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81.
The classical and quantum mechanics of a system of directly interacting relativistic particles is discussed. We first discuss
the spin-zero case, where we basically follow Rohrlich in introducing a set of covariant centre of mass (CM) and relative
variables. The relation of these to the classic formulation of Bakamjian and Thomas is also discussed. We also discuss the
important case of relativistic potentials which may depend on total four-momentum squared. We then consider the quantum mechanical
case of spin-half particles. The negative energy difficulty is solved by introducing a number of first class constraints which
fix the spinor structure of physical solutions and ensure the existence of proper CM and relative variables. We derive the
form of interactions consistent with Lorentz invariance, space inversion, time reversal and charge conjugation and with the
above mentioned first class constraints and find that it is analogous to that for the non-relativistic case. Finally the relationship
of the present work with some previous work is briefly discussed. 相似文献
82.
Maragoni Venkatesham Dasari Ayodhya Alle Madhusudhan Amrutham Santoshi Kumari Guttena Veerabhadram Kotu Girija Mangatayaru 《Journal of Cluster Science》2014,25(2):409-422
Stable silver nanoparticles have been synthesized using gum karaya acting as both reducing and stabilizing agent without using any synthetic reagent. The reaction is performed using water, which is an environmentally safe solvent. This reaction was carried out in an autoclave at a pressure of 15 psi and 120 °C temperature by varying the time. The influence of different parameters such as time, change of concentration of silver nitrate and concentration of gum karaya on the formation of silver nanoparticles has been studied. The synthesized silver nanoparticles are characterized by UV–Vis spectroscopy, FTIR, XRD and TEM. UV–Vis analysis of the sample confirmed the formation of silver nanoparticles exhibiting a sharp peak at a wavelength of 420 nm. TEM micrographs showed the formation of well-dispersed silver nanoparticles of size 2–4 nm. The antimicrobial activity of silver nanoparticles stabilized in gum karaya is tested against Escherichia coli, Micrococcus luteus and is found to be possessing inhibiting property. The silver nanoparticles stabilized in gum karaya exhibited very good catalytic activity and the kinetics of the reaction was found to be pseudo first order with respect to the 4-nitrophenol. 相似文献
83.
S. Sarkar A. D. Thakur C. V. Tomy G. Balakrishnan D. McK Paul S. Ramakrishnan A. K. Grover 《Pramana》2006,66(1):193-207
New experimental data are presented on the scan rate dependence of the magnetization hysteresis width ΔM(H) (∞ critical current densityJ
c(H)) in isothermalMH scans in a weakly pinned single crystal of Ca3Rh4Sn13, which displays second magnetization peak (SMP) anomaly as distinct from the peak effect (PE). We observe an interesting
modulation in the field dependence of a parameter which purports to measure the dynamical annealing of the disordered bundles
of vortices injected through the sample edges towards the destined equilibrium vortex state at a givenH. These data, in conjunction with the earlier observations made while studying the thermomagnetic history dependence inJ
c(H) in the tracing of the minor hysteresis loops, imply that the partially disordered state heals towards the more ordered state
between the peak field of the SMP anomaly and the onset field of the PE. The vortex phase diagram in the given crystal of
Ca3Rh4Sn13 has been updated in the context of the notion of the phase coexistence of the ordered and disordered regions between the
onset field of the SMP anomaly and the spinodal line located just prior to the irreversibility line. A multi-critical point
and a critical point in the (H,T) region of the Bragg glass phase have been marked in this phase diagram and the observed behavior is discussed in the light
of recent data on multi-critical point in the vortex phase diagram in a single crystal of Nb. 相似文献
84.
The reaction of [Cp*MoCl(4)] with an excess of LiBH(4), followed by thermolysis with tellurium powder in toluene, afforded a tricapped cubane cluster, [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (1), which represents an unprecedented metal-rich metallaborane cluster with a cubane core containing 58 cluster valence electrons (cve) and three metal-metal bonds. 相似文献
85.
R. Parimala R. Sridharan Maneesh L. Thakur 《Transactions of the American Mathematical Society》1998,350(3):1277-1284
Let be a field whose characteristic is different from 2 and 3 and let be a quadratic extension. In this paper we prove that for a fixed, degree 3 central simple algebra over with an involution of the second kind over , the Jordan algebra , obtained through Tits' second construction is determined up to isomorphism by the class of in , thus settling a question raised by Petersson and Racine. As a consequence, we derive a ``Skolem Noether' type theorem for Albert algebras. We also show that the cohomological invariants determine the isomorphism class of , if is fixed.
86.
Venkata Naresh Vema Y. Bharathi Kumari Sridhar Musulla Rama Krishnam Raju Addada Srinivasa Rao Alapati 《Tetrahedron letters》2019,60(14):986-988
A concise total synthesis of (3R),(5R)-5-hydroxy-de-O-methyllasiodiplodin and its epimer have been synthesized from commercially available (R)-propylene oxide and Orsellinic acid as starting materials. The key steps involved in the synthesis are Wittig reaction, epoxide ring opening with 1,3-dithiane intermediate and Yamaguchi macrolactonization. 相似文献
87.
Neeraj Sharma Meena Kumari Reena Sharma 《Journal of Thermal Analysis and Calorimetry》2012,107(1):225-229
The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C6H5C(O)NHO)] (I), [VO(C6H5C(O)NHO)2] (II), [VO(acac)(4-ClC6H4C(O)NHO)] (III), [VO(4-ClC6H4C(O)NHO)2] (IV) (where acac = (CH3COCHCOCH3
–) synthesized from the reactions of VO(acac)2 with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent
medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in
single step to yield VO2 as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability
for the complexes has been inferred as IV > I > III > II. 相似文献
88.
The solvent extraction behavior of multiple proton ionizable p-tert-butylcalix[4]arene and [6]arene carboxylic acid derivatives towards indium has been investigated along with an acyclic monomeric analogue from weakly acidic media into chloroform. The extraction mechanism is ion exchange and carboxylic acid groups are adequate ligating sites for extraction. The cyclic structure of calixarene ligands to accommodate the potential guest species and the cooperativity effect of multifunctional groups significantly affect the complexation behavior and calixarene derivatives are found to be excellent extractants over the monomeric analogue. The composition of the extracted complex depends on the solution pH and attempts to determine the composition of the extracted complex for the extraction of indium have been stymied by complications arising from the formation of polynuclear species of indium and bridged polymeric species of calixarene carboxylic acid derivatives. One mole of calix[4]arene derivative extracts 2.5 moles of indium whereas the calix[6]arene derivative tends to extract 4.0 moles of indium. The loaded indium is back extracted with 1 mol dm(-3) hydrochloric acid solution. Though quantitative back extraction of indium was achieved from the fully loaded calix[6]arene derivative, it was only achieved up to 85% in the case of the calix[4]arene derivative. 相似文献
89.
Navjeet Kaur Neha Ahlawat Pranshu Bhardwaj Yamini Verma Pooja Grewal Nirmala Kumari Jangid 《合成通讯》2020,50(6):753-795
AbstractOne of the highly emerging and an important aspect of organic chemistry is the metal catalyzed synthesis of heterocycles. The methods used earlier for the synthesis of heterocycles were significant in the organic synthesis and developing cost-effective, improved and facial methods were beneficial to construct the complex architectures. For the both stereoselective and regioselective synthesis of six-membered nitrogen containing heterocycles, cyclic reactions that are Ag-mediated have known to be very efficient. The present review covers the applications of Ag in the formation of six-membered nitrogen containing heterocycles. 相似文献
90.
Surgical sutures are probably the most widely used medical devices in healthcare applications for wound closure. During their application, sutures may be exposed to microorganisms present in the environment leading to bacterial biofilm formation, and thereon to surgical site infections. The physicochemical characteristics of the polymeric substrate play a major role in directing the behavior of the suture in a biological milieu. In such a context, it is necessary to develop sutures which actively repel and inhibit bacterial adherence and colonization on their surfaces. Drug eluting sutures have been proposed as a solution to this dilemma. Currently, bioactive agents (natural or synthetic) are being incorporated in polymeric materials via various methods including blending and compounding, surface functionalization and conjugation, and coating to render antimicrobial surgical sutures. However, each of these methods has its own pros and cons. Depending upon the nature of the substrate, an appropriate processing technique has to be chosen. In this article, we review the recent state-of-the-art developments and strategies in antimicrobial surgical suture fabrication. The efficacy and mechanism of these sutures in controlling infection is critically analyzed. However, such bioactive agent incorporated sutures have to be tested in clinically randomized trials to accurately gauze their applicability in a surgical setting. Presently, very few antimicrobial surgical sutures are available commercially. Therefore, there is a great scope for market development in this area. 相似文献