Die beplanningsproses en ruimtelike analise in stedelike gebiede: 'n Kritiese kommentaar oor enkele aspekte van die Suid-Afrikaanse praktyk

Town planning relates to procedures in which choices are made on the construction of urban space. As a professional field, it can therefore be regarded as a "... process of identifying and analyzing problems and exploring and assessing options open to an urban community in the pursuit of general goals and specific land development goals" (Chapin & Kaiser, 1979: 63 ). Town planning includes in this regard the preparation, determination and implementation of spatial policy within the framework of a spatial planning process. In the modern planning approach there is a rational cyclical planning process (Roberts, 1974: 33-40).*This article is written in Afrikaans

The measurement of residential sprawl in the Johannesburg Metropolitan Area

Residential development in large parts of the Johannesburg metropolitan area is characterized by sprawl conditions. A simulation model was utilized to indi­cate the extent of future sprawl. Mul­tiple regression and Monte Carlo sim­ulation were used to fore cast residential growth to the year 2005. A sprawl index was developed to measure and compare sprawl situations under alternative plan­ning strategies. This index formulates that sprawl is dependent on distance from the built boundary, distance to the dominant work place and dwelling unit density. Simulations show that sprawl will decrease when the overall density is increased, development is concen­trated along major transport corridors and incentives are used to attract devel­opment to slowly expanding areas.&nbsp

Nucleosynthesis in Massive Stars With Improved Nuclear and Stellar Physics

We present the first calculations to follow the evolution of all stable nuclei and their radioactive progenitors in stellar models computed from the onset of central hydrogen burning through explosion as Type II supernovae. Calculations are performed for Pop I stars of 15, 19, 20, 21, and 25 M_sun using the most recently available experimental and theoretical nuclear data, revised opacity tables, neutrino losses, and weak interaction rates, and taking into account mass loss due to stellar winds. A novel ``adaptive'' reaction network is employed with a variable number of nuclei (adjusted each time step) ranging from about 700 on the main sequence to more than 2200 during the explosion. The network includes, at any given time, all relevant isotopes from hydrogen through polonium (Z=84). Even the limited grid of stellar masses studied suggests that overall good agreement can be achieved with the solar abundances of nuclei between 16O and 90Zr. Interesting discrepancies are seen in the 20 M_sun model and, so far, only in that model, that are a consequence of the merging of the oxygen, neon, and carbon shells about a day prior to core collapse. We find that, in some stars, most of the ``p-process'' nuclei can be produced in the convective oxygen burning shell moments prior to collapse; in others, they are made only in the explosion. Serious deficiencies still exist in all cases for the p-process isotopes of Ru and Mo.Comment: 53 pages, 17 color figures (3 as separate GIF images), slightly extended discussion and references, accepted by Ap

IAC-Star: a Code for Synthetic Color-Magnitude Diagram Computation

The code IAC-star is presented. It generates synthetic HR and color-magnitude diagrams (CMDs) and is mainly aimed to star formation history studies in nearby galaxies. Composite stellar populations are calculated on a star by star basis, by computing the luminosity, effective temperature and gravity of each star by direct bi-logarithmic interpolation in the metallicity and age grid of a library of stellar evolution tracks. Visual (broad band and HST) and infrared magnitudes are also provided for each star after applying bolometric corrections. The Padua (Bertelli et al. 1994, Girardi et al. 2000) and Teramo (Pietrinferni et al. 2004) stellar evolution libraries and various bolometric corrections libraries are used in the current version. A variety of star formation rate functions, initial mass functions and chemical enrichment laws are allowed and binary stars can be computed. Although the main motivation of the code is the computation of synthetic CMDs, it also provides integrated masses, luminosities and magnitudes as well as surface brightness fluctuation luminosities and magnitudes for the total synthetic stellar population, and therefore it can also be used for population synthesis research. The code is offered for free use and can be executed at the site {\tt http://iac-star.iac.es}, with the only requirement of referencing this paper and crediting as indicated in the site.Comment: Astronomical Journal, in pres

Methyl 4-(piperidin-1-ylcarbon­yl)benzoate

In the title compound, C14H17NO3, the piperidine ring has a chair conformation and an intra­molecular C—H⋯O inter­action stabilizes the mol­ecular conformation. In the crystal, weak inter­molecular C—H⋯O inter­actions occur

Description of the Scenario Machine

We present here an updated description of the "Scenario Machine" code. This tool is used to carry out a population synthesis of binary stars. Previous version of the description can be found at http://xray.sai.msu.ru/~mystery//articles/review/contents.htmlComment: 32 pages, 3 figures. Corrected typo

Reaction Rates Uncertainties and the Production of F19 in AGB Stars

We present nucleosynthesis calculations and the resulting 19F stellar yields for a large set of models with different masses and metallicity. We find that the production of fluorine depends on the temperature of the convective pulses, the amount of primary 12C mixed into the envelope by third dredge up and the extent of the partial mixing zone. Then we perform a detailed analysis of the reaction rates involved in the production of 19F and the effects of their uncertainties. We find that the major uncertainties are associated with the 14C(alpha,gamma)18O and the 19F(alpha,p)22Ne reaction rates. For these two reactions we present new estimates of the rates and their uncertainties. The importance of the partial mixing zone is reduced when using our estimate for the 14C(alpha,gamma)18O rate. Taking into account both the uncertainties related to the partial mixing zone and those related to nuclear reactions, the highest values of 19F enhancements observed in AGB stars are not matched by the models. This is a problem that will have to be revised by providing a better understanding of the formation and nucleosynthesis in the partial mixing zone, also in relation to reducing the uncertainties of the 14C(alpha,gamma)18O reaction rate. At the same time the possible effect of Cool Bottom Processing at the base of the convective envelope should be included in the computation of AGB nucleosynthesis. This process could in principle help matching the highest 19F abundances observed by decreasing the C/O ratio at the surface of the star, while leaving the 19F abundance unchanged.Comment: 40 pages, 8 figures, accepted for publication on the Astrophysical Journa