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121.
CIDNP in the photolysis of tetrafluoro-1,4-benzoquinone was studied by using plane polarized light for excitation. Experiments show that the magnitude of CIDNP depends upon the polarization of the excitation light and thus provides evidence for the phototriplet mechanism in the initial electron spin polarization which subsequently leads to nuclear polarization by cross relaxation. 相似文献
122.
A well-developed classical theory is available for constant-voltage electrical field flow fractionation (EFFF). Recent experimental research, however, has demonstrated that pulsed fields may enhance retention in some cases. A generalized mathematical approach is presented for the prediction of retention ratios for any field type, pulsed or constant. The methodology is applied and demonstrated for a square wave protocol. Complex concentration profiles arise wherein particles are focused either towards the walls or into the channel center. The computational results indicate that pulsation can either increase retention time or decrease retention time by manipulating the effective electric field and suggest that separation resolution may also be improved. 相似文献
123.
Dr. Piyush K. Jain Vyas Ramanan Dr. Arnout G. Schepers Nisha S. Dalvie Apekshya Panda Dr. Heather E. Fleming Prof. Sangeeta N. Bhatia 《Angewandte Chemie (International ed. in English)》2016,55(40):12440-12444
The ability to remotely trigger CRISPR/Cas9 activity would enable new strategies to study cellular events with greater precision and complexity. In this work, we have developed a method to photocage the activity of the guide RNA called “CRISPR‐plus” (CRISPR‐precise light‐mediated unveiling of sgRNAs). The photoactivation capability of our CRISPR‐plus method is compatible with the simultaneous targeting of multiple DNA sequences and supports numerous modifications that can enable guide RNA labeling for use in imaging and mechanistic investigations. 相似文献
124.
Banerjee M Vyas VS Lindeman SV Rathore R 《Chemical communications (Cambridge, England)》2008,(16):1889-1891
A practical synthesis of 1,3,6,8-tetraisopropylpyrene and the isolation and X-ray structural characterization of its monomeric cation radical salt are described. 相似文献
125.
Vyas S Ali ME Hossain E Patwardhan S Datta SN 《The journal of physical chemistry. A》2005,109(19):4213-4215
We show that an ethylenic coupler provides a very strong intramolecular magnetic interaction. A recently synthesized nitronyl nitroxide derivative, D-NIT2, is investigated by ab initio quantum chemical methods. The broken symmetry approach yields a coupling constant -541 K that is in good agreement with the observed value in solid state. 相似文献
126.
Saulnier MG Langley DR Frennesson DB Long BH Huang S Gao Q Wu D Fairchild CR Ruediger E Zimmermann K St Laurent DR Balasubramanian BN Vyas DM 《Organic letters》2005,7(7):1271-1274
[reaction: see text] Both 6'- and 4'-fluoro-glycosylated indolo[2,3-a]carbazoles are substrates for base-induced loss of fluorine as a leaving group from sp3 carbon. In the case of alpha-N-glycosylated substrate 3, loss of fluorine from the 6'-position leads to 3,6-anhydroglucose analogue 1. A novel N12,N13-bridged sugar analogue 2 results from loss of 4'-fluorine from beta-N-glycosylated analogue 4. Both analogues 1 and 2 display topo I inhibitory potencies similar to camptothecin. 相似文献
127.
Investigations into the transition metal catalyzed aziridination of olefins with Bromamine-T as a new source of nitrene is presented in this account. Comparison of Chloramine-T and Bromamine-T in this reaction indicates that the latter is superior as the source of nitrene. Systematic study with several transition metal based catalysts suggests that Cu-halides are the best catalysts. A first report of aziridination under microwave and ultrasound irradiation conditions is also presented. Copper-catalyzed aziridination of methyl cinnamate with Bromamine-T did not proceed at ambient temperature but was effected smoothly under ultrasound irradiation to furnish trans-aziridine selectively, while under microwave irradiation, a mixture of cis and trans isomers, was obtained. It has been demonstrated that aziridination of olefins proceeds smoothly with inexpensive bleaching powder. Preliminary results of Rh-catalyzed benzylic insertion reactions with Bromamine-T are included in this account. 相似文献
128.
Himatkumar V. Patel Kavita A. Vyas Sudhanshu P. Pandey Francis Tavares P. S. Fernandes 《合成通讯》2013,43(18-19):1935-1940
A one-pot synthesis of 5,6-disubstituted-2-phenyl-3(2H)-pyridazinones 4 is achieved on treatment of carbanion of ethyl trimethlsiylacetate with phenylhydrazones of 1,2-dicarbonyl compounds 1. 相似文献
129.
In this work, de-watered cellulose pulp(DCP), obtained from a paper mill, have been acid-hydrolyzed to yield cellulose nano-whiskers (CNWs). As revealed from FESEM measurements, these CNW were found to possess a median length of 258.5 nm, diameter of 35.2 nm, and an aspect ratio of 7.3. The CNWs were also characterized by TGA, XRD and FTIR analysis. The CNWs were found to possess a fairly high Crystallinity Index (CI) of 0.925. The addition of cellulose at low concentration range, i.e., from 25 to 125 mg (nearly 1.25 to 6.25 weight percent of polymer sodium acrylate) caused an enhancement in water uptake of resulting hydrogels .The CNWs-loaded poly(SA) hydrogels showed chain relaxation controlled swelling in the medium of pH 7.4 as was confirmed from the swelling exponent ‘n’ values obtained using power function law‥ The second order kinetic model was found to fit well to the kinetic water uptake data. However, all the samples, when prepared in the form of films, did not show any remarkable increase in their mechanical strength. 相似文献
130.