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111.
The hypothesis that laser activation of glassy carbon (GC) electrodes is thermally driven was investigated by comparing simulated surface temperatures for several lasers and experimental conditions. Assuming no phase changes, the surface temperature vs. time profile for a laser pulse striking a GC electrode was predicted by finite difference simulation. It was predicted that peak surface temperature depends on power density, wavelength, pulse duration and the optical properties of the carbon. Experimentally, laser activation is weakly wavelength dependent for ascorbic acid and Fe
. The surface temperatures required for activation were consistent for different lasers, supporting the conclusion that laser activation is thermally driven. Furthermore, predicted surface temperatures during activation were below the melting point of carbon but well above the boiling point of water. The results should be useful for predicting the effectiveness of different laser conditions on electron transfer activation. 相似文献
112.
Linda J Obenauer-Kutner Rebecca Halperin Peter M Ihnat Christopher P Tully Ronald W Bordens Michael J Grace 《Microscopy and microanalysis》2005,11(1):37-41
Electron microscopy has a pivotal role as an analytical tool in pharmaceutical research. However, digital image data have proven to be too large for efficient quantitative analysis. We describe here the development and application of an automated image processing (AIP) program that rapidly quantifies shape measurements of recombinant adenovirus (rAd) obtained from digitized field emission scanning electron microscope (FESEM) images. The program was written using the macro-recording features within Image-Pro Plus software. The macro program, which is linked to a Microsoft Excel spreadsheet, consists of a series of subroutines designed to automatically measure rAd vector objects from the FESEM images. The application and utility of this macro program has enabled us to rapidly and efficiently analyze very large data sets of rAd samples while minimizing operator time. 相似文献
113.
Abstract— The quantum yields for the photohydration of dimethyluracil were determined for concentrations in the range 5 × 10--1--1 × 10--3M by use of 240–280 nm irradiation. The average quantum yield (0.0139 f 0.0005) was independent of both concentration and irradiation wavelength. 相似文献
114.
Thermolysis of perfluoroazidobenzene, perfluoro-4- azidotoluene, perfluoro-4-azidopyridine, 4-azido-3- chlorotrifluoropyridine, and 4-azido-3, 5-dichlorodifluoropyridine (ArFN3) in the presence of a large excess (. 10 molar) of 1,3,5-trimethyl- or 1,3,5-trimethoxy-benzene (ArH) gave the diarylamines expected from nitrene ‘insertions’ at nuclear CH bonds (ArFN3 + ArH→ArFNHAr + N2); product yields in the cases of the perfluorinated azides are the highest ever recorded for this type of reaction. By contrast, no recognisable products were obtained when either perfluoro-(2-azido-4-isopropylpyridine) or 2-azido- 4-chlorotrifluoropyridine were decomposed thermally in 1,3,5-trimethylbenzene. 相似文献
115.
The energy levels of a series of para substituted N,N-dimethylanilines p-MHnMe3?n C6H4NMe2 (n = 0?3, M = C or Si) for the ground and lower lying excited states have been determined in acetonitrile solution. The levels for the carbon compounds are all slightly destailized relative to N,N-dimethylaniline and the effects are rather insensitive to n. The stabilizations produced by silicon substituents on all levels are markedly affected by silicon's substituents, showing increasing perturbations with increasing n. It is concluded that variations in the interaction of the σ* system of the silyl substituent with the aniline π system, and not d orbital interactions, account for the trends observed. 相似文献
116.
The reactions of perfluoroalkyl- and perfluoroacyl-iminosulfur difluorides with chlorine monofluoride result in the preparation of perfluoroalkyldichloroamines and a new class of compounds N,N-dichloroperfluoroamides, RfC(O)NCl2, via the elimination of SF4. The amides, FC(O)NCl2 and CF3C(O)NCl2, in addition to 1,2-bis-(dichloroamino)tetrafluoroethane, Cl2NCF2CF2NCl2, are reported and characterized. The reactions of CIF with other sulfur(IV) imines proceed in an analogous manner to form perfluoroalkyl-dichloroamines via the elimination of the corresponding sulfur(IV) fluoride. 相似文献
117.
Alginate beads containing entrapped DNA were produced using both external and internal calcium sources, and coated with chitosan
or poly-l-lysine membranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level
of DNA protection fromnucleic acid hydrolysis, simulating gastrointestinal exposure. A method was developed to extract and
assay intracapsular DNA through a modified agarose electrophoresis system. Both external and internally gelled beads were
permeable to DNase (Mw=31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic
content alginate beads offered a higher level of DNA protection compared with coated beads with low guluronic alginate. No
apparent correlation was found with chitosan membrane molecular weight and degree of deacetylation; however, increasing poly-l-lysine molecular weight appeared to increase DNase exclusion from beads. At elevated levels of DNase exposure, DNA hydrolysis
was evident within all coated beads with the exception of those coated with the highest molecular weight poly-l-lysine (Mw=197.1 kDa), which provided almost total nuclease protection. Optimal combination then for DNA protection from nucleases is
a high guluronic alginate core, coated with high molecular weight poly-l-lysine. 相似文献
118.
119.
Sodium [2-13C,2-2H3]acetate was incorporated into cytochalasin B( 1 ) by Phoma exigua and into cytochalasin D ( 2 ) by Zygosporium masonii. The 13C-NMR. and 2H-NMR. of the metabolites showed that most of the deuterium was lost except at carbon atoms which are in polyketide chain-initiating units. 相似文献
120.
A palladium-catalysed four-component process is described involving carbon monoxide, allene and aryl/heteroaryl iodides generating (π-allyl) palladium species, which are intercepted by alkene tethered nitrogen nucleophiles to afford 1,6- and 1,7-dienones. Subsequent ring closing metathesis affords five- and six-membered N-heterocyclic enones. The N-heterocyclic enones are active dipolarophiles in 1,3-dipolar cycloaddition reactions as exemplified by azomethine ylide and nitrone cycloadditions. 相似文献