A two-stage evolution of Visakhapatnam-Paradip shelf,east coast of India,from magnetic studies

A detailed analysis of bathymetry and magnetic data of Visakhapatnam-Paradip shelf, east coast of India revealed three major structural lineaments over the shelf/slope of the area. Models derived from the anomalies associated with the trends indicate that trend A represents horst and graben type continental basement while trend B is due to a series of dyke intrusions. Trend C off Chilka lake forms the northward extension of 85°E lineation from deep sea Bengal Fan. A two stage evolution of the eastern continental margin of India has been inferred from the study of this part of the margin, viz., the rift stage evidenced by dyke intrusions of reverse polarity located within the inner part of the shelf and post-rift stage characterized by vertical tectonics in the form of a horst and graben type continental basement. The hotspot related aseismic 85°E ridge further complicated the tectonics of this part of the area.     

Thermodynamic and kinetic constraints on reaction rates among minerals and aqueous solutions. II. Rate constants,effective surface area,and the hydrolysis of feldspar

Analysis of experimental data reported by Lagache (1965, 1976), Evans (1965), Busenberg (1975), Busenberg and Clemency (1976), Holdren and Berner (1979), Siegel and Pfannkuch (1984), and Chou and Wollast (1984) with the aid of irreversible thermodynamics and transition state theory (Aagaard and Helgeson, 1977, 1982) suggests that at temperatures at least up to 650°C, the rate of both congruent and incongruent feldspar hydrolysis in aqueous solutions far from equilibrium at pH ? 10.6 ? (2300/T), where T stands for temperature in kelvins, is a function solely of effective surface area and pH at constant pressure and temperature. At higher pH, the rate is apparently pH-independent up to ~pH 8 at 25°C, where it again becomes pH-dependent at higher pH. Observations of scanning electron micrographs indicate that the cross-sectional area of etch pits on hydrolyzed feldspar grains is of the order of 10^?9 to 10^?8 cm² and that the ratio of the effective to total surface area (which may or may not change with reaction progress) ranges from <0.01 to 1, depending on the grain size, dislocation density, and the extent of comminution damage on the surfaces of the grains. Apparent rate constants retrieved from experimental data reported in the literature for feldspar hydrolysis in the lower pH-dependent range extend from ~10^?13 to ~10^?7 moles cm^?2 sec^?1 at temperatures from 25° to 200°C, which is consistent with activation enthalpies for albite and adularia of the order of 20 kcal mole^?1. In contrast, the apparent rate constants for the pH-independent rate law range from ~10^?16 to ~10^?11 moles cm^?2 sec^?1 at temperatures from 25° to 650°C, which requires an activation enthalpy for adularia of ~ 9 kcal mole^?1. These observations are consistent with surface control of reaction rates among minerals and aqueous solutions. The rate-limiting step in the pH-dependent case apparently corresponds at the lower end of the pH scale to breakdown of a protonated configuration of atoms on the surface of the reactant feldspar, but at higher pH the rate is limited by decomposition of an activated surface complex corresponding in stoichiometry to hydrous feldspar. In highly alkaline solutions, an activated complex containing hydroxyl ions apparently controls the rate of feldspar hydrolysis. Nevertheless, near equilibrium, regardless of pH the rate is proportional to the chemical affinity of the overall hydrolysis reaction.     

Late Quaternary paleoenvironments of an ephemeral wetland in North Dakota,USA: relative interactions of ground-water hydrology and climate change

This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 ¹⁴C yr BP to 11,100 ¹⁴C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 ¹⁴C yr BP and finally, at 8,500 ¹⁴C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500 ¹⁴C yr BP) to deciduous parkland, followed by grassland at 9,300 ¹⁴C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused the lower-elevation Wendel site to capture the ground water of up-gradient lakes.     

Analysis of Russian Hydroacoustic Data for CTBT Monitoring

—?As part of a collaborative research program for the purpose of monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT), we are in the process of examining and analyzing hydroacoustic data from underwater explosions conducted in the former Soviet Union. We are using these data as constraints on modeling the hydroacoustic source as a function of depth below the water surface. This is of interest to the CTBT because although even small explosions at depth generate signals easily observable at large distances, the hydroacoustic source amplitude decreases as the source approaches the surface. Consequently, explosions in the ocean will be more difficult to identify if they are on or near the ocean surface. We are particularly interested in records featuring various combinations of depths of explosion, and distances and depths of recording.¶Unique historical Russian data sets have now become available from test explosions of 100-kg TNT cast spherical charges in a shallow reservoir (87?m length, 25?m to 55?m width, and 3?m depth) with a low-velocity air-saturated layer of sand on the bottom. A number of tests were conducted with varying water level and charge depths. Pressure measurements were taken at varying depths and horizontal distances in the water. The available data include measurements of peak pressures from all explosions and digitized pressure-time histories from some of them. A reduction of peak pressure by about 60–70% is observed in these measurements for half-immersed charges as compared with deeper explosions. In addition, several peak-pressure measurements are also available from a 1957 underwater nuclear explosion (yield <10?kt and depth 30?m) in the Bay of Chernaya (Novaya Zemlya).¶The 100-kg TNT data were compared with model predictions. Shockwave modeling is based on spherical wave propagation and finite element calculations, constrained by empirical data from US underwater chemical and nuclear tests. Modeling was performed for digitized pressure-time histories from two fully-immersed explosions and one explosion of a half-immersed charge, as well as for the peak-pressure measurements from all explosions carried out in the reservoir with water level at its maximum (3?m). We found that the model predictions match the Russian data well.¶Peak-pressure measurements and pressure-time histories were simulated at 10?km distance from hypothetical 1-kt and 10-kt nuclear explosions conducted at various depths in the ocean. The ocean water was characterized by a realistic sound velocity profile featuring a velocity minimum at 700?m depth. Simulated measurements at that same depth predict at least a tenfold increase in peak pressures from explosions in the SOFAR channel as compared with very shallow explosions (e.g., ～3?m depth).¶ The observations and the modeling results were also compared with predictions calculated at the Lawrence Livermore National Laboratory using a different modeling approach. All results suggest that although the coupling is reduced for very shallow explosions, a shallow 1-kt explosion should be detectable by the IMS hydroacoustic network.     

Seasonal Forecasting for Climate Hazards: Prospects and Responses

One of the most promising developments for early warning of climate hazards is seasonal climate forecasting. Already forecasts are operational in many parts of the tropics and sub-tropics, particularly for droughts and floods associated with ENSO events. Prospects for further development of seasonal forecasting for a range of climatichazards are reviewed, illustrated with case studies in Africa, Australia, the U.S.A. and Europe. A critical evaluation of the utility of seasonal forecasts centres on vulnerability, communicationchannels, and effective responses. In contrast to short-term prediction, seasonal forecasts raise new issues of preparedness and the use of information.     

Winners, losers and curate's eggs: Urban and regional outcomes of Australian economic restructuring 1971–1991

Since the early 1970s the Australian economy has undergone major transformations common to other western industrialised countries. Jobs in manufacturing declined precipitately whilst the service economy grew, most significantly in producer services but also in lower skilled jobs. Tourism and services exports began to rival traditional agricultural and mining staples. Social outcomes, also typical of international trends, included rising unemployment and polarisation of incomes. Australia's changing global context, especially the nation's increasing orientation towards Asian growth economies, have underpinned restructuring. A political climate of economic rationalism has facilitated and accentuated restructuring. The economic shifts of the past quarter century have meant that everywhere the basis for economic growth has changed. Overlaying and reinforcing the re-definition of competitive advantage has been a shift in the pattern of agglomeration economies and diseconomies. New growth regions have emerged, others have had their prospects reinforced, and still others have had their outlook diminished in absolute or, more commonly, relative terms. The paper traces the regional outcomes of national economic restructuring and shifts in the balance of agglomeration economies and diseconomies over the period from 1971 to 1991. The focus is on the top end of the urban hierarchy, on specialised industrial cities where job loss from manufacturing has hit hard, amenity regions where international and domestic tourism have been major factors in growth, and non-metropolitan balances where growth has been uneven but generally low. Demographic, economic sectoral and welfare indicators are woven into a tableau of change expressed at national, intra-state and intrametropolitan scales.     

The precision nucleus counter (Pollak type) with automatic recording

Summary In order to obtain an automatic recording nucleus counter with greater accuracy than that ofVerzár, a precision photoelectric nucleus counter (Pollak type) with ceramic lining and internal diameter 2.5 cm has been substituted for the horizontal fog tube inVerzár's automat. Certain small alterations, have been made to the electric circuit of the recorder. The new arrangement can be easily calibrated and shows an accuracy approaching that of the precision counter operated under optimum conditions.

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Zusammenfassung Um einen automatischen Kondensationskernzähler von grösserer Genauigkeit als es der vonVerzár ist, zur Verfügung zu haben, wurde das horizontale Nebelrohr im Automaten vonVerzár durch einen photo-elektrischer Präzisions-Kernzähler (BauartPollak) mit unglasiertem Porzellanfutter und einem inneren Durchmesser von 2.5 cm ersetzt. An der elektrischen Schaltung der Registriereinrichtung wurden gewisse kleine Änderungen vorgenommen. Die neue Anordnung kann leicht geeicht werden und besitzt eine Genauigkeit, welche jene des Präzisions-Kernzählers unter optimalen Betriebsbedingungen erreicht.

     

Fisheries in upwelling regions — with special reference to peruvian waters

The anchovy population that is the basis of the Peru fishery, the world's largest, is a phytoplankton feeding species, supported by an upwelling based ecosystem. The fish is very short-lived and grows rapidly — both criteria for high turnover rate — high yield fisheries. The maximum sustainable yield is around 10 million metric tons. Analysis of the dynamics of the fishery suggests that the fleet is overbuilt, applying too much fishing effort, and slightly overfishing the population. In consequence, the population may be approaching a size and stress level at which it will be unstable.     

Comparison of photo-electric nuclei counters

Summary Three identical photo-electric nuclei counters have been compared in pairs using natural and artificially produced aerosols. The main results of comparisons were obtained in the laboratory under controlled conditions using nuclei stored in a gasometer, consisting of a radiosonde balloon inflated to a volume of 4000 litres. Because of its large size, it enables the constants in the decay law of condensation nuclei to be determined with greater accuracy than heretofore. The gasometer is more convenient, more easily stored after use and its cost is a very small fraction of that of a metal one. No effects detrimental to the stored gas or any other objection to its use have been found.The results of several thousand comparisons show that no two counters will record the same concentration of nuclei in samples taken simultaneously from the same enclosure. Each counter shows small random fluctuations of short period, ±3% of the concentration, with superimposed unpredictable variations of longer period. The differences in readings between any two counters depend on the concentration, the type and the relative amounts of the charged and uncharged nuclei in a sample. These differences, which seldom exceed ±20% of the concentration, are rather constant for several hours and even days. This feature enables allowances to be made for the differences and a routine of observations is suggested which has been successfully employed in the laboratory and in the open.Each counter exhibits, when operated continuously, a drift which consists of a tendency to indicate that the concentration of nuclei increases when a constant value or a slight decrease is expected theoretically.A study of the statistical analysis of the individual readings and a detailed investigation of the components of each counter have not lead to an elucidation and elimination of the differences between counters. The investigation of the differences is still proceeding.

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Zusammenfassung Drei identische photo-elektrische Kernzähler wurden paarweise mittels natürlicher und künstlich erzeugter Aerosole verglichen. Die Hauptresultate der Vergleichungen wurden im Laboratorium unter kontrollierten Bedingungen mit Hilfe von Kondensations-Kernen erhalten, welche in einem grossen Gasometer gespeichert worden waren. Dieser Gasometer besteht aus einen Radiosonde-Ballon, der auf ein Volumen von 4000 Litern aufgeblasen wurde. Wegen seiner Grösse ermöglicht er die Bestimmung der Konstanten des Abklingungs-Gesetzes der Kernkonzentration mit grösserer Genauigkeit als es bisher möglich war. Der neue Gasometer ist bequemer, kann, wenn nicht benötigt, leicht weggeräumt und aufbewahrt werden und kostet nur einen kleinen Bruchteil eines aus Metal hergestellten Gasbehälters. Es wurde kein schädlicher Einfluss der Gummihülle auf das gespeicherte Gas festgestellt und auf Grund unserer Beobachtungen besteht kein Einwand gegen die Benützung eines Gummigasometers.Die Resultate von mehreren tausend Vergleichungen lehren, dass keine zwei photoelektrischen Kernzähler die genau gleiche Konzentration der Kerne in Proben, welche gleichzeitig demselben Behälter entnommen werden, angeben. Jeder Kernzähler zeigt kurzperiodische, zufällige Schwankungen von ±3% der Konzentration, welche von nicht vorauszusagenden Variationen längerer Periode überlagert sind. Die Differenzen in den Lesungen irgend zweier photo-elektrischer Kernzähler hängen von der Konzentration der Kerne, ihrem Charakter und dem Verhältnis der Anzahl der geladenen und ungeladenen Kerne in der Probe ab. Diese Differenzen, welche selten ±20% der Konzentration übersteigen, sind während mehrerer Stunden und sogar Tage ziemlich konstant. Diese Eigenschaft ermöglicht es, die Differenzen in Rechnung zu ziehen und ein Beobachtungs-Schema vorzuschlagen, welches sowohl im Laboratorium als auch im Freien mit Erfolg angewendet wurde.Jeder photo-elektrische Kernzähler zeigte, wenn er ununterbrochen benützt wurde, einen Drift, der darin besteht, dass der Zähler eine kleine, mehr oder weniger stetige Zunahme in der Konzentration der Kerne vortäuscht, wenn konstante Kernzahl oder eine geringe Abnahme derselben theoretisch erwartet wird.Die statistische Analyse der Einzelmessungen und eine eingehende Untersuchung der Bestandteile jedes einzelnen photo-elektrischen Kernzählers hat zu keiner Aufklärung und Beseitigung der Differenzen der Kernzähler geführt. Die Untersuchung der Differenzen wird fortgesetzt.