A Bayesian approach to the estimation of maps between riemannian manifolds

Let \Theta be a smooth compact oriented manifold without boundary, embedded in a euclidean space and let \gamma be a smooth map \Theta into a riemannian manifold \Lambda. An unknown state \theta \in \Theta is observed via X=\theta+\epsilon \xi where \epsilon>0 is a small parameter and \xi is a white Gaussian noise. For a given smooth prior on \Theta and smooth estimator g of the map \gamma we derive a second-order asymptotic expansion for the related Bayesian risk. The calculation involves the geometry of the underlying spaces \Theta and \Lambda, in particular, the integration-by-parts formula. Using this result, a second-order minimax estimator of \gamma is found based on the modern theory of harmonic maps and hypo-elliptic differential operators.Comment: 20 pages, no figures published version includes correction to eq.s 31, 41, 4

Semiclassical treatment of fusion processes in collisions of weakly bound nuclei

We describe a semiclassical treatment of nuclear fusion reactions involving weakly bound nuclei. In this treatment, the complete fusion probabilities are approximated by products of two factors: a tunneling probability and the probability that the system is in its ground state at the strong absorption radius. We investigate the validity of the method in a schematic two-channel application, where the channels in the continuum are represented by a single resonant state. Comparisons with full coupled-channels calculations are performed. The agreement between semiclassical and quantal calculations isquite good, suggesting that the procedure may be extended to more sophisticated discretizations of the continuum.Comment: 11 pages, 5 figure

Low temperature dielectric relaxation in ordinary perovskite ferroelectrics: enlightenment from high-energy x-ray diffraction

Ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot be associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel–Fulcher–Tammann phenomenological equation. Results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.Postprint (author's final draft

Minimax Estimation of Nonregular Parameters and Discontinuity in Minimax Risk

When a parameter of interest is nondifferentiable in the probability, the existing theory of semiparametric efficient estimation is not applicable, as it does not have an influence function. Song (2014) recently developed a local asymptotic minimax estimation theory for a parameter that is a nondifferentiable transform of a regular parameter, where the nondifferentiable transform is a composite map of a continuous piecewise linear map with a single kink point and a translation-scale equivariant map. The contribution of this paper is two fold. First, this paper extends the local asymptotic minimax theory to nondifferentiable transforms that are a composite map of a Lipschitz continuous map having a finite set of nondifferentiability points and a translation-scale equivariant map. Second, this paper investigates the discontinuity of the local asymptotic minimax risk in the true probability and shows that the proposed estimator remains to be optimal even when the risk is locally robustified not only over the scores at the true probability, but also over the true probability itself. However, the local robustification does not resolve the issue of discontinuity in the local asymptotic minimax risk

Coherent optical control of correlation waves of spins in semiconductors

We calculate the dynamical fluctuation spectrum of electronic spins in a semiconductor under a steady-state illumination by light containing polarization squeezing correlations. Taking into account quasi-particle lifetime and spin relaxation for this non-equilibrium situation we consider up to fourth order optical effects which are sensitive to the squeezing phases. We demonstrate the possibility to control the spin fluctuations by optically modulating these phases as a function of frequency, leading to a non-Lorentzian spectrum which is very different from the thermal equilibrium fluctuations in n-doped semiconductors. Specifically, in the time-domain spin-spin correlation can exhibit time delays and sign flips originating from the phase modulations and correlations of polarizations, respectively. For higher light intensity we expect a regime where the squeezing correlations will dominate the spectrum.Comment: 17 pages, 8 figure

Процедурная седация и/или анальгезия: обзор литературы

АКТУАЛЬНОСТЬ: За последние десятилетия процедурная седация и/или анальгезия (ПС/ПСА) стала широко применяться с целью проведения диагностических исследований и малоинвазивных хирургических вмешательств во внеоперационных условиях. Представленные данные в литературе по ПС/ПСА содержат противоречивую информацию в отношении показаний, противопоказаний, рисков осложнений, базового уровня мониторинга и целевого уровня седации (ЦУС). ЦЕЛЬ ИССЛЕДОВАНИЯ: Провести анализ существующих практических рекомендаций, рандомизированных клинических исследований (РКИ), обзор данных литературы и систематизировать данные о возможностях использования седативных препаратов и наркотических анальгетиков в рамках процедурной седации. МАТЕРИАЛЫ И МЕТОДЫ: Проведен поиск в электронных базах PubMed, Medline, Embase, eLibrary рекомендаций по ПС/ПСА, РКИ и статей. РЕЗУЛЬТАТЫ: В обзоре литературы описаны уровни седации в порядке возрастания сложности и потенциального риска развития осложнений. Представлена сравнительная характеристика препаратов первой и второй линии для седации и обезболивания. Сформулированы минимальные требования к периоперационному мониторингу жизненно важных показателей, уровня седации и боли. ВЫВОДЫ: ПС/ПСА в плановом или неотложном порядке обеспечивает безопасное, комфортное и успешное выполнение диагностических исследований и малоинвазивных хирургических вмешательств. Принципы взаимодействия и введения седативных препаратов с наркотическими анальгетиками лежат в основе применения схем седации. Использование шкал имеет важное практическое значение для мониторинга динамики уровня седации и более тонкого управления дозами седативных препаратов. Абсолютных противопоказаний для ПС/ПСА нет. ПС/ПСА является востребованным направлением в современной практике анестезиолога-реаниматолога. Отсутствие в Российской Федерации регламентирующих документов по ПС/ПСА диктует необходимость разработки методических рекомендаций

Dexmedetomidine in anesthesia for planned endovascular myocardial revascularization

The aim of the study was to discuss a clinical case of dexmedetomidine in elective endovascular stenting of coronary arteries.Цель исследования — обсудить клинический случай применения дексмедетомидина при плановом эндоваскулярном стентировании коронарных артерий

Effect of dexmedetomidine on stented artery diameter during elective endovascular myocardial revascularization

The aim of the study was to evaluate the effect of monoanesthesia with dexmedetomidine on the diameter of the stented artery (proximal and distal to the site of stenosis) during elective endovascular stenting of the coronary arteries.Цель исследования – оценить влияние моно-анестезии дексмедетомидином на диаметр стентируемой артерии (проксимальнее и дистальнее места стеноза) при плановых эндоваскулярных стентированиях коронарных артерий

Поддержание минутного объема кровообращения при ортотопической трансплантации печени

Objective: to optimize procedures to maintain minute circulation volume at different stages of orthotopic liver transplantation. Subjects and methods. In the period 2005—2010, Sverdlovsk Regional Clinical Hospital One performed 32 orthotopic liver transplantations, including one retransplantation. The patients’ ASA class was (4—5). The operations were carried out under general anesthesia. The mean duration of surgery was 8.1 (range 5.8—10.5) hours. The investigators applied anesthesia based on iso-fluorane 0.6—0.9 MAC (by monitoring the anesthesia depth index with cerebral state index (CSI-40-60)), as well as extended central hemodynamic monitoring (prepulmonary hemodilution). All the operations were made via portofemoroaxillary bypass, by using a centrifugal Biopump. Eight surgical stages were identified: 1) run-in (after tracheal intubation); 2) liver mobilization; 3) partial bypass; 4) complete bypass (hepatectomy, a liver-free period); 5) reperfusion; 6) a postreperfusion period (bypass end); 7) biliary repair; 8) the end of an operation. The concentrations of blood parameters, electrolytes, acid-base balance, and the levels of lactate and glucose were examined. The data were processed statistically. Central hemodynamics was monitored by prepulmonary thermodilution, by calculating cardiac index (CI), stroke index, and total peripheral vascular resistance index (TPVRI) at the stages: liver mobilization, postreperfusion period (bypass end), and the end of surgery. Results. Even during partial bypass, there was a significant drop in mean blood pressure (MBP) as compared to the baseline levels (p<0.05). Reperfusion was also accompanied by a significant decrease in MBP and an increase in heart rate. At the end of reperfusion and in the postreperfusion period, TPVRI was halved (689.2±68.0) as compared to the baseline levels. In the postreperfusion period, central venous and pulmonary artery pressures were significantly increased by 32 and 21%, respectively. That period was marked by a significant rise in CI. Serum lactate and glucose elevations starting from the complete bypass stage were associated with the liver being excluded from the circulation and cannot be a marker of inadequate tissue perfusion. Conclusion. The decrease in MBP during portofemoroaxillary bypass is associated with hypovolemia and mainly with vasoplegia during reperfusion. Approaches to maintaining the adequate minute circulation volume depend on the surgical stage: sufficient preload is needed during complete bypass and it is expedient to combine an infused load with vasopressors for the correction of the reperfusion syndrome with low TPVR. Key words: liver transplantation, minute circulation volume, general anesthesia, central hemodynamics.Цель исследования — оптимизировать способы поддержания минутного объема кровообращения на различных этапах операции ортотопической трансплантации печени. Материал и методы. В период с 2005 по 2010 гг. в Свердловской областной клинической больнице №1 было выполнено 32 ортотопических трансплантаций печени, в том числе одна ретрансплантация. Класс больных по ASA — (4—5). Операцию проводили под общей анестезией. Средняя продолжительность операции составила 8,1 (5,8—10,5) часа. Использовали анестезию на основе изофлурана 0,6—0,9 МАК (под контролем индекса глубины анестезии CSI-40-60), расширенный мониторинг с контролем центральной гемодинамики (препульмональная гемодилюция). Все операции проходили с применением порто-бедренно-аксиллярного шунтирования с помощью центробежного насоса «Biopump». Было выделено 8 этапов операции: 1 — исходно (после интубации трахеи); 2 — мобилизация печени; 3 — частичный обход; 4 — полный обход (гепатэктомия, беспеченочный период); 5 — реперфузия; 6 — постреперфузионный период (конец обхода); 7 — билиарная реконструкция; 8 — конец операции. Исследовались концентрационные показатели крови, электролиты, кислотно-щелочное состояние, уровни лактата, глюкозы. Данные обработаны статистически. Центральная гемодинамика контролировалась с помощью метода препульмональной термодилюции с расчетом СИ, УИ, ИОПСС на этапах: мобилизация печени, постреперфузионный период (конец обхода), конец операции. Результаты. Достоверное (