Physical controls on sand composition and relative durability of detrital minerals during ultra‐long distance littoral and aeolian transport (Namibia and southern Angola)

Sediment in coastal Namibia to southern Angola is supplied dominantly from the Orange River with minor additional fluvial input and negligible modifications by chemical processes, which makes this a great test case for investigating physical controls on sand texture and composition. This study monitored textural, mineralogical and geochemical variability in beach and aeolian‐dune sands along a ca 1750 km stretch of the Atlantic coast of southern Africa by using an integrated set of techniques, including image analysis, laser granulometry, optical microscopy, Raman spectroscopy and bulk‐sediment geochemistry. These results contrast with previous reports that feldspars and volcanic detritus break down during transport, that sand grains are rounded rapidly in shallow‐marine environments, and that quartzose sands may be produced by physical processes. Mechanical wear is unable to modify the relative abundance of detrital components, including pyroxene and mafic volcanic rock fragments traditionally believed to be destroyed rapidly. The sole exceptions are poorly lithified or cleaved sedimentary/metasedimentary rock fragments, readily lost at the transition to the marine environment, and slow‐settling flaky micas, winnowed and deposited offshore. Coastal sediments tend to be depleted in relatively mobile amphibole, preferentially entrained offshore or re‐deposited in sheltered beaches, while less mobile garnet is retained onshore. No detrital mineral displays a significant increase in grain roundness after 300 to 350 km of longshore transport in high‐energy littoral environments from the Orange mouth to south of the Namib Erg, but all minerals get rapidly rounded after passing into the dunefield. Pyroxene and opaques get rounded faster than harder quartz and garnet, but sand mineralogy remains unchanged. Excepting strong transient selective‐entrainment effects, physical processes are unable to modify sand composition significantly. Selective mechanical breakdown can be largely neglected in quantitative provenance analysis of sand and sandstone even in the case of ultra‐long‐distance transport in high‐energy environments dominated by strong persistent winds and waves.     

Climate signal in varve thickness: Lake La Cruz (Spain), a case study

Lake La Cruz is a meromictic, karstic lake with annually laminated sediment formed by summer pulses of calcite deposition. The aim of this study was to explore the potential use of the laminated sediment from Lake La Cruz as a quantitative climate proxy, by calibrating lamina thickness against instrumental climate data. Statistical analysis of the relation between lamina thickness and the meteorological dataset indicated a high correlation between calcium carbonate lamina thickness and rainfall from December to March (r  = 0.725, P < 0.01, n = 35). Winter rainfall anomalies in the area are, in turn, highly negatively correlated with the North Atlantic Oscillation index (NAO, r = −0.832; P < 0.01; n = 53). We propose a regression model to infer past winter rainfall from calcium carbonate laminae thickness. These results highlight new possibilities for paleoenvironmental research using calcite laminated sediment records as climate proxies, especially to study past rainfall variability.     

Pressure and density gradients in H II Regions

Here we discuss the effects of large ambient pressures and decreasing density gradients on the observed properties of dusty UC hii regions. Dust absorption can effectively reduce the size of the photo ionized region, and density gradients can modify the spectral index of the emission. The effects of the density gradients seem to be present in both galactic and extragalactic HII regions.     

The Jolomba,Angola LL6 chondrite

Abstract— Accompanied by loud thunder at about 1.30 pm (local time) on 3 February 1974, a single stone weighing approx. 480 g was seen to fall and was recovered near the Jolomba village, Huambo District, Angola. The stone is strongly brecciated, has dark-greyish angular fragments within a lighter matrix and does not exhibit any chondritic textures. Jolomba consists of olivine (Fa 31), orthopyroxene (Fs 25), sodic plagioclase (An 11), sulphides (troilite), very scarce nickel-iron (Ni up to 56%), oxides (chromite and ilmenite) and apatite. Pervasive fracturing of silicates suggests that Jolomba suffered strong brecciation and partial recrystallization. Mineralogy and bulk chemical analysis indicate that Jolomba belongs to the LL group of chondrites (amphoterites). Uniform olivine and pyroxene composition, well-crystallized plagioclase and textural features in general indicate that Jolomba belongs to the petrologic type 6.     

A relation between ultraviolet excess and superficial gravity for Cepheids

A linear relation is calculated between the six-colour ultraviolet excess and superficial gravity for Cepheid variables. This excess appears to be a sensitive indicator of gravity behaviour for these stars.On leave from Departamento de Astronomia, Instituto Astronômico e Geofisico da Universidade de São Paulo, Brasil.     

DDO photometry and metallic abundances of E and SO galaxies and globular clusters of the LMC and SMC

Metallicity of 8 E and SO galaxies as well as that of red globulars of the LMC and SMC were obtained by means of DDO integrated photometry calibrated with galactic globular clusters (Bica and Pastoriza, 1983; hereafter referred to as Paper I). A correction was obtained in order to reduce the colors of the galaxies to zero redshift. The relation metallicity vsM _V for the galaxies is analyzed (adding to our sample the observations of McClure and Van den Bergh, 1968; and Faber, 1973a). For the Magellanic Clouds we found metallicity ranging from intermediate to poor.     

Economic restructuring, social re-composition and recent urban changes in Portugal

The productive restructuring process has affected more than just the economic field, because its effects have been felt on urbanisation processes, on social relations, and on the spatial organisation of society. Starting from the ‘metapolis’ concept, developed by Ascher (1995), we analyse the evolution of new forms of urban space in Portugal, arguing that new urban forms generate new social inequalities and, in extreme cases, social exclusion. Portugal is a semi-peripheral country that combines certain of the trends in social and economic organisation common to core countries, with certain trends more common in the developing world. Thus the understanding of urban change in Portugal is a complex task, made more difficult by the rapidity of processes since the mid 1970s. The Lisbon Metropolitan Area has been deeply affected by the productive restructuring process. The role of economic and urban policies in the Lisbon region is discussed, and an assessment is made of certain measures aimed at solving economic and social problems. This revised version was published online in August 2006 with corrections to the Cover Date.     

Forecasting El Niño and La Niña events using decision tree classifier

Theoretical and Applied Climatology - The El Niño-Southern Oscillation (ENSO) phenomenon affects the global climate by changing temperature and precipitation patterns mainly in tropical...     

Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.