3,174 research outputs found
Role of direct exchange and Dzyaloshinskii-Moriya interactions in magnetic properties of graphene derivatives: CF and CH
According to the Lieb's theorem the ferromagnetic interaction in
graphene-based materials with bipartite lattice is a result of disbalance
between the number of sites available for electrons in different
sublattices. Here, we report on another mechanism of the ferromagnetism in
functionalized graphene that is the direct exchange interaction between spin
orbitals. By the example of the single-side semihydrogenated (CH) and
semifluorinated (CF) graphene we show that such a coupling can partially or
even fully compensate antiferromagnetic character of indirect exchange
interactions reported earlier [Phys. Rev. B {\bf 88}, 081405(R) (2013)]. As a
result, CH is found to be a two-dimensional material with the isotropic
ferromagnetic interaction and negligibly small magnetic anisotropy, which
prevents the formation of the long-range magnetic order at finite temperature
in accordance with the Mermin-Wagner theorem. This gives a rare example of a
system where direct exchange interactions play a crucial role in determining a
magnetic structure. In turn, CF is found to be at the threshold of the
antiferromagnetic-ferromagnetic instability, which in combination with the
Dzyaloshinskii-Moriya interaction can lead to a skyrmion state.Comment: 10 page
Magnetically Mediated Transparent Conductors: InO doped with Mo
First-principles band structure investigations of the electronic, optical and
magnetic properties of Mo-doped InO reveal the vital role of magnetic
interactions in determining both the electrical conductivity and the
Burstein-Moss shift which governs optical absorption. We demonstrate the
advantages of the transition metal doping which results in smaller effective
mass, larger fundamental band gap and better overall optical transmission in
the visible -- as compared to commercial Sn-doped InO. Similar behavior
is expected upon doping with other transition metals opening up an avenue for
the family of efficient transparent conductors mediated by magnetic
interactions
Electric field gradients in s-, p- and d-metal diborides and the effect of pressure on the band structure and T in MgB
Results of FLMTO-GGA (full-potential linear muffin-tin orbital -- generalized
gradient approximation) calculations of the band structure and boron electric
field gradients (EFG) for the new medium-T superconductor (MTSC), MgB,
and related diborides MB, M=Be, Al, Sc, Ti, V, Cr, Mo and Ta are reported.
The boron EFG variations are found to be related to specific features of their
band structure and particularly to the M-B hybridization. The strong charge
anisotropy at the B site in MgB is completely defined by the valence
electrons - a property which sets MgB apart from other diborides. The boron
EFG in MgB is weakly dependent of applied pressure: the B p electron
anisotropy increases with pressure, but it is partly compensated by the
increase of core charge assymetry. The concentration of holes in bonding
bands is found to decrease slightly from 0.067 to 0.062 holes/B under
a pressure of 10 GPa. Despite a small decrease of N(E), the Hopfield
parameter increases with pressure and we believe that the main reason for the
reduction under pressure of the superconducting transition temperature, T,
is the strong pressure dependence of phonon frequencies, which is sufficient to
compensate the electronic effects.Comment: 12 pages, 3 figure
Outpatient management of patients with peripheral artery disease by cardiologists or surgeons: influence on the prognosis and prevalence of surgical interventions
Highlights. The study shows for the first time that during the three-year follow-up of patients with diseases of the arteries of the lower extremities in the observation groups of a general surgeon and a cardiologist, adverse events (myocardial infarction, stroke, amputation, disability) and deaths occurred more often in a surgeon than a cardiologist. The study proves the correctness and real benefit of such an approach with the involvement of a cardiologist to the outpatient stage of management of a complex cohort of patients with atherosclerosis of the vessels of the lower extremities.Aim. To study the effect the outpatient observation of patients with peripheral arteries disease (PAD) by cardiologists and surgeons has on timing and prevalence of reconstructive surgery and the prognosis of patients. Methods We analyzed the data on 585 PAD patients who underwent outpatient observation from 2010 to 2017, dividing them into 2 groups. The first group (131 patients) managed by an surgeon; the second (454 patients) managed by a cardiologist. Since the groups were not comparable in terms of the initial parameters, the comparability of patients in the groups (observation by a surgeon or by a cardiologist) was achieved using pseudorandomization. The follow-up period was three years; we assessed the incidence of deaths, adverse events, and the prevalence of reconstructive operations.Results. During a three-year follow-up the 1st group, compared with the 2nd, had more deaths in general (p<0.001), death from cardiac causes (p = 0.045), from stroke (p><0.001), as well as the total number of adverse events (p><0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients. Conclusion Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries. Keywords Peripheral atherosclerosis • Outpatient follow-up • Optimal drug therapy • Reconstructive surgery>˂ 0.001), death from cardiac causes (p = 0.045), from stroke (p˂ 0.001), as well as the total number of adverse events (p˂ 0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients.Conclusion. Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries.Highlights. The study shows for the first time that during the three-year follow-up of patients with diseases of the arteries of the lower extremities in the observation groups of a general surgeon and a cardiologist, adverse events (myocardial infarction, stroke, amputation, disability) and deaths occurred more often in a surgeon than a cardiologist. The study proves the correctness and real benefit of such an approach with the involvement of a cardiologist to the outpatient stage of management of a complex cohort of patients with atherosclerosis of the vessels of the lower extremities.Aim. To study the effect the outpatient observation of patients with peripheral arteries disease (PAD) by cardiologists and surgeons has on timing and prevalence of reconstructive surgery and the prognosis of patients. Methods We analyzed the data on 585 PAD patients who underwent outpatient observation from 2010 to 2017, dividing them into 2 groups. The first group (131 patients) managed by an surgeon; the second (454 patients) managed by a cardiologist. Since the groups were not comparable in terms of the initial parameters, the comparability of patients in the groups (observation by a surgeon or by a cardiologist) was achieved using pseudorandomization. The follow-up period was three years; we assessed the incidence of deaths, adverse events, and the prevalence of reconstructive operations.Results. During a three-year follow-up the 1st group, compared with the 2nd, had more deaths in general (p<0.001), death from cardiac causes (p = 0.045), from stroke (p><0.001), as well as the total number of adverse events (p><0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients. Conclusion Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries. Keywords Peripheral atherosclerosis • Outpatient follow-up • Optimal drug therapy • Reconstructive surgery>˂ 0.001), death from cardiac causes (p = 0.045), from stroke (p˂ 0.001), as well as the total number of adverse events (p˂ 0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients.Conclusion. Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries
Motivation for higher military education in modern Ukraine
Статья посвящена анализу мотивации получения высшего военного образования в Украине, которую предложено рассматривать на трех этапах выбора профессии, обучения в военном вузе и профессионального становления после получения образования. На основании проведенных авторских исследований качественными и количественными стратегиями выявлено, что на первом этапе основными факторами выбора профессии военнослужащего выступают престиж профессии, гарантия трудоустройства. Определенное влияние оказывают семейные традиции. Показано, что на втором этапе воздействие различных факторов формируют три группы курсантов по силе мотивационных компонентов для получения высшего военного образования: с высокой, средней и низкой силой мотивации. Проведенное исследование показало, что у курсантов доминируют такие ценностные ориентации, как здоровье, счастливая семейная жизнь, наличие хороших и верных друзей и материальная обеспеченность. На основании проведенного компаративного анализа продемонстрировано, что система ценностей курсантов идентична ценностям студентов, наряду с этим, их мотивация на получение профессии более устойчива, чем у последних. Анализ проблем профессионального становления на третьем этапе позволил очертить круг проблем, требующих решения в высших военных учебных заведениях. Среди них: содержание учебных программ, их идентичность практическим аспектам профессиональной деятельности, формирование субъектсубъектных отношений и другие.Статья посвящена анализу мотивации получения высшего военного образования в Украине, которую предложено рассматривать на трех этапах выбора профессии, обучения в военном вузе и профессионального становления после получения образования. На основании проведенных авторских исследований качественными и количественными стратегиями выявлено, что на первом этапе основными факторами выбора профессии военнослужащего выступают престиж профессии, гарантия трудоустройства. Определенное влияние оказывают семейные традиции. Показано, что на втором этапе воздействие различных факторов формируют три группы курсантов по силе мотивационных компонентов для получения высшего военного образования: с высокой, средней и низкой силой мотивации. Проведенное исследование показало, что у курсантов доминируют такие ценностные ориентации, как здоровье, счастливая семейная жизнь, наличие хороших и верных друзей и материальная обеспеченность. На основании проведенного компаративного анализа продемонстрировано, что система ценностей курсантов идентична ценностям студентов, наряду с этим, их мотивация на получение профессии более устойчива, чем у последних. Анализ проблем профессионального становления на третьем этапе позволил очертить круг проблем, требующих решения в высших военных учебных заведениях. Среди них: содержание учебных программ, их идентичность практическим аспектам профессиональной деятельности, формирование субъектсубъектных отношений и другие.This article analyzes the motivation of higher military education in Ukraine, which proposed to consider on three stages – the choice of profession, training in military high school and professional formation after education. Based on the author’s qualitative and quantitative research strategies the authors revealed that on the first stage the main factors of the choice of occupation are soldier prestige of the profession, a guarantee of employment. A certain influence family tradition has. It is shown that on the second stage the impact of various factors forms the three groups of military students on the power of motivational components for higher military education: high, medium and low power motivation. The study showed that the military students choose such values, like health, a happy family life, good and true friends, and financial stability. On the basis of comparative analysis demonstrated that the system of values of military students is identical to the values of students, along with it, their motivation to obtain the profession is more stable than the latter. Analysis of the problems of professional development at the third stage shows the range of problems to be solved in the higher military educational institutions. Among them: the content of the curriculum, their identity to practical aspects of professional activity, the formation of subjectsubject relations and others
Combining high conductivity with complete optical transparency: A band-structure approach
A comparison of the structural, optical and electronic properties of the
recently discovered transparent conducting oxide (TCO), nanoporous Ca12Al14O33,
with those of the conventional TCO's (such as Sc-doped CdO) indicates that this
material belongs conceptually to a new class of transparent conductors. For
this class of materials, we formulate criteria for the successful combination
of high electrical conductivity with complete transparency in the visible
range. Our analysis suggests that this set of requirements can be met for a
group of novel materials called electrides.Comment: 3 pages, 3 figures, submitted for publicatio
Phospholipse c inhibitor, u73122, stimulates release of hsp-70 stress protein from A431 human carcinoma cells
BACKGROUND: Accumulating evidences suggest that Hsp 70, the inducible component of Hsp70 family, might release from a living cell. Here we show that a pharmacological inhibitor of phospholipase C activity U73122 caused a 2–4 fold reduction of an intracellular level of Hsp70 in A431 human carcinoma cells. RESULTS: A depletion of Hsp70 under U73122 was a result of the protein release since it was detected in cell culture medium, as was established by immunoprecipitation and precipitation with ATP-agarose. The reduction of Hsp70 level was specifically attributed to the inhibition of PLC, since the non-active inhibitor, U73343, had no effect on Hsp70 level. The PLC-dependent decrease of Hsp70 intracellular level was accompanied by the enhanced sensitivity of A431 cells to the apoptogenic effect of hydrogen peroxide. Here for the first time we demonstrated one of the possibilities for a cell to export Hsp70 in PLC-dependent manner. CONCLUSION: From our data we suggest that phospholipase C inhibition is one of the possible mechanisms of Hsp70 release from cells
Cyclotron enhancement of tunneling
A state of an electron in a quantum wire or a thin film becomes metastable,
when a static electric field is applied perpendicular to the wire direction or
the film surface. The state decays via tunneling through the created potential
barrier. An additionally applied magnetic field, perpendicular to the electric
field, can increase the tunneling decay rate for many orders of magnitude. This
happens, when the state in the wire or the film has a velocity perpendicular to
the magnetic field. According to the cyclotron effect, the velocity rotates
under the barrier and becomes more aligned with the direction of tunneling.
This mechanism can be called cyclotron enhancement of tunneling
Electrochemical behavior of chloramphenicol on carbon electrodes in a microelectrochemical cell
Express determination of antibiotics is an extremely important task today. Portable electrochemical microdevices are a viable alternative to traditional methods of analysis. The development of such devices requires the study of redox processes in detail. This article is devoted to the comparative study of the electrochemical behavior of chloramphenicol in water solvents in standard laboratory and portable microelectrochemical cells. It was found that the electrochemical reduction of chloramphenicol proceeds via a 3-electron mechanism to the formation of a dimer. In the transition from the macrocell to the microcell, a decrease in the electrochemical reduction current and a shift of the peak potential to the cathode region are observed, which is apparently associated mainly with the type of the electrode material. The best characteristics of the direct electrochemical response were obtained in the differential pulse voltammetry mode. Under the selected operating parameters, the peak current of the electrochemical reduction of chloramphenicol is linearly dependent on the concentration of the antibiotic in the range of 2∙10–3–1∙10–5 M with a detection limit of 3∙10–5 M. Obtained characteristics are sufficient for the quality control of pharmaceuticals and can be improved through the use of organic and hybrid modifiers of the working electrode surface
Electronic band structure and carrier effective mass in calcium aluminates
First-principles electronic band structure investigations of five compounds
of the CaO-Al2O3 family, 3CaO.Al2O3, 12CaO.7Al2O3, CaO.Al2O3, CaO.2Al2O3 and
CaO.6Al2O3, as well as CaO and alpha-, theta- and kappa-Al2O3 are performed. We
find that the conduction band in the complex oxides is formed from the oxygen
antibonding p-states and, although the band gap in Al2O3 is almost twice larger
than in CaO, the s-states of both cations. Such a hybrid nature of the
conduction band leads to isotropic electron effective masses which are nearly
the same for all compounds investigated. This insensitivity of the effective
mass to variations in the composition and structure suggests that upon a proper
degenerate doping, both amorphous and crystalline phases of the materials will
possess mobile extra electrons
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