THE ADOPTION OF HIGH YIELDING WHEATS IN TUNISIA

Since 1966 strenuous efforts have been made to introduce into Tunisia some of the new high yielding wheat varieties in order to accelerate cereals production. This paper seeks to analyze some of the data now available on the new wheats in Tunisia and to explore some of the economic problems of increased cereals production with these varieties.Crop Production/Industries,

HOUSEHOLD DEMAND FOR PET FOOD AND THE OWNERSHIP OF CATS AND DOGS: AN ANALYSIS OF A NEGLECTED COMPONENT OF U.S. FOOD USE

Demand and Price Analysis,

RATLER: Robotic All-Terrain Lunar Exploration Rover

A robotic rover vehicle designed for use in the exploration of the Lunar surface is described. The Robotic All-Terrain Lunar Exploration Rover (RATLER) is a four wheeled all-wheel-drive dual-body vehicle. A uniquely simple method of chassis articulation is employed which allows all four wheels to remain in contact with the ground, even while climbing over step-like obstacles as large as 1.3 wheel diameters. Skid steering and modular construction are used to produce a simple, rugged, highly agile mobility chassis with a reduction in the number of parts required when compared to current designs being considered for planetary exploration missions. The design configuration, mobility parameters, and performance of several existing RATLER prototypes are discussed

NASCAP modelling computations on large optics spacecraft in geosynchronous substorm environments

The NASA Charging Analyzer Program (NASCAP) is used to evaluate qualitatively the possibility of such enhanced spacecraft contamination on a conceptual version of a large satellite. The evaluation is made by computing surface voltages on the satellite due to encounters with substorm environments and then computing charged particle trajectories in the electric fields around the satellite. Particular attention is paid to the possibility of contaminants reaching a mirror surface inside a dielectric tube because this mirror represents a shielded optical surface in the satellite model used. Deposition of low energy charged particles from other parts of the spacecraft onto the mirror was found to be possible in the assumed moderate substorm environment condition. In the assumed severe substorm environment condition, however, voltage build up on the inside and edges of the dielectric tube in which the mirror is located prevents contaminants from reaching the mirror surface

Provisional specification for satellite time in a geomagnetic environment

Satellites in geosynchronous orbit were experiencing operational anomalies. These anomalies are believed to be due to the environment charging the spacecraft surfaces to a point where discharges occur. In designing future satellites for long term operation at geosynchronous altitude, it is important that designers have a specification that will give the total time per year, the particle flux density and particle energies that their satellites can be expected to encounter in these substorm environmental conditions. The limited data currently available on the environmental conditions are used to generate the provisional specification given in this report

Charging characteristics of materials: Comparison of experimental results with simple analytical models

A one-dimensional model for charging of samples is used in conjunction with experimental data taken to develop material charging characteristics for silvered Teflon. These characteristics are then used in a one dimensional model for charging in space to examine expected response. Relative charging rates as well as relative charging levels for silvered Teflon and metal are discussed

The algal communities of colliery spoil heaps

A survey of the soil algae present on old coal mine spoil heaps at East Holywell, Tyne and Wear (O.S sheet NZ 37 ref. 313730 ) was carried out during 1979-1980. Samples were taken at monthly intervals from eight permanent quadratso The sites chosen provided a range of spoil types, including some devoid of higher plants and others where colonization was well developed. Algae were isolated and their density quantified using a dilution plate technique A limited flora was recorded at favourable sites on both shale (15 genera) and washeries waste (19 genera). The density of algae in the spoil at sites which were stable, moist and had a pH of about 7 was comparable to that reported for a range of natural soils Seasonal fluctuations in algal density were recorded with a general increase in spring and late summer and a decrease in autumn and winter. A marked decrease in mid-summer which coincided with a period of drought was recored at several sites. At five of the eight sites both a small number of algal species and low population densities were recorded. This was ascribed to the extreme nature of the physical and chemical environment. Evidence was however obtained that at one site the soil algae were acting as primary colonizers