Fluorine production in intermediate-mass stars

The 19F production during the first dozen thermal pulses of AGB stars with (M=3,Z=0.02), (M=6,Z=0.02) and (M=3,Z=0.001) is investigated on grounds of detailed stellar models and of revised rates for 15N(a,g)19F and 18O(a,g)22Ne. These calculations confirm an early expectation that 19F {\it is} produced in AGB thermal pulses. They also enlarge substantially these previous results by showing that the variations of the level of 19F production during the evolution is very sensitive to the maximum temperature reached at the base of the pulse. These variations are analyzed in detail, and are shown to result from a subtle balance between different nuclear effects (mainly 19F production or destruction in a pulse, and 15N synthesis during the interpulse), possibly super-imposed on dilution effects in more or less extended pulse convective tongues. Our calculations, as most others, do not predict the third dredge-up self- consistently. When parametrized, it appears that our models of intermediate-mass AGB stars are able to account only for the lowest 19F overabundances observed in solar-metallicity MS, S and C stars. That conclusion is expected to hold true for low-mass stars when F production results from secondary 13C only. Massive AGB stars, on the other hand, are not expected to build up large surface F abundanc- es. Therefore, the large F overabundance reported for the super Li-rich star WZ Cas (where HBB is supposed to be operating) remains unexplained so far. Our results for the (M=3,Z=0.001) star indicate that F surface overabundances can also be expected in low-metallicity stars provided that third dredge-ups occur after the early cool pulses. The relative increase in the surface 19F/12C ratio is, however, lower in the low-metallicity than in the solar-metallicity star. No observations areComment: 27 pages, includes figures, postcript file (A&A format, 15 pages including figures) can be found via anonymous ftp at ftp://obsftp.unige.ch/pub/mowlavi/fluor.ps.gz ; accepted by A&

Privatisation debates in Poland before and after communist demise: A comparative perspective

Poland and Hungary, the most persistent tinkerers with the Soviet economic system, became also the first communist countries to have allowed debates on the need to rearrange the structure of property rights in the economy as a way to improve its performance. Elsewhere, until the end of the 1980s, these debates were either explicitely rejected (as in Czechoslovakia or former G.D.R.) or much more limited (as in the USSR under Gorbachev). In what follows, the present writer will explain the politico-economic context, within which these debates were taking place, and will outline major options proposed there. Moving from minor to major changes formulated in the debate, I begin by presenting some proposals that kept the status of state ownership unchanged, and later evaluate further reaching ones. Also, these options, or most of them, had their predecessors in earlier debates in the West. Therefore, wherever important, linkages to these debates have been made as well.

Cometary spectroscopy and imaging

The objective is to investigate the spectroscopic and morphological characteristics of comets and selected minor planets over a wide range of heliocentric distances as they may suggest or constrain models of cometary processes, their formation environments and evolution. Direct images of all observable comets and 300-800 nm spectra of the brighter ones are obtained on a monthly basis with a charge coupled device spectrograph-camera. The direct images may be used for astrometry, photometry, and studies of coma and tail morphology. In some cases, anisotropic dust emission can provide information on the nucleus spin vector. Spectra may provide data on strengths of the principle emission for comparison of gas/dust ratios of a large sample of comets. Long integrations of minor planets in comet-like and nearby orbits are made to search for faint comae

Uncertainties in field-line tracing in the magnetosphere. <br>Part II: the complete internal geomagnetic field

International audienceThe discussion in the preceding paper is restricted to the uncertainties in magnetic-field-line tracing in the magnetosphere resulting from published standard errors in the spherical harmonic coefficients that define the axisymmetric part of the internal geomagnetic field (i.e. gn0 ± ?gn0). Numerical estimates of these uncertainties based on an analytic equation for axisymmetric field lines are in excellent agreement with independent computational estimates based on stepwise numerical integration along magnetic field lines. This comparison confirms the accuracy of the computer program used in the present paper to estimate the uncertainties in magnetic-field-line tracing that arise from published standard errors in the full set of spherical harmonic coefficients, which define the complete (non-axisymmetric) internal geomagnetic field (i.e. gnm ± ?gnm and hnm ± ?hnm). An algorithm is formulated that greatly reduces the computing time required to estimate these uncertainties in magnetic-field-line tracing. The validity of this algorithm is checked numerically for both the axisymmetric part of the internal geomagnetic field in the general case (1 ? n ? 10) and the complete internal geomagnetic field in a restrictive case (0 ? m ? n, 1 ? n ? 3). On this basis it is assumed that the algorithm can be used with confidence in those cases for which the computing time would otherwise be prohibitively long. For the complete internal geomagnetic field, the maximum characteristic uncertainty in the geocentric distance of a field line that crosses the geomagnetic equator at a nominal dipolar distance of 2 RE is typically 100 km. The corresponding characteristic uncertainty for a field line that crosses the geomagnetic equator at a nominal dipolar distance of 6 RE is typically 500 km. Histograms and scatter plots showing the characteristic uncertainties associated with magnetic-field-line tracing in the magnetosphere are presented for a range of illustrative examples. Finally, estimates are given for the maximum uncertainties in the locations of the conjugate points of selected geophysical observatories. Numerical estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, including the associated uncertainties in the locations of the conjugate points of geophysical observatories, should be regarded as "first approximations'' in the sense that these estimates are only as accurate as the published standard errors in the full set of spherical harmonic coefficients. As in the preceding paper, however, all computational techniques developed in this paper can be used to derive more realistic estimates of the uncertainties in magnetic-field-line tracing in the magnetosphere, following further progress in the determination of more accurate standard errors in the spherical harmonic coefficients

A framework for sustainable port planning in inland ports: a multistakeholder approach

In the European Union, all levels of government are convinced that an accelerated development of a modal shift towards inland navigation is one of the key requirements for reducing congestion and environmental externalities. This is becoming increasingly important, given the fast growing (road) transport needs at the macro-economic level. It is expected that inland ports can play a crucial role in achieving such a modal shift. However, many inland ports are confronted with important spatial, socio-economic and regulatory constraints as, historically, they have been located in the centre of large (capital) cities and other high density urban regions. As a result, they face constant pressure from a variety of stakeholders (urban residents, leisure industry, ecological movement, ?) and they must continuously defend their right of existence. The aim of this paper is to present a conceptual framework for inland port planning that builds upon a multistakeholder ? multicriteria approach, which takes into account all the short-term and long-term stakeholder preferences and objectives, in order to realize sustainable port development. This framework will also deal with the complexity of the port function in urban regions, as these ports/activities are in most cases dispersed over the urban region, whereby each port ?zone? has its own specific spatial, socio-economic, and regulatory characteristics. The combination of existing literature in the fields of (urban) port development and multicriteria analysis, and empirical evidence, gathered during the development of a strategic masterplan for the inland Port of Brussels, will permit the formulation of a new approach to inland port development.

The Direction of Australian Investment from 1985/86 to 1988/89

Using unpublished data at a disaggregated level, this paper provides a detailed picture of the direction of investment over the 1985/86 to 1988/89 investment boom. Most of the growth in non-farm capital expenditure has been concentrated in a few industries, in particular, office construction. We also calculate an improved measure of the proportion of manufacturing investment which was directed towards tradeable capacity. This shows a modest rise in the latter part of the period studied.