Caledonian metamorphism in part of northwest County Mayo,Ireland

Lewisian gneisses, Moinian and Dalradian sediments, and dolerites have been deformed and metamorphosed under Amphibolite Fades conditions. The metamorphic climax, with the growth of kyanite and staurolite, occurred after the cessation of the second deformational episode and before the onset of the third. Plagioclase growth ceased at or about the time of kyanite and staurolite nucleation. Metamorphic effects become less to the south and southeast while the most advanced stages occur around Inver. A single heat pulse appears to be not directly related to any structure.     

Zur Dynamotheorie stellarer und planetarer Magnetfelder I. Berechnung sonnenähnlicher Wechselfeldgeneratoren

Non-reflectionsymmetric turbulent motions in an electrically conducting fluid provide for an average electromotoric force α parallel to the average magnetic field . This effect – furthermore called α-effect – can lead to a self-excited built-up of magnetic fields by dynamo action. Since by actions of Coriolis forces turbulent motions in rotating systems generally are non-reflectionsymmetric, the explanation of stellar and planetary magnetic fields becomes possible. – In this first part spherical alternating field dynamos are calculated on conditions similar to those at the sun; α-effect and differential rotation provide for dynamo action. – The basic equations, which form a system of partial differential equations, are treated by a separation method; in this way our problem is transformed into a two-parametric eigenvalue problem for an infinite system of ordinary differential equations. The two eigenvalues determine the frequency and the amount of the induction actions necessary for the field maintenance. The solution of this problem was made by an electronic computer. – The results give evidence for the possibility of magnetohydrodynamic alternating field dynamos. Furthermore the magnitude of the calculated eigenvalues and the similarities between the calculated field and the observed solar magnetic field are showing that the sun realizes a dynamo of this kind.     

The radio luminosity function and the luminosity diameter function of extragalactic radio sources

On the basis of a radio index-surface brightness diagram recently published, the luminosity function and the luminosity diameter function are obtained. The uncertainties due to the incompleteness of the sample are of the same order as the statistical uncertainties. The luminosity function differs considerably from a simple power law and supports the distinction of two populations. The density of the weak population (P<10³⁵ W Hz⁻¹ ster⁻¹ at 1400 MHz) follows nearly a power law in P and increases towards small diameters at least down to I kpc. The density of the strong population (the high luminosity and small diameter part of which is occupied by the quasars) has a maximum between 10²⁵ and 10²⁸ W Hz⁻¹ ster⁻¹ and around 100 kpc. A strong evolution effect is clearly present and is in a good agreement with the models obtained from the log N-log S counts.     

Extraction and recovery of precious metals from electronic waste printed circuit boards by bioleaching acidophilic fungi

Printed circuit boards contain precious metals. They are produced in large volumes, rendering them an important component of the electronic waste. In view of the heterogeneity of the metals present, reprocessing of electronic waste is a heinous task. The present study focused on leaching of valuable metals from electronic waste printed circuit boards using Aspergillus niger DDNS1. The adaptation phases began at 0.1, 0.5 and 1.0% of fine powder of printed circuit boards with 10% inoculum and were optimized with three effective factors, viz. initial pH, particle size and pulp density, to achieve the maximum simultaneous recovery of the valuable metals. The interactions of these metals were also deciphered using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectrum and atomic absorption spectroscopy. The results indicated that extraction of the precious metals was accomplished mainly through the unique organic acids originating from A. niger DDNS1. The initial pH played an important role in the extraction of the precious metals and the metals precipitate formation. The leaching rate of the metals was generally higher at low powder dosage of printed circuit boards. The toxicity of the printed circuit boards had little effect on two-step bioleaching at the pulp density of 0.1% compared to one-step bioleaching. The two-step bioleaching process was followed under organic acid-forming conditions for the maximum mobilization of metals. Thus, the precious metals from printed circuit boards could be mobilized through fungal bioleaching which promises an important industrial application in recycling of electronic wastes.     

Rare earth elements in the clay fraction of coaliferous sediments of the Arkagalinskoe (Magadan district) and Dolinskoe (Sakhalin Island) coalfields

The study of REE distribution in the clay fraction of sedimentary rocks from two coalfields made it possible to distinguish several types of REE distribution, which correlate with their mineral composition. It is shown that the REE fractionation was related to the mineral reconstruction of the primary clay fraction and some detrital minerals in the course of postsedimentary transformations of rocks during diagenesis, early catagenesis, and beginning of late catagenesis. These transformations were governed by several factors, such as the composition of sediments; hydrochemical features of accumulation environment; the chemical composition, dynamics, and feeding sources of pore solutions; the porosity and permeability of sediments and rocks; and the content of organic matter and its reaction ability.     

Snow measurement techniques for land-surface-atmosphere exchange studies in boreal landscapes

Summary  Snow has been studied widely in hydrology for many decades whereas recent meteorological interest in snow is caused by increased emphasis on high latitudes and wintertime in climate-change research as well as by the need to improve weather-forecast models during these conditions. Ground-based measurements of snow properties are needed both to improve understanding of surface-atmosphere exchange processes and to provide ground truth to new remote-sensing algorithms. This justifies a review of techniques to measure snow in combination with establishment of criteria for the suitability of the methods for process studies. This review assesses the state-of-art in ground-based snow-measurement techniques in the end of the 1990s in view of their accuracy, time resolution, possibility to automate, practicality and suitability in different terrain. Methods for snow-pack water equivalent, depth, density, growth, quality, liquid-water content and water leaving the snow pack are reviewed. Synoptic snow measurements in Fennoscandian countries are widely varying and there is no single standard on which process-related studies can build. A long-term, continuous monitoring of mass and energy properties of a snow cover requires a combination of point-measurement techniques. Areally representative values of snow properties can be achieved through a combination of automatically collected point data with repeated manual, areally covering measurements, remote-sensing data and digital elevation models, preferably in a GIS framework. Received August 27, 1999     

A case study of warm air advection over a melting snow surface

When relatively warm, moist air moves over a snow surface, sensible heat and moisture are extracted from its lower layers and used to melt the snow. The depth of the cooled layer depends on horizontal wind speeds and the presence of high vertical wind shear. The mechanism for air mass modification appears to be turbulent mixing.