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.     

Formation Mechanism of Mud Bank Along the Southwest Coast of India

Mud bank formation during the southwest monsoon along the southwest coast of India remains an enigma to the researchers and coastal community in spite of several earlier studies. The present study attempts to unravel the mystery through a high-frequency, season-long time-series observation at Alappuzha, located at the southern part of the west coast of India, a region of frequent occurrence of mud bank. Using 7-month-long weekly time-series observation, we identified strong winds and high waves associated with onset of the southwest monsoon and subsequent three episodic atmospheric low-pressure events (LPEs).With the help of in situ time-series data, we show that the strong winds and high waves associated with southwest monsoon pre-conditions the near shore bottom sediment to bring it into suspension. The high amplitude waves associated with the southwest monsoon, while propagating from the deep water to shallow water region, interact with the bottom initiating bottom-sediment movement and its suspension due to wave refraction and shoaling. The sporadic occurrence of the atmospheric LPEs enhances the process of suspension of bottom sediment in the near shore region leading to the formation of fluid mud. Simulations with a cohesive sediment transport model yielded realistic estimates of sediment transport, in the presence of an onshore current, a pre-requisite for transporting the fluid mud toward the coast. The prevailing onshore upwelling current during the southwest monsoon provides the favorable pre-requisite conditions for transporting the fluid mud through depression channel network towards the coast. Once sufficient quantity and thickness of fluid mud is accumulated in the near shore region, it acts as a wave damper for subsequent high monsoon waves, as indicated by the time-series wave data, leading to the formation of tranquil mud bank region. Depression channel networks extending from the shelf to the coast off Alappuzha, Kochi, Ponnani, Beypore, and Ullal were found in the bathymetric charts, thus explaining why mud banks occur only at few locations in spite of the prevalence of similar monsoon conditions.     

Possible representation for discovery observations of stellar flares

It is shown that the chronology of flare star discoveries in the Pleiades cluster and the Orion association can be described satisfactorily by various distribution functions (gamma, binomial, decreasing exponential, and delta) for the mean frequencies of stellar flares. However, it has been found that this is due to the uncertainty in the observationally derived distribution function for the mean frequency of stellar flares. The most likely function is that derived by Ambartsumian, which has a physical basis.Translated fromAstrofizika, Vol. 38, No. 1, pp. 25–32, January–March, 1995.     

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.     

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     

Peculiarities of Dynamic Slip Nucleation in a Thin Granular Layer

Izvestiya, Physics of the Solid Earth - Abstract—Granular media determine the dynamics of many natural systems including faults in the Earth’s crust. The paper addresses the laboratory...     

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.