Towards the higher solubility and thermal stability of poly(aniline-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-bromoaniline)

In the current study, we have described the synthesis and the physical properties of poly(aniline-co-m-bromoaniline) conducting copolymers. The copolymers of different composition are essentially obtained by varying the molar feed ratio of the two monomers. The higher solubility of the copolymers could be procured as compared to polyaniline (PA) in different solvents. The electrical conductivity has been studied by two-probe method; at room temperature, the conductivity of the copolymer decreases upon increasing the molar ratio of m-bromoaniline monomer. The introduction of bromine (–Br) group reduces the degree of conjugation in the polymer chain. Thus, conduction of electrons is prohibited along the conjugated system. In the thermogravimetric analysis (TGA), a three-stage decomposition of the copolymer has been observed. The copolymers of poly(aniline-co-m-bromoaniline) are thermally stable at high temperature. The composition of the copolymer has been confirmed from the binding energies of C–C, C–N, and C–Br in the XPS study.     

Technical evaluation of in vivo abdominal fat and IMCL quantification using MRI and MRSI at 3 T

OBJECTIVES: The objectives of this study were to develop protocols that measure abdominal fat and calf muscle lipids with magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), respectively, at 3 T and to examine the correlation between these parameters and insulin sensitivity. MATERIALS AND METHODS: Ten nondiabetic subjects [five insulin-sensitive (IS) subjects and five insulin-resistant (IR) subjects] were scanned at 3 T. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were segmented semiautomatically from abdominal imaging. Intramyocellular lipids (IMCL) in calf muscles were quantified with single-voxel MRS in both soleus and tibialis anterior muscles and with magnetic resonance spectroscopic imaging (MRSI). RESULTS: The average coefficient of variation (CV) of VAT/(VAT+SAT) was 5.2%. The interoperator CV was 1.1% and 5.3% for SAT and VAT estimates, respectively. The CV of IMCL was 13.7% in soleus, 11.9% in tibialis anterior and 2.9% with MRSI. IMCL based on MRSI (3.8+/-1.2%) were significantly inversely correlated with glucose disposal rate, as measured by a hyperinsulinemic-euglycemic clamp. VAT volume correlated significantly with IMCL. IMCL based on MRSI for IR subjects was significantly greater than that for IS subjects (4.5+/-0.9% vs. 2.8+/-0.5%, P=.02). CONCLUSION: MRI and MRS techniques provide a robust noninvasive measurement of abdominal fat and muscle IMCL, which are correlated with insulin action in humans.     

Lorentz-Lorenz expression as a new analytical constant for fats (ghee) and oils

Zusammenfassung Der Farbstoff Fast Grey R.A. hat sich als empfindliches Reagens für die colorimetrische Mikrobestimmung von Zirkonium erwiesen. Man kann Zr-Konzentrationen zwischen 0,02 und 8 ppm bei einer Wellenlänge von 570 m bestimmen. Störend wirken u. a. die Kationen Cu²⁺, Ni²⁺ und Fe³⁺. Ascorbinsäure beseitigt jedoch die störende Wirkung nicht zu großer Mengen Eisen. U, Co, Al, Th, Bi, Zn, die Alkalien und die Seltenen Erden stören nicht.     

Strong communication complexity or generating quasi-random sequences from two communicating semi-random sources

The semi-random source, defined by Sántha and Vazirani, is a general mathematical mode for imperfect and correlated sources of randomness (physical sources such as noise dicdes). In this paper an algorithm is presented which efficiently generates “high quality” random sequences (quasirandom bit-sequences) from two independent semi-random sources. The general problem of extracting “high quality” bits is shown to be related to communication complexity theory, leading to a definition of strong communication complexity of a boolean function. A hierarchy theorem for strong communication complexity classes is proved; this allows the previous algorithm to be generalized to one that can generate quasi-random sequences from two communicating semi-random sources This research was supported in part by an IBM Doctoral Felloswhip and by NSF Grant MCS 82-04506.     

On two geometric problems related to the travelling salesman problem

The degree-K Minimum Spanning Tree (MST) problem asks for the minimum length spanning tree that has no vertex of degree greater than K. The Euclidean degree-K MST problem is known to be tractable for K ? 5; the degree-2 MST is simply the Euclidean path-TSP, which is NP-complete. It is proved that the Euclidean degree-3 MST problem is also NP-complete, thus leaving open only the case for K = 4. Among the most illustrious approximation algorithms is the heuristic for the Euclidean TSP due to Christofides. It is proved that implementing the “shortcutting phase” of Christofides' algorithm optimally is NP-hard (even so, Christofides' algorithm guarantees a tour which is no more than 50% longer than the optimal one).     

Atom-based 3D-QSAR,molecular docking,DFT, and simulation studies of acylhydrazone,hydrazine, and diazene derivatives as IN-LEDGF/p75 inhibitors

Structural Chemistry - Since HIV-1 integrase makes use of host genome machinery to accomplish the replication process, where LEDGF/p75 (a cellular cofactor) executes in the lentiviral integration...     

Parameter estimation of inverse Lindley distribution for Type-I censored data

In life testing experiments, Type-I censoring scheme has been widely used due to its simplicity and poise with considerable gain in the completion time of an experiment. This article deals with the parameter estimation of inverse Lindley distribution when the data is Type-I censored. Estimates have been obtained under both the classical and Bayesian paradigm. In the classical scenario, estimates based on maximum likelihood and maximum product of spacings coupled with their 95% asymptotic confidence interval have been obtained. Under the Bayesian set up, the point estimate is obtained by considering squared error loss function using Markov Chain Monte Carlo technique and highest posterior density intervals based on these samples are reckoned. The performance of above mentioned techniques are evaluated on the basis of their simulated risks. Further, a real data set is analysed for appraisal of aforementioned estimation techniques under the specified censoring scheme.     

Effect of Nitrogen and Fluorine Co‐substitution on the Structure and Magnetic Properties of Cr2O3

First‐principles density functional calculations were carried out to determine the structure as well as electronic and magnetic properties of N and F co‐substituted Cr₂O₃. The formation of strong Cr?N bonds upon substitution of oxygen with nitrogen leads to large distortions in the local structure and changes in magnetic moments, which are partly compensated by co‐substitution with fluorine. The effects of spin–orbit coupling are relatively weak, but its combination with local structural distortions gives rise to canting of spins and an overall magnetic moment in N, F co‐substituted Cr₂O₃. Experimentally, we observe spin canting in N, F co‐substituted Cr₂O₃ with considerable enhancement in the coercive field at low temperatures.     

Dianions of 7,7,8,8-tetracyano-p-quinodimethane and perfluorinated tetracyanoquinodimethane: information on excited states from lifetime measurements in an electrostatic storage ring and optical absorption spectroscopy

We have developed an experimental technique that allows us to study the physics of short lived molecular dianions in the gas phase. It is based on the formation of monoanions via electrospray ionization, acceleration of these ions to keV energies, and subsequent electron capture in a sodium vapor cell. The dianions are stored in an electrostatic ion storage ring in which they circulate with revolution times on the order of 100 micros. This enables lifetime studies in a time regime covering five orders of magnitude, 10(-5)-1 s. We have produced dianions of 7,7,8,8-tetracyano-p-quinodimethane and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (TCNQ-F(4)) and measured their lifetimes with respect to electron autodetachment. Our data indicate that most of the dianions were initially formed in electronically excited states in the electron transfer process. Two levels of excitation were identified by spectroscopy on the dianion of TCNQ-F(4), and the absorption spectrum was compared with spectra obtained from spectroelectrochemistry of TCNQ-F(4) in acetonitrile solution.     

A kinetic study of electron transfer from L-Ascorbic acid to sodium perborate and potassium peroxy disulphate in aqueous acid and micellar media

Kinetics of oxidation of L-ascorbic acid (H₂A) by sodium perborate (SPB) and peroxy disulphate (PDS) have been investigated in aqueous acid and micellar media. Reaction kinetics indicated first-order dependence on both |oxidant| and |H₂A|. Increase in ionic strength (μ) increased reaction rate only in H₂SO₄ media. Rate of SPB oxidation of H₂A has been accelerated by acidity in HNO₃ and HCl media while a decreasing trend is observed in HClO₄ and H₂SO₄ media. The results are interpreted by various theories of acidity functions. Reaction rate is enhanced by the addition of added |H₂O₂| indicating a H₂O₂ coordinated boron species to be active in the present system. In the absence of micelle, increase in |acid| altered the PDS(SINGLEBOND)H₂A reaction rate marginally (a very small positive effect with HClO₄ and negative effect with H₂SO₄). Most plausible mechanisms have been proposed on the basis of experimental results. Activation parameters evaluated for specific kinetic constants are in accord with outer sphere electron transfer mechanism. In SPB(SINGLEBOND)H₂A system, addition of anionic micelle (Sodium lauryl sulfate) increased the rate, stabilizing the cationic species in the transition state in all the acid media. Although rate of PDS oxidation of H₂A was catalyzed by TX and inhibited by SDS at critical micellar concentration (CMC) increase in |acid| (both HClO₄ and H₂SO₄) beyond 9.6 × 10⁻⁴ M decreased the rate of oxidation. This trend was explained due to the repulsive interaction of coanion, HA⁻, and negatively charged micellar species. © 1996 John Wiley & Sons, Inc.