Cohesion in lead chloride

The Born model is used as a method to assess the ionicity and the extent of covalent contribution to the binding in lead chloride. In the process, the Madelung constant (11·2429 with respect to cube root of unit cell volume) and cohesive energy (W _L) (484 kcal/mole) are evaluated. The theoreticalW _L, when compared with that derived from a thermochemical cycle indicates that PbCl₂ can be considered to be ‘predominantly ionic’.     

Raman and infrared spectra and normal vibrations of N-methylpropionamide and N-deuterated N-methyl propionamide

Raman and infrared spectra of N-methyl-propionamide and N-deuterated N-methyl-propionamide were recorded in various states of aggregation—pure amide, in solution and vapour state—and the frequency changes of the functional groups were studied. The implane skeletal vibrations of N-methyl-propionamide and its deuterated compound were calculated treating these molecules as six-body problems. The distribution of potential energy of each normal mode among various symmetry co-ordinates was calculated and the nature of the amide I, II and III bands and the mixing up of the inplane vibrational frequencies of N-methyl-propionamide and the deuterated amide are discussed on a quantitative basis.     

Calorimetric and Scattering Studies on Micellization of Pluronics in Aqueous Solutions: Effect of the Size of Hydrophilic PEO End Blocks,Temperature, and Added Salt

Micellar behavior of five ethylene oxide–propylene oxide (EO–PO) triblock copolymers, called Pluronics, with similar molecular weights of middle block PPO (～2250 g/mol) and varied percentages of poly(ethylene oxide) (10%, 40%, 50%, 70%, and 80%, referred to as L81, P84, P85, F87, and F88, respectively) was examined by thermal (isothermal titration calorimetry and high-sensitivity differential scanning calorimetry), spectral (UV–vis), and dynamic light scattering (DLS) techniques. Micellization was decreased with increasing hydrophilicity of copolymer but induced in the presence of salt. Critical micelle temperatures (CMTs) of copolymers at different concentrations, with and without sodium chloride, are reported. Viscosity and DLS results reveal that highly hydrophilic copolymers (F87 and F88) did not show significant change in micelle size even at temperatures close to cloud point, whereas micelle growth and sphere-to-rod transition occurred for P84 and P85. Surface tension of solutions in water and salt also show enhanced surface activity and salt-induced micellization. The CMTs for different systems using different methods are compared.     

Biosynthesis and Characterization of Pd and Pt Nanoparticles Using Piper betle L. Plant in a Photoreduction Method

An extremely rapid green approach that generates bulk quantities of nanocrystals of noble metals such as palladium (Pd) and platinum (Pt) nanoparticles (NPs) with a small sizes of 3.8 ± 0.2 and 2.1 ± 0.4 nm by using Piper betle L. (Piperaceae) leaf extract is described. The highly stable and monodispersed Pd and Pt NPs were obtained at 10 min of continuous sunlight exposure. The bio-reduced Pd and Pt NPs were further characterized by using UV–Visible spectroscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry measurements. The particles, although discrete, were predominately associated with the P. betle plant proteins, which makes them stable over long time periods. These synthesized biogenic Pd and Pt NPs were evaluated for their acute toxicity studies against aquatic organism, Daphnia magna.     

Temperature-Gradient-Directed NMR Monitoring of a [3 + 3]-Cyclocondensation Reaction Between Alkynone and Ethyl 2-Amino-1H-indole-3-carboxylate Toward the Synthesis of Pyrimido[1,2-a]indole Catalyzed by Cs2CO3

We describe a NMR strategy to resolve temperature-gradient-monitored real-time chemical reaction involving a [3 + 3]-cyclocondensation reaction between alkynone and ethyl 2-amino-1H-indole-3-carboxylate toward the synthesis of pyrimido[1,2-a]indole catalyzed by Cs₂CO₃. The in situ NMR study clearly indicates that the reactant undergoes [3 + 3]-cyclocondensation reaction through a concerted mechanism, resulting in the product formation. The detailed NMR spectroscopic data led to the optimization of the reaction conditions and quantitative analysis of the product accurately and efficiently.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Behavior of collagen films in presence of structure modifiers at solid–liquid interface

Films of soluble collagen extracted from rat‐tail tendon were studied at the solid–solution interface, and the surface energy of the films was evaluated. The films transferred onto solid substrates using the Langmuir–Blodgett film (LB film) technique were characterized using Fourier transform IR attenuated total reflectance spectroscopy and atomic force microscopy. The properties of the protein in contact with different structure modifiers like basic chromium sulfate (BCS) and formaldehyde (HCHO) were analyzed for the effect of various tanning agents on the protein structure. The thermal properties of the films were studied using differential scanning calorimetry. The results show that the film of collagen treated with BCS exhibits an increase in the peak temperature and enthalpy changes compared to the pure collagen as well as the protein with HCHO. These differences are attributed to the changes in the crosslinks arising from both coordinate–covalent and covalent interactions, respectively. The atomic force micrographs showed an increase in order for the collagen film with BCS compared to the HCHO treated analogue. A similar trend is seen in the surface energy parameters of the protein films on solid surfaces on reacting with BCS and HCHO, suggesting a molecular level ordering process in collagen assemblies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3859–3865, 2004     

Light-Front Hamiltonian,Path Integral and BRST Formulations of the Nielsen–Olesen (Bogomol’nyi) Model in the Light-Cone Gauges

Light-front Hamiltonian, path integral and BRST formulations of the Nielsen–Olesen (Bogomol’nyi) model in two-space one-time dimensions are investigated under the appropriate the light-cone gauges.     

Generalized parabolic sheaves on an integral projective curve

We extend the notion of a parabolic vector bundle on a smooth curve to define generalized parabolic sheaves (GPS) on any integral projective curve X. We construct the moduli spacesM(X) of GPS of certain type onX. IfX is obtained by blowing up finitely many nodes inY then we show that there is a surjective birational morphism from M(X) to M (Y). In particular, we get partial desingularisations of the moduli of torsion-free sheaves on a nodal curveY.     

NMR investigations of molecular motions inp-n-hexyloxybenzylidene-p′-n-propylaniline

Proton spin-lattice relaxation times,T ₁, have been measured in the smectic phases, S _G ² , S _G ¹ and S_A, and in the nematic phase of HxBPA, in the temperature range, 220K<T<360 K. In the S _G ¹ and S _G ² phases,T ₁ has been measured at 15 and 40 MHz. The (S _G ¹ →S _G ² ) and (S _G ² →S _G ¹ ) transitions are clearly seen as discontinuities inT ₁. The former transition is seen to be due to possible freezing or change of hydrocarbon chain motions of the molecule. Our data in the S _G ¹ phase have been fitted to a model in which anisotropic rotational diffusion of the end hydrocarbon chains as also that of the rigid part of the molecule are considered. In the nematic phase, at 351 K, the observed behaviour ofT ₁, measured in the frequency range, 5 to 40 MHz, agrees well with the theoretical predictions of Uklejaet al and Freed, who take into account long range collective order fluctuations and local reorientations. Using these theories, the correlation time for short range reorientations has been calculated from our results to be 4.3 × 10⁻¹⁰ and 1.1 × 10⁻⁹ s respectively.