In-plane deformation measurement using holographic moiré

The present paper analyses the factors affecting the quality of the moiré fringes for an arbitrary displacement and deformation of the object surface. Methods for the generation of auxiliary fringes are considered and their localisation is investigated. The physical significance of speckle displacement, both in the image plane and in the pupil plane, is pointed out.     

Natural antifungal compounds from the peels of Ipomoea batatas Lam

Three antifungal compounds have been isolated for the first time from the peels of Ipomoea batatas Lam. Their structures were established on the basis of 1D and 2D NMR spectra data as well as ESI-MS and IR analysis. Urs-13(18)-ene-3β-yl acetate was found to possess a weak activity against Sporothrix schenckii and Trichophyton metagrophytes fungi with an MIC value of 50 μg/mL each. Stigmasterol and 3-friedelanol were equally active against T. metagrophytes.     

Immobilization and Activation of a Single‐Site Chromium Catalyst for Ethylene Polymerization using MgCl2/AlRn(OEt)3 − n Supports

Summary: The effective immobilization and activation of a single‐site chromium catalyst for ethylene polymerization has been achieved using MgCl₂/AlR_n(OEt)_{3 − n} supports, without the use of methylaluminoxane (MAO) or a borate activator. High catalyst activity and a spherical polyethylene‐particle morphology is obtained. Furthermore, the single‐site characteristics of the catalyst are retained, the narrow molecular weight distribution of the polymers obtained are apparent from gel permeation chromatography (GPC) and confirmed by rheological characterization.

Shear frequency dependence of the storage modulus of (♦ and ▴) polyethylene ( = 1.8–1.9) prepared using an immobilized Cr catalyst, compared to (▪) a reference polymer having = 4.1.     

Polymer crystallisation: Role of metastability and the confluence of thermodynamic and kinetic factors

Consideration is given to the effect of size on the thermodynamic stability in situations where two or more phase variants compete in the course of a phase transformation. It is found that, pending on material parameters, a situation can arise where the stabilities of the competing phases invert with size. Such a size induced stability inversion can have a profound influence on phase development in general connecting also with the kinetics of the phase transformation. Specifically, this newly considered combination of interrelated thermodynamic (stability) and kinetic (rates) factors can provide an explanation for the frequently experienced dominance of metastable phases (the century old Ostwald Stage Rule). When applied to polymers, as in the example of polyethylene, it provides a new outlook for polymer crystallisation. Amongst others it creates a unified approach for the two, so far largely disconnected areas of chain folded and extended chain type crystallisation incorporating (not contradicting!) existing approaches within a widened framework.     

Linear sweep voltammetry of 9-β- -ribofuranosyluric acid 5′-monophosphate in aqueous and micellar media

Linear sweep voltammetric behaviour of 9-β- -ribofuranosyluric acid 5′-monophosphate (UA-9R-5′-P) has been studied in phosphate buffers of pH 3.0 and 7.0 at the pyrolytic graphite electrode in aqueous and micellar media. At pH 3.0 in the presence of non-ionic and anionic surfactants, UA-9R-5′-P exhibited a single well-defined 2e, 2H⁺ oxidation peak, whereas in the presence of cationic surfactant (CTAB) the oxidation peak I_a showed a tendency to split into two peaks indicating that the 2e, 2H⁺ oxidation of UA-9R-5′-P in peak I_a reaction occurs in two 1e steps. The effect of cationic surfactant at pH 3.0 is explained on the basis of hydrophobic penetration of cationic species in cationic micelles. The products of electrode reaction in micellar medium were found as alloxan, urea and ribosyl phosphate at pH 3.0 and ribose, allantoin and 5-hydroxyhydantoin 5-carboxamide at pH 7.0 and were similar to those observed in aqueous media.     

13C NMR shifts and conformations of substituted indans

¹³C NMR spectra of indan derivatives bearing substituents in the 1, 2, 5 and 6 positions are reported and assigned by LIS measurements and other techniques. Epimeric indanes bearing vicinal oxygen and phenyl or benzyl substituents show ring carbon shielding in the cis relative to the trans isomers, which is compared with corresponding cyclopentane shifts, and indicates the predominance of envelope conformations with pseudoaxial oxygen substituents for the cis isomers. Acetylation shifts show consistently larger shielding at C-β for the trans compounds. Introduction of oxygen at C-5 leads to asymmetric shielding effects at the ortho carbon atoms as soon as there is a substituent in the para position which can participate in mesomeric forms.     

Conformational analysis in diastereoisomer equilibria of square-pyramidal [C5H5(CO)2Mo pyridine-2-imine]PF6 complexes

Synthesis and characterization of sonic new square-pyramidal pyridine-2-imine complexes [C₅,H₅,(CO)₂,MoNC₅,H₄,CX=NCH(R₁)(R₂)]PF₆ with X = CH₃, C₆H₅ and chiral amine, 1-phenyl-isobutylamine and amino acid methyl ester H₂NCH(COOCH₃)(R) with (R) = (CH₂C₆H₅) and (C₂H₅) have been reported. In combination with Mo chirality (R) and (S), mixtures of two diastereoisomeric pairs of enantiomers with racemic amine and amino acids were obtained which were separated by fractional cystallization. The diastereoisomers differ in the chemical shift of most of their ¹H NMR signals and interconvert on heating in acetone-d₆ at 80°C for 80 hr and 40°C for 200 hr. On the basis of three conformational determining effects (i) C-H or C-alkyl of the asymmetric centre eclipses the ligand plane, (ii) MC₅H₅/C₆H₅ attraction and (iii) MC₅H₅/alkyl repulsion in order of decreasing significance, the chemical shifts of the C₅H₅ signals, their differences as well as the diastereoisomer ratio at equilibrium for all the complexes has been rationalised.     

The frequency and temperature dependence of the transverse optic mode self-energy in KCl

Measurements of the frequency dependence of the real and imaginary parts of the anharmonic self-energy of the q ≈ 0 transverse optic mode in KCl at 105 and 300 K are presented and compared to the predictions of theoretical calculations.