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91.
We prove general comparison theorems for eigenvalues of perturbed Schrödinger operators that allow proof of Lieb–Thirring bounds for suitable non-free Schrödinger operators and Jacobi matrices. 相似文献
92.
Philip Birch Bhargav Mitra Nagachetan M. Bangalore Saad Rehman Rupert Young Chris Chatwin 《Optics Communications》2010,283(24):4942-4948
The Difference of Gaussian (DOG) filter is widely used in optics and image processing as, among other things, an edge detection and correlation filter. It has important biological applications and appears to be part of the mammalian vision system. In this paper we analyse the filter and provide details of the full width half maximum, bandwidth and frequency response in order to aid the full characterisation of its performance. 相似文献
93.
Schmoeger E Paril C Tscheliessnig R Jungbauer A 《Journal of separation science》2010,33(20):3125-3136
The adsorption of plasmid DNA onto two different types of ceramic hydroxyapatite beads with a particle diameter of 20 μm, namely Ceramic Hydroxyapatite Type II and the Type III, which is not commercially available, were investigated. Type II and the Type III have a pore diameter of 80 and 240 nm, respectively. Equilibrium and dynamic binding capacity for a 4.9 kbp model plasmid on Ceramic Hydroxyapatite Type II and Type III were enhanced by addition of NaCl to the adsorption buffer. This result indicates that the adsorption mechanism cannot be solely explained by electrostatic interaction. The affinities of plasmid DNA for Ceramic Hydroxyapatite Type II (with a K(D) of ≈0.005 mg/mL) and to Hydroxyapatite Type III (with a K(D) of ≈0.045 mg/mL) were not affected by NaCl, whereas the binding capacity was. This observation corroborates the assumption that a change of the shape of the plasmid molecule is affected and could be the reason for increased binding capacity with salt. The maximal binding capacity shows that at least a part of the CHT II bead must be accessible for the plasmid, whereas CHT III can be saturated with the plasmid. In both cases, an extremely hindered transport takes place. 相似文献
94.
Exponentially growing cells of the PtK-2 line (ATCC No. CCL56, from the marsupial Potorous tridactylus) require protein and RNA synthesis in a limited period following UV-radiation damage for optimal recovery as colony formers [Overberg et al. (1988) Mutat. Res. 194, 83-92]. Overall behavior suggests the operation of damage-induced recovery processes. The capacity of confluent cell monolayers for infection with unirradiated herpes simplex virus 1 (HSV-1) is sharply reduced by UV-irradiation. We have followed capacity changes in exponentially growing cells after irradiation and varying amounts of photoreactivation by means of an infectious center assay. These changes closely parallel changes of colony formation. Spontaneous recovery of capacity in the dark occurs over approximately the same time period that the UV sensitivity of colony formation depends on macromolecular synthesis. The effect of photoreactivation is complementary rather than additive to this recovery, suggesting that the dark recovery in this period concerns pyrimidine dimers in cell DNA. 相似文献
95.
Tijana Ristić Tamilselvan Mohan Rupert Kargl Silvo Hribernik Aleš Doliška Karin Stana-Kleinschek Lidija Fras 《Cellulose (London, England)》2014,21(4):2315-2325
This investigation describes the interaction of trimethyl chitosans (TMCs) with surfaces of cellulose thin films. The irreversible deposition/adsorption of TMCs with different degrees of cationization was studied with regards to the salt concentration and pH. As substrates, cellulose thin films were prepared by spin coating from trimethylsilyl cellulose and subsequent regeneration to pure cellulose. The pH-dependent zeta potential of cellulose thin films and the charge of TMCs were determined by streaming potential and potentiometric charge titration methods. A quartz crystal microbalance with dissipation monitoring was further used as a nanogram sensitive balance to detect the amount of deposited TMCs and the swelling of the bound layers. The morphology of the coatings was additionally characterized by atomic force microscopy and related to the adsorption results. A lower degree of cationization leads to higher amounts of deposited TMCs at all salt concentrations. Higher amounts of salt increase the deposition of TMCs. Protonation of primary amino groups results in the immobilization of less material at lower pH values. The results from this work can further be extended to the modification of regenerated cellulosic materials to obtain surfaces, with amino- and trimethylammonium moieties. 相似文献
96.
Simon R Gomez Ruiz JA von Holst C Wenzl T Anklam E 《Analytical and bioanalytical chemistry》2008,391(4):1397-1408
A collaborative study on the analysis for 15 + 1 EU priority PAHs in edible oils was organised to investigate the state-of-the-art of respective analytical methods. Three spiked vegetable oils, one contaminated native sunflower oil, and one standard solution were investigated in this study. The results of 52 laboratories using either high-performance liquid chromatography with fluorescence detection or gas chromatography with mass-selective detectors were evaluated by application of robust statistics. About 95% of the laboratories were able to quantify benzo[a]pyrene together with five other PAHs included in the commonly known list of 16 US-EPA PAHs. About 80% of the participants also quantified seven additional PAHs in most samples, two of which were benzo[b]fluoranthene and benzo[k]fluoranthene, which were also known from the EPA list. Only about 50% of the participants quantified cyclopenta[cd]pyrene, benzo[j]fluoranthene, and benzo[c]fluorene. The robust relative standard deviations of the submitted results without discrimination between the methods applied ranged between 100% for 5-methylchrysene in spiked olive oil and 11% for the same analyte in spiked sunflower oil. The results clearly showed that for these analytes the methods of analysis are not yet well established in European laboratories, and more collaborative trials are needed to promote further development and to improve the performances of the respective methods. 相似文献
97.
Rupert S. J. Proctor Robert J. Phipps 《Angewandte Chemie (International ed. in English)》2019,58(39):13666-13699
Reactions that involve the addition of carbon‐centered radicals to basic heteroarenes, followed by formal hydrogen atom loss, have become widely known as Minisci‐type reactions. First developed into a useful synthetic tool in the late 1960s by Minisci, this reaction type has been in constant use over the last half century by chemists seeking to functionalize heterocycles in a rapid and direct manner, avoiding the need for de novo heterocycle synthesis. Whilst the originally developed protocols for radical generation remain in active use today, they have been joined in recent years by a new array of radical generation strategies that allow use of a wider variety of radical precursors that often operate under milder and more benign conditions. The recent surge of interest in new transformations based on free radical reactivity has meant that numerous choices are now available to a synthetic chemist looking to utilize a Minisci‐type reaction. Radical‐generation methods based on photoredox catalysis and electrochemistry have joined approaches which utilize thermal cleavage or the in situ generation of reactive radical precursors. This review will cover the remarkably large body of literature that has appeared on this topic over the last decade in an attempt to provide guidance to the synthetic chemist, as well as a perspective on both the challenges that have been overcome and those that still remain. As well as the logical classification of advances based on the nature of the radical precursor, with which most advances have been concerned, recent advances in control of various selectivity aspects associated with Minisci‐type reactions will also be discussed. 相似文献
98.
The methods of preparation of ReO3F are revised. ReO3F is an amorphous yellow solid that crystallizes into colorless needles after prolonged heating. Its structure is that of a fluorine and oxygen bridged chain with hexa coordinated rhenium atoms (a = 670.9(2), b = 596.6(2), c = 1030.6(4) pm, β = 90.057(7)°, space group P2/c. In presence of donor solvents ReO3F·2L (L = (C2H5)2O, (CH3)2O, THF) are formed. ReO2F3, if crystallized from HF, exists in two crystalline forms, both are fluorine bridged chain polymers. (ReO2F3‐I: a = 1539.7(3), b = 999.6(3), c = 924.4(2) pm, β = 95.25(1)°, space group P21/c; ReO2F3‐II: a = 544.9(1), b = 494.2(1), c = 1253.7(2) pm, β = 98.543(7)°, space group P21/c. ReO2F3 crystallizes from CFCl3 or SO2FCl as fluorine bridged cyclic trimer (a = 881.4(4), c = 822.1(6) pm, γ = 120°, space group P63/m, or fluorine bridged cyclic tetramer (a = 1107.8(2), b = 999.4(2), c = 1347.9(3) pm, space group Cmca). 相似文献
99.
Nachimuthu P Thevuthasan S Adams EM Weber WJ Begg BD Mun BS Shuh DK Lindle DW Gullikson EM Perera RC 《The journal of physical chemistry. B》2005,109(4):1337-1339
Disorder in Gd2(Ti(1-y)Zry)2O7 pyrochlores, for y = 0.0-1.0, is investigated by Ti 2p and O 1s near-edge X-ray absorption fine structure spectroscopy. Ti(4+) ions are found to occupy octahedral sites in Gd2Ti2O7 with a tetragonal distortion induced by vacant oxygen sites. As Zr substitutes for Ti, the tetragonal distortion decreases, and Zr coordination increases from 6 to 8. The migration of oxygen ions from 48f or 8b sites to vacant 8a sites compensate for the increased Zr coordination, thereby reducing the number of vacant 8a sites, which further reduces the tetragonal distortion and introduces more disorder around Ti. This is evidence for simultaneous cation disorder with anion migration. 相似文献
100.
Rupert Marx 《无机化学与普通化学杂志》1997,623(12):1912-1916
Preparation and Crystal Structure of Lithium Nitride Hydride, Li4NH, Li4ND Single phase Li4NH was prepared by the reaction of Li3N and LiH at 490°C. Its structure has been solved from x-ray and time-of-flight neutron powder diffraction data. Li4NH crystallizes in an ordered variant of the Li2O structure. N and H occupy the sites of two interpenetrating “extended” diamond lattices. Li occupies all N2H2 tetrahedral voids and is found to be shifted into a N2H tetrahedral face. As a result H is in compressed tetrahedral coordination by Li, while N is in bisdisphenoidal coordination by Li. Alternatively, the Li4NH structure may be regarded as a [Li4N]+threedimensional net, its voids being filled up with H?. Li4NH is a reactive solid, which decomposes to imide when in contact with N2 or H2 at some 400°C. 相似文献