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541.
Ray L. Frost Matt L. Weier Peter A. Williams Peter Leverett J. Theo Kloprogge 《Journal of Raman spectroscopy : JRS》2007,38(5):574-583
Raman and infrared spectroscopy enabled insights into the molecular structure of the sampleite group of minerals. These minerals are based upon the incorporation of either phosphate or arsenate with chloride anion into the structure, and as a consequence the spectra reflect the bands attributable to these anions, namely, phosphate or arsenate with chloride. The sampleite vibrational spectrum reflects the spectrum of the phosphate anion and consists of ν1 at 964 cm−1, ν2 at 451 cm−1, ν3 at 1016 and 1088 cm−1 and ν4 at 643, 604, 591 and 557 cm−1. The lavendulan spectrum consists of ν1 at 854 cm−1, ν2 at 345 cm−1, ν3 at 878 cm−1 and ν4 at 545 cm−1. The Raman spectrum of lemanskiite is different from that of lavendulan consistent with a different structure. Low wavenumber bands at 227 and 210 cm−1 may be assigned to CuCl transverse/longitudinal (TO/LO) optic vibrations. Raman spectroscopy identified the substitution of arsenate by phosphate in zdenekite and lavendulan. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
542.
George C. Bourantas Benjamin F. Zwick Theo Philippe Lavier Vassilios C. Loukopoulos Athanassios A. Dimas Adam Wittek Karol Miller 《国际流体数值方法杂志》2023,95(1):143-175
We present a strong form meshless solver for numerical solution of the nonstationary, incompressible, viscous Navier–Stokes equations in two (2D) and three dimensions (3D). We solve the flow equations in their stream function-vorticity (in 2D) and vector potential-vorticity (in 3D) formulation, by extending to 3D flows the boundary condition-enforced immersed boundary method, originally introduced in the literature for 2D problems. We use a Cartesian grid, uniform or locally refined, to discretize the spatial domain. We apply an explicit time integration scheme to update the transient vorticity equations, and we solve the Poisson type equation for the stream function or vector potential field using the meshless point collocation method. Spatial derivatives of the unknown field functions are computed using the discretization-corrected particle strength exchange method. We verify the accuracy of the proposed numerical scheme through commonly used benchmark and example problems. Excellent agreement with the data from the literature was achieved. The proposed method was shown to be very efficient, having relatively large critical time steps. 相似文献
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544.
Petra Schmid Claudia Peltz Vera M. F. Hammer Erich Halwax Theo Ntaflos Peter Nagl Max Bichler 《Mikrochimica acta》2000,133(1-4):143-149
Pumice from the “Minoan eruption” on Thera (Cyclades, Greece) was investigated to reveal the differences between the composition
of the bulk material, which contains a certain percentage of crystallites, and the pure glass phase. This is important for
the identification of vitric tephra layers found in the Eastern Mediterranean region in archaeological context and in deep
sea drilling cores. Eruption products, deposited at some distance, have usually lost their crystalline fraction due to gravity
separation and consist only of glass shards. Only major element distributions in such layers and in pumiceous glass phases
have been published up to now, but these data are not sufficient for a reliable identification of the volcanic source, as
several other eruptions are known to have produced chemically very similar layers in this region (Milos, Nisyros, Yali, Kos).
Therefore, a technique has been developed to separate the glass phase from the primary pumice to reveal differences in the
trace element distributions obtained by instrumental neutron activation analysis (INAA). X-ray diffractometry and microscopical
techniques were applied to check the purity of this fraction. The concentrations of the major constituents, in particular
Al, Ca, Fe, K, Mg, Mn, Na, Si, and Ti were determined by X-ray fluorescence (XRF) and electron probe microanalysis (EPMA),
those of Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Ti, Th, U, Yb and Zr by instrumental
neutron activation analysis and partly also by X-ray fluorescence. Subtle differences between the compositions of the glass
phase and the bulk material are explained by differentiation during partial crystallization and their applicability to the
classification of tephra layers is demonstrated. 相似文献
545.
The Effects of Two Stereoisomers of /V-Acetylcysteine on Photochemical Damage by UVA and Blue Light in Rat Retina 总被引:1,自引:0,他引:1
Eelco M. Busch Theo G. M. F. Gorgels Joan E. Roberts Dirk van Norren 《Photochemistry and photobiology》1999,70(3):353-358
High doses of light can cause damage to the retina, e.g. during intraocular surgery. Previously, thiols have been demonstrated to protect against retinal damage in various damage models. Such protection is very promising for clinical practice. Retinal light damage can be caused by a relatively short exposure to high irradiance levels. These conditions occur during intraocular surgery. In the current study we therefore investigated whether the thiol N-acetylcysteine protects against retinal light damage under high irradiance conditions in the rat retina. Two stereoisomers of this thiol were tested for protection against two spectrally defined types of retinal light damage. Shortly after administration N-acetyl-L-cysteine in doses of 270-1000 mg/kg intraperitoneally protected against 380 nm (UVA) light but not against 470 nm (blue) light. Two hours after injection the protection had diminished. We observed no protection by the stereoisomer N-acetyl-D-cysteine. From this study we conclude that N-acetyl-L-cysteine protects stereospecifically against retinal damage in the UV but not in the visible part of the spectrum. This limits the possible applications. 相似文献
546.
547.
Theo Fromme Lucie K. Tintrop Dr. Sven Reichenberger Prof. Dr. Torsten C. Schmidt Prof. Dr. Stephan Barcikowski 《Chemphyschem》2023,24(11):e202300089
Laser ablation in liquids has been established as a scalable preparation method of nanoparticles for various applications. Particularly for materials prone to oxidation, it is established to suppress oxidation by using organic solvents as a liquid medium. While this often functionalizes the nanoparticles with a carbon shell, the related chemical processes that result from laser-induced decomposition reactions of the organic solvents remain uncertain. Using a systematic series of C6 solvents complemented by n-pentane and n-heptane during the nanosecond laser ablation of gold, the present study focuses on the solvent-dependent influence on gas formation rates, nanoparticle productivity, and gas composition. Both the permanent gas and hydrogen formation was found to be linearly correlated with ablation rate, ΔHvap, and pyrolysis activation energy. Based on this, a decomposition pathway linked to pyrolysis is proposed allowing the deduction of first selection rules for solvents that influence the formation of carbon or permanent gases. 相似文献
548.
Ralph J.S. van Mechelen Jarno E.J. Wolters Sebastian Fredrich Christian J.F. Bertens Marion J.J. Gijbels Albert P.H.J. Schenning Leonard Pinchuk Theo G.M.F. Gorgels Henny J.M. Beckers 《Macromolecular bioscience》2023,23(10):2300075
Fibrosis of the filtering bleb is one of the main causes of failure after bleb-forming glaucoma surgery. Intraoperative application of mitomycin C (MMC) is the current gold standard to reduce the fibrotic response. However, MMC is cytotoxic and one-time application is often insufficient. A sustained-release drug delivery system (DDS), loaded with MMC, may be less cytotoxic and equally or more effective. Two degradable (polycaprolactone (PCL) and polylactic-co-glycolic acid (PLGA)) MMC-loaded DDSs are developed. Release kinetics are first assessed in vitro followed by rabbit implants in conjunction with the PRESERFLO MicroShunt. As a control, the MicroShunt is implanted with adjunctive use of a MMC solution. Rabbits are euthanized at postoperative day (POD) 28 and 90. The PLGA and PCL DDSs release (on average) 99% and 75% of MMC, respectively. All groups show functioning blebs until POD 90. Rabbits implanted with a DDS show more inflammation with avascular thin-walled blebs when compared to the control. However, collagen is more loosely arranged. The PLGA DDS shows less inflammation, less foreign body response (FBR), and more complete degradation at POD 90 when compared to the PCL DDS. Further optimization with regard to dosage is required to reduce side effects to the conjunctiva. 相似文献
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