The anisotropy of magnetic susceptibility of the Franciscan rocks of the Diablo Range,Central California

The authors measured the magnetic susceptibility anisotropy of approximately 400 specimens cut from oriented samples of greywacke taken at forty sites in a 1500 square-mile area in the Diablo Range, Central California.The magnetic fabric was judged to be of primary style at thirteen sites and to indicate that the direction of sediment transport was along an axis aligned N 60 E, with little variation in alignment over the area of the study. Rocks at the remaining sites were thought to have suffered slight but variable deformation, prior to folding, by a stress acting along an east-west axis.The rocks at five sites were metagreywackes. Although the metamorphism of these is believed to be the result of great pressure, there was no obvious effect of this pressure on the magnetic fabric.

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Zusammenfassung An ungefÄhr 400 Proben aus orientiert entnommenen Grauwacke-Handstücken von 40 LokalitÄten der Franciscan Formation (Diablo Range, Mittel-Kalifornien) wurde die Anisotropie der magnetischen SuszeptibilitÄt gemessen.Bei 13 LokalitÄten des Untersuchungsgebietes konnte ein kaum deformiertes primÄres magnetisches Gefüge festgestellt werden, das auf einen parallel N 60 E gerichteten Sedimenttransport mit geringer regionaler Variation der Einregelungsrichtung schlie\en lÄ\t. Die Gesteine der übrigen Aufschlüsse erfuhren vermutlich vor der Faltung eine geringe, aber unterschiedliche Deformation durch eine E-W gerichtete, horizontale Stresswirkung.Obwohl die Gesteine von 5 LokalitÄten Meta-Grauwacken sind, die nach allgemeiner Ansicht bei hohem Druck metamorphisiert wurden, konnte kein eindeutiger Einflu\ dieses Druckes auf das magnetische Gefüge festgestellt werden.

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Résumé Les auteurs mesurèrent l'anisotropie de susceptibilité magnétique dans à peu près 400 carottes orientées prises dans des blocs de grauwacke, prélevées à 40 sites sur une étendue de 4000 km² du Diablo Range de la Californie Centrale.On a estimé que la fabrique magnétique était d'un caractère primaire à treize de ces sites, et qu'elle suggérait que le transport du sédiment suivait l'axe d'orientation N 60 E, sans grande variation d'alignement dans toute l'étendue etudiée.Les roches des autres sites paraissaient avoir subi avant d'Être plissées des déformations peu importantes, mais variables, causées par un effort dans un axe orienté est-ouest.Les roches de cinq sites étaient des metagrauwackes. Bien que le métamorphisme de celles-ci résulte, à ce qu'il nous semble, d'une pression intense, la fabrique magnetique restait apparemment inchangée par cette pression.

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400 40 [ Franciscan (Diablo Range, ). 13 , , N 60 E . , -, , W. 5 - , , .

     

The depth of the deepest historical earthquakes

We useP andS times listed in the International Seismological Summary to relocate 23 historical earthquakes (1927–1963) reported as occurring at or below 670 km. In all cases, our relocated hypocenters are shallower than the starting depths; furthermore, all events converge to 691 km or less, with a precision estimated at ±10 km. This study upholds the results of Stark and Frohlich, who had usedpP–P times of post-WWSSN earthquakes to constrain reliable hypocentral depths to no greater than 684 km. In particular, we reject Rothé's claim that a 1963 event in the vicinity of New Guinea occurred at a depth of more than 780 km.     

Sustainable Utilisation of Fisheries as Governmentality: Constraining the Potential for Ecosystems‐Based Management?

This paper examines the constitution of ‘sustainable management’ within the context of the New Zealand marine environment. Firstly this paper examines the difference between ‘sustainable ecosystems’ and ‘sustainable utilisation’. The distinction is important if we are to make sense of the different ways in which various stakeholders (fishers, fisheries companies, scientists, fisheries managers and environmental groups) use ‘sustainability’ in the management of New Zealand's marine environment. We then examine how contestation results in sustainable management becoming a governmentality. We propose that such contestation transforms stakeholders into subjects whose everyday practices and relationships are influenced by seemingly incommensurable understandings of the lexicon that surrounds sustainable management. We conclude try considering how the potential revelation of new unknowns may be needed in order for disparate stakeholders to forge a unified approach to New Zealand's marine management.     

Helium escape from the Earth''s atmosphere: The charge exchange mechanism revisited

We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He⁺ ions and the major atmospheric constituents N₂, O₂, and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He⁺ ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.     

On the characteristics of eddies in the stable atmospheric boundary layer

A discussion of the cross-spectral properties of eddies in the lowest 40 m of the nocturnal boundary layer is presented. The study involves the analysis of meteorological data collected by the British Antarctic Survey at Halley Station, Antarctica, during the austral winter of 1986. Cross-spectral analysis is used to determine whether the nature of the observed eddies is primarily turbulent or whether their structure is characteristic of coherent internal gravity waves. It is found that the cross-spectral phases indicate the presence of turbulent eddies only when the local gradient Richardson number (Ri) is less than the critical value of 1/4. Trapped modes were only observed when an off-shore wind prevailed, indicating that topographic effects are responsible for their generation. The relative phases of velocity and temperature were often observed to change with height. This can be explained by examining the underlying meteorological conditions. On several occasions, regions of counter-gradient fluxes were detected. A physical explanation of this phenomenon is proposed.     

Reservoir resettlement in China: past experience and the Three Gorges Dam

This paper reviews involuntary resettlement resulting from dam-building, which has been ignored relative to the dominant focus of migration research in China, rural to urban migration. Reservoir resettlement in China has a long history, often of misery and hardship for those displaced. Relocatees affected by the Three Gorges Project (1994–2009) on the Yangtze River face a similar situation. In China priority has been given to building the dam to provide electricity, flood control and navigation. Less attention has been paid to the problems of the people affected by the reservoir inundation. The rural population forced to relocate and rural-urban migrants in general have been discriminated against by national policies.     

The morphology of n and no in auroral substorms

The effects of a typical auroral electron precipitation substorm sequence on odd nitrogen species in the thermosphere have been investigated. The analysis makes use of the time dependent model of the aurora developed by Roble and Rees (1977), which couples the thermal properties to the ionospheric chemistry and transport self-consistently and includes diffusive transport of NO, N(²D) and N(⁴S). A substantial increase in the E-region density of NO or of N(⁴S) is predicted, with the result depending on the production ratio of N(²D) to N(⁴S) in the aurorally dominant source mechanism, electron impact dissociation of N₂. A production ratio that favors N(²D) by a factor of one half or larger leads to enhancement of NO, while a ratio of $\text{1}\text{4}\text{N}\text{(}{}^2\text{D}\text{)+}\text{3}\text{4}\text{N}\text{(}{}^4\text{S}\text{)}$ results in a buildup of N(⁴S). The cyclical behaviour of the substorm, i.e. alternate intervals of electron precipitation and quiet periods, accentuates the scavenging effect of the initially dominant odd nitrogen species upon the less abundant one.     

A steady-state model for sulphur isotope fractionation in bacterial reduction processes

A model is developed to explain the isotope fractionation effects produced in laboratory experiments involving the reduction of sulphate to hydrogen sulphide by the bacterium Desulfovibrio desulfuricans. The approach differs from previous ones in its use of zero-order kinetics to describe the uptake of sulphate by the bacterium. Expressions are developed which relate the overall isotope effects produced by the bacterium to the ratios of backward to forward flows between its internal sulphur reservoirs. Other applications of this type of model are discussed, including the differences of isotopic composition between sulphate and hydrogen sulphide in the Black Sea and an unusual isotope effect observed in the course of bacterial nitrate reduction.     

The role of neutral winds and ionospheric electric field in forming stable sporadic E-layers

Using the combined measurements from a rocket flight through a stable intense sporadic E-layer, we examine the shortcomings of conventional wind shear theory of ion layer formation, principally in underestimating the role of the ambient ionospheric electric field. Our results imply that the ionospheric electric field may control the stability and precise location of such ionisation layers within a region of convergent ion flow.