Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states toward the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques

Electrostatically confined monolayer graphene quantum dots with orbital and valley splittings

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states towards the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques

Expert Assessment of a Ratio of Expenses at Construction of Oil Transport Infrastructure in the Arctic

When assessing the cost of construction and operation of transport infrastructure in the early stages of the investment process, there is a problem in the formalization of some indicators of the factors influencing decision-making. The temporary impossibility to express them in monetary or comparable natural quantities leads to uncertainty in the ratio between these two groups of factors. On the example of one of the discussed objects of oil transport infrastructure in the territory of the Russian Arctic, quantitative estimates of such uncertainties are obtained, the value of which was very weighty and variable depending on the considered alternative. The authors propose an approach based on the vector representation of factors, fuzzy set theory and expert estimates, which allows developing a criterion of the limit value of uncertainty, allowing making management decisions in the problems of choice. The corresponding model giving the possibility of calculation of such criterion is constructed

Large tunable valley splitting in edge-free graphene quantum dots on boron nitride

Coherent manipulation of binary degrees of freedom is at the heart of modern quantum technologies. Graphene offers two binary degrees: the electron spin and the valley. Efficient spin control has been demonstrated in many solid state systems, while exploitation of the valley has only recently been started, yet without control on the single electron level. Here, we show that van-der Waals stacking of graphene onto hexagonal boron nitride offers a natural platform for valley control. We use a graphene quantum dot induced by the tip of a scanning tunneling microscope and demonstrate valley splitting that is tunable from -5 to +10 meV (including valley inversion) by sub-10-nm displacements of the quantum dot position. This boosts the range of controlled valley splitting by about one order of magnitude. The tunable inversion of spin and valley states should enable coherent superposition of these degrees of freedom as a first step towards graphene-based qubits

Изотопный состав кислорода и водорода повторно-жильных льдов Центрального Ямала

New data on the distribution of the isotopes δ18О and δD of ice wedges in Central Yamal are presented. In the summer of 2019, the massive wedge ice was studied in the thermal circus of the third marine terrace. On the surface of the terrace, polygonal-vein relief is common with a polygon size of about 10–20 m. The largest ice wedge № 1 in the upper part was 1.5 m wide, and its visible depth in the outcrop amounted to 2.3 m. Perpendicular to this wedge, another one № 2 was opened with a width of 60 cm, and 20 m from them the wedge № 3 was opened along the strike. At the level of the head of the wedge № 1, radiocarbon AMS dating was performed based on a sample of host deposits, which showed that the ice in the upper part was about 13 thousand years old (the ice age was of 13.6 cal. BP). According to the isotopic characteristics (average values of δ18О = −24.8, and δD = −187.6 ‰), the ice corresponds to the Yamal ice-wedge ice, which was formed during the MIS‑2 isotopic stage (the end of the Late Pleistocene). The isotopic composition of oxygen indicates temperatures of the cold period of the vein formation from −22.8 to −26.8 °C (on average 7 °C colder than the present-day) and the January temperatures from −34.2 to −40.2 °C (on average 10 °C colder than the present-day). For some ice samples (11 out of 43), high values of deuterium excesses (dexc = 12÷17 ‰) were observed, which is unusual for this type of ice. A few examples of high dexc values of ice wedges are mentioned in the literature for sections of Seyakha yedoma, Cape Sabler and Bolshoi Lyakhovsky Island, and note that for the ice dated to the Late Pleistocene. The deuterium excess values may reflect the unstable climatic conditions of the Late Pleistocene associated with changes in the vapor source and the trajectories of the air masses over the continent.Приведены новые данные о распределении δ18О и δD в повторно-жильном льду Центрального Ямала. По своим изотопным характеристикам (средние значения δ18О = −24,8, а δD = −187,6 ‰) лёд соответствует жильным льдам Ямала, которые формировались в изотопную стадию МИС‑2 (конец позднего плейстоцена). Для некоторых образцов льда отмечены высокие значения дейтериевого эксцесса (dexc = 12÷17 ‰), что нехарактерно для этого типа льдов. Немногочисленные свидетельства высоких значений dexc в позднеплейстоценовом жильном льду описаны в литературе для раз‑ резов р. Сеяха, мыса Саблера и о. Большой Ляховский

Пневмомедиастинум: новый взгляд на старую проблему в условиях пандемии COVID-19

The aim of the study was to identify the risk factors of spontaneous pneumomediastinum and to determine its management strategy in patients with the novel coronavirus infection.Material and methods. Eighteen patients with spontaneous pneumomediastinum (SPM) hospitalized in the Center for Novel Coronavirus Infection of the Mechnikov Northwestern State Medical University from 2020 to 2021 were examined. The control group consisted of 18 persons selected using matched sampling. We analyzed symptoms, medical and life history, comorbidities, physical examination results, laboratory and instrumental data, and disease management of patients in both groupsResults. The groups were comparable by age and sex. Among all patients hospitalized with the novel coronavirus infection, spontaneous pneumomediastinum was registered in 1.3% (n=18). Analysis of symptoms, medical and life history, comorbidities, physical examination results, laboratory and instrumental data and disease management did not reveal significant differences between the groups. At the same time, the proportion of obese patients in the main group was lower than in the control group. Estimation of HR showed that the risk of spontaneous pneumomediastinum development was significantly lower in obesity (HR=0.14; 95% CI: 0.033–0.63, P=0.010).Conclusion. The risk of spontaneous pneumomediastinum is significantly lower in obese patients.Цель исследования — определение факторов риска спонтанного пневмомедиастинума и тактики его ведения у больных новой коронавирусной инфекцией.Материал и методы. Обследовали 18 пациентов со спонтанным пневмомедиастинумом (СПМ), госпитализированных в центр по лечению новой коронавирусной инфекции СЗГМУ им. И. И. Мечникова с 2020 по 2021 год. Группу контроля составили 18 человек, отобранные парно-сопряженным методом. Проанализировали жалобы, анамнез заболевания и жизни, коморбидный фон, физикальные данные, результаты лабораторных и инструментальных исследований, особенности терапии пациентов обеих группРезультаты. Группы были сопоставимы по возрасту и полу. Среди всех больных, госпитализированных с новой коронавирусной инфекцией, спонтанный пневмомедиастинум зарегистрировали в 1,3% (18). Анализ жалоб, анамнеза заболевания и жизни, коморбидного фона, физикальных данных, результатов лабораторных и инструментальных исследований, терапии пациентов в обеих группах статистически значимых отличий не выявил. В то же время, в основной группе доля больных с ожирением была меньше, чем в контрольной. Оценка ОШ показала, что при ожирении риск развития спонтанного пневмомедиастинума был статистически значимо меньше (ОШ=0,14; 95% ДИ: 0,033–0,63, р=0,010).Заключение. Риск развития спонтанного пневмомедиастинума статистически значимо ниже у больных с ожирением

Block Copolymers of Ethylene Oxide and Propylene Oxide: Prospects for Medical and Pharmaceutical Application in Russia

Block copolymers of ethylene oxide and propylene oxide (EO/PO block copolymers) are polymeric non-ionic surfactants with a high hydrophilic–lipophilic balance also referred to as pluronics, poloxamers, or proxanols. These compounds are among the most demanded modern excipients for the production of medicines. EO/PO block copolymers are used both in the production of traditional (liquid, semi-solid, and solid) dosage forms and as part of targeted delivery systems. The extensive application of EO/PO block copolymers is due to the diverse array of their properties, including not only solubilising, emulsifying, gelling, and other effects but also thermoreversibility, which is essential for developing in situ delivery systems and 3D printing technologies.The aim of the study was to evaluate the potential of EO/PO block copolymers for medicinal use and to assess the range of medicinal products approved in the Russian Federation that contain EO/PO block copolymers.This review presents an analysis of the register of poloxamer-containing medicines approved in the Russian Federation, a list of the largest manufacturers of EO/PO block copolymers in the world, and a study of the possibility to use copolymers for medical purposes. Currently, there are more than 10 chemical manufacturers producing EO/PO block copolymers for the pharmaceutical, biotechnology, and other industries around the world. EO/PO block copolymers are included in more than 60 medicinal products present in the Russian pharmaceutical market; this observation indicates the need to phase out the import of poloxamers

A Novel Laser-Based Zebrafish Model for Studying Traumatic Brain Injury and Its Molecular Targets

Traumatic brain injury (TBI) is a major public health problem. Here, we developed a novel model of non-invasive TBI induced by laser irradiation in the telencephalon of adult zebrafish (Danio rerio) and assessed their behavior and neuromorphology to validate the model and evaluate potential targets for neuroreparative treatment. Overall, TBI induced hypolocomotion and anxiety-like behavior in the novel tank test, strikingly recapitulating responses in mammalian TBI models, hence supporting the face validity of our model. NeuN-positive cell staining was markedly reduced one day, but not seven days, after TBI, suggesting increased neuronal damage immediately after the injury, and its fast recovery. The brain-derived neurotrophic factor (Bdnf) level in the brain dropped immediately after the trauma, but fully recovered seven days later. A marker of microglial activation, Iba1, was elevated in the TBI brain, albeit decreasing from Day 3. The levels of hypoxia-inducible factor 1-alpha (Hif1a) increased 30 min after the injury, and recovered by Day 7, further supporting the construct validity of the model. Collectively, these findings suggest that our model of laser-induced brain injury in zebrafish reproduces mild TBI and can be a useful tool for TBI research and preclinical neuroprotective drug screening. © 2022 by the authors.Saint Petersburg State University, SPbU: 73026081; Russian Science Foundation, RSF: 20-65-46006We thank Alisa S. Belova for technical support in experimental manipulations and cortisol assay. We also thank Anatoly A. Maslov for the idea of using laser radiation to introduce brain damage. A.V.K. lab is supported by St. Peterburg State University funds (Pure ID 73026081).This study was funded by Russian Science Foundation (grant No. 20-65-46006)

Additional Impact of Glucose Tolerance on Telomere Length in Persons With and Without Metabolic Syndrome in the Elderly Ukraine Population

Rationale: Association between different components of metabolic syndrome and the rate of age-related telomere shortening was reported repeatedly, although some findings are inconsistent across studies, suggesting the need for further research on the topic. In the present study, we examined relationships between different components of metabolic syndrome (MetS); glucose tolerance reflected in 2-h post-load plasma glucose (2hPG) levels and age on the leukocyte telomere length (LTL) in Ukraine population.Methods: The study was conducted on the 115 adult individuals residing in the Kyiv region (Ukraine). Among them, 79 were diagnosed with MetS according to the International Diabetes Federation definition. LTL were determined by a qPCR-based method. Multivariate logistic regression (MLR) and artificial neural networks (ANN) modeling were used for the analysis of the results. ROC-analysis was also performed to compare the predictively values of this models.Results: MetS was associated with a high (OR = 3.0 CI 1.3–6.7; p = 0.01) risk of having shorter telomeres that remained significant after adjusting for age, gender and 2hPG levels. Fasting plasma glucose (FPG) levels and other MetS components did not affect the magnitude of the relationship and did not reveal the independent influence of these factors. The level of 2hPG in turn, demonstrated a significant relationship (OR = 1.3 CI 1.0–1.6 per 1 mmol/l; p = 0.04) with LTL regardless of the presence of MetS. The non-linearity of the interactions between age, gender and 2hPG level was revealed by neural network modeling (AUC = 0.76 CI 0.68–0.84).Conclusion: Our study found that impaired glucose tolerance, but not FPG levels, affected the association between LTL and MetS, which may be also indicative for pathophysiological differences in these hyperglycemia categories. 2hPG levels can provide an opportunity for a more accurate diagnostics of MetS and for evaluating the rate of aging in patients with MetS. Further research, however, is needed to verify this assumption