Area and degree of occupation of the surface of precipitates of barium sulphate

Zusammenfassung Die spezifische Oberfläche von BaSO₄-Niederschlägen wurde bestimmt durch Messung des Austausches von Oberflächen-Ba-Ionen mit-radioaktiven Ba¹³¹-Ionen (spezifische Aktivität etwa 1 mc/g) einer gesättigten BaSO₄-Lösung. Die spezifische Oberfläche war 5150 cm²/g.Dann wurden die Adsorptionsisothermen von Farbstoffen (Kristallviolett, Methylenblau und Pikrinsäure) an der Oberfläche von BaSO₄-Teilchen bestimmt. Unter der Annahme, dass jedes Farbstoffmolekül im adsorbierten Zustand eine Oberfläche von 100 A² einnimmt, ergab sich ein maximaler Besetzungsgrad von 22–30%.     

Effects of water acidification on the distribution pattern and the reproductive success of amphibians

Summary Nine amphibian species were encountered in poorly buffered waters of The Netherlands (alkalinity 1 meq·l^–1). These soft water systems are highly sensitive to acidifying precipitation. The number of species as well as the percentage of waters which harbour amphibian populations are strongly reduced in the extremely acid pH-class . The reproductive success of amphibians is negatively affected by low pH. The eggs become heavily infested with fungi (Saprolegniaceae). In acidifying systems many physico-chemical parameters are significantly correlated with the pH of the water. Strongly acidified waters are characterized by low alkalinity, conductivity and ionic content but high acidity and high concentrations of (heavy) metals and ammonium and a high relative sulphate concentration. Culture experiments with eggs and larvae ofRana arvalis. Rana esculenta, Rana temporaria andBufo bufo show that apart from the pH, elevated aluminium, cadmium and ammonium contents may also affect the reproductive success of amphibians.     

Archaeology and age of a new hominin from Flores in eastern Indonesia

Excavations at Liang Bua, a large limestone cave on the island of Flores in eastern Indonesia, have yielded evidence for a population of tiny hominins, sufficiently distinct anatomically to be assigned to a new species, Homo floresiensis. The finds comprise the cranial and some post-cranial remains of one individual, as well as a premolar from another individual in older deposits. Here we describe their context, implications and the remaining archaeological uncertainties. Dating by radiocarbon (14C), luminescence, uranium-series and electron spin resonance (ESR) methods indicates that H. floresiensis existed from before 38,000 years ago (kyr) until at least 18 kyr. Associated deposits contain stone artefacts and animal remains, including Komodo dragon and an endemic, dwarfed species of Stegodon. H. floresiensis originated from an early dispersal of Homo erectus (including specimens referred to as Homo ergaster and Homo georgicus) that reached Flores, and then survived on this island refuge until relatively recently. It overlapped significantly in time with Homo sapiens in the region, but we do not know if or how the two species interacted.     

Discovery of the short gamma-ray burst GRB 050709

Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts. The latter are now known to have X-ray and optical afterglows, to occur at cosmological distances in star-forming galaxies, and to be associated with the explosion of massive stars. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow and (for the first time) the optical afterglow of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.