Rounded Step Research Articles

Effects of testosterone and follicle-stimulating hormone on spermatogenesis in adult mice during treatment with oestradiol.

SUMMARY Adult male mice were treated with oestradiol for 10 weeks and for the last half of this period they were given relatively large daily doses of testosterone and highly purified human pituitary follicle-stimulating hormone (FSH), singly and in combination. Oestradiol treatment reduced and testosterone restored the yields of mature (step 16) spermatids from round (step 7) spermatids, round spermatids from pachytene primary spermatocytes and pachytene from preleptotene spermatocytes. At the dose level used FSH was not effective alone but appeared to augment the effect of testosterone on the yield of round spermatids from preleptotene spermatocytes.

An interaction model of a supersonic laminar boundary layer on sharpand rounded backward facing steps.

An implicit finite-difference method is used to study the interaction of a laminar boundary layer with a supersonic, external, inviscid flow on a flat plate with a sharp or rounded backward facing step. The boundary-layer equations are used to describe the subsonic portion of the flow with the effect of transverse pressure gradients in the supersonic viscous region included through the use of an inviscid transverse momentum equation. Initial profiles are assumed to be similar (Blasius) in shape, but with the boundary-layer edge flow inclination not specified. The qualitative nature of the downstream flow is determined by the particular value of initial edge flow inclination chosen, with two families of solutions bounded by a particular solution which continues downstream on the body without separation. A perturbation in the initial edge flow inclination from this particular value results in a flowfield such as one would expect approaching a sharp backward facing step. A perturbation in the opposite direction results in a flowfield such as one would expect for a boundary layer separating from a smooth wall in an adverse pressure gradient. Computed wall pressure distributions agree well with experiments for both sharp and rounded corners and the computed flowfield for a rounded corner contains a separation shock whose location also agrees with experiment.

Threshold Effects inn−dScattering due to the Existence of the Di-Neutron

Use is made of a simple soluble model to evaluate the threshold effect which arises in the $n\ensuremath{-}d$ scattering cross section if the di-neutron exists. The model contains four parameters. They permit a large set of experimental data to be reproduced remarkably well. Various binding energies of the hypothetical di-neutron are assumed. The effect is a rounded step. Its height is about 20% of the total cross section for any reasonable value of the binding energy, if the value 8.26 F is assumed for the $n\ensuremath{-}d$ doublet scattering length.

Threshold Effects in Three-Body Channels

The possibility of obtaining threshold anomalies in reactions leading to three-particle channels is studied in detail. It is found that a threshold cusp or rounded step exists in reactions whose final three-body channels have at least one particle in common. The effect appears as a function of the momentum of the common particle while the total energy is fixed.

Effective potential approach to the threshold behaviour of cross sections

The study of the energy dependence of scattering and reaction cross sections near thresholds is performed by a method which has its basis in the construction of the effective potentials in every single channel. The formalism employed presents some advantage with respect to other kind of approaches in that it gives a simple physical description of the anomaly (cusp or rounded step) which appears in the scattering cross section at the opening up of a new channel. Furthermore, with this method it is effectively possible to give an explanation why the energy derivative of the scattering cross section is infinite when the threshold is approached from below. The effect is found to be purely quantum mechanical.