A low transmission loss THz polarization splitter based on dual-core optical fiber

We propose a design of a low loss terahertz polarization splitter based on a dual-core terahertz fiber with crossed dielectric strips in the fiber cross section. Low transmission loss is realized by extending the mode field to the air holes adjacent to the solid material. An 11.4-cm-long terahertz polarization splitter is obtained with the extinction ratio better than −15 dB and a bandwidth of 16 μm.     

Light figure spectroscopy of optically active anisotropic materials

Low order interference curves in optic-axis light figures of the optically active AgGaS₂ and TeO₂ are investigated in the visible spectral range at room temperature. Light figure patterns of AgGaS₂ are found not to be affected by optical activity within the incidence angles of 10° for which, according to our symmetry considerations, the normal component of gyration tensor is small and evolution of light figures with wavelength is overwhelmingly determined by optical anisotropy. The absolute value of this anisotropy is falling down to null when passing through the isotropic point, with the result of a remarkable change of the parameters of light figure patterns. Unlike the case of AgGaS₂ and consistently with our symmetry considerations, light figures of TeO₂ are influenced by optical activity especially strongly in low orders of interference. The obtained results are compared with similar results for optically inactive CaCO₃ and discussed in the frameworks of our recent analyses.     

γ-Rays-induced synthesis of hydrogels of vinyl ethers with stimuli-sensitive behavior

γ-Radiation method was applied to synthesize novel water-soluble and water-swelling polymers. Vinyl ether of ethylene glycol (VEEG), vinyl butyl (VBE) and vinyl isobutyl (VIBE) ethers were used as monomers. The synthesis of VEEG–VBE and VEEG–VIBE copolymers was carried out in a wide range of feed composition and absorbed dose. It was found that the hydrophobic–hydrophilic balance of the copolymers could be delicately varied by the copolymer composition as well as by the chemical structure of the alkyl substitute in the hydrophobic moiety. The copolymers exhibit thermo-sensitive behavior in water solutions. The value of transition temperature is considerably decreased at a higher concentration of the hydrophobic component in the copolymer composition.     

Study of a shock wave structure in gas mixtures on the basis of the Boltzmann equation

The structure of a shock wave for a binary gas mixture is studied on the basis of numerical solution of the complete kinetic Boltzmann equation for the model of hard sphere molecules. For the evaluation of the collision integral we apply a generalization of the conservative discrete ordinate method (the kernel method for a single gas was developed by Tcheremissine) for binary gas mixtures and for the case of cylindrical symmetry. The transition from up-stream to downstream uniform state is presented by macroscopic values and by distribution functions.     

Hydrothermal preparation of CuGaS2 crystallites with different morphologies

The CuGaS₂ crystallites with different morphologies were prepared at 160 °C through hydrothermal process by using CuCl, GaCl₃ solution, and thiourea as source materials. The samples were characterized by means of X-ray powder diffraction, element analysis, transmission electron microscopy, and photoluminescence (PL). In present route, as-prepared CuGaS₂ crystallites displayed spherical and whisker-like nanoparticles and snowflake-like micrometer particles. Room temperature PL spectrum of the snowflake-like crystallites exhibits a weak emission band at 540 nm and a broad strong emission band at 735 nm. The role that the reaction media played in the morphologies of the CuGaS₂ crystallites was investigated, and a possible reaction mechanism was proposed.     

Electronic coupling in covalently-linked MM quadruple bonds: M2δ to ligand π conjugation

Dimetal tetracarboxylates, M₂(O₂CR)₄, where R=alkyl and M=Mo or W, can be linked in a perpendicular or parallel manner through the agency of a variety of ligands to give ‘dimers of dimers’ [M₂(O₂CR)₃]₂(bridge), or extended chains. A ring of formula [M₂(O₂CR)₂(bridge)]₄ is an alternative to a chain [M₂(O₂CR)₃]₂(bridge)₂]_∞ and ‘molecular squares’ of formula [(RNCHNR)₂M₂(bridge)]₄ have recently been reported by Cotton and Murillo, where M=Mo and Rh and R=p-MeOC₆H₄. The electronic coupling between the M₂ units manifests itself in electrochemical data and in the electronic spectra of the compounds. The electronic coupling occurs by M₂δ to ligand π-conjugation and specific examples are illustrated for the bridging ligands oxalate, perfluoroteraphthalate, 1,8-anthracenedicarboxylate and 2,7-dioxynaphthyridine. Correlations of a variety of spectroscopic data and computations employing density functional theory are presented.     

High Solubility of Hetero-Valence Ion （Cu^2＋） for Reducing Phase Transition and Thermal Expansion of ZrV1.6P0.4O7

Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion （Cu^2＋） on the basis of an equal-valence substitution of P^5＋ for V^5＋. The temperature-dependent Raman spectra show that Zr0.9CU0.1V1.6P0.4O6.9 maintains a normal parent cubic structure till 173 K and transforms to a 3 × 3 × 3 cubic superstructure below 173K. Temperature dependent x-ray diffraction patterns of Zr0.9CU0.1V1.6P0.4O6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu^2＋ relates to an equal-valence substitution of smaller pH for P^5＋, which extends the bond angle of V（P）-O-V in ZrV1.6P0.4O7 close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.     

Corona discharge in electrospraying

The paper presents investigations of current–voltage and light emission characteristics of electrospraying of various liquids in atmospheric air. The spectroscopic measurements have shown that the onset of corona discharge coincides with the onset of electrospraying, with the voltage increasing. The emission intensity in selected spectral lines during electrospraying depends on spraying mode, discharge power and a kind of liquid. In the specific experimental conditions in air, mainly the N₂ second positive system, which is visible as violet faint light, has been recorded. The emission intensity of other gaseous species, which could be product of electrosprayed molecules decomposition or dissociation, was at very low level for the voltages applied, i.e., for glow or onset streamer discharges. From the measured light emission spectra of discharges from capillary nozzle and liquid jet, the dependence of the amplitude of selected spectral lines on capillary-nozzle voltage has been determined and it was found that this relation can be approximated by a third-degree polynomial function. This approximation has been supported by theoretical considerations. The presented results support the hypothesis that faint electrical discharges (glow, onset streamers) usually occur during and are inherent to electrospraying.     

Deep sub micrometer imaging of defects in copper pillars by X-ray tomography in a SEM

The potential of X-ray nanotomography hosted in a SEM in presented in this paper. In order to improve the detail detectability of this system, which is directly related to the X-ray source size, thin metal layers have been studied and installed in the equipment. A 3D resolution pattern has been created in order to determine the smallest detectable features by this setup. This sample is a 25 μm diameter copper pillar in which size-controlled holes have been milled using a plasma-focused ion beam. This pattern has then been scanned and the resulting 3D reconstruction demonstrates that the instrument is able to detect 500 nm diameter voids in a copper interconnection, as used in 3D integration.     

A comparison of two methods for estimating DCE-MRI parameters via individual and cohort based AIFs in prostate cancer: A step towards practical implementation

Multi-parametric Magnetic Resonance Imaging, and specifically Dynamic Contrast Enhanced (DCE) MRI, play increasingly important roles in detection and staging of prostate cancer (PCa). One of the actively investigated approaches to DCE MRI analysis involves pharmacokinetic (PK) modeling to extract quantitative parameters that may be related to microvascular properties of the tissue. It is well-known that the prescribed arterial blood plasma concentration (or Arterial Input Function, AIF) input can have significant effects on the parameters estimated by PK modeling. The purpose of our study was to investigate such effects in DCE MRI data acquired in a typical clinical PCa setting. First, we investigated how the choice of a semi-automated or fully automated image-based individualized AIF (iAIF) estimation method affects the PK parameter values; and second, we examined the use of method-specific averaged AIF (cohort-based, or cAIF) as a means to attenuate the differences between the two AIF estimation methods.