Transport and scattering in inhomogeneous quantum wires

We consider scattering and transport in interacting quantum wires that are connected to leads. Such a setup can be represented by a minimal model of interacting fermions with inhomogeneities in the form of sudden changes in interaction strength and/or velocity. The inhomogeneities generally cause relevant backscattering, so it is a priori unclear if a perfectly ballistic quantum wire can exist in the low temperature limit. We are able to identify such a perfectly conducting fixed point even for large abrupt changes, which in the considered model corresponds to a velocity matching condition. The general position dependent Green's function is calculated in the presence of a sudden change, which is confirmed numerically with high accuracy. The exact form of the interference pattern in the form of density oscillations around inhomogeneities can be used to estimate the effective strength of local backscattering sources.Comment: 5 pages, 3 figures. Published version. For more information and the latest version see http://www.physik.uni-kl.de/eggert/papers/index.htm

Deformations of Cayley submanifolds

Cayley submanifolds of R^8 were introduced by Harvey and Lawson as an instance of calibrated submanifolds, extending the volume-minimising properties of complex submanifolds in Kähler manifolds. More generally, Cayley submanifolds are 4-dimensional submanifolds which may be defined in an 8-manifold M equipped with a certain differential 4-form Phi invariant at each point under the spin representation of Spin(7). If this 4-form Phi is closed, then the holonomy of M is contained in Spin(7) and Cayley submanifolds are calibrated minimal submanifolds. McLean studied the deformations of closed Cayley submanifolds. The deformation problem is elliptic but in general obstructed. We show that for a generic choice of Spin(7)-structure, there are no obstructions, and hence the moduli space is a finite-dimensional smooth manifold. Then we study the deformations of compact, connected Cayley submanifolds with non-empty boundary contained in a given submanifold W of M, where we require that the Cayley submanifolds meet the submanifold W orthogonally. We show that for a generic choice of Spin(7)-structure, the Cayley submanifolds are rigid. Moreover, we show that also for a generic choice of the submanifold W, the Cayley submanifolds are rigid. We further discuss some examples for this deformation theory. In addition, we study the deformations of asymptotically cylindrical Cayley submanifolds inside asymptotically cylindrical Spin(7)-manifolds. We prove an index formula for the operator of Dirac type that arises as the linearisation of the deformation map and show that for a generic choice of Spin(7)-structure, there are no obstructions, and hence the moduli space is a finite-dimensional smooth manifold whose dimension is equal to the index of the operator of Dirac type. We further construct examples of asymptotically cylindrical Cayley submanifolds inside the asymptotically cylindrical Riemannian 8-manifolds with holonomy Spin(7) constructed by Kovalev

Increasing the Ratio of PP2A Core Enzyme to Holoenzyme Inhibits Tat-Stimulated HIV-1 Transcription and Virus Production

AbstractWe demonstrated previously that PP2A exists in many cell types as two abundant forms: (1) holoenzyme composed of two regulatory subunits, A and B, and a catalytic subunit C; and (2) core enzyme consisting of the A and C subunits. These two forms have different substrate specificities. Since published data suggested that HIV-1 transcription may be regulated by a cellular protein phosphatase, it was of interest to determine whether changing the ratio between PP2A core and holoenzyme affects HIV-1 gene expression. This question was addressed by expression in COS cells of an N-terminal mutant of the A subunit, AΔ5, which binds the C but not the B subunit. This resulted in an increase in the amount of core enzyme and a decrease in the amount of holoenzyme concomitant with the expected change in phosphatase activity. Tat-stimulated transcription from the HIV-1 LTR was inhibited 5-fold by mutant AΔ5, whereas mRNA synthesis directed by the actin promoter was not affected. Furthermore, virus production in COS, HeLa, and Jurkat T cells was inhibited 45-, 5-, and 3-fold, respectively, by mutant AΔ5. These results demonstrate that the balance between PP2A holoenzyme and core enzyme is important for HIV-1 gene expression and virus production

Альтернативная бизнес-модель на рынке услуг автосервиса

Цель работы – поиск и реализация масштабируемой бизнес-модели, для рынка автосервисных услуг, которая не применялась на этом рынке. Решены следующие задачи: 1.Проанализированы существующие бизнес - модели, методы их поиска и апробации. 2.Протестирована и модернизирована бизнес – модель. 3.Оценен потенциальный рынок проекта. 4.Составлена итоговая бизнес-модели. В качестве инструментов разработки бизнес-модели были использованы приемы ТРИЗ, тестирование проводилось при помощи "Customer development" и методики экспресс-опросов. Практическая значимость результатов данного исследования выражается в запуске проекта в формате стартапа.The goal is the research and implementation of a scalable business model for the market of car care services that is new for this market. The following tasks are solved: 1. The existing business models, methods of finding a correct one, and their approbation, have been analyzed. 2. Business model has been tasted and upgraded. 3. The potential market of the project has been estimated. 4. The final business model has been completed. Methodics as TRIZ, “Customer development” testing, express surveys, were used as tools for business model development. The practical significance of the results of this study is expressed in the launch of the project in a startup format

Разработка технологии изготовления детали «Червяк»

В процессе исследования был выполнен анализ технологичности детали, разработан технологический процесс, подобраны средства технологического оснащения для изготовления детали, подобраны режимы резания и рассчитаны минимальные припуски на обработку детали, произведен размерный анализ и построено граф дерево для технологического процесса. В результате исследования был разработан технологический процесс изготовления детали "Червяк цилиндрический", написана управляющая программа и карта наладки для токарного станка с ЧПУ, разработана принципиальная схема специального приспособления и рассчитано усилие зажима детали.During the study, an analysis of the manufacturability of the part was carried out, a technological process was developed, technological equipment was selected for the manufacture of the part, the cutting conditions were selected and the minimum allowances for the processing of the part were calculated, dimensional analysis was performed, and a graph tree was constructed for the technological process. As a result of the study, the technological process for manufacturing the Cylindrical Worm part was developed, a control program and a setup map for a numerical control lathe were written, a schematic diagram of a special tool was developed, and the clamping force of the part was calculated