A Preliminary Study of the Reaction of Two Disease Resistant Stocks of Chickens after Infection with Their Reciprocal Pathogens

In another publication the writer pointed out that five generations of selection for resistance to fowl typhoid in the chicken resulted in a decided decrease in the mortality of the selected stocks. Specifically, the effect of the selection was to decrease the mortality from approximately 85 percent in the unselected parental stock to slightly more than 10 percent in the fifth selected generation

An Inherited Eye Defect in the Guinea Pig

The data presented in this paper were obtained from the descendants of one defective-eyed male guinea pig that appeared in our colony several years ago. Notation was made of the defective eye, but as the male was being used in another experiment no matings were made at that time to determine whether the condition was genetic. However, when the same type of defect was later observed in the inbred descendants of this male, some matings were made to determine, if possible, the manner of inheritance of the condition

On the Inheritance of Resistance to Fowl Typhoid in Chickens

Studies at the Iowa Experiment Station during 1927 and 1928 indicate very clearly that selection is effective in increasing resistance to this disease

Random Scattering Matrices and the Circuit Theory of Andreev Conductances

The conductance of a normal-metal mesoscopic system in proximity to superconducting electrode(s) is calculated. The normal-metal part may have a general geometry, and is described as a ``circuit'' with ``leads'' and ``junctions''. The junctions are each ascribed a scattering matrix which is averaged over the circular orthogonal ensemble, using recently-developed techniques. The results for the electrical conductance reproduce and extend Nazarov's circuit theory, thus bridging between the scattering and the bulk approaches. The method is also applied to the heat conductance.Comment: 12 pages, RevTeX, including 2 figures with eps

A Study of the Inheritance and the Physiological Behaviour of Dwarfism Associated with an Eye Defect in Rats

Four dwarfed rats recently appeared in two separate closely related litters of an inbred strain of rats in our colony. There was associated with the dwarfed condition a marked opacity of the eyes apparently causing blindness

Inbreeding in the White Leghorn Fowl

A study, extending over a 10-year period, has been made of the effect of inbreeding in the White Leghorn breed of domestic fowl. The major object of this investigation was to study the effect of various intensities of inbreeding on the following characters: Fertility, hatchability, viability, days to first egg, egg production, egg size and body size. In the present investigation the degree of inbreeding was, in general, less intense than that from brother and sister or parent and offspring matings. One intensely inbred family, however, with the equivalent of brother and sister mating, was maintained successfully for nine generations. Six more or less distinct families, each with a somewhat different type and intensity of inbreeding but with a similar foundation ancestry, were developed. All individuals were selected primarily on the basis of high hatchability of their eggs, upon general vigor of the individual bird and of the offspring of each pair of birds. Other characters besides vigor and hatchability also were considered whenever practical. The ancestry of all the birds in the present generation of these 6 families may be traced to four males and seven females. One of the four original males (No. 823), however, has a greater degree o£ relationship to the present generation than any of the other foundation birds. This relationship still averages approximately 55 percent, with the lowest degree of relationship being 29 percent and the highest 61 percent. The relationship of the present generation to the other three foundation males does not exceed 5 percent. The relationship between brothers and sisters in the present generation chicks of the separate families ranges from 74 to 94 percent. The average inter-se relationship between the present chicks which are not sibs is above 50 percent. The inbreeding coefficients of the present birds range from 41 percent for the least inbred to 82 percent for the most intensely inbred family. There was no general decrease in percent of eggs fertile as the degree of inbreeding increased ; in fact some inbred families have shown an increase in percent of eggs fertile. There was a slow but gradual decline in the average percent hatchability of fertile eggs set for all inbreds as the inbreeding increased. The average hatchability for all inbreds, however, was in most cases well above 60 percent. In six of the families studied there was no general decrease in hatchability, which demonstrates that it is possible to maintain a reasonably safe level of hatchability under a system of intense inbreeding. There was a significant decrease in the number of days to first egg. The most intensely inbred birds on the average matured sexually 16 days earlier than the birds of the original non-inbred foundation stock. There was a general but not a consistent decrease in number of eggs laid during a given period as the inbreeding increased. An exception was observed for the 70 percent inbred group which compared favorably with the original non-inbred foundation birds in egg production. There was no marked decrease in 200-day egg production for anyone of the six separate families as a result of the inbreeding. The data on egg weight suggest no general decrease or increase in average egg weight as a result of the inbreeding. The results indicate that intensive inbreeding did not decrease materially the growth rate or adult body weight of the birds used in this experiment. With the exception of the 80 percent group, there was no increase in mortality in any of the groups up to 24 weeks of age. The pullet year mortality, however, showed a marked rise for the more intensely inbred birds with the exception of that group of birds having an inbreeding coefficient of 70 percent

Superconducting Proximity Effect and Universal Conductance Fluctuations

We examine universal conductance fluctuations (UCFs) in mesoscopic normal-superconducting-normal (N-S-N) structures using a numerical solution of the Bogoliubov - de Gennes equation. We discuss two cases depending on the presence (``open'' structure) or absence (``closed'' structure) of quasiparticle transmission. In contrast to N-S structures, where the onset of superconductivity increases fluctuations, we find that UCFs are suppressed by superconductivity for N-S-N structures. We demonstrate that the fluctuations in ``open'' and ``closed'' structures exhibit distinct responses to an applied magnetic field and to an imposed phase variation of the superconducting order parameter.Comment: (4 pages, 5 figures). Corrected typos in equations, added references, changed Fig. 5 and its discussions. Phys. Rev. B, accepted for publicatio

Two Generations of Selection with Reference to the Inheritance of Scurvy Resistance in Guinea-Pigs

Selection over two generations for increased and decreased resistance to scurvy in guinea-pigs has failed to produce conclusive evidence that the individual variations noted in resistance toward scurvy are inherited. An analysis of the effect of age, weight, and vigor as influencing resistance is presented and it is concluded that these factors, within the limits represented in the data, have not influenced the results. The results for the first generation of selection indicate a pronounced influence, but in the second generation the difference between the minus and plus selections is not significant

Giant Backscattering Peak in Angle-Resolved Andreev Reflection

It is shown analytically and by numerical simulation that the angular distribution of Andreev reflection by a disordered normal-metal -- superconductor junction has a narrow peak at the angle of incidence. The peak is higher than the well-known coherent backscattering peak in the normal state, by a large factor G/G_0 (where G is the conductance of the junction and G_0=2e^2/h). The enhanced backscattering can be detected by means of ballistic point contacts.Comment: Instituut-Lorentz, Leiden, The Netherlands, 4 pages, REVTeX-3.0, 3 figure