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241.
It is shown by means of a model that the renormalization and unitary gauges can be connected by a point transformation, and this fact is used to construct a formal proof of renormalization in the unitary gauge. The formal proof is then verified by demonstrating that for a fourth-order on-shell scattering process the S-matrix calculated directly in the unitary gauge is exactly equal to that calculated in the renormalization gauge. The calculation is refined to the point where it becomes purely graphical and this allows one to see by inspection how the cancellation of divergences occurs in the unitary gauge. The model considered here is Abelian, but it will be generalized to the non-Abelian case subsequently. 相似文献
242.
243.
To elucidate the reasons underlying the poor penetration of non-viral vectors in tissues, relating transport properties to
physico-chemical parameters of vectors may be crucial. These properties can be influenced by the presence of multiples labels
that are used. Therefore utilizing a vector with minimum of labels preferably not more than one is important to studying penetration
in tissues. The cell impermeant bisintercalating dye YOYO-1 was found suitable to both monitor the formation of complexes
between DNA and an amphipathic peptide LK15 and, to track their penetration in HCT116 spheroids by confocal microscopy. The
results revealed a limited decrease of fluorescence ascribed to the high affinity of YOYO-1 to bind DNA. The residual fluorescence
of complexes can be exploited to monitor penetration into spheroids, after correction for YOYO-1 attenuation, and to revealing
hyaluronidase-induced reduced binding. Hence high affinity dyes such as YOYO-1 with inefficiently quenched fluorescence may
be important to establish a relation between novel medicines characteristics and penetration in tissues. 相似文献
244.
Marijke WA de Backer Maike AD Brans Mieneke CM Luijendijk Keith M Garner Dianne MA van den Heuvel R Jeroen Pasterkamp Roger AH Adan 《BMC neuroscience》2010,11(1):94
Background
Multiple neuropeptides, sometimes with opposing functions, can be produced from one precursor gene. To study the roles of the different neuropeptides encoded by one large precursor we developed a method to overexpress minigenes and establish local secretion. 相似文献245.
A simple and sensitive method for the speciation of vanadium(III), (IV), and (V) was developed by using high performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICPMS). The EDTA-complexed vanadium species were separated on a strong anion exchange column with an eluent containing 2 mM EDTA, 3% acetonitrile, and 80 mM ammonium bicarbonate at pH 6. Each analysis was complete in 5 min. The detection limits were 0.6, 0.7 and 1.0 μg L−1 for V(III), V(IV), and V(V), respectively. The method was applied to coke pore water samples from an oilsand processing/upgrading site in Fort McMurray, Alberta, Canada and to Shewanella putrefaciens CN32 bacterial cultures incubated with V(V). In the coke pore water samples, V(IV) and V(V) were found to be the major species. For the first time, V(III) was detected in the bacterial cultures incubated with V(V). 相似文献
246.
R. T. Pardasani P. Pardasani C. K. Ojha D. Sherry V. Chaturvedi I. Sharma 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2435-2443
The condensation of 1,2- and 1,4-diketones with thiohydantoins to give tetrahydroquinodimethane and isatylidene derivatives respectively is described which may act as potential precursors for indigoid dyes as well as bioactive compounds. The synthesized compounds have been characterized by elemental analyses, spectral studies as well as by molecular modelling using PC WIN model. In addition, the newly synthesized products have been screened for antimicrobial activity. 相似文献
247.
Nordqvist A Björkelid C Andaloussi M Jansson AM Mowbray SL Karlén A Larhed M 《The Journal of organic chemistry》2011,76(21):8986-8998
Cinnamaldehyde derivatives were synthesized in good to excellent yields in one step by a mild and selective, base-free palladium(II)-catalyzed oxidative Heck reaction starting from acrolein and various arylboronic acids. Prepared α,β-unsaturated aldehydes were used for synthesis of novel α-aryl substituted fosmidomycin analogues, which were evaluated for their inhibition of Mycobacterium tuberculosis 1-deoxy-D-xylulose 5-phosphate reductoisomerase. IC(50) values between 0.8 and 27.3 μM were measured. The best compound showed activity comparable to that of the most potent previously reported α-aryl substituted fosmidomycin-class inhibitor. 相似文献
248.
Carney CE Tran AD Wang J Schabel MC Sherry AD Woods M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10372-10378
LnDOTA-tetraamide chelates (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) have received considerable recent attention as a result of their potential to act as PARACEST contrast agents for magnetic resonance imaging (MRI). Although PARACEST agents afford several advantages over conventional contrast agents they suffer from substantially higher detection limits; thus, improving the effectiveness of LnDOTA-tetraamide chelates is an important goal. In this study we investigate the potential to extend conformational control of LnDOTA-type ligands to those applicable to PARACEST. Furthermore, the question of whether δ- rather than α-substitution of the pendant arms could be used to control the chelate coordination geometry is addressed. Although δ-substitution does influence coordination geometry it does not afford control. However, it can play an important role in governing the conformation of the amide substituent relative to the chelate in such as way that suggests a PARACEST agent could be designed that has detection limits at least as low as a conventional MRI contrast agent. 相似文献
249.
An atmospheric ion lens incorporated into an electrospray ion source for capillary electrophoresis-mass spectrometry (CE-MS) is found to extend the stable operational regions for both flow rates and electrospray ionization (ESI) voltages. The stable operating conditions for the ESI source with and without the ion lens were characterized. The results showed that the stable operation region was widest when the voltage difference between the sprayer and the ion lens ranges from 2.6 to 2.8 kV, and under these condition, the CE-MS interface can be adapted to a broader range of electroosmotic and modifier flow rates. Modeling of the electric field in the electrospray ion source with the ion lens suggests that the extension of the stable region is attributed to the flatter equipotential surfaces around the sprayer tip and higher electric field strengths in the rest of the interface region. 相似文献
250.
Chemler SR 《Journal of organometallic chemistry》2011,696(1):150-158
Copper(II) carboxylates and chiral copper(II) triflate·bis(oxazoline) complexes promote and catalyze intramolecular alkene carboamination, diamination and aminooxygenation reactions, creating an array of nitrogen heterocycles. High diastereoselectivity and enantioselectivity can be achieved in these transformations. This account reviews the discovery and development of these useful and interesting reactions. 相似文献