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排序方式: 共有486条查询结果,搜索用时 15 毫秒
11.
McFarland KS Naples D Arroyo CG Auchincloss P de Barbaro P Bazarko AO Bernstein RH Bodek A Bolton T Budd H Conrad J Drucker RB Harris DA Johnson RA Kim JH King BJ Kinnel T Koizumi G Koutsoliotas S Lamm MJ Lefmann WC Marsh W McNulty C Mishra SR Nienaber P Nussbaum M Oreglia MJ Perera L Quintas PZ Romosan A Sakumoto WK Schumm BA Sciulli FJ Seligman WG Shaevitz MH Smith WH Spentzouris P Steiner R Stern EG Vakili M Yang UK 《Physical review letters》1995,75(22):3993-3996
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Arroyo CG King BJ Bachmann KT Bazarko AO Bolton T Foudas C Lefmann WC Leung WC Mishra SR Oltman E Quintas PZ Rabinowitz SA Sciulli FJ Seligman WG Shaevitz MH Merritt FS Oreglia MJ Schumm BA Bernstein RH Borcherding F Fisk HE Lamm MJ Marsh W Merritt KW Schellman HM Yovanovitch DD Bodek A Budd HS de Barbaro P Sakumoto WK Kinnel T Sandler PH Smith WH 《Physical review letters》1994,72(22):3452-3455
14.
Armstrong TA Bettoni D Bharadwaj V Biino C Borreani G Broemmelsiek D Buzzo A Calabrese R Ceccucci A Cester R Church M Dalpiaz P Dalpiaz PF Dimitroyannis D Fabbri M Fast J Gianoli A Ginsburg CM Gollwitzer K Govi G Hahn A Hasan M Hsueh S Lewis R Luppi E Macrí M Majewska AM Mandelkern M Marchetto F Marinelli M Marques J Marsh W Martini M Masuzawa M Menichetti E Migliori A Mussa R Palestini S Pallavicini M Passaggio S Pastrone N Patrignani C Peoples J Petrucci F Pia MG Pordes S Rapidis P Ray R 《Physical review D: Particles and fields》1996,54(11):7067-7070
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The oxidation of uric acid has been studied by thin-layer spectroelectrochemistry using an optically transparent gold minigrid electrode and enzymatically using peroxidase. Under both enzymatic and electrochemical conditions a u.v.-absorbing intermediate (λmax=302–304 nm between pH 7–9.3) is observed. This intermediate is proposed to be an imine-alcohol species formed by rapid hydration of the primary reaction product which is a diimine. Under the conditions employed in both the enzymatic electrochemical studies the imine-alcohol intermediate is hydrated in a first order reaction with an observed rate constant of 3.5×10?3s?1 between pH 7–9.3. This study establishes the similarity between the electrochemical and enzymatic oxidation of uric acid and indicates that electrochemical investigations of the redox behavior of purines can provide unique insights into their biological redox properties. 相似文献
17.
High Performance Liquid Chromatographic Analysis of Pharmaceuticals Using Oil-In-Water Microemulsion Eluent and Monolithic Column 总被引:1,自引:0,他引:1
Novel and efficient separations of pharmaceutical substances were achieved using oil-in-water microemulsion eluent and a conventional
C18 packing with a flow rate of 1 mL/min−1. Attempts to decrease analysis time was limited due to the high viscosity of the microemulsion which generated relatively
high back-pressures. Monolithic columns gave 3-fold lower back-pressures and allowed flow rates of 4 mL/min−1. with the same microemulsion mobile phase which permitted rapid separations to be achieved. Separation of a test-mix of paraben
preservatives was achieved in both isocratic and gradient mode in less than 1 min. The monolith-microemulsion combination
was applied to rapidly quantitatively analyse two formulated products with excellent linearity, accuracy and repeatability.
Quantitative analysis times were under 90 seconds. Successful quantitation of both nicotine lozenges and naprosyn tablets
was performed using this approach. 相似文献
18.
Abstract. Angiotensin is readily inactivated by ultraviolet light presumably due to the photosensitivity of its tyrosyl and phenylalanyl residues. Alkalinity promotes and acidity delays the biological decomposition. Under conditions of oxygen exclusion (i.e. under N2 or H2 ) the rate of decomposition is further depressed and when irradiation is carried out under hydrogen a biologically active product is formed. This altered angiotensin, judging from its chromatographic migration and dialysis rate, represents a polymerized form of angiotensin. Under identical irradiation conditions, angiotensin was coupled with C14 labelled pheny-lalanine which indicates that this residue might be the photoreactive species. The production of altered forms of angiotensin by ultraviolet irradiation was discussed with respect to possible utility in anti-metabolite, antigen or tracer work. 相似文献
19.
Simulations of diffusion-limited cluster-cluster aggregation (DLCA) with no restructuring, full restructuring, and partial restructuring have been performed. The scattering patterns produced from these aggregates have been simulated using the Rayleigh-Gans-Debye approximation. Pure DLCA aggregates produced a scattering pattern with the slope of the fractal region being about -1.8. In contrast, the slope of the fractal region of the scattering pattern for fully restructured aggregates was about -2.1, indicating an increase in fractal dimension. Partial restructuring at large length scales produced an upward turn in the scattering pattern at low qr(o), while at high qr(o) the fractal section of the pure DLCA aggregate was retained. This last result was expected and is consistent with the results and postulations of several other workers. This simulation shows that the type of scattering pattern often obtained from orthokinetic or sheared aggregation can be produced by restructuring of aggregates at large length scales. Copyright 2001 Academic Press. 相似文献
20.
S. F. Marsh N. G. Pope M. C. Miller 《Journal of Radioanalytical and Nuclear Chemistry》1988,123(2):655-665
An On-Line Gamma Monitor profiles the concentration of uranium, plutonium, and americium in waste and product streams of the anion exchange process used to purify plutonium at Los Alamos. The Monitor employs passive gamma Spectrometry to measure the 59.5-KeV and 129-KeV gamma rays of241Am and239Pu, respectively. Because the uranium impurity in typical process streams has no gamma ray suitable for passive measurement, a novel radiotracer technique is used. Uranium-237, always present in plutonium processed at Los Alamos as a minor alpha-decay daughter of241Pu, has a 6.8-day half-life and 208-KeV gamma energy, which make it an ideal radiotracer for macro amounts of uranium in the process. The On-Line Gamma Monitor is used routinely to provide Los Alamos operators with continuous, real-time process control information. 相似文献