Sampling Time Effects for Persistence and Survival in Step Structural Fluctuations

The effects of sampling rate and total measurement time have been determined for single-point measurements of step fluctuations within the context of first-passage properties. Time dependent STM has been used to evaluate step fluctuations on Ag(111) films grown on mica as a function of temperature (300-410 K), on screw dislocations on the facets of Pb crystallites at 320K, and on Al-terminated Si(111) over the temperature range 770K - 970K. Although the fundamental time constant for step fluctuations on Ag and Al/Si varies by orders of magnitude over the temperature ranges of measurement, no dependence of the persistence amplitude on temperature is observed. Instead, the persistence probability is found to scale directly with t/Dt where Dt is the time interval used for sampling. Survival probabilities show a more complex scaling dependence which includes both the sampling interval and the total measurement time tm. Scaling with t/Dt occurs only when Dt/tm is a constant. We show that this observation is equivalent to theoretical predictions that the survival probability will scale as Dt/L^z, where L is the effective length of a step. This implies that the survival probability for large systems, when measured with fixed values of tm or Dt should also show little or no temperature dependence.Comment: 27 pages, 10 figure

A multipurpose machine to study paramagnetic species on well defined single crystal surfaces

A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of the resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic species with a density of approximately 5 × 1011 spins/cm2, which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology

Negative thermoelectric power of melt mixed vapor grown carbon nanofiber polypropylene composites

Manuscript DraftIn this work, commercial vapor grown carbon nanofibers (CNF), produced by chemical vapor deposition (CVD), were melt extruded with polypropylene (PP) with the aim of analyzing their thermoelectric properties (i.e., electrical conductivity, thermoelectric power, power factor and figure of merit). Unexpectedly, all PP/CNF composites showed negative thermoelectric power (TEP) values instead of showing the typical positive TEP observed for this type of carbon-based polymer composites. These results can be attributed to the double layer structure surrounding the tubular core of the carbon nanofiber grown by the CVD method at 1100 °C, which may lead the intrinsically negative TEP contribution from the larger inner layer to counteract the positive TEP contribution from the smaller outer layer due to common oxygen doping. Overall, all composites showed negative TEP values around −8.5 μVK−1 and a maximum power factor of 1.75 × 10-3 μW m-1 K−2, corresponding to a figure of merit of 1.2 × 10-6 at room temperature. This study demonstrates that melt mixed polymer composites with large-diameter tubular carbon nanostructures and negative Seebeck coefficients can be directly produced with large-scale processing methods without requiring specific additives and/or deoxygenation treatments.POCI-01-0145-FEDER-007136, POCI-01-0145- FEDER-006941, POCI-01-0145-FEDER-016723, UID/CTM/00264/2019. FEDER funds through the Competitivity Factors Operational Programme - COMPETE 2020 and by national funds through FCT – Foundation for Science and Technology (project POCI-01-0145-FEDER-007136, POCI01-0145-FEDER-006941 and POCI-01-0145-FEDER-016723 and Strategic Funding UID/FIS/04650/2013 and UID/EEA/04436/2013). E. M. F. Vieira is grateful for financial support through the FCT grant SFRH/BPD/95905/201

Ультразвуковая и магнитнорезонансная семиотика компрессий и гипоплазии внутренних яремных вен

Highlights. Ultrasound and MR venography of internal jugular veins in case of unilateral cerebellar hypoplasia or extrinsic stenosis enables noninvasively and without contrast agents differentiation of these conditions due to local and region-specific indicators, including the area and velocity of blood flow, arterial-venous balance, visualization of low blood flow, compression factor, and the overall clinical picture of venous network of the neck remodeling and the development of collateral circulation.Aim. To compare the visual and hemodynamic characteristics of ultrasound and magnetic resonance venography of extrinsic stenosis and hypoplasia of internal jugular veins (IJV).Methods. Ultrasound and magnetic resonance (MR) venography were performed in 47 patients with extrinsic stenosis and 23 patients with hypoplasia of one of internal jugular veins, and in the control group (30 patients).Results. In case of obvious vein compression and deformation and local stenosis (65% on average), there is a decrease in the vein cross-sectional area by 2 times compared with the contralateral vein, the blood flow velocity in the stenotic vein in acute cases increases (on average, up to 45 cm/s), and in chronic cases it significantly (p = 0.00001) decreases (to 13 cm/s on average). The criteria for hypoplasia are the small caliber of the vein (on average 0.22 cm², within the range of 0.13–0.46 cm²) throughout its entire length - with the cross-sectional area not exceeding that of the common carotid artery, and the vein being 4 times smaller than IJV on contralateral side, as well as a significant (p = 0.0006) velocity increase on the contralateral side (on average 40.9±12.52 cm/s) with normal velocity in the hypoplastic vein. Ultrasound assessment of the arterial-venous balance (AVB) makes it possible to evaluate the contribution of each IJV to the outflow of venous blood from the brain separately. From the hypoplastic side it was only 11.01±6.72%, and from the stenotic side it was 18.22±17 42% on average, which is significantly (p = 0.000001) below the norm, but does not allow us to differentiate these conditions. The total AVB for IJVs on both sides was within normal values (65–85%), and the absence of a pronounced expansion of the vertebral veins during MR venography confirms their insignificant role in the compensatory mechanisms of ensuring adequate outflow of venous blood from the brain in cases of unilateral hypoplasia and extrinsic stenosis of IJV.Conclusion. Ultrasound and MR venography of internal jugular veins in cases of unilateral hypoplasia or extrinsic stenosis enable noninvasively and without contrast agents differentiation of these conditions due to local and region-specific indicators, including the area and velocity of blood flow, arterial-venous balance, visualization of low blood flow, compression factor, and the overall clinical picture of venous network of the neck remodeling and the development of collateral circulation.Основные положения. УЗ- и МР-венография внутренних яремных вен в случаях унилатеральной гипоплазии или стеноза при наружной компрессии позволяет неинвазивно и без применения контрастных средств дифференцировать эти состояния благодаря локальным и региональным признакам, включающим площадь и скорость кровотока, расчетный показатель венозно-артериального баланса, визуализацию эффектов низкого кровотока, обнаружение компремирующего фактора, а также общей картины ремоделирования венозной сети шеи и развития коллатерального кровотока.Цель. Сравнение локальных и региональных визуализационных и гемодинамических характеристик ультразвуковой (УЗ) и магнитно-резонансной (МР) венографии наружного стеноза и гипоплазии внутренних яремных вен (ВЯВ).Материалы и методы. УЗ- и МР-венография выполнена 47 пациентам с наружным стенозом и 23 больным с гипоплазией одной из внутренних яремных вен, а также в контрольной группе (30 человек).Результаты. При наружной компрессии с очевидной деформацией вены и локальным стенозом (в среднем 65%) отмечено уменьшение ее площади как минимум в 2 раза в сравнении с контралатеральной веной, скорость кровотока в стенозированной вене в острых случаях увеличивается (в среднем до 45 см/с), а при хроническом течении достоверно (p = 0,00001) уменьшается (в среднем до 13 см/с). Критериями гипоплазии выступают одинаково маленький калибр вены (в среднем 0,22 см², в диапазоне 0,13–0,46 см²) на всем ее протяжении с площадью, не превышающей площадь общей сонной артерии и в 4 раза меньшей, чем ВЯВ с противоположной стороны, а также достоверное (p = 0,0006) повышение скорости с противоположной стороны (в среднем 40,9±12,52 см/с) при нормальной скорости в гипоплазированной вене. УЗ-методика оценки венозно-артериального баланса (ВАБ) позволяет оценить вклад каждой ВЯВ в отток венозной крови от головного мозга по отдельности: со стороны гипоплазии он составляет только 11,01±6,72%, со стороны стеноза – в среднем 18,22±17,42%, что достоверно (p = 0,000001) ниже нормы, но не дифференцирует эти состояния. Суммарный ВАБ для ВЯВ с обеих сторон оказался в пределах нормальных значений (65–85%), а отсутствие по данным МР-венографии выраженного расширения позвоночных вен подтверждает их незначительную роль в компенсаторных механизмах обеспечения адекватного оттока венозной крови от головного мозга в случаях унилатеральных гипоплазии и наружного стеноза ВЯВ.Заключение. УЗ- и МР-венография внутренних яремных вен в случаях унилатеральной гипоплазии или стеноза при наружной компрессии позволяет неинвазивно и без применения контрастных средств дифференцировать эти состояния благодаря локальным и региональным признакам, включающим площадь и скорость кровотока, расчетный показатель ВАБ, визуализацию эффектов низкого кровотока, обнаружение компремирующего фактора, а также определение общей картины ремоделирования венозной сети шеи и развития коллатерального кровотока

Scattering theory and ground-state energy of Dirac fermions in graphene with two Coulomb impurities

We study the physics of Dirac fermions in a gapped graphene monolayer containing two Coulomb impurities. For the case of equal impurity charges, we discuss the ground-state energy using the linear combination of atomic orbitals (LCAO) approach. For opposite charges of the Coulomb centers, an electric dipole potential results at large distances. We provide a nonperturbative analysis of the corresponding low-energy scattering problem

Vapor grown carbon nanofiber based cotton fabrics with negative thermoelectric power

Vapor grown carbon nanofiber (CNF) based ink dispersions were used to dip-coat woven cotton fabrics with different constructional parameters, and their thermoelectric (TE) properties studied at room temperature. Unlike the positive thermoelectric power (TEP) observed in TE textile fabrics produced with similar carbon-based nanostructures, the CNF-based cotton fabrics showed negative TEP, caused by the compensated semimetal character of the CNFs and the highly graphitic nature of their outer layers, which hinders the p-type doping with oxygen groups onto them. A dependence of the electrical conductivity (r) and TEP as a function of the woven cotton fabric was also observed. The cotton fabric with the largest linear density (tex) showed the best performance with negative TEP values around - 8 lV K-1 , a power factor of 1.65 9 10-3 lW m-1 K-2 , and a figure of merit of 1.14 9 10-6 . Moreover, the possibility of a slight e- charge transfer or n-doping from the cellulose onto the most external CNF graphitic shells was also analysed by computer modelling. This study presents n-type carbon-based TE textile fabrics produced easily and without any functionalization processes to prevent the inherent doping with oxygen, which causes the typical p-type character found in most carbon-based TE materialsFEDER funds through COMPETE and by national funds through FCT – Foundation for Science and Technology within the project POCI-01-0145- FEDER-007136. E. M. F. Vieira is grateful for financial support through FCT with CMEMS-UMinho Strategic Project UIDB/ 04436/202

Brown bear attacks on humans : a worldwide perspective

The increasing trend of large carnivore attacks on humans not only raises human safety concerns but may also undermine large carnivore conservation efforts. Although rare, attacks by brown bears Ursus arctos are also on the rise and, although several studies have addressed this issue at local scales, information is lacking on a worldwide scale. Here, we investigated brown bear attacks (n = 664) on humans between 2000 and 2015 across most of the range inhabited by the species: North America (n = 183), Europe (n = 291), and East (n = 190). When the attacks occurred, half of the people were engaged in leisure activities and the main scenario was an encounter with a female with cubs. Attacks have increased significantly over time and were more frequent at high bear and low human population densities. There was no significant difference in the number of attacks between continents or between countries with different hunting practices. Understanding global patterns of bear attacks can help reduce dangerous encounters and, consequently, is crucial for informing wildlife managers and the public about appropriate measures to reduce this kind of conflicts in bear country.Peer reviewe

ИССЛЕДОВАНИЕ ДИНАМИКИ ТЕРРИТОРИАЛЬНОГО РАСПРОСТРАНЕНИЯ И ЭКОЛОГИИ РЕДКИХ МЛЕКОПИТАЮЩИХ ТАЕЖНОЙ ЕВРАЗИИ (НА ПРИМЕРЕ ЛЕТЯГИ PTEROMYS VOLANS, RODENTIA, PTEROMYIDAE) in English INVESTIGATION OF THE DYNAMICS OF REGIONAL DISTRIBUTION AND ECOLOGY OF RARE MAMMALS TAIGA EURASIA (FOR EXAMPLE Letyago PTEROMYS VOLANS, RODENTIA, PTEROMYIDAE)

This study of the spatial distribution and ecology of the flying squirrel during the turn of the 20th century provides a description of new methods and techniques for detecting and accounting flying squirrels in the forest zone of Eurasia. The flying squirrel population area covers the territory of 61 regions of Russia, including Kamchatsky Krai and Chukotka Autonomous District. The number of flying squirrels in Karelia especially to the east – in the Arkhangelsk region and Western Siberia – significantly exceeds that of Finland, but considerable spatial variability in the number is obvious through all the regions: there are areas where this animal is quite abundant, or inhabits all the territory rather evenly, and there are areas where it is completely absent in vast territories even with seemingly favourable conditions. The flying squirrel is quite difficult to study and the reasons of its absence in obviously favourable areas are still to be explained. Some reasons are: the specificity of favourable landscape, forest coverage pattern, trophic relationships with predators and genetic aspect. A number of hypotheses are supposed to be tested in the nearest future. Key words: accounting, flying squirrel, forest zone, home range, spatial distribution.Peer reviewe

Новообразования молочной железы с неопределенным потенциалом злокачественности (B3): опыт применения вакуум-ассистированной биопсии под ультразвуковой навигацией

INTRODUCTION: Introduction of breast cancer screening programs has led to an increase in detection of non-palpable masses requiring core needle biopsy. Masses that fall into B3 category based on the histological results of core biopsy specimens, are of interest precisely because of their uncertain malignant potential and the lack of a final consensus on their management.OBJECTIVE: To analyze the 3-year experience of ultrasound guided vacuum-assisted biopsy (VAB) in patients with B3 breast lesions based on the results of histological examination of core biopsy specimens.MATERIALS AND METHODS: Between June 2019 and June 2022, 163 VABs were performed. The study group included patients with category 2–4 breast lesions according to the BI-RADS scoring system. The decision to perform VAB was made by the oncologist in each specific case on the basis of anamnesis, clinical data and the results of core biopsy histological examination: in cases of B3 or B2 lesions with a discordant radiologic pattern.RESULTS: In 155 (95.0%) cases, the removed lesions were benign, invasive cancer was detected in 2 (1.2%) cases, ductal cancer in situ in 6 cases (3.8%). The сomplications included: in 5 (3.1%) cases, patients had pain after the procedure, and in 37 (22.7%) cases there was a hematoma. In 5 (3.1%) patients, residual tissue was found at the site of removed lesions. CONCLUSIONS: VAB is a safe alternative to exploratory surgery in patients with B3 lesions diagnosed by core biopsy.ВВЕДЕНИЕ: Внедрение программ скрининга рака молочных желез привело к увеличению частоты обнаружения непальпируемых образований, требующих проведения трепан-биопсии. Новообразования, попадающие в категорию B3, согласно результатам гистологического исследования трепанбиоптатов, вызывают интерес именно из-за их неопределенного потенциала злокачественности и отсутствия окончательного консенсуса дальнейшей тактики.ЦЕЛЬ: Проанализировать 3-летний опыт применения вакуум-ассистированной биопсии (ВАБ) под ультразвуковым контролем у пациенток с очаговыми новообразованиями молочных желез при полученных результатах гистологического исследования трепан-биоптатов.МАТЕРИАЛЫ И МЕТОДЫ: В период с июня 2019 г. по июнь 2022 г было выполнено 163 ВАБ. В группу исследования вошли пациентки с новообразованиями молочных желез категорий 2–4 по шкале BI-RADS. Решение о выполнении ВАБ принималось онкологом в каждом конкретном случае на основании анамнестических, клинических данных и результатов гистологического исследования трепан-биоптатов: при определении образований категории В3 или В2 при дискордантной лучевой картине.РЕЗУЛЬТАТЫ: В 155 (95,0%) случаях удаленные новообразования имели доброкачественный характер, инвазивный рак выявлен в 2 (1,2%) случаях, протоковый рак in situ — в 6 случаях (3,8%). Осложнения: в 5 (3,1%) случаях после проведенной процедуры у пациенток имелся болевой симптом, а в 37 (22,7%) случаях проведение процедуры сопровождалось появлением гематомы. У 5 (3,1%) пациенток была выявлена остаточная ткань в зоне удаленных новообразований.ЗАКЛЮЧЕНИЕ: Вакуум-ассистированная биопсия является безопасной альтернативой диагностической хирургии у пациенток с поражениями категории B3, диагностированными при трепан-биопсии