Properties of the detached F-type eclipsing binary,BK Pegasi

A misunderstanding of our interpretation of photometry of the detached eclipsing binary, BK Peg, is clarified.     

The induction and extraction of metallothioneins inArtemia

A small amount of heavy metal binding protein, identified by BioRad Protein Assay, has been isolated from the adult brine shrimp,Artemia franciscanus. This protein has an apparent molecular weight between 6000 to 9000 dalton. a UV absorption peak at 260 instead of 280 nm like most proteins; and has high affinity towards binding with radioactive labeled¹⁰⁹Cd. These characteristics are similar to that of metallothioneins reported for many vertebrate and invertebrate, marine and terrestrial animals. After the brine shrimp is exposed to a small amount of Cd²⁺ for 24 h, a large amount of metallothionein can be isolated, showing the inducibility of this detoxifying protein in the adultArtemia in a short period of time.     

Chloride in precipitation and streamwater for the upland catchment of river severn,mid-wales; some consequences for hydrochemical models

Variations in the concentration of Cl in rainfall and stream runoff are presented for two catchments in the Hafren forest of mid-Wales, Great Britain. Despite the large fluctuations in rainfall concentrations, Cl in the streamwater remains relatively constant. Using the two-reservoir Birkenes model, an attempt was made to simulate observed Cl in streamwater. The original model was unable to reproduce the observations and several modifications are suggested to provide better simulations. The resulting model is not the only one capable of reproducing the observations; other hydrochemical models will most probably also achieve this although emphasis will in each case be placed on different aspects. In this paper, it is suggested that the stochastic properties of water movement and chemical processes can account for the streamwater chemistry responses observed. On the catchment scale these processes will lead to an apparently deterministic behaviour that may well be described by simple relationships.     

Three-dimensional calculations of the formation of the presolar nebula from a slowly rotating cloud

The presolar nebula may have formed from the collapse of a very slowly rotating interstellar cloud. The first three-dimensional, hydrodynamical calculations of the collapse of such clouds are presented. The models include radiative transfer in the Eddington approximation, as well as detailed equations of state appropriate for the nonisothermal regime of protostellar evolution. Very slowly rotating clouds, i.e., those with initial ratios of rotational energy to gravitational energy of 10^?3 or less, avoid fragmentation and instead collapse to form single central objects, containing quasistatic cores with densities of about 10^?10 g cm^?3. These cores are, however, surrounded by significantly nonaxisymmetric regions, such that the presolar nebula would have been bar-like over the scale of the present solar system. This nonaxisymmetry, coupled with differential rotation, results in gravitational torques that produce rapid outward transfer of angular momentum. The center of the presolar nebula should then be able to contract and collapse to pre-main-sequence densities without suffering fission or fragmentation.     

Equilibrium models of differentially-rotating polytropic cylinders

The equilibrium structure of differentially rotating polytropic cylinders is determined numerically. We setn=3 and use a quadratic function for the law of differential rotation. We construct different models by varying the angular velocity at the axis and the ratio of the angular velocity at the surface to the angular velocity at the axis. By taking a decreasing function for the rotation law we are able to treat models with an angular velocity at the axis greater than the break-up velocity of uniformly rotating cylinders. We also determine whether a Richardson-like criterion for stability is violated in the models.     

Kinetics of the reactions of hydroxyl radicals with aliphatic ethers studied under simulated atmospheric conditions: Temperature dependences of the rate coefficients

Rate coefficients have been measured for the reactions of hydroxyl radicals with five aliphatic ethers over the temperature range 242–328 K. Competitive studies were carried out in an atmospheric flow reactor in which the hydroxyl radicals were generated by the photolysis of methyl nitrite in the presence of air containing nitric oxide. The reaction of OH with 2,3-dimethyl-butane was used as the reference reaction and the following Arrhenius parameters have been obtained for the reactions: OH+RORproducts: