Infrared Divergences in Light Front Field Theory and Coherent State Formalism

We discuss fermion self energy correction in light front QED using a coherent state basis. We show that if one uses coherent state basis instead of fock basis to calculate the transition matrix elements the true infrared divergences in δ m ² get canceled up to O(e ⁴). We show this in Light-front as well as in Feynman gauge.     

Ultrasonic and conductometric studies of NaCl solutions and study of ionicity of the liquid solution through the Walden plot and various ultrasonic parameters

Journal of Thermal Analysis and Calorimetry - In this paper, the thermo-physical and hydrodynamic properties of heat transfer nanofluids containing metal nanoparticles-decorated multi-wall carbon...     

Push–Pull Porphyrins via β-Pyrrole Functionalization: Evidence of Excited State Events Leading to High-Potential Charge-Separated States

A new set of free-base and zinc(II)-metallated, β-pyrrole-functionalized unsymmetrical push–pull porphyrins were designed and synthesized via β-mono- and dibrominated tetraphenylporphyrins using Sonogashira cross-coupling reactions. The ability of donors and acceptors on the push–pull porphyrins to produce high-potential charge separated states was investigated. The porphyrins were functionalized at the opposite β,β′-pyrrole positions of porphyrin ring bearing triphenylamine push groups and naphthalimide pull groups. Systematic studies involving optical absorption, steady-state and time-resolved emission revealed existence of intramolecular type interactions both in the ground and excited states. The push–pull nature of the molecular systems was supported by frontier orbitals generated on optimized structures, wherein delocalization of HOMO over the push group and LUMO over the pull group connecting the porphyrin π-system was witnessed. Electrochemical studies were performed to visualize the effect of push and pull groups on the overall redox potentials of the porphyrins. Spectroelectrochemical studies combined with frontier orbitals helped in characterizing the one-electron oxidized and reduced porphyrins. Finally, by performing transient absorption studies in polar benzonitrile, the ability of push–pull porphyrins to produce charge-separated states upon photoexcitation was confirmed and the measured rates were in the range of 10⁹ s⁻¹. The lifetime of the final charge separated state was around 5 ns. This study ascertains the importance of push–pull porphyrins in solar energy conversion and diverse optoelectronic applications, for which high-potential charge-separated states are warranted.     

Evaluation of a Novel Dechlorination Reaction as an Analytically Useful Derivatization Reaction Part 1. Stoichiometry,Mechanism and Yield Optimization

Abstract

A novel reaction for the dechlorination of polychlorinated biphenyls (PCBs) as well as most other chlorinated aromatic and aliphatic compounds is evaluated and discussed in terms of its potential for analytical purposes. The active dechlorinating agent is prepared through the reaction of molten sodium or potassium with polyethylene glycols (MW >200), in the absence of oxygen, to form the corresponding alkali metal glycolate, a powerful nucleophilic agent. Special emphasis is given to the mechanistic aspects of the reaction and their importance in terms of achieving high and reproducible yields with analytical quantities of substrate, in short periods of time. The contribution of the techniques: ESR, NMR, IR, UV, MS, GC-ECD, LC-EC, CIDNP-NMR, conductimetry and chloride analysis (amperometric) in elucidating the reaction mechanism and providing valuable kinetic data is illustrated. This reaction can potentially be applied to the determination of PCBs in waste oils.     

Size dependent structural and magnetic behaviour of CaFe2O4

CaFe₂O₄ nanocrystalline powders were synthesized through sol–gel treatment in which the stoichiometric mixing of various nitrates involving calcium and iron in presence of citric acid was performed. Subsequently, the as prepared sample was annealed at various temperatures in order to obtain the fine distribution of size including the bulk counterpart. The samples were then characterized using powder X-ray diffraction followed by ⁵⁷Fe Mössbauer spectroscopy, SQUID as well as vibrating sample magnetometry. The results of spectroanalyses revealed that the samples were formed in single phase cubic spinel structure and exhibits room temperature superparamagnetism, except the bulk one, which crystallizes in characteristic orthorhombic structure of CaFe₂O₄ and displays trivial coercivity and remanent magnetization at room temperature.     

Going Off the Grid: Iterative Model Selection for Biclustered Matrix Completion

We consider the problem of performing matrix completion with side information on row-by-row and column-by-column similarities. We build upon recent proposals for matrix estimation with smoothness constraints with respect to row and column graphs. We present a novel iterative procedure for directly minimizing an information criterion to select an appropriate amount of row and column smoothing, namely, to perform model selection. We also discuss how to exploit the special structure of the problem to scale up the estimation and model selection procedure via the Hutchinson estimator, combined with a stochastic Quasi-Newton approach. Supplementary material for this article is available online.     

Ni(II) and Cu(II) complexes of bidentate thiosemicarbazone ligand: Synthesis,structural, theoretical,biological studies and molecular modeling

The conventional condensation and refluxing process was employed to synthesize Ni(II) and Cu(II) complexes of Methylcarbamatethiosemicarbazone ligand. Reactions were carried out at the pH of 7. The molar ratio of the ligand and metal salt was 2:1. The structures of the synthesized metal complexes were suggested by different analytical techniques such as magnetic susceptibility, molar conductance, IR, EPR and UV spectroscopy. Experimental studies confirmed the octahedral geometry for all the complexes. The geometry of the ligand and complexes were also confirmed by theoretical studies. The complexes were investigated for biological action against pathogenic fungi (C. krusei, C. albican) and bacteria (S. aureus, E. coli). The antimicrobial results confirmed superior inhibition potential of the metal complexes as compared with the parent ligand. The enhanced antimicrobial activities might be due to the chelation. Molecular-docking assays confirmed the strong interaction of ligand with target antimicrobial protein DNA gyrase-B.