Renormalization of hole-hole interaction at decreasing Drude conductivity

The diffusion contribution of the hole-hole interaction to the conductivity is analyzed in gated GaAs/In$_x$Ga$_{1-x}$As/GaAs heterostructures. We show that the change of the interaction correction to the conductivity with the decreasing Drude conductivity results both from the compensation of the singlet and triplet channels and from the arising prefactor $\alpha_i<1$ in the conventional expression for the interaction correction.Comment: 6 pages, 5 figure

A Damping of the de Haas-van Alphen Oscillations in the superconducting state

Deploying a recently developed semiclassical theory of quasiparticles in the superconducting state we study the de Haas-van Alphen effect. We find that the oscillations have the same frequency as in the normal state but their amplitude is reduced. We find an analytic formulae for this damping which is due to tunnelling between semiclassical quasiparticle orbits comprising both particle-like and hole-like segments. The quantitative predictions of the theory are consistent with the available data.Comment: 7 pages, 5 figure

Spin and Charge Correlations in Quantum Dots: An Exact Solution

The inclusion of charging and spin-exchange interactions within the Universal Hamiltonian description of quantum dots is challenging as it leads to a non-Abelian action. Here we present an {\it exact} analytical solution of the probem, in particular, in the vicinity of the Stoner instabilty point. We calculate several observables, including the tunneling density of states (TDOS) and the spin susceptibility. Near the instability point the TDOS exhibits a non-monotonous behavior as function of the tunneling energy, even at temperatures higher than the exchange energy. Our approach is generalizable to a broad set of observables, including the a.c. susceptibility and the absorption spectrum for anisotropic spin interaction. Our results could be tested in nearly ferromagnetic materials.Comment: JETPL class, 6 pages, 2 figure

Virucidal properties of new multifunctional fibrous N-halamine-immobilized styrene-divinylbenzene copolymers

Virucidal properties of N-chlorosulfonamides immobilized on fibrous styrene-divinylbenzene copolymers have been studied. Corresponding materials with different functional group structures and chlorine content have been synthesized on FIBAN polymer carriers in the form of staple fibers and non-woven fabrics. The study has been conducted in general accordance with EN 14476 standard on poliovirus type-1 and adenovirus type-5. It has been found that all tested samples exhibit pronounced virucidal activity: regardless of the carrier polymer form, sodium N-chlorosulfonamides inactivated both viruses in less than 30s, and N,N-dichlorosulfonamides— in 30–60 s. The main mechanism of action of these materials, obviously, consists in the emission of active chlorine from the functional group into the treated medium under the action of the amino groups of virus fragments and cell culture. Considering the previously described antimicrobial and reparative properties of such materials, as well as their satisfactory physical and mechanical properties, the synthesized polymers are promising for the creation of medical devices with increased resistance to microbial contamination, such as protective masks, filter elements, longacting wound dressings, and others

Two-dimensional electron liquid with disorder in a weak magnetic field

We present the effective theory for low energy dynamics of a two-dimensional interacting electrons in the presence of a weak short-range disorder and a weak perpendicular magnetic field, the filling factor $\nu \gg 1$. We investigate the exchange enhancement of the $g$-factor, the effective mass and the decay rate of the simplest spin wave excitations at $\nu = 2 N + 1$. We obtain the enhancement of the field-induced gap in the tunneling density of states and dependence of the tunneling conductivity on the applied bias.Comment: 17 pages, no figure

СИНТЕЗ ТА АНТИБАКТЕРІАЛЬНІ ВЛАСТИВОСТІ 4-АМІНОФЕНІЛСУЛЬФОНАМІДУ, ІММОБІЛІЗОВАНОГО НА ПОЛІМЕРНОМУ НОСІЇ

The aim of the study. Today the immobilization of drugs to the polymeric carriers is increasingly important, due to the requirements to reduce the toxicity and prolongation of action of drugs. It is known the immobilization of the Sulfonamides on the Stiromali, methacrylate polymer matrices, wherein the pharmacologically active sulfanilamide easily remove from the polymer upon the application, by the acid hydrolysis. At the same time it is noted that immobilized sulfonamides derived from aminomethylated Styrene-divinylbenzene copolymer, although hydrolytic stability, maintain the antibacterial properties. In order to expand the examples of covalent immobilization of sulfonamides we synthesized 4-aminophenylsulfonamide on pellet and brous forms of styrene and divinylbenzene with SO2 as a bridging group.Materials and Methods. As a raw materials, we used the pellet macroporous sulfonated Styrene-divinylbenzene copolymer and copolymers Polypropylene and Styrene. Sulfochlorination of these copolymers the polymeric sulfonyl chlorides were obtained. This compounds were used in the reaction with 4-aminophenilsulfonamidom. Antibacterial properties of the material were studied by determining the growth inhibition zones of test E. coli K12 microorganism in a nutrient medium.Results and Discussion. The structure of synthesized immobilized 4-aminophenylsulfonamide proven by IR spectroscopy. It is shown that such materials exhibit a relatively pronounced antibacterial properties test culture of microorganisms E. coli K-12, in spite of their resistance to hydrolysis. Сonclusions. It is suggested that the hydrolysis of the materials takes place at a specic enzymatic catalysis in the medium with the release of 4-aminophenylsulfonamide.Мета роботи. У сучасних умовах іммобілізація лікарських засобів на полімерних носіях набуває все більшого значення, що пов’язане з вимогами до зменшення токсичності та пролонгації дії препаратів. Відома іммобілізація сульфаніламідних препаратів на стиромалі, метакрилатних полімерних матрицях, де фармакологічно активний сульфаніламід легко вивільняється з полімеру при застосуванні, в результаті кислотного гідролізу. Разом з тим спостерігається, що іммобілізовані сульфаніламіди, отримані на основі амінометильованого співполімеру стиролу з дивінілбензолом, незважаючи на стійкість до гідролізу, зберігають антибактеріальні властивості. З метою розширення прикладів ковалентної іммобілізації сульфаніламідів нами синтезовані 4-амінофенілсульфонаміди на гранульній і волокнистій формах співполімерів стиролу з дивінілбензолом через місткову групу SO2.Матеріали і методи. Як вихідну сировину використано макропористий гранульний співполімер стиролу з дивінілбензолом і сульфовані волокнисті форми прищепленого до поліпропіленової нитки співполімеру стиролу з дивінілбензолом. Сульфохлоруванням цих співполімерів отримано полімерні сульфохлориди, які використовували в реакції з 4-амінофенілсульфонамідом. Антибактеріальні властивості матеріалу досліджені за визначенням зон пригнічення росту тест-мікроорганізмів E.coli К-12 на поживному середовищі.Результати й обговорення. Будову синтезованих іммобілізованих 4-амінофенілсульфонамідів доведено методом ІЧ спектроскопії. Показано, що такі матеріали проявляють виражені антибактеріальні властивості щодо тест-культури мікроорганізмів E. coli К-12, незважаючи на їхню стійкість до гідролізу.Висновки. Зроблено припущення, що гідроліз матеріалів перебігає при специфічному ферментативному каталізі на поживному середовищі виділенням 4-амінофенілсульфонаміду

Out-of-Equilibrium Admittance of Single Electron Box Under Strong Coulomb Blockade

We study admittance and energy dissipation in an out-of-equlibrium single electron box. The system consists of a small metallic island coupled to a massive reservoir via single tunneling junction. The potential of electrons in the island is controlled by an additional gate electrode. The energy dissipation is caused by an AC gate voltage. The case of a strong Coulomb blockade is considered. We focus on the regime when electron coherence can be neglected but quantum fluctuations of charge are strong due to Coulomb interaction. We obtain the admittance under the specified conditions. It turns out that the energy dissipation rate can be expressed via charge relaxation resistance and renormalized gate capacitance even out of equilibrium. We suggest the admittance as a tool for a measurement of the bosonic distribution corresponding collective excitations in the system

Visualization of Nd3+-doped Laf3 Nanoparticles For Near Infrared Bioimaging via Upconversion Luminescence at Multiphoton Excitation Microscopyvisualization of Nd3+-doped Laf3 Nanoparticles For Near Infrared Bioimaging via Upconversion Luminescence at Multiphoton Excitation Microscopy

Recent developments in the field of biophotonics facilitate the raise of interest to inorganic nanoparticles (NPs) doped with Nd 3+ ions, because of their near-infrared (NIR) absorption. These NPs are interesting bioimaging probes for deep tissue visualization, while they can also act as local thermometers in biological tissues. Despite the good possibilities for visualization of NPs with Nd 3+ ions in NIR spectral range, difficulties arise when studying the cellular uptake of these NPs using commercially available fluorescence microscopy systems, since the selection of suitable luminescence detectors is limited. However, Nd 3+ ions are able to convert NIR radiation into visible light, showing upconversion properties. In this paper we found optimal parameters to excite upconversion luminescence of Nd 3+ :LaF 3 NPs in living cells and to compare the distribution of the NPs inside the cell culture of human macrophages THP-1 obtained by two methods. Firstly, by detecting the upconversion luminescence of the NPs in VIS under NIR multiphoton excitation using laser scanning confocal microscopy and secondly, using transmission electron microscopy

Swarmodroid 1.0: A Modular Bristle-Bot Platform for Robotic Active Matter Studies

Large swarms of extremely simple robots (i.e., capable just of basic motion activities, like propelling forward or self-rotating) are widely applied to study collective task performance based on self-organization or local algorithms instead of sophisticated programming and global swarm coordination. Moreover, they represent a versatile yet affordable platform for experimental studies in physics, particularly in active matter - non-equilibrium assemblies of particles converting their energy to a directed motion. However, a large set of robotics platforms is being used in different studies, while the universal design is still lacking. Despite such platforms possess advantages in certain application scenarios, their large number sufficiently limits further development of results in the field, as advancing some study requires to buy or manually produce the corresponding robots. To address this issue, we develop an open-source Swarmodroid 1.0 platform based on bristle-bots with reconfigurable 3D-printed bodies, external control of motion velocity, and basic capabilities of velocity profile programming. In addition, we introduce AMPy software package in Python featuring OpenCV-based extraction of robotic swarm kinematics accompanied by the evaluation of key physical quantities describing the collective dynamics. We perform a detailed analysis of individual Swarmodroids' motion characteristics and address their use cases with two examples: a cargo transport performed by self-rotating robots and a velocity-dependent jam formation in a bottleneck by self-propelling robots. Finally, we provide a comparison of existing centimeter-scale robotic platforms, a review of key quantities describing collective dynamics of many-particle systems, and a comprehensive outlook considering potential applications as well as further directions for fundamental studies and Swarmodroid 1.0 platform development.Comment: 18 pages, 7 figures, 1 table + Supplementary Information. Comments are welcom

Population Exposure Dose Reconstruction for the Urals Region

This presentation describes the first preliminary results of an ongoing joint Russian-US pilot feasibility study. Many people participated in workshops to determine what Russian and United States scientists could do together in the area of dose reconstruction in the Urals population. Most of the results presented here came from a joint work shop in St. Petersburg, Russia (11-13 July 1995). The Russians at the workshop represented the Urals Research Center for Radiation Medicine (URCRM), the Mayak Industrial Association, and Branch One of the Moscow Biophysics Institute. The US Collaborators were Dr. Anspaugh of LLNL, Dr. Nippier of PNL, and Dr. Bouville of the National Cancer Institute. The objective of the first year of collaboration was to look at the source term and levels of radiation contamination, the historical data available, and the results of previous work carried out by Russian scientists, and to determine a conceptual model for dose reconstruction