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The microwave compressor of a new design forms high-power rectangular pulses of a spatial length exceeding several folds the longitudinal dimension of a storage cavity. Similar to the known compressor with the single-mode circular cavity, the new one has small overall dimensions due to making the cavity as a meander formed by parallel waveguide sections. The input coupler is the input port of the first section, and the output unit is the output port of the last section. Unlike the known compressor, the waveguide elements of the proposed one are oversized. Requirements for the design are determined and characteristics are estimated. Comparing with the analog compressor, the gain of the proposed one is greater by 7 dB. The processes of energy storing and extraction and the characteristics of the X-band compressor were analyzed by computer simulation. The compressor was tested experimentally, and the results were compared with the simulation data. It was shown that the microwave compressor with the oversized compact cavity worked similar to the analog compressor.

The flexoelectric effect describes the electromechanical coupling of a strain gradient to a polarization and vice versa. This effect scales linearly with permittivity and strain gradients can get very high for dimensions on the micro and nanoscale. Even though the flexoelectric effect can be best exploited within micro or nanoelectromechanical systems (M/NEMS) applications, it has not been established in today`s M/NEMS device architectures as other transducer principles, like piezoelectricity. In this work, values of the converse flexoelectric coefficient for one of the most promising flexoelectric materials, titanium dioxide (TiO2) are provided. The experimental results are based on a carefull characterization of IrO2/TiO2/IrO2 cantilevers. Besides CMOS compatiblity TiO2 is selected as functional thin film material as it offers a very high permittivity and shows no hysteresis or saturation effects as it is neither ferro- nor paraelectric. Additionally, it guarantees a low cost, lead-free realization and can be directly integrated in a standard silicon MEMS fabrication process by sputter deposition. In order to correctly determine the flexoelectric coefficient, other electromechanical coupling effects are considered and assessed. The flexoelectric coefficient is shown to be µeff = 1.78 ± 0.16 nC m−1 at 10 kHz. The flexoelectric coupling constant with a value of 2.75 V is in good agreement with that theoretically predicted by Kogan`s estimate of 3.14 V.

—An analysis is performed for the characteristics of an interference microwave switch with distributed switched wave power as a device for outputting energy from an active resonant microwave compressor. The proposed device is a cascade of conventional microwave switches based on H-tees connected in series with straight arms. It is shown that such a switch can multiply reduce the switched wave power by uniformly distributing it across the switches of the tees, which is done by adjusting the lengths of the tee arms. It was also established that between the lengths there is a functional relationship in which uniform distribution is achieved. The results of an experimental study of the microwave switch of two and/or three tees at low and high power are presented.

Nanocrystalline diamond (NCD) layers functionalized with amine-containing functional groups have generated considerable interest as biocompatible substrates for attachment of biomolecules and cells with a view to biosensor and tissue engineering applications. Here we prepare nanoporous diamond layers with the surfaces modified by hydrogen plasma, oxygen plasma, and conformal 7 nm amine-containing plasma polymer (PP). Immobilization of bovine serum albumin (BSA) molecules is characterized on such surfaces. Grazing angle reflectance infrared spectroscopy as well as X-ray photoelectron spectroscopy show that concentration of amine-containing bonds after BSA exposure depends on the type of NCD surface modification. AFM measurements reveal that BSA proteins are physisorbed on H- and O-terminated diamond surfaces in different thicknesses and morphology. When the diamond layers are coated with the amine-containing PP, BSA molecules assume similar thickness and morphology, and their adhesion is significantly increased on both types of the diamond surfaces.

The article is devoted to the investigation of the influence of columns’ concrete body destruction size on the bearing capacity of building structures. The joint spatial work of steel strengthening structures with reinforced concrete constructions is investigated. The results of numerical modeling the stress-strain state of damaged reinforced concrete columns in the middle row of the industrial building are presented. The numerical modeling was executed in the system NASTRAN. It was carried out the numerical calculation of reinforced concrete column in the middle row without damages. Then it was modeled the column damage in form of a "downed" concrete angle to a depth of 50, 100 and 200 mm and denudation of bearing longitudinal armature at length of 1000 mm from supporting part of the column. In this case two separate models were investigated - with the location of damage from the compressed or extended side of the column. The conclusions about feasibility of columns strengthening by steel clip are made.

This paper proposes and describes in detail a new approach to the design of very compact active microwave compressors capable of providing rectangular pulses of up to 100 ns. The approach consists in using a storage cavity, which comprises linear waveguide sections connected by tees such that the cavity geometry can be 2-D or 3-D or can be variable to allow direct space-saving integration of a compressor into a microwave source. Also presented are the scattering matrix data on uniform wave propagation along the storage cavity with little reflection and on conditions necessary for such uniformity. The S-band experiments demonstrate the capability of storage cavities with two and three parallel waveguide sections of about 1 m long to produce rectangular pulses of duration 5, 15, and 25 ns with a power gain and output power of about 16 dB, 80 MW; 15 dB, 60 MW; and 13 dB, 40 MW, respectively. Our estimates suggest that 12 waveguide sections can provide a rectangular pulse of 100 ns with a power gain 10 dB.

We review the development and application of the Simplex approach for the solution of various QSAR/QSPR problems. The general concept of the simplex method and its varieties are described. The advantages of utilizing this methodology, especially for the interpretation of QSAR/QSPR models, are presented in comparison to other fragmentary methods of molecular structure representation. The utility of SiRMS is demonstrated not only in the standard QSAR/QSPR applications, but also for mixtures, polymers, materials, and other complex systems. In addition to many different types of biological activity (antiviral, antimicrobial, antitumor, psychotropic, analgesic, etc.), toxicity and bioavailability, the review examines the simulation of important properties, such as water solubility, lipophilicity, as well as luminescence, and thermodynamic properties (melting and boiling temperatures, critical parameters, etc.). This review focuses on the stereochemical description of molecules within the simplex approach and details the possibilities of universal molecular stereo-analysis and stereochemical configuration description, along with stereo-isomerization mechanism and molecular fragment “topography” identification.

First data on morphology of phytoliths was obtained for leaves, body, and inflorescence of Cannabis sativa found in 2 regions of the Khabarovsky region (Khabarovsk City and Bikinsky District). Optical microscopy revealed 5 phytoliths morphotypes in the scape, inflorescence, and in the leaves of the cannabis: shapeless, oval, segmented oval, club-shaped, and spikes. Size of phytoliths from various plant’s parts is found to be uniform, but their morphometry changes with respect to ratio among shapes. Shapeless dominate in the scape (68%), inflorescence, and in leaves (31.33%). Spikes are found in inflorescence (32%) as well as in scape (30%) and in leaves (10.6%).

In current work unique hexagonal microparticles of silicon oxide (phytolite), isolated from the red algae Tichocarpus crinitus, which grows in the Sea of Japan described. The structures of poytolites are characterized by the methods of optical microscopy and scanning electron microscopy. The role of these formations in plant life and the mechanism of their synthesis remains unclear.

This paper is devoted for idea that plants and mushrooms can cover defects or wounds using large silicon formations (phytolithes). Its observed huge phytolithes more than 500 mkm. The issue is not closed and needs to be comprehensively studied.

International audience; Interfaces are a major issue when designing ferroelectric nanostructured materials with tailored properties. In a context of integration and multifunctionality in the field of electronics, several strategies have been developed to control the microstructure and defect chemistry of interfaces that strongly impact the macroscopic properties. The suitability of the core-shell approaches that allow a subtle tuning of interface phenomena at different scales has been widely demonstrated. We focus here on the flexibility of the core-shell approach devoted to the processing of nanostructured ferroelectric composites. Our strategy relies on the use of advanced synthesis processes to design ferroelectric grains coated with shells of different nature, morphology and crystallinity. Typical examples will be reviewed with a specific attention on their impact on both microstructure and dielectric properties. Our approach, based also on the use of fast sintering technique, provides a guidance to design 3D bulk nanostructured ferroelectrics while controlling and/or exploiting size, interface and defects chemistry. The contribution of specific spectroscopies to probe interfacial chemistry and defects is underlined. The high density of interfaces in core-shell materials is obviously an advantage to target additional functionality such as magneto-electric coupling. This is illustrated in 3D composites and one dimensional nanostructures that coaxially combine electric and magnetic materials. The core-shell approach described here could be transferred to a much broader range of materials covering many functionalities provided a deeper understanding of the interfaces at the atomic scale is achieved and a further development of low temperature processing is reached.

Erbium doped zinc oxide (ZnO:Er) powder was synthesized by hydrothermal growth. The morphology changed from undoped nanorods to microrods. The effect of Er doping on luminescence properties of ZnO:Er was observed. Furthermore, annealing in air at elevated temperatures up to 700 °C results in additional modification of defect states and related luminescence properties. In particular, exciton-related UV emission band and the defect-related red emission band appear in all annealed samples. Er3+ infrared (IR) photoemission, the typical 4I13/2 → 4I15/2 transition, not observed in as grown samples with low Er concentration, occurs at room temperature in all ZnO:Er samples after annealing in air at elevated temperatures. Oppositely, the electron paramagnetic resonance (EPR) signal of Er3+ is getting weaker upon the annealing at elevated temperatures, disappearing completely at about 500 °C. The intensity of the g = 1.96 EPR spectrum, typical for ZnO structures, is getting decreased and almost disappears after the annealing at 500 °C but increasing again after the annealing at 600 °C and 700 °C. X-ray photoelectron spectroscopy and IR Raman spectroscopy suggested that annealing in air causes diffusion of Zn from the surface to the bulk and oxidation of Er to Er3+ in Er2O3 and Er(OH)x forms.

We review the different approaches to establish the boundary between the liquid and the quasi-gas fluid above the critical point. Some experimental data by inelastic X-ray scattering demonstrates different dynamical regimes: gas-like and liquid-like reminiscent of the subcritical domains. Theoretical models based on the Lennard-Jones and square well interparticle potentials together with phenomenological Van der Waals model confirm similar picture for the Widom line in supercritical domain. To minimize uncertainty experimental data we calculated extrema of response functions via fundamental equations of state. The shift of critical points under influences of impurities and nanoparticle adding is analyzed.

The principal aim of this work is to estimate the azeotrope breaking of ionic liquids (IL) in separation processes. The global phase diagram approach is applied to correlate azeotrope data for binary mixtures based only on critical properties and acentric factor of the individual components. Analytical expressions to predict azeotrope phenomena in terms of critical parameters of pure components and binary interaction parameters are given. The azeotrope breaking in binary refrigerant mixtures with ionic liquid adding is predicted. The eventual azeotrope appearance in the refrigerant – IL blends is discussed and conclusion about highly improbable azeotrope blend formation for these systems is given. Azeotrope breaking in the R134a – R1234yf blend at IL doping is considered as illustration of zeotrope behavior in the refrigerant – ILs mixtures.

The flexoelectric effect describes the electromechanical coupling of a strain gradient to a polarization and vice versa. This effect scales linearly with permittivity and strain gradients can get very high for dimensions on the micro and nanoscale. Even though the flexoelectric effect can be best exploited within micro or nanoelectromechanical systems (M/NEMS) applications, it has not been established in today`s M/NEMS device architectures as other transducer principles, like piezoelectricity. In this work, values of the converse flexoelectric coefficient for one of the most promising flexoelectric materials, titanium dioxide (TiO2) are provided. The experimental results are based on a carefull characterization of IrO2/TiO2/IrO2 cantilevers. Besides CMOS compatiblity TiO2 is selected as functional thin film material as it offers a very high permittivity and shows no hysteresis or saturation effects as it is neither ferro- nor paraelectric. Additionally, it guarantees a low cost, lead-free realization and can be directly integrated in a standard silicon MEMS fabrication process by sputter deposition. In order to correctly determine the flexoelectric coefficient, other electromechanical coupling effects are considered and assessed. The flexoelectric coefficient is shown to be μ eff= 1.78 ± 0.16 nC m-1 at 10 kHz. The flexoelectric coupling constant with a value of 2.75 V is in good agreement with that theoretically predicted by Kogan`s estimate of 3.14 V.

International audience; Layered vanadium oxides have been extensively explored due to their interesting metal-insulator transitions and energy conversion/storage applications. In the present study, we have successfully synthesized VO2 (A) polymorph powder samples by a single-step hydrothermal synthesis process and consolidated them using spark plasma sintering. The structural and electronic properties of VO2 (A) are measured over a large temperature range from liquid helium, across the structural transition (400-440 K) and up to 500 K. The structural analysis around this transition reveals an antiferrodistorsive to partially ferrodistorsive ordering upon cooling. It is followed by a progressive antiferromagnetic spin pairing which fully settles at about 150 K. The transport measurements show that, in contrast to the rutile archetype VO2 (R/M1), the structural transition comes with a transition from semiconductor to band-type insulator. Under these circumstances, we propose a scenario with a high temperature antiferrodistorsive paramagnetic semiconducting phase, followed by an intermediate regime with a partially ferrodistorsive paramagnetic semiconducting phase, and finally a low temperature partially ferrodistorsive antiferromagnetic band insulator phase with a possible V-V Peierls-type pairing.

Due to extraordinary properties and biocompatibility, diamond nanoparticles – nanodiamonds (NDs) are considered for various biomedical applications. Amongst other functional groups which may be grafted on the NDs surface, the amines (NHx) are highly demanded linkers for biomolecules and dyes. In this regard, a non-destructive, non-hazardous and low-cost method of NDs amination would further accelerate their industrial applications in biomedicine and life science. Here we present a study on NDs treatment using diffuse coplanar surface barrier discharge in the gas mixture H2:N2=1:1 at the atmospheric pressure. Detonation and high pressure–high temperature nanoparticles (D-NDs and HPHT-NDs) were used either as-received or air-annealed. The FTIR spectra confirmed the presence of N–H stretching vibrations for all kinds of NDs after the treatment. It was revealed by XPS and FTIR measurements that both kinds of D-NDs (as-received and air-annealed) exhibited higher content of -NH2 functions in the detected nitrogen groups than HPHT-NDs. The treatment of as-received D-NDs led to the conversion of -COOH groups to amides. A large increase of C–H bonds after the discharge treatment was found, especially for the annealed NDs forms. Raman spectroscopy revealed a decrease of sp2 carbon after the treatment of the as-received HPHT-NDs.

The microwave pulse compression procedure consists of excitation of a working mode in a resonant cavity and transforming the mode into an auxiliary one that is coupled to an output line. Both transforming and coupling involve switching. Transients were calculated by recursion relations giving higher accuracy at short time constants. Demonstration experiments were run in the X-band. The compressor prototype showed power amplification of 15 dB at an output pulse width of 2.7 ns and a peak power of 1.5 MW. Mode transformation efficiency approached 0.7. A sequence of nanosecond and sub-nanosecond microwave pulses within the length of an input feeding pulse can be, in principle, obtained.

Complex investigations of the thermal stability as well as Mn-dopant distribution depending on chemical composition and processing condition have been performed in heavily doped SrTi1-xMnxO3 nanoparticles with x = 0.2 and 0.4. Prepared nanopowders reveal stable enough cubic perovskite structure even after treatment in oxidizing atmosphere up to 1000 °C. At the same time treatment in reducing atmosphere leads to decrease of the Mn solubility limit. Mn distribution evidences a weak tendency of Mn ions to migrate to surface. This migration increases in air and decreases at treatment in oxygen atmosphere.

The jet of reactive effluents produced by surface dielectric barrier discharge was used to deposit PEO-like plasma polymers from di(ethylene) glycol vinyl ether. The jet was confined within the hollow space of either circular cross-section with substrate placed perpendicular to the jet, or rectangular cross-section with the walls used as substrates. The best 67% retention of the ethers was obtained for the circular channel, whereas it was only 50% for the rectangular channel. In the latter case, deposition at longer distances was possible. In both cases, the deposition started with the formation of islands that grew, coalesced and eventually built up a continuous coating.

In the laser --- electron beam head-on interaction electron energy can decrease due to radiation reaction, i.e. emission of photons. For 10--100~fs laser pulses and for the laser field strength up to the pair photoproduction threshold, it is shown that one can calculate the resulting electron and photon spectra as if the electron beam travels through a constant magnetic field. The strength of this constant field and the interaction time are found as functions of the laser field amplitude and duration. Using of constant field approximation can make a theoretical analysis of stochasticity of the radiation reaction much simpler in comparison with the case of alternating laser field, also, it allows one to get electron and photon spectra much cheaper numerically than by particle-in-cell simulations., Comment: I I Artemenko et al 2019 Plasma Phys. Control. Fusion 61 074003

Different designs of multichannel resonant microwave pulse compression systems operating in $X$ - and $S$ -bands are described. The output pulsed microwave power of these systems is expected to be severalfold greater than that of compression systems with a single output channel. These compression systems can be used as compact sources of high-power nanosecond-duration microwave pulses, sources of synchronized sequences of microwave pulses, and sources for development of phased arrays of compressed microwave pulses. In particular, the authors describe the characteristics of a two-channel $S$ -band resonant microwave pulse compression system with nanosecond-duration output pulse and an output pulsed microwave power of 1 GW. The operation of a four-channel $X$ -band compression system with a possible eightfold output pulsed microwave power increase, relatively to the microwave power in the cavity, is also described. The design of an eight-channel system with a 16-fold output pulsed microwave power increase is reviewed. The parameters of an $X$ -band compression system with multichannel output unit formed as a set of interference microwave switches extracting the energy in synchronism are presented.

Due to an extraordinary combination of intrinsic properties of diamond nanoparticles (DNPs), there is an increased demand for their usage in various areas. While a broad range of surface termination is often done by wet-chemical, UV-irradiation or plasma treatments, DNPs hydrogenation is still an open issue. Thermal annealing or microwave plasma treatment, both known as high-temperature processes, do not offer satisfactory solutions for DNPs hydrogenation. Here, we report on a new approach for plasma-assisted DNPs hydrogenation at temperatures below 100 °C. As-received detonation DNPs with size about 5 nm were annealed (oxidized) in air at 450 °C for 30 min to reduce non-diamond carbon content. Then the annealed DNPs were plasma treated using atmospheric-pressure diffuse coplanar surface barrier discharge in pure hydrogen at powers densities of 1.8 and 3.1 W/cm2. While infrared spectra of annealed DNPs were dominated by oxygen containing functional groups, plasma-hydrogenated DNPs revealed increase of bands of C-H stretching vibrations in the region of 2800-3000 cm-1 with only 5 min of plasma treatment. Prolonged plasma treatments up to 60 min resulted in the increase of C-H stretching vibrations and a decrease of C-O-C groups in the spectral region of 1000–1300 cm-1.

We study theoretically helical edge and surface states of 2D and 3D topological insulators (TI) tunnel-coupled to metal leads and show that their transport properties are strongly affected by contacts as the latter play a role of a heat bath and induce damping and relaxation of electrons in the helical states of TI. A simple structure that produces a pure spin current in the external circuit is proposed. The current and the spin current delivered to the external circuit depend on the relation between characteristic lengths: decay length due to tunneling, contact length and, in case of 3D TI, mean free path and spin relaxation length caused by momentum scattering. If the decay length due to tunneling is the smallest one, then the electric and spin currents are of order of the conductance quantum in 2D TI, and of order of the conductance quantum multiplied by the ratio of the contact width to the Fermi wavelength in 3D TI. A role of electron–electron interaction is discussed in case of 2D TI, and it is shown that in contrast to the conventional Luttinger liquid picture the interaction can be treated perturbatively. The presence of interaction results in suppression of density of states at the Fermi level and hence in decrease of the electric and spin currents.

Nanocrystalline diamond (NCD) films may be used in biosensing after modification of their surfaces with active functional groups. Here, surface functionalization of O- and H-NCD films with amine groups was made by 2 plasma-based processes: a) RF plasma treatment in ammonia, b) the deposition of thin amine-containing plasma polymer via RF magnetron sputtering of nylon target in Ar/N2 mixture. Amination of the NCD films by plasma treatment in NH3 caused an attachment of 1% of primary amines but destroyed the surface conductivity of H-NCD films. The 5% concentration of NH2 was detected on the NCD covered with the plasma polymer. Moreover, the surface conductivity of H-NCD films reached 10−7 S.

A series of high quality FexGa1−xBO3 single crystals with 0 ≤ x ≤ 1 was prepared and studied by electron magnetic resonance in the temperature range from 4 to 290 K. At low x, only the electron paramagnetic resonance (EPR) of diluted Fe3+ ions is present. The EPR spectra for different orientations of the magnetizing field have been computer simulated. With a conventional spin Hamiltonian including the Zeeman and fine-structure terms, two different sets of best-fit parameters have been found. This ambiguity has been resolved on the basis of the general spin Hamiltonian with parameters determined from the crystallographic data using the Newman superposition model. A detailed fitting to the experimental EPR spectra assuming statistical distributions of Fe3+ ligand coordinates has revealed the existence of a certain degree of local disorder in FexGa1−xBO3 single crystals.

We study theoretically helical edge states of 2D and 3D topological insulators (TI) tunnel-coupled to metal leads and show that their transport properties are strongly affected by contacts as the latter play a role of a heat bath and induce damping and relaxation of electrons in the helical states of TI. A simple structure that produces a pure spin current in the external circuit is proposed. The current and spin current delivered to the external circuit depend on relation between characteristic lengths: damping length due to tunneling, contact length and, in case of 3D TI, mean free path and spin relaxation length caused by momentum scattering. If the damping length due to tunneling is the smallest one, then the electric and spin currents are proportional to the conductance quantum in 2D TI, and to the conductance quantum multiplied by the ratio of the contact width to the Fermi wavelength in 3D TI.

A simple and compact gas aggregation cluster and nanoparticle source based on a planar magnetron (Haberland type) without mass separation was characterized. Such source produces a beam of neutral, positively and negatively charged particles that are dragged by a buffer gas expanding from the aggregation chamber. Sizes, speeds and charges of nanoparticles have been determined using a combination of TEM micrographs, electrostatic deflection setup and numeric modeling. The strong dependence of the velocity of the nanoparticles on their size was confirmed both experimentally and by modeling.

We discuss optical absorption in topological insulators and study possible photoelectric effects theoretically. We found that absorption of circularly polarized electromagnetic waves in two-dimensional topological insulators results in electric current in the conducting 1D edge channels, the direction of the current being determined by the light polarization. We suggest two ways of inducing such a current: due to magnetic dipole electron transitions stimulated by irradiation of frequency below the bulk energy gap, and due to electric dipole transitions in the bulk at frequencies larger than the energy gap with subsequent capture of the photogenerated carriers on conducting edge states.

We have applied Hierarchical QSAR Technology (HiT QSAR) to the prediction of antiviral effects of paired combinations of picornavirus replication inhibitors against poliovirus 1 (Mahoney) in vitro. The inhibition from all binary combinations of eight antivirals were investigated. Simplex representation of molecular structure (SiRMS) was used for the generation of molecular descriptors of both pure compounds and all dual mixture combinations. Predictive QSAR models were obtained using the partial least squares (PLS) method. Predictive power of the developed models was validated using eightfold external cross-validation (CV, $$Q_{\text{ext}}^{ 2}$$ = 0.67–0.93). Adequate models ( $$Q_{\text{ext}}^{ 2}$$ = 0.53–0.97) were obtained in the same way for predicting measured inhibitory concentrations at other levels (i.e., IC30, IC40, IC60, IC70). The usage of predicted values of these concentrations in the framework of the feature net (FN) approach led to an insignificant increase in the quality of the obtained QSAR models ( $$Q_{\text{ext}}^{ 2}$$ = 0.71–0.94). Developed QSAR models were analyzed and interpreted so that structural fragments and components of the combination promoting the antiviral activity were determined (e.g., 2-(4-methoxyphenyl)-4,5-dihydrooxazole or the combination of N-hydroxybenzimidoyl and 3-methylisoxasole). Then the resulting consensus model was used to predict novel potent combinations of drugs. Combinations of enviroxime with pleconaril, WIN52084, and rupintrivir and the mixture of rupintrivir with disoxaril were predicted to cause the most inhibition of poliovirus 1 replication. HiT QSAR proved itself as an adequate tool for QSAR analysis of mixtures and, although the method described here is suitable only for binary mixtures, it can be easily extended for more complex combinations.

We study theoretically transport properties of one-dimensional system of interacting electrons pinned by an impurity. Long-range Coulomb interaction in such a system is known to induce a 4 k F electron density modulation characterized by extremely slow, slower than any power law, decay of the density correlations which can be described as a one-dimensional Wigner crystal. We study non-stationary regime of conduction corresponding to sliding of the 1D Wigner crystal depinned by the applied voltage. In this regime the dc current is accompanied by current oscillations with frequency f = I ¯ / e . We calculate I–V curves and ac current generated by sliding. Our approach is based on the ideas of Luttinger liquid. We study also the case of magnetic impurity and show that applied voltage induces not only the electrical current, but also the spin current as well, in other words, the current becomes spin polarized. We find that a spin bias applied to the system contributes to electric current both in case of magnetic and non-magnetic impurity, and this is related to violation of the spin–charge separation at the impurity site.

Nanocomposite metal plasma polymer films were prepared by deposition of C:H plasma polymer particles using a Haberland type cluster source and overcoating of these particles by titanium layer by means of planar magnetron. This study is focused mainly on characterization of surface roughness of such films and its influence on other properties, such as surface chemistry and wettability. Selected samples were also subjected to biotests, namely to evaluate adhesion of human osteoblast-like MG63 cells.

The spin transport as the current flows through an impurity in a one-dimensional conductor is analyzed. The interacting electrons are described in terms of the Luttinger liquid theory. Both the Coulomb and short-range interactions are considered; the latter appears when the gate screens the long-range part of the Coulomb potential. The cases of magnetic and nonmagnetic impurities are considered. It has been revealed that, for a magnetic impurity, the electric current flow induces the generation of the spin current, which has direct and alternating components. At low temperatures and voltages, the current can be completely spin-polarized. For a nonmagnetic impurity, the spin current generation is absent. The spin current flowing though the wire affects the current-voltage characteristic for both magnetic and nonmagnetic impurities. The results have been obtained for a rather strong electron-electron interaction.

This study concerns the detailed characterization of RF magnetron sputtering of Nylon in Ar, Ar/N 2 and N 2 /H 2 working gas mixtures; the main attention is paid to the evaluation of influence of operational parameters on the deposition rate, plasma composition as well as on the chemical composition of the deposited thin films without their exposure to open air. Operational conditions were found to have strong impact on the composition of gaseous species flux on the substrate, namely on the presence of CN containing molecules, and in the case of ions also on their energy. This subsequently influences both the deposition rate and the chemical composition of the films. Regarding the deposition rate, the presence of nitrogen in the working gas mixture was found to cause higher production of longer chain fragments that enhances the deposition rate of the plasma polymeric films. The films deposited in Ar/N 2 and N 2 /H 2 mixtures possess also high and comparable amount of nitrogen. Nevertheless, the way in which nitrogen is bonded in the films is different in these two mixtures: according to the XPS analysis in films deposited in N 2 /H 2 mixture higher portion of nitrogen is present in the form of amines while films deposited in Ar/N 2 mixture exhibit a higher fraction of nitriles and imines.

Plasma polymer nanostructures were prepared by cluster beam deposition. The nanocluster source assembled in our laboratory is implementing a 2 in. planar magnetron operated in radio-frequency mode and follows the Haberland concept. Clusters were deposited on glass or silicon substrates without mass separation in order to get high deposition rates. C:H plasma polymer clusters with a typical size of about 100 nm (measured by AFM) were prepared by RF discharge in argon/hexane atmosphere. The influence of deposition conditions was studied with respect to size distribution (AFM and SEM), chemical and physical properties (XPS and FTIR) of resultant clusters.

Nanocluster films composed of Ti and TiO x were prepared using a gas aggregation cluster source. The films were first characterized immediately after their preparation and afterwards were allowed to oxidize in air at room temperature for a given time to study their aging. Selected nanocluster films were annealed at 420 °C in air for 1 h. The prepared nanocluster films were studied by a variety of methods in order to fully characterize their properties. Transmission electron microscopy (TEM) was utilized to determine size of the clusters. Chemical composition of the films was determined by X-ray Photoelectron Spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Optical properties were studied using ultraviolet–visible spectroscopy (UV–vis). Special attention was paid to the description of oxidation of the titanium nanoclusters and other changes in the films connected with aging.

Differently deposited amino functionalized surfaces were compared regarding their physico-chemical surface properties in connection with cell biological response. The nitrogen containing coatings were prepared on polished titanium alloy substrates by microwave or radio frequency discharges using allylamine and ethylenediamine as precursors, respectively, or by means of radio frequency magnetron sputtering of nylon 6.6 under N 2 /H 2 1:1 gas mixture. The chemical composition of the deposited films was determined by FT-IR and XPS analyses. Closed pinhole-free polymer films resistant to hydrolysis and delamination were detected in most cases. Advantageous medium hydrophilicities exist. The density of primary amino groups NH 2 /C differs on plasma polymerized allylamine (2.5%), and plasma polymerized ethylenediamine (3.7%) from the value on plasma sputtered nylon films in N 2 /H 2 1:1 atmosphere (7.2%), determined after preparation. The positively charged surfaces improve adhesion and spreading of MG-63 osteoblastic cells as initial cellular effect. Furthermore, it could be demonstrated that a direct correlation does not exist between the densities of primary amino groups and an enhanced cell growth. In fact, not only the primary amino groups but also other nitrogen-functional groups as e.g. acid amides or imides play a role for initial cell functions. All examined plasma polymer coatings enable the cells to literally melt into the structure of the titanium alloy substrate. The edges of the cells can hardly be distinguished from the surface.

Amino-rich polymeric coatings are widely used in biomedical applications, since they promote adsorption of diverse biomolecules or facilitate cell growth. As a consequence, there is a growing interest in fabrication of such coatings that is focused predominantly on the optimization of the deposition process in terms of high density of primary amino groups. In addition, the nature of biomedical applications requires also sufficient stability of the films in aqueous environments. This aspect is investigated in this contribution. In particular, the effect of water and phosphate buffer saline on the coatings prepared by RF magnetron sputtering of Nylon 6,6 in Ar/N 2 and N 2 /H 2 gas mixtures is evaluated. The samples exposed to liquids are characterized by various diagnostic methods and their properties are compared with samples stored on open air. It is found that the solubility of the coatings is strongly dependent on the working gas mixture: while the films prepared in Ar/N 2 mixtures are relatively stable in an aqueous environment, much faster dissolving and roughening of the films deposited using N 2 /H 2 gas mixtures was observed, which limits their applicability in the biomedical field. Moreover, it was found that chemical changes of the coatings are not significantly different for samples immersed into water or stored on open air.

A new method of deposition of nanocomposite gold/poly(ethylene oxide)-like thin films was investigated where gold was sputtered from an r. f. magnetron and poly(ethylene oxide)-like plasma polymer was simultaneously deposited via vacuum evaporation of conventional poly(ethylene oxide). Such method allows formation of the plasma polymer matrix with composition very close to that of precursor, a feature difficult to obtain in plasma polymerization processes. The films with different content of gold were prepared by varying the evaporation rate of poly(ethylene oxide) at constant power of the magnetron discharge. Chemical composition and cross-linking density of polymeric phase as well as the size distribution of gold nanoparticles were shown to be strongly dependent on the discharge power conditions. Stability of resultant nanocomposites in water was also studied. Such films are perspective for use in biomedical applications.

A new regime of electron transport through an impurity in 1D conductors, which resembles the Josephson effect in its manifestations, is predicted. Passage of current through the impurity under voltages above the threshold value is accompanied with generation of ac current oscillations. The temperature below which the effect can be observed, the threshold voltage, and the frequency range are determined by the impurity potential and the strength of electron-electron interaction. The generation line width and the current-voltage characteristics are determined.

The low-temperature heat capacity of a quasi-one-dimensional conductor in the Luttinger liquid state is studied for conductors with a charge density wave and without it. It is shown that pinning of the Luttinger liquid leads to localization of spins and a strong effect of the magnetic field on the thermodynamics of samples resembling the effect observed in recent experiments. We believe that this indicates the possibility of the formation of a Luttinger liquid in quasi-one-dimensional crystals.

studied the effect ofpressure of argon as working gas at a constant distance of5cm between PTFE target and a substrate. It was shownthat both the chemistry, and the roughness of the surfacechanged with the Ar pressure during sputtering. Theauthorsconsideredthesurfaceroughnesstobeimportantfor the targeted super-hydrophobic effect. However, theroughness did not increase gradually with the pressure,but increased by a sudden jump for the highest pressure70Pa used. This result was interpreted as indicatingthat the plasma polymer clusters (nano and microparticles)formedintheplasmavolumewereburiedinto the plasma polymer film growing on the substrate.This happened under particular deposition conditions(flow of argon, RF power, target-substrate distance) atAr pressure of about 70Pa and higher. Based onscanningelectron microscopy (SEM) micrographs, this seemed toconfirmthehypothesisthatfluorocarbonplasmapolymerparticlesoriginatingintheplasmavolume(dustyplasma)were eventually embedded into the film growing onthe substrate.On the other hand, several research groups claimed thatclusters (actually PTFE crystals) grown from CF

We study theoretically electronic transport through a contact of a quantum wire with 2D or 3D leads and find that if the contact is not smooth and adiabatic then the conduction is strongly suppressed below a threshold voltage $V_T$, while above $V_T$ the dc current $\bar I$ is accompanied by coherent oscillations of frequency $f=\bar I / e$. The effect is related to interelectronic repulsion and interaction of dc current with the Friedel oscillations near a sharp contact. In short conducting channels of length $L < L_0 \simeq \hbar v_F/eV_T$ and at high temperatures $T > T_0 \simeq eV_T/k_B$ the effect is destroyed by fluctuations., 10 pages, to be published in JETP Letters, vol. 91