Electron transport through interacting quantum dots

We present a detailed theoretical investigation of the effect of Coulomb interactions on electron transport through quantum dots and double barrier structures connected to a voltage source via an arbitrary linear impedance. Combining real time path integral techniques with the scattering matrix approach we derive the effective action and evaluate the current-voltage characteristics of quantum dots at sufficiently large conductances. Our analysis reveals a reach variety of different regimes which we specify in details for the case of chaotic quantum dots. At sufficiently low energies the interaction correction to the current depends logarithmically on temperature and voltage. We identify two different logarithmic regimes with the crossover between them occurring at energies of order of the inverse dwell time of electrons in the dot. We also analyze the frequency-dependent shot noise in chaotic quantum dots and elucidate its direct relation to interaction effects in mesoscopic electron transport.Comment: 21 pages, 4 figures. References added, discussion slightly extende

Coulomb Interaction and Quantum Transport through a Coherent Scatterer

An interplay between charge discreteness, coherent scattering and Coulomb interaction yields nontrivial effects in quantum transport. We derive a real time effective action and an equivalent quantum Langevin equation for an arbitrary coherent scatterer and evaluate its current-voltage characteristics in the presence of interactions. Within our model, at large conductances $G_0$ and low $T$ (but outside the instanton-dominated regime) the interaction correction to $G_0$ saturates and causes conductance suppression by a universal factor which depends only on the type of the conductor.Comment: 4 pages, no figure

Quantal Brownian Motion - Dephasing and Dissipation

We analyze quantal Brownian motion in $d$ dimensions using the unified model for diffusion localization and dissipation, and Feynman-Vernon formalism. At high temperatures the propagator possess a Markovian property and we can write down an equivalent Master equation. Unlike the case of the Zwanzig-Caldeira-Leggett model, genuine quantum mechanical effects manifest themselves due to the disordered nature of the environment. Using Wigner picture of the dynamics we distinguish between two different mechanisms for destruction of coherence. The analysis of dephasing is extended to the low temperature regime by using a semiclassical strategy. Various results are derived for ballistic, chaotic, diffusive, both ergodic and non-ergodic motion. We also analyze loss of coherence at the limit of zero temperature and clarify the limitations of the semiclassical approach. The condition for having coherent effect due to scattering by low-frequency fluctuations is also pointed out. It is interesting that the dephasing rate can be either larger or smaller than the dissipation rate, depending on the physical circumstances.Comment: LaTex, 23 pages, 4 figures, published vesio

Universal scaling of current fluctuations in disordered graphene

We analyze the full transport statistics of graphene with smooth disorder at low dopings. First we consider the case of 1D disorder for which the transmission probability distribution is given analytically in terms of the graphene-specific mean free path. All current cumulants are shown to scale with system parameters (doping, size, disorder strength and correlation length) in an identical fashion for large enough systems. In the case of 2D disorder, numerical evidence is given for the same kind of identical scaling of all current cumulants, so that the ratio of any two such cumulants is universal. Specific universal values are given for the Fano factor, which is smaller than the pseudodiffusive value of ballistic graphene (F=1/3) both for 1D (F=0.243) and 2D (F=0.295) disorder. On the other hand, conductivity in wide samples is shown to grow without saturation as \sqrt{L} and Log L with system length L in the 1D and 2D cases respectively.Comment: 9 pages, 7 figures. Published version, includes corrected figure for Fano facto

Персонализированная медицина критических состояний (обзор)

Personalized medicine (PM) is a major trend in health care development in the 21st century. This area includes studying risk factors for disease development (prediction), interventions for preventing diseases (prophylaxis), individualization of diagnosis and treatment (personalization), informing the patient on disease prevention and treatment (participation). In the recent years, an intense research to introduce the personalized medicine principles into the management of critically ill patients, has been under way. This includes identification of patient groups based on genomic research, development of diagnostic tests using molecular markers, creation of novel classes of drugs based on individual patient characteristics.The aim of the review is to summarize the available data on the implementation of the principles of PM in the routine practice of critical care institutions.We analyzed more than 300 sources of literature from the Pubmed and Scopus databases, as well as the RSCI database. Eighty five most relevant sources were selected for the review. The paper reports data on the organization and results of implementation of PM principles and advanced technologies, such as Emergency Medicine Sample Bank (EMSB), in the daily activity of clinics providing emergency critical care. The formation of the novel PM concept focused on the treatment of critically ill patients has been discussed. The review contains detailed data on the patterns of development of specific critical illnesses such as acute cerebrovascular events, acute respiratory distress syndrome, traumatic brain injury, shock, myocardial infarction, cardiac rhythm and conduction disturbances. Medication efficacy in view of individual genetic patient characteristics has also been highlighted. No research limitations on the subject were identified.Conclusion. The analysis of literature has demonstrated positive results of implementing PM principles in prevention, diagnosis and treatment of critically ill patients. Creation of Biobanks, development of training programs and regulatory documentation, advancing the scientific research, introduction of new methods of diagnosis and treatment will contribute to the implementation of PM principles in practical healthcare.Персонализированная медицина (ПМ) является главным вектором развития здравоохранения в XXI веке и включает направления, касающиеся факторов риска развития заболевания (предикативность), мероприятия по предотвращению заболевания (профилактика), индивидуализацию диагностики и лечения (персонализация), информирование пациента по вопросам профилактики и лечения заболевания (партисипативность). В последние годы ведется активная исследовательская работа, направленная на внедрение принципов ПМ в процесс оказания помощи пациентам, находящимся в критических состояниях. Это касается выделения групп пациентов на основе исследования генома, разработки диагностических тестов с использованием молекулярных маркеров, создания нового класса лекарств с учетом индивидуальных характеристик пациентов.Цель обзора — обобщить имеющиеся данные о внедрении принципов ПМ в практику работы медицинских учреждений, обеспечивающих лечение пациентов, находящихся в критическом состоянии.Провели анализ более 300 источников литературы международных баз данных Pubmed, Scopus и РИНЦ. Из общего массива отобрали 85 источников, которые в наибольшей степени соответствуют цели обзора.В обзоре представили сведения об организации и результатах внедрения принципов и передовых технологий ПМ, таких как банк образцов неотложной медицины — EMSB, в работу клиник, оказывающих неотложную помощь при критических состояниях. Рассмотрели формирование представлений о ПМ, в том числе признаки новой концепции, ориентированной на лечение пациентов в критическом состоянии. Изложили сведения о специфике развития конкретных критических состояний (острых нарушений мозгового кровообращения, острого респираторного дистресс-синдрома, черепно-мозговой травмы, шока, инфаркта миокарда, нарушений ритма и проводимости), а также об эффективности применения лекарственных препаратов, в зависимости от индивидуальных генетических особенностей пациентов.Ограничений исследований по вопросам темы не выявили.Заключение. Анализ данных литературы свидетельствует о позитивных результатах внедрения принципов ПМ в профилактику, диагностику и лечение больных в критических состояниях. Создание биобанков, разработка учебных программ и нормативной документации, активизация научных исследований, внедрение новых методов диагностики и лечения способствуют реализации принципов ПМ в практическом здравоохранении

Statistics of voltage fluctuations in resistively shunted Josephson junctions

The intrinsic nonlinearity of Josephson junctions converts Gaussian current noise in the input into non-Gaussian voltage noise in the output. For a resistively shunted Josephson junction with white input noise we determine numerically exactly the properties of the few lowest cumulants of the voltage fluctuations, and we derive analytical expressions for these cumulants in several important limits. The statistics of the voltage fluctuations is found to be Gaussian at bias currents well above the Josephson critical current, but Poissonian at currents below the critical value. In the transition region close to the critical current the higher-order cumulants oscillate and the voltage noise is strongly non-Gaussian. For coloured input noise we determine the third cumulant of the voltage.Comment: 9 pages, 5 figure