Minerals and the Common Fund for Commodities

This paper reviews the role of minerals in the Integrated Programme for Commodities and the objectives and problems of the Second Account of the Common Fund for Commodities (CFC). It focuses on the least developed countries in Africa, providing specific suggestions for R&D to improve mineral exploration techniques in rain forest and savanna regions; to reduce mine exploration costs; to design equipment suitable for mining narrow veins; to improve concentrating methods for certain ores and to optimize byproduct recovery; to reduce environmental impacts; and to use the waste products of mining. It also discusses demand oriented CFC projects and their policy implications.     

Sources and sinks of carbon dioxide in terrestrial ecosystems: Is the land's carbon budget balanced under the influence of man?

This contribution deals with the controversy between certain scientists on the role of terrestrial vegetation and soils in the global carbon cycle. The hypothesis of a significant net release from the vegetation, is rejected by geochemists because of the limited capacity of the ocean to take up this excess carbon dioxide. As for the man-influenced tropics, a comparison of the figures for the potential and the current phytomass, as well as plausible demographic arguments, support the assertion put forward by ecologists that the carbon budget of this zone cannot be balanced. The tropics lose about 1.7-3.9 × 10¹⁵ g/yr of carbon to the atmosphere; however, for several reasons, 0.5-2.8 × 10¹⁵ g/yr may be returned to land ecosystem, mostly in other climatic zones. Thus, a balance is achieved on combining low estimates for the losses with high estimates for the gains. From an ecological perspective, this solution is not a very probable one; nevertheless, it cannot conclusively be eliminated.     

Foaming in Pachycondyla: A new defense mechanism in ants

Summary When disturbed, two species of Malayan Pachycondyla release foam threads more than 10 cm in length or foam piles. The source of the proteinaceous foam is the enlarged venom gland, which is probably frothed up by air from the spiracles of the spiracular plates. The Dufour's gland normally producing hydrocarbons in stinging ants is atrophied. Therefore, absence of the Dufour's gland could be essential to the foaming ability, since the lipophilic hydrocarbons inhibit froth production in protein solutions. The release of foam is a mechanically acting defense mechanism, which is very effective against small mass-attacking ants. Pachycondyla species are also able to sting effectively.     

Geschlechtsbestimmung und Geschlechtsdifferenzierung

Sex determination in mammals proceeds like a cascade from the level of the sex chromosomes to the gonads, to the genital ducts, and finally to the expression of the male or female phenotype. At the level of the genital ducts male sex organs are induced by testosterone. Its action depends on an intact cytoplasmic androgen receptor protein. The testicular feminization mutation (Tfm) leads to loss of hormone binding capacity. Individuals with testes but female external phenotype develop. In the mouse the interaction of androgen insensitiveTfm cells with normal cells can be studied in mosaic individuals composed of both cell types, and in organ culture by recombination ofTfm and normal tissues. The experiments show that under the action of testosterone the normal cells express male differentiated cellular functions, whereas theTfm cells differentiate in female direction. In respect to proliferation and expression of male or female organ structures, however, both cell types communicate via local factors. Thus, instead of irregular malformations intersex organs develop.     

A retrospective Markovian model for ecosystem resource flow

Historic ecosystem resource flow is modeled as a retrospective discrete Markov chain to obtain the expected values and variances of compartmental residence times and numbers of intercompartmental transfers that compartmental standing crops have experienced since their latest entry into the ecosystem. The transition probabilities of the proposed retrospective Markovian model are either stationary or time inhomogeneous according to whether a steady state or non-steady state ecosystem, respectively, is analyzed.     

Snake fangs from the Lower Miocene of Germany: evolutionary stability of perfect weapons

There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stab-like application of highly toxic venoms. Our findings therefore indicate that the other components of the venom-delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.     

An assessment of the risks associated with polychlorinated biphenyls found in the stomach contents of stranded Indo-Pacific Humpback Dolphins (Sousa chinensis) and Finless Porpoises (Neophocaena phocaenoides) from Hong Kong waters

The risks to Indo-Pacific Humpback Dolphins and Finless Porpoises associated with polychlorinated biphenyls (PCBs) were assessed. Stomach contents from twelve stranded Humpback Dolphins and sixteen stranded Finless Porpoises were collected. Concentrations of total and isomer-specific PCBs in the stomach contents were determined using dual-column gas chromatography equipped with electron capture detectors (GC-ECD). Risks due to the PCBs were assessed in three scenarios, based on total PCBs (summation of 41 PCB congeners), total toxicity equivalency (TEQs) and PCB 118, using the toxicity reference values (TRVs) as the threshold effects benchmarks. The calculated risk quotients (RQs) showed that risks due to PCBs were generally low or negligible. Specifically, RQs from total TEQs and total PCBs for Finless Porpoises are below one, suggesting that PCBs should be a low risk for the Finless Porpoise in Hong Kong waters. However, the Humpback Dolphin has RQs larger than 1 for total TEQs and total PCBs when the 95th percentile data were used in the evaluation. This indicates that further investigation may be needed to examine more closely the potential impact of toxic contaminants in the habitat of the Humpback Dolphin.