A Partial Comparative Estimate of Three Methods for the Propagation of Infectious Agents in Developing Chick Embryos

Developing chick embryos have been employed rather extensively in this laboratory for the propagation of various infectious agents during the past three years. The method was used to study the effect of the various agents on chick embryos, to find an easy, efficient, and cheap method of rapid propagation, to aid in the identification of the various agents, and to isolate them or to test for their presence in various filtrates, exudates, and tissues. Thus there was no intention of critical tests of the different methods of chick embryo inoculations to determine which method was most satisfactory for each agent employed. However, partial tests or fairly complete tests have been made in some cases and certain conclusions are apparent

Bovine Encephalitis

In the study of sporadic bovine encephalitis it has been necessary to propagate the causative agent by animal passage. This has been rather expensive and time consuming where calves were employed and only slightly less so when guinea pigs were used. In an effort to find a more satisfactory method, chick embryos were inoculated with the peritoneal exudates or the ground liver and spleen of guinea pigs killed during the height of the disease. These materials were known to be high in concentration of the infectious agent. The methods of embroyo inoculation were those usually employed

A Study of Some Cases of Streptococcus Infection in Swine

The following is a report of the study of a number of sick hogs from which streptococci were isolated, together with an attempt to evaluate the significance of such microorganisms in diseased swine tissues. The hogs examined were from scattered herds, largely under 8 weeks of age. In some instances nothing was known of the condition of the droves of hogs concerned, either before or after the examinations. In others there was a fairly good history of the condition of the herd and the death losses. In general the cases may be divided into those in which the streptococci were present throughout the body tissues and those in which the infection was confined to the brain and its coverings or largely so. To obtain an understanding of the disease condition encountered in the various herds, some description of individual cases is given

Sporadic Bovine Encephalomyelitis

The infectious agent of sporadic bovine encephalomyelitis has now been propagated for nearly three years in developing chick embryos.This has afforded a convenient method of propagation while studying the causal agent. It is interesting that during all of this time in chick embryos, which represents more than 135 passages in series, there has been no apparent variation in the character of the infectious agent. It is as pathogenic for guinea pigs and cattle as when first isolated. Failure to recognize anything in the tissues of affected animals that would indicate the exact nature of the entity which causes the disease, led to an extension of the histological study to infected chick embryos, especially their membranes and yolk sacs

Swine Brucellosis: Results of Vaccination Experiment

This discussion will consist of a consideration of the results obtained in a recently concluded brucellosis vaccination or exposure experiment in hogs together with a brief review of the results reported by others

Scientific basis for safely shutting in the Macondo Well after the April 20, 2010 Deepwater Horizon blowout

As part of the government response to the Deepwater Horizon blowout, a Well Integrity Team evaluated the geologic hazards of shutting in the Macondo Well at the seafloor and determined the conditions under which it could safely be undertaken. Of particular concern was the possibility that, under the anticipated high shut-in pressures, oil could leak out of the well casing below the seafloor. Such a leak could lead to new geologic pathways for hydrocarbon release to the Gulf of Mexico. Evaluating this hazard required analyses of 2D and 3D seismic surveys, seafloor bathymetry, sediment properties, geophysical well logs, and drilling data to assess the geological, hydrological, and geomechanical conditions around the Macondo Well. After the well was successfully capped and shut in on July 15, 2010, a variety of monitoring activities were used to assess subsurface well integrity. These activities included acquisition of wellhead pressure data, marine multichannel seismic pro- files, seafloor and water-column sonar surveys, and wellhead visual/acoustic monitoring. These data showed that the Macondo Well was not leaking after shut in, and therefore, it could remain safely shut until reservoir pressures were suppressed (killed) with heavy drilling mud and the well was sealed with cement

Biomechanics of predator–prey arms race in lion, zebra, cheetah and impala

The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–impala, in their natural savannah habitat in Botswana. We show that although cheetahs and impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate

Higher dimensional VSI spacetimes

We present the explicit metric forms for higher dimensional vanishing scalar invariant (VSI) Lorentzian spacetimes. We note that all of the VSI spacetimes belong to the higher dimensional Kundt class. We determine all of the VSI spacetimes which admit a covariantly constant null vector, and we note that in general in higher dimensions these spacetimes are of Ricci type III and Weyl type III. The Ricci type N subclass is related to the chiral null models and includes the relativistic gyratons and the higher dimensional pp-wave spacetimes. The spacetimes under investigation are of particular interest since they are solutions of supergravity or superstring theory.Comment: 14 pages, changes in second paragraph of the discussio