Dimensional properties of graphs and digital spaces

Many applications of digital image processing now deal with three- and higher-dimensional images. One way to represent n-dimensional digital images is to use the specialization graphs of subspaces of the Alexandroff topological space ⁿ (where denotes the integers with the Khalimsky line topology). In this paper the dimension of any such graph is defined in three ways, and the equivalence of the three definitions is established. Two of the definitions have a geometric basis and are closely related to the topological definition of inductive dimension; the third extends the Alexandroff dimension to graphs. Diagrams are given of graphs that are dimensionally correct discrete models of Euclidean spaces, n-dimensional spheres, a projective plane and a torus. New characterizations of n-dimensional (digital) surfaces are presented. Finally, the local structure of the space ⁿ is analyzed, and it is shown that ⁿ is an n-dimensional surface for all n1.     

ZnO ultra-fine powders and films: hydrothermal synthesis,luminescence and UV lasing at room temperature

Zinc oxide ultra-fine crystalline powders and polycrystalline films of high optical quality were synthesized under soft hydrothermal conditions. The phase composition, crystal morphology, and luminescent properties of submicron ZnO powders and films were studied depending on synthesis conditions (system composition, precursor kind, solvent type and concentration, temperature). For the systems containing metallic zinc, the ZnO growth mechanism was suggested. The most intensive UV luminescence and the highest values of I_UV/I_VIS were observed for polycrystalline films grown on Zn substrates. Low-threshold UV lasing at room temperature was found for ZnO-films, grown in hydrothermal systems with hydroxide or halide solutions as solvents, E _th = 1–5 MW/cm². The lowest threshold was observed on the ZnO films grown using LiOH as a solvent and zinc nitrate as ZnO-precursor. Clear mode structures with line-width 0.3 nm are characteristic of the lasing spectra.     

What does integrability of finite-gap or soliton potentials mean?

In the example of the Schr?dinger/KdV equation, we treat the theory as equivalence of two concepts of Liouvillian integrability: quadrature integrability of linear differential equations with a parameter (spectral problem) and Liouville's integrability of finite-dimensional Hamiltonian systems (stationary KdV equations). Three key objects in this field-new explicit Psi-function, trace formula and the Jacobi problem-provide a complete solution. The Theta-function language is derivable from these objects and used for ultimate representation of a solution to the inversion problem. Relations with non-integrable equations are also discussed.     

CdTe nanoparticles display tropism to core histones and histone-rich cell organelles

The disclosure of the mechanisms of nanoparticle interaction with specific intracellular targets represents one of the key tasks in nanobiology. Unmodified luminescent semiconductor nanoparticles, or quantum dots (QDs), are capable of a strikingly rapid accumulation in the nuclei and nucleoli of living human cells, driven by processes of yet unknown nature. Here, it is hypothesized that such a strong tropism of QDs could be mediated by charge-related properties of the macromolecules presented in the nuclear compartments. As the complex microenvironment encountered by the QDs in the nuclei and nucleoli of live cells is primarily presented by proteins and other biopolymers, such as DNA and RNA, the model of human phagocytic cell line THP1, nuclear lysates, purified protein, and nucleic acid solutions is utilized to investigate the interactions of the QDs with these most abundant classes of intranuclear macromolecules. Using a combination of advanced technological approaches, including live cell confocal microscopy, fluorescent lifetime imaging (FLIM), spectroscopic methods, and zeta potential measurements, it is demonstrated that unmodified CdTe QDs preferentially bind to the positively charged core histone proteins as opposed to the DNA or RNA, resulting in a dramatic shift off the absorption band, and a red shift and decrease in the pholuminescence (PL) intensity of the QDs. FLIM imaging of the QDs demonstrates an increased formation of QD/protein aggregates in the presence of core histones, with a resulting significant reduction in the PL lifetime. FLIM technology for the first time reveals that the localization of negatively charged QDs to their ultimate nuclear and nucleolar destinations dramatically affects the QDs' photoluminescence lifetimes, and offers thereby a sensitive readout for physical interactions between QDs and their intracellular macromolecular targets. These findings strongly suggest that charge-mediated QD/histone interactions could provide the basis for QD nuclear localization downstream of intracellular transport mechanisms.     

Structure and Electrochemical Activity of C60 Fullerite Films

Results are presented from structural and electrochemical researches on C₆₀ films. The fullerite films were made by thermal vacuum evaporation and deposition on NaCl crystals. The substrate temperatures were 293-473 K. The examinations were made in a transmission electron microscope at 100 kV and by x-ray diffraction. Dark-field images were obtained from the individual fullerite particles and particularly from grains in continuous thin films, which showed stacking faults or twin boundaries. The numbers of these defects increase with the substrate temperature. The x-ray diffraction patterns of the fullerite films show extremely diffuse reflections together with a weak reflection around the FCC (111), which may be assigned to a hexagonal close packed HCP modification of fullerite. Rietveld's method was used in processing the x-ray patterns. The best fit between the experimental and theoretical diffraction lines was obtained with the following structure parameters: ratio of FCC phase (a = 1.4117 nm) and HCP phase (a = 0.9756 nm and c = 1.7084 nm) was 46/54 mass%. The electrochemical data indicate that a palladium-activated fullerite film shows prominent hysteresis, which confirms that certain hydride phases are formed at the surface of the C₆₀ film.

     

Experimental Study and Numerical Visualization of Physical Fields of Electromagnetic Pumps Constructed on Permanent Magnets

Pumps with magnet systems constructed on permanent magnets and performed in two manners like two-disk type and the cylindrical rotor type are discussed.First,by way of example we consider the experimental study of disk pump with straight channel;second,we analyse the results of numerical simulation of cylindrical pump in two cases,namely,of straight and U-bend forms of pump channels.At a high speed of pump rotation when induced magnetic field becomes essential in as against the applied field,i.e.when the skin-effect takes place,the pump characteristics are analyzed.Visualization of physical fields of the pumps is reported.     

Synthesis,crystal structure and magnetic properties of the new ternary indides REPd2In4 (RE = La,Ce, Pr,Nd)

The rare-earth-palladium-indides REPd₂In₄ (RE = La, Ce, Pr, Nd) were prepared by arc-melting of the elements and subsequent annealing at 750 °C. The compounds crystallize in a new structure type, space group Pmc2₁, Z = 10, Pearson code oP70. The structures can be described as built of Pd-centered trigonal prisms condensed via common edges. A structural comparison between the new structures and the related isostoichiometric compounds is discussed. The magnetic and electrical transport behavior of the REPd₂In₄ phases was studied from room temperature down to 1.7 and 4.2 K, respectively. While LaPd₂In₄ is a weak diamagnet, CePd₂In₄, PrPd₂In₄, and NdPd₂In₄ exhibit Curie–Weiss paramagnetism and long-range magnetic ordering below 2.4, 2.1 and 5.0 K, respectively. All the compounds studied exhibit metallic character of their electrical conductivity.     

Influence of Particle Size and Mixing Technology on Combustion of HMX/Al Compositions

In this work, two widely used components of high‐energy condensed systems – HMX and aluminium – were studied. Morphology, thermal behaviour, chemical purity and combustion parameters of HMX as a monopropellant and Al/HMX as a binary system were investigated using particles of different sizes. It was shown that in spite of the differences in composition and particle size, combustion velocities are almost identical for micrometer‐sized HMX (m‐HMX) and ultrafine HMX (u‐HMX) monopropellants under pressure from 2 to 10 MPa. Replacement of the micrometer‐sized aluminium with ultrafine one in the system with m‐HMX leads to a burning rate increase by a factor of 2.5 and the combustion completeness raise by a factor of 4. Two mixing techniques to prepare binary Al/HMX compositions were applied: conventional and ‘wet’ technique with ultrasonic processing in liquid. Applying wet mixing results in a burning rate increase of 18% compared to the conventional mixing for systems with ultrafine metal. The influence of the component's particle size and the composition microstructure on the burning rate of energetic systems is discussed and analysed.     

Comparative Study of Microwave Sintering of Zinc Oxide at 2.45, 30, and 83 GHz

Temperature gradients that develop in ceramic materials during microwave heating are known to be strongly dependent on the applied microwave frequency. To gain a better understanding of this dependence, identical samples of ZnO powder compacts were microwave heated at three distinct widely separated frequencies of 2.45, 30, and 83 GHz and the core and surface temperatures were simultaneously monitored. At 2.45 GHz, the approximately uniform "volumetric" heating tends to raise the temperature of the sample as a whole, but the interior becomes hotter than the exterior because of heat loss from the surface. At 30 and 83 GHz, this interior to exterior temperature difference was found to be reversed, especially for high heating rates. This reversal resulted from increased energy deposition close to the sample's surface associated with reduced skin depth. A model for solving Maxwell's equations was incorporated into a newly developed two-dimensional (2-D) heat transport simulation code. The numerical simulations are in agreement with the experimental results. Simultaneous application of two or more widely separated frequencies is expected to allow electronic tailoring of the temperature profile during sintering.