The effect of fluorine, boron and excess sodium on the critical curve in the albite–H2O system

Experiments to define the critical curve for a series of silicate melts in equilibrium with a hydrous fluid were carried out in a hydrothermal diamond anvil cell. Silicate compositions studied were albite with several wt% excess Na₂O, B₂O₃ and F₂O_-1. Complete miscibility between melt and water was observed at lower pressure and temperature conditions compared to pure albite for all compositions. For albite + excess Na₂O, the critical curve had been lowered by 143 and 247 °C at 10 kbar for 5 and 10 wt% excess Na. For albite +5 and 10 wt% F, the difference at 10 kbar was 147 and 246 °C respectively, and for albite +5 and 10 wt% B differences of 168 and 262 °C were found. These results are likely to be additive, with the presence of more than one of the components depressing the critical curve to even lower temperatures and pressures. The results suggest that in complex pegmatitic systems, complete miscibility between melt and fluid may be important in the final stages of crystallisation. The unusual properties of fluid phases under conditions close to the critical curve in a silicate melt-water system may be essential for the enrichment of trace elements in pegmatites as well as for the formation of typical pegmatite textures.     

A one dimensional wind profile model with stability and eddy viscosity estimations from sodar data

In a one-dimensional wind profile model, methods for eddy viscosity and stability estimations from sodar data have been evaluated with soundings. For eddy viscosity parameterization the ageostrophic method and mixing-length theory have been investigated. Three methods for estimating the static stability have been evaluated; a wind profile adjustment method, gravity wave analysis of sodar backscatter and flux profile functions for windspeed and standard deviation of vertical wind-speed. The wind profile model with variable momentum flux (VF) with height shows better results than an earlier constant flux model (Bergström, 1986). The VF model can be used for extending the sodar profile up to 1500 m.     

An integrated model for the assessment of the greenhouse effect: The Dutch approach

This paper describes a simulation policy model of the combined greenhouse effects of trace gases. With this model, the Integrated Model for the Assessment of the Greenhouse Effect (IMAGE) scenarios for the future impact of the greenhouse effect can be made, based on different assumptions for technological and socio-economic developments. The contribution of each trace gas can be estimated separately.Basically the model, consisting of a number of coupled modules, gives policy makers a concise overview of the problem and enables them to evaluate the impact of different strategies. Because the model covers the complete cause-effect relationship it can be utilized to derive allowable emission rates for the different trace gases from set effect related targets. Regular demonstration sessions with the simulation model have proven the importance of such science based integrated models for policy development.Four different scenarios are worked out for the most important trace gases (CO₂, CH₄, N₂O, CFC-11 and CFC-12). One of these scenarios can be regarded as a growth scenario unrestricted by environmental concerns. The others are based on different strategic policies. After the simulation of future trace gas concentrations global equilibrium temperature increases are computed. Finally the sea level rise, the most threatening effect of the greenhouse problem for the Netherlands, is estimated.Simulation results so far emphasize the importance of trace gases other than CO₂. The Montreal Protocol on reduction of CFC is found to stabilize the relative contribution of these substances to the greenhouse effect.     

Past and present state of the ichthyofauna of Lake Lugano

The evolution of the ichthyofauna of Lake Lugano (Lago di Lugano) during the past 120 years is characterized by the introduction of eight new fish species and by the possibly natural addition of the blenny (Blennius fluviatilis) in recent years. Introduced Salmonids such as charr (Salvelinus alpinus) and whitefish (Coregonus sp.) have established strong populations during the first half of this century, but have declined drastically thereafter. Likewise, the population of the native shad (Alosa fallax lacustris) has diminished significantly. A hydroacoustic survey of the pelagic fish stock of Lake Lugano in 1989 revealed the presence of a dense bleak (Alburnus albidus) population at 0 to 14 m depth. No other fish were found to be present in the pelagic zone. Oxygen and temperature distributions seem to confine the bleak to the uppermost layer in summer. In winter, very few fish were located by echosounding. Growth of bleak and roach (Rutilus rubilio) was difficult to interpret since data for comparison are lacking. Growth of perch (Perca fluviatilis) in the littoral zone was found to be slower than in other eutrophic lakes, for no obvious reason. Possible ways of restructuring the pelagic fish community are discussed.     

Eine Dünungsbeobachtung sowie die Beziehungen zum erzeugenden Windfeld

Summary Determining, with the aid of weather maps, the area and time of formation of swell observed in the subtropical region, the author found the practical methods developed by W. J. Pierson jun., G. Neumann and R. W. James [1953] to be superior to other proceedings. From a fixed point of observation (on the northern hemisphere) swell waves will be observed to turn in a counter clockwise sense if the generating depression is developing or intensifying at its very area of origin and if its distance is long enough.

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Sur l'observation d'une houle et sur les relations entre une houle et son aire génératrice

Résumé Cherchant à déterminer, à l'aide des cartes du temps, l'aire génératrice et le moment de génération d'une houle on trouve que les méthodes pratiques d'après W. J. Pierson le jeune, G. Neumann et R. W. James [1953] se montrent, dans le cas actuel, supérieures à d'autres procédés. Se trouvant à un point fixe d'observation, on aperçoit que sur l'hémisphère nord les ondulations de la houle causées par une dépression atmosphérique tournent en sens inverse des aiguilles d'une montre, à condition que la dépression en question se développe ou s'intensifie sur sa propre aire génératrice et qu'elle se trouve à une distance assez longue du point d'observation.

     

Potenzierte Faltung

Ohne Zusammenfassung     

Minerallagerstätten der Saar- Nahe- Senke

Zusammenfassung Der Verfasser gibt einen Überblick über die pfälzische Erzbildung, welcher wir die Entstehung kleiner Lagerstätten von Zinnober, von Schwerspat, von Kupfer und vermutlich auch Uran verdanken. Die Vorkommen stehen in engem räumlichem Zusammenhang mit Tholeyit- und Kuselitstöcken und -gängen. Die Erze wurden am Ende des Grenzlagervulkanismus abgesetzt, was dem Beginn der Oberrotliegendzeit entspricht.