FAMILY REALITIES IN THE 21ST CENTURY: POLICY OPTIONS AND DIRECTIONS

Agricultural and Food Policy,

Directionality effects in the transfer of X-rays from a magnetized atmosphere: Beam pulse shape

A formalism is presented for radiation transfer in two normal polarization modes in finite and semiinfinite plane parallel uniform atmospheres with a magnetic field perpendicular to the surface and arbitrary propagation angles. This method is based on the coupled integral equations of transfer, including emission, absorption, and scattering. Calculations are performed for atmosphere parameters typical of X-ray pulsars. The directionality of the escaping radiation is investigated for several cases, varying the input distributions. Theoretical pencil beam profiles and X-ray pulse shapes are obtained assuming the radiation is emitted from the polar caps of spinning neutron stars. Implications for realistic models of accreting magnetized X-ray sources are briefly discussed

World Commodity Model for Fertilizers: The alternative long-term prognosis of the world fertilizer production, consumption and trade on the basis of an econometric model

The Food and Agriculture Research Program at IIASA deals with the world's food problems on two fronts: firstly it analyzes future food problems by building a system of national policy models and secondly, it studies production factors of agriculture aimed at improving technologies and solving the world's food problems. Fertilizers play an important role among the production factors in agriculture, and their growing use in the future will contribute to higher food level supplies both in developed and developing countries. The fertilizer model presented here was constructed for alternative long-range projection, consumption, and world trade and can be linked to agricultural, industrial and global models. The author helped to develop the Hungarian national policy model on food production at IIASA and is therefore acquainted with the efforts, principles and methodological procedures used to develop both global models. He hopes that the publication of this document on future fertilizers problems by IIASA will contribute to a better understanding of world food problems in the future

GRB Precursors in the Fallback Collapsar Scenario

Precursor emission has been observed in a non-negligible fraction of gamma-ray bursts.The time gap between the precursor and the main burst extends in some case up to hundreds of seconds, such as in GRB041219A, GRB050820A and GRB060124. Both the origin of the precursor and the large value of the time gap are controversial. Here we investigate the maximum possible time gaps arising from the jet propagation inside the progenitor star, in models which assume that the precursor is produced by the jet bow shock or the cocoon breaking out of the progenitor. Due to the pressure drop ahead of the jet head after it reaches the stellar surface, a rarefaction wave propagates back into the jet at the sound speed, which re-accelerates the jet to a relativistic velocity and therefore limits the gap period to within about ten seconds. This scenario therefore cannot explain gaps which are hundreds of seconds long. Instead, we ascribe such long time gaps to the behavior of the central engine, and suggest a fallback collapsar scenario for these bursts. In this scenario, the precursor is produced by a weak jet formed during the initial core collapse, possibly related to MHD processes associated with a short-lived proto-neutron star, while the main burst is produced by a stronger jet fed by fallback accretion onto the black hole resulting from the collapse of the neutron star. We have examined the propagation times of the weak precursor jet through the stellar progenitor. We find that the initial weak jet can break out of the progenitor in a time less than ten seconds (a typical precursor duration) provided that it has a moderately high relativistic Lorentz factor \Gamma>=10 (abridged).Comment: 8 pages, accepted by ApJ, this version contains significantly expanded discussion and an additional figure, conclusions unchange

On the applicability of the layered sine-Gordon model for Josephson-coupled high-T_c layered superconductors

We find a mapping of the layered sine-Gordon model to an equivalent gas of topological excitations and determine the long-range interaction potentials of the topological defects. This enables us to make a detailed comparison to the so-called layered vortex gas, which can be obtained from the layered Ginzburg-Landau model. The layered sine-Gordon model has been proposed in the literature as a candidate field-theoretical model for Josephson-coupled high-T_c superconductors, and the implications of our analysis for the applicability of the layered sine-Gordon model to high-T_c superconductors are discussed. We are led to the conjecture that the layered sine--Gordon and the layered vortex gas models belong to different universality classes. The determination of the critical temperature of the layered sine-Gordon model is based on a renormalization-group analysis.Comment: 7 pages, accepted for publication in J. Phys.: Condens. Matte

Self-consistent models for Coulomb heated X-ray pulsar atmospheres

Calculations of accreting magnetized neutron star atmospheres heated by the gradual deceleration of protons via Coulomb collisions are presented. Self consistent determinations of the temperature and density structure for different accretion rates are made by assuming hydrostatic equilibrium and energy balance, coupled with radiative transfer. The full radiative transfer in two polarizations, using magnetic cross sections but with cyclotron resonance effects treated approximately, is carried out in the inhomogeneous atmospheres

Mars-Earth geographical comparisons: A pictorial view

A collection of pictorial comparisons of prominent physiographic features found on Mars and Earth, consisting of equal-scale side-by-side pairs or cartographic overlays is presented. Martian features compared with terrestrial ones include Vales Marineris, the Tharsis bulge, Olympus Mons, the Hellas and Argyre basins, areas of catastrophic flooding, and the polar regions. The illustrations are accompanied by a brief descriptive text and bibliography

A geographic comparison of selected large-scale planetary surface features

Photographic and cartographic comparisons of geographic features on Mercury, the Moon, Earth, Mars, Ganymede, Callisto, Mimas, and Tethys are presented. Planetary structures caused by impacts, volcanism, tectonics, and other natural forces are included. Each feature is discussed individually and then those of similar origin are compared at the same scale

World Atlas of large optical telescopes (second edition)

By early 1986 there will be over 120 large optical telescopes in the world engaged in astronomical research with mirror or lens diameters of one meter (39-inches) and larger. This atlas gives information on these telescopes and shows their observatory sites on continent sized maps. Also shown are observatory locations considered suitable for the construction of future large telescopes. Of the 126 major telescopes listed in this atlas, 101 are situated in the Northern Hemisphere and 25 are located in the Southern Hemisphere. The totals by regions are as follows: Europe (excluding the USSR), 30; Soviet Union, 9; Asia (excluding the USSR), 5; Africa, 9; Australia, 6; The Pacific, 4 (all on Hawaii); South America, 17; North America, 46 (the continental US has 38 of these). In all, the United States has 42 of the world's major telescopes on its territory (continental US plus Hawaii) making it by far the leading nation in astronomical instrumentation

Planetary size comparisons: A photographic study

Over the past two decades NASA spacecraft missions obtained photographs permitting accurate size measurements of the planets and moons, and their surface features. Planetary global views are displayed at the same scale, in each picture to allow visual size comparisons. Additionally, special geographical features on some of the planets are compared with selected Earth areas, again at the same scale. Artist renderings and estimated sizes are used for worlds not yet reached by spacecraft. Included with each picture is number designation for use in ordering copies of the photos