On the eigenvalues of kinematic α-effect dynamos

The kinematic α-effect dynamo problem is investigated in the case of an exterior perfect conductor. It is shown that certain approximate symmetries discovered in the numerical analysis of ROBERTS (1972) are exact for this case. As an illustration, an exact solution is given in a cylindrical geometry, where the equations can be written in terms of one variable. The implications for the earth's dynamo are discussed.     

Numerical simulation of undersea cable dynamics

A fully three-dimensional code has been written to compute the motion of a towed cable. The code is based on a robust and stable finite difference approximation to the differential equations derived from basic dynamics. A 3500-ft (1.07 km) cable pulled at 18.5 knots (34.3 km hr⁻¹) through a circular turn of 700 yd (0.64 km) radius has been computed in about half of the real time of the maneuver. The computed displacements are close to the measured ones; the changes in depth are within 2%.     

Analysis of mutations in the p53 tumor suppressor gene and Ki- and Ha-ras proto-oncogenes in hepatic tumors of European flounder (Platichthys flesus).

DNA from five tumors, three other-injured livers and two normal liver tissue samples from the European flounder were analyzed for mutations in exons 5-8 of the tumor suppressor gene p53 and at codons 12, 13 and 61 of Ha- and Ki-ras proto-oncogenes. No tumor-specific mutations were identified by direct sequencing and single-strand conformation polymorphism of these genes. A number of silent polymorphisms were noted in p53. In addition to a need for more extensive analyses of flounder liver tumor samples for ras or p53 mutations, other cancer-related genes should be investigated.     

Improved Resolution of Ambient Flow through Fractured Rock with Temperature Logs

In contaminant hydrogeology, investigations at fractured rock sites are typically undertaken to improve understanding of the fracture networks and associated groundwater flow that govern past and/or future contaminant transport. Conventional hydrogeologic, geophysical, and hydrophysical techniques used to develop a conceptual model are often implemented in open boreholes under conditions of cross-connected flow. A new approach using high-resolution temperature (±0.001°C) profiles measured within static water columns of boreholes sealed using continuous, water-inflated, flexible liners (FLUTe™) identifies hydraulically active fractures under ambient (natural) groundwater flow conditions. The value of this approach is assessed by comparisons of temperature profiles from holes (100 to 200 m deep) with and without liners at four contaminated sites with distinctly different hydrogeologic conditions. The results from the lined holes consistently show many more hydraulically active fractures than the open-hole profiles, in which the influence of vertical flow through the borehole between a few fractures masks important intermediary flow zones. Temperature measurements in temporarily sealed boreholes not only improve the sensitivity and accuracy of identifying hydraulically active fractures under ambient conditions but also offer new insights regarding previously unresolvable flow distributions in fractured rock systems, while leaving the borehole available for other forms of testing and monitoring device installation.     

Precipitation — elevation relationships over Sri Lanka

Summary The change of rainfall totals with height has been the subject of much investigation in many parts of the world. The rates of increase or decrease vary with the climatic regime experienced. This study of Sri Lankan rainfall shows that the relationship between height and mean annual rainfall is complex. Examples of increases and decreases of rainfall with height are found. The climatic regime of the area is important in controlling the level of maximum rainfall.With 7 Figures     

Impact of Sea-level Rise and Storm Surges on a Coastal Community

A technique to evaluate the risk of storm tides (the combination of a storm surge and tide) under present and enhanced greenhouse conditions has been applied to Cairns on the north-eastern Australian coast. The technique combines a statistical model for cyclone occurrence with a state-of-the-art storm surge inundation model and involves the random generation of a large number of storm tide simulations. The set of simulations constitutes a synthetic record of extreme sea-level events that can be analysed to produce storm tide return periods. The use of a dynamic storm surge model with overland flooding capability means that the spatial extent of flooding is also implicitly modelled. The technique has the advantage that it can readily be modified to include projected changes to cyclone behaviour due to the enhanced greenhouse effect. Sea-level heights in the current climate for return periods of 50, 100, 500 and 1000 years have been determined to be 2.0 m, 2.3 m, 3.0 m and 3.4 m respectively. In an enhanced greenhouse climate (around 2050), projected increases in cyclone intensity and mean sea-level see these heights increase to 2.4 m, 2.8 m, 3.8 m and 4.2 m respectively. The average area inundated by events with a return period greater than 100 years is found to more than double under enhanced greenhouse conditions.     

Ein Beitrag zur Struktur des Windes über Wien

Zusammenfassung Nach zweijährigen Parallelregistrierungen der Windgeschwindigkeit und Windrichtung in Wien-Hohe Warte am Rande der Stadt Wien und an einer Meßstelle in der Stadtmitte wird gezeigt, daß ein merklicher und jahreszeitlich veränderlicher Umgebungseinfluß gerade am Stadtrand auf die Windgeschwindigkeit einwirkt. Während der Vegetationsperiode ist die Bodenrauhigkeit erhöht, die Windgeschwindigkeit in den unteren Stufenwerten bis etwa 35 km/h wird verringert. Während der vegetationslosen Zeit ist die Bodenrauhigkeit viel geringer, die Häufigkeitsverteilung der Windgeschwindigkeit im Winter daher viel normaler. Es besteht ein scharfer Gegensatz zwischen den Sommer-und Wintermonaten ohne langsame Übergänge. Das Ergebnis dieses zunächst lokalen Vergleiches ist von allgemeiner Bedeutung für Windbeobachtungen in den gemäßigten Breiten mit Vegetationswechsel.

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Summary Based on two year's parallel observations of velocity and direction of wind at two stations, viz. the secular station Wien-Hohe Warte at the periphery and a station in the town-centre, it is shown that there exists a considerable and seasonally variable effect of local influences on the wind velocity, especially at the periphery of the town. During the vegetation period the roughness of the ground is increased and up to about 35 km/h the wind velocity is reduced. Out of the vegetation period the roughness of the ground is much smaller, the frequency distribution of wind velocity during the winter, therefore, shows more the normal features. There is a marked difference between the summer and winter months, and there exists no graduate change. The result of this local comparison seems to be of general interest to the climatology of wind in temperate latitudes with their seasonal change of vegetation.

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Résumé Pendant deux ans on a enregistré les vitesses et les directions des vents dans le cadre d'observations faites simultanément à la périphérie de la ville de Vienne (station météorologique «Hohe Warte») et à une station située au centre de cette ville. Les résultats démontrent que c'est précisément à la périphérie de la ville que l'aspect du sol exerce une influence très nette, la vitesse des vents, qui varie selon les saisons. Pendant la saison de végétation la «rugosité» du terrain étant plus grande, les vents moins forts (jusqu'à 35 km/h) sont affaiblis. En hiver, quand il n'y a pas de végétation, la rugosité du sol est moindre, et par conséquent les fréquences respectives des vents d'intensités diverses offrent un tableau mieux équilibré. Entre les mois d'hiver et les mois d'été, le contraste est très brusque; il n'y a pas de période de lente transition. Le résultat de ces essais, effectués seulement sur un plan local jusqu'à présent, est d'importance générale pour l'étude des vents dans les régions de climat tempéré, avec une végétation changeante.

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Mit 1 Textabbildung

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Herrn Prof. Dr.H. Ficker zum 75. Geburtstag gewidmet.