Towards a Graphene-Based Quantum Impedance Standard

Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10^7. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8x10^-8/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance

Conditions of motivation energy in vocational education

This article discusses the conditions of formation of the motivational component of energy-efficient competence of students – the future teachers of vocational training. Energy saving competence underlies the adoption of energy-efficient solutions in the home and at work and is regarded as one of the universal and basic competences modern specialistВ статье рассматриваются условия формирования мотивационной составляющей энергосберегающей компетентности у студентов – будущих педагогов профессионального обучения. Энергосберегающая компетентность лежит в основе принятия энергосберегающих решений в быту и на производстве и рассматривается в качестве одной из универсальных и базовых компетентностей современного специалист

Tyrosyl-DNA phosphodiesterase 1 initiates repair of apurinic/apyrimidinic sites

AbstractTyrosyl-DNA phosphodiesterase 1 (Tdp1) catalyzes the hydrolysis of the phosphodiester linkage between the DNA 3′ phosphate and a tyrosine residue as well as a variety of other DNA 3′ damaged termini. Recently we have shown that Tdp1 can liberate the 3′ DNA phosphate termini from apurinic/apyrimidinic (AP) sites. Here, we found that Tdp1 is more active in the cleavage of the AP sites inside bubble-DNA structure in comparison to ssDNA containing AP site. Furthermore, Tdp1 hydrolyzes AP sites opposite to bulky fluorescein adduct faster than AP sites located in dsDNA. Whilst the Tdp1 H493R (SCAN1) and H263A mutants retain the ability to bind an AP site-containing DNA, both mutants do not reveal endonuclease activity, further suggesting the specificity of the AP cleavage activity. We suggest that this Tdp1 activity can contribute to the repair of AP sites particularly in DNA structures containing ssDNA region or AP sites in the context of clustered DNA lesions

The Role of Pensioners in the American Electorate

The article examines fundamental demographic changes in the USA that have been shifting the electorate and as a result - American politics; with wide gaps between the generations on key social, economic, political issues. The US presidential elections since 1980 were dominated by baby boomers (born 1946-1964) and prior generations, who have cast the vast majority of votes in every presidential election. The 2016 electorate has been the most diverse in the US history due to strong growth of young generations, and especially among Hispanic eligible voters. Millennials (born 1981–1998) and X generation (born 1965-1980) surpassed Baby Boomers and more old generations whose choices differ significantly in many fields; but the key problem is who really votes. The age structure of the American electorate and its influence on the election results; the role of pensioners and those, who’ll retire in the nearest future, as voters at the federal and state levels are in focus

Magnetically operated nanorelay based on two single-walled carbon nanotubes filled with endofullerenes Fe@C20

Structural and energy characteristics of the smallest magnetic endofullerene Fe@C20 have been calculated using the density functional theory approach. The ground state of Fe@C20 is found to be a septet state, and the magnetic moment of Fe@C20 is estimated to be 8 Bohr magnetons. Characteristics of an (8,8) carbon nanotube with a single Fe@C20 inside are studied in the framework of the semiempirical approach. The scheme of a magnetic nanorelay based on cantilevered nanotubes filled with magnetic endofullerenes is elaborated. The proposed nanorelay is turned on as a result of bending of nanotubes by a magnetic force. Operational characteristics of such a nanorelay based on (8,8) and (21,21) nanotubes fully filled with Fe@C20 are estimated and compared to the ones of a nanorelay made of a (21,21) nanotube fully filled with experimentally observed (Ho3N)@C80 with the magnetic moment of 21 Bohr magnetons. Room temperature operation of (21,21) nanotube based nanorelays is shown.Comment: 18 pages, 9 figure

Topological entropy and blocking cost for geodesics in riemannian manifolds

For a pair of points $x,y$ in a compact, riemannian manifold $M$ let $n_t(x,y)$ (resp. $s_t(x,y)$) be the number of geodesic segments with length $\leq t$ joining these points (resp. the minimal number of point obstacles needed to block them). We study relationships between the growth rates of $n_t(x,y)$ and $s_t(x,y)$ as $t\to\infty$. We derive lower bounds on $s_t(x,y)$ in terms of the topological entropy $h(M)$ and its fundamental group. This strengthens the results of Burns-Gutkin \cite{BG06} and Lafont-Schmidt \cite{LS}. For instance, by \cite{BG06,LS}, $h(M)>0$ implies that $s$ is unbounded; we show that $s$ grows exponentially, with the rate at least $h(M)/2$.Comment: 13 page

Транспрофессионализм как предиктор преадаптации субъекта деятельности

The article analyzes the possibilities of transprofessionalism as a factor in the preadaptation of a personality to an uncertain professional future in a post-industrial society. The logical-semantic model of transprofessionalism and a heuristic model of an agent's preadaptation to uncertain professional future are presented. The foresight technology system was chosen as a methodology for developing transprofessionalism and predicting the social and professional future. It was focused on the formation of readiness for changes and the preadaptation for unpredictable future. The result of this technology is the convergence of a post-industrial society characteristics and semantic qualities of the professional future. The generalization of the research results allowed the authors to justify the possibility of high school training of transprofessionals with meta-professional skills who are ready to meet the challenges of the digital economy. The purpose of the research was to determine effective technologies for the training of innovative specialists (transprofessionals) on the basis of the developed transprofessional models of pre-adaptation to the professional future. The methodological basis of the study was non-classical psychology and a convergent approach. In the scientific substantiation of transprofessionalism as a predictor of preadaptation to the future, the concept of professional development, the multidimensional, transdisciplinary, competence and project approaches, as well as the modeling of the predictable future were used. The article presents the logical-semantic and heuristic models of convergence and transprofessionalism development, as well as foresight technologies for preparing agents for an uncertain professional future. The structure of transprofessionalism is revealed through a meaningful analysis and description of its components' interaction, which include the trans-fessional orientation, as well as the regulatory, vocational and educational, information and communication, operational and technological components. The intercoordinate space in the proposed model forms the psychological potential of the personality, its resource capabilities. Based on the analysis of trends and challenges of the post-industrial society, it was concluded that it is necessary to introduce into the educational process the technology of problem-oriented learning (PBL) and foresight technologies aimed at developing students' readiness for change, proactive goal-setting and self-design in a variable educational space (high humanitarian technologies, minors, design methods involving digital didactic tools, game technologies, discussions and moderation, etc.). Concerning practical significance, the materials of the article can be used for the preparation of transprofessional specialists who are ready for preadaptation of an uncertain social and professional future. © 2021 Tomsk State University. All rights reserved.The reported study was funded by RFBR, project number 18-013-01147

TDP1 deficiency sensitizes human cells to base damage via distinct topoisomerase I and PARP mechanisms with potential applications for cancer therapy

Base damage and topoisomerase I (Top1)-linked DNA breaks are abundant forms of endogenous DNA breakage, contributing to hereditary ataxia and underlying the cytotoxicity of a wide range of anti-cancer agents. Despite their frequency, the overlapping mechanisms that repair these forms of DNA breakage are largely unknown. Here, we report that depletion of Tyrosyl DNA phosphodiesterase 1 (TDP1) sensitizes human cells to alkylation damage and the additional depletion of apurinic/apyrimidinic endonuclease I (APE1) confers hypersensitivity above that observed for TDP1 or APE1 depletion alone. Quantification of DNA breaks and clonogenic survival assays confirm a role for TDP1 in response to base damage, independently of APE1. The hypersensitivity to alkylation damage is partly restored by depletion of Top1, illustrating that alkylating agents can trigger cytotoxic Top1-breaks. Although inhibition of PARP activity does not sensitize TDP1-deficient cells to Top1 poisons, it confers increased sensitivity to alkylation damage, highlighting partially overlapping roles for PARP and TDP1 in response to genotoxic challenge. Finally, we demonstrate that cancer cells in which TDP1 is inherently deficient are hypersensitive to alkylation damage and that TDP1 depletion sensitizes glioblastoma-resistant cancer cells to the alkylating agent temozolomide