Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic

Показатели цитокинового статуса у детей с ОРВИ на фоне терапии интраназальными препаратами интерферона

Objective: to study the dynamics of local and systemic cytokine production in children with different clinical forms of acute respiratory viral infections (ARVI), including COVID-19, and to assess the effectiveness of local interferon-based therapy.Patients and methods: The study included 180 patients aged from 1 month to 17 years with сonfirmed acute respiratory viral infections (ARVI), including COVID-19. Patients were divided into 2 groups (main and control) of 90 people each. In the main group patients received the intranasal interferon-based medicine Grippferon® in addition to the basic therapy, the control group patients received only basic therapy. The cytokine status was assessed by the content of IFN-α and -γ, IL-1β, IL-8, IL-4, IL-10, IL-17 in blood serum and in nasopharyngeal secretions by enzyme immunoassay kits ("Cytokine", St. Petersburg).Results: Statistically significant differences were revealed in the systemic and local content of individual cytokines in ARVI of different etiologies, depending on the level of damage to the respiratory tract. The use of the interferon-based medicine Grippferon® for intranasal use in children in the early stages of ARVI, including COVID-19, helps to decrease the high content of cytokines IL-1β and IL-8 in the nasopharynx by reducing the viral load. As a result, the duration of catarrhal disease symptoms and intoxication was also significantly reduced as well as the pathogen elimination time.Цель: изучить особенности динамики локальной и системной цитокиновой продукции у детей с разными клиническими формами ОРВИ, включая COVID-19, и оценить эффективность местной интерферонотерапии.Пациенты и методы: обследовано 180 пациентов в возрасте от 1 месяца до 17 лет с верифицированным диагнозом ОРВИ (включая COVID-19). Пациенты были разделены на 2 группы (основную и контрольную) по 90 человек каждая. В основной группе в составе комплексного лечения пациенты применяли интраназальный препарат рекомбинантного интерферона альфа-2b (IFN-α2b) Гриппферон®. Цитокиновый статус оценивали по показателям содержания IFN-α и -γ, IL-1β, IL-8, IL-4, IL-10, IL-17 в сыворотке крови и в назофарингеальных материалах методом иммуноферментного анализа.Результаты: выявлены статистически значимые различия в системном и локальном содержании отдельных цитокинов при ОРВИ разной этиологии в зависимости от уровня поражения респираторного тракта. Интраназальное применение препарата рекомбинантного IFN-α2b (Гриппферона) у детей в ранние сроки ОРВИ, в том числе при COVID-19, способствовало снижению высокого содержания цитокинов IL-1β и IL-8 в носоглотке за счет уменьшения вирусной нагрузки на организм, что приводило к сокращению продолжительности катаральных симптомов заболевания и интоксикации. Статистически значимо снижались и сроки элиминации возбудителей

Two Origins for the Gene Encoding α-Isopropylmalate Synthase in Fungi

BACKGROUND: The biosynthesis of leucine is a biochemical pathway common to prokaryotes, plants and fungi, but absent from humans and animals. The pathway is a proposed target for antimicrobial therapy. METHODOLOGY/PRINCIPAL FINDINGS: Here we identified the leuA gene encoding alpha-isopropylmalate synthase in the zygomycete fungus Phycomyces blakesleeanus using a genetic mapping approach with crosses between wild type and leucine auxotrophic strains. To confirm the function of the gene, Phycomyces leuA was used to complement the auxotrophic phenotype exhibited by mutation of the leu3+ gene of the ascomycete fungus Schizosaccharomyces pombe. Phylogenetic analysis revealed that the leuA gene in Phycomyces, other zygomycetes, and the chytrids is more closely related to homologs in plants and photosynthetic bacteria than ascomycetes or basidiomycetes, and suggests that the Dikarya have acquired the gene more recently. CONCLUSIONS/SIGNIFICANCE: The identification of leuA in Phycomyces adds to the growing body of evidence that some primary metabolic pathways or parts of them have arisen multiple times during the evolution of fungi, probably through horizontal gene transfer events

Conserved synteny at the protein family level reveals genes underlying Shewanella species’ cold tolerance and predicts their novel phenotypes

© The Authors 2009. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License. The definitive version was published in Functional & Integrative Genomics 10 (2010): 97-110, doi:10.1007/s10142-009-0142-y.Bacteria of the genus Shewanella can thrive in different environments and demonstrate significant variability in their metabolic and ecophysiological capabilities including cold and salt tolerance. Genomic characteristics underlying this variability across species are largely unknown. In this study, we address the problem by a comparison of the physiological, metabolic, and genomic characteristics of 19 sequenced Shewanella species. We have employed two novel approaches based on association of a phenotypic trait with the number of the trait-specific protein families (Pfam domains) and on the conservation of synteny (order in the genome) of the trait-related genes. Our first approach is top-down and involves experimental evaluation and quantification of the species’ cold tolerance followed by identification of the correlated Pfam domains and genes with a conserved synteny. The second, a bottom-up approach, predicts novel phenotypes of the species by calculating profiles of each Pfam domain among their genomes and following pair-wise correlation of the profiles and their network clustering. Using the first approach, we find a link between cold and salt tolerance of the species and the presence in the genome of a Na+/H+ antiporter gene cluster. Other cold-tolerance-related genes include peptidases, chemotaxis sensory transducer proteins, a cysteine exporter, and helicases. Using the bottom-up approach, we found several novel phenotypes in the newly sequenced Shewanella species, including degradation of aromatic compounds by an aerobic hybrid pathway in Shewanella woodyi, degradation of ethanolamine by Shewanella benthica, and propanediol degradation by Shewanella putrefaciens CN32 and Shewanella sp. W3-18-1.This research was supported by the U.S. Department of Energy (DOE) Office of Biological and Environmental Research under the Genomics: GTL Program via the Shewanella Federation consortium

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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Phonon contribution to electrical resistance of acceptor-doped single-wall carbon nanotubes assembled into transparent films

The electrical resistance of pristine and acceptor-doped single-wall carbon nanotubes assembled into transparent films was measured in the temperature range of 5 to 300 K. The doping was accomplished by filling the nanotubes with iodine or CuCl from the gas phase. After doping the films resistance appeared to drop down by one order of magnitude, to change the nonmonotonic temperature behavior, and to reduce the crossover temperature. The experimental data have been perfectly fitted in frames of the known heterogeneous model with two contributions: from the nanotube bundles (with quasi-one-dimensional conductivity) and from the interbundle electron tunneling. The doping was observed to decrease the magnitudes of both contributions. In this paper we have revealed the main reason of changes in the nanotube part. It is considered to be connected with the involvement of low-energy phonons, which start to participate in the intravalley scattering due to the shift of the Fermi level after doping. The values of the Fermi level shift into the valence band are estimated to be equal to -0.6 eV in the case of iodine doping and -0.9 eV in the case of CuCl doping. These values are in qualitative agreement with the optical absorption data.Peer reviewe

Laser-triggered proton acceleration from hydrogenated low-density targets

Synchronized proton acceleration by ultraintense slow light (SASL) in low-density targets has been studied in application to fabricated carbon nanotube films. Proton acceleration from low-density plasma films irradiated by a linearly polarized femtosecond laser pulse of ultrarelativistic intensity was considered as result of both target surface natural contamination by hydrocarbons and artificial volumetric doping of low-density carbon nanotube films. The 3D particle-in-cell simulations confirm the SASL concept [A. V. Brantov et al., Synchronized Ion Acceleration by Ultraintense Slow Light, Phys. Rev. Lett. 116, 085004 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.085004] for proton acceleration by a femtosecond petawatt-class laser pulse from realistic low-density targets with a hydrogen impurity, quantify the characteristics of the accelerated protons, and demonstrate a significant increase of their energy compared with the proton energy generated from contaminated ultrathin solid dense foils