Insulating state in tetralayers reveals an even-odd interaction effect in multilayer graphene

The absence of an energy gap separating valence and conduction bands makes the low-energy electronic properties of graphene and its multi-layers sensitive to electron-electron interactions. In bilayers, for instance, interactions are predicted to open a gap at charge neutrality, turning the system into an insulator, as observed experimentally. In mono and (Bernal-stacked) trilayers, interactions, although still important, do not have an equally drastic effect, and these systems remain conducting at low temperature. It may be expected that interaction effects become weaker for thicker multilayers, whose behavior should eventually converge to that of graphite. Here we show that this expectation does not correspond to reality by investigating the case of Bernal-stacked tetralayer graphene (4LG). We reveal the occurrence of a robust insulating state in a narrow range of carrier densities around charge neutrality, incompatible with the behavior expected from the single-particle band structure. The phenomenology resembles that observed in bilayers, but the stronger conductance suppression makes the insulating state in 4LG visible at higher temperature. To account for our findings, we suggest a natural generalization of the interaction-driven, symmetry-broken states proposed for bilayers. This generalization also explains the systematic even-odd effect of interactions in Bernal-stacked layers of different thickness that is emerging from experiments, and has implications for the multilayer-to-graphite crossover.Comment: 15 pages, 5 figures, This is the original submitted version of the manuscript whose final accepted version, following the review/editorial process, will appear in Nature Communication

Tuning a Circular p-n Junction in Graphene from Quantum Confinement to Optical Guiding

The motion of massless Dirac-electrons in graphene mimics the propagation of photons. This makes it possible to control the charge-carriers with components based on geometrical-optics and has led to proposals for an all-graphene electron-optics platform. An open question arising from the possibility of reducing the component-size to the nanometer-scale is how to access and understand the transition from optical-transport to quantum-confinement. Here we report on the realization of a circular p-n junction that can be continuously tuned from the nanometer-scale, where quantum effects are dominant, to the micrometer scale where optical-guiding takes over. We find that in the nanometer-scale junction electrons are trapped in states that resemble atomic-collapse at a supercritical charge. As the junction-size increases, the transition to optical-guiding is signaled by the emergence of whispering-gallery modes and Fabry-Perot interference. The creation of tunable junctions that straddle the crossover between quantum-confinement and optical-guiding, paves the way to novel design-architectures for controlling electronic transport.Comment: 16 pages, 4 figure

Prevalence of the relationship between anxiety and sleep quality in undergraduate students of the medical university

The purpose of the study is to identify the prevalence of the relationship between anxieties and sleep quality in young people of college age.Цель исследования – выявить распространенность взаимосвязи между тревожностью и качеством сна у молодых людей студенческого возраста

МЕТОДЫ ДИАГНОСТИКИ СТОРОЖЕВОГО ЛИМФАТИЧЕСКОГО УЗЛА У БОЛЬНЫХ РАКОМ МОЛОЧНОЙ ЖЕЛЕЗЫ

Objective: to provide various methods for sentinel lymph node detection considering their advantages and disadvantages.Material and Methods. The search of the relevant articles published in Pubmed, MedLine, RINTs, etc. database was conducted. 49 publications from 1970 to 2018 were analyzed.Results. Currently, sentinel lymph node biopsy (SLN biopsy) has become a worthy alternative to traditional lymphatic surgery for early breast cancer. SLN biopsy significantly decreases the number of postoperative complications caused by lymphadenectomy and improves the quality of life of cancer patients. So far, a large number of SLN detection techniques have accumulated. Each of these techniques has its own advantages and disadvantages.Conclusion. Despite a large number of SLN detection methods, the question of the optimal technique is currently debatable. Цель исследования – представить различные методы диагностики сторожевых лимфатических узлов, рассмотрев их достоинства и недостатки.Материал и методы. Проведен поиск статей, опубликованных в базах Pubmed, MedLine, РИНЦ, РГБ за 1970–2018 гг. Из 150 проанализированных публикаций в обзор вошли 50.Результаты. В настоящее время биопсия сторожевого лимфатического узла (СЛУ) стала достойной альтернативой традиционной хирургии на лимфатических путях при раннем раке молочной железы (РМЖ). Благодаря данной методике снизилось количество послеоперационных осложнений, вызванных лимфодиссекцией, а качество жизни больных значительно возросло. С момента появления и до настоящего времени накопилось большое количество техник определения СЛУ, каждая из которых имеет свои плюсы и минусы.Заключение. Несмотря на большое количество методов детекции СЛУ, вопрос об оптимальной технике в настоящее время остается дискуссионным.

METHODS FOR SENTINEL LYMPH NODE DETECTION IN PATIENTS WITH BREAST CANCER

Objective: to provide various methods for sentinel lymph node detection considering their advantages and disadvantages.Material and Methods. The search of the relevant articles published in Pubmed, MedLine, RINTs, etc. database was conducted. 49 publications from 1970 to 2018 were analyzed.Results. Currently, sentinel lymph node biopsy (SLN biopsy) has become a worthy alternative to traditional lymphatic surgery for early breast cancer. SLN biopsy significantly decreases the number of postoperative complications caused by lymphadenectomy and improves the quality of life of cancer patients. So far, a large number of SLN detection techniques have accumulated. Each of these techniques has its own advantages and disadvantages.Conclusion. Despite a large number of SLN detection methods, the question of the optimal technique is currently debatable