The mass and helium discrepancy in massive stars: The case Vela X-1

A NLTE-analysis is presented of high S/N spectra of the optical component of the standard massive X-ray binary Vela X-1. In combination with the orbital parameters we conclude that the optical star is highly helium enriched and is significantly overluminous compared to standard evolutionary tracks of massive accretion stars. We then propose a new accretion model able to explain these features.     

Evaluation of light emitting diode characteristics for a space-based plant irradiation source.

Light emitting diodes (LEDs) are a promising irradiation source for plant growth in space. Improved semiconductor technology has yielded LED devices fabricated with gallium aluminum arsenide (GaAlAs) chips which have a high efficiency for converting electrical energy to photosynthetically active radiation. Specific GaAlAs LEDs are available that emit radiation with a peak wavelength near the spectral peak of maximum quantum action for photosynthesis. The electrical conversion efficiency of installed systems (micromole s-1 of photosynthetic photons per watt) of high output LEDs can be within 10% of that for high pressure sodium lamps. Output of individual LEDs were found to vary by as much as 55% from the average of the lot. LED ratings, in mcd (luminous intensity per solid angle), were found to be proportional to total photon output only for devices with the same dispersion angle and spectral peak. Increasing current through the LED increased output but also increased temperature with a consequent decrease in electrical conversion efficiency. A photosynthetic photon flux as high as 900 micromoles m-2 s-1 has been produced on surfaces using arrays with LEDs mounted 7.6 mm apart, operating as a current of 50 mA device-1 and at an installed density of approximately 17,200 lamps m-2 of irradiated area. Advantages of LEDs over other electric light sources for use in space systems include long life, minimal mass and volume and being a solid state device.     

Computer analysis of the lineaments of Nepal

Various information has been obtained by computer analysis of the lineaments of Nepal. The data were carefully studied and correlated to establish the relationships of lineaments with geological units, structure, mineralization, etc. The lineament map of Nepal was prepared during 1977–1978; the lineament data were digitized in 1982—using a Hewlett Packard system 45 desktop computer—separated by area (east, central and west Nepal) and also according to geological units. By trial and error and using all variables, the different preferred orientation classes were identified for east, central and west Nepal. Lineaments were grouped according to length into less than 10 km, 10–20 km, 20–30 km and more than 30 km, for the entire country and also for major geological units, i.e., Siwalik (sub-Himalaya), Lesser Himalaya (midlands) and Higher Himalaya. Various rose diagrams and histograms showing frequency and lengths of lineaments were plotted for the different geological units and the different sectors. Lineaments associated with granites of major subdivisions were plotted separately and analysed.     

Synoptic observations of coronal transients and their interplanetary consequences

A small coronagraph has been placed in orbit to monitor the sun's outer corona from 2.5 to 10.0 solar radii, and five years of nearly continuous synoptic observations have now been completed. Rapid and sensitive image processing techniques have been developed to screen the data for transient phenomena, particularly coronal mass ejections (CMEs). About 50,000 coronal images have been examined, out of a five-year total of 68,000, and a standardized listing of more than 1,200 coronal transients for the period 1979–1982 has been prepared. These data have been analysed in the light of other available information, particularly on conditions in the interplanetary plasma. The dynamical characteristics of the active corona, as they are beginning to emerge from the data, are presented. We find that coronal mass ejections exercise significant influence on the interplanetary solar wind. They are the source of disturbances that are frequent and energetic, that tend to be somewhat focussed, that often reach shock intensity, and that propagate to large heliocentric distances, sometimes causing major geomagnetic storms.     

Potential defense applications of expert systems

The authors provide an overview of expert systems and how they may effect the development of future defense applications. Military uses of computers are outlined, and expert-systems fundamentals are described. Artificial research and development efforts by the military are examined, and potential military applications are discussed. Expert systems efforts at NASA, by the US Air Force, and for the Strategic Defence Initiative are considered     

Preliminary data of the thermal regime and circulation in the upper mesosphere and mesopause

Circulation and thermal structure for the 90–95 km region is described on the basis of the joint analysis of direct and indirect sounding data. Mean season charts of the 0.001 mb surface were compiled using data from meteor trials, ionospheric drifts, rocket launchings and data of the rotational temperature of hydroxyl emission.     

Some recent results in the interpretation of high brightness temperature microwave spike emission

Theoretical work on the interpretation of high brightness temperature microwave spike emission is reviewed, with emphasis upon recent contributions from the University of Maryland. Recent work on the interpretation of the spike emission as gyrosynchrotron masering is reviewed. Two alternative radiation mechanisms, stimulated plasma emission from the coherent intraction of electrostatic upper hybrid waves and from the interaction of electron plasma waves, are also discussed.     

Telerobotics: problems and research needs

With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of `telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA     

Matter streams in Algol-like systems

Simulations of the Algol-like binary CX Draconis, combined with IUE observations of the stream of material escaping the system can place limits on the inclination of the system and give estimates, via line profile synthesis, of the mass-loss rate at the L1 point.     

Matter streams in Algol-like systems

Simulations of the Algol-like binary CX Draconis, combined with IUE observations of the stream of material escaping the system can place limits on the inclination of the system and give estimates, via line profile synthesis, of the mass-loss rate at the L1 point.