Reduction of the Casimir force using aerogels

By using silicon oxide based aerogels we show numerically that the Casimir force can be reduced several orders of magnitude, making its effect negligible in nanodevices. This decrease in the Casimir force is also present even when the aerogels are deposited on metallic substrates. To calculate the Casimir force we model the dielectric function of silicon oxide aerogels using an effective medium dielectric function such as the Clausius-Mossotti approximation. The results show that both the porosity of the aerogel and its thickness can be use as control parameters to reduce the magnitude of the Casimir force.Comment: to appear J. Appl. Phy

Isometry invariance of exact correlation functions in various charts of Minkowski and de Sitter spaces

We consider quantum field theory with selfinteractions in various patches of Minkowski and de Sitter space-times. Namely, in Minkowski space-time we consider separately right (left) Rindler wedge, past wedge and future wedge. In de Sitter space-time we consider expanding Poincare patch, static patch, contracting Poincare patch and global de Sitter itself. In all cases we restrict our considerations to the isometry invariant states leading to maximally analytic propagators. We prove that loop corrections in right (left) Rindler wedge, in the past wedge (of Minkowski space-time), in the static patch and in the expanding Poincare patch (of de Sitter space-time) respect the corresponding isometries of the corresponding symmetric space-times. All these facts are related to the causality and analyticity properties of the propagators for the states that we consider. At the same time in the future wedge, in the contracting Poincare patch and in global de Sitter space-time infrared effects violate the isometries.Comment: 35 pages, 6 figures Additional references and minor clarifications added; version accepted to PR

On the Theory of Plasmon Dispersion in Electron-Doped Cuprates

© 2018, Pleiades Publishing, Inc. An explicit expression for the dynamic charge susceptibility for electron-doped cuprates has been derived. This expression accurately reproduces the wave vector dependence of the plasmon frequency observed in inelastic X-ray scattering experiments for Nd2 – xCexCuO4. The imaginary part of the charge susceptibility along the triangular path in the Brillouin zone is plotted. It is demonstrated that the spectral weight of the plasmon mode near q = 0 is negligibly low. The calculated frequencies of the plasmon mode for all wave vectors in the Brillouin zone turn out to lie outside the range of damping related to electron−hole excitations. A formula for the charge susceptibility is derived within the t−t′−t″−J model supplemented by the Coulomb interaction operator and three-site terms. The derivation is performed by the Green’s function technique employing the formalism of composite Hubbard operators and the Mori projection method, which have proved themselves in the analysis of collective spin excitations. The used Fourier transform of the Coulomb interaction corresponds to the monolayer model with a spatially periodic structure, which is embedded in a three-dimensional crystal lattice

Anatomy of the fragmented Hilbert space: eigenvalue tunneling, quantum scars and localization in the perturbed random regular graph

We consider the properties of the random regular graph with node degree $d$ perturbed by chemical potentials $\mu_k$ for a number of short $k$-cycles. We analyze both numerically and analytically the phase diagram of the model in the $(\mu_k,d)$ plane. The critical curve separating the homogeneous and clusterized phases is found and it is demonstrated that the clusterized phase itself generically is separated as the function of $d$ into the phase with ideal clusters and phase with coupled ones when the continuous spectrum gets formed. The eigenstate spatial structure of the model is investigated and it is found that there are localized scar-like states in the delocalized part of the spectrum, that are related to the topologically equivalent nodes in the graph. We also reconsider the localization of the states in the non-perturbative band formed by eigenvalue instantons and find the semi-Poisson level spacing distribution. The Anderson transition for the case of combined ($k$-cycle) structural and diagonal (Anderson) disorders is investigated. It is found that the critical diagonal disorder gets reduced sharply at the clusterization phase transition, but does it unevenly in non-perturbative and mid-spectrum bands, due to the scars, present in the latter. The applications of our findings to $2$d quantum gravity are discussed.Comment: 27 pages, 9 figures, 87 references + 4 pages, 4 figures in Appendice

Statistical Description of Hydrodynamic Processes in Ionic Melts with taking into account Polarization Effects

Statistical description of hydrodynamic processes for ionic melts is proposed with taking into account polarization effects caused by the deformation of external ionic shells. This description is carried out by means of the Zubarev nonequilibrium statistical operator method, appropriate for investigations of both strong and weak nonequilibrium processes. The nonequilibrium statistical operator and the generalized hydrodynamic equations that take into account polarization processes are received for ionic-polarization model of ionic molten salts when the nonequilibrium averaged values of densities of ions number, their momentum, dipole momentum and total energy are chosen for the reduced description parameters. A spectrum of collective excitations is investigated within the viscoelastic approximation for ion-polarization model of ionic melts.Comment: 24 pages, RevTex4.1-format, no figure

Steady Stokes flow with long-range correlations, fractal Fourier spectrum, and anomalous transport

We consider viscous two-dimensional steady flows of incompressible fluids past doubly periodic arrays of solid obstacles. In a class of such flows, the autocorrelations for the Lagrangian observables decay in accordance with the power law, and the Fourier spectrum is neither discrete nor absolutely continuous. We demonstrate that spreading of the droplet of tracers in such flows is anomalously fast. Since the flow is equivalent to the integrable Hamiltonian system with 1 degree of freedom, this provides an example of integrable dynamics with long-range correlations, fractal power spectrum, and anomalous transport properties.Comment: 4 pages, 4 figures, published in Physical Review Letter

Selfsimilarity and growth in Birkhoff sums for the golden rotation

We study Birkhoff sums S(k,a) = g(a)+g(2a)+...+g(ka) at the golden mean rotation number a with periodic continued fraction approximations p(n)/q(n), where g(x) = log(2-2 cos(2 pi x). The summation of such quantities with logarithmic singularity is motivated by critical KAM phenomena. We relate the boundedness of log- averaged Birkhoff sums S(k,a)/log(k) and the convergence of S(q(n),a) with the existence of an experimentally established limit function f(x) = lim S([x q(n)])(p(n+1)/q(n+1))-S([x q(n)])(p(n)/q(n)) for n to infinity on the interval [0,1]. The function f satisfies a functional equation f(ax) + (1-a) f(x)= b(x) with a monotone function b. The limit lim S(q(n),a) for n going to infinity can be expressed in terms of the function f.Comment: 14 pages, 8 figure

ФРАКЦИОННЫЙ РЕЗЕРВ КАК СПОСОБ ОПРЕДЕЛЕНИЯ ЗНАЧИМОСТИ ТАНДЕМНЫХ И БИФУРКАЦИОННЫХ СТЕНОЗОВ, ПОРАЖЕНИЯ СТВОЛА ЛЕВОЙ КОРОНАРНОЙ АРТЕРИИ J. MALLIDI, MD, MHS; A. LOTFI, MD, FSCAI (Перевод выполнили Н. А. Кочергин , А. М. Кочергина)

Subjects with tandem lesions bifurcation lesions, left main disease and acute coronary syndrome are not included in trials supporting fractional flow reserve (FFR)-guided revascularization. Assessment and interpretation of FFR in these clinical scenarios is technically challenging due to the unique changes in flow hemodynamics in each of these situations. The existing literature supports the safety of using FFR to guide revascularization in these situations; however, the evidence is limited and further research is warranted.Пациенты с тандемными и бифуркационными стенозами, поражением ствола левой коронарной артерии и острым коронарным синдромом не включаются в клинические исследования, изучающие фракционный резерв кровотока. Измерение фракционного резерва кровотока, а также интерпретация его результатов представляют особые затруднения, так как в каждом случае имеются особенности коронарной гемодинамики. Согласно имеющимся данным, определение фракционного резерва кровотока при проведении реваскуляризации миокарда является безопасным и эффективным методом, однако доказательная база недостаточна, что обусловливает потребность в дальнейших исследованиях

Внутрисосудистый ультразвук как метод выявления нестабильных атеросклеротических бляшек коронарных артерий (обзор литературы)

The vulnerable plaque is an atherosclerotic plaque which can lead to  thrombosis of a coronary artery with development of an acute coronary  syndrome. Most myocardial infarctions occur in people with average  levels of risk factors and thrombosis mostly originate from lesions that  are less severely narrowed. Thus, in most cases, these plaques are clinically silent before the “unheralded” acute event and would not  be considered eligible for preventive treatment based on current  guidelines. The main question is to identify thrombosis-prone  “vulnerable” plaques before they rupture or become destabilized. IVUS  is a useful tool in identifying high risk plaque features and vulnerable lesions in patients.Под нестабильной подразумевается бляшка, склонная к разрыву, которая может привести к  тромбозу коронарной артерии с развитием острого коронарного синдрома. Инфаркт  миокарда часто происходит у пациентов, которые имеют средний риск неблагоприятных кардиоваскулярных событий, причем тромбоз часто происходит в  поражениях коронарных артерий с умеренно выраженной степенью стеноза. Таким образом, в большинстве случаев такие бляшки клинически себя никак не проявляют до  развития острого события, а также не подлежат реваскуляризации согласно актуальным  рекомендациям. Одним из важных вопросов является выявление нестабильных бляшек с  целью разработки мер профилактики. Внутрисосудистый ультразвук с виртуальной гистологией – полезный и  эффективный метод выявления нестабильных бляшек, который позволяет определить  категорию пациентов с высоким риском неблагоприятных коронарных событий

Эффекты блокаторов рецепторов к ангиотензину II у пациентов со стабильной ишемической болезнью сердца

Highlights. The review synthesizes the results of clinical studies on the use of sartans. This topic is highly relevant due to the antihypertensive, metabolic and organ-protective effect of sartans, which can positively affect the course of coronary atherosclerosis.Abstract. Angiotensin II receptor blockers (sartans) are widely used to treat cardiovascular diseases. This class of drugs has antihypertensive and metabolic effects and organ-protective capabilities. Currently, sartans are of high interest due to their pleiotropic effect: improved lipid metabolism, antidiabetogenic action, nephroprotection, and, as a result, reduced total cardiovascular risk. The article presents an overview of clinical data on the use of sartans in patients with ischemic heart disease, the mechanisms of organ-protective effects and prospects of using this class of drugs for total cardiovascular risk reduction. The following data sources were used: e-Library, ClinicalTrials.gov, PubMed, trialbulletin.com, smartpatients.com, BioPortfolio.com.Основные положения. В обзоре систематизированы результаты клинических исследований группы лекарственных препаратов сартанов. Актуальность материала обусловлена наличием у сартанов не только антигипертензивного, но метаболических и органопротективных эффектов, которые могут положительно влиять на течение коронарного атеросклероза.Резюме. Блокаторы рецепторов к ангиотензину II (сартаны) - группа средств, широко применяемых для лечения сердечно-сосудистых заболеваний. Препараты этой группы демонстрируют не только антигипертензивное действие, но и ряд органопротективных и метаболических эффектов. В настоящее время отмечен интерес к данной группе препаратов с позиции их плейотропного эффекта: улучшения липидного обмена, антидиабетогенного действия, нефропротекции и, как следствие, снижения суммарного кардиоваскулярного риска. Статья представляет собой обзор данных о результатах использования сартанов у пациентов с ишемической болезнью сердца, механизмах органопротективного влияния и перспективах применения этой группы препаратов с целью воздействия на риск сердечно-сосудистых заболеваний. При подготовке статьи использованы ресурсы eLIBRARY.ru, ClinicalTrials.gov, PubMed, trialbulletin.com, smartpatients.com, BioPortfolio.com