A note on the paramagnetic resonance of free radical

Paramagnetic resonance in a free radical, Diphenyl-Picryl-Hydrazyl, has been studied and the results are compared with those of other workers. Low temperature work indicated that the transition from paramagnetic to antiferromagnetic state should occur at 1° K.     

Two parabolic generator kleinian groups

This paper is concerned with torsion-free Kleinian groups that are generated by two parabolic transformations. Our main result is that every such group of the second kind is geometrically finite; this is in response to a question raised by Riley. We also show that in the natural one (complex) dimensional setting, the space of torsion-free Kleinian groups of the second kind is path-connected. The first author was supported in part by NSF Grant #8701774.     

The Electron-Hole plasma in CdS between 5 K and room temperature

We investigate and analyze the time-integrated nonlinear optical behaviour of an electronhole plasma in CdS as a function of the temperature and the exciting intensity. The competition between the temperature dependences of the absorption tail and of the manyparticle effects leads with increasing temperature around 160 K to a turn-over from a red- to a blue-shift of the absorption edge under excitation. The frequency dependence of the absorption for high plasma concentrations is in good agreement with theoretical calculations.     

Detection of arsenic, antimony and tin in forensic toxicology by paper chromatography

Summary A paper chromatographic technique for the detection of arsenic, antimony and tin as applied to toxicological analysis has been described.     

On duality in linear fractional functionals programming

Summary The paper formulates a dual program for a given linear fractional functionals program (L.F.F.P.) and proves the duality theorem and its converse for the same. Special feature of the paper is that both the primal and the dual programs are L. F. F. Ps. and can easily be solved by the existing standard techniques.

---

Zusammenfassung Für ein lineares Optimierungsproblem, dessen Zielfunktion als Quotient zweier linearer Funktionen gegeben ist (LP-Problem mit gebrochener Zielfunktion), wird ein duales Problem formuliert und das Dualitätstheorem bewiesen. Es wird gezeigt, daß sowohl das primale als auch das duale Problem lineare Probleme mit gebrochener Zielfunktion sind und leicht mit den bekannten Standardtechniken gelöst werden können.

     

Preparation and characterization of silver-poly(vinylidene fluoride) nanocomposites: formation of piezoelectric polymorph of poly(vinylidene fluoride)

In situ Ag nanoparticles are produced on reduction of Ag+ with N,N-dimethylformamide in the presence of poly(vinylidene fluoride) (PVF2). The plasmon band transition is monitored with time in the reaction mixture for three sets of experiments by UV-vis spectroscopy. The plasmon band absorbance increases sigmoidally with log(time). Analysis of the data with the Avrami equation yields an exponent n value between 1.5 and 2.0, indicating two-dimensional nucleation with linear or diffusion controlled growth. The TEM study of the polymer nanocomposites (PNC) indicates both spherical and rodlike morphology for PNC0.5 and PNC2.5 samples, whereas the PNC11 sample has spherical and agglomerated structures (the numerical number associated with PNC indicates percentage (w/w) of Ag in the nanocomposite). The WAXS and FTIR studies indicate the formation of piezoelectric beta-polymorphic PVF2 in the nanocomposites. The DSC study indicates some increase of the melting point and enthalpy of fusion of PVF2 in the nanocomposite, although with increase in Ag nanoparticle concentration the increase is smaller. The crystallization temperatures of PNCs also increased, indicating nucleating effect of Ag nanoparticles in the composite. In the TGA curves, the PNCs exhibit a three-step degradation process. The degradation temperatures of PNCs are lower than that of PVF2. The storage modulus data indicate a significant reinforcement of the mechanical property in the PNCs where also the reinforcement effect decreases with increasing nanoparticle concentration. Both the loss modulus and tan delta plots indicate two peaks; the lower temperature peak has been attributed for glass transition temperature, whereas the higher one has been attributed to a similar type relaxation process for the crystalline-amorphous interface. The increase in the glass transition is marginal for the PNCs, but the increase of later transition temperature is somewhat higher. The FTIR study shows that the dipolar interaction of the >CF2 dipole with the surface charges of Ag nanoparticle stabilizes the nanoparticle in the nanocomposite.