Study of the dependence of 198Au half-life on source geometry

We report the results of an experiment to determine whether the half-life of \Au{198} depends on the shape of the source. This study was motivated by recent suggestions that nuclear decay rates may be affected by solar activity, perhaps arising from solar neutrinos. If this were the case then the $\beta$-decay rates, or half-lives, of a thin foil sample and a spherical sample of gold of the same mass and activity could be different. We find for \Au{198}, $(T_{1/2})_{\rm foil}/(T_{1/2})_{\rm sphere} = 0.999 \pm 0.002$, where $T_{1/2}$ is the mean half-life. The maximum neutrino flux at the sample in our experiments was several times greater than the flux of solar neutrinos at the surface of the Earth. We show that this increase in flux leads to a significant improvement in the limits that can be inferred on a possible solar contribution to nuclear decays.Comment: 5 pages, 1 figur

Discrete ordinates-Monte Carlo coupling: A comparison of techniques in NERVA radiation analysis

In the radiation analysis of the NERVA nuclear rocket system, two-dimensional discrete ordinates calculations are sufficient to provide detail in the pressure vessel and reactor assembly. Other parts of the system, however, require three-dimensional Monte Carlo analyses. To use these two methods in a single analysis, a means of coupling was developed whereby the results of a discrete ordinates calculation can be used to produce source data for a Monte Carlo calculation. Several techniques for producing source detail were investigated. Results of calculations on the NERVA system are compared and limitations and advantages of the coupling techniques discussed

Hereditary correlation of size and color characteristics in tomatoes

From the hereditary standpoint, color and size characters in either plants or animals are not equally well understood. In general, the inheritance of color, technically known as a qualitative character, has been rather satisfactorily determined. On the modern chromosome theory of heredity, the genetic factors responsible for the development of colors appear to be located on the various chromosomes of the species and apparently follow a regular, stable and predictable mode of inheritance from generation to generation. Environmental agencies play a relatively minor part in ;modifying such characters. It is for this reason, perhaps, that their inheritance has been so thoroly investigated

Inheritance of Fruit Shapes and Sizes in the Pepper and Tomato

Both Capsicum and Lycopersicum exhibit the same correlation between fruit shape and fruit size, a correlation which is wholly lacking for the same characters in the Cucurbits. In the pepper both positive and negative correlations of shape and size were discovered in F2 generations, the sign of the correlation being dependent on the parental combinations. Accordingly the cause for the correlations must be the genetic one of linkage, due to the presence of shape and size genes on the same chromosome, a fact which has already been reported for the tomato. Fruit sizes in both genera exhibit logarithmic rather than additive distributions

Genetic Stability of Tomato Diploids and Tetraploids Derived from Haploid

By doubling the chromosomes of a haploid tomato asexually (decapitation-callus technique) an absolutely homozygous diploid is produced. Ten generations of severe selection to break this pure line have resulted only in very minor changes, easily attributable to a normal mutation rate. Data on the effect of the selection pressure on dry weight of plants and on size and weight of fruits show no statistically significant effects in two selection lines and a barely significant ( 5 per cent point) effect in a third selection line. Only one major point-mutation was noted among the 12,000 experimental plants (a mutation to a recessive wiry form, different genetically from the original wiry mutant) and this occurred in the control lines. These results are directly opposed to the Russian worker, Lysenko\u27s claims that the tomato deteriorates in three to five generations. The original haploid, now carried on asexually for 12 years, has proved also to be remarkably stable, only one large bud-sport having been observed

The key node method: a highly-parallel alpha-beta algorithm

Journal ArticleA new parallel formulation of the alpha-beta algorithm for minimax game tree searching is presented. Its chief characteristic is incremental information sharing among subsearch processes in the form of "provisional" node value communication. Such "eager" communication can offer the double benefit of faster search focusing and enhanced parallelism. This effect is particularly advantageous in the prevalent case when static value correlation exists among adjacent nodes. A message-passing formulation of this idea, termed the "Key Node Method", is outlined. Preliminary experimental results for this method are reported, supporting its validity and potential for increased speedup

Fruit Size and Shape Genes on the First Chromosome of the Tomato

Genetic evidence has demonstrated the presence of a major factor for fruit size in the first linkage group of the tomato, linked inheritance being exhibited between fruit size and the genes for the tall-dwarf and the smooth-peach (pubescent) characters. In this same linkage group a major gene for fruit shape (ovate) has been found