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The few studies of the paleogeography of the Ukrainian Carpathians include the chronology of relief formation (Demeduke 1971), the development of vegetation (Malinovsky 1980) and the formation of the landscape (Miller 1961). Previous paleographic inferences were based on comparisons with natural alpine cycles (Koziy 1950, 1963; Tsys 1955, 1968; Tretyak and Kuleshko 1982). Neighboring areas to the west and south of the Ukrainian Carpathians are also insufficiently studied (Serebrany 1978).
In this paper we report the first results of the 327 MHz VLBI survey which has been carried out in the last two years to select potential candidate sources for the future SVLBI missions and to search for directions of small scattering-“holes” in the interstellar scattering medium. During the three VLBI sessions conducted so far, we observed about 80 sources. Preliminary data analyzed from the first part of the survey shows that at least 17 out of 50 sources have compact components with a size smaller than 30 mas.
The problem of binary asteroids orbit determination is of particular interest, given knowledge of the orbit is the best way to derive the mass of the system. Orbit determination from observed points is a classic problem of celestial mechanics. However, in the case of binary asteroids, particularly with a small number of observations, the solution is not evident to derive. In the case of resolved binaries the problem consists in the determination of the relative orbit from observed relative positions of a secondary asteroid with respect to the primary. In this work, the problem is investigated as a statistical inverse problem. Within this context, we propose a method based on Bayesian modelling together with a global optimisation procedure that is based on the simulated annealing algorithm.
We report static and time-resolved terahertz (THz) conductivity measurements of a highperformance thermoelectric material containing tellurium nanowires in a PEDOT:PSS matrix. Composites were made with and without sulfur passivation of the nanowires surfaces. The material with sulfur linkers (TeNW/PD-S) is less conductive but has a longer carrier lifetime than the formulation without (TeNW/PD). We find real conductivities at f = 1THz of σTeNW/PD = 160 S/cm and σTeNW/PD-S = 5.1 S/cm. These values are much larger than the corresponding DC conductivities, suggesting DC conductivity is limited by structural defects. The free-carrier lifetime in the nanowires is controlled by recombination and trapping at the nanowire surfaces. We find surface recombination velocities in bare tellurium nanowires (22m/s) and TeNW/PD-S (40m/s) that are comparable to evaporated tellurium thin films. The surface recombination velocity in TeNW/PD (509m/s) is much larger, indicating a higher interface trap density.
Thermoelectric (TE) materials have been studied during past decades since they can generate electricity directly from waste heat. Antimony chalcogenides (Sb2M3, M = S, Se, Te) are well known as one of the promising candidates among the inorganic TE materials. We report on the synthesis of Sb2Te3 nanoparticle via thermolysis method. A systematic study was done to investigate the effect of reaction time and ratio between the precursors as well as the method of cooling on the morphology and composition of obtained nanoparticles. The ratio between precursors was varied to study the effect on the morphology. Furthermore, the high purity phase Sb2Te3 was obtained by a rapid cooling process.
The maldigestion and malabsorption of fat in infants fed milk formula results due to the minimal production of pancreatic lipase. Thus, to investigate lipid digestion and absorption and mimic the situation in newborns, a young porcine exocrine pancreatic insufficient (EPI) model was adapted and validated in the present study. A total of thirteen EPI pigs, aged 8 weeks old, were randomised into three groups and fed either a milk-based formula or a milk-based formula supplemented with either bacterial or fungal lipase. Digestion and absorption of fat was directly correlated with the addition of lipases as demonstrated by a 30 % increase in the coefficient of fat absorption. In comparison to the control group, a 40 and 25 % reduction in total fat content and 26 and 45 % reduction in n-3 and n-6 fatty acid (FA) content in the stool was observed for lipases 1 and 2, respectively. Improved fat absorption was reflected in the blood levels of lipid parameters. During the experiment, only a very slight gain in body weight was observed in EPI piglets, which can be explained by the absence of pancreatic protease and amylase in the gastrointestinal tract. This is similar to newborn babies that have reduced physiological function of exocrine pancreas. In conclusion, we postulate that the EPI pig model fed with infant formula mimics the growth and lipid digestion and absorption in human neonates and can be used to elucidate further importance of fat and FA in the development and growth of newborns, as well as for testing novel formula compositions.
The paper is devoted to the method of computer simulation of protein interactions taking
part in photosynthetic electron transport reactions. Using this method we have studied
kinetic characteristics of protein-protein complex formation for four pairs of proteins
involved in photosynthesis at a variety of ionic strength values. Computer simulations
describe non-monotonic dependences of complex formation rates on the ionic strength as the
result of long-range electrostatic interactions. Calculations confirm that the decrease in
the association second order rate constant at low values of the ionic strength is caused
by the protein pairs spending more time in “wrong” orientations which do not satisfy the
docking conditions and so do not form the final complex capable of the electron
SiC thin films less than 1 μm thick are grown by thermal decomposition of CH3SiC13 in a hydrogen atmosphere in an open CVD system. The interface stress is shown to be depend on the growth conditions. The optimal conditions for the preparation of uniform SiC films have been determined. Thermal annealing of the films has also been studied, and the conditions that provide for relaxation of the interface stresses are determined.
III-Nitrides (GaN, AlN and other compounds) have attracted vast interest due to their unique properties and potential applications in optoelectronic devices operating in the blue and UV spectral regions and for the construction of electronic devices capable of operating under high power and high temperature conditions.
Nanocrystalline AlN powder were obtained by AMMONO method, in which nitridization of Al metal occurs in highly chemical active supercritical ammonia using both NH4Cl as mineralizer. The experiments were performed in the temperature range of 350-550 °C and pressure of 80-120 MPa in stainless steel autoclaves for up to 5 days. Nanocrystalline AlN were spontaneously nucleated on the lower walls of the autoclaves. The obtained AlN powder was characterized by X-ray diffraction. Nanocrystalline AlN powders with average crystallite size 20-30 nm were produced in the temperature range of 450-550 °C.
Steel surface saturation by nitrogen (nitriding) results in a high increase in surface hardness and a decrease in friction rate. This treatment is widely used to increase the lifetime of cutting tools and wearing parts in machines.
A new approach of steel surface treatment by using the vacuum arc discharge in nitrogen is presented. The apparatus uses two arc vacuum discharges. The first discharge is a metal vapor discharge and serves for both the cleaning- heating of the treated surface and for the initiation of the second vacuum arc discharge in nitrogen. The vacuum arc source of metallic plasma allows us the simultaneous implantation of desirable metals and surface saturation by nitrogen. The developed arc vacuum discharge method shortens the nitriding time 2 to 3 times in comparison to the glow discharge technology. The suggested method of the surface treatment is suitable for a wide variety of steels. The hardness measurement results of nitriding and combined chromium with nitriding treatments of several steel samples are presented and discussed.
In the present work, we report a detailed study based on transmission electron microscopy of the microstructure and composition of the Fe2O3: SnO2 nanometrical binary system obtained by sol-gel. We studied a set of samples based in a pure Fe2O3 material where we added SnO 2 from 0 to 50% Sn-Fe nominal content. The structure of our composites will change from pure a-Fe2O3 to the well-known cassiterite SnO 2 structure for high Sn content. Distortions on the structural parameters will be attributed to the presence Sn4+ ions on the α-Fe2O3 structure and Fe3+ ions on the SnO2 cassiterite structure.
The synthesis and self-assembly of a water-soluble, tricyclic, self-complementary heterocycle that features the hydrogen bond donor-acceptor arrays of both guanine (G) and cytosine (C) juxtaposed between a pyridine ring is presented. In solution, this tricycle, which has been termed xK1, self-assembles into Rosette Nanotubes (RNTs) that have an inner diameter of 1.4 nm. Unlike the RNTs formed from the bicyclic congener K1, we demonstrate that xK1 with its extended ð system, forms a J-type RNT assembly determined through UV-Vis, CD and fluorescence spectroscopy experiments. This observation brings the possibility of developing electrically conducting RNTs for applications in the areas of photovoltaics and molecular wires.
Photonic crystals currently hold exciting potential in waveguiding applications with the ability to greatly reduce waveguide bend radii, allowing for the realization of photonic networks with increased complexity and device density. Square spiral photonic crystals are comprised of periodic arrays of slanted cylindrical columns with periodic abrupt 90° changes in the column growth direction. The abrupt changes produce elbows which correspond to points in the three-dimensional diamond lattice, which are commonly referred to as diamond:n photonic crystal structures based on the nth nearest neighbor lattice point between column arms. The diamond:n structures are characterized by four parameters: column separation, spiral pitch, column diameter, and column growth angle. These structures have been shown theoretically to have a three-dimensional relative bandgap of approximately 15% for a direct silicon diamond:1 structure and approximately 24% for an inverse silicon diamond:5 structure with circular column cross sections. Silicon square spiral photonic crystals can be grown by a single-step thin film deposition process known as glancing angle deposition (GLAD), which utilizes rotation of lithographically patterned substrates and advanced control algorithms. While using GLAD to grow square spiral photonic crystals in a single-step process is desirable, it does have inherent limitations. Physical vapor deposited films deposited at oblique incidence angles form columns with angle ≤ 60° relative to the substrate normal. This deviates from the optimal diamond:1 and diamond:5 structures which require film growth angles of approximately 64° and 74°, respectively. Here we present SEM images of periodic silicon square spiral films grown with a vapor source incidence angle of 85° that indicate an average column tilt angle of 57˚ for films grown with the basic GLAD process and an average column tilt angle between 61˚ and 65˚ using an ion-assisted GLAD process. Photonic simulations indicating that square spiral films with complete three-dimensional photonic bandgaps are only achievable via ion-assisted GLAD are also presented.
A newly designed module was synthesized and found to self-assemble into rosette nanotubes (RN) in both water and methanol. Characterization using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) established the formation of analogous RNs in both solvents. However, the chiroptical outcome of the assemblies, observed by circular dichrosim (CD) spectroscopy, was found to be mirror image based solely on the solvent used. Preliminary molecular modeling studies indicated the formation of M and P helical rosette nanotubes, in agreement with the experimental observations. This work represents the first example of solvent-controlled helicity in a self-assembling supramolecular system.
In an effort to increase the internal and external diameter of the RNT's, tricyclic GΛC base derivatives (XGΛC) have been synthesized and characterized. Hierchichal self-assembly results in formation of RNT's with an increased diameter, as evidenced by AFM and TEM measurements. Progress on the derivitization and characterization of the XGΛC RNT's will be presented.
We characterized the optical nonlinearities of CdSe nanocrystals surrounded by rod-like CdS shells with ultrafast measurements of time-resolved photoluminescence. We measured the exciton-exciton interaction to be, depending on structure details, attractive or repulsive, by as much as 29 meV, due to the unique band alignment in the CdSe/CdS. This feature makes CdSe/CdS dot/rods promising gain media for solution-processable lasers, as it appears combined with 80% photoluminescence quantum yield, narrow size and shape distributions and the antenna effect of the CdS rod shell enhancing optical absorption by more than a factor 50 with respect to bare dots.
Carbon nanomaterials especially ultrananocrystalline diamond and nanocrystalline diamond films have attracted more and more interest due to their unique electrical, optical and mechanical properties, which make them widely used for different applications (e.g. MEMS devices, lateral field emission diodes, biosensors and thermoelectrics). Nanocrystalline diamond can also offer novel advantages for drug delivery development. Recent studies have begun to use nanocrystalline diamond for in-vivo molecular imaging and bio-labeling. To enable grafting of complex bio-molecules (e.g. DNA) the surface of ND requires specific fictionalization (e.g. H, OH, COOH & NH2). Due to the surface dipoles of functionalised nanodiamond band bending at the surface can be easily induced and from the measured band bending we can deduce the type of the fictionalization on the surface. The surface potential of H-terminated and OH terminated nanodiamond layers was investigated by Kelvin probe microscope. From the change of the surface potential value (as the departure of the material surface from the state of electrical neutrality is reflected in the energy band bending) the work function of the H-terminated nanodiamond layer was established to be lower than OH-terminated nanodiamond layer. The surface potential difference can be explained by the surface dipole induced by the electro-negativity difference between the termination atoms.