Effect of the extracts from Aristolochia indica Linn. on interception in female mice.

The crude petroleum ether, chloroform and alcoholic extracts from the roots of Aristolochia indica (Linn.) showed 100% interceptive activity in mature female mice at the single dose of 100 mg/kg body wt. The follow-up studies with the chloroform extract showed the most significant effect in the basic part and two acidic fractions at the single dose levels of 50 mg/kg body wt. No toxic effect was observed at the dose levels used.     

Jamming by shear

A broad class of disordered materials including foams, glassy molecular systems, colloids and granular materials can form jammed states. A jammed system can resist small stresses without deforming irreversibly, whereas unjammed systems flow under any applied stresses. The broad applicability of the Liu-Nagel jamming concept has attracted intensive theoretical and modelling interest but has prompted less experimental effort. In the Liu-Nagel framework, jammed states of athermal systems exist only above a certain critical density. Although numerical simulations for particles that do not experience friction broadly support this idea, the nature of the jamming transition for frictional grains is less clear. Here we show that jamming of frictional, disk-shaped grains can be induced by the application of shear stress at densities lower than the critical value, at which isotropic (shear-free) jamming occurs. These jammed states have a much richer phenomenology than the isotropic jammed states: for small applied shear stresses, the states are fragile, with a strong force network that percolates only in one direction. A minimum shear stress is needed to create robust, shear-jammed states with a strong force network percolating in all directions. The transitions from unjammed to fragile states and from fragile to shear-jammed states are controlled by the fraction of force-bearing grains. The fractions at which these transitions occur are statistically independent of the density. Jammed states with densities lower than the critical value have an anisotropic fabric (contact network). The minimum anisotropy of shear-jammed states vanishes as the density approaches the critical value from below, in a manner reminiscent of an order-disorder transition.     

Laser diffraction used to monitor strain in mechanoreceptors ofJasus verreauxi

Summary Laser diffraction patterns from crayfish abdominal mechanoreceptors have been observed and the corresponding sarcomere lengths calculated and then correlated with sensory nerve discharge frequencies.Our thanks are due to the Australian Research Grants Committee for provision of the lasers and camera, to Dr.K. S. Imrie for the design of the interfacing cards, to ProfessorP. Mason and ProfessorR. E. Aitchison for their encouragement and advice, and toI. Paterson andC. March for constructing the equipement.     

Antifertility effect of aristolic acid fromAristolochia indica (Linn) in female albino rabbits

Summary Aristolic acid experted significant antifertility effects in mature female rabbits without hampering the clinical chemical values in blood.Acknowledgments. We wish to thank Dr S. C. Pakrashi and his associate Mr P.P. Ghosh Dastidar for the plant extracts. Thanks are also due to the D.G. of ICMR for granting fellowship to B. Chakrabarty.     

A debris disk around an isolated young neutron star

Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars.     

Effects of actinomycin D on the distal end regeneration inHydra vulgaris Pallas

Zusammenfassung Actinomycin D-Wirkung auf die Mund-Tentakel-Regeneration beiHydra vulgaris. Auch später absterbende Tiere beginnen die Regeneration, was als Folge einer stabilen RNS angesehen wird.     

Reflexine,a new indole alkaloid ofRauwolfia reflexa

Summary Reflexine, a new indole alkaloid, has been isolated from the leaves ofRauwolfia reflexa Teijsm. and Binn. From spectral studies, chemical reactions and correlation with seredamine, reflexine is shown to be its C-17 epimer (IV).Grateful thanks are accorded to ProfessorR. H. Thomson, Dr.R. T. Brown, Dr.Nitya Nand and Dr.S. C. Pakrashi for spectral measurements. Financial assistance from CCRIMH, New Delhi, and UGC, New Delhi, are also thankfully acknowledged.