218 research outputs found
Oceanic structures of the Earth and the North Depression of Mars: A comparison of the formation mechanisms
The system of contemporary oceans on Earth and the North Depression of Mars are quasi-symmetrical in reference to the centers of of the hemispheres. Both systems had been formed over the common megacycle of evolution of planets and their origin is likely to have similar features. The formation of the Earth's oceanic system within the South Hemisphere seems to have proceeded in three stages: (1) the formation of a network of passive rifts at the center of the Gondwana; (2) the formation of the system of active rifts at the zones of forthcoming spreading; and (3) the spreading of the oceanic crust. The formation of the Mar's North Depression seems to have proceeded in two stages: (1) a formation of a dense network of grabens and faults at the center of the North Hemisphere over the upper mantle zone characterized by an anomalous warm-up and a density decrease; and (2) a collapse of the ancient crust and it's overflowing by basalts. The first stage of the ocean formation on Earth and Mars is similar. But there seems to have been a thinner lithosphere on Mars. The dense areal rifting was immediately followed by a total collapse
On the differences in continental rifting at the Earth, Mars and Venus
During the process of continental rifting on Earth, the lower ductile crust stretches, forming a neck, while the upper brittle crust is broken in blocks by faults, and the blocks sink down the thinned lower crust; if the stretching continues, the neck may break and a newly originated oceanic crust is formed at this place. The rift system structure depends on the depth of the boundary surface between the brittle crust and the ductile crust, the litospheric thickness, the tension value, etc.. The rigid brittle rifting when narrow necks form in the lower crust is characteristic of the contemporary Earth; on Mars the brittle rifting with large subsidence was characteristic of the Tharsis upland formation epoch. The ductile rifting is typical of the Venus. The differences in rheologic features of the lithospheres of different planets causes the variation in types of rifting
Different types of small volcanos on Venus
One of the studies of volcanic activity on Venus is the comparison of that with the analogous volcanic activity on Earth. The preliminary report of such a comparison and description of a small cluster of small venusian volcanos is represented in detail in this paper
A family of Nikishin systems with periodic recurrence coefficients
Suppose we have a Nikishin system of measures with the th generating
measure of the Nikishin system supported on an interval \Delta_k\subset\er
with for all . It is well known that
the corresponding staircase sequence of multiple orthogonal polynomials
satisfies a -term recurrence relation whose recurrence coefficients,
under appropriate assumptions on the generating measures, have periodic limits
of period . (The limit values depend only on the positions of the intervals
.) Taking these periodic limit values as the coefficients of a new
-term recurrence relation, we construct a canonical sequence of monic
polynomials , the so-called \emph{Chebyshev-Nikishin
polynomials}. We show that the polynomials themselves form a sequence
of multiple orthogonal polynomials with respect to some Nikishin system of
measures, with the th generating measure being absolutely continuous on
. In this way we generalize a result of the third author and Rocha
\cite{LopRoc} for the case . The proof uses the connection with block
Toeplitz matrices, and with a certain Riemann surface of genus zero. We also
obtain strong asymptotics and an exact Widom-type formula for the second kind
functions of the Nikishin system for .Comment: 30 pages, minor change
An Algebraic Model for the Multiple Meixner Polynomials of the First Kind
An interpretation of the multiple Meixner polynomials of the first kind is
provided through an infinite Lie algebra realized in terms of the creation and
annihilation operators of a set of independent oscillators. The model is used
to derive properties of these orthogonal polynomials
Critical behavior in Angelesco ensembles
We consider Angelesco ensembles with respect to two modified Jacobi weights
on touching intervals [a,0] and [0,1], for a < 0. As a \to -1 the particles
around 0 experience a phase transition. This transition is studied in a double
scaling limit, where we let the number of particles of the ensemble tend to
infinity while the parameter a tends to -1 at a rate of order n^{-1/2}. The
correlation kernel converges, in this regime, to a new kind of universal
kernel, the Angelesco kernel K^{Ang}. The result follows from the Deift/Zhou
steepest descent analysis, applied to the Riemann-Hilbert problem for multiple
orthogonal polynomials.Comment: 32 pages, 9 figure
Large Deviations for a Non-Centered Wishart Matrix
We investigate an additive perturbation of a complex Wishart random matrix
and prove that a large deviation principle holds for the spectral measures. The
rate function is associated to a vector equilibrium problem coming from
logarithmic potential theory, which in our case is a quadratic map involving
the logarithmic energies, or Voiculescu's entropies, of two measures in the
presence of an external field and an upper constraint. The proof is based on a
two type particles Coulomb gas representation for the eigenvalue distribution,
which gives a new insight on why such variational problems should describe the
limiting spectral distribution. This representation is available because of a
Nikishin structure satisfied by the weights of the multiple orthogonal
polynomials hidden in the background.Comment: 40 page
Three-Beam Triangulating Sensor
© Published under licence by IOP Publishing Ltd. The new high precision triangulating sensor for measuring distance and/or inclination angle with high temperature stability for a wide range of technical and technological applications is proposed. The corresponding measurement algorithm is considered and hardware allowing its implementation is developed. The preferable embodiment of three beam triangulating sensor comprises three laser radiation sources, CCD- array based image sensor including optical system, and control electronic unit
Внутриядерные включения в макрофагах ящерицы Lacerta agilis, экспериментально инвазированной скребнем Corynosoma strumosum
The purpose of the research: to study the cell response of non-natural paratenic host and encapsulation process of acanthocephalan Corynosoma strumosum in experiment for further comparison with encapsulation mechanism of this acanthocephalan in natural paratenic host. Materials and methods. Experiments were carried out on 24 lizards Lacerta agilis and one L. viridis. 17 encapsulated acanthocephalans were received from 13 of them. Acanthocephalans with capsules were prepared for electron microscopic analysis according to standard methods and examined in light (semithin sections) and under electron (in ultrathin sections) microscopes. Semithin sections were stained with methylene blue or a mixture of methylene blue and crystal violet. Ultrathin sections were stained with lead citrate. All capsules received in the experiment were investigated with the use of the light microscope; 1,5 and 10 day capsules were examined under electron microscope. Results and discussion. All acanthocephalans studied in this paper including those discovered one and half day after the start of experiment were enclosed in the thick cellular capsule with prevailing mononuclear and multinuclear macrophages. Single electron-dense inclusions of regular rounded shape surrounded by hallo of moderately dense material were found in approximately half of both types of nuclei. Nature of inclusions remained unknown. In the interpretation of results, it is necessary to take into account: 1) the presence of these inclusions in macrophage nuclei only; 2) their strictly ordinary positioning in the nucleus; 3) strictly spherical shape; 4) very high electronic density of their material, that exceeds the density of the nucleolus and chromatin; 5) presence of halo; 6) absence of visible pathological signs in nuclei and cell’s cytoplasm where these inclusions had been found. Their appearance is supposed to be connected with the overactivity of lizard macrophages caused by invasion of a parasitic worm.Цель исследований: изучение клеточного ответа неестественного паратенического хозяина и процесса инкапсуляции в нем скребня Corynosoma strumosum в условиях эксперимента для последующего сравнения с механизмом инкапсуляции этого скребня в естественном паратеническом хозяине. Материалы и методы. Опыты проводили на 24 ящерицах Lacerta agilis и одной L. viridis. От 13 из них были получены 17 инкапсулированных скребней. Скребней вместе с капсулами препарировали для электронно-микроскопических исследований по стандартной методике и изучали в световом (на полутонких срезах) и электронных (на ультратонких срезах) микроскопах. Полутонкие срезы окрашивали метиленовым синим или смесью метиленового синего и кристаллического фиолетового. Ультратонкие срезы контрастировали цитратом свинца. С применением светового микроскопа были исследованы все капсулы, полученные в эксперименте, электронно-микроскопически - капсулы в возрасте 1,5 и 10 сут. Результаты и обсуждение. Все исследованные скребни, включая и обнаруженных через полтора суток после начала эксперимента, были заключены в толстую клеточную капсулу, в составе которой преобладали одноядерные или мультиядерные макрофаги. Примерно в половине ядер были обнаружены одиночные электронно-плотные включения правильной округлой формы, окруженные гало из умеренно-плотного материала. Природа включений осталась неизвестной. При интерпретации результатов описанной находки необходимо учитывать: 1) наличие этих включений в ядрах только макрофагов; 2) строго одиночное расположение их в ядрах; 3) строго сферическая форма; 4) очень высокая электронная плотность образующего их материала, превышающая плотность ядрышка и хроматина; 5) наличие гало; 6) отсутствие видимых признаков патологии ядер и цитоплазмы клеток, в которых эти включения обнаружены. Предполагается, что их появление связано с повышенной активностью макрофагов ящерицы, вызванной инвазией паразитическим червем
Рифтовые системы шельфа Российской Восточной Арктики и арктического глубоководного бассейна: связь геологической истории и геодинамики
In our study, we have developed a new tectonic scheme of the Arctic Ocean, which is based mainly on seismic profiles obtained in the Arctic-2011, Arctic-2012 and Arctic-2014 Projects implemented in Russia. Having interpreted many seismic profiles, we propose a new seismic stratigraphy of the Arctic Ocean. Our main conclusions are drawn from the interpretation of the seismic profiles and the analysis of the regional geological data. The results of our study show that rift systems within the Laptev, the East Siberian and the Chukchi Seas were formed not earlier than Aptian. The geological structure of the Eurasian, Podvodnikov, Toll and Makarov Basins is described in this paper. Having synthesized all the available data on the study area, we propose the following model of the geological history of the Arctic Ocean: 1. The Canada Basin formed till the Aptian (probably, during Hauterivian-Barremian time). 2. During the Aptian-Albian, large-scale tectonic and magmatic events took place, including plume magmatism in the area of the De Long Islands, Mendeleev Ridge and other regions. Continental rifting started after the completion of the Verkhoyansk-Chukotka orogenу, and rifting occurred on the shelf of the Laptev, East Siberian, North Chukchi and South Chukchi basins, and the Chukchi Plateau; simultaneously, continental rifting started in the Podvodnikov and Toll basins. 3. Perhaps the Late Cretaceous rifting continued in the Podvodnikov and Toll basins. 4. At the end of the Late Cretaceous and Paleocene, the Makarov basin was formed by rifting, although local spreading of oceanic crust during its formation cannot be excluded. 5. The Eurasian Basin started to open in the Early Eocene. We, of course, accept that our model of the geological history of the Arctic Ocean, being preliminary and debatable, may need further refining. In this paper, we have shown a link between the continental rift systems on the shelf and the formation history of the Arctic Ocean.На основе российских сейсмических профилей, полученных в рамках проектов Арктика-2011, Арктика-2012 и Арктика-2014, составлена новая тектоническая схема Арктического океана. Приведены результаты интерпретации многих сейсмических профилей, представлена новая сейсмостратиграфия для Арктического океана. Основные выводы сделаны на основе интерпретации сейсмических профилей и на базе анализа региональных геологических данных. Показано, что рифтовые системы в пределах морей Лаптевых, Восточно-Сибирского и Чукотского были образованы не раньше аптского времени. Дано описание геологического строения бассейнов Евразийского, Подводников, Толля, Макарова и других. На основе синтеза всех данных получена следующая модель истории Арктического океана. 1. Канадский бассейн был образован до аптского времени (вероятно, в готериве-барреме). 2. В апте-альбе были крупномасштабные тектонические и магматические события: плюмовый магматизм был в районе поднятия Де-Лонга, на хребте Менделеева и в других областях. Континентальный рифтинг произошел сразу после окончания Верхоянско-Чукотской орогении и рифтинг был на шельфе морей Лаптевых, Восточно-Сибирского, Северо-Чукотского и Южно-Чукотского и на поднятии Чукотского плато; одновременно континентальный рифтинг начался в бассейнах Подводников и Толля. 3. В позднем мелу рифтинг, возможно, продолжился в бассейнах Подводников и Толля. 4. В конце позднего мела и в палеоцене в ходе рифтинга был образован бассейн Макарова; локальный спрединг океанической коры при формировании бассейна Макарова не исключен. 5. Евразийский бассейн начал образовываться в начале эоцена. Наша модель геологической истории Арктического океана является предварительной и дискуссионной. В целом, мы показали связь континентальных рифтовых систем на шельфах с историей раскрытия Арктического океана
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