Computation of Bhat's OMIT maps with different coefficients

The OMIT electron-density-map calculation is very effective in discovering errors in a macromolecular structure determination. A Fortran program called OMIT has been written to calculate such maps and an investigation has been carried out into which coefficients for the map calculation produce the best OMIT maps. Testing of the program on Savinase showed that the best overall results were obtained when |Fo| without figure of merit was used. In regions where the map is incorrect, the most interesting OMIT maps are produced when only the figure of merit, or modified SIGMAA coefficients, are used as the initial map amplitude coefficients. Thus, these tests suggest that such OMIT maps are particularly useful to reconstruct the macromolecular model in the grossly incorrect regions of the model.

Jupiter - friend or foe? II: the Centaurs

It has long been assumed that the planet Jupiter acts as a giant shield, significantly lowering the impact rate of minor bodies upon the Earth, and thus enabling the development and evolution of life in a collisional environment which is not overly hostile. However, in the past, little work has been carried out to examine the validity of this idea. In the second of a series of papers, we examine the degree to which the impact risk resulting from objects on Centaur-like orbits is affected by the presence of a giant planet, in a continuing attempt to fully understand the impact regime under which life on Earth has developed. The Centaurs, which occupy orbits beyond Jupiter, have their origins in the Edgeworth-Kuiper belt that extends beyond Neptune. The giant planets peturb the Centaurs, sending a significanr fraction into the inner Solar System where they become visible as short-period comets. In this work we present results which show that the presence of a giant planet can act to significantly change the impact rate of short-period comets on the Earth, and that a giant planet often actually increases the impact flux greatly over that which would be expected were it not present. (Shortened version of abstract.)Comment: 13 pages, 1 Figur

AIDS AND ECONOMIC GROWTH IN SOUTH AFRICA

Morbidity and mortality effects are introduced into a three sector, Ramsey-type model of economic growth. The model is calibrated to South African national accounts data and used to examine the potential impact of HIV/AIDS on economic growth. Simulation results suggest a 10% decrease in the size of the effective labor force would lead to a 10% decrease in the long run (steady state) GDP levels. Similarly, a 10% decrease in the number of laborers would lead to an 11% drop in long run GDP.Health Economics and Policy, International Development, Labor and Human Capital,

A microprocessor based, multi-channel low-temperature monitoring system

A multi-channel low-temperature monitoring system and its design considerations are presented. The system is microprocessor based and specially designed to interface thermoresistive sensors in cryogenic experiments. The system can be easily expanded to accept any type of physical transducer and to perform other output functions, ie control functions

Effects of partial wrist arthrodesis on loading at the radiocarpal joints

The radiocarpal joint plays an important role in the stabilization of the wrist joint. Degenerative diseases such as rheumatoid arthritis can destabilize the joint and compromise the kinematics of the carpal bones. Partial wrist arthrodesis in the rheumatoid wrist has been popular since its introduction in 1983 [1]. The procedure prevents ulnar drift of the carpus and prevents progression to a subluxed state as well as providing pain relief for the patient. The biomechanical consequences of arthrodesis at the radiocarpal joint have not been extensively explored. This study looks at the biomechanical changes on the load transfer through the radiocarpal joint after partial wrist fusion

Loading on the Scapho-Trapezium-Trapezoid joint during gripping

The scapho-trapezium-trapezoid (STT) joint is believed to be highly vulnerable to wear and has been identified clinically as a high risk joint in arthritic patients. A theoretical model [1] of the load transfer through the wrist during gripping, suggests high activity in the STT ligaments in order to stabilize the carpus. During gripping complicated loading patterns are seen in the carpal bones and various intercarpal joints comprising the wrist joint. The aim was to investigate contact stresses at the STT joint in comparison to those occuring at the radiocarpal joint. Finite element model was created of the whole wrist joint with physiological loading conditions applied

Fifth annual conference on Alaskan placer mining

An abridged format of papers, presentations and addresses given during the 1983 conference held on March 30-31, 1983 compiled and edited by Bruce W. Campbell, Jim Madonna, and M. Susan Husted.Partial funding was provided by the Carl G. Parker Memorial Publishing Fund, University of Alaska, Fairbanks, and the Mining and Mineral Resources Research Institute, U.S. Department of the Interior, Bureau of Mines

Sensitivity of p-mode absorption on magnetic region properties and kernel functions

Aims. Magnetohydrodynamic (MHD) sausage tube waves are excited in magnetic flux tubes by p-mode forcing. These tube waves carry energy away from the p-mode cavity which results in a source of absorption. We wish to see the effect of an ensemble of randomly distributed thin magnetic flux tubes on the absorption of p-modes for the model plage region and also study the effect of the spacial weighting function on the theoretically calculated absorption coefficients. Methods. We calculate the absorption coefficients of p modes for a model plage, assumed to consist of an ensemble of many thin magnetic flux tubes with randomly distributed plasma properties. Each magnetic flux tube in the ensemble is modelled as axisymmetric, non-interacting, vertically oriented and untwisted. Results. We find that the magnitude and the form of the absorption coefficient is sensitive to the plasma-beta of the tubes which is consistent with previous work. Both the random distribution used to model the ensemble of flux tubes and the spatial weighting function inherent to the measurement of the absorption affect the absorption. As the width of the weighting function increases, the absorption increases

Finite element model creation and stability considerations of complex biological articulation : the human wrist joint

The finite element method has been used with considerable success to simulate the behaviour of various joints such as the hip, knee and shoulder. It has had less impact on more complicated joints such as the wrist and the ankle. Previously published finite element studies on these multi bone joints have needed to introduce un-physiological boundary conditions in order to establish numerical convergence of the model simulation. That is necessary since the stabilising soft tissue mechanism of these joints is usually too elaborate in order to be fully included both anatomically and with regards to material properties. This paper looks at the methodology of creating a finite element model of such a joint focussing on the wrist and the effects additional constraining has on the solution of the model. The study shows that by investigating the effects each of the constraints, a better understanding on the nature of the stabilizing mechanisms of these joints can be achieved