Search

Recently, a novel data acquisition method has been proposed and experimentally implemented for differential phase-contrast computed tomography (DPC-CT), in which a conventional X-ray tube and a Talbot-Lau-type interferometer were utilized in data acquisition. The divergent nature of the data acquisition system requires a divergent-beam image reconstruction algorithm for DPC-CT. This paper focuses on addressing this image reconstruction issue. We have developed a filtered backprojection algorithm to directly reconstruct theDPC-CT images fromacquired fan-beam data. The developed algorithm allows one to directly reconstruct the decrement of the real part of the refractive index from the measured data. In order to accurately reconstruct an image, the data need to be acquired over an angular range of at least 180°? plus the fan angle. As opposed to the parallel beam data acquisition and reconstruction methods, a 180°?-rotation angle for the data acquisition system does not provide sufficient data for an accurate reconstruction of the entire field of view. Numerical simulations have been conducted to validate the image reconstruction algorithm. [ABSTRACT FROM AUTHOR]

Energy dispersive X-ray fluorescence (EDXRF) is a well-established and powerful tool for nondestructive elemental analysis of virtually any material. It is widely used for environmental, industrial, pharmaceutical, forensic, and scientific research applications to measure the concentration of elemental constituents or contaminants. The fluorescing atoms can be excited by energetic electrons, ions, or photons. A particular EDXRFmethod, monochromaticmicrofocus X-ray fluorescence (MμEDXRF), has proven to be remarkably powerful in measurement of trace element concentrations and distributions in a large variety of important medical, environmental, and industrial applications. When used with state-of-the-art doubly curved crystal (DCC) X-ray optics, this technique enables high-sensitivity, compact, low-power, safe, reliable, and rugged analyzers for insitu, online measurements in industrial process, clinical, and field settings. This new optic-enabled MμEDXRF technique, called high definition X-ray fluorescence (HD XRF), is described in this paper. [ABSTRACT FROM AUTHOR]

The transmission speed of optical network strongly depends on the impact of higher order dispersion. In presence of coherent crosstalk, which cannot be otherwise controlled by optical filtering, the impact of higher order dispersions becomes more pronounced. In this paper, the general expressions, that describe pulse deformation due to second- and fourth-order dispersions in a single-mode fiber, are given. The responses for such even-order dispersions, in presence of coherent crosstalk, are characterized by waveforms with long trailing edges. The transmission quality of optical pulses, due to both individual and combined influence of second- and fourth-order dispersions, is studied in this paper. Finally, the pulse shape and eye diagrams are obtained. [ABSTRACT FROM AUTHOR]

Energy dispersive X-ray fluorescence (EDXRF) is a well-established and powerful tool for nondestructive elemental analysis of virtually any material. It is widely used for environmental, industrial, pharmaceutical, forensic, and scientific research applications to measure the concentration of elemental constituents or contaminants. The fluorescing atoms can be excited by energetic electrons, ions, or photons. A particular EDXRFmethod, monochromaticmicrobeam X-ray fluorescence (MμEDXRF), has proven to be remarkably powerful in measurement of trace element concentrations and distributions in a large variety of important medical, environmental, and industrial applications. When used with state-of-the-art doubly curved crystal (DCC) X-ray optics, this technique enables high-sensitivity, compact, low-power, safe, reliable, and rugged analyzers for insitu, online measurements in industrial process, clinical, and field settings. This new optic-enabled MμEDXRF technique is known as high-definition X-Ray fluorescence (HD XRF). Selected applications of HD XRF are described in this paper including air particulate analysis, analysis of body fluid contamination at ppb levels, elemental mapping of brain tissue and bone samples, as well as analysis of toxins in toys and other consumer products. [ABSTRACT FROM AUTHOR]

Three series of novel formononetin derivatives were synthesized, in which formononetin and heterocyclic moieties were separated by 2-carbon, 3-carbon, and 4-carbon spacers. The chemical structures of these compounds were confirmed. All the derivatives were screened for antiproliferative activities against Jurkat cell line and HepG-2 cell line. In this paper, compounds prepared were also screened for their antibacterial activity of six bacterial strains. Compound 3b exihibited promising antibacterial activity against B. subtilis with minimal inhibitory concentration (MIC) value of 0.78 μg/mL, and compound 5e showed significant antiproliferative activities against Jurkat cell growth with IC50 of 1.35×10-4 μg/mL. The preliminary investigation of structure-activity relationships (SARs) was also discussed based on the obtained experimental data. [ABSTRACT FROM AUTHOR]

The performance of parallel beam multilayer optics, including a parabolic multilayer Osmic MaxFlux GO-13N and a flat custom multilayer, was evaluated experimentally and compared to Bragg-Brentano and traditional "parallel beam" or "thin film" optical geometries. A novel arrangement of a parabolic multilayer in the incident beam with a flat multilayer in the diffracted beam functioning as an analyzer crystal was proven effective for powder diffraction applications. The dual-optic configuration improves resolution while eliminating sample displacement and transparency errors as expected for a configuration with equatorial divergence below 100 arcseconds. Fundamental parameters fitting showed that the parabolic multilayer can be accurately modeled using a constant Gaussian function, while a long parallel-plate soller collimator requires a constant hat function. No additional convolutions are necessary for the diffracted-beam flat multilayer because of the lower acceptance angle. [ABSTRACT FROM AUTHOR]

A custom processor based on reconfigurable hardware technology is proposed in order to compute the figure of merit used to measure the quality of the fit of X-ray diffraction peaks. As the experimental X-ray profiles can present many peaks severely overlapped, it is necessary to select the best model among a large set of reasonably good solutions. Determining the best solution is computationally intensive, because this is a hard combinatorial optimization problem. The proposed processors, working in parallel, increase the performance relative to a software implementation. [ABSTRACT FROM AUTHOR]

Membrane-based separation of phenol/water mixtures with concentrations of phenol between 3wt% and 8wt% in the feed has been performed with nonmodified as well as cross-linked ethylene-methacrylic acid (E-MAA) copolymers with different amounts of methacrylic acid. As cross-linking agents, aluminium acetyl acetonate, which leads to ionically cross-linked membranes, and 2,3,5,6-tetramethyl-1,4-phenylene diamine and glycerine digycidether, leading to covalently cross-linked membranes, have been used. Generally, it was found that with increasing phenol content in the feed, the total flux is increasing whereas the enrichment factor is decreasing. Using nonmodified membranes with higher methacrylic acid monomer content in the polymer, lower fluxes and higher enrichment factors were observed. Investigation of different cross-linked membranes showed that with high phenol concentration in the feed, ionic cross-linking seems to be very promising. Furthermore, variation of feed temperature shows that ionically cross-linked membranes reached higher fluxes as well as higher enrichment factors at elevated temperatures. The temperature-dependent data were fitted based on an Arrhenius-type equation, and activation energies for the permeation of phenol and water through the membrane were calculated. [ABSTRACT FROM AUTHOR]

Thermodynamic functions, including enthalpy (Hθ) and entropy (Sθ) for 76 polychlorophenazines (PCPZs) in the gas state at 298.15 K and 101.325 kPa, have been calculated using the B3LYP/6-31G* level with Gaussian 03 program, and considered on solvation affects. Total free energy in water (Gw) was calculated with the same program. Based on these data, the isodesmic reactions were designed to calculate the standard formation heat (Δf Hθ) and standard free energy of formation in water (Δf Gwθ). The dependences of these thermodynamic parameters on the numbers and positions of chlorine substitution (NPCS) were discussed. It is suggested that Sθ , Δf Hθ, and Δf Gwθ of PCPZs varied greatly with NPCS. Moreover, the values of molar heat capacity at constant pressure (Cp,m) from 200 to 1800 K for PCPZ congeners were calculated using a statistical thermodynamics calculation program based on Gaussian output files, and the temperature-dependence relation of Cp,m was obtained using the least-squares method. In addition, according to the relative magnitude of their Δf Gwθ, the relative stability order of PCPZ congeners was theoretically proposed. [ABSTRACT FROM AUTHOR]

Scaling analyses based on subsurface layer instability were performed to explore the role of three independent (surface tension, gravity, and viscosity) influences on the mechanism of pulsating flame spread under normal and microgravity conditions. These three influences form two independent pi-numbers: the Marangoni (Ma) number and Grashof (Gr) number, which include the characteristic length scale ratio (depth of subsurface circulation)/(horizontal length of preheated liquid surface). The Prandtl (Pr) number was introduced to compensate for the different thermal diffusivity and kinematic viscosity of different liquids. Also a nondimensional flame spread rate, V/VD (= Vδ/D, where d is the quenching distance and D is the diffusivity of fuel vapor) was introduced. Using these nondimensional parameters, the flame spread mechanism was divided into two separate regimes: for the shallow liquid pool the nondimensional flame spread rate was correlated with {Gr0.2/(Ma·Pr)}1.0, while for the deep liquid pool it was correlated with {Gr0.2/(Ma·Pr)}1.5. [ABSTRACT FROM AUTHOR]