гетероталлическое половое воспроизведение. Целью работы было изучить биологию воспроизведения и жизненный цикл водоросли из биотопа с экстремально высокими уровнями освещённости, температуры и солёности. Впервые для данного вида приведено описание полового процесса, соответствующего типу IB2a по классификации Гайтлера. Определены кардинальные пункты — критические размеры клеток, обусловливающие переход из одной фазы жизненного цикла в другую. Приведён полный диапазон размеров клеток — от инициальных, появившихся в результате полового воспроизведения, до самых маленьких, наблюдавшихся при содержании в культуре. Рассмотрены основные положения теории жизненного цикла диатомовых водорослей, позволяющие выполнить анализ их природной популяции. Установлено, что популяция N. cf. thermaloides существует в месте отбора проб длительное время и представлена клетками, находящимися во всех фазах жизненного цикла
Experimental investigation of dynamical invariants in bipartite entanglement
The non-conservation of entanglement, when two or more particles interact,
sets it apart from other dynamical quantities like energy and momentum. It does
not allow the interpretation of the subtle dynamics of entanglement as a flow
of this quantity between the constituents of the system. Here we show that
adding a third party to a two-particle system may lead to a conservation law
that relates the quantities characterizing the bipartite entanglement between
each of the parties and the other two. We provide an experimental demonstration
of this idea using entangled photons, and generalize it to N-partite GHZ
states
Phase transition curves for mesoscopic superconducting samples
We compute the phase transition curves for mesoscopic superconductors.
Special emphasis is given to the limiting shape of the curve when the magnetic
flux is large. We derive an asymptotic formula for the ground state of the
Schr\"odinger equation in the presence of large applied flux. The expansion is
shown to be sensitive to the smoothness of the domain. The theoretical results
are compared to recent experiments.Comment: 8 pages, 1 figur
СОСТОЯНИЕ ЦЕРЕБРОВАСКУЛЯРНОГО КРОВОТОКА У ЛЮДЕЙ МОЛОДОГО ВОЗРАСТА НА РАННИХ СТАДИЯХ ГИПЕРТОНИЧЕСКОЙ БОЛЕЗНИ
Purpose. To assess arterial circulation inflow and venous outflow in extra and intracranial vessels in young patients with initially diagnosed hypertension with or without consistent hypertensive therapy in correlation to degree and stage of hypertensive disease (HD).Materials and methods. We have examined 82 patients (mean age 36,9±1,5), with HD of the 1-st degree, 63,4 % and 2-nd degree – 36,6 %, HD of the 1-st degree – 61 % and 2-nd degree – 39 %. He control group included – 28 healthy patients of the same age and having normal blood pressure. Circulation in extra and intracranial arteries and veins was studied by ultrasound apparatus Logiq 9 (GEHealthcare,USA).Results. Patients with hypertension disease reliably demonstrated blood flow decrease in carotid and cerebral arteries depending on the degree and stage of HD compared to healthy people with a normal blood pressure. Venous outflow in patients with AH of the 1-st degree and HD of the first stage was increasing objectively in relevance to the patients with AH of the 2-nd degree and HD of the 20nd stage and healthy patients. Later in patients with AH of the 2-nd degree and HD of the 2-nd stage internal jugular vein elasticity decrease was observed accompanied by diminishing of blood stream velocity.Conclusion. Patients with HD of 1-st and 20-nd stage and AH of 1-st and 2-nd degree demonstrate blood stream autoregulation in extra and intracranial arteries of the brain. Changes in venous outflow in AH and HD of the 1-st degree and stage are compensatory. Severity of AH and HD results in cerebral venous congestion confirmed by ultrasound signs.Цель. Оценка артериального притока и венозного оттока в экстра- и интракраниальных сосудах у больных молодого возраста с Г Б, впервые выявленной, и/или при отсутствии постоянной антигипертензивной терапии в зависимости от степени АГ и стадии заболевания.Материалы и методы. Обследовано 82 пациента (средний возраст 36,9±1,5 года): с Г Б I стадии – 63,4 % и II стадии – 36,6 %, АГ 1-й степени – 61 % и 2-й степени – 39 %. Контроль – 28 здоровых лиц того же возраста с нормальным АД. Состояние кровотока в экстра- и интракраниальных артериях и венах проводили ультразвуковым методом на аппарате Logiq 9 (GE Healthcare, USA). Результаты. У больных с Г Б наблюдалось достоверное по сравнению с лицами с нормальным АД снижение показателей кровотока в сонных и мозговых артериях в зависимости от степени АГ и стадии ГБ. Венозный отток у пациентов с АГ 1-й степени и Г Б I стадии достоверно возрастал по отношению к больным с АГ 2-й степени и Г Б II стадии и лицам с нормальным АД. В дальнейшем у больных с АГ 2-й степени и Г Б II стадии происходило снижение податливости ВЯВ, что сопровождалось и снижением в них скорости кровотока.Заключение. У больных молодого возраста с Г Б I–II стадии и АГ 1–2-й степени сохранена ауторегуляция кровотока в экстра- и интракраниальных артериях головы. Изменения со стороны венозного оттока при 1-й степени АГ и I стадии ГБ носят компенсаторный характер, с увеличением степени АГ и стадии ГБ выявляются ультразвуковые признаки венозного застоя в голове
Fano effect of a strongly interacting quantum dot in contact with superconductor
The physics of a system consisting of an Aharonov Bohm (AB) interferometer
containing a single level interacting quantum dot (QD) on one of its arms, and
attached to normal (N) and superconducting (S) leads is studied and elucidated.
Here the focus is directed mainly on N-AB-S junctions but the theory is capable
of studying S-AB-S junctions as well. The interesting physics comes into play
under the conditions that both the Kondo effect in the QD and the the Fano
effect are equally important.It is found the conductance of the junction is
suppressed as the Fano effect becomes more dominant.Comment: 4 pages, Talk to be given at the NATO Conference MQO, Bled, Slovenia
7-10 September 200
Magnetic Impurity in a Metal with Correlated Conduction Electrons: An Infinite Dimensions Approach
We consider the Hubbard model with a magnetic Anderson impurity coupled to a
lattice site. In the case of infinite dimensions, one-particle correlations of
the impurity electron are described by the effective Hamiltonian of the
two-impurity system. One of the impurities interacts with a bath of free
electrons and represents the Hubbard lattice, and the other is coupled to the
first impurity by the bare hybridization interaction. A study of the effective
two-impurity Hamiltonian in the frame of the 1/N expansion and for the case of
a weak conduction-electron interaction (small U) reveals an enhancement of the
usual exponential Kondo scale. However, an intermediate interaction (U/D = 1 -
3), treated by the variational principle, leads to the loss of the exponential
scale. The Kondo temperature T_K of the effective two-impurity system is
calculated as a function of the hybridization parameter and it is shown that
T_K decreases with an increase of U. The non-Fermi-liquid character of the
Kondo effect in the intermediate regime at the half filling is discussed.Comment: 12 pages with 8 PS figures, RevTe
Decoherence via Dynamical Casimir Effect
We derive a master equation for a mirror interacting with the vacuum field
via radiation pressure. The dynamical Casimir effect leads to decoherence of a
'Schroedinger cat' state in a time scale that depends on the degree of
'macroscopicity' of the state components, and which may be much shorter than
the relaxation time scale. Coherent states are selected by the interaction as
pointer states.Comment: 4 pages, 2 figure
Theory of output coupling for trapped fermionic atoms
We develop a dynamic theory of output coupling, for fermionic atoms initially
confined in a magnetic trap. We consider an exactly soluble one-dimensional
model, with a spatially localized delta-type coupling between the atoms in the
trap and a continuum of free-particle external modes. Two important special
cases are considered for the confinement potential: the infinite box and the
harmonic oscillator. We establish that in both cases a bound state of the
coupled system appears for any value of the coupling constant, implying that
the trap population does not vanish in the infinite-time limit. For weak
coupling, the energy spectrum of the outgoing beam exhibits peaks corresponding
to the initially occupied energy levels in the trap; the height of these peaks
increases with the energy. As the coupling gets stronger, the energy spectrum
is displaced towards dressed energies of the fermions in the trap. The
corresponding dressed states result from the coupling between the unperturbed
fermionic states in the trap, mediated by the coupling between these states and
the continuum. In the strong-coupling limit, there is a reinforcement of the
lowest-energy dressed mode, which contributes to the energy spectrum of the
outgoing beam more strongly than the other modes. This effect is especially
pronounced for the one-dimensional box, which indicates that the efficiency of
the mode-reinforcement mechanism depends on the steepness of the confinement
potential. In this case, a quasi-monochromatic anti-bunched atomic beam is
obtained. Results for a bosonic sample are also shown for comparison.Comment: 16 pages, 7 figures, added discussion on time-dependent spectral
distribution and corresponding figur
Probing quantum phases of ultracold atoms in optical lattices by transmission spectra in cavity QED
Studies of ultracold atoms in optical lattices link various disciplines,
providing a playground where fundamental quantum many-body concepts, formulated
in condensed-matter physics, can be tested in much better controllable atomic
systems, e.g., strongly correlated phases, quantum information processing.
Standard methods to measure quantum properties of Bose-Einstein condensates
(BECs) are based on matter-wave interference between atoms released from traps
which destroys the system. Here we propose a nondestructive method based on
optical measurements, and prove that atomic statistics can be mapped on
transmission spectra of a high-Q cavity. This can be extremely useful for
studying phase transitions between Mott insulator and superfluid states, since
various phases show qualitatively distinct light scattering. Joining the
paradigms of cavity quantum electrodynamics (QED) and ultracold gases will
enable conceptually new investigations of both light and matter at ultimate
quantum levels, which only recently became experimentally possible. Here we
predict effects accessible in such novel setups.Comment: 6 pages, 3 figure
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