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1.
Vasil G. Angelov 《Mathematische Nachrichten》1986,127(1):211-221
Let X be a complete uniform HAUSDORFF space with a uniformity generated by a saturated family of pseudometrics ?? = {?α(x, y): α ? A} and let T: X → X be a continuous mapping. The paper contains necessary and sufficient conditions for the existence of a new family of pseudometrics ??*={?*(x, y): α*?A*} generated the same topology such that T is contractive with respect to ??*. 相似文献
2.
Ejnik JW Todorov TI Mullick FG Squibb K McDiarmid MA Centeno JA 《Analytical and bioanalytical chemistry》2005,382(1):73-79
Urine uranium concentrations are the best biological indicator for identifying exposure to depleted uranium (DU). Internal exposure to DU causes an increased amount of urine uranium and a decreased ratio of 235U/238U in urine samples, resulting in measurements that vary between 0.00725 and 0.002 (i.e., natural and depleted uraniums 235U/238U ratios, respectively). A method based on inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was utilized to identify DU in urine by measuring the quantity of total U and the 235U/238U ratio. The quantitative analysis was achieved using 233U as an internal standard. The analysis was performed both with and without the reaction gas oxygen. The reaction gas converted ionized 235U+ and 238U+ into 235UO2+ (m/z=267) and 238UO2+ (m/z=270). This conversion was determined to be over 90% efficient. A polyatomic interference at m/z 234.8 was successfully removed from the 235U signal under either DRC operating conditions (with or without oxygen as a reaction gas). The method was validated with 15 urine samples of known uranium compositions. The method detection limit for quantification was determined to be 0.1 pg U mL–1 urine and an average coefficient of variation (CV) of 1–2% within the sample measurements. The method detection limit for determining 235U/238U ratio was 3.0 pg U mL–1 urine. An additional 21 patient samples were analyzed with no information about medical history. The measured 235U/238U ratio within the urine samples correctly identified the presence or absence of internal DU exposure in all 21 patients.The opinions and assertions expressed herein are those of the authors and are not to be construed as official or as representing the views of the Armed Forces Institute of Pathology, the Department of the Army, or the Department of Defense 相似文献
3.
Todor Todorov 《Transactions of the American Mathematical Society》1996,348(2):673-689
We prove the existence of solutions for essentially all linear partial differential equations with -coefficients in an algebra of generalized functions, defined in the paper. In particular, we show that H. Lewy's equation has solutions whenever its right-hand side is a classical -function.
4.
Arsenic Speciation in Urine and Blood Reference Materials 总被引:1,自引:0,他引:1
Todor I. Todorov John W. Ejnik Florabel G. Mullick Jose A. Centeno 《Mikrochimica acta》2005,151(3-4):263-268
Acute and chronic exposure to arsenic is a growing problem in the industrialized world. Arsenic is a potent carcinogen and
toxin in humans. In the body, arsenic is metabolized to produce several species, including inorganic forms, such as trivalent
(AsIII) and pentavalent (AsV), and the methylated metabolites such as monomethylarsonic acid, (MMAV), and dimethylarsinic acid (DMAV), in addition to arsenobetaine (AsB) which is ingested and excreted from the body in the same form. Each of these species
has been reported to possess a specific but different degree of toxicity. Thus, not only is the measurement of total As required,
but also quantification of the individual metabolites is necessary to evaluate the toxicity and risk assessment of this element.
There are a large number of reference materials that are used to validate methodology for the analysis of As in blood and
urine, but they are limited to total As concentrations. In this study, the speciation of five arsenic metabolites is reported
in blood and urine from commercial available control materials certified for total arsenic levels. The separation was performed
with an anion exchange column using inductively coupled plasma mass spectrometry as a detector. Baseline separation was achieved
for AsIII, AsV, MMAV, DMAV, and AsB, allowing us to quantify all five species. Excellent agreement between the total arsenic levels and the sum of the
speciated As levels was obtained. 相似文献
5.
It has been shown that under high-power laser UV irradiation (I = 108–1010 W/cm2, λ = 266 nm, τp = 30 ps) water becomes ionized by a two-photon mechanism to form some free radicals including the hydrated electron e?aq. 相似文献
6.
Todor Gramchev 《Monatshefte für Mathematik》1991,112(2):99-113
We study the weak limits
(t, .)of solutions to semilinear strictly hyperbolic systems and wave equations with initial datau
(0, .) approximating a distribution, 0 <
1. We propose an optimal link between the singularity of and the growth of the nonlinear term in order that
exists. In this way we extend some of the results in [3], [10], [13]. 相似文献
7.
V. Angelov V. Rusanov Ts. Bonchev Th. Woike S. Haussühl 《Zeitschrift für Physik B Condensed Matter》1991,83(1):39-44
The recoilless absorption probability factor,f, and recoilless reemission,f, both measured on Na2[Fe(CN)5NO]·2 H2O single crystals using the black filter technique, were found to be different. Unexpectedly, the results found weref>f. In the calculation off, selfabsorption in the scatterer, non-ideality of the black filter and the influence of non-resonant scattering processes have all been taken into account. By varying the scattering geometry for the incoming and outgoing -beam relative to the crystallographic axes only a change in the reemitted valuesf
a, fb, fc could be detected because of the long lifetime of the excited nucleus (10–7 s) relative to the lattice vibration frequencies (1012 Hz). 相似文献
8.
Ronald G. Cavell Christo M. Angelov Dean A. Mazzuca 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):625-628
Abstract: Chlorophosphines react with trivalent (silylamino)phosphines via a direct oxidative addition process with elimination of trimethyl silyl chloride to produce phosphino-phosphoranimines with concomitant formation of a P-P bond. Oxidation of the phosphine center with sulfur and an exchange transformation of the phosphine are discussed. 相似文献
9.
A Preparative Method for Crosslinking Proteins to DNA in Nuclei by Single-pulse UV Laser Irradiation
Abstract— Photocrosslinking of proteins to DNA by single-pulse UV laser has been used only in analytical experiments, carried out with reconstituted complexes of a single DNA binding protein and a labeled target sequence. Here we propose a large-scale technique for irradiation of nuclei, generating preparative quantities of covalently linked protein-DNA complexes for further analysis of the partner molecules. The use of a flow cuvette allows a milligram of DNA in either nuclei or chromatin to be irradiated by a single pulse within few minutes. The efficiency of crosslinking varies from 6 to 12% of the total nuclear proteins. The presence of histones and other chromosomal proteins in the crosslinked protein-DNA complexes was demonstrated by using specific antibodies. The irradiation procedure can be fully automated using a microcomputer. 相似文献
10.
Paolo Ravarino Dr. Santanu Panja Simona Bianco Dr. Todor Koev Dr. Matthew Wallace Prof. Dave J. Adams 《Angewandte Chemie (International ed. in English)》2023,62(4):e202215813
We use a pH-driven annealing process to convert between co-assembled and self-sorted networks in multicomponent gels. The initially formed gels at low pH are co-assembled, with the two components coexisting within the same self-assembled structures. We use an enzymatic approach to increase the pH, resulting in a gel-to-sol transition, followed by a hydrolysis to lower the pH once again. As the pH decreases, a self-sorted network is formed by a two-stage gelation process determined by the pKa of each component. This approach can be expanded to layered systems to generate many varied systems by changing composition and rates of pH change, adapting their microstructure and so allowing access to a far greater range of morphologies and complexity than can be achieved in single component systems. 相似文献