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941.
Ohne Zusammenfassung 相似文献
942.
P. Meunier A. Vinet H. G. K. Westenbrink D. A. van Dorp M. Gruber A. Fujita T. Numata T. Sakamoto F. H. Carr und E. A. Price 《Fresenius' Journal of Analytical Chemistry》1944,127(1):215-217
Ohne Zusammenfassung 相似文献
943.
Boros E Ferreira CL Cawthray JF Price EW Patrick BO Wester DW Adam MJ Orvig C 《Journal of the American Chemical Society》2010,132(44):15726-15733
We have investigated novel bifunctional chelate alternatives to the aminocarboxylate macrocycles NOTA (N(3)O(3)) or DOTA (N(4)O(4)) for application of radioisotopes of Ga to diagnostic nuclear medicine and have found that the linear N(4)O(2) chelate H(2)dedpa coordinates (67)Ga quantitatively to form [(67)Ga(dedpa)](+) after 10 min at RT. Concentration-dependent coordination to H(2)dedpa of either (68)Ga or (67)Ga showed quantitative conversion to the desired products with ligand concentrations as low as 10(-7) M. With (68)Ga, specific activities as high as 9.8 mCi nmol(-1) were obtained without purification. In a 2 h competition experiment against human apo-transferrin, [(67)Ga(dedpa)](+) showed no decomposition. Two bifunctional versions of H(2)dedpa are also described, and these both coordinate to (67)Ga at RT within 10 min. Complete syntheses, characterizations, labeling studies, and biodistribution profiles of the (67)Ga complexes are presented for the new platform chelates. The stability of these platform chelates is higher than that of DOTA. 相似文献
944.
Studies on the effect of different levels of toughener and flame retardants on thermal stability of epoxy resin 总被引:1,自引:0,他引:1
Baljinder K. Kandola Bhaskar Biswas Dennis Price A. Richard Horrocks 《Polymer Degradation and Stability》2010,95(2):144-152
A thermoplastic toughener, polyether sulphone (PES) and a number of different types of flame retardants were blended in different ratios with a commercial epoxy resin triglycidyl-p-aminophenol (TGAP) and 4,4-diamino diphenyl sulphone (DDS) a curing agent. The effect of type and levels of flame retardants (FR) and the toughening agent on the curing, thermal decomposition and char oxidation behaviour of the epoxy resin was studied by the simultaneous differential thermal analysis and thermogravimetric techniques. It was observed that the toughener slightly increases the curing temperature (by up to 20 °C) but had minimal effect on the decomposition temperature of the resin. Flame retardants, however affected all stages depending upon the type of flame retardant used. The curing peak for samples containing tougher and flame retardants although slightly changed depending upon the type of FR, was not more than ± 20 °C compared to that of samples containing toughener only. All flame retardants lowered the decomposition temperature of the epoxy resin. Phosphorus- and nitrogen-containing flame retardants reduced the char oxidation leading to more residual char, whereas halogen- containing flame retardants had less effect on this stage. 相似文献
945.
Rasha A. Ruhayel Joseph J. Moniodis Dr. Xiaohong Yang Dr. Jana Kasparkova Dr. Viktor Brabec Prof. Susan J. Berners‐Price Prof. Nicholas P. Farrell Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(37):9365-9374
Reported herein is a study of the unusual 3′–3′ 1,4‐GG interstrand cross‐link (IXL) formation in duplex DNA by a series of polynuclear platinum anticancer complexes. To examine the effect of possible preassociation through charge and hydrogen‐bonding effects the closely related compounds [{trans‐PtCl(NH3)2}2(μ‐trans‐Pt(NH3)2{NH2(CH2)6NH2}2)]4+ (BBR3464, 1 ), [{trans‐PtCl(NH3)2}2(μ‐NH2(CH2)6NH2)]2+ (BBR3005, 2 ), [{trans‐PtCl(NH3)2}2(μ‐H2N(CH2)3NH2(CH2)4)]3+ (BBR3571, 3 ) and [{trans‐PtCl(NH3)2}2{μ‐H2N(CH2)3‐N(COCF3)(CH2)4}]2+ (BBR3571‐COCF3, 4 ) were studied. Two different molecular biology approaches were used to investigate the effect of DNA template upon IXL formation in synthetic 20‐base‐pair duplexes. In the “hybridisation directed” method the monofunctionally adducted top strands were hybridised with their complementary 5′‐end labelled strands; after 24 h the efficiency of interstrand cross‐linking in the 5′–5′ direction was slightly higher than in the 3′–3′ direction. The second method involved “postsynthetic modification” of the intact duplex; significantly less cross‐linking was observed, but again a slight preference for the 5′–5′ duplex was present. 2D [1H, 15N] HSQC NMR spectroscopy studies of the reaction of [15N]‐ 1 with the sequence 5′‐d{TATACATGTATA}2 allowed direct comparison of the stepwise formation of the 3′–3′ IXL with the previously studied 5′–5′ IXL on the analogous sequence 5′‐d(ATATGTACATAT)2. Whereas the preassociation and aquation steps were similar, differences were evident at the monofunctional binding step. The reaction did not yield a single distinct 3′–3′ 1,4‐GG IXL, but numerous cross‐linked adducts formed. Similar results were found for the reaction with the dinuclear [15N]‐ 2 . Molecular dynamics simulations for the 3′–3′ IXLs formed by both 1 and 2 showed a highly distorted structure with evident fraying of the end base pairs and considerable widening of the minor groove. 相似文献
946.
Melanie J. Bugler Stephen T. Grimes Melanie J. Leng Simon D. Rundle Gregory D. Price Jerry J. Hooker Margaret E. Collinson 《Rapid communications in mass spectrometry : RCM》2009,23(18):2939-2951
Experimental measurements of the 18O/16O isotope fractionation between the biogenic aragonite of Viviparus contectus (Gastropoda) and its host freshwater were undertaken to generate a species‐specific thermometry equation. The temperature dependence of the fractionation factor and the relationship between Δδ18O (δ18Ocarb. – δ18Owater) and temperature were calculated from specimens maintained under laboratory and field (collection and cage) conditions. The field specimens were grown (Somerset, UK) between August 2007 and August 2008, with water samples and temperature measurements taken monthly. Specimens grown in the laboratory experiment were maintained under constant temperatures (15°C, 20°C and 25°C) with water samples collected weekly. Application of a linear regression to the datasets indicated that the gradients of all three experiments were within experimental error of each other (±2 times the standard error); therefore, a combined (laboratory and field data) correlation could be applied. The relationship between Δδ18O (δ18Ocarb. – δ18Owater) and temperature (T) for this combined dataset is given by: (T is in °C, δ18Ocarb. is with respect to Vienna Pee Dee Belemnite (VPDB) and δ18Owater is with respect to Vienna Standard Mean Ocean Water (VSMOW). Quoted errors are 2 times standard error). Comparisons made with existing aragonitic thermometry equations reveal that the linear regression for the combined Viviparus contectus equation is within 2 times the standard error of previously reported aragonitic thermometry equations. This suggests there are no species‐specific vital effects for Viviparus contectus. Seasonal δ18Ocarb. profiles from specimens retrieved from the field cage experiment indicate that during shell secretion the δ18Ocarb. of the shell carbonate is not influenced by size, sex or whether females contained eggs or juveniles. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
947.
We examine the problem of quantitative chemical measurement for well-identified substances, discuss the quantity called ‘amount
of substance’, the means of expressing it, and its physical SI unit the mole. The everyday quantity which is a number of entities
may be measured by the performance of two operations (identification and counting), the results of which may be communicated
with two items of information (their name and the number of entities). We distinguish nominal, ordinal, interval and ratio
scales of measurement and apply these to counting, referring to ordinal and cardinal numbers and Helmholtz’ analysis of measurement.
Counting may be by direct serial numeration, direct parallel numeration, or comparative numeration. We discuss the limitations
of serial numeration, the possibilities of parallel numeration, and the advantages of comparative numeration where a unit
for counting in multiples (such as the analyst’s mole) may be used to define a scale on which equal numbers of objects correspond
to equal values of some other physical quantity. We conclude that the numeration of very large numbers of objects is readily
achieved but with unavoidable uncertainty, using operations which compare numbers of entities either to numbers of other entities
or to some other quantity which accurately models numbers of entities. 相似文献
948.
Michael A. Parkes Jessica F. Lockyear Stephen D. Price 《International journal of mass spectrometry》2009,280(1-3):85
The reaction between Ar2+ and C2H2 has been studied, at centre-of-mass collision energies ranging from 3 to 7 eV, using a position-sensitive coincidence technique to detect the monocation pairs, which are formed. Sixteen different reaction channels generating pairs of monocations have been observed, these channels arise from double-electron-transfer, single-electron-transfer and chemical reactions forming ArC+. Examination of the scattering diagrams and energetic information extracted from the coincidence data indicate that double-electron-transfer is a direct process, which does not involve a collision complex, and the derived energetics point towards a concerted, not stepwise, mechanism for the two-electron-transfer. As is commonly observed, single-electron-transfer from C2H2 to Ar2+ takes place via a direct mechanism, again not involving complexation. Most of the C2H2+ products that are formed in the single-electron-transfer reactions possess significant (12–15 eV) internal energy and fragment rapidly within the electric field of the partner Ar+ ion. The chemical reactions appear to proceed via a direct mechanism involving the initial formation of ArCH+, which subsequently fragments to form ArC+. 相似文献
949.
Brigitte Städler Dr. Rona Chandrawati Andrew D. Price Dr. Siow‐Feng Chong Kerry Breheney Almar Postma Dr. Luke A. Connal Dr. Alexander N. Zelikin Dr. Frank Caruso Prof. 《Angewandte Chemie (International ed. in English)》2009,48(24):4359-4362
Fully loaded : Noncovalent anchoring of liposomes into polymer multilayered films with cholesterol‐modified polymers allows the preparation of capsosomes—liposome‐compartmentalized polymer capsules (see picture). A quantitative enzymatic reaction confirmed the presence of active cargo within the capsosomes and was used to determine the number of subcompartments within this novel biomedical carrier system.
950.
Parmar D Price K Spain M Matsubara H Bradley PA Procter DJ 《Journal of the American Chemical Society》2011,133(8):2418-2420
Lactones bearing two alkenes or an alkene and an alkyne undergo reductive cyclization cascades upon treatment with SmI(2)-H(2)O, giving decorated azulene motifs in excellent yields with good diastereocontrol. 相似文献