An aid to the development of Botswana's resources

There are no author-identified significant results in this report

Genetic Family and Stock Type Influence Simulated Loblolly Pine Yields from Wet Sites

Planting adapted families or a bulked seedlot of bare-root and container-grown-seedlings of loblolly pine (Pinus taeda L) were contrasted as cost effective alternatives for regenerating Arkansas\u27 wet sites. Survival data from two wet sites were used to simulate 15 years of growth. Containerized seedlings provided 17% greater survival than bare-root seedlings, but yielded a lower present net worth than bare-root seedlings. Planting families adapted to excessive moisture provided 7% greater survival and yielded a greater present net worth than planting a bulked seedlot consisting of adapted and poorly adapted families

The effect of flight line spacing on radioactivity inventory and spatial feature characteristics of airborne gamma-ray spectrometry data

Airborne Gamma Spectrometry (AGS) is well suited to the mapping of radioactivity in the environment. Flight parameters (e.g. speed and line spacing) directly affect the rate of area coverage, cost, and data quality of any survey. The influences of line spacing have been investigated for data from inter‐tidal, coastal and upland environments with a range of <sup>137</sup>Cs activity concentrations and depositional histories. Estimates of the integrated <sup>137</sup>Cs activity (‘inventory’) within specified areas and the shapes of depositional features were calculated for subsets of the data at different line spacings. Features with dimensions greater than the line spacing show variations in inventory and area of less than 3%, and features with dimensions less than the line spacing show larger variations and a decreased probability of detection. The choice of line spacing for a task is dependent on the dimensions of the features of interest and required edge definition. Options for line spacing for different tasks are suggested. It is noted that for regional mapping, even 5–10 km line spacing can produce useful data

A comparative study of the surface glaze characteristics of concrete treated with CO2 and high power diode lasers. Part II: mechanical, chemical and physical properties

The hardened ordinary Portland cement (OPC) surface layer of concrete which was glazed using a CO2 and a high power diode laser (see Part I of this paper) has been tested in order to determine the mechanical, chemical and physical characteristics of the glazes. The work showed that the generation of the surface glazes resulted in improved mechanical, chemical and physical properties over the untreated OPC surface of concrete. However, differences in the performance of the CO2 and HPDL generated glazes were observed. These are believed to be due to the differences in the morphology and microstructure of the glazes generated as a result of the differing beam absorption characteristics of the two lasers. Life assessment testing revealed that the laser glazed OPC surfaces effected an increase in actual wear life of 1.3 to 17.7 times over the untreated OPC surface of concrete depending upon the corrosive environment

First report of Metarhizium anisopliae IP 46 pathogenicity in adult Anopheles gambiae s.s. and An. arabiensis (Diptera; Culicidae).

The entomopathogenic fungus Metarhizium anisopliae isolate IP 46, originating from a soil sample collected in 2001 in the Cerrado of Central Brazil, was tested for its ability to reduce the survival of adult male and female Anopheles gambiae s.s. and An. arabiensis mosquitoes. A 6-h exposure to the fungus coated on test paper at a concentration of 3.3 x 106 conidia cm-2 reduced the daily survival of both mosquito species (HR = 3.14, p < 0.001), with higher risk of dying in An. gambiae s.s relative to An. arabiensis (HR = 1.38, p < 0.001). Fungal sporulation was observed in >95% of mosquito cadavers in the treatment groups. The results indicate that M. anisopliae IP 46 has the potential to be a bio-control agent for African malaria vector species, and is a suitable candidate for further research and development

Publications of the space physiology and countermeasures program, Musculoskeletal Discipline: 1980-1990

A 10-year cumulative bibliography of publications resulting from research supported by the musculoskeletal discipline of the space physiology and countermeasures program of NASA's Life Sciences Division is provided. Primary subjects are bone, mineral, and connective tissue, and muscle. General physiology references are also included. Principal investigators whose research tasks resulted in publication are identified by asterisk. Publications are identified by a record number corresponding with their entry in the life sciences bibliographic database, maintained by the George Washington University

Stanford Aerospace Research Laboratory research overview

Over the last ten years, the Stanford Aerospace Robotics Laboratory (ARL) has developed a hardware facility in which a number of space robotics issues have been, and continue to be, addressed. This paper reviews two of the current ARL research areas: navigation and control of free flying space robots, and modelling and control of extremely flexible space structures. The ARL has designed and built several semi-autonomous free-flying robots that perform numerous tasks in a zero-gravity, drag-free, two-dimensional environment. It is envisioned that future generations of these robots will be part of a human-robot team, in which the robots will operate under the task-level commands of astronauts. To make this possible, the ARL has developed a graphical user interface (GUI) with an intuitive object-level motion-direction capability. Using this interface, the ARL has demonstrated autonomous navigation, intercept and capture of moving and spinning objects, object transport, multiple-robot cooperative manipulation, and simple assemblies from both free-flying and fixed bases. The ARL has also built a number of experimental test beds on which the modelling and control of flexible manipulators has been studied. Early ARL experiments in this arena demonstrated for the first time the capability to control the end-point position of both single-link and multi-link flexible manipulators using end-point sensing. Building on these accomplishments, the ARL has been able to control payloads with unknown dynamics at the end of a flexible manipulator, and to achieve high-performance control of a multi-link flexible manipulator

Amazonian‐aged fluvial valley systems in a climatic microenvironment on Mars: Melting of ice deposits on the interior of Lyot Crater

Valley networks, regional drainage patterns suggesting liquid water stability at the surface, are confined to early in the history of Mars (the Noachian/Hesperian boundary and before), prior to a major climate transition to the hyperarid cold conditions of the Amazonian. Several later fluvial valley systems have been documented in specific Hesperian and Early Amazonian environments, and are thought to have formed due to local conditions. Here we describe fluvial valley systems within Lyot crater that have the youngest well-constrained age reported to date (Middle or Late Amazonian) for systems of this size (tens of km). These valleys are linked to melting of near-surface ice-rich units, extend up to ∼50 km in length, follow topographic gradients, and deposit fans. The interior of Lyot crater is an optimal micro-environment, since its low elevation leads to high surface pressure, and temperature conditions at its location in the northern mid-latitudes are sufficient for melting during periods of high-obliquity. This micro-environment in Lyot apparently allowed melting of surface ice and the formation of the youngest fluvial valley systems of this scale yet observed on Mars

Alpine river ecosystem response to glacial and anthropogenic flow pulses

Alpine glacier-fed river hydrology, chemistry and biology can vary significantly both in space and over diurnal to inter-annual timescales, as a function of dynamic inputs of water from snow, ice and groundwater. The sensitivity of biota to these water source dynamics potentially makes them susceptible to hydrological changes induced by anthropogenic activities, such as flow regulation, but most alpine studies have focused on intact rivers and during summer only. We examined the patiotemporal dynamics of physicochemical habitat and macroinvertebrate communities in a high (>2000m) altitude floodplain in the European Alps over an 18 month period. A novel insight is presented into the river system and macroinvertebrate community responses to both natural glacier melt driven expansion-contraction of unregulated river sites, and intermittent flow pulses due to hydropower regulation. Mainstem glacier-fed river sites displayed cyclical seasonal dynamics in macroinvertebrate community composition, shifting to be partly reminiscent of groundwater tributaries in winter then back to meltwater again in the following spring. Significant unimodal relationships were observed between glacial influence and macroinvertebrate community density, richness, Simpson's diversity, evenness and beta diversity. These relationships suggest that glacial influence can have positive effects on biodiversity where glacier meltwater mixes with non-glacial water and habitat diversity is maximised. Regulationinduced flow pulses led to inconsistent responses amongst macroinvertebrates, with no significant effects in summer 2008 but increased density and decreased taxonomic richness in 2009. Furthermore, macroinvertebrate community composition was not affected significantly by reservoir releases despite significant increases in water temperature and discharge at these times. The effects of alpine river management for hydropower production on macroinvertebrate communities in this river system appear to be relatively minor, but further studies need to be undertaken in other alpine locations to assess the generality of this finding