Crystalline constituents from euphorbiaceae—XIII : The structure of a new triterpene from Euphorbia nerifolia L.

From the leaves and stems of Euphorbia nerifolia Linn., a new triterpene was isolated besides friedelan-3α- andβ-ols, and taraxerol. From a study of its chemical reactions and spectral data, the new triterpene was shown to be glut-5(10)-en-1-one(3).     

Pippard relations and critical phenomena in binary liquid mixtures

The cylindrical approximation originally proposed by Pippard for the λ-transitions in one-component systems is extended to multicomponent systems. The application of the generalised Pippard relations to binary liquid mixtures is considered. The relations for He³ + He⁴ mixtures are shown to be equivalent to those obtained by earlier workers. The validity of the relation relating specific heat and thermal expansion for binary liquid systems is discussed on the basis of the measurements performed on the system methaonl +n-heptane. Lack of information on the behaviour of a few quantities prevents a quantitative test of the relation.     

Temperature corresponding to ultrasonic velocity maximum studies in aqueous solutions

Ultrasonic velocities in aqueous solutions of acetamide, dimethyl urea andβ-alanine at different concentrations in the temperature range of about 60°C to 80°C have been measured using an interferometer technique with an accuracy of ±0.003%. The temperature corresponding to velocity maximum at different concentrations is evaluated with an accuracy of ±0.2°C. The results are discussed in the light of the structure-breaking property of these substances in water.     

Synthesis and Antioxidant Activity of Bis‐oxazolyl/thiazolyl/imidazolyl 1,3,4‐Oxadiazoles and 1,3,4‐Thiadiazoles

A variety of symmetrical trisheterocycles bis‐oxazolyl/thiazolyl/imidazolylacetamido‐sulfonylmethyl 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles was prepared, and their antioxidant activity was studied. The compounds bisoxazolyl oxadiazole and bisoxazolyl thiadiazole having methyl substituent on the aromatic ring exhibited greater antioxidant activity than the standard ascorbic acid.     

Fresnel particle tracing in three dimensions using diffraction phase microscopy

We have developed a novel experimental technique for tracking small particles in three dimensions with nanometer accuracy. The longitudinal positioning of a micrometer-sized particle is determined by using the Fresnel approximation to describe the transverse distribution of the wavefront that originated in the particle. The method utilizes the high-sensitivity quantitative phase imaging capability of diffraction phase microscopy recently developed in our laboratory. We demonstrate the principle of the technique with experiments on Brownian particles jittering in water both in bulk and in the vicinity of a boundary. The particles are localized in space within an error cube of 20 nm x 20 nm x 20 nm for a 33 Hz acquisition rate and 20s recording time.