Ellipsoidal configurations in the de Sitter spacetime

The cosmological constant $\Lambda$ modifies certain properties of large astrophysical rotating configurations with ellipsoidal geometries, provided the objects are not too compact. Assuming an equilibrium configuration and so using the tensor virial equation with $\Lambda$ we explore several equilibrium properties of homogeneous rotating ellipsoids. One shows that the bifurcation point, which in the oblate case distinguishes the Maclaurin ellipsoid from the Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that, the cosmological constant allows triaxial configurations of equilibrium rotating the minor axis as solutions of the virial equations. The significance of the result lies in the fact that minor axis rotation is indeed found in nature. Being impossible for the oblate case, it is permissible for prolate geometries, with $\Lambda$ zero and positive. For the triaxial case, however, an equilibrium solution is found only for non-zero positive $\Lambda$. Finally, we solve the tensor virial equation for the angular velocity and display special effects of the cosmological constant there.Comment: 15 pages, 11 figures, published in Class. Quant. Grav. References adde

Оценка эффективности лечения новообразований печени по данным КТ и МРТ: дорожная карта для врача лучевой диагностики

The number of available methods for hepatic tumor treatment is steadily increasing. Except traditional surgical resection and systemic chemotherapy there are a lot of effective and increasingly used local methods such as Radiofrequency ablation, cryodestruction, transarterial chemoembolization. Radiologist should be able to assess treatment response and evaluate prognosis. We present review of literature on various systems for hepatic tumor treatment response evaluation. WHO, RECIST 1.0, RECIST 1.1, mRECIST and Choi criteria are thoroughly explained in terms of benefits and drawbacks. Also, texture analysis and diffusion-weighted imaging are discussed.В последние годы выбор различных вариантов терапии образований печени становится все шире, отмечается появление новых вариантов химио- и лучевой терапии. В настоящее время растет количество методов локального воздействия на опухоли, таких как радиочастотная абляция, криодеструкция, трансартериальная эмболизация. Клиническая оценка эффекта терапии не дает необходимого результата, поэтому возрастает потребность в адекватной оценке результатов лечения, основанной на данных методов КТ и МРТ. В данном литературном обзоре приводятся основные критерии оценки эффективности лечения опухолей различными видами воздействия. Отдельно рассматриваются критерии ВОЗ, RECIST, RECIST 1.1, mRECIST, Choi. Помимо этого обсуждаются новые методики объективизации эффектов терапии, основанные на оценке диффузионно-взвешенных изображений и текстурном анализе

Landscape science: a Russian geographical tradition

The Russian geographical tradition of landscape science (landshaftovedenie) is analyzed with particular reference to its initiator, Lev Semenovich Berg (1876-1950). The differences between prevailing Russian and Western concepts of landscape in geography are discussed, and their common origins in German geographical thought in the late nineteenth and early twentieth centuries are delineated. It is argued that the principal differences are accounted for by a number of factors, of which Russia's own distinctive tradition in environmental science deriving from the work of V. V. Dokuchaev (1846-1903), the activities of certain key individuals (such as Berg and C. O. Sauer), and the very different social and political circumstances in different parts of the world appear to be the most significant. At the same time it is noted that neither in Russia nor in the West have geographers succeeded in specifying an agreed and unproblematic understanding of landscape, or more broadly in promoting a common geographical conception of human-environment relationships. In light of such uncertainties, the latter part of the article argues for closer international links between the variant landscape traditions in geography as an important contribution to the quest for sustainability