Космический мусор, как следствие человеческой деятельности

В данной статье рассматриваются проблемы загрязнения космического пространства. В статьеописывается, какими опасными могут быть космические полеты, даже беспилотные спутники находятсяв постоянной опасности. Кроме того, что мы можем предпринять для устранения этих проблем, кпримеру, выведенные из строя спутники должны быть аккуратно утилизированы, их можноперенаправить на более низкую орбиту или они могут сгореть в плотных слоях атмосферы. Если непредпринять вовремя необходимые мероприятия, то они могут столкнуться с еще действующимиспутниками и вывести их из строя, а это может привести к цепной реакции. В статье описывается, какзащищены спутники от внешнего воздействия и что проблема их утилизации должна решаться еще настадии проектирования. Если мы уже на данном этапе времени займемся данной проблемой, то мысможем оставить будущим поколениям чистый и безопасный космос.Im vorliegenden Artikel werden die Probleme der Weltraumverschmutzung dargestellt. Der Artikelbeschreibt, wie gefahrlich die Weltraummissionen sein konnen, dass sogar unbemannte Satelliten der standigenGefahr ausgesetzt werden. Genauso erfahren wir, was wir gegen diese Gefahren tun konnen, z.B. ausgedienteSatelliten vorsichtig zu entsorgen,indemman sie auf eine andere Umlaufbahn bringt oder in den festen Schichten derErde vergluhen lasst. Wenn man dies nicht macht, so konnen sie mit den funktionierenden Satellitenzusammensto?en und diese au?er Betrieb setzen, was zur einen Kettenreaktion fuhren kann. Zudem beschreibt derText, wie die Satelliten geschutzt werden z.B. mit Hilfe von Schottelementen und dass man die Probleme derEntsorgung schon in der Projektierung angehen muss. Wenn wir dieses Problem schon heute angehen, souberlassen wir unserer nachfolgenden Generation einen sauberen und sicheren Weltraum

Carbon Ignition in Type Ia Supernovae: An Analytic Model

The observable properties of a Type Ia supernova are sensitive to how the nuclear runaway ignites in a Chandrasekhar mass white dwarf - at a single point at its center, off-center, or at multiple points and times. We present a simple analytic model for the runaway based upon a combination of stellar mixing-length theory and recent advances in understanding Rayleigh-Benard convection. The convective flow just prior to runaway is likely to have a strong dipolar component, though higher multipoles may contribute appreciably at the very high Rayleigh number (10$^{25}$) appropriate to the white dwarf core. A likely outcome is multi-point ignition with an exponentially increasing number of ignition points during the few tenths of a second that it takes the runaway to develop. The first sparks ignite approximately 150 - 200 km off center, followed by ignition at smaller radii. Rotation may be important to break the dipole asymmetry of the ignition and give a healthy explosion.Comment: 14 pages, 0 figures, submitted to ApJ, corrected typo in first author's nam

Direct Detection of Dark Matter Debris Flows

Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended "debris flows" in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earth's location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments. At Earth-frame speeds greater than 450 km/s, debris flow comprises more than half of the dark matter at the Sun's location, and up to 80% at even higher speeds. Therefore, debris flow is most important for experiments that are particularly sensitive to the high speed tail of the dark matter distribution, such as searches for light or inelastic dark matter or experiments with directional sensitivity. We show that debris flow yields a distinctive recoil energy spectrum and a broadening of the distribution of incidence direction.Comment: 22 pages, 7 figures; accepted for publication in PR

Gravitational Lensing Statistics in Universes Dominated by Dark Energy

We study lens statistics in flat, low-density universes with different equations of state $w=p_Q/\rho_Q$ for the dark energy component. Dark energy modifies the distance-redshift relation and the mass function of dark matter halos leading to changes in the lensing optical depth as a function of image separation. Those effects must, however, be distinguished from effects associated with the structure of dark matter halos. Baryonic cooling causes galaxy-mass halos to have different central density profiles than group- and cluster-mass halos, which causes the distribution of normal arcsecond-scale lenses to differ from the distribution of ``wide-separation'' (\Delta\theta \gtrsim 4\arcsec) lenses. Fortunately, the various parameters related to cosmology and halo structure have very different effects on the overall image separation distribution: (1) the abundance of wide-separation lenses is exremely sensitive (by orders of magnitude) to the distribution of ``concentration'' parameters for massive halos modeled with the Navarro-Frenk-White profile; (2) the transition between normal and wide-separation lenses depends mainly on the mass scale where baryonic cooling ceases to be efficient; and (3) dark energy has effects at all image separation scales. While current lens samples cannot usefully constrain all of the parameters, ongoing and future imaging surveys should discover hundreds or thousands of lenses and make it possible to disentangle the various effects and constrain all of the parameters simultaneously. (abridged)Comment: 15 pages, 11 figures, accepted for publication in Ap

Breaking Cosmological Degeneracies in Galaxy Cluster Surveys with a Physical Model of Cluster Structure

Forthcoming large galaxy cluster surveys will yield tight constraints on cosmological models. It has been shown that in an idealized survey, containing > 10,000 clusters, statistical errors on dark energy and other cosmological parameters will be at the percent level. It has also been shown that through "self-calibration", parameters describing the mass-observable relation and cosmology can be simultaneously determined, though at a loss in accuracy by about an order of magnitude. Here we examine the utility of an alternative approach of self-calibration, in which a parametrized ab-initio physical model is used to compute cluster structure and the resulting mass-observable relations. As an example, we use a modified-entropy ("pre-heating") model of the intracluster medium, with the history and magnitude of entropy injection as unknown input parameters. Using a Fisher matrix approach, we evaluate the expected simultaneous statistical errors on cosmological and cluster model parameters. We study two types of surveys, in which a comparable number of clusters are identified either through their X-ray emission or through their integrated Sunyaev-Zel'dovich (SZ) effect. We find that compared to a phenomenological parametrization of the mass-observable relation, using our physical model yields significantly tighter constraints in both surveys, and offers substantially improved synergy when the two surveys are combined. These results suggest that parametrized physical models of cluster structure will be useful when extracting cosmological constraints from SZ and X-ray cluster surveys. (abridged)Comment: 22 pages, 8 figures, accepted to Ap

Physical approximations for the nonlinear evolution of perturbations in dark energy scenarios

The abundance and distribution of collapsed objects such as galaxy clusters will become an important tool to investigate the nature of dark energy and dark matter. Number counts of very massive objects are sensitive not only to the equation of state of dark energy, which parametrizes the smooth component of its pressure, but also to the sound speed of dark energy as well, which determines the amount of pressure in inhomogeneous and collapsed structures. Since the evolution of these structures must be followed well into the nonlinear regime, and a fully relativistic framework for this regime does not exist yet, we compare two approximate schemes: the widely used spherical collapse model, and the pseudo-Newtonian approach. We show that both approximation schemes convey identical equations for the density contrast, when the pressure perturbation of dark energy is parametrized in terms of an effective sound speed. We also make a comparison of these approximate approaches to general relativity in the linearized regime, which lends some support to the approximations.Comment: 15 pages, 2 figure

Redefining the Missing Satellites Problem

Numerical simulations of Milky-Way size Cold Dark Matter (CDM) halos predict a steeply rising mass function of small dark matter subhalos and a substructure count that greatly outnumbers the observed satellites of the Milky Way. Several proposed explanations exist, but detailed comparison between theory and observation in terms of the maximum circular velocity (Vmax) of the subhalos is hampered by the fact that Vmax for satellite halos is poorly constrained. We present comprehensive mass models for the well-known Milky Way dwarf satellites, and derive likelihood functions to show that their masses within 0.6 kpc (M_0.6) are strongly constrained by the present data. We show that the M_0.6 mass function of luminous satellite halos is flat between ~ 10^7 and 10^8 M_\odot. We use the ``Via Lactea'' N-body simulation to show that the M_0.6 mass function of CDM subhalos is steeply rising over this range. We rule out the hypothesis that the 11 well-known satellites of the Milky Way are hosted by the 11 most massive subhalos. We show that models where the brightest satellites correspond to the earliest forming subhalos or the most massive accreted objects both reproduce the observed mass function. A similar analysis with the newly-discovered dwarf satellites will further test these scenarios and provide powerful constraints on the CDM small-scale power spectrum and warm dark matter models.Comment: 8 pages, 6 figure

Educational profession-oriented propaedeutic Russian language course as a basis of coming of international students of pre-university training stage into the educational medium of the higher medical institution

Цель статьи - рассмотреть некоторые способы и методы (фреймовый подход) формирования лингвокультурологической медицинской компетенции иностранных учащихся предвузовского этапа на занятиях по русскому языку общелитературного стиля в соответствии со спецификой их будущего обучения в русскоязычной среде медицинского вуза. Актуальность исследования заключается в том, что учебный пропедевтический курс русского языка, ориентированный на изучение иностранными учащимися языка медицинской науки, является важнейшим и необходимым условием для их обучения в медицинском университете. Преподавание основывается на использовании общедидактических и методических принципов начального обучения русскому языку будущих студентов- медиков, которые способствуют дальнейшему усвоению и совершенствованию учебно- профессиональных знаний в условиях русской языковой среды медицинского вуза. В процессе исследования были использованы следующие методы: теоретический и практический анализ научной литературы по методике преподавания иностранного языка и русского как иностранного, аудиовизуальное наблюдение, беседы с иностранными студентами, пробное обучение. Результаты. В процессе изучения русского языка иностранные учащиеся приобретают новые знания, расширяется их эрудиция, кругозор. Иностранные учащиеся предвузовского этапа входят в мир языка медицинской науки, знакомясь с элементами её лингвистической, коммуникативной и культурологической базы. Выводы: пропедевтический курс русского языка закладывает основы знаний о специфике изучения медицины на русском языке, которые помогут иностранным учащимся предвузовского этапа подготовки спустя год войти в образовательную среду медицинского университета.The aim of the research is to consider some ways and methods (frame approach) of forming lingual- cultural medical competence of international students of pre-University training stage at the Russian Language classes in accordance with the specifics of their future learning in Russian-speaking medium of higher medical institution. Relevance of the study lies in the fact that educational propaedeutic course of the Russian Language, focused on training foreign students the language of medical science, is the most important and necessary condition for their studying in the medical university. Training is based on the usage of general didactic and methodical principles of elementary level of teaching Russian the future medical students, which promoting further learning and mastering the educational-professional knowledge in the conditions of Russian speaking environment of higher medical institution. The author has used the following methods: theoretical and practical analysis of scientific literature on methods of teaching foreign language and Russian as a foreign language, audio-visual monitoring, interviews with foreign students, experimental teaching. Results. When learning Russian the international students get knowledge, enlarge their erudition, the outlook. International students of pre-University training stage come into the world of the Language of medical science, becoming acquainted with the elements of its linguistic, communicative and cultural base. Conclusion. The propaedeutic course of Russian lays foundations of knowledge of specifics of learning medicine in Russian, which will help international students of pre-university training stage to be admitted to the educational environment of medical University after the first year of studying