97 research outputs found
Ground state of graphite ribbons with zigzag edges
We study the interaction effects on the ground state of nanographite ribbons
with zigzag edges. Within the mean-field approximation, we found that there are
two possible phases: the superconducting (SC) phase and the excitonic insulator
(EI). The two phases are separated by a first-order transition point. After
taking into account the low-lying fluctuations around the mean-field solutions,
the SC phase becomes a spin liquid phase with one gapless charge mode.
On the other hand, all excitations in the EI phase, especially the spin
excitations, are gapped.Comment: 6 pages, 3 figure
Покрытия на основе двумерно упорядоченного линейно-цепочечного углерода для защиты титановых имплантатов от микробной колонизации
Purpose of the study – to evaluate the antibacterial activity and biological compatibility of alloy coatings based on two-dimensionally ordered linear chain carbon (TDOLCC).Materials and Methods. Coatings based on TDOLCC were synthesized using alloying additions like nitrogen (TDOLCC+N) and silver (TDOLCC+Ag) on the surfaces of titanium plates and polystyrene plates by the ion-stimulated carbon condensation in a vacuum. The authors examined the superficial bactericidal activity of the coatings and its resistance to mechanical effects. Coated plates were evaluated in respect of rate of microbial biofilms formation by clinical isolates with multiple and extreme antibiotic resistance. Specimens were colored with crystal violet solution to visualize the biofilms. Cytotoxic effect of coatings was evaluated in respect of primary culture of fibroblasts and keratinocyte cell line HaCaT.Results. The authors observed pronounced superficial bactericidal effect of TDOLCC+Ag coating in respect of microorganisms of several taxonomic groups independently of their resistance to antibacterial drugs. TDOLCC+Ag coating proved capable to completely prevent microbial biofilm formation by antibiotic resistant clinical isolates of S. aureus and P. aeruginosa. Silvercontaining coating demonstrated mechanical resistance and preservation of close to baseline level of superficial bactericidal activity even after lengthy abrasion treatment. TDOLCC based coatings did not cause any cytotoxic effects. Structure of monolayers formed in cavities coated by TDOLCC+N and TDOLCC+Ag was indistinguishable from the monolayers in cavities of control plates.Цель исследования — оценить антибактериальную активность и биологическую совместимость легированных покрытий металлоконструкций для остеосинтеза на основе двумерно упорядоченного линейно-цепочечного углерода (ДУ ЛЦУ).Материал и методы. Методом ионно-стимулированной конденсации углерода в вакууме на поверхностях титановых пластин и полистироловых планшетов синтезированы покрытия на основе ДУ ЛЦУ с легирующими добавками: азотом (ДУ ЛЦУ+N) и серебром (ДУ ЛЦУ+Ag). Изучена поверхностная бактерицидная активность покрытий и ее устойчивость к механическим воздействиям. На пластинах с покрытиями оценена интенсивность формирования микробных биопленок клиническими изолятами микроорганизмов со множественной и экстремальной антибиотикорезистентностью, для визуализации сформированных биопленок выполнено окрашивание образцов раствором кристаллического фиолетового. Оценка цитотоксичности покрытий выполнена в отношении первичной культуры фибробластов и клеточной линии кератиноцитов HaCaT.Результаты. Выявлен выраженный поверхностный бактерицидный эффект покрытий ДУ ЛЦУ+Ag в отношении микроорганизмов нескольких таксономических групп, не зависящий от их устойчивости к антибактериальным препаратам. Для покрытия ДУ ЛЦУ+Ag установлена способность полного предотвращения формирования микробных биопленок антибиотико-резистентными клиническими изолятами S. aureus и P. aeruginosa. Показана механическая устойчивость серебросодержащего покрытия с сохранением уровня поверхностной бактерицидной активности, близкого к исходному, даже после продолжительной абразивной обработки. Покрытия на основе ДУ ЛЦУ не вызывали цитотоксических эффектов. Структура монослоя, сформированного в лунках с покрытиями ДУ ЛЦУ+N и ДУ ЛЦУ+Ag, была неотличима от лунок контрольных планшетов
Prospects and possibilities of using thermomechanical microrobots for solving technological tasks in space
The possibilities of microrobots for inspection and technological operations on spacecraft board and in open space are analyzed. Utilization of such robots for operations on outer hulls of spacecraft and on internal units and aggregates is discussed
The type numbers of closed geodesics
A short survey on the type numbers of closed geodesics, on applications of
the Morse theory to proving the existence of closed geodesics and on the recent
progress in applying variational methods to the periodic problem for Finsler
and magnetic geodesicsComment: 29 pages, an appendix to the Russian translation of "The calculus of
variations in the large" by M. Mors
Hyperbolic chaos in self-oscillating systems based on mechanical triple linkage: Testing absence of tangencies of stable and unstable manifolds for phase trajectories
Dynamical equations are formulated and a numerical study is provided for
self-oscillatory model systems based on the triple linkage hinge mechanism of
Thurston -- Weeks -- Hunt -- MacKay. We consider systems with holonomic
mechanical constraint of three rotators as well as systems, where three
rotators interact by potential forces. We present and discuss some quantitative
characteristics of the chaotic regimes (Lyapunov exponents, power spectrum).
Chaotic dynamics of the models we consider are associated with hyperbolic
attractors, at least, at relatively small supercriticality of the
self-oscillating modes; that follows from numerical analysis of the
distribution for angles of intersection of stable and unstable manifolds of
phase trajectories on the attractors. In systems based on rotators with
interacting potential the hyperbolicity is violated starting from a certain
level of excitation.Comment: 30 pages, 18 figure
MHD characteristics of compression zone in plasma stream generated by MPC
An investigation of local MHD plasma parameters in flow and characterizations of plasma streams, generated by different types of plasma accelerators and magneto-plasma compressors, is one of actual and important from point of view basic plasma dynamics research and plasma applications in different technologies. The present paper devoted to analysis of magneto-hydrodynamic characteristics of the plasma stream generated by the MPC compact geometry. Such important parameters as spatial distributions of electric current and spatial distribution of electromagnetic force in plasma stream, plasma density and velocity in compression zone have been investigated.Исследование локальных МГД параметров плазмы в потоке и характеристик плазменных потоков, генерируемых различными видами плазменных ускорителей и магнито-плазменных компрессоров, является актуальной фундаментальной задачей физики плазмы. Настоящая работа посвящена анализу магнито- гидродинамических характеристик плазменного потока, генерируемого MПК. Были исследованы такие важные параметры, как пространственные распределения электрического тока и электромагнитной силы в плазменном потоке, плотность плазмы и скорость в зоне компрессии.Дослідження локальних МГД параметрів плазми в потоці та характеристик плазмових потоків, що генеруються різними видами плазмових прискорювачів і магніто-плазмових компресорів, є актуальною фундаментальною задачею фізики плазми. Дана робота присвячена аналізу магніто-гідродинамічних характеристик плазмового потоку, який генерується MПК. Були досліджені такі важливі параметри, як просторові розподіли електричного струму та електромагнітної сили в плазмовому потоці, густина плазми та швидкістьу зоні компресії
Bouncing and Accelerating Solutions in Nonlocal Stringy Models
A general class of cosmological models driven by a non-local scalar field
inspired by string field theories is studied. In particular cases the scalar
field is a string dilaton or a string tachyon. A distinguished feature of these
models is a crossing of the phantom divide. We reveal the nature of this
phenomena showing that it is caused by an equivalence of the initial non-local
model to a model with an infinite number of local fields some of which are
ghosts. Deformations of the model that admit exact solutions are constructed.
These deformations contain locking potentials that stabilize solutions.
Bouncing and accelerating solutions are presented.Comment: Minor corrections, references added, published in JHE
Complete event-by-event α/γ(β) separation in a full-size TeO2 CUORE bolometer by simultaneous heat and light detection
The CUORE project began recently a search for neutrinoless double-beta decay () of Te with a (1 ton) TeO bolometer array. In this experiment, the background suppression relies essentially on passive shielding, material radiopurity and anti-coincidences. The lack of particle identification in CUORE makes decays at the detector surface the dominant background, at the level of 0.01 counts/(keV kg y) in the region of interest (-value of of the order of 2.5 MeV). In the present work we demonstrate, for the first time with a CUORE-size (555 cm) TeO bolometer and using the same technology as CUORE for the readout of the bolometric signals, an efficient particle discrimination (99.9\%) with a high acceptance of the signal (about 96\%). This unprecedented result was possible thanks to the superior performance (10 eV RMS baseline noise) of a Neganov-Luke-assisted germanium bolometer used to detect a tiny (70 eV) light signal dominated by ()-induced Cherenkov radiation in the TeO detector. The obtained results represent a major breakthrough towards the TeO-based version of CUPID, a ton-scale cryogenic experiment proposed as a follow-up to CUORE with particle identification
Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method
This paper discusses hadron energy reconstruction for the ATLAS barrel
prototype combined calorimeter (consisting of a lead-liquid argon
electromagnetic part and an iron-scintillator hadronic part) in the framework
of the non-parametrical method. The non-parametrical method utilizes only the
known ratios and the electron calibration constants and does not require
the determination of any parameters by a minimization technique. Thus, this
technique lends itself to an easy use in a first level trigger. The
reconstructed mean values of the hadron energies are within of the
true values and the fractional energy resolution is . The value of the ratio
obtained for the electromagnetic compartment of the combined calorimeter is
and agrees with the prediction that for this
electromagnetic calorimeter. Results of a study of the longitudinal hadronic
shower development are also presented. The data have been taken in the H8 beam
line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM
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