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21.
22.
Ramdas S. Pathare Shivani Sharma Kandasamy Gopal Devesh M. Sawant Ram T. Pardasani 《Tetrahedron letters》2017,58(14):1387-1389
An efficient one-pot protocol for the synthesis of multi-substituted 2-pyrone derivatives from internal alkynes and unactivated alkenes is reported. The methodology involves difunctionalization of internal alkynes by using Pd(II) as a catalyst alongwith X-Phos as ligand via 6-endo transesterification and subsequent alkenylation pathway. Notable features include simple and easily available starting materials, including a range of unactivated alkenes, reduced synthetic steps and mild reaction conditions with high efficiency. 相似文献
23.
Munish Puri Shivani Gupta Parveen Pahuja Aneet Kaur J. R. Kanwar J. F. Kennedy 《Applied biochemistry and biotechnology》2010,160(1):98-108
β-D-galactosidase (EC 3.2.1.23) from Kluyveromyces marxianus YW-1, an isolate from whey, has been studied in terms of cell disruption to liberate the useful enzyme. The enzyme produced
in a bioreactor on a wheat bran medium has been successfully immobilized with a view to developing a commercially usable technology
for lactose hydrolysis in the food industry. Three chemical and three physical methods of cell disruption were tested and
a method of grinding with river sand was found to give highest enzyme activity (720 U). The enzyme was covalently immobilized
on gelatin. Immobilized enzyme had optimum pH and temperature of 7.0 and 40 °C, respectively and was found to give 49% hydrolysis
of lactose in milk after 4 h of incubation. The immobilized enzyme was used for eight hydrolysis batches without appreciable
loss in activity. The retention of high catalytic activity compared with the losses experienced with several previously reported
immobilized versions of the enzyme is significant. The method of immobilization is simple, effective, and can be used for
the immobilization of other enzymes. 相似文献
24.
Atenolol and propranolol (the β-blocking agents) and salbutamol (broncho- and vasodilator) were resolved into their enantiomers by adopting different modes of loading/impregnating the Cu(II) complexes of l-proline (l-Pro), l-phenylalanine (l-Phe), l-histidine (l-His), N,N-dimethyl-l-phenylalanine (N,N-Me2-l-Phe), and l-tryptophan (l-Trp) on commercial precoated normal phase plates. The three different approaches were (A) using the Cu(II)-l-amino acid complex as chiral mobile phase additive, (B) ascending development of plain commercial plates in the solutions of Cu complex, and (C) using a solution of Cu(II) acetate as mobile phase additive for the commercial TLC plates impregnated with ascending development of plates in the solutions of amino acid. Spots were located using iodine vapour. The results obtained for the three methods have been compared for their efficiency and the issue of involvement of the Cu(II) cation for the best performance of the three methods has been discussed with respect to the same mobile phase. The detection limit is 0.18 μg for each enantiomer. 相似文献
25.
The Er3+ -Yb3+ codoped in Li2O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion
luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( 4S3/2→4I15/2) and red emission peak at 670 nm ( 4F9/2→4I15/2) of Er3+ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum
result revealed that an important role of WO3 in the formation of glass network linkage with Li2O. Under this influence estimated lifetime of the 4I11/2 of Er3+ was 1.89 μs and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er2O3 concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission.
Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and
analyze the possible upconversion mechanism and process. 相似文献
26.
It is shown that a vorticity, constructed from the spin field of a quantum spinning plasma, combines with the classical generalized vorticity (representing the magnetic and the velocity fields) to yield a new grand generalized vorticity that obeys the standard vortex dynamics. Expressions for the quantum or spin vorticity and for the resulting generalized helicity invariant are derived. Reduction of the rather complex spinning quantum system to a well known and highly investigated classical form opens familiar channels for the delineation of physics peculiar to dense plasmas spanning solid state to astrophysical objects. A simple example is worked out to show that the magnetics of a spinning plasma can be much richer than that of the corresponding classical system. 相似文献
27.
We consider a parametrization of the lepton mixing matrix in which the deviations from maximal atmospheric mixing and vanishing reactor mixing are obtained in terms of small corrections from the charged lepton sector. Relatively large deviations for the reactor mixing angle from zero as indicated by T2K experiment can be obtained in this parametrization. We are able to further reduce the number of complex phases, thus, simplifying the analysis. In addition, we have obtained the sides of unitarity triangles and the vacuum oscillation probabilities in this parametrization. The Jarlskog rephasing invariant measure of CP violation at the leading order has a single phase difference which can be identified as Dirac-type CP violating phase in this parametrization. 相似文献
28.
Eleven chiral derivatizing reagents (CDRs) were used for preparation of diastereomers of (R,S)‐mexiletine containing a primary amino group in close proximity to the stereogenic center. One anhydride, namely [(S,S)‐O,O'‐di‐p‐toluoyl tartaric acid anhydride] was synthesized and (S)‐naproxen was used as such as the chiral derivatizing reagent. The other nine CDRs were synthesized by substituting one of the fluorine atoms in 1,5‐difluoro‐2,4‐dinitrobenzene with six amino acid amides and three amino acids. The diastereomers were separated by reversed‐phase high‐performance liquid chromatography. The method was validated for linearity, accuracy, limit of detection and limit of quantification. The limit of detection was found in the range of 10–30 pmol. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
29.
New series of phenylantimony chloride and antimony chloride with Schiff base ligands, L1H and L2H having N∩S and N∩O donor systems were synthesized under microwave irradiation using a domestic microwave oven. The reaction time was brought down from hours to a few seconds with improved yield as compared with conventional heating. All the ligands and their antimony(III) derivatives were characterized on the basis of microanalysis, elemental analyses, molecular weight determinations and spectral studies including IR, NMR (1H and 13C) and electronic spectral studies. A distorted trigonal bipyramidal and pseudo‐octahedral geometry around the antimony atom was tentatively proposed for these derivatives. The compounds were screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility properties. The treatment with the ligands and their phenylantimony derivatives at dose levels of 20 mg per rat per day did not cause any significant change in body weight, but a significant reduction in the weights of reproductive organs was observed. Arrest of spermatogenesis was noted at various stages with production of primary spermatocytes (preleptotene and pachytene), secondary spermatocytes and step‐19 spermatids found to be decreased. Biochemical parameters of tissues, i.e. protein, sialic acid, cholesterol content of testes and seminal vesicular fructose also showed significant reduction. Further, the serum testosterone concentrations were also decreased after treatment with ligands and their antimony(III) derivatives. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
30.
S. Mahajan W. Ito C. H. Cho T. Morishita 《Physica C: Superconductivity and its Applications》1994,220(3-4):227-232
We report on the fabrication and characteristics of sandwich-type tunnel junctions with highly crystalline sputtered a-axis oriented thin film of Y1Ba2Cu3O7-x (YBC) as the base and the counter electrode. The junctions have been fabricated on SrTiO3 (100) and MgO (100) substrates. A non-superconducting phase of YBC corresponding to a lattice constant of 4.08 Å is used as the barrier layer making this an all YBC sandwich junction. For all temperatures below Tce (R=0) of the device, a zero voltage current was observed. The critical current density (Jc) of the device was found to be dependent on the thickness of the barrier layer and the crystallinity of the a-axis oriented YBC electrodes. At 40 K, such a junction fabricated on a SrTiO3 (100) substrate was found to have a Jc of 1.8 X 104 A/cm2 and an IcRn product of 0.2 mV. 相似文献